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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

Thermal and chemical degradation of inorganic membrane materials. Topical report

Description: This report describes the results of a literature review to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate gaseous products produced by the gasification or combustion of coal in fixed-, fluidized-, and entrained-bed gasifiers, direct coal-fired turbines, and pressurized-fluidized-bed combustors. Several impurities, such as H{sub 2}S, NH{sub 3}, SO{sub 2}, NO{sub x}, and trace metal compounds are generated during coal conversion, and they must be removed from the coal gas or the combustor flue gas to meet environmental standards. The use of membranes to separate these noxious gases is an attractive alternative to their removal by sorbents such as zinc titanate or calcium oxide. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. The U.S. Department of Energy is supporting investigations to develop inorganic membranes for separating hydrogen from coal gas streams and noxious impurities from hot coal- and flue-gas streams. Membrane materials that have been investigated in the past include glass (silica), alumina, zirconia, carbon, and metals (Pd and Pt).
Date: April 1, 1994
Creator: Krishnan, G. N.; Sanjurjo, A.; Wood, B. J. & Lau, K. H.
Partner: UNT Libraries Government Documents Department

Low temperature, sulfur tolerant homogeneous catalysts for the water-gas shift reaction. Task 2, Test plan

Description: The objective of this project is to identify, prepare, test, characterize, and evaluate a practical, homogeneous catalyst for a water-gas shift process. The project effort is divided into the following five tasks: (1) Update SRI`s recent review of the literature on the catalysis of the water-gas shift reaction (WGSR) to include references after 1982 and those in the patent literature. Based on this review, SRI will choose ten candidate systems to be evaluated as to their abilities to catalyze the WGSR using syngas derived from gasified coal. (2) Develop a test plan designed to effectively evaluate both the catalysts and, to some extent, reactor configuration for WGSR catalysis. (3) Perform a series of experiments to identify the most effective and economical of the ten candidate catalysts and then further evaluate the reaction kinetics of at least one selected catalyst system to develop sufficient data to provide the basis for the work in Task 4. (4) Develop a mathematical model of the final candidate system that uses rate expressions to describe the catalytic process. (5) Perform a techno-economical evaluation of the catalyst in terms of a proposed plant design based on the reaction model, current costs, and standard chemical engineering practice and compare the proposed design with a conventional hydrogen plant.
Date: April 1, 1986
Creator: Laine, R. M.; Wood, B. J. & Krishnan, G. N.
Partner: UNT Libraries Government Documents Department

Thermal/chemical degradation of inorganic membrane materials

Description: The specific objectives of this program are to (1) identify and evaluate long-term degradation mechanisms for inorganic membranes exposed to hot coal gasification and combustion gas streams using data from the existing literature, (2) quantify the extent of the degradation process for the most serious mechanisms by performing experiments under laboratory-scale conditions, and (3) develop a predictive model that allows estimation of membrane degradation under operating conditions. To achieve the above objectives, the program is divided into the following tasks: (1) Development of evaluation methodology; (2) evaluation of potential long-term degradation mechanism; (3) submission of a topical report and a plan for experimental testing; (4) experimental testing; and (5) model development. Tasks 4 and 5 are separate options that may be exercised by the US Department of Energy at the conclusion of Task 3. Accomplishments are presented for Tasks 1, 2 and 3.
Date: September 1, 1993
Creator: Krishnan, G. N.; Sanjurgo, A. & Wood, B. J.
Partner: UNT Libraries Government Documents Department

The fate of alkali species in advanced coal conversion systems. Final report

Description: The fate of species during coal combustion and gasification was determined experimentally in a fluidized bed reactor. A molecular-beam sampling mags spectrometer was used to identify and measure the concentration of vapor phase sodium species in the high temperature environment. Concurrent collection and analysis of the ash established the distribution of sodium species between gas-entrained and residual ash fractions. Two coals, Beulah Zap lignite and Illinois No. 6 bituminous, were used under combustion and gasification conditions at atmospheric pressure. Steady-state bed temperatures were in the range 800--950{degree}C. An extensive calibration procedure ensured that the mass spectrometer was capable of detecting sodium-containing vapor species at concentrations as low as 50 ppb. In the temperature range 800{degree} to 950{degree}C, the concentrations of vapor phase sodium species (Na, Na{sub 2}O, NaCl, and Na{sub 2}SO{sub 4}) are less than 0.05 ppm under combustion conditions with excess air. However, under gasification conditions with Beulah Zap lignite, sodium vapor species are present at about 14 ppm at a temperature of 820{degree}. Of this amount, NaCl vapor constitutes about 5 ppm and the rest is very likely NAOH. Sodium in the form of NaCl in coal enhances the vaporization of sodium species during combustion. Vapor phase concentration of both NaCl and Na{sub 2}SO{sub 4} increased when NaCl was added to the Beulah Zap lignite. Ash particles account for nearly 100% of the sodium in the coal during combustion in the investigated temperature range. The fine fly-ash particles (<10 {mu}m) are enriched in sodium, mainly in the form of sodium sulfate. The amount of sodium species in this ash fraction may be as high as 30 wt % of the total sodium. Sodium in the coarse ash particle phase retained in the bed is mainly in amorphous forms.
Date: November 1, 1991
Creator: Krishnan, G. N. & 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

NH{sub 3}/H{sub 2}S advances

Description: The following preliminary conclusions can be derived from the above-mentioned experimental results: (1) HTSR-1, a nickel-based catalyst has a high activity for NH{sub 3} decomposition at 725{degree}C in simulated coal gas streams under low H{sub 2}S levels. (2) HTSR-1 when mixed with a desulfurization sorbent such as zinc titanate could decompose NH{sub 3} effectively until the removal of H{sub 2}S by zinc titanate decreases. (3) HTSR-1 continues to exhibit an activity for NH{sub 3} decomposition even after exposure to zinc titanate regeneration conditions. (4) MoS{sub 2} is also a catalyst for the decomposition of NH{sub 3}. However, its surface area needs to be maintained by addition of suitable stabilizing agents for sustained activity. Sorbent-catalyst samples of zinc titanate doped with cobalt-molybdenum were prepared by first crushing and sieving pellets of zinc titanate sorbents (L-3774M). The zinc titanate powders were then placed into an aqueous solution having the desired total amount of molybdenum (in the form of molybdic acid). The water was then dried and the powder heated and calcined. To add cobalt to the Mo-coated powder, the powder was then placed into a solution of cobalt nitrate containing the appropriate amount of the cobalt precursor followed by drying and calcination. The sorbent-catalyst samples were then activated (presulfided) by introducing H{sub 2}S in a controlled reducing environment. Samples of nickel-molybdenum-zinc titanate were prepared by using nickel nitrate instead of cobalt nitrate in the described procedure.
Date: August 1, 1993
Creator: Gupta, R. P.; Gangwal, S. K.; Krishnan, G. N. & Hung, S. L.
Partner: UNT Libraries Government Documents Department

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

Description: The goal of this program is to develop alkali-based disposable sorbents capable of reducing HCl vapor concentrations to less than 1 ppm in coal gas streams at temperatures in the 480 degree C to 750 degree C range 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 (fixed-, moving-, and fluidized-bed reactors), obtaining kinetic data for commercial reactor design, and updating the economics of the process.
Date: October 1, 1994
Creator: Krishnan, G. N.; Wood, B. J.; Canizales, A.; Gupta, R.; Sheluker, S. D. & Ayala, R.
Partner: UNT Libraries Government Documents Department

Thermal/chemical degradation of inorganic membrane materials

Description: The overall objective of this program is to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate gaseous products produced by the gasification or combustion of coal in fixed-, fluidized-, and entrained-bed gasifiers, direct coal-fired turbines, and pressurized-fluidized-bed combustors. Specific objectives of this program are to (1) quantify the extent of the degradation process for the three most detrimental mechanisms by performing laboratory-scale experiments, and (2) develop a predictive model for membrane degradation under operating conditions. At present, no inorganic membranes are commercially available for application in the high-temperature, high-pressure (HTHP) gas environments encountered in integrated gasification combined cycle (IGCC), pressurized fluidized bed combustion (PFBC), and direct coal fired turbine (DCFT) applications. Most of the inorganic membrane development efforts have focused on hydrogen separation membranes which may be used in an IGCC system for maximizing hydrogen production from coal gas or to remove H{sub 2}S and NH{sub 3} contaminants via thermal or catalytic decomposition of these contaminants. The candidate inorganic membranes may be grouped as follows: dense metallic membranes; silica based membranes; alumina based membranes; and carbon based membranes. Results are reported for membrane characterization done so far.
Date: October 1, 1994
Creator: Krishnan, G. N.; Sanjurjo, A.; Damle, A. S.; 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 &gt;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