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Gas based sponge iron from Vikram Ispat - A multi purpose product for steel manufacturing

M V Subba Rao

We at Vikram Ispat producing Sponge Iron i.e. DRI, HBI together through Gas based Technology based on HYLIII from the same reactor to suit the entire Metallic requirements of Steel Industry. This can be used as a prime metallic in Integrated Steel Plants, Mini steel Plants, Foundry etc. Customer can choose the DRI or HBI depending upon their other scrap mix and final product.

Important Characteristics of HYL Sponge Iron: -Equivalent Metallization

The balanced carbon content and lower percentage of iron oxide in sponge iron helps to increase the equivalent metallization index. The carbon in sponge iron mainly is in the form of iron carbide, reacts with oxygen in the unreduced oxide & increases metallization. % Equivalent metallization = % metallization + 6 (% of carbon) It indicates that the oxidized iron remain in the sponge iron can be fully reduced with the carbon which is available in the form of iron carbide & carbon. The carbon - oxygen reaction improves heat transfer, decreases hydrogen and nitrogen in the metal bath. Carbon available in the sponge iron pure and can be utilized completely in the steel making process. Chemical & Physical Characteristics of Sponge Iron will vary depending upon the quality of raw material being used. We at Vikram Ispat using iron ore pellets and iron ore with highest % of iron content available in the world. This not only improves the metallic yield but also easy to standardize the scrap mix for the Steel maker.

Hot Briquetted Sponge Iron (HBI)

HBI is directly reduced Iron in briquetted form with higher % of metallization and Carbon. Higher Density of HBI facilitates for Export coolant in converters, complete recovery of Iron in Induction & Electric Arc Furnaces. HBI producing at Vikram Ispat is 2 types, i.e Normal Carbon HBI Low carbon HBI

HBI with Normal Carobon

Total Fe : 92.5% Min Metallisation : 9.25% Min Carbon : 1.2+/-0.3% Sulphur : 0.015% Max Phosphorus : 0.04% Max The Normal Carbon HBI can be used as direct replacement of Scrap. In the case of Converter and EAF, it is an ideal Scrap mix as it does not changing other parameters. Depends up on economics it can be used up to 60% in EAF as batch charging, 100% in continuous charging in the feed mix, 15% to 30% in converters as coolant. In the case of Induction Furnace, we can go up to 70% to 80%. Theoretically 30% to 40% is best mix to keep other parameters like Power consumption, Ref consumption at par with scrap. Most of the ferrous foundries in India have started using this HBI due to higher purity and lower residual elements with balanced Carbon.

HBI With Low Carbon

Chemistry of this product is similar with Normal Carbon HBI with downward variation in Carbon %. This is best suited for induction furnace rather than EAR High Carbon Scrap can be reduced easily in EAF Steel making but in Induction Furnace it is not possible. By blending with low carbon HBI, carbon can be neutralized in IF. Availability of high carbon scrap is increasing in Indian market from Auto mobile and domestic sources. This scrap is generally selling to IF units through local scrap dealers. HBI with higher metallization and lower carbon helps to blend easily with high carbon scrap and produce steel with desired chemistry. This is also very easy to standardize scrap mix and avoid offheats. HBI with low carbon can be used up to 60 % to 70% in IF units. HBI can be used with batch charging or continues charging in IF. Slag removal is a crucial activity in steel making. Faster slag removal helps faster melting, low refractory wear and power consumptions. Delay in slag removal causes over boiling and thus loss of liquid metal & longer tap times. By stabilizing feed rate we can avoid bridging and cold bottom. In the case of bigger furnaces like 8 to 12 Mts. HBI can be charged directly with the help of magnet to save the time. HBI with low carbon is finding increasing use in Induction Furnace especially at coastal markets where they import lot of HMS, which comes with high carbon pieces normally. This can also be used with normal carbon scrap but limitation in percentage of use.

Direct Reduced Iron (DRI)

The chemistry of DRI is similar to HBI but further rich in chemistry. The size & shape of DRI allows easier in charging for Induction as well as EAF or Converters. Storage of DRI is a big task but by taking certain precautions while storing, we can avoid all types of problems. Higher % of Carbon & Iron Content in Vikram DRI, allows to use up to 90% in Induction, 50% to 60% in EAF batch charging, 100% in continuous charging. This also best suited for cast Iron Foundry to replace Pig Iron /Scrap up to certain extent.

Use of Sponge Iron in Converters

Converters to reduce the temperature of the metallic bath. When super sonic speed oxygen jet is injected into liquid pig iron excess heat produced due to chemical reaction. This extra heat is reduced by coolant to avoid extra pressure oh refractory lining and steel quality. Sponge Iron from Vikram Ispat is best suited for this application and can be used up to 30% as coolant. This also improves the productivity. Gas based Sponge Iron is an excellent virgin metallic to replace other materials like pig iron, Scrap, Iron ore etc for CONVERTERS.

Conclusion

We have seen substantial growth in using Sponge Iron in all types of Iron & steel making processes globally. Its demand is increasing at much faster rates due to shortage in availability of Scrap and also to raise the productivity. Manufactures realized that the use of Sponge Iron definitely improves the quality of final steel products & it is must to withstand the present competitive market conditions. Some Chemical, Refractory, Powder Metallurgy. Pharmaceutical units have been started replacing expensive Scrap with Sponge iron to get distinct Technical & economical advantages. In India the insufficient availability of indigenous scrap to meet increasing demand in Primary & Secondary Steel sectors makes sponge iron is only a feedstock. However the long-term growth of this sector will depend on the supportive measures extended by the Government particularly duties on imported scrap, Natural gas & Iron Ore etc.