Methane/coal dust/air explosions and their suppression by solid particle suppressing agents in a large-scale experimental tube

Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experimental tube, and an array of 44 equally spaced dust dispersion units was used to disperse coal dust particles into the tube. The methane/coal dust/air mixture was ignited by a 7 m long epoxypropane mist cloud explosion. A deflagration-to-detonation transition (DDT) was observed, and a self-sustained detonation wave characterized by the existence of a transverse wave was propagated in the methane/coal dust/air mixtures.The suppressing effects on methane/coal dust/air mixture explosions of three solid particle suppressing agents have been studied. Coal dust and the suppressing agent were injected into the experimental tube by the dust dispersion units. The length of the suppression was 14 m. The suppression agents examined in this study comprised ABC powder, SiO2 powder, and rock dust powder (CaCO3). Methane/coal dust/air explosions can be efficiently suppressed by the suppression agents characterized by the rapid decrease in overpressure and propagating velocity of the explosion waves.

► DDT process in methane/coal dust/air mixtures have been studied in a 199 mm diameter, 30.8 m long tube with strong ignition.
► The DDT distances of methane/coal dust/air mixtures under strong ignition range between 1.5 and 3.0 m.
► The self-sustained detonation wave in mixtures is characterized by the existence of a transverse wave and a spinning detonation wave structure.
► The propagation velocities of the detonation waves ranged between 1400 and 1750 m/s with pitch sizes between 310 mm and 530 mm.
► Methane/coal dust/air explosions can be efficiently suppressed by CaCO3 powder, SiO2 powder, and ABC powder clouds.