DRI - Sponge Iron

Sponge iron, also known as Direct Reduced Iron (DRI), is a metallic product formed by the direct reduction of iron ore (pellets or lumps) using a reducing gas (natural gas, syngas, or coal gas) or non-coking coal, at temperatures below the melting point of iron (800–1200°C).

• Called “sponge iron” because of its porous, sponge-like structure after oxygen removal.

• Acts as an excellent raw material for steelmaking in Electric Arc Furnaces (EAFs) and Induction Furnaces (IFs).

Uses of Sponge Iron

1. Steelmaking (Main Use)

   • As a substitute or supplement for scrap in EAFs and IFs.

   • Improves control over chemistry of steel due to low tramp elements.

2. Feedstock for Secondary Metallurgy

   • Blended with steel scrap to produce high-quality alloy & special steels.

3. Hot Briquetted Iron (HBI)

   • Compacted form of DRI for easier transport and storage.

Specifications of Sponge Iron

1. Physical Properties

· Appearance: Porous, metallic grey solid.

· Bulk Density: 1.6 – 1.9 t/m³

· Porosity: 35 – 40%

· Size: 5 – 18 mm (lumps)

· Reactivity: High (can re-oxidize if exposed to air/moisture → needs careful handling).

2. Chemical Properties (Typical Composition)

· Fe (Total Iron): 88 – 92%

· Fe (Metallic Fe): 80 – 86%

· Degree of Metallization: 85 – 92% (ratio of metallic Fe to total Fe)

· Carbon (C): 0.1 – 0.3% (depends on process)

· Gangue (SiO₂ + Al₂O₃): 4 – 8%

· Sulphur (S): <0.03%

· Phosphorus (P): <0.05%

Advantages of Sponge Iron

• High purity feedstock compared to scrap.

• Consistent quality, less tramp elements (Cu, Sn, Cr, etc.) than scrap.

• Energy efficient in steelmaking when used with scrap.

• Flexible use in different steelmaking furnaces (EAF, IF, BF charging).

Limitations

• Highly porous → prone to reoxidation and even self-heating during storage.

• Lower density than scrap → requires careful furnace burden management.