Green and efficient recovery of poly metals from converter sludge through reduction roasting and preparation of backfill from tailings

Converter sludge (CS) is a type of solid waste containing iron and poly metals that are not thoroughly utilized yet. A novel process combining reduction roasting with waste backfill was designed to optimize the recovery of poly metals and investigate the feasibility of waste tailings as mine backfill. The dust contained 66.57 % zinc oxide, which could be sold as a by-product to zinc smelters, with 92.65 % lead recovery and 95.36 % zinc recovery. The powdery reduced iron (PRI) was suitable for steelmaking, and 91.45 % of iron was recycled. During reduction, lead and zinc in CS were reduced and then volatilized, and iron recovery was enhanced by the formation and growth of metallic iron. The coarsening of metallic iron was dominated via surface and volume diffusion, and the average activation energy was 966.48 kJ/mol. The slump, yield stress, and 90-day compressive strength of the backfill prepared from tailings were 208 mm, 106 Pa, and 1.11 MPa, respectively, indicating that it could be used as the backfill for underground mined-out areas. This process presents excellent application prospects and provides innovative ideas for comprehensive and green disposal of CS.