REGSOLexpert: Entrainer Selection Tool for waste solvent recovery by batch distillation processes

A general procedure to systematize the search of several alternatives enabling the separation of non-ideal binary mixtures such as pressure-swing distillation, azeotropic and extractive distillation is presented. The use of heterogeneous entrainers is specially highlighted

Optimisation of heterogeneous batch extractive distillation

This paper considers the optimisation of batch extractive distillation, using heterogeneous entrainers for the first time. The objective function includes the maximum of overall profit and the optimisation variables are the entrainer flowrate and the reflux ratio that is an optimal combination of both decanted phases. Simulation and optimization is performed within MATLAB, by using a genetic algorithm coupled to a short-cut model of the distillation column. The performance of the optimisation scheme is illustrated through the separation of chloroform – methanol mixture with water considering either a constant or a piecewise constant policy for both optimization variables

Heterogeneous batch distillation processes for waste solvent recovery in pharmaceutical industry

A summary about our experiences in the introduction of heterogeneous entrainers in azeotropic and extractive batch distillation is presented in this work. Essential advantages of the application of heterogeneous entrainers are showed by rigorous simulation and experimental verification in a bench batch distillation column for separating several azeotropic mixtures such as acetonitrile – water, n hexane – ethyl acetate and chloroform – methanol, commonly found in pharmaceutical industry

Improved Design and Efficiency of the Extractive Distillation Process for Acetone–Methanol with Water

We show how thermodynamic insight can be used to improve the design of a homogeneous extractive distillation process, and we define an extractive efficiency indicator to compare the optimality of different designs. The case study is related to the separation of the acetone–methanol minimum boiling azeotrope with water. The process flow sheet includes both the extractive distillation column and the entrainer regeneration column. Insight from analysis of the ternary residue curve map and isovolatility curves shows that a lower pressure reduces the minimal amount of entrainer needed and increases the relative volatility of acetone–methanol in the extractive column. A 0.6 atm pressure is selected to enable the use of cheap cooling water in the condenser. We optimize the entrainer flow rate, adjusting both column reflux ratios and feed locations, by minimizing the total energy consumption per product unit. The total annualized cost (TAC) is calculated for all processes. Double-digit savings in energy consumption and in TAC are achieved compared to literature values. We then propose a novel efficiency indicator that describes the ability per tray of extractive section to discriminate the desired product between the top and the bottom of the extractive section. Shifting the feed trays’ locations improves the efficiency of the separation, even when less entrainer is used

On the Riemannian structure of the residue curves maps

In this paper, we revise the structure of the residue curve maps (RCM) theory of simple evaporation from the point of view of Differential Geometry. RCM are broadly used for the qualitative analysis of distillation of multicomponent mixtures within the thermodynamic equilibrium model. Nevertheless, some of their basic properties are still a matter of discussion. For instance, this concerns the connection between RCM and the associated boiling temperature surface and the topological characterization of the distillation boundaries. In this paper we put in evidence the Riemannian metric hidden behind the thermodynamic equilibrium condition written in the form of the van der Waals–Storonkin equation, and we show that the differential equations of residue curves have formal gradient structure. We discuss the first non-trivial consequences ofthis factfor the RCM theory ofternary mixtures

Reducing process cost and CO2 emissions for extractive distillation by double-effect heat integration and mechanical heat pump

Double-effect heat integration and mechanical heat pump technique are investigated for the extractive distillation process of the acetone–methanol minimum boiling azeotropic mixture with entrainer water and compared from the economical view by the total annual cost (TAC) and environmental aspect by CO2 emissions. Firstly, A novel optimal partial heat integration (OPHI) process is proposed and optimized through the minimization of a newly defined objective function called OF2 that describes the energy consumption used per product unit flow rate and allows comparison with the literature direct partial and full heat integration processes. We find that the minimum TAC is not achieved by the full heat integration process as intuition, but by the new OPHI process. Secondly, the vapour recompression (VRC) and bottom flash (BF) mechanical heat pump processes are evaluated with respect to energy and CO2 emissions. We proposed a new partial VRC and a new partial BF process in order to reduce the high initial capital cost of compressors. Overall the results show that compared to the conventional extractive distillation process the proposed OPHI process gives a 32.2% reduction in energy cost and a 24.4% saving in TAC while the full BF process has the best performance in environmental aspect (CO2 emissions reduce by 7.3 times)

Low pressure design for reducing energy cost of extractive distillation for separating Diisopropyl ether and Isopropyl alcohol

We show how reducing pressure can improve the design of a 1.0-1a mixture homogeneous extractive distillation process and we use extractive efficiency indicators to compare the optimality of different designs. The case study concerns the separation of the diisopropyl ether (DIPE)–isopropyl alcohol (IPA) minimum boiling azeotrope with heavy entrainer 2-methoxyethanol. We first explain that the unexpected energy cost OF decrease following an increase of the distillate outputs is due to the interrelation of the two distillate flow rates and purities and the entrainer recycling through mass balance when considering both the extractive distillation column and the entrainer regeneration column. Then, we find that for the studied case a lower pressure reduces the usage of entrainer and increases the relative volatility of DIPE–IPA for the same entrainer content in the extractive column. A 0.4 atm operating pressure is selected to enable the use of cheap cooling water in the condenser. We run an optimization of the entrainer flow rate, both columns reflux ratios, distillates and feed locations by minimizing the total energy consumption per product unit. Double digit savings in energy consumption are achieved while TAC is reduced significantly. An extractive efficiency indicator that describes the ability of the extractive section to discriminate the desired product between the top and the bottom of the extractive section of the extractive section is calculated for comparing and explaining the benefit of lowering pressure on the basis of thermodynamic insight

A Novel Method for Detecting and Computing Univolatility Curves in Ternary Mixtures

Residue curve maps (RCMs) and univolatility curves are crucial tools for analysis and design of distillation processes. Even in the case of ternary mixtures, the topology of these maps is highly non-trivial, as shown by Serafimov’s and Zhvanetskii’s classifications. We propose a novel method allowing detection and computation of the existence of univolatility curves in homogeneous ternary mixtures independently of the presence of azeotropes, which is particularly important in the case of zeotropic mixtures. The method is based on analysis of the geometry of the boiling temperature surface constrained by the univolatility or unidistribution condition. The introduced on the concepts of the generalized univolatility and unidistribution curves in the three dimensional composition – temperature state space that lead to a simple non iterative and efficient algorithm of computation of the univolatility curves. Two peculiar ternary systems, namely diethylamine – chloroform – methanol and hexane – benzene – hexafluorobenzene are used for illustration. When varying pressure, tangential azeotropy, bi-ternary azeotropy, saddle-node ternary azeotrope, and bi-binary azeotropy are found. In both examples, a distinctive crossing shape of the univolatility curve appears as a consequence of the existence of a common tangent point between the three dimensional univolatility hypersurface and the boiling temperature surface. Moreover, rare univolatility curves starting and ending on the same binary side are found

Isopropyl alcohol recovery by heteroazeotropic batch distillation

Solvent recovery is becoming a major issue in the pharmaceutical and specialty chemical industries. Solvent recovery by conventional batch distillation is limited by the frequent presence of azeotropes in the used solvent mixtures. Most distillation processes for the separation of azeotropic or difficult zeotropic mixtures involve the addition of an entrainer (homogeneous and heterogeneous azeotropic distillation or extractive distillation). In this study the recovery of IPA (isopropyl alcohol) from an industrial waste stream (IPA/water mixture) was studied by conventional batch distillation and heteroazeotropic batch distillation, using cyclohexane as entrainer. First the ternary IPA/water/cyclohexane azeotrope (boiling temperature of 64.1 °C), then the binary IPA/cyclohexane azeotrope (boiling temperature of 69.3°C) and finally pure IPA was distilled. 99.96 mass% IPA could be obtained by heteroazeotropic distillation, using cyclohexane as entrainer. By using this procedure the IPA recovery is 97.6%, which is high compared to the conventional distillation techniques. The binary azeotrope could be reused in a subsequent heteroazeotropic batch distillation

Computer-aided molecular design of alternative solvents based on phase equilibrium synergism in mixtures

A systematic methodology is proposed that finds binary azeotropic mixtures as new alternative solvents for the extraction process of volatile aroma molecules widely used in perfume and cosmetic industries. We investigated the use of the reverse engineering approach with Computer Aided Product Design (CAPD) instead of the traditional ‘trial and error’ approach. First, the design problem is defined from the real functionalities of the classical solvents. They are translated into physicochemical properties and the bound values for each property are defined. The reverse engineering method coupled to CAPD consists in using optimization techniques for building molecular structures that match as best as possible the complete set of target physicochemical properties, thus defining for each candidate a performance index. Property values are evaluated by using group contribution methods of each molecular structure generated by CAPD tool or by using database values. Acknowledging the contradictory relationship between two selected physicochemical properties i.e, low boiling temperature and high flash point which is rarely found in pure components, binary azeotropic mixtures were studied in order to enhance the global performance of solvent candidates. Dimethyl carbonate (DMC) is an existing solvent for the extraction of odorous molecules from plants that exhibits a good ratio between the boiling temperature and the flash point. It is selected as the key component for designing binary azeotropic mixtures. DMC. The global performance of the binary azeotropic mixtures was verified by means of calculations of the vapour-liquid equilibrium and liquid – liquid equilibrium using Modified UNIFAC method as thermodynamic method