三種不同蒸餾序列之控制策略開發

Abstract

儘管蒸餾的能耗高，但它仍然是分離揮發性混合物最廣泛使用的方法，每年約佔全球能源消耗的 3%。傳統的蒸餾程序存在重混效應，這會降低分離效率並增加能量需求。為了解決這些問題，雖然已提出如分隔壁塔（Dividing-Wall Columns, DWCs）等能量強化策略，但這些方法在控制上存在挑戰，尤其是在僅使用單一再沸器時需管理蒸氣分流。相比之下，堆疊複合蒸餾程序（或稱堆疊側線程序）透過側線抽取來減少重混效應，並藉由整合的再沸器-冷凝器熱交換器降低能耗。此設計不需蒸氣分流，但也帶來了新的控制挑戰：由於熱整合，系統失去了兩個控制自由度。值得注意的是，目前尚無針對堆疊側線程序控制性能的系統性研究。在本研究中，我們比較了傳統蒸餾程序、分隔壁塔與堆疊複合程序於等摩分離 BTX（三苯：苯、甲苯、二甲苯）時的動態控制行為。結果顯示，堆疊複合程序不僅具備優異的節能效果，亦展現出比分隔壁塔更佳的可控性，是一種具可行性與操作性的永續蒸餾設計方案。

Distillation remains the most widely used method for separating mixtures of volatile substances despite its high energy consumption, accounting for approximately 3% of global energy use annually. Traditional distillation sequences usually suffer from remixing effects that reduce separation efficiency and increase energy demand. The most widely-studied method for reducing the remixing effect is thermal coupling, including its embodiment as a dividing-wall column. Recently, however an alternative method called the stacked side-stream sequence has been shown to perform better in most cases. Dividing-wall columns face control challenges—particularly the need to manage vapor splits when only a single reboiler is used. A stacked side-stream sequence does not have a vapor split, but it introduces a different control challenge: the loss of two degrees of freedom due to thermal integration of a reboiler and a condenser. While hundreds of papers have been written on the control of dividing-wall columns, no prior studies have compared the control performance of stacked side-stream sequences with that of dividing-wall columns and conventional two-column sequences. Therefore, in this study, the dynamic control behavior of the conventional distillation sequence, the dividing-wall column, and the stacked side-stream sequence for the separation of BTX (benzene, toluene, xylene). Results show that the stacked side-stream sequence not only achieves superior energy savings but also demonstrates better controllability than the DWC, making it a promising option for sustainable and operable process design.