Statistical method for the determination of the ignition energy of dust cloud

Statistical method for the determination of the ignition energy of dust cloud - experimental validation

Bernard, Stephane / Lebecki, Kazimierz / Gillard, Philippe / Youinou, Loic / Baudry, Guillaume

Powdery materials such as metallic or polymer powders play a considerable role in many industrial processes. Their use requires the introduction of preventive safeguard to control the plants safety. The mitigation of an explosion hazard, according to the ATEX 137 Directive (1999/92/EU), requires, among other things, the assessment of the dust ignition sensitivity. PRISME laboratory (University of Orleans) has developed an experimental set-up and methodology, using the Langlie test, for the quick determination of the explosion sensitivity of dusts. This method requires only 20 shots and ignition sensitivity is evaluated through the 50 (energy with an ignition probability of 0.5). A Hartmann tube, with a volume of 1.3 1, was designed and built. Many results on the energy ignition thresholds of partially oxidised aluminium were obtained using this experimental device (Baudry, 2007) and compared to literature. 50 evolution is the same as MIE but their respective values are different and MIE is lower than 50 however the link between 50 and MIE has not been elucidated. In this paper, the Langlie method is explained in detail for the determination of the parameters (mean value 50 and standard deviation a) of the associated statistic law. The ignition probability versus applied energy is firstly measured for Lycopodium in order to validate the method. A comparison between the normal and the lognormal law was achieved and the best fit was obtained with the lognormal law. In a second part, the Langlie test was performed on different dusts such as aluminium, cornstarch, lycopodium, coal, and PA12 in order to determine 50 and a for each dust. The energies 05 and 10 corresponding respectively to an ignition probability of 0.05 and 0.1 are determined with the lognormal law and compared to MIE find in literature. 05 and 10 values of ignition energy were found to be very close and were in good agreement with MIE in the literature.