Entrainment probability of coal particle by bubble trailing vortex in coal flotation

Abstract

Understanding the effect of bubble trailing vortex on particle trajectory is an important precursor for reducing the ash content of coal flotation. Using a high-speed motion acquisition system, we investigated the coal particle trajectory around the cylinder. Two typical trajectories of coal particles around the cylinder were measured. Some particles settled down out of the trailing vortex region while some ones flowed up. The effects of particle density, particle size and fluid flow velocity on the entrainment probability was analyzed. The entrainment probability gradually increased as the coal particle size decreased, increased as the particle density decreased, and increased as the fluid flow velocity increased. The entrainment probability obviously increased as the particle flowability increased independently of particle size, and the increase in the entrainment probability mainly concentrated in the range of particle flowability less than 12.5. The flotation of glass beads was conducted. The flotation recovery increased as the glass bead size decreased, which matched well with the predicted entrainment probability. Our results can provide a valuable insight into the development of flotation technology for cleaner mineral flotation.