不同变质程度煤介电常数特性

Dielectric constant characteristics of different metamorphic coals

为了研究煤的介电常数随变质程度与测试频率之间的关系,通过Concept 80宽带介电谱测试系统测试在0.1～1.0 GHz频段范围内褐煤、长焰煤、气煤、贫瘦煤和无烟煤的介电常数。结果表明:不同变质程度煤的介电常数随测试频率的增加先减小后增加,测试频率在0.3 GHz左右时介电常数值最小,在1.0 GHz附近介电常数值最大;同一测试频率下,贫瘦煤的介电常数最大,依次为褐煤、气煤、长焰煤,无烟煤的介电常数最小。此外,通过5E-MAG6700全自动工业分析仪来研究煤介电常数随变质程度的内在因素,可以发现,煤的水分含量、含碳量和灰分含量对其介电常数有一定的影响,但不是决定因素,以上结论对于超宽带电磁波在煤层中传播的实验频段选择和对井下被困人员超宽带雷达生命信息钻孔探测具有一定指导意义。

In order to study the relationship between the permittivity of coal with the degree of deterioration and the test frequency,the permittivity of lignite,long-flame coal,gas coal,lean coal and anthracite in the range of 0.1~1.0 GHz frequency range were tested with the Concept 80 Broadband Dielectric Spectrum Test System.The results show that the permittivity decreases first and then increases with the increase of test frequency.When the test frequency is around 0.3 GHz,the dielectric constant value is the lowest,and the dielectric constant value is the highest around 1.0 GHz.At the same test frequency,the permittivity of lean coal was the largest,followed by lignite,gas coal and long flame coal,and the permittivity of anthracite was the smallest.In addition,through the 5 e-mag 6700 full-automatic industrial analyzer,the internal factors of the coal permittivity with the degree of deterioration are studied.According to the industrial analysis,the moisture content,carbon content and ash content of the coal have certain influence on the permittivity,but it was not the decisive factor.This conclusion has certain guiding significance for the selection of experimental frequency band of electromagnetic wave propagation in coal seam and for the borehole detection of UWB radar life information of downhole people trapped.