Iron Ore

Iron ore is a name given to a naturally occurring mineral from which iron (Fe) metal is extracted in various forms viz Hot metal/ DRI etc.

There are two major types of Iron ore used for iron making. These are Haematite Ore( Containing Ferric Oxide - Fe2O3) and Magnetite Ore (containing Ferro-Ferric Oxide – Fe3O4). When chemically pure, Haematite contains approximately 70% and Magnetite 72.4% iron . But usually iron content of ores ranges between 50-65/67% (rich ores) and 30-35% (lean ores); the remains being impurities known as Gangue (such as Alumina, silica etc.) and Moisture.

Iron ore is typically classified in grades, as High grade (+65% Fe), Medium grade (+62 – 65% Fe) and Low grade (-62% Fe).

Typically, the Integrated Steel Plants(ISPs) use medium/High grade Iron Ore whereas the Sponge Iron plants require only High Grade iron ore, preferably, with +67% Fe.

Lumpy/Fine Ore : Iron Ore is traded in lumps (i.e. sized ore) or in fines. Production/availability of lumps is limited by virtue of the natural occurrence and also because of generation of lot of fines during crushing of large lumps present in the run-of -mines.

Natural pellet : It is a term coined by producers like NMDC to designate sized iron ore used directly in Sponge Iron production.

Blue Dust : Blue Dust is the name given to naturally occurring, extremely friable, high grade Haematite Iron Ore powder.

Beneficiation of Ore : Very low grade Iron ore cannot be used in metallurgical plants and needs to be upgraded to increase the iron content and reduce the Gauge content. Processes adopted to upgrade ore is called Beneficiation.

Indian ores are : Indian ore is generally rich in iron (Fe) content but the Alumina content is very high which call for special adjustments/techniques for production of iron/steel at the cost of productivity and quality and hence money.

Beneficiation at KIOCL : KIOCL has set up a Beneficiation plant to beneficiate Magnetite ore with approximately 35% Fe to high grade Iron Ore Concentrates, part of which is also used for production of pellets inhouse, and part is exported.

Agglomeration of Iron Ore : Iron Ore Fines/blue dust cannot be charged in the blast furnace directly since they block the passage for ascending gas inside the fee. So, they are agglomerated (by igniting at lower temperature causing only interfacial fusion) into larger lumpy pieces with/without addition of additives like limestone, dolomite etc.

Two types of agglomerated products are commonly produced/ used in the industry namely Sinter and Pellet. Accordingly the processes are known as Sintering and Pelletising respectively :

(a) SINTER: Sinter is a clinker like aggregate which is normally produced from relatively coarser fine iron ore (normally –3mm) mixed with coke breeze (-3mm), limestone dolomite fines (-3mm) and other metallurgical return wastes from the plant.

Sinter is a much preferred input/raw material in blast furnaces. It improves BF operation and productivity and reduces coke consumption in blast furnace. Presently, more than 70% hot metal in the world (in India 50%) is produced through the sinter.

(b) PELLET: Pellets are normally produced in the form of Globules from very fine iron ore (normally –100 mesh) and mostly used for production of Sponge Iron in gas based plants, though they are also used in blast furnaces in some countries in place of sized iron ore.

Nearby pages
Ironclads, Ironsides, Irony, Iroquois, Irradiated Food, Irreducible Case