Experimental assessment on LPG fire extinguishing properties of three chemical powders before and after milling action

The extinguishing performance of three dry chemical powders (DCPs) was investigated through a lab-scale suppression system for liquefied petroleum gas (LPG) fire. The magnesium hydroxide (Mg(OH)(2)), sodium bicarbonate (NaHCO3), and commercial ABC - MAP powders are used to prepare two groups of samples: raw samples and milled samples. The effect of milling action on the properties of DCPs, such as the bulk density, microstructure, particle size, thermal decomposition, and the extinguishing performance, is analyzed. The density test revealed that the bulk density increased after milling, and the Mg(OH)(2) had a lower density than the other powders. The microstructure analysis showed that the milled powders had a smaller particle size and more regular shapes than raw powders. The thermal analysis demonstrated that the powder decomposition process was somewhat similar with a slight difference in initial decomposition temperature and degradation rate. The fire tests proved that the extinguishing efficacy greatly improved after the samples were milled. Moreover, the experiments indicated that the milled Mg(OH)(2) was superior in fire extinguishing to the other samples with shorter extinction time and less agent quantity consumed. Based on the results, it can be inferred that the milling action has a significant influence in enhancing the extinguishing mechanisms' efficiency of DCPs.