Non-coking coal, commonly known as thermal coal, is a type of coal primarily used for heat and energy generation. Unlike metallurgical (coking) coal, non-coking coal does not exhibit plasticity or caking behavior when heated. It does not soften, swell, or resolidify into coke and therefore cannot be used in blast furnaces for steel production.
The commercial value of non-coking coal is determined mainly by its calorific value and combustion efficiency rather than coke-forming properties. It is the most widely consumed coal globally and forms the backbone of thermal power plants, cement kilns, industrial boilers, and captive power units.
Geological & Rank Position
Non-coking coal can belong to multiple coal ranks:
✔ Lignite (low grade)
✔ Sub-bituminous coal
✔ Bituminous (thermal grade)
Most internationally traded thermal coal falls under bituminous non-coking coal, offering a balance of high calorific value, manageable ash, and stable combustion behavior.
Key Characteristics of Non-Coking Coal
High Calorific Value (GCV)
Typically ranges from 3,500 to 6,500 kcal/kg (≈ 15–27 MJ/kg), directly influencing power output, fuel consumption, and overall plant efficiency.
Non-Caking Nature
Does not soften or fuse when heated; remains granular or powdery during combustion and produces friable ash rather than solid coke mass.
Ash Content
Ranges from 8% to 45%. High ash reduces boiler efficiency and increases slagging, fouling, and disposal requirements. Washed coal is preferred for modern plants.
Moisture Content
Generally 5% – 25%. Higher moisture lowers effective calorific value and affects ignition, storage, and transport economics.
Volatile Matter
Typically 15% – 40%, aiding easy ignition, flame stability, and faster boiler start-up.
Sulfur Content
Usually 0.3% – 2%. Higher sulfur grades may require flue gas desulfurization and emission control systems.
Refining & Processing Properties
Coal Washing & Beneficiation
Removes dirt and mineral impurities, reduces ash, improves calorific value, lowers emissions, and enhances boiler performance.
Crushing, Screening & Sizing
Supplied as ROM coal, sized coal (6–50 mm), fines, or pulverized coal to ensure consistent feeding and combustion.
Blending
Different grades are blended to achieve target GCV, control ash fusion temperature, and optimize boiler efficiency.
Typical Technical Properties
Proximate Analysis (Indicative)
| Parameter | Typical Range |
|---|---|
| Moisture | 5% – 25% |
| Ash | 8% – 45% |
| Volatile Matter | 15% – 40% |
| Fixed Carbon | 30% – 55% |
Ultimate Analysis
| Component | Typical Range |
|---|---|
| Carbon | 45% – 75% |
| Hydrogen | 3% – 6% |
| Oxygen | 5% – 25% |
| Nitrogen | 0.5% – 2% |
| Sulfur | 0.3% – 2% |
Physical & Combustion Properties
| Property | Typical Value |
|---|---|
| GCV | 3,500 – 6,500 kcal/kg |
| HGI | 35 – 70 |
| Ash Fusion Temp | 1,100 – 1,400°C |
| Density | 1.2 – 1.5 g/cm³ |
Common Non-Coking Coal Grades
| Grade | GCV (kcal/kg) | Typical Use |
|---|---|---|
| Low Grade | 3,500 – 4,000 | Brick kilns, small boilers |
| Medium Grade | 4,000 – 5,000 | Cement plants, captive power |
| High Grade | 5,000 – 6,500 | Power plants, CPPs |
Available Forms & Supply Modes
✔ Run-of-Mine (ROM) Coal
✔ Washed / Beneficiated Coal
✔ Sized Coal (6–50 mm)
✔ Coal fines / pulverized coal
✔ Briquettes & pellets
✔ Bulk shipments, jumbo bags, containers
Applications of Non-Coking Coal
Power Generation
Thermal power plants, captive power plants, steam turbines.
Cement Industry
Kiln firing, pre-heater and calciner systems.
Industrial Boilers
Textile, chemical, paper & pulp industries.
Brick & Ceramic Industry
Brick kilns, tiles, and ceramic firing.
Lime & Mineral Processing
Limestone calcination and dolomite processing.
Gasification & Energy Conversion
Syngas production and coal-to-energy systems.
Advantages
✔ High energy output
✔ Cost-effective fuel
✔ Wide availability
✔ Easy handling & storage
✔ Suitable for large-scale combustion systems
Limitations & Operational Considerations
⚠ High ash disposal requirement
⚠ Emission control systems needed
⚠ Moisture reduces net efficiency
⚠ Not suitable for metallurgical coke
Modern plants mitigate these challenges using advanced boilers, emission control equipment, coal washing, and blending techniques.
Non-Coking vs Coking Coal
| Parameter | Non-Coking Coal | Coking Coal |
|---|---|---|
| Primary Use | Energy generation | Steelmaking |
| Caking Property | None | High |
| Coke Formation | No | Yes |
| Evaluation Basis | GCV, ash, moisture | CSR, CRI, FSI |
| Ash Tolerance | Higher | Lower |
Non-coking (thermal) coal is a reliable, high-volume energy fuel used globally for electricity generation and industrial heating. Its performance is driven by calorific value, ash behavior, moisture content, and combustion stability rather than metallurgical characteristics. With proper beneficiation and combustion technology, thermal coal continues to play a critical role in global energy and industrial supply chains.