Experimental study on variation law of electrical parameters and temperature rise effect of coal under DC electric field

Abstract

Joule heats which are generated by coals in an applied electric field are directly correlated with variation resistivity of electrical parameters of coals. Moreover, the joule heating effect is closely related with microstructural changes and relevant products of coal surface. In the present study, a self-developed applied direct current (DC) field was applied onto an experimental system of coals to investigate variation resistivity of electrical parameters of highly, moderately and lowly metamorphic coal samples. Moreover, breakdown voltages and breakdown field intensities of above three coal samples with different metamorphic grades were tested and calculated. Variation resistivity of electrical parameters of these three coal samples in 2 kV and 4 kV DC fields were analyzed. Results show that internal current of all coal samples increases continuously and tends to be stable gradually after reaching the “inflection point” at peak. The relationship between temperature rise effect on anthracite coal surface in an applied DC field and electrical parameters was discussed. The temperature rise process on anthracite coal surface is composed of three stages, namely, slowly warming, rapid warming and slow cooling to stabilize. The temperature rise effect on anthracite coal surface lags behind changes of currents which run through coal samples. There’s uneven temperature distribution on anthracite coal surface, which is attributed to the heterogeneity of coal samples. In the experiment, the highest temperature on anthracite coal surface 65.8 ℃ is far belower than the lowest temperature for pyrolysis-induced gas production of coals 200 ℃. This study lays foundations to study microstructural changes and relevant products on coal surface in an applied DC field.

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

“…Coal is a typical heterogeneous porous medium whose pore structure is one of the key parameters for evaluating it [4]. Pore structure not only determines the physical and mechanical properties of coal, but also controls the process of gas adsorption, desorption, diffusion, and seepage in a coal seam [5][6][7]. In particular, the adsorption capacity of coalbed methane (CBM) is closely related to the pore development degree and pore structure characteristics.…”

Compression self-sensibility of the concrete using high content carbon black with various measurement conditions

“…Therefore, the higher the excitation amperage, the higher the factor of resistivity variation. This phenomenon is like the effect of amperage on the resistivity of semiconductor materials or insulating materials [16].…”

Fractal Analysis of Coal Pore Structure Based on Computed Tomography and Fluid Intrusions

“…The study of the complex and rich structures inside coal bodies is an important basis for the investigation of their physical properties [1]. The pores of coal are closely related to the adsorption, desorption, and diffusion of coal seam gases and determine the volume of gas storage and efficiency of gas transport [2][3][4][5][6]. Gas diffusion in the pores of coal seams primarily occurs on microporous surfaces.…”