Dezincification of electric furnace dust by steel slag synergistic calcification carbothermal reduction

Resource utilization of metallurgical solid waste is vital for the sustainable development of the steel industry in the context of “dual carbon.” The calcification–carbothermal reduction method was employed to extract zinc and iron from electric furnace dust effectively. In this process, calcium oxide reacts with zinc ferrite to form dicalcium ferrite and zinc oxide, which further promotes the effective separation of zinc and iron. However, the addition of pure calcium oxide increases production costs for steel companies. Herein, a new process for dust removal and zinc recovery in electric furnaces has been developed, using electric furnace slag as a calcium agent and mineral trough ash as a reducing agent. Large amounts of dicalcium ferrate phases were detected in the carbothermal reduction products by steel slag synergistic calcification. The reaction mechanism was determined as ZnFe₂O₄ + CaO → Ca₂Fe₂O₅ + ZnO → Ca₂Fe₂O₅ + Zn(g). Such a two-step reaction path indicated that steel slag can effectively promote the reduction and volatilization of zinc. The experimental optimal roasting parameters were determined as roasting temperature of 1150 °C, roasting time of 45 min, calcium to zinc molar ratio of 1.1, and carbon to oxygen molar ratio of 0.8. The mass percentage of added steel slag was recorded as 21.83%, while that of mineral trough ash was 21.85%. Under these conditions, the zinc removal rate above 99% and the metallization rate of pellets of about 75.31% were achieved. Overall, the proposed method looks promising for future efficient separation of zinc and iron in industrial steel slag.