- Email: [email protected]
03219 High-temperature desulfurization of gases of integrated coal gasification combined cycle (ICGCC) process using regenerable metal oxides
03
The fuels have both a high content of volatile matter but differ prrncrpally for their ash content, which is approximately 1% and 56% in beech and sewage sludge, respectrvely. The attention was focused on the presence of particulate and tar in the producer gas which affect the process efficiency and give negative drawbacks in the utilization in motors or turbines for power generation. The influence of operating variables (i.e. process temperature and equivalence ratio) on the gasification performances was explored. Results show that the composition of the producer gas is quite independent of whatever fuel is gasified. As far as sewage sludge is concerned, process performances are poorer and steady state operation is difficult, because of the high elutriation rate of fines, the continuous increasing of the bed height and the interaction between ash and bed materials. The tar yield was always high for both fuels. Unexpectedly, the gasification of a blend of two fuels gave a minimum tar yield, probably ascribed to a catalytic effect. A difference was found comparing the comminution hehaviour of beech wood and dry sewage sludge. The former undergoes fragmentation with the generation of relatively large, elutriable fragments; the latter is principally subjected to mechanical abrasion, leading to a finer elutriable particulate, since the residual fuel particle after the devolatilization conserves a good mechanical resistance. 00103217 Gasification Sjostrom. K. Sure. Conrhrrs/. Rex. Swed.. Proc. Lisr Pur/x~pn~.~. 1999, 2737. Edited by Olsson E. Combustion is the most common manner for thermal conversion of biofuels. However, in some circumstances it is advantageous to gasify instead. If the goal is to produce as much electricity as possible for a given heat sink (such as district heating), gasification coupled to a gas turbine and then a steam turbine, so-called IGCC, is the preferred method. Electricity production on a smaller scale using internal combustion engines also requires gasification. Synthesis gas for production of methanol, ammonia and hydrogen may be obtained through gasification. Another advantage with gasification, as compared to combustion, is the possibility of cleaning the gasification gas from unwanted components instead of performing the cleaning on the flue gas after combustion, the latter having a far greater volume. A survey of different gasification processes will be made, focusing on those relevant for Sweden, such as atmospheric and pressurized fluid bed gasification for electricity production and steam gasification for production of synthesis gas. The gasification research at KTH will be described, focusing on on-going EC projects. Gasification for electricity is today a technology ready for demonstration. However, if a commercial unit to be installed in Sweden, the price relation between electricity and heat must change. 00103218 High-pressure pyrolysis and COz-gasification of coal maceral concentrates: conversions and char combustion reactivities Megaritis, A. er al. Fuel, 1999, 78, (8), 871882. Using a fixed-bed and a wire-mesh reactor, the gasification behaviour of maceral concentrations was examined. ‘Extents of gasification’ were calculated by subtracting sample weight loss during pyrolysis (Helium) from weight loss in CO*-gasification, The effect of holding time (10 and 200 s) and pressure (1 and 20 bar) on conversions and on combustion reactivities of chars were studied. During short hold-time gasification experiments (10 s), liptinites gave the highest conversions, followed by the vitrinites and the inertinites. Vitrinite conversions decreased sharply above 90% elemental-carbon content. Extents of gasification were found to be m the order: vitrinites > liptinites > inertinites. However, at 200 s, a marked increase in inertinite conversion translated into a clear change of relative ordering to: inertinites > vitrinites > liptinites. The high gasification reactivities of inertinites at longer times appear to he related to a more rigid and porous structure, but the late surge suggests that an induction period is needed. More detailed time series data are required. Relative combustion reactivities of chars were generahy observed to decrease with (i) pressure, (ii) time at temperature and (iii) mcreasing elemental carbon content. The data indicated that orders of gasification reactivities may he predicted from the order of combustion reactivities of pyrolysis chars. Inertinite concentrate chars were more reactive. However, when the inertinites were heated rapidly, the difference in reactivity between inettinite chars and other samples was reduced-possibly owing to melting at the higher heating rates. 00103219 High-temperature desulfurization of gases of integrated coal gasification combined cycle (ICGCC) process using regenerable metal oxides Ibarra, J. Ertr. Comnr.. [Rep.] EC’R. 1999, l-186. (In Spatush) Advanced integrated coal gasification combined-cycle (IGCC) power plants require the development of high-temperature regenerable desulfurization sorbents capable of removing H2S from coal gas to very low levels. In this project the hot gas cleaning of IGCC gases by zinc ferrites and related modified sorbents has been studied. Different stoichiometries and preparation techniques of sorbent (bulk samples, impregnation on alumina, co-precipitation and additives for porosity development) were investigated. A series of metal oxide sorbents including zinc titanates (ZT) and modified zinc ferrites containing copper (ZFC) and titanium (ZFT) oxides were prepared and studied in the process of HaS retention at high temperature The prepared sorbents (fresh, sulfided and regenerated) were characterized by Na adsorption at 77 K, mercury porosimetry, SEM-EDX, X-ray diffraction (XRD), XPS and Fourier Transform IR and Raman (FTIR, FT-Raman) spectroscopies. The thermal stability of the sorbent against
Gaseous fuels (derived gaseous fuels)
reduction was investigated by temperature programmed reduction (TPR). All prepared sorbents had high sulfur retention capacities with values ranging from 18 to 40 g S/l00 g sorhent as a function of the formulation of the samples. The kinetic behaviour of the sorbents was studted in a thermohalance. The sulfidation performances was investigated in a fixedbed micro-reactor in terms of breakthrough curves. The sulfidation process produced significant structural changes in the morphology and textural properties of the sorhents. Sphalerite (ZnS) and pyrrhotite (Fe&S) were identified in the sulfided samples. The textural properties of sulfided sorbents indicated a decrease of pore volume and specific surface area in relation to the fresh sotbents. Sulfided sorbents were easily regenerated without sulfate formation at 760°C using a gas containing 3% CL, 30% Hz0 and balance NI. A series of five cycles of sulfidation-regeneration were carried out in a thermobalance (200-400 pm) and fixed-bed reactor. A decrease of the reactivity with increasing number of cycles was observed for non-titanium containing sorhents. The tests of mechanical strength indicated that sorbents tend to increase then mechanical resistance with increasing number of cycles. In all prohahilrty, this was due to sintering reactions in regeneration. 00/03220 Identification of coal gasification via a neural network model Guo, B. er crl. Ranshuo Kexue Yu Jish, 1999. 5, (I), X3-90. (In Chmese) The pyrolysis of coal and the gasification of char occur at the same time as coal is being gasified in the presence of steam. Usually, a coal pyrolysis model is incorporated with a char gasification model to describe the steam gasification of coal. However, since the two parallel processes have some common products, it has been difficult to reasonably identify the parameters for each process individually. A new look at a modelling approach for coal gasification is presented in this article, which uses a neural network model to directly identify the comprehensive process involving both coal pyrolysis and char gasification. The model obtained good simulation results and allowed further insight into the mechanism of coal gasification. 00103221 Ignition method and apparatus for gasifiers Ikeda, Y. Jpn. Kokai Tokkyo, Koho JP 11 217,574 [99 217,5741 (Cl. ClOJ3/ 46), 10 Aug 1999, Appl. 1998132,311, 30 Jan 1998. 4. (In Japanese) In this paper, a method for the ignition of a coal gasifier is described, It comprises igniting an ignition burner above the slag pot and at the lower part of the gasifier, igniting a gasification burner by blowing the combustion flame from the ignition burner to the gasification burner with gaseous fuel supplied, and sequentially switching the gaseous fuel to solid fuel by switching valves after the temperature of the gasifier is increased. 00103222 Kinetic understanding of the chemical synergy under LPDME conditions-once-through applications Peng, X. D. er (11.C/rem. Eng. Sci.. 1999, 54, (I?--14). 278772792. A higher conversion is displayed by the single-step process of syngas to dimethyl ether (DME) than by the syngas-to-methanol process. This arises because of a synergy among the three simultaneous reactions, methanol synthesis, methanol dehydration and water gas shift, in the process. This paper analyses the role each reaction plays m the synergy using both experimental and simulated results. Under typical industrially relevant conditions using a commercially available catalyst system, the reaction system is far away from the thermodynamic equiltbrium, and the rates of the reactions are the prime determinant in realizing the beneficial effects of the synergy. Furthermore, feed gas composition strongly affects the potential benefit of the synergy on the process. This paper discusses the implications of this understanding for research and process applications. 00103223 Laboratory monitoring of technology in a shop for recovery of coking products Shved, V. S. c/ crl. Koks Khim, 1999. 3. 299.11. (In Russtan) A discussion takes place on the sampling and analysis of coke oven gas. 00103224 Low temperature CFB gasifier conceptual ideas and applications Stoholm, P. ef cl/. Proc. Int. Conf. Nrrrd. Eerl C~rhusr.. 1999, 1673.-1688. In this paper, a novel circulating fluidized hed (CFB) gasification process for volatile fuels such as biomass and many waste materials are described. The fuel is pyrolysed at, for example, 550°C in the CFB reaction chamber and the char residue is converted at, for example, 650°C in a separate bubbling fluidized bed (BFB) char gasification chamber located in the particle recirculation path. Due to the tendency for char particles to segregate to the upper part of the BFB they achieve a high retention time in the slowly fluidized BFB by recirculating mainly inert particles from the bottom. In a simple version of the process essentrally all of the air is added to the bottom of the BFB and the produced char gas is serving as fluidizing gas in the CFB reaction chamber. This way the product gas leaving the CFB reaction chamber obtains a higher heating value at around 11 MJ/Nm’ when using a biomass fuel with around 15 % moisture. In combination with the low process temperature, and not needing building height for char conversion in the CFB reaction chamber, the CFB reactor and off-gas system become very compact. The low temperatures also mean that agglomeration can be avoided even when using fuels such as unweathered straw with a high content of alkali and chlorine. Furthermore, the alkali and chlorine in the raw gas will mainly he in the solid state meaning that a high retention can be obtained simply by efficient partrcle separation. A number
Fuel and Energy Abstracts
November 2000
383
The fuels have both a high content of volatile matter but differ prrncrpally for their ash content, which is approximately 1% and 56% in beech and sewage sludge, respectrvely. The attention was focused on the presence of particulate and tar in the producer gas which affect the process efficiency and give negative drawbacks in the utilization in motors or turbines for power generation. The influence of operating variables (i.e. process temperature and equivalence ratio) on the gasification performances was explored. Results show that the composition of the producer gas is quite independent of whatever fuel is gasified. As far as sewage sludge is concerned, process performances are poorer and steady state operation is difficult, because of the high elutriation rate of fines, the continuous increasing of the bed height and the interaction between ash and bed materials. The tar yield was always high for both fuels. Unexpectedly, the gasification of a blend of two fuels gave a minimum tar yield, probably ascribed to a catalytic effect. A difference was found comparing the comminution hehaviour of beech wood and dry sewage sludge. The former undergoes fragmentation with the generation of relatively large, elutriable fragments; the latter is principally subjected to mechanical abrasion, leading to a finer elutriable particulate, since the residual fuel particle after the devolatilization conserves a good mechanical resistance. 00103217 Gasification Sjostrom. K. Sure. Conrhrrs/. Rex. Swed.. Proc. Lisr Pur/x~pn~.~. 1999, 2737. Edited by Olsson E. Combustion is the most common manner for thermal conversion of biofuels. However, in some circumstances it is advantageous to gasify instead. If the goal is to produce as much electricity as possible for a given heat sink (such as district heating), gasification coupled to a gas turbine and then a steam turbine, so-called IGCC, is the preferred method. Electricity production on a smaller scale using internal combustion engines also requires gasification. Synthesis gas for production of methanol, ammonia and hydrogen may be obtained through gasification. Another advantage with gasification, as compared to combustion, is the possibility of cleaning the gasification gas from unwanted components instead of performing the cleaning on the flue gas after combustion, the latter having a far greater volume. A survey of different gasification processes will be made, focusing on those relevant for Sweden, such as atmospheric and pressurized fluid bed gasification for electricity production and steam gasification for production of synthesis gas. The gasification research at KTH will be described, focusing on on-going EC projects. Gasification for electricity is today a technology ready for demonstration. However, if a commercial unit to be installed in Sweden, the price relation between electricity and heat must change. 00103218 High-pressure pyrolysis and COz-gasification of coal maceral concentrates: conversions and char combustion reactivities Megaritis, A. er al. Fuel, 1999, 78, (8), 871882. Using a fixed-bed and a wire-mesh reactor, the gasification behaviour of maceral concentrations was examined. ‘Extents of gasification’ were calculated by subtracting sample weight loss during pyrolysis (Helium) from weight loss in CO*-gasification, The effect of holding time (10 and 200 s) and pressure (1 and 20 bar) on conversions and on combustion reactivities of chars were studied. During short hold-time gasification experiments (10 s), liptinites gave the highest conversions, followed by the vitrinites and the inertinites. Vitrinite conversions decreased sharply above 90% elemental-carbon content. Extents of gasification were found to be m the order: vitrinites > liptinites > inertinites. However, at 200 s, a marked increase in inertinite conversion translated into a clear change of relative ordering to: inertinites > vitrinites > liptinites. The high gasification reactivities of inertinites at longer times appear to he related to a more rigid and porous structure, but the late surge suggests that an induction period is needed. More detailed time series data are required. Relative combustion reactivities of chars were generahy observed to decrease with (i) pressure, (ii) time at temperature and (iii) mcreasing elemental carbon content. The data indicated that orders of gasification reactivities may he predicted from the order of combustion reactivities of pyrolysis chars. Inertinite concentrate chars were more reactive. However, when the inertinites were heated rapidly, the difference in reactivity between inettinite chars and other samples was reduced-possibly owing to melting at the higher heating rates. 00103219 High-temperature desulfurization of gases of integrated coal gasification combined cycle (ICGCC) process using regenerable metal oxides Ibarra, J. Ertr. Comnr.. [Rep.] EC’R. 1999, l-186. (In Spatush) Advanced integrated coal gasification combined-cycle (IGCC) power plants require the development of high-temperature regenerable desulfurization sorbents capable of removing H2S from coal gas to very low levels. In this project the hot gas cleaning of IGCC gases by zinc ferrites and related modified sorbents has been studied. Different stoichiometries and preparation techniques of sorbent (bulk samples, impregnation on alumina, co-precipitation and additives for porosity development) were investigated. A series of metal oxide sorbents including zinc titanates (ZT) and modified zinc ferrites containing copper (ZFC) and titanium (ZFT) oxides were prepared and studied in the process of HaS retention at high temperature The prepared sorbents (fresh, sulfided and regenerated) were characterized by Na adsorption at 77 K, mercury porosimetry, SEM-EDX, X-ray diffraction (XRD), XPS and Fourier Transform IR and Raman (FTIR, FT-Raman) spectroscopies. The thermal stability of the sorbent against
Gaseous fuels (derived gaseous fuels)
reduction was investigated by temperature programmed reduction (TPR). All prepared sorbents had high sulfur retention capacities with values ranging from 18 to 40 g S/l00 g sorhent as a function of the formulation of the samples. The kinetic behaviour of the sorbents was studted in a thermohalance. The sulfidation performances was investigated in a fixedbed micro-reactor in terms of breakthrough curves. The sulfidation process produced significant structural changes in the morphology and textural properties of the sorhents. Sphalerite (ZnS) and pyrrhotite (Fe&S) were identified in the sulfided samples. The textural properties of sulfided sorbents indicated a decrease of pore volume and specific surface area in relation to the fresh sotbents. Sulfided sorbents were easily regenerated without sulfate formation at 760°C using a gas containing 3% CL, 30% Hz0 and balance NI. A series of five cycles of sulfidation-regeneration were carried out in a thermobalance (200-400 pm) and fixed-bed reactor. A decrease of the reactivity with increasing number of cycles was observed for non-titanium containing sorhents. The tests of mechanical strength indicated that sorbents tend to increase then mechanical resistance with increasing number of cycles. In all prohahilrty, this was due to sintering reactions in regeneration. 00/03220 Identification of coal gasification via a neural network model Guo, B. er crl. Ranshuo Kexue Yu Jish, 1999. 5, (I), X3-90. (In Chmese) The pyrolysis of coal and the gasification of char occur at the same time as coal is being gasified in the presence of steam. Usually, a coal pyrolysis model is incorporated with a char gasification model to describe the steam gasification of coal. However, since the two parallel processes have some common products, it has been difficult to reasonably identify the parameters for each process individually. A new look at a modelling approach for coal gasification is presented in this article, which uses a neural network model to directly identify the comprehensive process involving both coal pyrolysis and char gasification. The model obtained good simulation results and allowed further insight into the mechanism of coal gasification. 00103221 Ignition method and apparatus for gasifiers Ikeda, Y. Jpn. Kokai Tokkyo, Koho JP 11 217,574 [99 217,5741 (Cl. ClOJ3/ 46), 10 Aug 1999, Appl. 1998132,311, 30 Jan 1998. 4. (In Japanese) In this paper, a method for the ignition of a coal gasifier is described, It comprises igniting an ignition burner above the slag pot and at the lower part of the gasifier, igniting a gasification burner by blowing the combustion flame from the ignition burner to the gasification burner with gaseous fuel supplied, and sequentially switching the gaseous fuel to solid fuel by switching valves after the temperature of the gasifier is increased. 00103222 Kinetic understanding of the chemical synergy under LPDME conditions-once-through applications Peng, X. D. er (11.C/rem. Eng. Sci.. 1999, 54, (I?--14). 278772792. A higher conversion is displayed by the single-step process of syngas to dimethyl ether (DME) than by the syngas-to-methanol process. This arises because of a synergy among the three simultaneous reactions, methanol synthesis, methanol dehydration and water gas shift, in the process. This paper analyses the role each reaction plays m the synergy using both experimental and simulated results. Under typical industrially relevant conditions using a commercially available catalyst system, the reaction system is far away from the thermodynamic equiltbrium, and the rates of the reactions are the prime determinant in realizing the beneficial effects of the synergy. Furthermore, feed gas composition strongly affects the potential benefit of the synergy on the process. This paper discusses the implications of this understanding for research and process applications. 00103223 Laboratory monitoring of technology in a shop for recovery of coking products Shved, V. S. c/ crl. Koks Khim, 1999. 3. 299.11. (In Russtan) A discussion takes place on the sampling and analysis of coke oven gas. 00103224 Low temperature CFB gasifier conceptual ideas and applications Stoholm, P. ef cl/. Proc. Int. Conf. Nrrrd. Eerl C~rhusr.. 1999, 1673.-1688. In this paper, a novel circulating fluidized hed (CFB) gasification process for volatile fuels such as biomass and many waste materials are described. The fuel is pyrolysed at, for example, 550°C in the CFB reaction chamber and the char residue is converted at, for example, 650°C in a separate bubbling fluidized bed (BFB) char gasification chamber located in the particle recirculation path. Due to the tendency for char particles to segregate to the upper part of the BFB they achieve a high retention time in the slowly fluidized BFB by recirculating mainly inert particles from the bottom. In a simple version of the process essentrally all of the air is added to the bottom of the BFB and the produced char gas is serving as fluidizing gas in the CFB reaction chamber. This way the product gas leaving the CFB reaction chamber obtains a higher heating value at around 11 MJ/Nm’ when using a biomass fuel with around 15 % moisture. In combination with the low process temperature, and not needing building height for char conversion in the CFB reaction chamber, the CFB reactor and off-gas system become very compact. The low temperatures also mean that agglomeration can be avoided even when using fuels such as unweathered straw with a high content of alkali and chlorine. Furthermore, the alkali and chlorine in the raw gas will mainly he in the solid state meaning that a high retention can be obtained simply by efficient partrcle separation. A number
Fuel and Energy Abstracts
November 2000
383