Roasting process with sulfuric acid plays an important role in extracting Al2O3 from coal fly ash. The results indicate that Al conversion rate increases with appropriately increased acid concentration

the mass ratio of acid to ash and the roasted temperature

while the effect of roasted time is relatively small. The Al conversion rate can reach 92%-93% at recommended processing parameters: sulfuric acid concentration 80%

acid-ash mass ratio 1.5:1

roasted temperature 270℃ and roasted time 60 min. An analysis for TG/DSC and XRD data demonstrates that the roasting process can be divided to 3 steps: the first step is Al(HSO4)3 formation and water evaporation; the second the formation of Al(HSO4)3 and Al2(SO4)3·H2O

and the third Al2(SO4)3 formation from decompositions of Al2(SO4)3·H2O and Al(HSO4)3. The values of apparent activation energy for the three steps are 52.61

74.11

and 96.08 kJ·mol-1 respectively

an activation energy average of values obtained by Kissinger and Ozawa methods. Using the kinetics parameters estimated

such as activation energy

frequency factor

reaction order

three kinetic equations which correspond to three thermo-chemical reaction steps in the roasting process are established. These fundamental data and theoretical guideline provided in this paper could be used for the process design and optimization of sulfuric acid roasting process to extract alumina from coal fly ash.