Automatic Column Sequencing and Optimization for Homogeneous Azeotropic Mixtures

Abstract

A method is developed for determining feasible sequences for separating mixtures with binary azeotropes and optimizing each column in every sequence (including two-column subsequences for azeotropic distillation and solvent recovery) to determine which sequence has the lowest overall cost. This method can be applied automatically for different feed mixtures and feed compositions, which permits screening of process alternatives including different feed compositions. The results are illustrated using two case study systems: a five-component mixture with three binary azeotropes and one distillation region and a four-component mixture with one binary azeotrope and two distillation regions.

Automatic Design of Extractive Distillation Sequence for a Multicomponent Azeotropic System

“…TAC is used to make an economic evaluation of EDSs. It can be seen that the EDS with minimum TAC saves 64.53% of the cost compared with the EDS with maximum TAC and is more economical compared to the EDS based on the method reported in the paper …”

“…The multicomponent system of methyl acetate/methanol/ethanol/water, which has 8 singular points (including 4 binary azeotropes) is used to illustrate the feasibility of the methodology, as it is difficult to obtain the optimal EDS by heuristic rules. This example is taken from Tsai et al They presented potentially EDSs, and Aspen Plus software was used to optimize each column in turn. However, this method does not take into account the breaking of binary azeotrope in a multicomponent azeotrope system, and the optimization of each column reduces the design efficiency of the optimal EDS.…”

“…Sasi et al provide an algorithmic method for automatically synthesizing azeotrope distillation sequence without the introduction of solvents and evaluate these feasible splits by the rectification body method (RBM). Tsai et al proposed a method for separating multicomponent systems containing only binary azeotrope and conducted rigorous simulation optimization for each extractive distillation sequence (EDS). Although great efforts on the synthesis of distillation sequences of multicomponent azeotrope systems are involved, most of them focus on the empirical rule method based on residual curve maps.…”

Automatic Synthesis of Distillation Processes for the Separation of Homogeneous Azeotropic Multicomponent Systems

“…The existence of common terminals of the RC of both products indicates that both are situated in the same DR, while the evaluation of a common saddle (singular point with specific stability, see Section 3.1), which is approached by the RCs of both products, is considered as sufficient criteria that both products are also located in the same compartments of a DR, quantifying split feasibility. This so-called common saddle test has also been recently utilized by Tsai and Ward, 53 who integrated the test in an algorithm capable of deriving distillation sequences, which perform a series of sharp splits, combined with extractive distillation in order to separate binary azeotropic mixtures. Consequently, the approach is limited to homogeneous mixtures with binary azeotropes only, while neither curved-boundary nor pressure-swing distillation is considered for process synthesis.…”