Gas Dispersion in an Agitated Vessel Equipped with Large Impeller

Studies on bubble sizes in an aerated vessel have been conducted by several investigators for a Rushton turbine, but have rarely been conducted for large impellers developed recently. In this work, we tried to measure the bubble sizes in an aerated vessel agitated by a large impeller, which is a Maxblend or Hi-F Mixer, adding to a dual Rushton turbine as a standard configuration, using a high speed camera. As a result, it was found that there are not significantly large differences in the average bubble sizes for these three impellers. The average bubble sizes for the three impellers decrease almost proportionally with an increase in rotational speed and increase slightly with an increase in gassing rate, which corresponds to the results reported in the previous work. However, the bubble sizes at different axial positions for the two stage Rushton turbine decrease with an increase in the height. On the other hand, those for the Maxblend and Hi-F Mixer are approximately constant independent of axial position, which may indicate that large impellers can disperse almost uniform size bubbles throughout the vessel.