Cause analysis of spontaneous combustion in an ammonium nitrate emulsion explosive

• The root cause of spontaneous combustion in an ammonium nitrate emulsion explosive has been studied.
• The effects of sodium nitrite on the thermal stability of AN and emulsion explosive were measured.
• The sodium nitrite can substantially deteriorate the thermal stability of AN and emulsion explosives.

Emulsion explosives (EE) have been widely used in the mining industry for their comparatively high detonation performance and exceptionally good safety characteristics. However, an accidental spontaneous burning of an emulsion explosive occurred in March 24, 2014. The investigation of the accident showed that the reaction between crystalloid sodium nitrite and ammonium nitrate (AN) was likely the cause of the spontaneous burning. To investigate the stability of the EE mixed with crystalloid sodium nitrite, AN, crystalloid Sodium nitrite, and EE, were analyzed by differential scanning calorimeter (DSC), accelerating rate calorimeter (ARC) and Dewar test. The results indicated that crystalloid sodium nitrite could decrease the onset decomposition temperature of AN and EE and the induced thermal runaway is the reason for the accident.