Liquid-liquid Extraction Studies in a Pilot Scale Agitated Column

Abstract

A study has been made of the hydrodynamics and mass transfer characteristics of the Rotating Disc Contactor. The literature relating to this extractor and relevant phenomena, e.g. droplet break-up and coalescence, single drop mass transfer, axial mixing and phase inversion/flooding, has been reviewed. A 450 mm diameter, fourteen compartment R.D.C. was designed and operated with the system kerosene-acetone-water over a range of practical rotor speeds. The results were compared with those from a modified, existing 101 mm diameter R.D.C. The time to reach steady state varied with operating parameters and was approximately equal to the time taken for a total flow of two and a half times the column volume. Holdup of dispersed phase varied in an axial as well as a radial direction. Nearly equal drop sizes were generated at equal energy per unit volume in the two columns. Flooding rather than phase inversion defined the limiting capacities with the chosen system in both columns. Mass transfer efficiency was expressed in terms of overall coefficients. Drop size increased with mass transfer from kerosene-acetone (dispersed) to water (continuous) phase in both columns. Mathematical models were derived to determine: (a) Column diameter, and hence geometry, from data obtained on a pilot scale using a similar system, or from data with any system. (b) Column height, for large columns from data obtained on a pilot scale. These models were incorporated into a recommended design procedure.