複合式薄膜反應蒸餾製程於醋酸酯類系統之應用

Reactive Distillation-Pervaporation Hybrid Process for the Production of Ethyl Acetate & Isopropyl Acetate

李昇育(Sheng-Yu Li)

指導教授 ： 陳誠亮

國立臺灣大學/工學院/化學工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601809

摘要

本論文針對醋酸乙酯與醋酸異丙酯之酯化系統，結合了傳統的反應蒸餾與薄膜分離程序，提出了此兩種系統反應蒸餾與滲透蒸發複合程序穩態與動態架構的設計。以工業級醋酸與含水醇類作為進料標準，在適當的熱力學與動力學之模型之下先行探討反應蒸餾塔的設計。觀察兩系統的蒸餘曲線圖，塔頂出料之組成相當接近醇-酯-水三成分共沸物，因此於塔頂設置一分相槽，可有效地移除系統因酯化反應所產生的水；而有機相物流，則將其全回流至反應蒸餾塔。藉由此設計可於反應蒸餾塔精餾段中段的側流取出純度相當高之酯類。再將此側流透過滲透蒸發程序，提高產品純度至程序所需之規格。程序之最佳化的方法上，以年均總成本作為目標函數，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。和傳統的兩塔反應蒸餾程序相比，醋酸乙酯系統約節省13%之再沸器能耗，而醋酸異丙酯系統約節省20%之再沸器能耗。
在程序動態操作策略上，探討了兩種不同的控制架構，分別為反應蒸餾塔的單點以及雙點溫度控制。透過開環靈敏度的分析找出系統較佳的溫度控制板。在單點溫控的架構中，以反應物進料比控制一塔板溫度，並利用乙醇反應物之進料流率與純度估算反應蒸餾塔側流之流量；在雙點溫控架構方面，則是分別以反應物進料比與側流流率控制兩個塔板溫度。在兩控制架構的薄膜操作條件控制策略上，藉由對系統進行閉環靈敏度測試後可發現，以側流的流量可推估薄膜的操作溫度。模擬結果顯示，雙點溫度控制架構對於程序進料擾動(產能、進料組成改變)的排除有較佳的響應，尤其是在正方向之產能擾動方面，在控制過程中，其產品純度震盪自單點溫控的1 mol%改善至0.2 mol%。

關鍵字

醋酸乙酯 ； 醋酸異丙酯 ； 反應蒸餾 ； 滲透蒸發 ； 複合程序 ； 程序控制

並列摘要

This study raises a pervaporation (PV) – reactive distillation (RD) hybrid configuration for producing high purity ethyl and isopropyl acetate product. impure acetic acid and alcohol are the reactants to the system. From the residue curve map of these two systems, it was found that the overhead products of the RD column are the alcohol-water-acetate ternary azeotrope which are inside the liquid-liquid boundary. By implementing an overhead decanter, the water generated from the esterification can be removed effectively. Via the total reflux of the organic phase, a side stream with extremely high acetate purity can be drawn from the rectifying section of the RD column. Finally, pervaporation units are applied to remove water for producing high specification product. The total annual cost (TAC) analysis is used to determine the optimal design configuration. Compare to the traditional two column processes[1], the hybrid process for ethyl and isopropyl acetate can save about 13% and 20% reboiler duty respectively.
Based on the optimized hybrid process, two different control strategies – the single-point temperature control and the dual-point temperature control – are proposed to examine the performance of rejecting main disturbances to the process. A lot of simulation tests show that the single-point temperature control structure fails to maintain adequate product specification should the acid purity in feed is lower than a specific value. However, the dual-point temperature control structure can handle both throughput and feed composition disturbances quite well.

並列關鍵字

Ethyl acetate ； Isopropyl acetate ； Reactive distillation ； Pervaporation ； Hybrid process ； Process control

參考文獻

[1] Lai, I.-K.; Hung, S.-B.; Hung, W.-J.; Yu, C.-C.; Lee, M.-J.; Huang, H.-P., Design and control of reactive distillation for ethyl and isopropyl acetates production with azeotropic feeds. Chemical engineering science,2007, 62, (3), 878-898.

[3] Sander, U.; Soukup, P., Design and operation of a pervaporation plant for ethanol dehydration. Journal of membrane science,1988, 36, 463-475.

[4] Agreda, V. H.; Partin, L. R. Reactive distillation process for the production of methyl acetate. U.S. Patent 4,435,595, April 26, 1982.

[6] Keyes, D., Esterification processes and equipment. Industrial & Engineering Chemistry,1932, 24, (10), 1096-1103.

[7] SUZUKI, I.; YAGI, H.; KOMATSU, H.; HIRATA, M., Calculation of multicomponent distillation accompanied by a chemical reaction. Journal of Chemical Engineering of Japan,1971, 4, (1), 26-33.