Improving the Conductivity and Porosity of Coal with NaCl Solution for High-Voltage Electrical Fragmentation

摘要

High-voltage electrical pulse (HVEP) technology is a useful method to improve the pore structure of coal. However, the breakdown voltage of coal is very high; therefore, it is necessary to improve the conductivity of coal first to decrease its breakdown voltage before subjecting it to HVEP. In this work, a solution of NaCl was used for ameliorating the conductivity of Linhua anthracite coal and Hongliu bituminous coal. Both breakdown voltage and energy consumed by the coal sample saturated with the solution of NaCl decreased. The breakdown voltage of Linhua and Hongliu raw coal sample (RCS) was 3.44 and 2.88 times that of coal saturated with NaCl, respectively. The energy consumed by Linhua and Hongliu RCS was 11.82 and 8.21 times that of coal saturated with NaCl solution, respectively. Scanning electron microscopy images showed that the surface cracks on crushed coal samples after saturating with NaCl solution were more than those on RCS. Nuclear magnetic resonance results indicate that meso- and macropores were chiefly enhanced by the electrical breakdown. Chlorine and sodium elements were found on the surface of both Linhua and Hongliu coal through energy-dispersive spectroscopy point scanning, which indicates that these elements play a positive role in electrical breakdown. A Fourier transform infrared spectroscopy test showed that the discharge channel left a trail of burning on the surface of the coal sample and the changes in the functional groups after crushing.