【作者】 刘琳琳；

【导师】 都健； 姚平经；

【作者基本信息】 大连理工大学 ， 化学工程， 2013， 博士

【摘要】 质量交换网络(MEN)综合与换热网络(HEN)综合是过程工业实现“节能减排”的重要手段。本文首先根据多组分体系传质过程的特点,提出了能够处理不相容多组分体系质量交换网络综合问题的方法。随后以此为基础,以年度总费用(TAC)最小的质量-热量联合交换网络为目标,着重探索了MEN和HEN的同步综合策略。论文主要研究内容及结果如下：(1)为解决由组分溶解性能不同而导致的不相容问题,提出将传质单元理论塔板数作为优化变量的多组分体系MEN综合思想。将这种思想融入截断法与超结构法中,其中前者通过离散截断器、线性化传质方程和给定操作选项等简化手段,可大幅度线性化所建立的混合整数非线性(MINLP)数学模型,简化后的模型采用通用求解软件即可获得最优解；而后者通过与遗传模拟退火算法(GASA)相结合,则可实现目标网络在全局解空间内的最优化。研究表明,本文所提两种方法均能确保所得MEN中的组分浓度值为准确值,不存在文献中因选取“关键组分”而导致部分浓度值与传质单元不相符的情况发生,证明了本文方法在处理多组分体系MEN综合问题时更具合理性,能够用于解决不相容多组分体系的MEN综合问题。(2)针对单组分体系质量-热量联合交换网络综合问题,提出基于质量夹点法(MPT)和虚拟温-焓图法(PTHDA)的MEN和HEN同步综合方法。该方法首先在文献的两子网络耦合模式基础上引入贫流股旁路,以期更全面地实现MEN费用和HEN费用在联合交换网络TAC中的权衡。然后提出基于“流股存在性矩阵”和“温差贡献值矩阵”的两子网络同步综合策略,过程中流股的实际存在性、冷热性质和对应优化变量的值由这两个矩阵的乘积来确定。此策略的提出确保了在未知流股换热需求的情况下,本文所提方法仍能实现MEN和HEN的同步综合与优化设计。采用一个文献中的实例对所提方法进行了验证,结果表明无贫流股旁路时,本文所得最优结果与文献结果基本一致,证明了所提方法的有效性；而当有贫流股旁路时,所得最优TAC分别比文献结果和本文无贫流股旁路的结果低19.9%和21.2%,说明引入旁路流股能为解空间提供更多可行解,有可能获得更优的解。(3)针对多组分体系质量-热量联合交换网络综合问题,提出基于超结构法的多组分体系MEN和HEN同步综合方法。其中采用超结构法综合MEN,提出无区别换热网络超结构的概念用于HEN综合。无区别换热网络超结构在换热流股冷热性质不确定的情况下,可通过构造潜在换热流股间的匹配,为计算过程中实际存在流股所形成的HEN提供所有可能的结构选项,而在此基础上提出的同步综合策略则可实现MEN和HEN的同步综合。首先将该方法用于单组分算例,所得结果与前文结果基本一致,证明了所提同步综合策略的有效性。随后对一个多组分算例进行质量-热量联合交换网络的优化设计,优化过程中同时考察了传质温度和压力对传质相平衡方程的影响,证明该方法能够用于解决多组分体系的MEN和HEN同步综合问题。更多还原

【Abstract】 Mass exchange networks (MENs) and heat exchange networks (HENs) are among the most important contributors of process industries to realize the objective of energy conservation and emission reduction. According to the nature of mass transfer processes involving multiple components, MEN synthesis methods are proposed to handle the incompatible multi-component system problem at first in this thesis; then the simultaneous synthesis strategies for MEN and HEN are explored, with regarding the minimum total annual cost (TAC) of combined mass and heat exchange network as target. The main contents and results of this thesis are as follows:(1) To handle the incompatible problem that caused by the diverse solubility of components in multi-component systems, the synthesis though of setting tray numbers of mass exchange units as variables are proposed. Merge this thought into the interception method and the superstructure method, then the mixed integer non-linear program (MINLP) mathematical model of the former method can be significantly linearized and able to be solved by general solution software in case of using several simplification activities, including interceptors’ discretization, mass transfer equations’linearization and operation options’ pre-setting; the latter method can execute the global optimization and find the optimal solutions through its combination with genetic-simulated annealing algorithm (GASA). An example from literature is separately investigated using the proposed two methods. The obtained true concentration values can demonstrate the rationality and the application of the proposed methods in dealing with MEN synthesis problem of multi-component systems.(2) A method is presented for purpose of synthesizing the MEN and HEN in a single component system simultaneously. In this method, MEN and HEN in a combined mass and heat exchange network are designed using mass pinch technology (MPT) and pseudo T-H diagram approach (PTHDA), respectively. Based on the sub-networks coupling model in literature, the lean bypass streams, which are employed for sake of getting a more comprehensive tradeoff between the costs of MENs and HENs, are considered firstly in the method. Then, a simultaneous synthesis strategy is proposed based on the formation of steam existence matrix and stream temperature difference contribution value matrix. During the synthesis process, the existence feature, the hot or cold nature, as well as the corresponding variable value of any process stream can be identified through the product of these two matrices. This strategy is a guarantee for the simultaneous synthesis, especially in the case of hot/cold properties of heat exchange streams are unable to be predicted in advance. An example from literature is used to verify the proposed method, and the two cases of no bypass involved and having bypass involved are both investigated for comparison. Results indicate that the optimal network and TAC results of former case are both about the same with those obtained in literature; the optimal TAC of latter case is19.9%and21.2%lower than that of literature and former case, respectively. These comparison results can not only show the effectiveness of proposed method, but also can demonstrate the possibility of obtaining a better solution by involving bypass streams.(3) For multi-component systems, a superstructure-based method is proposed for their combined mass and heat exchange networks synthesis. In this method, MENs are designed with the pre-introduced superstructure method, HENs are supposed to be obtained using a new network representation called indistinct HEN superstructure. Indistinct HEN superstructure is possible to provide all possible network options in the case of hot/cold streams are unable to be pre-indentified. It is the basis of synthesis strategy which can ensure the simultaneous design of MENs and HENs. At last, the results of a single-component example and a multi-component example have demonstrated the effectiveness of this proposed method.更多还原