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Sponge iron also known as direct reduced iron is the product of reducing iron oxide in the form of iron ore and through the reaction with carbon in the form of coil. Further, it is melted at 1100° C which produces sponge iron. Let’s understand in-depth the uses and applications of sponge iron, the production process, and more.
Sponge iron plants in India
Since the year 2002, India has become the largest producer of sponge iron worldwide and 20% of the sponge iron is produced by India itself. The growth of the sponge iron industry has major success stories in the industrial sector of India after the liberalisation. The sponge iron industry has grown rapidly in the last five years and there are around 23 plants opened between the years 2000 to 2001 with a capacity of around 6.97 million tonnes (Mt). If we talk about the current scenario then around 206 sponge iron plants in the country with a capacity are there of around 19 Mt.
Application and uses of sponge iron
- Sponge iron is considered the best substitute for the item scrap. So, a higher percentage of raw material required for melting the steel. And it can be produced from the product instead of scraping.
- Sponge iron production has made a huge contribution to the continuous casting of the steel industry.
- This metal is also used to produce different steel items including DI pipes, TMT bars, etc. with the best quality.
- Sponge iron is one of the best materials that could be used for coolant in L.D. converters of integrated steel plants.
Sponge iron production process
- DRI unit
In the DRI plant, sponge iron is produced by using the solid reductant iron ore with carbonate materials such as coil. After, the reduction is carried out in a rotary kiln in which it is rotated at specific speed at the temperature of 800° to 1500° C. A process helps ensure that the raw material is moving from the feed end to the discharge end.
During the process of movement, the actual reductions of iron’s ore to iron take place. After the process of reduction, the material is discharged, and it is taken into the rotary cooler in which the product get cools down and is separated from the coal char. Some of the basic reactions that may be included in the process are-
-3Fe2MO3+ C0= 2Fe304+CO2
-FeO + Co= Fe+ CO2
- Electric arc furnace
Charging is being prepared as per the proposed chemistry for the targeted grade. Sponge Iron including ingredients along with the lime and charged in the arc furnace.
The melting form is accomplished with the help of the injection of energy into the charging material and the form of electrical energy with the help of three graphite electrodes. Carbon is injected into the furnace which reacts with oxygen that produces 02 and it bubbles through the bath. After CO reacts with the oxygen it is converted into O2 and it automatically generates heat. Once the final charge is melted the supervisors measure the temperature and a sample is drawn for determining the oxygen amount to be blown during the refining.
In the refining stage phosphorus is removed and the sulphur is removed as sulphide in the slag and better achieved in the production stage. Magnesium, silicone and aluminium react with the oxygen before the carbon forms oxides which directly go into slag. The carbon dioxide is produced because of the reaction of carbon with oxygen, bubbles through the bath that cause slag to form and have beneficial effects on the process. At the end of the process of refining the temperature measurement is taken and the sample is drawn for the analysis.
De-slagging – In the de-slagging process the slag layer is removed from the furnace. Phosphorus is transferred to the slag and it is done during the early stage of heating when temperature is low. The first de-slagging helps in removing the substantial protein from the phosphorus as P205.
Tapping – after reaching the appropriate composition, the tap hole is opened by the workers and metal is tapped into a ladle and it is sent to the casting unit. During the taping process, bulk alloys are added based on bottomless for the desired steel grid. In the steel, the de-oxidisers are added to control the oxygen content before the further process.
- Continuous ballet casting
From the EAF, molten steel is tapped within the ladle and taken into the continuous casting machine. Liquid steel is taken out from the letter into the tundish and then in the water-cooled mould. Continuously billets came out from the CCM and are being seized as per the length required.
- Rolling mill with thermex technology
The produced billets are reheated at the temperature of 1200°C and they are rolled into the specific sanctions of all of the material in the rolling mill unit. In the case of manufacturing the TMP re-bars, from the finishing standard of the rolling mill, the rebars are guided with the help of specifically designed thermex pipes to obtain the special property thermex steel process.
Advantages of sponge iron
Sponge iron has gained significant popularity over the years and is now considered a primary material rather than merely an alternative to scrapping in various industries. Here are some of its key benefits:
- Low sulphur content: DRI boasts a low sulphur content, making it a preferred choice for achieving higher-quality steel production.
- Controlled gangue elements: DRI contains limited and well-known gangue elements, allowing electric furnace operators to fine-tune their process parameters effectively. It is free from undesirable materials like copper, zinc, tin, chromium, tungsten, and molybdenum that are often present in scrap.
- Enhanced power levels: Continuous feeding of DRI into the Electric Arc Furnace (EAF) results in higher power levels compared to a 100% scrap charge under similar settings.
- Cooling agent in L.D. converter: Sponge iron can also serve as a substitute for ferrous scrap as a coolant in the L.D. Converter, reducing the likelihood of equipment breakages.
- Improved furnace productivity: Users of DRI experience higher furnace productivity. The elevated carbon monoxide (CO) content in the furnace reduces electrode oxidation, contributing to increased efficiency.
- Elimination of oxygen requirement: DRI eliminates the need for oxygen in scrap-cutting processes, streamlining operations, and reducing resource consumption.