Evaluation of Quality Parameters and Mineralogy of Iron Ore Pellets with Added Mill Scale

The present article focuses on incorporating mill scale, a steel plant solid waste, into the iron ore pelletization process. The characterization results indicated that the mill scale contained about 71% of Fe and predominantly consists of magnetite and wustite mineral phases. A detailed pelletization study is conducted using the mill scale at different proportions (0%, 10%, 20%, 30%, and 40%) in the feed blend. The impact of mill scale addition on various pellet properties, such as drop number, green and dry compressive strength and moisture content of green pellet, Cold Compressive Strength (CCS), porosity, Swelling Index (SI), Reduction Degradation Index (RDI), and Reducibility Index (RI) of fired pellets, has been investigated. Further, pellet mineralogy is analyzed using X-ray Diffraction and optical microscopy. Experimental results indicate that the mill scale addition of 10% in the feed mix leads to an improvement in pellet strength (CCS) achieving a CCS of 288 kg/pellet with about 24% porosity, 18% SI, 71% RI, and 2.5% RDI. However, a further increase in mill scale negatively affected the pellet properties. Further, the potential of coke rate reduction by the addition of mill scale is also studied in detail. Based on the experimental outcomes, the addition of the mill scale by 10% is beneficial in terms of effectively utilizing mill scale as well as improving the iron ore pellet properties.