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00699 Pyrolysis of coal maceral concentrates under pf-combustion conditions (II): changes in heteroatom partitioning as a function of rank
09
injection rates of more than 190 kg/tHM and productivities of 2.8 t/m’.24h have been realized in combination with a low total coke rate (less than 270 kg/tHM) and an excellent hot metal quality.
Process mechanisms of blast injection: what we know, and what we guess
99lOO695
furnace
fuel
Osinski, E. J. et al. Ironmaking Conf. Proc.. 1998, 57. 531-543. This paper presents a review on limitations of existing mathematical models of coal combustion, behaviour of coal particle in the stream of gases, conditions of mixing and combustion in the blowpipe, tuyere, and raceway. Also the factors controlling the combustion and the impact of coal injection on the overall process is looked at. A practical method of process stabilization, based on models already owned by most pig iron producers, is also proposed. 99100696
Pulverized coal Steel’s Great Lakes Division
injection
start up at National
Starosa, D. et al. Ironmaking Conf. Proc., 1998, 57, 379-394. On December 21, 1996 National Steel’s Great Lakes Division began pulverized coal injection at D4 Blast Furnace, and subsequently at B2 and Al in February, 1997. This paper briefly describes the facilities and key features. Also included is the preparation for start up, coal selection, training, start-up strategy and ramp up plan. Finally, experiences with start up, equipment capability and first year operating results are discussed.
Pyrolysis of coal in a fiuidized bed pyrolyzer 99100697 Li, H.-B. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7), 48-56. The first step of gasification and combustion in coal is pyrolysis. In a fluidized bed reactor, the secondary reaction of primary pyrolysis products in the freeboard can affect the final product composition. Therefore, by means of controlling the freeboard temperature and the residence time of primary pyrolysis products in the freeboard, favourable products can be produced. A Chinese bituminous coal is pyrolysed in a fluidized bed pyrolyser. The fluidization gas is N z. Coal is continuously fed into the pyrolyser (the feeding rate is about 1.8 g/min). Temperatures of the upper part (freeboard) and the lower part (dense phase) of the reactor within the range of 400-1000°C can be controlled, respectively. Along the freeboard there are four sampling points of products related to different residence times in the freeboard. In this paper, the effects of operation temperature of dense phase and freeboard, and the residence time of primary product gas in the freeboard on the product composition are investigated. The gaseous products are analysed by GC. Also given is a simple secondary pyrolysis model in the freeboard. Pyrolysis of coal maceral concentrates under pfcombustion conditions (I): changes in volatile release and char combustibility as a function of rank
99100696
Cai, H. -Y. et al. Fuel, 1998, 77, (12), 1273-1282. Examined was the pyrolytic behaviour of sets of maceral concentrates under conditions similar to those of pf-combustion. Using standard methods relative combustion reactivities of chars prepared during the pyrolysis experiments were compared. As expected, for samples of similar elemental C-content, total volatile release decreased as: liptinite > vitrinite > inertinite. The data indicates the absence of synergistic effects between vitrinite and inertinite during pyrolysis. In marked contrast to the order established for volatile release, combustion reactivities of maceral chars (of similar carbon content) may be ranked in the order: inertinite > vitrinite > liptinite. A direct comparison with maceral concentrates from the same coal was undertaken. Vitrinitel inertinite graded samples of a South African coal were pyrolysed at 150°C: these chars exhibited increasing reactivity with increasing inertinite concentration, but observed differences in reactivity between samples from the same coal were not large. Furthermore, for a higher rank coal, char reactivities were found to be essentially independent of original inertinite concentration. It is clearly possible for chars from low volatile coals to be relatively reactive. However, there appears to be no reason to suggest that ‘reactive inertinites’ might release volatile matter in quantities comparable to those of vitrinites from the same coal.
Pyrolysis of coal macerai concentrates under pf99/00699 combustion conditions (Ii): changes in heteroatom partitioning as a function of rank Cai, H. -Y. et al. Fuel, 1998, 77, (l2), 1283-1289. Investigated were differences between maceral types with respect to heteroatom partitioning during pyrolysis under conditions representative of pf-combustion. Pyrolysis experiments were carried out in a wire-mesh reactor; maceral concentrates and whole coals have been heated at 5000°C SK’ to 15OO”C, in atmospheric pressure helium. The proportion of Nretention in chars was found to increase, irrespective of maceral composition. However, char-N retention by inertinites was slightly less than that for vitrinites; retention by Tiptinites was clearly less than that for vitrinites. The general trend for sulfur retention was similar: for vitrinite and inertinite concentrates, sulfur retention increased from about 30 to 60% over the 72-95% elemental-C content interval. Once again, retention in liptinites was considerably lower for the three samples used in the study. Ash contents of the present set of samples suggest that it would not be realistic to discuss the present set of sulfur retention data in terms of organic sulfur alone. The work outlined above lead to several tentative conclusions, pinpointing areas where new structural work is required.
Combustion
(burners, combustion
systems)
Pyrolysis of coal tar pitch mixed in the presence of a graphite intercalation compound: a kinetic study
99/00700
Alain, E. et al. Fuel. 1998, 77, (6). 533-541. In order to determine the influence of the addition of first stage FeC13graphite intercalation compound (GIC) to coal tar pitch (CTP) on the formation and the development of the mesophase, a kinetic study has been carried out. The mesophase formation was followed by the determination of the THF insoluble fraction (THFI) of the solid residues, which were further characterized by polarized light microscopy. The presence of the Lewis acid has a great influence during the mesophase spherule formation and development. In the case of the CTP-GIG 8% mixture and the CTP the activation energy of the formation and the development of the mesophase (Es) is equal to I59 and 204 kJ/mol, respectively. This corresponds to a decrease of 22% of E, when the CTP is mixed with the GIC. The difficulties and mainly the limitations of the method used to calculate this activation energy by THFI measurements are highlighted. However, it is assumed that the mesophase formation and growth rates are accelerated in the presence of compounds such as GIG for two reasons: the absence of QI particles on the surface of the mesophase spherules and the catalytic activity of the Lewis acid.
Pyrolysis of coal tar pitch with graphite-MoCi5 intercalation compound
99/00701
Gerard, Let al. Fuel, 1998, 77, (6). 607-61 I. Pyrolysed was coal tar pitch (CTP) in the presence of graphite-MoCIj intercalation compound. (MoCIs-GIG). Only a third-stage GIG could be obtained using the classical two-temperature method. GIG concentrations in the starting mixtures were 2, 5 and 10 wt%. By characterization the samples were elemental analysis, X-ray diffraction and SEM. The distribution of GIG particle in the CTP matrix is homogeneous and their presence leads to a significant increase in green coke yield on pyrolysis, in agreement with many published results. On the green coke yield the influence of heating rate was also studied: the lower the heating rate, the higher the yield. After thermal treatment at 750°C molybdenum is always present in the green coke at a content close to the initial one, whereas most of the chlorine has been out-gassed. CTP-MoC15-GIG mixtures have a behaviour similar to that of CTP-FeCI?-GIG mixtures on pyrolysis. The final aim of this work is to synthesize catalysts supported on carbonaceous materials. 99ioo702 Pyrolysis of coals. I. Effect of atmosphere and temperature on pyrolysis Zhu, X. er al. Htradong Ligong Daxue Xtreboo, 1998, 24, (I), 37-41. (In Chinese) At 60 to -1200” under Hz or N1 at atmospheric pressure in a batch fixedbed reactor, pyrolysis experiments of Dong Sheng (Chinese) hituminous coal were carried out. Coal pyrolysis in Hz atmosphere, compared with in N2 atmosphere, gives an enhanced conversion rate, gas yields, and tar quality. The conversion rates and product yields of products were affected significantly by the pyrolysis temperature The conversion rate of coal and the yields of CH.+, CO, and CO? were increased with increasing temperature, but were hardly changed for Cz+ hydrocarbons and H20. 99l00703 Pyrolysis of pitch Yue, C. and Watkinson, A. P. Fuel, 1998, 77, (7), 695-71 I. Using thermogravimetric analysis kinetics of thermal pyrolysis of pitches from two heavy oil upgrading processes have been studied. Experiments were carried out at atmospheric pressure with heating rates of 25-150” min-’ to a final temperature of 800”. At temperatures below 150”, there is a little devolatilization of either pitch. At higher temperatures, the pyrolysis takes place in two stages. Single-stage, first-order reaction methods, including models which incorporate a Gaussian distribution of activation energies, were inadequate to interpret the thermogravimetric analysis results. A two-stage model which reflects changes in the chemical constitution or structure as conversion proceeds was necessary to describe the dependence of devolatilization rates on remaining volatile content. The transition between these two stages is a sharp one, occurring at about 450” for both pitches. The magnitudes of the activation energies suggest that both stages are kinetically controlled. 99/00704 Pyrolysis of sewage sludge as treatment process for the thermal utilization in firing places Storm, C. et al. DGMK Tagungsber., 1998, 9802, 303-310. (In German) In a pilot plant the utilization of pyrolysis gas from sewage sludge as secondary fuel for NO, reduction in a coal dust firing was studied. Entrained gasification was performed at 500-1100” and the obtained gas was used for NO, reduction at various air ratios. The NO, release could he decreased to <200 mgim’. The influence of the gasification temperature on gas yield and composition and on the properties of the solid residue was also determined. The strong bonding of heavy metals in the solid matrix was revealed by elution experiments of the solid residues.
99lOO705 Rate of spread of free-burning fuels In a wind tunnel
fires in woody
Catchpole, W. R. et al. Combust. Sci. Technol., 1998, 131 (l-6), l-37. Described are the results of 357 experimental fires conducted in an environmentally controlled large wind tunnel. The fires were burned over a range of particle sizes, fuel bed depths, moisture contents, packing ratios and wind speeds. Spread rate decreased with moisture content in a way
Fuel and Energy Abstracts
January 1999 69
injection rates of more than 190 kg/tHM and productivities of 2.8 t/m’.24h have been realized in combination with a low total coke rate (less than 270 kg/tHM) and an excellent hot metal quality.
Process mechanisms of blast injection: what we know, and what we guess
99lOO695
furnace
fuel
Osinski, E. J. et al. Ironmaking Conf. Proc.. 1998, 57. 531-543. This paper presents a review on limitations of existing mathematical models of coal combustion, behaviour of coal particle in the stream of gases, conditions of mixing and combustion in the blowpipe, tuyere, and raceway. Also the factors controlling the combustion and the impact of coal injection on the overall process is looked at. A practical method of process stabilization, based on models already owned by most pig iron producers, is also proposed. 99100696
Pulverized coal Steel’s Great Lakes Division
injection
start up at National
Starosa, D. et al. Ironmaking Conf. Proc., 1998, 57, 379-394. On December 21, 1996 National Steel’s Great Lakes Division began pulverized coal injection at D4 Blast Furnace, and subsequently at B2 and Al in February, 1997. This paper briefly describes the facilities and key features. Also included is the preparation for start up, coal selection, training, start-up strategy and ramp up plan. Finally, experiences with start up, equipment capability and first year operating results are discussed.
Pyrolysis of coal in a fiuidized bed pyrolyzer 99100697 Li, H.-B. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7), 48-56. The first step of gasification and combustion in coal is pyrolysis. In a fluidized bed reactor, the secondary reaction of primary pyrolysis products in the freeboard can affect the final product composition. Therefore, by means of controlling the freeboard temperature and the residence time of primary pyrolysis products in the freeboard, favourable products can be produced. A Chinese bituminous coal is pyrolysed in a fluidized bed pyrolyser. The fluidization gas is N z. Coal is continuously fed into the pyrolyser (the feeding rate is about 1.8 g/min). Temperatures of the upper part (freeboard) and the lower part (dense phase) of the reactor within the range of 400-1000°C can be controlled, respectively. Along the freeboard there are four sampling points of products related to different residence times in the freeboard. In this paper, the effects of operation temperature of dense phase and freeboard, and the residence time of primary product gas in the freeboard on the product composition are investigated. The gaseous products are analysed by GC. Also given is a simple secondary pyrolysis model in the freeboard. Pyrolysis of coal maceral concentrates under pfcombustion conditions (I): changes in volatile release and char combustibility as a function of rank
99100696
Cai, H. -Y. et al. Fuel, 1998, 77, (12), 1273-1282. Examined was the pyrolytic behaviour of sets of maceral concentrates under conditions similar to those of pf-combustion. Using standard methods relative combustion reactivities of chars prepared during the pyrolysis experiments were compared. As expected, for samples of similar elemental C-content, total volatile release decreased as: liptinite > vitrinite > inertinite. The data indicates the absence of synergistic effects between vitrinite and inertinite during pyrolysis. In marked contrast to the order established for volatile release, combustion reactivities of maceral chars (of similar carbon content) may be ranked in the order: inertinite > vitrinite > liptinite. A direct comparison with maceral concentrates from the same coal was undertaken. Vitrinitel inertinite graded samples of a South African coal were pyrolysed at 150°C: these chars exhibited increasing reactivity with increasing inertinite concentration, but observed differences in reactivity between samples from the same coal were not large. Furthermore, for a higher rank coal, char reactivities were found to be essentially independent of original inertinite concentration. It is clearly possible for chars from low volatile coals to be relatively reactive. However, there appears to be no reason to suggest that ‘reactive inertinites’ might release volatile matter in quantities comparable to those of vitrinites from the same coal.
Pyrolysis of coal macerai concentrates under pf99/00699 combustion conditions (Ii): changes in heteroatom partitioning as a function of rank Cai, H. -Y. et al. Fuel, 1998, 77, (l2), 1283-1289. Investigated were differences between maceral types with respect to heteroatom partitioning during pyrolysis under conditions representative of pf-combustion. Pyrolysis experiments were carried out in a wire-mesh reactor; maceral concentrates and whole coals have been heated at 5000°C SK’ to 15OO”C, in atmospheric pressure helium. The proportion of Nretention in chars was found to increase, irrespective of maceral composition. However, char-N retention by inertinites was slightly less than that for vitrinites; retention by Tiptinites was clearly less than that for vitrinites. The general trend for sulfur retention was similar: for vitrinite and inertinite concentrates, sulfur retention increased from about 30 to 60% over the 72-95% elemental-C content interval. Once again, retention in liptinites was considerably lower for the three samples used in the study. Ash contents of the present set of samples suggest that it would not be realistic to discuss the present set of sulfur retention data in terms of organic sulfur alone. The work outlined above lead to several tentative conclusions, pinpointing areas where new structural work is required.
Combustion
(burners, combustion
systems)
Pyrolysis of coal tar pitch mixed in the presence of a graphite intercalation compound: a kinetic study
99/00700
Alain, E. et al. Fuel. 1998, 77, (6). 533-541. In order to determine the influence of the addition of first stage FeC13graphite intercalation compound (GIC) to coal tar pitch (CTP) on the formation and the development of the mesophase, a kinetic study has been carried out. The mesophase formation was followed by the determination of the THF insoluble fraction (THFI) of the solid residues, which were further characterized by polarized light microscopy. The presence of the Lewis acid has a great influence during the mesophase spherule formation and development. In the case of the CTP-GIG 8% mixture and the CTP the activation energy of the formation and the development of the mesophase (Es) is equal to I59 and 204 kJ/mol, respectively. This corresponds to a decrease of 22% of E, when the CTP is mixed with the GIC. The difficulties and mainly the limitations of the method used to calculate this activation energy by THFI measurements are highlighted. However, it is assumed that the mesophase formation and growth rates are accelerated in the presence of compounds such as GIG for two reasons: the absence of QI particles on the surface of the mesophase spherules and the catalytic activity of the Lewis acid.
Pyrolysis of coal tar pitch with graphite-MoCi5 intercalation compound
99/00701
Gerard, Let al. Fuel, 1998, 77, (6). 607-61 I. Pyrolysed was coal tar pitch (CTP) in the presence of graphite-MoCIj intercalation compound. (MoCIs-GIG). Only a third-stage GIG could be obtained using the classical two-temperature method. GIG concentrations in the starting mixtures were 2, 5 and 10 wt%. By characterization the samples were elemental analysis, X-ray diffraction and SEM. The distribution of GIG particle in the CTP matrix is homogeneous and their presence leads to a significant increase in green coke yield on pyrolysis, in agreement with many published results. On the green coke yield the influence of heating rate was also studied: the lower the heating rate, the higher the yield. After thermal treatment at 750°C molybdenum is always present in the green coke at a content close to the initial one, whereas most of the chlorine has been out-gassed. CTP-MoC15-GIG mixtures have a behaviour similar to that of CTP-FeCI?-GIG mixtures on pyrolysis. The final aim of this work is to synthesize catalysts supported on carbonaceous materials. 99ioo702 Pyrolysis of coals. I. Effect of atmosphere and temperature on pyrolysis Zhu, X. er al. Htradong Ligong Daxue Xtreboo, 1998, 24, (I), 37-41. (In Chinese) At 60 to -1200” under Hz or N1 at atmospheric pressure in a batch fixedbed reactor, pyrolysis experiments of Dong Sheng (Chinese) hituminous coal were carried out. Coal pyrolysis in Hz atmosphere, compared with in N2 atmosphere, gives an enhanced conversion rate, gas yields, and tar quality. The conversion rates and product yields of products were affected significantly by the pyrolysis temperature The conversion rate of coal and the yields of CH.+, CO, and CO? were increased with increasing temperature, but were hardly changed for Cz+ hydrocarbons and H20. 99l00703 Pyrolysis of pitch Yue, C. and Watkinson, A. P. Fuel, 1998, 77, (7), 695-71 I. Using thermogravimetric analysis kinetics of thermal pyrolysis of pitches from two heavy oil upgrading processes have been studied. Experiments were carried out at atmospheric pressure with heating rates of 25-150” min-’ to a final temperature of 800”. At temperatures below 150”, there is a little devolatilization of either pitch. At higher temperatures, the pyrolysis takes place in two stages. Single-stage, first-order reaction methods, including models which incorporate a Gaussian distribution of activation energies, were inadequate to interpret the thermogravimetric analysis results. A two-stage model which reflects changes in the chemical constitution or structure as conversion proceeds was necessary to describe the dependence of devolatilization rates on remaining volatile content. The transition between these two stages is a sharp one, occurring at about 450” for both pitches. The magnitudes of the activation energies suggest that both stages are kinetically controlled. 99/00704 Pyrolysis of sewage sludge as treatment process for the thermal utilization in firing places Storm, C. et al. DGMK Tagungsber., 1998, 9802, 303-310. (In German) In a pilot plant the utilization of pyrolysis gas from sewage sludge as secondary fuel for NO, reduction in a coal dust firing was studied. Entrained gasification was performed at 500-1100” and the obtained gas was used for NO, reduction at various air ratios. The NO, release could he decreased to <200 mgim’. The influence of the gasification temperature on gas yield and composition and on the properties of the solid residue was also determined. The strong bonding of heavy metals in the solid matrix was revealed by elution experiments of the solid residues.
99lOO705 Rate of spread of free-burning fuels In a wind tunnel
fires in woody
Catchpole, W. R. et al. Combust. Sci. Technol., 1998, 131 (l-6), l-37. Described are the results of 357 experimental fires conducted in an environmentally controlled large wind tunnel. The fires were burned over a range of particle sizes, fuel bed depths, moisture contents, packing ratios and wind speeds. Spread rate decreased with moisture content in a way
Fuel and Energy Abstracts
January 1999 69