The effect of cell hydrodynamics on flotation performance

It is clear that along with gas dispersion characteristics, the energy dissipated by the impeller is process determining in flotation, and its effect on flotation kinetics has been widely studied. However, turbulent conditions inside a flotation cell have usually only been changed by varying impeller speed or air flowrate or both. Therefore, there is a need to investigate not only these variables but also how changes in impeller/stator mechanism size and design, cell aspect ratio and cell design affect turbulence. This should lead to a better understanding of the effect of cell hydrodynamics on flotation performance. The aim of this work was to evaluate the role of flotation cell hydrodynamics on flotation performance in a fully instrumented 3 m3 cell. The cell was operated at a copper concentrator in Australia with different combinations of airflow rates, impeller speeds and sizes and cell aspect ratio providing a wide range of hydrodynamic conditions. An analysis of the flotation cell performance showed that the overall copper recoveries were very similar for the conditions tested. However, by decoupling pulp effects from froth effects it was possible to determine whether the changes made affected the pulp zone and/or froth zone responses. The analysis showed that the overall recovery had the potential to be up to 10% higher if not limited by froth recovery. Comparing the metallurgical performance of the cell with the different hydrodynamic conditions it was found that the collection zone flotation rate was not directly related to overall energy dissipation, as is commonly observed at laboratory scale, where energy is usually only changed by varying impeller tip speed. Results suggest that it is the size of the turbulent zone, rather than just energy input, that affects flotation recovery.