Thermal decomposition characteristics and compatibility analysis of pulverized coal‐doped ammonium nitrate fuel oil (PCANFO) explosive by microcalorimeter

Abstract

AbstractIn order to study the compatibility of pulverized coal‐doped ammonium nitrate fuel oil (PCANFO) explosives and the effect of pulverized coal on the stability of ammonium nitrate fuel oil (ANFO) explosives, the thermal decomposition characteristics of ANFO explosives and three types of PCANFO explosives containing 5, 10 and 15 wt% pulverized coal were investigated. The initial stage of their thermal decomposition reactions was analyzed using the Arrhenius equation to determine kinetic parameters, including the heat of reaction (ΔH), apparent activation energy (Ea), and pre‐exponential factor (lnA). Additionally, the compatibility of PCANFO explosive was evaluated based on standard experimental method GJB 772 A–97 502.1. According to the study, the crystal transformation time of ammonium nitrate (AN) was extended by around 75 s by the addition of pulverized coal. The thermal decomposition time of ANFO explosive decreased as the amount of pulverized coal increased. The heat of reaction for the explosive samples was measured and found to be in the order of 2282 kJ kg−1, 3302 kJ kg−1, 3243 kJ kg−1, and 3301 kJ kg−1. The addition of pulverized coal to the system resulted in decreased thermal stability and an increase in the apparent activation energy, which was measured to be in the order of 185.5 kJ mol−1, 196.2 kJ mol−1, 235.5 kJ mol−1, and 262.5 kJ mol−1. A mixture of 5 % pulverized coal and ANFO explosive received a rating of level 1, indicating high compatibility. However, mixtures containing 10 % or more pulverized coal received a rating of level 4, indicating poor compatibility.