Interactions of ammonium nitrate with different additives: Thermodynamic analysis

In order to elucidate the influence of Ca and Mg carbonates with or without the presence of boron, manganese and copper compounds on the thermal stability of ammonium nitrate (AN), thermodynamic analysis of different reactions between AN and additives was carried out. Temperature dependency of Gibbs free energy changes ∆G T and equilibrium composition of reaction products were calculated for a set of reactions using the HSC software. Main solid compounds that can form in the systems of AN and carbonates, were Ca(NO 3 ) 2 and Mg(NO 3 ) 2 , Ca(OH) 2 and Mg(OH) 2 , CaO 2 and MgO 2 , CaO and MgO, and N-containing gaseous compounds NO, N 2 O and NO 2 . As a result of H 3 BO 3 , MnO 2 and CuSO 4 addition, the content of CuO, Cu 2 O and MnO as solids and SO 2 , SO 3 and HBO as gaseous reaction products reached the same level. Thereby, their equilibrium concentrations did not depend on the carbonate origin of CaCO 3 , MgCO 3 or CaMg(CO 3 ) 2 . Small amount of CuSO 4 , H 3 BO 3 or MnO 2 additive (0.01–0.05 mol) in the system, practically, did not influence the temperature dependencies of ∆G T of the reactions between AN and CaCO 3 or CaMg(CO 3 ) 2 . The influence of additives taken in the larger amount (0.5 mol) was evident and, depending on the additive and reaction, shifted their proceeding temperatures in either direction by more than 300–400 K.