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Mathematical model for the gasification of coal under pressure
Conference
Abstracts
are directly related to the sulfur concentration. Federal, state and local regulations limit the amount of sulfur that is present or the amount of sulfur oxides that can be emitted during the combustion of fossil fuels. The coal and electric utility industries use methods for the determination of sulfur in coal that require coal standards for calibration. In 1982 we reported on a new technique for the determination of sulfur as the ASS+ molecular ion by isotope dilution thermal ionization mass spectrometry. In this procedure, coal samples are spiked with enriched 34S and wet ashed in a closed system. The oxidized sulfur is reduced to As,S, and a small amount of this compound, equivalent to about 1 pg of sulfur, is mixed with silica gel on single Re lilament. The 32S/“4S ratio is determined by measuring the “ASHES+ and 75As34S+’ ion current on a Faraday detector. Since our initial report in 1982, high precision and high accuracy determinations of sulfur have been made on 30 fossil fuel Standard Reference Materials. The total uncertainty for homogeneous materials such as oils is about 0.5% relative and about 14% for coals ranging in concentration from 0.5 to 4.7% sulfur. For coals, the precision is a reflection of the heterogeneity rather than the precision of the technique. Details ofthe procedure, specific examples of recent determinations and the certification procedure will be presented.
The influence of the addition of chromium to active carbon on the desulphurization of flue gases
University of Mining and Metallurgy, Faculty of Energochemistry Coal and Physical Chemistry of Sorbents, 30-059 Krakbw, Poland Increasing environmental pollution makes desulphurization methods leaving no waste materials especially interesting. Active carbons unpromoted or containing cations such as alkali metals, manganese, iron, vanadium, nickel etc. were found to be applicable for SO, removal from flue gases. However, the influence of these cations on the structure of catalysts and the relationship between SO, removal efficiency and both active material distribution and catalyst texture has not been widely investigated. In order to improve SO, removal efficiency of active carbons. Polish active carbon N/m was impregnated with chromium nitrate or potassium perchromate aqueous solutions. The following aspects of catalyst structure were studied: (i) the influence of chromium compound and the amount added to active carbon on the active material distribution and catalyst texture; (ii) the relationship between the structure of chromium-promoted active carbon and SO, removal efficiency; and (iii) the stability of the samples towards the reaction mixture. The structure of the starting material and chromium-promoted active carbon catalysts was studied by low-temperature argon adsorption, while the oxidation degree and the distribution of active material was determined using XPS. The SO, removal efficiency was measured for the mixture containing ca. 2000ppm SO,, H,O and air in specially built catalytic equipment with on-line SO, U.V. analyser. It was found that the type of chromium compound influenced both the texture of the catalysts and the distribution of active material. On the other hand, the distribution determined SO, removal efficiency. The samples underwent certain changes during the reaction, depending on the starting material and the promoter compound used for impregnation.
E. Klose
model for the gasification of coal under pressure
and R. Kiipsel
Bergakademie O-9200
Freiberg,
Freiberg,
Institut
fiir Energieverfahrenstechnik,
Germany
A detailed mathematical description of technological processes is a prerequisite for the optimal operation and design of plants. A mathematical mode1 for the pressure gasification of solid fuels in the charged layer has been developed. With due consideration of the partial processes taking place in the pressure gasifier, the model deals with the parameters of reaction kinetics and of the transfer of matter and energy which are necessary for developing the model of a fixed-bed reactor. For calculating the concentration and temperature profiles for the solid and gas phases along the gasification bed height, a system of differential equations was obtained which was supplemented by some algebraic
714
Fuel 1993
T.g.-m.s. study of devolatilization products during the combustion of an Argonne Premium Coal sample 0. C. Kopp, E. L. Fuller Jr and A. D. Underwood Oak Ridge National Laboratory, Metals and Ceramics Division, Oak Ridge, TN 37831-6087, USA The development of a combined thermogravimetric-mass spectrometer system has made it possible to study reactions that occur during the combustion of carbonaceous materials and to relate these reactions to both temperature and mass changes. The thermogravimetric device is a Mettler Thermoanalyzer (model TA-1) whose effluent gases are routed to a UT1 Instruments (model 1OOOC) quadrapole mass spectrometer. Results for an Argonne Premium Coal sample are reported. The coal is sample A701, a high volatile bituminous coal (Lewiston-Stockton seam) from West Virginia (USA). Sample A701 is reported to contain 8 I % C. 5.5% H and 11% 0 on a dry basis. A 25 mg sample (35-60
mesh fraction) was heated to 750°C at 10°C min-‘. The oxidizing atmosphere used was a mixture of helium (80%) and oxygen (20%)
J. Klinik and 7: Grzybek
Mathematical
equations. The calculations showed good agreement with data measured in industrial plants. The model can be used to analyse pilot plant data, to select new operating conditions, to evaluate new process routes and to help design equipment.
Volume
72 Number
5
flowing at 121h-‘. The combined system makes it possible to simultaneously record the evolution of up to 12 components. During the oxidation of A701, at least three organic components were detected, including propane, ethane and methane. Whether ethane was an actual devolatilization product during heating or the result of fragmentation of propane by the mass spectrograph is not yet certain. Both propane and ethane appear to be released in two stages, i.e. as the result of two independent reactions. Initially it was expected that any methane originally present in the coal would have escaped during collection, processing and storage of the sample, or during evacuation of the thermoanalyser prior to introducing the helium-oxygen gas mixture; however, the methane curve clearly shows that it was evolved from the coal and not the result of fragmentation in the mass spectrometer. Finally, comparison of the curves for methane, propane (and ethane) with the carbon dioxide curve reveals that the evolution of methane and the first stage of evolution of propane (and ethane) occur during the initial stage of oxidation of the sample while the second stage of evolution of propane (and ethane) coincides more closely to the period of maximum generation of carbon dioxide.
Influence of metal ions on coal and carbon oxidation Igor A. Korobetskii, Urii 1/: Kuzmin, Elena I. Korobetskaya
Natalya
International Centre for Coal Research, 21, Kemerovo 650610, Russia
A. Proshina
Rukavishnikova
and
Str.
The influence of Fe ions present in coals and pure graphite was studied. Different coals with the same characteristics excluding Fe content differed in the rate of weight loss during cool oxygen plasma oxidation (COPO). But it has been impossible to exclude the influence of other factors (macerals, C, H, 0 content, vitrinite reflection etc.) during experiments with coals. Pure graphite was saturated with Fe ions by treatment with a solution of FeCI, in a radiofrequency (r.f.) field (27.12 MHz) at 25°C. After 3 h of this treatment graphite contained 25 wt% of FeCl,. This compound was tested by COP0 at 15@16o”C, oxygen flow 15 ml min- I, initial weight of sample 150 mg. The oxidation rate was decreased from 80 mg h- ’ for pure graphite to 15 mg h- ’ for intercalated graphite. X-ray diffraction of graphite before and after treatment by FeCI, was carried out on a DRON-2 diffractometer with Cu irradiation (I .5405 A). Ni filter, voltage 30 kV. and current 30 mA. Results of this investlgaiion showed a main reflex decrease of 13 times for the intercalated graphite compared to the pure graphite. It indicated changes in graphite with some increase of the amorphous part of the structure. The Fe ions intercalated in graphite structure may be centres for r.f. energy dissipation. This caused change in the interaction of the graphite structure and r.f. energy. During COP0 we believe r.f. energy interacts with oxygen in volume
Abstracts
are directly related to the sulfur concentration. Federal, state and local regulations limit the amount of sulfur that is present or the amount of sulfur oxides that can be emitted during the combustion of fossil fuels. The coal and electric utility industries use methods for the determination of sulfur in coal that require coal standards for calibration. In 1982 we reported on a new technique for the determination of sulfur as the ASS+ molecular ion by isotope dilution thermal ionization mass spectrometry. In this procedure, coal samples are spiked with enriched 34S and wet ashed in a closed system. The oxidized sulfur is reduced to As,S, and a small amount of this compound, equivalent to about 1 pg of sulfur, is mixed with silica gel on single Re lilament. The 32S/“4S ratio is determined by measuring the “ASHES+ and 75As34S+’ ion current on a Faraday detector. Since our initial report in 1982, high precision and high accuracy determinations of sulfur have been made on 30 fossil fuel Standard Reference Materials. The total uncertainty for homogeneous materials such as oils is about 0.5% relative and about 14% for coals ranging in concentration from 0.5 to 4.7% sulfur. For coals, the precision is a reflection of the heterogeneity rather than the precision of the technique. Details ofthe procedure, specific examples of recent determinations and the certification procedure will be presented.
The influence of the addition of chromium to active carbon on the desulphurization of flue gases
University of Mining and Metallurgy, Faculty of Energochemistry Coal and Physical Chemistry of Sorbents, 30-059 Krakbw, Poland Increasing environmental pollution makes desulphurization methods leaving no waste materials especially interesting. Active carbons unpromoted or containing cations such as alkali metals, manganese, iron, vanadium, nickel etc. were found to be applicable for SO, removal from flue gases. However, the influence of these cations on the structure of catalysts and the relationship between SO, removal efficiency and both active material distribution and catalyst texture has not been widely investigated. In order to improve SO, removal efficiency of active carbons. Polish active carbon N/m was impregnated with chromium nitrate or potassium perchromate aqueous solutions. The following aspects of catalyst structure were studied: (i) the influence of chromium compound and the amount added to active carbon on the active material distribution and catalyst texture; (ii) the relationship between the structure of chromium-promoted active carbon and SO, removal efficiency; and (iii) the stability of the samples towards the reaction mixture. The structure of the starting material and chromium-promoted active carbon catalysts was studied by low-temperature argon adsorption, while the oxidation degree and the distribution of active material was determined using XPS. The SO, removal efficiency was measured for the mixture containing ca. 2000ppm SO,, H,O and air in specially built catalytic equipment with on-line SO, U.V. analyser. It was found that the type of chromium compound influenced both the texture of the catalysts and the distribution of active material. On the other hand, the distribution determined SO, removal efficiency. The samples underwent certain changes during the reaction, depending on the starting material and the promoter compound used for impregnation.
E. Klose
model for the gasification of coal under pressure
and R. Kiipsel
Bergakademie O-9200
Freiberg,
Freiberg,
Institut
fiir Energieverfahrenstechnik,
Germany
A detailed mathematical description of technological processes is a prerequisite for the optimal operation and design of plants. A mathematical mode1 for the pressure gasification of solid fuels in the charged layer has been developed. With due consideration of the partial processes taking place in the pressure gasifier, the model deals with the parameters of reaction kinetics and of the transfer of matter and energy which are necessary for developing the model of a fixed-bed reactor. For calculating the concentration and temperature profiles for the solid and gas phases along the gasification bed height, a system of differential equations was obtained which was supplemented by some algebraic
714
Fuel 1993
T.g.-m.s. study of devolatilization products during the combustion of an Argonne Premium Coal sample 0. C. Kopp, E. L. Fuller Jr and A. D. Underwood Oak Ridge National Laboratory, Metals and Ceramics Division, Oak Ridge, TN 37831-6087, USA The development of a combined thermogravimetric-mass spectrometer system has made it possible to study reactions that occur during the combustion of carbonaceous materials and to relate these reactions to both temperature and mass changes. The thermogravimetric device is a Mettler Thermoanalyzer (model TA-1) whose effluent gases are routed to a UT1 Instruments (model 1OOOC) quadrapole mass spectrometer. Results for an Argonne Premium Coal sample are reported. The coal is sample A701, a high volatile bituminous coal (Lewiston-Stockton seam) from West Virginia (USA). Sample A701 is reported to contain 8 I % C. 5.5% H and 11% 0 on a dry basis. A 25 mg sample (35-60
mesh fraction) was heated to 750°C at 10°C min-‘. The oxidizing atmosphere used was a mixture of helium (80%) and oxygen (20%)
J. Klinik and 7: Grzybek
Mathematical
equations. The calculations showed good agreement with data measured in industrial plants. The model can be used to analyse pilot plant data, to select new operating conditions, to evaluate new process routes and to help design equipment.
Volume
72 Number
5
flowing at 121h-‘. The combined system makes it possible to simultaneously record the evolution of up to 12 components. During the oxidation of A701, at least three organic components were detected, including propane, ethane and methane. Whether ethane was an actual devolatilization product during heating or the result of fragmentation of propane by the mass spectrograph is not yet certain. Both propane and ethane appear to be released in two stages, i.e. as the result of two independent reactions. Initially it was expected that any methane originally present in the coal would have escaped during collection, processing and storage of the sample, or during evacuation of the thermoanalyser prior to introducing the helium-oxygen gas mixture; however, the methane curve clearly shows that it was evolved from the coal and not the result of fragmentation in the mass spectrometer. Finally, comparison of the curves for methane, propane (and ethane) with the carbon dioxide curve reveals that the evolution of methane and the first stage of evolution of propane (and ethane) occur during the initial stage of oxidation of the sample while the second stage of evolution of propane (and ethane) coincides more closely to the period of maximum generation of carbon dioxide.
Influence of metal ions on coal and carbon oxidation Igor A. Korobetskii, Urii 1/: Kuzmin, Elena I. Korobetskaya
Natalya
International Centre for Coal Research, 21, Kemerovo 650610, Russia
A. Proshina
Rukavishnikova
and
Str.
The influence of Fe ions present in coals and pure graphite was studied. Different coals with the same characteristics excluding Fe content differed in the rate of weight loss during cool oxygen plasma oxidation (COPO). But it has been impossible to exclude the influence of other factors (macerals, C, H, 0 content, vitrinite reflection etc.) during experiments with coals. Pure graphite was saturated with Fe ions by treatment with a solution of FeCI, in a radiofrequency (r.f.) field (27.12 MHz) at 25°C. After 3 h of this treatment graphite contained 25 wt% of FeCl,. This compound was tested by COP0 at 15@16o”C, oxygen flow 15 ml min- I, initial weight of sample 150 mg. The oxidation rate was decreased from 80 mg h- ’ for pure graphite to 15 mg h- ’ for intercalated graphite. X-ray diffraction of graphite before and after treatment by FeCI, was carried out on a DRON-2 diffractometer with Cu irradiation (I .5405 A). Ni filter, voltage 30 kV. and current 30 mA. Results of this investlgaiion showed a main reflex decrease of 13 times for the intercalated graphite compared to the pure graphite. It indicated changes in graphite with some increase of the amorphous part of the structure. The Fe ions intercalated in graphite structure may be centres for r.f. energy dissipation. This caused change in the interaction of the graphite structure and r.f. energy. During COP0 we believe r.f. energy interacts with oxygen in volume