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00014 Chemical and rheological characterization of air-blown coal-tar pitches
01 and heavier parts. In addition, microscopic petrographical characteristics have been investigated by MPV-III microscope. Combined with the screening and float-and-sink test, the distribution of macerals in coals with different sizes and densities have also been studied. It has been concluded that vitrinite is generally rich in coarser and lighter fractions of the coals, yet fusinite in finer and heavier fractions. Moreover, the mechanism which gives rise to the diversified distribution of petrographical constituents in coals has been studied by means of measurement of density and HGI of various lithotypes, in combination with the test of grinding. It is applicable, by means of selective grinding and gravitational preparation methods, to carry out separation of petrographical constituents.
Characterization of coal tar organics via gravity 99/00011 flow column chromatography Yu, L. E. et al. Fuel, 1998, 71, (S), 431-445. By utilizing gravity flow column chromatography, changes in the polarity distribution of two types of coal tar during secondary pyrolysis have been examined. Trends in the polarity distributions are used to evaluate the predominance of various transformation mechanisms throughout secondary pyrolysis. In addition to observing neutralization and mass transformation during the early stages of secondary pyrolysis, a consistent increase in acetylene, methane and much longer aliphatic compounds with extent of sooting was observed midway through secondary pyrolysis, suggesting that aromatic ring structures were opening and decomposing. By the late stages of secondary pyrolysis, both tars from sub-bituminous and high volatile bituminous coals exhibit similar polarity compositions, indicating that thermal conditions rather than original coal structure determine the ultimate polarity distributions for both types of coal tar. Based on the polarity distributions observed during various stages of secondary pyrolysis, preferred pathways for soot formation can be identified; it appears that the toluene fraction contains the predominant precursors for soot.
Characterization
of fuels for second-generation
::gol * Zevenhoven, C. A. P. and Hupa, M. Proc. Int. Conf. Fluid. Bed Combust, 1991, 14, (1) 213-221. A solid fuel is partly converted in a devolatilization step to produce a char and a pressurised fuel gas, followed by pressurised fluidized bed combustion of the char in second-generation PFBC technology. The fuel gas is led to the combustion chamber of a gas turbine after it is mixed with the PFBC off-gas, thus increasing the temperature at the inlet of the expansion turbine. Detailed information on the behaviour of solid fuels under pressurized conditions is, however, largely limited to steam and/or carbon dioxide gasification reactivates, obtained at a different combination of process parameters. In the present work, the effect of temperature, pressure and heating rates on the yields of volatiles and char residue reactivity has been measured for a set of fuels ranging from bituminous coal to wood. Laboratory conditions were typical for the carbonizer and combustion reactors in a second-generation PFBC system. A pressurized thermogravimetric reactor operated at heating rates of around 250 K/s and a pressurized grid heater operated at heating rates up to 3000 K/s were used to analyse fuel devolatilization and char reactivity against carbon dioxide or steam at temperatures between 800 and llOO”C, and 1, 10, or 25 bar total pressure. For comparison, a few experiments were repeated without a separate devolatilization step. The behaviour of the various fuels were compared and related to proximate and ultimate fuel analysis. Several empirical, ‘engineering’ equations are given.
Characterization of 99/00013 pyrolysis of coal asphaltenes
tar,
char
and
gas
from
Liu, Y. et al. Fuel, 1998, 11, (9/10), 1099-1105. Generated by a multiple precipitation procedure asphaltines were found to contain n-alkanes from Cl4 to C31, which show an odd over even preference. This result further indicates that alkyl chains or alkylene bridges appear mostly as substituents in the coal macromolecular network. Comparison of the elemental analysis and surface area of pyrolysis chars shows that the surface areas correlate well with the heteroatom content of chars and that of the original coals as well. However, the gasification reactivity in carbon dioxide of ash-free chars cannot be interpreted in terms of their surface area. During the pyrolysis of asphaltenes, chars were formed via the mesophase route. The polarized light optical microscopy of chars confirmed that fluidity of the carbonization system is a major factor controlling the optical texture of resultant chars. Pyrolysis of asphaltenes showed that most of the gaseous components are formed by the cleavage of weak bonds like aryl-alkyl-ethers and strong bonds, mainly methylene and biarylether bridges between the aromatic moieties and methyl groups on the aromatic rings in asphaltene structure.
Chemical and rheological characterization of air99/00014 blown coal-tar pitches MenCndez, R. et al. Carbon, 1998, 36, (J/8), 913-919. Isotropic pitches were produced with softening points ranging from 140 to 210°C when a commercial impregnating coal-tar pitch was air-blown at 215°C for 10, 18, 25 and 30 hours. The parent and treated pitches were characterized by elemental analysis, Fourier transform infrared, solubility in toluene and N-methylpyrrolidone, iodine adsorption and reflected light optical microscopy. Also investigated was the viscoelasticity of the pitches using transient shear and controlled strain oscillatory rheometry. The chemical characterization of the pitches suggested that, as air-blowing
Solid fuels (sources, winning, properties)
proceeded, larger molecules formed through dehydrogenative polymerization and cross-linking of the pitch molecules. The results obtained from transient shear and oscillatory rheometry showed that the parent impregnating pitch exhibited a viscous behaviour. In contrast, the air-blown pitches, which contained large aromatic molecules, showed viscoelastic properties.
Coal and rank petrography of Carboniferous seams in the Amasra coalfield, Turkey
99/ooo15
Upper
Karayigit, A. 1. et al. Int. 1. Coal Geol., 1998, 36, (3-4) 277-294. Within the Istanbul zone, the Amasra coalfield is a part of the Upper Carboniferous Zonguldak coal basin of Turkey. The mainly Westphalian aged coals were sampled from an underground mine and from cores from nine exploration wells and petrographical analysis and mean maximum vitrinite (telocollinite) reflectance (% R,,, in oil) were determined. The coals were characterized by low ash and low total sulfur contents, abundant vitrinite-group macerals and relatively abundant vitrite, dante and duroclarite microlithotypes. Vitrinite reflectance was in the range 0.581.04% R,,, indicating ranks from high volatile C bituminous to high volatile A bituminous coal. The % R,,, generally increases with increasing depth in the exploration wells, with gradients ranging from 0.21 to 0.40% R&km and an average of 0.30% R,,,/km. The highest value occurs in the south of the coalfield in a region of Hercynian folding and thrusting. The relationship between vitrinite reflectance and thrusts in the wells suggests that coal rank was developed mainly pre-thrusting but that some wells, arguably, show evidence for post-thrust coalification.
99lOOO16 Combustion rates of chars from high-volatile fuels for FCC application Sabato, S. et al. Proc. Int. Conf Fluid. Bed Comhust. 1997.14, (I), 135-143. Often associated with comminution is the fluidized bed combustion of high volatile fuels. The small size of carbon fines generated by comminution is such that their further combustion is largely controlled by the intrinsic kinetics of carbon oxidation, alone or in combination with intraparticle diffusion. The competition between fine combustion and elutriation strongly affects the efficiency of fixed carbon conversion and calls for thorough characterization of the combustion kinetics and of residence times of fines in a fluidized bed of coarse solids. In this paper intrinsic combustion kinetic and porosimetry data for chars from three high-volatile fuels suitable for FBC application are presented. Chars from a refuse derived fuel, a tyre derived fuel and a biomass are obtained from devolatilization, in fluidized bed, of fuel samples. Thermogravimetric analysis, mercury porosimetry and helium pycoometry are used to characterize the reactivity and the pore structure of the chars. Combustion rates are characterized over a wide range of temperatures (320-850°C) and oxygen partial pressures, covering the entire range of interest in fluidized bed combustion.
Composition of coal derived relationship with coal network structure
tars
Cooperative bituminous coal
swelling
99lOOO17
and
its
Chen, H. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7). J-11. Two Chinese coals, a bituminous coal (Yanzhou) and a lignite (Hongmiao), were used to study the composition of tars from pyrolysis under nitrogen and hydropyrolysis using GC and GC-MS. Discussed was the relationship between the tar composition and the coal structure. 99100018
effects
in solvent
of a
Yun, Y. and Suuberg, E. M. Energy Fuels, 1998, 12, (4). 798-800. Explored have been the relative abilities of mixtures of non-specifically and specifically interacting solvents to swell a Utah Blind Canyon bituminous coal. The results are consistent with published reports of the efficacy of such mixed solvent systems but show sensitivity to the choice of specifically interacting solvent. In such systems, the dynamics of the swelling also serve to confirm the general nature of the process. 99/00019
Coprocessing
Yanzhou
coal
with
petroleum
residue Ling, K. and Zou, G. Meitan Zhuanhua, 1997. 20, (2), 62-66. (In Chinese) One petroleum residue and three bituminous coals were coprocessed at 430” and 1.0 MPa (H) in a resonance stirring reactor. The results showed that the coal conversions increased with the increase of H/C atomic ratios and vitrinite in the coals. The bituminous coals and their remainders were analysed by FTIR.
Cost estimates and sensitivity analyses for the ammonia fiber explosion process
99l00020
Wang, L. et al. Appl. Biochemical Biotechnol., 1998, (70-12). (51-66). For each unit of the conceptual ammonia fibre explosion (AFEX) process, process designs were conducted, and fixed capital investment and operating costs were established AFEX costs about $20-40/t of dry biomass treated. Return on investment (ROI) calculations were also done for AFEX-treated materials (as digestibility-enhanced animal feeds), in conjunction with sensitivity analyses on the overall processing costs. Estimated ROB range from over 100%/y to negative, depending on the system variables. The most important variables are the cost of corn and corn fibre, whether or not drying is required, and ammonia loading. The study is of interest with respect to biomass pretreatment in production of fuels and chemicals by fermentation.
Fuel and Energy Abstracts
January 1999 3
Characterization of coal tar organics via gravity 99/00011 flow column chromatography Yu, L. E. et al. Fuel, 1998, 71, (S), 431-445. By utilizing gravity flow column chromatography, changes in the polarity distribution of two types of coal tar during secondary pyrolysis have been examined. Trends in the polarity distributions are used to evaluate the predominance of various transformation mechanisms throughout secondary pyrolysis. In addition to observing neutralization and mass transformation during the early stages of secondary pyrolysis, a consistent increase in acetylene, methane and much longer aliphatic compounds with extent of sooting was observed midway through secondary pyrolysis, suggesting that aromatic ring structures were opening and decomposing. By the late stages of secondary pyrolysis, both tars from sub-bituminous and high volatile bituminous coals exhibit similar polarity compositions, indicating that thermal conditions rather than original coal structure determine the ultimate polarity distributions for both types of coal tar. Based on the polarity distributions observed during various stages of secondary pyrolysis, preferred pathways for soot formation can be identified; it appears that the toluene fraction contains the predominant precursors for soot.
Characterization
of fuels for second-generation
::gol * Zevenhoven, C. A. P. and Hupa, M. Proc. Int. Conf. Fluid. Bed Combust, 1991, 14, (1) 213-221. A solid fuel is partly converted in a devolatilization step to produce a char and a pressurised fuel gas, followed by pressurised fluidized bed combustion of the char in second-generation PFBC technology. The fuel gas is led to the combustion chamber of a gas turbine after it is mixed with the PFBC off-gas, thus increasing the temperature at the inlet of the expansion turbine. Detailed information on the behaviour of solid fuels under pressurized conditions is, however, largely limited to steam and/or carbon dioxide gasification reactivates, obtained at a different combination of process parameters. In the present work, the effect of temperature, pressure and heating rates on the yields of volatiles and char residue reactivity has been measured for a set of fuels ranging from bituminous coal to wood. Laboratory conditions were typical for the carbonizer and combustion reactors in a second-generation PFBC system. A pressurized thermogravimetric reactor operated at heating rates of around 250 K/s and a pressurized grid heater operated at heating rates up to 3000 K/s were used to analyse fuel devolatilization and char reactivity against carbon dioxide or steam at temperatures between 800 and llOO”C, and 1, 10, or 25 bar total pressure. For comparison, a few experiments were repeated without a separate devolatilization step. The behaviour of the various fuels were compared and related to proximate and ultimate fuel analysis. Several empirical, ‘engineering’ equations are given.
Characterization of 99/00013 pyrolysis of coal asphaltenes
tar,
char
and
gas
from
Liu, Y. et al. Fuel, 1998, 11, (9/10), 1099-1105. Generated by a multiple precipitation procedure asphaltines were found to contain n-alkanes from Cl4 to C31, which show an odd over even preference. This result further indicates that alkyl chains or alkylene bridges appear mostly as substituents in the coal macromolecular network. Comparison of the elemental analysis and surface area of pyrolysis chars shows that the surface areas correlate well with the heteroatom content of chars and that of the original coals as well. However, the gasification reactivity in carbon dioxide of ash-free chars cannot be interpreted in terms of their surface area. During the pyrolysis of asphaltenes, chars were formed via the mesophase route. The polarized light optical microscopy of chars confirmed that fluidity of the carbonization system is a major factor controlling the optical texture of resultant chars. Pyrolysis of asphaltenes showed that most of the gaseous components are formed by the cleavage of weak bonds like aryl-alkyl-ethers and strong bonds, mainly methylene and biarylether bridges between the aromatic moieties and methyl groups on the aromatic rings in asphaltene structure.
Chemical and rheological characterization of air99/00014 blown coal-tar pitches MenCndez, R. et al. Carbon, 1998, 36, (J/8), 913-919. Isotropic pitches were produced with softening points ranging from 140 to 210°C when a commercial impregnating coal-tar pitch was air-blown at 215°C for 10, 18, 25 and 30 hours. The parent and treated pitches were characterized by elemental analysis, Fourier transform infrared, solubility in toluene and N-methylpyrrolidone, iodine adsorption and reflected light optical microscopy. Also investigated was the viscoelasticity of the pitches using transient shear and controlled strain oscillatory rheometry. The chemical characterization of the pitches suggested that, as air-blowing
Solid fuels (sources, winning, properties)
proceeded, larger molecules formed through dehydrogenative polymerization and cross-linking of the pitch molecules. The results obtained from transient shear and oscillatory rheometry showed that the parent impregnating pitch exhibited a viscous behaviour. In contrast, the air-blown pitches, which contained large aromatic molecules, showed viscoelastic properties.
Coal and rank petrography of Carboniferous seams in the Amasra coalfield, Turkey
99/ooo15
Upper
Karayigit, A. 1. et al. Int. 1. Coal Geol., 1998, 36, (3-4) 277-294. Within the Istanbul zone, the Amasra coalfield is a part of the Upper Carboniferous Zonguldak coal basin of Turkey. The mainly Westphalian aged coals were sampled from an underground mine and from cores from nine exploration wells and petrographical analysis and mean maximum vitrinite (telocollinite) reflectance (% R,,, in oil) were determined. The coals were characterized by low ash and low total sulfur contents, abundant vitrinite-group macerals and relatively abundant vitrite, dante and duroclarite microlithotypes. Vitrinite reflectance was in the range 0.581.04% R,,, indicating ranks from high volatile C bituminous to high volatile A bituminous coal. The % R,,, generally increases with increasing depth in the exploration wells, with gradients ranging from 0.21 to 0.40% R&km and an average of 0.30% R,,,/km. The highest value occurs in the south of the coalfield in a region of Hercynian folding and thrusting. The relationship between vitrinite reflectance and thrusts in the wells suggests that coal rank was developed mainly pre-thrusting but that some wells, arguably, show evidence for post-thrust coalification.
99lOOO16 Combustion rates of chars from high-volatile fuels for FCC application Sabato, S. et al. Proc. Int. Conf Fluid. Bed Comhust. 1997.14, (I), 135-143. Often associated with comminution is the fluidized bed combustion of high volatile fuels. The small size of carbon fines generated by comminution is such that their further combustion is largely controlled by the intrinsic kinetics of carbon oxidation, alone or in combination with intraparticle diffusion. The competition between fine combustion and elutriation strongly affects the efficiency of fixed carbon conversion and calls for thorough characterization of the combustion kinetics and of residence times of fines in a fluidized bed of coarse solids. In this paper intrinsic combustion kinetic and porosimetry data for chars from three high-volatile fuels suitable for FBC application are presented. Chars from a refuse derived fuel, a tyre derived fuel and a biomass are obtained from devolatilization, in fluidized bed, of fuel samples. Thermogravimetric analysis, mercury porosimetry and helium pycoometry are used to characterize the reactivity and the pore structure of the chars. Combustion rates are characterized over a wide range of temperatures (320-850°C) and oxygen partial pressures, covering the entire range of interest in fluidized bed combustion.
Composition of coal derived relationship with coal network structure
tars
Cooperative bituminous coal
swelling
99lOOO17
and
its
Chen, H. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7). J-11. Two Chinese coals, a bituminous coal (Yanzhou) and a lignite (Hongmiao), were used to study the composition of tars from pyrolysis under nitrogen and hydropyrolysis using GC and GC-MS. Discussed was the relationship between the tar composition and the coal structure. 99100018
effects
in solvent
of a
Yun, Y. and Suuberg, E. M. Energy Fuels, 1998, 12, (4). 798-800. Explored have been the relative abilities of mixtures of non-specifically and specifically interacting solvents to swell a Utah Blind Canyon bituminous coal. The results are consistent with published reports of the efficacy of such mixed solvent systems but show sensitivity to the choice of specifically interacting solvent. In such systems, the dynamics of the swelling also serve to confirm the general nature of the process. 99/00019
Coprocessing
Yanzhou
coal
with
petroleum
residue Ling, K. and Zou, G. Meitan Zhuanhua, 1997. 20, (2), 62-66. (In Chinese) One petroleum residue and three bituminous coals were coprocessed at 430” and 1.0 MPa (H) in a resonance stirring reactor. The results showed that the coal conversions increased with the increase of H/C atomic ratios and vitrinite in the coals. The bituminous coals and their remainders were analysed by FTIR.
Cost estimates and sensitivity analyses for the ammonia fiber explosion process
99l00020
Wang, L. et al. Appl. Biochemical Biotechnol., 1998, (70-12). (51-66). For each unit of the conceptual ammonia fibre explosion (AFEX) process, process designs were conducted, and fixed capital investment and operating costs were established AFEX costs about $20-40/t of dry biomass treated. Return on investment (ROI) calculations were also done for AFEX-treated materials (as digestibility-enhanced animal feeds), in conjunction with sensitivity analyses on the overall processing costs. Estimated ROB range from over 100%/y to negative, depending on the system variables. The most important variables are the cost of corn and corn fibre, whether or not drying is required, and ammonia loading. The study is of interest with respect to biomass pretreatment in production of fuels and chemicals by fermentation.
Fuel and Energy Abstracts
January 1999 3