The production of high value pig iron nuggets from steelmaking by-products - A thermodynamic evaluation

Zinc contaminated steelmaking by-products such as blast furnace (BF) dust and basic oxygen steelmaking (BOS) dust present a significant recycling challenge at integrated steelmaking plants. Rotary Hearth Furnaces (RHFs) provide an attractive route for recovery of Fe and Zn from these materials through carbothermal reduction of the oxides in the material to yield Direct Reduced Iron (DRI) and crude zinc oxide. The next generation of RHF processes such as ITmk3 and e-nugget produce pig iron nuggets from iron ore concentrates and coal, as iron and gangue separate in-situ without an additional melting unit. A computational study of the metal-slag system using FACTSAGE 7.3 suggests that production of pig iron nuggets of good quality (93.75 wt.% Fe, 4.3 wt.% C, 0.116 wt.% S, 0.66 wt.% Mn) can be produced from BF dust and BOS dust in a ratio of 37:63 with addition of 5.4 wt.% SiO2 and 1.51 wt% MgO at 1450 degrees C. These computational results are in good agreement with experimental studies on similar material and, as such, suggest a practically feasible process.