INTERNAL RECIRCULATION AND MIXING IN FLOTATION COLUMNS

The effect of column height and internal baffling on the mixing of the liquid phase inside the collection zone of flotation columns was inve stigated in this work by RTD and the mixed cells-in-series-with-backfl ow and the axial dispersion models were used to interpret the experime ntal results. The increase in column height subtly affected the mixing process, by influencing the transition from plug-flow-like to mixed f low conditions. The backflow was calculated in all cases as approximat ely 10% of the net incoming liquid flow, and 4 to 14 perfectly mixed c ells were found to represent the collection zone liquid-phase RTDs, wi th the higher number of cells corresponding to high liquid and low gas flowrates. Vertical baffles were found to enhance rather than attenua te the collection zone mixing.