Benefits of using sponge iron in steel production

The steel industry in India is massive, currently holding the second position in steel production. Sponge iron is one of the most crucial raw materials for steel production. Also known as Direct Reduced Iron (DRI), sponge iron has brought a revolution in the traditional iron-making methods, in terms of operational, economic, and environmental benefits.

In this article, we have explored what sponge iron is, how it is made and the benefits of sponge iron:

What is Sponge Iron?

Sponge iron is a form of metallic iron produced by reducing hematite iron ore. It has this sponge-like rough and porous texture which has earned its name—sponge iron.

The reduction process doesn’t involve melting, but other iron-making techniques like a blast furnace.

Composition of sponge iron

The primary material of sponge iron is metallic iron, which is present at about 88-94%. The rest contains trace elements such as carbon, silica, sulfur, and phosphorus.

How is Sponge Iron Produced?

The sponge iron production process involves the direct reduction of iron ore. During the process, oxygen is removed from the ore using a reducing gas (hydrogen or carbon monoxide) or solid carbon (coal).

The temperature required for the process is between  800°C to 1,200°C. It doesn’t lead to melting, hence the energy requirement is much lower making the process more sustainable.

There are several techniques used to manufacture sponge iron, such as:

1. Coal-Based Rotary Kiln Process

This is one of the popular and cost-effective methods for manufacturing sponge iron. The method involves mixing iron ore either in lumps or pallet forms with non-coking coal. The mixture is then poured in a rotary kiln which rotates slowly while heating the contents to about 1,000–1,100°C.

As the iron ore moves through the kiln, the carbon in coal reacts with the iron oxide, removing the oxygen and leaving behind metallic iron. Once the process is complete, the mixture is cooled and filtered.

2. Gas-Based Reduction Process

In this method, coal is replaced with natural gas, primarily methane. The natural gas is reformed into hydrogen (H) and carbon monoxide (CO) through a catalytic reaction.

These reformed gases react with the iron when heated in the shaft furnace at 800-1000°C and remove oxygen from the iron in its solid phase. This leads to the porous texture of sponge iron.

3. SL/RN Process

The SL/RN process is an excellent way to produce iron from low-quality iron ore. During the process iron ore, coal, and dolomite or limestone are heated ( 920°C-1100°C) and rotated inside the rotating kiln, and the iron is reduced.

4. HYL Process

Developed in Mexico, the HYL (Hot Yield Low) process is a highly efficient gas-based reduction system. The process is conducted in a shaft furnace, which yields sponge iron with exceptional metallization and energy efficiency.

Why is Sponge Iron used in Steel Production?

The Ministry of Steel has shared that crude steel production from April to February 2025 is 137.96 million tonnes (MT), which is 5% higher compared to the same period last year.

This substantial amount suggests the high demand in the steel industry. Sponge iron is widely used in the steel-making industry. There are quite a few reasons behind it. Let’s take a look:

1. Consistent Quality and Composition

When producing steel, the composition of the raw material matters. Especially for high-grade steel products such as automotive components, construction reinforcements, and specialty machinery.

In sponge iron, the chemical composition is consistent, unlike scrap steel. It contains a low content of sulfur, phosphorus, copper, and other tramp elements, so there are fewer impurities in the steel.

2. Improves Steel Properties

Steel has found its application in various industries. Whether it’s utensils or high-grade building materials, the potential is infinite. Steel made with sponge iron boasts:

• Superior tensile strength
• Better ductility
• Higher weldability

These properties make steel products safer, more durable, and suitable for complex engineering applications.

3. Higher Furnace Productivity

Sponge iron contains high amounts of iron, which increases the melting speed in the furnace. Direct reduced iron (DRI) also has very limited impurities which reduces slag formation.

4. Increases Energy Efficiency

Sponge iron production consumes less energy than traditional blast furnace operations. It eliminates the need for coke ovens and sinter plants, cutting down both capital and operational expenses.

5. Sustainable and Eco-Friendly

Decarbonizing has become a global challenge in the steel industry. The Ministry of Steel has launched the Green Steel Initiative to lower the carbon footprint in the steel industry.

Sponge iron can be a greener alternative, helping with:

• Lowering CO₂ emissions in gas-based processes
• Eliminating solid waste generation
• Reducing pollution due to coke usage

6. Reduces Scrap Dependency

Almost every steel plant uses scrap as raw material for recycling and lowering the environmental impact. However, the global scrap market can be volatile with quality issues, inconsistent supply, and rising prices becoming major concerns.

Even when scrap is unavailable, sponge iron helps to maintain production continuity as well as product quality.

7. Can be Obtained from Different Sources

Another advantage of sponge iron is that it can be produced from different raw materials. Whether it is iron ore lumps, pellets, or fines, manufacturers can produce sponge iron using different techniques.

It reduces the time, effort, and resources needed to source raw materials. Plus, sponge iron can be mixed with scrap which balances costs and performance in real time.

8. Economical in the Long Run

The initial setup costs for sponge iron plants can be significantly large. However, considering its long-term benefits, such as lower energy bills and raw materials costs, it may be ideal.

Manufacturers can avoid high-grade coking coal and replace it with more abundant thermal coal or natural gas, which are less expensive.

Wrap Up

The high demand in the steel industry requires smarter and cleaner raw materials. Sponge iron offers consistent quality, is environmentally friendly, and is economical, which makes it the ideal material to use in steel production.