Holdup of dispersed phase in a mixer-settler extraction column

Holdups in a stirred liquid-liquid dispersion were measured in a single-stage mixer-settler column equipped with a lifter turbine impeller. There was a large difference in dispersed phase holdup between the local positions above and below the impeller. The data of holdup below the impeller are described by a model based on a dispersed-phase transfer due to the holdup difference, those of holdup above the impeller by the relative velocity between the dispersed and the continuous phases. The transfer coefficient of the dispersed phase is given as a function of the agitation speed, the relative velocity being correlated with the agitation speed, the interfacial tension and the density difference between the phases.