Abstract: A new method was used to prepare Al2O3 from fly ash by NH4HSO4 roasting process. The effects of roasting temperature and molar ratio of Al2O3 in fly ash to NH4HSO4 on Al reaction rate were studied. The results showed that the control step of roasting reaction was solid layer diffusion, the reaction rate constant 1.25′10-3, 1.56′10-3 and 1.89′10-3 min-1 at 300, 350 and 400℃, and the activation energy calculated as 17.19 kJ/mol. The general kinetic equation was expressed as 1-2/3a-(1-a)2/3=0.0422exp[-17190/(RT)]t. The main roasted products were NH4Al(SO4)2 and NH4Fe(SO4)2 in the reaction process. The Al reaction rate reached more than 90% under the optimized conditions of 400℃, molar ratio of Al2O3 in fly ash to NH4HSO4 1:8 and roasting time 60 min.

Key words: fly ash, ammonium hydrogen sulfate, roasting, kinetics

摘要： 提出了NH4HSO4法焙烧粉煤灰提取Al2O3的新方法，考察了焙烧温度、粉煤灰中Al2O3与NH4HSO4摩尔比对粉煤灰中Al反应率的影响，研究了粉煤灰与NH4HSO4焙烧反应动力学. 结果表明，粉煤灰与NH4HSO4焙烧反应受固体产物层扩散控制，300, 350, 400℃下的反应速率常数分别为1.25′10-3, 1.56′10-3, 1.89′10-3 min-1，反应活化能为17.19 kJ/mol，反应动力学方程为1-2/3a-(1-a)2/3=0.0422exp[-17190/(RT)]t，最佳工艺条件为：焙烧温度400℃，Al2O3与NH4HSO4摩尔比1:8，焙烧时间60 min；该条件下Al反应率达90%以上，主要产物为NH4Al(SO4)2和NH4Fe(SO4)2.

关键词: 粉煤灰, 硫酸氢铵, 焙烧, 动力学