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Sample records for reactive gas solids

  1. Gas sampling system for reactive gas-solid mixtures

    DOEpatents

    Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

    1990-01-01

    An apparatus and method for sampling gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extends in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

  2. Gas sampling system for reactive gas-solid mixtures

    DOEpatents

    Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

    1989-01-01

    An apparatus and method for sampling a gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extend in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

  3. Method for reactivating solid catalysts used in alkylation reactions

    DOEpatents

    Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

    2003-06-17

    A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

  4. Method For Reactivating Solid Catalysts Used For Alklation Reactions

    DOEpatents

    Ginosar, Daniel M.; Thompson, David N.; Coates, Kyle; Zalewski, David J.; Fox, Robert V.

    2005-05-03

    A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

  5. A Model of Solid State Gas Sensors

    NASA Astrophysics Data System (ADS)

    Woestman, J. T.; Brailsford, A. D.; Shane, M.; Logothetis, E. M.

    1997-03-01

    Solid state gas sensors are widely used to measure the concentrations of gases such as CO, CH_4, C_3H_6, H_2, C_3H8 and O2 The applications of these sensors range from air-to-fuel ratio control in combustion processes including those in automotive engines and industrial furnaces to leakage detection of inflammable and toxic gases in domestic and industrial environments. As the need increases to accurately measure smaller and smaller concentrations, problems such as poor selectivity, stability and response time limit the use of these sensors. In an effort to overcome some of these limitations, a theoretical model of the transient behavior of solid state gas sensors has been developed. In this presentation, a model for the transient response of an electrochemical gas sensor to gas mixtures containing O2 and one reducing species, such as CO, is discussed. This model accounts for the transport of the reactive species to the sampling electrode, the catalyzed oxidation/reduction reaction of these species and the generation of the resulting electrical signal. The model will be shown to reproduce the results of published steady state models and to agree with experimental steady state and transient data.

  6. Gasification reactivities of solid biomass fuels

    SciTech Connect

    Moilanen, A.; Kurkela, E.

    1995-12-31

    The design and operation of the biomass based gasification processes require knowledge about the biomass feedstocks characteristics and their typical gasification behaviour in the process. In this study, the gasification reactivities of various biomasses were investigated in laboratory scale Pressurized Thermogravimetric apparatus (PTG) and in the PDU-scale (Process Development Unit) Pressurized Fluidized-Bed (PFB) gasification test facility of VTT.

  7. Chemical reactivity in solid-state pharmaceuticals: formulation implications.

    PubMed

    Byrn, S R; Xu, W; Newman, A W

    2001-05-16

    Solid-state reactions that occur in drug substances and formulations include solid-state phase transformations, dehydration/desolvation, and chemical reactions. Chemical reactivity is the focus of this chapter. Of particular interest are cases where the drug-substance may be unstable or react with excipients in the formulation. Water absorption can enhance molecular mobility of solids and lead to solid-state reactivity. Mobility can be measured using various methods including glass transition (T(g)) measurements, solid-state NMR, and X-ray crystallography. Solid-state reactions of drug substances can include oxidation, cyclization, hydrolysis, and deamidation. Oxidation studies of vitamin A, peptides (DL-Ala-DL-Met, N-formyl-Met-Leu-Phe methyl ester, and Met-enkaphalin acetate salt), and steroids (hydrocortisone and prednisolone derivatives) are discussed. Cyclization reactions of crystalline and amorphous angiotensin-converting enzyme (ACE) inhibitors (spirapril hydrochloride, quinapril hydrochloride, and moexipril) are presented which investigate mobility and chemical reactivity. Examples of drug-excipient interactions, such as transacylation, the Maillard browning reaction, and acid base reactions are discussed for a variety of compounds including aspirin, fluoxitine, and ibuprofen. Once solid-state reactions are understood in a pharmaceutical system, the necessary steps can be taken to prevent reactivity and improve the stability of drug substances and products. PMID:11325479

  8. Spatially Resolved Quantification of the Surface Reactivity of Solid Catalysts.

    PubMed

    Huang, Bing; Xiao, Li; Lu, Juntao; Zhuang, Lin

    2016-05-17

    A new property is reported that accurately quantifies and spatially describes the chemical reactivity of solid surfaces. The core idea is to create a reactivity weight function peaking at the Fermi level, thereby determining a weighted summation of the density of states of a solid surface. When such a weight function is defined as the derivative of the Fermi-Dirac distribution function at a certain non-zero temperature, the resulting property is the finite-temperature chemical softness, termed Fermi softness (SF ), which turns out to be an accurate descriptor of the surface reactivity. The spatial image of SF maps the reactive domain of a heterogeneous surface and even portrays morphological details of the reactive sites. SF analyses reveal that the reactive zones on a Pt3 Y(111) surface are the platinum sites rather than the seemingly active yttrium sites, and the reactivity of the S-dimer edge of MoS2 is spatially anisotropic. Our finding is of fundamental and technological significance to heterogeneous catalysis and industrial processes demanding rational design of solid catalysts. PMID:27072349

  9. Viscoelasticity Using Reactive Constrained Solid Mixtures

    PubMed Central

    Ateshian, Gerard A.

    2015-01-01

    This study presents a framework for viscoelasticity where the free energy density depends on the stored energy of intact strong and weak bonds, where weak bonds break and reform in response to loading. The stress is evaluated by differentiating the free energy density with respect to the deformation gradient, similar to the conventional approach for hyperelasticity. The breaking and reformation of weak bonds is treated as a reaction governed by the axiom of mass balance, where the constitutive relation for the mass supply governs the bond kinetics. The evolving mass contents of these weak bonds serve as observable state variables. Weak bonds reform in an energy-free and stress-free state, therefore their reference configuration is given by the current configuration at the time of their reformation. A principal advantage of this formulation is the availability of a strain energy density function that depends only on observable state variables, also allowing for a separation of the contributions of strong and weak bonds. The Clausius-Duhem inequality is satisfied by requiring that the net free energy from all breaking bonds must be decreasing at all times. In the limit of infinitesimal strains, linear stress-strain responses and first-order kinetics for breaking and reforming of weak bonds, the reactive framework reduces exactly to classical linear viscoelasticity. For large strains, the reactive and classical quasilinear viscoelasticity theories produce different equations, though responses to standard loading configurations behave similarly. This formulation complements existing tools for modeling the nonlinear viscoelastic response of biological soft tissues under large deformations. PMID:25757663

  10. Viscoelasticity using reactive constrained solid mixtures.

    PubMed

    Ateshian, Gerard A

    2015-04-13

    This study presents a framework for viscoelasticity where the free energy density depends on the stored energy of intact strong and weak bonds, where weak bonds break and reform in response to loading. The stress is evaluated by differentiating the free energy density with respect to the deformation gradient, similar to the conventional approach for hyperelasticity. The breaking and reformation of weak bonds is treated as a reaction governed by the axiom of mass balance, where the constitutive relation for the mass supply governs the bond kinetics. The evolving mass contents of these weak bonds serve as observable state variables. Weak bonds reform in an energy-free and stress-free state, therefore their reference configuration is given by the current configuration at the time of their reformation. A principal advantage of this formulation is the availability of a strain energy density function that depends only on observable state variables, also allowing for a separation of the contributions of strong and weak bonds. The Clausius-Duhem inequality is satisfied by requiring that the net free energy from all breaking bonds must be decreasing at all times. In the limit of infinitesimal strains, linear stress-strain responses and first-order kinetics for breaking and reforming of weak bonds, the reactive framework reduces exactly to classical linear viscoelasticity. For large strains, the reactive and classical quasilinear viscoelasticity theories produce different equations, though responses to standard loading configurations behave similarly. This formulation complements existing tools for modeling the nonlinear viscoelastic response of biological soft tissues under large deformations. PMID:25757663

  11. End-Member Formulation of Solid Solutions and Reactive Transport

    SciTech Connect

    Lichtner, Peter C.

    2015-09-01

    A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.

  12. Flowmeter for gas-entrained solids flow

    DOEpatents

    Porges, Karl G.

    1990-01-01

    An apparatus and method for the measurement of solids feedrate in a gas-entrained solids flow conveyance system. The apparatus and method of the present invention include a vertical duct connecting a source of solids to the gas-entrained flow conveyance system, a control valve positioned in the vertical duct, and a capacitive densitometer positioned along the duct at a location a known distance below the control valved so that the solid feedrate, Q, of the gas entrained flow can be determined by Q=S.rho..phi.V.sub.S where S is the cross sectional area of the duct, .rho. is the density of the solid, .phi. is the solid volume fraction determined by the capacitive densitometer, and v.sub.S is the local solid velocity which can be inferred from the konown distance of the capacitive densitometer below the control valve.

  13. Solid polymer battery electrolyte and reactive metal-water battery

    DOEpatents

    Harrup, Mason K.; Peterson, Eric S.; Stewart, Frederick F.

    2000-01-01

    In one implementation, a reactive metal-water battery includes an anode comprising a metal in atomic or alloy form selected from the group consisting of periodic table Group 1A metals, periodic table Group 2A metals and mixtures thereof. The battery includes a cathode comprising water. Such also includes a solid polymer electrolyte comprising a polyphosphazene comprising ligands bonded with a phosphazene polymer backbone. The ligands comprise an aromatic ring containing hydrophobic portion and a metal ion carrier portion. The metal ion carrier portion is bonded at one location with the polymer backbone and at another location with the aromatic ring containing hydrophobic portion. The invention also contemplates such solid polymer electrolytes use in reactive metal/water batteries, and in any other battery.

  14. Reactive vaporization of oxides in solid oxide fuel cell systems

    NASA Astrophysics Data System (ADS)

    Key, Camas Fought

    Metals such as chromium, aluminum and silicon are of extreme technological and industrial importance due to the corrosion resistance they offer in oxidizing environments at high temperature. Much of this robustness is based on the formation of a thin, well-adhered metal-oxide (MO) layer on the surface of the metal. In particularly corrosive environments or at high-enough temperatures and or pressures, the MO will chemically react with constituents in the surrounding gas, removing atoms from the solid. For many systems, material loss and subsequent mechanical failure is the foremost concern. However, in solid oxide fuel cell (SOFC) systems, the presence of gaseous metal species leads to severe degradation in electrochemical performance well before mechanical limits are reached. Reactive vaporization from ferritic stainless steels, chromia, aluminosilicates and a candidate electrode material (Sr2VMoO6), was investigated using the transpiration method. Two novel collection methods were employed: condensation of vapors on wafer collectors analyzed with Rutherford backscattering spectrometry (RBS); and, condensation of vapors on quartz wool analyzed via inductively coupled plasma mass spectroscopy (ICP-MS). Identification and quantification of vapor species provided assessment of material performance in SOFC environments. Experiments demonstrated that Cr vapor species from ferritic stainless steels used for SOFC interconnect applications could be reduced by as much as one order of magnitude through the application of barrier coatings. Base alloys were compared and exhibited a variety of Cr vaporization rates despite being similar in composition, thus illustrating the importance of minor elemental constituents in the alloy. Measurements identified Si as the primary volatile element in aluminosilicate materials when Si concentrations in the bulk material were as low as one percent. Aluminosilicate materials demonstrated a burn out phase during the first hundred hours at

  15. Design guidelines for solid-catalyzed reactive distillation systems

    SciTech Connect

    Subawalla, H.; Fair, J.R.

    1999-10-01

    In this paper the authors discuss design guidelines for solid-catalyzed reactive distillation systems. The guidelines are used to generate initial estimates for column pressure, reactive zone location, catalyst mass, reactant feed location, reactant ratio, reflux ratio, column diameter, number of equilibrium stages, and packed height. They form a part of a methodical design procedure that makes extensive use of both nonequilibrium (rate-based) and equilibrium-stage simulation models. Important choices prior to design include selection of reliable thermodynamic and reaction kinetic models. The authors tested the guidelines for two etherification systems and validated them experimentally for a hydration reaction. The results from a case study, the manufacture of tert-amyl methyl ether, are shown here. Superimposing reaction on separation leads to unique design trade-offs. Thus, column diameter depends both on maximum vapor velocity and on packing catalyst density, reactant ratios are a function of conversion and azeotrope formation, the operating pressure affects the relative volatility, chemical equilibrium, and reaction rate (reactive zone temperature), and the reflux ratio impacts both separation and conversion. The guidelines and procedures presented here simplify the detailed reactive column design considerably.

  16. Enhanced electrodes for solid state gas sensors

    DOEpatents

    Garzon, Fernando H.; Brosha, Eric L.

    2001-01-01

    A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

  17. Gas Phase Reactivity of Carboxylates with N-Hydroxysuccinimide Esters

    NASA Astrophysics Data System (ADS)

    Peng, Zhou; McGee, William M.; Bu, Jiexun; Barefoot, Nathan Z.; McLuckey, Scott A.

    2015-01-01

    N-hydroxysuccinimide (NHS) esters have been used for gas-phase conjugation reactions with peptides at nucleophilic sites, such as primary amines (N-terminus, ɛ-amine of lysine) or guanidines, by forming amide bonds through a nucleophilic attack on the carbonyl carbon. The carboxylate has recently been found to also be a reactive nucleophile capable of initiating a similar nucleophilic attack to form a labile anhydride bond. The fragile bond is easily cleaved, resulting in an oxygen transfer from the carboxylate-containing species to the reagent, nominally observed as a water transfer. This reactivity is shown for both peptides and non-peptidic species. Reagents isotopically labeled with O18 were used to confirm reactivity. This constitutes an example of distinct differences in reactivity of carboxylates between the gas phase, where they are shown to be reactive, and the solution phase, where they are not regarded as reactive with NHS esters.

  18. Method for generating a highly reactive plasma for exhaust gas after treatment and enhanced catalyst reactivity

    SciTech Connect

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2000-07-01

    This patent application describes a method and apparatus of exhaust gas remediation that enhance the reactivity of the material catalysts found within catalytic converters of cars, trucks, and power stations.

  19. Solid fuel volatilization to produce synthesis gas

    SciTech Connect

    Schmidt, Lanny D.; Dauenhauer, Paul J.; Degenstein, Nick J.; Dreyer, Brandon J.; Colby, Joshua L.

    2014-07-29

    A method comprising contacting a carbon and hydrogen-containing solid fuel and a metal-based catalyst in the presence of oxygen to produce hydrogen gas and carbon monoxide gas, wherein the contacting occurs at a temperature sufficiently high to prevent char formation in an amount capable of stopping production of the hydrogen gas and the carbon monoxide gas is provided. In one embodiment, the metal-based catalyst comprises a rhodium-cerium catalyst. Embodiments further include a system for producing syngas. The systems and methods described herein provide shorter residence time and high selectivity for hydrogen and carbon monoxide.

  20. A Gas-Kinetic Scheme for Reactive Flows

    NASA Technical Reports Server (NTRS)

    Lian,Youg-Sheng; Xu, Kun

    1998-01-01

    In this paper, the gas-kinetic BGK scheme for the compressible flow equations is extended to chemical reactive flow. The mass fraction of the unburnt gas is implemented into the gas kinetic equation by assigning a new internal degree of freedom to the particle distribution function. The new variable can be also used to describe fluid trajectory for the nonreactive flows. Due to the gas-kinetic BGK model, the current scheme basically solves the Navier-Stokes chemical reactive flow equations. Numerical tests validate the accuracy and robustness of the current kinetic method.

  1. APPARATUS FOR SHORT TIME MEASUREMENTS IN A FIXED-BED, GAS/SOLID REACTOR

    EPA Science Inventory

    An apparatus for exposure of a solid to reactive process gas is described which makes possible short time (≥ 0.3 to 15 s) exposures in a fixed-bed reactor. Operating conditions for differential reaction with respect to the gas concentration and rapid quench for arresting hi...

  2. Gas-solid flow in vertical tubes

    SciTech Connect

    Pita, J.A.; Sundaresan, S. )

    1991-07-01

    This paper reports on a computational study of fully-developed flow of gas-particle suspensions in vertical pipes which was carried out, using the model proposed recently by Sinclair and Jackson, to understand the predicted scale-up characteristics. It was shown that the model can capture the existence of steady-state multiplicity wherein different pressure gradients can be obtained for the same gas and solids fluxes. A pronounced and nonmonotonic variation of the pressure gradient required to achieve desired fluxes of solid and gas with tube diameter was predicted by the model, and this is explained on a physical basis. The computed results were compared with the experimental data. The model manifests an unsatisfactory degree of sensitivity to the inelasticity of the particle-particle collisions and the damping of particle-phase fluctuating motion by the gas.

  3. Pyrolysis process for producing condensed stabilized hydrocarbons utilizing a beneficially reactive gas

    DOEpatents

    Durai-Swamy, Kandaswamy

    1982-01-01

    In a process for recovery of values contained in solid carbonaceous material, the solid carbonaceous material is comminuted and then subjected to pyrolysis, in the presence of a carbon containing solid particulate source of heat and a beneficially reactive transport gas in a transport flash pyrolysis reactor, to form a pyrolysis product stream. The pyrolysis product stream contains a gaseous mixture and particulate solids. The solids are separated from the gaseous mixture to form a substantially solids-free gaseous stream which comprises volatilized hydrocarbon free radicals newly formed by pyrolysis. Preferably the solid particulate source of heat is formed by oxidizing part of the separated particulate solids. The beneficially reactive transport gas inhibits the reactivity of the char product and the carbon-containing solid particulate source of heat. Condensed stabilized hydrocarbons are obtained by quenching the gaseous mixture stream with a quench fluid which contains a capping agent for stabilizing and terminating newly formed volatilized hydrocarbon free radicals. The capping agent is partially depleted of hydrogen by the stabilization and termination reaction. Hydrocarbons of four or more carbon atoms in the gaseous mixture stream are condensed. A liquid stream containing the stabilized liquid product is then treated or separated into various fractions. A liquid containing the hydrogen depleted capping agent is hydrogenated to form a regenerated capping agent. At least a portion of the regenerated capping agent is recycled to the quench zone as the quench fluid. In another embodiment capping agent is produced by the process, separated from the liquid product mixture, and recycled.

  4. Microencapsulation of liquid and solid substances by reactive polymers.

    PubMed

    Shevchuk, O; Serdiuk, V; Bukartyk, N; Moncibovich, R; Tokarev, V

    2014-01-01

    This study is devoted to the development of techniques for the formation of polymeric microcapsules (MC) with either liquid or solid core and with the polymer shell containing diverse functional groups on the basis of new reactive functional copolymers (FC). Two approaches to the formation of MC containing FC shell that included the stages of "oil-in-water" or "water-in-oil" dispersion preparation followed by slow extraction of solvents from dispersed phase by dispersive media were examined. FC with the same structure was successfully applied for both "oil-in-water" and "water-in-oil" systems. Spherical MC with the liquid hydrocarbon core demonstrated essential increase in their volume after heating at the temperature exceeding a boiling point of hydrocarbon encapsulated. Presence of reactive groups in the MC shell opens up new opportunity for further tuning the MC properties via their interaction with proper compounds, particularly via graft-polymerisation of diverse vinyl monomers initiated from the MC surface. PMID:24697175

  5. Preliminary Results of Solid Gas Generator Micropropulsion

    NASA Technical Reports Server (NTRS)

    deGroot, Wilhelmus A.; Reed, Brian D.; Brenizer, Marshall

    1999-01-01

    A decomposing solid thruster concept, which creates a more benign thermal and chemical environment than solid propellant combustion, while maintaining, performance similar to solid combustion, is described. A Micro-Electro-Mechanical (MEMS) thruster concept with diode laser and fiber-optic initiation is proposed, and thruster components fabricated with MEMS technology are presented. A high nitrogen content solid gas generator compound is evaluated and tested in a conventional axisymmetric thrust chamber with nozzle throat area ratio of 100. Results show incomplete decomposition of this compound in both low pressure (1 kPa) and high pressure (1 MPa) environments, with decomposition of up to 80% of the original mass. Chamber pressures of 1.1 MPa were obtained, with maximum calculated thrust of approximately 2.7 N. Resistively heated wires and resistively heated walls were used to initiate decomposition. Initiation tests using available lasers were unsuccessful, but infrared spectra of the compound show that the laser initiation tests used inappropriate wavelengths for optimal propellant absorption. Optimal wavelengths for laser ignition were identified. Data presented are from tests currently in progress. Alternative solid gas generator compounds are being evaluated for future tests.

  6. Method for improved gas-solids separation

    DOEpatents

    Kusik, Charles L.; He, Bo X.

    1990-01-01

    Methods are disclosed for the removal of particulate solids from a gas stream at high separation efficiency, including the removal of submicron size particles. The apparatus includes a cyclone separator type of device which contains an axially mounted perforated cylindrical hollow rotor. The rotor is rotated at high velocity in the same direction as the flow of an input particle-laden gas stream to thereby cause enhanced separation of particulate matter from the gas stream in the cylindrical annular space between the rotor and the sidewall of the cyclone vessel. Substantially particle-free gas passes through the perforated surface of the spinning rotor and into the hollow rotor, from when it is discharged out of the top of the apparatus. Separated particulates are removed from the bottom of the vessel.

  7. Method for improved gas-solids separation

    DOEpatents

    Kusik, C.L.; He, B.X.

    1990-11-13

    Methods are disclosed for the removal of particulate solids from a gas stream at high separation efficiency, including the removal of submicron size particles. The apparatus includes a cyclone separator type of device which contains an axially mounted perforated cylindrical hollow rotor. The rotor is rotated at high velocity in the same direction as the flow of an input particle-laden gas stream to thereby cause enhanced separation of particulate matter from the gas stream in the cylindrical annular space between the rotor and the sidewall of the cyclone vessel. Substantially particle-free gas passes through the perforated surface of the spinning rotor and into the hollow rotor, from where it is discharged out of the top of the apparatus. Separated particulates are removed from the bottom of the vessel. 4 figs.

  8. Pore structure and reactivity changes in hot coal gas desulfurization sorbents

    SciTech Connect

    Sotirchos, S.V.

    1991-05-01

    The primary objective of the project was the investigation of the pore structure and reactivity changes occurring in metal/metal oxide sorbents used for desulfurization of hot coal gas during sulfidation and regeneration, with particular emphasis placed on the effects of these changes on the sorptive capacity and efficiency of the sorbents. Commercially available zinc oxide sorbents were used as model solids in our experimental investigation of the sulfidation and regeneration processes.

  9. Ultrasonic levitation for the examination of gas/solid reactions

    NASA Astrophysics Data System (ADS)

    Kavouras, A.; Krammer, G.

    2003-10-01

    An experimental setup based on acoustic levitation for the examination of gas/solid reactions is presented. In this setup single particles in the diameter range 1 mm-30 μm can be held against gravity for any wanted time in a defined gas atmosphere at elevated temperatures. The change of particle size, shape, and position can be measured and recorded using an optical device, consisting of a camera and a long range microscope. Basic experiments with inert particles of different shape and solid density have shown that the axial position of a reacting particle can be employed to derive its weight change. A method to evaluate this change of the recorded position for the according weight change is proposed. Exemplary results in the context of dry flue gas cleaning using Ca(OH)2 powder are presented. Single Ca(OH)2 particles are exposed to a well defined gas atmosphere and after some time these particles are retrieved from the ultrasonic field for further analyses. Only an in situ measurement of the particle weight change (i.e., without removing the particle from the well defined reactive atmosphere) brings information regarding the uptake of water by the sorbent, which accompanies SO2 and HCl absorption.

  10. Solid-state power supply for gas lasers

    NASA Astrophysics Data System (ADS)

    Bertolini, A.; Beverini, N.; Carelli, G.; Francesconi, M.; Nannizzi, M.; Strumia, F.; Ioli, N.; Moretti, A.

    2004-08-01

    A novel pulsed power supply for gas lasers is presented. The device uses only solid state components and is based on a capacitor bank discharge. Fast switching of the discharge is triggered by an insulated gate bipolar transistor. The terminal section of the power supply is a transformer designed to match the reactive capacitance of a gas discharge. Strokes up to 30 kV and 30 mA are achieved across the secondary windings of this transformer. The power supply delivers high voltage pulses with a duration between 0.5 and 50 μs and a repetition rate up to some kHz. The power supply has been tested on a longitudinal discharge quasi-cw regime CO2 laser. Laser pulses were generated with a duration down to the microseconds region, a peak power exceeding some kilowatts, and a repetition rate ranging from 200 Hz to a few kHz.

  11. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

    1994-11-29

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

  12. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    SciTech Connect

    Anderson, Iver E.; Lograsso, Barbara K.; Ellis, Timothy W.

    1994-01-01

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

  13. Nanocrystalline films for gas-reactive applications

    DOEpatents

    Eastman, Jeffrey A.; Thompson, Loren J.

    2004-02-17

    A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

  14. Multicomponent Transport in Polyatomic Reactive Gas Mixtures

    SciTech Connect

    Giovangigli, Vincent

    2011-05-20

    We investigate multicomponent reactive flow models derived from the kinetic theory of gases. We discuss in particular the conservation equations, the transport fluxes and the transport coefficients in weak and strong magnetic fields. The mathematical properties of the resulting hyperbolic-parabolic systems of partial differential equations modeling multicomponent flows are deduced from the underlying kinetic framework. The structure and solution of the transport linear systems associated with the evaluation of transport coefficients are also addressed. In particular, the convergence of iterative techniques is deduced from the properties of the linearized Boltzmann collision operator. The impact of multicomponent transport is also discussed, notably the importance of Soret effects in various flows and the impact of volume viscosity.

  15. Multicomponent Transport in Polyatomic Reactive Gas Mixtures

    NASA Astrophysics Data System (ADS)

    Giovangigli, Vincent

    2011-05-01

    We investigate multicomponent reactive flow models derived from the kinetic theory of gases. We discuss in particular the conservation equations, the transport fluxes and the transport coefficients in weak and strong magnetic fields. The mathematical properties of the resulting hyperbolic-parabolic systems of partial differential equations modeling multicomponent flows are deduced from the underlying kinetic framework. The structure and solution of the transport linear systems associated with the evaluation of transport coefficients are also addressed. In particular, the convergence of iterative techniques is deduced from the properties of the linearized Boltzmann collision operator. The impact of multicomponent transport is also discussed, notably the importance of Soret effects in various flows and the impact of volume viscosity.

  16. Evaluation of the effect of elastic joints on the auto-oscillation of spacecraft with gas-reactive direction systems

    NASA Technical Reports Server (NTRS)

    Sasin, G. G.

    1979-01-01

    A mathematical model was obtained, on the basis of the method of mixed coordinates, of a generalized flexible spacecraft at one end of which was appended the directive action of a system of gas reactive nozzles. Various structural forms were obtained functionally describing flexible spacecraft, as systems consisting of a solid central body with flexible structural elements joined to it.

  17. Solid surface mapping by inverse gas chromatography.

    PubMed

    Gutiérrez, M C; Osuna, S; Baráibar, I

    2005-09-16

    Inverse gas chromatography (IGC) at infinite dilution, is a technique for characterising solid surfaces. Current practice is the injection of n-alkane homologous series to obtain the free energy of adsorption of the CH2 group, from which the London component of the solid surface free energy, gamma(d)s, is calculated. A value around 40 mJ/m2 is obtained for poly(ethylene), and 30 mJ/m2 for a clean glass fibre, while the potential surface interactivity of a glass fibre is far greater than that of poly(ethylene). A specific component of the surface, in mJ/m2, should be calculated in order to obtain significant parameters. As applied up to date, when calculating the specific component of the surface energy, the fact that W(sp)a energy values are in a totally different scale than AN or DN values is a major drawback. Consequently, Ka and Kb values obtained are in arbitrary energy units, different from those of the London component measured by injecting the n-alkane series. This paper proposes a method to obtain Ka and Kb values of the surface in the same energetic scale than the London component. The method enables us to correct the traditional London component of a solid, obtaining a new value, where the amount of WaCH2 accounting for Debye interactions with polar sites, is excluded. As a result, an approach to surface mapping is performed in several different substrate materials. We show results obtained on different solid surfaces: poly(ethylene), clean glass fibre, glass beads, chemically modified glass beads and carbon fibre. PMID:16130707

  18. Gas-phase reactivity of ruthenium carbonyl cluster anions.

    PubMed

    Henderson, Matthew A; Kwok, Samantha; McIndoe, J Scott

    2009-04-01

    Partially-ligated anionic ruthenium carbonyl clusters react with alkenes, arenes, and alkanes in the gas phase; the products undergo extensive C-H activation and lose dihydrogen and carbon monoxide under collision-induced dissociation conditions. Triethylsilane and phenylsilane are also reactive towards the unsaturated clusters, and oxygen was shown to rapidly break down the cluster core by oxidative cleavage of the metal-metal bonds. These qualitative gas-phase reactivity studies were conducted using an easily-installed and inexpensive modification of a commercial electrospray ionization mass spectrometer. Interpretation of the large amounts of data generated in these studies is made relatively straightforward by employing energy-dependent electrospray ionization mass spectrometry (EDESI-MS). PMID:19185511

  19. Analysis of the gas phase reactivity of chlorosilanes.

    PubMed

    Ravasio, Stefano; Masi, Maurizio; Cavallotti, Carlo

    2013-06-27

    Trichlorosilane is the most used precursor to deposit silicon for photovoltaic applications. Despite of this, its gas phase and surface kinetics have not yet been completely understood. In the present work, it is reported a systematic investigation aimed at determining what is the dominant gas phase chemistry active during the chemical vapor deposition of Si from trichlorosilane. The gas phase mechanism was developed calculating the rate constant of each reaction using conventional transition state theory in the rigid rotor-harmonic oscillator approximation. Torsional vibrations were described using a hindered rotor model. Structures and vibrational frequencies of reactants and transition states were determined at the B3LYP/6-31+G(d,p) level, while potential energy surfaces and activation energies were computed at the CCSD(T) level using aug-cc-pVDZ and aug-cc-pVTZ basis sets extrapolating to the complete basis set limit. As gas phase and surface reactivities are mutually interlinked, simulations were performed using a microkinetic surface mechanism. It was found that the gas phase reactivity follows two different routes. The disilane mechanism, in which the formation of disilanes as reaction intermediates favors the conversion between the most stable monosilane species, and the radical pathway, initiated by the decomposition of Si2HCl5 and followed by a series of fast propagation reactions. Though both mechanisms are active during deposition, the simulations revealed that above a certain temperature and conversion threshold the radical mechanism provides a faster route for the conversion of SiHCl3 into SiCl4, a reaction that favors the overall Si deposition process as it is associated with the consumption of HCl, a fast etchant of Si. Also, this study shows that the formation of disilanes as reactant intermediates promotes significantly the gas phase reactivity, as they contribute both to the initiation of radical chain mechanisms and provide a catalytic route for

  20. Compact solid source of hydrogen gas

    DOEpatents

    Kravitz, Stanley H.; Hecht, Andrew M.; Sylwester, Alan P.; Bell, Nelson S.

    2004-06-08

    A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

  1. Harmonically Perturbed Gas-Solid Fluidized System

    NASA Astrophysics Data System (ADS)

    Nix, S. T.; Muller, M. R.

    1996-11-01

    Experiments were performed on a harmonically perturbed gas-solid fluidized system, to determine the extent to which the total system behaved as a liquid in regards to the aspects of resonant frequency, wave shapes, and damping effects. The fluidized system consists of a cylindrical alumina oxide/air fluidized bed which is vertically perturbed in a symmetrical fashion by externally vibrating the entire vessel. The external vibrations were carried out over various flow rates, amplitudes, and frequencies. The results obtained could then be compared to the natural frequencies of water for the same governing parameters by analytical means. The effects of excitations on the formation of voidage disturbances or "gas bubbles" was also investigated. Data acquisition enabled the determination of both the amplitude and frequency of the waves generated in the bath. Results indicate that external vertical vibration caused the mean surface level of the bed to drop. This can be attributed to a closer packing of the particles along with a decrease in the number and size of gas bubbles in the bed.

  2. Hydrodesulfurization reactivities of various sulfur compounds in vacuum gas oil

    SciTech Connect

    Ma, X.; Sakanishi, K.; Mochida, I.

    1996-08-01

    The hydrodesulfurization (HDS) of a vacuum gas oil (VGO) was performed at 360 C (6.9 MPa) over a commercial NiMo catalyst to examine the HDS reactivities of various sulfur compounds which exist in the VGO by means of quantitative pseudo-first-order kinetic analysis. Four representative types of aromatic-skeleton sulfur compounds were observed in the VGO: alkylbenzothiophenes (BTs), alkyldibenzothiophenes (DBTs), alkylphenanthro[4,5-b,c,d]thiophenes (PTs), and alkylbenzonaphthothiophenes (BNTs). Among these, alkyl-BTs exhibited the highest HDS reactivity, whereas alkyl-DBTs with alkyl substituents at the 4 and/or 6 positions appeared to have the least reactivity even though their aromatic-skeleton is smaller than those of both alkyl-PTs and -BNTs. Steric hindrance of alkyl groups at specific positions appears to be a major reason for the low reactivity. Quantum chemical calculations on representative sulfur compounds were carried out to compare molecular parameters with their different HDS reactivities.

  3. Study of Parameters Effect on Hydrodynamics of a Gas-Solid Chamber Experimentally and Numerically

    NASA Astrophysics Data System (ADS)

    Hamzehei, Mahdi; Rahimzadeh, Hassan

    2012-04-01

    In this research, gas velocity, initial static bed height and particle size effect on hydrodynamics of a non-reactive gas-solid fluidized bed chamber were studied experimentally and computationally. A multi fluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this chamber and momentum exchange coefficients were calculated by using the Syamlal- O'Brien drag functions. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops predicted by the simulations at different particle sizes and initial static bed height were in good agreement with experimental measurements at superficial gas velocity higher than the minimum fluidization velocity. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Furthermore, this comparison showed that the model can predict hydrodynamic behavior of gas solid fluidized bed chambers reasonably well.

  4. Mitigation technologies for hydrogen storage systems based on reactive solids.

    SciTech Connect

    Kanouff, Michael P.; Dedrick, Daniel E.; Khalil, Y. F.; Pratt, Joseph William; Reeder, Craig; Cordaro, Joseph Gabriel

    2010-11-01

    This paper describes mitigation technologies that are intended to enable the deployment of advanced hydrogen storage technologies for early market and automotive fuel cell applications. Solid State hydrogen storage materials provide an opportunity for a dramatic increase in gravimetric and volumetric energy storage density. Systems and technologies based on the advanced materials have been developed and demonstrated within the laboratory [1,2], and in some cases, integrated with fuel cell systems. The R&D community will continue to develop these technologies for an ever increasing market of fuel cell technologies, including, forklift, light-cart, APU, and automotive systems. Solid state hydrogen storage materials are designed and developed to readily release, and in some cases, react with diatomic hydrogen. This favorable behavior is often accomplished with morphology design (high surface area), catalytic additives (titanium for example), and high purity metals (such as aluminum, Lanthanum, or alkali metals). These favorable hydrogen reaction characteristics often have a related, yet less-desirable effect: sensitivity and reactivity during exposure to ambient contamination and out-of-design environmental conditions. Accident scenarios resulting in this less-favorable reaction behavior must also be managed by the system developer to enable technology deployment and market acceptance. Two important accident scenarios are identified through hazards and risk analysis methods. The first involves a breach in plumbing or tank resulting from a collision. The possible consequence of this scenario is analyzed though experimentally based chemical kinetic and transport modeling of metal hydride beds. An advancing reaction front between the metal hydride and ambient air is observed to proceed throughout the bed. This exothermic reaction front can result in loss of structural integrity of the containing vessel and lead to un-favorable overheating events. The second important

  5. Measurements of the negative ion density in reactive gas plasmas

    NASA Astrophysics Data System (ADS)

    Shindo, Masako; Ueda, Yoko; Kawai, Yoshinobu; Ishii, Nobuo

    1999-11-01

    The reactive gas plasmas, such as C_4F_8, SiH4 and SF6 gas plasmas, have been widely used in plasma etching or CVD. The radicals and ions species in these plasmas have been reported in a lot of study. However, the negative ion density has not been measured quantitatively, since the conventional Langmuir probe cannot be used due to film depositions on its surface. In this study, the negative ion density in the reactive gas plasmas was measured with a heated Langmuir probe and an 8-mm microwave interferometer as a function of gas flow rate and radial position. Furthermore, the following equation was suggested to estimate the negative ion density only from the probe measurements: fracI_+(X )I_+(Ar) = [ fracI_-(X)I_-(Ar) + fracN_-(X )N_+(Ar)√fracT_e(X)T_e(Ar) ] √fracM_+(Ar)M_+(X), where N- denotes negative ion density and the other characteristics represent the conventional ones. The positive ion mass M+ should be assumed properly. It was confirmed that this equation provides the negative ion density both in the magnetized plasmas, such as ECR plasmas, and non-magnetized plasmas.

  6. Gas-phase reactivity of novel Ziegler-Natta catalysts

    SciTech Connect

    Alameddin, N.G.; Eyler, J.R.; Richardson, D.E.

    1994-12-31

    The discovery of soluble group 4 metallocene-based catalysts for the Ziegler-Natta polymerization of olefins has generated considerable interest in the field. In particular, the versatility of the Cp (cyclopentadienyl) ligand has made practical the development of a host of novel catalysts which can produce extremely regiospecific and stereospecific polymers. With further improvements in activity and stability, these catalysts are expected to make a major impact on the polymerization industry. Presently, catalyst design is driven by using the steric and electronic properties of the ligands to guide the monomer addition. However, since these ligands have considerable steric bulk, the choice of solvent will significantly affect their catalytic properties. Therefore, an understanding of the intrinsic reactivity of these catalysts independent of a solvent is one of the first steps to building a better catalyst. The work in progress is a study of the reactivity of zircononene-based catalysts in the gas phase. The authors are in the process of studying the rates of reaction of a series of these compounds with H{sub 2} as well as with a number of olefins. In the gas phase, the intrinsic reactivity of these catalysts is revealed and their chemistry can be studied in detail.

  7. Visualizing Gas Adsorption on Porous Solids: Four Simple, Effective Demonstrations

    ERIC Educational Resources Information Center

    Cheung, Ocean

    2014-01-01

    Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for…

  8. Gas-potentiometric method with solid electrolyte oxygen sensors for the investigation of combustion.

    PubMed

    Lorenz, H; Tittmann, K; Sitzki, L; Trippler, S; Rau, H

    1996-09-01

    Gas-potentiometric analysis using oxide-ion-conducting solid electrolytes as stabilized zirconia is a worthwhile method for the investigation of combustion processes. In the case of gas and oil flames specific parameters like the flame contour, the degree of burn-out and mixing can be determined and information about flame turbulence and reaction density can be gained from the temporal resolution of the sensor signal. Measurements carried out with solid electrolyte oxygen sensors in a fluidized bed show that combustion processes of solid fuels are also analyzable. This analysis results in fuel specific burn-out curves finally leading to burn-out times and to parameters of a macrokinetics of the combustion process as well as to ideas about the burn-out mechanism. From the resulting constants of the effective reaction rate a reactivity relative to bituminous coal coke can be given for any solid fuel. PMID:15048356

  9. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2002-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime, high frequency, high power bursts of low-duty factor microwaves sufficient to generate a plasma discharge and passing a gas to be treated through the discharge so as to cause dissociative reduction of the exhaust gases and enhanced catalyst reactivity through application of the pulsed microwave fields directly to the catalyst material sufficient to cause a polarizability catastrophe and enhanced heating of the metal crystallite particles of the catalyst, and in the presence or absence of the plasma. The invention also includes a reactor for aftertreatment of exhaust gases.

  10. Reactive oxygen species production and discontinuous gas exchange in insects

    PubMed Central

    Boardman, Leigh; Terblanche, John S.; Hetz, Stefan K.; Marais, Elrike; Chown, Steven L.

    2012-01-01

    While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production. PMID:21865257

  11. Reactive oxygen species production and discontinuous gas exchange in insects.

    PubMed

    Boardman, Leigh; Terblanche, John S; Hetz, Stefan K; Marais, Elrike; Chown, Steven L

    2012-03-01

    While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production. PMID:21865257

  12. 40 CFR Appendix A to Subpart Pppp... - Determination of Weight Volatile Matter Content and Weight Solids Content of Reactive Adhesives

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Content and Weight Solids Content of Reactive Adhesives A Appendix A to Subpart PPPP of Part 63 Protection... Reactive Adhesives 1.0Applicability and Principle 1.1Applicability: This method applies to the... reactive adhesives. Reactive adhesives are composed, in large part, of monomers that react during...

  13. 40 CFR Appendix A to Subpart Pppp... - Determination of Weight Volatile Matter Content and Weight Solids Content of Reactive Adhesives

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Content and Weight Solids Content of Reactive Adhesives A Appendix A to Subpart PPPP of Part 63 Protection... Reactive Adhesives 1.0Applicability and Principle 1.1Applicability: This method applies to the... reactive adhesives. Reactive adhesives are composed, in large part, of monomers that react during...

  14. Etching radical controlled gas chopped deep reactive ion etching

    DOEpatents

    Olynick, Deidre; Rangelow, Ivo; Chao, Weilun

    2013-10-01

    A method for silicon micromachining techniques based on high aspect ratio reactive ion etching with gas chopping has been developed capable of producing essentially scallop-free, smooth, sidewall surfaces. The method uses precisely controlled, alternated (or chopped) gas flow of the etching and deposition gas precursors to produce a controllable sidewall passivation capable of high anisotropy. The dynamic control of sidewall passivation is achieved by carefully controlling fluorine radical presence with moderator gasses, such as CH.sub.4 and controlling the passivation rate and stoichiometry using a CF.sub.2 source. In this manner, sidewall polymer deposition thicknesses are very well controlled, reducing sidewall ripples to very small levels. By combining inductively coupled plasmas with controlled fluorocarbon chemistry, good control of vertical structures with very low sidewall roughness may be produced. Results show silicon features with an aspect ratio of 20:1 for 10 nm features with applicability to nano-applications in the sub-50 nm regime. By comparison, previous traditional gas chopping techniques have produced rippled or scalloped sidewalls in a range of 50 to 100 nm roughness.

  15. Pore structure and reactivity changes in hot coal gas desulfurization sorbents. Final report, September 1987--January 1991

    SciTech Connect

    Sotirchos, S.V.

    1991-05-01

    The primary objective of the project was the investigation of the pore structure and reactivity changes occurring in metal/metal oxide sorbents used for desulfurization of hot coal gas during sulfidation and regeneration, with particular emphasis placed on the effects of these changes on the sorptive capacity and efficiency of the sorbents. Commercially available zinc oxide sorbents were used as model solids in our experimental investigation of the sulfidation and regeneration processes.

  16. MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges

    PubMed Central

    Lu, Hanzhang; Liu, Peiying; Yezhuvath, Uma; Cheng, Yamei; Marshall, Olga; Ge, Yulin

    2014-01-01

    The brain is a spatially heterogeneous and temporally dynamic organ, with different regions requiring different amount of blood supply at different time. Therefore, the ability of the blood vessels to dilate or constrict, known as Cerebral-Vascular-Reactivity (CVR), represents an important domain of vascular function. An imaging marker representing this dynamic property will provide new information of cerebral vessels under normal and diseased conditions such as stroke, dementia, atherosclerosis, small vessel diseases, brain tumor, traumatic brain injury, and multiple sclerosis. In order to perform this type of measurement in humans, it is necessary to deliver a vasoactive stimulus such as CO2 and/or O2 gas mixture while quantitative brain magnetic resonance images (MRI) are being collected. In this work, we presented a MR compatible gas-delivery system and the associated protocol that allow the delivery of special gas mixtures (e.g., O2, CO2, N2, and their combinations) while the subject is lying inside the MRI scanner. This system is relatively simple, economical, and easy to use, and the experimental protocol allows accurate mapping of CVR in both healthy volunteers and patients with neurological disorders. This approach has the potential to be used in broad clinical applications and in better understanding of brain vascular pathophysiology. In the video, we demonstrate how to set up the system inside an MRI suite and how to perform a complete experiment on a human participant. PMID:25549106

  17. MRI mapping of cerebrovascular reactivity via gas inhalation challenges.

    PubMed

    Lu, Hanzhang; Liu, Peiying; Yezhuvath, Uma; Cheng, Yamei; Marshall, Olga; Ge, Yulin

    2014-01-01

    The brain is a spatially heterogeneous and temporally dynamic organ, with different regions requiring different amount of blood supply at different time. Therefore, the ability of the blood vessels to dilate or constrict, known as Cerebral-Vascular-Reactivity (CVR), represents an important domain of vascular function. An imaging marker representing this dynamic property will provide new information of cerebral vessels under normal and diseased conditions such as stroke, dementia, atherosclerosis, small vessel diseases, brain tumor, traumatic brain injury, and multiple sclerosis. In order to perform this type of measurement in humans, it is necessary to deliver a vasoactive stimulus such as CO2 and/or O2 gas mixture while quantitative brain magnetic resonance images (MRI) are being collected. In this work, we presented a MR compatible gas-delivery system and the associated protocol that allow the delivery of special gas mixtures (e.g., O2, CO2, N2, and their combinations) while the subject is lying inside the MRI scanner. This system is relatively simple, economical, and easy to use, and the experimental protocol allows accurate mapping of CVR in both healthy volunteers and patients with neurological disorders. This approach has the potential to be used in broad clinical applications and in better understanding of brain vascular pathophysiology. In the video, we demonstrate how to set up the system inside an MRI suite and how to perform a complete experiment on a human participant. PMID:25549106

  18. Disposal pathway for tritiated reactive metals and tritiated hydrogen gas

    SciTech Connect

    Antoniazzi, A. B.; Morton, C. S.

    2008-07-15

    Kinectrics and its predecessor company Ontario Hydro Research Div. (a division of Ontario Hydro) had a fully operational tritium laboratory on site since the early 1980's. During those years numerous projects and experiments were undertaken using hydrogen and tritium for the most part. Metals with an affinity for hydrogen are commonly employed as scavengers of hydrogenic gases from process streams or as hydrogen storage mediums. The two most common of these metals used were depleted uranium and a zirconium-iron alloy (SAES St198). The break-up of Ontario Hydro through deregulation activities resulted in the building of a new, smaller, tritium laboratory and the decommissioning of the original tritium laboratory. Decommissioning activities resulted in the need to safely dispose of these reactive metals. Disposal of these metals is not straight forward. For safe, long term, disposal it has been decided to oxidize the metals in a controlled fashion. The oxidized beds, containing the metals, will be sent to a radioactive waste site for long term storage. Options for disposal of tritiated hydrogen gas are presented and discussed. This paper provides a disposal pathway for tritiated reactive metals and hydrogen thereby closing the loop in tritium handling. (authors)

  19. Testing and evaluation of solid lubricants for gas bearings

    NASA Technical Reports Server (NTRS)

    Albrecht, P. R.; Fischer, W. H.

    1974-01-01

    The testing and results of testing solid film lubricants for gas lubricated bearing applications are reported. The tests simulated operational hazards of tilting pad gas bearings. The presence of a low coefficient of friction and the endurance of the solid film lubricant were the criteria for judging superior performance. All solid lubricants tested were applied to a plasma sprayed chrome oxide surface. Molybdenum disulfide and graphite fluoride were the solid lubricants tested; other test parameters included the method of application of the solid lubricant and the surface finish of the plasma sprayed coating. In general, the application of a solid film lubricant was found to significantly improve the coefficient of friction of the rubbing surfaces.

  20. Reactive gas atomization processing for Fe-based ODS alloys

    SciTech Connect

    Rieken, Joel R; Anderson, Iver E; Kramer, Matthew J; Odette, G R; Stergar, E; Haney, E

    2011-08-24

    Gas atomization reaction synthesis was employed as a simplified method for processing oxide dispersion forming precursor Fe-based powders (e.g., Fe–Cr–Y–Hf). During this process a reactive atomization gas (i.e., Ar–O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 50 nm) metastable Cr-enriched oxide shell that was used as a vehicle to transport oxygen into the consolidated microstructure. Subsequent elevated temperature heat treatment promoted thermodynamically driven oxygen exchange reactions between trapped films of Cr-enriched oxide and internal (Y, Hf)-enriched intermetallic precipitates, resulting in highly stable nano-metric mixed oxide dispersoids (i.e., Y–Hf–O) that were identified with X-ray diffraction. Transmission electron microscopy and atom probe tomography results also revealed that the size and distribution of the dispersoids were found to depend strongly on the original rapidly solidified microstructure. To exploit this, several oxide dispersion strengthened microstructures were engineered from different powder particle size ranges, illustrating microstructural control as a function of particle solidification rate. Additionally, preliminary thermal–mechanical processing was used to develop a fine scale dislocation substructure for ultimate strengthening of the alloy.

  1. Hybrid propulsion based on fluid-controlled solid gas generators

    NASA Technical Reports Server (NTRS)

    Cohen, Norman S.; Strand, Leon D.

    1993-01-01

    The use of fuel-rich solid (gas generator-type) propellants for hybrid propulsion affords some design and utilization efficiency advantages. Both forward and aft liquid injection control concepts are evaluated from the operational standpoints of ballistics, throttling, stability and extinguishment. Steady-state and non-steady ballistics analyses are employed for this evaluation. Stability of solid motor operation is enhanced by fluid injection with adequate injector pressure drop. Efficient throttling and reliable extinguishment are attained through a combination of solid propellant combustion tailoring, grain design, control valves and sensors. Initial results from a laboratory-scale slab combustor, combining a gas generator propellant with gaseous oxygen injection, are also presented.

  2. Reactivity and Characterization of Solid State Hydrodesulfurization Catalysts.

    NASA Astrophysics Data System (ADS)

    Lindner, James Henry

    1990-01-01

    The identification of the phase responsible for hydrodesulfurization (HDS) activity has been the subject of extensive research. In this study, model solid state catalysts prepared from elemental starting materials were synthesized, characterized, and then used to desulfurize thiophene at temperatures ranging from 200-400 ^circC and a pressure of one atmosphere. The results of this work indicate that an increased HDS activity can be correlated with the presence of a poorly crystalline molybdenum sulfide-like phase detected by XRD, HREM, or AEM. The formation of this sulfur-deficient, non-stoichiometric phase could be accomplished by either removing sulfur directly from the catalyst synthesis mixture to yield a non-stoichiometric MoS_{ rm 2-x} moiety, or by introducing a transition metal promoter such as Fe, Co, Ni, or Cu into the system. The promoter atoms induced structural changes in the molybdenum sulfide edge planes by effectively scavenging sulfur during catalyst synthesis to form promoter sulfide species, which enhanced the formation of a non-stoichiometric, highly active molybdenum sulfide. This morphological effect was the primary function of the promoter in this system. All model catalysts displayed similar structure in the (0002) basal plane of MoS_2; however, only the catalytically active samples showed a high concentration of defects and disorder in the (1010), (1011), and (1012) edge planes. The HREM images obtained from these edge planes and their correlation with HDS activity dramatically illustrated the importance of the often-discussed edge plane structure of MoS_2 and its significance on HDS catalysis. Normalization of the HDS activities for the solid state models and a commercial catalyst with O_2 or CO chemisorption uptakes suggested that a similarity may exist between the catalytically active sites of these materials. In-situ XPS revealed that increasing promoter atom concentrations resulted in a more complete reduction of the promoter atom; but

  3. Reactive Transport Modeling of Acid Gas Generation and Condensation

    SciTech Connect

    G. Zhahg; N. Spycher; E. Sonnenthal; C. Steefel

    2005-01-25

    Pulvirenti et al. (2004) recently conducted a laboratory evaporation/condensation experiment on a synthetic solution of primarily calcium chloride. This solution represents one potential type of evaporated pore water at Yucca Mountain, Nevada, a site proposed for geologic storage of high-level nuclear waste. These authors reported that boiling this solution to near dryness (a concentration factor >75,000 relative to actual pore waters) leads to the generation of acid condensate (pH 4.5) presumably due to volatilization of HCl (and minor HF and/or HNO{sub 3}). To investigate the various processes taking place, including boiling, gas transport, and condensation, their experiment was simulated by modifying an existing multicomponent and multiphase reactive transport code (TOUGHREACT). This code was extended with a Pitzer ion-interaction model to deal with high ionic strength. The model of the experiment was set-up to capture the observed increase in boiling temperature (143 C at {approx}1 bar) resulting from high concentrations of dissolved salts (up to 8 m CaCl{sub 2}). The computed HCI fugacity ({approx} 10{sup -4} bars) generated by boiling under these conditions is not sufficient to lower the pH of the condensate (cooled to 80 and 25 C) down to observed values unless the H{sub 2}O mass fraction in gas is reduced below {approx}10%. This is because the condensate becomes progressively diluted by H{sub 2}O gas condensation. However, when the system is modeled to remove water vapor, the computed pH of instantaneous condensates decreases to {approx}1.7, consistent with the experiment (Figure 1). The results also show that the HCl fugacity increases, and calcite, gypsum, sylvite, halite, MgCl{sub 2}4H{sub 2}O and CaCl{sub 2} precipitate sequentially with increasing concentration factors.

  4. Process of preparing nitrogen trifluoride by gas-solid reaction

    SciTech Connect

    Aramaki, M.; Kobayashi, Y.; Nakamura, T.; Nakano, H.; Suenaga, T.

    1985-09-24

    NF3 is prepared with good yields by reaction between fluorine gas and an ammonium complex of a metal fluoride, such as (NH4)3AIF6, in solid phase. The metal flouride ammonium complex may be one additionally containing an alkali metal, such as (NH4)2NaAIF6. The gas-solid reaction is carried out preferably at temperatures above 80 C. and at relatively low partial pressures of fluorine in the gas phase of the reaction system, so that the reaction is easy to control.

  5. Cyclodextrin-Based Solid-Gas Clathrates.

    PubMed

    Pereva, Stiliana; Himitliiska, Tsveta; Spassov, Tony; Stoyanov, Simeon D; Arnaudov, Luben N; Dudev, Todor

    2015-07-29

    "Cyclodextrin-gas" clathrates were obtained by crystallization from water solution of α-, β-, and γ-cyclodextrins (CDs) under pressure of the gas to be entrapped into the CD molecules. When the pressure is released, these clathrates are stable at ambient conditions and dissociate at elevated temperature, which makes them interesting for various applications as foam boosters in food and other industries. It was found that under these conditions α-CD forms clathrates with all of the gases used in this study (N2, N2O, CO2, Ar), whereas β- and γ-CDs can form clathrates only with N2. The concentration of the cyclodextrin and the temperature and pressure of the gas were varied for achieving higher clathrate yield and larger amount of embedded gas. Highest values of about 2 wt % were found for α-CD-N2O, as it releases in the temperature range of 40-60 °C. PMID:26132981

  6. CO2 sequestration using waste concrete and anorthosite tailings by direct mineral carbonation in gas-solid-liquid and gas-solid routes.

    PubMed

    Ben Ghacham, Alia; Cecchi, Emmanuelle; Pasquier, Louis-César; Blais, Jean-François; Mercier, Guy

    2015-11-01

    Mineral carbonation (MC) represents a promising alternative for sequestering CO2. In this work, the CO2 sequestration capacity of the available calcium-bearing materials waste concrete and anorthosite tailings is assessed in gas-solid-liquid and gas-solid routes using 18.2% flue CO2 gas. The objective is to screen for a better potential residue and phase route and as the ultimate purpose to develop a cost-effective process. The results indicate the possibility of removing 66% from inlet CO2 using waste concrete for the aqueous route. However, the results that were obtained with the carbonation of anorthosite were less significant, with 34% as the maximal percentage of CO2 removal. The difference in terms of reactivity could be explained by the accessibility to calcium. In fact, anorthosite presents a framework structure wherein the calcium is trapped, which could slow the calcium dissolution into the aqueous phase compared to the concrete sample, where calcium can more easily leach. In the other part of the study concerning gas-solid carbonation, the results of CO2 removal did not exceed 15%, which is not economically interesting for scaling up the process. The results obtained with waste concrete samples in aqueous phase are interesting. In fact, 34.6% of the introduced CO2 is converted into carbonate after 15 min of contact with the gas without chemical additives and at a relatively low gas pressure. Research on the optimization of the aqueous process using waste concrete should be performed to enhance the reaction rate and to develop a cost-effective process. PMID:26292776

  7. Corrosion-induced gas generation in a nuclear waste repository: Reactive geochemistry and multiphase flow effect

    SciTech Connect

    Xu, T.; Senger, R.; Finsterle, S.

    2008-10-15

    Corrosion of steel canisters, stored in a repository for spent fuel and high-level nuclear wastes, leads to the generation and accumulation of hydrogen gas in the backfilled emplacement tunnels, which may significantly affect long-term repository safety. Previous studies used H{sub 2} generation rates based on the volume of the waste or canister material and the stoichiometry of the corrosion reaction. However, iron corrosion and H{sub 2} generation rates vary with time, depending on factors such as amount of iron, water availability, water contact area, and aqueous and solid chemistry. To account for these factors and feedback mechanisms, we developed a chemistry model related to iron corrosion, coupled with two-phase (liquid and gas) flow phenomena that are driven by gas-pressure buildup associated with H{sub 2} generation and water consumption. Results indicate that by dynamically calculating H{sub 2} generation rates based on a simple model of corrosion chemistry, and by coupling this corrosion reaction with two-phase flow processes, the degree and extent of gas pressure buildup could be much smaller compared to a model that neglects the coupling between flow and reactive transport mechanisms. By considering the feedback of corrosion chemistry, the gas pressure increases initially at the canister, but later decreases and eventually returns to a stabilized pressure that is slightly higher than the background pressure. The current study focuses on corrosion under anaerobic conditions for which the coupled hydrogeochemical model was used to examine the role of selected physical parameters on the H{sub 2} gas generation and corresponding pressure buildup in a nuclear waste repository. The developed model can be applied to evaluate the effect of water and mineral chemistry of the buffer and host rock on the corrosion reaction for future site-specific studies.

  8. A generalized kinetic model for heterogeneous gas-solid reactions.

    PubMed

    Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A

    2012-08-21

    We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used. PMID:22920132

  9. A generalized kinetic model for heterogeneous gas-solid reactions

    NASA Astrophysics Data System (ADS)

    Xu, Zhijie; Sun, Xin; Khaleel, Mohammad A.

    2012-08-01

    We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used.

  10. Solid phase studies and geochemical modelling of low-cost permeable reactive barriers.

    PubMed

    Bartzas, Georgios; Komnitsas, Kostas

    2010-11-15

    A continuous column experiment was carried out under dynamic flow conditions in order to study the efficiency of low-cost permeable reactive barriers (PRBs) to remove several inorganic contaminants from acidic solutions. A 50:50 w/w waste iron/sand mixture was used as candidate reactive media in order to activate precipitation and promote sorption and reduction-oxidation mechanisms. Solid phase studies of the exhausted reactive products after column shutdown, using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirmed that the principal Fe corrosion products identified in the reactive zone are amorphous iron (hydr)oxides (maghemite/magnetite and goethite), intermediate products (sulfate green rust), and amorphous metal sulfides such as amFeS and/or mackinawite. Geochemical modelling of the metal removal processes, including interactions between reactive media, heavy metal ions and sulfates, and interpretation of the ionic profiles was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. Mineralogical characterization studies as well as geochemical modelling calculations also indicate that the effect of sulfate and silica sand on the efficiency of the reactive zone should be considered carefully during design and operation of low-cost field PRBs. PMID:20678863

  11. On the Superficial Gas Velocity in Deep Gas-Solid Fluidized Beds

    SciTech Connect

    Li, Tingwen; Grace, John; Shadle, Lawrence; Guenther, Chris

    2011-11-15

    The superficial gas velocity is one of the key parameters used to determine the flow hydrodynamics in gas–solids fluidized beds. However, the superficial velocity varies with height in practice, and there is no consistent basis for its specification. Different approaches to determine the superficial gas velocity in a deep gas–solids system are shown to cause difficulties in developing models and in comparing predictions with experimental results. In addition, the reference conditions for superficial gas velocity are important in modeling of deep gas–solids systems where there is a considerable pressure drop.

  12. SOLID GAS SUSPENSION NUCLEAR FUEL ASSEMBLY

    DOEpatents

    Schluderberg, D.C.; Ryon, J.W.

    1962-05-01

    A fuel assembly is designed for use in a gas-suspension cooled nuclear fuel reactor. The coolant fluid is an inert gas such as nitrogen or helium with particles such as carbon suspended therein. The fuel assembly is contained within an elongated pressure vessel extending down into the reactor. The fuel portion is at the lower end of the vessel and is constructed of cylindrical segments through which the coolant passes. Turbulence promotors within the passageways maintain the particles in agitation to increase its ability to transfer heat away from the outer walls. Shielding sections and alternating passageways above the fueled portion limit the escape of radiation out of the top of the vessel. (AEC)

  13. Analytical model for thermal boundary conductance and equilibrium thermal accommodation coefficient at solid/gas interfaces.

    PubMed

    Giri, Ashutosh; Hopkins, Patrick E

    2016-02-28

    We develop an analytical model for the thermal boundary conductance between a solid and a gas. By considering the thermal fluxes in the solid and the gas, we describe the transmission of energy across the solid/gas interface with diffuse mismatch theory. From the predicted thermal boundary conductances across solid/gas interfaces, the equilibrium thermal accommodation coefficient is determined and compared to predictions from molecular dynamics simulations on the model solid-gas systems. We show that our model is applicable for modeling the thermal accommodation of gases on solid surfaces at non-cryogenic temperatures and relatively strong solid-gas interactions (εsf ≳ kBT). PMID:26931716

  14. Electrochemical processes at solid electrode-electrolyte-gas interfaces

    SciTech Connect

    Youngblood, G.E.; Weber, W.J; Bates, J.L.

    1991-05-01

    Electrochemical reactions at solid electrolyte-electrode-gas interfaces are being investigated with ac impedance and dc polarization techniques using an unbonded interface cell (UIC). The UIC approach eliminates influence of sample size and interface morphology resulting from electrode-electrolyte fabrication. The electrochemical reactions of oxygen with solid electrode (La{sub 1-x}Sr{sub x}MnO{sub 3} or Pt) and solid electrolyte (0.08Y{sub 2}O{sub 3} - 0.92ZrO{sub 2}) interfaces are described. 6 refs., 4 figs., 2 tabs.

  15. Solid fuel combustion system for gas turbine engine

    DOEpatents

    Wilkes, Colin; Mongia, Hukam C.

    1993-01-01

    A solid fuel, pressurized fluidized bed combustion system for a gas turbine engine includes a carbonizer outside of the engine for gasifying coal to a low Btu fuel gas in a first fraction of compressor discharge, a pressurized fluidized bed outside of the engine for combusting the char residue from the carbonizer in a second fraction of compressor discharge to produce low temperature vitiated air, and a fuel-rich, fuel-lean staged topping combustor inside the engine in a compressed air plenum thereof. Diversion of less than 100% of compressor discharge outside the engine minimizes the expense of fabricating and maintaining conduits for transferring high pressure and high temperature gas and incorporation of the topping combustor in the compressed air plenum of the engine minimizes the expense of modifying otherwise conventional gas turbine engines for solid fuel, pressurized fluidized bed combustion.

  16. Hydrodynamics of semifluidization in gas-solid systems

    SciTech Connect

    Ho, T.C.; Yau, S.J.; Hopper, J.R.

    1985-01-01

    Semifluidized bed hydrodynamics, including minimum semifluidization velocity, packed bed formation and pressure drop across the bed, were studied in gas-solid fluidized beds. Experiments were carried out in beds of 0.203, 0.129 and 0.105 m I.D. Experimental parameters examined included gas velocity, semifluidized particles, static bed height and expansion ratio. Empirical and semi-empirical models were derived. The results were compared with those available in the literature.

  17. Miniature solid-state gas compressor

    DOEpatents

    Lawless, William N.; Cross, Leslie E.; Steyert, William A.

    1985-01-01

    A miniature apparatus for compressing gases is disclosed in which an elastomer disposed between two opposing electrostrictive or piezoelectric ceramic blocks, or between a single electrostrictive or piezoelectric ceramic block and a rigid surface, is caused to extrude into or recede from a channel defined adjacent to the elastomer in response to application or removal of an electric field from the blocks. Individual cells of blocks and elastomer are connected to effect a gas compression by peristaltic activation of the individual cells. The apparatus is self-valving in that the first and last cells operate as inlet and outlet valves, respectively. Preferred electrostrictive and piezoelectric ceramic materials are disclosed, and an alternative, non-peristaltic embodiment of the apparatus is described.

  18. Miniature solid-state gas compressor

    DOEpatents

    Lawless, W.N.; Cross, L.E.; Steyert, W.A.

    1985-05-07

    A miniature apparatus for compressing gases is disclosed in which an elastomer disposed between two opposing electrostrictive or piezoelectric ceramic blocks, or between a single electrostrictive or piezoelectric ceramic block and a rigid surface, is caused to extrude into or recede from a channel defined adjacent to the elastomer in response to application or removal of an electric field from the blocks. Individual cells of blocks and elastomer are connected to effect a gas compression by peristaltic activation of the individual cells. The apparatus is self-valving in that the first and last cells operate as inlet and outlet valves, respectively. Preferred electrostrictive and piezoelectric ceramic materials are disclosed, and an alternative, non-peristaltic embodiment of the apparatus is described. 9 figs.

  19. Turbulence modeling of gas-solid suspension flows

    NASA Technical Reports Server (NTRS)

    Chen, C. P.

    1988-01-01

    The purpose here is to discuss and review advances in two-phase turbulent modeling techniques and their applications in various gas-solid suspension flow situations. In addition to the turbulence closures, heat transfer effect, particle dispersion and wall effects are partially covered.

  20. An adhesion criterion in the gas solid interface

    NASA Technical Reports Server (NTRS)

    George, M. C.

    1973-01-01

    A theoretical model is developed to establish an adhesion criterion for the interaction of a gas atom or molecule with a nonmetallic surface. As a first approximation a linear lattice mass points of the solid surface is considered and the classical lattice dynamical model is used.

  1. Numerical Simulation of Gas-Solid Interfaces with Large Deformations

    SciTech Connect

    Vorobiev, O.Y.; Lomov, I.N.

    2000-02-01

    A method of treatment of multimaterial interfaces on Eulerian grids is developed which works well for mixtures of materials with diverse compressibilities and shear moduli. This makes it possible to use this method not only for problems of gas dynamics and solid mechanics but also to model fluid-structure interaction problems.

  2. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    EPA Science Inventory

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

  3. Bulk-density distributions of solids in the freeboard of a gas-solid fluidized bed

    SciTech Connect

    Shen, B.C.; Fan, L.T.; Walawender, W.P.

    1995-05-01

    The freeboard region above the bubbling zone of a gas-solid fluidized bed provides the space not only for the disengagement of particles but also for additional contact and reaction between the particles and gas. The flow pattern and behavior of particles as well as their bulk-density distribution in the freeboard have a significant impact on the efficiency of fluidization. The results of numerous previous experimental studies indicate that the bulk density of solids essentially decreases exponentially as a function of the height of the freeboard. In the present work, this distribution has been obtained by first derived the Fokker-Planck equation from the linearized equation of motion of a single particle and then transforming this Fokker-Planck equation into that for the bulk-density distribution of solids. Its simplification to the one-dimensional case readily gives rise to an exponential distribution and agrees well with the available experimental data.

  4. Transport coefficients of solid particles immersed in a viscous gas

    NASA Astrophysics Data System (ADS)

    Garzó, Vicente; Fullmer, William D.; Hrenya, Christine M.; Yin, Xiaolong

    2016-01-01

    Transport properties of a suspension of solid particles in a viscous gas are studied. The dissipation in such systems arises from two sources: inelasticity in particle collisions and viscous dissipation due to the effect of the gas phase on the particles. Here we consider a simplified case in which the mean relative velocity between the gas and solid phases is taken to be zero, such that "thermal drag" is the only remaining gas-solid interaction. Unlike the previous, more general, treatment of the drag force [Garzó et al., J. Fluid Mech. 712, 129 (2012)], 10.1017/jfm.2012.404, here we take into account contributions to the (scaled) transport coefficients η* (shear viscosity), κ* (thermal conductivity), and μ* (Dufour-like coefficient) coming from the temperature dependence of the (dimensionless) friction coefficient γ* characterizing the amplitude of the drag force. At moderate densities, the thermal drag model (which is based on the Enskog kinetic equation) is solved by means of the Chapman-Enskog method and the Navier-Stokes transport coefficients are determined in terms of the coefficient of restitution, the solid volume fraction, and the friction coefficient. The results indicate that the effect of the gas phase on η* and μ* is non-negligible (especially in the case of relatively dilute systems) while the form of κ* is the same as the one obtained in the dry granular limit. Finally, as an application of these results, a linear stability analysis of the hydrodynamic equations is carried out to analyze the conditions for stability of the homogeneous cooling state. A comparison with direct numerical simulations shows a good agreement for conditions of practical interest.

  5. Transport coefficients of solid particles immersed in a viscous gas.

    PubMed

    Garzó, Vicente; Fullmer, William D; Hrenya, Christine M; Yin, Xiaolong

    2016-01-01

    Transport properties of a suspension of solid particles in a viscous gas are studied. The dissipation in such systems arises from two sources: inelasticity in particle collisions and viscous dissipation due to the effect of the gas phase on the particles. Here we consider a simplified case in which the mean relative velocity between the gas and solid phases is taken to be zero, such that "thermal drag" is the only remaining gas-solid interaction. Unlike the previous, more general, treatment of the drag force [Garzó et al., J. Fluid Mech. 712, 129 (2012)]JFLSA70022-112010.1017/jfm.2012.404, here we take into account contributions to the (scaled) transport coefficients η^{*} (shear viscosity), κ^{*} (thermal conductivity), and μ^{*} (Dufour-like coefficient) coming from the temperature dependence of the (dimensionless) friction coefficient γ^{*} characterizing the amplitude of the drag force. At moderate densities, the thermal drag model (which is based on the Enskog kinetic equation) is solved by means of the Chapman-Enskog method and the Navier-Stokes transport coefficients are determined in terms of the coefficient of restitution, the solid volume fraction, and the friction coefficient. The results indicate that the effect of the gas phase on η^{*} and μ^{*} is non-negligible (especially in the case of relatively dilute systems) while the form of κ^{*} is the same as the one obtained in the dry granular limit. Finally, as an application of these results, a linear stability analysis of the hydrodynamic equations is carried out to analyze the conditions for stability of the homogeneous cooling state. A comparison with direct numerical simulations shows a good agreement for conditions of practical interest. PMID:26871141

  6. Thermal chemical-mechanical reactive flow model of shock initiation in solid explosives

    SciTech Connect

    Nicholls, A L., III; Tarver, C M

    1998-08-26

    The three dimensional Arbitrary Lagrange Eulerian hydrodynamic computer code ALE3D with fully coupled thermal-chemical-mechanical material models provides the framework for the development of a physically realistic model of shock initiation and detonation of solid explosives. The processes of hot spot formation during shock compression, subsequent ignition of reaction or failure to react, growth of reaction in individual hot spots, and coalescence of reacting hot spots during the transition to detonation can now be modeled using Arrhenius chemical kinetic rate laws and heat transfer to propagate the reactive flow. This paper discusses the growth rates of reacting hot spots in HMX and TATB and their coalescence during shock to detonation transition. Hot spot deflagration rates are found to be fast enough to consume explosive particles less than 10 mm in diameter during typical shock duration times, but larger particles must fragment and create more reactive surface area in order to be rapidly consumed.

  7. Reactive transport in a partially molten system with binary solid solution

    NASA Astrophysics Data System (ADS)

    Jordan, Jacob S.; Hesse, Marc A.

    2015-12-01

    Melt extraction from the Earth's mantle through high-porosity channels is required to explain the composition of the oceanic crust. Feedbacks from reactive melt transport are thought to localize melt into a network of high-porosity channels. Recent studies invoke lithological heterogeneities in the Earth's mantle to seed the localization of partial melts. Therefore, it is necessary to understand the reaction fronts that form as melt flows across the lithological interface between the heterogeneity and the ambient mantle. Here we present a chromatographic analysis of reactive melt transport across lithological boundaries, using the theory of hyperbolic conservation laws. This is an extension of linear trace element chromatography to the coupling of major elements and energy transport. Our analysis allows the prediction of the nonlinear feedbacks that arise in reactive melt transport due to changes in porosity. This study considers the special case of a partially molten porous medium with binary solid solution. As melt traverses a lithological contact, binary solid solution leads to the formation of a reacted zone between an advancing reaction front and the initial contact. The analysis also shows that the behavior of a fertile heterogeneity depends on its absolute concentration, in addition to compositional differences between itself and the refractory background. We present a regime diagram that predicts if melt emanating from a fertile heterogeneity localizes into high-porosity channels or develops a zero porosity shell. The theoretical framework presented here provides a useful tool for understanding nonlinear feedbacks in reactive melt transport, because it can be extended to more complex and realistic phase behaviors.

  8. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Vacchi, Isabella A.; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-01

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO.Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by

  9. Effects of various reactive gas atmospheres on the properties of bio-oil using microwave pyrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fast pyrolysis of lignocellulosic biomass produces organic liquids (bio-oil), bio-char, water, and non-condensable gases. The non-condensable gas component typically contains syngas (H2, CO and CO2) as well as small hydrocarbons (CH4, C2H6, and C3H8). Tail Gas Reactive Pyrolysis (TGRP), a patent p...

  10. Gas chromatograph-mass spectrometer (GC/MS) system for quantitative analysis of reactive chemical compounds

    DOEpatents

    Grindstaff, Quirinus G.

    1992-01-01

    Described is a new gas chromatograph-mass spectrometer (GC/MS) system and method for quantitative analysis of reactive chemical compounds. All components of such a GC/MS system external to the oven of the gas chromatograph are programmably temperature controlled to operate at a volatilization temperature specific to the compound(s) sought to be separated and measured.

  11. Uncertainties in reactive uptake coefficients for solid stratospheric particles—2. Effect on ozone depletion

    NASA Astrophysics Data System (ADS)

    Carslaw, Kenneth S.; Peter, Thomas; Müller, Rolf

    Uncertainties in reactive uptake coefficients for reactions involving HCl, ClONO2 and HOCl on nitric acid trihydrate (NAT) and sulfuric acid tetrahydrate (SAT) are shown to affect modeled Arctic stratospheric ozone depletion in a photochemical box model. The main contribution to the difference arises from the reaction ClONO2 + HCl → Cl2 + HNO3 in early to mid-winter. During this period, differences in predicted HCl and ClONO2 are more than 1 ppbv for several weeks when an upper limit for solid PSC existence is assumed. Ozone depletion is greater when liquid aerosols persist through the winter compared with cases where solid particles are assumed to form.

  12. Reactive Species Processes in Plasma-, Gas-, and Liquid-Phase

    NASA Astrophysics Data System (ADS)

    Reuter, Stephan; Winter, Joern; Hammer, Malte; Schmidt-Bleker, Ansgar; Iseni, Sylvain; Tresp, Helena; Dünnbier, Mario; Masur, Kai; Wende, Kristian; Weltmann, Klaus-Dieter

    2013-09-01

    Especially for the field of plasma medicine, plasmas interacting with liquids are of great interest for environmental, chemical, and biomedical applications. In this work we present optical diagnostics on atmospheric pressure plasma jets interacting with liquids. Combining the diagnostic results with numerical simulations yields an understanding of fundamental processes such as air species diffusion into the jet effluents or the influence on humidity. Especially for plasma treatment of physiological liquids in ambient air, atmospheric species play a key role. To achieve a desired reactive component output, the generation processes from these ambient air species are controlled. Plasma jets are characterized by planar laser induced fluorescence spectroscopy, by absorption and emission spectroscopy, and by flow simulations. With the gained knowledge we are able to tailor the reactive component composition and to influence plasma jet-liquid interaction. We show that reactive species generation within plasma treated liquid can be tuned and apply the findings to biological cells to investigate the effect of reactive oxygen and nitrogen species (RONS). The plasma treated liquids are investigated regarding their pH value, OH radicals, nitrate and nitrite, and H2O2 content. From the tailored plasma treatment a significant insight into the relevant transport processes in plasma treatment of liquids has been gained. Support by the German BMBF 03Z2DN11&12 is acknowledged.

  13. Space Shuttle Solid Rocket Nozzle Joint 2 Gas Path Study

    NASA Technical Reports Server (NTRS)

    Lui, R. C.; Hyer, R. L.

    1999-01-01

    Each Space Shuttle solid rocket nozzle contains five joints. By design, each nozzle joint utilizes room-temperature vulcanized (RTV) rubber as a thermal barrier to protect the nozzle metal parts and O-rings from heat degradation due to motor combustion gas. Typically, combustion gas does not penetrate through the RTV in nozzle Joints. However, Joint currently experiences gas penetration through the RTV over 90 percent of the time. The occurrence of Joint gas paths is a very complex phenomenon with several known contributors such as the unique geometry of the joint, motor pressure, nozzle vectoring, manufacturing induced RTV voids. RTV material capability, and joint skip (relative radial displacement of joint components). The occurrence of Joint gas paths appears to be a combination of these causes. To better understand the causes of gas paths in Joint, the circumferential locations of gas paths in the RTV were identified and correlated with nozzle vectoring, RTV closeour locations (where the RTV backfill is completed), and X-ray low-density. anomaly (LDA) indications. Results that no specific cause was determined.

  14. Gas-solid flow characteristics in high-density CFB

    NASA Astrophysics Data System (ADS)

    Wang, Xue-yao; Fan, Bao-guo; Wang, Sheng-dian; Xu, Xiang; Xiao, Yun-han

    2012-08-01

    The gas-solid flow characteristics in the riser of a high density CFB of square (0.27 m×0.27 m×10.4 m) or circular ( ϕ 0.187m×10.4 m) cross section, using Geldart B particles (quartz sand), was investigated experimentally. The influence of riser structure on the hydrodynamic behaviors of a high-density circulating fluidized bed was investigated. The solid circulation rate was up to 321 kg/(m2s) with the circular cross-section under the operating conditions of the main bed air velocity 12.1 m/s and loosen wind and back-feed wind flow 25.1 m3/h. Different operating conditions on realizing high density circulation was analyzed, while both solids circulation rate and particle holdup depended highly on operating conditions. The circulating gas-solid flow was accompanied by an evidently-dense character in the riser's bottom zone and became fully developed in the middle and upper zones.

  15. Gas-solid reaction-rate enhancement by pressure cycling

    NASA Astrophysics Data System (ADS)

    Sohn, H. Y.; Aboukheshem, M. B.

    1992-06-01

    An experimental study and mathematical modeling of the effects of external pressure cycling on gas-solid reactions have been conducted using the reduction of nickel oxide pellets by hy-drogen. Experiments were carried out in two phases: In the first phase, the intrinsic kinetic parameters were measured, and in the second phase, the gas-solid reaction was carried out under a constant or cycling external pressure. The effects of the frequency and amplitude of pressure cycling were studied at various reaction conditions. Pressure cycling substantially increases the overall rate of the reaction. A mathematical model was developed from the first principles to establish the extent of the overall reaction-rate enhancement and subsequently to analyze the experimental observations. The calculated values from the mathematical model are in good agreement with the experimental results. The effects are most pronounced when the overall rate under a constant pressure is controlled by diffusion. Depending on the reaction condition, a very large degree of rate enhancement could be achieved. Furthermore, low-amplitude pressure waves, like acoustic waves, could significantly increase the rates of gas-solid reactions.

  16. Sulfur gas emissions from stored flue gas desulfurization solids. Final report

    SciTech Connect

    Adams, D.F.; Farwell, S.O.

    1981-10-01

    The emissions of volatile, sulfur-containing compounds from the surfaces of 13 flue gas desulfurization (FGD) solids field storage sites have been characterized. The sulfur gas emissions from these storage surfaces were determined by measuring the sulfur gas enhancement of sulfur-free sweep air passing through a dynamic emission flux chamber placed over selected sampling areas. Samples of the enclosure sweep air were cryogenically concentrated in surface-deactivated Pyrex U traps. Analyses were conducted by wall-coated, open-tubular, capillary column, cryogenic, temperature-programmed gas chromatography using a sulfur-selective flame photometric detector. Several major variables associated with FGD sludge production processes were examined in relation to the measured range and variations in sulfur fluxes including: the sulfur dioxide scrubbing reagent used, sludge sulfite oxidation, unfixed or stabilized (fixed) FGD solids, and ponding or landfill storage. The composition and concentration of the measured sulfur gas emissions were found to vary with the type of solids, the effectiveness of rainwater drainage from the landfill surface, the method of impoundment, and the sulfate/sulfite ratio of the solids. The FGD solids emissions may contain hydrogen sulfide, carbonyl sulfide, dimethyl sulfide, carbon disulfide, and dimethyl disulfide in varying concentrations and ratios. In addition, up to four unidentified organo-sulfur compounds were found in the emissions from four different FGD solids. The measured, total sulfur emissions ranged from less than 0.01 to nearly 0.3 kg of sulfur per day for an equivalent 40.5 hectare (100 acre) FGD solids impoundment surface.

  17. Chemical reactivity of graphene oxide towards amines elucidated by solid-state NMR.

    PubMed

    Vacchi, Isabella A; Spinato, Cinzia; Raya, Jésus; Bianco, Alberto; Ménard-Moyon, Cécilia

    2016-07-14

    Graphene oxide (GO) is an attractive nanomaterial for many applications. Controlling the functionalization of GO is essential for the design of graphene-based conjugates with novel properties. But, the chemical composition of GO has not been fully elucidated yet. Due to the high reactivity of the oxygenated moieties, mainly epoxy, hydroxyl and carboxyl groups, several derivatization reactions may occur concomitantly. The reactivity of GO with amine derivatives has been exploited in the literature to design graphene-based conjugates, mainly through amidation. However, in this study we undoubtedly demonstrate using magic angle spinning (MAS) solid-state NMR that the reaction between GO and amine functions occurs via ring opening of the epoxides, and not by amidation. We also prove that there is a negligible amount of carboxylic acid groups in two GO samples obtained by a different synthesis process, hence eliminating the possibility of amidation reactions with amine derivatives. This work brings additional insights into the chemical reactivity of GO, which is fundamental to control its functionalization, and highlights the major role of MAS NMR spectroscopy for a comprehensive characterization of derivatized GO. PMID:27411370

  18. Oscillatory burning of solid propellants including gas phase time lag.

    NASA Technical Reports Server (NTRS)

    T'Ien, J. S.

    1972-01-01

    An analysis has been performed for oscillatory burning of solid propellants including gas phase time lag. The gaseous flame is assumed to be premixed and laminar with a one-step overall chemical reaction. The propellant is assumed to decompose according to the Arrenhius Law, with no condensed phase reaction. With this model, strong gas phase resonance has been found in certain cases at the characteristic gas-phase frequencies, but the peaking of the acoustic admittance is in the direction favoring the damping of pressure waves. At still higher frequencies, moderate wave-amplifying ability was found. The limit of low frequency response obtained previously by Denison and Baum was recovered, and the limitations of the quasi-steady theory were investigated.

  19. Quantitative determination of hydrogen in solids by gas chromatography.

    PubMed

    Addach, H; Berçot, P; Wery, M; Rezrazi, M

    2004-11-19

    Processes such as electroplating or acid cleaning are notorious causes of post-processing failure through hydrogen embrittlement. So, the determination of amounts of hydrogen in metals is of great importance. An analysis method for investigation of H content in solids has been established based on hot extraction and gas chromatography system. Hot extraction in inert gas enables complete and/or partial removal of the hydrogen from the samples. A gas chromatography system is used to determine quantitatively the amount of thermally desorbed hydrogen. An investigation of the baking operating conditions is made of the hydrogen desorption rate of zinc-plated steel parts. Then, an analysis of the polarisation conditions upon chromium electroplating is given. PMID:15584242

  20. Polar Effects Control the Gas-phase Reactivity of Charged para-Benzyne Analogs

    PubMed Central

    Wittrig, Ashley M.; Archibold, Enada F.; Sheng, Huaming; Nash, John J.; Kenttämaa, Hilkka I.

    2014-01-01

    The gas-phase reactivity of charged para-benzynes is entirely unexplored as they and/or their precursors tend to undergo ring-opening upon their generation. We report here a gas-phase reactivity study of two such benzynes, the 2,5-didehydropyridinium and 5,8-didehydroisoquinolinium cations, generated in a modified dual-linear quadrupole ion trap (DLQIT) mass spectrometer. Both biradicals were found to form diagnostic products with organic molecules, indicating the presence of two radical sites. As opposed to earlier predictions that the singlet-triplet (S-T) splitting controls the radical reactivity of such species, the 2,5-didehydropyridinium cation reacts much faster in spite of its larger S-T splitting. Calculated vertical electron affinities of the radical sites of the para-benzynes, a parameter related to the polarity of the transition states of their reactions, appears to be the most important reactivity controlling factor. PMID:25838787

  1. Supramolecular reactivity in the gas phase: investigating the intrinsic properties of non-covalent complexes.

    PubMed

    Cera, Luca; Schalley, Christoph A

    2014-03-21

    The high vacuum inside a mass spectrometer offers unique conditions to broaden our view on the reactivity of supramolecules. Because dynamic exchange processes between complexes are efficiently suppressed, the intrinsic and intramolecular reactivity of the complexes of interest is observed. Besides this, the significantly higher strength of non-covalent interactions in the absence of competing solvent allows processes to occur that are unable to compete in solution. The present review highlights a series of examples illustrating different aspects of supramolecular gas-phase reactivity ranging from the dissociation and formation of covalent bonds in non-covalent complexes through the reactivity in the restricted inner phase of container molecules and step-by-step mechanistic studies of organocatalytic reaction cycles to cage contraction reactions, processes induced by electron capture, and finally dynamic molecular motion within non-covalent complexes as unravelled by hydrogen-deuterium exchange processes performed in the gas phase. PMID:24435245

  2. The equivalent electrical permittivity of gas-solid mixtures at intermediate solid volume fractions.

    SciTech Connect

    Torczynski, John Robert; Ceccio, Steven Louis; Tortora, Paul Richard

    2005-07-01

    Several mixture models are evaluated for their suitability in predicting the equivalent permittivity of dielectric particles in a dielectric medium for intermediate solid volume fractions (0.4 to 0.6). Predictions of the Maxwell, Rayleigh, Bottcher and Bruggeman models are compared to computational simulations of several arrangements of solid particles in a gas and to the experimentally determined permittivity of a static particle bed. The experiment uses spherical glass beads in air, so air and glass permittivity values (1 and 7, respectively) are used with all of the models and simulations. The experimental system used to measure the permittivity of the static particle bed and its calibration are described. The Rayleigh model is found to be suitable for predicting permittivity over the entire range of solid volume fractions (0-0.6).

  3. Pressure dependence of the melting temperature of solids - Rare-gas solids

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert; Ferrante, John

    1991-01-01

    A method presented by Schlosser et al. (1989) for analyzing the pressure dependence of experimental melting-temperature data is applied to rare-gas solids. The plots of the logarithm of the reduced melting temperature vs that of the reduced pressure are straight lines in the absence of phase transitions. The plots of the reduced melting temperatures for Ar, Kr, and Xe are shown to be approximately straight lines.

  4. In Situ Control of Gas Flow by Modification of Gas-Solid Interactions

    NASA Astrophysics Data System (ADS)

    Seo, Dongjin; Ducker, William A.

    2013-10-01

    The boundary condition for gas flow at the solid-gas interface can be altered by in situ control of the state of a thin film adsorbed to the solid. A monolayer of ocatadecyltrichlorosilane (OTS) reversibly undergoes a meltinglike transition. When the temperature of an OTS-coated particle and plate is moved through the range of OTS “melting” temperatures, there is a change in the lubrication force between the particle and plate in 1 atm of nitrogen gas. This change is interpreted in terms of a change in the flow of gas mediated by the slip length and tangential momentum accommodation coefficient (TMAC). There is a minimum in slip length (290 nm) at 18°C, which corresponds to a maximum in TMAC (0.44). The slip length increases to 590 nm at 40°C which corresponds to a TMAC of 0.25. We attribute the decrease in TMAC with increasing temperature to a decrease in roughness of the monolayer on melting, which allows a higher fraction of specular gas reflections, thereby conserving tangential gas momentum. The importance of this work is that it demonstrates the ability to control gas flow simply by altering the interface for fixed geometry and gas properties.

  5. Slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Viani, Brian

    2013-01-29

    A slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures includes the steps of dissolving the gas mixture and carbon dioxide in water providing a gas, carbon dioxide, water mixture; adding a porous solid media to the gas, carbon dioxide, water mixture forming a slurry of gas, carbon dioxide, water, and porous solid media; heating the slurry of gas, carbon dioxide, water, and porous solid media producing steam; and cooling the steam to produce purified water and carbon dioxide.

  6. Reactivity of Mg-Al hydrotalcites in solid and delaminated forms in ammonium carbonate solutions

    NASA Astrophysics Data System (ADS)

    Stoica, Georgiana; Santiago, Marta; Abelló, Sònia; Pérez-Ramírez, Javier

    2010-10-01

    Treatment of Mg-Al hydrotalcites (LDHs, layered double hydroxides) in aqueous (NH 4) 2CO 3 at 298 K leads to composites of dawsonite, hydrotalcite, and magnesium ammonium carbonate. The mechanism and kinetics of this transformation, ultimately determining the relative amounts of these components in the composite, depend on the treatment time (from 1 h to 9 days), the Mg/Al ratio in the hydrotalcite (2-4), and on the starting layered double hydroxide (solid or delaminated form). The materials at various stages of the treatment were characterized by inductive coupled plasma-optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, thermogravimetry, and nitrogen adsorption at 77 K. The progressive transformation of hydrotalcite towards crystalline dawsonite and magnesium ammonium carbonate phases follows a dissolution-precipitation mechanism. A gradual decrease of the Mg/Al ratio in the resulting solids was observed in time due to magnesium leaching in the reacting medium. Dawsonite-hydrotalcite composite formation is favored at high aluminum contents in the starting hydrotalcite, while the formation of magnesium ammonium carbonate is favored at high Mg/Al ratios. The synthetic strategy comprising hydrotalcite delamination in formamide prior to aqueous (NH 4) 2CO 3 treatment is more reactive towards composite formation than starting from the bulk solid hydrotalcite.

  7. Acoustic Probe for Solid-Gas-Liquid Suspension

    SciTech Connect

    Tavlarides, L.L.; Sangani, Ashok

    2003-09-14

    The primary objective of the research project during the first funding period was to develop an acoustic probe to measure volume percent solids in solid-liquid slurries in the presence of small amounts of gas bubbles. This problem was addressed because of the great need for a non-invasive, accurate and reliable method for solids monitoring in liquid slurries in the presence of radiolytically generated gases throughout the DOE complex. These measurements are necessary during mobilization of salts and sediments in tanks, transport of these slurries in transfer lines to processing facilities across a site, and, in some instances, during high level waste processing. Although acoustic probes have been commonly used for monitoring flows in single-phase fluids (McLeod, 1967), their application to monitor two-phase mixtures has not yet fully realized its potential. A number of investigators in recent years have therefore been involved in developing probes for measuring the volume fractions in liquid solid suspensions (Atkinson and Kytomaa, 1993; Greenwood et al., 1993; Martin et al., 1995) and in liquid-liquid suspensions (Bonnet and Tavlarides, 1987; Tavlarides and Bonnet, 1988, Yi and Tavlarides, 1990; Tsouris and Tavlarides, 1993, Tsouris et al., 1995). In particular, Atkinson and Kytomaa (1993) showed that the acoustic technique can be used to determine both the velocity and the volume fraction of solids while Martin et al. (1995) and Spelt et al. (1999) showed that the acoustic probe can also be used to obtain information on the size distribution of the particles. In a recent testing of in-line slurry monitors with radioactive slurries suspended with Pulsair Mixers (Hylton & Bayne, 1999), an acoustic probe did not compare well with other instruments most probably due to presence of entrained gases and improper acoustic frequency range of interrogation. The work of the investigators cited has established the potential of the acoustic probe for characterizing

  8. Fluidization onset and expansion of gas-solid fluidized beds

    SciTech Connect

    Jones, O.C.; Shin, T.S.

    1984-08-01

    A simple, mass conservation-based, kinematic model is presented for accurately predicting both the onset of fluidization and the degree of (limit of) bed expansion in bubbling gas-solid fluidized beds. The model is consistant with inception correlations exisiting in the literature. Since the method has a sound physical basis, it might be expected to provide scaling between laboratory-scale fluidized beds and large-scale systems. This scaling ability, however, remains to be demonstrated as does the application to pressurized systems and where the terminal Reynolds numbers exceed 1000, (Archimedes numbers over about 3.2 x 10/sup 5/).

  9. Acoustic cross-correlation flowmeter for solid-gas flow

    DOEpatents

    Sheen, Shuh-Haw; Raptis, Apostolos C.

    1986-01-01

    Apparatus for measuring particle velocity in a solid-gas flow within a pipe includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals in response to said first and second detected signals; and means for cross-correlating said first and second output signals.

  10. Acoustic cross-correlation flowmeter for solid-gas flow

    DOEpatents

    Sheen, S.H.; Raptis, A.C.

    1984-05-14

    Apparatus for measuring particle velocity in a solid-gas flow within a pipe includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals; and means for cross-correlating said first and second output signals.

  11. Acoustic cross-correlation flowmeter for solid-gas flow

    NASA Astrophysics Data System (ADS)

    Sheen, S. H.; Raptis, A. C.

    1984-05-01

    An apparatus for measuring particle velocity in a solid-gas flow within a pipe is described. It includes: first and second transmitting transducers for transmitting first and second ultrasonic signals into the pipe at first and second locations, respectively, along the pipe; an acoustic decoupler, positioned between said first and second transmitting transducers, for acoustically isolating said first and second signals from one another; first and second detecting transducers for detecting said first and second signals and for generating first and second detected signals; and means for cross-correlating said first and second output signals.

  12. Cover and startup gas supply system for solid oxide fuel cell generator

    DOEpatents

    Singh, Prabhakar; George, Raymond A.

    1999-01-01

    A cover and startup gas supply system for a solid oxide fuel cell power generator is disclosed. Hydrocarbon fuel, such as natural gas or diesel fuel, and oxygen-containing gas are supplied to a burner. Combustion gas exiting the burner is cooled prior to delivery to the solid oxide fuel cell. The system mixes the combusted hydrocarbon fuel constituents with hydrogen which is preferably stored in solid form to obtain a non-explosive gas mixture. The system may be used to provide both non-explosive cover gas and hydrogen-rich startup gas to the fuel cell.

  13. Cover and startup gas supply system for solid oxide fuel cell generator

    DOEpatents

    Singh, P.; George, R.A.

    1999-07-27

    A cover and startup gas supply system for a solid oxide fuel cell power generator is disclosed. Hydrocarbon fuel, such as natural gas or diesel fuel, and oxygen-containing gas are supplied to a burner. Combustion gas exiting the burner is cooled prior to delivery to the solid oxide fuel cell. The system mixes the combusted hydrocarbon fuel constituents with hydrogen which is preferably stored in solid form to obtain a non-explosive gas mixture. The system may be used to provide both non-explosive cover gas and hydrogen-rich startup gas to the fuel cell. 4 figs.

  14. Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity

    DOEpatents

    Whealton, John H.; Hanson, Gregory R.; Storey, John M.; Raridon, Richard J.; Armfield, Jeffrey S.; Bigelow, Timothy S.; Graves, Ronald L.

    2001-01-01

    A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime (about 40 ps), high frequency (about 5G hz), high power bursts of low-duty factor microwaves sufficient to generate a dielectric barrier discharge and passing a gas to treated through the discharge so as to cause dissociative reduction of the exhaust gases. The invention also includes a reactor for generating the non-thermal plasma.

  15. Reactive Gas transport in soil: Kinetics versus Local Equilibrium Approach

    NASA Astrophysics Data System (ADS)

    Geistlinger, Helmut; Jia, Ruijan

    2010-05-01

    Gas transport through the unsaturated soil zone was studied using an analytical solution of the gas transport model that is mathematically equivalent to the Two-Region model. The gas transport model includes diffusive and convective gas fluxes, interphase mass transfer between the gas and water phase, and biodegradation. The influence of non-equilibrium phenomena, spatially variable initial conditions, and transient boundary conditions are studied. The objective of this paper is to compare the kinetic approach for interphase mass transfer with the standard local equilibrium approach and to find conditions and time-scales under which the local equilibrium approach is justified. The time-scale of investigation was limited to the day-scale, because this is the relevant scale for understanding gas emission from the soil zone with transient water saturation. For the first time a generalized mass transfer coefficient is proposed that justifies the often used steady-state Thin-Film mass transfer coefficient for small and medium water-saturated aggregates of about 10 mm. The main conclusion from this study is that non-equilibrium mass transfer depends strongly on the temporal and small-scale spatial distribution of water within the unsaturated soil zone. For regions with low water saturation and small water-saturated aggregates (radius about 1 mm) the local equilibrium approach can be used as a first approximation for diffusive gas transport. For higher water saturation and medium radii of water-saturated aggregates (radius about 10 mm) and for convective gas transport, the non-equilibrium effect becomes more and more important if the hydraulic residence time and the Damköhler number decrease. Relative errors can range up to 100% and more. While for medium radii the local equilibrium approach describes the main features both of the spatial concentration profile and the time-dependence of the emission rate, it fails completely for larger aggregates (radius about 100 mm

  16. Reactive solid-state dewetting of Cu-Ni films on silicon

    SciTech Connect

    Clearfield, Raphael; Railsback, Justin G.; Melechko, Anatoli V.; Pearce, Ryan C.; Hensley, Dale K.; Fowlkes, Jason D.; Fuentes-Cabrera, Miguel; Simpson, Michael L.; Rack, Philip D.

    2010-12-20

    The behavior of a 50 nm Cu-Ni alloy film on Si in a process of reactive solid-state dewetting is presented. The films were annealed at a range of temperatures (300-700 deg. C) in 1%H{sub 2} 99%N{sub 2} reducing atmosphere. The resulting alloy and silicide particles formed by film dewetting and film reaction with the substrate were distinguished by selective wet etching and examined by scanning electron microscopy and spectroscopy. After potassium hydroxide etch, regions that etch slower than silicon substrate have distribution statistics similar to the alloy and silicide particles prior to their removal, indicating strong coupling between mass transport across the interface and along the surface.

  17. PRESSURIZED SOLID OXIDE FUEL CELL/GAS TURBINE POWER SYSTEM

    SciTech Connect

    W.L. Lundberg; G.A. Israelson; R.R. Moritz; S.E. Veyo; R.A. Holmes; P.R. Zafred; J.E. King; R.E. Kothmann

    2000-02-01

    Power systems based on the simplest direct integration of a pressurized solid oxide fuel cell (SOFC) generator and a gas turbine (GT) are capable of converting natural gas fuel energy to electric power with efficiencies of approximately 60% (net AC/LHV), and more complex SOFC and gas turbine arrangements can be devised for achieving even higher efficiencies. The results of a project are discussed that focused on the development of a conceptual design for a pressurized SOFC/GT power system that was intended to generate 20 MWe with at least 70% efficiency. The power system operates baseloaded in a distributed-generation application. To achieve high efficiency, the system integrates an intercooled, recuperated, reheated gas turbine with two SOFC generator stages--one operating at high pressure, and generating power, as well as providing all heat needed by the high-pressure turbine, while the second SOFC generator operates at a lower pressure, generates power, and provides all heat for the low-pressure reheat turbine. The system cycle is described, major system components are sized, the system installed-cost is estimated, and the physical arrangement of system components is discussed. Estimates of system power output, efficiency, and emissions at the design point are also presented, and the system cost of electricity estimate is developed.

  18. An index for quantifying the aerobic reactivity of municipal solid wastes and derived waste products.

    PubMed

    Scaglia, Barbara; Adani, Fabrizio

    2008-05-01

    The organic matter contained in municipal solid waste (MSW) and in the MSW fractions obtained by mechanical separation has strong environmental impact when the waste is used as landfill. This is partly due to the biological activity that occurs under anaerobic conditions. Negative effects on the environment include unpleasant odors, biogas, leachate and biomass self-heating. Measuring the biological reactivity of waste with the help of indicators is an important tool to prevent waste impact. The aim of this study was to develop an index capable of describing the aerobic reactivity of waste, using both biological and chemical indicators. To develop this index, 71 MSW and MSW-product samples, including biologically treated MSW and mechanically separated MSW fractions, were analyzed. Fifty of the 71 samples analyzed represented MSWs and their derived products collected from a number of Italian waste plants and sites. The remaining 21 were MSW samples collected at different times during 8 different full-scale aerobic biological processes in four treatment plants used to reduce the biological reactivity of wastes. Five of these processes used the entire (unsorted) MSW, while the remaining three used the organic fraction of the MSW obtained by mechanical pre-treatment (waste sieving). Respirometric activity (Dynamic Respiration Index, DRI) and eluates characterization (chemical oxygen demand--COD, and 5 days biological oxygen demand--BOD5) were used as indicators of waste strength, as they had previously been reported to be indirect measures of waste impact on landfill. Summarizing all studied indicators, Principal Component Analysis (PCA) was used to develop the Putrescibility Index (Ip). The results revealed Ip index of 204+/-33 (mean+/-standard deviation) and 159+/-14 for the organic fraction of MSW and MSW untreated waste respectively, and of 106+/-16 and 101+/-22 for the corresponding biologically treated waste. PMID:18280541

  19. Water-Gas Shift and Methane Reactivity on Reducible Perovskite-Type Oxides

    PubMed Central

    2015-01-01

    Comparative (electro)catalytic, structural, and spectroscopic studies in hydrogen electro-oxidation, the (inverse) water-gas shift reaction, and methane conversion on two representative mixed ionic–electronic conducting perovskite-type materials La0.6Sr0.4FeO3−δ (LSF) and SrTi0.7Fe0.3O3−δ (STF) were performed with the aim of eventually correlating (electro)catalytic activity and associated structural changes and to highlight intrinsic reactivity characteristics as a function of the reduction state. Starting from a strongly prereduced (vacancy-rich) initial state, only (inverse) water-gas shift activity has been observed on both materials beyond ca. 450 °C but no catalytic methane reforming or methane decomposition reactivity up to 600 °C. In contrast, when starting from the fully oxidized state, total methane oxidation to CO2 was observed on both materials. The catalytic performance of both perovskite-type oxides is thus strongly dependent on the degree/depth of reduction, on the associated reactivity of the remaining lattice oxygen, and on the reduction-induced oxygen vacancies. The latter are clearly more reactive toward water on LSF, and this higher reactivity is linked to the superior electrocatalytic performance of LSF in hydrogen oxidation. Combined electron microscopy, X-ray diffraction, and Raman measurements in turn also revealed altered surface and bulk structures and reactivities. PMID:26045733

  20. Co-processing of agricultural plastic waste and switchgrass via tail gas reactive pyrolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mixtures of agricultural plastic waste in the form of polyethylene hay bale covers (PE) (4-37%) and switchgrass were investigated using the US Department of Agriculture’s tail gas reactive pyrolysis (TGRP) at different temperatures (400-570 deg C). TGRP of switchgrass and plastic mixtures significan...

  1. Characterization of zeolite structure and fluorocarbon reactivity using solid state NMR and x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Ciraolo, Michael Frank

    The research presented in this thesis involves a combination of techniques used to study the structure and interactions zeolites adsorbed with fluorocarbons. This research is specifically aimed at understanding the processes of adsorption, binding, and reactivity of fluorocarbons on cation exchanged faujasite type zeolites. The solid state ion exchange process has also been studied since it is one way to obtain materials with higher exchange levels, which has been shown to effect adsorption and catalytic activity. To improve the understanding of the adsorption and separation processes a time resolved in-situ synchrotron x-ray powder diffraction study has been undertaken. Since faujasite type zeolites have been found to be effective in separating mixtures of HFC-134 (CF2HCF2H) and HFC-134a (CFH2CF3) isomers, the adsorption of these fluorocarbons on NaY have been studied. It has been shown that both the extent of loading and the kinetics of the sorption process in molecular sieves can be followed using this technique. A model for the binding of hydrochlorofluorocarbon (HCFC) 124a (CF 2HCF2Cl) adsorbed on NaX at 100K has been determined using a combination x-ray and neutron powder diffraction and solid state NMR. Using Rietveld refinement of the diffraction data, the HCFC molecule was found localized in the zeolite cavities bound on either end by sodium cations in the SII and SIII' positions. The model is consistent with hydrogen bonding between the proton of the HCFC and the framework oxygen. The NMR results further confirm the model and are consistent with Na-F binding and HCFC-framework interactions. Solid-state MAS NMR, synchrotron X-ray powder diffraction and a mass spectrometer and gas chromatograph catalysis system have been used to study the reactivity of HCFC-124a (CF2HCF2Cl) on NaX, Zn 2+-exchanged NaX (ZnX) and Rb+-exchanged NaX (RbX). We have chosen to study HCFC-124a (CF2HCF2Cl) since HCFC-124a can undergo both dehydrofluorination and dehydrochlorination

  2. Iridium single atom tips fabricated by field assisted reactive gas etching

    NASA Astrophysics Data System (ADS)

    Wood, John A.; Urban, Radovan; Salomons, Mark; Cloutier, Martin; Wolkow, Robert A.; Pitters, Jason L.

    2016-03-01

    We present a simple, reliable method to fabricate Ir single atom tips (SATs) from polycrystalline wire. An electrochemical etch in CaCl2 solution is followed by a field assisted reactive gas etch in vacuum at room temperature using oxygen as an etching gas and neon as an imaging gas. Once formed, SATs are cooled to liquid nitrogen temperatures and their underlying structure is examined through evaporation of the apex atoms. Furthermore, a method is developed to repair Ir SATs at liquid nitrogen temperatures when apex atoms evaporate. This method may be used to fabricate Ir SAT ion sources.

  3. Organometallic synthesis, reactivity and catalysis in the solid state using well-defined single-site species

    PubMed Central

    Pike, Sebastian D.; Weller, Andrew S.

    2015-01-01

    Acting as a bridge between the heterogeneous and homogeneous realms, the use of discrete, well-defined, solid-state organometallic complexes for synthesis and catalysis is a remarkably undeveloped field. Here, we present a review of this topic, focusing on describing the key transformations that can be observed at a transition-metal centre, as well as the use of well-defined organometallic complexes in the solid state as catalysts. There is a particular focus upon gas–solid reactivity/catalysis and single-crystal-to-single-crystal transformations. PMID:25666064

  4. Experimental design for reflection measurements of highly reactive liquid or solid substances with application to liquid sodium

    SciTech Connect

    Chan, S.H.; Gossler, A.A.

    1980-06-30

    A versatile goniometer system with associated electronic components and mechanical instruments has been assembled. It is designed to measure spectral, specular reflectances of highly reactive liquid or solid substances over a spectral range of 0.3 to 9 ..mu.. and incidence angles of 12 to 30/sup 0/ off the normal direction. The capability of measuring reflectances of liquid substances clearly distinguishes this experimental design from conventional systems which are applicable only to solid substances. This design has been used to measure the spectral, specular reflectance of liquid sodium and preliminary results obtained are compared with those of solid sodium measured by other investigators.

  5. NiCr etching in a reactive gas

    SciTech Connect

    Ritter, J.; Boucher, R.; Morgenroth, W.; Meyer, H. G.

    2007-05-15

    The authors have etched NiCr through a resist mask using Cl/Ar based chemistry in an electron cyclotron resonance etch system. The optimum gas mixture and etch parameters were found for various ratios of Ni to Cr, based on the etch rate, redeposits, and the etch ratio to the mask. The introduction of O{sub 2} into the chamber, which is often used in the etching of Cr, served to both increase and decrease the etch rate depending explicitly on the etching parameters. Etch rates of >50 nm min{sup -1} and ratios of >1 (NiCr:Mask) were achieved for NiCr (80:20). Pattern transfer from the mask into the NiCr was achieved with a high fidelity and without redeposits for a Cl/Ar mix of 10% Ar (90% Cl{sub 2}) at an etch rate of {approx_equal}50 nm min{sup -1} and a ratio of 0.42 (NiCr:ZEP 7000 e-beam mask)

  6. A new model for gas/solid pipe flow

    SciTech Connect

    Wu, Bangxian; Chang, S.L.; Lottes, S.A.; Petrick, M.

    1995-12-31

    A new model of particle turbulent dispersion in vertical gas/solid pipe flow is presented in this paper. The essence of the model is to pay more attention to the active and discrete behavior of particles in the dispersion process in non-homogeneous turbulent vertical pipe flows using two-fluid approaches. In the new model, a non-gradient type of diffusion term is included in the expression of radial particle dispersion flux; the transport equation for particle turbulent kinetic energy (PTKE) is developed and solved for its distribution; the effect of intra-particle collision is considered for the generation and dissipation of PTKE; turbulence modulation due to particle presence is taken into account. Preliminary numerical results based on this new model are also presented in this paper.

  7. Reactive sputtering of titanium in Ar/CH4 gas mixture: Target poisoning and film characteristics

    SciTech Connect

    Fouad, O.A.; Rumaiz, A.; Shah, S.

    2009-03-01

    Reactive sputtering of titanium target in the presence of Ar/CH{sub 4} gas mixture has been investigated. With the addition of methane gas to above 1.5% of the process gas a transition from the metallic sputtering mode to the poison mode was observed as indicated by the change in cathode current. As the methane gas flow concentration increased up to 10%, the target was gradually poisoned. The hysteresis in the cathode current could be plotted by first increasing and then subsequently decreasing the methane concentration. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of carbide phases and the transition of the process from the metallic to compound sputtering mode as the methane concentration in the sputtering gas is increased. The paper discusses a sputtering model that gives a rational explanation of the target poisoning phenomenon and shows an agreement between the experimental observations and calculated results.

  8. A new method for the measurement of solids holdup in gas-liquid-solid three-phase systems

    SciTech Connect

    Wenge, F.; Chisti, Y.; Moo-Young, M.

    1995-03-01

    Gas-liquid-solid multiphase systems are commonly encountered in the chemical process industry, in bio-processing, and in environmental pollution abatement devices. A method for the measurement of gas and solids holdups in gas-liquid-solid multiphase devices is developed and tested. The method depends on measurements of hydrostatic pressures in the three-phase dispersion followed by interruption of gas flow, complete gas disengagement, and a second pressure measurement in the resulting two-phase solid-liquid slurry, over a short period of time (< 30 s). The proposed method is compared with results obtained with physical sampling of the multiphase flow in vertical up- and down-flow in a large airlift reactor (0.243 m diameter, 7.825 m overall height, 2.44 riser-to-downcomer cross-sectional area ratio). Applicability of the technique to slurries of glass beads in tap water is demonstrated for various sizes and concentrations of beads over a range of gas flow rates (0.070--0.150 {times} 10{sup {minus}3} m bead diameter, 2,500 kg/m{sup 3} solids density, 0.02--0.17 m/s superficial gas velocity).

  9. A solid state gas density monitor for gas insulated substation equipment

    SciTech Connect

    Saaski, E.W.; Hartl, J.C.

    1982-07-01

    A solid state gas density monitor has been developed for SF/sub 6/ service in gas-insulated substation equipment that is based on principles and construction techniques similar to ionization-type fire alarms. The monitor has a resolution of .7kPa (.1 psi) at 20/sup 0/C and, depending on ion chamber voltage and geometry, exhibits a linearity of /sup +//sub -/1 to /sup +//sub -/4. kPa (/sup +//sub -/.15 to /sup +//sub -/.6 psi) at 20/sup 0/C over the density range 0.20 to 0.66 MPa (30 to 95 psia) at 20/sup 0/C. The monitor incorporates two level contact closure actuated by gas density falling below one of two pre-set alarm limits, and an LCD read-out for visual monitoring and instrument calibration. The display presents density in terms of equivalent psia at 68/sup 0/F. (20/sup 0/C.).

  10. Generalized gas-solid adsorption modeling: Single-component equilibria

    SciTech Connect

    Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.

    2015-01-07

    Over the last several decades, modeling of gas–solid adsorption at equilibrium has generally been accomplished through the use of isotherms such as the Freundlich, Langmuir, Tóth, and other similar models. While these models are relatively easy to adapt for describing experimental data, their simplicity limits their generality to be used with many different sets of data. This limitation forces engineers and scientists to test each different model in order to evaluate which one can best describe their data. Additionally, the parameters of these models all have a different physical interpretation, which may have an effect on how they can be further extended into kinetic, thermodynamic, and/or mass transfer models for engineering applications. Therefore, it is paramount to adopt not only a more general isotherm model, but also a concise methodology to reliably optimize for and obtain the parameters of that model. A model of particular interest is the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm. The GSTA isotherm has enormous flexibility, which could potentially be used to describe a variety of different adsorption systems, but utilizing this model can be fairly difficult due to that flexibility. To circumvent this complication, a comprehensive methodology and computer code has been developed that can perform a full equilibrium analysis of adsorption data for any gas-solid system using the GSTA model. The code has been developed in C/C++ and utilizes a Levenberg–Marquardt’s algorithm to handle the non-linear optimization of the model parameters. Since the GSTA model has an adjustable number of parameters, the code iteratively goes through all number of plausible parameters for each data set and then returns the best solution based on a set of scrutiny criteria. Data sets at different temperatures are analyzed serially and then linear correlations with temperature are made for the parameters of the model. The end result is a full set of

  11. Generalized gas-solid adsorption modeling: Single-component equilibria

    DOE PAGESBeta

    Ladshaw, Austin; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.

    2015-01-07

    Over the last several decades, modeling of gas–solid adsorption at equilibrium has generally been accomplished through the use of isotherms such as the Freundlich, Langmuir, Tóth, and other similar models. While these models are relatively easy to adapt for describing experimental data, their simplicity limits their generality to be used with many different sets of data. This limitation forces engineers and scientists to test each different model in order to evaluate which one can best describe their data. Additionally, the parameters of these models all have a different physical interpretation, which may have an effect on how they can bemore » further extended into kinetic, thermodynamic, and/or mass transfer models for engineering applications. Therefore, it is paramount to adopt not only a more general isotherm model, but also a concise methodology to reliably optimize for and obtain the parameters of that model. A model of particular interest is the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm. The GSTA isotherm has enormous flexibility, which could potentially be used to describe a variety of different adsorption systems, but utilizing this model can be fairly difficult due to that flexibility. To circumvent this complication, a comprehensive methodology and computer code has been developed that can perform a full equilibrium analysis of adsorption data for any gas-solid system using the GSTA model. The code has been developed in C/C++ and utilizes a Levenberg–Marquardt’s algorithm to handle the non-linear optimization of the model parameters. Since the GSTA model has an adjustable number of parameters, the code iteratively goes through all number of plausible parameters for each data set and then returns the best solution based on a set of scrutiny criteria. Data sets at different temperatures are analyzed serially and then linear correlations with temperature are made for the parameters of the model. The end result is a full set

  12. A CFD study of gas-solid jet in a CFB riser flow

    SciTech Connect

    Li, Tingwen; Guenther, Chris

    2012-03-01

    Three-dimensional high-resolution numerical simulations of a gas–solid jet in a high-density riser flow were conducted. The impact of gas–solid injection on the riser flow hydrodynamics was investigated with respect to voidage, tracer mass fractions, and solids velocity distribution. The behaviors of a gas–solid jet in the riser crossflow were studied through the unsteady numerical simulations. Substantial separation of the jetting gas and solids in the riser crossflow was observed. Mixing of the injected gas and solids with the riser flow was investigated and backmixing of gas and solids was evaluated. In the current numerical study, both the overall hydrodynamics of riser flow and the characteristics of gas–solid jet were reasonably predicted compared with the experimental measurements made at NETL.

  13. Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes.

    PubMed

    Nakagawa, Kyuya; Namba, Akio; Mukai, Shin R; Tamon, Hajime; Ariyadejwanich, Pisit; Tanthapanichakoon, Wiwut

    2004-04-01

    Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates. PMID:15026233

  14. A Statistical Hot Spot Reactive Flow Model for Shock Initiation and Detonation of Solid High Explosives

    SciTech Connect

    Nichols, A L; Tarver, C M

    2002-07-01

    A statistical hot spot reactive flow model for shock initiation and detonation of solid high explosives developed in the ALE3D hydrodynamic computer code is presented. This model is intended to evolve into a physically correct description of the physical and chemical mechanisms that control the onset of shock initiation via hotspot formation, the growth (01 failure to grow) of these hotspots into the surrounding explosive particles, the rapid transition to detonation, and self-sustaining detonation. Mesoscale modeling of the shock compression and temperature dependent chemical decomposition of individual explosive particles are currently yielding accurate predictions of hot spot formation and the subsequent growth (or failure) of these hotspot reactions in the surrounding grains. For two- and three-dimensional simulations of larger scale explosive charges, a statistical hotspot model that averages over thousands of individual hotspot dimensions and temperatures and then allows exothermic chemical reactions to grow (or fail to grow) due to thermal conduction is required. This paper outlines a first approach to constructing a probabilistic hot spot formulation based on the number density of potential hotspot sites. These hotspots can then either ignite or die out if they do not exceed certain ignition criteria, which are based on physical properties of the explosive particles. The growing hot spots spread at burn velocities given by experimentally determined deflagration velocity versus pressure relationships. The mathematics and assumptions involved in formulating the model and practical examples of its usefulness are given.

  15. Bio-inspired solid phase extraction sorbent material for cocaine: a cross reactivity study.

    PubMed

    Montesano, Camilla; Sergi, Manuel; Perez, German; Curini, Roberta; Compagnone, Dario; Mascini, Marcello

    2014-12-01

    The binding specificity of a bio-inspired hexapeptide (QHWWDW) versus cocaine and four other drugs such as 3,4-methylenedioxy-N-methylamphetamine (MDMA), 3,4-methylenedioxy-N-ethylamphetamine (MDEA), phencyclidine and morphine was computationally studied and then experimentally confirmed in solid phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC/MS) detection. In simulation, the hexapeptide-drug complexes were docked with different scoring functions and considering pH chemical environment. In experimental, the cross reactivity of the selected hexapeptide was tested as SPE sorbent versus cocaine and other four drugs using buffer solutions at pH 4 and 7. Significant differences in specific retention were found between cocaine (97% of recovery) and both morphine (45% of recovery) and phencyclidine (60% of recovery), but less for ecstasies (average recovery 69%). In agreement with docking simulation, the hexapeptide showed the highest recovery with best specificity versus cocaine at pH 7 with an experimentally binding constant of 2.9 × 10(6)M(-1). The bio-inspired sorbent material analytical performances were compared with a commercial reversed phase cartridge confirming the hexapeptide specificity to cocaine and validating simulated data. PMID:25159425

  16. Impact of exhaust gas recirculation (EGR) on the oxidative reactivity of diesel engine soot

    SciTech Connect

    Al-Qurashi, Khalid; Boehman, Andre L.

    2008-12-15

    This paper expands the consideration of the factors affecting the nanostructure and oxidative reactivity of diesel soot to include the impact of exhaust gas recirculation (EGR). Past work showed that soot derived from oxygenated fuels such as biodiesel carries some surface oxygen functionality and thereby possesses higher reactivity than soot from conventional diesel fuel. In this work, results show that EGR exerts a strong influence on the physical properties of the soot which leads to enhanced oxidation rate. HRTEM images showed a dramatic difference between the burning modes of the soot generated under 0 and 20% EGR. The soot produced under 0% EGR strictly followed an external burning mode with no evidence of internal burning. In contrast, soot generated under 20% EGR exhibited dual burning modes: slow external burning and rapid internal burning. The results demonstrate clearly that highly reactive soot can be achieved by manipulating the physical properties of the soot via EGR. (author)

  17. Gas-Phase Neutral Binary Oxide Clusters: Distribution, Structure, and Reactivity toward CO.

    PubMed

    Wang, Zhe-Chen; Yin, Shi; Bernstein, Elliot R

    2012-09-01

    Neutral binary (vanadium-cobalt) oxide clusters are generated and detected in the gas phase for the first time. Their reactivities toward carbon monoxide (CO) are studied both experimentally and theoretically. Experimental results suggest that neutral VCoO4 can react with CO to generate VCoO3 and CO2. Density functional theory studies show parallel results as well as provide detailed reaction mechanisms. PMID:26292125

  18. Reactive Gas Environment Induced Structural Modification of Noble-Transition Metal Alloy Nanoparticles

    NASA Astrophysics Data System (ADS)

    Petkov, V.; Yang, L.; Yin, J.; Loukrakpam, R.; Shan, S.; Wanjala, B.; Luo, J.; Chapman, K. W.; Zhong, C. J.

    2012-09-01

    Noble-transition metal (noble=Pt,Au; transition=Co,Ni,Cu) alloy particles with sizes of about 5 nm have been studied by in situ high-energy x-ray diffraction while subjected to oxidizing (O2) and reducing (H2) gas atmospheres at elevated temperatures. The different gas atmospheres do not affect substantially the random alloy, face-centered-cubic structure type of the particles but do affect the way the metal atoms pack together. In an O2 atmosphere, atoms get extra separated from each other, whereas, in an H2 atmosphere, they come closer together. The effect is substantial, amounting to 0.1 Å difference in the first neighbor atomic distances, and concurs with a dramatic change of the particle catalytic properties. It is argued that such reactive gas induced “expansion shrinking” is a common phenomenon that may be employed for the engineering of “smart” nanoparticles responding advantageously to envisaged gas environments.

  19. Numerical Modeling of Reactive Multiphase Flow for FCC and Hot Gas Desulfurization Circulating Fluidized Beds

    SciTech Connect

    2005-07-01

    This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFB riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.

  20. ENVIRONMENTAL REACTIVITY OF SOLID STATE HYDRIDE MATERIALS: MODELING AND TESTING FOR AIR AND WATER EXPOSURE

    SciTech Connect

    Anton, D.; James, C.; Cortes-Concepcion, J.; Tamburello, D.; Brinkman, K.; Gray, J.

    2010-05-18

    To make commercially acceptable condensed phase hydrogen storage systems, it is important to understand quantitatively the risks involved in using these materials. A rigorous set of environmental reactivity tests have been developed based on modified testing procedures codified by the United Nations for the transportation of dangerous goods. Potential hydrogen storage material, 2LiBH4{center_dot}MgH2 and NH3BH3, have been tested using these modified procedures to evaluate the relative risks of these materials coming in contact with the environment in hypothetical accident scenarios. It is apparent that an ignition event will only occur if both a flammable concentration of hydrogen and sufficient thermal energy were available to ignite the hydrogen gas mixture. In order to predict hydride behavior for hypothesized accident scenarios, an idealized finite element model was developed for dispersed hydride from a breached system. Empirical thermodynamic calculations based on precise calorimetric experiments were performed in order to quantify the energy and hydrogen release rates and to quantify the reaction products resulting from water and air exposure. Both thermal and compositional predictions were made with identification of potential ignition event scenarios.

  1. Interaction of coal-derived synthesis gas impurities with solid oxide fuel cell metallic components

    NASA Astrophysics Data System (ADS)

    Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.; Edwards, Danny J.; Chou, Yeong-Shyung; Cramer, Carolyn N.

    Oxidation-resistant alloys find use as interconnect materials, heat exchangers, and gas supply tubing in solid oxide fuel cell (SOFC) systems, especially when operated at temperatures below ∼800 °C. If fueled with synthesis gas derived from coal or biomass, such metallic components could be exposed to impurities contained in those fuel sources. In this study, coupons of ferritic stainless steels Crofer 22 APU and SS 441, austenitic nickel-chromium superalloy Inconel 600, and an alumina-forming high nickel alloy alumel were exposed to synthesis gas containing ≤2 ppm phosphorus, arsenic and antimony, and reaction products were tested. Crofer 22 APU coupons coated with a (Mn,Co) 3O 4 protective layer were also evaluated. Phosphorus was found to be the most reactive. On Crofer 22 APU, the (Mn,Cr) 3O 4 passivation layer reacted to form an Mn-P-O product, predicted to be manganese phosphate from thermochemical calculations, and Cr 2O 3. On SS 441, reaction of phosphorus with (Mn,Cr) 3O 4 led to the formation of manganese phosphate as well as an Fe-P product, predicted from thermochemical calculations to be Fe 3P. Minimal interactions with antimony or arsenic in synthesis gas were limited to Fe-Sb and Fe-As solid solution formation. Though not intended for use on the anode side, a (Mn,Co) 3O 4 spinel coating on Crofer 22 APU reacted with phosphorus in synthesis gas to produce products consistent with Mn 3(PO 4) 2 and Co 2P. A thin Cr 2O 3 passivation layer on Inconel 600 did not prevent the formation of nickel phosphides and arsenides and of iron phosphides and arsenides, though no reaction with Cr 2O 3 was apparent. On alumel, an Al 2O 3 passivation layer rich in Ni did not prevent the formation of nickel phosphides, arsenides, and antimonides, though no reaction with Al 2O 3 occurred. This work shows that unprotected metallic components of an SOFC stack and system can provide a sink for P, As and Sb impurities that may be present in fuel gases, and thus complicate

  2. Gaseous pollutants emitted from a mechanical biological treatment plant for municipal solid waste: odor assessment and photochemical reactivity.

    PubMed

    Fang, Jingjing; Zhang, Hua; Yang, Na; Shao, Liming; He, Pinjing

    2013-11-01

    The concentrations and chromatographic profiles of gaseous pollutants emitted from a municipal solid waste (MSW) biological treatment plant were investigated to identify the major odor substances and atmospheric photochemical reactive species (PRS). Four methods were used to measure different gaseous pollutants in this study, including colorimetric tubes, gas chromatography with mass spectrometry/flame ionization detection/pulsed flame photometric detection (GC-MS/FID/PFPD) preceded by cold trap concentration, GC-FID preceded by solid-phase microextraction (SPME), and high-performance liquid chromatography (HPLC) after derivation by 2,4-dinitrophenylhydrazine (DNPH). Seventy-five gaseous compounds belonging to nine groups (nitrogen compounds, sulfur compounds, alkanes, alkenes, aromatics, terpenes, alcohols, carbonyls, and volatile fatty acids [VFAs]) were identified. In the pre-biotreatment facility, the total concentration of the gaseous pollutants reached the maximum value on day 7 (317 ppm). During the post-biotreatment process, the total concentration of gaseous pollutants decreased from 331 ppm at the beginning to 162 ppm in the end. The group with the greatest decrease was carbonyls, from 64 to 7.4 ppm, followed by alcohols, from 40 to 4.5 ppm, which were both oxygenated compounds. The proportion of aromatics was notably high in the pre-mechanical treatment facility, accounting for 50.6% of the total, revealing the xenobiotic compounds disseminated by stirring and agitating the waste in the initial stage. The proportions of nitrogen compounds were lower in the pre- and post-mechanical treatment facilities (1.5% and 6.9%) than in the pre- and post-biotreatment facilities (11.9% and 13:8%), suggesting that their generation was closely associated with waste degradation. The major odor compounds in the facilities were acetic acid, butyric acid, valeric acid, isovaleric acid, and dimethyl sulfide. The major PRS in the facilities were aromatics, acetaldehyde

  3. Gas-solid alkali destruction of volatile chlorocarbons

    SciTech Connect

    Foropoulos, J. Jr.

    1995-12-01

    Many chlorocarbons are environmental dangers and health hazards. The simplest perchlorinated hydrocarbon, carbon tetrachloride, is near the top of the list of hazardous compounds. Carbon tetrachloride was used as a cleaning fluid, solvent, and fire-extinguishing agent. The nuclear and defense complexes also employed great quantities of carbon tetrachloride and other chlorocarbons as cleaning and degreasing agents. Many sites nationwide have underground chlorocarbon contamination plumes. Bulk chlorocarbon inventories at many locations await treatment and disposal. Often the problem is compounded by the chlorocarbon being radioactively contaminated. Waste inventory and groundwater contamination problems exist for many other chlorocarbons, especially methylene chloride, chloroform, and tri- and tetrachloroethylene. In this work solid soda lime (a fused mixture of approximately 95% CaO and 5% NaOH in a coarse, granulated form) at 350 C to 400 C acts as the hydrolyzing degradation, and off-gas scrubbing medium. Within soda lime CO{sub 2} and HCl from hydrolysis and degradation convert immediately to calcium and sodium chlorides and carbonates, with water vapor as a volatile byproduct.

  4. Surface emission of landfill gas from solid waste landfill

    NASA Astrophysics Data System (ADS)

    Park, Jin-Won; Shin, Ho-Chul

    The surface emission of landfill gas (LFG) was studied to estimate the amount of LFG efflux from solid waste landfills using an air flux chamber. LFG efflux increased as atmospheric temperature increased during the day, and the same pattern for the surface emission was observed for the change of seasons. LFG efflux rate decreased from summer through winter. The average LFG efflux rates of winter, spring and summer were 0.1584, 0.3013 and 0.8597 m 3 m -2 h -1 respectively. The total amount of surface emission was calculated based on the seasonal LFG efflux rate and the landfill surface area. From the estimates of LFG generation, it is expected that about 30% of the generated LFG may be released through the surface without extraction process. As forced extraction with a blower proceeded, the extraction well pressure decreased from 1100 to -100 mm H 2O, and the LFG surface efflux decreased markedly above 80%. Thus, the utilization of LFG by forced extraction would be the good solution for global warming and air pollution by LFG.

  5. A new continuous device to perform S-L-G photocatalytic studies. [Solid-Liquid-Gas

    SciTech Connect

    Aguado, M.A.; Gimenez, J.; Simarro, R.; Cervera-March, S. )

    1992-07-01

    A new experimental device to carry out solid-liquid-gas photocatalytic studies is presented. It can operate as a continuous system with respect to both the gas and the liquid phase. The solid photocatalyst is held inside the system and is continuously recycled through it to enable the separation of the spent liquid. Steady values of liquid and gas composition as well as temperature and fluidodynamic variables can be set and controlled.

  6. Formation of ordered gas-solid structures via solidification in metal-hydrogen systems

    SciTech Connect

    Shapovalov, V.I. |

    1998-12-31

    This work contains theoretical discussions concerning the large amount of previously published experimental data related to gas eutectic transformations in metal-hydrogen systems. Theories of pore nucleation and growth in these gas-solid materials will be presented and related to observed morphologies and structures. This work is intended to be helpful to theorists that work with metal-hydrogen systems, and experimentalists engaged in manufacturing technology development of these ordered gas-solid structures.

  7. Gas-Phase Reactivity of Protonated 2-, 3-, and 4-Dehydropyridine Radicals Toward Organic Reagents

    NASA Astrophysics Data System (ADS)

    Adeuya, Anthony; Price, Jason M.; Jankiewicz, Bartłomiej J.; Nash, John J.; Kenttämaa, Hilkka I.

    2009-11-01

    To explore the effects of the electronic nature of charged phenyl radicals on their reactivity, reactions of the three distonic isomers of n-dehydropyridinium cation (n = 2, 3, or 4) have been investigated in the gas phase by using Fourier-transform ion cyclotron resonance mass spectrometry. All three isomers react with cyclohexane, methanol, ethanol, and 1-pentanol exclusively via hydrogen atom abstraction and with allyl iodide mainly via iodine atom abstraction, with a reaction efficiency ordering of 2 > 3 > 4. The observed reactivity ordering correlates well with the calculated vertical electron affinities of the charged radicals (i.e., the higher the vertical electron affinity, the faster the reaction). Charged radicals 2 and 3 also react with tetrahydrofuran exclusively via hydrogen atom abstraction, but the reaction of 4 with tetrahydrofuran yields products arising from nonradical reactivity. The unusual reactivity of 4 is likely to result from the contribution of an ionized carbene-type resonance structure that facilitates nucleophilic addition to the most electrophilic carbon atom (C-4) in this charged radical. The influence of such a resonance structure on the reactivity of 2 is not obvious, and this may be due to stabilizing hydrogen-bonding interactions in the transition states for this molecule. Charged radicals 2 and 3 abstract a hydrogen atom from the substituent in both phenol and toluene, but 4 abstracts a hydrogen atom from the phenyl ring, a reaction that is unprecedented for phenyl radicals. Charged radical 4 reacts with tert-butyl isocyanide mainly by hydrogen cyanide (HCN) abstraction, whereas CN abstraction is the principal reaction for 2 and 3. The different reactivity observed for 4 (as compared to 2 and 3) is likely to result from different charge and spin distributions of the reaction intermediates for these charged radicals.

  8. Gas-phase reactivity of protonated 2-, 3-, and 4-dehydropyridine radicals toward organic reagents.

    PubMed

    Adeuya, Anthony; Price, Jason M; Jankiewicz, Bartłomiej J; Nash, John J; Kenttämaa, Hilkka I

    2009-12-10

    To explore the effects of the electronic nature of charged phenyl radicals on their reactivity, reactions of the three distonic isomers of n-dehydropyridinium cation (n = 2, 3, or 4) have been investigated in the gas phase by using Fourier-transform ion cyclotron resonance mass spectrometry. All three isomers react with cyclohexane, methanol, ethanol, and 1-pentanol exclusively via hydrogen atom abstraction and with allyl iodide mainly via iodine atom abstraction, with a reaction efficiency ordering of 2 > 3 > 4. The observed reactivity ordering correlates well with the calculated vertical electron affinities of the charged radicals (i.e., the higher the vertical electron affinity, the faster the reaction). Charged radicals 2 and 3 also react with tetrahydrofuran exclusively via hydrogen atom abstraction, but the reaction of 4 with tetrahydrofuran yields products arising from nonradical reactivity. The unusual reactivity of 4 is likely to result from the contribution of an ionized carbene-type resonance structure that facilitates nucleophilic addition to the most electrophilic carbon atom (C-4) in this charged radical. The influence of such a resonance structure on the reactivity of 2 is not obvious, and this may be due to stabilizing hydrogen-bonding interactions in the transition states for this molecule. Charged radicals 2 and 3 abstract a hydrogen atom from the substituent in both phenol and toluene, but 4 abstracts a hydrogen atom from the phenyl ring, a reaction that is unprecedented for phenyl radicals. Charged radical 4 reacts with tert-butyl isocyanide mainly by hydrogen cyanide (HCN) abstraction, whereas CN abstraction is the principal reaction for 2 and 3. The different reactivity observed for 4 (as compared to 2 and 3) is likely to result from different charge and spin distributions of the reaction intermediates for these charged radicals. PMID:19902945

  9. Reactivity worth of gas expansion modules (GEMs) in the fast flux test facility

    SciTech Connect

    Campbell, L.R.; Nelson, J.V.; Burke, T.M.; Rawlins, J.A.; Daughtry, J.W.; Bennett, R.A.

    1986-01-01

    A new passive shutdown device called a gas expansion module (GEM) has been developed at Hanford Engineering Development Laboratory to insert negative reactivity during a primary system loss of flow in a liquid-metal reactor (LMR). A GEM is a hollow removable core component which is sealed at the top and open at the bottom. An argon gas bubble trapped inside the assembly expands when core inlet pressure decreases (caused by a flow reduction) and expels sodium from the assembly. The GEMs are designed so that the level of the liquid-sodium primary system coolant within a GEM is above the top of the core when the primary pumps are operating at full flow and is below the bottom of the core when the primary pumps are off. When a GEM is placed at the boundary of the core and radial reflector, the drop in sodium level increases core neutron leakage and inserts negative reactivity. The results of these measurements confirm the effectiveness of GEMs in adding negative reactivity in loss-of-flow situations. It follows, therefore, that the inherent safety of LMRs, comparable in size to the FFTF, can be enhanced by the use of GEMs.

  10. Experimental design for reflection measurements of highly reactive liquid or solid substances with application to liquid sodium. [LMFBR

    SciTech Connect

    Chan, S.H.; Gossler, A.A.

    1980-06-30

    This technical report describes the experimental part of a program on thermal radiation properties of reactor materials. A versatile goniometer system with associated electronic components and mechanical instruments has been assembled. It is designed to measure spectral, specular reflectances of highly reactive liquid or solid substances over a spectral range of 0.3 ..mu.. to 9 ..mu.. and incidence angles of 12/sup 0/ to 30/sup 0/ off the normal direction. The capability of measuring reflectances of liquid substances clearly distinguishes this experimental design from conventional systems which are applicable only to solid substances. This design has been used to measure the spectral, specular reflectance of liquid sodium and preliminary results obtained are compared with those of solid sodium measured by other investigators.

  11. Tuning the Reactivity of a Cu/ZnO Nanocatalyst via Gas Phase Pressure

    NASA Astrophysics Data System (ADS)

    Martínez-Suárez, Luis; Frenzel, Johannes; Marx, Dominik; Meyer, Bernd

    2013-02-01

    By calculation of a thermodynamic phase diagram we provide an atomistic understanding of the morphological changes in ZnO-supported Cu nanocatalysts, which are subject to strong metal-support interactions, in response to the redox properties of the surrounding gas phase, i.e., depending on temperature and pressure. The reactivity, and thus the strong metal-support interactions, of this catalyst is traced back to a redox-state dependent occupation of delocalized ZnO substrate bands and localized Cu cluster states at the Fermi level. It is shown that at the conditions of industrial methanol synthesis complex electronic charge transfer processes across the metal-support interface, driven by morphological and electronic changes, explain the enhanced catalytic reactivity toward CO2.

  12. Tuning the reactivity of a Cu/ZnO nanocatalyst via gas phase pressure.

    PubMed

    Martínez-Suárez, Luis; Frenzel, Johannes; Marx, Dominik; Meyer, Bernd

    2013-02-22

    By calculation of a thermodynamic phase diagram we provide an atomistic understanding of the morphological changes in ZnO-supported Cu nanocatalysts, which are subject to strong metal-support interactions, in response to the redox properties of the surrounding gas phase, i.e., depending on temperature and pressure. The reactivity, and thus the strong metal-support interactions, of this catalyst is traced back to a redox-state dependent occupation of delocalized ZnO substrate bands and localized Cu cluster states at the Fermi level. It is shown that at the conditions of industrial methanol synthesis complex electronic charge transfer processes across the metal-support interface, driven by morphological and electronic changes, explain the enhanced catalytic reactivity toward CO(2). PMID:23473174

  13. Characteristics of M=0 Helicon Wave Plasmas in Reactive Gas Environment

    NASA Astrophysics Data System (ADS)

    Miyake, S.; Setsuhara, Y.; Sakawa, Y.; Shoji, T.

    1997-10-01

    Plasma production in various reactive gases are more important in the actual plasma processing of mateirals than those in rare gas environment. Characteristics of high density plasmas produced by the m=0 azimuthal mode helicon wave in reactive gases in a nonuniform magnetic field is studied experimentally. Loop antennas of several turns are wound on a quartz tube of 38mm diameter to excite the m=0 helicon wave with a 3kW rf oscillator of 13.56MHz. Plasma production is performed in various dissociative gases (H_2,N_2,O2 and/or CF_4) in the pressure range around 0.1Pa and the rf wave fields are measured to know the excitation of the helicon wave in these gases. The plasma density jump from the range of 10^11 cm-3 to 10^12-13 cm-3 is observed for each gas at a critical rf power, after which the excitation of helicon wave is verified to propagate. The optical emission measurements indicate an efficient dissociation of molecules after the density jump. As an example of application of this type of discharge, the DC discharge characteristics in N_2+Ar gas on the cylindrical carbon target set for the sputtering process in the down stream region is studied in correlation with the properties of the helicon wave plasmas.

  14. Model for high rate gas flows in deformable and reactive porous beds

    SciTech Connect

    Weston, A M

    1985-01-08

    This report presents the development of a one dimensional planar Lagrange hydrodynamic computer model which describes the processes preceding detonation. The model treats gas flow, deflagration, and compaction in a porous bed of reactive material. The early part of deflagration to detonation experiment with porous HMX is simulated. Sensitivity of the simulation calculation to ignition and burn rate parameters is illustrated and discussed. The effects of changing the mean particle size of the porous material are investigated. There is widespread interest in runaway reaction hazards that may be associated with porosity in propellant and explosive materials. Experimentally, such reactions are initiated and observed in long, thick walled hollow tubes, filled with a granular porous bed of reactive material. We will present comparisons with an experiment on porous HMX to illustrate details of the model and to point out what we believe are important features of the observed phenomenon. A geometric finite element cell is devised that allows gas to flow through a compacting matrix. The experimental simulation considers the DDT process from initial squib burn through the onset of general matrix deflagration (convective burning), to the development of a fully dense compaction wave. While this simulation did not calculate turnover to detonation, it did illustrate that the transition occurred as soon as the compaction wave became fully dense. It is shown that deflagration and gas permeation lags compaction at the time of transition. This suggests that the actual transition involves an additional compaction dependent process. 18 references, 20 figures, 3 tables.

  15. An effusive molecular beam technique for studies of polyatomic gas-surface reactivity and energy transfer

    NASA Astrophysics Data System (ADS)

    Cushing, G. W.; Navin, J. K.; Valadez, L.; Johánek, V.; Harrison, I.

    2011-04-01

    An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(Tg, Ts; ϑ), on metal surfaces for which the impinging gas temperature, Tg, and surface temperature, Ts, can be independently varied, along with the angle of incidence, ϑ, of the impinging gas. Effusive beam experiments with Tg = Ts = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ϑ), which when averaged over the cos (ϑ)/π angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(Tg, Ts; ϑ) measurements for which Tg ≠ Ts provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the Tg of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111).

  16. Laser studies of chemical dynamics at the gas-solid interface

    NASA Astrophysics Data System (ADS)

    Cavanagh, Richard R.; King, David S.

    The DOE funded research program Laser Studies of Chemical Dynamics at the Gas-Solid Interface has taken a detailed, microscopic view of molecules desorbed from surfaces in order to gain an understanding of energy flow and interaction potentials and how these control chemical reactivity at interfaces. Successful completion of these experiments required technical expertise both in surface science and laser-based molecular dynamics, a collaborative situation that exists in the NIST center for Atomic, Molecular and Optical Physics. During the three year period covered by this progress report, our goal was to use state-resolved techniques to examine a single chemisorption system in detail, and to observe how changes in the interaction potential or method of surface excitation are manifest in the desorption dynamics. The system chosen was NO/Pt(111). Studies were undertaken in which the effects on the NO-Pt interaction potential of coadsorbates--both weakly (CO) and strongly (NH(sub 3)) interacting-- could be examined. In addition, attempts were to be made to study non- equilibrium dynamics by using pulsed laser heating.

  17. The Scattering of Gas Atoms from Solid Surfaces

    ERIC Educational Resources Information Center

    Walton, Alan J.

    1977-01-01

    Traditional undergraduate courses in gas kinetic theory encourage the view that in all collisions between a gas atom and a surface, the angle of incidence of the gas atom equals its angle of reflection. This article illustrates and explains the incorrectness in assuming specular reflection and zero dwell time. (Author/MA)

  18. How Properties of Solid Surfaces Modulate the Nucleation of Gas Hydrate

    PubMed Central

    Bai, Dongsheng; Chen, Guangjin; Zhang, Xianren; Sum, Amadeu K.; Wang, Wenchuan

    2015-01-01

    Molecular dynamics simulations were performed for CO2 dissolved in water near silica surfaces to investigate how the hydrophilicity and crystallinity of solid surfaces modulate the local structure of adjacent molecules and the nucleation of CO2 hydrates. Our simulations reveal that the hydrophilicity of solid surfaces can change the local structure of water molecules and gas distribution near liquid-solid interfaces, and thus alter the mechanism and dynamics of gas hydrate nucleation. Interestingly, we find that hydrate nucleation tends to occur more easily on relatively less hydrophilic surfaces. Different from surface hydrophilicity, surface crystallinity shows a weak effect on the local structure of adjacent water molecules and on gas hydrate nucleation. At the initial stage of gas hydrate growth, however, the structuring of molecules induced by crystalline surfaces are more ordered than that induced by amorphous solid surfaces. PMID:26227239

  19. DETERMINATION OF CHLOROETHENES IN ENVIRONMENTAL BIOLOGICAL SAMPLES USING GAS CHROMATOGRAPHY COUPLED WITH SOLID PHASE MICRO EXTRACTION

    EPA Science Inventory

    An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase mi...

  20. GAS PHASE EXPOSURE HISTORY DERIVED FROM MATERIAL PHASE CONCENTRATION PROFILES USING SOLID PHASE MICRO-EXTRACTION

    EPA Science Inventory

    EPA Identifier: F8P31059
    Title: Gas Phase Exposure History Derived from Material Phase Concentration Profiles Using Solid Phase Micro-Extraction
    Fellow (Principal Investigator): Jonathan Lewis McKinney
    Institution: University of Missouri - ...

  1. THE IMPACT OF MUNICIPAL SOLID WASTE MANAGEMENT ON GREENHOUSE GAS EMISSIONS IN THE UNITED STATES

    EPA Science Inventory

    Technological advancements in United States (U.S.) municipal solid waste (MSW) disposal and a focus on the environmental advantages of integrated MSW management have greatly reduced the environmental impacts of MSW management, including greenhouse gas (GHG) emissions. This study ...

  2. Cluster Size Dependence of Etching by Reactive Gas Cluster Ion Beams

    SciTech Connect

    Toyoda, Noriaki; Yamada, Iaso

    2008-11-03

    Mass-selected reactive gas cluster ion beams (GCIB) were formed using a permanent magnetic filter. Irradiations of CO{sub 2} GCIB on amorphous carbon films and irradiations of SF{sub 6} and SF{sub 6}/Ar mixed GCIB on Si surfaces were performed to study the cluster size dependence on etching yields by reactive GCIB. The reactive sputtering yield of carbon by CO{sub 2} GCIB was almost ten times higher than that by Ar GCIB. In the case of (CO{sub 2}){sub 20000} GCIB with energy of 20 keV (1 eV/atom), it showed the high sputtering yield of 200 atoms/ion, however, there was little crater formation on the carbon surface. It is thought that very soft etching without crater formation would take place in this condition. In the case of SF{sub 6} GCIB on Si, the etching depth of Si showed maximum value when the fraction of SF{sub 6} to Ar was around 50%. As the etching yield was higher than pure SF{sub 6} GCIB, there was a strong ion assisted etching effects in the case of Ar/SF{sub 6} mixed cluster ion irradiations.

  3. Solid Phase Microextraction On-Fiber Derivatization Using a Stable, Portable, and Reusable Pentafluorophenyl Hydrazine Standard Gas Generating Vial.

    PubMed

    Poole, Justen J; Grandy, Jonathan J; Gómez-Ríos, German A; Gionfriddo, Emanuela; Pawliszyn, Janusz

    2016-07-01

    Solid phase microextraction (SPME) on-fiber derivatization methods have facilitated the achievement of lower detection limits and targeted analysis of various substances that exhibit poor chromatographic behavior, thermal instability, or high reactivity while limiting the use of organic solvents. However, previously developed on-fiber derivatization methods have been hindered by poor loading reproducibility and standard lifetime due to derivatization reagent reactivity. In addition, this reactivity often results in these reagents demonstrating toxic effects, complicating handling and standard formulation. To address this, a reusable standard gas generating vial containing pentafluorophenyl hydrazine (PFPH) has been developed. With this development, SPME fibers can now be reproducibly loaded with derivatization reagent, from an easy to use and safe platform. Validation of the vial using C4-C9 linear aldehyde standards as target analytes demonstrated intrabatch vial reproducibility (2% relative standard deviation (RSD), n = 4), along with PFPH headspace stability over a period of 11 weeks, facilitating reduced reagent consumption due to standard longevity. In addition, reproducibility of the derivatization reaction was observed over 1 week (RSD < 9%), and the linear concentration range was evaluated using headspace extractions from aqueous aldehyde solutions (R(2) > 0.996, 10-200 ppb v/v). Finally, the PFPH-generating vial was applied to the monitoring of volatile aldehydes generated during meat spoilage, as well as an on-site application where the free and total concentration of formaldehyde was determined in car exhaust using a portable GC/MS. To the best of our knowledge, the standard gas generating vial proposed in this work is the first documented device for the long-term storage of reusable headspace standards for a reactive, toxic, and otherwise unstable derivatization reagent standard. PMID:27292013

  4. Acoustic probe for solid-gas-liquid suspensions. 1998 annual progress report

    SciTech Connect

    Tavlarides, L.L.; Sangani, A.S.; Greenwood, M.S.

    1998-06-01

    'The proposed research will develop an acoustic probe for monitoring particle size and volume fraction in slurries in the absence and presence of gas. The goals are to commission and verify the probe components and system operation, develop theory for the forward and inverse problems for acoustic wave propagation through a three phase medium, and experimentally verify the theoretical analysis. The acoustic probe will permit measurement of solid content in gas-liquid-solid waste slurries in tanks across the DOE complex.'

  5. DEVELOPMENT OF LOW-DIFFUSION FLUX-SPLITTING METHODS FOR DENSE GAS-SOLID FLOWS

    EPA Science Inventory

    The development of a class of low-diffusion upwinding methods for computing dense gas-solid flows is presented in this work. An artificial compressibility/low-Mach preconditioning strategy is developed for a hyperbolic two-phase flow equation system consisting of separate solids ...

  6. Fundamental equations of a mixture of gas and small spherical solid particles from simple kinetic theory.

    NASA Technical Reports Server (NTRS)

    Pai, S. I.

    1973-01-01

    The fundamental equations of a mixture of a gas and pseudofluid of small spherical solid particles are derived from the Boltzmann equation of two-fluid theory. The distribution function of the gas molecules is defined in the same manner as in the ordinary kinetic theory of gases, but the distribution function for the solid particles is different from that of the gas molecules, because it is necessary to take into account the different size and physical properties of solid particles. In the proposed simple kinetic theory, two additional parameters are introduced: one is the radius of the spheres and the other is the instantaneous temperature of the solid particles in the distribution of the solid particles. The Boltzmann equation for each species of the mixture is formally written, and the transfer equations of these Boltzmann equations are derived and compared to the well-known fundamental equations of the mixture of a gas and small solid particles from continuum theory. The equations obtained reveal some insight into various terms in the fundamental equations. For instance, the partial pressure of the pseudofluid of solid particles is not negligible if the volume fraction of solid particles is not negligible as in the case of lunar ash flow.

  7. Clustering Instability in Sedimenting Gas-Solid Suspensions and its Influence on Flow Properties.

    NASA Astrophysics Data System (ADS)

    Li, Xiaoqi; Yin, Xiaolong; Liu, Guodong

    2015-11-01

    It is well known that sedimentation or fluidization of solid particles through gas is unstable. Instability is usually recognized as particle clusters when the solid fraction is low, or as void `bubbles' when the solid volume fraction is high. Using particle-resolved numerical simulations, we studied cluster formation in gas-solid systems with gas-to-solid density ratio being 0.01 and 0.001. The particles are uniformly sized spheres with a terminal Re of 30. The solid fraction is 0.25. Up to 4808 particles were used such that the clustering phenomena can be adequately examined. In periodic computational domains whose lateral dimension is about eight particle diameters, nucleated particle clusters quickly coalesce and grow into traveling waves that span the entire width of the domain. Consequently, gas-solid drag is significantly increased compared to that in a homogeneous liquid-solid suspension, the lateral velocity variance is suppressed, and the particle velocity distributions are strongly non-Gaussian. When lateral dimension is increased to about thirty particle diameters, particle clusters never turn into width-spanning traveling waves. As results, the drag is similar to that in a homogeneous suspension, the lateral velocity variance is strongly enhanced and the vertical variance reduced, and particle velocity distributions are nearly Gaussian. These results suggest that the effect of particle clusters should be examined in domains with large lateral dimensions.

  8. METHOD FOR VARIATION OF GRAIN SIZE IN STUDIES OF GAS-SOLID REACTIONS INVOLVING CAO

    EPA Science Inventory

    The paper describes a method for varying grain size in studies of gas-solid reactions involving CaO. (Note: Introducing grain size as an independent experimental variable should contribute to improved understanding of reactions in porous solids.) Calcining 1 micrometer CaCO3 part...

  9. Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities

    NASA Astrophysics Data System (ADS)

    Dunmore, R. E.; Hopkins, J. R.; Lidster, R. T.; Lee, J. D.; Evans, M. J.; Rickard, A. R.; Lewis, A. C.; Hamilton, J. F.

    2015-03-01

    Hydrocarbons are key precursors to two priority air pollutants, ozone and particulate matter. Those with two to seven carbons have historically been straightforward to observe and have been successfully reduced in many developed cities through air quality policy interventions. Longer chain hydrocarbons released from diesel vehicles are not considered explicitly as part of air quality strategies and there are few direct measurements of their gaseous abundance in the atmosphere. This study describes the chemically comprehensive and continuous measurements of organic compounds in a developed megacity (London), which demonstrate that on a seasonal median basis, diesel-related hydrocarbons represent only 20-30% of the total hydrocarbon mixing ratio but comprise more than 50% of the atmospheric hydrocarbon mass and are a dominant local source of secondary organic aerosols. This study shows for the first time that, 60% of the winter primary hydrocarbon hydroxyl radical reactivity is from diesel-related hydrocarbons and using the maximum incremental reactivity scale, we predict that they contribute up to 50% of the ozone production potential in London. Comparing real-world urban composition with regulatory emissions inventories in the UK and US highlights a previously unaccounted for but, very significant under-reporting of diesel related hydrocarbons; an underestimation of a factor ~ 4 for C9 species rising to a factor of over 70 for C12 during winter. These observations show that hydrocarbons from diesel vehicles can dominate gas phase reactive carbon in cities with high diesel fleet fractions. Future control of urban particulate matter and ozone in such locations requires a shift in policy focus onto gas phase hydrocarbons released from diesels as this vehicle type continues to displace gasoline world-wide.

  10. Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities

    NASA Astrophysics Data System (ADS)

    Dunmore, R. E.; Hopkins, J. R.; Lidster, R. T.; Lee, J. D.; Evans, M. J.; Rickard, A. R.; Lewis, A. C.; Hamilton, J. F.

    2015-09-01

    Hydrocarbons are key precursors to two priority air pollutants, ozone and particulate matter. Those with two to seven carbons have historically been straightforward to observe and have been successfully reduced in many developed cities through air quality policy interventions. Longer chain hydrocarbons released from diesel vehicles are not considered explicitly as part of air quality strategies and there are few direct measurements of their gaseous abundance in the atmosphere. This study describes the chemically comprehensive and continuous measurements of organic compounds in a developed megacity (London), which demonstrate that on a seasonal median basis, diesel-related hydrocarbons represent only 20-30 % of the total hydrocarbon mixing ratio but comprise more than 50 % of the atmospheric hydrocarbon mass and are a dominant local source of secondary organic aerosols. This study shows for the first time that 60 % of the winter primary hydrocarbon hydroxyl radical reactivity is from diesel-related hydrocarbons and using the maximum incremental reactivity scale, we predict that they contribute up to 50 % of the ozone production potential in London. Comparing real-world urban composition with regulatory emissions inventories in the UK and US highlights a previously unaccounted for, but very significant, under-reporting of diesel-related hydrocarbons; an underestimation of a factor ~4 for C9 species rising to a factor of over 70 for C12 during winter. These observations show that hydrocarbons from diesel vehicles can dominate gas phase reactive carbon in cities with high diesel fleet fractions. Future control of urban particulate matter and ozone in such locations requires a shift in policy focus onto gas phase hydrocarbons released from diesels as this vehicle type continues to displace gasoline world-wide.

  11. REACTIVATION OF SOLIDS FROM FURNACE INJECTION OF LIMESTONE FOR SO2 CONTROL

    EPA Science Inventory

    The paper gives results of a characterization of post-furnace injection solids and flyash mixtures and their testing in a bench-scale reactor for the removal of SO2. Virtually no SO2 removal was observed with untreated solids. High SO2 capture occurred when the samples were hydra...

  12. Estimating production and consumption of solid reactive Fe phases in marine sediments from concentration profiles

    EPA Science Inventory

    1D diffusion models may be used to estimate rates of production and consumption of dissolved metabolites in marine sediments, but are applied less often to the solid phase. Here we used a numerical inverse method to estimate solid phase Fe(III) and Fe(II) consumption and product...

  13. Rapid hydrogen gas generation using reactive thermal decomposition of uranium hydride.

    SciTech Connect

    Kanouff, Michael P.; Van Blarigan, Peter; Robinson, David B.; Shugard, Andrew D.; Gharagozloo, Patricia E.; Buffleben, George M.; James, Scott Carlton; Mills, Bernice E.

    2011-09-01

    Oxygen gas injection has been studied as one method for rapidly generating hydrogen gas from a uranium hydride storage system. Small scale reactors, 2.9 g UH{sub 3}, were used to study the process experimentally. Complimentary numerical simulations were used to better characterize and understand the strongly coupled chemical and thermal transport processes controlling hydrogen gas liberation. The results indicate that UH{sub 3} and O{sub 2} are sufficiently reactive to enable a well designed system to release gram quantities of hydrogen in {approx} 2 seconds over a broad temperature range. The major system-design challenge appears to be heat management. In addition to the oxidation tests, H/D isotope exchange experiments were performed. The rate limiting step in the overall gas-to-particle exchange process was found to be hydrogen diffusion in the {approx}0.5 {mu}m hydride particles. The experiments generated a set of high quality experimental data; from which effective intra-particle diffusion coefficients can be inferred.

  14. Photochemical gas lasers and hybrid (solid/gas) blue-green femtosecond systems

    NASA Astrophysics Data System (ADS)

    Mikheev, L. D.; Tcheremiskine, V. I.; Uteza, O. P.; Sentis, M. L.

    2012-01-01

    The review summarizes milestones and major breakthrough results obtained in the course of the development of a photochemical method applied to optical excitation of gas lasers on electronic molecular transitions by radiation from such unconventional pump sources as high-temperature electrical discharges and strong shock waves in gas. It also describes principles and techniques applied in hybrid (solid/gas) high-intensity laser systems emitting in the blue-green spectral region, and discusses wavelength scaling of laser-matter interaction by the example of laser wake-field acceleration (LWFA), high-order harmonic generation (HHG) and “water window” soft X-ray lasers. One of the most significant results of the photochemical method development consists in emerging broad bandwidth lasers (XeF(C-A), Xe2Cl, and Kr2F) operating in the blue-green spectral range, which have potential for amplification of ultra-short (down to 10 fs) optical pulses towards the Petawatt peak power level. The main goal of this review is to argue that the active media of these lasers may provide a basis for the development of fs systems generating super-intense ultrashort laser pulses in the visible spectral range. Some specific hybrid schemes, comprising solid state front-ends and photodissociation XeF(C-A) power boosting amplifiers, are described. They are now under development at the Lasers Plasmas and Photonic Processes (LP3) Laboratory (Marseille, France), the P.N. Lebedev Physical Institute (Moscow, Russia) and the Institute of High-Current Electronics (Tomsk, Russia) with the aim of conducting proof-of-principle experiments. Some consequences of the visible-wavelength laser field interaction with matter are also surveyed to demonstrate advantages of short driver wavelength in the considered examples. One of the most important consequences is the possibility of coherent soft X-ray generation within the “water window” spectral range with the use of short wavelength driver pulses to

  15. A new method for total OH reactivity measurements using a fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-05-01

    The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date direct measurements of total OH reactivity have been either performed using a Laser Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton Transfer Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photo-Ionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were equivalent to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical

  16. Total OH reactivity measurements using a new fast Gas Chromatographic Photo-Ionization Detector (GC-PID)

    NASA Astrophysics Data System (ADS)

    Nölscher, A. C.; Sinha, V.; Bockisch, S.; Klüpfel, T.; Williams, J.

    2012-12-01

    The primary and most important oxidant in the atmosphere is the hydroxyl radical (OH). Currently OH sinks, particularly gas phase reactions, are poorly constrained. One way to characterize the overall sink of OH is to measure directly the ambient loss rate of OH, the total OH reactivity. To date, direct measurements of total OH reactivity have been either performed using a Laser-Induced Fluorescence (LIF) system ("pump-and-probe" or "flow reactor") or the Comparative Reactivity Method (CRM) with a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS). Both techniques require large, complex and expensive detection systems. This study presents a feasibility assessment for CRM total OH reactivity measurements using a new detector, a Gas Chromatographic Photoionization Detector (GC-PID). Such a system is smaller, more portable, less power consuming and less expensive than other total OH reactivity measurement techniques. Total OH reactivity is measured by the CRM using a competitive reaction between a reagent (here pyrrole) with OH alone and in the presence of atmospheric reactive molecules. The new CRM method for total OH reactivity has been tested with parallel measurements of the GC-PID and the previously validated PTR-MS as detector for the reagent pyrrole during laboratory experiments, plant chamber and boreal field studies. Excellent agreement of both detectors was found when the GC-PID was operated under optimum conditions. Time resolution (60-70 s), sensitivity (LOD 3-6 s-1) and overall uncertainty (25% in optimum conditions) for total OH reactivity were similar to PTR-MS based total OH reactivity measurements. One drawback of the GC-PID system was the steady loss of sensitivity and accuracy during intensive measurements lasting several weeks, and a possible toluene interference. Generally, the GC-PID system has been shown to produce closely comparable results to the PTR-MS and thus in suitable environments (e.g. forests) it presents a viably economical

  17. Liquid and gas permeabilities of unsaturated municipal solid waste under compression

    NASA Astrophysics Data System (ADS)

    Stoltz, Guillaume; Gourc, Jean-Pierre; Oxarango, Laurent

    2010-10-01

    A novel set of experimental apparatus was designed and constructed to study the changes in the fluid-flow properties of municipal solid waste (MSW) related to the physical evolution of its structure under compression. The vertical liquid and gas permeabilities of MSW samples were measured in a laboratory-constructed cell termed an oedopermeameter. Another original device, a gas pycnometer, was employed to assess the volumetric gas content of the porous medium. Finally, the horizontal gas permeability of the compressed MSW sample was measured using another laboratory-constructed cell called a transmissivimeter. The results made it possible to characterise the intrinsic gas permeability as a function of porosity. Additionally, gas permeability measurements of samples with different liquid contents allowed the derivation of gas permeability correlations as functions of the physical parameters of the medium. A unique relationship was found between the gas permeability and the volumetric gas content.

  18. Ozone uptake on glassy, semi-solid and liquid organic matter and the role of reactive oxygen intermediates in atmospheric aerosol chemistry.

    PubMed

    Berkemeier, Thomas; Steimer, Sarah S; Krieger, Ulrich K; Peter, Thomas; Pöschl, Ulrich; Ammann, Markus; Shiraiwa, Manabu

    2016-05-14

    Heterogeneous and multiphase reactions of ozone are important pathways for chemical ageing of atmospheric organic aerosols. To demonstrate and quantify how moisture-induced phase changes can affect the gas uptake and chemical transformation of organic matter, we apply a kinetic multi-layer model to a comprehensive experimental data set of ozone uptake by shikimic acid. The bulk diffusion coefficients were determined to be 10(-12) cm(2) s(-1) for ozone and 10(-20) cm(2) s(-1) for shikimic acid under dry conditions, increasing by several orders of magnitude with increasing relative humidity (RH) due to phase changes from amorphous solid over semisolid to liquid. Consequently, the reactive uptake of ozone progresses through different kinetic regimes characterised by specific limiting processes and parameters. At high RH, ozone uptake is driven by reaction throughout the particle bulk; at low RH it is restricted to reaction near the particle surface and kinetically limited by slow diffusion and replenishment of unreacted organic molecules. Our results suggest that the chemical reaction mechanism involves long-lived reactive oxygen intermediates, likely primary ozonides or O atoms, which may provide a pathway for self-reaction and catalytic destruction of ozone at the surface. Slow diffusion and ozone destruction can effectively shield reactive organic molecules in the particle bulk from degradation. We discuss the potential non-orthogonality of kinetic parameters, and show how this problem can be solved by using comprehensive experimental data sets to constrain the kinetic model, providing mechanistic insights into the coupling of transport, phase changes, and chemical reactions of multiple species in complex systems. PMID:27095585

  19. Greenhouse gas emission from soil amended with biochar made from hydrothermally carbonizing swine solids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar made from hydrothermally carbonizing swine solids was mixed with a 50/50 mixture of Norfolk Ap and E horizon at a rate of 20 g/kg. During the incubation period of 54 days, greenhouse gas (CO2 and N2O) emission fluxes were calculated by nonlinearly regressing time-series headspace gas concent...

  20. Vapor-liquid-solid epitaxial growth of Si1-xGex alloy nanowires: Composition dependence on precursor reactivity and morphology control for vertical forests

    NASA Astrophysics Data System (ADS)

    Choi, S. G.; Manandhar, P.; Picraux, S. T.

    2015-07-01

    Growth of high-density group IV alloy nanowire forests is critical for exploiting their unique functionalities in many applications. Here, the compositional dependence on precursor reactivity and optimized conditions for vertical growth are studied for Si1-xGex alloy nanowires grown by the vapor-liquid-solid method. The nanowire composition versus gas partial-pressure ratio for germane-silane and germane-disilane precursor combinations is obtained at 350 °C over a wide composition range (0.05 ≤ x ≤ 0.98) and a generalized model to predict composition for alloy nanowires is developed based on the relative precursor partial pressures and reactivity ratio. In combination with germane, silane provides more precise compositional control at high Ge concentrations (x > 0.7), whereas disilane greatly increases the Si concentration for a given gas ratio and enables more precise alloy compositional control at small Ge concentrations (x < 0.3). Vertically oriented, non-kinking nanowire forest growth on Si (111) substrates is then discussed for silane/germane over a wide range of compositions, with temperature and precursor partial pressure optimized by monitoring the nanowire growth front using in-situ optical reflectance. For high Ge compositions (x ≈ 0.9), a "two-step" growth approach with nucleation at higher temperatures results in nanowires with high-density and uniform vertical orientation. With increasing Si content (x ≈ 0.8), the optimal growth window is shifted to higher temperatures, which minimizes nanowire kinking morphologies. For Si-rich Si1-xGex alloys (x ≈ 0.25), vertical nanowire growth is enhanced by single-step, higher-temperature growth at reduced pressures.

  1. Vapor-liquid-solid epitaxial growth of Si1-xGex alloy nanowires. Composition dependence on precursor reactivity and morphology control for vertical forests

    DOE PAGESBeta

    Choi, S. G.; Manandhar, P.; Picraux, S. T.

    2015-07-07

    The growth of high-density group IV alloy nanowire forests is critical for exploiting their unique functionalities in many applications. Here, the compositional dependence on precursor reactivity and optimized conditions for vertical growth are studied for Si1- x Ge x alloy nanowires grown by the vapor-liquid-solid method. The nanowire composition versus gas partial-pressure ratio for germane-silane and germane-disilane precursor combinations is obtained at 350°C over a wide composition range (0.05 ≤ x ≤ 0.98) and a generalized model to predict composition for alloy nanowires is developed based on the relative precursor partial pressures and reactivity ratio. In combination with germane, silanemore » provides more precise compositional control at high Ge concentrations (x > 0.7), whereas disilane greatly increases the Si concentration for a given gas ratio and enables more precise alloy compositional control at small Ge concentrations (x < 0.3). Vertically oriented, non-kinking nanowire forest growth on Si (111) substrates is then discussed for silane/germane over a wide range of compositions, with temperature and precursor partial pressure optimized by monitoring the nanowire growth front using in-situ optical reflectance. For high Ge compositions (x ≈ 0.9), a “two-step” growth approach with nucleation at higher temperatures results in nanowires with high-density and uniform vertical orientation. Furthermore, increasing Si content (x ≈ 0.8), the optimal growth window is shifted to higher temperatures, which minimizes nanowire kinking morphologies. For Si-rich Si1- x Ge x alloys (x ≈ 0.25), vertical nanowire growth is enhanced by single-step, higher-temperature growth at reduced pressures.« less

  2. Method and apparatus for the separation of a gas-solids mixture in a circulating fluidized bed reactor

    SciTech Connect

    Vimalchand, Pannalal; Liu, Guohai; Peng, WanWang

    2010-08-10

    The system of the present invention includes a centripetal cyclone for separating particulate material from a particulate laden gas solids stream. The cyclone includes a housing defining a conduit extending between an upstream inlet and a downstream outlet. In operation, when a particulate laden gas-solids stream passes through the upstream housing inlet, the particulate laden gas-solids stream is directed through the conduit and at least a portion of the solids in the particulate laden gas-solids stream are subjected to a centripetal force within the conduit.

  3. Rapid Carbonation for Calcite from a Solid-Liquid-Gas System with an Imidazolium-Based Ionic Liquid

    PubMed Central

    Ibrahim, Abdul-Rauf; Vuningoma, Jean Bosco; Huang, Yan; Wang, Hongtao; Li, Jun

    2014-01-01

    Aqueous carbonation of Ca(OH)2 is a complex process that produces calcite with scalenohedral calcite phases and characterized by inadequate carbonate species for effective carbonation due to the poor dissolution of CO2 in water. Consequently, we report a solid-liquid-gas carbonation system with an ionic liquid (IL), 1-butyl-3-methylimidazolium bromide, in view of enhancing the reaction of CO2 with Ca(OH)2. The use of the IL increased the solubility of CO2 in the aqueous environment and enhanced the transport of the reactive species (Ca2+ and CO32−) and products. The presence of the IL also avoided the formation of the CaCO3 protective and passivation layer and ensured high carbonation yields, as well as the production of stoichiometric rhombohedral calcite phases in a short time. PMID:24968273

  4. Suppression of Tritium Retention in Remote Areas of ITER by Nonperturbative Reactive Gas Injection

    SciTech Connect

    Tabares, F. L.; Ferreira, J. A.; Ramos, A.; Rooij, G. van; Westerhout, J.; Al, R.; Rapp, J.; Drenik, A.; Mozetic, M.

    2010-10-22

    A technique based on reactive gas injection in the afterglow region of the divertor plasma is proposed for the suppression of tritium-carbon codeposits in remote areas of ITER when operated with carbon-based divertor targets. Experiments in a divertor simulator plasma device indicate that a 4 nm/min deposition can be suppressed by addition of 1 Pa{center_dot}m{sup 3} s{sup -1} ammonia flow at 10 cm from the plasma. These results bolster the concept of nonperturbative scavenger injection for tritium inventory control in carbon-based fusion plasma devices, thus paving the way for ITER operation in the active phase under a carbon-dominated, plasma facing component background.

  5. Ionized gas (plasma) delivery of reactive oxygen species (ROS) into artificial cells

    NASA Astrophysics Data System (ADS)

    Hong, Sung-Ha; Szili, Endre J.; Jenkins, A. Toby A.; Short, Robert D.

    2014-09-01

    This study was designed to enhance our understanding of how reactive oxygen species (ROS), generated ex situ by ionized gas (plasma), can affect the regulation of signalling processes within cells. A model system, comprising of a suspension of phospholipid vesicles (cell mimics) encapsulating a ROS reporter, was developed to study the plasma delivery of ROS into cells. For the first time it was shown that plasma unequivocally delivers ROS into cells over a sustained period and without compromising cell membrane integrity. An important consideration in cell and biological assays is the presence of serum, which significantly reduced the transfer efficiency of ROS into the vesicles. These results are key to understanding how plasma treatments can be tailored for specific medical or biotechnology applications. Further, the phospholipid vesicle ROS reporter system may find use in other studies involving the application of free radicals in biology and medicine.

  6. Reactive gas plasma specimen processing for use in microanalysis and imaging in analytical electron microscopy

    SciTech Connect

    Zaluzec, N.J.; Kestel, B.J.; Henriks, D.

    1997-01-01

    It has long been the bane of analytical electron microscopy (AEM) that the use of focused probes during microanalysis of specimens increases the local rate of hydrocarbon contamination. This is most succinctly observed by the formation of contamination deposits during focused probe work typical of AEM studies. While serving to indicate the location of the electron probe, the contamination obliterates the area of the specimen being analyzed and adversely affects all quantitative microanalysis methodologies. A variety of methods including: UV, electron beam flooding, heating and/or cooling can decrease the rate of contamination, however, none of these methods directly attack the source of specimen borne contamination. Research has shown that reactive gas plasmas may be used to clean both the specimen and stage for AEM, in this study the authors report on quantitative measurements of the reduction in contamination rates in an AEM as a function of operating conditions and plasma gases.

  7. Structure and reactivity of benzoylnitrene radical anion in the gas phase.

    PubMed

    Wijeratne, Neloni R; Wenthold, Paul G

    2007-12-01

    The open-shell benzoylnitrene radical anion, readily generated by electron ionization of benzoylazide, undergoes unique chemical reactivity with radical reagents and Lewis acids in the gas phase. Reaction with nitric oxide, NO, proceeds by loss of N2 and formation of benzoate ion. This novel reaction is also observed to occur with phenylnitrene anion, forming phenoxide. Similar reactivity was observed in the reaction between benzoylnitrene radical anion and NO2, forming benzoate ion and nitrous oxide. Electronic structure calculations indicate that the reaction has a high-energy barrier that is overcome by the energy released by bond formation. Benzoylnitrene radical anion also transfers oxygen anion to NO and NO2 as well as to CS2 and SO2. In contrast, phenylnitrene anion reacts with carbon disulfide by C+ or CS+ abstraction, forming S- or S2-. Electronic structure calculations indicate that benzoylnitrene in the ground state resembles a slightly polarized benzoate anion, but with a free radical localized on the nitrogen. PMID:18001090

  8. Accommodative Behavior of Non-porous Molecular crystal at Solid-Gas and Solid-Liquid Interface

    PubMed Central

    Mande, Hemant M.; Ghalsasi, Prasanna S.

    2015-01-01

    Molecular crystals demonstrate drastically different behavior in solid and liquid state, mainly due to their difference in structural frameworks. Therefore, designing of unique structured molecular compound which can work at both these interfaces has been a challenge. Here, we present remarkable ‘molecular’ property by non-porous molecular solid crystal, dinuclear copper complex (C6H5CH(X)NH2)2CuCl2, to reversibly ‘adsorb’ HCl gas at solid-gas interface as well as ‘accommodate’ azide anion at solid-liquid interface with crystal to crystal transformation. The latter process is driven by molecular recognition, self-assembly, and anchimeric assistance. The observed transformations are feasible due to breathing of inner and outer coordination sphere around metal center resulting in change in metal polyhedra for ‘accommodating’ guest molecule. These transformations cause changes in optical, magnetic, and/or ferroelectric property offering diversity in ‘sensing’ application. With the proposed underlying principles in these exceptional reversible and cyclic transformations, we prepared a series of compounds, can facilitate designing of novel multifunctional molecular materials. PMID:26411980

  9. Silicon oxynitride thin films synthesised by the reactive gas pulsing process using rectangular pulses

    NASA Astrophysics Data System (ADS)

    Aubry, E.; Weber, S.; Billard, A.; Martin, N.

    2011-09-01

    Silicon oxynitride thin films were synthesised by the reactive gas pulsing process using an argon, oxygen and nitrogen gas mixture from a semiconductor Si target. Argon and nitrogen were introduced at a constant mass flow rate, whereas oxygen gas was periodically supplied using a rectangular pulsed flow rate. The O2 injection time TON (or duty cycle α) was the only varied parameter. The influences of this parameter on the discharge behaviour, on the Si target voltage, and on the resulting chemical composition of the films were investigated. The temporal evolution of the total pressure exhibits exponential shape differing from the rectangular oxygen pulse shape, due to the response time of the gas flowmeter and to the progressive oxidation of the target and the chamber walls. During the TON time, the preferential adsorption of the introduced O2 induces a decay in Si target voltage. Reversion to the nitrided mode is still possible as soon as the O2 injection is stopped. The elemental analyses assessed by secondary neutral mass spectrometry (SNMS) showed that the O/N ratio within silicon oxynitride films linearly depends on the TON time. Increasing the duty cycle α over a certain value results in an oxidised steady state formation during the TON time. This formation was observed by real time measurements of the emission lines ratio I(O*)/I(Ar*) indicative of the O2 partial pressure and confirmed by the time derivative of the target voltage. During the TOFF time, the alternation with the nitrided mode becomes impossible, leading to the specific synthesis of stoichiometric SiO2 films.

  10. Assessment of alternative disposal methods to reduce greenhouse gas emissions from municipal solid waste in India.

    PubMed

    Yedla, Sudhakar; Sindhu, N T

    2016-06-01

    Open dumping, the most commonly practiced method of solid waste disposal in Indian cities, creates serious environment and economic challenges, and also contributes significantly to greenhouse gas emissions. The present article attempts to analyse and identify economically effective ways to reduce greenhouse gas emissions from municipal solid waste. The article looks at the selection of appropriate methods for the control of methane emissions. Multivariate functional models are presented, based on theoretical considerations as well as the field measurements to forecast the greenhouse gas mitigation potential for all the methodologies under consideration. Economic feasibility is tested by calculating the unit cost of waste disposal for the respective disposal process. The purpose-built landfill system proposed by Yedla and Parikh has shown promise in controlling greenhouse gas and saving land. However, these studies show that aerobic composting offers the optimal method, both in terms of controlling greenhouse gas emissions and reducing costs, mainly by requiring less land than other methods. PMID:27118738

  11. Defect-related relaxation processes in irradiated rare gas solids

    NASA Astrophysics Data System (ADS)

    Savchenko, E. V.; Grigorashchenko, O. N.; Gumenchuk, G. B.; Ogurtsov, A. N.; Frankowski, M.; Smith-Gicklhorn, A. M.; Bondybey, V. E.

    Electronic and atomic relaxation processes in preirradiated solid Ar doped with N-2 were studied with a focus on the role of radiative electronic transitions in relaxation cascades. Combining methods of activation spectroscopy - thermally stimulated and photon-stimulated exoelectron emission, a new channel of relaxation induced by photon emission from metastable N atoms was detected. It was shown that in insulating materials with a wide conduction band photons of visible range can release electrons from both kinds of traps - shallow (lattice defects) and deep thermally disconnected ones. Correlation in the charge recombination reaction yield and the yield of low temperature desorption - important relaxation channel in a preirradiated solid - clearly demonstrates interconnection between atomic and electronic processes of relaxation.

  12. Production of amylases from rice by solid-state fermentation in a gas-solid spouted-Bed bioreactor

    PubMed

    Silva; Yang

    1998-07-01

    A gas-solid spouted-bed bioreactor was developed to produce amylases from rice in solid-state fermentation by Aspergillus oryzae. The spouted-bed bioreactor was developed to overcome many of the problems inherent to large-scale solid-state fermentation, including mass- and heat-transfer limitations in the conventional tray reactors and solids-handling difficulties seen in packed-bed bioreactors. The solid-state fermentation results from the tray-type reactor with surface aeration were poor because of mass- and heat-transfer problems. A packed-bed bioreactor with continuous aeration through the rice bed produced high protein and enzymes, but the fermented rice was difficult to remove and process due to the formation of large chunks of rice aggregates knitted together with fungal mycelia. Also, the fermentation was not uniform in the packed bed. The spouted-bed bioreactor with intermittent spouting with air achieved high production levels in both total protein and enzymes (alpha-amylase, beta-amylase, and glucoamylase) that were comparable to those found in the packed-bed bioreactor, but without the nonuniformity and solids-handling problems. However, continual spouting was found to be detrimental to this solid-state fermentation, possibly because of shear or impact damage to fungal mycelia during spouting. Increasing spouting frequency from 4-h intervals to 1-h intervals decreased protein and enzyme production. Other operating conditions critical to the fermentation include proper humidification to prevent drying of the substrate and control of reactor wall temperature to prevent excessive condensation, which would interfere with proper spouting. PMID:9694679

  13. Gas-phase structure and reactivity of the keto tautomer of the deoxyguanosine radical cation.

    PubMed

    Feketeová, Linda; Chan, Bun; Khairallah, George N; Steinmetz, Vincent; Maître, Philippe; Radom, Leo; O'Hair, Richard A J

    2015-10-21

    Guanine radical cations are formed upon oxidation of DNA. Deoxyguanosine (dG) is used as a model, and the gas-phase infrared (IR) spectroscopic signature and gas-phase unimolecular and bimolecular chemistry of its radical cation, dG˙(+), A, which is formed via direct electrospray ionisation (ESI/MS) of a methanolic solution of Cu(NO3)2 and dG, are examined. Quantum chemistry calculations have been carried out on 28 isomers and comparisons between their calculated IR spectra and the experimentally-measured spectra suggest that A exists as the ground-state keto tautomer. Collision-induced dissociation (CID) of A proceeds via cleavage of the glycosidic bond, while its ion–molecule reactions with amine bases occur via a number of pathways including hydrogen-atom abstraction, proton transfer and adduct formation. A hidden channel, involving isomerisation of the radical cation via adduct formation, is revealed through the use of two stages of CID, with the final stage of CID showing the loss of CH2O as a major fragmentation pathway from the reformed radical cation, dG˙(+). Quantum chemistry calculations on the unimolecular and bimolecular reactivity are also consistent with A being present as a ground-state keto tautomer. PMID:25942055

  14. Variation of the reactivity of solids near the interface reagent-product of the topochemical reaction

    NASA Astrophysics Data System (ADS)

    Boldyrev, V. V.; Lomovsky, O. I.; Zaikova, T. O.; Gavrilov, E. F.

    1984-01-01

    During the topochemical decomposition of ammonium perchlorate and copper hypophosphite an enhanced acid concentration occurs near the reagent-product interface. Concentration profiles of the acid were observed after the treatment of the partially decomposed crystals by indicator solution and by microphotometry. Profiles exhibit the diffusive characteristics. The diffusion coefficient is 10 -10 cm 2/sec for ammonium perchlorate and 10 -9 cm 2/sec for copper hypophosphite at 20°C. It is concluded that the variation of the reactivity near the interface is due to the enhanced acid concentration.

  15. Fault reactivation and seismicity risk from CO2 sequestration in the Chinshui gas field, NW Taiwan

    NASA Astrophysics Data System (ADS)

    Sung, Chia-Yu; Hung, Jih-Hao

    2015-04-01

    The Chinshui gas field located in the fold-thrust belt of western Taiwan was a depleted reservoir. Recently, CO2 sequestration has been planned at shallower depths of this structure. CO2 injection into reservoir will generate high fluid pressure and trigger slip on reservoir-bounding faults. We present detailed in-situ stresses from deep wells in the Chinshui gas field and evaluated the risk of fault reactivation for underground CO2 injection. The magnitudes of vertical stress (Sv), formation pore pressure (Pf) and minimum horizontal stress (Shmin) were obtained from formation density logs, repeat formation tests, sonic logs, mud weight, and hydraulic fracturing including leak-off tests and hydraulic fracturing. The magnitude of maximum horizontal stress (SHmax) was constrained by frictional limit of critically stressed faults. Results show that vertical stress gradient is about 23.02 MPa/km (1.02 psi/ft), and minimum horizontal stress gradient is 18.05 MPa/km (0.80 psi/ft). Formation pore pressures were hydrostatic at depths 2 km, and increase with a gradient of 16.62 MPa/km (0.73 psi/ft). The ratio of fluid pressure and overburden pressure (λp) is 0.65. The upper bound of maximum horizontal stress constrained by strike-slip fault stress regime (SHmax>Sv>Shmin) and coefficient of friction (μ=0.6) is about 18.55 MPa/km (0.82 psi/ft). The orientation of maximum horizontal stresses was calculated from four-arm caliper tools through the methodology suggested by World Stress Map (WMS). The mean azimuth of preferred orientation of borehole breakouts are in ~65。N. Consequently, the maximum horizontal stress axis trends in 155。N and sub-parallel to the far-field plate-convergence direction. Geomechanical analyses of the reactivation of pre-existing faults was assessed using 3DStress and Traptester software. Under current in-situ stress, the middle block fault has higher slip tendency, but still less than frictional coefficient of 0.6 a common threshold value for

  16. Fictitious domain method for fully resolved reacting gas-solid flow simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Longhui; Liu, Kai; You, Changfu

    2015-10-01

    Fully resolved simulation (FRS) for gas-solid multiphase flow considers solid objects as finite sized regions in flow fields and their behaviours are predicted by solving equations in both fluid and solid regions directly. Fixed mesh numerical methods, such as fictitious domain method, are preferred in solving FRS problems and have been widely researched. However, for reacting gas-solid flows no suitable fictitious domain numerical method has been developed. This work presents a new fictitious domain finite element method for FRS of reacting particulate flows. Low Mach number reacting flow governing equations are solved sequentially on a regular background mesh. Particles are immersed in the mesh and driven by their surface forces and torques integrated on immersed interfaces. Additional treatments on energy and surface reactions are developed. Several numerical test cases validated the method and a burning carbon particles array falling simulation proved the capability for solving moving reacting particle cluster problems.

  17. Evaluation of wall boundary condition parameters for gas-solids fluidized bed simulations

    SciTech Connect

    Li, Tingwen; Benyahia, Sofiane

    2013-10-01

    Wall boundary conditions for the solids phase have significant effects on numerical predictions of various gas-solids fluidized beds. Several models for the granular flow wall boundary condition are available in the open literature for numerical modeling of gas-solids flow. In this study, a model for specularity coefficient used in Johnson and Jackson boundary conditions by Li and Benyahia (AIChE Journal, 2012, 58, 2058-2068) is implemented in the open-source CFD code-MFIX. The variable specularity coefficient model provides a physical way to calculate the specularity coefficient needed by the partial-slip boundary conditions for the solids phase. Through a series of 2-D numerical simulations of bubbling fluidized bed and circulating fluidized bed riser, the model predicts qualitatively consistent trends to the previous studies. Furthermore, a quantitative comparison is conducted between numerical results of variable and constant specularity coefficients to investigate the effect of spatial and temporal variations in specularity coefficient.

  18. Aqueous extractive upgrading of bio-oils created by tail-gas reactive pyrolysis to produce pure hydrocarbons and phenols

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tail-gas reactive pyrolysis (TGRP) of biomass produces bio-oil that is lower in oxygen (~15 wt% total) and significantly more hydrocarbon-rich than traditional bio-oils or even catalytic fast pyrolysis. TGRP bio-oils lend themselves toward mild and inexpensive upgrading procedures. We isolated oxyge...

  19. Distillation and isolation of commodity chemicals from Bio-oil made by tail-gas reactive prolysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Owing to instabilities, very little has been accomplished with regards to simple cost-effective separations of fast-pyrolysis bio-oil. However, recent developments in the use of tail-gas reactive pyrolysis (TGRP) (Mullen and Boateng 2013) provide higher quality bio-oils that are thermally stable. We...

  20. Solid State Structure-Reactivity Studies on Bixbyites, Fluorites and Perovskites Belonging to the Vanadate, Titanate and Cerate Families

    NASA Astrophysics Data System (ADS)

    Shafi, Shahid P.

    This thesis primarily focuses on the systematic understanding of structure-reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in-situ techniques including powder x-ray diffraction and thermogravimetric-differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure-reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite-type oxide ion conductor Ce1-xInxO2-delta (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO 3-delta perovskites and the subsequent CO2-capture reaction

  1. Vapor-liquid-solid growth of GaN nanowires by reactive sputtering of GaAs

    NASA Astrophysics Data System (ADS)

    Mohanta, P.; Chaturvedi, P.; Major, S. S.; Srinivasa, R. S.

    2013-02-01

    Uniformly distributed nanosized Au-Ga alloy particles were formed on ultrathin Au coated quartz substrate by sputtering of GaAs with argon at 700 °C. Subsequent deposition of GaN by reactive sputtering of GaAs in 100 % nitrogen results in the growth of GaN nanowires. X-ray diffraction analysis confirmed the formation of hexagonal GaN. Field emission gun scanning electron microscopy studies show that the nanowires are of average length 400±50 nm and average diameter 40±5 nm. The presence of spherical Au-Ga nanoparticles of diameter ˜ 50 nm at the top of the nanowires suggests that the growth takes place by vapor-liquid-solid mechanism.

  2. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    SciTech Connect

    Thies, C.; Geddis, A.M.; Guzman, A.G.

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1{degrees}C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm{sup 3} with less than 1% error.

  3. Pulsed flashover of solid dielectric materials in compressed gas environment

    SciTech Connect

    Tewari, Somesh Vinayak E-mail: svtewari@barc.gov.in; Sharma, Archana; Mittal, K. C.

    2015-06-24

    An experimental investigation of surface flashover characteristics of PMMA and POM is studied in compressed nitrogen gas environment with nitrogen as the background gas. The operating pressure range is from 1kg/cm{sup 2} to 4kg/cm{sup 2}. It is observed that the breakdown voltage of PMMA is higher than POM owing to a higher permittivity mismatch between POM- nitrogen interface as compared to the PMMA- nitrogen interface. The reduction in spacer efficiency with pressure for PMMA is 11% as compared to POM which shows a higher reduction of 18%. This paper further emphasizes on the role of energy level and density of charge carrier trapping centers for a reduced breakdown voltage in POM as compared to PMMA.

  4. Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas

    NASA Astrophysics Data System (ADS)

    Nordmark, H.; Nagayoshi, H.; Matsumoto, N.; Nishimura, S.; Terashima, K.; Marioara, C. D.; Walmsley, J. C.; Holmestad, R.; Ulyashin, A.

    2009-02-01

    Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi2 particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H2 flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi2 particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiHx species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi2 particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi2 particles on their tips as well as sometimes being incorporated into their structure.

  5. Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas

    SciTech Connect

    Nordmark, H.; Holmestad, R.; Nagayoshi, H.; Matsumoto, N.; Nishimura, S.; Terashima, K.; Marioara, C. D.; Walmsley, J. C.; Ulyashin, A.

    2009-02-15

    Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi{sub 2} particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H{sub 2} flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi{sub 2} particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiH{sub x} species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi{sub 2} particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi{sub 2} particles on their tips as well as sometimes being incorporated into their structure.

  6. Flow Mapping in a Gas-Solid Riser via Computer Automated Radioactive Particle Tracking (CARPT)

    SciTech Connect

    Muthanna Al-Dahhan; Milorad P. Dudukovic; Satish Bhusarapu; Timothy J. O'hern; Steven Trujillo; Michael R. Prairie

    2005-06-04

    Statement of the Problem: Developing and disseminating a general and experimentally validated model for turbulent multiphase fluid dynamics suitable for engineering design purposes in industrial scale applications of riser reactors and pneumatic conveying, require collecting reliable data on solids trajectories, velocities ? averaged and instantaneous, solids holdup distribution and solids fluxes in the riser as a function of operating conditions. Such data are currently not available on the same system. Multiphase Fluid Dynamics Research Consortium (MFDRC) was established to address these issues on a chosen example of circulating fluidized bed (CFB) reactor, which is widely used in petroleum and chemical industry including coal combustion. This project addresses the problem of lacking reliable data to advance CFB technology. Project Objectives: The objective of this project is to advance the understanding of the solids flow pattern and mixing in a well-developed flow region of a gas-solid riser, operated at different gas flow rates and solids loading using the state-of-the-art non-intrusive measurements. This work creates an insight and reliable database for local solids fluid-dynamic quantities in a pilot-plant scale CFB, which can then be used to validate/develop phenomenological models for the riser. This study also attempts to provide benchmark data for validation of Computational Fluid Dynamic (CFD) codes and their current closures. Technical Approach: Non-Invasive Computer Automated Radioactive Particle Tracking (CARPT) technique provides complete Eulerian solids flow field (time average velocity map and various turbulence parameters such as the Reynolds stresses, turbulent kinetic energy, and eddy diffusivities). It also gives directly the Lagrangian information of solids flow and yields the true solids residence time distribution (RTD). Another radiation based technique, Computed Tomography (CT) yields detailed time averaged local holdup profiles at

  7. Prediction of Ablation Rates from Solid Surfaces Exposed to High Temperature Gas Flow

    NASA Technical Reports Server (NTRS)

    Akyuzlu, Kazim M.; Coote, David

    2013-01-01

    A mathematical model and a solution algorithm is developed to study the physics of high temperature heat transfer and material ablation and identify the problems associated with the flow of hydrogen gas at very high temperatures and velocities through pipes and various components of Nuclear Thermal Rocket (NTR) motors. Ablation and melting can be experienced when the inner solid surface of the cooling channels and the diverging-converging nozzle of a Nuclear Thermal Rocket (NTR) motor is exposed to hydrogen gas flow at temperatures around 2500 degrees Kelvin and pressures around 3.4 MPa. In the experiments conducted on typical NTR motors developed in 1960s, degradation of the cooling channel material (cracking in the nuclear fuel element cladding) and in some instances melting of the core was observed. This paper presents the results of a preliminary study based on two types of physics based mathematical models that were developed to simulate the thermal-hydrodynamic conditions that lead to ablation of the solid surface of a stainless steel pipe exposed to high temperature hydrogen gas near sonic velocities. One of the proposed models is one-dimensional and assumes the gas flow to be unsteady, compressible and viscous. An in-house computer code was developed to solve the conservations equations of this model using a second-order accurate finite-difference technique. The second model assumes the flow to be three-dimensional, unsteady, compressible and viscous. A commercial CFD code (Fluent) was used to solve the later model equations. Both models assume the thermodynamic and transport properties of the hydrogen gas to be temperature dependent. In the solution algorithm developed for this study, the unsteady temperature of the pipe is determined from the heat equation for the solid. The solid-gas interface temperature is determined from an energy balance at the interface which includes heat transfer from or to the interface by conduction, convection, radiation, and

  8. Strategy for understanding gas-solid riser hydrodynamics and other LANL status items

    SciTech Connect

    Kashiwa, B. A.

    2002-01-01

    The talk presents the status of work in progress in the area of momentum transport theory in turbulent gas-solid multiphase flow. Previous installments have reported details of the theory, and validation results. This talk provides a grand overview of how the details of dynamic simulations in 3D, 2D, 1D and 0D, all fit together to form a consistent strategy for understanding gas-solid riser hydrodynamics. The circulating fluidized bed is the canonical example for showing how the strategy works. Performance of the procedure is shown by comparison to data recently obtained by Sandia National Laboratory. Status of other LANL efforts is also mentioned.

  9. Sequestration of flue gas CO₂ by direct gas-solid carbonation of air pollution control system residues.

    PubMed

    Tian, Sicong; Jiang, Jianguo

    2012-12-18

    Direct gas-solid carbonation reactions of residues from an air pollution control system (APCr) were conducted using different combinations of simulated flue gas to study the impact on CO₂ sequestration. X-ray diffraction analysis of APCr determined the existence of CaClOH, whose maximum theoretical CO₂ sequestration potential of 58.13 g CO₂/kg APCr was calculated by the reference intensity ratio method. The reaction mechanism obeyed a model of a fast kinetics-controlled process followed by a slow product layer diffusion-controlled process. Temperature is the key factor in direct gas-solid carbonation and had a notable influence on both the carbonation conversion and the CO₂ sequestration rate. The optimal CO₂ sequestrating temperature of 395 °C was easily obtained for APCr using a continuous heating experiment. CO₂ content in the flue gas had a definite influence on the CO₂ sequestration rate of the kinetics-controlled process, but almost no influence on the final carbonation conversion. Typical concentrations of SO₂ in the flue gas could not only accelerate the carbonation reaction rate of the product layer diffusion-controlled process, but also could improve the final carbonation conversion. Maximum carbonation conversions of between 68.6% and 77.1% were achieved in a typical flue gas. Features of rapid CO₂ sequestration rate, strong impurities resistance, and high capture conversion for direct gas-solid carbonation were proved in this study, which presents a theoretical foundation for the applied use of this encouraging technology on carbon capture and storage. PMID:23181908

  10. High-Resolution Simulations of Gas-Solids Jet Penetration Into a High Density Riser Flow

    SciTech Connect

    Li, Tingwen

    2011-05-01

    High-resolution simulations of a gas-solids jet in a 0.3 m diameter and 15.9 m tall circulating fluidized bed (CFB) riser were conducted with the open source software-MFIX. In the numerical simulations, both gas and solids injected through a 1.6 cm diameter radial-directed tube 4.3 m above the bottom distributor were tracked as tracers, which enable the analysis of the characteristics of a two-phase jet. Two jetting gas velocities of 16.6 and 37.2 m/s were studied with the other operating conditions fixed. Reasonable flow hydrodynamics with respect to overall pressure drop, voidage, and solids velocity distributions were predicted. Due to the different dynamic responses of gas and particles to the crossflow, a significant separation of gas and solids within the jet region was predicted for both cases. In addition, the jet characteristics based on tracer concentration and tracer mass fraction profiles at different downstream levels are discussed. Overall, the numerical predictions compare favorably to the experimental measurements made at NETL.

  11. Characterization of the specific solid-water interfacial area-water saturation relationship and its import to reactive transport

    SciTech Connect

    Saripalli, Kanaka P.; Freedman, Vicky L.; McGrail, B. Peter; Meyer, Philip D.

    2006-05-01

    A modified rate equation for the dissolution of minerals in the unsaturated zone was proposed using a solid-water interfacial area (asw) varying as a function of water saturation (Sw). Vadose zone phenomena, such as infiltration, were discussed as example scenarios where such re-formulation may be useful. A constitutive relationship for the asw - Sw was derived, and used to formulate an approximate model of the proposed rate equation. Implementation of this new model in the reactive transport code CRUNCH was used to evaluate the influence of a changing asw on reactive transport behavior of silica in the vadose zone. These simulations clearly demonstrate that a changing asw can have a significant impact on the silica distribution profiles in the vadose zone. This is to be expected because changes in asw are substantial in the dry Sw range, whereas they are only moderate in the relatively wet region. These findings have significant implications for contaminant transport in the vadose zone, especially in arid regions. Ignoring the effect of a changing asw is likely to result in an overestimation of the net contaminant fluxes in these cases, which leads to highly conservative risk assessments. In case of nutrient flux calculations coupled with dissolution phenomena, it may lead to an overestimation of nutrient availability. Additional theoretical and experimental verification of the proposed models would be valuable.

  12. Structured grid generation using a CAD solid model for an aero-gas turbine combustion system

    SciTech Connect

    Eccles, N.C.; Manners, A.P.

    1996-12-31

    An aero-gas turbine combustion system was used to demonstrate the problems of creating a single block structured grid suitable for CFD predictions from a designer`s parametric solid model. The solid model had to be filtered of sub-grid detail and computational fluid volumes generated from the solid model of the metal. Alternative methods of transferring the geometry from the CAD package to the grid generator were considered. The type and method of grid generation was found to influence all stages in manipulating the geometry.

  13. Formation of the Giant Planets by Concurrent Accretion of Solids and Gas

    NASA Technical Reports Server (NTRS)

    Hubickyj, Olenka

    1997-01-01

    Models were developed to simulate planet formation. Three major phases are characterized in the simulations: (1) planetesimal accretion rate, which dominates that of gas, rapidly increases owing to runaway accretion, then decreases as the planet's feeding zone is depleted; (2) occurs when both solid and gas accretion rates are small and nearly independent of time; and (3) starts when the solid and gas masses are about equal and is marked by runaway gas accretion. The models applicability to planets in our Solar System are judged using two basic "yardsticks". The results suggest that the solar nebula dissipated while Uranus and Neptune were in the second phase, during which, for a relatively long time, the masses of their gaseous envelopes were small but not negligible compared to the total masses. Background information, results and a published article are included in the report.

  14. Modeling of Interior Ballistic Gas-Solid Flow Using a Coupled Computational Fluid Dynamics-Discrete Element Method.

    PubMed

    Cheng, Cheng; Zhang, Xiaobing

    2013-05-01

    In conventional models for two-phase reactive flow of interior ballistic, the dynamic collision phenomenon of particles is neglected or empirically simplified. However, the particle collision between particles may play an important role in dilute two-phase flow because the distribution of particles is extremely nonuniform. The collision force may be one of the key factors to influence the particle movement. This paper presents the CFD-DEM approach for simulation of interior ballistic two-phase flow considering the dynamic collision process. The gas phase is treated as a Eulerian continuum and described by a computational fluid dynamic method (CFD). The solid phase is modeled by discrete element method (DEM) using a soft sphere approach for the particle collision dynamic. The model takes into account grain combustion, particle-particle collisions, particle-wall collisions, interphase drag and heat transfer between gas and solid phases. The continuous gas phase equations are discretized in finite volume form and solved by the AUSM+-up scheme with the higher order accurate reconstruction method. Translational and rotational motions of discrete particles are solved by explicit time integrations. The direct mapping contact detection algorithm is used. The multigrid method is applied in the void fraction calculation, the contact detection procedure, and CFD solving procedure. Several verification tests demonstrate the accuracy and reliability of this approach. The simulation of an experimental igniter device in open air shows good agreement between the model and experimental measurements. This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during the interior ballistic cycle and to predict dynamic collision phenomena at the individual particle scale. PMID:24891728

  15. Acoustic probe for solid-gas-liquid suspensions. 1997 annual progress report

    SciTech Connect

    Tavlarides, L.L.; Sangani, A.S.

    1997-01-01

    'Acoustic probes have shown promise to be quite effective in determining the solid content in solid-liquid suspensions. However, the presence of small amounts of gas in the waste slurries stored in tanks across the DOE complex prevents straightforward application for characterization of these slurries. The proposed research will develop an acoustic probe for monitoring particle size and volume fraction in slurries in the absence and the presence of gas bubbles. Theoretical Analysis Accomplished: Attenuation of sound waves depends on the size distribution of the solids and the volume fraction of solids. These can in principle be calculated from attenuation measured over a range of frequencies. However, small amounts of bubbles distort the measured attenuation. A typical result from theoretical analysis for the attenuation of solid- gas-liquid systems is given in Figure 1. The total attenuation of a sound wave v(o) equals the sum of contributions by a large number of ''bins'' of particle sizes. This notion yields the following equation for the (hitherto) unknown number density of solid particles as a function of particle radius N(a): j k(o,a)N(a)da = v(o), where the kernel k(o,a) is obtained from analysis. If N(a) is given, the above equation is used to calculate the attenuation v(o). This is referred to as solving the ''forward problem''. Solving for N(a) with v(o) given is the ''inverse problem''. A complication that one faces when trying to solve the inverse problem is that the stated problem is mathematically ill-posed, i.e., small fluctuations in v(o) cause large fluctuations in the result for the number density. Therefore the problem needs to be ''regularized'', i.e., the stated problem needs to be changed slightly such as to make it well-posed. This has been done by others for gas-liquid systems in the past. This approach is currently being applied in the present project to solid-liquid systems. As is shown in Figure 2, it successfully recovers the number

  16. Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

    NASA Technical Reports Server (NTRS)

    Davy, W. C.; Green, M. J.; Lombard, C. K.

    1981-01-01

    The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

  17. Solid waste generation from oil and gas industries in United Arab Emirates.

    PubMed

    Elshorbagy, Walid; Alkamali, Abdulqader

    2005-04-11

    Solid wastes generated from oil and gas industrial activities are very diverse in their characteristics, large in their amounts and many of which are hazardous in nature. Thus, quantifying and characterizing the generated amounts in association with their types, classes, sources, industrial activities, and their chemical and biological characteristics is an obvious mandate when evaluating the possible management practices. This paper discusses the types, amounts, generation units, and the factors related to solid waste generation from a major oil and gas field in the United Arab Emirates (Asab Field). The generated amounts are calculated based on a 1-year data collection survey and using a database software specially developed and customized for the current study. The average annual amount of total solid waste generated in the studied field is estimated at 4061 t. Such amount is found equivalent to 650 kg/capita, 0.37 kg/barrel oil, and 1.6 kg/m3 of extracted gas. The average annual amount of hazardous solid waste is estimated at 55 t and most of which (73%) is found to be generated from gas extraction-related activities. The majority of other industrial non-hazardous solid waste is generated from oil production-related activities (41%), The present analysis does also provide the estimated generation amounts per waste type and class, amounts of combustible, recyclable, and compostable wastes, and the amounts dumped in uncontrolled way as well as disposed into special hazardous landfill facilities. The results should help the decision makers in evaluating the best alternatives available to manage the solid wastes generated from the oil and gas industries. PMID:15811669

  18. pH-Responsive Gas-Water-Solid Interface for Multiphase Catalysis.

    PubMed

    Huang, Jianping; Cheng, Fangqin; Binks, Bernard P; Yang, Hengquan

    2015-12-01

    Despite their wide utility in laboratory synthesis and industrial fabrication, gas-water-solid multiphase catalysis reactions often suffer from low reaction efficiency because of the low solubility of gases in water. Using a surface-modification protocol, interface-active silica nanoparticles were synthesized. Such nanoparticles can assemble at the gas-water interface, stabilizing micrometer-sized gas bubbles in water, and disassemble by tuning of the aqueous phase pH. The ability to stabilize gas microbubbles can be finely tuned through variation of the surface-modification protocol. As proof of this concept, Pd and Au were deposited on these silica nanoparticles, leading to interface-active catalysts for aqueous hydrogenation and oxidation, respectively. With such catalysts, conventional gas-water-solid multiphase reactions can be transformed to H2 or O2 microbubble reaction systems. The resultant microbubble reaction systems exhibit significant catalysis efficiency enhancement effects compared with conventional multiphase reactions. The significant improvement is attributed to the pronounced increase in reaction interface area that allows for the direct contact of gas, water, and solid phases. At the end of reaction, the microbubbles can be removed from the reaction systems through changing the pH, allowing product separation and catalyst recycling. Interestingly, the alcohol oxidation activation energy for the microbubble systems is much lower than that for the conventional multiphase reaction, also indicating that the developed microbubble system may be a valuable platform to design innovative multiphase catalysis reactions. PMID:26524337

  19. Proton conductive tantalum oxide thin film deposited by reactive DC magnetron sputtering for all-solid-state switchable mirror

    NASA Astrophysics Data System (ADS)

    Tajima, K.; Yamada, Y.; Bao, S.; Okada, M.; Yoshimura, K.

    2008-03-01

    Our developed all-solid-state switchable mirror as a smart window is consisted in multi-layer of Mg4Ni/Pd/Ta2O5/WO3/ITO/glass and can switch reversibly from the reflective state to the transparent one. The development of high performance solid electrolyte thin film of Ta2O5 is important for fast speed switching and high durability of the device. In this work, we have investigated the electrochemical property of Ta2O5 thin film deposited by reactive DC magnetron sputtering. The effect of thickness on electrochemical and proton conductivities of Ta2O5 thin film was investigated. The Ta2O5 thin film with a thickness of 400 nm had better proton conductivity of 1.5×10-9 S/cm measured by AC impedance method. The transmittance at wavelength of 670 nm of the device with 400 nm thick Ta2O5 thin film was changed from 0.1% (reflective state) to 51% (transparent state) within 10 s by applying voltage of 5 V. The device showed high durability up to two-thousand switching cycles.

  20. Reactivation of a thermostable lipase by solid phase unfolding/refolding effect of cysteine residues on refolding efficiency.

    PubMed

    Godoy, César A; de las Rivas, Blanca; Bezbradica, Dejan; Bolivar, Juan M; López-Gallego, Fernando; Fernandez-Lorente, Gloria; Guisan, Jose M

    2011-09-10

    Lipase from Geobacillus thermocatenulatus (BTL2) was immobilized in two different matrixes. In one derivative, the enzyme was immobilized on agarose activated with cyanogen bromide (CNBr-BTL2) via its most reactive superficial amino group, whereas the other derivative was covalently immobilized on glyoxyl agarose supports (Gx-BTL2). The latter immobilization protocol leads to intense multipoint covalent attachment between the lysine richest region of enzyme and the glyoxyl groups on the support surface. The resulted solid derivatives were unfolded by incubation under high concentrations of guanidine and then resuspended in aqueous media under different experimental conditions. In both CNBr-BTL2 and Gx-BTL2 derivatives, the oxidation of Cys residues during the unfolding/refolding processes led to inefficient folding for the enzyme because only 25-30% of its initial activity was recovered after 3h in refolding conditions. Dithiothreitol (DTT), a very mild reducing agent, prevented Cys oxidation during the unfolding/refolding process, greatly improving activity recovery in the refolded forms. In parallel, other variables such as pH, buffer composition and the presence of polymers and other additives, had different effects on refolding efficiencies and refolding rates for both derivatives. In the case of solid derivatives of BTL2 immobilized on CNBr-agarose, the surface's chemistry was crucial to guarantee an optimal protein refolding. In this way, uncharged protein vicinities resulted in better refolding efficiencies than those charged ones. PMID:22112565

  1. 2D fluid simulations of discharges at atmospheric pressure in reactive gas mixtures

    NASA Astrophysics Data System (ADS)

    Bourdon, Anne

    2015-09-01

    Since a few years, low-temperature atmospheric pressure discharges have received a considerable interest as they efficiently produce many reactive chemical species at a low energy cost. This potential is of great interest for a wide range of applications as plasma assisted combustion or biomedical applications. Then, in current simulations of atmospheric pressure discharges, there is the need to take into account detailed kinetic schemes. It is interesting to note that in some conditions, the kinetics of the discharge may play a role on the discharge dynamics itself. To illustrate this, we consider the case of the propagation of He-N2 discharges in long capillary tubes, studied for the development of medical devices for endoscopic applications. Simulation results put forward that the discharge dynamics and structure depend on the amount of N2 in the He-N2 mixture. In particular, as the amount of N2 admixture increases, the discharge propagation velocity in the tube increases, reaches a maximum for about 0 . 1 % of N2 and then decreases, in agreement with experiments. For applications as plasma assisted combustion with nanosecond repetitively pulsed discharges, there is the need to handle the very different timescales of the nanosecond discharge with the much longer (micro to millisecond) timescales of combustion processes. This is challenging from a computational point of view. It is also important to better understand the coupling of the plasma induced chemistry and the gas heating. To illustrate this, we present the simulation of the flame ignition in lean mixtures by a nanosecond pulsed discharge between two point electrodes. In particular, among the different discharge regimes of nanosecond repetitively pulsed discharges, a ``spark'' regime has been put forward in the experiments, with an ultra-fast local heating of the gas. For other discharge regimes, the gas heating is much weaker. We have simulated the nanosecond spark regime and have observed shock waves

  2. Decorative black TiCxOy film fabricated by DC magnetron sputtering without importing oxygen reactive gas

    NASA Astrophysics Data System (ADS)

    Ono, Katsushi; Wakabayashi, Masao; Tsukakoshi, Yukio; Abe, Yoshiyuki

    2016-02-01

    Decorative black TiCxOy films were fabricated by dc (direct current) magnetron sputtering without importing the oxygen reactive gas into the sputtering chamber. Using a ceramic target of titanium oxycarbide (TiC1.59O0.31), the oxygen content in the films could be easily controlled by adjustment of total sputtering gas pressure without remarkable change of the carbon content. The films deposited at 2.0 and 4.0 Pa, those are higher pressure when compared with that in conventional magnetron sputtering, showed an attractive black color. In particular, the film at 4.0 Pa had the composition of TiC1.03O1.10, exhibited the L* of 41.5, a* of 0.2 and b* of 0.6 in CIELAB color space. These values were smaller than those in the TiC0.29O1.38 films (L* of 45.8, a* of 1.2 and b* of 1.2) fabricated by conventional reactive sputtering method from the same target under the conditions of gas pressure of 0.3 Pa and optimized oxygen reactive gas concentration of 2.5 vol.% in sputtering gas. Analysis of XRD and XPS revealed that the black film deposited at 4.0 Pa was the amorphous film composed of TiC, TiO and C. The adhesion property and the heat resisting property were enough for decorative uses. This sputtering process has an industrial advantage that the decorative black coating with color uniformity in large area can be easily obtained by plain operation because of unnecessary of the oxygen reactive gas importing which is difficult to be controlled uniformly in the sputtering chamber.

  3. Effect of reactive gas (oxygen/chlorine/fluorine) etching on the magnetic flux of a high moment write pole material

    SciTech Connect

    Zhang Jinqiu; Liu Feng; Chen Lifan; Miloslavsky, Lena

    2010-05-15

    Effect of reactive gas (oxygen/chlorine/fluorine) etching on NiFe magnetic properties was investigated. Experimental data showed 40% magnetic property degradation for F-containing gas etching, 10% degradation for O-containing gas etching, and 5% degradation for Cl-containing gas etching processes. X-ray diffraction analysis indicated that the crystallographic orientation remained the same upon the reactive gas etching, which is due to the low ion energy in plasma etching process as opposed to ion milling process with high input energy. It is proposed that the reported magnetic property degradation was mainly caused by the nonmagnetic dead layer formation, rather than the changes in the crystallographic orientation. The dead layer was determined by the NiFe thickness dependence of remnant magnetic flux variations between pre-etched and postetched samples. The dead layer remained nearly constant for O-containing gas etching process with increasing plasma processing time. The nonmagnetic dead layer of {approx}40-50 A formed in O-containing etching gas was observed in transmission electron microscopy cross-sectional image and was in very good agreement with the calculated value based on magnetic flux measurements. Combined magnetic and physical characterizations suggest that the dead layer thickness saturates at the initial stage of the plasma etching and magnetic property remained unchanged with increasing etching duration upon formation of the dead layer.

  4. Application of the carbon dioxide-barium hydroxide hydrate gas-solid reaction for the treatment of dilute carbon dioxide-bearing gas streams

    SciTech Connect

    Haag, G.L.

    1983-09-01

    The removal of trace components from gas streams via irreversible gas-solid reactions in an area of interest to the chemical engineering profession. This research effort addresses the use of fixed beds of Ba(OH)/sub 2/ hydrate flakes for the removal of an acid gas, CO/sub 2/, from air that contains approx. 330 ppM/sub v/ CO/sub 2/. Areas of investigation encompassed: (1) an extensive literature review of Ba(OH)/sub 2/ hydrate chemistry, (2) microscale studies on 0.150-g samples to develop a better understanding of the reaction, (3) process studies at the macroscale level with 10.2-cm-ID fixed-bed reactors, and (4) the development of a model for predicting fixed-bed performance. Experimental studies indicated fixed beds of commercial Ba(OH)/sub 2/.8H/sub 2/O flakes at ambient temperatures to be capable of high CO/sub 2/-removal efficiencies (effluent concentrations <100 ppB), high reactant utilization (>99%), and an acceptable pressure drop (1.8 kPa/m at a superficial gas velocity of 13 cm/s). Ba(OH)/sub 2/.8H/sub 2/O was determined to be more reactive toward CO/sub 2/ than either Ba(OH)/sub 2/.3H/sub 2/O or Ba(OH)/sub 2/.1H/sub 2/O. A key variable in the development of this fixed-bed process was relative humidity. Operation at conditions with effluent relative humidities >60% resulted in significant recrystallization and restructuring of the flake and subsequent pressure-drop problems.

  5. Reactivity of Ozone with Solid Potassium Iodide Investigated by Atomic Force Microscopy

    SciTech Connect

    Mulleregan, Alice; Brown, Matthew A.; Ashby, Paul D.; Ogletree, D. Frank; Salmeron, Miquel; Hemminger, John C.

    2008-04-14

    The reaction of ozone with the (100) plane of solid potassium iodide (KI) was investigated using atomic force microscopy (AFM). The reaction forming potassium iodate (KIO{sub 3}) initiates at step edges prior to reacting on the flat terraces. Small domains of KIO{sub 3}, initially 3.8 {angstrom} in height are formed on the top of step edges. Following reaction at the step edge, domains of KIO{sub 3} are formed across the terraces. With prolonged exposure to ozone, KIO{sub 3} domains nucleate further growth until the surface is evenly covered with KIO{sub 3} particles that are 4-6 nm in height, at which point the surface is passivated and the reaction terminates.

  6. Modular High-Temperature Gas-Cooled Reactor short term thermal response to flow and reactivity transients

    SciTech Connect

    Cleveland, J.C.

    1988-01-01

    The analyses reported here have been conducted at the Oak Ridge National Laboratory (ORNL) for the US Nuclear Regulatory Commission's (NRC's) Division of Regulatory Applications of the Office of Nuclear Regulatory Research. The short-term thermal response of the Modular High-Temperature Gas-Cooled Reactor (MHTGR) is analyzed for a range of flow and reactivity transients. These include loss of forced circulation (LOFC) without scram, moisture ingress, spurious withdrawal of a control rod group, hypothetical large and rapid positive reactivity insertion, and a rapid core cooling event. The coupled heat transfer-neutron kinetics model is also described.

  7. Solid oxide fuel cell having compound cross flow gas patterns

    DOEpatents

    Fraioli, Anthony V.

    1985-01-01

    A core construction for a fuel cell is disclosed having both parallel and cross flow passageways for the fuel and the oxidant gases. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte wall consists of cathode and anode materials sandwiching an electrolyte material. Each interconnect wall is formed as a sheet of inert support material having therein spaced small plugs of interconnect material, where cathode and anode materials are formed as layers on opposite sides of each sheet and are electrically connected together by the interconnect material plugs. Each interconnect wall in a wavy shape is connected along spaced generally parallel line-like contact areas between corresponding spaced pairs of generally parallel electrolyte walls, operable to define one tier of generally parallel flow passageways for the fuel and oxidant gases. Alternate tiers are arranged to have the passageways disposed normal to one another. Solid mechanical connection of the interconnect walls of adjacent tiers to the opposite sides of the common electrolyte wall therebetween is only at spaced point-like contact areas, 90 where the previously mentioned line-like contact areas cross one another.

  8. A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.

    PubMed

    Ng, C W W; Feng, S; Liu, H W

    2015-03-01

    Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%. PMID:25489976

  9. Particle-Resolved Direct Numerical Simulation for Gas-Solid Flow Model Development

    NASA Astrophysics Data System (ADS)

    Tenneti, Sudheer; Subramaniam, Shankar

    2014-01-01

    Gas-solid flows in nature and industrial applications are characterized by multiscale and nonlinear interactions that manifest as rich flow physics and pose unique modeling challenges. In this article, we review particle-resolved direct numerical simulation (PR-DNS) of the microscale governing equations for understanding gas-solid flow physics and obtaining quantitative information for model development. A clear connection between a microscale realization and meso/macroscale representation is necessary for PR-DNS to be used effectively for model development at the meso- and macroscale. Furthermore, the design of PR-DNS must address the computational challenges of parameterizing models in a high-dimensional parameter space and obtaining accurate statistics of flow properties from a finite number of realizations at acceptable grid resolution. This review also summarizes selected recent insights into the physics of momentum, kinetic energy, and heat transfer in gas-solid flows obtained from PR-DNS. Promising future applications of PR-DNS include the study of the effect of number fluctuations on hydrodynamics, instabilities in gas-solid flow, and wall-bounded flows.

  10. Greenhouse gas emission and groundwater pollution potentials of soils amended with raw and carbonized swine solids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research is to study the greenhouse gas emission and groundwater pollution potentials of the soils amended with raw swine solids and swine biochars made from different thermochemical conditions. Triplicate sets of small pots were designed: 1) control soil with a 50/50 mixture o...

  11. Utilization of the Recycle Reactor in Determining Kinetics of Gas-Solid Catalytic Reactions.

    ERIC Educational Resources Information Center

    Paspek, Stephen C.; And Others

    1980-01-01

    Describes a laboratory scale reactor that determines the kinetics of a gas-solid catalytic reaction. The external recycle reactor construction is detailed with accompanying diagrams. Experimental details, application of the reactor to CO oxidation kinetics, interphase gradients, and intraphase gradients are discussed. (CS)

  12. Analysis of Indirect Emissions Benefits of Wind, Landfill Gas, and Municipal Solid Waste Generation

    EPA Science Inventory

    Techniques are introduced to calculate the hourly indirect emissions benefits of three types of green power resources: wind energy, municipal solid waste (MSW) combustion, and landfill gas (LFG) combustion. These techniques are applied to each of the U.S. EPA's eGRID subregions i...

  13. A solid ceramic electrolyte system for measuring redox conditions in high temperature gas mixing studies

    NASA Technical Reports Server (NTRS)

    Williams, R. J.

    1972-01-01

    The details of the construction and operation of a gas mixing furnace are presented. A solid ceramic oxygen electrolyte cell is used to monitor the oxygen fugacity in the furnace. The system consists of a standard vertical-quench, gas mixing furnace with heads designed for mounting the electrolyte cell and with facilities for inserting and removing the samples. The system also contains the highinput impedance electronics necessary for measurements and a simplified version of standard gas mixing apparatus. The calibration and maintenance of the system are discussed.

  14. Gas-Phase Reactivity of Cesium-Containing Species by Quantum Chemistry.

    PubMed

    Šulková, Katarína; Cantrel, Laurent; Louis, Florent

    2015-09-01

    Thermodynamics and kinetics of cesium species reactions have been studied by using high-level quantum chemical tools. A systematic theoretical study has been done to find suitable methodology for calculation of reliable thermodynamic properties, allowing us to determine bimolecular rate constants with appropriate kinetic theories of gas-phase reactions. Four different reactions have been studied in this work: CsO + H2 = CsOH + H (R1), Cs + HI = CsI + H (R2), CsI + H2O = CsOH + HI (R3), and CsI + OH = CsOH + I (R4). All reactions involve steam, hydrogen, and iodine in addition of cesium. Most of the reactions are fast and (R3) and (R4) proceed even without energetic barrier. In terms of chemical reactivity in the reactor coolant system (RCS) in the case of severe accident, it can be expected that there will be no kinetic limitations for main cesium species (CsOH and CsI) transported along the RCS. Cs chemical speciation inside the RCS should be governed by the thermodynamics. PMID:26237575

  15. Noble-transition metal nanoparticle breathing in a reactive gas atmosphere.

    PubMed

    Petkov, Valeri; Shan, Shiyao; Chupas, Peter; Yin, Jun; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

    2013-08-21

    In situ high-energy X-ray diffraction coupled to atomic pair distribution function analysis is used to obtain fundamental insight into the effect of the reactive gas environment on the atomic-scale structure of metallic particles less than 10 nm in size. To substantiate our recent discovery we investigate a wide range of noble-transition metal nanoparticles and confirm that they expand and contract radially when treated in oxidizing (O2) and reducing (H2) atmospheres, respectively. The results are confirmed by supplementary XAFS experiments. Using computer simulations guided by the experimental diffraction data we quantify the effect in terms of both relative lattice strain and absolute atomic displacements. In particular, we show that the effect leads to a small percent of extra surface strain corresponding to several tenths of Ångström displacements of the atoms at the outmost layer of the particles. The effect then gradually decays to zero within 4 atomic layers inside the particles. We also show that, reminiscent of a breathing type structural transformation, the effect is reproducible and reversible. We argue that because of its significance and widespread occurrence the effect should be taken into account in nanoparticle research. PMID:23828235

  16. Atmospheric reactivity of hydroxyl radicals with guaiacol (2-methoxyphenol), a biomass burning emitted compound: Secondary organic aerosol formation and gas-phase oxidation products

    NASA Astrophysics Data System (ADS)

    Lauraguais, Amélie; Coeur-Tourneur, Cécile; Cassez, Andy; Deboudt, Karine; Fourmentin, Marc; Choël, Marie

    2014-04-01

    Methoxyphenols are low molecular weight semi-volatile polar aromatic compounds produced from the pyrolysis of wood lignin. The reaction of guaiacol (2-methoxyphenol) with hydroxyl radicals has been studied in the LPCA simulation chamber at (294 ± 2) K, atmospheric pressure, low relative humidity (RH < 1%) and under high-NOx conditions using CH3ONO as OH source. The aerosol production was monitored using a SMPS (Scanning Mobility Particle Sizer); the SOA yields were in the range from 0.003 to 0.87 and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. Transmission (TEM) and Scanning (SEM) Electron Microscopy observations were performed to characterize the physical state of SOA produced from the OH reaction with guaiacol; they display both liquid and solid particles (in an amorphous state). GC-FID (Gas Chromatography - Flame Ionization Detection) and GC-MS (Gas Chromatography - Mass Spectrometry) analysis show the formation of nitroguaiacol isomers as main oxidation products in the gas- and aerosol-phases. In the gas-phase, the formation yields were (10 ± 2) % for 4-nitroguaiacol (1-hydroxy-2-methoxy-4-nitrobenzene; 4-NG) and (6 ± 2) % for 3- or 6-nitroguaiacol (1-hydroxy-2-methoxy-3-nitrobenzene or 1-hydroxy-2-methoxy-6-nitrobenzene; 3/6-NG; the standards are not commercially available so both isomers cannot be distinguished) whereas in SOA their yield were much lower (≤0.1%). To our knowledge, this work represents the first identification of nitroguaiacols as gaseous oxidation products of the OH reaction with guaiacol. As the reactivity of nitroguaiacols with atmospheric oxidants is probably low, we suggest using them as biomass burning emission gas tracers. The atmospheric implications of the guaiacol + OH reaction are also discussed.

  17. Inert gas purgebox for Fourier transform ion cyclotron resonance mass spectrometry of air-sensitive solids

    NASA Astrophysics Data System (ADS)

    May, Michael A.; Marshall, Alan G.

    1994-03-01

    A sealed rigid ``purgebox'' makes it possible to load air- and/or moisture-sensitive solids into the solids probe inlet of a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer. A pelletized sample is transferred (in a sealed canister) from a commercial drybox to a Lucite(R) purgebox. After the box is purged with inert gas, an attached glove manipulator is used to transfer the sample from the canister to the solids probe of the mass spectrometer. Once sealed inside the inlet, the sample is pre-evacuated and then passed into the high vacuum region of the instrument at ˜10-7 Torr. The purgebox is transparent, portable, and readily assembled/disassembled. Laser desorption FT/ICR mass spectra of the air- and moisture-sensitive solids, NbCl5. NbCl2(C5H5)2, and Zr(CH3)2(C5H5)2 are obtained without significant oxidation. The residual water vapor concentration inside the purgebox was measured as 100±20 ppm after a 90-min purge with dry nitrogen gas. High-resolution laser desorption/ionization mass spectrometry of air-sensitive solids becomes feasible with the present purgebox interface. With minor modification of the purgebox geometry, the present method could be adapted to any mass spectrometer equipped with a solid sample inlet.

  18. Performance of a Zerovalent Iron Reactive Barrier for the Treatment of Arsenic in Groundwater: Part 2. Geochemical Modeling and Solid Phase Studies

    EPA Science Inventory

    Arsenic uptake processes were evaluated in a zerovalent iron reactive barrier installed at a lead smelting facility using geochemical modeling, solid-phase analysis, and X-ray absorption spectroscopy techniques. Aqueous speciation of arsenic plays a key role in directing arsenic...

  19. A study of tritium in municipal solid waste leachate and gas

    SciTech Connect

    Mutch Jr, R. D.; Mahony, J. D.

    2008-07-15

    It has become increasingly clear in the last few years that the vast majority of municipal solid waste landfills produce leachate that contains elevated levels of tritium. The authors recently conducted a study of landfills in New York and New Jersey and found that the mean concentration of tritium in the leachate from ten municipal solid waste (MSW) landfills was 33,800 pCi/L with a peak value of 192,000 pCi/L. A 2003 study in California reported a mean tritium concentration of 99,000 pCi/L with a peak value of 304,000 pCi/L. Studies in Pennsylvania and the UK produced similar results. The USEPA MCL for tritium is 20,000 pCi/L. Tritium is also manifesting itself as landfill gas and landfill gas condensate. Landfill gas condensate samples from landfills in the UK and California were found to have tritium concentrations as high as 54,400 and 513,000 pCi/L, respectively. The tritium found in MSW leachate is believed to derive principally from gaseous tritium lighting devices used in some emergency exit signs, compasses, watches, and even novelty items, such as 'glow stick' key chains. This study reports the findings of recent surveys of leachate from a number of municipal solid waste landfills, both open and closed, from throughout the United States and Europe. The study evaluates the human health and ecological risks posed by elevated tritium levels in municipal solid waste leachate and landfill gas and the implications to their safe management. We also assess the potential risks posed to solid waste management facility workers exposed to tritium-containing waste materials in transfer stations and other solid waste management facilities. (authors)

  20. A solid oxide fuel cell system fed with hydrogen sulfide and natural gas

    NASA Astrophysics Data System (ADS)

    Lu, Yixin; Schaefer, Laura

    Hydrogen sulfide (H 2S) occurs naturally in crude petroleum, natural gas, volcanic gases, hot springs, and some lakes. Hydrogen sulfide can also result as a by-product from industrial activities, such as food processing, coke ovens, paper mills, tanneries, and petroleum refineries. Sometimes, it is considered to be an industrial pollutant. However, hydrogen can be decomposed from H 2S and then used as fuel for a solid oxide fuel cell (SOFC). This paper presents an examination of a simple hydrogen sulfide and natural gas-fed solid oxide fuel cell system. The possibility of utilization of hydrogen sulfide as a feedstock in a solid oxide fuel cell is discussed. A system configuration of an SOFC combined with an external H 2S decomposition device is proposed, where a certain amount of natural gas is supplied to the SOFC. The exhaust fuel gas of the SOFC is after-burned with exhaust air from the SOFC, and the heat of the combustion gas is utilized in the decomposition of H 2S in a decomposition reactor (DR) to produce hydrogen to feed the SOFC. The products are electricity and industry-usable sulfur. Through a mass and energy balance, a preliminary thermodynamic analysis of this system is performed, and the system efficiency is calculated. Also in this paper, the challenges in creating the proposed configuration are discussed, and the direction of future work is presented.

  1. A nanostructured surface increases friction exponentially at the solid-gas interface.

    PubMed

    Phani, Arindam; Putkaradze, Vakhtang; Hawk, John E; Prashanthi, Kovur; Thundat, Thomas

    2016-01-01

    According to Stokes' law, a moving solid surface experiences viscous drag that is linearly related to its velocity and the viscosity of the medium. The viscous interactions result in dissipation that is known to scale as the square root of the kinematic viscosity times the density of the gas. We observed that when an oscillating surface is modified with nanostructures, the experimentally measured dissipation shows an exponential dependence on kinematic viscosity. The surface nanostructures alter solid-gas interplay greatly, amplifying the dissipation response exponentially for even minute variations in viscosity. Nanostructured resonator thus allows discrimination of otherwise narrow range of gaseous viscosity making dissipation an ideal parameter for analysis of a gaseous media. We attribute the observed exponential enhancement to the stochastic nature of interactions of many coupled nanostructures with the gas media. PMID:27596851

  2. Modeling of ultrasound transmission through a solid-liquid interface comprising a network of gas pockets

    SciTech Connect

    Paumel, K.; Baque, F.; Moysan, J.; Corneloup, G.; Chatain, D.

    2011-08-15

    Ultrasonic inspection of sodium-cooled fast reactor requires a good acoustic coupling between the transducer and the liquid sodium. Ultrasonic transmission through a solid surface in contact with liquid sodium can be complex due to the presence of microscopic gas pockets entrapped by the surface roughness. Experiments are run using substrates with controlled roughness consisting of a network of holes and a modeling approach is then developed. In this model, a gas pocket stiffness at a partially solid-liquid interface is defined. This stiffness is then used to calculate the transmission coefficient of ultrasound at the entire interface. The gas pocket stiffness has a static, as well as an inertial component, which depends on the ultrasonic frequency and the radiative mass.

  3. Coal/biomass fuels and the gas turbine: Utilization of solid fuels and their derivatives

    SciTech Connect

    DeCorso, M.; Newby, R.; Anson, D.; Wenglarz, R.; Wright, I.

    1996-06-01

    This paper discusses key design and development issues in utilizing coal and other solid fuels in gas turbines. These fuels may be burned in raw form or processed to produce liquids or gases in more or less refined forms. The use of such fuels in gas turbines requires resolution of technology issues which are of little or no consequence for conventional natural gas and refined oil fuels. For coal, these issues are primarily related to the solid form in which coal is naturally found and its high ash and contaminant levels. Biomass presents another set of issues similar to those of coal. Among the key areas discussed are effects of ash and contaminant level on deposition, corrosion, and erosion of turbine hot parts, with particular emphasis on deposition effects.

  4. Solid Sorbents for CO2 Capture from Post-Combustion and Pre-Combustion Gas Streams

    SciTech Connect

    Siriwardane, R.V.; Robinson, C.; Stevens, R.W.

    2007-08-01

    A novel liquid impregnated solid sorbent was developed for CO2 removal in the temperature range of ambient to 60 °C for both fixed bed and fluidized bed reactor applications. The sorbent is regenerable at 60-80 °C. Multi-cycle tests conducted in an atmospheric bench scale reactor with simulated flue gas demonstrated that the sorbent retains its CO2 sorption capacity with CO2 removal efficiency of about 99%. A second, novel solid sorbent containing mixture of alkali earth and alkali compounds was developed for CO2 removal at 200-315 °C from high pressure gas streams (i.e., suitable for IGCC systems). The sorbent showed very high capacity for CO2 removal from gas streams containing 28% CO2 at 200 °C and 11.2 atm during lab-scale flow reactor tests as well as regenerability at 375 °C.

  5. A nanostructured surface increases friction exponentially at the solid-gas interface

    PubMed Central

    Phani, Arindam; Putkaradze, Vakhtang; Hawk, John E.; Prashanthi, Kovur; Thundat, Thomas

    2016-01-01

    According to Stokes’ law, a moving solid surface experiences viscous drag that is linearly related to its velocity and the viscosity of the medium. The viscous interactions result in dissipation that is known to scale as the square root of the kinematic viscosity times the density of the gas. We observed that when an oscillating surface is modified with nanostructures, the experimentally measured dissipation shows an exponential dependence on kinematic viscosity. The surface nanostructures alter solid-gas interplay greatly, amplifying the dissipation response exponentially for even minute variations in viscosity. Nanostructured resonator thus allows discrimination of otherwise narrow range of gaseous viscosity making dissipation an ideal parameter for analysis of a gaseous media. We attribute the observed exponential enhancement to the stochastic nature of interactions of many coupled nanostructures with the gas media. PMID:27596851

  6. Modeling of ultrasound transmission through a solid-liquid interface comprising a network of gas pockets

    NASA Astrophysics Data System (ADS)

    Paumel, K.; Moysan, J.; Chatain, D.; Corneloup, G.; Baqué, F.

    2011-08-01

    Ultrasonic inspection of sodium-cooled fast reactor requires a good acoustic coupling between the transducer and the liquid sodium. Ultrasonic transmission through a solid surface in contact with liquid sodium can be complex due to the presence of microscopic gas pockets entrapped by the surface roughness. Experiments are run using substrates with controlled roughness consisting of a network of holes and a modeling approach is then developed. In this model, a gas pocket stiffness at a partially solid-liquid interface is defined. This stiffness is then used to calculate the transmission coefficient of ultrasound at the entire interface. The gas pocket stiffness has a static, as well as an inertial component, which depends on the ultrasonic frequency and the radiative mass.

  7. Radiation-induced reactions of COH 2 gas mixtures over various solid catalysts

    NASA Astrophysics Data System (ADS)

    Nagai, S.; Arai, H.; Hatada, M.

    Studies have been carried out of radiation-induced reactions of COH 2 gas mixtures in the presence of various solid catalysts in order to find possibilities of synthesizing organic raw materials from COH 2 by radiation for the future. The solid catalysts studied include Fischer-Tropsch catalyst (FeCu supported by diatomaceous earth), titania(TiO 2), and silica gel. Analysis of the reaction products over Fischer-Tropsch catalyst or semiconductors such as TiO 2 and ZnOCr 2O 3 reveals that these solid catalysts do not sensitize the radiation chemical reaction of COH 2 but show the secondary effects on the reaction so as to induce the hydrogenation of olefins produced by the catalytic reaction and of aldehydes produced in gas phase by radiation. On the other hand, silica gel and other insulators such as alumina have been found to exhibit high catalytic activity in the formation of hydrocarbons from COH 2 under electron beam irradiation at 300°C. It has been shown experimentally that secondary reactions between H 2 and carbonaceous solid produced from CO make a substantial contribution to the formation of hydrocarbons from COH 2 over silica gel. In an attempt to find the role of silica gel in the reaction to produce hydrocarbons, radiation-induced reactions have been studied of H 2 with the carbonaceous solid that had been produced by irradiation of CO in the absence of solid catalyst, over TiO 2, or over silica gel. The results indicate that silica gel not only enhances the yields of CO 2 and carbonaceous solid from CO but also promotes hydrogenation reactions of the carbonaceous solid under electron beam irradiation.

  8. Landfill gas generation after mechanical biological treatment of municipal solid waste. Estimation of gas generation rate constants.

    PubMed

    Gioannis, G De; Muntoni, A; Cappai, G; Milia, S

    2009-03-01

    Mechanical biological treatment (MBT) of residual municipal solid waste (RMSW) was investigated with respect to landfill gas generation. Mechanically treated RMSW was sampled at a full-scale plant and aerobically stabilized for 8 and 15 weeks. Anaerobic tests were performed on the aerobically treated waste (MBTW) in order to estimate the gas generation rate constants (k,y(-1)), the potential gas generation capacity (L(o), Nl/kg) and the amount of gasifiable organic carbon. Experimental results show how MBT allowed for a reduction of the non-methanogenic phase and of the landfill gas generation potential by, respectively, 67% and 83% (8 weeks treatment), 82% and 91% (15 weeks treatment), compared to the raw waste. The amount of gasified organic carbon after 8 weeks and 15 weeks of treatment was equal to 11.01+/-1.25kgC/t(MBTW) and 4.54+/-0.87kgC/t(MBTW), respectively, that is 81% and 93% less than the amount gasified from the raw waste. The values of gas generation rate constants obtained for MBTW anaerobic degradation (0.0347-0.0803y(-1)) resemble those usually reported for the slowly and moderately degradable fractions of raw MSW. Simulations performed using a prediction model support the hypothesis that due to the low production rate, gas production from MBTW landfills is well-suited to a passive management strategy. PMID:18954969

  9. Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

    2013-04-01

    Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  10. A study of pneumatic conveying of gas-solid flow for industrial application

    NASA Astrophysics Data System (ADS)

    Al-Khateeb, Khalid A. S.; Tasnim, Rumana; Khan, Sheroz; Mohammod, Musse; Arshad, Atika; Shobaki, Mohammed M.; Haider, Samnan; Saquib, Nazmus; Rahman, Tawfilur

    2013-12-01

    The complicated nature of gas-solids' physical properties have challenged the researchers over past decades who have led their efforts in developing its' flow sensing and measurement methods. The term 'gas-solid flow' signifies dilute- or dense-phase flow with a very little concentration of solids. For conducting such flow measurement, generally velocity profile and volumetric concentration of the flow particles being conveyed are needed to be measured. An important application of gas-solid flow has taken root in the form of biomass flow in pneumatic conveying systems, and its' online measurement has proven to be an exigent research pursuit. Additionally the other applications have been explored in power plants, food, chemical and automobiles industries as well. This paper aims at exploring the evolution of flow measurement methods along with a brief explanation on existing fundamental sensing techniques. Furthermore, the most recent patents developed for such measurements in pneumatic conveying pipelines are scrutinized along with their concomitant pros and cons.