Multicomponent three-phase azeotropic distillation. 3. Modern thermodynamic models and multiple solutions

Cairns, Brett P.; Furzer, I. A.

doi:10.1021/ie00103a042

Cited by 35 publications

(21 citation statements)

References 19 publications

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“…In this regard, Kingsley and Lucia (1988) and Widagdo et al (1989Widagdo et al ( , 1992 show that in place of stable three-phase (VLL) solutions, multiple two-phase (VL) solutions are often computed, each of which is unstable. Furthermore, Cairns and Furzer (1990~) show, for the dehydration of ethanol with 2,2,4-trimethylpentane, that spurious solutions are computed when the second liquid phase is not modeled. In many towers, stability analysis must be performed very carefully to properly solve the MESH equations.…”

Section: Mche Journal January1996mentioning

confidence: 99%

Journal review. Azeotropic distillation

Widagdo¹,

Seider²

1996

AIChE Journal

332

229

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Recent and ongoing research in the distillation of nonideal mixtures is reviewed focusing on advances in the methodologies for the synthesis, design, analysis and control of separation sequences involvinghomogeneous and heterogeneous azeotropic towers. Maps of residue curves and distillation lines are examined, as well as geometric methods for the bynthesis and design of separation sequences, trends in the steady-state and dynamic analysis of homogeneous and heterogeneous towers, the nonlinear behavior of these towers, and strategies for their control.Emphasis is placed on the methods of computing all of the azeotropes associated with a multicomponent mixture, on the features that distinguish azeotropic distillations from their zeotropic counterparts, on the potential ,for steady-state multiplicity, and on the existence of maximum and minimum reflux bounds. Important considerations in the selection of entrainers are examined. For the synthesis of separation trains, when determining the feasible product compositions, the graphical methods are clarified, especially the conditions under which distillation bounduries can be crossed and bounding strategies under finite reflux. The application of geometric theory to locate the fuced points, at minimum reflux, is reviewed in connection with homotopy-continuation algorithms for this purpose. The use of homotopy-continuation algorithms, especially for the steadystate simulation of heterogeneous azeotropic distillations, is justified. Methods for phase stability analysis are reviewed in connection with the location of real bifurcation points at phase transitions, an important feature of algorithms for the dynamic simulation of heterogeneous azeotropic distillations. Azeotropy and polyazetropyfueotrope, an ancient Greek word that translates as "to 96 January 1996 Vol. 42, No.

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Section: Mche Journal January1996mentioning

confidence: 99%

Journal review. Azeotropic distillation

Widagdo¹,

Seider²

1996

AIChE Journal

332

229

View full text Add to dashboard Cite

show abstract

“…Their dynamic simulation results are consistent with the five steady states reported by Kovach and Seider (1987b). Cairns and Furzer (1990) study the multiplicities by Magnussen et al (1979) using the UNIFAC(VLE) model. Two of the steady states were obtained only by ignoring the phase splitting and hence they conclude that these profiles are fictitious.…”

Section: Introductionmentioning

confidence: 99%

Multiple Steady States in Heterogeneous Azeotropic Distillation

Bekiaris¹

1995

Computers &Amp; Chemical Engineering

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In this article we study multiple steady states in ternary heterogeneous 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 show how the distillate and bottom product paths can be located for tray or packed columns, with or without decanter and with different types of condenser and reboiler. We derive a necessary and sufficient condition for the existence of these multiple steady states based on the geometry of the product paths. We also locate in the composition triangle the feed compositions that lead to these multiple steady states. 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.

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“…[1][2][3][4][5][6][7] Regarding azeotropic distillation operations, Bossen et al found four steady states for the dehydration of ethanol with benzene by dynamic simulation. 8 Also, Gü ttinger and Morari found two stable steady states caused by the vapor-liquid equilibrium for the ternary homogeneous methanol-methylbutyrate-toluene (MMT) system on an industrial pilot column.…”

Section: Introductionmentioning

confidence: 99%

Startup of Homogeneous Azeotropic Distillation Sequences with Multiple Steady States

Scenna

Benz

Rodríguez

et al. 2005

Ind. Eng. Chem. Res.

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The operability of an azeotropic sequence, which consists of an azeotropic distillation column with multiple steady states and an entrainer recovery column with the corresponding recycle stream, is analyzed by dynamic simulation during its startup. The goal is to study the effect of the recycle stream on the start-up performance. The well-known benzene-heptane-acetone (BHA) system is studied. Given open-loop (manual) start-up strategies, the way in which the system reaches different steady states by applying different start-up configurations and/or policies can be observed through the temperature profile evolutions. These are generated using different initial charges in one or both columns, and by applying different schedules for the evolution of the operative variables. Indeed, a partition of the start-up policy space yielding different solutions is achieved. Therefore, it is possible to identify a set of critical values for the supervision of the startup. Based on these results, very simple closed-loop start-up policies, using a simple PI controller, are analyzed. The study shows that the desired steady state can always be obtained by providing a minimum benzene flow rate, which has to be maintained during the startup. Thus, a methodology that uses dynamic simulation to search systematically suitable start-up procedures is presented. An adequate start-up operation mode (minimizing start-up time) is determined for the BHA system. Moreover, this start-up strategy is also applied to another well-known system with multiplicity: the methanol-methylbutyrate-toluene (MMT) case. In this example, the start-up time is also reduced to a minimum, in comparison with all the other policies explored.

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Multicomponent three-phase azeotropic distillation. 3. Modern thermodynamic models and multiple solutions

Cited by 35 publications

References 19 publications

Journal review. Azeotropic distillation

Journal review. Azeotropic distillation

Multiple Steady States in Heterogeneous Azeotropic Distillation

Startup of Homogeneous Azeotropic Distillation Sequences with Multiple Steady States

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