98/01864 Pilot-scale studies using a hydrocyclone and froth flotation for the production of beneficiated coal fractions for improved coal liquefaction : Cloke, M. et al. Fuel, 1997, 76, (13), 1217–1223

Abstract

The air-sparged hydrocyclone (ASH), known as a new type of efficient flotation apparatus, was used in grinding-classification circuit to control the overgrinding of hydrophobic materials after some modifications by the authors. The overgrinding of hydrophobic materials, resulted from the fact that the hydrophobic materials have higher density than the hydrophilic materials, has been known as a knotty problem. The modified ASH is designed with a relatively small length/diameter ratio, and a thick vortex finder wall is introduced, and the annular underflow opening between a pedestal and the cylindrical wall is replaced by a wide angle cone apex opening and a horizontal baffle that is positioned above the apex opening. Concentration and classification exist simultaneously in the modified ASH. Sample ore from Hongtoushan Copper Mine was used to investigate the concentration and classification characteristics in the modified ASH. In particular, the effects of design and operation parameters on the copper recovery and enrichment ratio and the classification efficiency in different particle size fractions were considered for a ⊘75 mm modified ASH. From a variety of runs, it can be concluded as follows: (1) the copper enrichment ratio of the finest particle size fraction (−400 mesh) in overflow of the ASH is always larger than 1.0, while those of the other coarser particle size fractions are not all the same; (2) not only is the copper in overflow is enriched by the flotation in the ASH, but also the classification efficiency is improved to some extent by the flotation; and (3) to consider both the concentration and classification in the ASH, the optimum design and operation parameters are different from that in the case of an ASH being just used for flotation, e.g., the ratio of the overflow opening area to the underflow opening area of this modified ASH should be larger than that of the flotation ASH.