Hybrid Extraction Distillation Research Articles

Hybrid process for separation of morpholine−water mixture: A rigorous design with experimental confirmation based on LLE and VLE data

The separation of morpholine from the aqueous effluent stream is carried out using an efficient hybrid extraction-distillation (HED) system using commercially viable solvents 2-ethyl hexanol and toluene, which makes heteroazeotrope with water. This paper investigated the tie-line, mutual solubility and VLE measurements, and thermodynamic modeling. On comparing the two solvents, 2-ethyl hexanol emerged as an appropriate extractant. The experimental tie-line data regressed by the NRTL model and a deviation of 0.8 indicates a good correlation between experimental and predicted data. Further, the process is designed, simulated, and optimization is performed by minimizing total annual cost (TAC) as the objective function. At extract/solvent to feed ratio S/F of 0.78 mol fraction, number of stages, NT of 28, 99.8% morpholine recovered in the extract phase with TAC of $23.3×104/y. Subsequently, the extract phase is fed to the heteroazeotropic distillation column to remove moisture followed by the final recovery column. Finally, a laboratory-scale experiment was conducted to verify the separation performance in the downscaled (3.5×50 cm) counter-current extraction column.

Hybrid extraction distillation for downstream purification of 2, 3-butanediol, and ethanol from fermentation broth

2,3-Butanediol is a valuable specialty chemical used in various industries and as a fuel additive. The bio-based production is significant as it's renewable and not reliant on petroleum feedstock. However, purifying 2,3-butanediol from complex fermentation broth is challenging. An integrated hybrid extraction distillation (HED) approach was developed to address this. The process was optimized using butyl acetate solvent, resulting in a maximum recovery efficiency of 91.39 % and purity of 99.99 % for 2,3-butanediol. Simultaneously, 92.22 % ethanol was recovered with 99.11 % purity. The solvent, 96 % of which was recovered, had a purity of 98.38 % and could be successfully recycled. This promising process has the potential for scaling up on a pilot scale.

Simultaneous optimization of hybrid extraction-distillation process based on rigorous models considering the effect of operating pressure

Hybrid extraction-distillation process has shown its strength in energy saving over pure distillation process; however, the widely used sequential iterative optimization method and the ignorance of optimizing distillation column operating pressure would miss a better optimal design. In this work, a rigorous pseudo-transient (PT) tray model and a steady-state optimization algorithm assisted by PT model were applied to realize the simultaneous optimization of column structural parameters and operating conditions. Two case studies were optimized to validate the correctness and the effectiveness of the proposed method. The optimal results revealed that it is more economically favorable to treat design specifications of product purity as inequality constraints to expand the search space of optimization. In the water/PM separation case study, the optimal operating pressures that facilitate separation in strippers help reduce the TAC by 14.64%, thanks to smaller reboiler duties per unit feed and smaller circulating stream flow rates. In addition, a heat integration design is feasible which reduces the TAC by 35.43%. This case study emphasizes the importance of optimizing operating pressures for such type of process.

Process intensification for the biological production of the fuel precursor butyric acid from biomass

The production of fuels from lignocellulosic biomass is key to reduce our reliance on petroleum and to promote a sustainable bioeconomy. Butyric acid (BA) is a promising chemical precursor for the production of renewable diesel and jet fuels. BA can be biologically produced from lignocellulosic sugars. However, challenges associated with product selectivity and recovery must be overcome to achieve industrially relevant metrics. Here, we evaluate various fermentation configurations and demonstrate near-homo-butyrate production by using the biocatalyst Clostridium tyrobutyricum. We also develop an advanced in situ product recovery process based on hybrid extraction-distillation (HED-ISPR) and conduct techno-economic analyses and life cycle assessments. We demonstrate that the HED-ISPR process lowers the overall capital and operating expenses and environmental impact compared to other traditional fermentation processes. Overall, BA minimum product selling price from biomass is 55% of the current BA selling price from petroleum, a significant decrease toward viable renewable fuel production.

COSMO-susCAMPD: Sustainable solvents from combining computer-aided molecular and process design with predictive life cycle assessment

Sustainable solvents are crucial for chemical processes and can be tailored to applications by Computer-Aided Molecular and Process Design (CAMPD). Recent CAMPD methods consider not only economics but also environmental hazards and impacts. However, holistic environmental assessment needs to address the complete life cycle of solvents. Here, we propose a CAMPD framework integrating Life Cycle Assessment (LCA) of solvents from cradle-to-grave: COSMO-susCAMPD. The framework builds on the COSMO-CAMPD method for predictive design of solvents using COSMO-RS and pinch-based process models. Cradle-to-grave LCA is enabled by combining predictive LCA from cradle-to-gate using an artificial neural network with gate-to-grave life cycle inventory data from the process models. The framework is applied to design solvents in a hybrid extraction-distillation process. The results highlight the need for cradle-to-grave LCA as objective function: Heuristics, economics, or cradle-to-gate LCA lead to suboptimal solvent choices. COSMO-susCAMPD thus enables the holistic environmental design of solvents using cradle-to-grave LCA.

Conceptual design, optimization, and carbon emission analysis for the acrylonitrile/acetonitrile/water separation processes

In this work, we firstly report on the rigorous design, optimization, and carbon emission analysis of the processes separating acrylonitrile (AN), acetonitrile (AC), and water. Two bi-sectional processes, which integrate heterogeneous extractive distillation with hybrid extraction-distillation (the HHED process), and that with pressure swing distillation (the HPSD process), are proposed. Compared with the existing configuration, operation using 30% less entrainer amount is found feasible for both processes, leading to 9.8% energy saving. Also, the optimized HHED process saves 4.8% total annual cost (TAC) and 5.8% carbon emission from the optimized HPSD process. Besides, implementing a vapor recompression cycle on the optimized HHED process reduces 31.1% CO2 emission but increases 6.6% of TAC. On the other hand, the heat-integrated HPSD process with an economizer design does not outperform the non-integrated HHED process. Finally, separation using heterogeneous azeotropic distillation or hybrid extraction-distillation process in single is conceptually rejected. Through this work, the industrial guidance could be provided.

Model-based evaluation of a membrane-assisted hybrid extraction-distillation process for energy and cost-efficient purification of diluted aqueous streams

The concentration of diluted aqueous streams is an important task in bio-based production processes, as well as the recovery of valuable impurities prior to wastewater purification. Affinity-based separation processes, such as liquid-liquid extraction, are generally considered favorable to distillation, which however is regularly used for solvent recovery. To reduce the effort for a solvent-based extraction and improve the economic performance, an extended hybrid process concept is considered, which exploits energy-efficient pressure-driven membrane separations, i.e. reverse osmosis or nanofiltration, for preconcentration. The current work presents a systematic evaluation of this process for purification of a diluted aqueous γ-valerolactone stream, considering two solvents. The potential economic savings are first evaluated in a model-based assessment prior to an experimental screening of suitable membranes. Finally, a detailed economic evaluation of the processes is conducted by an optimization-based process design. The proposed approach allows to quickly identify a considerable saving potential for the membrane-assisted hybrid process.

Separation of low molecular weight alcohols from water with deep eutectic solvents: Liquid-liquid equilibria and process simulations

Low molecular weight alcohols such as ethanol, propanol and butanol are currently gaining attention owing to their complete combustion and higher calorific value. These low molecular weight alcohols are obtained by ABE (acetone−butanol−ethanol) fermentation, where they are produced within an aqueous phase. Extraction is contemplated as one of the effective methods for the separation of these lower alcohols from aqueous phase through a solvent. The solvent explored here relates to the formulation of Deep Eutectic Solvent (DES) comprising of DL-menthol (Hydrogen Bond Donor) + decanoic acid (Hydrogen Bond Acceptor). The current work adopts a multiscale approach leading with DES preparation and subsequent batch scale Liquid-Liquid Equilibria (LLE) measurement and finally concludes through process simulation studies. The experimental LLE data of DES (1)-Alcohol (2)-Water (3) gave a higher affinity towards alcohol and lower solubility with water. The experimental results were thereafter regressed with the NRTL model using the additional constraint where a positive tangent plane distance is imposed for all the tie lines within the Gibbs energy of mixing (Gm) surface. The average absolute RMSD values correlated via NRTL and COSMO-SAC model were found to be 0.003 and 0.008 respectively. A flow sheet with a hybrid extraction-distillation system is then proposed and simulated for the solvent recovery, scale-up and cost analysis.

Energy-efficient design of extraction-distillation process for 2,2,3,3-tetrafluoro-1-propanol/water separation with thermodynamically verified liquid-liquid and vapor-liquid equilibrium behaviors

Design of 2,2,3,3-tetrafluoro-1-propanol (TFP)/water separation process by energy-saving hybrid extraction-distillation system is investigated in this paper. Solvent extraction is one of the most promising energy-efficient separation methods because the major part of this separation is achieved through an extraction column without needing of reboiler duty. Thus, by utilizing a hybrid extraction-distillation separation process, huge economic potential can be realized with an important prerequisite of finding an effective solvent for the liquid-liquid separation. In this work, an efficient solvent of diisopropyl ether (DIPE) is found for this separation process. The thermodynamic model used in the investigation not only satisfies the experimental data of ternary liquid-liquid equilibrium, but also predicts well the behavior of binary vapour-liquid equilibrium, showing the credibility of simulation study. Another important aspect of this paper is to also consider the way to achieve a minimum density difference of liquid-liquid extraction in the analysis. It is found that the proposed extraction-distillation system by utilizing DIPE as solvent not only can achieve over 100 kg/m3 density difference in the extraction column, but also can significantly reduce total annual cost by 51.1%, as compared to that of a heterogeneous dividing-wall column system recently published in open literature.

Design and optimization of an acetic acid recovery system via extraction–distillation using an isopropyl acetate + isopropanol mixed solvent

Azeotropic distillation incorporating liquid–liquid extraction was used for the dehydration of dilute acetic acid (HAc) solution. A hybrid extraction–distillation process was designed and simulated using isopropyl acetate + isopropanol (IPA-01 + IPA-02) as a solvent (an extractant and an entrainer), and the same processes using pure isopropyl acetate (100IPA-01) and pure ethyl acetate were also simulated. An optimal composition of the solvent was determined to be the mixture of 82 wt% IPA-01 and 18 wt% IPA-02 (82IPA-01/18IPA-02). The result shows that the operating costs and capital costs of the process using IPA-01 + IPA-02 solvent are lower than that using 100IPA-01 solvent. The optimal design of the hybrid extraction–distillation process making use of 82IPA-01/18IPA-02 as a solvent brought a reduction of the total annual cost by about 35.36% and 47.89% compared to those of the 100IPA-01 and ethyl acetate solvents, respectively.

Dynamics of hybrid processes with mixed solvent for recovering propylene glycol methyl ether from wastewater with different control structures

It is important to investigate the dynamic controllability of hybrid extraction-distillation with mixed solvent due to economic factors and control. The dynamic control of the hybrid extraction-distillation with mixed solvent is complex due to the proportions of the mixed solvent and hybrid extraction-distillation. In this paper, the dynamic control process of the hybrid extraction-distillation using a mixed solvent (70 mol% chloroform and 30 mol% 2-ethylhexanoic acid) was studied. During the dynamic control process, four control structures were evaluated via feed disturbances. Three control structures (fixed reflux ratio, reflux ratio/feed flow rate, and heat duty of reboiler/feed flow rate) achieved good performance when introduced with ±20% feed flow rate disturbances. The composition-reflux ratio cascade control structure can achieve good performance when introduced with ±20% feed composition disturbances. In terms of the total annual cost and carbon emissions, the mixed solvent process is superior to the single solvent process. However, in terms of the control effect, the single solvent process is superior to the mixed solvent process. The dynamic controllability of hybrid processes with mixed solvent basically meets the product purity requirements and demonstrates economy. This paper provides guidance for industrial green production.

Novel reaction-hybrid-extraction-distillation process for furfuryl alcohol production from raw bio-furfural

Research in the fields of biofuels and biochemicals production from lignocellulosic biomass has increased significantly in recent years. Furfuryl alcohol (FFA), which is the most important derivative of furfural, is of great industrial interest owing to its use in foundry technology. The only method to produce FFA is from hemicellulose-rich agricultural wastes. Thus it is considered a key green chemical in C5-based biorefinery. However, the conventional process is energy-intensive and has a low degree of integration owing to the lack of improvement. In this study, a comprehensive reaction-distillation (RD) process producing FFA from raw bio-furfural is proposed. Subsequently, a novel hybrid extraction-distillation process is suggested for improving the developed RD process. Heat integration is considered for both conventional and hybrid processes. All processes were simulated using Aspen Plus V.9. The total annual cost (TAC) and total carbon dioxide emissions (TCE) were evaluated for a fair comparison between these developed processes. The results indicate that the proposed integrated hybrid process can achieve substantial improvement as compared to the conventional process. In particular, this proposed configuration can reduce the TAC and TCE by up to 88.5% and 92.2%, respectively, compared to the RD process.

Design of Epichlorohydrin-Oriented Quaternary System Separation via Hybrid Extraction–Distillation Process

The allyl chloride (ALC) epoxidation method for preparing epichlorohydrin (ECH) has outstanding advantages such as atom efficiency and environmental friendliness. However, the separation of ECH from the ECH/H2O/ALC/methanol (MET) quaternary system is still a great challenge for industrial interest. A hybrid extraction–distillation process is explored in this work to overcome the defects of high energy consumption and low efficiency in the process with separate extraction or distillation. At first, ALC is recommended as the solvent. Then the flow sheet of a hybrid extraction–distillation process was designed and subsequently optimized using Aspen Plus according to the total annual cost (TAC) minimum principle. Last, several different settings of the distillation column were explored and an optimal combination with an ECH purity of 0.998 and a maximum savings of 37.26% TAC was found. The results show that the hybrid extraction–distillation process is feasible and beneficial to industrialization of the propo...

Purification of 2,3-butanediol from fermentation broth: process development and techno-economic analysis

Background2,3-Butanediol (2,3-BDO) is a synthetic chemical compound that also can be produced by biomass fermentation, which is gaining share in the global market as an intermediate product for numerous applications, i.e. as liquid fuel or fuel additive. Several metabolic engineering fermentation strategies to enhance the production of 2,3-BDO were developed. However, the recovery of 2,3-BDO from its fermentation broth remains a challenge due to its low concentration and its solubility in water and other components. Thus, a cost-effective recovery process is required to deliver the required purity of 2,3-BDO. This paper presents a new process development and techno-economic analysis for 2,3-BDO purification from a fermentation broth.ResultsConventional distillation and hybrid extraction-distillation (HED) processes are proposed in this study with detailed optimization and economic analysis. Particularly, a systematic solvent selection method was successfully implemented to determine a good solvent for the proposed HED configuration based on numerous experimental data obtained with each solvent candidate. NRTL and UNIQUAC property methods were evaluated to obtain binary interaction parameters of 2,3-BDO through rigorous Aspen Plus regression and validated using experimental data. Total annual cost (TAC)-based optimization was performed for each proposed configuration. Even though the HED configuration required 9.5% higher capital cost than conventional distillation, placing an extraction column before the distillation column was effective in removing water from the fermentation broth and significantly improved the overall process economics.ConclusionsOleyl alcohol was found to be the most suitable solvent for the HED of 2,3-BDO due to its high distribution coefficient and high selectivity. The proposed HED drastically reduced reboiler duty consumption and TAC by up to 54.8 and 25.8%, respectively. The proposed design is expected to be used for the commercial scale of 2,3-BDO production from fermentation process.

Process Design and Optimization of an Acetic Acid Recovery System in Terephthalic Acid Production via Hybrid Extraction–Distillation Using a Novel Mixed Solvent

An extraction and distillation hybrid process using a novel mixed solvent was proposed for enhancing acetic acid recovery during terephthalic acid production. Feasible hybrid extraction–distillation schemes were designed, simulated, and optimized for two mixed solvents, p-xylene + methyl acetate, and p-xylene + ethyl acetate, based on liquid–liquid equilibrium data for a quaternary system containing methyl acetate or ethyl acetate with p-xylene, acetic acid, and water. A hybrid process using the p-xylene + methyl acetate mixed solvent was found to generate the desired purity of acetic acid with a lower energy consumption and higher product yield than conventional extraction processes. Results showed that the proposed hybrid extraction–distillation process improves the process economics remarkably: the hybrid process using the p-xylene + methyl acetate and p-xylene + ethyl acetate mixed solvent reduced a total annual cost by 14% and 6%, respectively, compared with the conventional hybrid process using the ...

Potential for Significant Energy-Saving via Hybrid Extraction–Distillation System: Design and Control of Separation Process for n-Propanol Dehydration

The hybrid extraction–distillation separation system is a process combining liquid–liquid extraction and also distillation. This hybrid system can be viewed as a derivative of the heterogeneous azeotropic distillation method. In this work, the potential for significant energy-saving via this hybrid process is demonstrated with both conceptual illustration and a case study of n-propanol dehydration. Diisopropyl ether (DIPE) is selected as the extraction solvent considering its favorable properties of density, heat of vaporization, and lower toxicity. Since the solvent flow rate is the most important design degree-of-freedom in this process that influences overall energy consumption, an iterative optimization procedure is conducted to minimize total annual cost. Furthermore, a novel control strategy is proposed on the basis of closed-loop and open-loop sensitivity tests. Here, an adjustable solvent flow rate during dynamic control allows steady-state operation at the optimal condition. Dynamic simulation re...

Massive, automated solvent screening for minimum energy demand in hybrid extraction–distillation using COSMO-RS

An automated approach for large-scale solvent screening is presented based on a comprehensive process-level assessment. In this solvent screening approach, COSMO-RS is used to efficiently predict physical properties for large numbers of solvents without the need for experimental data. The predicted thermodynamical behavior is used in pinch-based separation models for a thermodynamically sound and robust calculation of the minimum energy demand. With this approach, the performance of a hybrid extraction–distillation process is evaluated fully automated for more than 4600 solvents. The massive solvent screening approach is successfully applied to purification of the bio-based platform chemical γ-valerolactone (GVL). Novel promising solvents are identified. A reduction of 63% is achieved in minimum energy demand using the best predicted solvent in comparison to the literature benchmark. Restricting the approach to known classes of solvents, we still find a reduction of 31%. The process-level assessment overcomes the limitations of heuristics based on physical properties only, and allows for efficient and robust solvent screening.

Design and Control of a Hybrid Extraction–Distillation System for the Separation of Pyridine and Water

An improved separation method is proposed for the separation of pyridine and water as compared to previous separation designs. By using n-propyl format or diisopropyl ether (DIPE) as solvent, a hybrid extraction–distillation system can be designed for this separation task. Because the main extraction column does not require steam, significant savings in the operating cost and also the total annual cost can be realized as compared to the previous designs based on heterogeneous azeotropic distillation. Considering the density differences in each stage of the extraction column and in the decanter, DIPE is a more practically favorable solvent for reaching equilibrium in each stage for liquid–liquid separation. Dynamic control of this hybrid extraction–distillation system is also investigated. It is found that a trade-off between optimal steady-state design and dynamic controllability needs to be made in order to properly reject feed flow rate and feed composition disturbances.

Separation of butanol from acetone–butanol–ethanol fermentation by a hybrid extraction–distillation process

The alternative fuel butanol can be produced via acetone–butanol–ethanol (ABE) fermentation from biomass. The high costs for the separation of ABE from the dilute fermentation broth have so far prohibited the industrial-scale production of bio-butanol. In order to facilitate an effective and energy-efficient product removal, we suggest a hybrid extraction–distillation downstream process with ABE extraction in an external column. By means of computer-aided molecular design (CAMD), mesitylene is identified as novel solvent with excellent properties for ABE extraction from the fermentation broth. An optimal flowsheet is developed by systematic process synthesis which combines shortcut and rigorous models with rigorous numerical optimization. Optimization of the flowsheet structure and the operating point, consideration of heat integration, and the evaluation of the minimum energy demands are covered. It is shown that the total annualized costs of the novel process are considerably lower compared to the costs of alternative hybrid or pure distillation processes.