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

Fertilisers containing ammonium nitrate are the most efficient sources of nitrogen used in agriculture. The major hazard associated with production, storage and transport of materials containing this compound is its liability to rapid decomposition, or even detonation under certain conditions. Properly selected calcium and magnesium carbonates may increase the thermal stability of ammonium nitrate. The aim of this research was to determine the influence of the carbonate mineral type and composition on phase transitions and decomposition process of fertiliser-grade ammonium nitrate. The article focuses on the methodology of thermal analysis of samples containing ammonium nitrate with carbonates and points out the phenomena and thermal characteristics that should be taken into consideration when testing fertiliser mixtures. Two different sample preparation methods allowed for investigating processes that may occur in inappropriate storage and transport conditions as well as during the production of fertiliser. The measurements were taken using techniques of differential thermal analysis and thermogravimetry coupled with mass spectrometry. The results showed that too high a level of carbonates reactivity can cause problems during the production of fertiliser, reducing the effectiveness of the filler in a final product.