Computational studies of gas-liquid-solid flows in froth flotation*

Froth flotation, where buoyant bubbles are used to separate hydrophobic particles from a slurry and bring them to the top of a tank where they can be skimmed off, is the most widely used mineral separation technique. While many of the processes involved are reasonably well understood, their complex interactions make it difficult to predict the overall selectivity. Here we use fully resolved numerical simulations to examine the interactions of large bubbles with smaller hydrophobic and hydrophilic particles. The bubbles are followed using a front-tracking/finite volume method and the solid particles are included as regions of different density with zero deformation gradient. The Generalized Navier Boundary Condition (GNBC) is used to model the triple-point, for particles sticking to bubbles. We show results for single and several bubbles moving through fluid containing many solid particles and discuss how the various governing parameters, such as bubble size and deformability and the volume fraction of both the gas and the solids affect the rate at which bubbles collect hydrophobic particles. Preliminary results for the formation of particle laden foam at the free surface are also shown.