Development of Coating Granulation Process at Commercial Sintering Plant for Improving Productivity and Reducibility

摘要

An advanced granulation process for treatment of raw mixtures was developed to improve sinter productivity and reducibility through fundamental and applied studies. Proper selection of the coating time is the most important factor for achieving improvement, because destruction of quasi-particles proceeds together with granulation in the drum mixer. The advanced granulation process is characterized by coating coke breeze and limestone on the surface of quasi-particles which have been granulated in the primary part of the drum mixer. Coke breeze and limestone are injected from the end of the drum mixer by the belt conveyor at high speed to achieve coating on the quasi-particles. Because these two materials segregate in the quasi-particles, this process controls the excess melting reaction between iron ore and limestone. Fundamental studies and commercial plant trials showed that the desirable melt fluidity resulting from the above-mentioned segregation enhanced permeability in the sintering bed. The superior reducibility of the sinter product depends on the diffusible structure retaining micro pores originating in the relict ores. Commercial sinter plants at JFE Steel's West Japan Works with an annual production capacity of 13.5 million tons have already introduced the new granulation process. The new process remarkably improves both the productivity and reducibility of sinter products in spite of the recent prevalence of inferior ores. In addition to improving the sintering operation, this granulation process also contributes significantly to improve blast furnace operation, including both higher productivity and lower reducing agent rate.