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煤制生物气产出规律及其同位素分馏效应

Production law of biogenic gas made from coal and its isotope fractionation effect
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摘要 为了探索生物成因煤层气机理,选取低阶煤作为煤制生物气的母质,采用携带产甲烷菌的煤层矿井水为菌源,在高纯氮气环境中向500 mL产气瓶(反应瓶)中加入40 g煤样、20 mL富集后的菌种液、380 mL培养基完成接种,之后将产气瓶置于37℃下的振动培养箱中开展为期90 d的厌氧产气模拟实验。研究结果显示,在厌氧封闭条件下,气体产出方式以乙酸发酵为主,产气效率较慢,产气过程受环境pH值的影响较大,进入产气稳定期后(>30 d),pH值与校正后的产气量随产气时间延续总体呈现同步变化规律,产酸菌与产甲烷菌的数量、丰度和活性直接影响了产气环境的pH值和产气量。产出气组分以CH4和CO2为主,存在极少量的氢气,气体组成偏干,CH4和CO2含量随稳定产气时间的延长呈现明显的同步变化规律。90 d的产气过程中,δ^13C1值均小于-55‰;δ^13C(CO2)值介于-20.8‰~-10.7‰,平均为-16.38‰;δD1值介于-361‰~-332‰,平均为-348‰,可以判定产出气中CH4和CO2均为有机生物成因气;煤制生物气中CH4和CO2碳同位素组成变化的主要原因是2次重要的继承性同位素分馏效应造成的,第1次分馏作用发生在生成乙酸过程中,由于有机母质本身脂族甲基碳同位素组成偏轻,而羧基碳同位素组成偏重,这种碳同位素组成特点在生成乙酸过程中得以继承;第2次分馏作用发生在乙酸发酵生成CH4和CO2过程中,乙酸中的甲基通过加氢形成CH4,而羧基通过去氢形成CO2,造成甲基本身的轻碳同位素被分馏到CH4中,而羧基的重碳同位素被分馏到CO2中。因此总体表现出产出生物气的轻碳同位素被分馏到CH4中,而重碳同位素被分馏到CO2中,δ^13C1越轻,δ^13C(CO2)越重,两者呈现负相关关系;90 d的产气时间里,微生物作用时间越长,甲烷碳同位素组成越轻,具有明显的富集轻碳同位素的趋势。 To explore the mechanism of biogenic coalbed methane,the low-rank coal was selected as the parent material of biogenic gas,and the coalbed mine water carrying methanogenic bacteria was used as the source of bacteria.In a high-purity nitrogen environment,a 40 g of coal sample,20 mL of enriched bacterial solution,and 380 mL of medium were added into the 500 mL gas producing cylinder(reaction cylinder)for inoculation.After that,these gas producing cylinders were placed in a vibration incubator at 37℃for a 90-day anaerobic gas production simulation experiment.Results show that the gas production mode is dominated by an acetic acid fermentation in a closed condition.Gas production efficiency is relatively low,and the process of gas production is greatly affected by the environmental pH.After entering the gas production stable period(>30 d),the pH value and the corrected gas production generally show a synchronous variation law with the gas production time.The number,abundance and activity of acid-producing bacteria and methanogens directly affect the gas environment pH and gas production.CH4 and CO2 are the main components of the produced gas,with a small amount of hydrogen.The CH4 and CO2 contents show an obvious synchronous variation law with the extension of stable gas production time.During the 90-day gas production process,theδ^13C1 value is less than-55‰,and theδ^13C(CO2)value is between-20.8‰~-10.7‰,with an average of-16.38‰.TheδD1 value is between-361‰~-332‰,with an average of-348‰.It can be determined that CH4 and CO2 in the gas production are organic biogenic gas.The change of carbon isotope composition of CH4 and CO2 is mainly caused by two important inherited isotope fractionation effects.The first fractionation of carbon isotope composition occurs in the process of acetic acid formation,due to the aliphatic methyl carbon isotope composition of organic parent material is relatively light,while the carboxyl carbon isotope composition of that is relatively heavy.The carbon isotope composit
作者 简阔 傅雪海 韩作颖 许小凯 周丹 茹忠亮 王观宏 郭晨 JIAN Kuo;FU Xuehai;HAN Zuoying;XU Xiaokai;ZHOU Dan;RU Zhongliang;WANG Guanhong;GUO Chen(College of Energy and Materials Engineering,Taiyuan University of Science and Technology,Jincheng 048011,China;State Key Laboratory of Coal and CBM Co-mining,Jincheng 048012,China;Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process,Ministry of Education,China University of Mining and Technology,Xuzhou 221008,China;College of Geology and Environment,Xi’an University of Science and Technology,Xi’an 710054,China)
出处 《煤炭学报》 EI CAS CSCD 北大核心 2020年第7期2602-2609,共8页 Journal of China Coal Society
基金 国家自然科学基金资助项目(41904118) 山西省煤层气联合研究基金资助项目(2015012001) 山西省应用基础研究计划面上青年基金资助项目(201901D211284)。
关键词 生物成因气 继承性同位素分馏效应 产气规律 低阶煤 乙酸发酵 biogenic gas inherited effect of isotope fractionation gas production law low-rank coal acetic acid fermentation
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