Alkali desilicated coal fly ash as substitute of bauxite in lime-soda sintering process for aluminum production

By desilication treatment, the Al(2)O(3)/SiO(2) molar ratio of coal fly ash could be improved to the range of 1.63-2.0. The desilicated coal fly ash (DSCFA) was enriched in alumina extraction. A processing technology was developed for alumina extraction from the DSCFA with the lime sintering process. Ca/(SiO(2)+TiO(2)) molar ratio, and NaO/Al(2)O(3) molar ratio, sintering time, and temperature were the most significant parameters impacting on the aluminum extraction efficiency. The optima aluminum extraction efficiency was obtained under conditions of Ca/(SiO(2)+TiO(2)) molar ratio of 2.0, NaO/Al(2)O(3) molar ratio of 0.98, and sintering at 1 200 degrees C for 60 min. A standard industrial dissolution method was used under conditions of caustic ratio (alpha(k)=n(NaO)/n(Al(2)O(3)) of 2.0, Al(2)O(3) concentration of 50 g/L, sodium hydroxide concentration(N(k)) of 60.78 g/L, Na(2)CO(3) concentration of 10 g/ L, temperature of 85 degrees C and dissolution duration of 10 min. The final aluminum extraction efficiency was 90%.