Recovery of Zn and Fe from Steelmaking By-Products by Ar Plasma Smelting

Iron-containing by-products have high recycling value as an iron source due to the high content of Fe. However, some impurities in by-products limit their recycling. In particular, zinc in by-products are repeatedly vaporized and recrystallized inside a blast furnace, which deteriorates the operation. It is necessary to remove zinc from by-products by the zinc removal process such as RHF (rotary hearth furnace). However, due to the low removal ratio of zinc in RHF using coal as reducing agent, it is difficult to achieve carbon neutrality. This research investigated the removal of zinc and the recovery of zinc and iron from zinc-containing by-products by Ar plasma smelting. Two kinds of by-products used in this study contained 0.89 and 3.39 wt% of zinc oxide, respectively. One by-product (BP-A) resulted in a mixture of metallic iron and FeO remaining inside the crucible after Ar plasma smelting. The recovery ratio of iron in the product was evaluated as 94.2%, and the removal ratio of zinc was calculated to be 95.6%. The recovery ratio of zinc collected in the form of dust outside the crucible was calculated as 92.5%. The other by-product (BP-B), produced because of Ar plasma, was mostly FeO, and 82.6% of iron was recovered. In total, 96.4% of zinc from BP-B was removed, and 73.1% of zinc was recovered as dust. By the thermodynamic calculation in terms of FactSage 8.2, the temperature of the sample during plasma smelting was expected to be 2500 °C. The main gases generated during smelting were H2, CO and CO2 which were formed at the initial stage of the process.