Concentration profiles were determined in both phases

The UNIFAC group contribution model has been utilized for prediction of liquid-liquid equilibrium data of multicomponent aromatics extraction systems from the limited knowledge of binary V-L-E and mutual solubilities. Computational methods have been developed for estimation of the group interaction parameters for all possible combinations of the groups encountered In the process of aromatics extraction using sulfolane, so that it is possible to predict L-L-E data of the actual aromatics extraction systems comprising any number of components. The validity of the prediction method for L-L-E has been tested for three ternary systems: cyclohexane-benzenesulfolane, n -hexane-benzene-sulfolane, and n-heptane-toluene-sulfolane at 298, 323, 348, and 373 K. The predicted values are in good agreement with the corresponding experimental data from the literature for all three systems except near the respective phiit points. This has been demonstrated for a typical six-component aromatics extraction system at 373 K.

A generalized solution is presented of the transient backflow model equations, for use in determining the backmixing ratio for stagewise extraction columns from pulse tracer injection data obtained over a wide range of operating conditions. Results obtained with this model agreed with those given by earlier solutions for restricted boundary conditions. The generalized solution was also used successfully to predict the tracer response for a Kiihni column in which a tracer pulse was injected into the end stage and samples were withdrawn from two downstream stages. It was observed that numerical instability can occur in all solutions a t short response times for low values of the backflow ratio, a, and a relatively large number of stages.