外源H2对沼气发酵体系的影响

以水稻秸秆为原料，在30 L搅拌发酵罐中55℃下进行厌氧发酵产沼气实验，探索外源H₂的连续导入对发酵过程的影响。结果表明：外源H₂的导入可以实现沼气的原位提纯，CH₄相对平均体积分数从69.6%可提高到94.4%（搅拌速度100 r·min^-1），同时CO₂相对平均体积分数从30.4%降低至5.6%（搅拌速度100 r·min^-1）；对比无搅拌的小试装置，搅拌速度为50 r·min^-1时，搅拌可将外源H₂的利用率从91.0%提高到93.1%，转化率从85.0%提高到96.8%；外源氢的导入可明显促进丙酸、丁酸和异丁酸的降解，可有效地避免发酵过程中VFAs的累积问题，同时搅拌的加强对发酵体系乙酸分解产CH₄和沼液中CO₂的消耗也有明显的促进作用，最终使得沼液的pH略有上升；外源H₂的通入与搅拌改变了发酵系统内的微生物群落组成比例，但并未对系统内的产CH₄微生物群落结构产生明显的影响。

Effect of exogenous H2 on biogas fermentation system

The biogas fermentation was carried out in 30 L anaerobic stirred-tanks at 55℃ by using straw as substrate, in which the effect of exogenous H₂ was particularly investigated. The results showed that the in-situ upgrading of biogas by means of introducing exogenous H₂ was realized. At the stirring rate 100 r·min^-1, the relative average volume of CH₄ fraction increased from 69.6% to 94.4% while the relative average volume of CO₂ fraction decreased from 30.4% to 5.6%. Compared with the bench-scale experiment without stirring, the utilization and conversion of the exogenous H₂ increased from 91.0% to 93.1% and from 85.0% to 96.8%, respectively, at the stirring rate of 50 r·min^-1. The introduction of exogenous H₂ significantly promoted the degradation of propionic acid, butyric acid and isobutyric acid, which could effectively avoid the accumulation of volatile fatty acids in the fermentation process. At the same time, the strong agitation had an important influence on the decomposition of acetic acid and the consumption of CO₂ in the biogas slurry. In addition, the introduction of exogenous H₂ could change the proportion of the methanogenic microorganism in the fermentation system without obviously affecting the methanogenic microbial community.