Interactions of ammonium nitrate with different additives

Abstract

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(NO3)2 and Mg(NO3)2, Ca(OH)2 and Mg(OH)2, CaO2 and MgO2, CaO and MgO, and N-containing gaseous compounds NO, N2O and NO2. As a result of H3BO3, MnO2 and CuSO4 addition, the content of CuO, Cu2O and MnO as solids and SO2, SO3 and HBO as gaseous reaction products reached the same level. Thereby, their equilibrium concentrations did not depend on the carbonate origin of CaCO3, MgCO3 or CaMg(CO3)2. Small amount of CuSO4, H3BO3 or MnO2 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 CaCO3 or CaMg(CO3)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.