温度效应下煤体吸附瓦斯热力学及动力学特征

Thermodynamicand kinetic characteristics of gas adsorption by coal under temperature effect

为研究煤体与瓦斯相互作用的热力学与动力学特征,利用自主研发的煤系气流固耦合试验平台,开展298、308、318、328、338 K温度点煤体等温吸附试验,分析温度效应下煤体吸附瓦斯热力学参数、吸附动力学特征。试验结果表明:随温度升高,煤体瓦斯吸附量逐渐降低,等温吸附曲线符合Langmuir型变化规律;煤体等量吸附热随吸附量的增加而增大,变化范围为-10.191~-7.127 kJ/mol;煤体吸附瓦斯为放热物理过程,温度升高抑制煤体吸附瓦斯能力,煤体极限吸附热为-11.369 kJ/mol;不同温度吸附自由能和吸附熵均小于0,分别为-6.958~-2.452 kJ/mol和-14.085~-12.607 J/(mol·K);动力学模型拟合中,吸附平衡时的瓦斯吸附量随温度升高而降低,吸附速率常数与温度呈正线性关系。煤体吸附瓦斯为动态放热过程,随温度升高,瓦斯气体分子能量逐渐大于煤体孔隙吸附势能,吸附质态瓦斯逐渐转变为游离态瓦斯,煤体吸附瓦斯能力下降。

In order to study the thermodynamic and kinetic characteristics of the interaction between coal and gas,the isothermal adsorption tests of coal at 298,308,318,328 and 338 K were carried out.In this paper,the thermodynamic parameters and adsorption kinetic characteristics of coal gas adsorption under temperatures effect were analyzed by using the self-developed coal gas-solid coupling test platform.The results show that with the increase in temperature,the gas adsorption capacity of coal decreases gradually,and the isothermal adsorption curve conforms to the Langmuir type change rule.The isosteric adsorption heat of coal increases with the increase of adsorption capacity,and the variation range is-10.191 to-7.127 kJ/mol.The adsorption of coal gas is an exothermic physical process.The increase in temperature inhibits the adsorption capacity of coal gas,and the limited adsorption heat of coal is-11.369 kJ/mol.The adsorption free energy and adsorption entropy at different temperatures were less than 0,which were-6.958 to-2.452 kJ/mol and-14.085 to-12.607 J/(mol·K),respectively.In the kinetic model fitting,the gas adsorption amount at adsorption equilibrium decreases with the temperature increase,and the adsorption rate constant is positively linear with temperature.The adsorption of coal gas is a dynamic exothermic process.With the increase in temperature,the molecular energy of gas is gradually greater than the adsorption potential energy of coal pores.The adsorbed gas gradually transforms into free gas,and the adsorption capacity of coal gas decreases.