超声波作用下煤体微观结构的试验研究

Experimental study on micro-structure of coal by ultrasonic treatment

为了揭示声震法提高煤层气抽采率的微观机理,通过扫描电镜、比表面积及孔径分析仪、核磁共振分析仪,试验研究了超声波处理对煤微观结构的影响。试验研究表明:超声波的机械振动效应能清洗干净含水煤体表面及裂隙通道中的微颗粒,打开煤中的封闭孔,局部破碎松软煤体,产生新的裂隙;超声波处理后,煤的总孔容、比表面积、平均孔径、孔隙率增大,T_2谱峰值增大、煤孔裂隙连通性增加,有利于煤层气的解吸、扩散和渗流;超声波处理后,煤对N_2吸附量增加,吸附与解吸过程存在吸附滞后现象,形成较大的滞后环,滞后环属于类型C;煤的孔隙、裂隙结构受超声波空化效应、机械振动效应和热效应的影响。研究内容为声震法提高煤层气抽采率提供了依据。

This paper is devoted to reveal the microscopic mechanism of ultrasonic vibrating to improve coalbed methane extraction rate. The effects of ultrasonic treatment on the micro-structure of coal is investigated using scanning electron microscopy, surface area and aperture analyzer, and nuclear magnetic resonance analyzer. The results show that the vibration of ultrasonic can clean the micro-particles on the surface of the water-containing coal and in crack channel, open the sealing pores in the coal, and partially break the loose coal, thus creating new cracks in coal. After the ultrasonic treatment, the total pore volume, specific surface area, average pore diameter, porosity, and T2 spectrum peak of coal all increase. The connectivity of coal pore fracture also increases, which is beneficial to the desorption, diffusion, and seepage of coalbed methane. Furthermore, the N2 adsorption ability of coal increases after ultrasonic treatment because there is adsorption hysteresis in the process of adsorption and desorption, which results in the formation of a large type C hysteresis loop in the isothermal adsorption desorption curve. The porous and fissure structures of coal are changed by ultrasonic cavitation, mechanical vibration, and thermal effect. This study provides a reference for improving coalbed methane extraction rate using ultrasonic treatment.