Thermodynamic Modeling of Elemental Distributions of Trace Elements in Non-ferrous Iron Residue Hydrogen Reduction

Every year millions of tons of iron residue are generated as a by-product of zinc production. Stabilized landfilled iron residue contains recoverable metals that could be valorized with further processing. Pyrometallurgical processing allows the recovery of valuable metals while simultaneously producing a clean slag that can then be further utilized. A thermodynamic model was developed with FactSage version 8.0. The focus was on minor element behavior and distribution of elements between phases. Calculations were performed at 1200–1400°C and pressure of 1 atm with both pure H₂ and H₂-Ar mixtures used as a reductant. Also, the concentrations of Pb and Zn in the input were varied. The results showed that a liquid alloy phase forms consisting mostly of either Cu, As and Pb or Fe, As and Cu. It was noted that a higher Ar total gas amount in reduction decreased the mass fraction of the liquid alloy and increased the evaporation of elements into fume dust. S, Bi, Pb, Ge and Zn were observed to evaporate fully, while As, In, Sb and Ag evaporated only partially. The results need to be verified experimentally.