Hindrance and suppression characteristics of local whole-inerting zone on flame propagation of methane/coal dust deflagration

Abstract To investigate the suppression of local whole-inerting on the flame propagation of methane/coal dust deflagration. N2 was used as the loading gas to dispersed the fly ash into a fixed zone of the pipe and thus form local whole-inerting zone (contained N2-Fly ash), and the widths of inerting zone were determined by theoretical calculation. The deflagration experiments under different concentrations of fly ash in inerting zone and different widths of inerting zone were conducted by using vertical combustion pipe. Results indicate that the flame maximum height, bottom velocity and temperature of methane/coal dust deflagration were decreased obviously with the fly ash concentration and inerting zone width increased. The inerting zone aggravated the attenuation amplitude of flame velocity at deceleration period, and the velocity difference (Δv) between the maximum velocity and the bottom velocity was increased obviously. These combinations (concentration, width) can suppress significantly the deflagration flame propagation: (100 g/m3, 30 cm), (200 g/m3, 25 cm), (300 g/m3, 25 cm), (400 g/m3, 25 cm), (500 g/m3, 20 cm) and (600 g/m3, 15 cm). The inerting zone can suffocate the deflagration flame, and contained N2 and fly ash which can hinder the coal decomposition and the combustion reaction through dilution effect, heat absorption, heat insulation and free radicals consumption, so that deflagration reaction and flame propagation were weakened.