Thermal decomposition mechanism of ammonium nitrate and potassium chloride mixtures

Abstract

The thermal decomposition of ammonium nitrate (AN) and potassium chloride (KCl) mixtures was investigated. The thermal properties were studied using differential scanning calorimetry (DSC), and the evolved gas was analyzed using thermogravimetry with mass spectrometry and pressurized DSC coupled with mass spectrometry (TG-DTA-MS and PDSC-MS). DSC measurements of AN/KCl mixtures in sealed and sealedseparated sample pans showed a sharp exothermic decomposition and lower onset temperature than pure AN, whereas AN/KCl in an open pan exhibited an endothermic reaction. In the sealed-separated pan, a separator with a pinhole divided the KCl and AN physically and the evolved gas could interact with both AN and KCl. TG-DTA-MS results revealed that HCl gas was evolved from AN/KCl, which indicated that the reaction of KCl with HNO 3 dissociated from AN formed HCl, and subsequent destabilization of AN. However, the TG-DTA-MS results did not indicate the violent exothermic reaction due to using an open pan and ordinary pressure conditions. PDSC-MS was used to observe two exothermic reactions of AN/KCl and analyze the evolved gases from the reactions. A violent first exothermic reaction was accompanied by a large amount of N 2 and N 2 O gases without H 2 O, and a second exothermic reaction accompanied by H 2 O, N 2 O, and other gases occurred subsequently. The reactions are HCl þ HNO 3 ! NO 2 Cl þ H 2 O ! Cl þ NO 2 þ H 2 O, which have a lower energy barrier by 103 kJ mol -1 than the energy barrier that is needed for HNO 3 homolysis cleavage, which is triggered by pure AN decomposition, HNO 3 ! OH þ NO 2 . We therefore concluded that AN reacts with KCl to produce Cl radicals via HCl and NO 2 Cl, and the Cl radical triggers a radical chain reaction of AN.

Solvent-deficient synthesis of nanocrystalline Ba0.5Sr0.5Co0.8Fe0.2O3-δ powder

“…An exothermic decomposition of NH 4 NO 3 started at a temperature of about 230°C [23]. The observed shifting of the large exothermic peak in the DTA signal was probably due to the intense heating of the sample in the air atmosphere.…”

Atmospheric emission of NO from mining explosives: A critical review

“…In the melt, the ionic species react with each other (Chowdhury and Thynell, 2010). This begins with an endothermic dissociation step (Equation 14), followed by decomposition of HNO 3 and subsequent oxidation of NH 3 according to Equations 15, 16 and 17, respectively (Izato and Miyake, 2015;Oxley et al, 1989;Oxley et al, 2002;Rosser, 1963;Cagnina et al, 2013;Skarlis et al, 2014). In practice, the decomposition period depends on the imposed heating rate and distribution of particle sizes.…”

“…Heating of solid ammonium nitrate from room temperature proceeds through three recrystallisation phase changes leading to melting at around °C and subsequent evaporative decomposition, usually completed by 300 °C, in laboratory studies involving thermogravimetric analysers, depending on sample size and heating rate. Unlike other solid explosives (Beckstead et al, 2007), the elementary reactions associated with the evaporative decomposition of ammonium nitrate remain incompletely understood, but appear to advance initially both by ionic and radical mechanisms in the condensed phase (Izato and Miyake, 2015). In comparison, the ensuing gas-phase reactions attracted considerable research interest that has led to adequate grasp of their behaviour.…”

“…transfer constraints that affect the reaction pathways. Finally, catalysts, such as chlorides or pyrite can significantly modify the reaction mechanisms, both in condensed and gas phases, usually accelerating the decomposition of ammonium nitrate and increasing the NO x emission (MacNeil et al, 1997;Izato and Miyake, 2015;Priyananda et al, 2015;Xu et al, 2015).…”

Effect of carbonate minerals on the thermal stability of fertilisers containing ammonium nitrate

“…The thermal stability of this salt can be reduced by various impurities, among which the most dangerous are chlorides, acids and some organic compounds [18][19][20][21][22]. This property of ammonium nitrate was the cause of many devastating events, both accidental and deliberate [10,[23][24][25][26].…”