Computation Programming of McCabe-Thiele and Ponchon-Savarit Methods for SHORT-CUT Distillation Design

Abstract

Using modern computer programming resources, a computer code has been developed in the MatLAB programming environment, which allows the use of the McCabe-Thiele and Ponchon-Savarit methods for SHORT-CUT distillation design. The McCabe-Thiele and Ponchon-Savarit methods are easy to apply, are not time consuming, and allow the easy visualization of the interrelationships among variables. In order to describe all the programming steps of these methods, a combination of different types of MatLAB functions has been used. The optimum reflux ratio is determined by using volume criteria, whichallows minimizing the volume of the distillation column and thereby reducing the total cost of a distillation unit. To evaluate the accuracy of the results, a comparison between the results produced by graphical methods and those calculated by other SHORT-CUT methods and rigorous calculations has been carried out. To perform this, the ChemCAD 7.1.5 simulator has been used. The SHORT-CUT distillation module in this simulator uses the Fenske-Underwood-Gilliland (FUG) method. For rigorous estimation, the SCDS multi-stage vapor-liquid equilibrium module in ChemCAD software environment has been used. SCDS is a rigorous multi-stage vapor-liquid equilibrium module which simulates any single column calculation including distillation columns, absorbers, reboiler and strippers. The results produced by graphical methods are closer to the rigorous-calculation results than to the FUG SHORT-CUT method ones, with respect both to the reflux ratio and to the bottom and top light-key mass fraction.