Strengthening Sintering of Limonitic Nickel Laterite by Substituting Ferronickel Tailings for Sintering Fluxes

Ferronickel tailings, by-products from nickel laterite direct reduction-magnetic separation process, are now stored up in large quantities with low utilization because of the high MgO content. In this paper, ferronickel tailing with 5.82% Fe, 0.51% Ni, 44.08% SiO2, and 31.98% MgO was adopted to replace the traditional Mg-bearing flux, i.e. serpentine. The laboratory pot sintering tests show that, this new technique increases sinter productivity and tumble index by 4.12% and 10.63%, respectively, and reduces solid fuel rate by 6.35%. The mineralogical study of product sinter shows that the addition of ferronickel tailing contributes to the increase of the amount of SFCA by 4.03%. Mg and Al elements were found to migrate into magnetite grains to form three types of spinel solid solutions, i.e. (Fe, Mg)Fe2O4, Fe (Fe, Al)2O4, and (Fe, Mg)·(Fe, Al)2O4. Meanwhile, eutectic compound melts were obtained by the co-melting of kirschsteinite (CaO·FeO·SiO2), monticellite (CaO·MgO·SiO2), and fayalite (2FeO·SiO2).