Entrainer selection rules for the separation of azeotropic and close-boiling-temperature mixtures by homogeneous batch distillation process

Batch distillation of nonideal mixtures usually produces the azeotropes oft en associated with those mixtures. Among various techniques available to br eak azeotropes, azeotropic and extractive distillation processes have a pla ce of choice. They rely upon the selection of a suitable entrainer. Entrain er screening is therefore a key step for the synthesis and design of these processes. From an analysis of all ternary residue curve maps under assumpt ions of a large number of stages and total reflux/reboil ratio, we devise i n this paper a complete set of rules for the selection of a suitable entrai ner enabling the separation of minimum- and maximum-boiling azeotropic bina ry mixtures and close-boiling-temperature binary mixtures. These rules comp lete previously published rules and expand by many times the set of entrain er alternatives previously considered. Feasible batch distillation processe s can always be obtained considering two batch task sequences using rectifi er and stripper configurations. The effect of distillation boundary curvatu re on the selection of entrainers is analyzed, and in this case, a sequence of up to a three batch distillation configurations must be used to separat e the original mixture components. Several practical examples are shown to illustrate the application of the defined rules in each studied case.