- 學位論文
利用最適化演算法與捷徑法進行反應蒸餾塔的設計
Design of Reactive Distillation Process via Rigorous Optimization and Shortcut Methods
摘要
近年來，反應蒸餾技術的發展已經相當成熟，尤其是在可行性分析，程序設計或者控制架構設計都有相當程度的進展。因此，吾人面對一個反應蒸餾的設計，通常都可以藉由前人已經建立的觀念與知識，來分析其概念設計的可行性。一旦概念設計是可行的話，程序工程師會想更進一步知道該設計是否可以用捷徑式設計的方法做前置設計的分析，或者是否可以利用最適化方法找到最經濟的設計以做為未來詳細設計的基礎。 針對反應蒸餾塔的最適化設計，本研究首先將應用模擬退火演算法進行反應蒸餾程序的最適化設計，並且採用信賴度高的商用模擬軟體(Aspen Plus)來建立反應蒸餾程序的模式，而模擬退火演算法和商用程序模擬軟體(Aspen Plus)之間連結的介面是採用Visual Basic Application (VBA)。雖然利用模擬退火演算法得到設計結果沒辦法保證是全域最佳解，但是與傳統方法相較之下，它可以更有效率且得到的解與最佳的設計相距不遠。 針對反應蒸餾塔的捷徑式設計，最大的困難就是要決定反應區內的觸媒填充量。本研究將先針對兩成份的異構物反應系統，以逆流式串級汽液反應器的概念發展出一套捷徑式設計的流程。研究發現在無限個反應器串連在一起的情況下，會有出現理論最小觸媒的填充量，並且推導一個解析解的公式來描述它。接著，在不需要詳細的程序模式，便可藉由最小觸媒填充量可以用來估算真實的觸媒填充量，以及反應蒸餾塔的其他設計參數，如反應段板數、分離板板數。研究結果顯示此捷徑式設計方法應用於三個兩成份反應的真實系統，其估算結果與最適化設計相較下，年總成本相差不到10%。 最後，將最小觸媒填充量的概念延伸至更複雜的系統，包括兩成份雙聚合、三成份、四成份以及具有共沸物等反應系統，探討在何種反應類型與何種反應蒸餾架構才具有最小觸媒填充量。研究結果顯示只有以下三個條件同時存在下才具有最小觸媒填充量，其一是反應系統內至少要有一反應物的沸點必須沸點是最重或者最輕；其二是反應蒸餾架構的反應段必須在塔的上半段或是下半段；其三是分離段內(汽提段或是精餾段)的狹點(pinch point)必須落在具有正向反應的區域內。
並列摘要
The development of reactive distillation (RD) processes has matured significantly in the last decade, especially for the progress in the feasibility analysis, design, and control. However, two questions still often come up: (1) Can a shortcut method be employed for preliminary design? (2) How can a near-optimal design be obtained efficiently for further detailed study? In this work, these two questions are addressed. To obtain a near-optimal design, a derivative-free optimization approach, simulated annealing (SA), is employed for the optimization of the RD column design and the SA algorithm is implemented in the Visual Basic Application which interfaces with the process simulator, Aspen Plus. This method gives an equally good or better design than the optimal flowsheet obtained from the sequential design approach. More importantly, this is achieved with much more efficient computing. To develop a shortcut method, determination of the catalyst mass is a challenging problem in the conceptual design of reactive distillation systems. We use the concept of countercurrent cascaded vapor-liquid reactors (CCRs) to develop a shortcut method for the design of binary reactive distillation columns. An analytical expression for the theoretical minimum catalyst loading can be derived as the number of CCRs approaches infinity. On the basis of this theoretical catalyst loading, we present a calculation procedure to obtain the catalyst mass and other basic process parameters without a detailed model. Three real binary systems are used to illustrate this shortcut method, and the results show that the estimated shortcut designs are similar to the optimal designs. Furthermore, the concept of the minimum catalyst loading is extended to more complex systems, including ternary and quaternary ideal systems and non-ideal systems with azeotropes. The results show that a minimum catalyst loading exists only if three conditions are met: (1) the RD column has a one-sided reaction zone (top or bottom) and products are withdrawn from the other side, (2) One of the reactants or an azeotrope containing a reactant is the heaviest or the lightest and (3) The pinch point in the separation section of the RD column is located in the zone with positive reaction extent.
參考文獻
延伸閱讀
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