查看更多>>摘要：The global steel industry is currently making a bold transition toward decarbonization and carbon neutrality, driven by worldwide initiatives to mitigate climate change. In this context, hydrogen-based ironmaking has emerged as a key technology for reducing CO_2 emissions. At the same time, however, the introduction of hydrogen as a reductant has highlighted new issues related to raw materials, particularly the degradation (powdering), softening, and melting that can occur under high-temperature conditions in the furnace. Although these phenomena may resemble certain aspects of conventional CO-based ironmaking, research shows that hydrogen enrichment can alter both the onset and severity of powdering and melting. Consequently, both fundamental scientific understanding and applied engineering solutions are necessary to ensure stable operations in hydrogen-enriched processes.
查看更多>>摘要：The global steel industry is currently making a bold transition toward decarbonization and carbon neutrality, driven by worldwide initiatives to mitigate climate change. In this context, hydrogen-based ironmaking has emerged as a key technology for reducing CO_2 emissions. At the same time, however, the introduction of hydrogen as a reductant has highlighted new issues related to raw materials, particularly the degradation (powdering), softening, and melting that can occur under high-temperature conditions in the furnace. Although these phenomena may resemble certain aspects of conventional CO-based ironmaking, research shows that hydrogen enrichment can alter both the onset and severity of powdering and melting. Consequently, both fundamental scientific understanding and applied engineering solutions are necessary to ensure stable operations in hydrogen-enriched processes.
Koki MOMMADaisuke MARUOKAEiki KASAITaichi MURAKAMI...
719-727页
查看更多>>摘要：Currently, the Japanese steel industry is developing the technologies to reduce 30% of domestic CO_2 emissions from iron- and steelmaking industry using an innovative ironmaking process such as the COURSE50 project, which focuses on H_2 reduction and CCUS technologies. On the other hand, it has been reported that an increasing H_2 gas ratio in the blast furnace reducing gas promotes the low temperature reduction disintegration of the iron ore pellet. In this study, the low temperature reduction disintegration mechanism of self-fluxing pellet under higher hydrogen condition at 500℃ was examined. During hydrogen reduction which proceeds uniformly, the fine cracks with few micrometers in the primary particles form. It leads to the formation of fine particles with the size of less than 0.1 mm on the surface of the pellet. Increase in the particles with few millimeters makes a significant impact on the permeability of the blast furnace. On the other hand, CO reduction without hydrogen gas proceeds topochemically, and volumetric fracture progresses with generation of the cracks with several millimeters in length due to the stress difference between near the surface and in the center of pellet. Under higher H_2 conditions, reduction proceeds uniformly, so such cracks causing volume fractures are hard to form, but the finer cracks are easier formed than the case of CO reduction, and the amounts of finer particles increases.
Koki MOMMADaisuke MARUOKAEiki KASAITaichi MURAKAMI...
719-727页
查看更多>>摘要：Currently, the Japanese steel industry is developing the technologies to reduce 30% of domestic CO_2 emissions from iron- and steelmaking industry using an innovative ironmaking process such as the COURSE50 project, which focuses on H_2 reduction and CCUS technologies. On the other hand, it has been reported that an increasing H_2 gas ratio in the blast furnace reducing gas promotes the low temperature reduction disintegration of the iron ore pellet. In this study, the low temperature reduction disintegration mechanism of self-fluxing pellet under higher hydrogen condition at 500℃ was examined. During hydrogen reduction which proceeds uniformly, the fine cracks with few micrometers in the primary particles form. It leads to the formation of fine particles with the size of less than 0.1 mm on the surface of the pellet. Increase in the particles with few millimeters makes a significant impact on the permeability of the blast furnace. On the other hand, CO reduction without hydrogen gas proceeds topochemically, and volumetric fracture progresses with generation of the cracks with several millimeters in length due to the stress difference between near the surface and in the center of pellet. Under higher H_2 conditions, reduction proceeds uniformly, so such cracks causing volume fractures are hard to form, but the finer cracks are easier formed than the case of CO reduction, and the amounts of finer particles increases.
查看更多>>摘要：For decreasing carbon dioxide emission from iron- and steelmaking industry, hydrogen utilization in the blast furnace has been considered. Iron ore sinter is one of the major iron sources for the blast furnace. It is known that the effects of the hydrogen concentration in the reducing gas on the reducibility and reduction disintegration of the sinter are strong. In this study, the evaluation of the mineral phase of the Mosaic EmBedding Iron Ore Sintering (MEBIOS) sinter and reducibility using a laboratory scale furnace simulated the blast furnace condition with high hydrogen concentration and the experimental blast furnace were carried out. MEBIOS sinter has higher ratio of the mineral phases, i.e., hematite and acicular calcium ferrite with primary hematite, showing higher reducibility compared to the conventional sinters. The value of JIS-RDI of the MEBIOS sinter decreases with an increase in that of JIS-RI, which is the reverse trend of the conventional sinter. Further, the basket charge test with the experimental blast furnace confirmed that the MEBIOS sinter shows high reducibility under the condition of high hydrogen concentration while the reduction disintegration behavior at low temperature is similar to conventional sinter.
查看更多>>摘要：For decreasing carbon dioxide emission from iron- and steelmaking industry, hydrogen utilization in the blast furnace has been considered. Iron ore sinter is one of the major iron sources for the blast furnace. It is known that the effects of the hydrogen concentration in the reducing gas on the reducibility and reduction disintegration of the sinter are strong. In this study, the evaluation of the mineral phase of the Mosaic EmBedding Iron Ore Sintering (MEBIOS) sinter and reducibility using a laboratory scale furnace simulated the blast furnace condition with high hydrogen concentration and the experimental blast furnace were carried out. MEBIOS sinter has higher ratio of the mineral phases, i.e., hematite and acicular calcium ferrite with primary hematite, showing higher reducibility compared to the conventional sinters. The value of JIS-RDI of the MEBIOS sinter decreases with an increase in that of JIS-RI, which is the reverse trend of the conventional sinter. Further, the basket charge test with the experimental blast furnace confirmed that the MEBIOS sinter shows high reducibility under the condition of high hydrogen concentration while the reduction disintegration behavior at low temperature is similar to conventional sinter.
Koki MOMMADaisuke MARUOKAEiki KASAITaichi MURAKAMI...
739-748页
查看更多>>摘要：It has been reported that an increasing H_2 gas ratio of the reducing gas in the blast furnace promotes the low temperature reduction disintegration of the iron ore pellet. Reduction of the pellet sample proceeds uniformly under higher H_2 condition at 500℃. Microcracks with the size of several micrometer form at the primary particles of iron oxide and it promote fine particles formation after the drum test. Macrocracks with the size of several millimeter form inside of the pellet after reduction and it promotes the volumetric destruction. In this study, the temperature dependence of reduction disintegration of self-fluxing pellet under higher H_2 condition was examined. Pellet sample was reduced under CO and CO-H_2 gas conditions at 600℃ and 700℃. After reduction, the disintegration test was conducted using the drum. Under higher H_2 condition at 600℃, the density of microcracks decreases with increasing reduction degree and it leads to lower of the RDI value than that at 500℃. The reason is that the volumetric expansion by the reduction from hematite to magnetite at 600℃ is not significant compared with that at 500℃. The difference of reduction degree at the center and near the surface of the pellet increases with increasing the reduction temperature. Reduction reaction proceeds more topochemically by increasing reduction temperature and the addition of hydrogen. This change leads the macrocrack formation, which is same mechanism under CO gas condition at 500℃. At 700℃, on the other hand, this microcrack was not observed because the volumetric expansion by the reduction is lower than that at lower temperature. Therefore, the effect of hydrogen addition on disintegration is not significant at 700℃.
Koki MOMMADaisuke MARUOKAEiki KASAITaichi MURAKAMI...
739-748页
查看更多>>摘要：It has been reported that an increasing H_2 gas ratio of the reducing gas in the blast furnace promotes the low temperature reduction disintegration of the iron ore pellet. Reduction of the pellet sample proceeds uniformly under higher H_2 condition at 500℃. Microcracks with the size of several micrometer form at the primary particles of iron oxide and it promote fine particles formation after the drum test. Macrocracks with the size of several millimeter form inside of the pellet after reduction and it promotes the volumetric destruction. In this study, the temperature dependence of reduction disintegration of self-fluxing pellet under higher H_2 condition was examined. Pellet sample was reduced under CO and CO-H_2 gas conditions at 600℃ and 700℃. After reduction, the disintegration test was conducted using the drum. Under higher H_2 condition at 600℃, the density of microcracks decreases with increasing reduction degree and it leads to lower of the RDI value than that at 500℃. The reason is that the volumetric expansion by the reduction from hematite to magnetite at 600℃ is not significant compared with that at 500℃. The difference of reduction degree at the center and near the surface of the pellet increases with increasing the reduction temperature. Reduction reaction proceeds more topochemically by increasing reduction temperature and the addition of hydrogen. This change leads the macrocrack formation, which is same mechanism under CO gas condition at 500℃. At 700℃, on the other hand, this microcrack was not observed because the volumetric expansion by the reduction is lower than that at lower temperature. Therefore, the effect of hydrogen addition on disintegration is not significant at 700℃.
查看更多>>摘要：The efficiency of blast furnaces is adversely affected by coke degradation via gasification. Considering the utilization of hydrogen-enriched blast furnaces, it is essential to investigate the reaction and degradation behaviors of coke at different temperatures. In this study, coke gasification experiments were conducted under CO_2 and H_2O atmospheres at different temperatures to prepare cokes with a conversion ratio of 0.2. The reaction rate of the H_2O gasification reaction was higher than that of the CO_2 gasification reaction at the same temperature. The activation energies for CO_2 and H_2O gasification were 150.2 and 126.0 kJ/mol, respectively. After gasification, the shrinkage ratio was low by H_2O gasification at 1 273 K and increased with increasing temperature, indicating that the surface reaction became the control factor that consumed the coke matrix with increasing temperature. On the other hand, the shrinkage ratio by CO_2 gasification tended to be stable from 1 273 to 1 673 K. Furthermore, the increase in the porosity of coke by H_2O gasification was lower than that by CO_2 gasification at higher temperatures. In addition, the strength of the coke via H_2O gasification was higher than that of the coke via CO_2 gasification.
查看更多>>摘要：The efficiency of blast furnaces is adversely affected by coke degradation via gasification. Considering the utilization of hydrogen-enriched blast furnaces, it is essential to investigate the reaction and degradation behaviors of coke at different temperatures. In this study, coke gasification experiments were conducted under CO_2 and H_2O atmospheres at different temperatures to prepare cokes with a conversion ratio of 0.2. The reaction rate of the H_2O gasification reaction was higher than that of the CO_2 gasification reaction at the same temperature. The activation energies for CO_2 and H_2O gasification were 150.2 and 126.0 kJ/mol, respectively. After gasification, the shrinkage ratio was low by H_2O gasification at 1 273 K and increased with increasing temperature, indicating that the surface reaction became the control factor that consumed the coke matrix with increasing temperature. On the other hand, the shrinkage ratio by CO_2 gasification tended to be stable from 1 273 to 1 673 K. Furthermore, the increase in the porosity of coke by H_2O gasification was lower than that by CO_2 gasification at higher temperatures. In addition, the strength of the coke via H_2O gasification was higher than that of the coke via CO_2 gasification.
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NSTL