Purification process of CO2 in dark fermentation

• Main Authors: Yong-Fang Liu, 劉永豐
• Other Authors: Shu-Yii Wu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/76128697119274547069

碩士 === 逢甲大學 === 化學工程學所 === 100 === Hydrogen is a clean green energy that has been considered as the most promising alternative energy to substitute fossil fuels in the future. Feng Chia University biohydrogen research group has shown great achievements in fermentative hydrogen production. However, due to the biohydrogen production not only produces hydrogen but also carbon dioxide, the hydrogen with carbon dioxide of fermentative biogas production can’t be used directly. Therefore, the study is designing a process which combined carbon dioxide capturing and the bio-hydrogen purifying. First, the effects of the loading, desorption efficiency, cost and environmental tolerance are studied with different absorbents in terms of potassium glycinate (KGLY), potassium sarcosinate (KSAR), [Choline][Proline], Mono-ethanolamine (MEA) and tri-ethanolamine (TEA). The results were obtained with the operating conditions of absorbent concentration of 2.5 M, temperature of absorption and desorption are 20oC and 130oC, respectively. The results shows that MEA is the best absorbent, the loading is 0.77 mol CO2/mol MEA, desorption efficiency is 90%; the optimal operating condition of MEA is operated with the concentration of 7.5M and temperature of 20oC; the loading is 0.59 mol CO2/mol MEA. Then, exploration the kinetics of absorption/ desorption of carbon dioxide in MEA, the results shown as follows: kMEA,abs = 2.96×104 exp(-549/T); kMEA,des = 6.57×103 exp(-7189/T). Simulation of purification process was evaluated by Aspen Plus. The optimum operating parameters for lab scale are as follow: flow rate of 7.5 M MEA is 0.6 L/h, stages of absorber are 10, and stages of stripper are 15, and recover 98% hydrogen form absorber and 63% carbon dioxide from stripper. The optimum operating parameters for pilot scale are as follow: flow rate of 7.5 M MEA is 13 L/h, stages of absorber are 15, and stages of stripper are 14, and recover 98% hydrogen from absorber and 89% carbon dioxide from stripper. Purged gas are classified into several different grades: industrial, food and beverage grade of carbon dioxide; industrial and fuel grade of hydrogen, the simulation shows that the critical efficiency scale and energy efficiency are 0.9 m3 and 0.27 and that fuel grade hydrogen and beverage grade carbon dioxide were obtained. From the result of this study found that biohydrogen production with purification process are promising and have economical benefit. This experimental data can be referenced as scale-up parameters in designing a continuously H2/CO2 separator as well.