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 furnace was performed in NKK Fukuyama Works. Iron ore fines, s uch as sinter feed are directly charged into the fluidized bed. This f luidized bed was so designed as to form a dense bubbling bed and equip the circulating device. The reduction characteristics of iron ore fin es were clarified through the operation in the integrated test plant. According to the above results and the simulation model based on the e lutriation behavior, the appropriate residence time of coarse became 3 0-60 min to reduce the iron ore to 20-25% reduction degree in 800-degr ees-C bed temperature. The effect of circulation of fines was not quan titatively clear in the test, but the favorable circulation ratio was estimated with a mathematical model. Moreover, it was found that the c ollection efficiency of cyclone was closely related to the yields of p rereduced ore and the circulation ratio influenced on the losses of pr oducts.