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02374 Equilibrium speciation of As, Cd, Cr, Hg, Ni, Pb, and Se in oxidative thermal conversion of coal — a comparison of thermodynamic packages
01
Solid fuels (preparation)
99102369 Concerning solubility of coal in mixed solvents Painter, P. C. et al. Prepr. Symp. -Am. Chem. Sot., Div. Fuel Chem., 1998, 43, (4), 913-916. An assessment of the enhanced solubility of Upper Freeport coal in mixed N-methylpyrrolidone (NMP)-carbon disulfide solvent with respect to the self-association properties of NMP. It was found that the addition of a nonpolar solvent breaks up the self-association of NMP. Thus, diluting NMP with a non-polar co-solvent would impart a thermodynamic advantage to the solvent system prior to mixing it with the coal. It is suggested that the strong osmotic forces exerted by this solvent on the expanded coal ‘gel’ lead to fracture. Thus some of the enhanced solubility of the coal in the mixed solvents was due to the presence of macroscopic particles broken off from the samples.
due to COz formation. Water also enhanced the cleavage of aryl-ether bonds. These cleavage reactions are more pronounced in GN coal than in TB coal, probably due to a higher concentration of activated ether structures in GN coal. The extensive depolymerization of TB coal is presumed to be responsible for the disruption of non-covalent interactions. The role of Hz in these heat treatment conditions is considered to be predominantly hydrogenation of polyaromatic sites with the help of mineral matter and scavenging radicals, which arose from cleavage of weak aliphatic ether bonds. The coal samples treated in Hz-Hz0 donated more hydrogen to anthracene during their co-pyrolysis, which is attributed mainly to a reduced tendency of the treated samples to undergo radical-generating reactions.
99102370 Dry high temperature coal gas cleaning for gasification combined cycles - system integration and process optimization
Equilibrium speciation of As, Cd, Cr, Hg, Ni, Pb, and Se in oxidative thermal conversion of coal - a comparison of thermodynamic packages
Kloster, R. et al. High Temp. Gas Clean., [Pap. Int. Symp. Exhib. Gas Clean. High Temp./, 3rd, 1996, 743-755. Edited by Schmidt, E., lnstitut fur Mechanische Verfahrenstechnik und Mechanik der Universitaet Karlsruhe, Karlsruhe, Germany Energy and exergy losses from water quenching and cooling down and heating up of coal-derived gas can be avoided in IGCC power plants by the replacement of wet gas scrubbing systems with dry, high-temperature gas cleaning. Thus plant efficiency will be improved. If desulfurization by zinc titanate within the coal gas stream was taken into account, l-4% of the chemical raw gas energy, depending on the sulfur content of the coal, is converted into heat and bypasses the gas turbine process via steam generation. The heat released during dry desulfurization, resulting from the highly exothermic reactions, in particular the sorbent regeneration, is recovered in the regenerator offgas cooler and sulfur condenser. Hot gas cleaning thus becomes a heat source instead of a heat sink, which is the case with wet gas cleaning. It was calculated that by simply replacing the wet gas cleaning system by a hot gas cleaning system in a state-of-the-art IGCC of Puertollano type with oxygen-blown gasification resulted in an efficiency increase of 0.8%. Moreover, the increase is 1.3% for an IGCC with airblown lignite gasification. A further benefit from hot gas cleaning is that a clean fuel gas can be produced at temperatures in excess of 600°C without reheating. Increasing the fuel gas temperature in front of the gas turbine combustion chamber also improves efficiency. Overall efficiency can be improved by 0.8% by an increase of 300°C to 500°C. 99102371
Drying of biomass particles in fixed and moving
beds
Saastamoinen, J. and Impala, R. Drying ‘96, [Proc. Int. Drying Symp.], IOth, 1996, A, 349-356. Edited by Strumillo, C. and Pakowski, Z., Lodz Technical University, Poland. Both experimental and theoretical consideration is given to the drying of biomass fuel particles in fixed and moving beds with hot gas or steam. A single particle drying model is coupled with a model describing heat and moisture transfer in the gas phase of the bed. To reach a certain degree of drying the size of the bed depends mostly on the following parameters: particle size, particle moisture content, gas inlet temperature, gas inlet moisture content and gas mass flow rate.
99102374
Frandsen, F. et al. High Temp. Gas Clean., (Pap. Int. Symp. Exhib. Gas Clean. High Temp.), 3, 1996, 462-473. Edited by Schmidt, E., Institut fur Mechanische Verfahrenstechnik und Mechanik der Universitaet Karlsruhe. Karlsruhe, Germany. This paper predicts the equilibrium speciation of the trace elements arsenic, cadmium, chromium, mercury, nickel, lead and selenium in a model system. Ideal gas and pure condensed phases are assumed, and the presence of a sorbent material for sulfur capture is also considered. The model system is based on a demonstration-scale pressurized fluidized bed combustor and fires a Pittsburgh No. 8 bituminous coal, using dolomite as sorbent for sulfur capture. It is equipped with a ceramic filter for particulate removal. The study compares four different thermodynamic packages (MINGTSYS, NASACET89, FACT and SOLGASMIX) over the temperature range (700-2000 K), at pressures of 1 and 20 atm. Almost identical equilibrium distributions were predicted by the four packages for arsenic, mercury and selenium, while for cadmium, chromium, nickel and lead, differences occurred in the output from each package. This may be the result of the different solution techniques, convergence criteria and/or thermodynamic input-data used in the thermodynamic packages. An outline of the equilibrium distributions, the comparison and a discussion of reasons for variations in results with different thermodynamic packages is presented. A comparison between measured and predicted partitioning data is also given. 99102375 Gasification of a brown coal chunk in flowing air Butala, V. and Novak, P. Energy, 1999, 24, (1). 61-67. The gasification rate was measured of chunks of coal with a high content of volatiles, average size of 65 x 47 x 38 mm and an initial weight of 120 f 7 g. The influence of air temperature and velocity on the gasification rate was studied in a tubular experimental device. The time dependencies of the gasification rate and some gaseous species on air temperature and velocity were observed. A discontinuity appeared during gasification, which is not apparent on burning small coal pieces or coal dust.
oxidation of coal on
Hydrogenation of sub-bituminous and bituminous coals pre-treated with water-soluble nickel-molybdenum or cobalt-molybdenum catalysts
Lopez, D. et al. Fuel, 1998, 77, (14) 1623-1628. Spontaneous combustion can result from coal oxidation with molecular oxygen at low temperatures. In this study, four Colombian coals were oxidized in a stove at temperatures between 30-150°C. In the presence of anthracene, the oxidized samples were heat-treated in an autoclave under nitrogen pressure at 420°C. The main hydrogenated product was 9,10dihydroanthracene. The results showed that oxidation of the samples drastically reduced the amount of hydrogen transferred to the aromatic solvent. Furthermore, this varies with the coal rank. The samples were analysed further using Fourier transform infra-red analysis, solvent swelling and coal conversion to solute products in tetrahydrofuran. The mechanism by which coal reacts with molecular oxygen was found to be strongly dependent on temperature. The initial stage of coal oxidation was the same for all coals studied, i.e. the attack by molecular oxygen on the hydrogen in the a position. However, the chemical functionality to which the (L CHz group is attached determines the path followed thereafter. It is suggested that the products can be differentiated from low- and high-rank coals in this way.
Redlich, P. J. et al. Fuel, 78, (1) 83-88. Ni/Mo and CO/MO are two of the most commonly used and effective catalysts used in coal liquefaction. Recent work has reported a -40 wt% difference in conversion between Ni/Mo and Co/MO-treated Loy Yang brown coal hydrogenated at 400°C without added solvent or sulfur. However, this study shows that under the same reaction conditions the difference in conversion between Ni/Mo and Co/MO-treated coal decreases with increasing carbon content (rank) of the coal (Wyoming, Wadge, Surat Basin). Furthermore, for a bituminous Surat Basin coal the pattern of catalytic activity of Ni, Co, MO and their combinations differs from that for a brown (Loy Yang) coal as follows. In no-solvent, no-added-sulfur hydrogenations, the catalytic activity of the individual metals was much greater for the Surat Basin coal, but the increased activity of Ni and Co did not carry over to increased promotion of MO catalysis by these metals. The effect of added sulfur on the activity of the individual metals was also different for the two coals. The distribution of the catalyst metals in the coal particles was different in the Loy Yang and Surat Basin coals, but this cannot explain all the observed differences in catalytic behaviour.
99102376
Effect of low-temperature hydrogen-transfer capabillty
99102372
Effects of water and molecular hydrogen on heat 99102373 treatment of Turkish low-rank coals Artok, L. et al. Energy Fuels, 1998, 12, (6), 1200-1211. Low-severity heat treatment (285-330°C) was applied to two low-rank Turkish coals, Tunchilek (TB) sub-bituminous and Goynuk (GN) lignite, both as original coals and after demineralization with HCl(aqueous)/ HF(aqueous) treatment. The experimental conditions further varied; water was added to only a portion of each sample and the atmoshperes were either Na or Hz. The samples processed in Hz-Ha0 combination seemed to be more dissociated or decomposed than those processed in Nz-Hz0 or in Hz without water. The enhancing effect of water in decarboxylation reactions was indicated by gas analyses and spectroscopy of the samples. These also established that the oxygen rejection from the coals was mainly
99lQ2377 Hydroliquefaction of coal Ammo, M. et al. Jpn. Kokai Tokkyo Koho JP 10 298,556 (98 298.5561, (Cl. ClOG1/06), 10 Nov 1998, Appl. 971107,569, 24 Apr 1997, 7 pp. (In Japanese) The hydrogenation of coal was carried out with the addition of solvents at 20-48O”C and 10-20 MPa. One wt% iron hydroxide or pyrite was used as the catalyst and sulfur was used as the catalyst aid. The heavy liquefied composition containing iron sulfide which was separated after hydrogenation was recycled into the hydrogenation process. In the gas phase of the hydrogenation process, HzS gas was maintained at 0.4-1.5 ~01%. Furthermore deactivation of the catalyst was prevented.
Fuel and Energy Abstracts
July 1999 251
Solid fuels (preparation)
99102369 Concerning solubility of coal in mixed solvents Painter, P. C. et al. Prepr. Symp. -Am. Chem. Sot., Div. Fuel Chem., 1998, 43, (4), 913-916. An assessment of the enhanced solubility of Upper Freeport coal in mixed N-methylpyrrolidone (NMP)-carbon disulfide solvent with respect to the self-association properties of NMP. It was found that the addition of a nonpolar solvent breaks up the self-association of NMP. Thus, diluting NMP with a non-polar co-solvent would impart a thermodynamic advantage to the solvent system prior to mixing it with the coal. It is suggested that the strong osmotic forces exerted by this solvent on the expanded coal ‘gel’ lead to fracture. Thus some of the enhanced solubility of the coal in the mixed solvents was due to the presence of macroscopic particles broken off from the samples.
due to COz formation. Water also enhanced the cleavage of aryl-ether bonds. These cleavage reactions are more pronounced in GN coal than in TB coal, probably due to a higher concentration of activated ether structures in GN coal. The extensive depolymerization of TB coal is presumed to be responsible for the disruption of non-covalent interactions. The role of Hz in these heat treatment conditions is considered to be predominantly hydrogenation of polyaromatic sites with the help of mineral matter and scavenging radicals, which arose from cleavage of weak aliphatic ether bonds. The coal samples treated in Hz-Hz0 donated more hydrogen to anthracene during their co-pyrolysis, which is attributed mainly to a reduced tendency of the treated samples to undergo radical-generating reactions.
99102370 Dry high temperature coal gas cleaning for gasification combined cycles - system integration and process optimization
Equilibrium speciation of As, Cd, Cr, Hg, Ni, Pb, and Se in oxidative thermal conversion of coal - a comparison of thermodynamic packages
Kloster, R. et al. High Temp. Gas Clean., [Pap. Int. Symp. Exhib. Gas Clean. High Temp./, 3rd, 1996, 743-755. Edited by Schmidt, E., lnstitut fur Mechanische Verfahrenstechnik und Mechanik der Universitaet Karlsruhe, Karlsruhe, Germany Energy and exergy losses from water quenching and cooling down and heating up of coal-derived gas can be avoided in IGCC power plants by the replacement of wet gas scrubbing systems with dry, high-temperature gas cleaning. Thus plant efficiency will be improved. If desulfurization by zinc titanate within the coal gas stream was taken into account, l-4% of the chemical raw gas energy, depending on the sulfur content of the coal, is converted into heat and bypasses the gas turbine process via steam generation. The heat released during dry desulfurization, resulting from the highly exothermic reactions, in particular the sorbent regeneration, is recovered in the regenerator offgas cooler and sulfur condenser. Hot gas cleaning thus becomes a heat source instead of a heat sink, which is the case with wet gas cleaning. It was calculated that by simply replacing the wet gas cleaning system by a hot gas cleaning system in a state-of-the-art IGCC of Puertollano type with oxygen-blown gasification resulted in an efficiency increase of 0.8%. Moreover, the increase is 1.3% for an IGCC with airblown lignite gasification. A further benefit from hot gas cleaning is that a clean fuel gas can be produced at temperatures in excess of 600°C without reheating. Increasing the fuel gas temperature in front of the gas turbine combustion chamber also improves efficiency. Overall efficiency can be improved by 0.8% by an increase of 300°C to 500°C. 99102371
Drying of biomass particles in fixed and moving
beds
Saastamoinen, J. and Impala, R. Drying ‘96, [Proc. Int. Drying Symp.], IOth, 1996, A, 349-356. Edited by Strumillo, C. and Pakowski, Z., Lodz Technical University, Poland. Both experimental and theoretical consideration is given to the drying of biomass fuel particles in fixed and moving beds with hot gas or steam. A single particle drying model is coupled with a model describing heat and moisture transfer in the gas phase of the bed. To reach a certain degree of drying the size of the bed depends mostly on the following parameters: particle size, particle moisture content, gas inlet temperature, gas inlet moisture content and gas mass flow rate.
99102374
Frandsen, F. et al. High Temp. Gas Clean., (Pap. Int. Symp. Exhib. Gas Clean. High Temp.), 3, 1996, 462-473. Edited by Schmidt, E., Institut fur Mechanische Verfahrenstechnik und Mechanik der Universitaet Karlsruhe. Karlsruhe, Germany. This paper predicts the equilibrium speciation of the trace elements arsenic, cadmium, chromium, mercury, nickel, lead and selenium in a model system. Ideal gas and pure condensed phases are assumed, and the presence of a sorbent material for sulfur capture is also considered. The model system is based on a demonstration-scale pressurized fluidized bed combustor and fires a Pittsburgh No. 8 bituminous coal, using dolomite as sorbent for sulfur capture. It is equipped with a ceramic filter for particulate removal. The study compares four different thermodynamic packages (MINGTSYS, NASACET89, FACT and SOLGASMIX) over the temperature range (700-2000 K), at pressures of 1 and 20 atm. Almost identical equilibrium distributions were predicted by the four packages for arsenic, mercury and selenium, while for cadmium, chromium, nickel and lead, differences occurred in the output from each package. This may be the result of the different solution techniques, convergence criteria and/or thermodynamic input-data used in the thermodynamic packages. An outline of the equilibrium distributions, the comparison and a discussion of reasons for variations in results with different thermodynamic packages is presented. A comparison between measured and predicted partitioning data is also given. 99102375 Gasification of a brown coal chunk in flowing air Butala, V. and Novak, P. Energy, 1999, 24, (1). 61-67. The gasification rate was measured of chunks of coal with a high content of volatiles, average size of 65 x 47 x 38 mm and an initial weight of 120 f 7 g. The influence of air temperature and velocity on the gasification rate was studied in a tubular experimental device. The time dependencies of the gasification rate and some gaseous species on air temperature and velocity were observed. A discontinuity appeared during gasification, which is not apparent on burning small coal pieces or coal dust.
oxidation of coal on
Hydrogenation of sub-bituminous and bituminous coals pre-treated with water-soluble nickel-molybdenum or cobalt-molybdenum catalysts
Lopez, D. et al. Fuel, 1998, 77, (14) 1623-1628. Spontaneous combustion can result from coal oxidation with molecular oxygen at low temperatures. In this study, four Colombian coals were oxidized in a stove at temperatures between 30-150°C. In the presence of anthracene, the oxidized samples were heat-treated in an autoclave under nitrogen pressure at 420°C. The main hydrogenated product was 9,10dihydroanthracene. The results showed that oxidation of the samples drastically reduced the amount of hydrogen transferred to the aromatic solvent. Furthermore, this varies with the coal rank. The samples were analysed further using Fourier transform infra-red analysis, solvent swelling and coal conversion to solute products in tetrahydrofuran. The mechanism by which coal reacts with molecular oxygen was found to be strongly dependent on temperature. The initial stage of coal oxidation was the same for all coals studied, i.e. the attack by molecular oxygen on the hydrogen in the a position. However, the chemical functionality to which the (L CHz group is attached determines the path followed thereafter. It is suggested that the products can be differentiated from low- and high-rank coals in this way.
Redlich, P. J. et al. Fuel, 78, (1) 83-88. Ni/Mo and CO/MO are two of the most commonly used and effective catalysts used in coal liquefaction. Recent work has reported a -40 wt% difference in conversion between Ni/Mo and Co/MO-treated Loy Yang brown coal hydrogenated at 400°C without added solvent or sulfur. However, this study shows that under the same reaction conditions the difference in conversion between Ni/Mo and Co/MO-treated coal decreases with increasing carbon content (rank) of the coal (Wyoming, Wadge, Surat Basin). Furthermore, for a bituminous Surat Basin coal the pattern of catalytic activity of Ni, Co, MO and their combinations differs from that for a brown (Loy Yang) coal as follows. In no-solvent, no-added-sulfur hydrogenations, the catalytic activity of the individual metals was much greater for the Surat Basin coal, but the increased activity of Ni and Co did not carry over to increased promotion of MO catalysis by these metals. The effect of added sulfur on the activity of the individual metals was also different for the two coals. The distribution of the catalyst metals in the coal particles was different in the Loy Yang and Surat Basin coals, but this cannot explain all the observed differences in catalytic behaviour.
99102376
Effect of low-temperature hydrogen-transfer capabillty
99102372
Effects of water and molecular hydrogen on heat 99102373 treatment of Turkish low-rank coals Artok, L. et al. Energy Fuels, 1998, 12, (6), 1200-1211. Low-severity heat treatment (285-330°C) was applied to two low-rank Turkish coals, Tunchilek (TB) sub-bituminous and Goynuk (GN) lignite, both as original coals and after demineralization with HCl(aqueous)/ HF(aqueous) treatment. The experimental conditions further varied; water was added to only a portion of each sample and the atmoshperes were either Na or Hz. The samples processed in Hz-Ha0 combination seemed to be more dissociated or decomposed than those processed in Nz-Hz0 or in Hz without water. The enhancing effect of water in decarboxylation reactions was indicated by gas analyses and spectroscopy of the samples. These also established that the oxygen rejection from the coals was mainly
99lQ2377 Hydroliquefaction of coal Ammo, M. et al. Jpn. Kokai Tokkyo Koho JP 10 298,556 (98 298.5561, (Cl. ClOG1/06), 10 Nov 1998, Appl. 971107,569, 24 Apr 1997, 7 pp. (In Japanese) The hydrogenation of coal was carried out with the addition of solvents at 20-48O”C and 10-20 MPa. One wt% iron hydroxide or pyrite was used as the catalyst and sulfur was used as the catalyst aid. The heavy liquefied composition containing iron sulfide which was separated after hydrogenation was recycled into the hydrogenation process. In the gas phase of the hydrogenation process, HzS gas was maintained at 0.4-1.5 ~01%. Furthermore deactivation of the catalyst was prevented.
Fuel and Energy Abstracts
July 1999 251