Experimental and numerical simulation study on thermal decomposition model of ammonium nitrate

High heating rates is one typical character under fire scenario and thermal decomposition behavior of ammonium nitrate (AN) under high heating rates is still unclear. In the current study, a thermal decomposition model of AN was developed to predict thermal decomposition process under high heating rates by a numerical simulation solver Thermakin2Ds based on experimental results. To be more specific, average apparent activation energy and pre-exponential factor were calculated as 75.16 kJ/mol and 3.6×10³ s⁻¹ respectively according to simultaneous thermal analyzer (STA) experimental results. Thermal decomposition products were determined as H₂O, N₂O, NO₂, and HNO₃ by thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR) experiments. The obtained information was utilized for modelling and determining the most reliable thermal decomposition numerical model of AN. The simulated mass loss and mass loss rate at 10 K/min by the model were accordance with experimental data. The prediction ability was verified at heating rates of 5, 16, 25 K/min. Finally, thermal decomposition processes at higher heating rates of 100, 125, 150, and 200 K/min were predicted. This work is significantly meaningful for the storage safety of AN, providing theoretical guidance for preventing the occurrence of AN explosion from the early fire stage.