EXTRACTING ALUMINA FROM COAL FLY ASH USING ACID SINTERING-LEACHING PROCESS

Local shortages of bauxite in recent years present a challenge to the development of sustainable aluminum industry in China. Coal fly-ash from coal-fired power plants is rich in Al2O3 content with potential use as a resource for alumina refinery. This paper will describe recent investigation in extracting Al2O3 from coal fly-ash using an acid sintering-leaching process. Thermal weight loss testing against temperature is first carried out to find out an appropriate sintering temperature so as to avoid heavy volatilization of the coal fly ash - H2SO4 (98 %) mixture. Then, the mixture is subjected to sintering at 220 degrees C, dissolving in water at 85 degrees C, adjusting alkali level in solution by CaCO3, removing iron by KMnO4 and MnSO4, precipitating Al-2(SO4)(3)center dot 17H(2)O particles, and heating-treated at 850 degrees C to produce Al2O3 powders. The rate of recycling Al2O3 can reach 70 - 90 % with relative lower processing temperature and less solid residues.