Utilization of self reducing pellet in blast furnace is one of the effective technologies to mitigate the CO2 emissions in the steel industry. However, there are not sufficient researches on how the pellet behaves around cohesive zone. Therefore, purpose of this study is to clarify the effect of slag melting behavior on metal-slag separation behavior. In order to simulate the behavior around cohesive zone, electrolytic iron powder, carbon powder, and synthetic slag were prepared as reduced iron, residual carbon and slag components, respectively. They were well mixed as given mass ratios decided from the composition of the self reducing pellet. Different kinds of slag compositions were adopted to change properties, such as melting temperature and viscosity. The mixtures were pressed into tablets and used as experimental samples. "In-situ" observations of metal-slag separation behavior in the mixtures during constant rate heating were done by a laser microscope combined with infra-red furnace and metal-slag separation temperatures were decided. Following results were obtained. The metal-slag separation behavior was dominated largely by agglomeration behavior of liquid phase of iron. The separation surely occurred when both phases of iron and slag change to liquid phases. At the same time, the separation could also occur even if a small amount of solid phases still remained in the mixture. In this experimental condition, the effect of slag melting temperature on the separation was larger than the effect of slag's viscosity.KEY WORDS: slag melting temperature; viscosity of slag; metal-slag separation behavior; agglomeration behavior of Fe-C liquid; laser microscope; "in-situ" observation.

緒言炭材内装塊成鉱の高炉利用は，COKo-Ichiro OhnO, Masashi KaimOtO, Takayuki maeda, Koki nishiOKa and Masakata shimizu Synopsis : Utilization of self reducing pellet in blast furnace is one of the effective technologies to mitigate the CO 2 emissions in the steel industry. However, there are not sufficient researches on how the pellet behaves around cohesive zone. Therefore, purpose of this study is to clarify the effect of slag melting behavior on metal-slag separation behavior. In order to simulate the behavior around cohesive zone, electrolytic iron powder, carbon powder, and synthetic slag were prepared as reduced iron, residual carbon and slag components, respectively. They were well mixed as given mass ratios decided from the composition of the self reducing pellet. Different kinds of slag compositions were adopted to change properties, such as melting temperature and viscosity. The mixtures were pressed into tablets and used as experimental samples. "Insitu" observations of metal-slag separation behavior in the mixtures during constant rate heating were done by a laser microscope combined with infra-red furnace and metal-slag separation temperatures were decided. Following results were obtained. The metal-slag separation behavior was dominated largely by agglomeration behavior of liquid phase of iron. The separation surely occurred when both phases of iron and slag change to liquid phases. At the same time, the separation could also occur even if a small amount of solid phases still remained in the mixture. In this experimental condition, the effect of slag melting temperature on the separation was larger than the effect of slag's viscosity. Key words : slag melting temperature; viscosity of slag; metal-slag separation behavior; agglomeration behavior of Fe-C liquid; laser microscope; "in-situ" observation.

Synopsis : Mill Scale has higher iron contents and produces heat by the oxidation reaction in the sintering process. For this reason, it is expected that use of Mill Scale in the sinter operation will reduce the amount of coke breeze consumption. For the purpose of examining the influence of Mill Scale on melt penetrability and sinterability, we carried out melt penetration tests and sinter pot tests. Melt penetrability in the sintering process is an important factor that affects the quality of iron ore sinter. Our melt penetration tests lead following conclusions. Melt penetrability of Mill Scale is so high that increased blending ratio of Mill Scale causes lower permeability, which eventually leads to lower productivity. We, however, anticipated that we may be able to control the melt penetrability if we blend Mill Scale closely with iron ore which has the nature of lower melt penetrability. We arranged that a higher ratio of Mill Scale can be blended with such iron ore in proximity in the preparatory granulation method. We used the granular in the pot tests. In the result, oxidation reaction of Mill Scale was inhibited because Mill Scale contained in the pseudo-particle had reduced contact area with air. We confirmed that both permeability and productivity were improved by the method to control the melt penetrability mentioned above, even at higher blending ratio of Mill Scale.