National Mineral Development Corporation Limited (NMDC) is having fully developed mechanized iron ore mining and processing complexes at Bailadila in Chattisgarh and Donimalai in Karnataka states having a total capacity of 15.00 million tonnes of run of mine ore per annum Initially, these mines were developed primarily for export of iron ore lump to Japan and other eastern countries as there was demand for lump ore only. During crushing and wet processing of iron ore on an average 15 to 18 percent slimes (-100 mesh) are produced in the iron mines of NMDC as classifier overflow (O/F). About 50 to 65 percent by weight of slimes could be recovered and upgraded to +64 percent Fe by processing classifier o/f adopting hydrocycloning. The concentrate obtained by hydro-cyclone meets the specifications for blending with normal classifier sand (fines) for sinter making. With the technological improvements and innovations now a days the -100 mesh fraction in the sinter feed could be accepted up to 40 percent. For this reason and to avoid the loss of super fine higher grade iron ore in the form of slime, it has become inevitable to process this using a suitable technique. The processing of slimes increases the quantity of high grade fine concentrate without affecting the quality and also increase the life of tailing dam. Keeping this in view, NMDC adopted a simple process flowsheet for beneficiation of iron ore slimes to produce high-grade concentrate using hydro-cyclones.The hydro-cyclone for beneficiation of slimes in the process plants at Bailadila-14 Bailadila-5, Chattisgarh State and Donimalai Karnataka State for recovery of iron ore values from slimes are being operated successfully (Appendix I). Classifier O/F contain -65# about 15 to 18 percent w.r.o. slimes. By introducing cyclone and operating at optimized parameters at a cut size -200# could able to recover about 16 to 17 percent w.r.o. as fines.
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