New correlations for slip velocity and characteristic velocity in a rotary liquid–liquid extraction column

Abstract

In this research work, the hydrodynamic behavior of a Kühni extraction column has been investigated for determination of slip velocity and characteristic velocity for three different liquid–liquid systems with and without mass transfer conditions and toluene–water system with the presence of silica nanoparticles. The effects of the agitation speed, dispersed as well as continuous phase velocity, and interfacial tension were studied. The findings revealed that an increase in agitation speed and continuous phase velocity led to the reduction of slip velocity while it increased with increasing dispersed phase velocity. More buoyancy and faster upward movement of larger drops accelerate the slip velocity in the dispersed to continuous phase mass transfer condition as compared with the case of no mass transfer. In addition, the slip velocity decreased in the experimental conditions with nanoparticles because of the decrease in Sauter mean drop diameter and the increase in the holdup. Empirical correlations for prediction of slip and characteristic velocities are recommended. The results of the proposed correlations were compared with the experimental data obtained from the literature and the present investigation. Findings of this study demonstrated that the proposed correlations gave accurate predictions for slip velocity and characteristic velocity.