Characteristics of electric field strengthening between coal-mineral particles under microwave irradiation

Both thermal and non-thermal effects induced by microwave radiation can produce a series of effects on coal and rock, and microwave induced discharge is one of the phenomena of microwave non-thermal effects. Coal has a porous and ore-rich skeleton structure with strong heterogeneity. Its internal pores and minerals can affect the electric field. The microwave discharge phenomenon and electric field strengthening characteristics between different component particles are quite different. At present, the relevant researches mainly focus on the coal matrix in the coal body, ignoring the influence of the minerals in the coal body and the irregular shape of the minerals themselves. As a result, the discharge mechanism between real mineral particles and the factors affecting its discharge intensity are still unclear. Therefore, the shape of real coal and rock particles scanned by electronic X-ray tomography (XCT) was described by drawing software, and COMSOL Multiphysics software was used by in this work to discuss the electric field strengthening characteristics of real coal and rock particles under a microwave field and the causes. The results show that the propagation mode and polarization characteristics of microwave have a significant effect on the enhancement of the intergranular electric field, and the intensity of the intergranlar electric field is the largest in x propagation and y polarization. Compared with the other five particle combinations, the particle size and spacing have the most obvious effect on the electric field strengthening of the pyrite-pyrite combination, and the best effect of the electric field strengthening of the coal-rock particle combination appears in the case of large particle size and no spacing. The change of the Angle between particles has a certain influence on the effect of electric field strengthening, and the maximum value of electric field strengthening corresponding to each particle shape appears when the Angle is 0°. The electric field strengthening effect of regular ore particles (round, square, pentagon, etc.) is directly related to the roundness coefficient of the particles. The maximum electric field strength between particles occurs when the Angle of particle tip is about 60° and the roundness coefficient is 0.71. However, the electric field intensity of irregular ore particles has no relation with roundness coefficient and fractal dimension, but gradually increases with the increase of curvature. In addition, the degree of graphitization of carbonaceous materials has a great influence on the electric field strengthening effect, and the electric field intensity increases with the increase of graphitization degree.