應用數學規劃法作跨廠區冷卻水網路之最適化設計

Abstract

在冷卻水網路設計的文獻中，大部分只討論具有單一個冷卻器網路(heat exchanger network)的冷卻水系統(cooling water system)；而本論文則是對於跨廠區的冷卻水網路，意即具有多個冷卻器網路的冷卻水系統，提出一套完整的數學模式，同時此模式也能夠包含過去學者對單一冷卻器網路提出的模式。 本研究對於跨廠區的冷卻水網路，依據工廠需求的操作情況不同，將系統分成五種情境(Scenario A~Scenario E)來討論。首先以目標函數(1)最少冷卻水消耗量，對一個虛擬的例子做五種情境的最適化並比較結果；接著，基於目標函數(1)的結果，更進一步考量系統中其他成本，再以目標函數(2)最小年總成本對五種情境做最適化分析，並比較跨廠區冷卻水整合與只有工廠內部整合成本(或冷卻水)的節省。此外，在不同管線成本下，評估系統作跨廠區整合的潛力。最後，也考慮可選擇的管徑種類有限的情況下計算管線成本，做年總成本最適化。

To date, research in cooling water system has only focused on a single cooling water network. For the purpose to enhance reuse possibilities of cooling water and to further reduce cooling water requirement, the idea of inter-plant cooling water integration was recently proposed. This work aims to develop a mixed-integer nonlinear program (MINLP) formulation for the synthesis of inter-plant cooling water networks based on superstructures. The newly proposed model can be also used to include some other cooling water integration schemes that have been published in literature. In this work, five different integration schemes are analyzed. For each scheme, two objective functions are considered which involve the minimization of cooling water supply and total annualized cost. In the latter case, two kinds of cost functions are adopted for the estimation of piping cost. An example is used to illustrate the proposed formulation and the optimal results for different schemes are compared with each other. Furthermore, the impact of piping cost on inter-plant cooling water network design is also examined.