Experimental Study on Collaborative Electric Furnace Dust Reduction with Multi-solid Waste in Steel Plants: Turning Waste into Treasure, Saving Energy and Reducing Emissions

Rotary hearth furnaces and rotary kilns are the mainstream methods for large-scale treatment of electric furnace dust (EAFD) in steel companies, but they require a large amount of energy and have low product quality. The roasting conversion–separation technology uses calcium oxide to promote the conversion of zinc–iron spinel in EAFD into zinc oxide and dicalcium ferrite, but adding calcium oxide additionally increases production costs. Converter sludge (OGS) is rich in iron oxides and valuable components such as CaO, CaCO₃, ZnFe₂O₄, etc. The free calcium oxide and calcium carbonate can be used as substitutes for pure calcium oxide. This paper designed a multi-solid waste collaborative reduction roasting process to realize the recovery of zinc and iron elements from OGS and EAFD and explore the feasibility of industrial treatment in rotary hearth furnace. The results show that harmful OGS can be used as the calcium agent in the roasting process. The calcium carbonate in OGS not only improves the conversion of iron oxide into metallic iron, but the decomposed CaO can promote the conversion of zinc–iron spinel in OGS and improve the dezincification effect. Better conditions are: 60% OGS, n_C/n_O = 1.2, roasting temperature 1150°C, roasting for 25 min; zinc content in the reduction product is 0.21%, and metallization rate is 78.53%, which can be used as a high-quality substitute or coolant for scrap steel raw materials in the steelmaking process. This process can realize green and comprehensive utilization of EAFD and OGS and is expected to achieve industrialization.