Electric arc furnace dust is a byproduct from steelmaking, contained up to 50%wt of zinc ferrite. It also contains about 10-20%wt of zinc oxide and the other metal oxides. Approximately 100,000 tons of EAF dust are generated per annum within Thailand. All of the dust has been sent to landfill. The objective of this research is to investigate the kinetics mechanism of the decomposition of zinc ferrite in EAF dust to obtain zinc oxide and iron oxide by using iron powder as a reducing agent. The process was carried out by mixing zinc ferrite or EAF dust with iron powder then compressed them in a mold. The samples from compression were treated by pyrometallurgical process. The factors required to be concerned were temperatures, particle sizes of iron powder, and mole ratios of zinc ferrite per iron powder, respectively. The treated samples were analyzed by X-ray diffraction (XRD) in order to characterize zinc ferrite phase transformation. It was found that the quantity of zinc ferrite, both either pure zinc ferrite and zinc ferrite in EAF dust, were decreased after treating by the pyrometallurgical process when increasing treating time from 30 to 180 minutes at 600°C, the particle size of iron powder at 10 micron, and the mole ratio of zinc ferrite per iron powder at 1:3. Moreover about 70%wt of zinc ferrite was decomposed and the products obtained were zinc oxides (ZnO) and iron oxides (Fe3O4, FeO, Fe2O3). The reduction of zinc ferrite with iron powder was well-defined taking place by diffusion thru product layer control. The activation energy of the reduction process was found to be 47.21±2.83 kJ/mol. Therefore, the decomposition of zinc ferrite by iron powder could be carried out at 1 atm with low pyrometallurgical temperature (600°C) and equipped with hydrometallurgical process to obtain high zinc yield.
THERMODYNAMIC ANALYSIS OF ZINC FERRITE DECOMPOSITION IN ELECTRIC ARC FURNACE DUST BY LIME
