关键词: 硫酸铵, 热分解, 分解动力学, 热重分析

Abstract:

Thermal decomposition of ammonium sulfate can provide ammonium bisulfate solution and ammonia water for the process of leaching fly ash with ammonium bisulfate solution to extract alumina.It is of great significance to study the mechanism and thermal decomposition kinetics of its thermal decomposition process.The products of the decomposition process were characterized by X-ray diffraction，mass spectrometry and Fourier transform infrared spectroscopy，proving that the decomposition products of ammonium sulfate were ammonium hydrogen sulfate，ammonium pyrosulfate，ammonia，water，nitrogen and sulfur dioxide.The characterization method combined with thermogravimetric analysis showed that the thermal decomposition process of ammonium sulfate was divided into three stages：the decomposition of ammonium sulfate to form ammonium bisulfate and ammonia gas，the dehydration of ammonium bisulfate to form ammonium pyrosulfate，and the decomposition of ammonium pyrosulfate.The Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose model-free methods were used to calculate the activation energy for each stage.The Coats–Redfern method was used to determine the most likely dyna-mic mechanism function for each stage.The results showed that the average activation energy was E=125.21 kJ/mol in the first stage，and ln A=18.46；the average activation energy of the second stage was E=110.21 kJ/mol and ln A=13.94；the average activation energy of the third stage was E=97.70 kJ/mol and ln A=8.44.

Key words: ammonium sulfate, thermal decomposition, decomposition kinetics, thermogravimetric analysis