| In the current situation of shortage of energy resources,there is a kind of biomass energy-biogas has received widespread attention,and the construction of biogas projects at home and abroad has developed rapidly in recent years.However,biogas contains 0.1% 3% of H2S,which will cause serious corrosion to equipment and even cause safety accidents during use and transportation.Therefore,desulfurization of biogas is indispensable.Compared with the traditional desulfurization method,the in-situ desulfurization of the micro-oxygen method avoids the problems of large investment cost,high operating cost,troublesome replacement of the desulfurization agent,and will cause secondary pollution.This method improves the desulfurization efficiency and has broad development prospects.Based on the research of the research group,this paper builds a small test device that can continuously introduce trace oxygen,adopts the second feeding method for fermentation,and improves the measurement method of the daily biogas production,so that biogas can be obtained more accurately.The daily production of biogas can be obtained more accurately,and the daily H2S production can be used to control the oxygen flow.In this experiment,turfgrass was used as the fermentation substrate,and the biogas slurry was used as the inoculum.Under the condition of medium temperature?35±1??,and 0,1,2,3 times the oxygen content of H2S was introduced into the fermentation bottle.The effects of different feeding methods on the biogas gas production law and daily production were investigated.The effects of different oxygen fluxes on biogas production,biogas components,desulfurization efficiency,and VFAs concentration and p H in biogas slurry were investigated.After the fermentation,the high-throughput sequencing of the microbial community in the biogas slurry was conducted to analyze the effect of oxygen flux on the community structure of methanogens in the fermentation system.The experimental results show that the secondary feeding mode has changed the gas production law compared to the primary feeding mode.The daily biogas production and cumulative gas production of the mid-fermentation period showed significant turning points,which significantly increased the daily biogas production and cumulative production.In this feeding method,the amount of O2 that is 1,2,or 3times the amount of H2S is fed into the system.Compared with the control group,thebiogas production law of the experimental group has not changed significantly.Under the conditions of 2 and 3 times oxygen,the cumulative gas production of biogas is significantly higher than that of the control group,which is about 25.9% and 16.8%higher,respectively.The volume fraction and daily production of CH4 in the experimental group were higher than those in the control group as a whole.At the end of fermentation,the amount of CH4 produced by the 2-fold oxygen group reached the maximum value.The 3-fold oxygen group was slightly lower than the 2-fold oxygen group,but it was about 4.2 and 2.4 percentage points higher than the control group.The residual oxygen content at the initial stage of fermentation is high,and gradually decreases as the fermentation progresses,and remains at a low level.After the second feeding,it fluctuates,but gradually decreases.When the oxygen flux is 3 times,the residual oxygen content in the system is higher than that of the other groups,but it does not exceed 0.5%,which does not inhibit the fermentation.At the end of fermentation,the H2S removal efficiency of the 1 and 2 times oxygen groups reached73.3% and 93.1%,respectively,which was greatly improved compared to the intermittent oxygenation method.The H2S removal efficiency of the 3 times oxygen group reached 96.2%,and there was a flat trend,indicating that the amount of O2 continued to increase,and the desulfurization rate did not increase significantly.The accumulation of total VFAs is obvious in the early stage of fermentation,and trace O2 has a weak inhibitory effect on the stage of hydrogen and acetic acid production,but gradually disappears as the fermentation proceeds.And as the fermentation progresses,the consumption of isobutyric acid is the most obvious.The O2 introduced in the 2?3times oxygen group did not inhibit the degradation of VFAs.At the same time,the p H changes with the change of VFAs,and the overall trend is increasing,but it is always maintained in the range of 6.5 8.5.The introduction of trace oxygen changed the microbial community structure,but did not destroy the community structure of methanogens,and increased the community abundance and diversity of methanogens.Methanosaeta and Methanospirillum flora account for more than 80% of the total methanogens and are in an advantageous position.The introduction of trace oxygen into the fermentation system can effectively expand the advantages of Methanospirillum,Methanocorpusculum and Methanosarcina at the genus level,reduce the toxicity of H2S to methanogens,improve their activity,and promote the increase of biogas and methane production.Moreover,trace oxygen reduces the toxic effect of H2S on methanogens,improves the activity of methanogens,accelerates their growth and reproduction,greatly increases the content of methanogens in biogas slurry,and at the same time makes methane production continue to increase. |
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