Ternary Azeotropic Mixtures Research Articles

Double-partitioned dividing wall column for a multicomponent azeotropic system

In this work, we propose the development of a dividing wall column (DWC) for the separation of ternary azeotropic mixture using an entrainer. Traditionally, this type of complex ternary system is traditionally separated in a triple column extractive distillation (TCED), among which, the first column is served as an extractive distillation. For this, at first, the first two towers are proposed to transform into a single column with a dividing wall. The resulting scheme is called here as extractive single-partitioned dividing wall column (ESPDWC). Subsequently, further intensification is made by merging all three columns of TCED into a single unit with two dividing walls, from which, one can get three products and the entrainer simultaneously with reasonably high purity. This proposed configuration is named as extractive double-partitioned dividing wall column (EDPDWC). To make the proposed extractive DWCs more practical, the heat transfer through the internal dividing wall is taken into account. For the separation of a ternary azeotropic mixture (tetrahydrofuran-methanol-water) with the use of an entrainer (ethylene glycol), the performance improvement of the proposed DWCs is quantified over the conventional TCED in terms of energy and cost savings. It appears that the proposed double-partitioned extractive DWC secures a better performance than its single-partitioned counterpart for the sample multiple binary azeotropes case.

Basic Principles of a Hybrid Distillation and Pervaporation Unit in a Single Column: an Analytic Tool

Distillation-Pervaporation Hybrid Systems (DPHS) are a relatively novel technology for separating multicomponent azeotropic mixtures, due to pervaporation is not limited by the liquid-vapor (LV) equilibria. However, conventional Distillation-Pervaporation Hybrid Systems, where the pervaporation unit is externally connected to the distillation column, have several drawbacks in the pervaporation unit, for instance high resistance to heat and mass transfer and an inter stage heating system is required between the pervaporation modules. Distillation-Pervaporation in a Single Unit (DPSU) is a novel concept where the pervaporation membrane is located inside the distillation column working as a packing bed in a section of the column. Due to it is a new concept, there is little data about its separation behavior. However, DPSU is able to overcome distillation boundaries. In this work, a simplified model is used to evaluate the separation of ternary homogenous azeotropic mixtures and thermodynamic conditions in a DPSU column. A pervaporation sections located in rectifying and stripping sections were studied. Two topological types, based on Serafimov’s topological classification, were selected as case studies: acetone-isopropanol-water (1.0-2) and ethyl acetate-ethanol-methanol (2.0-2b) mixtures. The effects of the DPSU column on the mixture topology, such a perturbation of stationary points, are studied. It is possible to overcome distillation boundaries using a selective membrane but also new stationary points in middle of the composition space appear.

Heat-integrated triple-column pressure-swing distillation process with multi-recycle streams for the separation of ternary azeotropic mixture of acetonitrile/methanol/benzene

The steady-state economics and dynamic controllability of heat-integrated triple-column pressure-swing distillation (TCPSD) process are explored by taking the separation of ternary mixture of acetonitrile, methanol and benzene as demonstrating example. The performance evaluation indicators of second-law efficiency and CO2 emissions are employed to rank different arrangements except only reference of total annual cost (TAC). Compared to the conventional process, the economically optimum flowsheets are the partially heat-integrated processes (Cases 1 and 2) since it can reduce about 20.00% in TAC, 35.19% in energy-saving and enhancement of 48.77% in thermodynamic efficiency. Dynamic control of the economic efficient processes are also investigated. A series of control structures are developed and assessed by the throughput and feed composition disturbances, which are divided to two categories including control schemes with or without split ratio of the distillate stream of second column. The snowballing effect is efficiently attenuated by control schemes (CS4 and CS5) with the ratio strategy to adjust the recycle stream flowrate for partial Case 1. These control strategies are also applied to partial Case 2, the stable regulatory control is achieved, yet oscillation phenomena for the response of condenser heat removal of second column exists for control strategies without split ratio scheme, while it is efficiently handled by the split ratio scheme coupling with pressure compensated temperature-composition cascade control strategy.

Design and control of an energy-efficient alternative process for the separation of methanol/toluene/water ternary azeotropic mixture

Abstract Separation of a ternary mixture containing methanol/toluene/water is a tough task because toluene forms azeotropes with both methanol and water. A recent paper proposed using N-methyl-2-pyrrolidone as heavy entrainer and included a two-column extractive distillation system plus a decanter for the separation of this ternary mixture. In this paper, an energy-efficient simpler process composed of an extraction column and a regular distillation column is investigated in order to achieve the same separation task. Water is used as the solvent to extract methanol from toluene in the extraction column. Toluene is obtained as raffinate while extract phase containing water and methanol is sent to a distillation column for the purification of these two components. Because water itself is a component in the separation mixture, there is no need to introduce any foreign component into the system and hence avoid the possibility of contaminating the products. To compare the optimal result of this design flowsheet with the recently published separation method, our proposed design provides 56.3% savings in total annual cost and 57.1% savings in annual operating cost. Furthermore, a control structure with adjustable solvent flowrate is devised for our proposed process based on the results of open-loop and closed-loop sensitivity tests. Closed-loop dynamic responses show that all products can be maintained at high purity despite large throughput and feed composition disturbances.

Classification for ternary flash point mixtures diagrams regarding miscible flammable compounds

Flash point is a major indicator on the study of fire and explosion hazards of liquid mixtures. Mixtures presenting a minimum flash point behavior are particularly dangerous. It has been shown before that minimum/maximum flash point mixtures could be related with azeotropic behavior under some conditions. Since the 70's a classification of ternary azeotropic mixtures has been developed based on the topological properties of residue curve maps arising from the simple evaporation equilibrium model. In this paper we show that such a general classification also exists for flash point diagram of miscible flammable compound ternary mixtures and that it could help anticipate fire and explosion hazard in ternary mixtures. The demonstration is based on the construction of an auxiliary theoretical system under equilibrium equivalent to a non-equilibrium flash point system.

Energy-saving thermally coupled ternary extractive distillation process by combining with mixed entrainer for separating ternary mixture containing bioethanol

The major intrinsic obstacle of extractive distillation is the high energy consumption. It is an actual problem for reducing energy consumption of extractive distillation processes. Two thermally coupled ternary extractive distillation processes were studied to separate the ternary azeotropic mixture tetrahydrofuran/ethanol/water using a single component solvent (dimethyl sulfoxide) and a mixed solvent (dimethyl sulfoxide and ethylene glycol) as entrainer. The optimal conditions of all ternary extractive distillation processes were obtained based on the minimal total annual cost. Thermodynamic efficiency and CO2 emissions index were also considered to evaluate the energy efficiency and environmental impact of alternative ternary extractive distillation processes. The results show that the use of mixed entrainer can result in reduction in both energy consumption and total annual cost for the same ternary extractive distillation configuration. Comparisons of the conventional ternary extractive distillation process and thermally coupled ternary extractive distillation process 1 (combining extractive distillation column with entrainer-recovery column) with mixed entrainer show that a thermally coupled extractive distillation sequence with a side rectifier present the best results. However, thermally coupled ternary extractive distillation process 2 (combining extractive distillation column with entrainer-recovery column) does not show good result due to existence of remixing effect.

Extractive Distillation Process Combined with Decanter for Separating Ternary Azeotropic Mixture of Toluene-Methanol- Water

The mixture of toluene-methanol-water is difficult to separate because of the formation of toluene-methanol and toluene-water azeotropes. Extractive distillation process with two-column decanter (EDTCD) was improved to separate the system. The process was optimized by the software named Extractive Distillation Optimization Software (EDOS) which based on the minimum total annual cost (TAC). A comparison of the EDTCD and the traditional extractive distillation with triple-column (TEDT) indicated that the former was much more economical. In this comparison, n-methyl-2-pyrrolidone (NMP) and diethylene glycol (DEG) was used as a heavy entrainer in EDTCD and TEDT. The choice of thermodynamic model was discussed in this paper, and the model of UNIQUAC was used in the two processes. The results show that high purity of toluene, methanol and water can be obtained from the process of EDTCD, and it can save 34 % TAC than the process of TEDT.

Comparison of Conventional Extractive Distillation and Heat Integrated Extractive Distillation for Separating Tetrahydrofuran/Ethanol/Water

The distillation is one of the most energy-intensive unit operations in the chemical and pharmaceutical processes. As to the separation of azeotropic mixtures, energy consumption is even more critical. Extractive distillation is an important technique to separate binary or multiple azeotropes. It is important for the extractive distillation processes to achieve the energy consumption reducing. In recent years, partially thermally coupled distillation columns have been applied in extractive distillation to decrease the energy consumption. In this paper, the mixture of tetrahydrofuran, ethanol and water is separated by conventional extractive distillation and partially thermally coupled extractive distillation. The economics of steady state design for the conventional extractive distillation and partially thermally coupled extractive distillation process are explored by calculating total annual costs (TAC). The result showed that more than 16.3 % energy savings and 6.3 % TAC savings can be achieved by the partially thermally coupled extractive distillation process when compared with the conventional extractive distillation process. Partially thermally coupled extractive distillation is an effective way to achieve energy-saving and gain the economic for the separation of ternary azeotropic mixtures.

Control of extractive distillation process for separating heterogenerous ternary azeotropic mixture via adjusting the solvent content

Abstract The existence of heterogeneous azeotrope of toluene-water and homogenous azeotrope of toluene-methanol makes it difficult to separate the toluene-methanol-water mixture. Two methods of three column extractive distillation and two column extractive distillation using decanter were explored to separate the ternary azeotrope. Diethylene glycol and N-methyl-2-pyrrolidone were used as heavy solvent in the two processes, respectively. The UNIQUAC physical model was used in both simulations. Based on the minimum total annual cost, variables of the two processes were optimized and the results indicated the two column extractive distillation using decanter can save 51.4% of total annual cost than three column extractive distillation. The dynamics of two column extractive distillation using decanter was studied due to its superiority of economics. Several common control schemes were used to investigate the controllability of two column extractive distillation using decanter and all schemes showed poor controllability on feed composition disturbances. An improved control structure was designed to achieve better control of the process. In the improved control scheme, the temperature controller of column C1 was replaced by a proportional controller, and a certain amount of solvent flow rate was increased. The integral squared error was calculated to compare the dynamic performances of the improved control structure with different solvent flow rate, and a suitable amount of solvent was found in view of the controllability and economy.

Optimization of the composition of mixed entrainer for economic extractive distillation process in view of the separation of tetrahydrofuran/ethanol/water ternary azeotrope

AbstractBACKGROUNDThere are three binary azeotropes in the tetrahydrofuran/ethanol/water ternary system at atmospheric pressure. Ternary extractive distillation (ED) processes were studied to separate the ternary azeotropic mixture using two single component solvents and a mixed solvent as entrainer.RESULTBased on the sequential iterative optimization procedure, the minimal total annual costs (TACs) of the ternary extractive distillation process using ethylene glycol (EG), dimethyl sulfoxide (DMSO), and the mixture of DMSO and EG as entrainer were obtained. Compared with two single component entrainers DMSO and EG, the TAC of the extractive distillation process with mixed entrainer (60 mol% DMSO + 40 mol% EG) decreases by 6.55% and 31.88%, respectively. Furthermore, the reboiler heat duties of two extractive distillation columns (EDCs) with mixed entrainer were compared with two single component entrainers.CONCLUSIONThe results show that the optimal ED process using mixed entrainer performs better than that using single component entrainers from the perspective of economics. Moreover, there is a tradeoff between the reboiler heat duties of two EDCs, which can be adjusted by changing the entrainer performance in two EDCs. The use of mixed entrainer enhances the flexibility of the tradeoff because it only needs to change the composition of the mixed entrainer. © 2017 Society of Chemical Industry

Pervaporation separation of a ternary azeotrope containing ethyl acetate, ethanol and water using a buckypaper supported ionic liquid membrane

In this study, the pervaporation separation characteristic of a buckypaper supported ionic liquid membrane (BP-SILM-70) in a ternary azeotropic mixture of ethyl acetate/ethanol/water was investigated. The sorption characteristics of the membrane were assessed through a liquid sorption study, and the preference of the membrane to interact with the components in the feed mixtures was evaluated based on binary interaction parameters. Prior to the pervaporation of the ternary mixture system, pervaporation studies of binary mixture systems composed of ethyl acetate/water, ethanol/water and ethyl acetate/ethanol were performed to evaluate the inter-molecular interaction between these components and their tendency to interact with the BP-SILM-70. The membrane was subsequently applied to the pervaporation separation of the ternary azeotrope system, and the effects of the feed temperature and downstream pressure on the pervaporation performance of the membrane were systemically investigated. The BP-SILM-70 exhibited a good pervaporation performance with a total permeation flux of 385.33g·m−2·h−1 and a separation factor as high as 247 at a temperature of 30°C and a downstream pressure of 0.667kPa. The pervaporation result suggests that the use of BP-SILM-70 has great potential to attain a good balance in the trade-off between the permeation flux and the separation factor.

A review of ternary azeotropic mixtures advanced separation strategies

In most multi-component systems, the predominant non-ideality occurs which lead to the occurrence of an azeotrope. The ternary systems classification and study are summarized in first part of this review. The next part covers thermodynamic knowledge of residue curve maps, univolatility and unidistribution curves. A feasibility criterion based on thermodynamic properties of ternary diagram is presented, they are considered as powerful tool for the flow-sheet development and conceptual design. Separation of azeotropic mixtures and close boiling mixtures require non-conventional distillation processes, among which the leading processes are pressure-swing distillation if the composition of the azeotrope changes significantly with pressure, azeotropic distillation, extractive distillation, reactive distillation, and salt-effect distillation. The final section provides an overview of concepts, history, and recent strategies in these non-conventional distillations.

Application of the partially thermally coupled distillation flowsheets for the extractive distillation of ternary azeotropic mixtures

An application is considered of the extractive distillation flowsheets with partially thermally coupled columns for the separation of ternary azeotropic mixtures with the different type of vapor–liquid equilibrium diagrams. The feasible extractive distillation flowsheets with such columns are identified for all types of the ternary azeotropic mixture vapor–liquid equilibrium diagrams. The manifold of flowsheets is the search space to identify the optimal arrangement for the separation of the individual mixture. An applicability analysis of all possible extractive distillation flowsheets for all types of vapor–liquid equilibrium diagram decreases the number of feasible configurations for the selection of the optimal extractive distillation sequence for the mixture with unique vapor–liquid equilibrium diagram separation. For example, in the case of benzene–cyclohexane–toluene mixture distillation with N-methylpyrrolidone as an entrainer, only 10 extractive distillation flowsheets instead of 22 potential ones must be analyzed, calculated and optimized for the identification of the best extractive distillation arrangement.

A novel method for the search and identification of feasible splits of extractive distillations in ternary mixtures

This article describes a novel general method for the search and identification of possible splits of extractive distillations in any ternary azeotropic mixture – the method of infinitely sharp splits. This method finds all feasible product compositions that can be obtained in an extractive column at infinite height and finite reflux. Limiting parameters of mode for the entrainer flow rate and the reflux ratio are determined fast and robustly from the local K-values (vapor–liquid distribution coefficients) of all three components along the sides of the concentration triangle. For the given product specifications the method additionally determines the required number of trays in all the column sections. Hence, both operating and investment costs can quickly be analyzed without cumbersome simulations. The method can be extended to multi-component mixtures.

On the attainable region for process networks

In this work the attainable region (AR) concept for process networks with outlet flow rate specifications is introduced for the first time. For process unit models to which the infinite dimensional State‐space conceptual framework is applicable, it is shown that identification of AR boundary membership is equivalent to feasibility assessment of an infinite linear program (ILP). A number of important AR properties are then theoretically established, including AR convexity, and representation of the AR in a concentration state space of reduced dimension. Finite dimensional approximations of the aforementioned ILP are then employed in creating increasingly accurate approximations of the AR. A case study for the vapor‐liquid equilibrium‐based separation of a ternary azeotropic mixture is used to illustrate the proposed method. The quantified two‐ and four‐Dimensional ARs indicate that acetone mole fractions above 0.79 (acetone/methanol azeotrope) are attainable for the considered outlet flow rate ratios. © 2013 American Institute of Chemical Engineers AIChE J, 60: 193–212, 2014

Rebuttal to “Comments on “Boiling Points of Ternary Azeotropic Mixtures Modeled with the Use of the Universal Solvation Equation and Neural Networks’”

Rebuttal to “Comments on “Boiling Points of Ternary Azeotropic Mixtures Modeled with the Use of the Universal Solvation Equation and Neural Networks’”

Comment on “Boiling Points of Ternary Azeotropic Mixtures Modeled with the Use of the Universal Solvation Equation and Neural Networks”

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondenceNEXTComment on “Boiling Points of Ternary Azeotropic Mixtures Modeled with the Use of the Universal Solvation Equation and Neural Networks”Shunlong Ma and Shaojun Li*View Author Information Key Laboratory of Advanced Control and Optimization for Chemical Processes, Ministry of Education, East China University of Science and Technology, Shanghai 200237, People’s Republic of China*Tel.: +86-21-64253820. E-mail: [email protected]Cite this: Ind. Eng. Chem. Res. 2013, 52, 1, 543–544Publication Date (Web):December 14, 2012Publication History Published online14 December 2012Published inissue 9 January 2013https://doi.org/10.1021/ie302909bCopyright © 2012 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views266Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (136 KB) Get e-AlertsSUBJECTS:Chemical structure,Layers,Mixtures,Neural networks,Transition temperature Get e-Alerts

Boiling Points of Ternary Azeotropic Mixtures Modeled with the Use of the Universal Solvation Equation and Neural Networks

Azeotropic mixtures, an important class of technological fluids, constitute a challenge to theoretical modeling of their properties. The number of possible intermolecular interactions in multicomponent systems grows combinatorially as the number of components increases. Ab initio methods are barely applicable, because rather large clusters would need to be calculated, which is prohibitively time-consuming. The quantitative structure–property relationships (QSPR) method, which is efficient and extremely fast, could be a viable alternative approach, but the QSPR methodology requires adequate modification to provide a consistent treatment of multicomponent mixtures. We now report QSPR models for the prediction of normal boiling points of ternary azeotropic mixtures based on a training set of 78 published data points. A limited set of meticulously designed descriptors, together comprising the Universal Solvation Equation (J. Chem. Inf. Model.2009, 49, 634), was used to provide input parameters for multiple regression and neural network models. The multiple regression model thus obtained is good for explanatory purposes, while the neural network model provides a better quality of fit, which is as high as 0.995 in terms of squared correlation coefficient. This model was also properly validated and analyzed in terms of parameter contributions and their nonlinearity characteristics.

Flowsheet synthesis and complex distillation column design for separating ternary heterogeneous azeotropic mixtures

The boundary value method for design of distillation columns separating ternary heterogeneous azeotropic mixtures is extended to include complex configurations, i.e. columns with integrated decanters and with multiple heterogeneous stages; double-feed columns; columns with intermediate decanters. The methods can be used for establishing product feasibility in a column and evaluating a column design in terms of cost. Multiple feasible designs can be generated for a given set of product specifications, according to the reflux ratio, number of heterogeneous stages and liquid phase ratio; these designs may be evaluated with respect to operating and equipment costs. Case studies illustrate the design method. An algorithmic approach is presented for synthesising novel sequences for separating, by distillation and decanting, ternary heterogeneous azeotropic mixtures. Existing synthesis procedures that consider only simple single-feed columns with decanters and integrated decanters are extended to include more industrially relevant options such as columns with several heterogeneous stages, double-feed columns, columns with intermediate decanters, and those accepting a heterogeneous liquid feed. With these advanced column configurations included in the synthesis method, a wider range of sequences may be considered systematically, allowing sequences that are more economically attractive than conventional designs to be identified. A case study illustrates the approach.

ASPECTS OF MULTICOMPONENT MIXTURE SEPARATION IN THE PRESENCE OF SELECTIVE SOLVENTS

The extractive and autoextractive distillation of ternary and quaternary azeotropic solvent mixtures was adopted to demonstrate the relation between the structure of phase diagram of the azeotropic systems and the operating parameters of the extractive distillation column based on the relative volatility criterion. A set of separation schemes belonging to different structural classes have been investigated. The separation scheme that has the lower energy consumption is revealed for separation of four-component solvent mixtures—acetone-n-butanol-chloroform (or toluene) and dimethylformamide—that were used in the production of thermal stabilizer stabilin-9.