The Effect of Inert Salts on Explosive Emulsion Thermal Degradation

Abstract

Ammonium nitrate fuel oil (ANFO) explosive emulsions are comparatively safe, effective and low‐cost products for mining operations. They consist of a supersaturated ammonium nitrate solution dispersed as droplets in a continuous fuel phase. Here we apply a previously developed bench‐top Nuclear Magnetic Resonance (NMR) Pulsed Field Gradient (PFG) technique to monitor the emulsion droplet size distribution in ANFO explosive emulsions as a function of time stored at an elevated temperature of 50 °C; we thus investigate the subtle effect of adverse storage conditions on emulsion stability. Storage at 50 °C for 12 weeks lead to a ∼60 % increase in mean droplet size, whereas a sample stored at 21 °C experienced no change in mean droplet size. The addition of inert salts (calcium nitrate or sodium nitrate) to the ammonium nitrate solution was also considered in terms of their ability to enable stable storage of the emulsions at 50 °C. An addition of 5 wt% calcium nitrate to the aqueous phase was required to suppress any thermal degradation of the explosive emulsions whilst a much lower dosage of only 1 wt% sodium nitrate was required to realise the same stabilizing effect.

Interpol review of the analysis and detection of explosives and explosives residues

“…They used Nuclear Magnetic Resonance (NMR) Pulsed Field Gradient (PFG) and found storage at 50° Celsius for 12 weeks lead to a 60% increase in mean droplet size. Adding 5% calcium nitrate to the aqueous phase suppressed this thermal degradation [ 602 ]. X-Ray Ion Mobility Spectrometry …”

Safety considerations of static sensitization emulsification technology for Kings-type emulsion explosives based on quadratic linear programming algorithm

“…In the literature [16], the effect of highspeed mixing of emulsifier blades on the thermal safety of emulsified substrates was investigated by combining the rotational speed factor and temperature factor properties through computational hydrodynamics. The literature [17] applied the NMR pulsed field gradient technique and analyzed that temperature does not have a great influence on the emulsification process of emulsified explosives, but the addition of ammonium nitrate fuel oil degrades the emulsion concentration quickly and improves the safety.…”