Scientists Advance Understanding of DRI in Modern Steel Production

Have you ever wondered what goes into the production of steel beyond scrap metal? One of the steel industry’s best-kept secrets is a remarkable semi-finished product known as Direct Reduced Iron (DRI). This material plays a crucial role in modern steelmaking, offering a cleaner and more efficient alternative to traditional methods.

Direct Reduced Iron, or DRI, is a high-purity iron product obtained by removing oxygen from iron ore in its solid state—without melting it. This process relies on reducing agents such as carbon monoxide and hydrogen to strip oxygen atoms from iron ore molecules, leaving behind nearly pure metallic iron. Think of it as a delicate chemical operation where oxygen is carefully extracted, leaving only iron behind.

There are two primary methods for producing DRI:

• Gas-Based DRI: The most widely used method, gas-based DRI production is often integrated with electric arc furnace (EAF) steel mills, forming compact "mini-mills." Natural gas is converted into carbon monoxide and hydrogen, which then react with iron ore in a reduction furnace. The resulting DRI can be fed directly into an EAF while still hot, saving energy. Some producers also transport DRI to other steel plants or sell it to third parties.
• Coal-Based DRI: Predominantly used in countries like India, this method employs rotary kilns where coal serves as both fuel and reducing agent. The product, locally known as "sponge iron," is typically produced in smaller quantities but remains an economical solution for regional steel production. Notably, India sourced approximately 57% of its crude steel from EAFs (2016 data), with sponge iron playing a key role.

DRI is not pure iron—it contains residual impurities. When produced from iron ore with 65.5%–68% iron content, its typical composition includes:

• Metallization Rate: 92.0%–96.0%
• Total Iron Content: 86.1%–93.5%
• Metallic Iron Content: 81.0%–87.9%
• Carbon Content: 1.0%–4.5%
• Sulfur Content: 0.001%–0.03%
• Phosphorus Pentoxide (P₂O₅): 0.005%–0.09%
• Gangue (SiO₂, Al₂O₃, CaO, MgO, MnO, etc.): 3.9%–8.4%
• Particle Size: 4–20 mm
• Bulk Density: 1.6–1.9 t/m³

DRI is highly reactive and prone to re-oxidation when exposed to air, which can generate heat and lead to spontaneous combustion. To mitigate risks, strict handling and storage protocols are enforced. The International Maritime Organization (IMO) classifies DRI as a Group B cargo (chemically hazardous) and MHB (materials hazardous only in bulk), requiring transportation under inert gas (usually nitrogen) to prevent oxidation.

The primary use of DRI is as a feedstock in electric arc furnace (EAF) steelmaking. Compared to scrap metal, DRI offers several advantages:

• Consistent Composition: DRI has fewer impurities, allowing for better control over steel quality.
• Low Residual Elements: It contains minimal harmful elements (e.g., copper, nickel, chromium), making it ideal for high-grade steel production.
• Enhanced Efficiency: Adding DRI to EAFs accelerates melting, reducing production time and energy consumption.

Beyond EAFs, DRI is also used in blast furnaces and foundries.

As environmental regulations tighten, the steel industry is under pressure to reduce carbon emissions. DRI presents a cleaner alternative to conventional ironmaking, particularly when produced using hydrogen as a reducing agent. This method, known as hydrogen-based DRI, is considered a cornerstone of sustainable steel production.

With its growing importance, DRI is poised to play a pivotal role in the steel industry’s transition toward greener practices.

In addition to DRI, other iron ore-derived metallics contribute to steel production:

• Hot Briquetted Iron (HBI): A denser, more stable form of DRI, HBI is easier to transport and store.
• Pig Iron: Produced in blast furnaces, pig iron has high carbon content and serves as a key steelmaking ingredient.
• Granulated Pig Iron (GPI): Used as a coolant in blast furnaces or as feedstock in EAFs and foundries.