Desulfurization kinetics of high lead and zinc sulfide containing slag with oxygen blowing

The desulfurization process of lead and zinc slag is an important smelting process to obtain lead and zinc. The aim of this paper is to study the desulfurization process of high lead and zinc sulfide containing slag with oxygen blowing. The predominance area diagrams of the Pb-Zn-Fe-S-O system (Pb/(Fe+Pb+Zn)=0.176, Zn/(Fe+Pb+Zn)=0.56) at various temperature were thermodynamically constructed. The physical properties, the chemical composition and the phase transformation of the desulfurization slag were investigated. The thermodynamic results indicated that lead, zinc, and iron can be oxidized to form high lead and zinc slag. The experimental results illustrated that the sulfur content in the oxidation slag can be reduced to less than 1% as temperature increased up to 1573 K. The XRD analysis of as-quenched slag shows the PbS and ZnS phase decreased, while zincite and spinel phase (ZnxFe3-xO4+y) emerged and increased as the reaction time increased. The desulfurization process of molten slag were considered to be the first-order reaction and the apparent activation energy was estimated to be 44.46 kJ/mol. Under the experimental conditions, the mass transfer in the gas and liquid phase was likely to be the restrictive step.