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Abstract
A full-scale Microcel™ flotation column was trialled at the BHP Coal Peak Downs Mine and Saraji Mine coal preparation plants for the treatment of 0.5 mm × 0 (−500 μm) coal. By using deep froths and counter-current froth washing, the Microcel™ columns have been demonstrated to achieve substantially lower product ash compared to conventional flotation cells when treating slimes fractions. This paper reports the results of modelling the pulp behaviour in a full-scale Microcel™ treating −500 μm coal. The results suggest that the conventional theory and scale-up design criteria need to acknowledge a very significant degree of mixing when applied to the treatment of coarse ( −500 μm) coal.
The scale-up and design criteria for the Microcel™ are based on the assumption that the material within the cell behaves according to a ‘plug flow’ model. However, with a considerable portion of slurry recycled, a plug flow model conceivably does not agree with the observations or conceptual view of the pulp, and a perfect mixer model, or combination model, should more accurately describe the system.
The results of pulp sampling, tracer tests and on-line logging of differential pressure were used to improve the understanding of the conditions in the Microcel™ when applied to -500 μm coal flotation.