Extractive Dividing-wall Column Research Articles

Extractive Distillation of Isobutyl Alcohol and Isobutyl Acetate Using Dimethyl Sulfoxide: Process Design and Intensification

AbstractWe have designed a separation process of isobutyl alcohol (52.0 mol%) and isobutyl acetate (48.0 mol%) mixture using conventional extractive distillation (ED) and extractive dividing‐wall column (E‐DWC) with the solvent dimethyl sulfoxide (DMSO). The binary mixture exhibits a minimum boiling azeotrope that is sensitive to pressure. Thermodynamic analyses have shown that the vacuum pressures work better compared to the atmospheric pressure when DMSO is the solvent. Based on the separation with a purity of 99.9 mol%, the E‐DWC process has resulted in 9.6 % and 4.8 % reductions in the total annual cost and CO2 emission rates, respectively, in comparison to the conventional method. After further intensification using the heat pump technique, the E‐DWC process with the solvent DMSO has provided more than 40.0 % reduction in energy consumption compared to the ED systems studied in the literature using the solvents butyl propionate and dimethylformamide.

The design and control of heat-integrated EDWC processes for the separation of THF/IPA/water

Extractive dividing wall columns (EDWC) and heat integration are effective process intensification strategies for separating azeotropes. In this study, the steady-state and dynamic control for the separation of tetrahydrofuran/isopropanol/water using a combination of EDWC and heat integration with intermediate reboilers are systematically investigated. The feasibility of the extractive distillation process is evaluated by analyzing the thermodynamic characteristics of the mixture through phase diagrams, and the three-column extractive distillation (TCED) process is established as the basic process. To enhance the energy and economic efficiencies, as well as environmental sustainability, three improved processes are proposed. Compared with TCED, the optimal process (E-EDWC-HI2) reduces the total annual costs, energy consumption, and CO2 emissions by 22.35 %, 41.77 %, and 26.28 %, respectively. In addition, a dynamic control structure is proposed for the E-EDWC-HI2, which exhibits robustness against disturbances in the feed flow rate and composition. This study provides guidance for the design and dynamic control of complex distillation processes.

Design and control of a novel multi-product extractive dividing wall column process for recycling organics from wastewater

The wastewater from a pharmaceutical plant consists of a tetrahydrofuran/isopropanol/water azeotrope. This investigation utilizes dimethyl sulfoxide as an extractant and employs an extractive dividing wall column to separate the aforementioned azeotrope. The extractive dividing wall columns are constructed with single, double, and triple partition walls, and a multi-objective genetic algorithm is used to optimize the operational parameters of the separation process. Of these columns, the extractive dividing wall columns with triple partition walls show the most favorable economic, environmental, and energy utilization performance, and it has a lower risk of combustion and explosion. Compared to the conventional design, the use of triple-partition extractive dividing wall columns results in a 22.13 % and 10.54 % reduction in total annual cost and CO2 emissions, respectively, and an increase in thermodynamic efficiency of 2.66 %. Studying the dynamic characteristics of this process reveals its excellent dynamic controllability.

Automated method for designing extractive dividing wall columns used to separate minimum azeotropic mixtures with a heavy entrainer

Despite that the extractive divided wall column (E-DWC), which is one of the best examples of process intensification, has already found an industrial application, its design remains a new area of research. None of the few studies that have been published in the literature present a method for designing an E-DWC. Therefore, the first and fully automated design method, for the separation of minimum boiling azeotropic mixtures with a heavy entrainer (class (1.0–1a)-m1) using an extractive dividing wall column, is developed in this work. The developed method is based on the values of the phase equilibrium constant along the sides of composition simplex, with the help of the composition profile properties in the infinitely sharp splits mode and difference point equations. The efficiency of this new design method was tested on the separation of two ternary azeotropic mixtures that belong to class 1.0–1a-m1. The results show that the column trajectories, along the E-DWC, obtained by the rigorous simulation are in very good agreement with those calculated by the new design method. These results prove the reliability and accuracy of the new method.

Energy, Exergy, Economic, and Environmental Analysis of the Vapor Recompression-Assisted Liquid-Only Transfer Extractive Dividing Wall Column for Separating Minimum-Boiling Point Azeotropes

Energy, Exergy, Economic, and Environmental Analysis of the Vapor Recompression-Assisted Liquid-Only Transfer Extractive Dividing Wall Column for Separating Minimum-Boiling Point Azeotropes

Energy-saving exploration of separation for EG/1,2-BDO binary azeotrope based on energy, environmental and economic analysis

In the synthesis of ethylene glycol (EG) from syngas, the inevitable by-product, 1,2-butanediol (1,2-BDO), is generated. Additionally, EG and 1,2-BDO form minimum boiling homoazeotrope, which is a challenge for conventional distillation method. To address this, four processes, extractive distillation process (EDP), extractive distillation with heat integration process (HI-EDP), side-stream extractive distillation process (SSEDP), and extractive dividing wall column process (EDWCP), are used for the separation of EG/1,2-BDO binary system. Firstly, a combination of VLE analysis and COSMO-SAC model analysis was employed to select appropriate entrainers (eugenol). Subsequently, interaction region indicator (IRI) was utilized to reveal the extractive distillation mechanism at the molecular level, demonstrating the feasibility of eugenol as an entrainer for separating EG/1,2-BDO mixture. Next, simulations of the EDP, HI-EDP, SSEDP, and EDWCP processes were conducted through Aspen Plus V11. The optimal process parameters for each flowsheet were determined by the minimum Total Annual Cost (TAC). Furthermore, the process performance was evaluated from economic, energy, and environmental aspects. The EDWCP process demonstrates superior performance compared to the EDP process, with reductions of 16.79% in TAC, 17.6% in TOC, and 14.8% in TCC. Additionally, emissions of acidic gases of decreased by 19.78%, while thermal efficiency improved by 32.91%. EDWCP process represent enormous potential in the field of energy efficiency, economy and environment.

Proportional-Integral Control and ARX-based Model Predictive Control for Extractive Dividing Wall Column

Extractive dividing wall column (EDWC) is a typical process intensification technology and possesses significant energy-saving prospects, while the poor dynamic controllability hinders its industrialization goal. In this work, taking the benzene and cyclohexene azeotrope separation as an example, a proportional-integral (PI) control structure based on four-point temperature control loops is proposed for EDWC by considering temperature difference as the discriminant criterion. Subsequently, to improve the control performance of EDWC, two model predictive control (MPC) structures based on auto-regressive with external input (ARX) model obtained from closed-loop identification and linear time-invariant state-space (LTI-SS) model, respectively, are studied for EDWC. The performance of three control structures is tested by ±20 % feed flow rate and composition disturbances, and further quantitatively evaluated by integral absolute error (IAE). The dynamic responses demonstrate that the ARX-based MPC structure achieves the best control performance in the presence of feed flow rate and composition disturbances, which can be attributed to the capability of the identified ARX model to track the dynamic features of EDWC accurately.

Design and Multiobjective Optimization of a Novel Double Extractive Dividing Wall Column with a Side Reboiler Scheme for the Recovery of Ethyl Acetate and Methanol from Wastewater

Design and Multiobjective Optimization of a Novel Double Extractive Dividing Wall Column with a Side Reboiler Scheme for the Recovery of Ethyl Acetate and Methanol from Wastewater

Dynamic control of an energy-saving process with two extractive dividing-wall columns for separation of acetone/methanol/butanone/tert-butyl alcohol mixtures

In the chemical and petrochemical industries, an azeotropic mixture of acetone/methanol/butanone/tert-butanol needs to be separated for high-purity products. Following a previous work in which an energy-saving process composed of two extractive dividing-wall columns (EDWCs) was developed for the quaternary system, this paper focuses on the issue of dynamic control for this process. Several control strategies in combined with temperature control, temperature-difference control and composition control are established to maintain the purity of all products in the face of disturbances in feed flow and feed composition. Dynamic simulations demonstrate that a conventional temperature control structure provides very poor control while a control strategy that used three-temperature-difference control for both EDWCs is the most effective.

Extractive-dividing-wall column and multi-objective optimizations of green entrainer-based ultra-high-purity recovery of methyl di glycol and N-Methyl-2-Pyrrolidone

The waste solvent is frequently generated from the processes that highly rely on solvents. Diethylene glycol monomethyl ether or methyl di glycols (MDG) and N-methyl-2-pyrrolidone (NMP) are representative valuable solvents used broadly and removed as waste solvents during the semiconductor material manufacturing processes. Although waste solvent can be practically retrieved by distillation, azeotropic waste solvent mixture only can be recovered by advanced distillation process. In this study, optimal extractive distillation and extractive-dividing wall column are used to recover waste solvent. The process is optimized by multi-objective optimization using genetic algorithm by linking Aspen Plus® and MATLAB. All optimal cases are compared in terms of energy, exergy, economic and environmental parameter. As a result, the potential energy, total annual cost saving and exergy efficiency for extractive dividing wall column are 26.29%, 24.15% and 21.02%, respectively. Exergy loss that is associated with the number of trays can be significantly reduced by optimization while exergy loss that is associated with remixing only can be significantly reduced by dividing-wall column. Further, multi-objective optimization using a genetic algorithm and a range of population provides various results that determine process selection.

Improving the economic saving, environmental sustainability, and energy efficiency of separating acetone/n-heptane mixture via heat pump-assisted extractive dividing wall column with heat exchanger network

Improving the economic saving, environmental sustainability, and energy efficiency of separating acetone/n-heptane mixture via heat pump-assisted extractive dividing wall column with heat exchanger network

Economic, thermodynamic, environmental, and inherent safety investigation of heat pump-assisted extractive dividing wall column for separating binary azeotrope

Inherently safer design during the preliminary design stage is vital to reduce the potential risks and accidents of new process design. So far, little effort has been paid to incorporating inherent safety assessment into the techno-evaluation of heat-integrated extractive dividing wall column processes toward sustainable development. To this end, this paper proposes a systematic methodology for designing the energy-efficient extractive dividing wall column processes by applying heat pump and feed preheating techniques to separate binary azeotrope. The proposed approach gradually recovers the waste heat within the process, and the separation of acetonitrile and water is selected as a case. The results show that the total energy consumption, total annual cost, and the CO2 emissions of heat-integrated extractive dividing wall column processes are significantly reduced compared to conventional design, and the thermodynamic efficiency is simultaneously improved. In the process evaluation stage, the inherent safety analysis is performed regarding the Process Route Index and Process Stream Index. Such indices give insights into process safety performance in terms of the overall process and individual streams. The results of the inherent safety investigation show the intensified extractive dividing wall column by a single heat pump performs better than the dual heat pump-assisted process. This multi-criterion evaluation demonstrates a trade-off between inherent safety performance and energy saving in applying a heat pump system in conjunction with the distillation process.

New single-column extractive distillation with heavy entrainer to separate binary azeotropic mixtures

Extractive distillation with heavy entrainer is widely used in the separation of binary azeotropic mixtures. While a large amount of energy is always consumed in conventional two-column processes. A new flash tank-assisted single-column extractive distillation with heavy entrainer (FT-SCED) is proposed in this paper. The side vapor-phase stream with high heavy component content is withdrawn from the extractive column, and then it is partly condensed in a flash tank. By this means, the high-purity light and heavy products can be achieved from the overheads of column and flash tank, respectively. To obtain the proposed process, an initial single column extractive distillation with heavy entrainer is designed firstly. Then the flash tank is added into the process on the basis of the thermodynamic feasibility analysis. Genetic Algorithm procedure is employed to optimize the independent variables of the obtained process. Two case studies show that the proposed process has lower annual total cost compared with conventional extractive distillation and extractive dividing wall column. PI control strategies are established for the proposed processes in two cases. The dynamic control results show that these control strategies handle feed flowrate and composition disturbances excellently.

Optimization and control of extractive distillation for formic acid-water separation with maximum-boiling azeotrope

It is urgent to develop sustainable chemical process through process intensification, especially for the energy-intensive distillation process. Formic acid-water forms maximum azeotrope which is purified by pressure-swing distillation in Kemira–Leonard (K-L) process and extraction plus distillation in BASF route. However, either process for this maximum azeotrope separation is energy-intensive. In the present work, by selecting the effective heavy entrainer, extractive distillation and extractive dividing wall column was firstly synthesized and optimized with genetic algorithm for formic acid-water separation. Based on optimal design, the energy consumption and CO2 emission among these proposed and existent processes were compared, and extractive distillation shows its strength for achieving high efficiency and sustainability. Then multi-loop PI control scheme and linear model predictive control based on temperature and temperature difference were developed, respectively. Dynamic response validates the control performance superiority of advanced controllers, especially for controlled variables with large overshoot, oscillations and settling time.

Intensification and performance assessment of ethanol production process by hydrogenation of methyl acetate

Fuel ethanol has attracted wide attention due to its advantages of environmental friendliness, high octane number, and excellent explosion resistance. In this paper, the design and intensification for the ethanol production process by hydrogenation of methyl acetate is developed. The conventional process containing reaction units and separation units is established. The separation units are optimized upon minimum the total annual cost (TAC). Subsequently, the dividing wall column (DWC) and extractive dividing wall column (EDWC) techniques are applied to obtain the DWC-EDWC intensified process. The results show that the TAC, CO2 emissions, and total energy consumption (TEC) of the DWC-EDWC intensified process are reduced by 9.4%, 14.9%, and 28.7%, respectively. To further improve thermodynamic efficiency, the DWC-EDWC with intermediate reboiler (DWC-IR-EDWC) intensified process is proposed. It is indicated that the DWC-IR-EDWC intensified process has more advantages in the economy. Finally, pinch technology is carried out to make full use of the heat of process streams. Compared with the conventional process, the TAC, CO2 emissions, and TEC of the modified process with heat exchange networks (HENs) are reduced by 23.7%, 29.3%, 65.4%, respectively, and the thermodynamic efficiency is increased by 9.1%.

Towards sustainable separation and recovery of dichloromethane and methanol azeotropic mixture through process design, control, and intensification

AbstractBackgroundHere we analysed the possibility of improving the sustainability performance for the recovery of dichloromethane and methanol from a binary azeotropic mixture using different energy‐intensified extractive distillation‐based processes: side‐stream extractive distillation (SSED), thermally coupled extractive distillation (TCED), and extractive dividing wall column (EDWC). The sustainability performance of the different processes was analysed based on three main factors: total annual cost (TAC), CO2 emissions, and condition number.ResultsThe EDWC was found to give the best improvement in terms of TAC and CO2 emissions by about 18% and 21%, relative to conventional extractive distillation (CED). These however were traded‐off by the increase in conditional number (CN) by 186 times, signifying a complex dynamic characteristic for the EDWC. Thus, the SSED was suggested as an alternative sustainable option as it also provides significant improvement in TAC and CO2 emissions by about 11%, and 18% with respect to the CED, whilst providing the least reduction in operational controllability, as evidenced by the marginal increase in the CN of about 1.5 times. We also investigated the dynamic performance of the SSED and found that the SSED provides identical dynamic performance in handling both ±10% throughput and ±5% feed composition disturbances as those of the CED.ConclusionAmong the different processes, SSED is the best sustainable alternative that provides compromised steady‐state (i.e. TAC and CO2 emissions) and dynamic (i.e. control) performance for the recovery of dichloromethane and methanol. © 2022 Society of Chemical Industry (SCI).

Multi-objective optimization of sustainable extractive dividing-wall column process for separating methanol and trimethoxysilane azeotrope mixture

The design and optimization of distillation process for separating azeotropes has attracted extensive attentions in decades. Currently, due to the high emphasis on environmental and social effect, it is necessary to incorporate relevant criteria into the objective function in addition to the economic indicators for approaching a more sustainable process. This paper aims to improve the process for separating the azeotropic mixture of methanol and trimethoxysilane via multi-objective optimization based on NSGA-II. Firstly, the performance of three processes, i.e., pressure-swing distillation, extractive distillation, and extractive dividing wall column (EDWC) distillation, is optimized and compared by using total annual cost (TAC) as the objective function, demonstrating that the EDWC distillation process is the preferred process. Subsequently, a heat pump assisted EDWC process (HP-EDWC) is proposed, and the multi-objective optimization is carried out based on NSGA-II algorithm with three criteria including TAC, carbon emission, and the thermodynamic efficiency, to obtain a set of Pareto solutions, which are then evaluated by using a multi-criteria decision-making method of TOPSIS to give the optimal solution. As a result, the values of TAC, carbon emission, and thermodynamic efficiency of the optimal HP-EDWC process are 90.30×104 $/year, 501.07 kg/h, and 26.02%, respectively.

Comparison of different extractive distillation processes for chloroform/n‐hexane separation: design and control

AbstractBackgroundWhen extracting total glycosides from Panax notoginseng, a waste liquid containing chloroform and n‐hexane will be produced. These waste liquids are not separated and recycled in time, which will not only waste resources but also cause environmental pollution. Chloroform and n‐hexane form an azeotrope which cannot be separated by ordinary distillation methods. This study proposes three extractive distillation processes to separate the chloroform/n‐hexane azeotrope: conventional extractive distillation (ED), side‐stream extractive distillation (SSED) and extractive dividing wall column (EDWC). The total annual cost (TAC) and carbon dioxide (CO2) emissions of the three options were compared, and the optimal process was selected. Furthermore, this research developed dynamic control of the optimal process.ResultsCompared with ED, from the perspective of economic indicators, the SSED process showed 18.9% reduction in TAC yet the EDWC process showed 33.2% reduction in TAC. In terms of CO2 emission indicators, the EDWC process also is more advantageous. Three control structures thus were developed for EDWC: applying ±5% or ±10% feed flow disturbance, and feed composition disturbance. The results show that CS3 with temperature composition cascade control structure can perfectly control all disturbances.ConclusionThis paper designs an economical, environmentally friendly and controllable chloroform/n‐hexane azeotropic separation process, which can provide a reference for the industrial application of chloroform/n‐hexane separation. © 2022 Society of Chemical Industry (SCI).

Simulation and Optimization of the Separation of Methanol-Dimethyl Carbonate Azeotrope by Extractive Dividing Wall Column

The extractive distillation of a methanol and dimethyl carbonate (DMC) azeotrope system was taken as an example, and the simulation and optimization of the conventional extractive process (CEP) and extractive dividing wall column (EDWC) were carried out by Aspen Plus software. In order to meet the requirements of separation, lower energy consumption and investment cost were obtained by using a univariate analysis of the optimal operating parameters of the EDWC. The coupling mechanism of the EDWC was described. The results showed that the number of theoretical plates of EDWC was 36, which was lower than the sum of theoretical plates in the two columns of CEP. At the same time, compared with the CEP, the energy consumption of the EDWC could save up to 16.09% and 11.85%, respectively.

Different extractive distillation processes for isopropanol dehydration using low transition temperature mixtures as entrainers

Low transition temperature mixtures (LTTMs) are effective and environmental-friendly entrainers for extractive distillation. However, process intensification for the LTTMs extractive distillation process is less studied. This paper provides a techno-economic study for the separation of isopropanol and water by extractive distillation using ChCl/EG1:2 as entrainer. Firstly, the σ-profiles based on the COSMO-SAC model, the residue curve maps and univolatility lines are used to investigate the advantages of ChCl/EG1:2 over ethylene glycol. Then, the conventional extractive distillation (CED) system with EG or ChCl/EG1:2 entrainers are simulated and optimized by non-dominated sorting genetic algorithm-II (NSGA-II) method with targets of minimum total annual cost (TAC), minimum CO2 emissions and minimum global energy consumption (GEC). The TAC of the CED process using ChCl/EG1:2 as entrainer is reduced by 13.75% than that of the process using ethylene glycol as entrainer. Finally, in order to reduce energy consumption, the processes of extractive dividing wall column (EDWC) and the side-stream extractive distillation system (SED) with ChCl/EG1:2 as entrainer are simulated and optimized. The results show that the EDWC with ChCl/EG1:2 can save 23.83% of TAC, 23.43% of CO2 emissions and 22.66% of GEC compared with the CED process using EG as entrainer.