Production of Specification-Grade Ferrosilicomanganese from Off-Grade Fe–Mn Ores

A three-stage technological scheme is proposed to produce qualified ferrosilicomanganese from a low-grade ferruginous manganese ore. At the first stage, selective solid-phase reduction of iron with hydrogen is carried out. Then, after separation melting of the ore metallization products to form a by-product metal and a manganese-containing slag, manganese and silicon are reduced from the slag with carbon to form ferrosilicomanganese. The results of thermodynamic modeling of the process of reducing manganese and silicon from a high-manganese slag are presented. Manganese monoxide is shown to react with silicon dioxide in the slag to form the Mn2SiO4 tephroite. Upon heating above 1750 K, the reduction of manganese from this compound is found to begin. As the temperature increases to 1800 K, manganese and silicon form the metallic Mn5Si3 phase. On further heating, the amount of manganese in a gas phase increases. Experimental results on producing ferrosilicomanganese from a slag after separation melting are presented. The possibility of producing ferrosilicomanganese without harmful impurities is shown. The synthesized alloy contains 9.29 wt % silicon, 48.72 wt % manganese, and iron for balance. However, a significant amount of manganese (25.89 wt %) is retained in the slag phase, indicating its incomplete reduction. The results obtained can be used in developing theoretical and technological foundations for processing ferruginous manganese ores with a high phosphorus content, which cannot be processed by the existing technologies.