Liquid-Liquid Extraction in Agitated Contactors Involving Droplet Coalescence and Redispersion

Abstract

Rotary agitated liquid-liquid extractors have been classified in terms of the rate of energy imparted to the dispersed phase, and whether contact is stagewise or differential. In the high energy contactors a droplet coalescence-redispersion mechanism predominates, The literature pertaining to these extractors has been examined and the important phenomena such as droplet break-up and coalescence, phase inversion, mass transfer and backmixing have been reviewed, The prediction of drop sizes and interfacial areas, and the extension of mathematical models from batch systems to continuous ones is discussed. A six-inch diameter sixteen compartment Oldshue-Rushton column was designed and constructed to study hydrodynamics and mass transfer. Cyclic phase inversion, a pseudo-steady state condition, under which stable operation is possible under high dispersed phase loading, was investigated. A design equation has been developed to predict mean drop sizes in the contactor in terms of column geometry, system properties and operating parameters, Mass transfer coefficients were computed, using previously established backmixing correlations. The mechanism of phase inversion in agitated contactors is explained. Conclusions are drawn with respect to phase inversion, flooding, drop sizes and mass transfer coefficients in agitated contactors