Separation of azeotropic mixtures : tools for analysis and studies on batch distillation operation

Abstract

Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system.

For the development of separation processes for azeotropic mixtures, there is a need for insight into the fundamental phenomena of nonideal and azeotropic phase equilibria. This thesis includes a detailed survey on azeotropic phase equilibriumdiagrams of ernarymixtures. Diagram analysis is shown to be an efficient tool for prediction of feasible separations. As a simplifying concept it is proposed that all feasible structures of ternary azeotropic phase equilibrium diagrams can be qualitatively represented by a few elementary cells of which only four have so far been reported to exist. This greatly reduces the complexity of azeotropic istillation analysis and is a key to a simple evaluation of the possibilities and limitations of azeotropic mixtures separation.

Insights gained from continuous azeotropic distillation is extended to the operation of batch distillation with focus on the dynamics and control of multivessel and extractive batch distillation as processes for separating azeotropic mixtures. Practical implications of this renewed insight for the fine- and specialty chemical industries are given in the concluding pages of the thesis.