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02017 Rheological behavior of coal-fly-ash and clay slip
04 99102012 Method for treating dioxane containing incinerator fly ash Miike, K. and Mochida, H. Jpn. Kokai Tokkyo Koho JP 10 146,574 [98 146,574) (Cl. B09B3/00), 2 Jun 1998, Appl. 96/309,304, 20 Nov 1996, 5 pp. (In Japanese) In this method, the fly ash is treated by adding of an oxidizing acid to the ash and heating the mixture at >lOO”C to decompose the dioxane. The fly ash may be extracted with water or HCI before the oxidation treatment. Platinum or palladium may be used as catalyst for the oxidation and the oxidizing acid is selected from HzSO,, and HNOj.
99102013 Physicochemical properties of unburned carbon from fly ash Ann, Y. K. and Yang, J. I. Chawon Risaikring, 1998, 7, (1). 14-19. (In Korean) Investigated were the physicochemical properties of residual or unburned carbon obtained from fly ash. The flotation method was used to extract carbon-enriched samples from fly ash. Analysis then took place on the carbon content and chemical composition of the recovered carbon sample. The ash in the carbon sample was also examined. The unburned carbon characterization included measurement of size distribution, surface area, crystal structure and density.
99102014 Pilot study of COHPAC for reduction of particulate matter, mercury and acid gas emissions at a coal-fired power plant Lapatnick, L. N. et al. Prepr. Ext. Abstr. ACS Natl. Meet., Am. Chem. Sot., Div. Environ. Chem., 1998, 38, (2), 166-169. This paper describes the promising potential in COHPAC (pulse-jet fabric filter) for removing residual particulate matter from flue gases that pass through electrostatic precipitators. Active carbon injection is slightly-tomarginally effective in removing mercury from the flue gases.
99lO201S Preparation of surfactants from a byproduct of fossil fuel biodesulfurization Lange, E. A. and Lin, Q. Prepr. Am. Chem. Sot., Div. Pet. Chem., 1998,43, (4) 550-552. Heterocyclic sulfur compounds can be removed from fossil fuels, such as diesel fuel, by biocatalytic desulfurization, an alternative refinery hydrotreating process. The heterocyclic sulfur compounds from the fuel were the selectively oxidized through a multi-step enzymic pathway to produce water-soluble sulfur compounds as by-products without degrading the hydrocarbon matrix. 2-(2-Hydroxyphenyl)benzene sulfinic acid was prepared by base-catalysed hydrolysis of dibenzothiophone at a high pH and then transferred to sulfonic acid by reaction with HzOz. The Cs and Cm alkylethers and show good surfactant properties. Process for the regeneration of partially deacti99102016 vated hydrocarbon-synthesis catalysts using a cyclic carbon monoxide purge Leviness, S. C. and Mitchell, W. N. US 5,817,701 (Cl. 518-700; CO7C27/ 00), 6 Ott 1998, Appl. 850,565, 2 May 1997, 11 pp. The rapid regeneration of partially deactivated Fischer-Tropsch catalysts used in slurry hydrocarbon synthesis processes takes place by employing a cyclic process. Here, the synthesis gas or CO flow into the slurry is stopped to halt the hydrocarbon synthesis reaction, the CO purged out of the slurry with a CO-free purge gas in the presence of hydrogen, the catalyst regenerated with a hydrogen-containing rejuvenating gas and the hydrocarbon synthesis reaction restarted by passing the synthesis gas feed back into the reactor. All or a portion of the purge gas and/or the rejuvenating gas may be recycled during the purge and/or rejuvenation, respectively. The hydrogen required during the purge is typically part of the purge gas.
99102017 Rheological behavior of coal-fly-ash and clay slip Lee, K.-G. et al. Yoop Hakhoechi, 1998, 35, (2), 180-184. (In Korean) This paper examined the rheological behaviour of fly ash 70 wt%-clay 30 wt% slip in which non-plastic fly ash was a major component. The effects of deflocculant and coagulant (CaS04) on the rheological behaviour of ashclay slip have been systematically investigated. Ash-clay slip has been characterized on the basis of the time dependent rheology using the gelcurve test. The dispersion mechanism of ash-clay slip is the steric stabilization by the NazSiOs coating of cenospheres surface. A coagulated slip seems to have a new network structure and shows the gelation behaviours which makes it possible to use direct coagulated casting (DCC).
Separation of solids using perforated metal foils 99102016 after brown coal-fired furnaces Winkler, B. Fortschr.-Ber. VDI, Reihe 3, 1998, 544, (i-ix), 1-161. (In German) A review of theoretical, laboratory and pilot plant studies of brown coalfired furnace flue gases filtration through perforated metal foil. High solid removal rates at low pressure drop were achieved. A theoretical description of the process is presented.
By-products
related to fuels
99102019 Simultaneous removal of nitrogen oxides and fly ash from coal-based power-plant flue gases Saracco, G. and Specchia, V. Appl. Therm. Eng., 1998, 18, (ll), 10251035. In principle, catalytic filters are capable of performing shallow-bed dust filtration plus a catalytic reaction, promoted by a catalyst deposited in their inner structure. Such a feature may allow potential cost reduction in several environmental applications, particularly flue-gas treatment of pressurized fluidized bed coal combustors. Lab-scale VzOs/TiOz-deposited filters were prepared, characterized and tested for their activity towards the SCR reaction. The effect of operating temperature, superficial feed velocity and amount of deposited catalyst on NO conversion was determined. Wide operating margins were observed in which nearly complete NO abatement was achieved with negligible by-product release for superficial velocities typical of the industrial practice (5-65 m/h). 99102020 Strength development at low temperatures in coal ash deposits Hurley, J. P. et al. Prog. Energy Cornbust. Sci., 1998, 24, (6), 513-521. In coal-fired energy systems at temperatures below approximately 1900”F, ash particles formed are relatively hard and not prone to sticking to system surfaces. However, if the ash collects on a surface not exposed to a shearing gas flow such as the downstream side of a heat exchanger or the surface of a hot-gas filter, the deposit can develop enough strength over a period of minutes to days SO that it becomes difficult to remove, in some cases growing to sizes that impede the flow of gas. This paper presents data from ongoing measurements of the significance of ash and gas composition, deposit temperature and time on the rates of strength development in simulated low-temperature ash deposits. In order to explain the possible mechanisms of strength development, preliminary results of surface composition and particle-size distribution analyses of the ash, including submicron material, are also presented.
99102021 Studies of the specific gravity of some Indian coal ashes Pandian, N. S. et al. J. Test. Eval., 1998, 26, (3), 177-186. The handling and disposal of ash is one of the major problems faced by coal-based thermal power stations. Among the various uses of fly ash, the major quantity of ash produced is used in geotechnical engineering apphcattons such as construction of embankments, as a backfill material, etc. The generally low specific gravity of fly ash, resulting in low unit weight as compared to soils, is an attractive property for its use in geotechnical applications. In general, the specific gravity of coal ash lies around 2.0, but can vary to a large extent (1.6 to 3.1). This variation is due to the combination of various factors like gradation, particle shape and chemical composition. Specific gravity has therefore been studied in depth for three Indian coal ashes. 99102022 Studies on the phase mineralogy and leaching characteristics of coal fly ash Khanra, S. et al. Wafer, Air, Soil Pollut., 1998, 107, (l-4) 251-275. Some Indian coal fly ashes were studied as to their phase mineralogy and leaching characteristics in order to assess their safe disposal in abandoned coal mines. Since fly ash contains a number of toxic trace elements, the leaching of fly ash was tested using strong acid/alkali solutions and distilled water under different conditions in the temperature range of 30-100°C. It was found that the concentration of various metals in leachates depends on their chemical nature and association with mineral phases of ash. The distribution of toxic trace elements in fly ash and their leachability were found to depend on the amount of unburnt carbon and iron in fly ash. In an alkali medium, the leaching of iron and toxic trace elements from fly ash was negligible leading to the conclusion that alkali treatment of coal fly ash is safe for use in the refilling of coal mines.
99102023 A study of carbonaceous components of some fly ashes used commercially in concrete Hill, R. L. and Majors, R. K. Prepr. Symp. Am. Chem. Sot., Div. Fuel Chem., 1998, 43, (4), 975-979. Samples of fly ash from two power plants were studied and those which produced a relatively broad range of foam index (FI) values at comparable loss on ignition (LOI) were selected for further testing. Most of the surface area (BET, Nz) of the fly ashes resides with carbon particles and the surface area correlated well with both air in mortar and the FI measurements, yielding an inverse and positive relationship, respectively. DTA appeared not to be a useful prognostic tool for the performance of fly ash in air entrainment in concrete. The hypothesis that the lower temperature region of the multipeak exotherm produced during analysis represents highadsorptive isotropic carbon was not substantiated. Further study of the lowtemperature shoulder of the exotherm found that acid-washing significantly affects peak shape and temperature. The data suggest that this may be related to the removal from the carbon surface of catalytic species which, when present, lower the ignition temperature of carbon.
Fuel and Energy Abstracts
May 1999
207
99102013 Physicochemical properties of unburned carbon from fly ash Ann, Y. K. and Yang, J. I. Chawon Risaikring, 1998, 7, (1). 14-19. (In Korean) Investigated were the physicochemical properties of residual or unburned carbon obtained from fly ash. The flotation method was used to extract carbon-enriched samples from fly ash. Analysis then took place on the carbon content and chemical composition of the recovered carbon sample. The ash in the carbon sample was also examined. The unburned carbon characterization included measurement of size distribution, surface area, crystal structure and density.
99102014 Pilot study of COHPAC for reduction of particulate matter, mercury and acid gas emissions at a coal-fired power plant Lapatnick, L. N. et al. Prepr. Ext. Abstr. ACS Natl. Meet., Am. Chem. Sot., Div. Environ. Chem., 1998, 38, (2), 166-169. This paper describes the promising potential in COHPAC (pulse-jet fabric filter) for removing residual particulate matter from flue gases that pass through electrostatic precipitators. Active carbon injection is slightly-tomarginally effective in removing mercury from the flue gases.
99lO201S Preparation of surfactants from a byproduct of fossil fuel biodesulfurization Lange, E. A. and Lin, Q. Prepr. Am. Chem. Sot., Div. Pet. Chem., 1998,43, (4) 550-552. Heterocyclic sulfur compounds can be removed from fossil fuels, such as diesel fuel, by biocatalytic desulfurization, an alternative refinery hydrotreating process. The heterocyclic sulfur compounds from the fuel were the selectively oxidized through a multi-step enzymic pathway to produce water-soluble sulfur compounds as by-products without degrading the hydrocarbon matrix. 2-(2-Hydroxyphenyl)benzene sulfinic acid was prepared by base-catalysed hydrolysis of dibenzothiophone at a high pH and then transferred to sulfonic acid by reaction with HzOz. The Cs and Cm alkylethers and show good surfactant properties. Process for the regeneration of partially deacti99102016 vated hydrocarbon-synthesis catalysts using a cyclic carbon monoxide purge Leviness, S. C. and Mitchell, W. N. US 5,817,701 (Cl. 518-700; CO7C27/ 00), 6 Ott 1998, Appl. 850,565, 2 May 1997, 11 pp. The rapid regeneration of partially deactivated Fischer-Tropsch catalysts used in slurry hydrocarbon synthesis processes takes place by employing a cyclic process. Here, the synthesis gas or CO flow into the slurry is stopped to halt the hydrocarbon synthesis reaction, the CO purged out of the slurry with a CO-free purge gas in the presence of hydrogen, the catalyst regenerated with a hydrogen-containing rejuvenating gas and the hydrocarbon synthesis reaction restarted by passing the synthesis gas feed back into the reactor. All or a portion of the purge gas and/or the rejuvenating gas may be recycled during the purge and/or rejuvenation, respectively. The hydrogen required during the purge is typically part of the purge gas.
99102017 Rheological behavior of coal-fly-ash and clay slip Lee, K.-G. et al. Yoop Hakhoechi, 1998, 35, (2), 180-184. (In Korean) This paper examined the rheological behaviour of fly ash 70 wt%-clay 30 wt% slip in which non-plastic fly ash was a major component. The effects of deflocculant and coagulant (CaS04) on the rheological behaviour of ashclay slip have been systematically investigated. Ash-clay slip has been characterized on the basis of the time dependent rheology using the gelcurve test. The dispersion mechanism of ash-clay slip is the steric stabilization by the NazSiOs coating of cenospheres surface. A coagulated slip seems to have a new network structure and shows the gelation behaviours which makes it possible to use direct coagulated casting (DCC).
Separation of solids using perforated metal foils 99102016 after brown coal-fired furnaces Winkler, B. Fortschr.-Ber. VDI, Reihe 3, 1998, 544, (i-ix), 1-161. (In German) A review of theoretical, laboratory and pilot plant studies of brown coalfired furnace flue gases filtration through perforated metal foil. High solid removal rates at low pressure drop were achieved. A theoretical description of the process is presented.
By-products
related to fuels
99102019 Simultaneous removal of nitrogen oxides and fly ash from coal-based power-plant flue gases Saracco, G. and Specchia, V. Appl. Therm. Eng., 1998, 18, (ll), 10251035. In principle, catalytic filters are capable of performing shallow-bed dust filtration plus a catalytic reaction, promoted by a catalyst deposited in their inner structure. Such a feature may allow potential cost reduction in several environmental applications, particularly flue-gas treatment of pressurized fluidized bed coal combustors. Lab-scale VzOs/TiOz-deposited filters were prepared, characterized and tested for their activity towards the SCR reaction. The effect of operating temperature, superficial feed velocity and amount of deposited catalyst on NO conversion was determined. Wide operating margins were observed in which nearly complete NO abatement was achieved with negligible by-product release for superficial velocities typical of the industrial practice (5-65 m/h). 99102020 Strength development at low temperatures in coal ash deposits Hurley, J. P. et al. Prog. Energy Cornbust. Sci., 1998, 24, (6), 513-521. In coal-fired energy systems at temperatures below approximately 1900”F, ash particles formed are relatively hard and not prone to sticking to system surfaces. However, if the ash collects on a surface not exposed to a shearing gas flow such as the downstream side of a heat exchanger or the surface of a hot-gas filter, the deposit can develop enough strength over a period of minutes to days SO that it becomes difficult to remove, in some cases growing to sizes that impede the flow of gas. This paper presents data from ongoing measurements of the significance of ash and gas composition, deposit temperature and time on the rates of strength development in simulated low-temperature ash deposits. In order to explain the possible mechanisms of strength development, preliminary results of surface composition and particle-size distribution analyses of the ash, including submicron material, are also presented.
99102021 Studies of the specific gravity of some Indian coal ashes Pandian, N. S. et al. J. Test. Eval., 1998, 26, (3), 177-186. The handling and disposal of ash is one of the major problems faced by coal-based thermal power stations. Among the various uses of fly ash, the major quantity of ash produced is used in geotechnical engineering apphcattons such as construction of embankments, as a backfill material, etc. The generally low specific gravity of fly ash, resulting in low unit weight as compared to soils, is an attractive property for its use in geotechnical applications. In general, the specific gravity of coal ash lies around 2.0, but can vary to a large extent (1.6 to 3.1). This variation is due to the combination of various factors like gradation, particle shape and chemical composition. Specific gravity has therefore been studied in depth for three Indian coal ashes. 99102022 Studies on the phase mineralogy and leaching characteristics of coal fly ash Khanra, S. et al. Wafer, Air, Soil Pollut., 1998, 107, (l-4) 251-275. Some Indian coal fly ashes were studied as to their phase mineralogy and leaching characteristics in order to assess their safe disposal in abandoned coal mines. Since fly ash contains a number of toxic trace elements, the leaching of fly ash was tested using strong acid/alkali solutions and distilled water under different conditions in the temperature range of 30-100°C. It was found that the concentration of various metals in leachates depends on their chemical nature and association with mineral phases of ash. The distribution of toxic trace elements in fly ash and their leachability were found to depend on the amount of unburnt carbon and iron in fly ash. In an alkali medium, the leaching of iron and toxic trace elements from fly ash was negligible leading to the conclusion that alkali treatment of coal fly ash is safe for use in the refilling of coal mines.
99102023 A study of carbonaceous components of some fly ashes used commercially in concrete Hill, R. L. and Majors, R. K. Prepr. Symp. Am. Chem. Sot., Div. Fuel Chem., 1998, 43, (4), 975-979. Samples of fly ash from two power plants were studied and those which produced a relatively broad range of foam index (FI) values at comparable loss on ignition (LOI) were selected for further testing. Most of the surface area (BET, Nz) of the fly ashes resides with carbon particles and the surface area correlated well with both air in mortar and the FI measurements, yielding an inverse and positive relationship, respectively. DTA appeared not to be a useful prognostic tool for the performance of fly ash in air entrainment in concrete. The hypothesis that the lower temperature region of the multipeak exotherm produced during analysis represents highadsorptive isotropic carbon was not substantiated. Further study of the lowtemperature shoulder of the exotherm found that acid-washing significantly affects peak shape and temperature. The data suggest that this may be related to the removal from the carbon surface of catalytic species which, when present, lower the ignition temperature of carbon.
Fuel and Energy Abstracts
May 1999
207