The further development of the extraction of alumina that is produced in the calcination process of ammonium sulfate mixed with fly ash was limited because of the lack of systematic theoretical study. In order to aggrandize the research of the calcination process

the kinetics and reaction mechanism of the calcinationswere studied. The result suggests that there are two stages in the calcination process

and the alumina extraction rate increases swiftly in the initial stage

but slows down increasing in the later stage. The apparent activation energy of the initial and later stages equals to 13.31 and 35.65 kJ·mol

-1

respectively. In the initial stage

ammonium sulfate reacts directly with mullite in the fly ash to form ammonium aluminum sulfate

while in the later stage

aluminum sulfate is formed by the reaction between ammonium aluminum sulfate and ammonium sulfate.