高温水蒸汽作用后长焰煤细观结构的显微CT研究

Micro CT study of microstructure of long flame coal after high temperature steam

利用显微CT技术研究了不同高温水蒸汽作用下长焰煤试样的细观结构。研究表明:热解温度低于300℃时,自由水及气体的散失造成裂纹的产生,当热解温度高于300℃时,有机质热解形成了相互贯通的裂隙网络,且孔裂隙主要在有机质内形成;热解分为3个阶段,300℃之前煤样缓慢热解,孔裂隙缓慢增加;300~500℃之间为热解加剧阶段,煤样孔隙率增加明显;热解温度高于500℃时,热解最为充分,煤样孔隙率急剧增加;550℃热解温度作用后,煤样的体孔隙率达到32.35%,较25℃下煤样的体孔隙率提高了9.82倍;300℃是热解阈值点,热解温度高于阈值点时,不同层理面发育良好,形成相互贯穿形成了孔隙网络,加快了热解作用,为热解产物提供了运移通道。

The microstructure of long flame coal samples subjected to different high temperature steam was studied by means of micro CT technique. The results show that when the pyrolysis temperature is lower than 300 ℃, the loss of free water and gas leads to the formation of cracks. When the pyrolysis temperature is higher than 300 ℃, the interconnecting crack network is formed in the pyrolysis of organic matter, and the pores and cracks are mainly formed in the organic matter. Pyrolysis can be divided into three stages. Before 300 ℃, coal samples are pyrolyzed slowly, and pores and cracks increase slowly. The pyrolysis intensifies between 300 ℃ and 500 ℃, and the porosity of coal samples increases obviously. When the pyrolysis temperature is higher than 500 ℃, the pyrolysis is the most complete and the porosity of coal samples increases sharply. After 550 ℃, the volume porosity of the coal sample reaches 32.35%, which is 9.82 times higher than that at 25 ℃. Moreover, 300 ℃ is the threshold point of pyrolysis. When the pyrolysis temperature is higher than the threshold point, different bedding planes are well developed,forming a pore network through each other, accelerating pyrolysis and providing a migration channel for pyrolysis products.