A Method for the Design of Divided Wall Columns

Abstract

A divided wall column has been modeled as a Petlyuk column with no heat transfer across the column wall. The feed to the column has been generalized as a mixture of saturated liquid and vapor (0 <q <1). The pinch compositions at connection points, the Fenske equation and the Gilliland correlations, which have been commonly used by previous investigators to design divided wall columns, have not been applied. In contrast, a shortcut method based on Underwood's equations has been introduced. Moreover, it is shown that the split of the internal reflux over both sides of the middle wall of the column is bounded and a method for choosing the proper value of the split ratio is suggested. This is a novel approach not attempted before by investigators.

Extension of a Method for the Design of Divided Wall Columns

“…Therefore, in the prefractionator (section 1) one has to remove A from the bottom and C, D and E from the top. Thus, the method of calculation of the preferred split is similar to that given for ternary mixtures in a previous paper by the current authors [4].…”

“…The method of calculation is similar to that given for the ternary case in a previous paper by the current authors [4]. For convenience, the expressions P a i x i;j a i Àu′ and P a i x i;j a i Àw′ are denoting, as E(x i,j ,u′) and E(x i,j ,w′).…”

“…The acceptable value occurs when h′ lies in the range of a A > h′ > a B . By the method of approximation described in connection with ternary mixtures [4], one finds that for b ≤ b P , h′ would be equal to h 1 . However, when b is grater than b P , h′ has a new value.…”

“…They explained their method for ternary feed but solved a case study with five components and used their preliminary optimization for a rigorous simulation. Sotudeh and Hashemi Shahraki [4] presented a method for design of divided wall columns with ternary mixtures and an arbitrary feed quality, q 1) . They introduced a shortcut method only based on Underwood's equations.…”

A Shortcut Design for Kaibel Columns Based on Minimum Energy Diagrams

“…F=1 mol/s) and the column diameter will depend on the chosen feed rate. Some shortcut methods have been proposed for design of 3-product columns (Triantafyllou and Smith 1992;Sotudeh and Hashemi Shahraki 2007). One approach is to extend the existing methods of conventional columns to dividing wall columns by representing the Petrlyuk column by three conventional columns.…”