Computer simulation and design of binary distillation on a personal computer

A compiled BASIC computer code was developed for use on a personal computer with 256K random access memory to design a binary distillation column. The code ran successfully for seven test cases ranging from ideal and non-ideal systems. Execution times were less than two hours.

The computer code developed consisted of the following elements: Ponchon-Savarit for estimation of the number of theoretical stages: UNIFAC for vapor-liquid equilibrium prediction; choice of either Ideal, Yen-Alexander departure functions, Soave-Redlich-Kwong Equation of State to predict enthalpy; heat exchanger sizing; tower sizing and cost estimation. Optional routines included estimation of column heat loss and Murphree stage efficiencies.

Theoretical number of stages and minimum reflux estimation compared favorably with previous work for benzene-toluene systems. Stage estimates deviated less than 6% and minimum reflux varying between 4.3% and 29.1%. The methanol-water system varied 3% for the minimum reflux estimation with no deviation for stage estimation. The highly non-ideal systems of ethanol-water and n-propanol-water produced deviations in excess of 58% for both minimum reflux and stage estimations. The deviations were found to be due to the UNIFAC prediction of liquid phase activity coefficients.