Combustion Boiler Fuels

Overview

Engineering reference data for Combustion Boiler Fuels in combustion engineering.

Key Formulas

Heat Release

$Q = \dot{m} \cdot HV$

Fuel energy release rate.

Air-Fuel Ratio

$AF = \frac{m_{air}}{m_{fuel}}$

Mass of air per mass of fuel.

Excess Air

$EA = \frac{O_2}{21 - O_2} \times 100\%$

From flue gas oxygen measurement.

Variables

Symbol	Description	Unit
$Q$	Heat release rate	W
$\dot{m}$	Mass flow rate	kg/s
$HV$	Heating value	J/kg
$AF$	Air-fuel ratio	—

Fuel Properties Overview

The choice of fuel significantly impacts combustion efficiency, emissions, and system design. Key properties include heating value, density, and combustion air requirements.

Combustion Efficiency & Excess Air

Optimal combustion requires balancing fuel and air supply. Key performance metrics include:

Combustion Efficiency is calculated as: $\eta_{comb} = \frac{Q_{used}}{Q_{released}} = \frac{m_{fuel} \times HV - m_{flue} \times c_{p} \times (T_{flue} - T_{amb})}{m_{fuel} \times HV}$

Excess Air is vital for complete combustion but reduces efficiency. It can be calculated from flue gas oxygen concentration: $EA = \frac{O_2}{21 - O_2} \times 100\%$

Key Definitions

• Wobbe Index: A measure of the interchangeability of fuel gases. It is the ratio of the heating value to the square root of its specific gravity. Two gases with the same Wobbe Index provide the same heat output under the same operating pressure.
• Adiabatic Flame Temperature: The maximum temperature achieved by a flame when no heat is lost to the surroundings. It depends on fuel composition and oxidizer concentration.
• Net (Lower) Calorific Value (LCV): The heat released by combustion when water in the combustion products remains as vapor. This is the relevant value for most industrial boiler calculations.
• Gross (Higher) Calorific Value (HCV): The total heat released, including the latent heat contained in the water vapor of the combustion products.

Interactive Charts

References

• Original Source