Multiple Steady-States Analysis and Unstable Operating Point Stabilization in Homogeneous Azeotropic Distillation with Intermediate Entrainer

Abstract

The steady-state multiplicity in azeotropic distillation processes has been theoretically predicted and verified experimentally for decades. However, it is a tough task to detect all the steady-state solutions. The purpose of this article is 2-fold: first, it provides a systematical study on the multiplicity in homogeneous azeotropic distillation with intermediate entrainer and a novel strategy is proposed to find all the steady-state solutions using "Design Specs/Vary" in Aspen Plus. Operating on the unstable steady-state branch benefits both energy saving and reducing capital investment with the product quality specified. Because of the great benefits that operating on the unstable steady-state branch offers, the second purpose is to present suitable control schemes to stabilize the operating point on the unstable steady-state branch to achieve robust control.

Isobaric Vapor–Liquid Equilibrium Measurements and Calculations Using Nontraditional Models for the Association Systems of Ethyl Acetate + 2-Ethylhexanoic Acid and Propyl Acetate + 2-Ethylhexanoic Acid at Atmospheric Pressure

“…Azeotropic distillation , uses the distribution of the different components in the two vapor–liquid phases to achieve separation by multiple mass and heat transfer processes between the two phases. In pressure swing distillation, − the relative volatilities of substances can be altered by changing the pressure to achieve a separation effect. Extractive distillation − can separate mixtures by adding a third component (called an extractant or solvent) to the raw material liquid to change the relative volatilities of the original components.…”

Design of a Dividing‐Wall Column Considering its Multiple Steady State Characteristic

“…These extra degrees of freedom also lead to MSS in DWC distillation. This phenomenon has been studied and verified by some researchers . Wayburn and Seader , have been the first to report the existence of MSS in an interlinked separation column, using a differential arc‐length homotopy continuation method.…”

New structure-based models for the prediction of normal boiling point temperature of ternary azeotropes

“…Ordinary distillation cannot be utilized directly to separate azeotropes due to the absence of an interphase compositional differential. Several special distillation methods including azeotropic distillation, [1][2][3] extractive distillation, 4,5 and pressure swing distillation 6 have been used for the azeotrope separation. Understanding of the azeotropic properties including the boiling point is important for preliminary evaluations aimed at designing of the distillation process.…”