Study on extracting alumina from fly ash by compound additive activation method

According to the chemical and mineral composition characteristics of the fly ash，alumina can be ex- tracted from fly ash through the calcining method by using sodium carbonate and calcium carbonate additives． The effects on leaching rate of alumina have been investigated． The results showed that the fly ash can be acti- vated effectively and the leaching rate of alumina can be improved to more than 92% through this method． The best process parameters were the ratio of raw materials，i． e． the material weight ratio of fly ash，calcium car- bonate and sodium carbonate was 1． 0∶1． 2∶0． 9． The activating temperature was 850℃- 900℃，activating time was 3 h． This process has a potential application prospect and improves the value of comprehensive utilization of fly ash．