An exergy balance equation which relates to heat and mass transfer on distillation stages was derived from the theory of non - equilibrium thermodynamics. This equation was used to analyze an ethylene distillation tower

and the result checked satisfactorily with that of the equilibrium thermodynamic exergy analysis. In a multiphase discontinuous system

each phase may be considered as a subsystem and all subsystems are separated by interfaces. With appropriate hypotheses

the equation of exergy loss relating to energy and mass transfer through interfaces may be expressed as follows: Thus

profound insight into distillation process could be gained to provide ideas for further improvement of the distillation scheme.