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04421 Reduction of toxic trace elements in coal by advanced cleaning
07
So/id fuels (preparation)
modifiers for the coal particles. The agglomerates were smaller and more hydrophobic. The clean coal recovery increased substantially with a lowering of the ash content for these type of coals.
97104414 grinding
Mill power for high-pressure
grinding
rolls in coal
Austin, L. G. Miner. Metall. Prowss.. 1997. 14, (3). 18-26. For six coals and a crystal quartz, the grinding force, gap dimension mass flow rate, and net mill power were measured using an instrumented laboratory high-pressure grinding roller mill. A technique was developed to estimate the compressive stress-strain curves for compression of the materials in the mill plus the effects of elastic decompression. To reconcile the mill power and grinding pressure results, it was necessary to allow for energy recovery on decompression. Between the form of the stress-strain curves or the variation of specific mill power factor and the Hardgrove grindability index (HGI), no clea correlation was discovered, but coals with the lowest and highest HGls gave significantly different results to the other coals. Feeds < 140 mesh flowed more rapidly than coarser feeds and would not build up high grinding pressures. Therefore, shearing and fluid-like properties were more evident, rather than compression as a locked bed.
A model for softening 97104415 heated at different rates.
and resolidification
of coals
Matsuoka, K. et al. ISIJ lnt., 1997, 31, (6). 566-572. An examination of needle penetration and dilation characteristics for cylindrical coal pellets upon heating was carried out. The net penetration depth, obtained from the observed penetration and dilation curves, was analysed by an equation of motion to derive the apparent viscosity of coal. Mass loss due to volatiles release and yields of pyridine extract were also measured for the pellets. Changes in the apparent viscosity with heating were explained by a simple model with the following assumptions: (1) coal behaved instantaneously as a Newtonian fluid, (2) coal consists of two reactive components; one converting to semi-coke via an intermediate along with volatiles release and the other converting to volatiles directly, (3) the intermediate is represented by the pyridine extract and hehaves as a liquid, whereas the others behave as solids, and (4) the apparent viscosity change is described by Vand’s equation for a slurry combined with Andrade’s equation for liquid viscosity.
Numerical investigation 97104416 a beater wheel mill with classifier
of the grinding
process
in
Anagnostopoulos, _I. and Bergeles, G. J. Eng. Gas Turbines Power., 1997, 119, (3). 723-733. A two-dimensional simulation of the gas flow field and of the dynamic behaviour of lignite particles inside beater wheel mills with classifier was numerically investigated. A large number of representative particles are tracked using Lagrangian equations of motion. in combination with a stochastic model for particle turbulent dispersion. All the important mechanisms associated with the particle motion through the mill are modelled. A special model is constructed to simulate the fragmentation of impacting particles and to calculate the size distribution of the final mill product. The models are regulated on the basis of available data from grinding mills of the Greek lignite power stations. The numerical code can predict the locations of significant erosion and estimate the amount of particle mass that circulates through the mill via the classifying chamber. Remarkable differences were discovered in the extent of erosion at different locations of the mill. Information concerning the significant role of the leading blades arrangement inside the classifier on its classification performance and efficiency is provided.
97104417 Observations and studies of float and sink centrifugation of fine coal at Nottingham University Kizgut, S. et al. Changing Scopes Miner. Process., Proc. Int. Miner. Process. Symp., 6th. 1996, 435-439. Edited by Kemal, M., Balkema, Rotterdam, The Netherlands. The paper describes a comparative centrifugal and static bath float and sink test made on a classified coal sample of -38 + 20 rrrn and -20 Irm size groups. The objective of the study was to modify a density separation test method to control products of maceral separation study which had been conducted on a heavy medium cyclone rig. Densities of 1.30 and I.60 g/cm’ were chosen to examine the effect of a large amount of material having a density very close to separation density at low densities and the effect of viscosity at relatively high density that cited as main restriction for the use of inorganic salt solutions and even some organic liquids. A sodium polytungstate solution and a surfactant were used as the separation medium.
97104418
Pulverized
coal flowability
Fuel and Energy Abstracts
Pyrite recovery
mechanisms
in coal flotation
Kawatra, S. K. and Eisele. T. C. Inr. J. Miner. Promss.. 1997. SO. (3). 187-201. During flotation of high-sulfur coal in most operating coal-cleaning plants, a significant amount of pyrite is recovered in the froth. This is helieved to result from pyrite particles floating due to hydrophohicity. However, there is no use of pyrite depressants for industrial coal flotation, which suggests that the mechanism of pyrite flotation is not properly understood. In order to reduce pyrite recovery during flotation. it is first necessary to identify the primary recovery mechanism, so that the appropriate method for correcting the problem can be selected. In this paper, flotation of liberated pyrite due to its intrinsic hydrophohicity is shown not to be an important mechanism for recovery of pyrite from freshly ground coal. and that the bulk of the floated pyrite the froth either as a result of simple entrainment of by mechanical locking with floatable coal particles. The experiments were carried out using hoth a conventional flotation cell, and a horizontally baffled flotation column. 97104420
The reduction
in moisture
measurina
time of dried
lignite Rajagopalan, S. Enere Corri~er.c-.Mgnrt.. 1997, 38, (7), 697-hYY. Before being fed to the press for making briquettes. lignite taken from dryers is s&jected to miisture tests to evaluate the pe;formance of the dryers in reducing the moisture of the wet lignite from the mines. A quick and approximate estimation of the moisture content of the dried lignite from the dryers is required for a number of times. to adjust the dryer operating parameters. Knowledge of the moisture content lost from the sample after 10 minutes was found to be enough to have a reasonable estimate of the total moisture ccmtent of the sample. 97104421
advanced
Reduction cleaning
of toxic
trace
elements
in
coal
by
Smit, F. J. Proc. Amu. Irrt. Pirrshqh Coal Conf.. 1996, 13. (2). 87Y-884. In continuous bench-scale circuits, advanced cleaning by column flotation and selective agglomeration were used to determine the residual concentrations of 12 toxic trace-element impurities in five coals. For each of the trace elements, the reduction in concentration from the amount in the ROM parent coals and the amount in the washed test coals was also determined on a heating value basis.
97104422 anhydrous
Removal of organic sulfur HF and superacid HFIBFJ
in coal
by the use of
Shimizu, K. et al. Chemical LFU., 1997, (9). 943-944. Anhydrous hydrogen fluoride and HF was combined with a small amount of boron trifluoride desulfurized high-sulfur coal in the presence of hydrocarbons without Hz in mild reaction conditions. HF removed mainly sulfide and oxidized sulfur. HF/BFx decreased thiophene sulfur as well as sulfide and oxidized sulfur although the extent of desulfurization was almost the same as that with HF alone.
97104423 A simulation circuit design
of slime circulation
and the effect of
Nazimko, L. I. and Nazimko, V. V. Cocll Prep., 1996, 17, (3-4), 21.5-232. The results of the accumulation of slimes in the coal preparation plant circuit include inefficient operation of the coal cleaning equipment, loss of coal, increases in product coal ash, and increased maintenance and operating costs. To maximize the plant operation, control of the plant circuit slimes content and slimes removal are required. To this end, the authors developed a simulator model, based on accumulation and production of the slimes, feed fluctuations and real-time circuit operation. This programme makes it possible to simulate and analyse preparation plant flowsheets of water circulation to maximize plant operation. Slime accumulation can be reduced by about 50% and the time for attaining slimes equilibrium in the plant water circuits can experience about hh% reduction.
97104424 extraction
Solvent
swelling
of coal for improved
supercritical
Hu, H. et al. Ranliao Huaxue Xuehao., lYY7,25, (3). 223-226. (In Chinese) Supercritical extraction of Xinglong coal took place with toluene in an autoclave apparatus following its swelling in pyridine. THF and methanol. separately. The objective was to investigate the effect of solvent swelling on coal extraction. The results indicated that the swelling pre-treatment of coal with THF or pyridine can effectively enhance conversion and light-fraction yield of supercritical extraction process. In the investigated temperature range of 340 to 400°C. the pyridine swollen coal showed a much higher conversion and lower gas yield than untreated coal. High solvent-to-coal ratio and high extraction pressure were beneficial to supercritical extraction of pyridine swollen coal. In addition, FTIR and SEM of pyridine swollen coal and untreated coal were examined to investigate variations of the coal structure during solvent swelling.
improver
Ono, R. et al. PCT Int. Appl. WO 97 36,009 (Cl. C2195/00), 2 Ott 1997, JP Appl. 96/68,513, 25 Mar 1996, 62 pp. (In Japanese) Water-soluble inorganic salts having a polar group are the materials for improving the flowability of pulverized coal for metallurgical furnace or combustion furnace. These are affixed to dried pulverized coal having an average HGI >30 coal at an injection port of a metallurgical furnace or a combustion furnace.
384
97104419
November
1997
97104425 Solving mass balance problems in coal processing using the constrainedlweighted least-squares method Peng, F. F. and Chang, D. Coal Prep., 1996, 17, (3-4) 199-213. The paper describes the use of the constrained/weighted least-squares method for solving the mass balance problems of separators with multiproduct streams in coal preparation plants. An algorithm was developed to solve consistent data and to estimate relative mass flow rates of coal
So/id fuels (preparation)
modifiers for the coal particles. The agglomerates were smaller and more hydrophobic. The clean coal recovery increased substantially with a lowering of the ash content for these type of coals.
97104414 grinding
Mill power for high-pressure
grinding
rolls in coal
Austin, L. G. Miner. Metall. Prowss.. 1997. 14, (3). 18-26. For six coals and a crystal quartz, the grinding force, gap dimension mass flow rate, and net mill power were measured using an instrumented laboratory high-pressure grinding roller mill. A technique was developed to estimate the compressive stress-strain curves for compression of the materials in the mill plus the effects of elastic decompression. To reconcile the mill power and grinding pressure results, it was necessary to allow for energy recovery on decompression. Between the form of the stress-strain curves or the variation of specific mill power factor and the Hardgrove grindability index (HGI), no clea correlation was discovered, but coals with the lowest and highest HGls gave significantly different results to the other coals. Feeds < 140 mesh flowed more rapidly than coarser feeds and would not build up high grinding pressures. Therefore, shearing and fluid-like properties were more evident, rather than compression as a locked bed.
A model for softening 97104415 heated at different rates.
and resolidification
of coals
Matsuoka, K. et al. ISIJ lnt., 1997, 31, (6). 566-572. An examination of needle penetration and dilation characteristics for cylindrical coal pellets upon heating was carried out. The net penetration depth, obtained from the observed penetration and dilation curves, was analysed by an equation of motion to derive the apparent viscosity of coal. Mass loss due to volatiles release and yields of pyridine extract were also measured for the pellets. Changes in the apparent viscosity with heating were explained by a simple model with the following assumptions: (1) coal behaved instantaneously as a Newtonian fluid, (2) coal consists of two reactive components; one converting to semi-coke via an intermediate along with volatiles release and the other converting to volatiles directly, (3) the intermediate is represented by the pyridine extract and hehaves as a liquid, whereas the others behave as solids, and (4) the apparent viscosity change is described by Vand’s equation for a slurry combined with Andrade’s equation for liquid viscosity.
Numerical investigation 97104416 a beater wheel mill with classifier
of the grinding
process
in
Anagnostopoulos, _I. and Bergeles, G. J. Eng. Gas Turbines Power., 1997, 119, (3). 723-733. A two-dimensional simulation of the gas flow field and of the dynamic behaviour of lignite particles inside beater wheel mills with classifier was numerically investigated. A large number of representative particles are tracked using Lagrangian equations of motion. in combination with a stochastic model for particle turbulent dispersion. All the important mechanisms associated with the particle motion through the mill are modelled. A special model is constructed to simulate the fragmentation of impacting particles and to calculate the size distribution of the final mill product. The models are regulated on the basis of available data from grinding mills of the Greek lignite power stations. The numerical code can predict the locations of significant erosion and estimate the amount of particle mass that circulates through the mill via the classifying chamber. Remarkable differences were discovered in the extent of erosion at different locations of the mill. Information concerning the significant role of the leading blades arrangement inside the classifier on its classification performance and efficiency is provided.
97104417 Observations and studies of float and sink centrifugation of fine coal at Nottingham University Kizgut, S. et al. Changing Scopes Miner. Process., Proc. Int. Miner. Process. Symp., 6th. 1996, 435-439. Edited by Kemal, M., Balkema, Rotterdam, The Netherlands. The paper describes a comparative centrifugal and static bath float and sink test made on a classified coal sample of -38 + 20 rrrn and -20 Irm size groups. The objective of the study was to modify a density separation test method to control products of maceral separation study which had been conducted on a heavy medium cyclone rig. Densities of 1.30 and I.60 g/cm’ were chosen to examine the effect of a large amount of material having a density very close to separation density at low densities and the effect of viscosity at relatively high density that cited as main restriction for the use of inorganic salt solutions and even some organic liquids. A sodium polytungstate solution and a surfactant were used as the separation medium.
97104418
Pulverized
coal flowability
Fuel and Energy Abstracts
Pyrite recovery
mechanisms
in coal flotation
Kawatra, S. K. and Eisele. T. C. Inr. J. Miner. Promss.. 1997. SO. (3). 187-201. During flotation of high-sulfur coal in most operating coal-cleaning plants, a significant amount of pyrite is recovered in the froth. This is helieved to result from pyrite particles floating due to hydrophohicity. However, there is no use of pyrite depressants for industrial coal flotation, which suggests that the mechanism of pyrite flotation is not properly understood. In order to reduce pyrite recovery during flotation. it is first necessary to identify the primary recovery mechanism, so that the appropriate method for correcting the problem can be selected. In this paper, flotation of liberated pyrite due to its intrinsic hydrophohicity is shown not to be an important mechanism for recovery of pyrite from freshly ground coal. and that the bulk of the floated pyrite the froth either as a result of simple entrainment of by mechanical locking with floatable coal particles. The experiments were carried out using hoth a conventional flotation cell, and a horizontally baffled flotation column. 97104420
The reduction
in moisture
measurina
time of dried
lignite Rajagopalan, S. Enere Corri~er.c-.Mgnrt.. 1997, 38, (7), 697-hYY. Before being fed to the press for making briquettes. lignite taken from dryers is s&jected to miisture tests to evaluate the pe;formance of the dryers in reducing the moisture of the wet lignite from the mines. A quick and approximate estimation of the moisture content of the dried lignite from the dryers is required for a number of times. to adjust the dryer operating parameters. Knowledge of the moisture content lost from the sample after 10 minutes was found to be enough to have a reasonable estimate of the total moisture ccmtent of the sample. 97104421
advanced
Reduction cleaning
of toxic
trace
elements
in
coal
by
Smit, F. J. Proc. Amu. Irrt. Pirrshqh Coal Conf.. 1996, 13. (2). 87Y-884. In continuous bench-scale circuits, advanced cleaning by column flotation and selective agglomeration were used to determine the residual concentrations of 12 toxic trace-element impurities in five coals. For each of the trace elements, the reduction in concentration from the amount in the ROM parent coals and the amount in the washed test coals was also determined on a heating value basis.
97104422 anhydrous
Removal of organic sulfur HF and superacid HFIBFJ
in coal
by the use of
Shimizu, K. et al. Chemical LFU., 1997, (9). 943-944. Anhydrous hydrogen fluoride and HF was combined with a small amount of boron trifluoride desulfurized high-sulfur coal in the presence of hydrocarbons without Hz in mild reaction conditions. HF removed mainly sulfide and oxidized sulfur. HF/BFx decreased thiophene sulfur as well as sulfide and oxidized sulfur although the extent of desulfurization was almost the same as that with HF alone.
97104423 A simulation circuit design
of slime circulation
and the effect of
Nazimko, L. I. and Nazimko, V. V. Cocll Prep., 1996, 17, (3-4), 21.5-232. The results of the accumulation of slimes in the coal preparation plant circuit include inefficient operation of the coal cleaning equipment, loss of coal, increases in product coal ash, and increased maintenance and operating costs. To maximize the plant operation, control of the plant circuit slimes content and slimes removal are required. To this end, the authors developed a simulator model, based on accumulation and production of the slimes, feed fluctuations and real-time circuit operation. This programme makes it possible to simulate and analyse preparation plant flowsheets of water circulation to maximize plant operation. Slime accumulation can be reduced by about 50% and the time for attaining slimes equilibrium in the plant water circuits can experience about hh% reduction.
97104424 extraction
Solvent
swelling
of coal for improved
supercritical
Hu, H. et al. Ranliao Huaxue Xuehao., lYY7,25, (3). 223-226. (In Chinese) Supercritical extraction of Xinglong coal took place with toluene in an autoclave apparatus following its swelling in pyridine. THF and methanol. separately. The objective was to investigate the effect of solvent swelling on coal extraction. The results indicated that the swelling pre-treatment of coal with THF or pyridine can effectively enhance conversion and light-fraction yield of supercritical extraction process. In the investigated temperature range of 340 to 400°C. the pyridine swollen coal showed a much higher conversion and lower gas yield than untreated coal. High solvent-to-coal ratio and high extraction pressure were beneficial to supercritical extraction of pyridine swollen coal. In addition, FTIR and SEM of pyridine swollen coal and untreated coal were examined to investigate variations of the coal structure during solvent swelling.
improver
Ono, R. et al. PCT Int. Appl. WO 97 36,009 (Cl. C2195/00), 2 Ott 1997, JP Appl. 96/68,513, 25 Mar 1996, 62 pp. (In Japanese) Water-soluble inorganic salts having a polar group are the materials for improving the flowability of pulverized coal for metallurgical furnace or combustion furnace. These are affixed to dried pulverized coal having an average HGI >30 coal at an injection port of a metallurgical furnace or a combustion furnace.
384
97104419
November
1997
97104425 Solving mass balance problems in coal processing using the constrainedlweighted least-squares method Peng, F. F. and Chang, D. Coal Prep., 1996, 17, (3-4) 199-213. The paper describes the use of the constrained/weighted least-squares method for solving the mass balance problems of separators with multiproduct streams in coal preparation plants. An algorithm was developed to solve consistent data and to estimate relative mass flow rates of coal