Understanding the influence of HPGR on PGM flotation behavior using mineralogy

Due to the very fine grained nature and complexity of the platinum bearing ores from the Bushveld Complex in South Africa, numerous processing operations have investigated alternate comminution devices that can be used to liberate the platinum group minerals of the Merensky and UG2 ores at a coarser grind, at reduced energy consumption and increased throughput. In this study, the mineralogy and flotation performance of product from the high pressure grinding rolls (HPGR) was evaluated and compared to a conventional ball mill product with the aim of determining whether the HPGR product could be used for flotation without any further grinding. Results show that for both the Merensky and UG2 platinum ores, the HPGR product showed more fines and less coarse content compared to the ball mill product. No conclusive evidence of preferential liberation was observed for samples prepared by particle bed breakage. The best flotation results were obtained from the ball mill product. The results from this study have shown the definite need for an integrated approach for the interpretation of the results that extends beyond just measurements of valuable mineral liberation.