Mass transfer into highly viscous liquid circulated forcibly in bubble column with draft tube

To promote liquid circulation in an airlift bubble column with an inner dra ft tube, a propeller was set in inside the draft tube. By revolving the pro peller, the liquid is forced to flow upward in the draft tube and to flow d own in the annulus. For a bubble column of constant diameter and a highly v iscous liquid, the effects of the diameter of the draft tube and the revolu tion rate of the propeller oil gas holdup, liquid circulation rate and volu metric mass transfer coefficient were investigated experimentally. In the pressure drop throughout the circulation of highly viscous liquid in the internal airlift bubble column, the pressure drops at the walls of the draft tube and in the annulus were much larger than the other pressure dro ps. By the combination of previous dimensionless empirical equations, the avera ged volumetric mass transfer coefficient in the whole bubble column was est imated relatively well. The additive liquid stream generated by the revolution of the propeller pro moted the increase of gas holdup in the annulus and the increase of volumet ric mass transfer coefficient.