Fire extinguishing and explosion suppression characteristics of explosion suppression system with N2/APP after methane/coal dust explosion

The study aims to examine the suppression performance of an inhibitor after a methane/coal dust explosion. The design of an explosion suppression system included the carrier gas of nitrogen (N2) with an inhibitor of ammonium polyphosphate (APP). The study investigated fire extinguishing and explosion suppression of methane/coal dust by N2/APP in a vertical pipe. Flame propagation characteristics were measured by a high-speed camera, micro-thermocouple, and pressure sensor. The residues after the explosion were characterized chemically by X-ray photoelectron spectroscopy, and the thermal decomposition characteristics of coal dust and APP in the N2 atmosphere were analyzed by synchronous thermal analysis. Experimental results show that the explosion suppression system can effectively hinder the flame propagation of methane/coal dust explosion. The flame height, bottom velocity, and temperature were all weakened significantly. The optimum level of suppressant minimizes the explosion pressure and suppresses the flame significantly. In addition, the fire extinguishing and explosion suppression mechanisms of N2/APP were summarized. The suppression method used in this study blocks the explosion after it occurs rather than preventing it through premixed inerting.