等压扩散下CO2对不同变质程度煤中CH4置换效应的影响

为了研究等压扩散条件下不同变质程度煤中CO₂置换CH₄特征规律，选择无烟煤、瘦煤和气肥煤3种煤样，进行了不同等压扩散压力下的等压扩散置换实验。实验结果表明:随着煤变质程度的增加煤吸附CH₄和CO₂的能力表现出逐渐增强的趋势，且CO₂的吸附量大于CH₄的吸附量；随着实验点扩散压力的增加，CO₂对CH₄的绝对置换量和置换率均随之增加，CO₂对CH₄的注置比却随之降低。在实验煤样变质程度范围内，CH₄置换率与煤变质程度和CO₂注置比均呈负相关关系。研究成果对井下注CO₂置换煤层CH₄的工程技术和理论具有指导意义。 

Influence of CO2 on the replacement effect of CH4 in coal of different metamorphic grade under isobaric diffusion

To study the characteristics of CH₄ replacement by CO₂ under isobaric diffusion, samples of metamorphic coal, anthracite, lean coal and gas-fat coal were selected to carry out experiment of isobaric diffusion replacement under different isobaric diffusion pressure. Experimental results show that with the increase of coal metamorphism, the CH₄ and CO₂ adsorption capacity of coal is gradually enhanced, and the CO₂ adsorption capacity of coal is greater than CH₄; with the increase of diffusion pressure at the experimental point, the absolute volume and replacement rate of CO₂ for CH₄ increases, but the CH₄ replacement ratio of CO₂ injection decreases. In the range of the metamorphic degree of the experimental coal samples, the CH₄ replacement rate is negatively correlated with the coal metamorphism degree and ratio of replacement to CO₂ injection. The research results have guiding significance for the engineering technology and the theory of CH₄ replacement by injecting CO₂ into coal seam.