Effect of the nozzle type on the integrity of dust particles in standard explosion tests

The effect of the standard dust dispersers, rebound nozzle and annular nozzle, in the 20 L explosion vessel on the particle integrity has been quantified. Dispersion testswere run and measurements of the particle size before and after dispersion and of the elastic recovery of the materialswere performed. The effect of the dispersion pressure was also studied. Different dustswere tested: lycopodium, nicotinic acid, ascorbic acid, anthraquinone, active carbon, and paracetamol. Results show that particle breakage occurs at any conditions for all the dusts investigated, except for lycopodium. It is also found that dispersion through the rebound nozzle generates a more significant variation in particle size than dispersion through the annular nozzle. Furthermore, higher fractional loss is observed with increasing dispersion pressure. All these results suggest that the measurement of the explosion and flammability parameters according to the standard procedure may lead to misleading results. Thus, a novel dust dispersion method should be proposed in order to avoid failure in measurement of dust explosion/flammability parameters.