Design/optimization of ternary heterogeneous azeotropic distillation sequences

Abstract

Various strategies for sequencing heterogeneous azeotropic distillations have been explored. The design and optimization of these systems by simulation-based methods is generally acknowledged to be a very difficult problem (Kingsley and Lucia, 1988). In this article, a simple and accurate design and optimization procedure has been developed. The method does not involve any recycle convergence loops and has been applied successfully to several test problems. Unlike the simulation-based methods, our method is robust to changes in the system optimization variables (e.g., reflux ratio in the azeotropic column).In order to demonstrate the method, w e present design and optimization results for the dehydration of ethanol using a benzene entrainer. Our optimal designs consume significantly less energy than state-of-the-art designs reported in the literature.

Optimal Extractive Distillation Process for Bioethanol Dehydration

“…For example, Ryan and Doherty (1989) assumed a composition of 94.9 %wt (88 %mol) ethanol which is rather close to the azeotropic composition, while other authors (Kiss and Suszwalak, 2012;Li and Bai, 2012) selected more practical compositions of about 93.5 %wt (85 %mol). The problem is how to select this key design parameter such that the energy requirements and the capital cost of the two sections of the process (pre-concentration and dehydration of ethanol) are economically balanced to minimize the overall costs.…”

Analysis and Conceptual Design of Ternary Heterogeneous Azeotropic Distillation Processes

“…1 All of these mixtures have very similar topology (two homogeneous binary azeotropes, one heterogeneous binary azeotrope, one heterogeneous ternary azeotrope, and a similar sequence of boiling temperatures). Therefore, the vanishing of a CDR at lower reflux is characteristic for heterogeneous mixtures with a residue curve map topology similar to the one in Figure 1 for EWC.…”

“…The dehydration of a binary ethanol-water mixture using benzene or cyclohexane as an entrainer is a commonly known example of these types of processes. [1][2][3] In recent years, new approximative methods for the determination of the minimum energy demand [4][5][6][7][8] and for the prediction of feasibility 9-12 of a distillative separation of ternary and multicomponent nonideal mixtures have been developed. The focus of all of these publications has been largely restricted to homogeneous separations.…”

∞/∞-Analysis of heterogeneous distillation processes

“…They are feasibility studies of heterogeous distillation processes. Figure 14 shows a heterogeneous azeotropic distillation process for the separation of a binary mixture of water and ethanol using benzene as heterogeneous entrainer (Ryan and Doherty, 1989;Stichlmair and Fair, 1998). The feed contains 0.05 mol/mol ethanol, the specification for both products is set to ≥ 0.99 mol/mol.…”