Vapor Liquid Equilibrium (VLE)

The equilibrium between the liquid and vapor phases of the system to be subjected to distillation is represented by vapor liquid equilibrium (VLE) diagram. Distillation columns are designed based on boiling point properties in the mixture being separated. Thus, the size particularly height of distillation column are determined by VLE data for the mixture.

The above figure shows binary mixture that has uniform vapor liquid equilibrium that is relatively easy to separate.