To address the issue of low extraction efficiency of aluminum from fly ash in pulverized coal furnaces due to its mullite structure, a process combining high—temperature enhanced decalcification with medium recycling to remove calcium and extract alumina from activated fly ash clinker was proposed. The optimal process parameters for decalcification and alumina extraction were determined through single-factor experiments. The results indicate that the optimal decalcification conditions are reaction temperature of 160 ℃, hydrochloric acid concentration of 12%, and reaction time of 4 h. Under the conditions, the CaO removal rate exceeds 98%, while the Al₂O₃ dissolution rate is effectively suppressed below 5%. The optimal alumina extraction conditions are temperature of 60 ℃, hydrochloric acid concentration of 26%, and reaction time of 0.5 hours, achieving an Al₂O₃ dissolution rate of over 93% and controlling the Ca²⁺ concentration in the leachate below 0.39 g/L. Innovatively, a closed-loop calcium chloride recycling system is constructed, enabling recovery rate of over 90% for the activator in filtrate reuse tests. The process can achieve efficient calcium-aluminum separation and recycling of additives, offering a low-carbon solution for alumina extraction from fly ash.

fly ash  /  activation  /  calcium chloride  /  decalcification  /  alumina