Design and optimization of distillation systems via. computer

A computer program has been written for the design of a binary distillation column. The program calculates the total annual operating cost at a specified reflux ratio. Other variables calculated include: number of trays, installed cost, energy usage, and optimum feed point.

The program can solve ideal as well as non-ideal systems. Well established UNIQUAQ correlations were used to get the vapor-liquid equilibria. The Yen-Alexander correlations were used to predict enthalpies. For the calculation of distillation column variables, the code used the method of Ponchon-Savarit. This is a more rigorous method than that of McCabe-Thiele.

The code was checked with Benzene-Toulene as an example of an ideal system and with Ethanol-Water as a non-ideal system. For the ideal system, the code gave 1.15579 as a minimum reflux, and 1.248 for the optimum reflux. This compared favorably to Peter's graphical solution (McCabe-Thiele) of 1.14 and 1.25 respectively. The code predicted a total annual operating cost at optimum reflux of $103,580 compared to Peter's graphical result of $99,000. For the non—ideal case, the code was checked with the problem solved by Manzoor. The results for feed plate position and total number of plates were in complete agreement with the Manzoor's results. The feed plate was predicted to be the fifth plate and the total number of plates was seven. The only difference was the minimum reflux ratio. The code gave this ratio as 0.454, compared to Manzoor's value of 0.434.