THERMAL HAZARD ASSESSMENT OF OXIDIZER SOLUTIONS AND EMULSION EXPLOSIVES UTILIZING ACCELERATING RATE AND DEWAR CALORIMETRY

摘要

When attempting to quantify the hazards associated with the manufacture and use of emulsion explosives, a key parameter is the temperature at which either the oxidizer solution or the emulsion begins to self-heat through exothermic decomposition, the "onset" temperature. Oxidizer solutions are typically concentrated aqueous solutions of nitrates and other inorganic oxidizers, used in the manufacture of emulsion explosives. Although not as violently reactive as the explosives themselves, it is well known that oxidizer solutions can decompose explosively. Several accidents at ammonium nitrate plants are testimony to this. As well, numerous international instances, in which pumping emulsion explosives has resulted in accidents as a result of increased thermal sensitivity under these conditions, make determination of the "onset" temperature an important safety consideration. Self-heating occurs for a particular material when the rate of heat generation is greater than the rate of heat loss to the environment. For a given experimental or practical geometry, heat losses are greater for small samples, so the thermal onset temperature decreases with increasing sample size. In practice, oxidizer solutions and emulsion explosives are manufactured and transported in quantities of the order of 20,000 kg. In comparison, convenient laboratory quantities are less than 1 kg. As a consequence, any laboratory studies that aim to provide results that are applicable to large-scale situations must be designed so as to minimize heat losses to the environment. In this study, accelerating rate calorimetry (ARC) and adiabatic Dewar experiments were carried out on oxidizers used in the manufacture of emulsion explosives, their aqueous solutions, a bulk explosive matrix and a detonator-sensitive packaged explosive. ARC and Dewar experiments were carried out in both closed and vented experimental configurations. The effect of water levels on the oxidizer solutions was investigated. The results obtained using the two different experimental techniques are compared.