Process for the recovery of alumina from fly ash

In the process for recovering alumina from fly ash containing oxides of alumina, silica and other metals wherein the fly ash is mixed with calcium carbonate to form a mixture, the mixture is heated from 1350.degree. to 1400.degree. C. for a period of time sufficient to form a clinker containing a soluble calcium aluminate compound, the clinker is reduced to a powder, and the powder is contacted with dilute sodium carbonate solution to dissolve the soluble calcium aluminate compound, thereby recovering the alumina, the improvement comprising, adding from about 2 to 10 weight percent carbon and elemental sulfur to the fly ash-calcium carbonate mixture before sintering, the sulfur to carbon ratio being from 0.5 to 1.5, heating the mixture to 1100.degree. to 1300.degree. C. for a period of time sufficient for the sulfur to react with the alumina and calcium to form a clinker containing a calcium sulfoaluminate compound, whereby upon reducing the clinker to powder and contacting the powder with dilute sodium carbonate solution, the amount of alumina recovered from the fly ash is increased.