CDF simulation of bubble-particle collisions in mineral flotation cells

The efficiency of the flotation process depends highly on the initial contact between the air bubble and the mineral particle. To enhance this contact, flotation cells are designed to achieve good mixing between the suspending solids and the dispersing air. CFD simulation of flotation cells provides an opportunity to analyse the influence of variations in design features and operating conditions on the performance of flotation cells. A laboratory flotation cell designed by CSIRO Minerals and a cylindrical tank fitted with a Rushton turbine used as a flotation machine have been modelled. The impeller and cell geometries have been set up using multi-blocking and sliding mesh techniques. Complex two-phase flow fields within the cells are predicted. Three-dimensional profiles of the turbulence dissipation rates and volumetric fraction of the air are also obtained. These form the basis for determining the number of bubble-particle collisions per unit time and unit volume. These profiles are important for locating positions within flotation cells where the initial contacts between bubbles and particles are made. Collision rates in the CSIRO flotation cell and the stirred tank have been compared. As flotation machines, the CSIRO cell is superior because of the higher maximum collision rate in comparison to the stirred tank.