Detonation Research
Research conducted into reactive ground was not able to experimentally verify that reactive sulphide is a catalyst or contributor to the detonation of bulk explosives apart from being a source of heat from the exothermic chemical reaction of sulphide, contained in reactive ground, and nitrates contained in bulk explosive. It was demonstrated that ammonium nitrate (AN) emulsion (ANE) loaded into a lined hot blast hole will detonate due to heat alone. During the project a local incident occurred where a tanker of ANE detonated due to the resulting fire from a collision. The accepted risk of ANE detonating due to events such as this was assumed to be negligible due to the high-water content and lack of sensitization. This incident motivated the authors to explore the role of heat energy in the causation of this detonation. A review of literature identified that the pathway to heat induced detonation of AN is essentially unknown with there being more than 80 proposed AN decomposition reaction. Experimental results and review of incidences of spontaneous detonation identified that: decomposition of ammonium nitrate always occurs before detonation, the heat source must be at the top of the explosive column for detonation to occur, and high levels of heat energy are required.
A pathway to detonation was postulated whereby decomposition of ammonium nitrate results in ammonia. The ammonia is then cracked at high temperature to product hydrogen. The reaction does not produce oxygen, so the hydrogen accumulates until exposed to air. Hydrogen in air has an autoignition temperature of approximately 600°C and ignition of the hydrogen leads to detonation of the AN. This pathway to detonation was experimentally verified by both detection of hydrogen and detonation.