Steady state modeling of perforated plate extraction columns

A linear steady state model is developed for perforated plate liquid–liquid extractors conducting a slow pseudo first order reaction in the extract phase. The model assumes complete mixing of the continuous phase on each individual stage and plug flow of the uniformly sized dispersed phase droplets. An analytical relationship is developed to relate the achievable purification within a given number of actual plates in terms of three dimensionless parameters which are the extraction factor, a mass transfer rate factor, and a reaction rate enhancement factor. The developed model enabled the expression of the effect of the mass transfer and extraction factors on the overall cascade efficiency in the case of physical extraction and to demonstrate the qualitative and quantitative implications of the enhancing chemical reaction. It is also applicable in the analysis of the steady state control of the extract and raffinate product compositions in an existing column. In this case, the operating range constraints arising from the non-linear hydrodynamics relating the above three dimensionless parameters to the phase flow rates have to be considered.