Electric Arc Furnace Dust Treatment by the Combination of Pyro/Hydrometallurgical Processes

Abstract

This project researched a mechanism of the decomposition of zinc ferrite (ZnFe2O4) to be zinc oxide (ZnO) and calcium ferrite (Ca2Fe2O5) by using calcium oxide (CaO) from lime as a reducing agent. Zinc ferrite was mostly found in electric arc furnace dust (EAFD), which is a by product from a steel making industry. The experiment was simple as following. The EAFD was mixed with lime in mole ratio of zinc ferrite and calcium oxide at 1:2, 1:3 and 1:4 and then compressed into pellets. Effects of mole ratio, temperatures and times on the decomposition were studied. The conditions used in these experiments were 800, 900, 1,000 and 1,100 oC for 2, 4 and 6 hours. The results showed that the suitable conditions for the decomposition of zinc ferrite by calcium oxide could be as low as 800 oC for only 2 hours with mole ratio of zinc ferrite from EAFD and calcium oxide from lime as 1:2. A solubility test was provided to processed samples at the conditions as 0.1 M hydrochloric acid (HCl) at 50 oC for 20 minutes. It was found that EAFD from pyrometallurgical treatment could be decomposed to be zinc oxide and the following by hydrometallurgical treatment could recovery high zinc yield from the remaining residue. However, EAFD treated by only hydrometallurgical process obtained lower zinc recovery due to the high stability of zinc ferrite in HCl and most of the solutions.