不同煤阶煤体吸附储存CO_2膨胀变形特性试验研究

Experimental study on swelling characteristics of CO_2 adsorption and storage in different coal rank

利用自主研发的气体等温吸附装置并辅以TST3827动静态应变测试系统,针对4种不同煤阶的煤样试件,在恒定温度(50℃)不同吸附压力条件下,研究了不同煤阶煤样CO_2吸附特性及煤样的吸附变形规律。结果表明:煤体CO_2吸附量与煤阶密切相关,在相同的吸附压力条件下,CO_2吸附量随着煤阶的增大而增大;不同煤阶煤样的等温吸附曲线类似,煤样的CO_2过剩吸附量随吸附压力变化曲线呈现出先升高后降低的特点,在8 MPa左右达到最大值;不同煤阶煤体吸附CO_2后引起的变形也具有类似的变化趋势,即随着CO_2压力的增大,体积应变先增大后趋于稳定,体积应变可以用引入CO_2密度的DR模型进行描述,且随着煤阶的增大,体积应变逐渐减小;由于煤体层理结构特征,煤体在垂直于层理方向的应变约为平行于层理方向应变的1.8~2.3倍;煤体体积应变与绝对吸附量在气态CO_2中呈线性增长关系,当CO_2达到超临界状态以后随着绝对吸附量增加体积应变趋于稳定,且煤体吸附相同量CO_2产生的体积应变随煤阶的增大而减小。

Based on the gas isothermal adsorption device developed by ourselves and the TST3 827 dynamic and static strain test system,the isothermal adsorption test of CO2 was carried out under different adsorption pressure conditions at constant temperature（ 50 ℃） for four different coal samples to study the adsorption capacity of different coal rank samples in CO2 and the swelling caused by adsorption.The results show that the adsorption capacity of CO2 is closely related to the coal rank.Under the same adsorption pressure,the adsorption capacity of CO2 increases with the increase of coal rank.The isothermal adsorption curves of different coal rank samples are similar,and the excess adsorption capacity of coal samples increases first and then decreases with the adsorption pressure,and reaches the maximum at about 8 MPa.The deformation of the different rank coal due to adsorption in CO2 also has a similar trend,that is,with the increase of CO2 pressure,the volume strain increases first and then tends to be stable,and the volume strain can bedescribed by DR model introducing CO2 density,and with the increase of coal rank,the volume strain gradually decreases.Due to the structural characteristics of the coal,the strain in the direction perpendicular to the bedding is about1.8-2.3 times that of the parallel strain in the bedding direction.The volume strain and the absolute adsorption capacity of the coal are linearly increasing in the gaseous CO2,and when the CO2 reaches the supercritical state,the volume strain tends to be stable with the absolute adsorption capacity,and the volumetric strain of coal with the same adsorption amount of CO2 is reduced with the increase of coal rank.