丙酮-四氢呋喃-水混合物的清洁分离工艺的概念设计

引言 四氢呋喃（THF）既是一种性能优良的贵重有机溶剂,又是一种重要的有机合成中间体,因此在制药、涂料、皮革等领域应用广泛．当四氢呋喃用作溶剂时,由于其不被消耗,往往需要进行回收．但四氢呋喃易与水、丙酮等其他极性溶剂形成共沸物,而生产中又常需要四氢呋喃的纯度足够高,进而增加了分离提纯难度．     

Systematic design of an extractive distillation for maximum‐boiling azeotropes with heavy entrainers

Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum‐boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two‐column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone–chloroform azeotropes with five potential entrainers. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3898–3910, 2015     

A review of extractive distillation from an azeotropic phenomenon for dynamic control

Extractive distillation is an effective method for separating azeotropic or close boiling point mixtures by adding a third component. Various technologies for performing the extractive distillation process have been explored to protect the environment and save resources. This paper focuses on the improvement of these advanced technologies in recent years. Extractive distillation is retrieved and analyzed from the view of phase equilibrium, selection of solvent in extractive distillation, process design, energy conservation, and dynamic control. The quantitative structure–property relationship used in extractive distillation is discussed, and the future development of extractive distillation is proposed to determine how the solvent affects the relative volatility of the separated mixture. In the steady state design, the relationship between the curvature of the residue curve and parameters of the optimal steady state is also highlighted as another field worthy of further study to simplify the distillation process.     

Synthesis,experiments and simulation of heterogeneous batch distillation processes

The presence of azeotropes in multicomponent mixtures complicates the design of batch distillation separation processes widely used in pharmaceutical and speciality chemical industries. Most of those processes include the use of a homogeneous entrainer to ease the separation. We describe novel methods to break azeotropes using an entrainer that is partially miscible with one of the initial binary mixture components. We depict some of the advantages of heterogeneous batch distillation processes: more design alternatives for the separation of an azeotropic binary mixture than with homogeneous batch distillation, batch distillation boundary crossing thanks to a controlled reflux of the entrainer-rich phase, simplified distillation sequences as a consequence of less distillation tasks. Three examples based on the separation of non-ideal azeotropic or close boiling point binary mixtures through heterogeneous batch distillation are simulated using a commercial batch distillation package. Experiments validate the simulated separation of a minimum boiling azeotropic mixture.     

A simulation study on selection of optimized process for azeotropic separation of methanol and benzene: Internal heat integration and economic analysis

This work provides an insight into the separation of azeotropic mixtures by using two different techniques: pressure swing distillation and extractive distillation. Both methods are used to separate an azeotropic mixture of methanol and benzene. This mixture exhibits a minimum boiling azeotrope at temperature 57.97 °C and pressure 1 bar with mole fractions of 0.61 and 0.39 for methanol and benzene, respectively. However, the azeotropic point in methanol and benzene mixture is pressure sensitive, which can be shifted by changing pressure with a process called pressure swing distillation. Extractive distillation with suitable solvent is another method to separate such kind of mixture. Both methods are rigorously simulated and optimized for minimum heat duties. Internal heat integration is applied too for increasing energy efficiency. New optimization techniques are carried out with process simulator Aspen HYSYS V8.4 and results reveal the best method for separation of methanol and benzene azeotropic mixture.     

萃取精馏技术及其在分离过程中的应用

对萃取精馏技术及其在分离过程中的研究与应用进行了讨论。从萃取精馏的基本原理与操作类型、溶剂的物理特性与筛选方法等方面进行了介绍,同时列举了萃取精馏技术在一些物系分离中的应用。最后指出了萃取精馏技术的研究方向。     

结合图论和基团贡献法的非均相共沸精馏挟带剂设计

非均相共沸精馏挟带剂的计算机辅助分子设计(CAMD)由分子合成、分子筛选及分子确认3个环节递进构成。在分子合成环节,预选基团,限定合成分子的基团总数及类型,基于图论原理实现由基团到分子的自动合成。在分子筛选环节,依据基础物性筛选指标形成基础分子库,输入待分离物系,采用非均相共沸物形成判据筛选出若干候选分子。在分子确认环节,由非均相共沸温度及组成、挟带剂的汽化热等参数组成模糊综合评判函数,实现分子排序,从而输出一组较优挟带剂。以乙酸-水物系、乙腈-乙酸乙酯物系为例,得到了相应设计结果,与文献结果进行了对比。研究表明该方法及所编程序具备可靠实用性,可为近沸程及共沸混合物分离过程的开发与设计提供先导性支持。     

萃取精馏及进展

萃取精馏是一种特殊精馏方法 ,适用于近沸点物系和共沸物的分离。萃取精馏按操作方式可分为连续萃取精馏和间歇萃取精馏 ,间歇萃取精馏是近年发展起来的新的萃取精馏方法。萃取精馏的关键是溶剂的选择 ,以往萃取精馏采用的溶剂是单一溶剂 ,近年来人们开始研究使用混合溶剂 ,取得了良好效果     

甲醇-丙酮共沸物分离的研究进展

主要介绍了甲醇-丙酮共沸物系变压精馏和萃取精馏两种分离方法的研究进展。经过比较,萃取精馏方法在经济成本方面更具有显著优势。关于萃取精馏,首先阐述了萃取剂的选取以及近些年来萃取剂的研究,主要集中在3个方面:传统单一溶剂、各种盐类和离子液体。其次还介绍了各种萃取剂所对应的气液平衡模型的应用情况和操作条件的优化等方面,并对萃取精馏及其萃取剂的应用提出了展望。     

Design of extractive distillation for the separation of close-boiling mixtures: Solvent selection and column optimization

A practical methodology for the design and optimization of extractive distillation is proposed in this work. The extractive distillation is generally applied to the separation of close-boiling mixtures, which by conventional distillation is difficult to separate. The design and optimization of extractive distillation is more complex than that of the conventional distillation when considering the selection of suitable solvent to enhance the separation. Currently, the solvent selection can be effectively handled by the assistance of the computer-aided molecular design (CAMD) approach. The selection result may however be inconclusive due to the lack of accurate or missing parameters in the property model. In this work, the experimental verification and the property parameter determination were proved to be necessary as an additional step to achieve a successful and reliable design. The overall design methodology was illustrated through an industrial separation of C8-Aromatics mixture.     

Feasibility of heterogeneous batch distillation processes

Synthesis of heterogeneous batch distillation is discussed, which aims at splitting azeotropic mixtures by adding an entrainer partially miscible with one of the initial binary mixture components. Key operational parameters are identified such as the amount of entrainer added in the ternary feed, the reflux policy, and the vapor line position by examples. Synthesis and operation are less straightforward for heterogeneous batch distillation than those for the homogeneous case, but offer many advantages: more design alternatives, simplified distillation sequences, a lower consumption of entrainer, and a crossing of distillation boundaries by the still path. Feasibility is assessed using simplified modeling and confirmed using a commercial batch process simulator package. Synthesis expectations and simulated results are verified throughout bench-plant experiments for the separation of the acetonitrile—water mixture using acrylonitrile as a light heterogeneous entrainer.     

常规间歇萃取精馏分离苯-环己烷的研究

通过一个常规间歇萃取精馏实验装置,考察了不同萃取剂在不同回流比及萃取溶剂加入速率情况下对分离苯-环己烷共沸体系的影响。结果表明,二元混合溶剂能够解决单一溶剂的选择性与溶解性相矛盾的问题;且在同等条件下,综合性能优于单一溶剂;随着溶剂加入速率和操作回流比的增加,产品的产量逐渐提高,尤其重要的是混合溶剂间歇萃取精馏技术与简单溶剂间歇萃取精馏技术相比并不复杂。     

Separation of aqueous isopropanol by reactive extractive distillation

A new separation method of reactive extractive distillation is proposed for the separation of isopropanol and water, using the mixture of ethylene glycol (C₂H₆O₂) and glycollic potassium (C₂H₅O₂K) as an entrainer. Vapor–liquid‐equilibrium (VLE) measurements confirmed that the entrainer was effective for this separation. Using a feed/solvent volume ratio of 1:1, isopropanol with a concentration over 96.0% weight fraction was obtained by the reactive extractive distillation process and the azeotropic point was eliminated. A novel process of separating isopropanol and water is designed on the basis of reactive extractive distillation to obtain the product with different concentrations, which may have a lasting value in industry. © 2002 Society of Chemical Industry     

Energy Evaluation of Ethanol Dehydration with Glycol Mixture as Entrainer

Extractive distillation of ethanol dehydration using glycols as entrainers is proposed. Specifically, ethanol dehydration of an azeotropic mixture in the presence of ethylene glycol + glycerol mixture is evaluated. Simulation is performed and the vapor‐liquid equilibrium of ethanol + water + ethylene glycol + glycerol is predicted with the NRTL model. Minimization of energy consumption in both extractive and regeneration columns is attempted. Optimal operating parameters of the process including glycol concentration in the solvent mixture, main feed, and entrainer feed trays, total number of theoretical trays, and heat supplied to the reboiler are determined in order to achieve a specified distillate purity of 99.9 mol % ethanol.     

萃取精馏复合溶剂的复配选择

提出按溶剂之间复配形成氢键的情况和修正的UNIFAC模型相结合的方法选择分离共沸体系的萃取精馏复合溶剂。准确测量了共沸体系与萃取精馏单溶剂和复合溶剂的汽液平衡数据,结果表明采用的萃取精馏单溶剂和复合溶剂的选择方法具有较好的准确度,模拟值与实验值比较,相对偏差均小于9%。通过综合比较得到分离乙酸乙酯-乙醇、乙醇-水和环己烷-苯3个共沸体系的最佳复合溶剂及配比。在最佳复合溶剂组成下,原共沸体系的相对挥发度达到最大值,该值优于组成复合溶剂的单溶剂所达到的分离效果。在最佳复合溶剂组成下,改变原料体系组成,复合溶剂组成对原料体系相对挥发度的影响趋势基本相同,这表明复合溶剂在萃取精馏塔内不同原料组成下均能较好地增加体系的相对挥发度,为工业上在萃取精馏过程中使用复合溶剂提供了理论依据。     

异丙醇-环己烷萃取精馏过程模拟与优化

利用化工流程模拟软件Aspen Plus对异丙醇-环己烷共沸物系的双塔连续萃取精馏过程进行了模拟计算与优化。首先根据溶剂相似相溶原理,先初选出糠醛和硝基苯作为备选溶剂,再通过汽液平衡试验及ChemCAD模拟筛选,确定糠醛为最适宜溶剂,选择NRTL模型作为物性方法,使用RadFrac模块进行模拟计算,并利用灵敏度分析模块对各工艺参数进行优化。结果表明,最适宜工艺方案为：萃取精馏塔理论塔板数为30,原料在第26块板进料,溶剂在第12块板进料,物质的量回流比为1.8,溶剂质量比为3∶1;溶剂回收塔理论板数为15,进料位置在第10块板,物质的量回流比为1.0。分离效果可达到环己烷质量分数为99.74%,异丙醇质量分数为99.61%。模拟和优化结果为分离过程的优化操作和设计提供了依据。     

六甲基二硅烷-甲苯-水混合物的清洁分离工艺设计

在对六甲基二硅烷(HMDO)-甲苯-水三元体系进行了热力学分析的基础上,应用化工流程模拟软件ASPEN PULS对工艺过程进行模拟。提出了共沸蒸馏、萃取的分离方案,筛选了5种共沸剂,结果表明丙酮为最佳共沸剂。丙酮与HMDO-水形成共沸物,分离甲苯;共沸物通过萃取的方式分离HMDO;水与丙酮可以通过普通精馏的方法得以分离,整个过程中的共沸精馏溶剂和萃取剂-水全部循环使用,没有废液的排放,实现了清洁生产。提出的工艺方案可为工业装置设计提供参考。     

萃取精馏分离甲醇-苯

采用萃取精馏的方法分离甲醇-苯的共沸物系。首先采用UNIFAC基团贡献理论并结合经验选取萃取剂,最终确定萃取剂为氯苯。对常压下甲醇 苯物系应用UNIFAC模型计算各组分的汽液相组成,并进行汽液平衡实验验证,计算结果与实验数据吻合较好。通过间歇萃取精馏实验进一步考察验证所选萃取剂的分离效果。结果表明,氯苯能够打破甲醇-苯的共沸,进而分离甲醇和苯。溶剂物质的量之比为1、回流比为3、填料塔理论板数为30、溶剂回收段理论塔板数为4时产品甲醇回收率达到98%,说明氯苯能够作为萃取剂分离甲醇-苯二元共沸物系。最后,对甲醇-苯物系的连续精馏过程应用Aspen Plus进行了模拟计算,并且考察了回流比、萃取剂进料流率等参数对产品纯度的影响规律,为进一步实验研究及工业应用提供理论和实践基础。     

萃取精馏分离苯/环己烷共沸体系模拟与优化

以糠醛作为萃取剂分别使用常规萃取精馏、隔壁塔萃取精馏和差压热集成萃取精馏对苯和环己烷体系进行分离研究,使用流程模拟软件Aspen Plus V8.4进行模拟分析,对初步设计的三稳态流程,分别进行灵敏度分析,使用多目标遗传算法对过程进行整体优化以获得最优结构参数。结果表明,隔壁塔萃取精馏和差压热集成萃取精馏相对于常规萃取精馏所需再沸器热负荷可分别减小21.5%和15.7%。对三工艺流程进行经济性分析,发现与常规流程相比,隔壁塔萃取精馏的年总费用下降了6.0%,而差压热集成萃取精馏年总费用增加了50.8%,为萃取精馏分离苯/环己烷共沸体系工业化设计提供了理论依据和设计参考。