Upgrading Low-Grade Iron Ore by Magnetizing Roasting using Sawdust
Low-grade iron ore sample was collected from Gangra mines in Nimba Liberia. The ore was subjected to XRD and XRF analysis and was found to contain 63.1% Fe2O3, 25.4% SiO2, 9.1% Al2O3, and 2.4% LOI. 561.5 g . 1684.5g raw ore was crushed, ground, screened to 2 mm particle size below and chosen for the study. 561.5g of this portion was subjected to dry magnetic separation and 50 g magnetic fraction was obtained and the remaining 1123.3g was divided in to two even portions and subjected each to three separate rounds of reduction roasting for 30 and 50 minutes and 61.4% and 65.9% of magnetic fractions were obtained, respectively. The mineral phase transformation of hematite to magnetite and other induced mineralogical properties due to reduction roasting were investigated using, energy dispersive spectroscopic EDX, scanning electron microscope SEM x-ray diffraction (XRD) and x-ray fluoresce (XRF) techniques. The effects of reduction variables such as time (30-50 mins), temperature (750-950oC), and the reductant dosage were investigated as parameters that influenced the process. Carbon was obtained from carbonization of sawdust and was characterized and used as reductant. The results showed that the iron content in the magnetic fraction can be increased from 63.1% to 86.3% with parameters as follows: 950oC heating temperature, average roasting time of 40 minutes, crushing, grinding, and mixing time of 2 minutes, reductant dosage of 10 g carbon 565.1 g of sample, and magnetic field strength of 0.2 Tesla. Complete hematite phase transformation to magnetite was obtained at the preceding conditions. Phase transformation was studied as a function of different roasting parameters and magnetic susceptibility. The feasibility of industrial application of reduction roasting followed by magnetic separation applied to low grade iron ore separation involving waste processing of sawdust as source of carbon as reductant is included.