在本研究中，我們發展出增進化工廠中既有水網路操作彈性的經驗性翻修策略，具體言之，即利用文獻中已發展成熟的彈性指標 (Swaney and Grossmann, 1985) 來定量描述任何給定水網路適應不確定干擾之能力。由於彈性指標模型是一個混合整數非線性規劃 (MINLP) 模式，我們無法保證相應最佳化過程的收斂，因此提出了兩個能求解促進效率的技巧：(一) 將給定網路消耗最小純水量時的操作條件，當作該規劃的初值，(二) 利用Bandoni (2000) 提出的平滑函數來消除MINLP模型的二元變數。另外，我們也根據解決大量的簡易例題獲得的經驗，發展出一系列能放寬彈性指標模型最佳解中觸發條件的翻修設計方案，除了增加純水供應率的上限以外，我們還考慮兩個修改結構的方法為：(一) 加入或刪除連接管線，(二) 增加新的廢水處理單元或取代既有廢水處理單元。最後，我們以一系列的案例研究來展示上述策略的可行性及有效性。

A heuristical revamp strategy is developed in this work to improve the operational flexibility of existing water networks. The well-established concept of flexibility index (Swaney and Grossmann, 1985) is adopted for quantitatively characterizing the ability of any given water network to cope with all uncertain disturbances. Since the flexibility index model is a mixed-integer nonlinear program (MINLP), the convergence of the corresponding numerical optimization process is not guaranteed. Two solution techniques have been developed to promote efficiency, namely, (1) generating the initial guesses by minimizing freshwater consumption rate of the nominal network, and (2) incorporating the smoothing functions suggested by Bandoni et al. (2000) to eliminate the binary variables in the MINLP model. A set of design heuristics have also been developed to identify possible revamp measures to relax the active constraints in the optimal solution of flexibility index model. This flexibility enhancement approach was derived empirically from the insights gained in solving a large number of simple examples. Other than increasing the upper limit of freshwater supply rate, two structural modifications are considered as the main revamp options, i.e., (1) inserting/deleting pipeline connections and (2) adding/replacing treatment units. Several case studies are presented in this thesis to demonstrate the effectiveness of proposed strategy.

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