Extractive Distillation Process Research Articles

Production of fuel grade anhydrous ethanol: a review

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

폐 유기용제로부터 Methylene Chloride 회수를 위한 Dimethyl Sulfoxide 추출 용매를 이용한 증류공정 최적화 설계(Ⅰ) - 추출 증류 Column의 최적화 설계 -

The purpose of this study is to recover at least 1,700 kg/hr of methylene chloride with a purity of 99.9 % or higher from waste organic solvents discharged after being used as a cleaning agent in semiconductor and display manufacturing processes, and the moisture content of the final porduct is less than 1 ppm by changing the variables such as the feed stage of raw matrial and DMSO, reflux ratio. Its final purpose is to design an optimal extractive distillation process system. Based on the analysis results, it turned out that the optimum feed stage for introducing raw materials(Waste organic solvent) into the extractive distillation column(T-01) is the 65th stage. As a result of analyzing the heat duty of re-boiler and the purity of MC, the MC recovery flow rate, the water concentration, etc. to select the optimum feed stage and the optimum inflow flow rate of DMSO, it turned out that the optimum feed stage of DMSO is the third stage and the optimum inflow flowr ate of DMSO is 1 ,2000 k g/hr. As a result of analyzing the purity of MC and the MC recovery flow rate according to the reflux ratio of the extractive distillation column(T-01), it was found that when the reflux ratio is 3.5, the purity of MC could be maintained 0.999 as Mass fraction and the MC recovery flow rate is maximum.

Dynamic control of heat pump assisted extractive distillation process for separation of ethyl acetate/isopropanol/water mixture

AbstractBACKGROUNDControlling the behavior of processes for the recovery of ethyl acetate and isopropanol from industrial wastewater is a hot topic. In this work, dynamic control structures of the extractive distillation process and heat pump combined with feeding preheating extractive distillation process are researched. The control performance of the proposed control structures is tested by adding feed flow and composition disturbance. In these two processes, two‐point temperature control structure is first used.RESULTSThe results show that this structure can maintain product purity within a reasonable range under disturbance. Furthermore, the composition controller is used to improve control performance.CONCLUSIONThe improved structure can effectively meet the requirements of product purity. The heat pump combined with feeding preheating extractive distillation process can use the same control structure as the extraction process and show good controllability. This study has a certain guiding value for the research of chemical dynamic control. © 2021 Society of Chemical Industry (SCI).

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

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

Energy-efficient recovery of tetrahydrofuran and ethyl acetate by triple-column extractive distillation: entrainer design and process optimization

An energy-efficient triple-column extractive distillation process is developed for recovering tetrahydrofuran and ethyl acetate from industrial effluent. The process development follows a rigorous hierarchical design procedure that involves entrainer design, thermodynamic analysis, process design and optimization, and heat integration. The computer-aided molecular design method is firstly used to find promising entrainer candidates and the best one is determined via rigorous thermodynamic analysis. Subsequently, the direct and indirect triple-column extractive distillation processes are proposed in the conceptual design step. These two extractive distillation processes are then optimized by employing an improved genetic algorithm. Finally, heat integration is performed to further reduce the process energy consumption. The results indicate that the indirect extractive distillation process with heat integration shows the highest performance in terms of the process economics.

Optimization and eco-efficiency analysis of extractive distillation processes with different solvents for separating the ternary mixture embedding two azeotropes

The selection of feasible solvent is of great significance for separating azeotropes via extractive distillation since various solvents can cause different product orders, flowsheet structures, and eco-efficiencies of extractive distillation processes. Limited efforts are focused on the effect of various solvents on the separation of ternary mixtures embedding two azeotropes, especially for the design of the extractive dividing-wall column separation configurations. To fill the research gap, the separation of azeotropic mixtures embedding two azeotropes is investigated using extractive distillation method with various solvents through taking the methyl acetate/ethyl acetate/methanol mixture as an example. First, the theoretical thermodynamic feasibility of four solvents including ethylene glycol, dimethyl sulfoxide, chlorobenzene, and aniline is explored. The individual light-heavy component orders are determined through the thermodynamic insights including the construction of the pseudo binary vapor–liquid phase equilibrium diagrams and overall phase diagrams with residue curves and iso-volatility curves after adding solvents, while are further verified using σ-profiles from microscopic mechanism. Second, the conceptual design of the extractive distillation flowsheets including conventional extractive distillation and extractive dividing-wall column separation configurations with individual solvents is performed. The effects of various solvents on the flowsheet structures and product orders are analyzed. Afterwards, the extractive distillation flowsheets are simulated and optimized economically to minimize the total annual costs through the genetic algorithm, except for the solvent ethylene glycol due to the unfeasibility of realistic simulation. The eco-efficiency analysis is performed via quantifying the Eco-Indicator 99 and thermodynamic performances as well as economic costs. The results indicate that the extractive distillation processes with dimethyl sulfoxide or chlorobenzene as solvent can show a certain degree of advantage compared with that using aniline as solvent in terms of eco-efficiency. The optimal separation configuration is the extractive dividing-wall column containing two dividing-walls with CB as solvent, and its Eco-efficiency Comparison Index increased to 80.54% compared to the worst scheme that is the extractive dividing-wall column containing one dividing-wall with AN as solvent.

Investigation of multi-objective optimization for integrating design and control of ionic liquid-based extractive distillation

Extractive distillation is widely accepted and commercialized for separating azeotrope mixtures, but using traditional organic solvents leads to intrinsic obstacles such as the high energy requirement and solvent-related environmental problems. Benefiting from the development of green solvents, using ionic liquids instead of traditional solvents as entrainers for extractive distillation has attracted wide attention. This paper presents a multi-objective optimization strategy to integrate the design and control of the ionic liquid-based extractive distillation processes. In the optimization processes, the condition number (CN) and total annual cost (TAC) are minimized as the objective functions to evaluate the control properties and design of three different separation systems. The optimization results are shown by the Pareto front, which is based on trade-offs between controllability and economics. The environmental impact is evaluated by the environmental impact potential of energy for each system in a posterior stage during the optimization processes. Designs with minimum TAC (PT), trade-off designs between TAC and CN (PO) and designs with minimum CN (PC) on Pareto front are optimized and compared. The results show that the increase of reflux ratio can improve the control properties for the ionic liquid-based extractive distillation processes. Furthermore, the dynamic simulation of PT and PO are carried out to compare their dynamic responses based on the same dynamic control structure, and PO shows better performance in the aspects which include maximum deviation and residual error of dynamic response.

Extractive distillation using ionic liquids-based mixed solvents combined with dividing wall column

To further reduce the energy consumption, investment and operating costs of the extractive distillation (ED) process, this study focuses on the process intensification by the combination of ionic liquids-based mixed entrainers and dividing wall column (DWC) for methanol/ethanol/water separation process. Based on the process simulation results, energy efficiency, economic and environmental impact assessments were carried out and compared with the benchmarked ED process using ethylene glycol as entrainer. The ternary ED process using the ionic liquids-based mixed entrainer can reduce the total annual cost (TAC) by about 5.98% and the energy consumption by 2.93%. The TAC and energy consumption for the proposed ternary ED process with DWC using the ionic liquids-based mixed entrainer can be reduced by 7.81% and 4.52%, respectively. The novel ED process shows the high energy efficiency, low economy cost and low CO2 emissions with a great industrial application prospect when compared to the benchmarked process.

Enhanced process for energy efficient extraction of 1,3-butadiene from a crude C4 cut

1,3-butadiene is an essential platform chemical for producing rubberlike polymers, which is extracted from C4 hydrocarbons that are produced through steam cracking. The current state-of-the-art technology is the BASF process that uses thermally coupled extractive distillation (ED) followed by two distillation columns. However, the process requires high temperature heat input, thus high cost hot utility and reduces the possibility for process heat integration.To solve these issues, this study proposes novel enhancements: the ED part is modified with intermediate heating and the classic columns are replaced with a heat pump assisted dividing wall column (DWC). Rigorous simulations were carried out in Aspen Plus for a typical ED process. The intermediate reboiler system is designed to maximize the possible process heat recovery. The results show that the heat pump assisted DWC is able to reduce the energy intensity of the classic distillation section of the BASF process by 54.8% and reduces the total annual costs by 29.9%. Additionally, the intermediate reboiler reduces the energy intensity of the ED section by 8.3% while also reducing the CAPEX of the system due to the need for a smaller recycle compressor. In combination, these modifications are able to achieve up to a 21% reduction in the energy intensity of the overall process, with a payback time of 1 year.

Extractive distillation of benzene, toluene, and xylenes from pyrolysis gasoline using methylsulfonylethane as a cosolvent

AbstractHighly efficient separation of benzene, toluene, and xylenes (BTXs) from pyrolysis gasoline is very important in petrochemical industries. Though the extractive distillation (ED) process is simpler and consumes less energy compared with liquid–liquid extraction process, it is difficult for a single solvent, for example, sulfolane, to achieve both high purity and high yield of BTXs. In this work, methylsulfonylethane (MSE) was chosen as a cosolvent to improve the selectivity of sulfolane after solvent screening, and factors that may affect the selectivity of the composite solvent were fully investigated, such as the content of cosolvent, solvent to feed ratio, the composition of the feed, and temperature. Furthermore, 240 h of continuous extractive distillation and solvent recovery experiment was carried out using sulfolane (85 wt%)–MES (15 wt%) mixture as solvent. The purity of mixed aromatics obtained was 99.83%, and the yield was as high as 99.7%.

Desulfurization of Fluid Catalytic Cracking Naphtha by Extractive Distillation: A Universal Simulation Method Established Using the Universal Quasi-Chemical Functional Group Activity Coefficient Model

The extractive distillation process is gradually being used for the desulfurization of fluid catalytic cracking (FCC) naphtha because of its excellent octane number protection performance during desulfurization. The key to this process is the separation of sulfides. However, the composition of FCC naphtha is complicated and easily changes, which seriously affect the separation performance. The operating conditions need to be adjusted frequently with the change in the different properties of feedstocks, which cost time, manpower, and investment. In this study, we introduce a simulation method using the universal quasi-chemical functional group activity coefficient (UNIFAC) model to predict the process of desulfurization. In the simulation, the group binary parameters for the UNIFAC model seriously affect the reliability of the method. Therefore, the lacking parameters of the solvent and sulfides were first regressively calculated by the experimental results of the binary vapor–liquid equilibrium (VLE). All the values of (D–J) by the Herington integral method were under 10, which means that the parameters obtained in this work were well correlated to those of the VLE experiments. Based on this, the prediction simulation method was established and the maximum error of the compositions of the products between simulation and real-oil experiment was only 0.5 wt %. According to the simulation, 98% of sulfides could be extracted under the optimal conditions (113 °C at the extraction column, 178 °C at the solvent recycle column, etc.). The rule of the extraction of sulfides was thiophene sulfur > mercaptan sulfur > thioether sulfur, which is consistent with the VLE study results. The sulfur content of the raffinate oil was decreased to 9.3 mg/kg. It well met the latest gasoline standard and is appropriate for the prediction of the desulfurization of FCC naphtha by the extractive distillation process.

Conceptual design of the triple-column extractive distillation processes with single entrainer and double entrainer for separating the N-hexane/acetone/chloroform ternary multi-azeotropic mixture

Currently, there are very limited efforts on investigating triple-column extractive distillation process with single entrainer (S-TCED) for separating ternary multi-azeotropic mixture with special phase behavior. Therefore, two counter-intuitive methods, including conventional S-TCED and double side-stream S-TCED, are proposed for separating the N-hexane/acetone/chloroform mixture containing four azeotropes, in comparison with the correspondingly intuitive method of triple-column extractive distillation process with double entrainer (D-TCED). First, dimethyl sulfoxide is selected to break azeotropes and increase the relative volatility through vapor liquid equilibrium analysis and maximum selectivity calculation. Subsequently, the conceptual design of extractive distillation flowsheets is performed via thermodynamic insights, especially for two S-TCED configurations. Genetic algorithm is adopted to optimize separation schemes with the minimal total annual cost (TAC). The optimization results show that two S-TCED flowsheets can perform the separation of the ternary multi-azeotropic mixture, and even cause the slight reduction in TAC compared to their corresponding D-TCED configurations, respectively.

Design and optimization for the separation of cyclohexane-isopropanol-water using mixed extractants with thermal integration based on molecular mechanism

With the improvement of people's living standards, higher requirements are put forward for food safety, variety and quality. Edible oil is essential in people's life, but the production and processing process will produce a lot of waste, it is necessary to develop efficient and energy-saving treatment technology. Taking the wastewater containing ternary azeotropic system of cyclohexane-isopropanol-water produced in rapeseed oil production as an example, cyclohexane and isopropanol were separated and recovered by extractive distillation. Through the analysis of relative volatility, density functional theory and molecular mechanism, the suitable extractants of DMSO and EG were selected from the perspective of action mechanism. Aiming at the lowest economic cost, optimize the parameters of the process with single solvent and the mixed solvents by sequential iterative method, and further to determine the optimal process parameters and the optimal ratio of mixed extractant. In addition, the effects of single extractant and mixed extractant on the azeotropic system of extractive distillation were compared in terms of thermodynamic efficiency and environmental impact. The results shown that, compared with the single extractant, the extractive distillation process using the mixed extractant can save 30.71% and 16.71%, the thermodynamic efficiency was increased by 24.13% and 16.72%, GWP was reduced by 19.32% and 3.77%, AP was decreased by 19.26% and 3.43%. Combined with thermal integration technology, the economic cost was further reduced by 28.12%, the thermodynamic efficiency was increased by 10.49%, GWP and AP were reduced by 51.72% and 51.78% respectively on the basis of the optimal extractive distillation process with mixed extractants. The results shown that cyclohexane and isopropanol can be effectively recovered from the wastewater produced in rapeseed oil production by using mixed extractant and heat integrated energy-saving technology in extractive distillation process, which is of great significance for food safety, resource saving and environmental protection, and has guiding significance for the separation of other similar azeotropes.

Production of hydrocarbon based solvent with low aromatic content using ASPEN Plus

The solvent is a liquid that can dissolve or extract specific materials. Solvents are needed for most chemical transformations to increase contact between reagents and catalysts. It also holds an important role in many studies, industrial chemical processes, coatings, and formulations of consumer products, however, most of the hydrocarbon-based solvents based still contain high aromatic content of benzene, toluene, and xylene which are carcinogenic chemicals. The separation of aromatic hydrocarbons from a mixture of C4-C10 aliphatic hydrocarbons is a complex process, due to its close boiling points and some combinations can form azeotropes. The general distillation process is not the right choice for the separation of aromatic hydrocarbons from a mixture of C4-C10 aliphatic hydrocarbons. Possible processes are liquid-liquid extraction, extractive distillation, and azeotropic distillation. In this study, extractive distillation using ASPEN Plus was performed to simulate the process. The crude feed composition used contains 77.13% aromatic compounds so that the separation technology used uses the extractive distillation process using sulfolane as a solvent. The variables used are the ratio of the crude feed to sulfolane (1:10, 1:15, 1:20), the number of stages (30, 40, 50), feed stage (15,20,25). Based on the simulation results, the best result was obtained by using the ratio of the crude feed to sulfolane of 1:10, with the number of stages 30, and the feed stage on the 25th stage.

Optimal Design of an Ionic Liquid (IL)-Based Aromatic Extractive Distillation Process Involving Energy and Economic Evaluation

Extractive distillation (ED) can be used to separate mixtures with low relative volatilities that are even close to unity. It is widely adopted for the separation of aromatics and nonaromatics in the petrochemical industry. Selecting a suitable solvent is of paramount importance to ED processes. Ionic liquids (ILs) are increasingly being considered as potential options to replace organic solvents in ED processes due to their favorable properties including high boiling points and extremely low volatilities. In this work, a nonexperimental solvent screening approach, i.e., computer-aided ionic liquid design (CAILD), is employed to identify the optimal ILs. Using a novel design objective and several structural and property constraints on IL, we have identified 1,3-dimethylpyridinium tetrafluoroborate ([C1mPy][BF4]) as the best IL solvent by solving a formulated CAILD-based mixed-integer nonlinear programming problem. The separation performance of this IL is further evaluated with rigorous process simulation in Aspen Plus. Besides, process simulation of the aromatic ED process using sulfolane as the benchmark organic solvent is performed. Furthermore, a systematic analysis of the energy consumption and the process economy is conducted by investigating the optimized simulation results of the studied aromatic ED process. The [C1mPy][BF4]-based process with an assumed IL price of 50 $/kg can reduce the capital cost by 35.2%, the operating cost by 11.8%, and the total annual cost by 31.2%. The IL price at the break-even point of replacing sulfolane with [C1mPy][BF4] in the aromatic ED process is 91.03 $/kg.

Advanced hybrid optimization methods for the design of complex separation processes

While the need for more efficient and integrated processes for the separation of non-ideal and azeotropic mixtures mandates model-based design methods, the resulting mixed-integer problems are highly nonlinear and particularly hard to solve without proper initialization. In order to handle such complex design problems, two hybrid optimization methods are presented in the current contribution. Both methods rely on a nested approach, which integrates a polylithic modeling and solution strategy, based on the solution of successively refined nonlinear programming problems, with an upper level metaheuristic for the initialization and optimization of discrete design decisions. Both methods are evaluated for two case studies. The optimization of a simple column design problem allows for the direct comparison with an available global deterministic optimization solver for identifying the global optimal solution. The optimization of an extractive distillation process with simultaneous solvent selection and energy integration illustrates the potential complexity that can be handled effectively.

Dynamic control analysis of eco-efficient double side-stream ternary extractive distillation process

The novel contribution of this paper is to implement the dynamic control investigation for the energy-saving double side-stream ternary extractive distillation configuration with constructing the practical and workable plumbing arrangement taking the representative example of separating a ternary benzene/isopropanol/water mixture. The new proposed control scheme achieves the stable regulatory control at rejecting the large disturbances of throughput and feed composition, wherein the particularly key control loops are controlling the product isopropanol composition by adjusting the extractant flow rate into extractive column C2 with simultaneously regulating the reflux ratio in extractive column C1 to abate the solvent dilution effect through composition cascade temperature control loops.

Energy efficient and environmentally friendly pervaporation-distillation hybrid process for ternary azeotrope purification

Isopropanol and acetonitrile are important chemical raw materials that are widely used in the chemical industry. However, mixtures of acetonitrile, isopropanol, and water are difficult to separate as these compounds form azeotropes. The solvents were screened based on their relative volatility and toxicity. To reduce the energy consumption, a heat pump-assisted extractive distillation process was proposed. Furthermore, the pervaporation–distillation hybrid process was studied. Life cycle assessment was used to evaluate the environmental impact of the processes. The total annual cost and energy consumption of the hybrid process were 21.11% and 45.91% lower, respectively, than those of the basic process. The values of global warming potential and acid potential of the hybrid process are 810.57 and 1.45, respectively, which are the smallest among those of processes studied. It is concluded that the hybrid process can not only reduce energy consumption, but is also more environmentally friendly than the other processes.

Energy-efficient extractive distillation combined with heat-integrated and intermediate reboilers for separating acetonitrile/isopropanol/water mixture

A conventional triple-column extractive distillation is researched for the separation of acetonitrile/isopropanol/water mixture with ethylene glycol (EG) as entrainer. In this article, the pressure-relative volatility curve is investigated to find the suitable pressure of column. To achieve the further energy saving, three heat-integrated schemes and two heat-integrated combined with intermediate reboilers schemes are researched based on the conventional extractive distillation. Both two heat integration with intermediate reboilers schemes shown the better performance than other schemes since the further analysis of the energy, exergy, economic and environment (4E) were investigated. For the most energy saving design, PHI-IHI2, it has 48.50% energy-saving, 70.73% exergy efficiency enhanced, 36.24% reduction in total annual cost (TAC) and 48.55% reduction in gas emissions with the comparison of the conventional extractive distillation (CED) process. The result shows the extractive distillation combined with heat-integrated and intermediate reboilers presented great energy-efficient, economy saving and environment friendly for separating acetonitrile/isopropanol/water mixture.

Eco-Efficient Heat-Integrated Extractive Distillation Process Using Ionic Liquid as Entrainer for Ethyl Acetate-Isopropyl Alcohol-Water Mixture

Eco-Efficient Heat-Integrated Extractive Distillation Process Using Ionic Liquid as Entrainer for Ethyl Acetate-Isopropyl Alcohol-Water Mixture