The Influence of High-Temperature Roasting on the Phase Composition of Pellets Based on Aluminum Slags and Their Testing in the Smelting of Ferrosilicon

This paper examines a resource-saving technology for ferrosilicon smelting using industrial waste, specifically aluminum slag and aspiration dust from ferroalloy production. A technological approach is proposed based on the preliminary pelletization of finely dispersed aluminum slag to improve the physicochemical properties of the charge materials and ensure their efficient use in the metallurgical process. Pellets were produced by granulation in a disk granulator using a lignosulfonate binder, followed by drying and high-temperature firing in the temperature range of 600–800 °C. Microstructural and energy-dispersive analysis revealed the formation of a stable aluminosilicate matrix, represented predominantly by mullite-like phases, ferrosilicate inclusions, and calcium–magnesium silicates. The formation of these phases contributes to the strengthening of the pellet structure and the formation of intergranular bonds during heat treatment. Experimental ferrosilicon smelting was conducted in a laboratory ore-thermal electric arc furnace. The results demonstrated a stable electrothermal smelting regime, satisfactory charge layer gas permeability, and effective reduction processes. The resulting alloy corresponds to FS-45 ferrosilicon grade with a silicon content of approximately 48%. It was established that aluminum slag-based pellets actively participate in the formation of an aluminosilicate slag system of the SiO₂-Al₂O₃-CaO-MgO type, ensuring favorable slag physicochemical properties and efficient separation of the metallic and slag phases. The proposed approach enables the incorporation of industrial waste into metallurgical production, reducing the environmental impact, and increasing the resource efficiency of silicon ferroalloy production processes.