Effect of Al2O3 particle size reduction on aluminium dust explosion

Abstract To investigate the effect of Al2O3 particle size on an aluminum explosion, the overpressure and flame velocity in a vertical duct were evaluated. The results show that the inhibitory effect of submicron Al2O3 is best, while the inhibitory effect increases with increasing inerting ratio. However, the inhibitory effect of micron Al2O3 does not increase significantly after the inerting ratio exceeds 40%. For high-concentration aluminum powder, 0.8 μm Al2O3 with an inerting ratio less than 20% promotes aluminum explosion. As the inerting ratio increases beyond 20%, however, the overpressure decreases. Furthermore, Al2O3 inhibits the formation of the intermediate product AlO and decreases the flame brightness. As the inerting ratio of 0.8 μm Al2O3 reaches 50%, the white patches in the flame image disappear. The results of scanning electron microscopy showed that the explosion products agglomerate and some dot-like protrusions appear on the surface of the unburned aluminum particles. The inhibition mechanism was qualitatively investigated. Physical heat absorption is proven to play a limited role. Thermal radiation and chemical inhibition play a key role. The chemical effect mainly influences the surface reaction energy source.