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Mixed-conducting ceramic membranes for partial oxygenation of methane

Description: The most significant cost associated with the conventional partial oxidation of methane is that of an oxygen plant. Our new technology offers a way to lower this cost, and in this paper we explore the technology that is based on dense ceramic membranes and that uses air as the oxidant for methane-conversion reactions. Mixed-conducting ceramic materials have been produced from mixed-oxide systems of the La-Sr-Fe-Co-O (SFC) type, in the form of tubes and bars. Thermodynamic stability of the tubes was studied as a function of oxygen partial pressure by high-temperature XRD. Mechanical properties were measured and found to be adequate for a reactor in the case of SFC-2: Electronic and ionic conductivities were measured; SFC-2 is unique in the sense that the ratio of ionic to electronic conductance is close to unity. Performance of the membrane tubes was good only with SFC-2. Fracture of other SFC tubes was the consequence of an oxygen gradient that introduced a volumetric lattice difference between the inner and outer walls. SFC-2 tubes provided methane conversion efficiencies of >99% in a reactor. These tubes have operated for >1000 h.
Date: May 1, 1995
Creator: Balachandran, U.; Dusek, J.T.; Maiya, P.S.; Mieville, R.L.; Kleefisch, M.S.; Udovich, C.A. et al.
Partner: UNT Libraries Government Documents Department

Ceramic membranes for partial oxygenation of hydrocarbon fuels to high-value-added products

Description: This report describes the design of a membrane reactor for converting methane into value added products. The design includes an outer tube of perovskite which contacts air, an inner tube of zirconium oxide which contacts methane, and a bonding layer of a mixture of zirconium oxide and perovskite.
Date: December 31, 1994
Creator: Balachandran, U.; Dusek, J.T.; Kleefisch, M.S. & Kobylinski, T.P.
Partner: UNT Libraries Government Documents Department

Effects of Fuel Ethanol Use on Fuel-Cycle Energy and Greenhouse Gas Emissions

Description: We estimated the effects on per-vehicle-mile fuel-cycle petroleum use, greenhouse gas (GHG) emissions, and energy use of using ethanol blended with gasoline in a mid-size passenger car, compared with the effects of using gasoline in the same car. Our analysis includes petroleum use, energy use, and emissions associated with chemicals manufacturing, farming of corn and biomass, ethanol production, and ethanol combustion for ethanol; and petroleum use, energy use, and emissions associated with petroleum recovery, petroleum refining, and gasoline combustion for gasoline. For corn-based ethanol, the key factors in determining energy and emissions impacts include energy and chemical usage intensity of corn farming, energy intensity of the ethanol plant, and the method used to estimate energy and emissions credits for co-products of corn ethanol. The key factors in determining the impacts of cellulosic ethanol are energy and chemical usage intensity of biomass farming, ethanol yield per dry ton of biomass, and electricity credits in cellulosic ethanol plants. The results of our fuel-cycle analysis for fuel ethanol are listed below. Note that, in the first half of this summary, the reductions cited are per-vehicle-mile traveled using the specified ethanol/gasoline blend instead of conventional (not reformulated) gasoline. The second half of the summary presents estimated changes per gallon of ethanol used in ethanol blends. GHG emissions are global warming potential (GWP)-weighted, carbon dioxide (CO2)-equivalent emissions of CO2, methane (CH4), and nitrous oxide (N2O).
Date: February 8, 1999
Creator: Saricks, C.; Santini, D. & Wang, M.
Partner: UNT Libraries Government Documents Department


Description: Devonian gas shales underlie approximately two-thirds of Kentucky. In the shale, natural gas is adsorbed on clay and kerogen surfaces. This is analogous to methane storage in coal beds, where CO{sub 2} is preferentially adsorbed, displacing methane. Black shales may similarly desorb methane in the presence of CO{sub 2}. Drill cuttings from the Kentucky Geological Survey Well Sample and Core Library were sampled to determine CO{sub 2} and CH{sub 4} adsorption isotherms. Sidewall core samples were acquired to investigate CO{sub 2} displacement of methane. An elemental capture spectroscopy log was acquired to investigate possible correlations between adsorption capacity and mineralogy. Average random vitrinite reflectance data range from 0.78 to 1.59 (upper oil to wet gas and condensate hydrocarbon maturity range). Total organic content determined from acid-washed samples ranges from 0.69 to 14 percent. CO{sub 2} adsorption capacities at 400 psi range from a low of 14 scf/ton in less organic-rich zones to more than 136 scf/ton. There is a direct correlation between measured total organic carbon content and the adsorptive capacity of the shale; CO{sub 2} adsorption capacity increases with increasing organic carbon content. Initial estimates based on these data indicate a sequestration capacity of 5.3 billion tons of CO{sub 2} in the Lower Huron Member of the Ohio Shale of eastern Kentucky and as much as 28 billion tons total in the deeper and thicker parts of the Devonian shales in Kentucky. Should the black shales of Kentucky prove to be a viable geologic sink for CO{sub 2}, their extensive occurrence in Paleozoic basins across North America would make them an attractive regional target for economic CO{sub 2} storage and enhanced natural gas production.
Date: July 29, 2005
Creator: Nuttall, Brandon C.
Partner: UNT Libraries Government Documents Department

Organic carbon cycling in landfills: Model for a continuum approach

Description: Organic carbon cycling in landfills can be addressed through a continuum model where the end-points are conventional anaerobic digestion of organic waste (short-term analogue) and geologic burial of organic material (long-term analogue). Major variables influencing status include moisture state, temperature, organic carbon loading, nutrient status, and isolation from the surrounding environment. Bioreactor landfills which are engineered for rapid decomposition approach (but cannot fully attain) the anaerobic digester end-point and incur higher unit costs because of their high degree of environmental isolation and control. At the other extreme, uncontrolled land disposal of organic waste materials is similar to geologic burial where organic carbon may be aerobically recycled to atmospheric CO{sub 2}, anaerobically converted to CH{sub 4} and CO{sub 2} during early diagenesis, or maintained as intermediate or recalcitrant forms into geologic time (> 1,000 years) for transformations via kerogen pathways. A family of improved landfill models are needed at several scales (molecular to landscape) which realistically address landfill processes and can be validated with field data.
Date: September 1, 1997
Creator: Bogner, J. & Lagerkvist, A.
Partner: UNT Libraries Government Documents Department

Energy and biomass recovery from wastewater. Final report, December 1989--December 1990

Description: The goal of the project was to demonstrate in a large pilot study that domestic sewage could be converted to useful products, mainly substitute natural gas and clean water, using two low-cost biological processes -- a high-rate anaerobic treatment unit followed by a hydroponic plant treatment system. The anaerobic attached film expanded bed (AAFEB) and the Nutrient Film Technique (NFT) are two innovative technologies developed over more than a decade at Cornell University. Documentation of this biological system for 52 months at flows up to 40 s/d (greater than 10,000 gal/d) showed the system to be highly successful. This report covers the last 12 months of this jointly sponsored NYSERDA/GRI study. Efforts were made to document the empirical relationships between system loading rate and effluent quality. Although the sewage temperatures varied from 7{degrees}C to 28{degrees}C and little modification of reactor temperatures were made, low temperatures had minimal effects on the purification capabilities. Effluent quality was excellent (BOD and SS less than 5 mg/1) with plant nutrients removed to less than 1 mg/l for total nitrogen and total phosphorus at low hydraulic loadings (less than 3 cm/d). Sludge generation was less than at conventional primary plants and much less than at conventional secondary facilities. The economics of the hypothesized system appear promising.
Date: June 1, 1995
Creator: Jewell, W.J.; Cummings, R.J.; Nock, T.D.; Hicks, E.E. & White, T.E.
Partner: UNT Libraries Government Documents Department

1995 Protocol for Working Group VIII: Influence of environmental changes on climate. US-Russia agreement on cooperation in the field of protection of the environment and natural resources. Final report, January 1, 1994--December 31, 1994

Description: Cooperative research programs of Russia and the United States concerned with global warming and climatic change are briefly described.
Date: May 1, 1995
Partner: UNT Libraries Government Documents Department

Gasoline from natural gas by sulfur processing. Quarterly report No. 7, January--March 1995

Description: This report presents the work performed at the Institute of Gas Technology (IGT) during the seventh program quarter from January 1--March 31, 1995, under Department of Energy (DOE) Contract No. DE-AC22-93PC92114. This program has coordinated funding for Task 1 from IGT`s Sustaining Membership Program (SMP), while DOE is Funding Tasks 2 through 8. Progress in all tasks is reported here. The overall objective of this research project is to develop a catalytic process to convert natural gas to liquid transportation fuels. The process consists of two steps that each use catalysts and sulfur-containing intermediates: (1) converting natural gas to CS{sub 2} and (2) converting CS{sub 2} to gasoline-range liquids. Experimental data will be generated to demonstrate the potential of catalysts and the overall process. During this quarter, progress in the following areas has been made: Two new batches of catalysts were prepared for the reaction of methane with hydrogen sulfide to produce carbon sulfide; potential commercializing partners were contacted. Several companies expressed interest in possible applications of this technology.
Date: April 1, 1995
Creator: Erekson, E.J.
Partner: UNT Libraries Government Documents Department

Direct aromatization of methane. Quarterly technical progress report No. 9, October 1, 1994--December 31, 1994

Description: Further experiments have been performed on the assisted pyrolysis by the addition of a free-radical initiator, as well as on the initiation of pyrolysis by a solid surface using a variety of catalysts. The reaction has been studied in the temperature range of 850-1100{degrees}C, methane flow rates of 475-1000 Scc/min, and ethane flow rates of 21-42 Scc/min. Significant reduction in the pyrolysis temperature was observed in both cases, with measurable amounts of methane being converted at temperatures as low as 850{degrees}C. When ethane was added as a free-radical initiator, the major pyrolysis products were ethylene and propylene at temperatures below 950{degrees}C. At higher pyrolysis temperatures, the selectivity shifted toward benzene and acetylene which became the main analyzable products at 1050{degrees}C and 1100{degrees}C.
Date: May 30, 1995
Partner: UNT Libraries Government Documents Department

Direct catalytic conversion of methane and light hydrocarbon gases. Final report, October 1, 1986--July 31, 1989

Description: This project explored conversion of methane to useful products by two techniques that do not involve oxidative coupling. The first approach was direct catalytic dehydrocoupling of methane to give hydrocarbons and hydrogen. The second approach was oxidation of methane to methanol by using heterogenized versions of catalysts that were developed as homogeneous models of cytochrome-P450, an enzyme that actively hydroxylates hydrocarbons by using molecular oxygen. Two possibilities exist for dehydrocoupling of methane to higher hydrocarbons: The first, oxidative coupling to ethane/ethylene and water, is the subject of intense current interest. Nonoxidative coupling to higher hydrocarbons and hydrogen is endothermic, but in the absence of coke formation the theoretical thermodynamic equilibrium yield of hydrocarbons varies from 25% at 827{degrees}C to 65% at 1100{degrees}C (at atmospheric pressure). In this project we synthesized novel, highly dispersed metal catalysts by attaching metal clusters to inorganic supports. The second approach mimics microbial metabolism of methane to produce methanol. The methane mono-oxygenase enzyme responsible for the oxidation of methane to methanol in biological systems has exceptional selectivity and very good rates. Enzyme mimics are systems that function as the enzymes do but overcome the problems of slow rates and poor stability. Most of that effort has focused on mimics of cytochrome P-450, which is a very active selective oxidation enzyme and has a metalloporphyrin at the active site. The interest in nonporphyrin mimics coincides with the interest in methane mono-oxygenase, whose active site has been identified as a {mu}-oxo dinuclear iron complex.We employed mimics of cytochrome P-450, heterogenized to provide additional stability. The oxidation of methane with molecular oxygen was investigated in a fixed-bed, down-flow reactor with various anchored metal phthalocyanines (PC) and porphyrins (TPP) as the catalysts.
Date: June 1, 1995
Creator: Wilson, R.B. Jr.; Posin, B.M. & Chan, Yee-Wai
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of dense ceramic membranes for partial oxidation of methane

Description: In this technology, air is used as the oxidant for methane conversion reactions, thiu eliminating tne need for an expensive oxygen plant. Mixed-conducting ceramic materials have been produced from mixed-oxide system of the La-Sr-Fe-Co-O (SFC) type, in the form of tubes and bars. Thermodynamic stability of the tubes was studied vs oxygen partial pressure by high-temperature XRD. Mechanical properties of the SFC-2 (SrFeCo{sub 0.5}O{sub x}) material were adequate for reactor use. Electronic and ionic conductivities showed that SFC-2 is unique in that its ratio of ionic to electronic conductance is close to unity. Performance of the membrane tubes was good only with SFC-2. Fracture of other SFC tubes was consequence of an oxygen gradient that introduced a volumetric lattice difference between the inner and outer walls. SFC-2 tubes provided methane conversion efficiencies >99% in a reactor and have operated successfully for >1000 h.
Date: June 1, 1995
Creator: Balachandran, U.; Ma, B.; Dusek, J.T.; Picciolo, J.J.; Mieville, R.L.; Maiya, P.S. et al.
Partner: UNT Libraries Government Documents Department

Carbon-13 isotopic abundance and concentration of atmospheric methane for background air in the Southern and Northern Hemispheres from 1978 to 1989

Description: Atmospheric methane (CH{sub 4}) may become an increasingly important contributor to global warming in future years. Its atmospheric concentration has risen, doubling over the past several hundred years, and additional methane is thought to have a much greater effect on climate, on a per molecule basis, than additional C0{sub 2} at present day concentrations (Shine et al. 1990). The causes of the increase of atmospheric CH{sub 4} have been difficult to ascertain because of a lack of quantitative knowledge of the fluxes (i.e., net emissions) from the numerous anthropogenic and natural sources. The goal of CH{sub 4} isotopic studies is to provide a constraint (and so reduce the uncertainties) in estimating the relative fluxes from the various isotopically distinct sources, whose combined fluxes must result in the measured atmospheric isotopic composition, after the fractionating effect of the atmospheric removal process is considered. In addition, knowledge of the spatial and temporal changes in the isotopic composition of atmospheric CH{sub 4}, along with estimates of the fluxes from some of the major sources, makes it possible to calculate growth rates for sources whose temporal emissions trends would be difficult to measure directly.
Date: March 1995
Creator: Stevens, C. M.; Sepanski & Morris, L. J.
Partner: UNT Libraries Government Documents Department


Description: On-board production of hydrogen for fuel cells for automotive applications is a challenging developmental task. The fuel processor must show long term durability and under challenging conditions. Fuel processor catalysts in automotive fuel processors will be exposed to large thermal variations, vibrations, exposure to uncontrolled ambient conditions, and various impurities from ambient air and from fuel. For the commercialization of fuel processors, the delineation of effects on catalyst activity and durability are required. We are studying fuels and fuel constituent effects on the fuel processor system as part of the DOE Fuel Cells for Transportation program. Pure fuel components are tested to delineate the fuel component effect on the fuel processor and fuel processor catalysts. Component blends are used to simulate ''real fuels'', with various fuel mixtures being examined such as reformulated gasoline and naptha. The aliphatic, napthenic, olefin and aromatic content are simulated to represent the chemical kinetics of possible detrimental reactions, such as carbon formation, during fuel testing. Testing has examined the fuel processing performance of different fuel components to help elucidate the fuel constituent effects on fuel processing performance and upon catalyst durability. Testing has been conducted with vapor fuels, including natural gas and pure methane. The testing of pure methane and comparable testing with natural gas (97% methane) have shown some measurable differences in performance in the fuel processor. Major gasoline fuel constituents, such as aliphatic compounds, napthanes, and aromatics have been compared for their effect on the fuel processing performance. Experiments have been conducted using high-purity compounds to observe the fuel processing properties of the individual components and to document individual fuel component performance. The relative carbon formation of different fuel constituents have been measured by monitoring carbon via in situ laser optics, and by monitoring carbon buildup on the catalyst surface. The fuel processing ...
Date: May 2001
Creator: Borup, R.; Inbody, M.; Morton, B. & Brown, L.
Partner: UNT Libraries Government Documents Department

Effect of inlet conditions on the performance of a palladium membrane reactor

Description: Palladium membrane reactors (PMR) will be used to remove tritium and other hydrogen isotopes from impurities, such as tritiated methane and tritiated water, in the exhaust of the International Thermonuclear Experimental Reactor. In addition to fusion-fuel processing, the PMR system can be used to recover tritium from tritiated waste water. This paper investigates the effect of inlet conditions on the performance of a PMR. A set of experiments were run to determine, independently, the effect of inlet compositions and residence time on performance. Also, the experiments were designed to determine if the injected form of hydrogen (CH{sub 4} or H{sub 2}O) effects performance. Results show that the PMR operates at optimal hydrogen recovery with a broad range of inlet compositions and performance is shown to increase with increased residence time. PMR performance is shown to be independent of whether hydrogen is injected in the form of CH{sub 4} or H{sub 2}O.
Date: October 1, 1997
Creator: Birdsell, S.A.; Willms, R.S.; Arzu, P. & Costello, A.
Partner: UNT Libraries Government Documents Department

The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

Description: We are investigating the structure/activity relationships of the bacterial enzyme methane monooxygenase, which catalyzes the specific oxidation of methane to methanol. We then utilize this information to design and synthesize inorganic coordination complexes that mimic the function of the native enzyme but are more robust and have higher catalytic site density. We envision these catalysts to be useful in process catalytic reactors in the conversion of methane in natural gas to liquid ethanol.
Date: March 1, 1995
Creator: Watkins, B.E. & Satcher, J.H.
Partner: UNT Libraries Government Documents Department

The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

Description: A binuclear, unsymmetric coordinating ligand that is an effective metal chelator has been designed and synthesized. The new ligand has been shown to react readily with iron(II)/(III) forming a variety of coordination complexes. The binuclear complexes are of significant interest since they represent proof-of-principle for the development of coordinatively asymmetric, binuclear metal chelate compounds. Although this structural type of chelator now appears to be common in biological systems, it has not been previously described for inorganic coordination chemistry. The isolation of oxidation products will be helpful in establishing reaction mechanism(s) of these complexes with molecular oxygen. It is expected that this ligand and derivatives of it will play an important role in the development of bioinorganic complexes that aim to mimic enzyme active sites that function by substrate interaction at only one metal site of a multimetal active site.
Date: July 1, 1995
Creator: Watkins, B.E. & Satcher, J.H.
Partner: UNT Libraries Government Documents Department

ERC Program Overview

Description: The carbonate fuel cell promises highly efficient, cost-effective, environmentally superior power generation from pipeline natural gas, coal gas, biogas, and other gaseous and liquid fuels. ERC has been engaged in the development of this unique technology since the late 1970s, primarily focusing on the development of the Direct Fuel Cell (DFC) technology [1-6] pioneered by ERC. The DFC design incorporates the unique internal reforming feature which allows utilization of a hydrocarbon fuel directly in the fuel cell without requiring any external reforming reactor and associated heat exchange equipment. This approach provides upgrading of waste heat to chemical energy; thereby, it contributing to higher overall efficiency for conversion of fuel energy to electricity with low levels of environmental emissions. Among the internal reforming options, ERC has selected the Indirect Internal Reforming (IIR) - Direct Internal Reforming (DIR) combination as its baseline design. ERC plans to offer commercial DFC power plants in various sizes, initially focusing on the MW-scale units. The plan is to offer standardized, packaged MW-scale DFC power plants operating on natural gas or other hydrocarbon-containing fuels for commercial sale by the end of the decade. These power plants, which can be shop-fabricated and sited near the user, are ideally suited for distributed generation, industrial cogeneration, and uninterrupted power for military bases. After gaining experience from the early MW-scale power plants, and with maturing of the technology, ERC expects to introduce larger power plants operating on natural gas and/or coal gas or other fuels in the beginning of the 21st century. ERC has completed a technology program for product design verification, a predecessor of the current program, where the power plant design as well as the technology development were carried out to support a full-size field demonstration. These activities culminated in 130 kW stack tests in ERC's subscale power plant, ...
Date: August 1, 1996
Creator: Maru, H.; Farooque, M.; Carlson, G.; Patel, P.; Yuh, C.; Bentley, C. et al.
Partner: UNT Libraries Government Documents Department

DOE final report: Studies on the microbial formation of methane

Description: The microbial formation of methane is carried out by methanogens which are found wherever active anaerobic degradation of organic matter occurs. We developed a procedure for reliable culture of 'Methanococus jannaschii' which yields 8 g wet weight of cells per liter of medium. To initiate a study of proteomics, this organism was grown at two levels of hydrogen partial pressure, very low (650 Pa) and high (178 kPa). When cells were exposed to hydrogen excess conditions, they possessed very low or undetectable levels of four flagella-related polypeptides, whereas, when hydrogen became limiting, these proteins were synthesized. Thus, use of proteomics showed, for the first time, that this methanogen can regulate expression of proteins, and these experiments open the door for general studies of regulation in this hyperthermophile.
Date: April 1, 2001
Creator: Wolfe, Ralph S.
Partner: UNT Libraries Government Documents Department

Modeling of homogeneous charge compression ignition (HCCI) of methane

Description: The operation of piston engines on a compression ignition cycle using a lean, homogeneous charge has many potential attractive features. These include the potential for extremely low NO{sub x} and particulate emissions while maintaining high thermal efficiency and not requiring the expensive high pressure injection system of the typical modem diesel engine. Using the HCT chemical kinetics code to simulate autoignition of methane-air mixtures, we have explored the ignition timing, burn duration, NO{sub x} production, indicated efficiency and power output of an engine with a compression ratio of 15:1 at 1200 and 2400 rpm. HCT was modified to include the effects of heat transfer. This study used a single control volume reaction zone that varies as a function of crank angle. The ignition process is controlled by varying the intake equivalence ratio and varying the residual gas trapping (RGT). RGT is internal exhaust gas recirculation which recycles both heat and combustion product species. It is accomplished by varying the timing of the exhaust valve closure. Inlet manifold temperature was held constant at 330 Kelvins. Results show that there is a narrow range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50% and NO{sub x} levels below 100 ppm.
Date: May 1, 1997
Creator: Smith, J.R.; Aceves, S.M.; Westbrook, C. & Pitz, W.
Partner: UNT Libraries Government Documents Department

Preflame zone structure and main features of fuel conversion in atmospheric pressure premixed laminar hydrocarbon flames

Description: This report describes the structure study of the premixed hydrocarbon-oxidizer Bunsen flames burning at the atmospheric pressure and also the ones with some inhibitors added. Studies were performed on hexane, propane, methane, acetylene, and hexene flames.
Date: August 25, 1995
Creator: Ksandopulo, G.I.
Partner: UNT Libraries Government Documents Department

Thomson scattering from inertial confinement fusion plasmas

Description: Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Flat disks coated with thin multilayers of gold and beryllium were with one laser beam to produce a two ion species plasma with a controlled amount of both species. Thomson scattering spectra from these plasmas showed two ion acoustic waves belonging to gold and beryllium. The phase velocities of the ion acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species and are in good agreement with theoretical calculations. These open geometry experiments further show that an accurate measurement of the ion temperature can be derived from the relative damping of the two ion acoustic waves. Subsequent Thomson scattering measurements from methane-filled, ignition-relevant hohlraums apply the theory for two ion species plasmas to obtain the electron and ion temperatures with high accuracy. The experimental data provide a benchmark for two-dimensional hydrodynamic simulations using LASNEX, which is presently in use to predict the performance of future megajoule laser driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Applied to NIF targets, this flux limitation has little effect on x- ray production. The spatial distribution of x-rays is slightly modified but optimal symmetry can be re-established by small changes in power balance or pointing. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well described by the calculations. This result implies that stagnation in gas-filled hohlraums occurs too late to directly affect the capsule implosion in ignition experiments.
Date: July 8, 1997
Creator: Glenzer, S.H.; Back, C.A. & Suter, L.J.
Partner: UNT Libraries Government Documents Department

A survey of processes for producing hydrogen fuel from different sources for automotive-propulsion fuel cells

Description: Seven common fuels are compared for their utility as hydrogen sources for proton-exchange-membrane fuel cells used in automotive propulsion. Methanol, natural gas, gasoline, diesel fuel, aviation jet fuel, ethanol, and hydrogen are the fuels considered. Except for the steam reforming of methanol and using pure hydrogen, all processes for generating hydrogen from these fuels require temperatures over 1000 K at some point. With the same two exceptions, all processes require water-gas shift reactors of significant size. All processes require low-sulfur or zero-sulfur fuels, and this may add cost to some of them. Fuels produced by steam reforming contain {approximately}70-80% hydrogen, those by partial oxidation {approximately}35-45%. The lower percentages may adversely affect cell performance. Theoretical input energies do not differ markedly among the various processes for generating hydrogen from organic-chemical fuels. Pure hydrogen has severe distribution and storage problems. As a result, the steam reforming of methanol is the leading candidate process for on-board generation of hydrogen for automotive propulsion. If methanol unavailability or a high price demands an alternative process, steam reforming appears preferable to partial oxidation for this purpose.
Date: March 1, 1996
Creator: Brown, L.F.
Partner: UNT Libraries Government Documents Department

Cold-moderator scattering kernel methods

Description: An accurate representation of the scattering of neutrons by the materials used to build cold sources at neutron scattering facilities is important for the initial design and optimization of a cold source, and for the analysis of experimental results obtained using the cold source. In practice, this requires a good representation of the physics of scattering from the material, a method to convert this into observable quantities (such as scattering cross sections), and a method to use the results in a neutron transport code (such as the MCNP Monte Carlo code). At Los Alamos, the authors have been developing these capabilities over the last ten years. The final set of cold-moderator evaluations, together with evaluations for conventional moderator materials, was released in 1994. These materials have been processed into MCNP data files using the NJOY Nuclear Data Processing System. Over the course of this work, they were able to develop a new module for NJOY called LEAPR based on the LEAP + ADDELT code from the UK as modified by D.J. Picton for cold-moderator calculations. Much of the physics for methane came from Picton`s work. The liquid hydrogen work was originally based on a code using the Young-Koppel approach that went through a number of hands in Europe (including Rolf Neef and Guy Robert). It was generalized and extended for LEAPR, and depends strongly on work by Keinert and Sax of the University of Stuttgart. Thus, their collection of cold-moderator scattering kernels is truly an international effort, and they are glad to be able to return the enhanced evaluations and processing techniques to the international community. In this paper, they give sections on the major cold moderator materials (namely, solid methane, liquid methane, and liquid hydrogen) using each section to introduce the relevant physics for that material and to show ...
Date: August 1, 1998
Creator: MacFarlane, R.E.
Partner: UNT Libraries Government Documents Department

Modeling and data analysis of a palladium membrane reactor for tritiated impurities cleanup

Description: A Palladium Membrane Reactor (PMR) is under consideration for the tritium plant for the International Thermonuclear Experimental Reactor (ITER). The ITER reactor exhaust will contain tritiated impurities such as water and methane. Tritium will need to be recovered from these impurities for environmental and economic reasons. For this purpose a promising device, PMR, has been proposed. The PMR is a combined permeator and catalytic reactor. Shift catalysts are used to foster reactions such as water-gas shift, H{sub 2}O + CO {yields} H{sub 2} + CO{sub 2}, and methane steam reforming, CH{sub 4} + H{sub 2}O {yields} 3H{sub 2} + CO. Due to thermodynamic limitations these reactions only proceed to partial completion. Thus, a Pd/Ag membrane, which is exclusively permeable to hydrogen isotopes, is incorporated into the reactor. By maintaining a vacuum on the permeate, product hydrogen isotopes are removed, enabling the reactions to proceed to completion. A model has been developed to study the complex interactions in a PMR so that the optimal design can be determined. The model accounts for the coupled effects of transport-limited permeation of hydrogen isotopes and chemical reactions. The permeation model is an extension of previous models that include the effects of temperature, wall thickness, reaction-side pressure, and permeate-side pressure. Reaction rates for methane steam reforming and the water-gas shift reaction are incorporated into the model along with the respective reverse reactions. The model is compared to PMR data and used to investigate the concentration and pressure profiles in the reactor. Due to the interactions of permeation and reaction complex profiles can be produced in a PMR. For example, the water concentration often increases after the inlet to the PMR to a maximum value, and then decreases to the low values expected with a PMR. Detailed information like this is required for the design and ...
Date: July 1, 1995
Creator: Birdsell, S.A. & Willms, R.S.
Partner: UNT Libraries Government Documents Department