Experimental Investigation of Decentralized Process Control for Reactive Dividing-Wall Columns

The reactive dividing-wall column (RDWC) presents a highly integrated process that enables significant reductions in investment costs and energy consumption. However, the high degree of integration of this apparatus causes numerous interactions between kinetics, vapor-liquid equilibrium, and mass transfer. To ensure a reliable operation of the RDWC, suitable control schemes need to be developed and experimentally validated. A decentralized control scheme for the RDWC is presented and for the first time experimentally investigated on an RDWC pilot plant. A comparison of experimental and simulated data is carried out and shows good agreement.     

Synthesis of High‐Purity Methylal via Extractive Catalytic Distillation

An integrated continuous process, which combines catalytic distillation and extractive distillation in one column, is investigated for the synthesis of high‐purity methylal from methanol and formalin in the presence of a cation‐exchange resin catalyst. A feed with methanol:formaldehyde 2:1 molar ratio is chosen to evaluate the effects of operating parameters, such as extractant feeding position, ratio of extractant to feed, reflux ratio, and reboiler temperature, on the continuous synthesis of methylal. Under the optimum operating conditions and with water as extractant, the extractive catalytic distillation process operated continuously, producing a methylal purity of 98.7 % (H₂O: < 1.30 %) with 98.0 % formaldehyde conversion.     

隔壁共沸精馏塔分离异丙醇水溶液的模拟

提出一种单塔共沸精馏生产无水异丙醇的新工艺流程,即采用隔壁塔替代常规共沸精馏流程中的脱水塔及提浓塔。应用Aspen Plus模拟软件,对隔壁共沸精馏塔流程及常规共沸精馏流程进行了模拟,比较了两种流程的液相组成、温度、汽液相流量及能耗,结果显示新工艺流程可以节省能耗14.6%,并能降低设备投资费用和操作费用。其模拟结果还需试验进一步验证。     

隔板式反应精馏技术的研究进展

隔板式反应精馏技术是一种将隔板式精馏塔和传统反应精馏工艺相结合,反应和分离过程高度强化的复杂技术。简要介绍了隔板式反应精馏技术的特点,并重点论述了该技术在国外的应用以及控制和优化的方法,概述了隔板式反应精馏塔在国内的发展现状,最后指出该技术在节能减排的大环境下将有非常大的发展前景和应用价值。     

连续反应精馏合成乙酸异丙酯

以乙酸和异丙醇为原料通过连续反应精馏合成乙酸异丙酯，实验研究了影响反应的因素，结果表明最佳合成条件为：酸醇比1：1．2，回流比3，异丙醇的进料流量2mL／min，硫酸用量为乙酸体积的2％，乙酸异丙酯的最大收率为92．5％。     

Reactive dividing-wall column for the co-production of ethyl acetate and n-butyl acetate

Reactive dividing-wall column (RDWC) technology plays a critical role in the energy saving and high efficiency of chemical process. In this article, the process of co-producing ethyl acetate (EA) and n-butyl acetate (BA) with RDWC was studied. BA was not only the product, but also acted as entrainer to remove the water generated by the two esterification reactions. Experiments and simulations of the co-production process were carried out. It was found that the experimental results were in good agreement with the simulation results. Two kinds of RDWC structures (RDWC-FC and RDWC-RS) were proposed, and the co-production process operating parameters of the two types of RDWC were optimized by Aspen Plus respectively. The optimal operating parameters of the RDWC-FC were determined as follows: 0.6 of the reflux ratio of aqueous phase (RR), 0.66 of the vapor split (R_V) and 0.51 of the liquid split (R_L). And the optimal operating parameters of the RDWC-RS were shown as follows: RR was 0.295 and R_V was 0.61. Furthermore, the energy saving analysis of the co-production process was based on the annual output of 10000 tons of EA, compared with the traditional reaction distillation (RD) to prepare EA and BA, the reboiler duty of the RDWC-FC column could save 20.4%, TAC saving 23.6%; RDWC-RS reboiler energy consumption could save 17.0%, TAC 22.2%.     

背包进料的背包式反应精馏生产甲缩醛的模拟

提出了一种具有背包进料的背包式反应精馏生产甲缩醛的新工艺,将部分甲醇直接加入到背包反应器中.应用过程模拟软件Aspen Plus对工艺过程进行了模拟计算,采用RADFRAC严格计算模型模拟精馏塔部分,采用NRTL方程模拟反应器部分,重点考察了进料方案和甲醇进料量对新工艺过程的影响.模拟结果表明,当仅在最靠近塔顶的背包反...     

Analysis of the Start‐up Process for Reactive Distillation

The start‐up procedure of a distillation column is a time‐ and energy‐consuming process. Further, the products during the start‐up time are off specification and cannot easily be recycled as for conventional distillation but must costly be disposed of. In this paper, a process model to simulate the barely analyzed start‐up procedure for a reactive distillation from the cold and empty state to steady state is presented. The start‐up of a reactive distillation column has been modeled with gPROMS. The advantage of a cold and empty start‐up is the consistent and reproducible initialization. Commercial simulators do not give the opportunity to start form a cold and empty state, e.g., a column modeled with Hysys must be shut down from a steady state to be able to model the complete start‐up process, which is not possible, for example, for a batch process. Also, a change in the describing equations and discontinuities in process variables is difficult to handle within the simulation. In this paper, the start‐up strategies normally used for distillation without reaction are examined and applied to reactive distillation. It will be shown that the widely used strategy of total reflux is not suitable for reactive distillation. A simplified model to derive a time constant which describes the influence of parameter setting changes, like heating power, reflux ratio and feed composition on the start‐up time, is introduced and validated.     

Implementation of Ethanol Dehydration Using Dividing-Wall Heterogeneous Azeotropic Distillation Column

In this article, the design and optimization procedures of a dividing-wall column for heterogeneous azeotropic distillation (DWC-A) using cyclohexane as an entrainer for ethanol dehydration are investigated. The proposed procedures can detect the optimal values of the design variables and thereby guarantee the minimum energy requirements, which is related to the minimum CO₂ emissions and the lowest total annual cost (TAC). Since ethanol and water form an azeotrope under atmosphere pressure, a conventional heterogeneous azeotropic distillation sequence (CHADS), including an azeotropic column and a recovery column, is usually used to perform the ethanol dehydration process. However, due to high energy requirements and equipment investments of CHADS, the TAC is at a relatively high level. DWC-A can be used to eliminate the condenser of the second column and decrease the degree of back-mixing. Both CHADS and DWC-A are simulated with Aspen Plus®, and the results show that DWC-A has an energy saving of 42.17% and the TAC reduction of 35.18% along with higher thermodynamic efficiency and reduction in greenhouse gas emissions.     

催化精馏在合成甲缩醛中的应用

开发了由离子交换树脂型固体酸催化剂和不锈钢丝网构成的催化填料。在内径25mm、高1000mm的玻璃反应精馏塔内进行的甲醇与甲醛合成甲缩醛的反应表明, 该催化填料具有优良的催化反应活性和高效的产物分离能力。2000h寿命考察未见活性衰退迹象。在内径150mm、高5400的不锈钢反应精馏塔内的反应同样达到了小试的水平, 显示了该催化填料良好的工业应用前景。     

甲缩醛反应精馏过程模拟

通过实验取得了甲醛和甲醇合成甲缩醛的反应参数;建立了其连续生产工艺的数学模型,利用ASPEN PLUS软件对甲醛和甲醇缩合生成甲缩醛进行了模拟,结果表明反应精馏连续生产甲缩醛的工艺是可行的,转化率高达99%,并得到含甲缩醛99%的产物,同时确定了进料板和反应区.     

Multiple Analysis in a Reactive Distillation Column for the Synthesis of tert‐Amyl Methyl Ether

tert‐Amyl methyl ether (TAME) is produced via reactive distillation. A simulation is set up and controlled on Aspen HYSYS v 8.0 for generating the highest purity of TAME. This simulation includes a plug‐flow reactor and a reactive distillation column. Emphasis was put on finding the optimal operating conditions of the reactive distillation column in order to get the maximum purity of TAME. The operational parameters were reflux ratio, number of reactive stages in the distillation column, and condenser pressure. The results indicated the optimal reflux ratio and condenser pressure which could be adapted to industrial scale.     

乙酸乙酯反应精馏生产工艺模拟研究

以实际生产数据为基础,运用化工稳态模拟计算软件ASPEN PLUS,在建立现有乙酸乙酯酯化工艺仿真模型的基础上,对现有工艺进行改进,采用催化剂循环的方式,建立了生产乙酸乙酯的反应精馏新体系的计算机仿真模型。模拟研究结果表明：乙酸乙酯的带循环反应精馏新工艺是可行的,在相同的进料条件、相同的设备规格下,相比于现有生产工艺,新工艺提高生产能力约24％,同时降低了能耗和节省了设备投资。     

Design and Control of Ionic Liquid‐Catalyzed Reactive Distillation for n‐Butyl Acetate Production

A simulation study of n‐butyl acetate production with the [Hpy][HSO₄] ionic liquid catalyst was performed. Due to the lack of phase equilibrium data, the binary interaction parameters of the NRTL model for ionic liquid and reactive species were calculated by the COSMO‐RS technique. A reactive distillation process with recycled ionic liquid stream was proposed, and the column configuration was optimized by minimization of the total annual capital. The novel process is considerably efficient and economic compared to the traditional reactive distillation process of nonionic liquids. With the steady‐state parameters, a plant‐wide control structure was further developed to evaluate the robustness of the control system by exerting the disturbances of feed flow rate and feed composition. Dynamic simulation results suggest that the control scheme with a composition controller is timely and effective.     

Reactive Distillation for Solvent Regeneration after Biphasic Carboxylic Acid Esterification

Emulsion-enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1-octanol in an emulsified regime with 4-dodecylbenzenesulfonic acid (4-DBSA) or Ni(DBSA)₂ as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester-laden solvent with methanol. The regenerated solvent is reused in the extraction step.     

一种反应精馏生产醋酸正丙酯的方法

通过对传统的间歇法生产醋酸正丙酯工艺进行系统分析,针对传统工艺物耗高以及废水排放量大,污染环境等缺点,提出醋酸正丙酯生产连续反应精馏—加盐萃取—间歇精馏联合流程,在采用该流程的条件下,原料正丙醇与醋酸消耗比传统工艺降低3 1%,在减少废水排放量的同时,醋酸正丙酯的总收率可以从92 71%提高到94 8%。     

Predictions for Start‐Up Processes of Reactive Distillation Column via Artificial Neural Network

The time consumed in starting up the unit with appropriate holdups can form an important part of the total distillation time, particularly for reactive distillation systems with large holdups. Also, the products formed during the start‐up time are off specification, and are not easily recycled as for traditional distillation, but must be carefully disposed of, which can be very costly. A back‐propagation algorithm artificial neural network model is presented as a tool to assess the start‐up process for a given reactive distillation system. All the data required for training and testing the artificial neural network have been generated using the CHEMCAD simulator, version 5.2–0. The values for the learning rate, momentum term, and gain term of the artificial neural network have been taken as 0.01, 0.6, and 1.0, respectively. From the case studied in this work, it can be seen that a good start‐up policy can reduce both the energy and time requirements in the start‐up phase of reactive distillation processes. Results from predictions show the time consumed in the start‐up period has an average error of 2.833 %, and a maximum error of 7.600 %, for the case studied here. The accuracy of the model will depend upon the data available and the type of model being approximated.     

Entrainer selection for the synthesis of fatty acid esters by Entrainer-based Reactive Distillation

In this research it is demonstrated that, due to the similarities between Entrainer-based Reactive Distillation and azeotropic distillation, the same selection rules can be applied to select a suitable entrainer. From a list of suitable entrainers for the azeotropic distillation of isopropanol and water, cyclohexane and isopropyl acetate are chosen. Residue curve maps, simulations of the distillation section of the column, and simulations of the total Entrainer-based Reactive Distillation concept show that both can be used as an entrainer in Entrainer-based Reactive Distillation. Whether the Entrainer-based Reactive Distillation concept will be feasible, depends strongly on the kinetics of the reaction.     

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。     

在离子交换树脂作用下甲缩醛合成反应本征动力学

将强酸性离子交换树脂作为甲缩醛合成的反应的催化剂,采用测温法测定了在其作用下甲缩醛合成反应本征动力学数据,提出了经验动力学模型,并由反应温度与反应时间的关系直接设计了模型参数。