Extracting alumina from fly ash by calcination of sulfuric acid

Hydrated aluminium sulfate Al2(SO4)3·18H2O were prepared by activating, magnetic separation, calcined by sulfuric acid, leaching by hot water, crystallization processes using fly ash and sulfuric acid as raw materials. Metallurgy level alumina were prepared by calcining aluminium sulfate, γ-Al2O3 dissolved by alkali, decomposition of sodium aluminate solution and calcining aluminium hydroxide processes. The influence of activation of fly ash, the temperature and the time of acid calcination on the rate of alumina extracted from fly ash was studied. And the units including aluminium sulfate dissolving, crystallization, calcining aluminium sulfate and preparing metallurgy level alumina were studied. The whole flow chart was confirmed. The extracting efficiency of Al2O3 can reach 93.6 percent under the optimum conditions. The γ-Al2O3 powder and SO3 gas were gotten by calcining aluminium sulfate, and sulfuric acid was prepared by SO3 gas to realize the acid circulation.