Safer emulsion explosives resulting from NOx inhibition

Abstract

Ammonium nitrate (NH4NO3, AN) is a major commodity chemical. Its principal uses are as a fertilizer and an explosive. Ammonium nitrate is inherently unstable and has been the cause of numerous accidental explosions, sometimes with hundreds of deaths. We have investigated the thermal decomposition and methods of inhibiting the critical reactions of ammonium nitrate. NOx gas was shown to accumulate during an induction period and lead to the generation of nitrous acid (HNO2). Removal of NOx by adsorption or reduction provides alternative approaches to inhibition. In this work we reveal alternative methods to inhibit accidental ammonium nitrate explosions. Layered double hydroxides, such as hydrotalcite, were found to be very effective at inhibiting and delaying detonation by adsorbing NOx. Urea, traditionally used to inhibit explosions, was found to be very ineffective at higher temperatures (above ∼ 80 °C). However, the addition of MnO2 catalysts to urea increased its efficiency at temperatures up to ∼ 130 °C. The urea/MnO2 catalyst system was a highly effective inhibitor for preventing thermal decomposition of ammonium nitrate over a wide temperature range.