Preparation of high-purity crystalline aluminum chloride based on aluminum separation from circulating fluidized bed fly ash

Abstract

Improving the purity of aluminum products can significantly enhance the comprehensive utilization value of fly ash. In the present paper, a novel process of preparing high-purity aluminum chloride of 99.99% from the aluminum-rich circulating fluidized bed fly ash by acid leaching-recrystallization method was developed, and the leaching kinetics and mechanism were further investigated. The alumina extraction efficiency was 87.9% and the filtration rate of the leached slurry reached 2.5 m3·m−2·h−1 under the optimal conditions of 150 °C, 2 h, hydrochloric acid with a concentration of 20% and the liquid-to-solid ratio of 5. The alumina leaching process followed the shrinking unreacted core model, and the process was controlled by a chemical reaction with an activation energy of 34.90 kJ/mol. Finally, high-purity aluminum chloride was prepared by introducing HCl gas into the leaching solution during three cycles of recrystallization.