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 modelling 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 phases has not been studied for the case of distillation processes. A reasonable alternative approach to modelling of a three-phase distillation column can be found where the liquid–liquid interface is treated as equilibrium. The adequacy of this modification is supported by phenomena observed on distillation trays, e.g. strong agitation of liquid phases. The resulting combined non-equilibrium and equilibrium model is compared to the classical equilibrium model and also to experimental data for ethanol–water–cyclohexane separation in a number of examples.