Abstract
An experimental study was performed on the flow regimes for gas-liquid flow in a throat, dispersed bubble size and gas hold-up for the bubble column employing an ejector as a gas distributor. The flow regimes in the throat are classified into four regions (slug flow, annular flow, bubble flow and jet flow) and the flow regime map is presented by plotting the ratio of gas to liquid flow rate, G/L against the Froude number based on the liquid velocity through the throat uLT, Fr (=uLT2/gDT). Dependencies of bubble size distribution, gas hold-up, εG, and volume surface mean bubble diameter, dBυs, on Fr and G/L markedly change near the critical Froude number Frc. In the slug and annular flow regions, Fr≤Frc, bubble size distribution is broad and its standard deviation increases with increasing G/L and εG nearly equals the gas hold-up in the bubble column at the same gas flow rate, εG0. In the bubble and jet flow regions, Fr> Frc, small bubbles of 14 mm in diameter are uniformly dispersed in the column, and εG increases and dBvs decreases with increasing Fr and/or decreasing ratio of nozzle-to-throat diameter, DN/DT. The mean bubble diameter and the gas hold-up for each region classified above are correlated with Fr, G/L and DN/DT.
