Investigation on the Dripping Behavior of Primary Slag Melt in the Cohesive Zone of the Blast Furnace Through Iron or Oxide Funnel

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Alumina content in the iron ore imported to Japan is increasing year by year and some problems for the blast furnace operation due to the use of the high alumina containing sinter are reported. Since all of iron ore used in Japanese iron making companies is imported from overseas such as Australia, Brazil and so on, the problems caused by the lower grade ore should be solved as soon as possible. Though the true mechanism of harmful effect of alumina on the blast furnace operation is not known up till now due to the very complex phenomena in the blast furnace, it is generally considered that the alumina in the sinter would act the important role mainly on the behavior of primary melt formed in the sinter during the reduction. Keeping such background in view, this study aims to clarify the mechanism of harmful effect of alumina on the blast furnace operation. The behavior of primary melt, which is formed in the sinter at the cohesive zone of the blast furnace has been simulated by dripping molten slag through iron or oxide funnel. The effects of basicity, A12O3 and Fe_tO_<>O contents in the five kinds of slags on the dripping temperature) and hold-up on the funnel have been discussed. It was found that the eutectic melt formed in the sinter would play important role for the dripping behavior of slag melt in the blast furnace or hold-up phenomenon of slag melt among fine pore in reduced iron and ore particle. Al_2O_<>increases the hold-up degree of the slag melt on the funnel and its effect becomes much significant in the acidic and low Fe_tO_<>O containing slag. It was estimated that the increase of the slag hold-up by Al_2O_<> in the ore could result in the harmful effect on the permeability resistance and indirect reduction rate of the sinter in the blast furnace.