Effect of capacitance on physicochemical evolution characteristics of bituminous coal treated by high-voltage electric pulses

Abstract The pore and microcrystalline structure of coal are studied by combining field emission-scanning electron microscopy (FE-SEM), nuclear magnetic resonance (NMR), and Raman spectroscopy to better understand the physicochemical evolution of bituminous coal treated by high-voltage electric pulses (HVEP) under different capacitance conditions. Experimental results show that the capacitance has no significant impact on the breakdown voltage of the coal body during HVEP treatment. However, increasing the capacitance can effectively increase the porosity of coal cores. In particular, the influence of increasing the capacitance on the macropores is obviously more significant than that on the micropore; besides, increasing the capacitance improved connectivity between the mesopores and macropores. In addition, following HVEP treatment, the microcrystalline defect of coal became smaller and pore arrangement more orderly. Thus, the larger the capacitance is, the more is the energy injected into the coal and the more obvious the change of the coal microcrystalline structure.