Law of relative dielectric constant of coal under different stresses and gas pressures

Abstract

In order to study the law of the relative dielectric constant of coal containing gas, the relative dielectric constant of coal containing gas under different stress and gas pressure is studied by using self-made electrical parameter test system, and the effect of stress and gas pressure on the relative dielectric constant of coal containing gas is analyzed.The research results show that the relative dielectric constant of coal containing gas increases with the increase of the axial pressure and gas pressure under the same frequency.The pore size in coal was compressed with increasing stress and the overlap space increases between the electron cloud of coal molecular, which make the electron cloud transfered easily and make the polarizability and the relative dielectric constant increase.The higher coal adsorbing gas capacity, the more gas adsorption amount in coal under the same gas pressure, which make the coal pore structure be affected significantly, the adsorption heat and the coal expansion deformation much higher.Finally, the relative dielectric constant could be affected significantly.The mechanism of the changes of relative dielectric is mainly compressive effect of electronic polarization, ionic polarization, steering polarization and interface polarization in coal.

Keywords

• coal containing gas
• relative dielectric constant
• polarization
• stress