Assessment of Coal Permeability in Cyclic Treatment with Liquid Nitrogen

The article describes the lab-scale tests of permeability of long-flame coal from the Mokhovsky Coal Mine in Kuzbass depending on the intensity of cyclic treatment of coal with liquid nitrogen. The freezing effect on jointing was assessed by the change in the gas flow and in the ultrasound velocity. It is found that permeability of the test coal in compression rises up to commercially significant values. To reach this effect, it is sufficient to implement three–four cycles of treatment with liquid nitrogen. The treatment decreases the ultrasonic P-wave velocity by up to 6%, which points at the increase in the volumetric density of microcracks.