A bubble-particle interaction model for flotation combining hydrodynamic and surface forces
Schimmoller, Brian Keith
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It is generally recognized that the recovery of particles from a flotation pulp is controlled by (i) the flotation rate constant and (ii) the residence time distribution of the particles. In the present work, theoretical and experimental analyses have been carried out to develop methods for predicting these parameters from first principles considerations. In order to predict the flotation rate constant, a bubble-particle interaction model has been developed using a dynamic force balance to determine the trajectory of a particle as it approaches a rising air bubble. The trajectory has been used to determine the probability of bubble-particle attachment, from which the flotation rate constant can be readily obtained. The model is unique in that it simultaneously considers the effects of hydrodynamic and surface forces on the interaction between bubbles and particles. Model predictions have been shown to be in good agreement with results from bubble-particle attachment experiments for narrowly-sized coal and silica samples. In the present work, the residence time distribution of particles in column flotation has been examined by conducting experimental tracer tests. These tests have been performed with two tracer materials to characterize mixing for both the liquid and the solids in a single system. The measured residence time distributions have shown that the assumption of equating liquid and solids residence time distributions is inappropriate, except for very small and low density particles. At larger sizes and higher densities, the correction formula advocated by Dobby and Finch (1985) has been shown to adequately predict the solids residence time.
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