Aluminium thermal reduction process for preparing ferrosilicon and alumina from fly ash

There has been a focus on environmental protection and the recycling of solid waste resources, particularly fly ash and aluminum dross. Increasing efforts have been made towards the utilization of fly ash in an efficient fashion. In this paper, a process was introduced for producing alumina-rich slag and ferrosilicon alloy simultaneously by means of aluminothermic reduction of fly ash with aluminium dross. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirm the formation of spherical ferrosilicon alloy encased in a loose and porous alumina matrix during the aluminothermic reduction process. Thermodynamic calculations showed indicated that reduction temperature of SiO2 and mullite decreased in the presence of Fe2O3. Under conditions of a temperature of 1673 K, ratio of aluminium dross to fly ash (A/F), and reduction time of 20 minutes, the magnetic fraction contains 85.89% ferrosilicon, while the non-magnetic fraction exhibits an alumina content of 79.42%. This process provides a solution with potential environmental and economic benefits for the application of fly ash and aluminum ash.