Extractive distillation: recent advances in operation strategies

Abstract

<jats:title>Abstract</jats:title><jats:p>Extractive distillation is one of the efficient techniques for separating azeotropic and low-relative-volatility mixtures in various chemical industries. This paper first provides an overview of thermodynamic insight covering residue curve map analysis, the application of univolatility and unidistribution curves, and thermodynamic feasibility study. The pinch-point analysis method combining bifurcation shortcut presents another branch of study, and several achievements have been realized by the identification of possible product cut under the following key parameters: reflux ratio, reboil ratio, and entrainer-feed flow rate ratio. Process operation policies and strategy concerning batch extractive distillation processes are summarized in four operation steps. Several configurations and technological alternatives can be used when extractive distillation processes take place in a continuous or batch column, depending on the strategy selected for the recycle streams and for the main azeotropic feeds.</jats:p>

Systematic design of an extractive distillation for maximum‐boiling azeotropes with heavy entrainers

“…While 1.0-1a class is defined to separate a minimum boiling azeotrope using a heavy entrainer or a maximum boiling azeotrope with a light entrainer, 1.0-2 class is defined for the separation of a minimum boiling azeotrope with a light entrainer or a maximum boiling azeotrope with a heavy entrainer. Our previous work 36 has concluded that up to 53% of azeotropic mixtures that are suitable for separation using extractive distillation belong to Serafimov's classes including 0.0-1 (lowrelative-volatility mixtures), 37 1.0-1a, 1.0-1b, 1.0-2 (azeotropic mixtures with light, intermediate, or heavy entrainers forming no new azeotrope), 18,27,28,38 2.0-1, 2.0-2a, 2.0-2b, 2.0-2c (azeotropic mixtures with an entrainer forming one new azeotrope). 20 Corresponding to the maximum boiling azeotrope separation with a heavy entrainer, Serafimov's class 1.0-2 ternary diagram is represented on Figure 3.…”

Optimal Design and Effective Control of Triple-Column Extractive Distillation for Separating Ethyl Acetate/Ethanol/Water with Multiazeotrope

“…In this study, the separation of azeotrope mixtures (i.e., EtOH/EtAC, EtOH/water, and EtAC/water) with a heavy entrainer (E) belongs to the class 1.0-1a of Serafimov’s classification. − The general feasibility criterion for the separation of nonideal systems incorporating the RCMs and isovolatility line is illustrated in Figure .…”

Review of extractive distillation. Process design, operation, optimization and control

“…Comparison of all processes leads to recommend the use of BED-I with a heavy entrainer. With a light entrainer the BES-I column configuration was recommended (Lang et al, 1999;Varga, 2006;Shen et al, 2015c) but a batch rectifier configuration is also possible (Stéger et al, 2005;Varga et al, 2006aVarga et al, , 2006b. Table 6 summarizes the configurations recommended when using batch extractive distillation process for the separation of minimum or maximum boiling azeotrope or low relative volatility mixtures with a heavy, light or intermediate boiling entrainer (Varga, 2006) With a heavy entrainer, the main load F AB is initially in the still, the batch column is a rectifier with an extractive and a rectifying section (Fig.…”