Experiment and simulation of selective cracking of coal samples by plasma

The plasma crushing technology has been widely used in many fields,and some related researches show that it has a good application prospect in the field of coal fracturing. In order to investigate the law of crack propagation in coal treated by plasma technology,the law of coal breakage under the impact of plasma was studied through a self-de- signed plasma test platform by means of experiment and numerical simulation. In the experiment,with the coal crushed by plasma being the research object,the fracture and mineral phases in Hongliu bituminous coal were extracted ac- cording to different thresholds with the aid of the three-dimensional visualization software Dragonfly. Meanwhile,the law of crack propagation along different directions was analyzed in depth. Furthermore,based on the numerical simula- tion software Comsol Mul-tiphysics,the distribution of electric field intensity in mineral-bearing coal under plasma impact was analyzed. The results show that an interconnected fracture network is formed in the coal under the impact of plasma,and the cracks diverge from the electrode center to all sides. The breaking effect is better at both ends near the electrode,indicating that the breaking effect of the coal is positively correlated with the concentration of electric field. The more concentrated the electric field is,the greater the energy is,and the better the breaking effect is. Besides,the fractures distribute along minerals in both the axial direction and the plane,revealing that the electrical field distorts at the interface between minerals and fractures. The distribution of minerals induces the initiation of fractures. The influ- ence of mineral and pore in coal on the electrical field was verified through numerical simulation. The results suggest that the electrical field intensity will distort in dielectrics with different dielectric constants. Lower field intensity will be formed inside the dielectric when the electrical field passes through the dielectric with a high dielectric constant, whereas higher field intensity will be formed inside the dielectric when the electrical field passes through the dielectric with a low dielectric constant. The numerical simulation results are a supplementary explanation to the experimental re- sults,and the experimental results are the embodiment and validation of the macroscopic results of numerical simula- tion.