乳酸乙酯製程之反應蒸餾系統與不同分離組態之設計與經濟評估

本論文針對乳酸乙酯之酯化系統，提出兩組不同生產乳酸乙酯之商業化製程。整組架構可分為反應區域以及分離區域。在適當的熱力學與動力學模型之下，先探討針對Miller等人1的反應區域來改善。藉由觀察反應區域第一根反應蒸餾塔塔內之各成分摩爾組成分佈，可以發現乳酸乙酯組成最高點並非出現在塔底，而是在接近塔底的板。因此在第一根反應蒸餾塔取出一股高純度乳酸乙酯側流來取代原先的產物分離塔。最後在反應段僅需兩反應蒸餾塔即可實現生產高純度乳酸乙酯之目標，其一為乳酸乙酯酯化塔，其次為水解塔進行不純物水解。　　在分離區域的設計上，以兩組不同的組態－萃取蒸餾與薄膜，處理來自反應區域的水與乙醇混合物。萃取蒸餾系統在處理水與乙醇的混合物上，甘油為一相當合適的萃取劑。其原因在於比起傳統萃取劑而言，甘油提取水的效果更好。除此之外，在考量製程的綠化上，甘油為無毒化合物，因此適合作為分離水與乙醇的萃取劑。在薄膜程序上，選用商業化薄膜－PERVAP® 2201。由於來自反應區域的水含量高於薄膜操作上限，因此選用複合式的方法，先將物流送至傳統蒸餾塔進行除水，而後再由滲透蒸發程序分離乙醇與水。　　程序之最適化上，以年均總成本作為目標函數，針對以上兩組製程探討不同設計與操作變數對於系統的影響以求得最佳之設計組態。結果顯示，相較於傳統的萃取蒸餾法，以滲透蒸發複合程序結合兩反應蒸餾塔製程來生產乳酸乙酯較具經濟效益。總計節省76%之操作成本與31%之年均總成本。

關鍵字

乳酸乙酯；程序設計；反應蒸餾；萃取蒸餾；滲透蒸發

並列摘要

Two commercial scale ethyl lactate (L1E) production processes are studied in the work. The L1E processes can be divided into the reaction part and the separation section. For the reaction part, instead of the three-column design presented by Miller et al1, the proposed configuration only contains two reactive distillation (RD) columns, where the L1E product is taken from the first RD column as a sidedraw. This novel improvement can reduce 22.26% of energy consumption in the reaction part. Additionally, disparate separation approaches such as extractive distillation (ED) and the pervaporation (PV) are then implemented to deal with the ethanol/water azeotrope. Economics for alternative configurations are analyzed to find the most competitive and cost-effective process. As a result, the RD with PV design can save at least 31.47% of total annual cost compared to the RD with ED configuration.

並列關鍵字

Ethyl Lactate ； Process design ； Reactive distillation ； Extractive distillation ； Pervaporation

參考文獻

(1) Miller, D. J.; Asthana, N.; Kolah, A.; Lira, C. T. Process for Production of Organic Acid Esters. US 7,652,167, Jan. 26, 2010.

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乳酸乙酯製程之反應蒸餾系統與不同分離組態之設計與經濟評估

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