SOLID FUELS

What Are Solid Fuels?

Solid fuels are combustible materials in solid form used to generate heat and energy through combustion or gasification. They include coal (lignite, sub-bituminous, bituminous, and anthracite), biomass (wood chips, pellets, agricultural residues), coke, charcoal, and solid refuse-derived fuels (RDF). Understanding their thermal properties is essential for power generation, industrial heating, and energy efficiency optimisation.

Why Thermal Property Testing of Solid Fuels Matters

Thermal property data directly governs combustion system design, fuel handling, emission control, and energy accounting. Inaccurate thermal characterisation leads to suboptimal combustion conditions, reduced boiler efficiency, increased emissions, and feedstock quality problems. Testing provides the data needed to:

• Evaluate and compare alternative fuel sources
• Optimise combustion process parameters
• Meet regulatory requirements for energy and environmental compliance
• Characterise biomass and waste-derived fuels for co-firing applications

Key Thermal Properties of Solid Fuels

Calorific Value (Heating Value)

Calorific value is the most fundamental thermal property of a solid fuel, expressing the amount of heat released per unit mass during complete combustion. It is measured as:

• Gross Calorific Value (GCV / Higher Heating Value, HHV): Total heat release including condensation of water vapour in combustion products
• Net Calorific Value (NCV / Lower Heating Value, LHV): Heat release excluding latent heat of water condensation — the value relevant to most practical combustion systems

Calorific value is determined by bomb calorimetry (ASTM D5865, ISO 1928).

Proximate Analysis

Proximate analysis characterises solid fuels by four key parameters:

• Moisture Content: Reduces effective calorific value and affects ignition and handling
• Volatile Matter: The fraction that vaporises on heating — governs ignition speed and flame behaviour
• Fixed Carbon: The non-volatile combustible fraction that burns as a solid char
• Ash Content: Non-combustible inorganic residue that affects slagging, fouling, and disposal

Ultimate Analysis (Elemental Analysis)

Ultimate analysis determines the weight percentages of carbon, hydrogen, nitrogen, sulphur, oxygen, and ash. This data is essential for calculating stoichiometric air requirements, CO₂ emission factors, and sulphur dioxide (SO₂) emission predictions.

Ash Fusion Temperature

Ash fusion temperature testing (ASTM D1857, ISO 540) determines the temperatures at which coal or biomass ash softens, deforms, and flows. Low ash fusion temperatures indicate slagging risk in combustion chambers and must be accounted for in boiler design and operation.

Thermogravimetric Analysis (TGA)

TGA measures the mass loss of a fuel sample as a function of temperature under a controlled atmosphere (inert or oxidising). It provides kinetic data on devolatilisation, char combustion, and combustion reactivity — critical for computational fluid dynamics (CFD) modelling of combustion processes.

Industrial Applications

Power plants, cement kilns, lime kilns, steel mills, and district heating boilers all depend on thermal property data for fuel specification, procurement, and combustion optimisation. Biomass and waste fuel co-firing programmes in existing coal plants require detailed thermal and chemical characterisation before implementation.

Conclusion

Thermal property testing of solid fuels is essential for understanding their combustion behaviour, energy output, and environmental impact. By evaluating parameters such as calorific value, proximate and ultimate composition, ash behaviour, and thermal degradation characteristics, industries can optimise fuel selection, improve combustion efficiency, and ensure compliance with regulatory standards. Accurate characterisation supports reliable and sustainable energy generation across power, industrial, and waste-to-energy applications.

Why Choose Infinita Lab for Solid Fuel Thermal Testing?

Infinita Lab provides comprehensive solid fuel thermal analysis, including calorific value by bomb calorimetry, proximate and ultimate analysis, ash fusion temperature, and TGA through our accredited laboratory network. Our experts deliver compliant, accurate results supporting fuel qualification and compliance programmes.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.

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