Radial liquid velocity distribution in an external-loop airlift column with a tapered riser

Radial and axial liquid velocity distributions in the tapered riser were in vestigated theoretically and experimentally. The liquid velocity distributi ons were computed by solving the Navier-Stokes equation numerically based o n a modified mixing-length theory. Both radial and axial components of liqu id velocity were taken into account. As a result, we found that the radial velocity component was much smaller than the axial velocity component. For a cylindrical column, which means no tapered section, a simplified solution was obtained. The simplified solution was found to agree well with the rig orous numerical solution even in the tapered riser. To confirm the validity of the present hydrodynamic model, the velocity distributions in the taper ed riser were measured by an electric probe method using KCI solution as a tracer. The measured velocity distributions agreed with the computed ones, except in the vicinity of the bottom of the tapered riser at high gas flow rates.