Study of the use of aluminium-containing waste in ferrosilicon production

This article presents the results of a study to select the most cost-effective raw materials for producing ferrosilicon and aluminum. Ash and slag waste from Ekibastuz coal (Kazakhstan) and aluminum slag were selected as the primary materials for producing pellets. Studies of the physicochemical properties of the resulting pellets revealed the presence of refractory minerals (mullite and sillimanite) in the experimental pellets. An analysis of the physicochemical properties revealed that heating the first batch of pellets in an oxidizing environment at temperatures of 1000–1200 °C predominantly resulted in the formation of mullite and quartz, as confirmed by X-ray diffraction and petrographic analysis. Thermodynamic diagram analysis showed that aluminum silicates begin to decompose in the range of 1650–2050 °C, with mullite decomposing at 1800 °C. A characteristic feature of this range is the formation of aluminum carbide, which, in the presence of excess silica, is easily neutralized to form ferrosilicon and aluminum. Above 2050 °C, silicon carbide in the charge sharply decreases, and the concentration of silicon and aluminum in the metal increases. Silicon carbide is primarily consumed in reaction with alumina, silicon suboxides, and aluminum to form a silicon-aluminum alloy.