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Wednesday, February 27, 2008

Environment-friendly Corex process of iron and steel making:

Environment-friendly Corex process of iron and steel making:

The highlight of the process is it does not require coking coal. The process differs from the conventional blast furnace route; where un-treated non-coking coal can be directly used for ore reduction and melting work, eliminating the need for coking plants. The use of lump ore or pellets also dispenses with the need for sinter plants.

The ability to operate without coke gives this process two environmental advantages over the conventional blast furnace. First, because coke ovens are not needed, all of the problems associated with the generation of benzene and other coal tar byproducts are eliminated. Second, the dust problems associated with blast furnaces are also eliminated because the off-gas is used as fuel. This process along with direct reduction of iron (DRI) process is being implemented in many countries. The off-gas obtained being used to fuel the adjoining DRI plant.

Viewing the process from the coal-route perspective, non-metallurgical coal is directly charged into the melter gasifier. Due to the high temperatures predominating in the dome of the melter gasifier (in excess of 1000 °C), a portion of the hydrocarbons released from the coal during devolatilization are immediately dissociated to carbon monoxide and hydrogen. Undesirable by-products such as tars and phenols, etc. are destroyed and therefore cannot be released to the atmosphere. Combustion with oxygen injected into the melter gasifier results in the generation of a highly efficient reduction gas. Hot metal and slag tapping are carried out as in conventional blast furnace practice. The quality of the hot metal is equivalent to that produced in a blast furnace.

Environmental Aspects: In this system emissions contain only insignificant amounts of NOx, SO2, dust, phenols, sulphides and ammonium. Emission values already exceed by far future European standards. Also, waste-water emissions from are far lower than those in the conventional blast-furnace route. These environmental features are additional key reasons for the attractiveness of the present system.


Daniel said...

I'm afraid that COREX does require metallurgical coke, perhaps even as high as 10-15% of the total fuel burden, so COREX is certainly far-from perfect.
I don't have any evidence for you, but I have expert colleagues in the industry that are "in the know".


Reply from Partha Das Sharma on comment of Daniel:

COREX® technology – It is an industrially and commercially proven direct smelting reduction process that allows for cost-efficient and environmentally compatible production of hot metal directly from iron ore and non-coking coal. This is the only alternative to the conventional blast furnace route consisting of sinter plant, coke oven and blast furnace. It distinguishes itself from the blast furnace route by: (i) Direct use of non-coking coal as reducing agent and energy source and (ii) Iron ore can be directly and feasibly charged to the process in form of lump ore, pellets and sinter.
In this technology, iron ore (lump ore, pellets, sinter or a mixture thereof) are charged into a reduction shaft where they are reduced to direct reduced iron (DRI) by a reduction gas moving in counter flow. Discharge screws convey the DRI from the reduction shaft into the melter gasifier, where final reduction and melting takes place in addition to all other metallurgical reactions. Hot metal and slag tapping are done as in conventional blast furnace practice. Coal is directly charged into the melter gasifier. Coal combustion by oxygen injected into the melter gasifier results in the generation of a highly efficient reduction gas. This gas exits the melter, is cooled and is then blown into the reduction shaft, reducing the iron ores in counter flow to DRI, as described above. The gas leaving the reduction shaft is cooled and cleaned and is suitable for a wide range of applications (e.g., power generation, DRI production or use in reheating furnaces).
Benefits of this process -
(i) Substantially reduced specific investment costs and operation costs compared with conventional blast furnace route,
(ii) Outstanding overall environmental compatibility, as less carbon dioxide is produced;
(iii) Use of COREX export gas for a wide range of applications,
(iv) Use of a wide variety of iron ores and coals,
(v) Elimination of coking plants,
(vi) Hot-metal quality suitable for all steel applications.
COREX process of iron making is in operation at (i) Mittal Steel South Africa, Saldanha Steel Works, South Africa; (ii) Jindal South West Steel, Toranagallu Works, India; (iii) Posco, Pohang Works, Korea; (iv) Baosteel, China (v) Essar steel, India etc.


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