REDUCTION BEHAVIOR OF IRON-ORE FINES AND CIRCULATION CHARACTERISTICS OF FINES IN PREREDUCTION FLUIDIZED-BED

The operation of prereduction fluidized bed combined with an in-bath s melting reduction furnace was performed in NKK Fukuyama Works. Iron or e fines, such as sinter feed are directly charged into the fluidized b ed. This fluidized bed was so designed as to form a dense bed and equi p the circulating device. The reduction characteristics of iron ore fi nes were clarified through the operation in the integrated test plant. According to the above results and the simulation model based on the elutriation behavior, the appropriate residence time of coarse became 30-60 min to reduce the iron ore to 20-25% reduction degree in 800-deg rees-C bed temperature. The effect of circulation of fines was not qua ntitatively clear in the test, but the favorable circulation ratio was estimated with a mathematical model. Moreover, it was found that the collection efficiency of cyclone was closely related to the yields of prereduced ore and the circulation ratio influenced on the losses of p roducts. Therefore, the circulation ratio was considered to be determi ned from the viewpoints of the effect on the reduction degree of fines and the losses of products.