Citation

Yashima M. J. Japan Soc. Safety Eng. 2022; 61(2): 102-112.

Vernacular Title

水素化マグネシウム粉じんの爆発・火災の特性

Copyright

(Copyright © 2022, Japan Society for Safety Engineering)

DOI

10.18943/safety.61.2_102

PMID

unavailable

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.

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本研究では3 種類の大きさのMgH2 粉（Dv,50：18，40，72μm）の燃焼性を調べた．実験の結果，爆発下限濃度は25 ～60 g/m3，MIE は2.1 ～24 mJ，堆積状態での発火温度は370 ～390℃であった．浮遊粉じん状態での発火温度は500 ～580℃で，比較のため用いたMg 粉のそれの610℃よりも低かった．熱面での発火では，水素の脱離後にMg 粉が先に発火し，その後，粉体層に滞留していた水素と空気の予混合気に引火する．また，Mg 粉の発火については，脱離する水素により保護的な酸化膜が粉体内側から破壊されることで，新生面で酸素と反応しやすくなり，発火に至ることが考えられた．発熱性に関して，雰囲気温度に対する水分の影響を調べた結果，少なくとも50℃よりも低い温度で保管すべきであることがわかった．

Language: ja

Keywords

dust explosions; dust fire; Hydrogen storage alloys; metal combustion; 水素吸蔵合金; 粉じん爆発; 粉体火災; 金属燃焼