Abstract: Dry fermentation is a potential trend in biogas industry, but the slow start-up and uneven mass transfer in the fermentation system block its application. In this study, wet fermentation was adopted as the start-up phase of dry fermentation to promote two-stage anaerobic fermentation. The effect of the fermentation time of the first wet fermentation stage (3 d, 5 d, 10 d, 15 d and 25 d) on the two-stage anaerobic fermentation was investigated. Lignocellulose degradation and SCOD (soluble chemical oxygen demand) changes in the first-stage wet fermentation were tested and the kinetics analysis for the two-stage fermentation process was fitted. The total methane yield of the whole fermentation with the wet fermentation period of 3, 5, 10, 15 and 25d were 208.17, 185.83, 218.63, 219.44 and 218.85 ml·(g VS)^-1, respectively, which indicated that the period of wet fermentation stage above 10 d was necessary to guarantee biogas production of the dry fermentation process. Kinetics fitting analysis showed that the RC model was more suitable for the experimental study on anaerobic fermentation process, compared with the GM and LM models.

Key words: dry anaerobic fermentation, anaerobic start-up, two-stage fermentation, corn

摘要： 干式发酵过程由于需水量少而成为目前国内外沼气行业的一个重要发展趋势，但是干式发酵存在启动慢和传质不均匀的局限性。采用湿式发酵作为干式发酵的接种启动阶段，将湿式和干式联合，从而力求解决干式发酵的局限性，发展出湿干结合的两级厌氧发酵产沼气工艺，以提高干式发酵技术的效率。采用秸秆为底物进行两级厌氧发酵，考察了第一级湿式发酵时间对后续干式发酵的影响。设置3、5、10、15和25 d五个不同湿式发酵周期进行实验，结果表明，湿式发酵周期为10、15和25 d实验组的累计两级甲烷产气能力相当，分别为218.63、219.44和218.85 ml·（g VS）^-1，3 d[208.17 ml·（g VS）^-1]和5 d[185.83 ml·（g VS）^-1]实验组产气量均较低。从产气量、降解程度和实际工艺等角度综合分析得出，湿式发酵周期为10 d之后转入第二级干法发酵效果最佳。动力学拟合分析表明，RC（reaction curve）模型较GM（Modified Gompertz）和LM（Modified Logistic）模型更适用于本实验研究的厌氧发酵过程的数据模拟。

关键词: 干式发酵, 厌氧启动, 两级发酵, 秸秆