PERFORMANCE OF JET PLATES IN PULSED LIQUID-LIQUID EXTRACTION COLUMNS.

Abstract

Jet plates with elevated rims around their openings are assumed to improve the performance of pulsed extraction columns. A comparison with conventional plates was carried out in a pilot-plant size column with the system of water, toluene and acetone. Hold-up, drop size, backmixing and axial concentration profiles in both phases were measured simultaneously. Mass transfer coefficients were evaluated from measured data by minimising the deviations of measured concentration profiles from model prediction using standard and open-end stagewise backflow models. Equations from the literature for prediction of drop size, hold-up and backmixing coefficients were modified by recalculating the empirical coefficients from recent data to enable quantification of trends and replacement of missing values. The transfer coefficents correlated against actual velocity of the dispersed phase rised to a power between 0.6 and 1, the influences of pulsation velocity, drop size and actual velocity of the continuous phase being by an order of magnitude smaller. The magnitude of the transfer coefficients was comparable to those measured earlier under similar conditions in a reciprocating plate extraction column where, however, the mentioned additional influences were more important.

A strong influence of mass transfer direction on hydrodynamic parameters was observed. Transferring acetone from continuous water into dispersed toluene, the jet plates flooded at higher specific loading and the transfer coefficients were above those observed on conventional plates. In the opposite direction no significant differences were found.