Parameters affecting the thermal behaviour of emulsion explosives

There have been numerous international instances over the last several year s in which pumping of an emulsion explosive has resulted in an accident. To address the sensitivity of emulsion explosives to various parameters inclu ding pressure, a study of a particular ammonium nitrate (AN) based emulsion explosive has been undertaken using the ARC (accelerating rate calorimeter ) and a Tian-Calvet heat flux calorimeter (HFC). The effects of pressure and both inert and oxidizing atmospheres on thermal behaviour were determined and compared with similar results obtained for A N per se. All the results for the emulsion explosive suggest an increased t hermal hazard when operating in air in contrast with the observations for t he same measurements in Argon. No such difference in the results for AN in air and Argon was observed. Significantly lower onset temperatures are observed in air from both the AR C and HFC measurements on the emulsion explosive. This observation is belie ved to be the result of oxidation of the oil phase in the emulsion. Additio nally, the ARC results show some dependence on the choice of the initial te mperature; a lower initial temperature results in an elevated onset tempera ture. Sample size also appears to be a factor influencing the onset tempera ture for both the HFC and ARC results. At a heating rate of 0.1 degrees C min(-1), the HFC results show a complex exotherm pattern far the emulsion in both Argon and air, but the latter res ults give a decidedly earlier onset temperature and a slightly larger Delta H. A complex exotherm pattern is expected for the decomposition of AN but, for the emulsion in air, oxidation of the oil phase further complicates th e result. Crown Copyright (C) 1999 Published by Elsevier Science B.V. All r ights reserved.