CFD simulation of multiple dust explosion occurred in a flour mill

Dust explosions pose a serious hazard to both personnel and equipment in industries that handles combustible powders. Although prevention and mitigation technology of dust explosions has progressed greatly, continual accidents in the process industries demonstrate the need for improved knowledge in this area (Mercan, 2016; Russo et al., 2017). On July 16, 2007, a primary explosion followed by secondary explosions happened in the Cordero mill (Italy) and 5 persons died (Marmo et al., 2012). The accident occurred at the end of the loading operation of a tanker, when a surplus of flour was overcharged. This extra amount was then pneumatically conveyed to a silo placed in the flour-warehouses, by connecting the tanker to the pneumatic transport line through one of the tanker hoses. The flour was loaded at a low flow rate, and hence a low concentration of flour in the duct occurred. The source of ignition of the dust cloud was attributed to an electrostatic arc that took place in the pneumatic transport duct (Marmo et al., 2012). The technical enquire found signs of the explosion in the duct: internal pressure provoked evident deformation of the duct. As widely discussed in the literature (Fiorentini and Marmo 2019; Marmo et al., 2013), Computational Fluid Dynamics can be a valid aid to forensic engineering because it allows to discern the incidental sequence that is more adherent to the evidence. The aim of this work is to reproduce the conditions present in the mill at the time of the accident using the CFD-code DESC, which is being developed for simulating dust explosions in complex geometries. The results obtained from the simulations were compared to the damage observed after the accident in order to identify the more credible scenario. Simulations with different levels of flour in the silo, concentration of dust in the air mixture and position of ignition were performed. Analysis of results revealed the effect of different parameters on the severity of dust explosion, not only limited to the case study investigated, in order to adopt the appropriate prevention and protection measures.