Chemical beneficiation of chromite ore to improve the chromium-to-iron ratio for ferrochrome production

Ferrochrome (FeCr), a relatively crude alloy comprised primarily of iron (Fe) and chromium (Cr), is vital for the production of stainless steel. FeCr is produced from chromite ore, the most important source of virgin Cr units. FeCr producers are only paid per mass unit of Cr content in the FeCr, i.e. in US¢/lb contained Cr, according to the current global FeCr markets pricing structure. Consequently, FeCr producers transport a large fraction of their product weight, i.e. the Fe content of the FeCr, without any benefit. The Fe content in the FeCr produced depends on the chromite spinel Cr/Fe ratio. Therefore, the selective removal of Fe from the chromite spinel using different combinations of chromite pre-oxidation, pre-reduction, and sulphuric acid leaching was investigated. The Cr/Fe ratio of the case study ores could be increased from 1.57 up to ∼23.4. However, Cr recovery decreased significantly under experimental conditions to achieve such high Cr/Fe ratios. More desirable Cr/Fe ratios of >2 up to ∼4.28 were achieved while maintaining Cr recoveries of >90%.