(84d) On Finite Speed of Diffusion Effects on Murphree Plate Efficiency

The McCabe and Thiele method for design of multi-stage binary distillation tray tower includes the following main steps:

Step I: Derivation of Operating Line from Mass Balance

Step II: Representation of Equilibrium Line from

Thermodynamic Models and Experiments

Step III: Mass Transfer Effects lumped into a parameter

called Efficiency

Step IV: Step of the number of stages needed to meet

the desired objectives

The real line can be calculated using the lumped parameter called efficiency. The diffusion from the liquid phase to the interface and from the interface to the bulk of the vapor phase is transient in nature. It has been shown (Sharma,K. R., Damped Wave Transport and Relaxation, (2005), Elsevier, Amsterdam, Netherlands) Fick's law of diffusion can be modified to include a ballistic term without violation of second law of thermodynamics. This way the finite speed of mass propagation can be accounted for. In this study, the hyperbolic PDE are solved for in the liquid and vapor phases and the effect of finite speed of mass propagation on the real line is studied. For systems with large relaxation times the concentration can undergo subcritical damped oscillations in concentration.