A new method for mathematical modeling of a distillation operation from non-equilibrium approach has been studied. The primary purpose of the study was to develop a model to simulate the mechanism of mass transfer between a continuous phase and the bubbles of a dispersed phase in a distillation column. The second major purpose of this work was to utilize and test the model of estimating the tray efficiency.

Distillation was considered to be purely a mass transfer process, where the less volatile component is transferred from vapor to liquid phase, and the more volatile component from liquid to vapor phase. The theoretical analysis of mass transfer consisted of (1) convective mass transfer during bubble formation and (2) unsteady-state molecular diffusion of bubbles to the continuous phase. In a plate column, plug flow was assumed as the liquid flow pattern across the plate, from the submerged inlet weir to the overflow outlet weir. The material and energy balances were modeled to a section perpendicular to the direction of liquid flow on the plate.

The model was used in studying the following: (1) a binary separation using a one-stage column having a single-bubble cap; (2) a binary separation in a multi-stage column with a single-bubble cap; a binary separation in amulti-stage column with a given multi-cap arrangement; and a ternary separation in a multi-stage column with two bubble caps. The comparisons of the model predictions, with the data obtained from published literature, showed that the model can successfully simulate distillation operations.