DRI from Recycled Iron Bearing Wastes for Lower Carbon in the Blast Furnace

Reduction of Fe-bearing FINEX process waste and carbon composite pellets from 1 373 K to 1 573 K to produce DRI (direct reduced iron) for use in the blast furnace was investigated using a modified thermo-gravimetric analyzer. Reduction from the initial Fe2O3 was not uniform throughout the composite pellet. Oxygen removal from the Fe2O3 rich composite pellets over 84% was only observed at 1 573 K. Lower temperatures resulted in significantly un-reduced FeOt due to the premature consumption of the carbon. A peripheral boundary of FeOt.Al2O3 and 2FeO center dot SiO2 phases surrounding the reducible FeOt was observed in some of the partially reduced cross-sectional SEM (scanning electron microscope) images that could hinder reduction. From the apparent activation energy, interfacial reaction seems to affect the kinetics of the Fe-bearing process waste composite pellets. Bursting of pre-dried composite pellets containing less than 2 mass% moisture was simulated in a RHF hearth simulator. From direct observation of pellets charged between 1 173 K to 1 573 K, medium-sized pellets between 9.4 to 12.4 mm diameter showed less bursting of the pellet, when charged below 1 273 K. In addition, modification of the physical strength of the hard bedrock formed from pellet bursting could be softened with additions of SiO2.