环己烷/异丁醇共沸体系的共沸精馏和变压精馏流程模拟与优化

使用Aspen Plus V8.4对环己烷/异丁醇共沸物系的共沸精馏和变压精馏流程进行了模拟与优化。选用乙醇为共沸剂,分别建立了共沸精馏和变压精馏的全局流程,研究了原料进料位置、回流比和共沸剂进料位置对分离效率的影响,得到了2种分离方法的操作参数和工艺参数。结果表明,共沸精馏流程的原料最佳进料位置为14块板,最小回流比为3.00,共沸剂的最佳进料位置为第一块板。变压精馏流程中减压塔最佳进料位置为第8块板,总理论板数为10块板,最小回流比为1.144,最小理论板数为8块板。同时,对2个工艺流程进行了经济分析。结果表明,变压精馏的年总费用比共沸精馏下降了62.7%。     

乙醇、二氧六环、甲醇和水的共沸精馏模拟

针对含有甲醇和二氧六环的乙醇-水体系,提出采用共沸精馏两塔流程的方法实现脱水,选择环己烷为共沸剂,分析了体系中各组分间的共沸特点,利用流程模拟软件Aspen plus对流程进行模拟计算。结果表明,采用两塔流程的方法可以将进料中的水脱除到0.05%(质量分数)以下,进料中的甲醇可从回收塔塔釜排出,模拟结果与实际工业数据基本吻合。     

共沸精馏分离醋酸-丁烯醛的模拟及优化

运用Aspen Plus的RadFrac精馏模块,选择NRTL活度系数方程和Hayden-O’connell逸度系数方程的热力学模型对醋酸-丁烯醛-水体系共沸精馏分离醋酸-丁烯醛进行了模拟计算,计算值与现场实测值吻合。分析了原料进料位置、共沸剂进料位置、回流比、进料比等参数变化对醋酸-丁烯醛-水体系共沸精馏分离效果与能耗的影响,并进行了参数优化。结果表明,原工艺经参数优化后,可较大程度降低能耗,同时提高分离效果。     

不同类型双效精馏流程节能特性的研究

本研究利用工程模拟软件,选择乙醇-水二元物系为模型,对不同类型的3种双效精馏流程(平流双效精馏、顺流双效精馏和逆流双效精馏)进行了流程模拟,考查了不同的原料组成、不同的进料温度在分离要求相同的情况下,与普通精馏塔相比,各类型流程节能率的变化情况。结果表明,(1)原料组成变化对平流双效精馏节能率基本没影响,进料温度在泡点下,平流双效精馏节能率更高;(2)对于顺流双效精馏,进料温度的变化对其节能率的影响较大,进料温度越高两种流程的节能率越低,原进料组成中轻组分含量越多,节能率越高;(3)逆流双效精馏流程适合进料中低沸组分浓度高于高沸组分浓度的物系精馏分离。低沸组分的浓度越大,应用逆流双效精馏流程的节能率会越高。对于逆流双效精馏流程的3种不同流程的节能率均随着进料温度的升高而下降。     

共沸精馏分离2-甲基吡啶和水

采用共沸精馏的方法分离2-甲基吡啶和水二元均相共沸物系。选取环己烷作为共沸剂,利用流程模拟软件Aspen Plus对共沸精馏塔进行模拟计算,分析了不同共沸剂用量、塔底采出量以及进料位置等操作参数对产品纯度、共沸剂的损失量以及精馏塔热负荷的影响,模拟结果表明当精馏塔的塔板数为21,共沸剂的用量为3600kg/h,塔底采出量为888kg/h,原料进料位置在第15块板时,共沸精馏塔塔底可得到质量分数为99.54%的2-甲基吡啶,塔顶分相罐下层可采出质量分数为99.97%的水。最后,通过间歇共沸精馏实验对以环己烷为共沸剂分离2-甲基吡啶-水物系的效果进行检验,结果表明共沸精馏塔塔底2-甲基吡啶的质量分数达99.85%,塔顶水相可采出质量分数达99.96%的水,证明了该工艺路线具有良好的可行性。     

共沸精馏分离醋酸-水模拟研究

通过Aspen P lus软件建立了对二甲苯(PX)、水、醋酸共沸精馏分离模型,采用Hayden-O’Connell关联式对气相逸度系数进行校正。讨论了PX加入量、回流比、进料位置等对共沸精馏过程的影响,得出适宜的PX加入量为m(PX)∶m(H2O)=2∶1,回流比为5,较佳的进料位置在精馏塔中部第20块塔板。     

碳酸二甲酯-甲醇共沸体系分离的模拟与控制

作为一种新环保型化工产品,碳酸二甲酯近年来在各行业中得到了广泛应用。由于碳酸二甲酯产品中常含有与之形成共沸物的甲醇,因此需要特殊工艺对其进行分离。本文利用Aspen Plus软件建立了严格稳态模型,对比了萃取精馏、共沸精馏和变压精馏分离碳酸二甲酯-甲醇二元共沸物的3种分离工艺,并以系统能耗为目标进行单变量分析,得到最低能耗下的萃取精馏、共沸精馏、变压精馏工艺参数。稳态分析结果表明:萃取精馏过程能耗只占变压精馏的29.0%、占共沸精馏的30.2%,其节能优势明显。在此基础上,采用Aspen Dynamics软件对萃取精馏最佳工艺进行了控制研究,提出了两种控制结构。结果表明,含有固定再沸器/进料比例的改进控制结构能够有效地应对进料流量与进料组成扰动,保证碳酸二甲酯和甲醇产品纯度。     

氯化氢-水变压精馏工艺的研究与模拟

利用氯化氢-水体系在不同压力下共沸组成变化较大的特性,采用变压精馏工艺分离该共沸物。基于Aspen Plus流程模拟软件,采用ELECNRTL物性模型进行模拟,模拟结果表明:在10kPa和400kPa压力下,共沸组成变化大于5%;采用变压精馏可以有效分离氯化氢和水,得到的氯化氢气体与稀酸水中氯化氢的质量分数可分别达到99.96%和0.9%,其中高压塔15块理论板,进料为顶部进料,减压塔20块理论塔板,进料位置为第10块理论板,回流比为0.5。     

变压精馏分离异丁醇-乙酸异丁酯工艺模拟

基于异丁醇-乙酸异丁酯共沸体系的特性分析,提出了建立变压精馏过程分离异丁醇-乙酸异丁酯的工艺方法。利用Aspen Plus模拟软件,以产品异丁醇和乙酸异丁酯质量分数为约束变量,过程能耗最低为目标函数,对该体系进行了工艺模拟与优化,考察了理论板数、进料位置、回流进料比等参数对分离效果的影响。结果表明最优条件为:减压塔操作压力20 k Pa,理论塔板数60,进料位置30,回流比8.5;常压塔操作压力100 k Pa,理论塔板数30,进料位置22,回流比5。在此条件下,得到质量分数不低于0.998的异丁醇和乙酸异丁酯产品,回收率均达到99.9%以上。     

变压精馏分离乙酸乙酯-正己烷共沸物的动态特性

乙酸乙酯和正己烷均为重要的有机溶剂,广泛应用于医药、橡胶、油漆等领域。由于乙酸乙酯和正己烷常压下形成共沸物,需采用特殊工艺对其进行分离。基于乙酸乙酯-正己烷二元共沸体系的压力敏感性,利用Aspen Plus软件,以年度总费用(TAC)最小为目标函数,模拟和优化了变压精馏稳态工艺,其中高压塔和低压塔的操作压力分别采用6 atm和1 atm,所得乙酸乙酯和正己烷产品纯度均大于99.9%。在此基础上,利用Aspen Dynamics软件考察了变压精馏工艺不同控制方案的有效性。结果表明:Q_R/F比例控制结构能够有效地应对进料流量扰动,且响应速度快,但在处理进料组分干扰时稍显不足。组分-温度串级控制能有效的改善进料组分扰动对产品纯度的影响。Q_R/F比例控制结构与组分-温度串级控制结构联用在变压精馏工艺中可实现稳健的控制,能够有效保证乙酸乙酯和正己烷产品纯度。     

Energy saving in acetic acid process using an azeotropic distillation column with a side stripper

Dilute acetic acid is obtained primarily from fermentation and synthesis processes and cannot be produced by simple distillation due to relatively low volatility of acetic acid compared to water. Instead, an azeotropic distillation is applied to increase the concentration of dilute acetic acid. When acetic acid is extracted from a dilute aqueous solution using a solvent mixture of ester and alcohol, its recovery requires an energy-intensive azeotropic distillation. In the water stripping process that follows azeotropic distillation, two distillation columns handle the acetic acid and water mixture in similar composition. Therefore, the two columns can be combined as a side stripper connected to the azeotropic distillation column. The energy-saving effect is examined with the HYSYS (Aspentech Corporation) evaluation of the process. Compared to the conventional process, the modified process suggests 39% reduction in heating duty and 24% coolant savings. The economic analysis shows 32% decrease in investment and 36% utility savings. Based on heat utilization analysis, the thermodynamic efficiency is enhanced by 11%.     

Investigating the need of a pre-concentrator column for acetic acid dehydration system via heterogeneous azeotropic distillation

In our previous study [Chien, I.L., Zeng, K.L., Chao, H.Y., Liu, J.H. (2004). Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation. Chemical Engineering Science 59(21), 4547-4567.], an acetic acid dehydration system has been designed. The suitable entrainer selected for that system is iso-butyl acetate. Design and control of the system has been studied in detail to maintain high-purity bottom acetic acid concentration and also keep a small acetic acid loss through top aqueous draw. In that previous study, the feed composition is assumed to contain equal molar of acetic acid and water. However, in a typical waste acid recovery application, the above assumption may be too rich in acetic acid. In this paper, a feed stream containing 80 mol% water and 20 mol% of acetic acid is investigated. Several design alternatives can be deduced including one commonly used in industry by adding a pre-concentrator column in the upstream of a heterogeneous azeotropic distillation column. The necessity of this pre-concentrator column from design and control view points will be thoroughly investigated in this paper. The final recommended process design is a tradeoff between total annual cost (TAC) and operability of the system. The recommended design is a single heterogeneous azeotropic distillation column with aqueous reflux stream. Very wide feed composition and flow rate changes can be handled by this design with proper choice of the overall control strategy.     

煤制乙二醇装置联产碳酸二甲酯精馏工艺优化

在煤制乙二醇的生产过程中,会副产碳酸二甲酯（DMC）、甲酸甲酯、甲缩醛等,目前煤制乙二醇联产残液大都未进行有效分离和纯化,只能作为低纯度碳酸二甲酯或廉价杂醇处理,这样不仅造成甲醇损耗,而且降低了装置应有的经济性,因此经济合理地回收碳酸二甲酯具有重要的意义。由于甲醇与DMC形成二元共沸物,常规精馏方法无法将二者彻底分离。本文总结了各种DMC-甲醇分离方法,并优选采用变压精馏技术进行甲醇与DMC分离。利用煤制乙二醇中富含碳酸二甲酯以及甲醇、甲酸甲酯等杂质的副产残液为原料,提出3种改进工艺,获得99.9%以上高纯度DMC产品。计算结果表明,3种工艺方法分别适用于含量低于高压共沸组成、高于常压共沸组成、90%以上浓度DMC物料的分离,实现以更低能耗、更优化流程获得高纯度DMC产品。     

叔丁醇-水-环己烷体系恒沸精馏过程模拟研究

本文运用Aspen plus过程模拟软件模拟计算了叔丁醇-水-环己烷恒沸精馏过程,计算出了各塔板的温度和气液相流量及组成,同时考察了理论塔板数和最小共沸剂流量及全塔热负荷的关系;加料板位置的变化对恒沸精馏塔分离效果的影响;以及设备压强的变化对共沸精馏的影响。     

Control structure selection of increased-pressure extractive distillation process for DMC-MeOH azeotropic mixture

Producing dimethyl carbonate (DMC) as a green chemical with the desired purity is important in the industry. Although studies on the steady-state design of energy-efficient extractive distillation processes are important for the purification of DMC-methanol (DMC-MeOH) azeotropic mixtures, the dynamic controllability of these processes is also critical in the case of feed condition changes, and it should be investigated carefully. Results of the limited studies in the literature show that changing the operating pressures in extractive distillation processes might have different effects on the dynamic controllability of different systems. Thus, in this study, alternative control strategies are developed for a recently proposed increased-pressure extractive distillation process to separate DMC-MeOH mixture. All control structures are designed using inferential temperature controllers, which have a general acceptance in industrial applications. Effects of different ratio controllers are investigated by evaluating the dynamic responses of control structures for disturbances in feed flowrate and composition. Two metrics including integral absolute error and steady-state deviation of purities are used in the evaluation of alternatives. Results of dynamic simulations show that a control structure including reflux ratio controller is not a suitable strategy for this process. It is demonstrated that a control structure including reflux to feed ratio controller for both distillation columns is necessary for the robust and efficient control of a pressure-increased extractive distillation process. These efficient dynamic results support the economic advantage of increased-pressure extractive distillation process separating DMC-MeOH azeotropic mixtures.     

共沸蒸馏脱水技术在纳米材料制备中的应用

介绍了共沸蒸馏脱水的基本原理和置换剂的选择条件,综述了共沸蒸馏脱水技术在纳米材料制备中的应用,探讨了共沸蒸馏脱水在纳米粉体制备过程中的防团聚机理,指出了共沸蒸馏脱水技术目前还存在的问题和今后的研究方向.     

Separation of ethylene glycol, 1,2-butanediol and 1,2-propanediol with azeotropic distillation

1,2-butanediol (1,2-BDO) and 1,2-propanediol (1,2-PDO) are inevitably side produced in the ethylene glycol (EG) production processes from non-petroleum routes, but are very difficult to separate by the ordinary distillation method because of the closeness of their boiling temperatures to EG, thus compromise the economy of these processes. The azeotropic distillation process using 1-octanol (CPO) as an entrainer to separate EG and 1,2-BDO mixture with or without 1,2-PDO was studied in this paper. Four binary vapour–liquid equilibrium data of EG-1,2-BDO, EG-CPO, 1,2-BDO-CPO, and 1,2-PDO-CPO were measured using an Ellis equilibrium kettle and regressed with the thermodynamic model of non-random two liquid to obtain the corresponding binary interaction parameters. On this basis, azeotropic distillations with CPO as an entrainer were designed to separate EG and 1,2-BDO with or without 1,2-PDO. The complete separation processes, including the azeotropic distillation and CPO recovery process consisting of extraction with H₂O and subsequent distillation, were simulated and optimized with Aspen Plus for both the EG-1,2-BDO binary mixture and the EG-1,2-BDO-1,2-PDO ternary mixture. The simulation results show that the azeotropic distillation method with CPO as an entrainer can effectively separate the mixture of EG-1,2-BDO and EG-1,2-BDO-1,2-PDO, achieving EG of 99.90% purity with 99.98% recovery and 1,2-BDO of 99.30% purity with 99.45% recovery for the binary mixture, and achieving EG of 99.90% purity with 99.80% recovery, 1,2-BDO of 99.35% purity with 99.35% recovery, and 1,2-PDO of 90.59% purity with 94.38% recovery for the ternary mixture. These processes are promising for industrial application and can significantly improve the economy of non-petroleum EG production.     

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．     

乙醇脱水塔内两相和三相共沸精馏

研究了乙醇脱水塔内的两相共沸精馏和汽液液三相共沸精馏过程。利用Aspen plus模拟软件对乙醇脱水塔内4种工况的精馏曲线、共沸剂浓度分布、回流量和再沸器能耗进行了分析比较。结果表明,苯做共沸剂时,脱水塔内两相共沸精馏和汽液液三相共沸精馏的精馏曲线、共沸剂浓度分布、回流量和再沸器能耗相近,脱水塔精馏曲线都跨越了精馏边界,并且共沸剂在塔内大多数板上都有较高浓度分布。而环己烷做共沸剂时,两相共沸精馏工况和汽液液三相共沸精馏工况条件下的脱水塔内精馏曲线、共沸剂浓度分布、回流量和再沸器能耗有较大差别。汽液液三相共沸精馏工况条件下,环己烷在塔内大多数板上有较高浓度分布,起到较好的脱水作用,而两相共沸精馏工况条件下脱水塔内共沸剂仅分布在塔顶几块塔板上,塔内多数板上没有起到共沸剂作用。     

单乙醇胺(MEA)间歇萃取精馏甲醇-丙酮研究

用常规的间歇萃取精馏实验装置,研究了以单乙醇胺(MEA)为萃取剂间歇萃取精馏分离甲醇—丙酮恒沸物的过程。考察了萃取剂、全回流时间、共沸物组成、溶剂与混合物的体积比、回流比等因素对萃取精馏分离甲醇—丙酮共沸体系的影响,从而得出最优的萃取条件。