MEASUREMENT AND ANALYSIS OF SMALL BUBBLE-SIZE DISTRIBUTIONS

Bubble size distributions were measured at different depths in a 1 m d iameter by 2 m length column cell test rig fitted with Cominco sparger s. A population balance model has been used to describe the distributi ons over the length of the column cell and to investigate the extent t o which bubble coalescence occurs. The model adequately predicts the m ean bubble size and the bubble size distribution due to bubble growth only, at positions up to 40 cm above the point of injection. The model is based upon a coalescence efficiency and variable relative velociti es of the coalescing bubbles, and it was found that a constant coalesc ence efficiency was applicable for small bubble size distributions. Th e deviations from the model at points further up the column indicates that the coalescence mechanism described by the model is not adequate for large bubble size distributions which behave differently from smal l bubble size distributions.