Moderation of Al dust explosions by micro- and nano-sized Al2O3powder.

Adding solid inertants to combustible dust is one measure to prevent and mitigate dust explosions. Al2O3 at four particle size distributions was used to determine the minimum ignition energy (MIE) and maximum explosion pressure (Pmax) of aluminum dust and thus examine the effect of particle size on the inerting efficiency. It was interesting to observe that nano-sized Al2O3 powder showed excellent promise as a solid inertant, having inerting efficacy superior to that of micro-sized Al2O3. In addition to thermal inhibition, nano Al2O3 contributed to explosion moderation by binding Al particles together forming larger-sized aggregates that reduce dispersion in the dust clouds, and thus alleviate explosion hazards. Ignition sensitivity increased when micro-sized Al2O3 was admixed at 5 or 10% with 1000-1500 g/m3 Al mixtures, an effect apparently caused by a 20% decrease in effective particle size distribution brought on by the Al2O3 addition. Generally, increasing the amount of admixed Al2O3 increased MIE and decreased Pmax of Al dust clouds, and decreasing the particle size of Al2O3 resulted in better inerting performance on moderating both the likelihood of the ignition and the consequence of the explosion.