Some aspects of rate-based modelling and simulation of three-phase distillation columns

The application of the bate-based approach to the dynamic and stationary mo delling of three-phase distillation columns is presented. The main problem can be seen in finding adequate models for the mass and heat transfer over phase interfaces to be utilised in the Maxwell-Stefan equations. While for the vapour-(continuous) liquid interface, there are a number of methods and data available, the interface between continuous and dispersed liquid phas es has not been studied for the case of distillation processes. A reasonabl e alternative approach to modelling of a three-phase distillation column ca n be found where the liquid-liquid interface is treated as equilibrium. The adequacy of this modification is supported by phenomena observed on distil lation trays, e.g. strong agitation of liquid phases. The resulting combine d non-equilibrium and equilibrium model is compared to the classical equili brium model and also to experimental data for ethanol-water-cyclohexane sep aration in a number of examples. (C) 2001 Elsevier Science Ltd. All rights reserved.