Heterogeneous Azeotropic Distillation Process Research Articles

Economic, environmental, energy, exergy (4E) analysis and simulated annealing algorithm optimization of dividing-wall column-intensified heterogeneous azeotropic pressure-swing distillation process

This work presents an approach for the recovery of high purity cyclohexane (CYCLO) and tertiary butyl alcohol (TBA) from wastewater. After thermodynamic analysis, a heterogeneous azeotrope-pressure swing distillation process (HAPSD) with a decanter is proposed. The heterogenous azeotrope distillation with a high-pressure column and a dividing-wall column process (HADWC) is also being developed to propose a green and sustainable process. The novel processes are optimized using simulated annealing algorithm (SAA). Those processes are optimized by simulated annealing algorithm by linking Aspen Plus and MATLAB via taking the total annual cost (TAC) as objective function. Three energy-efficient HADWC processes are proposed based on the process intensification approach of heat pump and heat integration technologies. All processes are evaluated for multi-criteria performance including economy, energy consumption, gas emissions and thermodynamic efficiency. As the result, HADWC-HP-HI process shows the best performance with 31.79%, 53.46%, 50.69%, and 57.94% reducing over the conventional HAPSD process in terms of TAC, energy consumption, gas emissions and thermodynamic efficiency, respectively.

Energy-efficient heterogeneous triple-column azeotropic distillation process for recovery of ethyl acetate and methanol from wastewater

The challenging separation of ethyl acetate (EtAC) and methanol (MeOH) from wastewater involves two azeotropes and a distillation boundary. Although extractive distillation (ED) has been explored, the heterogeneous region within the ternary azeotropic mixture has been overlooked, which suggests the possibility of using a decanter to cross the distillation boundary when the feed composition is present in the heterogeneous region. This study introduces a novel heterogeneous triple-column distillation (NHTCD) that eliminates the external solvent injection, simplifying the complex ED processes. The NHTCD process is developed via a systematic approach, comprising conceptual design based on thermodynamic insights and process optimization to determine the optimum configuration. Furthermore, heat integration (HI) and heat pump-vapor recompression (HP-VR) techniques were explored for energy conservation. Evaluation of energy, economic, and environmental (3E) aspects shows that the hybrid HP-VR with HI NHTCD process outperforms ED, achieving 87 %, 57 %, and 86 % reductions in energy, economic, and environmental emissions, respectively.

Energy-saving design and optimization of pressure-swing-assisted ternary heterogenous azeotropic distillations

A huge amount of energy is always consumed to separate the ternary azeotropic mixtures by distillations. The heterogeneous azeotropic distillation and the pressure-swing distillation are two kinds of effective technologies to separate heterogeneous azeotropes without entrainer addition. To give better play to the synergistic energy-saving effect of these two processes, a novel pressure-swing assisted ternary heterogeneous azeotropic distillation process is proposed firstly. In this process, the ternary heterogeneous azeotrope is decanted into two liquid phases before refluxed into the azeotropic distillation column to avoid the aqueous phase remixing, and three columns’ pressures are modified to decrease the flowrates of the recycle streams. Then the dividing wall column and heat integration technologies are introduced to further reduce its energy consumption, and the pressure-swing assisted ternary heterogeneous azeotropic dividing wall column and its heat integration structure are achieved. Genetic Algorithm procedure is employed to optimize the proposed processes. The design results show that the proposed processes have higher energy efficiencies and lower CO2 emissions, compared with the published ternary heterogeneous azeotropic distillation process.

Application of dividing wall column in azeotropic distillation with intermediate boiling-point heteroazeotrope: Simulation and optimization

Dividing wall column (DWC), as a proven process intensification technology, has been used widely in separation of ideal multi-components, and some azeotrope systems. For heterogeneous azeotrope with the potential possibility of crossing distillation boundary by liquid-liquid splitting, it is advantageous to integrate liquid-liquid decanter with distillation column, especially with DWC to further simplify flowsheets and reduce energy consumption. In this work, existing heterogeneous azeotrope separation processes are described, and an innovative DWC-based process (MHADWC) is proposed for intermediate boiling-point heteroazeotropic systems. Then an industrial case of MIPK system, is used to evaluate mentioned configurations by rigorous simulation and optimization. These configurations are compared and analyzed in detail on energy consumption, exergy analysis and equipment invest. The results show that, from the perspective of process energy consumption, MHADWC process has the most advantages, because it saves 37% of energy consumption; if both equipment costs and exergy recovery are taken into account, HADWC2 has a higher thermodynamic efficiency (43.5%) at its TAC and can be used as a preferred target. And in this work, purification of an intermediate boiling-point heteroazeotrope is the main difference of these processes compared with the well-known heterogeneous azeotropic distillation process where the top vapor product is the lowest boiling point of the ternary system.

Heterogeneous Azeotropic Extractive Coupled Heat Pump Distillation for Triethylamine‐Dichloromethane‐Acetone‐Water

AbstractThere are three kinds of binary azeotropes and one kind of a near‐boiling compound with clamping zone characteristics in the triethylamine‐dichloromethane‐acetone‐water system, which belongs to complex quaternary systems. A four‐column distillation process of heterogeneous azeotropic extraction for the separation of the system was designed, simulated, and optimized to obtain more suitable process parameters and energy consumption distribution of each column. On this basis, taking the total annual cost (TAC) as the comprehensive economic evaluation index and CO2 emission as the environmental evaluation index, the thermal integration technology and mechanical vapor recompression (MVR) heat pump technology were applied to the energy‐saving research of the distillation process for the system. The results indicate that compared with the conventional four‐column heterogeneous azeotropic extractive distillation process, the thermal integration distillation process and single‐column MVR heat pump coupled thermal integration distillation process can save energy consumption and TAC, and it can reduce CO2 emission.

Investigation of energy-efficient heat pump assisted heterogeneous azeotropic distillation for separating of acetonitrile/ethyl acetate/n-hexane mixture

The conventional distillation is hard to accomplish the separation of acetonitrile/ethyl acetate/n-hexane mixture. Herein, a heterogeneous azeotropic distillation (HAD) without adding entrainer is proposed to separate ternary mixture. The proposed scheme is optimized via the simulated annealing algorithm and minimum total annual cost (TAC) is used as objective functions. To minimize energy consumption, heat pump is added on the basis of optimal heterogeneous azeotropic distillation and heat integration technology is used to further improve the energy recovery. The TAC, gas emission, energy consumption and exergy destruction are used to discuss the economy and environmental protection of processes. Among all the processes, the heat pump with higher preheating temperature (HPT) assisted HAD process by combining with heat integration (HAD-HPT-HI) has best performances on economic, environment, energy and exergy. Compared with conventional HAD process, the HAD-HPT-HI achieves the reductions of 52.17%, 68.86%, 65.87% and 65.46% on TAC, total energy consumption, gas emissions and exergy destruction, respectively.

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.

A systematic method for optimum heterogeneous azeotropic distillation systems with vapor recompression

In this work, a systematic method is proposed to determine the optimum combination of self-heat recuperation technology (SHRT) and heterogeneous azeotropic distillation (HAD). The heat exchanger network and vapor recompression heat pump are applied to develop the energy-saving HAD process based on SHRT (HAD-SHRT). Then the heat exchanger network (HEN) is utilized to optimize HAD-SHRT process through minimizing the hot utility utilization. Pyridine/water and 1,4-Dioxan/water systems are studied to examine the feasibility of the systematic method. The results show that the systematic method can effectively handle the combinations of SHRT and HAD. When the maximum heat provided by the compressed stream is greater than or equal to the hot utility requirement of the reboiler, the overhead vapor is directly compressed to provide heat for the bottom stream. Otherwise, adding preheater or auxiliary reboiler are favorable options with regard to economic and energy-saving performance.

Improving the performance of heterogeneous azeotropic distillation via self-heat recuperation technology

Azeotropic distillation is one of the most energy intensive processes and widely used to separate thermos-sensitive azeotropes. In this work, several heterogeneous azeotropic distillation processes based on the vapor recompression heat pump (VRHP) and self-heat recuperation technology (SHRT) are proposed to study the energy-saving performance. The results show that the heterogeneous azeotropic distillation process based on self-heat recuperation technology (HAD-SHRT) has better performance in economic and environment. In HAD-SHRT process, the sensible heat and latent heat of the vapor streams are recuperated and supplied to the reboilers. The remaining sensible heat is supplied to the preheaters through the heat exchanger network (HEN). Adding a preheater can reduce the duty of compressor by increasing the initial temperature of the stream. Compared with the conventional heterogeneous distillation process, the HAD-SHRT process can save 38.50% of TAC, 93.30% of CO2 emissions, and 80.92% of energy consumption. The thermodynamic efficiency can increase to 13.51%.

Energy-efficient heterogeneous extractive distillation system for the separation of close-boiling cyclohexane/cyclohexene mixture

Abstract Cyclohexane and cyclohexene are close-boiling compounds with relative volatility extremely close to unity, thus, separation via conventional distillation is impractical. In this paper, an energy-efficient heterogeneous extractive distillation system using ethylene glycol as heavy entrainer is proposed. By adding ethylene glycol into the system, large liquid-liquid envelope will form. However, the principle of separation is not exclusively the formation and split of heterogeneous azeotrope like that of a typical heterogeneous azeotropic distillation process, but also because of ethylene glycol greatly enhances the relative volatility of cyclohexane over cyclohexene when treated as a heavy entrainer. The proposed heterogeneous extractive distillation column includes a top decanter and no rectifying section. After establishing the base design of the proposed system, energy-saving schemes are also suggested to further reduce the total annual cost and the annual operating cost. The results show that the proposed heterogeneous extractive distillation system with a process-to-process heat exchanger has the predominant benefit of the lowest total annual cost. To compare the optimal result of this design flowsheet with a recently published separation method utilizing two reactive-distillation columns, our proposed design is much more economical with 61.4% savings in total annual cost and 64.6% savings in annual operating cost.

Optimization of liquid–liquid extraction combined with either heterogeneous azeotropic distillation or extractive distillation processes to reduce energy consumption and carbon dioxide emissions

The mixture of propylene glycol methyl ether and water form a minimum-boiling azeotrope. To separate the binary azeotropic system, energy-saving liquid–liquid extraction combined with either heterogeneous azeotropic distillation or extractive distillation processes based upon traditional two-column heterogeneous azeotropic distillation and three-column extractive distillation processes were proposed, using chloroform and 2-ethylhexanoic acid as solvents, respectively. The minimum total annual cost (TAC), based on a sequential iterative optimization procedure, and CO2 emissions for the two processes were determined. Liquid–liquid extraction combined with heterogeneous azeotropic distillation process achieved significant reductions of 40.24% in the TAC and 45.37% in CO2 emissions compared with the traditional two-column heterogeneous azeotropic distillation process. The liquid–liquid extraction combined with extractive distillation process achieved TAC and CO2 emission reductions of 34.18% and 43.95%, respectively, compared with the traditional three-column extractive distillation process. Thus, the two processes are more attractive in terms of both economics and environmental protection.

Experimental studies and thermodynamic analysis of isobaric vapor-liquid-liquid equilibria of 2-propanol + water system using n-propyl acetate and isopropyl acetate as entrainers

Heterogeneous azeotropic distillation is a widely used technique in chemical industries for the purification of alcohols from their aqueous mixtures. This study aims at exploring the possibility of using n-propyl acetate and isopropyl acetate as entrainers for heterogeneous azeotropic distillation to effect the separation of 2-propanol + water azeotropic mixture. A novel yet simple still was constructed to measure the vapor-liquid equilibrium (VLE) and vapor-liquid-liquid equilibrium (VLLE) data for the binary and ternary systems. The isobaric VLE data for the binary systems 2-propanol + water, 2-propanol + n-propyl acetate and 2-propanol + isopropyl acetate and isobaric VLLE data for the ternary systems 2-propanol + water + n-propyl acetate and 2-propanol + water + isopropyl acetate were measured at atmospheric pressure. Subsequently, the experimental data was compared with predictions by thermodynamic models such as UNIFAC, UNIQUAC and NRTL. The feasibility of the entrainers n-propyl acetate and isopropyl acetate in separating the azeotropic mixture 2-propanol + water was studied using the Residue Curve Map (RCM). The experimental data showed the existence of a ternary homogeneous azeotrope in the 2-propanol + water + n-propyl acetate system and a heterogeneous ternary azeotrope in the 2-propanol + water + isopropyl acetate system. Since the heterogeneous azeotropic distillation process depends on the presence of ternary heterogeneous azeotrope, n-propyl acetate is not considered a suitable entrainer for the separation of 2-propanol + water mixture. Finally, a separation sequence for the heterogeneous azeotropic distillation of 2-propanol + water system using isopropyl acetate as entrainer has been proposed.

MINLP optimization of a heterogeneous azeotropic distillation process: Separation of ethanol and water with cyclohexane as an entrainer

Heterogeneous distillation processes are widely used in industry for the separation of azeotropic and close-boiling mixtures. This paper addresses the optimization of a heterogeneous distillation process for the separation of an azeotropic ethanol/water mixture using cyclohexane as an entrainer. Starting from a given process superstructure a MINLP problem is set up to consider continuous as well as discrete decision variables such as the feed locations and the number of stages of the distillation columns. A modified Generalized Benders Decomposition algorithm to account for non-convexities of the model equations solves the MINLP problem. The algorithm can be attached via Visual Basic for Applications (VBA) to any commercial process simulator with NLP and VBA capabilities. Various optimization runs show that the algorithm is easily applicable and returns solutions independent of the initial values.

Comparison of alternative distillation processes for the maximum-boiling ethylenediamine dehydration system

An investigation and comparative analysis on the design and control of the maximum-boiling ethylenediamine (EDA) dehydration system is made in this work. Extractive distillation (ED) and heterogeneous azeotropic distillation (HAD) are used to separate EDA/water mixture that forms a maximum-boiling homogeneous azeotrope. 1,4-butanediol (BDO) and n-propyl acetate (NPAC) are selected as the suitable heavy/light entrainer from three candidate ones for each distillation process respectively. Savings of 17.80% in energy consumption and reduction of 26.26% in minimal total annual cost (TAC) can be obtained by comparing optimum design of ED process to that of HAD process for this system. Moreover, an initial control structure (CS) and an improved one are established for each distillation process. Finally, the comparison of dynamic responses indicates that the HAD process represents an alternative at the stand point of dynamic control for this system.

A semicontinuous approach for heterogeneous azeotropic distillation processes

The separation of azeotropes has substantial energy and investment costs, and the available methods require high capital costs for reconstruction of process plants. As an alternative, a semicontinuous configuration that utilizes an existing plant with minor modifications has been explored. In this paper, a semicontinuous, heterogeneous azeotropic distillation process is proposed and acetic acid dehydration process is used as a case study. To carry out the simulation work, Aspen HYSYS® simulation software is used along with MATLAB® and an interface program to handle the mode-transition of the semicontinuous process. Sensitivity analyses on operating parameters are performed to identify the process limits. Comparisons are made to conventional heterogeneous azeotropic distillation, and dividing-wall distillation column on the annual cost. The results proved that the semicontinuous system is the best setup in terms of total annual costs and energy requirements.

Thermodynamic Analysis and Process Simulation of Ethanol Dehydration via Heterogeneous Azeotropic Distillation

The heterogeneous azeotropic distillation process is widely used to separate nonideal binary mixtures into their constituent pure components. This method uses the addition of a third component, called an entrainer, to cause liquid–liquid phase separation over a broad range of compositions in the ternary phase diagram. Ethanol dehydration was used as a case study and diisopropyl ether and isobutyl alcohol were analyzed as possible entrainers in a heterogeneous azeotropic distillation. In this way, isobaric vapor–liquid–liquid equilibrium was measured for the ethanol + water + diisopropyl ether or + isobutyl alcohol ternary mixtures at 101.3 kPa. The data were correlated by the NRTL and UNIQUAC models, and a set of parameters for each model was obtained. A separation sequence for ethanol dehydration using diisopropyl ether was proposed. The simulation of the separation sequence was carried out satisfactorily by commercial software (Aspen Hysys) using the thermodynamic model UNIQUAC with the binary parameter...

Conceptual design of heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer

The synthesis of a heterogeneous azeotropic distillation process for ethanol dehydration using 1-butanol as entrainer is presented. The residue curve map of the ethanol/water/1-butanol mixture is computationally generated using non-random two- liquid thermodynamic model. It is found that 1-butanol leads to a residue curve map topological structure different from that generated by typical entrainers used in ethanol dehydration. Synthesised by residue curve map analysis, the distillation flowsheet for ethanol dehydration by 1-butanol comprises a double-feed column integrated with an overhead decanter and a simple column. The double-feed column is used to recover water as the top product, whereas the simple column is used for recovering ethanol and 1- butanol. The separation feasibility and the economically near-optimal designs of distillation columns in the flowsheet are evaluated and identified by using the boundary value design method. The distillation flowsheet using 1-butanol is compared with the conventional process using benzene as entrainer. Based on their total annualised costs, the ethanol dehydration process using 1-butanol is less economically attractive than the process using benzene. However, 1-butanol is less toxic than benzene.

Online switching of entrainers for acetic acid dehydration by heterogeneous azeotropic distillation

Traditionally, a foreign chemical such as isobutyl acetate (IBA) is used as an entrainer in a heterogeneous azeotropic distillation (HAD) column to separate acetic acid (HAc) and water. However, the loss of this entrainer may contaminate the process of manufacturing terephthalic acid because of the recycle of product streams to an oxidation reactor and other parts of the process. In the study, use of p-xylene (PX), a component indigenous to the terephthalic acid process and already present in the feed to the HAc dehydration column, as the entrainer for the separation of HAc and water is investigated. Optimization results show that using the HAD process with PX as the entrainer not only overcomes the shortcomings of IBA as the entrainer but also requires less energy consumption. Moreover, we demonstrate that it is possible to dynamically transform the HAD column with IBA as the entrainer into the HAD column with PX as the entrainer, without the need of shutdown and startup. The key to successful implementation of such a dynamic transition is to maintain a proper PX inventory inside the HAD column. While simple sidedraw flow control can be used, it will create PX imbalance if there is a flow measurement bias. A temperature control scheme was found to accelerate such a transition and maintain HAc purities at their designed values.

Synthesis and textural evolution of alumina particles with mesoporous structures

Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl − in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 4 2− can promote above morphology evolution and then transformed into γ-Al 2O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g −1 even after calcinations at 1173 K.

Azeotropic distillation-assisted preparation of nanoscale gamma-alumina powder from waste oil shale ash

A combined process was proposed for the utilization of waste oil shale ash (OSA) in the production of gamma-alumina nanoparticles. The process consisted of two stages, leaching and sintering. The ultrasonic technique followed by a heterogeneous azeotropic distillation process in the presence of polyethylene glycol (PEG) was carried to ensure complete elimination of the residual water in the precipitate. The structural and morphological properties of the calcined nanocrystalline powders were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), Brunauer–Emmett–Teller nitrogen-gas adsorption method (BET). The as-prepared precursor hydroxides were analyzed using thermogravimetric–differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results indicated that the gamma-alumina powder with a uniform particle is well dispersed and the particle size is 20–40 nm; the waste OSA can be utilized to produce gamma-alumina nanoparticles.