Recovery of Iron Values from Iron Ore Slimes of Donimalai Tailing Dam

Abstract

During production of calibrated (sized) ore, more than 50 % of the generated fines and rejects (Slimes) cannot be directly utilised in iron making due to its unfavourable granulometry, low iron content, high alumina and silica content. Approximately 10–20 % of the process plant input is discarded as slimes into slime ponds/tailing dams. Tailing dams are now considered as a threat due to hazardous nature and acute shortage of land for storing. More over these slimes also pose threat to the environment. Recovery of iron values from slimes results in economic benefit by utilisation of waste as a resource and minimizes the land requirement, surface degradation, ground water pollution, destruction of forests. These slimes after beneficiation are agglomerated (Pelletisation) and can be used as burden for the blast furnace. This research work presents the route for beneficiation of slimes by removing gangue in the slimes to an acceptable level to produce hot metal through blast furnace route. Research has been carried out effectively and efficiently to utilise the iron ore slimes from the slime ponds of Donimalai iron ore mine. The slime sample from tailing pond of Donimalai iron ore mine was collected and transported to R&D Centre, NMDC Limited, Hyderabad. The ‘as received’ slime sample assayed 49.40 % Fe, 13.51 % SiO₂, 8.44 % Al₂O₃, 5.16 % loss on ignition and all other trace elements were within the critical limits. The ‘as received’ sample contains around 7 % moisture. It has a bulk density of 1.74 t/m³ and specific gravity of 3.7. Screen assay analysis was carried out with the ‘as received’ sample. Optimisation studies were carried out for desliming by using hydro-cyclone. Hydro-cyclone underflow was subjected to magnetic separation. It is possible to produce a concentrate which assayed 65.93 % Fe, 1.45 % SiO₂, 1.94 % Al₂O₃ and 1.56 % loss on ignition with a yield of 45.18 % with a recovery of 60 % iron values.