Investigation of magnesium dust explosion: Particle morphology effects on dispersion, ignition, and suppression

Magnesium (Mg) dust explosions pose a severe threat in the powder processing industries, necessitating thorough consideration of particle morphology effects on explosion dynamics. This study independently developed a visualized particle image velocimetry system and a vertical combustion duct platform to investigate the dynamic response differences between spherical magnesium powders (SMg) and irregular magnesium powders (IMg) throughout the dispersion-ignition-explosion chain. Additionally, the suppression effect of melamine polyphosphate (MPP) on Mg dust explosions was evaluated, and its suppression mechanism was revealed through explosion residues analysis and numerical simulations of gas-phase reactions. The results indicated that IMg exhibited superior dispersibility and higher turbulence intensity than SMg, leading to elevated dust concentration in the critical ignition region, thereby promoting faster ignition and flame propagation. Furthermore, when the MPP addition reached 60 wt%, the maximum flame propagation velocities (Vmax) of SMg and IMg at 400 g/m3 were attenuated by 89.2 % and 84.1 %, respectively, while peak apparent flame temperatures (Tp) decreased to 182 °C and 437 °C. MPP suppressed Mg dust explosions through a dual mechanism of oxygen source competition and chain reaction termination, with enhanced effectiveness in SMg systems due to the easier formation of a protective barrier. During the gas-phase reaction, MPP facilitates the catalytic recombination suppression cycle (HPO3 ⇔ HOPO ⇔ PO3), converting O radicals into H2O, while NH2 radicals derived from NH3 scavenge residual O radicals. This study highlights the critical role of particle morphology in modulating Mg dust explosion risk, providing scientific guidance for establishing inherently safer systems in Mg-related industries.