Development of a novel mining explosive formulation to eliminate nitrogen oxide fumes

Abstract

Post-blast nitrogen oxide fumes (NOx) from coal overburden blasting may occur in a variety of geological conditions with the use of bulk ammonium nitrate (AN) based explosive products. In Australia, government directives to stop blasting activities because of NOx fume incidences have led to costly delays in production, which has directly impacted on the ability of operations to meet production targets. Nitrogen oxide and nitrogen dioxide can cause serious health risks to persons exposed, with excessive levels of NO₂ also affecting the viability of flora and root systems. A number of research projects in Australia have focussed on minimising the risk of NOx fumes by better understanding the behaviour of current explosive products. The main outcomes from these projects have been the development and implementation of guidelines or administrative controls to minimise the NOx fume risk and reduce the potential exposure to the hazard. This paper describes preliminary work to provide a step-change solution that has the potential to completely eliminate the NOx hazard. A novel formulation that substitutes the use of AN with oxygenated water (OW) as the main oxidising agent has been developed and recently patented as part of a PhD program at The University of Queensland. The detonation properties of mixtures made with OW and fuel were studied. Unconfined velocities of detonation (VODs) tests of OW sensitised mixtures were conducted. It was found that for reliable detonation to occur, a minimum level of sensitisation must be accomplished. Adequately sensitised mixtures, with a water content of 47% by weight, were able to detonate at velocities in the range of 2600–5000 m s⁻¹, with a critical diameter of the order of 23 mm. The recorded detonation velocities were clearly dependent on the mixture density and charge diameter, similar to the non-ideal behaviour of AN-based commercial explosives.

Keywords

Nitrogen oxide fumes Blasting agent Explosive formulation Detonation velocity Oxygenated water

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