Thermal radiation contribution to metal dust explosions

Abstract : Dust explosions remain a safety and scientific challenge. There has been a gradual evolution in the prevention and mitigation of dust explosions over the past twenty years. This evolution results partly from a better understanding of the phenomena involved; namely the properties and characteristics of dust explosions, the propagation of the flame through dust clouds, the ignition and the combustion time of particles and the incidence of the size and concentration of particles. Today, the modeling of this type of explosions is generally derived from the modeling of gas explosion because of the similarities between the flame propagation processes in both media at least for some categories of dusts. Flour, starches and sulfur powder certainly belong to this panel because it was shown that the particles are gasified ahead of the combustion zone and that heat conduction through the front leads to this transformation. The situation might be different if the particles do not evaporate and/or if the major part of the combustion process is heterogeneous. This may occur with fine metal particles as aluminum. In particular, the combustion process might be heterogeneous and results in the presence of solid residues at very high temperature potentially transferring most of the thermal energy to the reactants (aluminum particles) by thermal radiation. Only very few experimental observations and theoretical considerations are available but seem to confirm that thermal radiation exchange is significant in the thermal balance of the flame and that it could lead to a dramatic acceleration of the flame. The aim of this work is to investigate further this phenomenology.