Hydrodynamics of gas-agitated liquid-liquid extraction columns

Abstract

Although the non-agitated extraction columns (spray column, packed column, perforated plate column, sieve plate column, etc) can handle high flow rates and are simple and cheap, there have been relatively few applications of these columns because they suffer from serious backmixing of the continuous phase. It was shown that the backmixing is reduced when the spray column is operated with dense packing of drops. Another way of increasing the efficiency of a non-agitated extraction column is to introduce an inert gas (air, nitrogen, oxygen) as a mixing agent in the two-phase liquid-liquid (L-L) system. This method of energy introduction increases the turbulence within the new three-phase gas-liquid-liquid (G-L-L) system, which causes an improved dispersion of droplets, and, consequently, a higher dispersed phase holdup and therefore a great mass transfer area. The present study reports the hydrodynamics in the non-agitated extraction columns, as well as the axial dispersion for the two- and three-phase systems.