Recovery of Cr,Ni and Fe from dust generated in stainless steelmaking

During stainless steel production in an electric arc furnace, the dust generated amounts to around 1% of the charge weight. This dust contains chromium, zinc and other heavy metal oxides; therefore, its final disposal in special landfill sites is expensive. On the other hand, the content of chromium oxide (∼9 wt%), nickel oxide (∼2·5 wt%) and iron oxides (∼47 wt%) can be recovered by reduction with carbon or Fe–Si. In this paper, the dust was physically and chemically characterised, and used in the manufacture of composite pellets with carbon and Fe–Si. These pellets were added to iron–carbon melts at a temperature around 1600°C. After smelting-reduction, the recovery yields of Cr, Ni, and Fe were determined. These yields were: (i) with Fe–75%Si as reductant – Ni ∼90%, Cr ∼90%, Fe ∼90%; and (ii) with coal as reductant – Ni ∼12%, Cr ∼35%, Fe ∼90%). A preliminary economic evaluation for Brazilian conditions showed that the process is sustainable depending on the landfill cost for dusts and the availability of inexpensive Fe–Si. When coal is used as reductant, the electric energy becomes the main cost component and the above recycling process becomes economically feasible with landfill costs higher than US$ 150 t⁻¹.