Characterisation of Metal Debris in Grinding and Flotation Circuits

An extensive body of work exists on the impact of grinding media composition on media wear, valuable mineral surface chemistry and subsequent separation from gangue species. However, the literature is limited in describing what happens to metal (either tramp metal from upstream processes, or grinding media debris) in the grinding and flotation processes. This study aims at characterisation and deportment of metal debris within the grinding and flotation circuits of three Australian concentrators. The results show a remarkable range of "metallic" morphologies and sizes, with a considerable amount of metal debris circulating in the hydrocyclone/mill circuit while fine fractions proceed to downstream flotation. Chemical and mineralogical characterisation revealed notable metal debris contribution from upstream equipment such as loader teeth and high speed steel tools, coupled with mild steel grinding media. Surface chemistry and mineral association analysis suggest sulphide mineral oxidation at reactive metal debris surfaces, causing possible limitation of flotation performance and process economics.