反应器网络综合优化方法的研究进展

反应器网络综合优化方法在选择反应器类型和反应工艺条件时,比传统的方法表现出了很大的优势。综述了各类反应器网络综合优化方法的基本原理和研究进展,并分析了它们的优缺点。这些方法有基于过程特征的方法,包括可得区法和导数分析法;超结构优化法;目标类方法,包括目标法、构造目标法和构造MINLP法;以及经验推断法和分布参数法等。最后分析了这方面研究的发展趋势。     

复杂第III类反应体系反应器网络综合

在第I, II类反应体系反应器网络综合研究的基础上,对第III类复杂反应体系的反应器网络综合问题进行求解,基于第III类反应体系的阶段性特征,提出反应系踪、瞬时反应物、瞬时产物及瞬时选择性的概念,发展了反应器网络综合的分段导数分析法,提出了分段导数分析的三步策略和分析步骤. 通过对两个实例的分析说明了进行第三类反应体系的反应器网络综合的方法. 结果表明,所提出的分段导数分析法不但简单可靠,且通过优化可获得最优反应器网络结构.     

反应器网络多目标综合优化

通过反应系统综合优化获得经济效益好、对环境友好的反应系统是大多化工厂提高全流程整体经济和环境性能的重要手段。反应器网络综合优化方法主要包括可得区法、导数分析法、超结构优化法、目标类法、经验推断法和分布参数法等,然而却很少有文献报道对反应器网络进行多目标综合优化。由于过程中往往存在多个相互冲突的目标函数,所以仅仅依靠单目标对反应器网络进行综合优化已显得不合适。本文采用分布参数法建立多目标优化模型,目标函数为经济最大化和环境影响最小,并采用非支配排序基因算法(NSGA-Ⅱ)进行优化得到Pareto最优解集。     

基于二维传递模型的反应器网络综合

反应器网络综合的任务在于寻求适宜的反应器类型、尺寸及反应单元间的连接关系并确定各反应器的操作条件,其研究方法主要包括超级结构法和目标法,采用的基本单元均为一维理想模型。文中同时考虑传质、传热、流体流动以及反应动力学,通过偏微分方程描述轴向及径向上的温度、浓度分布,建立了二维反应器模型。基于该二维传递模型,采用状态空间构建反应器网络,并以年度总费用为目标函数评价反应器系统的经济性。最后,以提出的模型对环氧丙烷反应器网络进行了优化设计,实例验证了方法的有效性。     

基于粒子群算法的动态多目标优化

针对碳二氢生产中的反应器动态优化问题,目前虽然有多种算法对生产过程进行优化,但大部分只是对单一目标进行求解,提出一种更为灵活的反应器动态求解方法。在该方法中,首先构建碳二氢目标函数,然后采用多目标粒子群算法和分段线性函数参数法结合的方式对目标函数的进行求解,以提高整体搜索能力,得到碳二氢反应器动态优化的最优解。最后,以实际乙烯碳二加氢化工反应过程为例进行实验验证,结果证明,通过该方法进行求解的目标函数无论是在收敛性,还是在优化的平均值等方面,都比SADE-eCD和NSGA-II算法具有优势,说明该算法在反应器动态优化中是切实可行的。     

反应路径和反应器网络同步寻优

反应过程优化主要包括反应路径综合和反应器网络综合,反应路径综合研究原料到目标产物的化学转化途径,反应器网络综合的任务在于寻求适宜的反应器类型、尺寸以及反应器单元间的连接关系,并确定各反应器的最优操作条件。传统的研究将二者孤立,文中以功能性催化剂排列为切入点,提出了同步优化反应路径和反应器网络的超级结构法。通过优化生产目标产物反应过程中多种功能性催化剂的排列,得到生产目标产物的最优反应路径,并同步优化得到装填特定功能性催化剂反应器的网络结构。用提出的方法优化设计了对二甲苯的生产工艺流程,得到装填功能性催化剂反应器的网络,与装填单催化剂的反应器相比,等反应时间下,对二甲苯产率提高22.73%,实例验证了方法的有效性。     

基于CSTR的反应器网络综合双层优化算法

反应器网络综合问题一般都是复杂的非线性规划问题,在分析基于全混流反应器的反应器网络模型特点的基础上,提出了求解该模型的双层优化算法. 通过将反应器网络综合非线性规划问题分解为物流流量和反应器体积空间的线性优化和浓度空间的优化搜索问题,降低了所求解问题的规模和难度,同时利用全局优化算法进行浓度空间的优化搜索,提高了求得全局最优解的概率. 实例研究表明,双层优化算法可以更准确地给出最优的反应器网络结构以及网络中反应器的类型和大小.     

用遗传算法进行多流股换热器网络综合的研究

建立了多流股换热器网络综合数学模型，该模型改进了文献中等温混合的不合理假设。多流股换热器网络综合问题本质上是一个混合整数非线性规划问题(MINLP)，这类问题的非凸非线性的特性使得目标函数存在多个局部最优解。传统的基于梯度的搜索方法在处理这类问题时由于计算规模庞大且极易陷于局部最优解而不再适用，而遗传算法却为解决这类问题提供了很有希望的一个方向。因而对遗传算法求解多流股换热器网络综合问题进行了研究，提出了可以自动产生可行的多流股换热器网络的方法策略，最后通过两个例题说明所提方法是可行的。     

带有热储罐的间歇过程换热网络综合

间歇过程流股对时间的依赖性增加了其换热网络综合的难度。提出了一种采用间接换热进行换热网络综合的方法,且考虑了直接换热,同时提出了合并热储罐的方法,并利用热储罐的特点合并间接换热中的换热器,用以减少设备费用,以热储罐中介质的温度为变量以年度总费用最小为目标函数建立非线性规划数学模型,确定热储罐内介质温度,最后将该方法应用于实例中证明此方法的有效性。     

具有基质抑制的流加反应器计算机模拟和优化

以单位时间内获得尽可能多的细胞生物量为目标函数,建立了流加反应器最优化模型。通过引入哈密尔顿函数和庞特雅金最小值原理,求解了这个最优化模型。此外,以安德鲁方程为例,还对几种特殊的流加反应器进行了计算机模拟,并给出了最优化计算结果。     

基于废料削减的反应器网络综合—环境指标瞬时值

Waste reduction is gaining importance as the preferred means of pollution prevention. Reactor network synthesis is one of the key parts of chemical process synthesis. In this study, a geometric approach to reactor network synthesis for waste reduction is presented. The bases of the approach are potential environment impact （PEI） rate-law expression, PEI balance and the instantaneous value of environmental indexes. The instantaneous value can be derived using the PEI balance, PEI rate-law expression and the environmental indexes. The optimal reactor networks with the minimum generation of potential environment impact are geometrically derived by comparing with areas of the corresponding regions. From the case study involving complex reactions, the approach does not involve solving the complicated mathematical problem and can avoid the dimension limitation in the attainable region approach.     

基于瞬时目标函数曲线特性的反应器网络综合

It is believed that whether the instantaneous objective function curves of plug-flow-reactor (PFR) and continuous-stirred-tank-reactor (CSTR) overlap or not, they have a consistent changing trend for complex reactions(steady state, isothermal and constant volume). As a result of the relation of the objective functions (selectivity or yield) to the instantaneous objective functions (instantaneous selectivity or instantaneous reaction rate), the optimal reactor network configuration can be determined according to the changing trend of the instantaneous objective function curves. Further, a recent partition strategy for the reactor network synthesis based on the instantaneous objective function characteristic curves is proposed by extending the attainable region partition strategy from the concentration space to the instantaneous objective function-unreacted fraction of key reactant space. In this paper,the instantaneous objective function is closed to be the instantaneous selectivity and several samples axe examined to illustrate the proposed method. The comparison with the previous work indicates it is a very convenient and practical systematic tool of the reactor network synthesis and seems also promising for overcoming the dimension limit of the attainable region partition strategy in the concentration space.     

反应器网络综合分区法中的简捷计算

针对定态、等温、恒容、单股进料的复杂反应过程,首先将反应器网络综合可得区分区法由浓度空间拓展至瞬时选择性-关键反应物未转化率（S-x）空间,然后根据分区法中两条重要曲线的特性（选择性最大曲线dS/dx=0,单程收率最大曲线S=0）建立了以废料最少为目标的反应器网络基本组成单元（PFR和CSTR）的数学模型,并以Van de Vusse反应模式为例将其应用于由分区法确定的最优反应器网络结构的模拟计算.计算结果与文献值一致,表明本文所用方法具有一定的简捷性和实用性.     

基于模糊神经网络的环管反应器故障诊断

环管反应器是丙烯聚合工艺中的主要反应设备之一.环管反应器运行过程中故障产生原因与征兆参数之间的影响关系比较模糊、复杂,不能准确地用数学关系式表述.针对此种情况,总结出环管反应器温度升高时可能的故障原因及征兆参数,并用模糊理论进行处理,再运用神经网络建立了环管反应器故障诊断系统.故障诊断实例表明,该系统具有较高的可靠性.     

Heterogeneously Catalyzed Epimerization of Menthol Stereoisomers – An Instructive Example to Account for Diffusion Limitations in Complex Reaction Networks

The heterogeneously catalyzed epimerization of menthol stereoisomers is an important step in the synthesis of (–)‐menthol by the Haarmann and Reimer process. For an accurate design of a technical reactor, the intrinsic kinetics as well as pore diffusion limitations have to be taken into account. The epimerization consists of a complex reaction network and so a simple approach using effectiveness factors based on Thiele moduli is not possible. In this work, a method is presented to simultaneously calculate the change in concentrations in the bulk phase as well as within the porous particles with time (fixed bed reactor) or local position (batch reactor). A commercially available numerical software was used to solve the differential equations.     

A case study for reactor network synthesis: the vinyl chloride process

A key objective of the integrated reactor network synthesis approach is the development of waste minimizing process flowsheets (Lakshmanan & Biegler, 1995). With increasing environmental concerns in process design, there is a particularly strong need to maximize conversion to product and avoid generation of wasteful byproducts within the reactor network. This also avoids expensive treatment and separation costs downstream in the process. In this study, we present an application of the mixed integer nonlinear programming (MINLP)-based reactor network synthesis strategy developed by Lakshmanan and Biegler (1996a). Here we focus on applying these reactor network synthesis concepts to the vinyl chloride monomer production process. Vinyl chloride is currently produced by a balanced production process from ethylene, chlorine and oxygen with three separate reaction sections: oxychlorination of ethylene; direct chlorination of ethylene; and pyrolysis of ethylene dichloride. The hydrogen chloride produced in the pyrolysis reactor is used completely in the oxychlorination reactor. Byproducts such as chlorinated hydrocarbons and carbon oxides are generated by these reaction sections. These are studied using reaction kinetic models for the three reaction sections. The case study results in optimal reactor networks that improve the conversion of ethylene to vinyl chloride and minimize the formation of byproducts. These results are used to generate an improved flowsheet for the production of vinyl chloride monomer. Moreover, an overall profit maximization, that includes the effect of heat integration, is presented and a set of recommendations that improve the selectivity of vinyl chloride production are outlined. Finally, the optimal reactor structures, overall conversion and annual profit are shown to be only mildly sensitive with respect to small changes in the kinetic parameters.     

IDEAS based synthesis of minimum volume reactor networks featuring residence time density/distribution models

This work addresses for the first time, the synthesis of globally minimum volume reactor networks, featuring segregated flow reactors (SFR) and/or maximum mixedness reactors (MMR), with the same normalized residence time density (NRTd) function. Global optimality is ascertained by demonstrating that the input–output information maps of SFR and MMR with general RTd/RTD models satisfy all properties required for the application of the infinite dimensional state-space (IDEAS) approach to the RTd/RTD reactor network synthesis problem. The resulting IDEAS formulation is shown to possess a number of novel properties, which can be used to facilitate its solution. The power of the proposed methodology is demonstrated on three case studies featuring segregated laminar flow reactors (SLFR) in which the Trambouze reaction scheme is carried out. In one of the case studies, the identified reactor network is shown to have volume that is as low as half the volume of a single reactor.