A simplified and general approach to distillation with parallel streams: The cases of para- and metastillation

This work presents a general approach for calculating the total number of ideal stages in para- and metastillation. The proposed methodology is based on the adaptation of the original McCabe-Thiele methodology. Parastillation involves the division of vapor phase, at the bottom of the column, into two or more streams that flow upward along the equipment, contacting, in alternate trays, the whole of the liquid phase flow. On the other hand, metastillation corresponds exactly to the opposite case: the division of liquid phase into two or more streams and their contact with the entire vapor phase in alternate trays. The methodology for calculating the operating and feed lines is presented in detail for para- and metastillation in case of dividing the respective phase in two streams. Afterwards the approach is generalized for any integer number of divisions. A specific discussion is dedicated to the feed plate in order to develop a simplified but coherent representation of the feed line. Based on the calculated results for different binary mixtures' volatilities, the advantages of distillation with parallel streams are discussed.