Reduction of electric arc furnace dust by graphite powders under microwave irradiation

Electric arc furnace dust was reduced by graphite powder under microwave irradiation. After Zn was removed as a vapour, Fe was successfully recovered as a metal drop after 300 s microwave irradiation (2·45 GHz, 1·7 kW). The maximum temperature and heating rate increased with increasing carbon equivalent Ceq (the mole ratio of carbon/oxygen to reduce ZnFe2O4 and ZnO, yielding CO gas). The maximum recovery ratio of Fe (0·87) was obtained when Ceq = 1. A glassy slag phase, with environmentally harmful elements fixed within, was obtained by SiO2 addition. However, with increasing SiO2 addition, the recovery ratio of Fe decreased. It was considered that the heat generated on the surface of the graphite was partially used to increase the temperature of the added SiO2, and the duration at the maximum temperature decreased with increasing SiO2 addition. Consequently, the optimised condition for the reduction of electric arc furnace dust was obtained with addition of 6% graphite and 2·4%SiO2 powders under microwave irradiation for 300 s.