Kinetics of decomposition of mullite and corundum in coal fly ash under highly alkaline condition

Abstract

Abstract Decomposition kinetics of mullite and corundum in coal fly ash with highly alkaline solution was studied. The effects of the reaction temperature and reaction time on decomposition rates of mullite and corundum and alumina extraction efficiency were investigated. The results show that increasing reaction temperature and reaction time increases the decomposition rates of mullite and corundum and alumina extraction efficiency, with the decomposition temperature of mullite lower than that of corundum. After 90 min reaction at 220 °C, more than 100 g alumina was extracted when recycling 1 L of alkaline solution. The decomposition processes of mullite and corundum corresponded with the shrinking unreacted core model, and the reaction rate was under chemical reaction control, with the activation energies of mullite and corundum being 67.46 and 161.82 kJ/mol, respectively.