Cfd simulation of bubble-particle collisions in mineral flotation cells

The efficiency of the flotation process depends highly on the initial conta ct between the air bubble and the mineral particle. To enhance this contact , flotation cells are designed to achieve good miring between the suspendin g solids and the dispersing air. CFD simulation of flotation cells provides an opportunity to analyse the influence of variations in design features a nd operating conditions on the performance of flotation cells. A laboratory flotation cell designed by CSIRO Minerals and a cylindrical tank fitted wi th a Rushton turbine used as a flotation machine have been modelled. The im peller and cell geometries have been set lip using multi-blocking and slidi ng mesh techniques. Complex two-phase flow fields within the cells are pred icted. Three-dimensional profiles of the turbulence dissipation rates and v olumetric fraction of the air are also obtained. These form the basis for d etermining the number of bubble-particle collisions per unit time and unit volume. These profiles al-e important for locating positions within flotati on 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. (C) 2000 Elsevier Science Ltd. All rights reserved.