Conceptual Design of Non-Ideal Mixture Separation With Light Entrainers

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 (F E /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 F E /F. The profiles of the stripping, extractive, and rectifying sections are calculated by equations considering S and F E /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.

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

“…5c-f) and the determination of the location of the extractive stable node enabling a feasible extractive distillation process. Similar figures are found in the literature for the (0.0-1) extractive separation class (low˛mixture separation with a heavy entrainer) (Rodríguez-Donis et al, 2009b) and for the (1.0-2) extractive separation class (minT azeotrope separation with a light entrainer) (Gerbaud and Rodriguez-donis, 2014;Shen et al, 2015bShen et al, , 2016. Following these opening works, a systematic exploration of the feasible separation of minimum or maximum boiling azeotropes with either heavy, intermediate or light entrainers was carried out for the batch extractive distillation process.…”

“…It was falsely assumed for decades that the unique feasibility rule for the extractive distillation process was the (1.0-1a) class separation, corresponding to the homogeneous extractive distillation of a minT azeotropic mixture with a heavy entrainer or of a maxT azeotropic mixture with a light entrainer (1.0-1a occurrence 21.6% among azeotropic diagrams). But some twenty works published between 1990 and 2013 explored which ternary diagrams would be suited for extractive distillation (Laroche et al, 1991(Laroche et al, , 1992a; Wahnschafft and Westerberg, 1993; Knapp and Doherty, 1994;Petlyuk et al, 1999Petlyuk et al, , 2015Serafimov et al, 2008;Kotai and Lang, 2005;Kotai et al, 2007;Lang, 1992;Lang et al, 1994Lang et al, , 1995Lang et al, , 1999Lang et al, , 2000aLelkes et al, 1998aLelkes et al, ,b,c, 2002Lelkes et al, , 2003aModla et al, 2001Modla et al, , 2003Rev et al, 2003;Stéger et al, 2005Stéger et al, , 2006Varga et al, 2006a,b) until the general feasibility rules discussed in the previous section were enounced (Rodríguez-Donis et al, 2009a,b, 2010, 2012aGerbaud and Rodriguez-donis, 2014;Shen et al, , 2015bShen et al, , 2016 For homogeneous extractive distillation with an entrainer forming no new azeotrope, the feasible diagrams belong to the following classes: (1.0-1a) (separation of minT with E heavy or maxT with E light, occurrence 21.6% among azeotropic diagrams), (1.0-2) (separation of maxT with E heavy or minT with E light, occurrence 8.5%), (1.0-1b) (minT with E light or maxT with E heavy, occurrence 0.4%), and (0.0-1) (low mixture with all type of E, see occurrences in Reshetov and Kravchenko (2007). Besides, when the entrainer forms a new azeotrope, ternary diagrams classes (2.0-1) (occurrence 0.6%), (2.0-2a) (occurrence 0.4%), (2.0-2b) (occurrence 21.0%) and (2.0-2c) (occurrence 0.9%) ...…”

“…No thorough analysis has been made for the intermediate boiling entrainer feed location. The continuous column configuration with a heavy entrainer has dominated in the literature cited in the reference list, whereas the use of a light entrainer has been investigated by only a few people (Gmehling and Möllmann, 1988;Laroche et al, 1991Laroche et al, , 1992aLaroche et al, , 1992bPetlyuk et al, 1999;Shen et al, 2015aShen et al, , 2016.…”

Comparison of alternative methods for methyl acetate + methanol + acetic acid + acetic anhydride mixture separation

“…The pressure choice in distillation columns in the pressure-swing distillation complex will affect the change of the azeotrope's composition and hence the amount of recycle flows. The same azeotropic mixture can be separated by extractive distillation with different solvents: heavy [11][12][13][14], light [15], or mixed [16] entrainers. Thus, each flowsheet will be characterized by its energy consumption.…”