Explosion and Fire Characteristics of Magnesium Hydride Powder

Abstract

In this study, the combustibility of MgH2 powder （Dv,50: 18, 40, 72 µm） of three sizes was conducted. As a result of the experiment, the lower limit of explosion concentration was 25 to 60 g /m³, the MIE was 2.1 to 24 mJ, and the ignition temperature in the deposited state was 370 to 390 ℃. The ignition temperature in the suspended dust state was 500 to 580 ℃, which was lower than that of the Mg powder used for comparison （610℃）. In the hot surface ignition, Mg powder ignites first after the desorption of hydrogen, and then ignites the premixed gas of hydrogen and air retained in the powder layer. Regarding the ignition of Mg powder, it is considered that the desorbing hydrogen destroys the protective oxide film from the inside of the powder, which makes it easier to react with oxygen on the new surface, leading to ignition. As a result of examining the effect of moisture on the ambient temperature with respect to heat generation, it should be stored at a temperature lower than 50 ℃ at most.