Computational Studies of the Dynamics of Disperse Gas-Liquid-Solid Mixtures

Froth flotation, where buoyant bubbles are used to separate hydrophobic particles from hydrophilic ones in 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, fully resolved numerical simulations, where the bubbles are followed using a front-tracking/finite volume method and the solid particles are included as rigid regions of different density, are used to examine the rate of capture of hydrophobic particles by a buoyant bubble. Heavy hydrophobic particles colliding with a gas bubble attach to the bubble and are carried with it as it rises and here a single bubble in a periodic domain containing several particles is followed for a long enough time for the bubble to gather most of the particles. The effect of the volume fraction and size of solid particles, and the deformability of the bubble on the rate of accumulation of particles on the bubble is examined for modest bubble Reynolds numbers. Preliminary results for several bubbles rising through a suspension of both hydrophobic and hydrophilic particles are also shown.