Study On The Electrical Characteristics Of Coal In The Process Of Coalbed Methane Adsorption

After absorbing methane,the coal will change its electric conductivity.This capability is mainly manifested by the resistivity of coal.By studying the relationship between adsorption capacity and resistivity,it can indirectly reflect the change of gas content of coal through resistivity.This paper mainly through the coal sample adsorption/desorption experiment and measured in the process of coal sample resistivity change situation,then analysis it is concluded that under the condition of adsorption capacity of different coal sample resistivity change regulation,and analysis of factors affecting the resistivity of coal samples.The main conclusions are as follows:The industrial analysis of the selected coal samples shows that the ash content of durain columnar samples is larger than that of columnar samples containing vitrain;The volatile content is columnar samples containing vitrain larger than durain columnar samples;and the content of fixed carbon has little difference.The experiments of mercury injection and liquid nitrogen adsorption were carried out by manual stripping vitrain and durain.The results show that the pore connectivity of durain is better,the pore throat distribution is relatively uniform,the average pore throat radius is large.While the pore connectivity of vitrain is poor,the distribution uniformity of the pore throat is not as good as that of durain,and the average pore throat radius is also smaller than that of durain.In the process of adsorption,the resistivity of coal samples decreases with the increase of the adsorption of methane gas,and the initial decrease is larger,and the later decrease decreases.The change conforms to the form of a quadratic function.In the process of desorption,the resistivity value will rise slightly with the desorption and the change conforms to the form of a linear function.In the process of rising pressure,the water deposited in the throat of the coal hole is wetted and spread in the inner wall of the hole and throat.With the increase of pressure,the wetting of water is homogenized and the resistivity of coal sample is reduced.During the depressurization,partial water vaporized and moved along with the methane gas,making the resistivity of the coal sample slightly rebounded.By comparing the experimental data of durain columnar samples and columnar samples containing vitrain,it can be found that the resistivity of columnar samples containing vitrain is less than that of durain columnar samples,and the resistivity is also smaller when the content of vitrain is more.It is said that the resistivity of vitrain is less than that of durain.The existence of water changes the main mode of electrical conductivity of coal samples,and can enhance the electrical conductivity of coal samples.With the increase of water content,the conductivity is stronger.However,with the increase of water content,the enhancement of coal sample resistivity is gradually reduced.