Selective sulphidation of impurities in weathered ilmenite. Part 1 – Applicability to different ilmenite deposits and simulated Becher kiln conditions

A novel approach for the removal of chrome-bearing spinel impurities (chromite) from weathered ilmenite concentrates has been proposed. This involves a two-stage process where in Stage 1 the spinel impurities are subjected to selective surface sulphidation followed by physicochemical separation in Stage 2. In this Part 1 paper, the applicability of the selective sulphidation of spinel impurities at 1100 °C was investigated for different ilmenite concentrates sourced from the Murray Basin region in south-eastern Australia and from Bangka Island Indonesia. The results demonstrated that the selective sulphidation of the impurities can be applied to the Murray Basin ilmenites. This was indicated by the formation of sulphide-rich rims on the spinel impurities. The chrome spinels from the Indonesian ilmenite, however, were not sulphidised. This was most likely due to the refractory nature of the spinels as they contain higher concentrations of Mg and Al. The current study also simulated an industrial Becher kiln process in a laboratory roller-bed-furnace. The results show that the selective sulphidation conditions can be achieved using char and sulphur sources. It was also observed from these experiments that Mn impurities are also sulphidised. The current study also identified and presented the range of high temperature and gaseous conditions (pO₂ and pS₂) that promote the selective sulphidation of Mg, Mn, Sn and Y impurities.