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煤与瓦斯突出事件发生与否及突出强度,地下不可开采的煤层封存温室气体CO2,以及注CO2提高煤层甲烷的采收率,以上三个方面都与煤中CO2的吸附和扩散过程密切相关.应用自行研制的新装置,研究了CO2气体在河北峰峰矿区大淑村矿和梧桐庄矿、山西大同晋华宫矿三种煤样中吸附和扩散的性质,分析其等温吸附机理,并获得了扩散系数模型.结果表明,在一定压力范围内,煤体吸附CO2气体满足Langmuir单分子层吸附模型,其吸附等温线为非标准的双曲线形状;同一温度压力条件下,煤体的CO2吸附能力随其镜质组分含量的增加呈增大趋势,而中等煤级的煤样吸附能力最小.研究发现,CO2在煤体中的解吸扩散(出扩散)系数D并不是恒定不变的,而随质量分数(CO2分压)的降低而减小,一定范围内还与CO2的质量分数呈线性关系变化.本研究中,煤体CO2扩散系数的数量级约为10-4~10 2mm2/s,其中大淑村煤、梧桐庄煤、晋华宫煤中CO2扩散系数D值的总范围依次为3×10 4~8×10 3,2×10 4~4×10 3和2×10 4~4×10 3mm2/s.本文的吸附性研究和扩散系数模型能帮助研究煤与瓦斯突出、评价温室气体CO2的煤层封存和提高煤层甲烷采收率的可行性.
The occurrence of coal and gas outburst and its outstanding intensity, underground non-exploitable sequestration of greenhouse gas CO2, and injection of CO2 to improve the recovery of methane in coal seams, all of which are closely related to the process of CO2 adsorption and diffusion in coal. The adsorption and diffusion of CO2 gas in three coal samples, Dashucun Mine and Wutongzhuang Mine in Fengfeng Mining Area, Hebei Province, and Jinhuagong Mine in Datong, Shanxi Province were studied by means of a new device developed by ourselves. The isothermal adsorption mechanism was analyzed and obtained The diffusion coefficient model was established.The results show that the adsorption of CO2 gas on the coal satisfies Langmuir monolayer adsorption model within a certain pressure range and the adsorption isotherm is a non-standard hyperbolic shape. Under the same temperature and pressure conditions, Its ability increases with the increase of the content of vitrinite, while the adsorption capacity of coal sample of medium rank coal is the smallest.The study found that the coefficient of desorption diffusion (diffusion) coefficient of CO2 in coal is not constant, But decreased with the decrease of mass fraction (CO2 partial pressure), and also changed linearly with the mass fraction of CO2 within a certain range.In this study, the magnitude of CO2 diffusion coefficient of coal was about 10-4-102mm2 / s Among them, big The total range of the diffusion coefficient D of CO2 in coal, Wutongzhuang coal and Jinhuagong coal is 3 × 10 4 ~8 × 10 3, 2 × 10 4 ~ 4 × 10 3 and 2 × 10 4 ~ 4 × 10 3mm2 / s.The adsorption study and diffusion coefficient model in this paper can be used to study the coal and gas outburst, evaluate the sequestration of coalbed methane by greenhouse gases and improve the feasibility of coalbed methane recovery.