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This paper deals with the dynamic behavior of simultaneous reaction-separation systems which operate at or near the chemical equilibrium in the liquid phase. The process under study comprises a whole set of “instantaneous”, and very fast reversible reactions where the difference in volatilities favors both the progress of reaction and product separation. The main aim of our study is to gain a deeper understanding of the dynamic behavior of distillation columns by using a model that is simple and efficient, yet informative. This kind of model is outstanding for synthesis and design of control schemes which require a careful modelling and understanding of process response to different changes in the environment. We use a suitable transformation of variables (after Barbosa and Doherty, 1988b) in order to define a new set of state variables; as a result, the balance equations become identical to those for conventional distillation. Also, an efficient physicochemical algorithm that can handle both the original and new state variables is used. Thus, a composition-holdup dynamic model is simulated in the “transformed field” using a stage-by-stage approach. To further reduce computational time, the transformed problem has also been solved by means of a reduction procedure based on approximating by orthogonal polynomials the transformed composition and flow profiles in the column. The performance of the two proposed methods are compared by using the top section of a quaternary reactive column. The results obtained shown that reactive distillation dynamics has certain peculiarities derived from superimposing reaction and separation phenomena. 相似文献
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Zhiwen Qi Yinmei Ye Ruisheng Zhang Zunhong Yu 《Chemical Engineering Communications》2000,180(1):61-82
The equations describing the steady state operation of distillation column with simultaneous equilibrium chemical reactions have been transformed into a new set or MESH equations by introducing transrormed composition, flow rate and enthalpy variables. The new set of equations are similar to equations describing traditional non-reactive distillation, and it is general when one or several reactions occur and inert components are present.
An algorithm combining relaxation method and modified Newton-Raphson method is proposed to solve the new equations, the relaxation method is used to estimate initial values, while the modified Newton-Raphson method is used to set solution. The reactive distillation processes of MTBE synthesis with n-butane and the separation of meta- and para-xylene are simulated as numerical examples 相似文献
An algorithm combining relaxation method and modified Newton-Raphson method is proposed to solve the new equations, the relaxation method is used to estimate initial values, while the modified Newton-Raphson method is used to set solution. The reactive distillation processes of MTBE synthesis with n-butane and the separation of meta- and para-xylene are simulated as numerical examples 相似文献
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反应精馏制苯甲酸苄酯的研究 总被引:2,自引:0,他引:2
研究开发了由对苯二甲酸二甲酯生产过程中副产物粗苯甲酸甲酯酯交换制备苯甲酸苄酯的反应精馏工艺。在酯过量情况下,通过正交实验,确定了最佳工艺条件,并考察了催化剂用量、酯醇比和反应温度三因素对苄酯收率的影响。与间歇釜式反应相比,反应精馏技术用于苯甲酸甲酯醇解制苯甲酸苄酯大大提高了酯过量下的反应收率。 相似文献
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Kai Sundmacher Liisa K. Rihko Ulrich Hoffmann 《Chemical Engineering Communications》1994,127(1):151-167
In the present paper a comparative consideration is given for the physico-chemical phenomena involved in homogeneously and heterogeneously catalyzed reactive distillation processes (RDP). The processes are classified qualitatively by dimensionless parameter groups derived from the balances for vapor, liquid and solid phases according to the principles of irreversible thermodynamics. The groups are applied to analyze industrial processes and experimental data for esterification, etherification and alkylation regarding different catalysts, operating conditions and configurations of plants. The mathematical models published until today and the experimental results are contrasted taking the parameter groups as a basis. This gives a discrimination of the models and some recommendations for their applicability. 相似文献
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This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
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Moshood J. Olanrewaju 《Chemical Engineering Communications》2013,200(3):267-292
This study demonstrates that state observers can be developed and applied to infer the composition profiles of reactive distillation columns from noise-contaminated temperature measurements. The design and implementation of a Kalman filter (KF) and a Luenberger observer (LO) are carried out, and their performances are quantitatively assessed. The reliability, accuracy, and robustness of the two designs method are examined and compared quantitatively. The design and implementation of a Luenberger observer are simpler and easier to carry out than those of a Kalman filter. On the other hand, a Kalman filter is found to be more robust to a noisy measurements, erroneous initial estimates, and model uncertainties. A Luenberger observer could be used for composition estimation of reactive distillation when an ideal model of the system can reasonably approximate the real system; otherwise, a Kalman filter is recommended to be applied in more practical situations. 相似文献
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A reactive distillation process is proposed for manufacturing dimethyl carbonate (DMC) through the transesterification reaction of ethylene carbonate (EC) with methanol. Modeling and simulation of the reactive distillation column have been carried out to study the effects of operating conditions, such as the reflux ratio, the number of theoretical plates, the feed ratio, the top effluent, the liquid holdup, and the feed location, on EC conversion and product composition at the top of the reactive distillation column. The calculated results show that a complete EC conversion can be achieved. The model reliability is analyzed under different Murphree tray efficiencies, showing no considerable difference between the equilibrium and nonequilibrium models for this system. And the calculated results are verified by experimental data and commercial operation of a dimethyl carbonate plant of 10,000 tons per year. 相似文献
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A reactive distillation process is proposed for manufacturing dimethyl carbonate (DMC) through the transesterification reaction of ethylene carbonate (EC) with methanol. Modeling and simulation of the reactive distillation column have been carried out to study the effects of operating conditions, such as the reflux ratio, the number of theoretical plates, the feed ratio, the top effluent, the liquid holdup, and the feed location, on EC conversion and product composition at the top of the reactive distillation column. The calculated results show that a complete EC conversion can be achieved. The model reliability is analyzed under different Murphree tray efficiencies, showing no considerable difference between the equilibrium and nonequilibrium models for this system. And the calculated results are verified by experimental data and commercial operation of a dimethyl carbonate plant of 10,000 tons per year. 相似文献
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<正>在伴有多个反应的分离过程数学模拟中,反应量的存在使模型变量增多,非线性增强.文献[1~3]在普通精馏的基础上,提出了不同的算法来改进收敛性.他们对各种反应类型,均以动力学计算反应量,迭代变量多,算法也较复杂.Doherty针对平衡反应过程,提出了变换组成变量的概念计算反应相平衡.本文引入此概念,并对流率、焓等物理量进行了相应的变换,使变换后的反应精馏过程数学模型在形式上与普通精馏过程的模型完全一致.并以修正的Newton-Raphson法对对二甲苯和邻二甲苯的反应精馏过程进行了计算. 相似文献
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通过对酯交换反应精馏塔操作条件的分析,在现有生产工况下,采用统计调优操作法,建立了酯交换率及其影响因素的数学模型,该模型与生产实际相符.根据数学模型和实际操作经验,确定出了最优操作条件.按优化条件操作,酯交换率可达99.5%以上. 相似文献
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采用柱状阳离子交换树脂S-54作催化剂研究了叔丁醇脱水的反应精馏过程.在实验基础上建立了该过程的数学模型,采用超松弛法,并以动态方程逼近计算稳态过程对模型进行了求解,计算结果与实验结果吻合良好.在以上研究基础上考察了不同进料流量、进料组成、进料位置以及不同回流比等对反应转化率的影响,进行了上述工艺操作参数的模拟寻优,得到以下结论:反应精馏操作实现了水从反应体系中的有效移除,减小了水对反应的阻害作用,使叔丁醇接近完全分解;同时改变操作压力可以适用不同温度热源的热量回收要求. 相似文献
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根据基础数据研究,提出以DMF为溶剂从焦化苯中分离微量正庚烷的萃取精馏法,采用三对角矩阵-2N Newton-Raphson联合法对萃取精馏塔进行了模拟计算,通过优化计算得到萃取精馏塔、正庚烷回收塔及苯回收塔的操作条件,为分离焦化苯中微量正庚烷流程的建立提供依据。 相似文献
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连续反应精馏合成正硅酸乙酯的研究 总被引:1,自引:0,他引:1
讨论了连续反应精馏合成乙酯的新工艺,将反应和精馏在一个设备中完成,考察了釜温、进料温度、进料速度、回流量及进料口位置对连续反应精馏的影响,筛选较佳的工艺条件。 相似文献
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Anton A. Kiss J. J. Pragt C. J. G. van Strien 《Chemical Engineering Communications》2013,200(11):1366-1374
This work presents a novel integrated reactive-separation design based on a dividing-wall column (DWC) applied to an industrial case study within AkzoNobel Chemicals. To the best of our knowledge this is one of the first reported industrial applications of a reactive DWC. Due to changing market conditions, one of the by-products in a plant became more economically attractive than the main product. However, the design of the existing plant does not allow an increase of the by-product production rate at the cost of the main product. To solve this problem we developed a novel integrated design that combines reaction and separation into a feasible reactive DWC that allows 35% savings in capital and 15% savings in energy costs. This article describes the novel reactive DWC design, presents the rigorous simulation results, and makes a comparison with the base case alternative. 相似文献