Sponge iron, also known as DRI, is obtained from direct reduction of iron Pellet. The name of the product is due to its form of porous spherical (pellet) with a sponge-like appearance. Sponge Iron has a high grade of iron, which is more used today due to the shortage of iron scrap and its high price and its making environmental problems.
Sponge iron grade:
The grade and amount of iron in sponge iron is between 84% to 95%. This high grade of iron makes sponge iron a good source for steel production. As mentioned, It is obtained from recycling natural or processed iron ore that has not reached the melting temperature.
Application of Sponge Iron:
Sponge iron is a good substitute for iron scrap, so a high percentage of the raw material needed for steel melting can be produced from this product instead of scrap.
One of the most important applications of sponge iron is in induction furnaces in which it is possible to be replaced by about 50% with scrap. In addition, sponge iron has made a major change in the continuous casting of the steel industry.
Why Use of Sponge Iron?
About 66.3% of the world’s crude steel is produced by the blast furnace method, and about 31.2% is produced by direct reduction and the use of electric furnaces. Although most crude steel production in the world is produced by the blast furnace method, the followings justify the use of direct reduction and electric furnaces:
- This method is faster.
- The cost of setting up a Blast furnace is higher than a direct reduction unit and electric furnace at the corresponding capacities.
- Metallurgical coke, one of the raw materials needed for blast furnace, comes from coking coal, which has limited resources and is also expensive. To produce one ton of crude steel using blast furnace, according to the world standards, it requires at least 1.5 tones of iron ore and 450 kg of metallurgical coke, sometimes increasing to 3 tones of iron ore and 1 ton of coke. As a result, since gas can be used as a reduction material in the direct reduction method, and despite the enormous gas resources in some countries, the Blast furnace method actually loses its advantage.
- The Blast furnace method has more environmental limitations than the direct reduction method.
- The Blast furnace at high capacity (at least 1.5 million tones per year) has more economic justification, while the direct reduction method can also be used in small steel plants being justifiable economically.
- Sponge iron can be converted into hot briquetted iron (HBI) for easier transportation or storage. However, it is difficult to carry the agglomerate, which is the blast furnace feed.
- In the process of direct reduction, natural gas can be used without removing its impurities.
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