A liquid-liquid extractor model based on UNIFAC

A steady state liquid-liquid extractor model using the UNIFAC group contribution method for phase equilibria has been developed. A heuristic method, which limits the number of stage calculations per iteration to a low number is used, according to the residuals calculated in the previous iteration, the method either selects or rejects a stage for the calculations. With this approach, the same accuracy in results have been obtained at about half the computing time with respect to without use of heuristic method. The model has been applied to simulate staged extractors as well as continuous extractors (plate columns). The model is based on a very robust flash calculation routine and on a versatile package (UNIFAC) for the prediction of thermodynamic properties.