The gas holdup ε and the volumetric liquid-phase mass transfer coefficient k_La were studied experimentally in a bubble column with a draught tube and with gas dispersion into the annulus. It has been shown that ε and k_La increase with increasing gas velocity and frothing ability of liquid, while the dimensions of the column have a minor effect on ε and k_La. Based on these observations, empirical equations for ε and k_La are proposed which are applicable to columns with diameters of 0.1-0.3 m.
It was shown also that at the same gas velocity the values of ε and k_La in this column are larger than those in a bubble column without a draught tube, when a liquid with frothing ability is used.