A rigorous computing procedure for multicomponent distillation design has been developed. In each iteration of the procedure

a simplified stage-to-stage calculation is followed by a rigorous operating calculation. The former calculates the equilibrium stages required for each tower section and the suitable feed stage locations

whereas the latter checks whether recoveries of key components are as required. In the stage-to-stage calculation and the operating calculation

the concept of the fractional theoretical stage is used by means of Murphree efficiency

thus the number of equilibrium stages is conceived as a continuous parameter. This treatment has the advantages of making the calculation converge precisely to the required recoveries of key components

reducing the computation work

and locating the suitable feed stages. By using a correlation developed from the Fenske equation

and based on the relevant data from operating calculation

the distribution of each component between distillate and bottomn and also total moles of products are obtained. If the required recoveries are not satisfied

a new iteration is performed together with the newly calculated vapor and liquid flow profiles. This procedure can be applied to conventional multicomponent distillation as well as multifeed complex distillation. It has been used for debutanizer

de-propanizer

acetic acid-formic acid-water tower

acetone-methanol-iso-propanol-water tower and acetone-chloroform-benzene tower. The number of iterations ranges from two to four.