Pressure-swing Distillation Research Articles

Economical process design of reactive-extractive distillation combining variable pressure and heat integration for separating a ternary azeotropic mixture

Research and development of environmentally friendly processes that can generate significant profits has always been a focus of attention in pharmaceutical and chemical fields. In this study, a novel reactive-extractive pressure-swing distillation (REPSD) process was designed to separate tetrahydrofuran (THF)-methanol-water (TMW) ternary azeotropic mixtures. Ethylene oxide (EO) is reacted with water to form ethylene glycol (EG) in a reactive distillation (RD) column, which removes the water from the mixture. Then, the THF-methanol (TM) mixture is separated by extractive distillation (ED) and pressure-swing distillation (PSD). A multi-objective genetic algorithm (MUOGA) with total annual cost (TAC) and total capital cost (TCC) as objective functions, along with heat integration techniques were used to optimise the designed REPSD process. Optimal operating conditions to achieve maximum economic benefits were obtained for the process. Subsequently, the environmental benefits of the process were evaluated. The results showed that the proposed REPSD with heat integration can significantly reduce the TAC and CO2 emissions by 29.1 and 26.9 %, respectively, compared to existing optimal heat integration extractive distillation (HIED) processes. This study provides a new perspective on the separation and purification of ternary azeotropic mixtures.

Heat Pump-Assisted extractive Pressure-Swing distillation with integrated feed Preconcentration/Solvent recovery for Isopropanol-Benzene-Water separation

Recently, heat-integrated pressure-swing distillation (HIPSD) has been explored for recovering isopropanol and benzene from wastewater, but the process remains highly energy-intensive. Given the dilute nature of the feed, intensified extractive distillation with an integrated preconcentration column (IEDP) is more suitable. However, previous research has often overlooked the critical role of pressure and lacked rigorous optimization of operating pressure in such systems. In this article, we developed novel extractive pressure-swing distillation with integrated feed preconcentration/solvent recovery column (IEPSD) by introducing a pressure-swing configuration and incorporate energy-saving technologies to achieve more sustainable and cost-effective separation processes. First, thermodynamic analysis is conducted to explore the effect of pressure on extractive pressure-swing distillation. Then, a parallel genetic algorithm is applied for rigorous optimization, followed by the application of heat integration and heat pump. The IEPSD is superior to IED in terms of total annual cost (TAC) and CO2 emission. With the inclusion of energy-saving technologies, IEDPHI and IEPSDHI further reduced TAC by 5.29% and 7.40%, and cut CO2 emissions by 25.18% and 24.03%, respectively, compared to their base processes. The use of a heat pump is particularly advantageous for IEPSD due to its lower boiling temperatures under vacuum pressure, leading to the development of IEPSDHIHP, which offered an additional 22.36% CO2 reduction and marginally lower TAC than IEPSDHI. Ultimately, IEPSDHIHP proves to be the best option, offering a 51.15% TAC reduction and 68.42% CO2 emissions reduction compared to HIPSD. In summary, the developed IED and IEPSD processes, especially with heat integration and heat pump technologies, offer significant economic and environmental advantages over conventional HIPSD.

Exploration and multi performance evaluation of process intensification for separation of ethyl tert-butyl ether/ethanol from wastewater

Ethyl tert-butyl ether is a green gasoline additive that enhances fuel efficiency and can play an essential role in improving fuel performance. This study explored the separation of wastewater containing ethyl tert-butyl ether and ethanol by changing the pressure and adding reactions based on extractive distillation, using the synergistic effect of the entrainer, pressure, and chemical reaction. By utilizing coupling technology and process intensification concepts, developed a comprehensive series of intensified processes that have clarified the interaction mechanisms between the extractive distillation process (EDP), pressure swing extractive distillation process (PSEDP), and reactive extractive distillation process (REDP). Studying the separation and purification mechanisms of products and intermediates during the reaction process provides theoretical and practical support for optimizing chemical processes. Comparative analysis showed that the reactive extraction pressure swing distillation process (REPSDP) had preeminent economic and environmental benefits. The total annual cost of PSEDP, REDP, and REPSDP was reduced by 5.88 %, 1.68 %, and 10.08 %, respectively, compared with EDP. The gas emissions of PSEDP, REDP, REPSDP, and REPSDP with heat integration process (HI-REPSDP) are all lower than those of EDP. HI-REPSDP saves 47.59 % of gas emissions compared to EDP, highlighting its environmental benefits. HI-REPSDP has the best energy efficiency, reducing energy consumption by 47.58 % compared to EDP, significantly improving the energy utilization rate. It was found that the introduction of heat integration technology had a significant improvement effect. This research has crucial theoretical and practical value and provides guidance and reference for achieving a clean and efficient production process.

Energy-efficient separation of a ternary azeotropic mixture via azeotropic reflux-induced sequences based on the intensified pressure-swing distillation

The recovery and separation of chloroform, acetonitrile and ethanol from waste water involving two azeotropes and a distillation boundary has emerged as a pivotal concern in the pursuit of environmental protection and resource conservation. Herein, the energy-efficient separation design of the ternary azeotropic mixture based on a triple-column pressure-swing distillation (TCPSD) process with five azeotropic reflux induced sequences is comprehensively investigated. The suitable operating pressure range of the distillation columns and the potential optimal distillation sequence is investigated based on the thermodynamic intrinsic probe. According to the optimal distillation sequence, further process intensification strategies are proposed to improve the thermodynamic efficiency encompassing the heat integration pressure-swing distillation (HI-PSD), heat pump assisted pressure-swing distillation (HP-PSD), and a combination of heat pump assisted and heat integration pressure-swing distillation (HPHI-PSD). It unveils the economic preeminence of the HI-PSD process, characterized by the lowest total annual cost (TAC) in a shorter payback period (3 to 7 years). Conversely, both the HP-PSD and HPHI-PSD processes exhibit superior environmental performance on CO2 emissions of 111.46 kg/h and 119.78 kg/h respectively, with the HP-PSD demonstrating prolonged economic viability and the HPHI-PSD showcasing heightened thermodynamic efficiency of a 65.12 % improvement. This study potentially provides a theoretical basis for devising industrial separation schemes for analogous pressure-sensitive ternary azeotropic systems.

Sustainable investigation and process intensification on the separation of ternary organic wastewater with heterogeneous characteristics

The tetrahydrofuran (THF)/water/n-propyl acetate (PROAC) mixture, which is categorized into class 2.0-2b-C, exhibits pressure-sensitive property along with heterogeneous regions in its phase diagram. Conventional pressure-swing distillations with different separation sequences (PSD-PTW, PSD-PWT) and a novel three-column heterogeneous azeotropic pressure-swing distillation (T-HAPSD) are designed to complete the separation. The PSD section of T-HAPSD combines three columns into two columns. The HAD section of T-HAPSD is more energy-efficient owing to the automatic separation in the decanter. T-HAPSD is more economical than conventional pressure-swing distillation. Heat integration and Self-heat recuperation technology (SHRT) are then introduced to reduce energy consumption and costs. Finally, the five processes are evaluated from four aspects (economy, energy, environment and exergy). The best of five processes is T-HAPSD-SHRT with 37.83% reduction in TAC, 51.17% reduction in TEC, 48.83% reduction in gas emissions and 52.63% reduction in exergy destruction when compared with PSD-PTW.

Enhancing exergy efficiency and environmental sustainability in pressure swing azeotropic distillation

This study explores the economic, energetic, exergy efficiency, and environmental benefits of energy integration in pressure-swing distillation, focusing on the separation of tetrahydrofuran/water and acetone/chloroform azeotropes. Heat integration and heat pump techniques are applied to reduce energy consumption. Three energy-efficient configurations are examined, comparing total annual cost (TAC), total energy consumption (TEC), CO2 emissions, and second-law efficiency. In the tetrahydrofuran/water system, heat integration and heat pump technologies outperform conventional processes, achieving up to 50.2% TAC reduction, 59.6% TEC reduction, 82.8% CO2 emission reduction, and thermodynamic efficiencies up to 23.5%. In the acetone/chloroform system, similar improvements are observed, with up to 70.9% TAC reduction, 87.2% CO2 emission reduction, and thermodynamic efficiencies up to 17.6%. These findings demonstrate the effectiveness of energy-saving strategies, endorsing process intensification for environmentally sustainable azeotropic mixture separations.

A novel intermediate heat exchange intensified extractive pressure-swing distillation process for efficiently separating n-hexane-tetrahydrofuran-ethanol

The new intensified strategy can be used in special distillation processes to achieve energy savings. Through analyzing the influence of different extractants and pressure on the separation performance of n-hexane-tetrahydrofuran-ethanol. system, extractive pressure-swing distillation process (EPSD) using dimethyl sulfoxide as extractant was proposed. Multi-objective optimization was performed to definite the best operating parameters of EPSD. Based on the phenomenon that the temperature of high-temperature column top is lower than low-temperature column bottom, making it impossible to perform traditional thermal integration, an intermediate heat exchange intensified process (IHE-EPSD) was developed. The performance influencing factors and heat exchange network of IHE-EPSD were analyzed to obtained the optimal IHE-EPSD process. Three heat integration schemes of the IHE-EPSD were designed to further save energy consumption. Finally, the processes were assessed from economy, energy, environment and exergy. The results indicate that the IHE-EPSD process exhibits excellent separation performance, achieving the efficient separation of n-hexane-tetrahydrofuran-ethanol.

Efficient separation of alcohol ester via extractive distillation and pressure swing distillation based on molecular interaction mechanism analysis

N-amyl alcohol, n-amyl formate, n-propanol and n-propyl formate are all organic solvents with important industrial application value. In industrial production, related alcohol ester azeotropic systems are often generated. Therefore, it is necessary to study the refining process of these substances. The work designed purification processes for two different azeotropic systems of alcohol esters via extractive distillation and pressure swing distillation methods. The required binary interaction parameters were obtained through vapor–liquid equilibrium experiments. Based on experimental data, a suitable entrainer was determined through different methods of analysis. The processes were optimized with the economic cost as the objective. In addition, it evaluated and analyzed different processes from multiple perspectives. This work explores the purification process of alcohol ester systems, providing theoretical guidance for achieving efficient separation of alcohol ester systems.

Evaluation of dimethyl carbonate production process from CO2 by rigorous simulation and detailed optimization

AbstractThe CO2‐derived dimethyl carbonate (DMC) synthesis process becomes greatly attentive but suffers high energy consumption in DMC distillation process. In this work, the DMC‐MeOH azeotropes separation process by pressure swing distillation and extractive distillation was compared, and key operating parameters, including the total number of trays and the feeding position of the mixture liquid, were optimized with the minimum total annual cost (TAC) as the objective function. On the basis of this optimization, economic evaluation of different distillation processes was conducted, and it was found that extractive distillation was more economical than pressure swing distillation. The application of the dividing‐wall distillation process upgraded by extractive distillation can significantly reduce the minimum annual total cost by 37.4% and 10.7% compared to the original pressure swing distillation and extractive distillation process, respectively. The optimization of relevant heat exchange network based on pinch technology resulted in energy consumption reduction by 27.2% and 25.9% for its hot and cold utilities, respectively. Carbon life cycle assessment (LCA) on the DMC distillation process revealed over 50% of energy as well as carbon emissions from steam consumption, whose reduction can significantly minimize CO2 emissions, energy consumption, and ultimate cost. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Process comparison and performance evaluation of different entrainers for pressure swing extractive distillation refining gasoline additives based on multi-objective optimization and process intensification

As a new gasoline additive, methyl tertiary amyl ether (TAME) can improve the antiknock performance and quality of gasoline. This study uses an energy-saving process for separating TAME/methanol (MeOH)/H2O by pressure-swing extractive distillation with different entrainers based on multi-objective optimization and 4E analysis. The 1entrainers are screened by the difference in relative volatility of components under different entrainer conditions, and the electrostatic potential of the molecular surface of the system and entrainers are analyzed. Multi-objective optimization of the pressure swing extractive distillation process with 5 different entrainers is carried out based on the generation non-dominated sorting genetic algorithm (NSGA-Ⅱ) optimization scheme, and the Pareto frontier is optimized by the minimum distance method. The results indicate that the extraction schemes of 1,3-propanediol (PDO) and dimethyl sulfoxide (DMSO) have excellent economic and environmental benefits through comprehensive analysis. As an effective means of process intensification, the application of heat pump technology can further reduce process costs and environmental pollution. The coefficient of heating performance (COP) is used to find the most suitable pairing route for heat pump-assisted processes, achieving the goal of reducing gas emissions and energy use. Then, different processes are evaluated in terms of economy, energy consumption, environment, and exergy loss. The results show that the process intensification scheme based on heat pump technology can effectively improve the economic and environmental benefits of the process, reducing the annual total cost (TAC) and gas emissions by 9.19% and 23.55%, respectively. This study provides the selection and reference for azeotrope separation of TAME and recycling of wastewater.

Novel side-reactor dividing wall column and reactive distillation process for enhanced electronic-grade propylene glycol monomethyl ether acetate production

The semiconductor industry is experiencing rapid growth and has become one of the largest sectors in the world. Propylene glycol monomethyl ether acetate (PGMEA) is prized for its exceptional properties and its ability to meet the stringent requirements as a solvent for electronic processing. This work aims to enhance the production of electronic-grade PGMEA through a practical and advanced intensified configuration. First, the kinetic reactor for propylene glycol monomethyl ether (PGME) synthesis has been modeled and pinpointed optimal operating conditions through sensitivity analysis. Subsequently, several process alternatives incorporating intensified techniques, such as the dividing wall column (DWC), pressure swing distillation (PSD), reactive DWC (RDWC), and side-reactor DWC (SR-DWC), have been investigated. These processes have been systematically designed and optimized through a sequential design procedure. Response surface methodology, a practical optimization method, has been employed to optimize the complex column's structure with the help of Aspen Plus and Minitab. Energy requirements and costs of all process alternatives were evaluated for a fair comparison. The SR-DWC-RD process has emerged as the most promising option, as it can save up to 11.5 % in energy requirements and 19.9 % in total annual costs. This practical design, complete with detailed optimal design parameters, presents significant opportunities for improving industrial PGMEA production.

Reactive distillation with inter-integrated vapor permeation for 1,3-Dioxolane production: Experiments, modeling, process analysis and design

To overcome the problem of difficult separation of the 1,3-dioxane (DOL)-H2O azeotrope in the production of DOL, a new high-integrated technology via reactive distillation (RD) with inter-integrated vapor permeation (VP) (abbreived as R-VP-D) was established. A series of R-VP-D experiments were conducted to find the effect of dedydration on reactant conversion and DOL content in the distillate. A two-dimensional VP module modeled by Aspen Custom Modeler (ACM) was combined with two RD modules in Aspen Plus to simulate the entire R-VP-D process, and the R-VP-D model was verified by experimental results. Then, by this model, systematic research on VP inserting position and membrane area on the reaction performance, reboiler and condenser duty, catalyst load, and TAC of the R-VP-D column was performed. The mechanism of how dehydration promotes reaction was explored. Finally, a new RD-VP-D technology for producing 99.9wt% DOL was designed and optimized. Two goals were achieved by inserting VP: obtaining a DOL-H2O mixture that crosses the azeotropic point in the distillate and improving reaction performance by removing by-product H2O. Under the optimal parameter, the energy consumption per unit product was reduced by 3.9% with less equipment, a simpler process, and less required land area compared with the RD with pressure swing distillation technology reported in the literature, and CO2 emissions were reduced by 4.0%. The reason why promotion effect is insignificant was explored, which is related to which of separation or reaction is the control step in RD process.

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.

Feasibility of Different Methods for Separating n-Hexane and Ethanol

Conventional distillation methods cannot effectively separate the components of an azeotropic mixture since both phases have the same composition, thereby preventing further separation. Additional techniques such as pressure swing distillation or distillation with entrainers are often employed to overcome this limitation and achieve separation. The aim of this investigation was to select the most effective method for separating n-hexane and ethanol. The feasibility of three methods was analyzed: reduced pressure distillation, extractive distillation, and liquid–liquid extraction. The mutual solubility of n-hexane and prepared deep eutectic solvents (DESs) (nine hydrophilic: choline chloride with glycerol, ethylene glycol, or carboxylic acid (malic, citric, glycolic); tetramethylammonium chloride with glycolic acid; lactic acid with glycerol; K2CO3 with glycerol or ethylene glycol; two hydrophobic: menthol with decanoic or dodecanoic acid) was experimentally determined. Extraction experiments were conducted to test the solubility of DESs in the feed mixture. The effect of changing DES-to-feed mass ratio was further investigated with choline chloride–glycerol (1:2). The same DES and both hydrophobic DESs were able to increase the relative volatility and enhance the separation of ethanol and n-hexane. Based on the obtained results, extraction was selected as the most effective method for the separation of n-hexane and ethanol.

Energy-saving extractive distillation system using o-xylene as an entrainer for the high-purity separation of dimethyl carbonate/methanol azeotrope

The pressure-swing distillation traditionally used in the industry for separating dimethyl carbonate/methanol (DMC/MeOH) commonly suffers from high energy consumption and challenges in achieving high-purity separation due to the existence of pinch zone. Hence, energy-saving extractive distillation system is explored to achieve the high-purity separation of DMC/MeOH azeotrope. With the analyses of isovolatility and residue curve maps based on Wilson model calibrated by vapor–liquid equilibrium experimental data, an extractive distillation process using O-Xylene (OX) as the most suitable entrainer were modeled and experimentally validated. Furthermore, design, optimization, and comparison of an extractive distillation process and a pressure-swing distillation process for producing 10000 t DMC/a are investigated. It is demonstrated that the extractive distillation process presents significant economic and emission advantage, specifically with 34.66 % and 26.95 % reductions in operating cost (OC) and in total annual cost (TAC) respectively, as well as 42.53 % reduction in CO2 emissions. This work should provide a feasible and promising approach to energy saving, low-carbon, and high-purity separation of DMC/MeOH azeotrope.

Optimal design and operation of reactive distillation systems and reactive dividing wall systems with pressure swing distillation and hybrid distillation-pervaporation

Process intensification is essential in exploring more energy-efficient processes, and key examples related to fluid separations are reactive distillation and hybrid distillation-pervaporation processes. This work will consider the reaction and separation of a general quaternary reactive system with a minimum boiling binary azeotrope AC, in a reactive distillation column where, given the thermodynamics limitations, further downstream separation is required. Low and high chemical equilibrium is considered for the reaction. For the downstream purification, both pressure swing distillation and a hybrid distillation-pervaporation process are considered. For each of the structures, their intensified equivalent dividing wall structures are also considered, including a hybrid reactive dividing wall system. It is shown that reactive distillation followed by a hybrid distillation-pervaporation system can save up to 24% energy compared to reactive distillation with pressure swing separation, and that the dividing wall column counterpart structures have lower production-based total annualised costs than the corresponding base systems.

Novel dynamic control structure of reactive distillation process for isopropanol production via transesterification

Due to the complicated interaction between reaction and separation in a column, it was inherently challenging to design a control structure for the reaction distillation process. In this research, the control structures of the hybrid reactive distillation process combining pressure-swing distillation (RDC-HDC) and its thermal coupling (RDWC-HDC) processes, were explored for producing isopropanol (IPA) by isopropyl acetate (IPAC) with methanol (MeOH) transesterification. The control performances of only temperature control and temperature difference control schemes for RDC-HDC process were first investigated. The research results displayed that double temperature control (CS3) and temperature difference control schemes (CS4–1, CS4–2 and CS5) for the RDC-HDC process could shorten the maximum transient deviation, amplitude of oscillations and setting time in face with ±20% throughout and ±5% feed composition disturbances. To further improve control characteristics and make control structures concise, a novel control strategy (CS6) by a proportional controller adjusted by reverse action of an IPAC component controller in 34 trays for keeping IPAC composition at a certain range in the RDC-HDC process was developed based on the closed loop analysis before and after disturbance. The application of the innovative control structures (CST4) to the RDWC-HDC process was equally feasible in face of ±10% throughout and ±5% feed composition disturbances. The analysis of integral of squared error (ISE) indicated that a novel control strategy (CS6 and CST4) had better robustness and dynamic performance. These studies contributed to the development of controllability for hybrid reactive distillation processes to produce chemicals for reaction and separation.

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.

Design and energy-saving strategy of sustainable pressure-swing distillation with thermally and electrically coupled intensification for separating ternary mixture with multiple azeotropes

The separation of ternary mixtures that form multiple azeotropes is frequently encountered in industry. Benefiting from the pressure-sensitive nature of the azeotropic mixture, the pressure-swing distillation (PSD) is promising to realise the separation without introducing foreign solvents. However, the wide application of PSD seems challenging from an energetic point of view. This work has developed a sustainable PSD process with thermally and electrically coupled intensification to decrease energy consumption, taking the separation of homogeneous acetonitrile/ethanol/water mixture as a demonstrating example. Two conventional PSD processes with different product sequences are designed through the ternary phase diagram and further optimised using the NSGA-II, considering multiple objectives, including total capital cost, total operating cost, and CO2 emissions. The optimal solution is selected by the TOPSIS analysis for each sequence and is then intensified with thermal heat integration and electricity-driven heat pump techniques. The results show that, in comparison to the non-heat-integrated PSD process, the proposed intensified design can dramatically reduce the total annual cost by up to 48%, simultaneously decreasing CO2 emissions by up to 60% and boosting energy efficiency. The present study can be of reference for designing a sustainable PSD process in ternary azeotropic separation.

Applied of Phase Equilibrium to Simulate Pressure Swing Distillation of 1-Butanol + Water Mixtures

Applied of Phase Equilibrium to Simulate Pressure Swing Distillation of 1-Butanol + Water Mixtures