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For the purpose of reducing specific coke breeze consumption, we examined the influence which the morphology of coke breeze and pseudo-particles structure have on sintering quality. As a means to control the morphology of coke breeze in pseudo-particles, we delayed the timing of coke breeze addition in granulation process of sintering materials. As a result, when we added more coke breeze in the latter stage of granulation, we noticed that granulating property as well as permeability were improved. Also, much of coke breeze stayed on the surface layer of pseudo-particles or in free particle, which led to improved quality and burn through speed (abbreviated as BTS).When we added the entire charge of coke breeze in the latter stage, combustion quality of coke breeze was improved. However, conduction and accumulation of heat turned down, which resulted in deteriorating yield due to the exhaust heat loss.Therefore, we searched for a ratio of the second-stage addition favorable for improving yield by making a higher raw material bed.With the second-stage addition at 50%, we were able to build a higher raw material bed through improvement in sinter quality and permeability, while maintaining good BTS. As a result, expanded area in the sintering bed with temperature at 1 200°C or higher led to liquid phase growth, which finally enabled the reduction in coke breeze consumption without causing deterioration in both yield and shutter index.KEY WORDS: coke breeze; the second-stage addition ratio; granulation; the morphology of a coke breeze; combustion quality; liquid phase ratio; yield.

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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.