不同含水率条件下软煤等温吸附特性及膨胀变形特性

Isothermal adsorption and swelling deformation characteristics of soft coal under different moisture content

为研究水分对煤等温吸附特性及膨胀变形特性的影响,以软煤为研究对象,采用煤层瓦斯吸附解吸变形动态测试装置开展了不同含水率条件下煤吸附瓦斯过程中的吸附量与膨胀变形量同步测试实验,分析了水分对煤等温吸附特征和膨胀变形特征的影响,探讨了吸附膨胀变形量与吸附量的关系。结果表明,水分的存在抑制煤的吸附膨胀变形,煤样含水率由0增大到3.13%,极限吸附膨胀变形量由10.185×10-3线性减小到4.262×10-3,减小幅度为58.15%;而随着含水率的增加,饱和吸附量先减小后增加,含水率为1%左右时饱和吸附量达最小值。不同含水率煤样的吸附膨胀变形量与吸附量关系并不呈现单一规律:0~0.75%含水率的煤样含水率低,游离态瓦斯对煤膨胀变形整体表现为促进作用,煤样在吸附量达到饱和后仍能随瓦斯压力的增大继续产生膨胀变形,吸附膨胀变形量与吸附量呈抛物线拟合关系;煤样含水率增大到1.42%~1.66%时,水的软化作用和堵塞作用导致游离态瓦斯对煤基质的压缩作用产生的压缩变形量与对微裂隙的扩容作用产生的膨胀变形量抵消,吸附膨胀变形量达到极限值所需瓦斯压力与吸附量达到饱和所需瓦斯压力相当,吸附膨胀变形量与吸附量呈线性拟合关系;含水率进一步增大到2.66%~3.13%时,水的软化作用和堵塞作用使游离态瓦斯对煤膨胀变形整体表现为抑制作用,煤样在吸附膨胀变形量达到极限值后仍能随瓦斯压力的增大继续吸附瓦斯,吸附膨胀变形量与吸附量呈幂函数拟合关系。

In order to study the influence of moisture on the isothermal adsorption and swelling deformation characteristics of coal,taking soft coal as the research object,the synchro testing experiments were carried out to measure the swelling deformation and adsorption of coal in the process of gas adsorption under different moisture content by a Gas Adsorption/Desorption-induced Deformation Dynamic Testing Equipment.The influence of moisture on isothermal adsorption characteristics and swelling deformation characteristics of coal was analyzed according to the experiment results,the relationship between swelling deformation and adsorption has also been discussed.The results showed that,the existence of water inhibited the swelling deformation,the water content of coal samples increases from 0 to 3.13%,the limit swelling deformation decreases linearly from 10.185×10-3 to 4.262×10-3,with a decrease of 58.15%.With the increase of moisture content,the saturated adsorption decreased first and then increased,and the saturated adsorption reached the minimum value when the moisture content was about 1%.The relationship between the swelling deformation and adsorption is complex,obedient to various laws:When the moisture content is only 0-0.75%,the swelling deformation lagged behind the adsorption to the extreme value because of free gas promotes the swelling deformation of coal,and the swelling deformation and adsorption show a parabola fitting relationship.When the moisture content increased to 1.42%-1.66%,the compression deformation caused by the compression effect of free gas on the coal matrix is offset by the swelling deformation caused by the expansion of micro cracks due to the softening and blocking effects of water.The pressure required for the swelling deformation to reach the extreme value is equivalent to the gas pressure required for the adsorption to reach saturation,and the swelling deformation and adsorption show a linear fitting relationship.When the moisture content further increased to 2.66%-3.13%,the softening and blocking effect of water make the free gas inhibit the coal swelling deformation as a whole.After the swelling deformation reaches the extreme value,the coal samples can continue to absorb gas with the increase of gas pressure,and the swelling deformation and adsorption show a power function fitting relationship.