Synergetic Utilization of Zinc-Bearing Dust by Carbothermic Reduction-Roasting Process: Phase Transformation and Morphological Evolution

An economic and effective strategy synchronously utilizing blast furnace bag dust (BF-BD) and converter-removing dust (C-RD) by carbothermic reduction roasting is reported to achieve separation and recovery of iron and zinc. In this paper, the effect of operating parameters on the recovery rate and remove rate of Fe and Zn from BD and GD was initially studied by synergetic carbothermic roasting reduction. The optimized parameters include a reduction temperature pf 1200 °C, a reduction time of 90 min, a FC/O of 2.0, and a proportion of C-RD/BF-BD of 7:3, and the removal efficiency of Zn and metallization degree of Fe reached 98.35% and 90.58%, respectively. The phase transformation and stepwise reduction behavior of wüstite (ZnO) x (FeO) 1− x , spinel Zn x Fe 1− x Al 2 O 4 , olivine Zn x Fe 2− x SiO 4 , and gehlenite Zn z Fe 2− x SiAl 2 O 7 are systematically investigated by SEM–EDS, XRD, TG/DTG, and thermodynamic analyses. It was found that the formation of wüstite (ZnO) x (FeO) 1− x as an intermediates plays an crucial role in the formation of metallic Zn–Fe–C alloy. Phase transformation and reduction mechanisms of C-RD and BF-BD and the interfacial reaction formation mechanism of wüstite (ZnO) x (FeO) 1− x were discussed and clarified in synergistic carbothermic reduction process. Graphical Abstract