Minimum entrainer flows for extractive distillation: A bifurcation theoretic approach

Shortcut methods for nonideal multicomponent distillation: 3. Extractive distillation columns

“…Knapp and Doherty (1994) formulate this criterion and relate separation feasibility to the appearance of saddle-node bifurcation points and branching points. Saddle-node bifurcation points are extremal points of the pinch branch with respect to the reflux ratio.…”

Thermodynamic Topological Analysis of Extractive Distillation of Maximum Boiling Azeotropes

“…The extractive profile map analysis enables identification of feasible and unfeasible regions for the composition in the extractive section of the column. Those regions are bounded by extractive stable and unstable separatrices crossing at saddle extractive singular points (Knapp and Doherty, 1994).The rcm singular points become the singular points of the extractive profile map with an opposite stability for the heavy entrainer case. Then for the 1.0-2 class, increasing the entrainer flowrate, the extractive profile singular points SN extr,A and SN extr,B originating from A and B move towards the entrainer vertex.…”

Detrimental influence of excessive fractionation on reactive distillation

“…Distillation adds value to a process by separating components with different volatilities. Increasing the separation power of a distillation column in the design phase (by adding more theoretical stages to the column) or during operation (by increasing the internal vapor and liquid flows), improves the performance of the column by increasing the purity of at least one of the distillation products, except in some azeotropic columns (Knapp and Doherty, 1994). Although this premise does not necessarily hold for reactive distillation, as change in fractionation may have an undesirable effect on the reaction by changes in the composition profile, it might be expected that a column with more theoretical stages should potentially be capable of adding more value to a process than a shorter column.…”