1. Separation Columns (Distillation and absorption)
Dr. Kh. Nasrifar
Department of Chemical and Petrochemical Engineering

2. Importance and industrial relevance of azeotropic distillation
• Need for efficient recovery and recycle of organic solvents in chemical industry
• Most liquid mixtures of organic solvents form azeotropes that complicate the synthesis and conceptual design of recovery processes
• Distillation is the most common unit operation in recovery processes because of
its ability to produce high purity products
• Azeotropes make separation impossible by normal distillation but can be also
utilised to separate mixtures not ordinarily separable by normal distillation
• Azeotropic mixtures may often be effectively separated by distillation by adding a
third component, called entrainer
• Thus, knowledge of the limitations and possibilities in azeotropic distillation
is a topic of great practical and industrial interest

3. Terminology
• The methods and tools presented in this lecture also appply for:
− Azeotropic mixtures
− Close boiling systems
− Low relative volatility systems
• Original components A and B: The components that form the azeotrope and need to be separated
• Entrainer: A third component (E or C) added to enhance separation
• Binary azeotrope: Azeotrope formed by two components
• Ternary azeotrope: Azeotrope formed by three components
• Homogeneous azeotrope: Azeotrope where the forming components are miscible
• Heterogeneous azeotrope: Azeotrope where the forming components are immiscible

4. Overview: Azeotropic distillation methods
i) Pressure swing distillation
ii) Hybrid methods (membrane + distillation)
iii) Homogeneous azeotropic (homoazeotropic) distillation
iv) Heterogeneous azeotropic (heteroazeotropic) distillation
v) Extractive distillation