沼液回流对牛粪厌氧发酵产气特性及其动力学的影响
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北京市科技计划课题资助项目(D141100001214002、Z151100001115010)


Effect of Liquid Digestate Recirculation on Biogas Production and Fermentation Kinetics for Anaerobic Digestion of Cattle Manure
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    摘要:

    在中温条件(37±1)℃下采用连续搅拌反应器(CSTR)研究了沼液长期回流对牛粪厌氧发酵过程中产气特性及其微生物动力学的影响,对不同有机负荷下发酵罐运行参数的动态变化进行了持续监测,并进行了相关的动力学分析。结果表明:在水力停留时间为40 d,有机负荷为3.0 g/(L?d)的条件下,将50%的沼液进行回流时,能够提高基质产甲烷率,促进厌氧发酵系统中微生物的合成代谢,但由于难降解物质累积,传质效果降低仍使得回流组日产气量及甲烷产量呈下降趋势,处理组的沼气容积日产气量从1.07 L/L逐渐降至0.83 L/L,降低了22.4%。沼液回流引起了pH值、NH+4-N、溶解性化学需氧量(SCOD)等指标的升高,但未达到抑制水平。回流导致牛粪厌氧发酵产气量下降的最主要因素可能是由于粘度从50 mPa?s迅速升高至116 mPa?s而引起的传热传质阻力变大。在以牛粪为原料的沼气工程应用沼液回流工艺时需要合理选择回流比例或在回流前对沼液进行适当的处理来保证工程的长期稳定运行。

    Abstract:

    The effect of recirculating the liquid fraction of digestate on the mesophilic anaerobic digestion of cattle manure was investigated using laboratory-scale continuous stirred tank reactors. The hydraulic retention time (HRT) of 40 d was employed. Recirculation was implemented after the anaerobic digestion process was stable at the organic loading rate of 3.0 g/(L?d). However, the recirculation eventually caused the accumulation of organic and inorganic substances, which led to the inhibition of hydrolysis and methanogenesis. The daily biogas yield was decreased by 22.4% when the liquid fraction of digestate was recirculated to substitute 50% of the tap water used for feedstock dilution. The concentrations of ammonia and volatile fatty acids did not reach the inhibitory levels. However, the accumulation of refractory organics, which were more pronounced in the recycling reactors, led to the decrease of methane production. According to the results of kinetic analysis, the microbial anabolism was promoted by the recirculation. The results indicate that choosing a proper recirculation rate and adopting reasonable pretreatment measures are indispensable to avoid the negative influence caused by the accumulation of potentially harmful substances. The proposed approach will lower the amount of generated effluents, and the product of anaerobic digestion with this method will contain high solid content, which will decrease the transportation costs and the storage capacity requirements.

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吴树彪,黎佳茜,李伟,董仁杰.沼液回流对牛粪厌氧发酵产气特性及其动力学的影响[J].农业机械学报,2015,46(10):241-246. Wu Shubiao, Li Jiaxi, Li Wei, Dong Renjie. Effect of Liquid Digestate Recirculation on Biogas Production and Fermentation Kinetics for Anaerobic Digestion of Cattle Manure[J]. Transactions of the Chinese Society for Agricultural Machinery,2015,46(10):241-246.

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  • 收稿日期:2014-12-24
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  • 在线发布日期: 2015-10-10
  • 出版日期: 2015-10-10