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01715 Effect of wet screening on particle size distribution and coal properties
01 Solid fuels (sources, winning, properties)
0l
SOLID FUELS Sources, winning, properties
04/01709 Acidity distribution of carboxyl groups in Loy Yang brown coal: its analysis and the change by heat treatment Murakami, K. et al. Journal of Colloid and Interface Science, 2003, 260, (1), 176-183. Brown coals have a considerable number of acidic functional groups of which the main component is carboxyl groups, and the acidity has a wide distribution. In this paper, changes of the acidity distribution were examined by aqueous titration when brown coal was heat-treated to control its acidity distribution. For Loy Yang brown coal from Australia dried at 50°C under vacuum (LY50), the acid disassociation constant, Ka, was distributed over a wide pKa range between 2 and 9. Then, using Gaussian functions, the acidity distribution was divided into four groups, which were characterized by average pKa values: average pKa value of 3.8 (hereafter referred to as Group A), 5.2 (Group B), 6.8 (Group C), and 8.3 (Group D). Among them, Groups A, B, and C were assigned to carboxyl groups. From the changes of the number of carboxyl groups when brown coal was heat-treated up to 400°C, it was found that the way of decrease was different among these acidic groups. The decrease of the amount of carboxyl groups in Group C was significant, and at 325°C most of them disappeared. On the other hand, the carboxyl groups in Group A remained even at a high temperature of 400°C. The structures around carboxyl groups for LY50 and their structural changes by heat treatment were estimated approximately using the known pKa values for simple carboxylic acids and the pKa values calculated by the MOPAC program for complicated carboxylic acids.
04/01710 Coal combustion characteristics based on the release of carbon dioxide Zou, X. et al. Ranliao Huaxue Xuebao, 2003, 31, (2), 185-188. (In Chinese) A new low-cost apparatus used to study the character of coal combustion in place of a thermogravimetric analyser was developed based on the CO2 release. In order to prove the new idea, CO2 concentration of fore coal samples during ignition, combustion and burnout was measured by the apparatus developed by the authors. The characters of special mechanism based on the relation between the temperature and CO2 concentration (t-CO2), also the derivative curve Dt-COz were obtained. The change of CO2 can indirectly estimate the coal combustion characters.
04/01711 Cushioning tests of weathered coal on different impact surfaces Sahoo, R. K. et al. Bulk Solids Handling, 2003, 23, (1), 28-33. Degradation characteristics of weathered Ensham coal samples were tested using a drop apparatus to minimize the fines generation during transportation and handling through the Gladstone Port Authority's ship loading facilities. Laboratory stockpiles, made of Ensham coal, were exposed to weathering conditions for different periods of time. These coal samples, weathered for 1 month, 3 months, 6 months, 9 months and a year, were tested using a drop apparatus to measure the percentage of fines generation. It was found that the rate of fines generation increases with the period of weathering. The fines generation of weathered coal increased up to 6 months of weathering, thereafter, the fines generation reaches an almost constant value, To detect the influence of the material onto which the coal is dropped, samples of 1 month and 3 months weathered coal with different percentages of initial fines were dropped onto a steel surface, a conveyor belt surface and on a coal surface (laboratory stockpiles). The fines generation of 1 month and 3 months weathered coal was the least on the coal surface compare to the other two impact surfaces. Cushioning tests with cushioned coal and coal with initial 30% of fines showed that the difference of fines generation between 3 months and 1 month weathered coal were the same for the three different surfaces. For weathered coal with initial 30% of fines, the cushioning effect was stronger if the coal dropped on the conveyor belt or the coal surface. For normal non-weathered coal, however, the cushioning effect was stronger when it was dropped on the steel surface.
04/01712 Determination of Cd, Hg, Pb and TI in coal and coal fly ash slurries using electrothermal vaporization inductively coupled plasma mass spectrometry and isotopic dilution Maia, S. M. et al. Journal of Analytical Atomic Spectrometry, 2003, 18, (4), 330-337.
242
Fuel and Energy Abstracts
July 2004
A method was studied for the detection of Cd, Hg, Pb and T1 in coal and in coal fly ash, using slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry and isotope dilution. The slurry, 25 mg m1-1, was prepared by mixing the powered sample (_<36-45 gm) with acid solutions (nitric acid for coal and nitric and hydrofluoric acids for coal fly ash) and submitting the mixture to an ultrasonic agitation, letting it stand afterwards in a water bath at 60 ° for 2 h. An ultrasonic probe was used to homogenize the slurry in the autosampler cup just before its introduction into the graphite tube. The best conditions were detected regarding analysis of sensitivity, furnace temperature program, amount of modifier, acid concentration, gas flow rate and particle size. For Hg, the pyrolysis stage was omitted and a low vaporization temperature was used (450-1000°); the residual matrix was eliminated in the first step of the following cycle. The modifiers used were: Pd for Cd and T1; Au, Ir or Pd for Hg; Ir or Pd for Pb. The accuracy of the method was checked by analysing six certified coal refined materials (SARM 20, SARM 19, BCR Number 40, BCR Number 180, BCR Number 181 and NIST 1630a) and one certified coal fly ash (NIST 1633b). With one exception (Hg in BCR Number 180), the found concentrations were typically within 95% confidence interval of the certified values, or close enough to the recommended values, as long as the samples were ground to a small enough particle size. The limits of d'etection were typically around 0.08 gg g-l, 0.03 gg g a and 0.02 gg g i for Cd, Hg, Pb and TI, respectively. The precision was also adequate with relative standard deviations of usually <5%.
04/01713 Development of the meso- and macroporous structure of coals with rank as analysed with small angle neutron scattering and adsorption experiments Prinz, D. et al. Fuel, 2004, 83, (4 5), 547 556. Small angle neutron scattering and adsorption experiments have been performed on a series of humic coals from the Ruhr Basin, Germany. The coals represent the range of rank (0.76-2.23% vitrinite reflectance) within the basin and nearly the complete rank range of bituminous coals. The experiments were carried out in order to get information about changes of the meso- and macroporous structure within the coals as related to rank. Results indicate that the structural parameter of the molecular component of the coals are displaying an exponential behaviour with rank, which is in excellent agreement with the loss of functional oxygen groups.
04/01714
Dielectric characterization of coals
Fornies-Marquina, J. M. et al. Canadian Journal of Physics, 2003, 81, (3), 599-610. Application of an electromagnetic analysis for coal characterization is attempted. By time domain reflectometry, dispersion spectra in the DC - 5 GHz range of a wide variety of coals are obtained for room temperature. Static permittivity and relaxation frequency of the different samples are compared with parameters obtained by chemical analysis. Comparison reveals the usefulness of the electromagnetic characterization for the establishment of coal rank, and shows how an analysis of the dielectrical characteristic parameters can provide approximate ideas about moisture, elemental carbon, hydrogen, and sulfur contents.
04/01715 Effect of wet screening on particle size distribution and coal properties Govender, A. and van Dyk, J. C. Fuel, 2003, 82, (18), 2231 2237. Wet screening is one of the methods used to remove fine material from the coal feed to gasification. Sasol Synfuels in South Africa undertook an investigation to quantify fine coal generation in the coal supply to gasification. Coal samples were wet screened in the laboratory and results compared to the normal dry screening procedure. It was found that the fines ( 0.5 mm) increased almost five times when the coal was wet screened compared to dry screening. This study was subsequently initiated by Sasol Technology R&D to establish the mechanism of fine coal generation during wet screening, as well as the effect of wet screening on particle size distribution (PSD) and chemical properties of coal. Changes in the PSD and chemical properties of coal from individual coal sources used at Sasol Synfuels were compared. Composite coal samples with a predetermined PSD of all individual coal sources used at Sasol Synfuels were screened under wet and dry conditions. The PSD was again determined after screening, as well as the mineral composition (by X-ray diffraction) of the fines. Results indicated that wet screening caused clay minerals to be removed from the coal structure leading to an increase in the fines. This removal of minerals weakened the coal structure causing further size degradation of coarser fractions.
04/01716 Effects of rapid preheating on coal structure and coke strength Matsuura, M. et al. Tetsu to Hagane, 2003, 89, (5), 565 572, Japanese)
(In
0l
SOLID FUELS Sources, winning, properties
04/01709 Acidity distribution of carboxyl groups in Loy Yang brown coal: its analysis and the change by heat treatment Murakami, K. et al. Journal of Colloid and Interface Science, 2003, 260, (1), 176-183. Brown coals have a considerable number of acidic functional groups of which the main component is carboxyl groups, and the acidity has a wide distribution. In this paper, changes of the acidity distribution were examined by aqueous titration when brown coal was heat-treated to control its acidity distribution. For Loy Yang brown coal from Australia dried at 50°C under vacuum (LY50), the acid disassociation constant, Ka, was distributed over a wide pKa range between 2 and 9. Then, using Gaussian functions, the acidity distribution was divided into four groups, which were characterized by average pKa values: average pKa value of 3.8 (hereafter referred to as Group A), 5.2 (Group B), 6.8 (Group C), and 8.3 (Group D). Among them, Groups A, B, and C were assigned to carboxyl groups. From the changes of the number of carboxyl groups when brown coal was heat-treated up to 400°C, it was found that the way of decrease was different among these acidic groups. The decrease of the amount of carboxyl groups in Group C was significant, and at 325°C most of them disappeared. On the other hand, the carboxyl groups in Group A remained even at a high temperature of 400°C. The structures around carboxyl groups for LY50 and their structural changes by heat treatment were estimated approximately using the known pKa values for simple carboxylic acids and the pKa values calculated by the MOPAC program for complicated carboxylic acids.
04/01710 Coal combustion characteristics based on the release of carbon dioxide Zou, X. et al. Ranliao Huaxue Xuebao, 2003, 31, (2), 185-188. (In Chinese) A new low-cost apparatus used to study the character of coal combustion in place of a thermogravimetric analyser was developed based on the CO2 release. In order to prove the new idea, CO2 concentration of fore coal samples during ignition, combustion and burnout was measured by the apparatus developed by the authors. The characters of special mechanism based on the relation between the temperature and CO2 concentration (t-CO2), also the derivative curve Dt-COz were obtained. The change of CO2 can indirectly estimate the coal combustion characters.
04/01711 Cushioning tests of weathered coal on different impact surfaces Sahoo, R. K. et al. Bulk Solids Handling, 2003, 23, (1), 28-33. Degradation characteristics of weathered Ensham coal samples were tested using a drop apparatus to minimize the fines generation during transportation and handling through the Gladstone Port Authority's ship loading facilities. Laboratory stockpiles, made of Ensham coal, were exposed to weathering conditions for different periods of time. These coal samples, weathered for 1 month, 3 months, 6 months, 9 months and a year, were tested using a drop apparatus to measure the percentage of fines generation. It was found that the rate of fines generation increases with the period of weathering. The fines generation of weathered coal increased up to 6 months of weathering, thereafter, the fines generation reaches an almost constant value, To detect the influence of the material onto which the coal is dropped, samples of 1 month and 3 months weathered coal with different percentages of initial fines were dropped onto a steel surface, a conveyor belt surface and on a coal surface (laboratory stockpiles). The fines generation of 1 month and 3 months weathered coal was the least on the coal surface compare to the other two impact surfaces. Cushioning tests with cushioned coal and coal with initial 30% of fines showed that the difference of fines generation between 3 months and 1 month weathered coal were the same for the three different surfaces. For weathered coal with initial 30% of fines, the cushioning effect was stronger if the coal dropped on the conveyor belt or the coal surface. For normal non-weathered coal, however, the cushioning effect was stronger when it was dropped on the steel surface.
04/01712 Determination of Cd, Hg, Pb and TI in coal and coal fly ash slurries using electrothermal vaporization inductively coupled plasma mass spectrometry and isotopic dilution Maia, S. M. et al. Journal of Analytical Atomic Spectrometry, 2003, 18, (4), 330-337.
242
Fuel and Energy Abstracts
July 2004
A method was studied for the detection of Cd, Hg, Pb and T1 in coal and in coal fly ash, using slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry and isotope dilution. The slurry, 25 mg m1-1, was prepared by mixing the powered sample (_<36-45 gm) with acid solutions (nitric acid for coal and nitric and hydrofluoric acids for coal fly ash) and submitting the mixture to an ultrasonic agitation, letting it stand afterwards in a water bath at 60 ° for 2 h. An ultrasonic probe was used to homogenize the slurry in the autosampler cup just before its introduction into the graphite tube. The best conditions were detected regarding analysis of sensitivity, furnace temperature program, amount of modifier, acid concentration, gas flow rate and particle size. For Hg, the pyrolysis stage was omitted and a low vaporization temperature was used (450-1000°); the residual matrix was eliminated in the first step of the following cycle. The modifiers used were: Pd for Cd and T1; Au, Ir or Pd for Hg; Ir or Pd for Pb. The accuracy of the method was checked by analysing six certified coal refined materials (SARM 20, SARM 19, BCR Number 40, BCR Number 180, BCR Number 181 and NIST 1630a) and one certified coal fly ash (NIST 1633b). With one exception (Hg in BCR Number 180), the found concentrations were typically within 95% confidence interval of the certified values, or close enough to the recommended values, as long as the samples were ground to a small enough particle size. The limits of d'etection were typically around 0.08 gg g-l, 0.03 gg g a and 0.02 gg g i for Cd, Hg, Pb and TI, respectively. The precision was also adequate with relative standard deviations of usually <5%.
04/01713 Development of the meso- and macroporous structure of coals with rank as analysed with small angle neutron scattering and adsorption experiments Prinz, D. et al. Fuel, 2004, 83, (4 5), 547 556. Small angle neutron scattering and adsorption experiments have been performed on a series of humic coals from the Ruhr Basin, Germany. The coals represent the range of rank (0.76-2.23% vitrinite reflectance) within the basin and nearly the complete rank range of bituminous coals. The experiments were carried out in order to get information about changes of the meso- and macroporous structure within the coals as related to rank. Results indicate that the structural parameter of the molecular component of the coals are displaying an exponential behaviour with rank, which is in excellent agreement with the loss of functional oxygen groups.
04/01714
Dielectric characterization of coals
Fornies-Marquina, J. M. et al. Canadian Journal of Physics, 2003, 81, (3), 599-610. Application of an electromagnetic analysis for coal characterization is attempted. By time domain reflectometry, dispersion spectra in the DC - 5 GHz range of a wide variety of coals are obtained for room temperature. Static permittivity and relaxation frequency of the different samples are compared with parameters obtained by chemical analysis. Comparison reveals the usefulness of the electromagnetic characterization for the establishment of coal rank, and shows how an analysis of the dielectrical characteristic parameters can provide approximate ideas about moisture, elemental carbon, hydrogen, and sulfur contents.
04/01715 Effect of wet screening on particle size distribution and coal properties Govender, A. and van Dyk, J. C. Fuel, 2003, 82, (18), 2231 2237. Wet screening is one of the methods used to remove fine material from the coal feed to gasification. Sasol Synfuels in South Africa undertook an investigation to quantify fine coal generation in the coal supply to gasification. Coal samples were wet screened in the laboratory and results compared to the normal dry screening procedure. It was found that the fines ( 0.5 mm) increased almost five times when the coal was wet screened compared to dry screening. This study was subsequently initiated by Sasol Technology R&D to establish the mechanism of fine coal generation during wet screening, as well as the effect of wet screening on particle size distribution (PSD) and chemical properties of coal. Changes in the PSD and chemical properties of coal from individual coal sources used at Sasol Synfuels were compared. Composite coal samples with a predetermined PSD of all individual coal sources used at Sasol Synfuels were screened under wet and dry conditions. The PSD was again determined after screening, as well as the mineral composition (by X-ray diffraction) of the fines. Results indicated that wet screening caused clay minerals to be removed from the coal structure leading to an increase in the fines. This removal of minerals weakened the coal structure causing further size degradation of coarser fractions.
04/01716 Effects of rapid preheating on coal structure and coke strength Matsuura, M. et al. Tetsu to Hagane, 2003, 89, (5), 565 572, Japanese)
(In