Effect of system properties on the performance of liquid-liquid extraction columns—1: Packed column

Abstract

Mean drop size, fractional hold-up of dispersed phase, and axial mixing have been determined in a 72 mm dia. packed column, packed with 8 mm glass Raschig rings, using the systems toluene-acetone-water and MIBK-acetic acid-water, in an attempt to assess the effects of the solute transfer processes on column operation. For the MIBK-system, where the packing size corresponded to the normal recommended conditions d p > d FC (packing size greater than the critical size of packing), solute presence and the direction of solute transfer was found to affect drop size, fractional hold-up and the axial mixing in the dispersed phase appreciably, in a manner which was consistent with either suppressed or enhanced coalescence characteristics according to the appropriate changes in solute system. For the toluene system, however, with the packing size corresponding to the condition d p < d FC, the drop behaviour was dominated by the action of the packing void spaces and mean drop size was independent of solute presence and direction of transfer. In both cases, axial mixing in the continuous phase was independent of solute effects, except in so far as these changes modified hold-up of the dispersed phase.