Study On The Influencing Factors Of Lignite Microbial Gas Generation And The Correlation Between Microbial Population And Metabolism

The existing scale of natural gas resources is difficult to meet China's growing industrial and living needs.The development of unconventional natural gas can not only reduce the cost of coal resource extraction,but also an inevitable requirement for sustainable energy development.Coalbed methane can be divided into thermogenic coalbed methane and biogenic coalbed methane according to the formation reasons.At present,researchers generally believe that biogenic coalbed methane is mainly converted from large-scale organic compounds in coal to small molecules by the original methanogenic flora in the coal bed Organic compounds are then converted into biomethane.In this paper,the methanogenic bacteria enriched in the coal seam produced water from the Sihe mining area in Shanxi Province was used as exogenous bacteria to conduct biogas production experiments on Shenghua Shengli lignite in Inner Mongolia.The significant effects of particle size and other factors on methane generation were investigated,and the correlation analysis between flora,gas production and environmental factors was performed.Qualitative and quantitative analysis of the bacterial flora before and after feeding in the biological gas-forming process,the liquid chromatography-mass spectrometry technique was used to determine the metabolites contained in the sample supernatant at different periods,and the inherent relationship between the bacterial flora and metabolism was established.The residual coal after microbial fermentation was quantified by FTIR experiments and infrared peak fitting.The study found:(1)The results of single factor analysis of variance showed that the lignite particle size factor had a significant effect on gas production,and the 90-day fermentation cycle particle size factor group(160 mesh)had the best gas production.Correlation analysis showed that the content of methanogens Methanosarcina and Methanobacterium increased with the increase of coal particle size in the particle size factor group,and the gas production also increased significantly.(2)The methane content of the experimental group supplemented with inorganic nitrogen increased again after a short period of 51 days,and the methane production continued to increase,reaching 703 m L at the 90 th day,a 29.5% increase compared with the control group.Bacterial high-through put test results show that Clostridium,Citrobracter,Desulfovibrio,Pseudomonas,Paraclostridium,Bacteroides,Macellibacteroides,Rummeliibacillus,Enterococ cus,Morganella,etc.are more abundant bacteria types.Archaea are Methanobacterium,Methanocorpusculum,Methanosarcina,Methanospirillum,Methanofollis,Methanoculleus,Candidatus Methanomethylophilus,etc.The results of real-time quantitative PCR showed that the bacterial population of bacteria and archaea had fallen to a low level before feeding.The supplementation of nitrogen source caused the bacterial population to grow and reproduce rapidly,and the methane production and content ratio increased again.(3)The components of metabolites have changed significantly during the fermentation gas production process.The most compound species were detected in the supernatant at 50 d,which is presumed to be closely related to the highest rate of methane production from lignite during this period.During the gas production process,the content of aromatic substances is continuously reduced,which indicates that these substances are continuously decomposed and used as the main matrix of gas production.The predominant Pseudomonas in the samples collected at the initial stage of gas production has the function of synthesizing biological surfactants,which can partially dissolve lignite and degrade aromatic substances at the same time.The existence of Clostridium runs through the entire fermentation process.It is a type of anaerobic fermentation bacteria that can degrade aromatic compounds and produce various organic acids.It may also play the role of fatty acid oxidant.Desulfovibrio belongs to ?-proteobacteria and is an obligate anaerobic bacterium.In addition to generating methanogenic substrates,it also provides a hydrogenase electron donor for methanogenic bacteria.It is speculated that the supplementation of nitrogen source caused the increase of Desulfovibrio content,which explained the increase of methane production to some extent.The sequencing results showed that Methanosarcina was always in a dominant position in the archaeal flora,indicating that acetylated methanogenesis was the main route.(4)Compared with the raw coal sample of the control group,some groups of lignite changed after microbial degradation,indicating that the microorganisms affected the chemical structure of the coal sample during the gas production process.At the same time,some groups change regularly with the change of influencing factors(particle size mesh number).Compared with other groups,the high-mesh array with the best gas production has the lowest degree of aromatic ring condensation,the lowest degree of branching of the fatty chain,and the highest degree of loss of oxygen-containing functional groups such as hydroxyl groups.