3.2.5. Effect of agitation speed
The agitation speed is varied to determine its effect on the mixing time in the tank agitated by RDT, HCDT and PBTD. The impellers are all located at T/3 and the holdup of the dispersed oil phase is 10%. As shown in Fig. 6, the mixing time decreases obviously with an increase in impeller speed as in the case of liquid–liquid dispersion. In the presence of aeration, less energy is available for liquid phase mixing and circulation compared with the ungassed situation at the same impeller speed, which leads to the mixing time curves for the gas–liquid–liquid system lie above that for the liquid–liquid system.