Material flow analysis of zinc during the manufacturing process in integrated steel mills in China

The steel manufacturing process involves not only the substance flow of iron from iron-bearing materials to steel products but also the circulation and movement of many additional elements. In this study, the flow and circulation of zinc during coking, sintering, blast furnace (BF) ironmaking, basic oxygen furnace (BOF) steelmaking, and continuous casting processes, which has been neglected, was analyzed in an integrated iron and steel mill throughout 2013. The results indicated that approximately 2,317 tonnes (t) of zinc from steelmaking raw materials were input into the studied steel mill in 2013, of which 58.8% originated from iron ore fines, 22.3% from pellets, and 8.8% from lumps. Although 1,212 t of zinc was discharged along with coking chemical products and steel slag after magnetic separation or iron-bearing dust and sludge, 1,105 t of zinc remained within the circulation. According to this research, we inferred that approximately 142 kilotonnes of zinc, 2.7% of China's zinc production in 2013, and approximately 1.5 million tonnes in total from 2000 to 2017 were concentrated in BF and BOF dust or sludge. This large amount of zinc has been ignored by Chinese steelmakers and zinc producers, although it should be used as a resource for zinc recycling. Thus, integrated steel mills should develop pertinent treatments targeting these fractions to prevent and handle the hazards from the circulation and concentration of zinc inside their premises.