Extractive Distillation Process Research Articles

The Impact of Feed Composition on Entrainer Selection in the Extractive Distillation Process

The selection of entrainers primarily focuses on their ability to alter the relative volatility. However, the impact of feed composition on entrainer selection has often been overlooked. In this study, we conducted two case analyses of the minimum azeotropic mixtures in the ethyl acetate–ethanol and acetone–methanol systems to explore how the feed composition influences the entrainer selection when aiming for maximum economic efficiency. Additionally, the impact of the entrainer type (positive or reverse) on the economic benefits was also investigated. The cases revealed that economic benefits will be notably enhanced when the selected entrainer preferentially targets and removes the low-content component as the light key component. For the two cases studied, when the feed composition was 0.2–0.8, compared to preferentially separating the high-content component, preferentially separating the lower-content component resulted in a reduction in energy consumption by more than 24.14% and 22.72%, respectively. The results show that the ideal entrainer should be capable of converting the higher-content component in the feed into the heavy key component.

Applicability exploration and sustainable assessment of heat integration and vapor recompression heat pump to side-stream extractive distillation processes for separating ternary azeotropic system

The side-stream extractive distillation (SSED) process is attracting extensive attention due to its high energy efficiency for separating ternary azeotropic mixture. However, the correlation between the bottom temperature level of distillation columns depending on the flowrates and compositions of side streams and the introduction of heat integration (HI) and vapor recompression heat pump (VRHP) technology is ignored. In the work, a range of initialization extractive distillation processes including one conventional extractive distillation (CED) process and five SSED processes considering different flowrates, compositions, and feed locations of side streams are proposed for separating acetonitrile/isopropanol/water ternary azeotropic system. The optimization results with the minimum the total annual costs (TAC) as the optimization objective show that not all SSED schemes are superior to the CED separation process, and the SSED separation schemes can achieve up to a 2.72 % reduction in the TAC. Following that, the HI and VRHP assisted extractive distillation schemes are proposed based on the temperature levels between the top and bottom of different distillation columns and compressor restraints for the initialization extractive distillation schemes mentioned after optimization. Moreover, sustainable evaluations covering economy, energy consumption, environment, and energy utilization are implemented for the extractive distillation schemes proposed. The evaluation results indicate that the CED-HI scheme overcomes all SSED-HI and SSED-VRHP schemes in terms of economic costs, but the optimal SSED-HI processes can reduce 8.77 % of energy consumption and 4.73 % of CO2 emissions, while the energy utilization raised from 1.70 % to 1.78 % compared to the CED-HI process.

Study on the separation of methyl-ethyl-ketone / isopropanol / water ternary mixture by energy-efficient extractive distillation processes

The separation of ternary mixtures of methyl-ethyl-ketone (MEK)/isopropanol (IPA)/water, which are produced through chemical processes, is an imperative task aimed at reducing energy expenditures and mitigating environmental contamination. In the industry, Ethylene glycol (EG) and dimethyl sulfoxide (DMSO) are commonly employed as extractants. The selection of EG as the extractant was based on an investigation into the impact of relative volatility. Three distinct processes, namely conventional extractive distillation (CED), side-stream extractive distillation (SED), and heat pump extractive distillation (HPED), were evaluated by total annual cost (TAC), total energy consumption (TEC) and carbon dioxide emissions (CO2 emissions). The results demonstrate that both the enhanced SED and HPED processes effectively decrease energy consumption. Specifically, the TEC for the SED process exhibits a reduction of 15.36% compared to the CED process, resulting in a TAC saving of 9.06% and a decrease in CO2 emissions by 12.37%. Similarly, the HPED process surpasses the CED process by achieving a TAC saving of 15.41% and a CO2 emissions reduction of 22.61%. Consequently, this research presents a novel approach for the separation of MEK/IPA/water, offering significant practical implications.

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.

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.

Improved extractive distillation process using dual decanters

Novel distillation configurations continue to appear in the literature despite the predictions made many decades ago that distillation had attained the status of a mature and stagnant technology needing no further research and development. The driving force for improvement has traditionally been energy conservation, but political decisions related to environmental and sustainability issues have provided additional motivation for improving the efficiencies of chemical and petroleum processes. Since distillation columns require a large fraction of the total energy used in these processes, there is a significant incentive to improve process efficiency.An excellent example of this activity is a paper in which a conventional three-column extractive distillation configuration is compared with a novel two-column process that includes a single decanter. The chemical separation system is a ternary mixture of methanol, water and toluene, which is important in the pharmaceutical industry. The new configuration reduces total annual cost by 50%.The purpose of this paper is to propose a simple modification of the two-column configuration that reduces energy costs by an additional 14% by using two decanters in series operating at different temperatures.

A novel reactive-extractive distillation process for separation of water/methanol/tetrahydrofuran mixtures

The design of separation systems for the purification of azeotropic mixtures is of great importance in the chemical industries from economic and environmental points of view. Two novel reactive-extractive distillation (RED) processes, new design (I) and new design (II), were proposed for separating the azeotropic mixture of water/methanol/tetrahydrofuran (THF). These processes were compared to a conventional extractive distillation (ED) process. New design (I) employs dimethyl sulfoxide as a solvent, while new design (II) utilizes ethylene glycol. Ethylene oxide was introduced to the first column in both designs, enabling the in-situ production of ethylene glycol, a valuable byproduct. This is a novel solution to separate water from the azeotropic mixture by reaction between ethylene oxide and water. Aspen Plus software was used to simulate and design the processes. Both suggested designs were compared economically with the base design which is an ED process. According to the results, the new design (I) is more cost-effective and environmentally friendly alternative to the base design and the new design (II). It has a lower total capital cost and produces less carbon dioxide. Additionally, it generates a valuable by-product, ethylene glycol, which can be sold for substantial revenue. As a result, the new design (I) is the preferred choice for replacing the conventional extractive distillation method.

Separation of the cyclohexane-benzene mixture by the extractive distillation process using ethylene glycol as a solvent

The importance of cyclohexane lies in the fact that it is the main precursor for the production of Nylon 6 and Nylon 6.6, two of the most important synthetic fibers. Cyclohexane (CHX) is produced by catalytic hydrogenation of benzene (BZ), where cyclohexane with benzene is obtained as a product. Since CHX and BZ have close boiling temperatures, and similar molecular structures, their separation by conventional binary distillation is complicated. Thus, ethylene glycol (EG) was selected as a solvent in an extractive distillation (ED) process for the separation of the CHX-BZ mixture in Aspen Plus V9®; where the use of ethylene glycol as a solvent allowed us to obtain cyclohexane and benzene with purities of 99.91 mol%. In addition, compared to the extractive distillation with heat integration (EDHI) process that uses [C5(MIM)2][NTf2]2 + H2O as a mass separation agent; the use of EG as a solvent promotes an energy decrease of 41.14%, a saving of 55.07% in the Total Annual Cost (TAC), and a decrease of 72.38% in CO2 emissions. These outcomes underscore the efficacy of ethylene glycol as a suitable solvent in the purification of the cyclohexane-benzene mixture.

Efficient purification of n-butanol by thermally coupled extractive distillation with mixed entrainer

To solve the problems of difficult separation of azeotropes and high energy consumption in the preparation of n-butanol from the fermented mother liquor, this study focused on the separation process integration of water/acetone/ethanol/n-butanol mixture based on the combination of mixed entrainer and thermally coupled distillation technology. Based on quantum chemical calculations, the molecular polarity and weak interaction between the entrainer and the mixture to be separated were studied at the molecular scale, and the separation mechanism of extractive distillation was revealed. Based on the simulation results, the three different configurations' process performance was evaluated and compared to the benchmark conventional extractive distillation process with ethylene glycol as the entrainer. The thermally coupled extractive distillation process with mixed entrainers can reduce the total annual cost by about 39.87%, reduce energy consumption and acid gas emissions by 46.53%, and improve the thermodynamic efficiency by 47.57%. The thermally coupled extractive distillation process with mixed entrainers is an economical, energy-saving, and environmentally friendly production scheme superior to the conventional extractive distillation process. The thermally coupled extractive distillation process, as an essential energy-saving technology for producing n-butanol from fermentation mother liquor, has broad development prospects.

Dual-objective optimization and energy efficiency enhancement of natural decantation assisted extractive distillation process for n-butanol/isobutanol/water separation

Isobutanol (i-BuOH) and n-butanol (n-BuOH) are widely used as solvents and organic raw materials in fine chemical and pharmaceutical fields. Hence the recovery of high-purity products from chemical industrial effluent containing i-BuOH and n-BuOH is of great significance to improve economic and environmental benefits. In this article, two extractive distillation processes with or without natural decantation are developed with 1,4-butanediol as entrainer, namely CED and NDED. In order to obtain the optimal process parameters under the trade-off between economic and environmental benefits, the two processes are optimized with total annual cost (TAC) and CO2 emissions as objective functions by a non-sorting genetic algorithm. Further, a heat integrated extractive distillation process with natural decantation and vapor recompressed heat pump is designed and investigated, namely HI-NDED-VRHP. Finally, a fair multi-criteria evaluation is conducted on all three optimal processes in terms of TAC, CO2 emissions, and total energy consumption (TEC). The results show that the HI-NDED-VRHP process is highly eco-efficient, which can reduce TAC by 18.9%, CO2 emissions 44.2% and TEC 44.7% than the CED process and decrease TAC by 12.4%, CO2 emissions 36.7% and TEC 37.1% than the NDED process.

Design and multi-objective optimization of hybrid extractive distillation process for separating the toluene-methanol-water ternary azeotrope

Cleaner production and sustainable development are still hot topics for modern industry. Developing green technology with low energy consumption, low pollution, and low cost has always been the common pursuit of chemical, petroleum, pharmaceutical, and other industries. This article proposes an environmentally friendly and efficient solvent, glycerol, for the separation of the ternary azeotrope of toluene-methanol-water. Three feasible extractive distillation schemes were designed and optimized, while the double-column extractive distillation process with a decanter demonstrated superior performance when glycerol was used as the solvent. Additionally, the multi-objective genetic algorithm was employed to optimize these separation processes and determine the optimal operating conditions, taking total annual cost (TAC), CO2 emissions (ECO2), and separation efficiency (Eext) as target performance indicators to achieve the objectives of energy conservation, consumption reduction, and emission reduction. Results demonstrated that the newly proposed scheme can significantly reduce the total annual cost by up to 33.1 % and CO2 emissions by 50.5 % compared with the existing separation process. This work provides a new insight to separate and purify the multiple systems by extractive distillation in industry.

Insight into dynamic safety characteristics of extractive distillation process considering independent protection

This work explores the integration of dynamic simulation with the concept of protection layers to assess the dynamic safety of an extractive distillation operation. This particular study concentrates on the separation process of acetonitrile from water using ethylene glycol as the entrainer. It appraises the efficacy of different independent protection layers — ranging from basic process control systems, critical alarms, and operator interventions, to safety instrumented systems and pressure relief valves — against various potential risk scenarios. The study considers scenarios leading to overpressure situations, such as failures in the condenser system, surges in hot steam supply, or severe disturbances in feed. Using Aspen Dynamics for detailed dynamic simulation and safety evaluation, the study examines the response and effectiveness of each protection layer meticulously. It employs a scenario-based safety analysis to gauge the dynamic safety performance and the effectiveness of the protection layers. The research underscores the value of scenario analysis in grasping the dynamic responses of the distillation process and the spread of irregularities through the system. This understanding is crucial for estimating the process safety time and for crafting an efficient safety system.

Integrated process design and self-optimizing control: A probabilistic approach

This work introduces a probabilistic-based integrated process design and self-optimizing control approach grounded in a steady-state model, aiming to strike a balance between solution reliability and optimality. The proposed approach offers a practical and cost-effective solution by considering disturbances as random variables with known probability distribution functions. To propagate these disturbances to process outputs, the unscented transform method is utilized alongside rigorous first-principles process models. Additionally, probability levels are assigned to process constraints based on user-defined specifications, providing flexibility to tailor the design to desired risk confidence levels. The effectiveness and benefits of the approach are demonstrated through an application on an extractive distillation process with pre-concentration.

Design and multi-objective optimization of novel side-stream reactive-extractive distillation process with intermediate reboiler for recovering ethanol and 1,4-dioxane from wastewater

Conventional distillation methods cannot separate ternary mixtures containing multiple azeotropes. This article designs two reaction distillation processes to recovery ethanol and 1,4-dioxane from wastewater, and a novel side-stream reactive-extractive distillation process with intermediate reboiler (SREDIR) process for the first time is proposed to separate this mixture. Taking economy and entropy generation as objective functions, multi-objective genetic algorithm is used to optimize the processes. It is concluded that all the proposed reaction distillation processes are energy-saving than the existing extractive distillation process for recoverying ethanol and 1,4-dioxane from wastewater. This existing process is an indirect extractive distillation process with DMSO as entrainer with heat integration (IED-DMSO-HI) process. Compared with IED-DMSO-HI process, the SREDIR process is economic since its total annual cost is reduced by 64.30%. However, the total entropy generation of SREDIR process is increased by 16.06%. Therefore, if there are high thermodynamic requirements for the separation process, reactive distillation requires careful 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.

Design and 4E analysis of heat pump-assisted extractive distillation processes with preconcentration for recovering ethyl-acetate and ethanol from wastewater

The separation of ternary azeotropes with a high content of one component using extractive distillation is energy intensive, and the introduction of preconcentration can significantly improve process economy. In this paper, the conventional three-column extractive distillation (TCED), four-column extractive distillation (FCED) with preconcentration, and three-column extractive distillation with integrated distillation column (TCED-IDC) are established and economically optimized to minimize the total annual cost (TAC) for recovering ethyl-acetate (EAc) and ethanol (EtOH) from wastewater containing a large amount of water. The preconcentration and solvent recovery functions can be integrated in IDC. Following that, the vapor recompression heat pump (VRHP) is introduced to further reduce energy consumption for the TCED-IDC process. The two VRHP-TCED-IDC processes are correspondingly designed. Simultaneously, the processes proposed are evaluated in terms of economy, energy consumption, environment and exergy destruction (4E analysis). The environmental analysis is performed via calculating Global Warming Potential (GWP) index using Life Cycle Assessment method. The two VRHP-TCED-IDC processes demonstrate superior performances with regard to 4E analysis. The most efficient VRHP-TCED-IDC process reduce over 32.0 %/16.0 %/6.8 % of TAC, 53.4 %/42.4 %/33.7 % of energy consumption, 62.0 %/53.0 %/45.9 % of GWP, and 49.7 %/35.7 %/29.3 % of exergy destruction compared to the TCED/FCED/TCED-IDC processes, respectively.

Eco-efficiency analysis and intensification of cryogenic extractive distillation process for separating CO2–C2H6 azeotrope through vapor recompression strategy

The cryogenic extractive distillation process for CO2-ethane separation from natural gas involves four distillation columns in series and a rather high amount of energy from boiler and refrigeration compressors. This study proposes the intensification of a real plant located in China using a vapor recompression (VR) strategy to revamp it. The conventional process and the intensification configurations were designed by simulation in UniSim software. A utility plant with cooling water, steam generation, and propane refrigeration sections was also considered for realistic results regarding water consumption, CO2 emissions, and utility costs. Additionally, in order to establish an overall means for performance analysis, such indicators were grouped in a joint evaluation approach using the Comparative Eco-Efficiency Index. Results show that the VR1 scheme applied between the depropanizer condenser and the deethanizer reboiler provides savings of 24.2 % and 24.5 % in energy and water consumption, respectively; therefore, savings of 25.5 % and 21.4 % in CO2 emissions and utility costs were achieved, respectively, which increased the process's eco-efficiency by 41.9 %. As a point of interest, 33 months are necessary to recover the corresponding investment on the compressor and heat exchanger.

Sustainable and efficient process design for wastewater recovery of cyclohexane/isopropyl alcohol azeotrope by extractive distillation based on multi-objective genetic algorithm optimization

Cyclohexane and isopropyl alcohol are widely used in the chemical and pharmaceutical industries. There is a strong industrial need for the refinement of cyclohexane and isopropyl alcohol. In this study, the recovery of cyclohexane and isopropyl alcohol from wastewater was carried out sustainably and efficiently by extractive distillation. The suitability of ethylene glycol as entrainer was determined by relative volatility analysis. The process was optimized via multi-objective optimization, and the extractive distillation process obtained optimal parameters and process scheme. Finally, a comprehensive analysis was conducted to evaluate the economic, environmental and exergy efficiency of different process schemes. The results show that the extractive distillation coupled pervaporation technology has a 14.07% lower total annual cost than extractive distillation, and the pervaporation technology reduces gas emissions by 15.65% compared to the extractive distillation. This work explores the recovery of cyclohexane and isopropyl alcohol from wastewater by different process schemes, which has certain guiding significance for the sustainable and efficient separation of ternary azeotrope.

Molecular mechanism-based extractant screening and process design for the separation of methanol/dimethyl carbonate azeotrope

The separation of methanol/dimethyl carbonate azeotrope is an important process in the industrial production of dimethyl carbonate. Extractive distillation is an effective separation method, which can ensure the full utilization of resources and achieve sustainable development. In this work, an extractant screening method based on density functional theory (DFT) was proposed. By comparing the interaction energy difference, the optimal extractant (dimethyl sulfoxide, DMSO) was obtained. The molecular mechanism of action between the extractant and the separated components was explained. The separation order of the components of the extraction distillation process was obtained by the magnitude of the interaction energy. The σ-profile curve and isovolatility curves method were used to verify the effectiveness of the proposed method. A new separation process with DMSO as an extractant was designed. With the lowest total annual cost (TAC) as the goal, sensitivity analysis and cyclic iteration method is used to optimize the parameters involved in the process to determine the best process parameters. Heat integration technology is introduced to further reduce energy consumption. TAC, energy utilization efficiency, and global warming potential (GWP) were used to evaluate the process. Compared with the reported optimal extractant methyl salicylate, the TAC of the simple process using DMSO as the extractant was reduced by 9.08%. The heat-integrated process with DMSO shows a TAC reduction of 17.17% compared to the simple process. And the energy utilization efficiency and GWP were increased by 40.90% and decreased by 31.88%, respectively. The results show that the extractant screened by DFT method is applied to the azeotrope separation, which makes the process have good economic benefits, low energy consumption, and less environmental impact.

Inherently safer design and multi-objective optimization of extractive distillation process via computer-aided molecular design, thermal stability analysis, and multi-objective genetic algorithm

The extractive distillation is a commonly used method for the separation of azeotrope in the chemical industry. In this article, we investigate the safety issue of the extractive distillation process for targeted audience process engineers from the perspective of process safety. We conduct inherently safer design and multi-objective optimization of extractive distillation processes for the separation of methyl acetate/methanol via computer-aided molecular design, thermal hazard analysis, and multi-objective genetic algorithm. Firstly, the entrainers with good safety and separation performances are pre-screened by computer-aided molecular design (CAMD) based on flash point and entrainer selectivity. Then the entrainers with top-ranking separation performance are manually screened based on vapor-liquid equilibria. Next, the Pareto front solution is obtained by optimizing both safety and economic objective functions using a multi-objective genetic algorithm. Finally, the thermal hazard of the entrainer is also investigated via DSC (Differential scanning calorimetry) test. Finally, the optimization result and thermal hazard investigation demonstrate that 1,3-propanediol is inherently safer than dimethyl sulfoxide (DMSO) as a common entrainer in terms of not only a fire hazard but also a thermal hazard for the separation of methyl acetate/methanol mixture. The optimal TAC using 1,3-propanediol as an entrainer is 3.72% lower than that of dimethyl sulfoxide, and the corresponding GISI is 57.73% lower than that of dimethyl sulfoxide. As for DMSO, thermal decomposition can occur near its normal boiling point (189 ℃) and 1,3-propanediol, can be thermally stable over 330 ℃.