Pilot Scale Froth Flotation Studies To Upgrade Nigerian Itakpe Sinter Grade Iron Ore To A Midrex-Grade Super-Concentrate

Abstract

The sinter grade concentrate of Itakpe iron ore found in the North Central Kogi state of Nigeria with cumulative undersize of 6.34% and 2.12% passing 90µm and 63µmsieves, respectively, and that assayed 63.63% Fe, 5.90% silica and 0.72% alumina was ground in ball mill to produce a pilot plant froth flotation feed with cumulative undersize of 74.37% and 42.94% for 90µm and 63µm sieves, respectively. The ball mill discharge was then treated in three stages of roughing, cleaning and re-cleaning in a pilot plant froth flotation process line and the products obtained gave 66.66%, 66.51%, 65.44% (Fe) and total acid (silica and alumina) contents of 4.22%, 4.39%, 5.15%, respectively, for the three stages. The super-concentrate obtained also gave 81.13%, 55.19% and 30.57% cumulative undersize for 90µm, 63µm and 45µm sieves, respectively. The results obtained showed that the roughing stage of the flotation process produced a super-concentrate that fall in the range of 66% to 68% for use in midrex direct reduction plant at the Delta Steel Plant, Nigeria. The lowest total acid gangue content of 4.22% was also obtained for the roughing stage, indicating that the two subsequent processes of cleaning and re-cleaning were not needed. Although, the total acid content of 4.22% for the roughing stage product slightly exceeds the upper limit of 3.50% for the Midrex process, Itakpe sinter grade concentrates with up to 5% acid gangue has been successfully used at the Delta Steel Plant Midrex plant.