An efficient, general method for computation of countercurrent separation processes with axial dispersion

Abstract

Abstract A calculational method is proposed for the simulation of steady‐state, multisolute, countercurrent extraction with axial dispersion. The method provides for complex chemical‐equilibrium and phase‐equilibrium relationships, and accounts for the individual resistances of the liquid phases in the calculation of mass‐transfer rates. The solution procedure follows that developed by Newman (1967, 1968) for systems of simultaneous, second‐order difference equations. Three example problems are solved to demonstrate the efficiency and flexibility of the method. These include (1) an example from McSwain and Durbin (1966), (2) calculation of axial‐dispersion and mass‐transfer parameters from experimental data for the extraction of acetic acid from water by a tertiary amine in an RDC extractor, and (3) simultaneous extraction of solutes that interact in an acid‐base complexing reaction at the liquid‐liquid interface. The examples all assume that extraction is governed by interphase mass‐transfer rates and cell‐wise backmixing; however, the method is also applicable to equilibrium‐stage separators, separators described by the diffusional model of axial dispersion, and other countercurrent separation processes.