Effect of pyroxenite flux on the quality and microstructure of hematite pellets

Pellet properties are largely governed by the type and amount of oxide and bonding phases formed during induration and their stability during the reduction. In the present study, effect of MgO in the form of pyroxenite on melt formation and microstructure during the induration of hematite pellets was examined. Optical and electron microscope studies with EDS and X-ray mapping were carried to understand the amount and chemistry of different phases formed at different levels of MgO by varying the pyroxenite addition. These pellets were characterized for their strength and swelling index under blast furnace reduction conditions. Based on silicate slag chemistry formed in the fired pellets, microstructure and pellet quality, 5% pyroxenite addition to get 1.5% MgO in pellets found to be optimum flux dosage. Pellets with this optimized chemistry were also found superior to acid pellets in terms of reduction degradation index, reducibility and softening melting characteristics. Formation of magnesioferrite and high melting point slag with low FeO content in the fired pellets could be attributed to the improved performance of pyroxenite pellets.