Pressure-swing Distillation Research Articles

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

Mechanism Analysis and Multiobjective Optimization of Efficient and Energy-Saving Separation of Green Fuel Additives via Extractive Pressure Swing Distillation with an Ionic Liquid Mixed Entrainer

Mechanism Analysis and Multiobjective Optimization of Efficient and Energy-Saving Separation of Green Fuel Additives via Extractive Pressure Swing Distillation with an Ionic Liquid Mixed Entrainer

Waste Lignocellulosic Biomass as a Source for Bioethanol Production

Synthetically produced biofuels play a critical role in the energy transition away from fossil fuels. Biofuels could effectively lower greenhouse gas (GHG) emissions and contribute to better air quality. One of these biofuels is bioethanol, which could act as a gasoline replacement. For this purpose, a simulation of bioethanol production through lignocellulosic biomass fermentation, focused on distillation, was carried out in simulation software Aspen Plus. Since the possibility of absolute ethanol production through distillation is limited by the ethanol–water azeotrope, pressure swing distillation (PSD) was used to obtain fuel-grade ethanol (EtOH) with a fraction of 99.60 wt.%. The flowsheet was optimised with NQ analysis, which is a simple optimisation method for distillation columns. We found that the PSD has the potential to concentrate the EtOH to a desired value, while simultaneously removing other unwanted impurities whose presence is a consequence of pretreatment and fermentation processes.

Evaluation and control of energy‐efficient processes for separating epichlorohydrin‐oriented quaternary system

AbstractBACKGROUNDThe direct epoxidation of allyl chloride is a clean and efficient synthesis method for producing epichlorohydrin (ECH), which is a crucial organic intermediate widely used in the fields of renewable energy and aerospace. However, the presence of multiple azeotropes in the synthesized product using this method complicates the separation process and results in high energy consumption. To efficiently separate high‐purity ECH, this paper investigates and analyzes three separation schemes based on phase‐equilibrium analysis: hybrid extractive distillation (HED), pressure swing distillation (PSD) and three‐column batch distillation (TCBD).RESULTSThe operating parameters of the three separation processes are optimized by the sequential iterative optimization method such that the minimum total annual cost can reach $493 491 yr−1. The thermal integration method is used for process energy‐saving optimization, and the total annual cost can be further reduced by 6.9%. In addition, a comprehensive evaluation based on economic, energy, environmental and exergy analysis is conducted, and reveals that the TCBD process with thermal integration is optimal. A control structure is designed for the TCBD process to enhance its robustness such that the purity of ECH remains above 99.9 mol% under ±10% disturbances in feed flowrate and composition.CONCLUSIONSCompared with the HED and PSD processes, the TCBD process has better economic and environmental benefits, and its control structure can effectively resist disturbances. It is reasonable to believe that the TCBD process can be an excellent solution for the industrial production of ECH. © 2024 Society of Chemical Industry (SCI).

Enviro-economic investigation of Novel heat-integrated configurations for pressure swing distillation

Pressure Swing Distillation is a widely adopted solution for the separation of pressure-sensitive azeotropic mixtures in various chemical industries. While this method yields high-purity products, it comes with inherent challenges such as elevated operating costs and energy consumption. However, the temperature differential between the two columns involved presents a compelling opportunity for heat integration. In this study, 18 distinct heat integration scenarios were systematically evaluated using a process simulation software to identify the optimal column configuration for minimizing the Total Annualized Cost. These scenarios span five categories: the Conventional Method, Partial Heat Integration, Full Heat Integration, Internal Heat Integration Distillation Column, and External Heat Integration Distillation Column. The Vapor Recompression Column and Divided Wall Column schemes were applied to each method. Genetic Algorithm served as the optimization tool to determine the best arrangement with TAC as the objective function. Additionally, the environmental impact, assessed through CO2 emissions, was considered. Results indicate that the most economically and environmentally friendly solution is the I-HIDiC with divided wall columns, incorporating VRC systems in both columns. This approach offers a remarkable 66.5% cost savings and a substantial 96.3% reduction in CO2 emissions.

Novel process development and mechanism analysis of purification of polymer monomers by combining pressure swing distillation and extraction distillation

Methyl methacrylate is a new polymer material monomer, which is often used in the manufacture of plexiglass, and has very high industrial application value. Producing high purity methyl methacrylate requires a clean and effective separation process. In this work, an efficient separation method of methyl methacrylate/water/methanol azeotrope based on pressure swing distillation coupled extractive distillation is established. The best entrainer in terms of both environmental impact and effectiveness is chosen by examining the impact of relative volatility. The feasibility of pressure swing distillation and the best separation order are determined by ternary phase diagram analysis. A multi-objective optimization method is used to optimize the three designed processes, targeting gas emissions and total annual costs, thereby obtaining the best process plans and parameters. On this basis, the optimal thermal integration design of the three processes is carried out. The analysis of the four processes is conducted from the viewpoints of the energy, economy, environment and exergy. The findings demonstrate that the pressure swing extractive distillation process when combined can significantly increase economy and lessen mixture separation difficulty. Compared with the traditional process, the total annual cost, gas emission and energy loss are reduced by 8.20%, 10.46%, 11.69%, and the effective energy utilization rate is 50.31%. The development of this process is of great significance for the recovery of wastewater containing methyl methacrylate and methanol and the separation of high-purity methyl methacrylate.

Efficient separation of cresol isomers using azeotropic coupling pressure-swing distillation: From separation mechanism to process integration

In this work, an azeotropic coupling pressure-swing distillation separation technology was proposed for the first time to achieve efficient separation of near-boiling complex separation systems in coal chemical wastewater, namely cresol isomers (m-cresol and p-cresol), and achieves process intensification by introducing heat-integration technology. Vapor-liquid equilibrium data and relative volatility analysis were used to screen suitable entrainer. Quinoline is considered to be the most potential entrainer. Quantum chemical calculations were performed to reveal the separation mechanism of the entrainer and the system to be separated at the molecular scale to demonstrate the feasibility of quinoline as an entrainer for the separation of cresol isomers. Based on the Aspen Plus V11 platform, two processes of APSDP and HI-APSDP were built. HI-APSDP can save 31.31% in TAC, reduce 39.50% in total energy consumption and gas emissions, and increase 26.01% in thermodynamic efficiency compared with APSDP. HI-APSDP process is an economical, energy-saving, and environmentally friendly production scheme superior to the APSDP process, which will have essential development prospects in coal chemical wastewater (cresol isomers) treatment.

Selective synthesis of methyl ethyl carbonate intensified by reactive distillation from consecutive transesterification of methyl carbonate and ethanol

Reactive distillation (RD) can be effectively used to improve the selectivity of the intermediate product for complex multi-reaction schemes, which involves using distillation to manipulate the column profiles in the RD column (RDC) to attribute the desired reaction and the manipulating reactions to facilitate separation. As the demand for ethyl methyl carbonate (EMC) has increased significantly due to its structural characteristics, the selective synthesis of EMC from the consecutive transesterification of dimethyl carbonate (DMC) and ethanol (EtOH) in the presence of azeotropes between reactants and products was studied as featured reaction schemes. The basic resin catalyst KC161 is utilized to build the kinetic reaction model and supplement the primary data for the process design. The pilot-scale RD experiments are explored to verify the feasibility and the reliability of the model. The impact of critical operation and structure parameters on the conversion and selectivity of the reaction and the azeotropes formed in the system were analyzed. A hybrid distillation process containing an RDC, pressure-swing distillation columns, and a regular distillation column, was designed and optimized based on minimized total annual cost (TAC) using a sequential iterative algorithm. 0. 9997 (mole purity) EMC and 0. 9999 (mole purity) diethyl carbonate (DEC) were obtained with EMC selectivity up to 0.863%.

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.

ETHYL ALCOHOL - WATER SEPARATION BY EXTRACTIVE DISTILLATION: SIMULATION USING ASPEN PLUS™ AND EXPERIMENTAL VALIDATION

Dilute ethyl alcohol (ethanol, EtOH) is produced using fermentation (< 20 mass%), but it needs to be further purified because it contains large water content. EtOH forms an azeotrope with water and to separate this azeotrope, advanced separation processes like pressure swing distillation (PSD), azeotropic distillation (AD), and extractive distillation (ED) are employed. In this work, ethylene glycol (EG) was used as an entrainer in extractive distillation. Vapour liquid equilibrium (VLE) data was used to validate the chosen rigorous thermodynamic model. To find a workable range of operating parameters, sensitivity analysis was performed to find out the number of stages (N), feed stage (NF), distillate rate (DR), and reflux ratio (RR). Simulation shows that use of accurate operating parameters and correct entrainer can help to obtain almost pure EtOH (99.89 mole %, 99.92 mass %). In order to validate the theoretical findings from the simulation, experimental investigations in the form of batch and semi - batch distillation runs were conducted. It was seen from these runs that it is indeed possible to obtain EtOH with high purity. It was also verified that EG can be separated and recycled back with high purity with a very high recovery.

Comparative Analysis: Trays versus Packed Columns in Pressure-Swing Distillation for the Separation of Tetrahydrofuran, Water and Ethanol Azeotropic Mixture

Comparative Analysis: Trays versus Packed Columns in Pressure-Swing Distillation for the Separation of Tetrahydrofuran, Water and Ethanol Azeotropic Mixture

Exploring Exergy Performance in Tetrahydrofuran/Water and Acetone/Chloroform Separations

Distillation is significantly influenced by energy costs, prompting a need to explore effective strategies for reducing energy consumption. Among these, heat integration is a key approach, but evaluating its efficiency is paramount. Therefore, this study presents exergy as an energy quality indicator, analyzing irreversibility and efficiencies in tetrahydrofuran/water and acetone/chloroform distillations. Both systems have equimolar feed streams, yielding products with 99.99 mol% purity. The simulations are performed using Aspen Plus™, enabling evaluation at the column level, as a standalone process, or from a lean perspective that considers integration opportunities with other plants. The results show that, despite anticipated energy savings from heat integration, economic viability depends on pressure sensitivity. The results demonstrate that heat-integrated extractive distillation for acetone/chloroform raises utility energy consumption. Exergy calculations comparing standalone and total site integration reveal the variation in distillation efficiency with operation mode. Global exergy efficiency in both extractive and pressure-swing distillation depends on the fate of condenser duty. In heat-integrated extractive distillation, global exergy efficiency drops from 8.7% to 5.7% for tetrahydrofuran/water and 11.5% to 8.3% for acetone/chloroform. Similarly, heat-integrated pressure-swing distillation sees global exergy efficiency decrease from 34.2% to 23.7% for tetrahydrofuran/water and 9.5% to 3.6% for acetone/chloroform, underscoring the nuanced impact of heat integration, urging careful process design consideration.

A novel sustainable separation process based on special azeotropic behavior of benzene/ethanol/butanone: Process design and multi-performance evaluation

Special azeotropic behaviors of complex mixtures can be used to develop distillation processes to realize energy-saving separation. Based on the residual curves of the system at different pressures and an examination of the impact of several extractants on the relative volatility, the pressure-swing distillation (PSD) process and the extractive distillation (ED) process were proposed to separate benzene/ethanol/butanone azeotrope. According to the characteristic of the azeotropic disappearance of ethanol/butanone with increasing pressure, two new extractive pressure-swing distillation (EPSD) processes were developed and compared with PSD as well as ED. To be able to determine the optimal operating parameters for various processes, the non-dominated sorting genetic algorithm II (NSGA-Ⅱ) was utilized. Heat integration was designed for the EPSD processes to reduce energy consumption. The above processes were evaluated in four aspects of the economy, energy, environment and exergy. The relationship between the four performances of different processes and the normal distance was discussed. The results indicate that the EPSD processes show better performance than the ED and PSD processes. Compared with the two EPSD processes, the total annual cost (TAC) of the heat integrated EPSD processes (HI-EPSD) was reduced by 13.2% and 14.4%, the total gas emissions of CO2, SO2 and NOX were also reduced by 23.6% and 27.2%, respectively. Hence, coupling the ED process with the PSD process and heat integration can both better improve the separation performance of distillation.

Pilot-scale azeotrope purification of dimethyl carbonate by cost-efficient pervaporation-assisted distillation

The production processes of dimethyl carbonate (DMC) typically involve an excess amount of methanol, and therefore, the separation of DMC from methanol is essential in the chemical industry. While pressure swing distillation is commonly used for this separation, it is an energy-intensive process. Pervaporation, on the other hand, has been found to be a more energy-efficient method, especially when a suitable inorganic or ceramic membrane is used. The use of polymeric membranes is not recommended due to the high operating temperatures required. Hybrid silica membranes, such as HybSi®, have emerged as a promising option for this purpose. In this study, we conducted both laboratory and pilot-scale pervaporation experiments along with pilot-scale pervaporation-assisted distillation experiments, and carried out process simulations to evaluate the potential cost savings in DMC purification using a HybSi® membrane. The cost of purification was calculated per ton of DMC produced, and results demonstrated cost savings compared to the base case using pressure swing distillation. These savings were attributed to reduced operating and capital expenditures resulting from lower energy consumption and a more compact design. Our results indicate that the use of HybSi® membranes has the potential to revolutionize the DMC production process and provide a more sustainable and cost-effective solution.

Heat utilized pressure swing distillation (PSD) process for the separation of the maximum boiling azeotrope HCl and Water in the Cu-Cl Cycle

The four-step copper-chlorine cycle is utilized for hydrogen production from water. Intermediate copper and chlorine compounds facilitate the process, while all other reactants are regenerated and recycled, forming a closed-loop system. Hydrolysis of CuCl2, leading to the formation of Cu2OCl2 and dilute HCl, is a crucial step that uses a large excess of steam to ensure completion of reaction leading to the formation of dilute hydrochloric acid which needs to be recycled for the electrolysis reaction, requiring removal of the azeotrope between HCl and water. This study explores the utilization of pressure swing distillation (PSD) for concentrating HCl above azeotropic composition. Separation of the aqueous mixture of HCl and water using PSD is optimized using a sequential iterative optimization technique, focusing on process intensification. Integration of a simple heat-utilized FE-Process results in a reduction of TAC and energy cost (4.27% TAC and 7.20% energy cost) compared to the process without heat integration. A higher feed composition of HCl (8 mol %) leads to savings of ∼ 38.75% in TAC and a reduction of 53.06% in CO2 emissions compared to a lower feed composition (2.53 mol % HCl). The heat-utilized FE-Process with a higher feed composition is more economically viable for the separation of HCl and water.

Novel hybrid reactive-extractive distillation for separation of tetrahydrofuran, ethanol, and water azeotropic system with rigorous side reactions consideration

This study builds upon our previous research work (Ind. Eng. Chem. Res. 2023, 62, 27, 10,601–10,610), which investigated the impact of considering the side reactions in the hybrid reactive-extractive distillation (RED). Our prior investigation revealed a significant challenge, as the inclusion of side reactions led to staggering spikes in energy consumption and total annual cost (TAC), seemingly rendering the performance of RED impractical. In this study, we present another possible scenario for considering side reactions in RED and highlight that RED with side reactions can still be a superior alternative to conventional distillation methods, even when side reactions are considered. This work was exemplified by using the recovering tetrahydrofuran (THF) and ethanol (EtOH) from waste effluent. We explore two different cases: Case 1 involves a side-reaction-free RED configuration reproduced as the base case, while the introduction of side reactions resulted in an increase in TAC by about 79.2% and a rise in total energy consumption by about 69%. Implementing a vacuum system (Case 2) substantially reduced the TAC by about 39% and energy consumption by about 20.5%. Although Case 2 outperformed Case 1 economically, it fell short of the base case due to additional capital costs. In contrast, Case 2 exhibited a lower TAC by 58% relative to the conventional pressure swing distillation.

Energy-saving design and multi-objective optimisation of triple-column pressure-swing distillation configuration for separating n-propanol/benzene/water mixture with multiple azeotropes

The separation of ternary azeotropic mixtures with multiple azeotropes is often encountered in industrial wastewater treatment. This study explores separating the n-propanol/benzene/water mixture with three binary azeotropes and one ternary azeotrope via pressure-swing distillation (PSD). Two conventional PSD schemes are designed based on the ternary phase diagram. The multi-objective genetic algorithm facilitates the optimisation task for each sequence, taking the total annual cost, CO2 emissions, and thermodynamic efficiency as the objective functions. Then, the selection of the optimal solution from the Pareto front is performed using the technique for order preference by similarity to the ideal solution. Subsequently, energy-saving methods, including direct heat integration, heat pump, and heat exchanger network, are introduced into each optimal non-heat-integrated PSD process to address the drawback of tremendous total energy consumption. Finally, the proposed 12 energy-efficient PSD designs are compared with the conventional PSD cases in multiple aspects. The optimisation results highlight the importance of operating pressures as variables in the multi-objective optimisation problem. In addition, the W-B-N sequence shows superiority over the W-N-B sequence in decreasing cost and gas emissions and enhancing energy efficiency. The proposed energy-saving PSD design with direct heat integration, heat pump, and heat exchanger network gives the lowest cost amongst the 14 processes, being up to a reduction of 39% compared to the corresponding conventional PSD design.

Design and evaluation of a novel process for green hydrogen production in the iodine–sulfur cycle via pressure-swing distillation of HIx (HI-I2-H2O)

In striving for carbon neutrality, hydrogen energy serves as a sustainable solution, and the iodine–sulfur (IS) cycle stands out as the most promising method for hydrogen production. The separation and purification of HI from the HIx (HI-I2-H2O) mixture holds significant research value, as they constitute the crucial aspect of the iodine–sulfur cycle in hydrogen production. Due to the azeotropic behavior of HI and H2O, the HIx system poses a considerable challenge. In this research, a technique for purifying HI via pressure-swing distillation was developed, exploiting the changes in azeotropic points under varying pressure conditions. The most effective method for HI purification was determined to be a three-column pressure-swing distillation configuration, as revealed by Aspen Plus phase diagrams and process topology mapping. It yielded H2O and I2 at the top of the first column, I2 at the bottom of the second column, and HI at the top of the third column with an HI recovery rate of 97 %. By analyzing the Bunsen reaction kinetics of the core reaction in the IS system, a comprehensive method for evaluating the separation and reaction coupling quality network of HIx cycle system using Bunsen-factor (B-factor) was proposed. The B-factor elucidates the correlation between the Bunsen reaction rate and the concentrations of [H+], [I-], [I3-], as well as the pH level. A comprehensive analysis of the B-factor was conducted for the pressure-swing distillation topologies of the HIx system, and the results were contrasted with those of alternative separation processes. The findings indicated that the three-column pressure-swing distallation is the most suitable option for both separation and reaction quality in a recycled network. The total energy consumption of the newly designed HIx three-column process is 352 MJ/kmol, rendering it more economical and beneficial than other processes. This study presents a pressure-swing distillation method for HI separation and purification, which is broadly applicable in IS cycles and aids in achieving large-scale production of green H2. This method enables the achievement of the dual-carbon objective, which seeks to mitigate carbon emissions while safeguarding the environment.