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Research On Methane Effectiveness Of Mixed Substrates With Cattle Manure And Corn Straw In Two-phase Anaerobic Digestion

Posted on:2015-05-24Degree:MasterType:Thesis
Country:ChinaCandidate:X B MengFull Text:PDF
GTID:2181330422492231Subject:Environmental Engineering
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With rapid development of world economy, the destruction of the ecological environment, energy shortages and pattern change, people come to realize that the importance and necessity of developing renewable clean energy. Anaerobic fermentation technology can make a harmless handling with waste organic resources, such as crops straw and animal manure, and produce renewable energy—biogas. Biogas can be used to generate energy, such as electricity and heating, and biogas slurry and residue can be used as fertilizer. It realizes the sustainable development of agriculture combined with animal husbandry and virtuous cycle of matter and energy flow in the agricultural ecosystem. At the same time, it can also bring considerable economic benefits.At present, anaerobic fermentation with a single substrate has carried out a large number of researches, however, co-digestion is gradually been widely recognized at home and abroad with the advantages of high efficiency and stability. In addition, mesophilic anaerobic fermentation in north cold area often brings negative economic benefits, which makes the promotion of anaerobic fermentation technology limited. Therefore, in combination with the practical operation of HaiLin farm, this study discussed methane-producing efficiency using cow manure and corn straw as mixed substrate with a two-phase anaerobic digestion system. This research promoted a scheme about the optimization of operation parameters in view of the low temperature condition. The main research results were as follows.The four factors such as temperature and C/N were investigated on the effects of anaerobic fermentation biogas production efficiency by orthogonal design. Results showed the four factors on impact of biogas yield in order as temperature,TS,method of pretreatment,C/N, and finally got the optimal fermentation parameters from cow manure and corn straw for:35℃, straw with alkali treatment,15%TS, the C/N ratio of25:1.The acidification-phase was fed with cow manure and alkali treated straw according to the15%TS and C/N of25:1,and operated60d by the way of sequencing batch type under mesophilic fermentation of35℃. It had the lowest pH and the highest concentration of VFA and SCOD when operated at a HRT of48d, which is the optimal substrate for methanogenic-phase. TN had maintained within800~1000mg/L, which was favor to run the fermentation system stably and ammonia inhibition phenomenon wasn’t appeared. Starting-up and running the methanogenic-phase with a HRT of30d and an OLR of1.0kg VS/m3d and2.0kg VS/m3d,biogas and methane production reached720ml/L d and213ml CH4/g VS, and the efficiency of substrate converted methane presented positive correlation with OLR. Through analyses with FTIR and SEM, main ingredients in corn straw could be separated and degraded effectively during the operation of the acidification-phase.Research on efficiency of producing methane in gradient cooling way, biogas production decreased along with the lower temperature. It obtained a stable biogas production of4350ml/d at35℃, and when the temperature dropped to32℃,29℃,27℃and25℃, production decreased by9.30%,30.23%,45.35%and9.30%respectively. It had not significant effect on methane content by the change of temperature and the value remained between55.4%and57.5%. The highest biogas production was2850±60ml under an OLR of3.0kg VS/m3·d at25℃. The study showed biogas production and methane conversion rate reached at596.5ml/L d and113.9ml CH4/g VS in the condition of operating at a HRT of40d.
Keywords/Search Tags:two-phase anaerobic digestion, co-digestion, low temperature, organicwaste, biogas production
PDF Full Text Request
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