Response of Reverse Flotation on Iron Ore Slimes Varying in Size Distribution and Assay Content

In view of the depletion of high grade iron ores, steel producers have adopted various beneficiating techniques to utilize the medium and low grade iron ores. M/s JSW too has adopted the beneficiation of ores to make use of medium and low grade iron ore. The efficiency of most commonly used technology for beneficiation of iron ores such as spiral concentration and magnetic separation become inefficient with the content of higher amount of ultra fines. Iron ore slimes generated during the beneficiation process carry considerable iron into the tailings. The slimes comprise particles of very fine sizes (-25µm) with high concentrations of impurities like alumina and silica and impose inefficient recoveries of iron bearing minerals. In this context reverse flotation studies are carried out with an emphasis to reduce iron loss in tails. Initial trials on spiral classifier overflow (COF) sample confirmed that the amine collector SOKEM 503C is comparatively more efficient than the SOKEM 522C and SOKEM 524C. To improve upon the grade and recoveries with the said collector, COF sample is subjected to two stage de-sliming followed by flotation. The outcome of study established that i) Improvement in product grade with the feed of narrow size range, ii) Iron bearing particle in finest size will have a tendency to migrate into froth fraction during initial stage of froth collection period, iii) Increased feed grade leads to increased iron loss in tailing and iv) Flotation on underflows of 5” and 3” cyclone independently, yields comparatively better grade and recoveries i.e. 63.0%Fe and 55.2% respectively rather than flotation separation on a blend of both the underflow of 5” and 3” hydrocyclone