NONIDEAL MULTICOMPONENT DISTILLATION - USE OF BIFURCATION-THEORY FOR DESIGN

A method for the design of distillation systems for nonideal multicomponent mixtures is described, offering an alternative to extensive performance simulations. The basis is an analysis of the pinches or "fixed points" in the model equations and the results are widely applicable because approximations such as constant volatilities and ideal solutions are unnecessary. Tangent pinches are represented naturally as turning points in the diagram of pinch composition vs. reflux ratio, giving a basis for designs that alleviate the effects of tangent pinches in certain nonideal mixtures. An efficient computational approach for design is demonstrated in examples for homogeneous liquid mixtures, containing as many as four components, with and without azeotropic behavior. The results are in excellent agreement with detailed performance simulations.