CHARACTERIZATION OF THE DOWNFLOW SECTION OF AN AIRLIFT COLUMN USING BUBBLE SIZE DISTRIBUTION MEASUREMENTS

Bubble size distributions in an airlift column were investigated with an emphasis on the downflow section. Measurements have been made using direct photographic techniques in conjunction with image analysis in a split cylinder airlift column. Information extracted from these measurements includes local gas hold-up, variation of Sauter mean bubble diameter with column length, and liquid circulation velocity. An air-tap water system was studied for purposes of comparison, while effects of electrolyte concentration and viscosity were studied using salt water, and two carboxymethyl cellulose (CMC) concentrations in water, respectively. The effect of energy input was studied by varying air flow rate to produce superficial velocities ranging from 2·59 cm/s to 10·36 cm/s.