在工業中,稀薄共沸混合物的分離一直以來都是個非常重要的議題,由於共沸點的性質會在特定溫度下產生相同氣相與液相組成的混合物,因此無法透過傳統蒸餾來取得高純度產品,烯丙醇與水之混合物為其中一個例子,由於該混合物會產生最低溫度共沸點,以至於困難取得純烯丙醇與水。本研究將探討於兩種進料組成條件下各製程節能效果,於烯丙醇與水的等摩爾進料條件中,設計出雙塔萃取蒸餾、雙塔熱整合萃取蒸餾與本研究分別以兩種液-液萃取劑所提出之複合式萃取-蒸餾四個製程;於烯丙醇與水的稀薄進料條件中,除了提出上述四種製程外,還多了三塔萃取蒸餾與三塔熱整合萃取蒸餾兩個製程。根據結果顯示,以預熱進料的熱整合設計能夠減少萃取蒸餾系統的年度總成本,尤其三塔萃取蒸餾熱整合相比於兩塔萃取蒸餾系統可節省21.3%年度總成本。複合式萃取-蒸餾系統於兩種進料條件下皆展現了很高的省能潛力,其中於稀薄進料條件下,對比於雙塔萃取蒸餾系統,以甲基正丁基醚為溶劑可節省53.6%年度總成本,以苯為溶劑更可節省62.1%年度總成本。最後本研究提出兩種控制架構探討以MNBE為溶劑之複合式製程的動態干擾排除能力,根據結果顯示,在分別進料烯丙醇濃度與進料流量±20%變化下,第一種控制架構透過保守添加過量的溶劑,能將產品濃度維持在初始狀態附近,而第二種架構儘管有較大之新穩態偏差,但其具有較佳的經濟優勢。
In industry, the separation of dilute azeotrope has always been a very important issue. Since the nature of the azeotrope will produce a mixture of the same gas phase composition and liquid phase composition at a specific temperature, high purity product cannot be achieved by conventional distillation. The product, a mixture of allyl alcohol and water, is one of the examples, since the mixture will produce the minimum-boiling azeotrope, so that it is difficult to obtain pure allyl alcohol and water. This study investigated the energy-saving effect of each process under the conditions of two feed compositions. In the equal-molar feed conditions of allyl alcohol and water, two-column extractive distillation(ED), two-column ED with heat-integrated and two hybrid extraction-distillation systems(HED) were designed. In the dilute feed conditions of allyl alcohol and water, in addition to the above four processes, two more processes, triple-column ED and triple-column ED, are proposed. According to the results, the feed-effluent-heat-exchanger can reduce the total annual cost of the ED system, especially the triple-column ED with heat integration can save 21.3% of the total annual cost compared to the two-column ED system. The HED exhibits high energy-saving potential under both feed conditions. Under dilute feed conditions, HED with methyl n-butyl ether can save 53.6% of the total annual cost compared to two-column ED. Save 62.1% of the total annual cost for HED with benzene. Finally, this study proposes two control structures to explore the dynamic interference rejection capability of the MNBE solvent-based hybrid process. According to the results, the first control structure is based on the change of the feed allyl alcohol concentration and the feed flowrate ±20%. By conservatively adding an excess of solvent, the product concentration can be maintained near the initial state, while the second structure has a better economic advantage despite the large new steady-state deviation.
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