Particle size dependence in flotation derived from a fundamental model of the capture process

Abstract

A flotation model is described wherein particle collection is considered to occur by particle-bubble collision followed by the particle sliding over the bubble during which attachment may occur. Collision is quantified by a collision efficiency E C. The existing model for E C is extended by including particle inertia. Attachment is quantified by an attachment efficiency E A calculated as the fraction of particles which reside on the bubble for a time greater than the induction time. These calculations use recent data on the liquid velocity distribution over the upper half of rigid spheres. Collection efficiency E K is given by E K= E C· E A. Detachment is not considered. The model is examined and shown to agree with much experimental data. For example the maximum observed in recovery vs particle size ( d p) can be explained as E C increases with increasing d p, while E A decreases. The decrease in selectivity at fine sizes is in accord with the model result that for very small particle sizes E A is large even for long induction times. A decrease in bubble size does increase E K but does not improve selectivity. A high particle density (> 5 g cm −3) is shown to cause a sharp peak in recovery vs size and a decreased maximum size of flotability. Finally, the effects of bubble concentration are explored.