煤中甲烷赋存形式是其吸附能力的表征，也是其扩散和渗透特性研究的基础，厘清煤中甲烷赋存形式对煤矿瓦斯抽采和灾害防治具有重要意义。运用低压氮气和低压二氧化碳吸附法对不同变质程度的6个煤样微观孔隙结构进行定量分析，基于微孔填充和单层吸附理论研究煤中甲烷极限吸附平衡状态，建立表征煤样甲烷吸附能力的量化方法，最后通过甲烷极限吸附实验结果验证理论结果的可靠性，获得甲烷在煤储层不同尺度孔隙结构中的赋存特征及其吸附能力的控制因素。结果表明:煤中0.38~1.50 nm孔隙结构的甲烷吸附能力受限于微孔孔容，而大于1.50 nm孔隙结构的甲烷吸附能力受孔隙表面积控制;6个煤样的孔隙结构中微孔孔容为0.028~0.065 cm³/g、占66.1%~96.6%，微孔比表面积为75.4~197.3 m²/g、占82.8%~98.2%;微孔填充计算的甲烷吸附量为14.50~32.27 cm³/g，孔隙外表面积计算的甲烷吸附量为0.10~7.31 cm³/g，计算的甲烷极限吸附量为14.60~33.35 cm3/g;通过实验获得的甲烷极限吸附量为13.30~35.75 cm3/g，与理论计算结果具有较好的相关性;说明煤中甲烷主要以微孔填充形式吸附在微孔孔隙中，5个煤样以微孔填充形式吸附的甲烷量超过极限吸附量的91%以上，0.38~0.76 nm微孔结构提供的甲烷吸附能力占总吸附能力的41.27%~55.32%;仅XQ煤样由于外比表面积的吸附作用，使其微孔填充形式吸附的甲烷量为极限吸附量的73.74%，0.38~0.76 nm微孔结构提供的甲烷吸附能力占总吸附能力的37.51%。

The form of methane storage in coal is the characterization of its adsorption capacity and the basis of methane diffusion and seepage studies.Therefore,clarifying the form of methane storage in coal is of great sig-nificance to coal mine gas extraction and disaster prevention.Based on low pressure N₂ adsorption and low pressure CO₂ adsorption experiments,the quantitative analyses were performed on investigating microscopic pore structures of six coal samples with different metamorphisms.A methodology for quantitatively characterizing the methane adsorption capacity of coal samples was proposed according to the investigation on the optimal adsorption equilibrium of methane in coal based on the theory of micropore filling and monolayer adsorption.The reliability of the theoretical results was then verified by the optimal methane adsorption experiments and the characteristics of methane occurrence in the pore structure of different scales in coal reservoirs and the control factors of its adsorption capacity were obtained.The study reveals that the methane adsorption capacity of the 0.38-1.50 nm pores in coal is mainly restricted by the micropore volume,as for the pores exceeding 1.5 nm,the methane ad-sorption capacity is controlled by the pores’external surface area.The volume of micropores of the six samples is 0.028-0.065 cm³/g,contributing 66.1%-96.6% of the total pore volume,and the specific surface area of the mi-cropores of the six samples is 75.4-197.3 m²/g,contributing 82.8%-98.2% of the total specific surface area.The adsorption capacity calculated through the micropore filling methodology,the external surface area of micropores and theoretical optimal adsorption is 14.50-32.27 cm3/g,0.01-7.31 cm³/g and 16.13-33.35 cm³/g,respectively.The optimal adsorption capacity obtained through the experiments is 13.30-35.75 cm³/g,which displays a good correlation with the theoretical calculations.The evidence above indicates that the methane in coal is mainly stored through the form of micropore filling.Five out of the six investigated samples’ methane adsorption amount through micropore filling exceed 91% of the optimal adsorption capacity,where the methane adsorption in the 0.38-0.76 nm microporous structure accounts for 41.27%-55.32% of the total amount.As an exception the methane adsorption amount through micropore filling of XQ sample contributes 72.73% of the optimal adsorption capacity due to its adsorption on the external surface,where the methane adsorption in the 0.38-0.76 nm microporous structure accounts for 37.51% of the total amount.

1 研究方法

   1.1 煤样制备

   1.2 煤的孔隙测定方法

   1.3 煤的甲烷吸附实验方法

   1.4 煤的甲烷吸附能力表征方法

2 实验结果

   2.1 煤的孔隙实验结果

   2.2 煤的甲烷吸附实验结果

3 煤中甲烷赋存方式讨论

   3.1 甲烷单分子层吸附的可能性

   3.2 甲烷分子微孔填充的可能性

   3.3 煤中甲烷的主要赋存方式

4 结论