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Multiple Steady States in Homogeneous Azeotropic Distillation

Bekiaris, Nikolaos and Meski, George A. and Radu, Christian M. and Morari, Manfred (1993) Multiple Steady States in Homogeneous Azeotropic Distillation. California Institute of Technology , Pasadena, CA. (Unpublished)

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In this article we study multiple steady states in ternary homogeneous azeotropic distillation. We show that in the case of infinite reflux and an infinite number of trays one can construct bifurcation diagrams on physical grounds with the distillate flow as the bifurcation parameter. Multiple steady states exist when the distillate flow varies non-monotonically along the continuation path of the bifurcation diagram. We derive a necessary and sufficient condition for the existence of these multiple steady states based on the geometry of the distillation region boundaries. We also locate in the composition triangle the feed compositions that lead to these multiple steady states. We further note that most of these results are independent of the thermodynamic model used. We show that the prediction of the existence of multiple steady states in the case of infinite reflux and an infinite number of trays has relevant implications for columns operating at finite reflux and with a finite number of trays. Using numerically constructed bifurcation diagrams for specific examples, we show that these multiplicities tend to vanish for small columns and/or for low reflux flows. Finally, we comment on the effect of multiplicities on column design and operation for some specific examples.

Item Type:Report or Paper (Technical Report)
Additional Information:We acknowledge gratefully the financial support of the Donors of the Petroleum Research Fund administered by the American Chemical Society and of the I. S. Latsis Foundation. We also thank Prof. Skogestad (Norwegian Technical University, Trondheim) for several enlightened discussions. Finally, we thank Prof. Doherty and Jeffrey Knapp (University of Massachusetts, Amherst) for providing us thermodynamic data and subroutines.
Group:Control and Dynamical Systems Technical Reports
Subject Keywords:distillation, azeotropic distillation, multiplicity, distillation design, extractive distillation
Record Number:CaltechCDSTR:1993.001
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Usage Policy:You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.
ID Code:28043
Deposited By: Imported from CaltechCDSTR
Deposited On:22 Jul 2006
Last Modified:03 Oct 2019 03:28

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