M K Mohanta

Utilization of Iron Ore Slimes: A Future Prospective

In India, iron ores processing industries play a vital role in the Indian economy. During the washing and processing of iron ores, slimes less than 0.15 mm are generated and discarded into the tailing pond. These slimes need processing as they cannot be used directly in blast furnaces. In the present investigation, a typical iron ore slime sample containing 59.22% Fe, 4.76% SiO2, and 4.57% Al2O3 was taken. The desliming operation was carried out by using 2” Mozley hydrocyclone. The process variables used to attain the optimum condition of desliming include the spigot opening, the feed pressure, and the diameter of the vortex finder maintaining the pulp density at 10% solid. The deslimed sample was treated by different techniques including an enhanced gravity separator to achieve iron concentrate with 65% Fe so that it can be used for steel making through pelletization. The yield of the magnetic concentrate is about 46.8% with 65% Fe. To improve the yield, the overflow from 2” hydrocyclone and the rejects from magnetic separation were deslimed and processed to recover the iron values. The final concentrate is 74% yield with 64.8% Fe, 1.76% SiO2, and 1.8% Al2O3.

Enhancing the Utilization Potential of a Low Grade Chromite Ore through Extensive Physical Separation

Low grade chromite ore with less than 30% Cr2O3 was investigated with a view to enhance its utilization potential. The ore contained olivine, serpentine, and chrysotile as the gangue minerals. The chromite mineral contained alumina, magnesia, and FeO in its lattice. Critical mineralogical assessment indicated that enrichment to a level of 39-43% Cr2O3 may be possible. Beneficiation of the ore was undertaken using gravity based methods. Inadequate liberation prevented any significant enrichment at 0.9 mm top size. At 0.3 mm top size, the spiral concentration generated a concentrate with 40.5% Cr2O3 from the coarser fraction. The finer fraction was treated in a shaking table to generate another concentrate with 41.6% Cr2O3. The final combined concentrate assayed 41.2% Cr2O3 with a Cr/Fe ratio of 2.27. The middling from both treatments were rich in chromite content and were recommended to be included in the concentrates. Chromite recovery from the coarse reject was also beneficial. It was recommended that 8-10% solids content of the reject stream with 0.02 kg/t of Magnafloc flocculant may be used to achieve best settling characteristics of the reject fines.