多流股换热器网络综合方法在原油预热系统中的应用

以原油常减压蒸馏装置原油预热网络为研究对象,进行了多流股换热器网络的实例综合. 基于超结构物理模型建立了改进的多流股换热器网络综合数学模型,提出将该网络综合问题由混合整数非线性规划问题转化为简单的非线性规划问题的求解策略,并利用改进的遗传/模拟退火新算法进行了原油预热网络的综合. 与Hextran软件的综合结果以及现场换热网络的对比表明,本模型和求解策略可以应用于工业规模的多流股换热器网络综合,有可能取得较好的经济效益.     

低温过程多流股换热器网络综合

多流股换热器主要应用在低温过程领域.本文针对低温过程换热器网络的特点,基于流股虚拟温度的T-H图提出了利用遗传/模拟退火算法进行低温过程换热网络综合的方法.低温过程传热温差较小,在流股温差贡献值的选取上充分考虑了流股热力学平均温度的影响,使其取值更加合理;冷公用工程的利用不同于常温换热网络,温度越低其相应的费用越高,通过采用分批-逐次利用的原理分配冷公用工程,得到冷公用工程的温位及相应的匹配位置,能够有效地利用过程系统的传热温差,降低换热网络的操作费用;该方法利用虚拟T-H图法产生初始解,具有决策变量少,产生初始解均为可行的特点,能显著提高遗传模拟退火算法的计算效率,并适用于不同材质、不同传热膜系数网络的设计和优化;以国内某乙烯装置脱甲烷塔预冷系统综合为实例进行了分析.     

用伪并行遗传/模拟退火算法进行多流股换热器网络综合的研究

The multi-stream heat exchanger network synthesis (HENS) problem can be formulated as a mixed integer nonlinear programming model according to Yee et al. Its nonconvexity nature leads to existence of more than one optimum and computational difficulty for traditional algorithms to find the global optimum. Compared with deterministic algorithms, evolutionary computation provides a promising approach to tackle this problem. In this paper, a mathematical model of multi-stream heat exchangers network synthesis problem is setup. Different from the assumption of isothermal mixing of stream splits and thus linearity constraints of Yee et al., non-isothermal mixing is supported. As a consequence, nonlinear constraints are resulted and nonconvexity of the objective function is added. To solve the mathematical model, an algorithm named GA/SA (parallel genetic/simulated annealing algorithm) is detailed for application to the multi-stream heat exchanger network synthesis problem. The performance of the proposed approach is demonstrated with three examples and the obtained solutions indicate the presented approach is effective for multi-stream HENS.     

基于流股虚拟温度综合大规模多流股换热器网络

Effective temperature level of stream, namely stream pseudo temperature, is determined by its actual temperature and heat transfer temperature difference contribution value. Heat transfer temperature difference contribution value of a stream depends on its heat transfer film coefficient, cost per unit heat transfer area, actual temperature, and so on. In the determination of the suitable heat transfer temperature difference contribution values of the stream, the total annual cost of multistream heat exchanger network （MSHEN） is regarded as an objective function, and genetic/simulated annealing algorithm （GA/SA） is adopted for optimizing the heat transfer temperature difference contribution values of the stream. The stream pseudo temperatures are subsequently obtained. On the basis of stream pseudo temperature, optimized MSHEN can be attained by the temperature-enthalpy （T-H） diagram method. This approach is characterized with fewer decision variables and higher feasibility of solutions. The calculation efficiency of GA/SA can be remarkably enhanced by this approach and more probability is shown in searching the global optimum solution. Hence this approach is presented for solving industrial-sized MSHEN which is difficult to deal by traditional algorithm. Moreover, in the optimization of stream heat transfer temperature difference contribution values, the effects of the stream temperature, the heat transfer film coefficient, and the construction material of heat exchangers are considered, therefore this approach can be used to optimize and design heat exchanger network （HEN） with unequal heat transfer film coefficients and different of construction materials. The performance of the proposed approach has been demonstrated with three examples and the obtained solutions are compared with those available in literatures. The results show that the large-scale MSHEN synthesis problems can be solved to obtain good solutions with the modest computational effort.     

多组分多股流相变换热器的传热计算

多组分多股流相变换热器在气体液化分离及石油化工中获得广泛应用,其传热计算远较一般换热器复杂。本文对涉及露点、泡点、密度、平衡常数、热物性参数以及传热计算等问题进行了探讨。     

热负荷和超结构级数对多流股换热器网络综合的影响

多流股换热器网络是一种复杂的换热器网络.在优化的双流股换热器网络的基础上进行多流股换热器网络的综合.在考虑工程应用中换热器热负荷受限制的条件下,通过对换热器网络超结构模型中级数进行合理的取值,来减少遗传模拟退火算法程序的计算量和提高计算效率;同时确定了级数的设定方法.最后将级数的设定方法应用于两个例题,效果良好.     

多股流换热器网络及其衍生网络法综合优化

在介绍了多股流换热器网络特点及其与传统网络区别的基础上,提出了一种基于衍生网络的多股流换热器网络综合优化方法,重点在衍生网络的生成、多股流换热器网络的合成以及全局优化格式的生成等方面进行了探讨,结果表明,采用衍生网络的方法能够实现多股流换热器网络的优化.     

低温多股流板翅式换热器设计优化方法研究进展

针对多股流体流动换热、复杂翅片结构优化、多重通道排布匹配以及低温工程应用等特点,本文归纳分析了低温多股流板翅式换热器结构设计中凸显的流股换热匹配、通道分配排列、多物理场叠加以及低温特殊工况下的应用等问题。总结了在通道结构优化与零部件设计中,通过翅片通道传热流动特性及相关性能评价方法来指导结构选型。文章还深入分析国内外现状,讨论了板翅式换热器的研究热点与发展方向。文章指出低温多股流板翅式换热器应用于大型空分等石化工业流程中优势明显,可显著提高气体液化率,降低实际能耗,进而提升系统运行效率。因此,对于实际应用中可能遇到的设计问题,应考虑结合局部换热网络与多流股匹配、翅片结构设计与通道排列算法优化、多场仿真与试验研究等手段形成合理优化方法和设计框架,来摆脱目前传统经验试凑所带来的限制。     

LNG一级五股流板翅式换热器的研究与开发

对天然气低温液化领域中LNG多股流板翅式换热器的总体结构和研究开发现状进行了说明,对第1阶段在五股流板翅式换热器中将36℃的天然气冷却至-53℃以便进入二级预冷段的工艺流程进行了论述,并说明了涉及的主要原理和技术解决方案,最后指出了LNG板翅式换热器进一步的研究方向和有待解决的问题。     

多股流板翅式换热器的微分与优化数值研究

采用微分计算模型对多股流板翅式换热器的优化设计问题进行了研究,提供了一种有效的通道排列方法,并编制出了相应的计算程序.利用该程序,对不同初始长度和不同片厚的多种情况进行了计算.计算结果发现,换热器初始长度对最终的收敛长度没有影响,但片厚对计算结果的影响较大.通过一个数值计算实例验证了上述方法的可行性和有效性.     

改进的无分流换热器网络最优综合法

提出了不分流换热网络改进的同步最优综合混合整数非线性规则模型，通过引入处理带０－１整型变量的规则，提出了采用非线性规划求解换网络综合ＭＩＮＬＰ问题的方法，只需求解ＮＬＰ问题就可得到连续变量和０－１变量同步优化的网络结果。算例表明，该模型和方法是有效的。     

基于专家系统和遗传算法的换热网络的建模和优化

A new superstructure from of heat exchanger networks(HEN) is proposed based on expert system (ES). The new superstructure from is combined with the practical engineering.The different investment cost formula for different heat exchanger is also presented based on ES.The mathematical model for the simultaneous optimization of network configuration is established and solved by a genetic algorithm.This method can deal with larger scale HEN synthesis and the optimal HEN configuration is obtained automatically.Finally,a case study is presented to demonstrate the effectiveness of the method.     

基于温度和热容流率同时变化的有分流换热网络弹性设计的研究

A new superstructure model of heat exchanger networks (HEN) with stream splits based on rangers of streams supply temperatures and heat capacity flow rates is presented. The simultaneous optimal mathematical model of flexible HEN synthesis is established too. Firstly, the streams with rangers of supply temperatures and/or the streams with the rangers of heat capacity flow rates are pretreated; Secondly, several rules are proposed to establish the superstructure model of HEN with splits and the simultaneous optimal mathematical model of flexible HEN; Thirdly, the improving genetic algorithm is applied to solve the mathematical model established at the second step effectively, and the original optimal structure of HEN based on the maximum operation limiting condition can be obtained easily; Finally, the rules of heat exchange unit merged and the heat load of heat exchanger relaxed are presented, the flexible configuration of HEN satisfied the operation condition between the upper and down bounds of supply temperature and heat capacity flow rates can be obtained based on the original optimal structure of HEN by means of these rules. A case study demonstrates the method presented in this paper is effective     

过程工业换热网络合成研究进展

阐述了过程工业换热网络优化设计的基本方法,分别指出了夹点技术、数学规划法和人工智能法的基本原理、优缺点、应用领域及国内外的发展状况,并对其做了展望,指出需要更接近于工程实际的考虑.     

Synthesis of heat exchanger networks with nonisothermal phase changes

Most literature on the synthesis of heat exchanger networks via mathematical programming methods has dealt with phase changes by assuming nearly isothermal conditions. Many multicomponent phase changes of practical interest (e.g., those in sub‐ambient processes) occur over ranges of temperatures and exhibit nonlinear temperature‐enthalpy relations (T‐H curve). In such cases, isothermal approximations may lead to inferior or unacceptable networks. In this article, we propose a mixed‐integer nonlinear programming formulation and a solution algorithm to incorporate nonisothermal phase changes in heat exchanger network synthesis. We approximate the nonlinear T‐H curves via empirical cubic correlations, and propose a procedure to ensure minimum temperature approach at all points in the exchangers. Our approach successfully solves two industry examples and shows promise for significant cost reductions when compared with existing processes. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

多周期操作工况下换热网络的弹性设计

提出了基于专家系统的多周期换热网络的超结构形式及弹性设计方法。首先通过专家系统确定各周期操作工况下物流的分流及匹配禁止情况,在此基础上建立网络多周期操作工况下的超结构模型;然后用遗传算法对上述模型进行求解;最后用分解协调法对网络结构和匹配单元同时进行优化。该方法不仅能自动地合成多周期操作工况的换热网络最优流程结构,而且能同时满足网络在各操作工况下的各种工艺限制条件。最后,通过某个换热网络的最优合成设计,说明本方法的有效性和应用前景。     

基于遗传算法的原油混合优化研究

对原油混合优化问题进行了研究,在模型建立过程中综合考虑了原油的储运调度约束和混合原油属性约束,并计入了装置加工的可变成本,使之更加符合生产实际,采用遗传算法来求解模型,通过实例分析,证明了模型和算法的有效性。     

基于动态机理模型的换热网络弹性分析方法

提出状态空间离散化的思想,建立换热器的动态机理模型,然后通过Simulink模块化连接的方法,对换热网络进行弹性分析。这种方案不但能充分考虑各换热器的面积、结构和位置,而且能准确反映各物流的流量、温度分别变化和同时变化时各换热器出口温度随时间的变化趋势和平稳后的温度,还提高了弹性分析准确度和解决了装置中存在控制器的问题。该方法采用模块化连接,应用和调整方便。