Coking Coal, also known as metallurgical coal, is a special grade of bituminous coal that possesses the ability to soften, swell, and re-solidify into a strong, porous mass known as coke when heated in the absence of air. This property is essential for blast furnace ironmaking and forms the backbone of the global steel industry.
Coking coal is classified into distinct grades based on its coking strength, fluidity, ash, volatile matter, and coke quality parameters. Each grade plays a specific role in coke blend optimization and steel plant performance.
Coal Rank Position
| Coal Rank | Carbon Content | Calorific Value | Coking Property |
|---|---|---|---|
| Lignite | Low | Low | Non-coking |
| Sub-Bituminous | Medium | Medium | Non-coking |
| Bituminous (Coking) | High | High | Coking |
| Anthracite | Very High | Very High | Non-coking |
Major Coking Coal Grades
1. Hard Coking Coal (HCC)
Hard Coking Coal is the premium grade with excellent coke strength and fluidity. It forms strong coke capable of supporting the blast furnace burden.
| Typical Parameters | Range |
|---|---|
| Ash | 7 – 10% |
| VM | 18 – 25% |
| CSR | > 65 |
| CSN | 7 – 9 |
2. Medium Coking Coal (MCC)
Used in blends to optimize coke cost and quality. MCC provides good coke yield but lower strength than HCC.
| Typical Parameters | Range |
|---|---|
| Ash | 10 – 14% |
| VM | 20 – 28% |
| CSR | 55 – 65 |
| CSN | 5 – 7 |
3. Semi-Soft Coking Coal (SSCC)
Lower coking strength coal used mainly as a blending component.
| Typical Parameters | Range |
|---|---|
| Ash | 12 – 18% |
| VM | 25 – 35% |
| CSR | 45 – 55 |
| CSN | 3 – 5 |
4. Pulverized Coal Injection (PCI) Coal
Injected directly into blast furnaces to reduce coke consumption. PCI coal does not require strong coking properties.
| Typical Parameters | Range |
|---|---|
| VM | 18 – 35% |
| Ash | < 12% |
| HGI | > 55 |
Typical Chemical & Mechanical Properties
| Property | Typical Range |
|---|---|
| Fixed Carbon | 55 – 70% |
| Volatile Matter | 18 – 35% |
| Ash | 7 – 18% |
| Moisture (ARB) | 6 – 10% |
| Sulfur | < 0.8% |
| GCV | 6,500 – 7,500 kcal/kg |
| HGI | 45 – 70 |
Coking & Metallurgical Behavior
Softens and fuses between 350–500°C
Re-solidifies into porous coke above 1,000°C
Provides mechanical strength and permeability in blast furnaces
Acts as fuel, reductant, and structural support
Processing & Preparation
Coal washing and beneficiation
Blending of multiple grades for optimal coke quality
Size control and moisture management
Coke oven carbonization (by-product recovery)
Major Global Sources
Australia (largest exporter)
United States
Canada
Russia
Mozambique
Indonesia (PCI & SSCC)
Applications
Steel Industry: Blast furnaces, coke ovens
Foundries: Metallurgical coke production
PCI Systems: Coke rate reduction
Sinter & Pellet Plants: Energy and carbon source
Coking Coal vs Thermal Coal
| Parameter | Coking Coal | Thermal Coal |
|---|---|---|
| Main Use | Steelmaking | Power generation |
| Coking Ability | Yes | No |
| Carbon Structure | Plastic / reactive | Non-plastic |
| Value | Higher | Lower |
Quality Standards & Testing
Proximate & ultimate analysis
Crucible Swelling Number (CSN)
CSR / CRI testing
Gieseler fluidity
ASTM / ISO / IS standards
Coking Coal Grades are critical inputs for steel manufacturing, directly influencing coke strength, blast furnace productivity, fuel efficiency, and overall steel quality. Selecting the right grade and blend is essential for cost optimization, operational stability, and metallurgical performance.