Carbochlorination of alumina and silica from high-alumina fly ash

To systematically and efficiently evaluate the roles of various parameters on the carbochlorination process, the five-level Taguchi method was used to investigate the carbochlorination of alumina and silica from high-alumina fly ash. A four-stage carbochlorination mechanism of fly ash was proposed. The results revealed that under optimum conditions, the highest chlorination rates of Al2O3 and SiO2 were 85.8% and 74.0%, respectively. From the five-level Taguchi test, the impact sequence of the operating parameters for the chlorination rate of Al2O3 and SiO2 was reaction time, temperature, carbon: alumina molar ratio, Cl-2 flow rate, and pellet diameter. Variance analyses showed that the reaction time had significant effects on the extraction of Al2O3 and SiO2 from fly ash by the carbochlorination method. The phase characterization of the samples showed that the stable structure of the spherical particles can be easily broken by the carbochlorination process.