AN ON-SITE EVALUATION OF DIFFERENT FLOTATION TECHNOLOGIES FOR FINE COAL BENEFICIATION

This paper presents the results of an investigation of the performance of a number of different flotation cell technologies for the benefici ation of fine coal. The work was conducted on-site at the Grootegeluk Colliery in the northern Transvaal province of South Africa, using a p ilot-scale conventional column cell, a pilot-scale Jameson-type cell, and an air-sparged hydrocyclone (ASH). In addition, characterisation a nd conventional batch flotation tests were conducted in the laboratory in the Department of Chemical Engineering at the University of Cape T own. All three units tested on-site demonstrated improved selectivity compared to conventional subaeration flotation. In the column cell, op timum performance could only be achieved at very low throughputs. Subs tantial losses of coal occurred in the coarser size fractions. The Jam eson-type cell was able to operate effectively at about double the thr oughput of the column cell at similar recoveries. Coal recovery in the coarser size fractions was still poor, but better than that of the co lumn cell. The ASH was characterised by a very high throughput, more t han 150 times that of the column cell on the basis of solids capacity per unit cross-sectional area. However, the ASH required more than thr ee times the reagent dosage of the other two units to achieve this. Th e ASH performed particularly well in the recovery of the coarser size fractions, but was less effective than the other cells on the finer si ze fractions. Overall, the best performance for this application was t hat of the Jameson cell, owing to its higher capacity in comparison to the column cell. The high reagent requirement of the ASH makes this t echnology uneconomic in this application.