Experimental study of the effect of typical halides on pyrolysis of ammonium nitrate using model reconstruction

The energetic material ammonium nitrate (AN) is used as an industrial raw material; however, it presents a pyrolysis and explosion hazard during transportation and storage, especially when mixed with impurities. To study the effects of typical halides on the thermal decomposition kinetics of AN, a series of precision thermogravimetric analysis experiments at four heating rates were carried out in a nitrogen atmosphere. Based on derivative thermogravimetric analysis, the addition of sodium halides was found to change the kinetic reaction mechanism of AN pyrolysis. The activation energies were obtained using the isoconversional method, and the pre-exponential factor was derived from the kinetic compensation effect. Models of the kinetic reaction mechanism were reliably reconstructed by combining composite kinetic data processing methods, namely, model-free method, model-fitting method, and parameter simulation. A comprehensive analysis showed that the addition of sodium halides shifts the kinetic mechanism of the pyrolysis of AN toward different dominant reaction models (such as reaction order models, power law models, or phase boundary control models) than those of the original reaction model. The results are helpful as a reference and provide guidance for the determination of AN pyrolysis behavior and the simulation of parameters.