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

Abstract

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 C _eq (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 C _eq = 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.