Azeotropic Distillation

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Hatice Baspinar Kucuk - One of the best experts on this subject based on the ideXlab platform.

Manfred Morari - One of the best experts on this subject based on the ideXlab platform.

  • influence of impurities on the control of heterogeneous Azeotropic Distillation columns
    Industrial & Engineering Chemistry Research, 2002
    Co-Authors: Jan Ulrich, Manfred Morari
    Abstract:

    A concept is presented for the design of heterogeneous Distillation columns under aspects of operability. The column behavior is analyzed using residue curve maps and a theoretical finite reflux/infinite length column. In particular, the influence of impurities on the operation of the column is discussed. Depending on the impurities, different control schemes with different designs of the process have to be used to guarantee robust performance. In this paper, robustness is not against modeling errors but against typical nonlinear phenomena such as the disappearance of the phase split in the decanter. The theoretical findings are illustrated by steady-state and dynamic simulations of an industrial column where a heavy-boiling organic substance is dewatered using methyl tert-butyl ether as a light entrainer.

  • experimental study of multiple steady states in homogeneous Azeotropic Distillation
    Industrial & Engineering Chemistry Research, 1997
    Co-Authors: Thomas E Guttinger, Cornelius Dorn, Manfred Morari
    Abstract:

    Bekiaris et al. (1993) explained the existence of multiple steady states in homogeneous ternary Azeotropic Distillation, on the basis of the analysis of the case of infinite reflux and infinite column length (infinite number of trays). They showed that the predictions of multiple steady states for such infinite columns have relevant implications for columns of finite length operated at finite reflux. In this article, experiments are described for the ternary homogeneous system methanol−methyl butyrate−toluene which demonstrate the existence of multiple steady states (output multiplicities) caused by the vapor−liquid−equilibrium. The experiments on an industrial pilot column show two stable steady states for the same feed flow rate and composition and the same set of operating parameters. The measurements are in excellent agreement with the predictions obtained for infinite columns using the ∞/∞ analysis tools as well as with stage-by-stage simulation results. These experiments represent the first publishe...

  • multiple steady states in heterogeneous Azeotropic Distillation
    Industrial & Engineering Chemistry Research, 1993
    Co-Authors: Nikolaos Bekiaris, George Amir Meski, Manfred Morari
    Abstract:

    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 nonmonotonically 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

  • multiple steady states in homogeneous Azeotropic Distillation
    American Control Conference, 1993
    Co-Authors: Nikolaos Bekiaris, George Amir Meski, Cristian M Radu, Manfred Morari
    Abstract:

    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, multiple steady states exist when the distillate flow varies non-monotonically along the continuation path of the bifurcation diagram with the distillate flow as the bifurcation parameter. 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 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.

  • homogeneous Azeotropic Distillation separability and flowsheet synthesis
    Industrial & Engineering Chemistry Research, 1992
    Co-Authors: Lionel Laroche, Nikolaos Bekiaris, Henrik Weisberg Andersen, Manfred Morari
    Abstract:

    When designing a homogeneous Azeotropic sequence which separates a binary azeotrope into two pure products, we must first choose the entrainer. In the case of homogeneous Azeotropic Distillation, separability at finite reflux and at infinite reflux are not equivalent and must be examined separately. By analyzing the profiles of columns operated at infinite reflux in detail, we have shown that a binary azeotrope can be separated with only one Distillation column. We present a necessary and sufficient condition which identifies such situations. We have found a necessary and sufficient condition for separability in a two-column sequence. When separation is feasible, this condition indicates the flowsheet of the corresponding separation sequence. We have also shown that separation is always feasible in a three-column separation if the azeotrope we want to separate is a saddle. Finally, we examine two situations where separation is feasible at finite reflux but not at infinite reflux.

Huanyi Chao - One of the best experts on this subject based on the ideXlab platform.

  • design and control of acetic acid dehydration system via heterogeneous Azeotropic Distillation
    Chemical Engineering Science, 2004
    Co-Authors: Lung I Chien, Kailuen Zeng, Huanyi Chao, Jun Hong Liu
    Abstract:

    Acetic acid dehydration is an important operation in the production of aromatic acid, such as terephthalic acid or in the manufacture of cellulose acetate. Although acetic acid and water does not form azeotrope, but using simple Distillation to separate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus it is more customary in industry to use an entrainer via a heterogeneous Azeotropic Distillation column system for the separation. In this study, a suitable entrainer is selected from three candidate acetates through rigorous steady-state simulation of this system. Optimum process design and operating condition are determined to keep high-purity bottom acetic acid composition and also keep a small acetic acid loss through top aqueous draw. Furthermore, the overall control strategy of this column system is proposed to hold both bottom and top product specifications in spite of feed rate and feed composition load disturbances. The proposed overall control strategy is very simple requiring only one tray temperature control loop inside the heterogeneous Azeotropic column.

  • design and control of a complete heterogeneous Azeotropic Distillation column system
    Industrial & Engineering Chemistry Research, 2004
    Co-Authors: Ilung Chien, Kailuen Zeng, Huanyi Chao
    Abstract:

    In this work, design and control of an industrial-scale complete heterogeneous Azeotropic Distillation column system of isopropyl alcohol (IPA) + water (H2O) with cyclohexane (CyH) as an entrainer is investigated. There are two feasible approaches to design the complete flowsheet for the separation of IPA and H2O. One approach is to use a total of three columns and another simpler design is to use only two columns. From total annual cost (TAC) analysis, optimum design of the two-column approach has been established and it is much more economical than the three-column approach. The suitable control strategy of this complete heterogeneous Azeotropic Distillation column system has also been studied extensively in this paper. From process analysis and dynamic simulation, the developed overall control strategy is rather unconventional which seems to contradict several common control heuristics. The proposed control strategy requires two temperature-control loops in the first column and one temperature-control ...

  • design and control of a complete heterogeneous Azeotropic Distillation column system
    Industrial & Engineering Chemistry Research, 2004
    Co-Authors: Ilung Chien, Kailuen Zeng, Huanyi Chao
    Abstract:

    Abstract In this work, design and control of a complete heterogeneous Azeotropic Distillation column system of isopropyl alcohol (IPA) + water (H2O) with cyclohexane (CyH) as an entrainer is investigated. There are two feasible approaches to design the complete flowsheet for the separation of IPA and H2O. One approach is to use total of three columns, another simpler design is to only use two columns. From TAC (Total Annual Cost) analysis, the simpler approach is more economical. The suitable control strategy for this complete heterogeneous Azeotropic Distillation column system is also studied in this paper. From process analysis and dynamic simulation, the overall control strategy is developed which requires two temperature loops in the first column and one temperature loop in the second column. The overall control strategy is tested with composition and flow rate variations in the fresh feed stream. The specifications of the IPA product and waste water composition are all met despite of the various disturbances

William L Luyben - One of the best experts on this subject based on the ideXlab platform.

  • control of the maximum boiling acetone chloroform Azeotropic Distillation system
    Industrial & Engineering Chemistry Research, 2008
    Co-Authors: William L Luyben
    Abstract:

    The literature contains a number of papers that study the control of Azeotropic Distillation systems. Both homogeneous and heterogeneous azeotropes have been considered, but all of the systems considered in these control papers deal only with minimum-boiling azeotropes. These azeotropes are caused by molecular repulsion between different types of chemical components and are more common than systems in which molecular attractions occur that result in maximum-boiling azeotropes. There appears to be no papers that study the control of this type of Azeotropic system. This paper explores the design and control of the maximum-boiling Azeotropic acetone/chloroform Distillation system. The normal boiling points of the two pure components are 329.4 and 334.3 K, while the Azeotropic boils at 337.6 K at 1 atm with a composition of 34.09 mol % acetone. A two-column extractive Distillation process is used with dimethyl sulfoxide as the solvent. The two components are separated into 99.5 mol % pure products leaving in ...

  • design and control of a fully heat integrated pressure swing Azeotropic Distillation system
    Industrial & Engineering Chemistry Research, 2008
    Co-Authors: William L Luyben
    Abstract:

    If the composition of a binary homogeneous azeotrope changes significantly with pressure, the chemical components can be efficiently separated by using two Distillation columns that operate at different pressures. This process is called pressure-swing Azeotropic Distillation. This paper updates the work of Abu-Eishah and Luyben (Ind. Eng. Chem. Process Des. Dev. 1985, 24, 132−140). These authors studied a partially heat-integrated two-column system in which an auxiliary reboiler permitted independent adjustment of vapor boilup in both columns. In the present paper, the two columns operate in the “neat” mode without any auxiliary reboiler. The details of achieving rigorous steady-state and dynamic simulations of the neat system in Aspen Plus and Aspen Dynamics are discussed. The condenser duty in the high-pressure column must equal the reboiler duty in the low-pressure column. The heat-transfer rate depends on the temperatures on the hot and cold sides in the condenser/reboiler, which change with varying p...

  • Control of a multiunit heterogeneous Azeotropic Distillation process
    AIChE Journal, 2006
    Co-Authors: William L Luyben
    Abstract:

    An investigation of the design and control of a system in which a heterogeneous azeotrope permits the use of a decanter to cross a Distillation boundary is reported. The specific numerical example is the classical production of anhydrous ethanol from an ethanol/water mixture using benzene as the entrainer. The feed is an ethanol/water mixture with composition that is near the binary azeotrope, which has been produced in an upstream binary Distillation column. The process consists of two columns in which the addition of benzene takes the water out the top of the first column, producing high-purity ethanol out the bottom. The overhead vapor is condensed and forms two liquid phases. The organic benzene-rich phase provides reflux to the first column. The aqueous phase is fed to a second Distillation column that produces high-purity water out the bottom and recycles the distillate back to the first column. The steady-state convergence of this two-column system with two-recycles if very difficult. Convergence is achieved by using a dynamic model. A plantwide control scheme is developed and is shown to provide stable base-level regulatory control for very large disturbances. The control structure has a counter-intuitive feature. The aqueous level in the decanter is controlled by manipulating the flow rate of the aqueous stream from the decanter. The action of the level controller is the reverse of what is used conventionally, that is, if the level is increasing, the exit flow rate is decreased.

David J P C Suszwalak - One of the best experts on this subject based on the ideXlab platform.

  • enhanced bioethanol dehydration by extractive and Azeotropic Distillation in dividing wall columns
    Separation and Purification Technology, 2012
    Co-Authors: Anton A. Kiss, David J P C Suszwalak
    Abstract:

    Abstract The industrial production of anhydrous bioethanol requires energy demanding Distillation steps to overcome the Azeotropic behavior of the ethanol–water mixture. In spite of the recent developments in pervaporation and adsorption with molecular sieves, the large scale production is still dominated by extractive and Azeotropic Distillation as the separation technology of choice. This study proposes novel Distillation technologies for enhanced bioethanol dehydration, by extending the use of dividing-wall columns (DWC) to energy efficient extractive Distillation (ED) and Azeotropic Distillation (AD). Notably, DWC is one of the best examples of proven process intensification technology in Distillation, as it allows significantly lower investment and operating costs while also reducing the equipment and carbon footprint. For both ED and AD cases a classic sequence of two Distillation columns and the alternative based on DWC are optimized using the state of the art sequential quadratic programming (SQP) method. A mixture of 85 mol.% ethanol is dehydrated using ethylene glycol and n -pentane as mass separating agents in an extractive and Azeotropic Distillation setup, respectively. The results of the rigorous simulations performed in Aspen Plus show that energy savings of 10–20% are possible for the novel process intensification alternatives based on DWC, while using less equipment units as compared to the conventional ED and AD configurations.

  • enhanced bioethanol dehydration by extractive and Azeotropic Distillation in dividing wall columns
    Separation and Purification Technology, 2012
    Co-Authors: Anton A. Kiss, David J P C Suszwalak
    Abstract:

    Abstract The industrial production of anhydrous bioethanol requires energy demanding Distillation steps to overcome the Azeotropic behavior of the ethanol–water mixture. In spite of the recent developments in pervaporation and adsorption with molecular sieves, the large scale production is still dominated by extractive and Azeotropic Distillation as the separation technology of choice. This study proposes novel Distillation technologies for enhanced bioethanol dehydration, by extending the use of dividing-wall columns (DWC) to energy efficient extractive Distillation (ED) and Azeotropic Distillation (AD). Notably, DWC is one of the best examples of proven process intensification technology in Distillation, as it allows significantly lower investment and operating costs while also reducing the equipment and carbon footprint. For both ED and AD cases a classic sequence of two Distillation columns and the alternative based on DWC are optimized using the state of the art sequential quadratic programming (SQP) method. A mixture of 85 mol.% ethanol is dehydrated using ethylene glycol and n -pentane as mass separating agents in an extractive and Azeotropic Distillation setup, respectively. The results of the rigorous simulations performed in Aspen Plus show that energy savings of 10–20% are possible for the novel process intensification alternatives based on DWC, while using less equipment units as compared to the conventional ED and AD configurations.