Abstract
A method is proposed to study the separation of minimum-, maximum-boiling azeotropic, and low volatility mixtures with a light entrainer, to investigate feasible regions of the key operating parameters reboil ratio (S) and entrainer - feed flowrate ratio (FE/F) for continuous processes. The thermodynamic topological predictions are carried out for 1.0–2, 1.0–1a, and 0.0–1 Serafimov’s class diagrams. It relies upon the knowledge of residue curve maps, along with the univolatility line, and it enables the prediction of possible products at the bottom of the column and limiting values of FE/F. The profiles of the stripping, extractive, and rectifying sections are calculated by equations considering S and FE/F, and they bring information about the location of singular points and possible composition profile separatrices that could impair process feasibility. Providing specified product composition and recovery, the approximate calculations are compared with rigorous simulations of extractive distillation processes. Separating non-ideal mixtures using a light entrainer provides more opportunities for the case when it is not easy to find an appropriate heavy or intermediate entrainer
Highlights
IntroductionA suitable entrainer commonly should be a miscible, heavy boiling component
In extractive distillation, a suitable entrainer commonly should be a miscible, heavy boiling component
The general feasibility criterion is valid for either component A or B in the mixtures of 1.0-1a, i.e., either of them can be drawn as first bottom product using a stripper configuration that depends on the univolatility line location at any location on the edge B-E (A-E) side or B-E side
Summary
A suitable entrainer commonly should be a miscible, heavy boiling component. It should form no new azeotrope, and interact differently with the components to be separated, causing the changes of relative volatilities, and thereby ease the separation. Rodriguez-Donis et al (2012a) mainly focused on thermodynamic topological insight of how knowledge of the location of univolatility lines and residue curve analysis help in assessing the feasibility of batch extractive distillation. It was not further tested for continuous operation
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