Research articleImproving the performance of coal flotation using oscillatory air supply

•Column flotation of coals was improved using oscillatory air to replace steady air.•A fluidic oscillator was used to change the air flow from steady to oscillatory.•Gas dispersion, gas holdup, foam stability, and axial mixing of fluid were studied.

Froth flotation is the most widely used method for beneficiation of fine coals. In flotation, the size of air bubbles is an important factor affecting the separation efficiency. The size of air bubbles generated by passing air through a bubble diffuser/sparger can be reduced by changing the air flow pattern from steady to oscillatory. In the present work, coal flotation with oscillatory air supply generated by a fluidic oscillator was investigated and the results were compared with those obtained with steady air flow. The flotation tests were carried out at semi-continuous mode using a laboratory-scale flotation column. The results suggest that use of the fluidic oscillator can lead to substantial reagent cost savings and help improve coal flotation efficiency. Further experiments were carried out to fundamentally understand the effect of different air flow patterns on the flotation performance. Compared to steady air flow, oscillatory air flow results in better gas dispersion, higher gas holdup, higher foam stability, and less axial mixing of fluid inside the flotation column.