Processing of low grade iron ore from Singhbhum-north Orissa craton using gravity concentration techniques

Abstract

Processing of low grade hematitic iron ores is inevitable as a result of depletion of high grade ores and rapid trend of increase in production of iron and steel in recent times. In view of this, beneficiation studies were carried out on a low grade hematitic iron ore based on the mineralogical characteristics of the sample. Basically, gravity concentration techniques were used for separation of iron bearing minerals from associated gangues. The sample was sized into four fractions keeping in view of their usage as lump -30+8 mm feed to blast furnace and fines-1 -8+1 mm and fines-2 -1+0.15 mm for sinter feed. The ultrafines (-0.15mm) can be used for as green pellets DRI feed. Suitable gravity concentration techniques were applied to different sized fractions for their iron enrichment. The washed lumps of -30+8 mm size, when subjected to heavy media separation at specific gravity 2.9, there is appreciable enrichment in the quality with 92.5% yield. Jigging of washed fines-1, indicated that the concentrate with yield of 45.0%, assaying 62.11% Fe could be obtained. Tabling of washed fines-2 showed that there is a substantial improvement in Fe (62.53%) 42.6 % yield and reduction of silica and alumina in the concentrate. Desliming of the -0.15 mm fraction using hydrocyclone was carried out to get a cyclone underflow product. The cyclone underflow was subsequently treated in a Wilfley table with slime deck to enrich it further. The tabling could produce about 15.7% yield with 63.9% Fe. Based on the above studies, process flow-sheet was developed for low grade iron ore from Singhbhum-north Orissa craton using various gravity concentration techniques, so as to produce reasonable grade of lumps and fines.