基于经济目标和分解协调策略的换热网络最优设计

分析了换热网络在过程系统中的功能 ,从火用分析和火用经济学的角度提出了换热网络最优合成设计的实用火用经济目标函数 ,它包含了网络的流动火用损费 ,且可分解为各个换热单元的总费用之和 .在换热网络目标函数可分解性的基础上 ,本文又进一步提出了换热网络分解协调优化的研究策略 ,它是在各个匹配单元 (子系统 )和整个换热网络结构 (复杂系统 )之间进行优化协调 ,并获得换热网络的最优结构和各匹配单元的最优操作参数 .最后 ,通过一换热网络的最优合成 ,说明了该方法的应用前景     

同时考虑流动损费和传热强化的换热网络合成

详细论证了在求解换热网络优化狭点温差△T_mtn,opt过程中,同时考虑换热器流动(火用)损、匹配单元优化和传热强化的必要性.提出以“Supertargeting”所给出的最优狭点温差为初值向狭点温差增大的方向寻求最优解的方法.文中对影响△T_min,ovt大小及其与初值之差的经济条件和复合线特性进行了讨论;提出了新的换热网络优化合成策略.用3个实例来说明所提出方法的优越性.     

同时考虑流动损费和传热强化的换热网络合成

详细论证了在求解换热网络优化狭点温差△T_mtn,opt过程中,同时考虑换热器流动(火用)损、匹配单元优化和传热强化的必要性.提出以“Supertargeting”所给出的最优狭点温差为初值向狭点温差增大的方向寻求最优解的方法.文中对影响△T_min,ovt大小及其与初值之差的经济条件和复合线特性进行了讨论;提出了新的换热网络优化合成策略.用3个实例来说明所提出方法的优越性.     

多周期操作工况下热换网络的弹性设计

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。最后用分解协调法和网络结构和匹配单元同时进行优化。该方法不仅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     

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。     

甲醇合成及精馏单元的热集成

夹点技术是换热网络优化设计的一种方法,本文利用夹点技术对甲醇合成及精馏单元进行了系统用能分析,找出了用能状况不尽合理之处.将甲醇合成及精馏两个单元作为一个系统整体考虑,提出了甲醇合成及精馏单元的换热网络优化方案.优化后整个系统可以节约低压蒸汽22.2%,节约循环冷却水14.9%.     

基于持续节能的多周期换热网络优化设计

在石油化工工业中,换热网络的操作条件时常发生改变,尤其是结垢热阻随运行时间不断增大。针对操作条件的改变,有研究者提出多周期换热网络最优综合的设计与改造方法。但是,这些方法不涉及结垢热阻对设计结果的影响。然而,换热器结垢不可避免,传热系数随之改变,将导致操作工况偏离最优值,难以实现持续节能优化。以多周期换热网络优化为基础,提出一种基于持续节能的多周期换热网络综合设计方法,以换热网络累积总费用为目标函数,考虑换热器结垢对多周期换热网络优化结果的影响,进而实现多周期换热网络的最优综合。首先,结合示例分析换热器结垢对多周期换热网络优化结果的影响,得出考虑到结垢热阻的影响多周期换热网络在各个周期内的优化结果将改变;然后,基于持续节能优化,以换热网络累积总费用为目标函数,提出一种多周期换热网络优化方法;最后,结合示例验证了该设计方法的有效性。     

基于持续节能的多周期换热网络优化设计

在石油化工工业中,换热网络的操作条件时常发生改变,尤其是结垢热阻随运行时间不断增大。针对操作条件的改变,有研究者提出多周期换热网络最优综合的设计与改造方法。但是,这些方法不涉及结垢热阻对设计结果的影响。然而,换热器结垢不可避免,传热系数随之改变,将导致操作工况偏离最优值,难以实现持续节能优化。以多周期换热网络优化为基础,提出一种基于持续节能的多周期换热网络综合设计方法,以换热网络累积总费用为目标函数,考虑换热器结垢对多周期换热网络优化结果的影响,进而实现多周期换热网络的最优综合。首先,结合示例分析换热器结垢对多周期换热网络优化结果的影响,得出考虑到结垢热阻的影响多周期换热网络在各个周期内的优化结果将改变;然后,基于持续节能优化,以换热网络累积总费用为目标函数,提出一种多周期换热网络优化方法;最后,结合示例验证了该设计方法的有效性。     

过程全局夹点分析与超结构MINLP相结合的能量集成最优综合法

提出了过程全局夹点分析与超结构混合整数非线性规划 (MINLP)相结合的能量集成最优综合法 .各单过程内部换热优化匹配后 ,进行各过程剩余冷、热负荷与公用工程系统的全局夹点分析 ,确定全局热集成目标 ,在此基础上建立包含过程剩余热负荷产生各等级蒸汽、剩余冷负荷使用各等级蒸汽加热的各种可能匹配方案的公用工程换热网络超结构及其MINLP模型 ,采用混合连续进化算法求解得到过程与公用工程换热网络最优改造方案 .大型乙烯装置能量集成应用算例表明 ,可充分发挥全局夹点分析法确定改造目标的简洁实用性和超结构MINLP寻求最佳方案的优点     

智能法合成最优换热网络

本文给出了合成最优换热网络时物流匹配换热的规则,结合设计实践和生产经验制定出物流匹配换热的人工智能图表,给出了合成步骤.依此,不必反复迭代调优,而用解析的方法一次就可以合成最优或接近最优的换热网络.经过大量实例考核,取得了令人满意的结果.     

Heat Exchanger Network Integration Considering Flow Exergy Loss

This work describes a systematic procedure to integrate a heat exchanger network (HEN) considering heat and flow exergy consumptions. The flow exergy consumption by the HEN is calculated by means of pressure drop correlation and stepwise optimization. Case studies reveal that the flow exergy loss changes the two‐way trade‐off between the operating cost and the capital cost in the traditional method. The introduction of heat exergy loss adds the weight of energy cost by considering both the external utility consumption and internal heat exergy loss in the HEN, which benefits heat recovery and energy conservation at the cost of more area and investment. In contrast, the flow exergy loss shifts the balance to the capital cost by adding the cost relating to area in terms of flow frictional dissipation.     

Margin design,online optimization,and control approach of a heat exchanger network with bypasses

During the life cycle operation of a heat exchanger network (HEN), factors such as equipment aging, gradually decrease heat transfer performance and increase energy consumption. Industrial HEN design currently fails to effectively solve these problems. To resolve this problem, we present an online optimization and control approach method for an HEN with bypasses. The approach is based on the principles of sustainable energy conservation during the life cycle. The area margin of the heat exchanger is gradually released via bypass adjustment, thereby resulting in energy conservation. First, bypasses are set on the HEN to enhance HEN control and enable optimal manipulation of the equipment. Then, the total cumulative cost increment of the HEN, including the increment of utility costs and equipment investment costs, is regarded as the objective function. The effects of the heat transfer efficiency of the heat exchanger and the effects of bypass adjustment are also taken into account. We solve the optimal design margin of the HEN, thereby providing an operational space for optimal control. Finally, using the margin optimization design of the HEN with bypasses as basis, we treat the cumulative costs of the HEN in a certain cycle as the objective function to solve the optimal opening dynamically. While, we present an optimal control structure, which is combined with existing conventional control loops. The HEN of a given crude distillation unit in a refinery is chosen as the research object. And, results illustrate the effectiveness and application prospects of the proposed method.     

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。     

考虑本质安全的换热网络多目标优化

由于国内外重大化工事故的频发及化工行业节能降耗的需求日益迫切,研究本质更安全的换热网络多目标优化具有重要意义。采用评价指数的方法,对换热网络的本质安全易爆性、毒性、存量进行量化表征。采用数学规划法分别建立换热网络经济与本质安全易爆性、毒性、存量同步优化数学模型。采用归一化法构建经济和安全的目标函数。通过算例研究发现,考虑易爆性,倾向于不易爆流股间换热,减少易爆流股换热次数;考虑毒性,倾向于减少有毒流股流经换热器的次数;考虑存量倾向于减少换热网络的总存量。最后综合考虑易爆性、毒性、存量作为安全指标与经济同步优化,通过算例研究表明,多目标优化的最优换热网络在很大程度上取决于经济权重的选取。     

Exergy as an objective function to MINLP problems in process synthesis

The optimal layout of a chemical plant is determined by both economic and environmental aspects. The mathematical approach to this problem is given by representing the process through a superstructure, including any foreseeable process topology. It is described by integer variables, whereas real variables arise from the unit models and the thermodynamic calculations. By including process constraints and an objective function, a Mixed Integer Nonlinear Programming (MINLP) optimization problem is postulated. In this paper MINLP algorithms are combined with a technique for the exergy analysis of chemical processes for the preliminary screening of process alternatives. The exergy analysis as a screening technique is advantageous due to a significantly smaller amount of required data and computing time, compared with true optimization, including cost estimation at an earlier stage of process synthesis and analysis. Thus, a broader solution space can be examined. The subsequent cost analysis has then only to be focused on a reduced set of parameters.     

基于参数k、z优化的换热网络温差贡献值设计方法

提出了一种可以降低换热网络运行费用的基于参数k、z优化的换热网络设计方法, 使得网络结构更加简化, 特别适用于流体传热系数有差异的换热网络合成问题。该优化设计方法将网络运行总费用作为目标函数, 以参数k、z的优化为基础, 通过网络约束确定参数的寻优区间, 经二维寻优得到最优参数k_opt和相似文献   

功热交换网络综合的研究进展

功和热是化工工业中使用能源的两种最主要方式,由于流股压力、温度操作需要消耗大量的功热,因此研究功热的协同利用对于提高过程整体能源利用率具有重要的意义。本文首先概述了基于热力学分析的功热交换网络综合的研究情况,以系统?耗最小为目标探讨压缩机、膨胀机优化配置与换热网络用能瓶颈的耦合关系,揭示了功热协同利用的作用机制。然后系统地总结了以年度总费用最小为目标的数学规划模型综合功热交换网络的研究进展,探寻压力操作路径、流股功/热交换匹配、公用工程消耗量及设备投资之间的有效权衡;最后对后续研究进行展望,指出可进一步探究考虑流股冷热性质判定的功热交换网络同步综合、公用工程系统优化与功热交换网络同步设计的耦合等。     

Design of heat exchanger network based on entransy theory

The heat exchanger network (HEN) synthesis problem based on entransy theory is analyzed. According to the characteristics of entransy representation of thermal potential energy, the entransy dissipation represents the irreversibility of the heat transfer process, the temperature difference determines the entransy dissipation, and four HEN design steps based on entransy theory are put forward. The present study shows how it is possible to set energy targets based on entransy and achieve them with a network of heat exchangers by an example of heat exchanger network design for four streams. In order to verify the correctness of the heat exchanger networks design method based on entransy theory, the synthesis of the HEN for the diesel hydrogenation unit is studied. Using the heat exchange networks design method based on entransy theory, the HEN obtained is consistent with energy targets. The entransy transfer efficiency of HEN based on entransy theory is 92.29%, higher than the entransy transfer efficiency of the maximum heat recovery network based on pinch technology.