Liquid-dispersed contactors backmixed

The determination of the driving force for the interfacial mass transfer is very difficult in extraction columns since no pure plug flow exists within the column This is one of the most important differences between gas-liquid and liquid-Uquid contactors. Because of the small density differences in liquid-liquid systems there exists a relatively high rate of axial backmixing of dispersed as well as of continuous phase. Backmixing reduces the concentration differences along the column height. 

Juvekar and Sharma (50) only compared their results with those of Mashelkar (58) but found good agreement. However, unlike packed column, it is exceedingly difficult to accept the ideal flow pattern of Table 4 for many bubble column applications. Indeed, the backmixing in the liquid phase is unavoidable and it usually reduces the contactor performance. Many authors (7,59-64) have employed the axial dispersion model for the liquid phase -in some cases the gas phase too. One of the most sophisticated design procedure was described by Deckwer (63,64) who showed that... 

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