Coal Preparation » Fine Coal
This report provides detailed information on coal flotation with oscillatory air supply at laboratory scale. The oscillatory air flow was generated from steady air flow by using two different devices. The majority of the coal flotation tests were carried out for different coking coal samples using a semi-continuous test rig with a column 5 cm in diameter and 135 cm long equipped with a conventional gas diffuser/sparger. It was found that use of oscillatory air supply to replace steady air flow would lead to increased product yield by at least 14 percentage points with more significant improvement achieved for oxidised coal and ultrafine coal. Use of oscillatory air supply would also increase plant throughput capacity, reduce reagent costs, and improve tolerance to variance in water quality. A cost-benefit analysis found that use of oscillatory air flow could potentially lead to increased profit. It is recommended that in-plant trials be carried out to corroborate this finding.
Use of oscillatory air supply to replace steady air flow found no difference in the batch-mode mechanical flotation of coals.
This project advanced the fundamental understanding of the effect of different air flow patterns on column flotation of coals. Compared to steady air flow, oscillatory air flow would result in better gas dispersion, higher gas holdup, higher foam stability, and less axial mixing of fluid inside the flotation column.