Characteristics of energy release and ignition hazards of ammonium nitrate in storage under strong shock and accidental stimulation

Abstract

In recent years, many accidents caused by deflagration/explosion of ammonium nitrate(AN) have been reported worldwide, which not only cause casualties, property losses, but also cause irreversible damage to local buildings. Facing the increasingly complex explosive behavior of hazardous chemicals that threaten public safety, it is urgent to fully grasp the energy release and destructive characteristics of AN to provide data and technical support for the safety evaluation, management and emergency response of hazardous chemicals. This paper investigates AN in a typical storage state, designs related experiments from its own energy (explosion heat), strong shock-to-detonation transition process(Lagrangian gauge measurements), flow field characteristics of shock waves (free field overpressure distribution, shock wave spectrum analysis), and ignition hazard after explosion (fireball area, ignition radius) to reveal the reaction process and energy release behavior under strong shock stimulation. It was discovered that AN exhibits a characteristic non-self-sustaining detonation phenomenon in which only a portion of the material will explode under strong shock stimulation. This is because AN has a slow energy release rate in the loosely packed state, which leaves insufficient energy to support the stable propagation of the detonation/deflagration wave front. The overpressure energy is only 12% TNT equivalent, and 75% of its energy is concentrated at 0∼150Hz. This means that buildings near the chemical plant should keep as much of a suitable distance as possible during the transportation and storage of dangerous chemicals like AN. Furthermore, excessive building height should be avoided, as increased height generally leads to a reduction in natural vibration frequency, without considering the material's own properties.