基于压汞法的焦作矿区无烟煤孔隙特征研究

    Study on pore characteristics of anthracite in Jiaozuo Mining Area based on mercury intrusion porosimetry

    • 摘要: 煤的孔隙结构是瓦斯的主要赋存空间及运移路径。为明确焦作矿区无烟煤的孔隙结构特征,采用压汞法对其软煤、硬煤的孔隙结构特征进行研究,揭示煤样内部孔隙的复杂构造,分析软煤、硬煤的孔面积、孔体积及孔径分布等孔隙结构参数的差异性。结果表明:硬煤中的可见孔和裂隙构成了总孔体积的主要部分,占总孔体积的23.55%~63.72%,软煤的这一比例明显较低,仅为3.18%~30.82%;软煤的小孔、中孔和大孔体积普遍高于硬煤,这反映了两者在孔隙发育程度上的差异;软煤、硬煤的孔面积集中在孔径5.5~100.0 nm区间内,该范围的孔面积占总孔面积的94.3%~99.7%,即这一孔径范围在孔隙结构中占主导地位,其中,微孔面积占相当大的比例(52.5%~78.1%),而中孔和大孔面积之和相对较少,仅占0.3%~5.7%,可见孔和裂隙对孔面积的贡献微乎其微;软煤的进汞和退汞曲线不重合,这一现象说明相较于硬煤,软煤中含有更多的开放性孔隙及墨水瓶状孔隙;相反,硬煤的进退汞曲线高度重合,证明硬煤的孔隙连通性相较于软煤更为优良;通过压汞法测得的数据显示,软煤的平均孔径为34.8 nm,硬煤的平均孔径为35.6 nm,两者相差不大,均在20.1~58.5 nm范围内波动。

       

      Abstract: Coal pore structure serves as the main storage space and migration pathway for gas. To clarify the pore structure characteristics of anthracite in Jiaozuo Mining Area, mercury intrusion porosimetry was adopted to investigate the pore structure features of soft coal and hard coal. The complex pore structure inside coal samples was revealed, and the differences in pore structure parameters such as pore area, pore volume and pore size distribution between soft coal and hard coal were analyzed. The results show that visible pores and fractures in hard coal constitute the major portion of the total pore volume, accounting for 23.55%-63.72%, whereas this proportion in soft coal is considerably lower, only 3.18%-30.82%. The volumes of small pores, mesopores and macropores in soft coal are generally higher than those in hard coal, reflecting the difference in pore development degree between the two. The pore areas of soft coal and hard coal are concentrated in the range of 5.5-100 nm, which contributes 94.3%-99.7% of the total pore area, indicating that this pore size range plays a dominant role in the pore structure. Among them, micropore area accounts for a considerable proportion of 52.5%-78.13%, while the total area of mesopores and macropores is relatively small, only 0.3%-5.7%, and the contribution of visible pores and fractures to pore area is negligible. The mercury intrusion and extrusion curves of soft coal do not coincide, indicating that soft coal contains more open pores and ink-bottle-shaped pores compared with hard coal. In contrast, the mercury intrusion-extrusion curves of hard coal are highly overlapping, proving that hard coal has better pore connectivity than soft coal. The average pore size measured by mercury intrusion porosimetry is 34.8 nm for soft coal and 35.6 nm for hard coal, showing little difference between the two, both fluctuating within the range of 20.1-58.5 nm.

       

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