Backmixing in Karr Reciprocating-Plate Extraction Columns

A study of backmixing in the continuous phase has been presented for a 50 mm diameter Karr reciprocating-plate extraction column using the two-phase system kerosene/tributyl phosphate (continuous)-phenol-water (dispersed). The column was operated in the emulsion region with nylon plates of 45% open area. Backmixing was determined using the unsteady-state tracer injection technique in which tracer concentrations at two distinct locations in the column were measured. Operating parameters, including frequency and amplitude of agitation and solvent and aqueous-phase flow rates, have been studied over a range of values to investigate their influence on the extent of backmixing in the continuous phase. A model based on the "two-zone approach" model used for predicting backmixing performance in a pulsed perforated-plate column (Prvcic, L. M.; Pratt, H. R. C.; Stevens, G. W. AIChE J. 1989, 35, 18451855) has been refitted for the current data to predict the effects of continuous-phase backmixing in a Karr reciprocating-plate column. Results indicate that the backmixing coefficient can be predicted within 13% using this model.