Effects of physical and chemical factors on the suppressant enhanced explosion parameter (SEEP) in flame propagation of metal dust layers

• Published in: Fuel (Guildford) 2023-02, Vol.334, p.126620, Article 126620
• Main Authors: Meng, Fanyi, Hou, Xiaochen, Amyotte, Paul, Li, Chang, Yuan, Chunmiao, Bu, Yajie, Chen, Haiyan, Li, Gang
• Format: Article
• Language: English
• Subjects: Dust layer; Fire hazard; Metal powder; SEEP; Solid inertants
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2022.126620

•Low-boiling metals are prone to SEEP (physical factor) when mixed with decomposable inertants.•The mixed dust of high-boiling metals with strong stable inertants is less likely to lead SEEP.•Exothermic reaction of metals with inertants is a chemical factor that leads to SEEP.•Combustion of gases from decomposition of inertants is another chemical factor. Adding solid inertants to metal dust is an effective means of reducing the risk of dust fires and explosions. However, inertants that can effectively suppress the metal dust deflagration could somehow violently enhance the fire hazard of the same metal dust layer. This severe risk has not been well recognized and discussed in depth. To investigate the physical and chemical factors that cause the SEEP phenomenon, flame propagation experiments on mixed dust layers were performed using three common metal dusts (Mg, micro Ti, nano Ti) and five commonly used inertants (NH4H2PO4, NaHCO3, CaCO3, SiO2, CaO). The results indicate that the physical factors were the vaporization of metal dust and the destruction of the oxide layer by the gas from the decomposition of inertants. The chemical factors behind SEEP were the exothermic chemical reaction of metal dust with inertants, and the combustion of the gases released by the decomposition of inertants. Both factors significantly increased the severity of a fire in the dust layers, and in some cases, the chemical factors increased the likelihood of an explosion. Regardless of physical or chemical factors, the mass percentage of inertants in the mixed dust layers that lead to SEEP has a relatively wide range. Therefore, research on the use of solid inertant technology to prevent or mitigate dust explosions should fully consider the physicochemical properties of metal dust. The results are supposed to be used as a comprehensive guide for selecting suitable inertants for metal dust to prevent fire and explosion incidents.