Abstract:

Previous research has shown that kimberlite ores are amenable to microwave treatment. However, a detailed study of the application of high-power microwave-assisted comminution is lacking. In this paper, the microwave heating behaviour of a volcaniclastic kimberlite (VK) was investigated at both the bench and pilot scales. Firstly, to elucidate the heating mechanisms, permittivity measurements were combined with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies. Secondly, bench-scale microwave (BMW) testing confirmed that the VK was very microwave responsive with significant macrofracturing, especially at a coarser particle size. Thirdly, preliminary pilot-scale microwave processing was done in both batch (BP) and continuous (CP) manners. The BP tests experienced macrofracturing, while the CP tests did not. These results demonstrated the importance of residence time and hence specific energy input. Fourthly, timed SAG mill grinding tests were performed on the following samples: as-received (AR), BMW, BP, and CP. Both the particle size distributions (PSDs) and the quantity of fines (<850 μm) were determined. Compared to the AR sample, the BMW and the BP samples generated more fines, while the CP sample yielded a coarser PSD. Thus, the amount of fines generated was related to the specific energy input. Finally, more research is planned both to develop an improved understanding of the mechanisms and to enhance the process at the pilot scale.

Keywords: Comminution, Energy, Kimberlite, Microwaves, Permittivities, Pilot-Scale, TGA/DSC

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Ron Hutcheon