UNIFIED CORRELATIONS FOR THE PREDICTION OF DROP SIZE IN LIQUID-LIQUID-EXTRACTION COLUMNS

Correlation of the average drop size in eight different types of extra ction columns, namely, rotating disk, asymmetric rotating disk, Kuhni, Wirz-II, pulsed perforated-plate, Karr reciprocating-plate, packed, a nd spray columns, is presented. A unified correlation for mechanically agitated columns consists of a two-term additive model involving the ratio of interfacial tension to buoyancy forces at low agitation and t he theory of isotropic turbulence at high agitation. This model has fu rther been extended to another two-term correlation, wherein the compa rtment height and gravitational constant have been introduced to adequ ately allow for the effect of various variables on the drop size. Only in the case of mixer-settler type Wirz-II columns was the drop size f ound to be affected by the dispersed-phase holdup. The drop size in un agitated packed columns is determined simply by the ratio of interfaci al tension to buoyancy forces, the constant of proportionality in the correlation being a function of the physical properties. The treatment accorded to spray columns is similar to that used for agitated column s, except that the drop Size at high nozzle velocities (jetting region ) is controlled by the ratio of interfacial to kinetic energies.