Measuring the effect of breakage mode and top size on coal liberation using the RhoVol densimetric analysis machine

Coal from the Waterberg coalfield is associated with high mineral that necessitates the need for beneficiation to improve the grade. Comminution is usually employed for ore processing and the liberation of valuable coal macerals from the gangue. In this study, the effect of breakage mode and top size on coal liberation was investigated using the RhoVol densimetric analyser. RhoVol densimetric analysis show that subjecting the 16 mm feed sample to either compressive or impact breakage to top size 12 mm had little effect on the liberation of clean coal products of RD <1.4. Size reduction to top size 8 mm significantly increased the mass yield of clean coal products to 14.4% for compressive breakage and 17.9% in the case of impact breakage. A substantial increase in the mass yield of clean coal products was also observed when the top size was reduced to 6 mm for both breakage modes. Particle breakage to top size below 6 mm, i.e. to top size 4 mm had no significant effect on the mass yield of clean coal products for both breakage mechanisms. For both breakage mechanisms, top size reduction decreased the number of near-dense particles while the quantity of liberated middlings and clean coal products increased. PSD analysis show that impact breakage was more effective in the reduction of coarser agglomerates to finer particles as compared to compressive breakage. Compared to compressive breakage, impact breakage was more effective in the liberation of the coal and improved the mass yield of clean coal products.