The effect of particle size polydispersity on the explosibility characteristics of aluminum dust

This paper reports experimental results elucidating the effect of particle size polydispersity (sigma(D)) on the explosion severity of aluminum dust. Five mixtures with a median diameter (D-50) of 15 mu m and sigma(D) values of 0.95, 1.17, 1.48, 1.87, and 2.51, were systematically prepared by mixing original aluminum samples having narrow size distributions. The explosion severity of each sample was determined in a 36 L dust explosion vessel by measuring the maximum pressure (P-max), the maximum rate of pressure rise ((dP/dt)(max)), and the deflagration index (K-St). Interestingly, we found that values of P-max and K-St revealed an increase in explosion severity as sigma(D) increases, where the latter presented a more dramatic effect due to the contribution of fine particles on the combustion kinetics. The effect of dust concentration on the explosion propagation was analyzed comparing the time span to reach (dP/dt)(max), (tau), during a dust explosion. tau was obtained from the experimental pressure traces of the original samples and their mixtures. The values of P-max and K-St, were plotted as a function of the median diameter (D-50) and the volume-(D-4,D-3) and surface-(D-3,D-2) weighted mean diameter. We observed that D-3,D-2 provided a better description of the average sample size and D-50 is inadequately related to the real hazard potential of aluminum dust. Therefore, we suggest that the explosion hazard characterization of these types of materials should be reported in terms of D-3,D-2 and sigma(D). (C) 2013 Elsevier B.V. All rights reserved.