Simulation of primary-slag melting behavior in the cohesive zone of a blast furnace, considering the effect of Al 2 O 3
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I. INTRODUCTION
DUE to the lack of high-grade iron-ore resources in the world, impurities such as phosphorus, crystalline water, and alumina in the iron ore imported to Japan are being increased,[1] and the change of iron-ore composition is resulting in some problems for the blast furnace operation in Japanese ironmaking companies.[2,3,4] Actually, it is reported that a small increase in the amount of alumina could exhibit negative effects on the gas-permeability resistance and the reducibility of the iron-ore sinter in the lower part of the blast furnace, and it also increases the slag volume. In addition, the increase of alumina in the ore could also cause harmful effects in the iron-ore sintering process such as the decrease of producibility, yield strength, and quality of the sintered product.[2,3,5] Since all of the iron ore used by Japanese ironmaking companies is imported from overseas (from Australia, Brazil, and so on), the problems caused by the lowergrade ore should be solved as soon as possible. The true mechanism of the harmful effect of alumina on the blast furnace operation was not known up until now, due to the very complex phenomena in the blast furnace. It MITSUTAKA HINO, Professor, and TETSUYA NAGASAKA, Associate Professor, are with the Department of Metallurgy, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. AKITOSHI KATSUMATA, formerly Graduate Student, Department of Metallurgy, Graduate School of Engineering, Tohoku University, is Researcher, Research Laboratories, Nippon Yakin Kogyo Co. Ltd., Kawasaki 210-0823, Japan. KEN-ICHI HIGUCHI, Senior Researcher, and KAZUYOSHI YAMAGUCHI, Chief Researcher, are with the Ironmaking Process, Process Technology Research Laboratories, Technical Development Bureau, Nippon Steel Corporation, Futts 293-8511, Japan. NORIMITSU KON-NO, formerly General Manager, Ironmaking Process, Process Technology Research Laboratories, Technical Development Bureau, Nippon Steel Corporation, is Board Director, Research and Development Division, Nippon Shokubai Co. Ltd., Osaka 541-0043, Japan. Manuscript submitted January 8, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS B
is generally estimated that the alumina in the sinter would play an important role, mainly in the behavior of the primary melt formed in the sinter during the reduction. The primary melt is formed in the iron-ore sinter near the softening or cohesive zone of the blast furnace. It is reported that the large amount of alumina is concentrated in the primary melt, even if the increment of alumina content in the ore is small, for example, from 1.5 to 1.8 pct.[6] Therefore, it is reasonable to consider that the small amount of increase of alumina in the iron ore would result in a large effect on the behavior of the primary melt. If this primary melt could penetrate the microporosity of the sinter or become trapped among gaps in the sinter, the gas-permeability resistance in the lower part of the furnace would increase and the reducibility of the sinter would decrease due to the smaller e
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