Carbothermic Microwave Processing for the Enrichment of Iron Ore Fines

Abstract

The current study investigates the beneficiation of iron ore fines by the carbothermal process using muffle and microwave furnace. The muffle furnace reduction was found useful for the separation of iron-bearing phases from the quartz impurities and concentrate with iron purity of ~ 64%, recovery of 98%, and a yield of 84.5% is achieved at 900 °C, 9% charcoal in 1 h. Incorporating coal as a reductant followed a similar trend as charcoal, although the leaner reduction rate leads to limited fayalite formation and, consequently, better magnetic property at a higher temperature. The microwave exposure of ore led to a temperature of ~ 750 °C in 15 min, and the ore-reductant mixture attained 960 °C with charcoal and ~ 800 °C with coal. The microwave reduction yielded comparable concentrate iron grade-recovery with muffle furnace reduction at comparatively lower carbon dosage (6%), suggesting better carbon utilization. Meanwhile, coal-based microwave reduction followed the opposite trend as muffle furnace reduction, and iron grade decreases with an increase in carbon dosage. The optimal conditions of 6% charcoal and 800 W yielded concentrate of 63.8% Fe, 99% recovery with 87.4% product yield. The maximum separation efficiency of the muffle furnace reduction is 80% at 1000 °C with 18% charcoal compared to 70% in the microwave at 6% charcoal, indicating the latter route is efficient and economical. The separation efficiency remains unaltered with carbon dosage suggesting minimal carbon required for achieving maximum separation is 6% C. The metallization of the product of microwave reduction was the functionality of reductant dosage and increases exponentially with carbon dosage. The ferrite formation is initiated at 12% C with maximum metallization of 38.5% at 27% charcoal and 900 W power. The maximum metallization in muffle furnace reduction is 16% at 1000 °C and 18% C. The techno-economic comparison indicates incorporating microwave reduction reduces processing time by 25%, and the carbon consumption is reduced by 35.5%.

Graphical Abstract