Influence of lime-containing additives on thethermal behaviour of ammonium nitrate

Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious disadvantages - being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different time-containing substances - mainly Estonian limestone and dolomite - as internal additives on thermal behaviour of AN. Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition tip to 900 degrees C (10 degrees C min(-1)) in a stream of dry air or N-2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR). The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the decomposition of AN in air or in N-2. At the thermal treatment of AN's blends with CaCO3, MgCO3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism - depending on the origin and the content of additives, partially or completely, through the formation of Mg(NO3)(2) and Ca(NO3)(2).