甲醇和三甲氧基硅烷共沸物分离过程模拟和优化

三甲氧基硅烷（trimethoxysilane）是合成功能性有机硅化合物的重要中间体。在以甲醇和硅为原料合成三甲氧基硅烷的工业化生产过程中,过量的甲醇和产物三甲氧基硅烷会形成最高共沸物。本文探究了变压精馏、萃取精馏和隔壁塔萃取精馏三种分离提纯甲醇和三甲氧基硅烷的工艺,以最小年度总费用（TAC）为目标函数,运用混合整数非线性规划（MINLP）对三种流程进行了优化,比较了三种流程的效率和二氧化碳排放量。结果表明,与变压精馏相比,通过隔壁塔萃取精馏分离甲醇与三甲氧基硅烷共沸物具有明显的优势。分离100kmol/h甲醇（摩尔分数50.00%）和三甲氧基硅烷的TAC从198.84万美元/年降低到98.93万美元/年,降幅高达50.25%,效率从8.17%提高到13.82%,二氧化碳排放量从1217.53kg/h减少到684.22kg/h,减少了43.80%。     

减压逆流多效精馏回收膜工业废水中的DMAC

针对膜工业中所产生的质量分数为5%～15%的N,N-二甲基乙酰胺(DMAC)废水,提出了分离DMAC废水减压逆流的双效、三效和四效精馏工艺流程。通过实验和Aspen流程模拟对多效精馏的工艺进行了研究。利用响应面法(RSM)对多效流程进行了优化,以最小年度总费用(TAC)为目标函数,确定了回收废水中DMAC最佳方案为减压逆流三效精馏工艺。     

离子液体萃取剂萃取精馏分离丙酸甲酯+甲醇共沸物

以离子液体(ILs)[BMIM][NTF₂]和[HMIM][NTF₂]为萃取剂，萃取精馏分离丙酸甲酯+甲醇共沸物，通过分子模拟分析了ILs促进目标共沸物的分离机理；基于汽液平衡实验数据，获得新的NRTL热力学模型参数；选用常规的二组分双塔分离流程，实现了目标共沸体系的分离。作为对比，同时构建了以苯酚为萃取剂的萃取精馏和变压精馏流程。基于Aspen Plus软件平台，分析了上述各流程分离单元主要操作参数对分离过程性能的影响，考察并对比了各流程能耗、年总成本(TAC)和碳排放。结果表明：离子液体工艺可实现丙酸甲酯+甲醇共沸物的有效分离，产品纯度达到99.9%(质量分数)，[HMIM][NTF₂]工艺与[BMIM][NTF₂]、苯酚及变压精馏工艺相比，TAC降低11.68%～43.68%、CO₂排放减少32.11%～68.46%。结果可为共沸物丙酸甲酯+甲醇分离新工艺设计及优化提供理论支撑和实际指导。     

乙二醇萃取精馏分离乙醇-四氢呋喃的最优工艺

对乙二醇萃取精馏分离乙醇-四氢呋喃共沸体系的工艺基于年度总费用最小进行了优化设计。采用设计规定与序贯迭代优化程序考察了双塔萃取精馏工艺与三塔萃取精馏工艺的经济性。结果表明,最优方案与原料组成有关,当四氢呋喃摩尔分数小于37%时,采用三塔萃取精馏工艺最优;当四氢呋喃摩尔分数大于37%时,采用双塔萃取精馏工艺最优。     

萃取精馏分离甲醇-乙腈共沸体系的过程模拟

运用Aspen Plus软件对双塔萃取精馏工艺分离甲醇-乙腈共沸物的过程进行模拟与分析,筛选出最佳萃取剂为环丁砜,物性方程选wilson。运用Sensitivity工具确定了此流程最佳工艺参数和分离效果,产品纯度如下:甲醇的质量分数达99.95%,乙腈的质量分数达99.99%。     

变压精馏分离乙酸甲酯和甲醇共沸物

乙酸甲酯和甲醇共沸物对压力变化敏感,因此采用变压精馏工艺对共沸物进行高效分离。低压塔和高压塔压力分别设置为101.325 kPa和810.600 kPa。基于相图分析,确定了精馏序列和工艺流程。以年度总费用(TAC)最小为原则,优化了进料位置、回流比、塔板数等设计变量,确定了最佳工艺参数。工艺优化完成后,通过调节双塔的回流比,对高压塔的冷凝器和低压塔的再沸器进行了完全热集成。由结果可知:在低压塔回流比为0.9,高压塔回流比为2.07时,完全热集成变压精馏工艺的TAC最小。相比无热集成的变压精馏工艺,完全热集成工艺的设备投资和能耗费用均明显降低,最终TAC费用节约31.40%,在经济上更合理,也为类似的共沸物分离工艺提供了一定的技术参考。     

分壁式萃取精馏分离乙腈-正丙醇的模拟研究

利用Aspen Plus软件,采用N,N-二甲基甲酰胺作萃取剂,研究了分壁式萃取精馏和常规双塔萃取精馏方法对该混合物的分离,均能实现混合物的有效分离。其中分壁式萃取精馏得到正丙醇和乙腈的质量分数分别为99.12%和99.59%。和常规双塔萃取精馏相比,分壁式萃取精馏流程再沸器热负荷降低11.02%,冷凝器热负荷降低17.69%,实现了有效节能。     

粗甲醇经单塔分离作为MTO、二甲醚原料甲醇的方案探讨

介绍了甲醇合成过程中控制粗甲醇中水含量的方法,分析了以单塔分离脱除粗甲醇中轻组分的技术方案,得出的结论是:控制合成原料气中二氧化碳体积分数为2.5%左右时,粗甲醇中水质量分数在5%左右,粗甲醇采用单塔分离脱除轻组分后,可作为MTO或二甲醚装置的原料。与现有的多塔精馏工艺相比,采用粗甲醇单塔分离,简化了粗甲醇的精制流程,降低了设备投资和生产成本,可为MTO和二甲醚项目工艺方案的设计提供借鉴。     

热集成变压精馏分离乙二胺-水共沸体系的模拟优化

针对乙二胺-水共沸物组成对压力较为敏感的特性,采用部分热集成变压精馏工艺分离该共沸物。先利用Aspen Plus软件对该工艺进行稳态模拟,再以理论塔板数、进料位置、回流比为优化变量,水和乙二胺的纯度为约束,以年度总费用（total annual cost,TAC）为目标函数建立乙二胺-水共沸体系分离系统的优化设计模型。采用列队竞争算法对该分离过程主要工艺参数进行优化,得到了变压精馏分离乙二胺-水体系的最佳工艺操作参数及设备参数。模拟结果表明,利用算法对多变量进行同时优化可得到更具经济效益的分离系统,与传统优化结果相比,可降低TAC约7.31%。在此基础上,对高压塔的操作压力进行优化分析,将其由2atm提升至4atm（1atm=101325Pa）,并对流程其他参数进行优化,可显著降低TAC约24.62%。进一步,采用部分热集成比普通变压双塔精馏降低TAC约21.87%     

分壁式萃取精馏分离环己烷-环己烯的模拟与优化

使用Aspen Plus化工流程模拟软件,以二甲基亚砜为萃取剂,研究了分壁式萃取精馏过程和双塔萃取精馏过程对环己烷-环己烯混合物的分离。结果表明,2种方法均可实现二者的有效分离,其中分壁式萃取精馏过程得到的环己烷和环己烯质量分数分别为99.53%和99.25%。与双塔萃取精馏过程相比,分壁式萃取精馏过程再沸器热负荷降低3.92%,冷凝器热负荷降低15.26%,可以有效节能。     

最小有效能损耗的多组分精馏流程优化设计

提出了以有效能损耗最小为目标、同时又考虑热集成的多组分复杂精馏塔序列优化设计新策略。该复杂精馏塔模型:1股进料、2股出料,每块理论板上均可有中间冷凝器或再沸器。复杂精馏过程的设计步骤是:①根据过程有效能最小确定优化塔序列;②对每个塔优化设计出含中间换热器的复杂塔;③考虑多效且允许热集成的复杂精馏流程,以塔压为决策变量,以精馏过程有效能损耗最小为目标,建立并优化设计出一个热集成的复杂精馏流程。一个3组分精馏过程的例子表明所提策略简单有效,可用来指导多组分精馏过程的优化设计。     

甲醇-乙醇-水三元系精馏分离流程研究

提出了甲醇 乙醇 水三元系的分离问题。计算结果表明 ,足够量甲醇的存在可破坏乙醇和水之间的共沸现象 ,使采用普通精馏制取高浓度乙醇成为可能。当甲醇浓度大于 0 .6 15摩尔分率时 ,乙醇和水之间的共沸点完全消失。可通过循环甲醇调整进料中甲醇的含量 ,一定量甲醇的循环可显著降低精馏塔的投资费用。在示例中 ,有甲醇循环时的最小塔费用仅相当于无甲醇循环时的 40 %。实验结果证实了流程的可行性 ,相近的流程已应用于工业生产中。     

The second law optimal state of a diabatic binary tray distillation column

A new numerical procedure to minimize the entropy production in diabatic tray distillation columns has been developed. The method was based on a least square regression of the entropy production at each tray. A diabatic column is a column with heat exchangers on all trays. The method was demonstrated on a distillation column separating propylene from propane. The entropy production included contributions from the heat transfer in the heat exchangers and the mass and heat transfer between liquid and vapor inside the distillation column. It was minimized for a number of binary tray distillation columns with fixed heat transfer area, number of trays, and feed stream temperature and composition. For the first time, the areas of heat exchange were used as variables in the optimization. An analytical result is that the entropy production due to heat transfer is proportional to the area of each heat exchanger in the optimal state. For many distillation columns, this is equivalent to a constant driving force for heat transfer. The entropy production was reduced with up to 30% in the cases with large heat transfer area and many trays. In large process facilities, this reduction would ideally lead to 1-2 GWh of saved exergy per year. The most important variable in obtaining these reductions is the total heat transfer area. The investigation was done with a perspective to later include the column as a part in an optimization of a larger process. We found that the entropy production of the column behaved almost as a quadratic function when the composition of the feed stream changed. This means that the feed composition is a natural, easy variable for a second law optimization when the distillation column is a part of a process. The entropy production was insensitive to variations in the feed temperature.     

Divided wall distillation column: rationalization of degree of freedom analysis

The present work attempts to rationalize the degrees of freedom analysis of a divided wall distillation column for steady-state simulation using detailed mathematical model, which contains the MESHD equations (conventional MESH equation plus the pressure drop equation). In a divided wall distillation column, pressure difference plays an important role in deciding vapour and liquid flow rates across trays in the divided section. It is observed that for a given divided wall distillation column or Petlyuk column operating under steady state conditions with known feed and condenser pressure, the degrees of freedom is four. This is one higher than that for a conventional distillation column with three product streams (distillate, bottoms and the intermediate product). If this extra degrees of freedom is used to specify liquid split, then no extra degrees of freedom is left to specify vapour split ratio.     

A rigorous calculation method for the minimum stages in multicomponent distillation

A computer method is presented using stage by stage component material balances and nonideal vapor liquid equilibria to calculate the minimum stages for a given key component split in a multicomponent distillation. The calculated results also include an overall material balance and the distillate to feed ratio. These results are useful for optimal distillation column design.     

浆料催化精馏制备甲缩醛

研究了以甲醇和甲醛为原料,以大孔径强酸性阳离子交换树脂为催化剂,通过浆料催化精馏工艺制备甲缩醛的可行性。考察了催化剂含量、进料醇醛比、进料总流量和回流比等因素对该过程的影响。在选定的试验条件下,甲缩醛收率可达89%以上,塔顶甲缩醛的质量分数可达0.99以上。结果表明,该工艺用于制备甲缩醛是可行的。     

Experimental investigation on a membrane distillation based micro-separator

In this work a novel micro-separator combining the sweep gas membrane distillation principle with micro-fluidic channels was designed and tested for the separation of a mixture of methanol and water with a low to high methanol concentration. The performance of the new separation device was studied with different liquid–vapor/gas membrane contactors with respect to the separation factor and the distillate flux rate by varying the relevant operating parameters of the process like the methanol concentration in the feed (5–70 wt.%), the feed temperature (40–65 °C), the feed flow rate (up to 30 ml/min), and the flow rate of the inert carrier gas nitrogen (up to 600 ml/min at standard conditions). For all performed experiments, the feasibility of the separation has been proved and the possibility to separate mixtures with high methanol concentration by using a membrane distillation based micro-separator has been for the first time reported. The inert gas flow rate was identified as the crucial operating parameter influencing the separation performance of the micro-separator. In addition, the selection of an appropriate membrane liquid–vapor/gas contactor was found to be an important design parameter for the reduction of temperature polarization effects.     

四产品Kaibel隔壁精馏塔分离丙二醇混合物的模拟与节能分析

研究了包含甲醇、水、丙二醇和二丙二醇四组分混合物的分离问题,针对混合物的特征和分离要求,提出四产品Kaibel隔壁精馏塔的分离工艺,并利用Aspen Plus软件对Kaibel塔进行设计与节能分析。首先,设计了分离四组分混合物的三塔精馏流程（TCD）和热集成三塔精馏流程（HTCD）;其次,开展了四产品Kaibel塔分离四组分混合物的模拟研究,取得了满足分离要求的塔设计参数;最后,采用能量衡算和㶲损失分析相结合的方法,对Kaibel塔的用能特征进行了分析和比较。研究表明,与热集成三塔精馏流程相比,四产品Kaibel塔在操作费用方面不占优势,但在设备投资方面具有明显优势,可以实现在一个塔内四组分的分离,总㶲损失可降低9.41%。     

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.