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The sulfidation of calcined limestone and dolomite was studied in an ambient pressure quartz thermogravimetric analyzer (TGA) reactor unit at 982°C. Comparative sulfidation experiments were performed with and without the presence of HCl using both calcined limestone and dolomite in two particle sizes. The reactant gas contained H2S, H2, H2O, and nitrogen. The H2S and HCl content of the reactant gas was chosen to represent oxygen-blown and air-blown coal gasification environments. The results of this study indicate that the addition of both steam and HCl enhances the overall rate of sulfidation reaction and that the rate is linearly dependent on the HCl content of the reactant gas up to 100 ppm for limestone and 150 ppm for dolomite. The sulfidation reaction rate is insensitive to HCl concentrations above these levels for these sorbents. The results obtained in this study suggest that the enhancement of the sulfidation reaction rate in the presence of HCl is caused by surface phenomena that are related to the presence of steam.

The overall objective of this study is to determine the effect of implementation of the new and more stringent EPA Protocol Test Method involving sulfide containing waste, on the suitability of the oxidized spent sorbents from gasification of of high sulfur coals for disposal in landfills, and to determine the optimum operating conditions in a ``final`` hydrolysis stage for conversion of the residual calcium sulfide in these wastes to materials that are suitable for disposal in landfills. An additional objective is to study the effect of ash on the regeneration and ash-sorbent separation steps in the Spent Sorbent Regeneration Process (SSRP). To achieve these objectives, a large set of oxidized samples of sulfided calcium-based sorbents (produced in earlier ICCI-funded programs) as well as oxidized samples of gasifier discharge (containing ash and spent sorbent) are tested according to the new EPA test protocol. Samples of the oxidized spent sorbents that do not pass the EPA procedure are reacted with water and carbon dioxide to convert the residual calcium sulfide to calcium carbonate. During this quarter, samples of oxidized sulfided calcium-based sorbents, including untreated calcium sulfide-containing feed materials, were analyzed using both weak acid and more stringent strong acid tests. Preliminary analysis of the H{sub 2}S leachability test results indicate that all samples (including those that were not oxidized) pass the EPA requirement of 500 mg H{sub 2}S per kg of solid waste. However, under the strong acid test procedure, samples containing more than 2.5% calcium sulfide fail the EPA requirement.

The overall objective of this study is to determine the effectiveness of the copper-chromite sorbent (developed in previous ICCI-funded projects) for longer duration application under optimum conditions in the temperature range of 550{degrees}-650{degrees}C to minimize sorbent reduction and degradation during the cyclic process. To achieve this objective, several formulations of copper chromite sorbents are prepared. These sorbent formulations are screened for their desulfurization and regeneration capability at predetermined temperatures and gas residence times. The durability of the best sorbent formulation identified in the screening tests is evaluated in ``long-term`` durability tests conducted at the optimum operating conditions. This includes testing the sorbent in pellet and granular forms in packed- and fluidized-bed reactors. During this quarter, twenty one copper chromite-based sorbent formulations were prepared. Two sorbent formulations that have acceptable crush strength, designated as CuCr-10 and CuCr-21, were tested over 5 and 6 cycles respectively. The results indicate that both sorbents are reactive toward H{sub 2}S at 650{degrees}C and that the reactivity of the sorbents are relatively constant over the first 5 to 6 cycles. The H{sub 2}S prebreakthrough concentrations were generally about 20 to 30 ppm, making them suitable for IGCC application.

The objective of this investigation is to evaluate two novel copper-based sorbents, namely copper-chromium and copper-cerium, for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650 to 850 C. Such high temperatures will be required for the new generation of gas turbines (inlet > 750 C) in Integrated Gasification Combined Cycle (IGCC) systems. Results of fixed-bed reactor tests conducted in this quarter, indicate that, at 750 C, pre-reduction with H{sub 2} in the presence of H{sub 2}O does not effect the performance of either sorbent for H{sub 2}S removal. For the pre-reduced CuCr{sub 2}O{sub 4} sorbent, copper utilization before the first H{sub 2}S breakthrough is substantially higher in synthesis feed gas mixture than in feed gas containing 30 Vol% H{sub 2}, and slightly lower than in 10 vol% H{sub 2}. In sulfidation-regeneration testing of copper- and additive-rich sorbents, chromium-rich CuO-3Cr{sub 2}O{sub 4} sorbent demonstrated very high H{sub 2}S removal efficiency and high copper conversion levels (comparable to that of the 1:1 molar composition sorbent). Similar results were obtained with the cerium-rich CuO-3CeO{sub 2} sorbent, but only for the first cycle. The H{sub 2}S removal performance of both copper-rich sorbents was inferior to that ofmore » the respective 1:1 molar compositions. CuO-CeO{sub 2} sorbent testing in a TGA indicates no appreciable decrease in the sulfidation rate over 5 1/2 cycles. However, weight changes during regeneration of the CuO-CeO{sub 2} suggest that some copper or cerium sulfates formed.« less

The objective of this study is to obtain data on the rates of reaction between, hydrogen sulfide (H{sub 2}S) and uncalcined calcium-based sorbents under operating conditions relevant to first stage (carbonizer) of Advanced Two-Stage Pressurized Fluidized-Bed Combustors (PFBC). In these systems the CO{sub 2} partial pressure in the first stage generally exceeds the equilibrium value for calcium carbonate decomposition. Therefore, removal of sulfur compounds takes place through the reaction between H{sub 2}S and calcium carbonate. To achieve this objective the rates of reaction between hydrogen sulfide and uncalcined calcium-based sorbents will be determined by conducting tests in pressurized thermogravimetric analyzer (TGA) and high-pressure/high-temperature fluidized-bed reactor (HPTR) units. The effects of sorbent type, sorbent particle size, reactor temperature and pressure, and CO{sub 2} and H{sub 2}S partial pressures on the sulfidation reaction rate will be determined. During this quarter, the high-pressure thermogravimetric analyzer (HPTGA) unit was installed and the shakedown process was completed. Several tests were conducted in the HPTGA unit to establish the operating procedure and the repeatability of the experimental results. Sulfidation by conducting the baseline sulfidation tests. The results are currently being analyzed.

The objective of this investigation is to evaluate two novel copper-based sorbents, namely copper-chromium and copper-cerium, for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650{degree} to 850{degree}. Such high temperatures will be required for the new generation of gas turbines (inlet >750{degree}C) in Integrated Gasification Combined Cycle (IGCC) systems. The effect of pre-reduction with H{sub 2}, in the presence of H{sub 2}O on the performance of the sorbents in cyclic sulfidation/regeneration, was studied in a thermogravimetric analyzer (TGA) and in a fixed-bed reactor at 750{degree}C. The results of the TGA tests indicate that pre-reduction of the sorbents is very fast in either 10% or 30% H{sub 2}. Without sorbent pre-reduction, sulfidation consists of two-stages, a reduction-dominating and a sulfidation-dominating stage. Sulfidation apparently takes place before reduction is complete. During regeneration some copper/cerium sulfates may have formed and Cu{sub 2}O may have formed in addition to CuO. The fixed-bed reactor tests show that at 750{degree}C: (1) prereducing the CuO-Cr{sub 2}O{sub 3} with H{sub 2} does not effect the reactivity of the sorbent towards H{sub 2}S at either the high or low H{sub 2} feed gas concentrations and (2) when 30% H{sub 2} was usedmore » during sulfidation of either sorbent, the first H{sub 2}S breakthrough occurs earlier than when 10% H{sub 2} was used.« less

The objective of this study is to obtain data on the rates of reaction between hydrogen sulfide (H{sub 2}S) and uncalcined calcium-based sorbents under operating conditions relevant to first stage (carbonizer) of Advanced Two-Stage Pressurized Fluidized-Bed Combustors (PFBC). In these systems the CO{sub 2} partial pressure in the first stage generally exceeds the equilibrium value for calcium carbonate decomposition. Therefore, removal of sulfur compounds takes place through the reaction between H{sub 2}S and calcium carbonate. To achieve this objective, the rates of reaction between hydrogen sulfide and uncalcined calcium-based sorbents will be determined by conducting tests in pressurized thermogravimetric analyzer (TGA) and high-pressure/high-temperature fluidized-bed reactor (HPTR) units. The effects of sorbent type, sorbent particle size, reactor temperature and pressure, and CO{sub 2} and H{sub 2}S partial pressures on the sulfidation reaction rate will be determined. A pressurized TGA unit has been purchased by IGT for use in this project.

The objective of this investigation is to evaluate two novel copper-based sorbents, namely copper-chromium and copper-cerium, for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650{degree} to 850{degree}C. Such high temperatures will be required for the new generation of gas turbines (inlet >750{degree}C) in Integrated Gasification Combined Cycle (IGCC) systems. The effect of pre-reduction on the performance of the sorbents as well as the rate of different reactions occurring in cyclic sulfidation/regeneration, were studied in a thermogravimetric analyzer (TGA). Sulfidation was conducted with and without H{sub 2} and H{sub 2}O, and with and without pre-reduction in H{sub 2} or H{sub 2}/H{sub 2}O. The results of these tests indicate that reduction and regeneration of both sorbents occurs rapidly. Sulfidation of CuCr{sub 2}O{sub 4}, in H{sub 2}O-free and H{sub 2}-/H{sub 2}O-free gas indicates the possible sulfidation of both copper and chromium. Small quantities of SO{sub 2}, were released during sulfidation suggesting the possible oxidation of H{sub 2}S by the sorbent. Regeneration of the CuCr{sub 2}O{sub 4} was complete while regeneration of the CuO-CeO{sub 2} indicated possible limited sulfate formation.

The objective of this investigation is to determine the kinetics of reactions involving partially sulfided dolomite and oxygen, which is needed for the design of the reactor system for the stabilization of sulfide-containing solid wastes from gasification of high sulfur coals. During this quarter, samples of the partially sulfided dolomite were reacted with oxygen in the fluidized-bed reactor at different operating conditions. The test parameters included the effects of solid residence time, sorbent particle size, and reaction pressure. The reacted solids were analyzed to determine the extent of CaS conversion to CASO{sub 4}. The results of these tests indicate that the rate of sulfation reaction increases with decreasing sorbent particle diameter and increasing pressure. Classical gas/solid reaction models, including the shrinking core model, the uniform conversion model, and the grainy pellet model, were applied to the experimental data of CaS sulfation. However, none of these models appears to be capable of predicting the measured CaS conversion with acceptable accuracy, indicating that these classical models should be modified to obtain better agreement between experimental and theoretical results.

The objective of this investigation is to evaluate two novel copper-based sorbents (i.e. copper-chromium and copper-cerium) for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650{degrees} to 850{degrees}C. In this program, structural and kinetic studies are conducted on various compositions of the two selected copper-based sorbents to determine the optimum sorbent composition. The effect of operating conditions on the performance of the sorbents alone with the stability and regenerability of the selected sorbents in successive sulfidation/regeneration operation are determined. Parametric multicycle desulfurization tests were conducted this quarter in a bench-scale (5-cm-diameter) quartz reactor at one atmosphere using the CuCr{sub 2}O{sub 4} and CuO/CeO{sub 2} sorbents. The parameters studied included temperature, space velocity, and feed gas composition. Both sorbents were able to reduce the H{sub 2}S concentration of the reactor feed gas to

The objective of this investigation is to determine the kinetics of reactions involving partially sulfided dolomite and oxygen, which is needed for the design of the reactor system for the stabilization of sulfide-containing solid wastes from gasification of high sulfur coals. To achieve this objective, samples of partially sulfided dolomite are reacted with oxygen at a variety of operating conditions in a fluidized-bed reactor, where external diffusion limitations are avoided by using small quantities of the sorbent and maintaining a high flow rate of the reactant gas. The reacted sorbents are analyzed to determine the extent of conversion as a function of operating variables including sorbent particle size, reaction temperature and pressure, and oxygen concentration. Samples of the partially sulfided dolomite were reacted with oxygen in the fluidized-bed rector at different operating conditions. The test parameters included the effects of solid residence time, oxygen concentration, and reaction temperature. The reacted solids were analyzed to determine the extent of CaS conversion to CaSO{sub 4}. The results of the tests conducted so far in the project indicate that the extent of conversion increase with increasing oxygen concentration and the solid residence time. The rate of reaction appears to be very sensitive tomore » the reaction temperature.« less

The objective of this investigation is to evaluate two novel copper-based sorbents (i.e. copper-chromium and copper-cerium) for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650[degree] to 850[degree]C. New sorbent compositions from the selected Cu-Cr-O and Cu-Ce-O binary oxides were prepared and characterized by BET N[sub 2]-desorption surface area measurement following various calcination/time-temperature exposures. The general trends reported last quarter (on 11 different compositions) were validated this quarter in that both binary oxides lose surface area as the amount of CuO is increased. Time-resolved sulfidation tests were conducted at 850[degree]C using the equimolar CuO.Cr[sub 2]O[sub 3] composition. The two selected binary oxides prepared in larger qauntities (for testing in a two-inch reactor) have physical properties typical of the sorbents prepared in past programs. Two multicycle desulfurization tests, conducted this quarter on the Cu-Ce-O sorbent at 850[degree]C, using a feed gas containing 5000 ppm H[sub 2]S, 10 vol % H[sub 2] and 10 vol % H[sub 2]O at a space velocity (STP) of 2000 h[sup [minus]1], demonstrated high sulfur removal efficiency for the first one or two cycles, and a significant reduction in efficiency in the following cycles.

The objective of this investigation is to evaluate two novel copper-based sorbents, namely Cu-Cr and Cu-Ce, for their effectiveness in removing hydrogen sulfide from fuel gas in the temperature range of 650 to 850 C. Such high temperatures will be required for the new generation of gas turbines in Integrated Gasification Combined Cycle systems. Structural and kinetic studies were conducted on various compositions of the two Cu-based sorbents to determine the optimum sorbent composition. The effect to operating conditions on the performance of the sorbents along with the stability and regenerability of the selected sorbents in successive sulfidation/regeneration operation were determined. Overall, the CuO-lean binaries (with Cr{sub 2}O{sub 3} or CeO{sub 2}) may benefit the H{sub 2}S breakthrough levels. While this is at the expense of sulfur capacity for the Cu-Cr-O sorbents, it may not affect the capacity of the Cu-Ce-O sorbents. Parametric multicycle desulfurization tests were conducted in a bench-scale quartz reactor at one atmosphere using the CuCr{sub 2}O{sub 4} and CuO-CeO{sub 2} sorbents. The parameters studied included temperature, space velocity, and feed gas composition. Both sorbents were able to reduce the H{sub 2}S concentration of the reactor feed gas from 5,000 ppmv to less than 1 ppmv tomore » 10 ppmv at 750 to 850 C. Both sorbents were found to consume H{sub 2} and produce SO{sub 2} during the initial stages of sulfidation. Analysis of partially sulfided samples identified predominantly Cu metal, the additive oxide and small amounts of oxidic copper. For the Cu-Cr-O sorbents, the latter is apparently sufficient to keep the H{sub 2}S pre-breakthrough levels as low as has been reported in this work. For the Cu-Ce-O sorbents, in which very little or no oxidic copper remained, the low H{sub 2}S levels may be due to the participation of CeO{sub 2}, whose sulfidation is promoted by Cu.« less

The objective of this investigation was to determine the effects of SO{sub 2} partial pressure and reaction temperature on the conversion of sulfide containing solid wastes from coal gasifiers to stable and environmentally acceptable calcium sulfate, while preventing the release of sulfur dioxide during the stabilization step. An additional objective of this study was to investigate the use of the Spent Sorbent Regeneration Process (SSRP) to regenerate spent Ca-based sorbent, from a fluidized-bed gasifier with in-bed sulfur capture, for recycling to the gasifier. To achieve these objectives, selected samples of partially sulfided sorbents were reacted with oxygen and SO{sub 2} at various operating conditions and the extent of CaS and CaO conversion were determined. Partially sulfided dolomite was used in sulfidation/regeneration over several cycles and the regeneration efficiency and sorbent reactivity were determined after each cycle. The results of the stabilization tests show that partially sulfided Ca-based sorbents (both limestone and dolomite) can be sulfated at temperatures above 1500{degrees}F resulting in high CaS conversion without release of SO{sub 2} producing environmentally acceptable material for disposal in landfills. The results also indicate that spent dolomite can be regenerated in the SSRP process, in successive cycles, with high regeneration efficiency without lossmore » of reactivity toward hydrogen sulfide.« less

The objective of this investigation is to evaluate several novel copper-based binary oxides for their suitability as regenerable sorbents for hot gas cleanup application in the temperature range of 650{degrees} to 850{degrees}C. During this quarter cyclic sulfidation/regeneration tests of the sorbents Cu{sub 2}Cr-O and Cu-Ce-0 were conducted using different compositions of the feed gases to investigate the effects of H{sub 2}0, H{sub 2} and CO. These tests were conducted in a packed-bed microreactor at 850{degrees}C. The results of these tests showed that H{sub 2} and CO (along with C02) had a significant effect on the H{sub 2}S pre-breakthrough levels, whereas H{sub 2}0 did not have an effect. The physical properties of the fresh and reacted samples of the Cu-2Cr-O and Cu-Ce-0 sorbents prepared in this program and used in the cyclic sulfidation/regeneration tests were also measured. In addition, sulfidation/regeneration tests were conducted using two commercial copper chromite sorbents (G-13 and G-89, United Catalyst, Inc.) and a zinc titanate sorbent (L-3014) in a one-inch fluidized-bed reactor at 650{degrees}C. The G-13 sorbent appears to have a much higher sulfur capacity than the G-89 sorbent.

The objective of this investigation is to determine the effects of SO{sub 2} partial pressure and reaction temperature on the conversion of sulfide containing solid wastes from coal gasifiers to stable and environmentally acceptable calcium sulfate, while preventing the release of sulfur dioxide through undesirable side reactions during the stabilization step. An additional objective of this program is to investigate the use of the Spent Sorbent Regeneration Process (SSRP) to regenerate spent limestone, from a fluidized-bed gasifier with in-bed sulfur capture, for recycling to the gasifier. To achieve these objectives, selected samples of partially sulfided sorbents will be reacted with oxygen at a variety of operating conditions under sufficient S0{sub 2} partial pressure to prevent release of sulfur from the solids during stabilization that reduces the overall sorbent utilization. Partially sulfided limestone will also be regenerated with water using the SSRP to produce calcium hydroxide and release sulfur as H{sub 2}S. The regenerated sorbent will be dewatered, dried and pelletized. The reactivity of the regenerated sorbent toward H{sub 2}S will also be determined.

The objective of this investigation is to evaluate several novel copper-based binary oxides for their suitability as regenerable sorbents for hot gas cleanup application in the temperature range of 650{degrees} to 850{degrees}C. To achieve this objective, several novel copper-based binary oxide sorbents will be prepared. Experimental tests will be conducted at ambient pressure to determine the stability, sulfidation capacity, regenerability, and sulfidation kinetics of the novel sorbents. Tests will also be conducted at high pressure for the determination of the sulfidation reactivity, regenerability, and durability of the sorbents. The attrition characteristics of the sorbents will also be determined.

The objective of this investigation is to determine the effects of SO, partial pressure and reaction temperature on the conversion of sulfide containing solid wastes from coal gasifiers to stable and environmentally acceptable calcium-sulfate, while preventing the release of sulfur dioxide through undesirable side reactions during the stabilization step. An additional objective of this program is to investigate the use of the Spent Sorbent Regeneration Process (SSRP) to regenerate spent limestone, from a fluidized-bed gasifier with in-bed sulfur capture, for recycling to the gasifier. To achieve these objectives, selected samples of partially sulfided sorbents will be reacted with oxygen at a variety of operating conditions under sufficient S0{sub 2} partial pressure to prevent release of sulfur from the solids during stabilization that reduces the overall sorbent utilization. Partially sulfided limestone will also be regenerated with water to produce calcium hydroxide and release sulfur as H{sub 2}S. The regenerated sorbent will be dewatered, dried and pelletized. The reactivity of the regenerated sorbent toward H{sub 2}S will also be determined.

In the catalytic liquefaction of coal using zinc chloride, the recovery of the various spent zinc products is a prime requirement if the process is to be economically feasible. After hydrogenation, depending on the extent of coal conversion to liquid and gaseous products, about one third of the applied zinc is found with the liquids and two thirds remain with the char. The zinc associated with the liquid product is readily recovered with a water wash. The zinc associated with the char can be recovered by means of water and hydrochloric acid leaches to the extent of 70% of that present. The remaining char associated zinc (15–20% of that originally applied to the coal) is incorporated within the organic matrix of the char. A room temperature concentrated nitric acid leach is required to liberate the remaining zinc from the char. Ultimate recoveries of 98.5–99.7% are possible with the combined water, hydrochloric acid and nitric acid leach sequence.

The Institute of Gas Technology has conducted a fundamental research program to determine the technical feasibility of and to prepare preliminary process evaluations for two new approaches to coal gasification. These two concepts were assessed under two major project tasks: Task 1. CO/sub 2/-Coal Gasification Process Concept; Task 2. Internal Recirculation Catalysts Coal Gasification Process Concept. The first process concept involves CO/sub 2/-O/sub 2/ gasification of coal followed by CO/sub 2/ removal from the hot product gas by a solid MgO-containing sorbent. The sorbent is regenerated by either a thermal- or a pressure-swing step and the CO/sub 2/ released is recycled back to the gasifier. The product is a medium-Btu gas. The second process concept involves the use of novel ''semivolatile'' materials as internal recirculating catalysts for coal gasification. These materials remain in the gasifier because their vapor pressure-temperature behavior is such that they will be in the vapor state at the hotter, char exit part of the reactor and will condense in the colder, coal-inlet part of the reactor. 21 refs., 43 figs., 43 tabs.