【作者】 王爱宽；

【导师】 秦勇；

【作者基本信息】 中国矿业大学 ， 地球化学， 2010， 博士

【摘要】 阐明微生物与煤中有机质相互作用而生气的特征和机理,是深入理解煤层气成因及创新煤层气开采方法的重要基础。为此,本文以昭通盆地褐煤为对象开展次生生物煤层气生成的模拟实验研究,并对生气机制进行了探讨。研究发现,褐煤样品中有本源活性厌氧细菌存在,以厌氧纤维素分解菌为主,硫酸盐还原菌极少;成功富集到本源产甲烷菌,以革兰氏阳性杆菌为主,个体差异较大。在此基础上,以富集到的本源菌为菌源,利用褐煤样品为底物进行了生物气生成模拟实验。结果表明:本源厌氧菌经过适应期后,能够利用褐煤有机质大量生气;次生生物气经历了两个产气周期,第一周期为腐植组产气期,第二周期是惰质组、稳定组产气期。认为产甲烷菌数量和腐植组含量直接影响生成潜力,矿物质对生气量影响明显;第一个周期的生气机理是乙酸发酵,第二个周期有CO2还原作用参与其中。结果显示:所生成甲烷的δ13C1值和δD均处于次生生物气正常范围;δ13C1随着降解时间延长而变轻,这主要受底物类型和甲烷生成途径控制;12C有明显从原煤向生物气中迁移的特征,认为母源继承关系和显微组分构成是造成迁移行为差异的重要原因。同时发现:在厌氧细菌降解作用下,褐煤族组分中饱和烃是受微生物降解的主要成分,厌氧细菌对偶数碳烷烃的降解能力更强,对正构烷烃的降解能力强过对异构烷烃的降解,低碳数的正构烷烃受降解程度大于高碳数烷烃,降解后期长链烷烃才受到明显的生物降解作用。基于实验结果认为,褐煤次生生物气产出是多种微生物共同作用的结果。随降解活动的进行,体系中优势微生物、生物酶发生改变和更替,引起pH值和VFA含量变化。降解初期发酵细菌为优势菌种,产甲烷菌和辅酶F420活性受到酸性物质的抑制。随后,产氢产乙酸菌成为优势菌,它们利用发酵细菌代谢产物产生乙酸和氢,两者之间具有食物链关系。辅酶F420活性在静止期后增长迅速,并在产气高峰期达到最大,体现本源产甲烷菌对褐煤底物的良好适应性,是评价产气量高低的有效指标。通过改变生气条件,研究底物类型、褐煤粒度、矿井水和煤矸石对褐煤生物气生成的影响。结果表明:不同配比的酵母浸出液、甲醇和乙酸钠溶液对生物气生成具有抑制或激活作用,较小粒度褐煤有利于提高生气率,不同比例矿井水的添加能够有效增加次生生物气产量。煤矸石本身不能作为基质被厌氧细菌利用。更多还原

【Abstract】 Elucidating the characteristics and mechanism of the reaction of microorganisms and organic matter in coal to produce bio-gas is a very important foundation to the further understanding of the genesis of coalbed gas and the innovation of coalbed gas exploration. So we select the brown coal in Zhaotong basin as the research object to study the generation of secondary biogenic coalbed gas, and then discuss its generation mechanism.The results show that, the brown coal samples have active anaerobic bacteria, in which cellulose decomposition bacteria are in the majority and sulfate-reducing bacteria are very few. Local methanogen are successfully enrichment cultivated and they are mainly G+ bacillus, and the individual sizes have large differences. Based on that, the local bacteria and brown coal samples are selected as bacterial sources and substrates to study the generation of secondary biogenic gas from the brown coal. The results prove that, after resting period, the local anaerobic bacteria could use the brown coal to produce a large amount of biogenic gas. Secondary biogenic coalbed gas has two generation periods. The substrate that is biodegraded to produce gas in the first period is humic matter, which in the second period is inertinite and liptinite. The amount of methanogen and content of humic matter in the brown coal influences the generation potential of secondary biogenic coalbed gas directly and the mineral in coal has significant effect on the production of the secondary biogenic coalbed gas. The generation path way of CH4 in the first cycle is acetate fermentation and the second with CO2-reduction involved.The results show that, the value of bothδ13C1 andδD of the produced CH4 are in the normal distribution ranges compared with those of biogenic methane. With the time increasesδ13C1 decreases, which is mainly controlled by the substrate style and the generation path way of CH4. 12C significantly transfers from raw coal to biogenic methane and the reason may be the inheriting from original source and the component of organic maceral in coal. Meanwhile, it is found that, by the degradation of anaerobic bacteria, saturated hydrocarbon in the brown coal group is the main biodegraded composition. Anaerobic bacteria degradation ability to even-numbered alkane is stronger than to odd-numbered alkane, to n-alkanes stronger than to isoalkane, to n-alkanes with lower carbon number stronger than to n-alkanes with more carbon number, and only in the later stage of biodegradation the long chain alkanes starts to be degraded by bacteria significantly.Based on the experimental results, the generation of secondary biogenic coalbed gas from brown coal is considered to be the result of interaction of various microorganisms. With the biodegradation, the dominate bacteria and enzyme in the system are changed and replaced, which leads to the changes of pH and concentrations of VFA. In the initial stage of biodegradation, fermentation bacteria is the dominate bacteria and methanogen and activity of coenzyme F420 are inhibited by the acid matter produced by fermentation bacteria. Syntrophic acetogenic bacteria become dominate bacteria followed by fermentation bacteria. They use the metabolites from fermentation bacteria to produce acetate and H, which shows the food chain relationship with fermentation bacteria. Activity of coenzyme F420 increases quickly after resting period and reaches the maximum at the peak of biogas generation, showing the good adaptability of local methanogen to brown coal substrate and activity of coenzyme F420 is the effective index to evaluate the biogas production.Through changing the gas production conditions, the effects of different styles of substrate, brown coal size, mineral drainage and gangue on the generation of secondary biogenic coalbed gas from brown coal are studied. The results show that, different ratios of yeast extract, methanol and odium acetate solution have inhibition or activation effect on the generation of the secondary biogenic coalbed gas. Smaller brown coal size is good for increasing the gas production. The adding of mining drainage with different proportions activates the production of the secondary biogenic coalbed gas effectively. Gangue itself can not be substrate used by anaerobic bacteria.更多还原