MORE ON MIXING OF VISCOUS LIQUIDS IN BUBBLE COLUMNS*

Four aspects of liquid-phase mixing in semi-batch bubble columns operating with viscous and non-Newtonian liquids were studied: the influence of the central plume on mixing rate, the velocity profiles, the gas hold-up, and the back-mixing. Three regimes of the bubble-induced mixing were identified and associated with the mode of the central plume. One of the modes, due to a moderate gas rate, was found to lead to optimal mixing. Also the gas hold-up and the degree of back-mixing were associated with the central plume mode. A model of the velocity profile proposed earlier was now modified and extended to apply also to the turbulent regime.