秦雷 王平 林海飞 赵鹏翔 马超 石钰

摘 要：为精细化表征低温液氮作用下的煤体孔隙结构，运用氮气吸附法与压汞法，针对褐煤、烟煤和无烟煤3种煤阶，进行液氮冻结处理煤样的孔隙测试和分析。通过孔径分布和比表面积分布2个参数描述液氮冻结前后煤体孔隙结构的变化。实验结果表明，经过单次液氮冻结180 min后，在同一压力下，3种煤体氮气吸附量增加，进汞量增加;3种煤体孔隙的孔径增加。研究得出，单次液氮冻结180 min后，3种煤体的孔径和孔容出现增加，比表面积出现减少;单次液氮冻结处理对不同煤体作用效果不同，褐煤孔容增加最为明显，增加了0.017 8 cm3/g，烟煤孔容增量仅为褐煤孔容增量的35.4%.无烟煤比表面积减少了0.000 8 cm3/nm/g，分別为褐煤和烟煤比表面变化量的2.67倍和1.6倍。高阶煤体微孔发育程度高于中低阶煤体，经过单次液氮冻结180 min处理，煤体孔隙结构改变明显。关键词：液氮致裂;氮气吸附;压汞法;孔径分布;孔容中图分类号：TD 712

文献标志码：A

文章编号：1672-9315（2020）06-0945-08

DOI：10.13800/j.cnki.xakjdxxb.2020.0602开放科学（资源服务）标识码（OSID）：

Advanced characterization of pore structure of liquid nitrogen frozen

coal using nitrogen adsorption and mercury intrusion methods

QIN Lei1，2，WANG Ping1，2，LIN Hai-fei1，2，ZHAO Peng-xiang1，2，MA Chao1，2，SHI Yu1，2

（1.

College of Safety Science and Engineering，Xian University of Science and Technology，Xian 710054，China;

2.Key Laboratory of Western Mine Exploitation and Hazard Prevention，Ministry of Education，

Xian University of Science and Technology，Xian 710054，China）

Abstract：In order to finely characterize the pore structure of coal under the action of low-temperature liquid nitrogen more finely，the pore test  of coal samples treated with liquid nitrogen was carried out using nitrogen adsorption method and mercury intrusion method for three coal ranks of lignite，bituminous coal and anthracite.Two parameters of pore size distribution and specific surface area distribution are used to describe the changing of coal pore structure before and after freezing of liquid nitrogen.

The test results show that after a single freezing of liquid nitrogen for 180 minutes， under the same pressure，the nitrogen adsorption capacity of the three coals increases and the mercury intake decreases;the pore diameters of the three coals increase.The study concluded that after a single freezing of liquid nitrogen for 180 minutes，the pore size and pore volume of the three coal bodies increased， and the specific surface area decreased;the effect of a single freezing of liquid nitrogen on different coal bodies was different， and the pore volume of lignite increased most obviously.With an increase of 0.017 8 cm3/g， the pore volume increment of bituminous coal is only 35.4% of that of lignite.The specific surface area of anthracite changed by 0.000 8 cm3/nm/g， which was 2.67 times and 1.6 times of the change of the specific surface of lignite and bituminous coal，respectively.The degree of micropore development in high-rank coals is higher than that of low-and middle-rank coals. After a single freeze of liquid nitrogen for 180 minutes，the pore structure of the coal has changed significantly.

Key words：liquid nitrogen fracking;nitrogen adsorption;mercury intrusion method;aperture distribution;pore volume

0 引 言

瓦斯作为矿井五大灾害之首，长期影响煤矿安全生产[1]。据统计，2019年我国煤矿共发生瓦斯事故182起，占煤矿总事故的9.3%.同时，作为一种清洁能源，瓦斯的高效抽采利用可改善我国的能源结构[2]。无论是瓦斯防治还是利用，必须进行瓦斯抽采。由于我国煤层具有微孔隙、低渗透等特点，瓦斯抽采前必须对煤层进行增透。在煤層致裂技术方面，很多致裂手段被用于煤层增透中并取得了一些成果[3-7]，液氮致裂增透技术作为一种无水化煤层致裂技术逐渐受到重视[8-10]。……