无烟煤基质表面CO2和CH4的吸附热力学分析
Adsorption Thermodynamics Analysis of CO2 and CH4 on Anthracite Matrix Surface
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摘要: 以四川煤田无烟煤为研究对象,采用高精度智能重量吸附仪测定了288、308、328 K 3个温度下CO2和CH4的吸附等温线,分析了CO2和CH4在煤基质表面的吸附热力学特性。结果表明:CH4的亨利常数低于CO2,CH4在煤基质表面的吸附亲和力较弱;温度可以降低亨利常数,进而减弱CO2和CH4与煤的相互作用;CH4的负值的吉布斯自由能变和表面势能大于CO2,CO2在煤上吸附的自发性更高,吸附也更容易;随着压力增大,负值的吉布斯自由能变和表面势能逐渐减小,高压更有利于气体的吸附;CO2的等量吸附热和熵变随吸附量的增加呈现增加趋势,而CH4的等量吸附热和熵变随吸附量的增加呈现降低趋势;CO2的等量吸附热和熵变大于CH4。Abstract: Taking the anthracite sampled from Sichuan coalfield as the research object, the adsorption isotherms of CO2 and CH4 at the temperatures of 288 K, 308 K and 328 K are determined by the high precision intelligent weight adsorption instrument, and the adsorption thermodynamics properties of CO2 and CH4 on coal matrix surface are studied. Research results show that Henry’s constant of CH4 is lower than that of CO2, and CH4 has the weaker affinity on coal matrix surface. The increase of temperature can reduce Henry’s constant and thereby weaken the interaction of coal matrix surface and both of gases. The negative Gibbs free energy change and surface potential energy of CH4 are higher than those of CO2, which reveals that CO2 adsorption on anthracite is more spontaneous and favorable. With the increase of pressure, the negative Gibbs free energy change and surface potential energy decrease gradually, and the high pressure can facilitate gas adsorption. With the increase of adsorption amount, the isosteric heat of adsorption and entropy loss of CO2 rise, while the isosteric heat of adsorption and entropy loss of CH4 decrease. The isosteric heat of adsorption and entropy loss of CO2 are both bigger than those of CH4.