Alumina extraction from fly ash by MgO modified soda sintering method: Waste reduction and utilization

摘要

Bauxite import accounts for over 60% of the total consumption of China's alumina industry, and the domestic resource is to be soon depleted in about ten years. At the same time, coal-fired power plants have been generating fly ash in large amounts, which can be used to extract alumina among many applicaitons. Various methods for the alumina extraction from fly ash have been tested, developed and demonstrated in China. Generally, soda sintering methods can be more easily deployed than acid leaching methods, but it is also apparent that soda sintering methods tend to geneate more waste of little value. In this work, MgO has been added to replace CaO, and the replacement could reduce the output of extraction residue, spare a lot of energy by lowering the sintering termperature, and retain a high rate of alumina extraction. As a raw material for quality products such as heat insulator, the extraction residue, which is composed mainly of MgO·SiO_2, could be more efficiently used than CaO·SiO_2 or 2CaO·SiO_2.