Mineralogical and separation characteristics of iron ore fines from Bellary – Hospet, India with special emphasis on beneficiation by flotation

Abstract

The depletion of high grade iron ore and increased generation of fines during mining and handling and demand for high grade iron ore fines for pellet making and export has necessitated the processing of low to medium grade fines. Physical separation methods were found to be inadequate to process fine sized ores due to reduced selectivity of separation. An attempt has been made to understand the intricate associations between different mineral phases of iron ore fines from Bellary- Hospet area, India from XRD, as well as Electron microscopy studies. XRD studies indicated that hematite and goethite are the iron bearing minerals in order of abundance and quartz and kaolinite form the gangue. EPMA studies on these ores show the presence of gibbsite as the only alumina bearing phase and apatite as phosphorous bearing mineral. Traces of alumina, present as solid solution in the iron oxide minerals has also contributed Al2O3 to the ores. Electron microscope studies indicated that gibbsite grains are in the range of 10 to 50 microns and are intimately associated with the iron oxide phases. Particle Size Analysis and Heavy Medium Separation (HMS) tests on different size fractions provided the insight into the liberation and separation characteristics of the material. d80 of the material was found to be 40.5 microns. 20.6% by weight of the material can be treated as fairly liberated and obtained as a concentrate assaying 66.29% Fe, 2.15% SiO2 and 1.17% Al2O3 from the feed assaying 60.43% Fe, 6.88% SiO2 and 3.26% Al2O3. This defines the lower bench mark for theoretical recovery and grade of the concentrate. Further, scope exists for increase in recovery of iron values from the partially liberated particles without diluting the concentrate grade in terms of allowable limits of alumina (not more than 2.5%) for pellet making. Considering all these factors, flotation appears to be the only industrially viable process to recover these iron values with acceptable grade, recovery and alumina in the concentrate.