Experimental study on the influence of conductive solution concentration on the cracking and penetration enhancement of coal of high-voltage electrical pulse

In order to test the effect of solution concentration on the cracking and penetration enhancement of coal of high-voltage electrical pulse, aqueous solution and NaCl solutions with concentration of 0.5 mol/L, 1.0 mol/L, 1.5 mol/L and 2.0 mol/L are used as the conductive medium. The high-voltage electrical pulse discharge system is used to conduct the cracking experiment on similar coal samples, and the cracking effect is analyzed by ultrasonic detection technology. The experimental results show that: when water is used as a conductive solution, the peak discharge pressure is 1.26 MPa, while when NaCl solution is used as a conductive medium, the peak discharge pressure is significantly increased. The first wave acoustic time difference of coal samples after NaCl solution experiment is also higher than that of coal samples after aqueous solution experiment, and the internal fracture reconstruction effect of coal samples is more significant. The results show that adding conductive solution can optimize the conductivity of coal samples. With the increase of the concentration of conductive solution, the peak of discharge pressure increases. The discharge of high-voltage electrical pulse in a certain concentration of sodium chloride solution can increase the utilization rate of electric energy converted into plasma channel energy. The increase of the concentration of conductive solution can strengthen the conductivity of coal samples and optimize the cracking and anti-reflection effect of high-voltage electrical pulse discharge. However, as the concentration continues to rise, the peak discharge pressure of 2.0 mol/L NaCl solution only increases from 2.20 MPa to 2.25 MPa compared with 1.5 mol/L NaCl solution, and the change of the first wave acoustic time difference between the two solutions is not significant. The cracking of coal samples is similar. At this time, the adsorption capacity of various conductive ions reaches saturation state, The number of adsorbed ions in the coal remains basically unchanges, so the electrical conductivity of the coal remains basically unchanged.