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01997 Requirements on residual materials for the injection into blast furnaces
09 Combustion (burners, combustion systems) 04/01996 Radiative combustion of pyrolyzing fuel in a cylindrical combustor Han, C. Y. Fuel, 2004, 83, (3), 343-351. Investigation on ignition and flame propagation of pyrolyzing fuel in a cylindrical combustor is accomplished. The pyrolyzing fuel of cylindrical shape is concentrically located in a combustor sustained at high temperature. Due to gravity, the buoyancy motion is inevitably incurred in the combustor and this affects the flame initiation and propagation behaviour. The radiative heat transfer due to absorption gas plays an important role since it absorbs and emits radiative energy. Numerical studies have been performed over various parameters relevant to gas radiation as well as overheat ratios. The ignition criterion is decided on experimental basis. For the case of relatively small overheat ratio, the gas absorption reduces the flow intensity by the far-reaching effect of radiation. Visible blue flame hence does not evolve. For a high overheat ratio, the strong visible blue flame is generated and selfpropagates. The gas radiation makes the considerable effect on ignition delay and flame thickness as well as thermal and reactive nature of visible blue flame.
04/01997 Requirements on residual materials for the injection into blast furnaces Buchwalder, J. et al. ISSTech Conference Proceedings, 1st, Indianapolis, IN, United States, Apr. 27-30, 2003, 2003, 1956 1970. The use of auxiliary reductants and other process optimization measures has decreased average weighted coke consumption at Germany's remaining 14 basic hot metal producing blast furnaces to 352 kg/tonne of hot metal (HM). In addition to pulverized coal and oil, residual materials such as waste plastics and animal fat are also injected into some blast furnaces. With the introduction of the new EU end-of-life vehicle (ELV) regulation, the recycling of problematic automotive shredder residues (ASR) by injection into blast, furnaces is under discussion, and is being tested so that the steel industry can also contribute towards fulfilling the requirements of the directive. A prerequisite for this is the appropriate degree of beneficiation of ASR to prevent problems with blast furnace operation, and hot metal impurities. The injection of ASR of a highly varied chemical composition alongside coal or oil, with all its effects on the material and energy balance, is calculated and critically analysed using a blast furnace balance model. As a result it can be stated that, in principle, ASR can be injected into blast furnaces if certain requirements are met. Its physical properties must guarantee pneumatic conveyance and gasification of the material in the raceway. With regard to chemical composition, all elements or compounds that affect the blast furnace process, such as chlorine, zinc, alkalis and lead, aid the content of nonferrous metals (copper, chromium, nickel, vanadium), that can only be removed partially, or not at all, from the hot metal or crude steel, must be kept extremely low. For smooth blast furnace operation, ASR with sufficient quality must be continuously supplied from a reliably operating beneficiation plant.
04/01998 Soot nanostructure: dependence upon synthesis conditions Vander Wal, R. L. and Tomasek, A. J. Combustion and Flame, 2004, 136, (1-2), 129-140. This article addresses the differences in soot nanostructure based upon formation and growth conditions. Fuel structure effects can be masked or accentuated depending upon both temperature and rate of increase. Low temperature yields an amorphous soot for all fuels studied here, regardless of flow rate. High temperature yields different results depending upon the rate of increase. A rapid increase as realized by a high flow rate emphasizes pyrolysis kinetics that favour polyaromatic hydrocarbons (PAHs) with five-rnembered rings leading to soots with many shells and capsules: a highly curved nanostructure. Slower rates result in a different pyrolysis chemistry leading to graphitic soot, as characterized by extended graphitic segments oriented parallel to each other. Reflecting high thermodynamic stability, PAils may resist decomposition and yield a less graphitic soot nanostrueture using either a fast or a slow temperature increase. In contrast, ethanol produces a highly curved nanostructure using either temperature increase rate.
04/01999 The influence of swirl angles on flame stability in pilot-scale plant Nettleton, M. A. Fuel, 2004, 83, (2), 253-256. The article presents observations on the behaviour of coal dust-air flames imposed in pilot-scale plant by variations in the angle of swirl of the secondary, air stream. It suggests some explanations for the existence of limits of stability, with the most probable for the lower one being the increase in dwell time of mixed eddies in the furnace, mitigating any stochastic increase in delays in mixing or in chemical ignition or, most likely, a combination of both. Two possible interpretations are offered for the occurrence of an upper limit. One is an increase in heat losses from the flame to the cooler furnace walls and the second is based on the concept of flame stretch. Some of the
276
Fuel and Energy Abstracts
July 2004
contrasts between the probable behaviour in pilot- and full-scale plant are emphasised and suggestions made, where present results might be applied to the latter.
04/02000 The shape and movement of hearth in the furnace for a new ironmaking process Huang, D. and Lu, W.-K. ISSTech Conference Proceedings, Ist, Indianapolis, IN, United States, Apr. 27-30, 2003, 2176-2185. The thermal-chemical aspects of a new and high efficient coal-based ironmaking process using a hearth furnace have been established in laboratory and in pilot plant scale with financial support of AISI members and US department of Energy. Conceptual designs of the hearth furnace that meet the requirements of this new process are presented.
04/02001
Upgrading of coal tar in supercritical water
Ma, C. et al. Ranliao Huaxue Xuebao, 2003, 31, (2), 103-110. (In Chinese) Using a batch autoclave, preliminary study was made on the reaction of coal tar in supercritical water. Attention was centred on the influence of temperature, residence time and density of water on both composition and yield of products. Experiments were performed between 390 ° ~ 480 °, solvent density 0,32 g/cm 3 ~ 0.44 g/cm 3, and reaction time up to 80 rain. Compared with the traditional pyrolysis of coal tar under normal pressure or high pressure, during the upgrading of coal tar in SCW, light oil is increased at the expense of gas and coke products, probably due to the cage effect of SCW in the pyrolysis of coal tar. SCW may be an ideal medium for up-grading of coal tar and can suppress gas formation and coking of coal tar. In order to get light oil as much as possible, the optimal conditions are: temp. 450 °, density of water 0.40 g/cm3 and residence time 20 rain. The yield of light oil (HS) is 51.55 w % under these conditions, 30% higher compared with that in the raw material.
04/02002 Validation of coal combustion model by using experimental data of utility boilers Yamamoto, K. et al. Nippon Kikai Gakkai Ronbunshu, B-hen, 2003, 69, (679), 730-736. (In Japanese) Applicability of a coal combustion model was validated by using experimental data of utility boilers. The coal combustion model had gasification and NOx reaction submodels and it was developed by using a small drop-tube-furnace (coal feed rate 0.6 kwh ). A turbulence combustion simulation program was developed by introducing the coal combustion model. The simulation program was validated by comparing with 23 experimental results that contained different plant, load and coal data. The temperature difference between simulated and experimental results was <30°C at the exit of the furnace. The characteristic of coal burnout that was decreased with increasing load was predicted. The NOx concentration difference between simulated and experimental results was <15%. The coal combustion model was applicable to the utility boilers as same as the drop-tube-furnace.
04/02003 Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part V. Combined effects of Na concentration and char structure on char reactivity Wu, H. et al. Fuel, 2004, 83, (1), 23-30. A set of NaCl-loaded Loy Yang brown coal was pyrolysed in a thermogravimetric analyser between 600 and 900°C. The char sample after pyrolysis was cooled down directly for in situ reactivity measurement with air. The results indicated that the volatilisation of Na during pyrolysis is an important reason for the existence of catalyst loading saturation level with Na as a catalyst in char because the char prepared at high temperature had a limited holding capacity for Na. Under the experimental conditions in this study, the char reactivity showed good linear correlation with the Na concentration in the reacting char. Peak pyrolysis temperature, affecting the release of C1 and distribution of Na in char, is an important factor governing the correlation between the char reactivity and Na concentration in char. The catalytic activity of Na is a result of the interaction between Na and char and thus is greatly dependent on the char/carbon structure. At high char conversion levels where the char structure is more inert and highly condensed, the catalytic activity of Na is reduced compared with its activity at low char conversion levels. The catalytic activity of Na depends on the structure of char.
04/01997 Requirements on residual materials for the injection into blast furnaces Buchwalder, J. et al. ISSTech Conference Proceedings, 1st, Indianapolis, IN, United States, Apr. 27-30, 2003, 2003, 1956 1970. The use of auxiliary reductants and other process optimization measures has decreased average weighted coke consumption at Germany's remaining 14 basic hot metal producing blast furnaces to 352 kg/tonne of hot metal (HM). In addition to pulverized coal and oil, residual materials such as waste plastics and animal fat are also injected into some blast furnaces. With the introduction of the new EU end-of-life vehicle (ELV) regulation, the recycling of problematic automotive shredder residues (ASR) by injection into blast, furnaces is under discussion, and is being tested so that the steel industry can also contribute towards fulfilling the requirements of the directive. A prerequisite for this is the appropriate degree of beneficiation of ASR to prevent problems with blast furnace operation, and hot metal impurities. The injection of ASR of a highly varied chemical composition alongside coal or oil, with all its effects on the material and energy balance, is calculated and critically analysed using a blast furnace balance model. As a result it can be stated that, in principle, ASR can be injected into blast furnaces if certain requirements are met. Its physical properties must guarantee pneumatic conveyance and gasification of the material in the raceway. With regard to chemical composition, all elements or compounds that affect the blast furnace process, such as chlorine, zinc, alkalis and lead, aid the content of nonferrous metals (copper, chromium, nickel, vanadium), that can only be removed partially, or not at all, from the hot metal or crude steel, must be kept extremely low. For smooth blast furnace operation, ASR with sufficient quality must be continuously supplied from a reliably operating beneficiation plant.
04/01998 Soot nanostructure: dependence upon synthesis conditions Vander Wal, R. L. and Tomasek, A. J. Combustion and Flame, 2004, 136, (1-2), 129-140. This article addresses the differences in soot nanostructure based upon formation and growth conditions. Fuel structure effects can be masked or accentuated depending upon both temperature and rate of increase. Low temperature yields an amorphous soot for all fuels studied here, regardless of flow rate. High temperature yields different results depending upon the rate of increase. A rapid increase as realized by a high flow rate emphasizes pyrolysis kinetics that favour polyaromatic hydrocarbons (PAHs) with five-rnembered rings leading to soots with many shells and capsules: a highly curved nanostructure. Slower rates result in a different pyrolysis chemistry leading to graphitic soot, as characterized by extended graphitic segments oriented parallel to each other. Reflecting high thermodynamic stability, PAils may resist decomposition and yield a less graphitic soot nanostrueture using either a fast or a slow temperature increase. In contrast, ethanol produces a highly curved nanostructure using either temperature increase rate.
04/01999 The influence of swirl angles on flame stability in pilot-scale plant Nettleton, M. A. Fuel, 2004, 83, (2), 253-256. The article presents observations on the behaviour of coal dust-air flames imposed in pilot-scale plant by variations in the angle of swirl of the secondary, air stream. It suggests some explanations for the existence of limits of stability, with the most probable for the lower one being the increase in dwell time of mixed eddies in the furnace, mitigating any stochastic increase in delays in mixing or in chemical ignition or, most likely, a combination of both. Two possible interpretations are offered for the occurrence of an upper limit. One is an increase in heat losses from the flame to the cooler furnace walls and the second is based on the concept of flame stretch. Some of the
276
Fuel and Energy Abstracts
July 2004
contrasts between the probable behaviour in pilot- and full-scale plant are emphasised and suggestions made, where present results might be applied to the latter.
04/02000 The shape and movement of hearth in the furnace for a new ironmaking process Huang, D. and Lu, W.-K. ISSTech Conference Proceedings, Ist, Indianapolis, IN, United States, Apr. 27-30, 2003, 2176-2185. The thermal-chemical aspects of a new and high efficient coal-based ironmaking process using a hearth furnace have been established in laboratory and in pilot plant scale with financial support of AISI members and US department of Energy. Conceptual designs of the hearth furnace that meet the requirements of this new process are presented.
04/02001
Upgrading of coal tar in supercritical water
Ma, C. et al. Ranliao Huaxue Xuebao, 2003, 31, (2), 103-110. (In Chinese) Using a batch autoclave, preliminary study was made on the reaction of coal tar in supercritical water. Attention was centred on the influence of temperature, residence time and density of water on both composition and yield of products. Experiments were performed between 390 ° ~ 480 °, solvent density 0,32 g/cm 3 ~ 0.44 g/cm 3, and reaction time up to 80 rain. Compared with the traditional pyrolysis of coal tar under normal pressure or high pressure, during the upgrading of coal tar in SCW, light oil is increased at the expense of gas and coke products, probably due to the cage effect of SCW in the pyrolysis of coal tar. SCW may be an ideal medium for up-grading of coal tar and can suppress gas formation and coking of coal tar. In order to get light oil as much as possible, the optimal conditions are: temp. 450 °, density of water 0.40 g/cm3 and residence time 20 rain. The yield of light oil (HS) is 51.55 w % under these conditions, 30% higher compared with that in the raw material.
04/02002 Validation of coal combustion model by using experimental data of utility boilers Yamamoto, K. et al. Nippon Kikai Gakkai Ronbunshu, B-hen, 2003, 69, (679), 730-736. (In Japanese) Applicability of a coal combustion model was validated by using experimental data of utility boilers. The coal combustion model had gasification and NOx reaction submodels and it was developed by using a small drop-tube-furnace (coal feed rate 0.6 kwh ). A turbulence combustion simulation program was developed by introducing the coal combustion model. The simulation program was validated by comparing with 23 experimental results that contained different plant, load and coal data. The temperature difference between simulated and experimental results was <30°C at the exit of the furnace. The characteristic of coal burnout that was decreased with increasing load was predicted. The NOx concentration difference between simulated and experimental results was <15%. The coal combustion model was applicable to the utility boilers as same as the drop-tube-furnace.
04/02003 Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part V. Combined effects of Na concentration and char structure on char reactivity Wu, H. et al. Fuel, 2004, 83, (1), 23-30. A set of NaCl-loaded Loy Yang brown coal was pyrolysed in a thermogravimetric analyser between 600 and 900°C. The char sample after pyrolysis was cooled down directly for in situ reactivity measurement with air. The results indicated that the volatilisation of Na during pyrolysis is an important reason for the existence of catalyst loading saturation level with Na as a catalyst in char because the char prepared at high temperature had a limited holding capacity for Na. Under the experimental conditions in this study, the char reactivity showed good linear correlation with the Na concentration in the reacting char. Peak pyrolysis temperature, affecting the release of C1 and distribution of Na in char, is an important factor governing the correlation between the char reactivity and Na concentration in char. The catalytic activity of Na is a result of the interaction between Na and char and thus is greatly dependent on the char/carbon structure. At high char conversion levels where the char structure is more inert and highly condensed, the catalytic activity of Na is reduced compared with its activity at low char conversion levels. The catalytic activity of Na depends on the structure of char.