Explosion Suppression Mechanism of Flame Retardant Powders on Aluminum Dust Cloud Explosion

In order to reduce the hazard of aluminum dust cloud explosion accident, it is necessary to analyze the suppression mechanism of effective flame retardant powder. Based on the explosion suppression experiment in transient flame propagation system, three flame retardant powders, ABC powder (ammonium dihydrogen phosphate), MCA powder (melamine cyanurate) and MPP powder (melamine pyrophosphate) were studied by simultaneous thermal analysis. The results showed that ABC powder could achieve flame retardant effect mainly by endothermic decomposition producing non-combustible gas and the endothermic evaporation of product. While MCA and MPP would decompose to inert gas, and generate intermediate products isocyanic acid and phosphorus radicals respectively, which will consume massive oxygen atoms. During the heating process of aluminum powder, the core aluminum expansion would break through the alumina film, and oxide again. The addition of flame retardant powder would delay this process, but there was no linear relationship between delay time and explosion suppression effect.