褐煤热损伤过程中的孔裂隙细观特性研究
Study on Mesoscopic Characteristics of Pores and Cracks During Thermal Damage of Lignite
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摘要: 利用高温气体加热设备,对褐煤进行不同温度的加热处理,通过电镜扫描观察到其表面的破坏形式,利用高精度的CT对试样进行X射线扫描,从宏观方面得到其破坏形式的同时对CT图像进行二值化处理,得到不同温度段褐煤的孔隙率以及裂纹的长度以及宽度。结果表明:温度作用下,褐煤固体颗粒之间产生热应力使得有机质得到热解的现象称为热破裂;热破裂效应在温度高于200 ℃后作用明显,200 ℃以下,褐煤孔裂隙演化主要是因为内部自由水及气体散失导致,200 ℃以后,热破裂占据主导作用,孔裂隙发育增幅变大,孔隙率较常温状态下增加了6.83%;热损伤低温阶段,褐煤破坏以细长裂隙为主,当温度高于200 ℃后,破坏形式以不规则的椭圆形为主。Abstract: Using high temperature gas heating equipment, lignite is heated at different temperatures. The failure forms on the surface were observed by scanning electron microscopy, and the samples were X-ray scanning with high-precision CT. The failure forms were obtained macroscopically and the CT images were processed in binarization to obtain the porosity of lignite and the length and width of cracks in different temperature sections. The results showed that under the action of temperature, thermal stress generated between solid particles of lignite resulted in the pyrolysis of organic matter, which is thermal fracture. The thermal fracture effect is obvious when the temperature is higher than 200 ℃. Below 200 ℃, the evolution of lignite pores and fractures is mainly caused by internal free water and gas loss. After 200 ℃, thermal fracture played a dominant role, and the growth rate of pores and fissures increased greatly, and the porosity increased by 6.83% compared with normal temperature. In the low temperature stage of thermal damage, the destruction of lignite is dominated by long and thin cracks. When the temperature is higher than 200 ℃, the failure form is dominated by irregular ellipses.
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