液氮作用下煤体孔隙演变对吸附解吸特性的影响  

Effect of Pore Evolution on Adsorption and Desorption Characteristics of Coal Under the Action of Liquid Nitrogen

作　　者：李磊 李晓伟 王杰 赵东 LI Lei;LI Xiaowei;WANG Jie;ZHAO Dong(College of Safety and Emergency Management Engineering,Taiyuan University of Technology,Taiyuan,Shanxi 030024,China;Key Laboratory of In-situ Property Improving of Ministry of Education,Taiyuan University of Technology,Taiyuan,Shanxi 030024,China)

机构地区：[1]太原理工大学安全与应急管理工程学院,山西太原030024 [2]太原理工大学原位改性采矿教育部重点实验室,山西太原030024

出　　处：《矿业研究与开发》2021年第8期94-100,共7页Mining Research and Development

基　　金：国家自然科学基金项目(51904197);山西省自然科学基金项目(201801D121283)。

摘　　要：为研究液氮作用下煤体孔隙演变规律和液氮处理次数对甲烷吸附解吸特性的影响,以山西阳泉无烟煤为例,进行了液氮作用下孔隙演变的压汞试验和一系列吸附解吸试验。结果表明:(1)煤样经4次液氮处理后,不同尺度的孔隙数量均有不同程度的增加,其中液氮处理对大孔数量增加的贡献最大,液氮致裂增透归因于3个原因:孔隙连通,孔裂隙扩展,孔裂隙增生;(2)随着液氮处理次数的增加,液氮处理对甲烷最终吸附量的影响不断减弱,低吸附压力下Freundlich公式能够较好地描述甲烷的等温吸附;(3)改进的Lagergren吸附动力学公式能够更加准确的描述吸附量随时间的变化,煤吸附气体的时间效应几乎不受液氮处理次数的影响,液氮冻融损伤煤体能够促进煤中甲烷的解吸扩散渗流,煤样在液氮处理4次后解吸收益达到最佳。研究结论对原位煤层液氮致裂改性,增产煤层气工艺提供了理论依据。In order to study the pore evolution of coal under the action of liquid nitrogen and the effect of treatment times of liquid nitrogen on the adsorption and desorption characteristics of methane,the mercury intrusion experiments and a series of adsorption and desorption experiments were carried out on Yangquan anthracite coal in Shanxi Province.The results are concluded as follows.Firstly,after 4 times of liquid nitrogen treatment,the number of pores at different sizes increased in varying degrees in coal samples,and the liquid nitrogen treatment contributes the most to the increase of the number of macropores.The cracking and permeability enhancement caused by liquid nitrogen can be attributed to three reasons,including pore connectivity,pore fracture expansion and pore fissure proliferation.Secondly,with the increase of liquid nitrogen treatment times,the effect of liquid nitrogen treatment on the final adsorption capacity of methane is weakened continuously.In addition,the Freundlich formula can better describe the isothermal adsorption of methane at low adsorption pressure.Thirdly,the improved Lagergren adsorption kinetic formula can describe the change of adsorption capacity with time more accurately,and the time effect of coal adsorbed gas is almost not affected by liquid nitrogen treatment times.And the freeze-thaw damage of coal body can promote the desorption and diffusion of methane in coal.After 4 times of liquid nitrogen treatment,the desorption yield is the best.The study results can provide a certain theoretical basis for in-situ liquid nitrogen fracturing modification and increasing coalbed methane production technology.

关 键 词：液氮 孔隙演变 压汞试验 吸附动力学 强化解吸 

分 类 号：TD712[矿业工程—矿井通风与安全]