Abstract

MALAN, W.; AKDOGAN, G.; BRADSHAW, S.  and  BEZUIDENHOUT, G.A.. The recovery of platinum group metals from low-grade concentrates to an iron alloy using silicon carbide as reductant. J. S. Afr. Inst. Min. Metall. [online]. 2015, vol.115, n.5, pp.375-383. ISSN 2411-9717.

The purpose of the study was to investigate the feasibility of SiC reduction of low-grade concentrates from Lonmin's Rowland and Easterns operations with respect to metal fall and PGM recovery. These concentrates are rich in SiO₂ and MgO with low concentrations of chalcopyrite and Cr₂O₃. Pd is the most abundant of the PGMs. SiC reduction of samples was conducted at 1600°C with 2.5-3.5 kg SiC per 100 kg concentrate. PGM recoveries for Easterns concentrate were better than for Rowland. More than 85% of the Ir and Pd and almost 60% of the Pt were recovered with 3.5 kg SiC per 100 kg concentrate. SEM of slag samples showed little entrainment of metallic prills compared to Rowland samples. This was attributed to the relatively higher melt viscosities of the Rowland concentrate. In order to decrease slag viscosity and to enhance PGM recovery, the FeO content of the Easterns concentrate was increased with the addition of 10 kg converter slag per 100 kg concentrate. Ir and Pd recoveries were increased to about 95%, while Pt recovery was around 70%. On the basis of these results an optimum feed ratio between Easterns and Rowland concentrates and converter slag is proposed. Carbothermic reduction of the optimum charge was also compared to SiC reduction. Carbothermic reduction yielded a marginally higher metal fall; however, the calculated gas emissions and energy requirements were higher than for SiC reduction.

Keywords : SiC reduction; PGM recovery; LG concentrates; FactSage modelling.

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