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Development of Disposable Sorbents for Chloride Removal from High-Temperature Coal-Derived Gases

Description: The integrated coal-gasification combined-cycle approach is an efficient process for producing electric power from coal by gasification, followed by high-temperature removal of gaseous impurities, then electricity generation by gas turbines. Alternatively, molten carbonate fuel cells (MCFC) may be used instead of gas turbine generators. The coal gas must be treated to remove impurities such as hydrogen chloride (HCl), a reactive, corrosive, and toxic gas, which is produced during gasification from chloride species in the coal. HCl vapor must be removed to meet environmental regulations, to protect power generation equipments such as fuel cells or gas turbines, and to minimize deterioration of hot coal gas desulfurization sorbents. The objectives of this study are to: (1) investigate methods to fabricate reactive sorbent pellets or granules that are capable of reducing HCl vapor in high-temperature coal gas streams to less than 1 ppm in the temperature range 400{degrees}C to 650{degrees}C and the pressure range 1 to 20 atm; (2) testing their suitability in bench-scale fixed- or fluidized-bed reactors; (3) testing a superior sorbent in a circulating fluidized- bed reactor using a gas stream from an operating coal gasifier; and (4) updating the economics of high temperature HCl removal.
Date: December 31, 1996
Creator: Krishnan, G.N.; Canizales, A.; Gupta, R. & Ayala, R.
Partner: UNT Libraries Government Documents Department

Development of disposal sorbents for chloride removal from high-temperature coal-derived gases

Description: The objective of this program is to develop alkali-based disposable sorbents capable of reducing HCl vapor concentrations to less than 1 ppmv in coal gas streams at temperatures in the range 400{degrees} to 750{degrees}C and pressures in the range 1 to 20 atm. The primary areas of focus of this program are investigation of different processes for fabricating the sorbents, testing their suitability for different reactor configurations, obtaining kinetic data for commercial reactor design, and updating the economics of the process.
Date: November 1, 1995
Creator: Krishnan, G.N.; Wood, B.J. & Canizales, A.
Partner: UNT Libraries Government Documents Department

A preliminary study of carbon deposition on zinc ferrite sorbents. Topical report for Task 9

Description: A preliminary study was conducted to determine the feasibility of cumulative carbon deposition on zinc ferrite sorbents under conditions relevant to desulfurization of hot coal gas from the KRW fluidized bed gasifier operating in the air-blown mode. Thermodynamic calculations indicated that the range of conditions under which carbon deposition and carbide formation occur can be broadened if the gas contains less than equilibrium levels of methane. These calculations also indicated that dissociation of CO and reduction of CO by hydrogen are potential pathways for carbon deposition on the sorbent.
Date: August 1, 1991
Creator: Krishnan, G. N.; Wong, V. K. & Wood, B. J.
Partner: UNT Libraries Government Documents Department

A preliminary study of carbon deposition on zinc ferrite sorbents

Description: A preliminary study was conducted to determine the feasibility of cumulative carbon deposition on zinc ferrite sorbents under conditions relevant to desulfurization of hot coal gas from the KRW fluidized bed gasifier operating in the air-blown mode. Thermodynamic calculations indicated that the range of conditions under which carbon deposition and carbide formation occur can be broadened if the gas contains less than equilibrium levels of methane. These calculations also indicated that dissociation of CO and reduction of CO by hydrogen are potential pathways for carbon deposition on the sorbent.
Date: August 1, 1991
Creator: Krishnan, G.N.; Wong, V.K. & Wood, B.J. (SRI International, Menlo Park, CA (United States))
Partner: UNT Libraries Government Documents Department

Thermal and chemical degradation of inorganic membrane materials. Final report, August 1992--May 1995

Description: SRI International conducted a theoretical and experimental program to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate the gaseous products of coal gasification. A variety of developmental efforts are underway, including a number of projects sponsored by the US Department of Energy (DOE), to improve the selectivity and permeability of porous inorganic membranes. DOE is also sponsoring efforts to extend the use of metallic membranes to new applications. Most developmental efforts have focused on hydrogen separation by inorganic membranes, which may be used to maximize hydrogen production from coal gas or to remove H{sub 2}S and NH{sub 3} contaminants via thermal or catalytic decomposition in integrated-gasification combined-cycle (IGCC) systems. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. Membrane materials that have been investigated include glass (silica), alumina, carbon, and metals (Pd and Pt). This report describes inorganic membrane materials, long term membrane exposure tests, membrane permeation tests, coal gasifier exposure tests, conclusions, and recommendations.
Date: May 1, 1995
Creator: Damle, A.S.; Krishnan, G.N.; Sanjurjo, A.; Wood, B.J. & Lau, K.H.
Partner: UNT Libraries Government Documents Department

Thermal/chemical degradation of inorganic membrane materials

Description: The objective of this program is to evaluate the long-term thermal and chemical degradation of inorganic membranes that are developed to separate gases produced by coal combustion and coal gasification. Membrane materials tested include alumina, vycor, platinum foil, and palladium foils. The porosity, permeability, and characterization of physical and chemical changes after exposure to hot gas streams is described.
Date: December 1, 1995
Creator: Krishnan, G.N.; Damle, A.S.; Sanjurjo, A.; Wood, B.J. & Lau, K.H.
Partner: UNT Libraries Government Documents Department

Catalytic Ammonia Decomposition for Coal-Derived Fuel Gases

Description: The objective of this study is to develop and demonstrate catalytic approaches for decomposing a significant percentage (up to 90 percent) of the NH{sub 3} present in fuel gas to N{sub 2} and H{sub 2} at elevated temperatures (550 to 900{degrees}C). The NH{sub 3} concentration considered in this study was {similar_to}1,800 to 2,000 ppmv, which is typical of oxygen-blown, entrained-flow gasifiers such as the Texaco coal gasifier being employed at the TECO Clean Coal Technology Demonstration plant. Catalysts containing Ni, Co, Mo, and W were candidates for the study. Before undertaking any experiments, a detailed thermodynamic evaluation was conducted to determine the concentration of NH{sub 3} in equilibrium with the Texaco gasifier coal gas. Thermodynamic evaluations were also performed to evaluate the stability of the catalytic phases (for the various catalysts under consideration) under NH3 decomposition conditions to be used in this study. Two catalytic approaches for decomposing NH{sub 3} have been experimentally evaluated. The first approach evaluated during the early phases of this project involved the screening of catalysts that could be combined with the hot-gas desulfurization sorbents (e.g., zinc titanate) for simultaneous NH{sub 3} and H{sub 2}S removal. In a commercial system, this approach would reduce capital costs by eliminating a process step. The second approach evaluated was high-temperature catalytic decomposition at 800 to 900{degrees} C. In a commercial hot-gas cleanup system this could be carried out after radiative cooling of the gas to 800 to 900{degrees}C but up stream of the convective cooler, the hot particulate filter, and the hot-gas desulfurization reactor. Both approaches were tested in the presence of up to 7,500 ppmv H{sub 2}S in simulated fuel gas or actual fuel gas from a coal gasifier.
Date: December 31, 1996
Creator: Gangwal, S.K.; Gupta, R.P.; Portzer, J.W.; Turk, B.S.; Krishnan, G.N.; Hung, S.L. et al.
Partner: UNT Libraries Government Documents Department

NOVEL TECHNOLOGIES FOR GASEOUS CONTAMINANTS CONTROL

Description: The overall objective of this project is to develop technologies for cleaning/conditioning the syngas from an integrated gasification combined cycle (IGCC) system to meet the tolerance limits for contaminants such as H{sub 2}S, COS, NH{sub 3}, HCN, HCl, and alkali for fuel cell and chemical production applications. RTI's approach is to develop a modular system that (1) removes reduced sulfur species to sub-ppm levels using a hybrid process consisting of a polymer membrane and a regenerable ZnO-coated monolith or a mixed metal oxide sorbent; (2) removes hydrogen chloride vapors to sub-ppm levels using an inexpensive, high-surface area material; and (3) removes NH{sub 3} with acidic adsorbents. RTI is working with MEDAL, Inc., and North Carolina State University (NCSU) to develop polymer membrane technology for bulk removal of H{sub 2}S from syngas. These membranes are being engineered to remove the acid gas components (H{sub 2}S, CO{sub 2}, NH{sub 3}, and H{sub 2}O) from syngas by focusing on the ''solubility selectivity'' of the novel polymer compositions. The desirable components of the syngas (H{sub 2} and CO) are maintained at high-pressure conditions as a non-permeate stream while the impurities are transported across the membrane to the low pressure side. RTI tested commercially available and novel materials from MEDAL using a high-temperature, high-pressure (HTHP) permeation apparatus. H{sub 2}S/H{sub 2} selectivities >30 were achieved, although there was a strong negative dependence with temperature. MEDAL believes that all the polymer compositions tested so far can be prepared as hollow fiber membrane modules using the existing manufacturing technology. For fuel cell and chemical applications, additional sulfur removal (beyond that achievable with the membranes) is required. To overcome limitations of conventional ZnO pellets, RTI is testing a monolith with a thin coating of high surface area zinc-oxide based materials. Alternatively, a regenerable sorbent developed by DOE/NETL (RVS-1) is ...
Date: September 30, 2001
Creator: Turk, B. S.; Merkel, T.; Lopez-Ortiz, A.; Gupta, R. P.; Portzer, J. W.; Krishnan, G. N. et al.
Partner: UNT Libraries Government Documents Department