Some comminution experiences of an industrial mixed sulphide ore in a pilot plant

The performance of an industrial grinding-classification circuit has recently been investigated. The aim was to obtain a screw classifier overflow with dmax < 150 mm and d50 @ 50 mm with small proportions of ultrafines, to be further treated using highly efficient flotation techniques. The performance was unsatisfactory especially because classifier efficiency achieved at the most 54.5 %, with imperfection of 0.71 and a significant proportion of >150 mm grains with dmax = 400? mm and of < 10 mm grains reporting in the overflow. Therefore, a complete overhaul of the entire plant set up was required, in particular, the perform-ance of the grinding-classification circuit, which leaves room for improvement. This paper is con-cerned with the results obtained from a systematic experimental investigation carried out in a pilot plant, comprising a ball mill and screw classifier, varying the different influencing parameters. We achieved a classification efficiency 66.7 ¸ 70.4 %, an imperfection 0.42 ¸ 0.48, a classifier overflow with < 10 mm ~13 %, dmax @180? mm, >150 mm 0.1 ¸ 0.2 %. Pilot plant energy consump-tion was 8.10 kWh per t treated, of which, on average, 7.94 kWh/t with respect to industrial grind-ing section. Further improvement in the performance of the pilot plant grinding section can be probably achieved replacing the screw classifier with a hydrocyclone.