Minimum ignition energy for micro and nano flash powders



The minimum ignition energy (MIE) of dust clouds is required to assess the electrostatic ignition risk. Recently, the growing number of accidents shows that fire and explosions occurring in fireworks industry are due to electrostatic discharge (ESD). The objective of the this paper is to discuss the various practical concerns during the handling of flash powders of various compositions containing potassium nitrate, sulfur, and aluminum in fireworks. These powders form dust clouds and cause fires and explosions because the MIEs of these dust clouds are very low. This study is carried out with powders of various sizes ranging from micron and nanometer. The measurements are done by using a 1.2-L Hartmann apparatus. The experimental results show that the MIEs for flash powders are in the range from 89.2 to 19.8 mJ for micron- and nano-sized particles. The experimental results are given for various changes, such as: electrode gap, electrode material, and dust concentration, dust composition, etc. If the nano flash powder is mixed with micron powders, the MIE is greatly reduced, and it becomes extremely combustible. Therefore, it is imperative for fireworks manufacturers, or anyone handling these dusts, to take precautionary measures to prevent fires and explosions involving ESDs. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2012