24 research outputs found
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Hydrogen Separation Membranes
Get PDFA likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatings appeared relatively stable in air and in a simple simulated gasification atmosphere at elevated temperature. Because the electron-beam coating instrument suffered irreparable breakdown, several alternative methods were tested in an effort to produce a nitrogen-impermeable, hydrogen-permeable membrane on porous sintered steel substrates. None of the preparation methods proved successful in sealing the porous substrate against nitrogen gas. To provide a nitrogen-impermeable ZnS material to test for hydrogen permeability, two ZnS infrared sample windows were purchased. These relatively thick ''membranes'' did not show measurable permeation of hydrogen, either due to lack of absorption or a negligible permeation rate due to their thickness. To determine if hydrogen was indeed adsorbed, thermogravimetric and differential thermal analyses tests were performed on samples of ZnS powder. A significant uptake of hydrogen gas occurred, corresponding to a maximum of 1 mole H{sub 2} per 1 mole ZnS at a temperature of 175 C. The hydrogen remained in the material at ambient temperature in a hydrogen atmosphere, but approximately 50% would be removed in argon. Reheating in a hydrogen atmosphere resulted in no additional hydrogen uptake. Differential scanning calorimetry indicated that the hydrogen uptake was probably due to the formation of a zinc-sulfur-hydrogen species resulting in the formation of hydrogen sulfide. The zinc sulfide was found to be unstable above approximately 200 C, probably with the reduction to metallic zinc with the evolution of hydrogen sulfide. The work has shown that ZnS is not a viable candidate for a high-temperature hydrogen separation membrane
Task 6.5/6.7.1 - Materials for Gas Separation and Hydrogen Separation Membranes
No full textCatalytic gasification of coal to produce H2- and CH4-rich gases for consumption in molten carbonate fhel cells is currently under development; however, to optimize the fiel cell performance and extend its operating life, it is desired to separate as much of the inerts as possible from the fuel gas before they enter the fiel cell. In addition, the economics of the integrated gasification combined cycle (IGCC) can be improved by separating as much of the hydrogen as possible from the fuel, since hydrogen is a high-value product. One process currently under development by the Energy& Environmental Research Center (EERC) for accomplishing this gas separation and hot-gas cleanup involves gas separation membranes. These membranes are operated at temperatures as high as 800 `C and pressures up to 300 psig. Some of these membranes can have very small pores (30-50 ~), which inefllciently separate the undesired gases by operating in the Knudsen diffision region of mass transport. Other membranes with smaller pore sizes (<5 ~) operate in the molecular sieving region of mass transport phenomena. Dissolution of atomic hydrogen into thin metallic membranes made of platinum and palladium alloys is also being developed. Technological and economic issues that must be resolved before gas separation membranes are commercially viable include improved gas separation efficiency, membrane optimization, sealing of membranes in pressure vessels, high burst strength of the ceramic material, pore thermal stability, and material chemical stability. Hydrogen separation is dependent on the temperature, pressure, pressure ratio across the membrane, and ratio of permeate flow to total flow
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Task 6.5/6.7.1 - Materials for Gas Separation and Hydrogen Separation Membranes
Get PDFCatalytic gasification of coal to produce H2- and CH4-rich gases for consumption in molten carbonate fuel cells is currently under development; however, to optimize the fuel cell performance and extend its operating life, it is desired to separate as much of the inerts as possible from the fuel gas before they enter the fuel cell. In addition, the economics of the integrated gasification combined cycle (IGCC) can be improved by separating as much of the hydrogen as possible from the fuel, since hydrogen is a high-value product. One process currently under development by the Energy & Environmental Research Center (EERC) for accomplishing this gas separation and hot-gas cleanup involves gas separation membranes. These membranes are operated at temperatures as high as 8000 C and pressures up to 300 psig. Some of these membranes can have very small pores (30-50 ~), which inefficiently separate the undesired gases by operating in the Knudsen diffusion region of mass transport. Other membranes with smaller pore sizes ( <5 ~) operate in the molecular sieving region of mass transport phenomena. Dissolution of atomic hydrogen into thin metallic membranes made of platinum and palladium alloys is also being developed. Technological and economic issues that must be resolved before gas separation membranes are commercially viable include improved gas separation efficiency, membrane optimization, sealing of membranes in pressure vessels, high burst strength of the ceramic material, pore thermal stability, and material chemical stability. Hydrogen separation is dependent on the temperature, pressure, pressure ratio across the membrane, and ratio of permeate flow to total flow
Task 2.10 - Advanced Sampling and Analysis of Fine Particulates
No full textThe objectives of this study are to develop a sampling method to capture the fine particulate and classiyi the particulate according to their size and chemistry. When developing the sampling method, two criteria need to be met: 1) the particulate are randomly dispersed on the sampling media and 2) the sampling media can be put directly into a scanning electron microscope (SEM) for analysis to prevent any alteration of the particulate. Several methods for the sampling and analysis of fine particulate are to be tested. Each sampling test will be analyzed using the FPT technique for collecting the size, shape, and chemical composition of 1500 to 2000 individual fine particulate. The FPT data will be classified using cluster analysis and principal component analysis to provide a classification system for these particles. As reported previously, particulate samples were collected using the advanced hybrid particulate collector (AHPC) on the inlet port of the particulate test combustor (PTC) when the Absaloka coal was burned in early April. The samples were collected at the inlet rather than the outlet port because of the loading that was expected and the temperature at which the PTC was run. Samples at the inlet were expected to see a much greater particulate loading than at the outlet because of the efficiency of the particulate collection device on the PTC. Also, polycarbonate filters cannot withstand temperatures above 230oC for long periods of time; therefore, a quick loading time was required. The samples were briefly scanned and photographed using the SEM to determine the best particulate loading time. The particulate were too close together on the 20- and 30-second polycarbonate filters to be able to analyze individual particles. The particle dispersion on the vitreous carbon substrate appeared to be the best of the four samples. Aerosols were produced from pure 1.0 M aqueous solutions of NaCl, Na2S04, (NHq)2SOo, NHqNO~, and K20 (KOH) using a Tri-Jet Model 3460 aerosol generator and collected by direct impingement on a vitreous carbon substrate. Because NaCl is the normal aerosol produced with the generator, it was briefly examined using SEM to determine the degree of dispersion. Good dispersion with nearly all particulate size below 2 pm and the majority in the O.1-pm range was achieved with a substrate collection time of 2-3 minutes. The brief examination also demonstrated that the sample could be introduced directly into the SEM for analysis with no prior carbon coating or other preparation and that charging of the sample was minimal
Task 3.0 - Advanced Power Systems Subtask 3.18 - Ash Behavior in Power Systems
No full textAsh behavior in power systems can have a significant impact on the design and performance of advanced power systems. The Energy & Environmental Research Center (EERC) has focused significant effort on ash behavior in conventional power systems that can be applied to advanced power systems. This initiative focuses on filling gaps in the understanding of fundamental mechanisms of ash behavior that has relevance to commercial application and marketable products. This program develops methods and means to better understand and mitigate adverse coal ash behavior in power systems and can act to relieve the U.S. reliance on diminishing recoverable oil resources, especially those resources that are not domestically available and are fairly uncertain
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Task 3.0 - Advanced Power Systems Subtask 3.18 - Ash Behavior in Power Systems
Get PDFAsh behavior in power systems can have a significant impact on the design and performance of advanced power systems. The Energy & Environmental Research Center (EERC) has focused significant effort on ash behavior in conventional power systems that can be applied to advanced power systems. This initiative focuses on filling gaps in the understanding of fundamental mechanisms of ash behavior that has relevance to commercial application and marketable products. This program develops methods and means to better understand and mitigate adverse coal ash behavior in power systems and can act to relieve the U.S. reliance on diminishing recoverable oil resources, especially those resources that are not domestically available and are fairly uncertain
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Task 2.10 - Advanced Sampling and Analysis of Fine Particulates
Get PDFThe objectives of this study are to develop a sampling method to capture the fine particulate and classiyi the particulate according to their size and chemistry. When developing the sampling method, two criteria need to be met: 1) the particulate are randomly dispersed on the sampling media and 2) the sampling media can be put directly into a scanning electron microscope (SEM) for analysis to prevent any alteration of the particulate. Several methods for the sampling and analysis of fine particulate are to be tested. Each sampling test will be analyzed using the FPT technique for collecting the size, shape, and chemical composition of 1500 to 2000 individual fine particulate. The FPT data will be classified using cluster analysis and principal component analysis to provide a classification system for these particles. As reported previously, particulate samples were collected using the advanced hybrid particulate collector (AHPC) on the inlet port of the particulate test combustor (PTC) when the Absaloka coal was burned in early April. The samples were collected at the inlet rather than the outlet port because of the loading that was expected and the temperature at which the PTC was run. Samples at the inlet were expected to see a much greater particulate loading than at the outlet because of the efficiency of the particulate collection device on the PTC. Also, polycarbonate filters cannot withstand temperatures above 230oC for long periods of time; therefore, a quick loading time was required. The samples were briefly scanned and photographed using the SEM to determine the best particulate loading time. The particulate were too close together on the 20- and 30-second polycarbonate filters to be able to analyze individual particles. The particle dispersion on the vitreous carbon substrate appeared to be the best of the four samples. Aerosols were produced from pure 1.0 M aqueous solutions of NaCl, Na2S04, (NHq)2SOo, NHqNO~, and K20 (KOH) using a Tri-Jet Model 3460 aerosol generator and collected by direct impingement on a vitreous carbon substrate. Because NaCl is the normal aerosol produced with the generator, it was briefly examined using SEM to determine the degree of dispersion. Good dispersion with nearly all particulate size below 2 pm and the majority in the O.1-pm range was achieved with a substrate collection time of 2-3 minutes. The brief examination also demonstrated that the sample could be introduced directly into the SEM for analysis with no prior carbon coating or other preparation and that charging of the sample was minimal
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Low-Temperature Ash Sintering and Strength Development
Get PDFThe objective of the project is to develop fundamental sintering-viscosity relationships for coal-type ash at relatively low temperatures, with the end result being a simplified soot-blowing index for power systems. This involves correlating several important factors which control the ease of deposit removal, including deposit strength, deposit porosity, chemical composition, and temperature. Testing was performed on ashes derived from three coals and two biomass materials along with a standard soda-lime glass. The coals were selected because detailed analyses as well as ash samples were already available. Sintering characteristics of the ashes were to be determined by observation using an HSM and video recording system, with a stainless steel microscope stage chamber constructed to allow the use of corrosive gas atmospheres. The measurements would allow calculation of the viscosity of liquid phases as the sintering progressed, using the Frenkel and other sintering models. The sintering behavior and viscosity would be correlated with ash mineralogy and chemistry and information on bench-scale deposit strength and porosity to develop an initial relationship to predict deposit removability
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Ash Emissivity Characterization and Prediction
Get PDFThe increased use of western subbituminous coals has generated concerns regarding highly reflective ash disrupting heat transfer in the radiant zone of pulverized-fuel boilers. Ash emissivity and reflectivity is primarily a function of ash particle size, with reflective deposits expected to consist of very small refractory ash materials such as CaO, MgO, or sulfate materials such as Na{sub 2}SO{sub 4}. For biomass fuels and biomass-coal blends, similar reflectivity issues may arise as a result of the presence of abundant organically associated calcium and potassium, which can transform during combustion to fine calcium, and potassium oxides and sulfates, which may act as reflective ash. The relationship of reflectivity to ash chemistry is a second-order effect, with the ash particle size distribution and melting point being determined by the size and chemistry of the minerals present in the starting fuel. Measurement of the emission properties of ash and deposits have been performed by several research groups (1-6) using both laboratory methods and measurements in pilot- and full-scale combustion systems. A review of the properties and thermal properties of ash stresses the important effect of ash deposits on heat transfer in the radiant boiler zone (1)
