Stronger together ? Influence of the agglomeration on nanopowders explosion

Abstract : Among the factors influencing dust explosion, the particle size distribution (PSD) is both one of the most important and the most complex to consider. For instance, it is commonly accepted that the explosion sensitivity increases when the particle size decreases. Such an assertion may be questionable for nano-objects which easily agglomerate. However, agglomerates can be broken during the dispersion process. Correlating the explosion parameters to the actual PSD of a dust cloud at the moment of the ignition becomes then essential. Powders were characterized before and during their dispersion using in situ laser particle size measurement and a fast mobility particle sizer. The turbulence was determined by particle image velocimetry. The explosion severity and sensitivity of nanocellulose was determined under various operating conditions and for wet and dried powders. The impact of the turbulence on the flame kernel growth was highlighted using a flame propagation tube. It appears that the ignition sensitivity of nanocellulose depends on the PSD and on water activity whereas its explosion severity is less modified by the presence of agglomerates in the raw powder.