Processes for Beneficiation of Iron Ores Mar28

Processes for Beneficiation of Iron Ores...

Processes for Beneficiation of Iron Ores ¬†Iron is an abundant element in the earth’s crust averaging from 2 % to 3 % in sedimentary rocks to 8.5 % in basalt and gabbro. Because iron is present in many areas, it is of relatively low value and thus a deposit must have a high percentage of metal to be considered ore grade. Typically, a deposit must contain at least 25 % iron to be considered economically recoverable. Over 300 minerals contain iron but five minerals are the primary sources of iron ore. They are (i) magnetite (Fe3O4), (ii) hematite (Fe2O3), (iii) goethite (Fe2O3.H2O),¬† (iv) siderite (FeCO3), and (v) pyrite (FeS2). Mining of iron ores requires drilling, blasting, crushing, screening, and blending of the ores. Crushing and screening are an integral part of ore producing facilities. Crushing usually involves a primary crusher and secondary crushers operating in closed circuit with vibrating screens. Equipment selection is determined largely by the friability of the ore. Most of the screening operations on high grade ores are dry except when the fines fraction can be effectively upgraded by desliming. Iron ores normally fall within one of the three categories namely (i) direct shipping, or high grade ores, which contain enough iron to be charged to the iron making furnace directly and may only require crushing, screening, and blending, (ii) associated low grade merchant ores which occur around the high grade ores that can be mined concurrently and which require minor upgrading by washing to increase their iron content, (iii) low grade ores that requires extensive crushing, grinding and concentration to produce an acceptable concentrate. The iron ores that fall within these three categories have quite different processing requirements. To obtain a uniform product, ores of different grades, compositions, and sizes...