The Effect of Natural Convection on Thermal Explosion in Open Storage Silo

Abstract In cylindrical storage silos, exothermic reactions carry the inherent danger of triggering a thermal explosion. Such an explosion can transpire when the rate at which heat is generated by the chemical reaction exceeds the heat dissipated through conduction and convection. Frank-Kamenetskii defined a parameter δ to indicate that the explosion occurred when its critical value was exceeded. This study aims to delve into the principles of thermal ignition, clarifying the behavior of exothermic reactions within ventilated open granular silos. The findings include a series of plots that demonstrate an increase in δ with increasing Rayleigh number, particularly when natural convection is pronounced. The study also examines the location of the hot spot, which moves from the center to the top of the vessel because of buoyancy forces. Additionally, for minimal Rayleigh values, lower Biot numbers lead to reactions occurring at lower temperatures, suggesting that a reduced Biot number indicative of poor surface ventilation heightens the risk of explosion and diminishes the stabilizing influence of natural convection. Furthermore, the findings show that the storage time has been improved from approximately 6 months to 12 months with an increase in the Biot number and at a Rayleigh value of 103. This analysis of the role of natural convection relative to that of thermal explosions provides valuable knowledge for enhancing storage safety protocols to prevent thermal explosions in such storage environments.