Smelting–Aluminothermic Reduction of HCFeMn Slag in a 200 kW DC Arc Furnace

High-carbon ferromanganese (HCFeMn) slag, a significant byproduct, represents both an environmental challenge and a valuable resource for metal recovery. In this study, aluminothermic reduction of HCFeMn slag was assessed in a 200 kW DC (direct-current) arc furnace, smelting 2009 kg of slag with 202 kg of recycled aluminium scrap and 382 kg of burnt lime over 20 taps. The average specific energy requirement was 0.87 kWh kg−1 of charge (0.74–0.98 kWh kg−1 tap-to-tap). The slag-to-metal ratio was 4.79–6.68 kg/kg, against 1.1–1.6 kg/kg for conventional carbothermic manganese ferroalloy production (1.2–1.6 kg/kg HCFeMn, 1.1–1.3 kg/kg SiMn); because this ratio is high, the specific energy per tonne of alloy recovered exceeds the 4.0–4.5 MWh/t typical of conventional submerged-arc SiMn (silicomanganese) furnaces. Thus, the advantage lies in the low electrical demand per unit of charge and the absence of fossil reductant. The aluminium reductant efficiency ranged from 55.14 to 91.89% (campaign mean 60%), with Mn recovery of 47–81% and Fe recovery rising from 33–38% to over 90%, tracking the power increase from 130 to 180 kW. The emissions were approximately 1.35 t of CO2 per tonne of alloy, a 60–65% decrease relative to conventional carbothermic HCFeMn production (3.0–4.0 t CO2) and an 80% decrease relative to the cradle-to-gate SiMn benchmark (6.94 t CO2), with negligible direct process CO2 emissions, SO2 emissions of 0.312 kg/t alloy, and pre-abatement particulates of 10.4 kg/t alloy, using recycled aluminium scrap that requires up to 95% less energy than primary aluminium. The results demonstrate direct valorisation of industrial HCFeMn slag as the HAlMan process feedstock at Technology Readiness Level (TRL) 6.