A techno-economic approach for magnetising roasting of iron ore composite pellet using conventional and hybrid microwave furnace

The present study aims to enhance the iron ore fines through reduction roasting using a muffle and hybrid microwave furnace. The Taguchi statistical design was used to optimise the process variables such as temperature, time, and reductant concentration. The reduction roasting was followed by multi-pass low-mid intensity magnetic separation to treat the low-grade iron ore fines (Fe 44.53%, 40.13% silica). The results showed that the conventional reduction roasting at optimum conditions (800 degrees C, 60 min, 7% coal) produced a concentrate with 52.6% Fe grade and 77.3% recovery. The microwave roasting produced a concentrate with 53.06% Fe grade and 75.7% recovery at 750 degrees C, 2 min, and 7% coal as the reductant. The effect of both heating methods on compressive strength (CCS) and surface morphology was also studied. The results indicated that microwave heating resulted in a finer and more porous structure that improved the reducibility and ease of grinding. The techno-economic comparison showed that microwave reduction reduced the processing time by 85% and energy consumption by 73%. The study concludes that microwave heating followed by multi-pass magnetic separation can significantly improve the economic viability of exploiting lean iron ore fines.