GAS DISPERSION AND BUBBLE SIZE DISTRIBUTION IN DUAL IMPELLER STIRRED VESSELS

摘要

Bubble size distribution in aerated vessels with different dual impellers are determined by an improved photoelectric capillary method. The results of measurement show that characteristics of bubble size distribution curves can be used to predict the value of transitional rotation speed as it was observed in a single Rushton turbine system. In the circulation region between two impellers, the characteristics of gas dispersion and bubble size distribution are very similar to the upper circulation region of the results of Smith et al. (1987) in the single impeller system. However, more coalescence effect was found in the system I due to its two radial flow impellers. In the upper recirculation region, the performance of gas dispersion of the dual turbine system does not differ so much from the middle recirculation region except the average size of bubbles is larger than that of the middle recirculation region due to the coalescence effect of the upper impeller and rising bubble flow near the wall and baffle area. In the same region of the system with one Rushton impeller and one axial flow impeller, only slight effect of the increase in N on the average size of the bubble is observed. [References: 8]