A new smelting reduction process with a coke packed bed has been developed for iron, chromium, and nickel recovery from BOF dust, and for simultaneous recovery of zinc and iron from the electric arc furnace dust. The process is characterized by direct use of fine raw materials without agglomeration, recovery of almost the whole amount of zinc and lead, and no emission of secondary waste, compared with the conventional recovery methods.The commercial plant for BOF dust recycling has been operating stably with a metal production capacity of 200 tons per day. The blast condition is controlled so that the temperature at the lower tuyere level becomes higher than 1 550°C, which is the condition required for the smelting reduction of chromium and iron oxides.The validity of the process idea for EAF dust recycling was confirmed and the key technologies were established through the pilot plant tests with a scale of 10 tons per day. It was found that zinc oxide was almost completely reduced and vaporized at the thermal state of the furnace, T melt м1 550°C, which allowed chromium and iron to be reduced. The control of the temperature and CO 2 /CO ratio of the top gas was important for the prevention of zinc adhesion on the wall of the furnace top.
(1 ) The circulation rate of iron ore increased as the particle size decreased and the average solid holdup in the riser increased. The circulation rate also increased as the gas velocity in the riser increased.(2)The gas velocity and solid holdup were considered to affect the carrying over of particles as driving force and probability, respectively. Theore circulation rate, Gs, was proportional to the product of Fr number and the average solid holdup, (1 -~), in the riser.(3)The rate controlling step in the reduction of very fine ore was considered to be chemical reaction.On the other hand, the reduction of larger ore was affected by both chemical reaction and diffusion in the particles.
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