Instantaneous bond number for a particle detaching from a bubble

In almost all mineral flotation systems the particles and bubbles are brought into contact with each other under turbulent flow conditions which although beneficial in promoting particle-bubble collisions, at the same time increase the probability of particle detachment. Often the detachment of a particle is described in terms of a modified Bond number (expressed as ratio of attachment force to detachment force) greater than 1.0 however very few studies include attachment force in the numerical modelling. Acknowledging the dynamic interaction of bubble-particle aggregate in an actual flotation system, in this work, a dynamic model of the particle motion on the bubble interface was developed based on Schulze's theory considering contributions from gravity, buoyancy, pressure force, capillary force and the fluid drag. The purpose of this modelling was to check the consistency of the particle detachment criterion at Bond number greater than 1.0. Transient magnitudes of both the attaching and detaching forces were presented and the resulting temporal variation of the Bond number was reported. It was found that during the process of particle motion, although the Bond number exceeded the limiting value of 1.0, the particle still remained attached to the bubble interface. It appears that the criterion holds good only for a steady state case when the Bond number remains less than 1.0 and not for a dynamic case where the Bond number may exceed 1.0. (C) 2015 Elsevier B.V. All rights reserved.