Flotation of coarse coal particles in a three-phase gas-solid-liquid fluidised bed

The role of bubble and flotation reagents in the recovery of coal particles in three-phase gas-solid-liquid fluidised beds is investigated in this study. The flow rate and flotation yield in the presence or absence of bubbles were determined. The effect of bubbles attached to lower density and larger coal particles experiencing fluidised bed flotation is also discussed and validated by captured images. It is found that upward bubbly flows can significantly decrease the superficial velocity of liquid required to keep particles suspended and facilitates the capture of particles by bubble. The presence of a flotation collector improves this process and a decreased superficial flow velocity creates a relative quiescent hydrodynamic condition that enhances coarse particle-bubble aggregation and weakens the detachment of coarse particles from bubbles. The results indicate that flotation in a three-phase fluidised bed is a promising method to improve coarse coal particle separation.