Azeotropic Distillation Process Research Articles

Dimethyl carbonate/methanol separation by azeotropic distillation with water: An alternative process driven by low-pressure steam

This study reported a conceptual design of dimethyl carbonate/methanol (DMC/MET) separation via an azeotropic distillation (AD) process with water as the entrainer. Water can form a minimum azeotrope with DMC, stripping DMC from MET via a distillation column. Meanwhile, the liquid–liquid equilibrium can lift the DMC fraction from the azeotropic composition to a much higher level with a decanter. It enables the subsequent distillation column to produce pure DMC. The techno-economic analysis after process optimization demonstrated that the total annualized cost (TAC) of the AD process is 13.8 % lower than the conventional extractive distillation (ED) process. Subsequently, heat integration and double-effect distillation were introduced to further increase the energy efficiency. The improved AD process is also superior to the improved ED process (31.7 % energy cost and 4.1 % TAC saved). Moreover, the moderate temperature of the reboilers of the AD process with water as the entrainer further elevates its superiority since industrial waste heat can be applied in this case.

Improved solution thermodynamics modeling in pervaporation

The current work features a system-level design of pervaporation processes (typically utilized to break azeotropes) that is solution thermodynamics-based (inclusive of validated excess thermodynamic properties). Unlike the standard pervaporation modeling methodology in the literature, the current method (referred to here as PervapS3) deconstructs the membrane module into its constituent units, and the material and energy flows were mathematically validated. These amendments to the previous methodology (i.e., leaf-wise modeling, mathematical validation, and inclusion of excess thermodynamic properties) revealed significant deviations in key parameter values. For a given large-scale pervaporation process dehydrating aqueous isopropanol, the total membrane area and energy requirement calculated were up to 22% and 19% less than the values calculated using the previous methodology. Moreover, due to the inclusion of excess thermodynamic properties in the PervapS3 method, the minimum separation work and the second law (thermodynamic) efficiency were up to 94% and 78% less. In other words, the previous pervaporation modeling methodology overestimated membrane area, energy requirement, minimum separation work, and second law efficiency. Considering a conventional azeotropic distillation process for comparison with pervaporation, it was observed that the simulation-based distillation models from the literature were inclusive of the system non-idealities. Per the previous method, the non-ideal second law efficiency of azeotropic distillation would be compared against the ideal second law efficiency of pervaporation, overestimating the latter. The non-ideal second law efficiency must be employed to facilitate a fairer and more accurate comparison of disparate separation technologies.

Thermally coupled distillation columns without vapor transfer – Current state and further needs

Reducing the energy requirements is one essential pillar in the effort to reduce the carbon footprint of the energy intensive chemical industry. Thermal coupling of distillation columns and the equipment-integrated implementation in dividing wall columns can be considered a mature and established technology to reduce the energy demand of distillation sequences. Despite the widespread investigations and applications, the vaporous transfer stream between thermally linked columns or vapor split in the dividing wall column is associated with certain limitations. Some of these can effectively be overcome by adding an additional column section with reboiler or condenser to the thermally linked column, converting the bidirectional transfer of liquid and vapor to a unidirectional liquid transfer, which mandates additional investment, but provides an additional degree of freedom and retains the energy saving potential of the thermally coupled sequence. Although these so-called Liquid-Only-Transfer (LOT) sequences have been introduced almost 25 years ago, the process concept is receiving an increasing interest in recent years, with specific focus on conceptual design and control studies. The current review provides a methodological overview on synthesis, design and control studies for LOT-sequences, considering zeotropic and azeotropic distillation processes. It analyzes the advantages and challenges of this interesting process concept and highlights research areas and questions that still require additional attention.

A different strategy to reduce energy consumption for designing heterogeneous decanter-assisted advanced pressure-swing distillation process

In this work, we aim to explore the feasibility of integrating two strategies, i.e., (1) introducing a small quantity of solvent as a makeup stream and (2) employing a decanter, to develop an energy-efficient pressure swing distillation process for ternary azeotropic separation. The addition of a minor amount of solvent aims to facilitate the transition of the feed composition from outside the liquid–liquid equilibrium region to within it. This transition could enable the use of a decanter, thereby promoting a more energy-efficient separation process with reduced reliance on pressure-driven mechanisms. A systematic approach was proposed to explore this concept, involving the different thermodynamic features for conceptual design followed by process optimization and process evaluation. This approach was exemplified using a mixture containing chloroform, ethanol, and water. Two solvent and decanter-assisted triple-column pressure-swing azeotropic distillation (SD-TCPSAD) process were developed and evaluated against the conventional triple-column pressure swing distillation in terms of economic, energy, and environmental performance. Among the three configurations, SD-TCPSAD I exhibited the most favorable outcomes, achieving a 61 %, 69 %, and 69 % improvement in economic, energy, and environmental impact. These improvements were primarily attributed to the utilization of smaller column sizes, the utilization of different heating utilities, and a substantial decrease in overall energy consumption.

Economic, environmental, energy, exergy (4E) analysis and simulated annealing algorithm optimization of dividing-wall column-intensified heterogeneous azeotropic pressure-swing distillation process

This work presents an approach for the recovery of high purity cyclohexane (CYCLO) and tertiary butyl alcohol (TBA) from wastewater. After thermodynamic analysis, a heterogeneous azeotrope-pressure swing distillation process (HAPSD) with a decanter is proposed. The heterogenous azeotrope distillation with a high-pressure column and a dividing-wall column process (HADWC) is also being developed to propose a green and sustainable process. The novel processes are optimized using simulated annealing algorithm (SAA). Those processes are optimized by simulated annealing algorithm by linking Aspen Plus and MATLAB via taking the total annual cost (TAC) as objective function. Three energy-efficient HADWC processes are proposed based on the process intensification approach of heat pump and heat integration technologies. All processes are evaluated for multi-criteria performance including economy, energy consumption, gas emissions and thermodynamic efficiency. As the result, HADWC-HP-HI process shows the best performance with 31.79%, 53.46%, 50.69%, and 57.94% reducing over the conventional HAPSD process in terms of TAC, energy consumption, gas emissions and thermodynamic efficiency, respectively.

Energy-efficient heterogeneous triple-column azeotropic distillation process for recovery of ethyl acetate and methanol from wastewater

The challenging separation of ethyl acetate (EtAC) and methanol (MeOH) from wastewater involves two azeotropes and a distillation boundary. Although extractive distillation (ED) has been explored, the heterogeneous region within the ternary azeotropic mixture has been overlooked, which suggests the possibility of using a decanter to cross the distillation boundary when the feed composition is present in the heterogeneous region. This study introduces a novel heterogeneous triple-column distillation (NHTCD) that eliminates the external solvent injection, simplifying the complex ED processes. The NHTCD process is developed via a systematic approach, comprising conceptual design based on thermodynamic insights and process optimization to determine the optimum configuration. Furthermore, heat integration (HI) and heat pump-vapor recompression (HP-VR) techniques were explored for energy conservation. Evaluation of energy, economic, and environmental (3E) aspects shows that the hybrid HP-VR with HI NHTCD process outperforms ED, achieving 87 %, 57 %, and 86 % reductions in energy, economic, and environmental emissions, respectively.

Production of gasohol by azeotropic distillation

AbstractA new azeotropic distillation process is presented to produce gasohol in an adequate concentration of bioethanol and isooctane, which emulates the properties of gasoline ready to use in conventional combustion engines. Since the mixing step is eliminated, there are significant economic savings which imply a competitive price of bioethanol. A comparison is provided with the traditional bioethanol dehydration process, extractive distillation. Both processes were simultaneously designed and optimized with differential evolution with a Tabu list algorithm (DETL) in order to reduce the total annual cost (TAC). Results showed that when obtaining E10 biofuel, a blend of up to 10% ethanol and 90% unleaded isooctane, via azeotropic distillation, over 40% of the TAC is saved compared to obtaining pure alcohol dehydrating through extractive distillation. Moreover, the reduction in carbon dioxide emissions results in an average of 27%.

Energy-saving design and optimization of pressure-swing-assisted ternary heterogenous azeotropic distillations

A huge amount of energy is always consumed to separate the ternary azeotropic mixtures by distillations. The heterogeneous azeotropic distillation and the pressure-swing distillation are two kinds of effective technologies to separate heterogeneous azeotropes without entrainer addition. To give better play to the synergistic energy-saving effect of these two processes, a novel pressure-swing assisted ternary heterogeneous azeotropic distillation process is proposed firstly. In this process, the ternary heterogeneous azeotrope is decanted into two liquid phases before refluxed into the azeotropic distillation column to avoid the aqueous phase remixing, and three columns’ pressures are modified to decrease the flowrates of the recycle streams. Then the dividing wall column and heat integration technologies are introduced to further reduce its energy consumption, and the pressure-swing assisted ternary heterogeneous azeotropic dividing wall column and its heat integration structure are achieved. Genetic Algorithm procedure is employed to optimize the proposed processes. The design results show that the proposed processes have higher energy efficiencies and lower CO2 emissions, compared with the published ternary heterogeneous azeotropic distillation process.

Thermodynamic efficiency of membrane‐assisted distillation processes

AbstractMembrane processes are considered as comparably mild separation processes offering the potential for significant energy savings compared with azeotropic distillation processes. Despite higher investment and material costs, they are of particular interest for improving the energy efficiency in the chemical industry. However, energy savings of more than 20%–30% are rarely reported and even a general superiority can be disputed. To further elucidate this controversial, the current study pursues a quantitative assessment of the thermodynamic efficiency of pervaporation and vapor permeation processes with stand‐alone distillation and hybrid membrane‐assisted distillation processes for the separation of azeotropic mixtures. The results confirm the case‐dependent potential of distillation processes to outperform membrane‐assisted separations in terms of energy efficiency, considering proper heat integration. Although energy efficiency is becoming significantly important, it should be considered in the context of economic performance to determine an optimal trade‐off and to select the best process alternative during conceptual process design.

Separation of ethylene glycol, 1,2‐butanediol and 1,2‐propanediol with azeotropic distillation

Abstract1,2‐butanediol (1,2‐BDO) and 1,2‐propanediol (1,2‐PDO) are inevitably side produced in the ethylene glycol (EG) production processes from non‐petroleum routes, but are very difficult to separate by the ordinary distillation method because of the closeness of their boiling temperatures to EG, thus compromise the economy of these processes. The azeotropic distillation process using 1‐octanol (CPO) as an entrainer to separate EG and 1,2‐BDO mixture with or without 1,2‐PDO was studied in this paper. Four binary vapour–liquid equilibrium data of EG‐1,2‐BDO, EG‐CPO, 1,2‐BDO‐CPO, and 1,2‐PDO‐CPO were measured using an Ellis equilibrium kettle and regressed with the thermodynamic model of non‐random two liquid to obtain the corresponding binary interaction parameters. On this basis, azeotropic distillations with CPO as an entrainer were designed to separate EG and 1,2‐BDO with or without 1,2‐PDO. The complete separation processes, including the azeotropic distillation and CPO recovery process consisting of extraction with H2O and subsequent distillation, were simulated and optimized with Aspen Plus for both the EG‐1,2‐BDO binary mixture and the EG‐1,2‐BDO‐1,2‐PDO ternary mixture. The simulation results show that the azeotropic distillation method with CPO as an entrainer can effectively separate the mixture of EG‐1,2‐BDO and EG‐1,2‐BDO‐1,2‐PDO, achieving EG of 99.90% purity with 99.98% recovery and 1,2‐BDO of 99.30% purity with 99.45% recovery for the binary mixture, and achieving EG of 99.90% purity with 99.80% recovery, 1,2‐BDO of 99.35% purity with 99.35% recovery, and 1,2‐PDO of 90.59% purity with 94.38% recovery for the ternary mixture. These processes are promising for industrial application and can significantly improve the economy of non‐petroleum EG production.

Application of dividing wall column in azeotropic distillation with intermediate boiling-point heteroazeotrope: Simulation and optimization

Dividing wall column (DWC), as a proven process intensification technology, has been used widely in separation of ideal multi-components, and some azeotrope systems. For heterogeneous azeotrope with the potential possibility of crossing distillation boundary by liquid-liquid splitting, it is advantageous to integrate liquid-liquid decanter with distillation column, especially with DWC to further simplify flowsheets and reduce energy consumption. In this work, existing heterogeneous azeotrope separation processes are described, and an innovative DWC-based process (MHADWC) is proposed for intermediate boiling-point heteroazeotropic systems. Then an industrial case of MIPK system, is used to evaluate mentioned configurations by rigorous simulation and optimization. These configurations are compared and analyzed in detail on energy consumption, exergy analysis and equipment invest. The results show that, from the perspective of process energy consumption, MHADWC process has the most advantages, because it saves 37% of energy consumption; if both equipment costs and exergy recovery are taken into account, HADWC2 has a higher thermodynamic efficiency (43.5%) at its TAC and can be used as a preferred target. And in this work, purification of an intermediate boiling-point heteroazeotrope is the main difference of these processes compared with the well-known heterogeneous azeotropic distillation process where the top vapor product is the lowest boiling point of the ternary system.

Heterogeneous Azeotropic Extractive Coupled Heat Pump Distillation for Triethylamine‐Dichloromethane‐Acetone‐Water

AbstractThere are three kinds of binary azeotropes and one kind of a near‐boiling compound with clamping zone characteristics in the triethylamine‐dichloromethane‐acetone‐water system, which belongs to complex quaternary systems. A four‐column distillation process of heterogeneous azeotropic extraction for the separation of the system was designed, simulated, and optimized to obtain more suitable process parameters and energy consumption distribution of each column. On this basis, taking the total annual cost (TAC) as the comprehensive economic evaluation index and CO2 emission as the environmental evaluation index, the thermal integration technology and mechanical vapor recompression (MVR) heat pump technology were applied to the energy‐saving research of the distillation process for the system. The results indicate that compared with the conventional four‐column heterogeneous azeotropic extractive distillation process, the thermal integration distillation process and single‐column MVR heat pump coupled thermal integration distillation process can save energy consumption and TAC, and it can reduce CO2 emission.

Investigation of solution acidity influence on the morphological structure and physical and mechanical properties of particle-reinforced tungsten alloys

Yttria-stabilized zirconia particle–reinforced tungsten alloys were fabricated by using azeotropic distillation process coupled with powder metallurgy techniques. The influence of pH value of the original solution on the precursor powders’ morphology and wear and mechanical properties of alloys was deeply studied. It showed that the precursor powder synthesized under solution with pH of 2 possesses finer particle size. The grain sizes of tungsten reinforced alloys obtained with different pH values vary from 2 to 6 μm, extremely smaller than that of pure tungsten. When pH value increases from 2 to 8, more and more bonding zirconia particles are obtained. The reinforced tungsten alloy prepared based on the solution of pH equal to 2 has better morphological and mechanical properties than the other two alloys prepared based on the solution of pH values of 5 and 8, respectively. The wear resistance of the reinforced tungsten alloy increases firstly and then decreases with the doping amount of zirconia particles. It is confirmed that the pH 2 value and chemical composition of the tungsten alloy with 3.0 wt. % Zr(Y)O2 exhibit the best wear resistance. The mechanical properties of the particle-reinforced tungsten alloy are improved with the decrease of pH value. The ultimate compressive strength and ultimate strain values of pH 2 reach to 1009 MPa and 0.23, respectively. The evolution of the relative density and associated porosity increases with the pH value. The abrasion mechanism was analyzed in detail.

Control of the azeotropic distillation process for separation of acetonitrile and water with and without heat integration

A novel acetonitrile/water azeotropic distillation scheme shows obvious economic advantages. It is of great significance to study the dynamic controllability of this process. In this work, the dynamic control structures of the non heat-integration and full heat-integration azeotropic distillation are studied. The control ability of the proposed control structures is tested by adding flow disturbance and composition disturbance. For the non heat-integration scheme, the conventional PID control structure and composition controller is used to achieve effective control when a disturbance occurs. For the full heat-integration scheme, the temperature difference control scheme and the composition controller are used to handle disturbances. This control structure reduces the stabilization time and makes the purity of the product return to the set value. The effect of different makeup flow on the purity of acetonitrile under different disturbances is discussed. Moreover, two control strategies are synthetically analyzed and compared by calculating integral of squared error. Considering economy and controllability, it is concluded that control strategy of heat-integrated azeotropic distillation has more advantages. This study has certain guiding value for the research of chemical dynamic control.

Production of fuel grade anhydrous ethanol: a review

Alcoholic fermentation of fermentable carbon sources like molasses and table sugar using yeast are typical route in producing alcohol particularly known as bioethanol (C2H5OH). The key challenge encountered in bioethanol production process is to eliminate the impurity presence within the bioethanol which mainly water. Distillation is an energy extensive process which commonly used to recover ethanol up to 95% purity due to the presence of azeotropic composition. The distillation will no longer appropriate for further purification once the azeotrope composition has reached. Nonetheless, to be able to use as a viable fuel for gasoline engine or for any other utilizations where the purity is a major concern, further dehydration steps are needed producing an absolute ethanol. Few studies have been investigated on various dehydration methods for producing anhydrous ethanol, including azeotropic distillation, extractive distillation, adsorption, membrane pervaporation, and solvent extraction process. This review offers an insight into currently used technology on the ethanol dehydration methods and the future prospect on the continuous improvement particularly on the process energy requirement and efficiency will be discussed.

Conceptual design, optimization, and carbon emission analysis for the acrylonitrile/acetonitrile/water separation processes

In this work, we firstly report on the rigorous design, optimization, and carbon emission analysis of the processes separating acrylonitrile (AN), acetonitrile (AC), and water. Two bi-sectional processes, which integrate heterogeneous extractive distillation with hybrid extraction-distillation (the HHED process), and that with pressure swing distillation (the HPSD process), are proposed. Compared with the existing configuration, operation using 30% less entrainer amount is found feasible for both processes, leading to 9.8% energy saving. Also, the optimized HHED process saves 4.8% total annual cost (TAC) and 5.8% carbon emission from the optimized HPSD process. Besides, implementing a vapor recompression cycle on the optimized HHED process reduces 31.1% CO2 emission but increases 6.6% of TAC. On the other hand, the heat-integrated HPSD process with an economizer design does not outperform the non-integrated HHED process. Finally, separation using heterogeneous azeotropic distillation or hybrid extraction-distillation process in single is conceptually rejected. Through this work, the industrial guidance could be provided.

Design, Simulation, and Pilot Verification of a Coupled Azeotropic and Extractive Distillation Process for the Production of Propylene Oxide with High Purity

To obtain the production of propylene oxide (PO) with high purity, a coupled azeotropic and extractive separation process is proposed to remove the impurities such as aldehyde, methanol, methyl for...

Comparison of Complete Extractive and Azeotropic Distillation Processes for Anhydrous Ethanol Production Using Aspen Plus™ Simulator

Performance of the extractive and azeotropic distillation processes using ethylene glycol and cyclohexane as solvents, respectively, for anhydrous ethanol production, were investigated using 02 RadFrac columns each and solvent recycling streams via simulation in Aspen Plus™ Simulator. Both operate at 1 atm, and feed flow rate equals to 100 kmol.h-1 (ethanol – 0.896 and water – 0.104 in mole fractions at the azeotropic point). The NRTL-RK was the model used for extractive and azeotropic distillations. The anhydrous ethanol purity from top of the 1st column of the extractive distillation (22 stages) was 99.50 % (on a mole basis) and water with 99.20 % of purity at the top of the 2nd column. On the other hand, in the azeotropic distillation, the 1st column (30 stages) had a bottom product of anhydrous ethanol purity of 99.99 % and water with 99.99 % of purity in the 2nd column, also at the bottom. Both processes produced anhydrous ethanol with a high-grade purity required by the standard norms ASTM D4806, EN 15376, and ANP 36. However, the extractive distillation spent 1,928.2 kW in the reboilers against 4,680.3 kW in the azeotropic distillation, demonstrating extractive distillation is the most economical option. Consequently, the energy consumption is an essential analysis for choosing the type of distillation, when an azeotropic mixture needs a good separation task. Finally, the extractive distillation demonstrated to be much more competitive than azeotropic distillation for this type of mixture although azeotropic distillation obtained a higher purity of anhydrous ethanol.

Efficient optimization-based design of energy-integrated azeotropic distillation processes

The separation of azeotropic mixtures is frequently performed by extractive or heteroazeotropic distillation processes. The design of these processes requires careful selection of a suitable solvent and is specifically challenging since feasibility and optimality of the processes require consideration of the closed loop design including solvent recovery. Consideration of energy integration further complicates the design task and is usually conducted as post-evaluation step. The current publication proposes an efficient optimization-based design approach, which allows for the direct evaluation of several energy-integrated process concepts, while significantly reducing manual effort and computational time through a polylithic modeling and solution approach. The developed approach allows for a simultaneous evaluation of solvent selection and energy integration and is illustrated for different case studies, including the evaluation extractive and heteroazeotropic distillation for the dehydration of ethanol, as well as the evaluation of multiple solvent candidates for the extractive distillation of acetone and methanol.

Azeotropic distillation for 1-propanol dehydration with diisopropyl ether as entrainer: Equilibrium data and process simulation

Azeotropic distillation process is widely used to separate non-ideal binary mixtures into their constituent pure components. 1-Propanol dehydration was used as case study and diisopropyl ether was analysed as possible entrainer in an azeotropic distillation. The separation of some alcohols from their aqueous solution is a challenging task because these aqueous mixture forms minimum boiling azeotrope.In this way, isobaric vapor-liquid and vapour-liquid-liquid equilibrium data were measured for the 1-propanol+ water + diisopropyl ether ternary mixture at 101.3 kPa. The data were correlated by NRTL and UNIQUAC models.A separation sequence (a decanter and a single-feed distillation column) for 1-propanol dehydration using diisopropyl ether was proposed. The simulation of the separation sequence was carried out satisfactorily by Aspen Hysys® using the thermodynamic model NRTL with the binary parameters obtained in this work. Moreover, the effect of temperature decantation was investigated in order to reduce the energy demand of the process.