Thermal Decomposition Mechanism of Desilication Coal Fly Ash by Low-Lime Sinter Method for Alumina Extraction

Abstract

The extraction of alumina from desilicated coal fly ash (DCFA) has been carried out by using lime and soda through the low-lime sinter method. The effects of sintering temperature, N/(A+S) [Na2O/(Al2O3+SiO2)] and C/S (CaO/SiO2) molar ratios on the calcination products were characterized. The results showed that the major component in DCFA could be decomposed and to form NaAlSiO4 at 700°C, and then converted into NaAlO2 and Na2CaSiO4 at 1000°C. At the sintering temperature of 1050°C with the molar ratio of N/(A+S) and C/S were 0.9–1.1 respectively, the alumina extraction ratio of 90>% could be obtained.