AUTOMATIC SCREENING OF ENTRAINERS FOR HOMOGENEOUS AZEOTROPIC DISTILLATION

Extended rules and an automatic procedure for the determination of the structure of simple distillation residue curve maps for ternary mixtures are described. The procedure makes use of results from directed graph theory and is based on an adjacency matrix representation. Simple distillation boundaries are determined as thermodynamically and topologically consistent connections between the singular points (i.e., azeotropes and pure components) and correspond to the nonzero entries of the adjacency matrix. The procedure requires only a knowledge of boiling temperatures and approximate compositions of any azetropes in the mixture. This is sufficient to uniquely determine the structure of the map in most cases and enables the rapid identification of feasible entrainers. The incorporation of topological and thermodynamic constraints also makes it possible to detect certain inconsistencies in the boiling temperature data. We show three classes of maps of feasible entrainers for breaking minimum boiling azeotropes, with a corresponding column arrangement in each case; one of these is the classic extractive distillation. The method is applied to screen numerous entrainers for the separation of ethanol/water and butanol/butyl acetate mixtures.