Improving column flotation of oxidized or ultrafine coal particles by changing the flow pattern of air supply

This paper proposes a simple method to improve the flotation performance of oxidized or ultrafine coals, that is, use of a solenoid valve to change the flow pattern of air supplied to a flotation column with a bubble diffuser/sparger. In the present work, the flotation tests were carried out at semi-continuous mode using a laboratory-scale flotation column to upgrade a coking coal in the absence of collector. An investigation of the effect of the frequency of oscillatory air on the flotation performance found that the preferred frequency was around 36 Hz. Further flotation tests for the coking coal with oxidation or without oxidation, at fine and ultrafine size fractions, were carried out with oscillatory air supply at 36 Hz, and the obtained results were substantially better than their counterparts with steady air flow.