反应隔壁精馏塔合成乙酸丁酯模拟研究

提出用反应隔壁精馏塔合成乙酸丁酯的工艺流程,以反应隔壁精馏塔代替常规乙酸正丁酯反应精馏塔和乙酸正丁酯产品精制塔,将反应隔壁精馏过程和常规反应精馏生产过程模拟比较,在相同生产能力和产品纯度要求下,反应隔壁精馏塔可降低能耗30%以上,同时可减少设备投资。最后,对提出的反应隔壁生产乙酸丁酯的生产流程进行优化,考察进料位置、采出进料比、副塔液相分配比等因素对乙酸丁酯生产过程能耗和乙酸丁酯产品纯度的影响,并得到适宜的生产操作条件。     

渣油制氨气化—变换系统流程模拟

本文对UBE型渣油制氨的气化—变换系统进行稳态模拟。用马丁-候状态方程作为热力学模型来计算真实气体的热力学性质,并在此基础上引入平衡温距的概念来描述高温高压下的气化反应。根据Prausnitz提出的方法建立了8.7MPa压力下的汽液平衡模型,用校正的动力学方程来计算变换反应速度,采用序贯模块法进行了流程模拟。以设计工况为基准的实例分析表明模拟结果与实际数据符合良好。对各关键单元进行的模拟操作分析,为该系统的优化计算和改进现行操作工况提供了较好的依据。     

基于过程数据的空分系统参数估计

根据空分系统模型特点确定模拟计算中待估计参数,包含热力学参数以及设备参数。文献中通常采用常规浓度的实验气液平衡数据回归热力学参数,由于实验浓度达不到高纯度范围,热力学参数用于高纯度体系模拟时误差较大,故采用过程数据估计。考虑到待估参数较多,提出了通过分析参数全局灵敏度来判断关键参数,以减小参数估计的规模,估计参数由原来的10个减少到2个关键参数。基于过程数据采用最小二乘法对关键参数进行参数估计。将优化后的关键参数值应用于模拟计算,计算结果与5个实际工况测量值进行对比,可以看出模拟结果与实际工况吻合较好;将优化热力学参数代入热力学方程进行相平衡计算,并与实验气液平衡数据以及未优化的参数计算的结果进行比较,优化后参数的计算结果更加逼近于实验相平衡数据。     

基于塔板组成线的反应精馏图解设计

图解设计法,可以相对较少的已知数据快速、直观地获得反应精馏塔的结构和操作参数。本文在转换组成变量的基础上,系统地推导了反应精馏塔板组成线方程及设计可行性判据,提出了基于塔板组成线进行反应精馏图解设计的策略,并对理想反应体系进行了实例设计计算。研究结果表明：利用塔板组成线进行反应精馏设计可同时获得多组可行设计方案,比现有精馏线和剩余曲线设计方法更为有效,并有利于设计的优化和经济效益评价。     

芳烃联合装置邻二甲苯精馏塔流程模拟与优化

化工流程模拟软件不断发展,越来越多的化工装置开始采用流程模拟来优化装置的操作。基于精馏过程的实际运行数据,建立了能够良好描述装置实际运行工况的模型,实现了对芳烃联合装置邻二甲苯精馏过程的流程模拟。利用Aspen Plus建立装置模型,按照工艺条件及产品分离要求,使用设计规定工具,对采用精馏方式从混合C8～C10物料中分离邻二甲苯(OX)工艺进行研究。模拟结果与实际工业过程数据相符,能够满足工业建模的要求。基于模型,研究了进料塔板位置、回流比和塔顶采出量等变量对装置稳定运行的影响,从进料塔板,塔顶采出量和进料组分等方面提出了优化建议。研究结果表明:精馏塔塔顶采出量为OX产品主要杂质异丙苯(IPB)含量的显著影响因素。据此提出了包括回流比和塔顶采出量参数的优化方案,可以使主要杂质异丙苯的含量下降40%的同时,每年可节省燃料成本。     

基于分析的乙烯装置蒸汽系统操作优化

针对乙烯装置蒸汽系统的操作参数优化问题,从系统能效视角提出了一种基于分析的优化方法。在建立蒸汽供应和转换设备模型的基础上,依据蒸汽系统的结构建立了各级蒸汽的平衡模型和约束方程。基于Aspen Plus流程模拟软件建立了乙烯过程的流程模拟系统,建立了可计算蒸汽和动力需求的非线性黑箱模型。通过集成蒸汽平衡模型、设备模型和流程模拟黑箱模型,以蒸汽系统能效最大为优化目标,采用两步计算方法,可得到蒸汽系统内各设备的最优操作条件。乙烯装置的实例分析验证了该方法的有效性。     

盐-水-乙醇-乙二醇体系汽液平衡的预测

电解质溶液汽液平衡的预测和计算是是热力学的一个重要研究领域,是加盐萃取精馏模拟计算的重要基础,精 确的推算电解质溶液的汽液平衡数据有着十分重要的理论和实际意义。本文改进了计算电解质溶液汽液平衡的LI- QUAC模型,用计算水-乙醇-乙二醇体系汽液平衡更为精确的NRTL模型代替lIQUAC模型中的UNIFAC模型来计 算溶剂分子间相互作用对超额Gibbs自由能的影响,并据此推算出两种盐-水-乙醇-乙二醇体系的汽液平衡数据, 与本文实验数据及文献数据比较,结果比较满意。该模型对电解质溶液汽液平衡的进一步研究以及加盐萃取精馏的工 程计算均具有一定的指导意义。     

常压下丙醛-水-甘油体系汽液平衡测定与关联

采用单循环汽液平衡釜测定了常压条件下丙醛-水的二元以及丙醛-水-甘油三元汽液平衡数据。运用MATLAB中求解非线性最小二乘法问题的函数Lsqnonli,结合丙醛-水的二元汽液平衡实验据,迭代出了Margules、Vanlaar、Wilson和UNIQAC四个方程的二元模型参数。通过计算值和实验值的比较,Wilson方程的相对误差均小于5%,故选择Wilson方程为本体系的适合模型。将测定的丙醛-水-甘油三元汽液平衡数据与模型参数带入Wilson方程求得的三元汽液平衡数据相比较,相对误差均小于5%,由此验证了本文Wilson模型参数的可靠性。本文的测定结果和计算结果为丙醛-水-甘油体系的萃取精馏模拟选择了合适的模型,关联得到的Wilson模型参数,为萃取精馏过程的模拟计算打下基础,同时也为丙醛和水混合液的有效分离提供了一定基础数据。     

加盐萃取精馏制取无水乙醇的过程模拟

以改进的LIQUAC模型为热力学基础,编写了计算电解质溶液汽液平衡的子程序,并将其链接到化工流程模拟软件PRO/Ⅱ5.10中,进而模拟了加盐萃取精馏制取无水乙醇的工艺流程。模拟结果与工业生产的实际情况基本符合。在此基础上,将此工艺与本文及其它文献中模拟的溶盐精馏、萃取精馏和共沸精馏等各种制取无水乙醇的工艺进行了比较研究。     

酯交换合成碳酸二乙酯反应精馏工艺的模拟

碳酸二乙酯是一种性能优良的绿色溶剂,在锂离子电池行业中应用广泛。以碳酸二甲酯和乙醇为原料,采用反应精馏工艺生产碳酸二乙酯是目前的主流工艺。由于该反应分为两步进行,因此如何调节工艺参数来提高反应物转化率和产品收率是工业生产中的重要问题。本文以实验得出的动力学方程、UNIQUAC热力学模型,应用Aspen Plus流程模拟软件实现了工业实际反应精馏工艺流程的模拟,详细讨论了进料位置、回流比、进料配比等因素对反应精馏塔性能的影响。结果表明,模拟值与实验值吻合良好,在回流比为4.5～5,混合进料第20块板,进料醇酯比2.5:1,反应段（2～31）块板,空速小于0.18 hr^-1时,反应精馏塔性能最佳。模拟结果对反应精馏合成碳酸二乙酯的工艺设计和过程优化具有重要指导意义。     

Model reduction and optimization of reactive batch distillation based on the adaptive neuro-fuzzy inference system and differential evolution

This paper considers the application of the adaptive neuro-fuzzy inference system (ANFIS) instead of the highly nonlinear model of a reactive batch distillation column for optimization. The architecture has been developed for fuzzy modeling that learns information from a data set, in order to compute the membership function and rule base in accordance with the given input–output data. In this work, the differential evolution algorithm has been employed for optimization of operation policy of reactive batch distillation for producing ethyl acetate. In optimization, minimal batch time and high purity of product are considered, and reflux ratio and final batch time are taken as decision parameters. The results show that the reduced model (ANFIS) is able to properly create a robust model of the reactive batch distillation, and CPU use is reduced to 1/18,000 of that of a real mathematical model. The highest yield and mole fraction of ethyl acetate were achieved through the use of the obtained optimization policy.     

Model predictive control of reactive distillation for benzene hydrogenation

Benzene hydrogenation via reactive distillation is a process that has been widely adopted in the process industry. However, studies in the open literature on control of this process are rare and seem to indicate that conventional decentralized PI control results in sluggish responses when the reactive distillation column is subjected to disturbances in the feed concentration. In order to overcome this performance limitation, this work investigates model predictive control (MPC) strategies of a reactive distillation column model, which has been implemented in gPROMS. Several MPCs based upon different sets of manipulated and controlled variables are investigated where the remaining variables remain under regular feedback control. Further, MPC controllers with output disturbance correction and, separately, with input disturbance correction have been investigated. The results show that the settling time of the column can be reduced and the closed loop dynamics significantly improved for the system under MPC control compared to a decentralized PI control structure.     

Two-point control of a reactive distillation column for composition and conversion

Reactive distillation is a hybrid process with dual process objectives: reactant conversion and product composition. Control schemes for reactive distillation frequently neglect the effect of the principal operating parameters on the reactant conversion, and this has a detrimental effect on the overall process profitability. An ETBE reactive distillation column has been used as a case study to show how a two-point control configuration, which recognises the importance of both composition and conversion, can be developed and implemented for a reactive distillation process. The combined composition and conversion control configuration was tested using SpeedUp dynamic simulations and proved to be effective in maintaining a high isobutylene conversion despite process disturbances. The two-point control scheme also had superior disturbance rejection capability, especially for feed rate changes, and composition set-point sensitivity compared with a one-point control scheme.     

Plant-wide design and control of acetic acid dehydration system via heterogeneous azeotropic distillation and divided wall distillation

Energy-saving plant-wide design and plant-wide control of an acetic acid dehydration system with the feed containing methyl acetate and p-xylene are investigated in the study. A heterogeneous azeotropic distillation using isobutyl acetate as an entrainer is designed to obtain high-purity acetic acid at the column bottom and to keep a small acetic acid loss through the top aqueous draw. The accumulation of p-xylene in the column is avoided by adding a side product stream. The mixture in the aqueous phase of decanter, containing mostly water, methyl acetate, and isobutyl acetate is separated using a divided wall distillation column. The whole acetic acid dehydration system includes a heterogeneous azeotropic distillation column and a divided wall distillation column.The control strategies using temperature loops are proposed for this acetic acid dehydration system. For the heterogeneous azeotropic distillation column, the requirements for acetic acid compositions in both the aqueous phase of the decanter and the column bottom can be satisfied by designing entrainer inventory temperature control and cascade temperature control simultaneously. The stages of controlled temperatures are chosen by singular value decomposition and closed-loop analysis methods based on the criteria of minimum entrainer makeup. For the divided wall distillation column, steady-state analysis methods are used for the selection of proper controlled and manipulated variables and the determination of their pairings. Dynamic simulation results demonstrate that the proposed plant-wide control strategy can maintain product purities and reject external disturbances in feed flow and composition changes as well as internal disturbances such as changes in liquid and vapor splits.     

乙酸甲酯催化精馏水解塔过程模拟

分析乙酸甲酯催化精馏水解过程,建立该实验塔物理模型,据此合理简化,建立平衡级与固定床相结合的数学模型及其计算方法.应用该模型方法对本工艺试验的3种催化精馏塔型,分别按2种工况模拟实验过程,得到了与实测数据吻合良好的计算结果.验证了该模型和计算方法的适用性和准确性,能够为过程放大和工艺条件优化提供可靠数据.     

恒沸精馏乙酸丁酯和正丁醇过程的优化

乙酸丁酯和正丁醇是两种重要的有机化工原料,广泛应用在化工和制药行业中.在青霉素提取过程中产生大量的含乙酸丁酯、正丁醇、水的混合物,如何将其分离,有实际的意义.本文介绍皂化处理方法和恒沸精馏分离方法,通过利用3A分子筛优化恒沸精馏工艺过程,从而达到节能降耗20%的目的.     

Control of integrated processes: A case study on reactive distillation in a medium-scale pilot plant

This paper deals with the systematic design of a multivariable controller for a medium-scale reactive distillation column that is operated in semi-batch mode. This is a challenging problem because of the time-varying and strongly nonlinear dynamics of the process and considerable deviations of the behaviour of the real plant from the rigorous model used for process design. The design procedure consists of three steps: first, a suitable control structure that enables the operation of the column near the economically optimal operating point is determined based upon the rigorous nonlinear process model. In a second step, a linear model of the column is identified from experiments and used to compute the best attainable control performance for the chosen control structure. In this step, actuator limitations and model uncertainties described by confidence intervals that were obtained in the identification procedure are considered. In the third step, the resulting high-order controller is approximated by a low-order controller that gives nearly the same performance and preserves robust stability for the computed uncertainty bounds. The controller performance is demonstrated in a series of experiments that were performed at the real reactive distillation column.     

乙二醇单丁醚催化精馏塔开车过程的动态模拟研究

对以环氧乙烷和正丁醇为原料,通过催化精馏法合成乙二醇单丁醚的催化精馏塔开车过程的动态行为进行了模拟研究。提出了1项适用于本工艺体系特点的开车策略。建立了催化精馏塔开车过程的动态数学模型,通过模拟计算得到了从开车至达到系统稳定需要的时间,研究和分析了开车过程中塔内温度、组分浓度、热负荷、反应速率及汽液相流量等的动态分布特征,并同试验结果进行了比较。研究揭示了催化精馏塔开车过程的基本规律,为工艺优化和控制策略的建立奠定了重要基础。     

Linear controller design and performance limits of binary distillation column subject to disturbances with bounds on magnitudes and rates of change

In this paper, we present an application of linear controller design via convex optimization to a binary distillation column and determine its limits of performance. Disturbances of distillation process are characterized as input signals with bounded magnitudes and rates of change. Performance measures of top and bottom control loops are defined as the maximum deviation magnitudes of top and bottom compositions, respectively. This performance is often referred to as the worst-case norm of convolution systems under such disturbances. The convex optimization and the ellipsoid algorithm are applied to design linear controllers and, at the same time, determine the best achievable performance of the closed-loop system. Then, a series of convex optimization problems are efficiently solved to give a trade-off curve representing limits of performance between the top and bottom compositions. The trade-off curve provides a practical insight into the design specification that cannot be achieved for the distillation column control with dynamic controller configuration. To confirm the results, we undertake computer simulation using nonlinear dynamical model of the distillation column. Closed-loop responses of the chosen optimal linear controller are consistent with the trade-off curve and yields superior performance than that of a conventional decentralized PI controller.