煤中可溶有机质对煤的孔隙结构及甲烷吸附特性影响

采用四氢呋喃对临涣7煤和祁南3煤进行微波辅助抽提,进行了原煤和残煤等温吸附实验和低温氮气吸附测试,对比分析了抽提前后原煤和残煤的甲烷吸附量和比表面积、孔分布情况,并理论测算煤中可溶有机质吸附溶解甲烷量.结果表明,残煤的甲烷吸附能力低于原煤;抽提后,煤的比表面积和总孔体积增大,平均孔径减少,影响煤吸附气体能力的主要孔径为1.7~5.0 nm,且该范围内的孔数有不同程度的增加;压力为0.1~5.0 MPa时,两煤样中可溶有机质吸附溶解的甲烷量分别为0.45~4.22 mL/g、0.69~4.99 mL/g,最大吸附量分别占到原煤最大吸附量的30%和38%.分析认为,煤中可溶有机质占据部分煤中孔隙,影响煤孔隙结构,同时,在压力的作用下,甲烷可以溶解和吸附煤中可溶有机质.

Effect of soluble organic matter in coal on its pore structure and methane sorption characteristics

In order to study the effect of soluble organic matter within coal on its characteristics of gas adsorption, the organic matters in coal seam 7＃ (Linhuan) and coal seam 3＃ (Qinan) were extracted with THF at 30 ℃ under atmospheric pressure by microwave-assistant extraction. Adsorption isotherm experiments and low temperature nitrogen adsorption test were made for raw coal and their residues. The gas adsorbance, specific surface area and pore size distribution were analyzed. Gas adsorbance of soluble organic matter was theoretically calculated. The results show that CH₄-adsorption capacity of raw coal is stronger than those of their residues. After extraction, the specific surface area and total pore volume increase and average pore size decreases. Meanwhile, methane adsorption capacity is mainly influenced by 1.7~5.0 nm pores. Methane adsorbances of soluble organic matter are 0.45~4.22 and 0.69~4.99 mL/g, which account for 30% and 38% of the maximum adsorption capacity of raw coal under 0.1~5.0 MPa. Soluble organic matter occupies part of pores of coal, which influences structure of pores in coal. At the same time, the methane can be dissolved and adsorbed in soluble organic matter of coal under pressure.