Explosive Emulsion Characterisation using Nuclear Magnetic Resonance

Explosive emulsions are frequently employed in mining operations as they offer a comparatively robust, safe and effective product. These are typically formulated as concentrated ammonium nitrate solutions dispersed in an oil phase in the form of a highly concentrated water-in-oil emulsion. Being highly concentrated, determining the droplet size distribution (which is critical to assessing long-term emulsion stability and explosive effectiveness) of these emulsions is challenging. Here we demonstrate that this is readily achieved using bench-top Nuclear Magnetic resonance (NMR) Pulsed Field Gradient (PFG) techniques. The initial mean droplet size is shown to decrease with an increase in the concentration of ammonium nitrate or emulsifier or when inert salt was added to the composition, it was found to increase as the concentration of the aqueous (oxidiser) phase was increased. The emulsion droplet size distributions were observed to remain constant for a 3-month period over the composition range explored.