In order to improve the efficiency of the desulfurization process utilizing the mechanical stirring method, the effect of flux dispersion on the hot metal desulfurization reaction was investigated in 1/8-scale water model and 70 kg-scale hot metal experiments.Flux dispersion behavior is divided into three stages, i.e., "non-dispersion," "transition," and "complete dispersion." The desulfurization rate increases remarkably from the "non-dispersion" to the "complete dispersion" stage, corresponding to the change in the condition of particle dispersion.The relationship between the impeller position and the vortex depth is defined as the dispersion index, I. When the dispersion index was over 1, complete dispersion occurred in water model experiments, and the apparent rate constant increased remarkably in hot metal experiments.The observed diameter of the desulfurization slag was 1.4 mm, which is in good agreement with the calculated value, 1.55 mm. This means that fine desulfurization flux aggregates immediately after the addition of the flux. In order to increase desulfurization efficiency, it is important to control this particle aggregation.

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Recently, low coke rate blast furnace operation has been required in response to the rising cost of coking coal. However, the thickness of the coke layer decreases in low coke rate operation. Since it is known that the gas permeability of the blast furnace deteriorates as the coke layer thickness decreases, it is important to determine the minimum coke layer thickness for stable blast furnace operation. On the other hand, the minimum coke layer thickness has not been clarified due to a lack of equipment capable of measuring the effect of the coke layer thickness on permeability.In this study, a new experimental device called the cohesive zone simulator was developed to clarify the minimum coke layer thickness. In the cohesive zone, gas flows horizontally along the coke layer. In order to quantify the effect of the coke layer thickness on permeability, this horizontal gas flow should be simulated. Therefore, this simulator simulates a horizontal gas flow.Next, the effect of the coke layer thickness was quantified by using the cohesive zone simulator. The results showed that melting iron ore penetrated into the coke layer and closed part of the layer. These phenomena caused a deterioration of permeability under thin coke layer thickness conditions. Finally, a pressure drop estimation model considering penetration of the coke layer by melting ore was developed with the aim of quantifying the minimum coke slit thickness.

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