中煤级煤变形产气过程及其机理探讨

Gas generation during middle-rank coal deformation and the preliminary discussion of the mechanism

煤在变形作用过程中是否会发生化学变化而产生气体以及产气机理是长期争论的基础问题。以中煤级煤为例,进行了次高温高压变形产气实验,实验过程中尽量避免实验煤样中残存气体和可能发生热解作用对实验结果的影响。收集实验产出的气体并测试其成分,并结合不同变形条件下的煤的元素质量测试分析和红外光谱分析结果,得出:中煤级煤在发生变形作用过程中,能够产生新的甲烷气体;实验过程中,新产生甲烷气体的量受到实验温度、围压与轴压的影响,并表现出随着煤变形作用的增强而增加的趋势;随着煤变形的增强,煤结构中的C,H元素的含量和甲基含量均表现出逐渐降低的趋势。因此认为,煤在构造应力作用下发生变形时,不仅改变了煤的物理结构,而且能够改变其化学结构并产生甲烷气体,且变形越强烈,损失的C,H元素及甲基越多,产生的甲烷也越多。进一步提出构造(变形)煤中甲烷气体的赋存状态可能并非仅仅是传统观念的物理吸附,还可能存在以低键能化学键的形式赋存的化学吸附状态。

It is a long-debated issue if there is a chemical structure change and gas generation during coal deformation and if so,what is the mechanism of gas generation.In our work,sub-high-temperature and subhigh-pressure deformation experiments were performed on fat coal,and during the experiments,excluded the impact of the residual gas in coals and the process of pyrolysis.The gas generated in the experiments were collected for examination and the chemical variations of coals under different deformation conditions were revealed by elemental analysis and Fourier transform infrared spectrometer(FTIR).Conclusions are achieved as following:The middle-rank coal can generate methane during the deformation process;The amount of collected gas in the experiments,which shows an increasing trend with the reinforcement of coal deformation,is affected by the experimental temperature,confining pressure and axial pressure;By contrast,the content of car-bon and hydrogen element as well as methyl shows a decrease trend with the enhancement of coal deformation.Based on the above results,conclude that the deformation under tectonic stress can not only change the physical structure of the coal,but also change its chemical structure,and thus contributes to the generation of methane.Further evidence demonstrate that the more strongly it deforms,the more carbon,hydrogen and methyl will decrease,and meantime the more methane will be produced.Besides,we also propose that the methane can exist in coals not only by physical adsorption as we typically expect,but also in the form of weak chemical bonds,which is chemisorption.