Selective reduction of electric arc furnace dust in carbon monoxide

Electric arc furnace (EAF) dust is produced when steel scrap, particularly automobile scrap, is melted in an EAF. These dusts are classified as hazardous wastes but contain a substantial amount of zinc whose recovery is economically attractive. The dusts also contain a significant amount of iron oxide, but the recovery of the iron is not economical. Therefore, selective reduction of zinc oxide is important, and a number of industrial processes use this approach. In the present research, a thermodynamic study of the reduction of an EAF dust in carbon monoxide was performed using the Facility for Analysis of Chemical Thermodynamics (F*A*C*T) computational system. The results demonstrated that the selective reduction of the zinc in the dust, while at the same time maintaining the iron in an oxide form, was thermodynamically feasible. The theoretical zinc recoveries ranged from 96 to 98 percent. To test the theory, in-flight reduction experiments were performed in a carbon monoxide atmosphere. X-ray diffraction studies showed that to remove the maximum fraction of zinc from the dust, some of the iron oxide must be reduced to metal. Therefore, the experimental reactor was not capable of operating in a completely selective manner. The experimental zinc recoveries agreed with the reported industrial values, which also indicated that to achieve the highest recoveries of zinc, some reduction of iron was required.