煤体理化结构特征及其对瓦斯吸附热力学的影响

为研究煤的理化结构特征及其对瓦斯吸附热力学的影响,通过低温液氮吸附实验和傅里叶红外光谱实验对煤的理化结构进行了表征,采用等温吸附实验测定了不同温度下贫煤和长焰煤的瓦斯吸附曲线,利用Langmuir模型和Freundlich模型分别对吸附数据进行了拟合,并基于2种模型计算了吸附热力学参数△G°。研究结果表明:基于Freundlich模型的吸附△G°适合描述瓦斯吸附热力学特性,不同温度下煤对瓦斯的吸附均为自发过程;长焰煤的孔隙结构更有利于吸附过程的进行,而贫煤的表面化学结构更有利于瓦斯的吸附;煤对瓦斯的吸附量受煤体孔隙结构及表面化学官能团的共同作用,吸附△G°可较好的体现煤体孔隙结构特征的差异,结合吸附量和吸附△G°可更全面地评价不同变质程度煤对瓦斯的吸附性能。

Characteristics of coal physicochemical structure and its effect on thermodynamic of gas adsorption

To study the physicochemical structure characteristics of coal and its effect on the thermodynamic of gas adsorption, the physicochemical structure of coal was characterized by low pressure nitrogen adsorption and FTIR experiment. The gas adsorption curves of lean coal and long-flame coal at different temperatures were measured using isothermal adsorption experiment. Langmuir model and Freundlich model were used to fit the empirical data and the thermodynamic parameter △G° based on two models was calculated. The results show that Freundlich model is suitable to describe the thermodynamic process of gas adsorption and the gas adsorption process is characterized by spontaneous at different temperatures. It was found that the pore structure of long flame coal is more beneficial to the adsorption process, while the surface chemical structure of lean coal benefits the adsorption process more.The joint action of pore structure and functional groups affects the adsorption capacity of gas. Besides, △G° obviously shows the different characteristics of pore structure of coal. Thus, the adsorption amount and △G° should be considered together for comprehensive evaluation on the adsorption performance of gas with different metamorphic degrees coals.