Chang Guo

Experimental study on the microscopic characteristics affecting methane adsorption on anthracite coal treated with high-voltage electrical pulses

The low gas permeability of coal formations with limited coal pores and fractures leads to difficulty in coalbed methane exploration. High-voltage electrical pulse has a potential application in enhanced coalbed methane recovery. In this study, we discuss the microscopic characteristics of anthracite coals treated by high-voltage electrical pulse. We find that C, O, and other coal elements constituting oxygenic groups, which mainly account for gas adsorption, decreased slightly after high-voltage electrical pulse treatment, indicating that elemental variation may have little influence on gas adsorption. The scanning electron microscopy and low-pressure nitrogen gas adsorption (LP-N2GA) results show that the cumulative micropore volumes of high-voltage electrical pulse-treated coals were much larger than those of original coals. The mercury intrusion porosimetry results show that the cumulative macropore volumes, which act as gas migration channels in coal increased. Additionally, high-voltage electrical pulse-treated coals were found to have smaller entrapment areas, indicating that gas migration was enhanced.

Effect of filling ratio on premixed methane/air explosion in an open-end pipe:

The propagation characteristics of premixed methane/air explosion under different filling ratios (20%, 30%, 40%, 50%, 60%, and 100%) were studied using an experimental system. The results indicate that the peak overpressure showed a decreasing trend at the initial stage but then showed an increasing trend until reaching its maximum value under different filling ratios. As the explosion propagated to the open end, the overpressure showed a downtrend. At this point, the flame speed initially increased along the pipe but then dropped dramatically. In addition, the explosion overpressure and flame speed increased with the increase of filling ratio. However, when the filling ratio reached 50%, the explosion overpressure and flame speed tended to be stable and the increase was not obvious. These results will be of great importance in evaluating the explosive damage to equipment and human personnel working in coal mines or other chemical industries.

The effect of bend positions on premixed methane–air explosion overpressures in ducts

Bend structures in process industries can enhance gas explosions. Many researchers have studied their effects on flame propagations or overpressure evolutions with experiments or numerical simulations. In this work, three bends with different angles ranging from obtuse to acute were examined, and the effect of bend positions on gas explosions was also studied in the experiments. It was found that the peak overpressure evolutions under three different angles experienced three different stages, i.e. a slight downtrend before the bend, a sudden uptrend in and after the bend, and a following downtrend. The explosion violence was enhanced due to a reflection wave and flame tip wrinkle. The peak overpressure increased when the bend angles decreased because of stronger reflection and turbulence under a smaller bend angle. Additionally, the bend shortened the distance at which the peak overpressure reached its maximum values. However, the bend positions had little effect on the maximum overpressure in the ducts.