High-voltage thermal breakdown has great potential application in permeability enhancement of coal seam. The characteristics of the breakdown channel, coal element, porosity and microscopic coal petrography of coal un...High-voltage thermal breakdown has great potential application in permeability enhancement of coal seam. The characteristics of the breakdown channel, coal element, porosity and microscopic coal petrography of coal under high-voltage electric load were experimentally studied. The coal interior left apparent tracks due to electric current burning with high temperature. The percentage of C, O, Al, Fe, and Si had slightly decreased, while the content of element N increased obviously. Low-pressure nitrogen gas adsorption(LP-N_2GA) and mercury intrusion analysis showed that coal porosity increased. The increases of micropores and mesopores are beneficial to promotion of the ability of gas storage, and the increase of macropores could enhance the gas seepage and migration. The results of scanning electron microscope(SEM) show that there are many exogenous fractures in coal, which is also beneficial to gas seepage and migration. The results lay a theoretical foundation for application of high-voltage thermal breakdown in coal mines.展开更多
为了研究烟草粉尘阴燃发生的影响因素,运用锥形量热仪测定粉尘的热释放速率,改进现有的粉尘层最低着火温度测试仪,将3组不同粒径的的烟草粉尘置于热表面上进行阴燃实验研究。结果表明:制丝粉、切片粉、卷包烟末热释放速率峰值分别为90...为了研究烟草粉尘阴燃发生的影响因素,运用锥形量热仪测定粉尘的热释放速率,改进现有的粉尘层最低着火温度测试仪,将3组不同粒径的的烟草粉尘置于热表面上进行阴燃实验研究。结果表明:制丝粉、切片粉、卷包烟末热释放速率峰值分别为90、91、75 k W/m2,切片粉火焰传播速度最快。峰值最低的卷包烟末于50 s左右率先热释放,切片粉制丝粉随后分别于75、80 s左右进行热释放;阴燃过程可进行阶段性分析,其中水分蒸发燃料氧化放热阶段粉尘温度相对稳定攀升,于氧化放热阶段温度突变,因此控制阴燃的产生,必须于水分蒸发燃料氧化放热阶段之前控制其发展趋势,做出相应有效的预警方案;粉尘顶层率先发生阴燃,随后阴燃逐渐向下传播直至粉尘完全燃尽;粉尘层达到阴燃温度时,顶层升温速率最高,中层底层在未发生阴燃时,顶层阴燃有预热作用;阴燃时间和实验持续时间都是随着粒径的增大而增大;粒径越小阴燃各阶段持续时间越短,致使阴燃越迅速越难控制。展开更多
基金provided by the Scientific Research Foundation of the State Key Lab.of Coal Mine Disaster Dynamics and Control(No.2011DA105287-FW201509)the National Natural Science Foundation of China(No.51474211)the Innovation Team of CUMT(No.2014QN001)
文摘High-voltage thermal breakdown has great potential application in permeability enhancement of coal seam. The characteristics of the breakdown channel, coal element, porosity and microscopic coal petrography of coal under high-voltage electric load were experimentally studied. The coal interior left apparent tracks due to electric current burning with high temperature. The percentage of C, O, Al, Fe, and Si had slightly decreased, while the content of element N increased obviously. Low-pressure nitrogen gas adsorption(LP-N_2GA) and mercury intrusion analysis showed that coal porosity increased. The increases of micropores and mesopores are beneficial to promotion of the ability of gas storage, and the increase of macropores could enhance the gas seepage and migration. The results of scanning electron microscope(SEM) show that there are many exogenous fractures in coal, which is also beneficial to gas seepage and migration. The results lay a theoretical foundation for application of high-voltage thermal breakdown in coal mines.
文摘为了研究烟草粉尘阴燃发生的影响因素,运用锥形量热仪测定粉尘的热释放速率,改进现有的粉尘层最低着火温度测试仪,将3组不同粒径的的烟草粉尘置于热表面上进行阴燃实验研究。结果表明:制丝粉、切片粉、卷包烟末热释放速率峰值分别为90、91、75 k W/m2,切片粉火焰传播速度最快。峰值最低的卷包烟末于50 s左右率先热释放,切片粉制丝粉随后分别于75、80 s左右进行热释放;阴燃过程可进行阶段性分析,其中水分蒸发燃料氧化放热阶段粉尘温度相对稳定攀升,于氧化放热阶段温度突变,因此控制阴燃的产生,必须于水分蒸发燃料氧化放热阶段之前控制其发展趋势,做出相应有效的预警方案;粉尘顶层率先发生阴燃,随后阴燃逐渐向下传播直至粉尘完全燃尽;粉尘层达到阴燃温度时,顶层升温速率最高,中层底层在未发生阴燃时,顶层阴燃有预热作用;阴燃时间和实验持续时间都是随着粒径的增大而增大;粒径越小阴燃各阶段持续时间越短,致使阴燃越迅速越难控制。