A method to produce coke in 'lump' form with high strength and reactivity through the addition of a catalyst was investigated in order to improve blast furnace reaction efficiency. The addition of Ca compounds to coal before carbonization was found to considerably increase the reactivity of the coke at a low temperature range in the thermal reserve zone of a blast furnace. Furthermore it was proved that strong, highly reactive 'lump' form coke could be produced by adding a Ca-rich non-caking coal and adjusting the coal blend composition. Based on this fundamental study, the Ca-rich coke was successfully produced in coke ovens on a commercial scale, both at Kimitsu and Muroran works. The use of the Ca-rich coke in the Muroran No. 2 blast furnace was found to cause a decrease in the reducing agent rate by 10 kg/t-p. This technology, producing coke of high reactivity and strength through catalyst addition, is promising as a means of improving the reaction efficiency of a blast furnace.

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Usage of highly reactive coke in order to decrease the thermal reserve zone temperature in blast furnaces is promising to increase reaction efficiency in blast furnaces and to decrease the reducing agent rate. We focused on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. When the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the thermal reserve zone temperature (900°C), which causes a decrease in the thermal reserve zone temperature, while conventional coke barely reacts and is protected from degradation. It was also confirmed that the catalytic activity of Fe and that of K is independent of each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease the thermal reserve zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

Coke strength is mainly determined by pores and cracks that cause fracture of coke. In this study, connected pores that were considered to cause fracture of coke were investigated. In order to evaluate connected pores quantitatively, low roundness pores (whose roundness were below 0.2) were measured by image analysis technique of microscopic photographs of cokes. The relationship between the amount of low roundness pores and coke strength (DI 150 6) showed a good correlation. It is thought that the amount of low roundness pores is one of the factors determining coke strength.

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Iron-coke having various amount of M.Fe were produced in laboratory scale and the influence of M.Fe content in Iron-coke on reaction behavior under the condition simulating blast furnace has been investigated. Cold strength of Iron-coke products was decreased with an increase of mixing ratio of iron ore mostly due to a prevention of dilatation of coal particles by iron ore, resulting in weak bonding of coal particles. Nevertheless formed Iron-coke with iron ore in the fraction up to 30% would have enough strength for use in blast furnace as nut coke. Both CRI and JIS-reactivity were enhanced by increasing ratio of mixed iron ore, confirming the catalysis effect of M.Fe. The temperature at which carbon consumption started was lowered with an increase of T.Fe in coke. Formed Iron-coke containing 43% of T.Fe started reaction consuming its carbon at lower temperature than conventional coke by 150°C. Furthermore, consumed carbon ratio was improved by M.Fe installation to coke due to increasing gasification. Process evaluation with using Iron-coke in blast furnace was performed by BIS test. It was revealed that using formed Iron-coke having 43% of T.Fe for blast furnace resulted in an increase of shaft efficiency by 6.8%. It was found that to lower the reducing agent rate in blast furnace by decreasing the temperature of thermal reserve zone, lowering the beginning temperature of coke reaction was effective. Usage of Iron-coke having M.Fe catalyst within coke matrix is one of the methods.