複合式生質酒精脫水純化製程之設計與經濟評估

Design and Economic Evaluation of Hybrid Separation Systems for Bioethanol Dehydration

黃傑(Jay Huang)

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(2019年)

https://doi.org/10.6342/NTU201903841

摘要

由於全球石化原料枯竭與溫室效應導致氣候變遷的問題日益嚴重，生質酒精一方面可以做為燃料取代部份的汽油；另一方面其原料來源大多為木質纖維素材料，因此兼具生態環保與永續再生的生質酒精成為極具潛力的替代能源之一。生質酒精的原料大多經由發酵程序後取得，濃度非常稀薄約只有2-5 mol%，然而要做為汽油濃度須達99.5 mol%以上，除了必須克服水與乙醇系統中存在的共沸組成89 mol%，還需要降低因分離出大量水分所需的能耗。
近年來有非常多關於分離水與乙醇的文獻，而本研究中以萃取蒸餾、共沸蒸餾、薄膜分離三大類為主要稀薄生質酒精去水純化製程，其中結合Aspen Plus V8.8的模擬結果與Python的年度總成本計算，以最小年度總成本為目標函數找尋各程序最適化設計。
本研究結果顯示，在以乙醇純度5 mol%為進料、99.5 mol%為目標出料下，萃取蒸餾中先以預蒸餾方式提濃至78 mol%的脫水純化製程擁有最小的年度總成本，與傳統兩塔萃取蒸餾製程相比較節省了76%的能耗與71%的總成本。而複合式滲透蒸發蒸餾製程則因為昂貴的薄膜設備成本為次佳，節省了82%的能耗與57%的總成本。

關鍵字

生質酒精 ； 去水純化 ； 萃取蒸餾 ； 共沸蒸餾 ； 滲透蒸發 ； 複合程序

並列摘要

Problems concerning the shortage of fossil raw materials and greenhouse effect leading global climate change are far from solved. Bioethanol is considered to be the most promising sustainable biofuel of the future. In order to be used in the fuel, bioethanol produced from fermentation stage, obtained at a concentration around 2 to 5 mol%, must be concentrated to at least 99.5 mol%. The high amount of water in the feed leads to higher separation energy cost, and ethanol–water azeotrope existing in the purification process needs to overcome.
In the present works, there are a lot of methods to break azeotrope between ethanol and water. In this study, extractive distillation, azeotropic distillation and membrane separation are the main processes for bioethanol dehydration. In order to find the optimal design of each processes with minimum total annual cost (TAC), combine with the simulation results by Aspen Plus V8.8 and TAC by Python.
The results show that, under the 5 mol% bioethanol feed, the extraction distillation with preconcentrated distillation column is has the lowest TAC. Compared with the conventional process, it saves 76% of energy consumption and 71% of TAC. The pervaporative distillation is the second lower process due to expensive membrane equipment. It saves 82% of energy consumption and 57% of TAC.

並列關鍵字

Bioethanol ； Dehydration ； Extractive distillation ； Azeotropic distillation ； Pervaporative distillation ； Hybrid processes

參考文獻

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