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Solid Fuel Combustion Calculator

Calculate stoichiometric oxygen, dry and wet combustion air, major flue-gas volumes and gas flow for coal, biomass and solid waste from ultimate analysis and excess-air coefficient.

SOLID FUEL COMBUSTION CALCULATION

Combustion air and flue-gas calculation from fuel ultimate analysis

A solid fuel combustion calculation starts with the elemental composition of the fuel. Carbon, hydrogen, sulfur, oxygen and nitrogen determine the theoretical oxygen demand, while fuel moisture, air humidity and the excess-air coefficient influence the amount of wet combustion air and the final flue-gas volume. This calculator brings those linked calculations together in one browser-based engineering tool for coal, biomass and solid waste.

Use the calculator when you need a transparent estimate of stoichiometric oxygen, theoretical dry and wet air, carbon dioxide, water vapor, sulfur dioxide, nitrogen, stoichiometric flue gas, real flue gas and the corresponding gas-flow rate. The input balance check also helps identify an ultimate analysis that does not sum to 100% before the results are used.

Source-model fidelity: the numerical constants and equations are preserved from the original implementation. The calculator uses 22.41, 0.21, 0.79 and 1.61 exactly as supplied; no thermodynamic “updates” are substituted.
ENGINEERING / COMBUSTION

Ultimate analysis & operating inputs

Enter the as-received mass percentages, air moisture parameter x, excess-air coefficient λ and fuel flow rate. Results update instantly in the browser.

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Ultimate-analysis balance: C + H + N + O + S + W + M100%
The ultimate-analysis values do not sum to 100%. Check the analysis basis or transcription before using the results.
λ is below 1. The original equation is still evaluated, but this is outside the usual excess-air interpretation.
Stoichiometric O₂—m³N O₂/kg fuel
Stoichiometric dry air—m³N/kg fuel
Stoichiometric wet air—m³N/kg fuel
Wet-air flow rate—m³N/h
CO₂ volume—m³N/kg fuel
H₂O volume—m³N/kg fuel
SO₂ volume—m³N/kg fuel
N₂ volume—m³N/kg fuel
Stoichiometric flue gas—m³N/kg fuel
Real flue gas—m³N/kg fuel
Flue-gas flow rate—m³N/h

Real flue-gas composition by volume terms

The bars are a decomposition of the same terms already summed in the real-flue-gas equation; they do not add a new combustion model.

HOW TO USE THE RESULTS

What the solid fuel combustion calculator tells you

The first result is the stoichiometric oxygen requirement: the oxygen volume required by the supplied elemental analysis under the equations used by this model. Dividing that requirement by the oxygen fraction of dry air gives the theoretical dry-air demand. The wet-air calculation then includes the entered air-moisture parameter.

The excess-air coefficient λ is used to move from theoretical conditions to the real flue-gas calculation. At λ = 1, the calculation represents the stoichiometric case used by the source model. Increasing λ introduces additional air and therefore increases the air-derived nitrogen and residual oxygen terms in the real flue gas. This makes λ one of the most important operating inputs when estimating combustion-air and stack-gas volumes.

Typical engineering uses

  • Estimate combustion-air requirements for coal, biomass or solid-waste fuels from an ultimate analysis.
  • Compare fuels with different carbon, hydrogen, oxygen, sulfur and moisture contents on the same calculation basis.
  • Estimate normal-volume flue-gas production per kilogram of fuel and convert it to an hourly gas flow using the fuel feed rate.
  • Inspect how changing the excess-air coefficient affects the calculated real flue-gas volume.
  • Provide reproducible intermediate values for teaching, preliminary engineering analysis and comparison with independent process calculations.

Understanding flue-gas composition

The chart decomposes the same terms used in the real-flue-gas equation into CO₂, SO₂, N₂, H₂O and O₂ volume terms. It is therefore a visualization of the implemented calculation, not a chemical-equilibrium or emissions-prediction model. The calculator does not predict pollutants such as NOx, carbon monoxide, hydrocarbons or particulate matter, and it should not be used as a regulatory emissions-compliance model.

For related energy-engineering calculations, see the Building Wall Heat Transfer Calculator or browse all WattCostLab calculators.

METHODOLOGY

Equations used

The equations below reproduce the original calculation sequence. Percent inputs are converted by division by 100 exactly where the original PHP does so.

Stoichiometric oxygen volume
VoO₂ = (22.41/12)·Ci + [22.41/(2·2)]·Hi + (22.41/32)·(Si − Oi)
Stoichiometric dry air
Voa = VoO₂ / 0.21
Stoichiometric wet air
Voau = [1 + 1.61·(x/100)] · Voa
Carbon dioxide
VCO₂ = (22.41/12)·Ci
Water vapor
VH₂O = (22.41/2)·Hi + (22.41/18)·Wi + 1.61·(x/100)·Voa
Sulfur dioxide
VSO₂ = (22.41/32)·Si
Nitrogen
VN₂ = (22.41/28)·Ni + 0.79·Voa
Stoichiometric flue gas
Voga = VCO₂ + VSO₂ + VN₂ + VH₂O
Real flue gas
Vga = VCO₂ + VSO₂ + [(22.41/28)Ni + 0.79λVoa] + [(22.41/2)Hi + (22.41/18)Wi + 1.61λ(x/100)Voa] + 0.21(λ−1)Voa

Reference publication

L. S. Paraschiv, A. Serban and S. Paraschiv, “Calculation of combustion air required for burning solid fuels (coal / biomass / solid waste) and analysis of fluegas composition,” Energy Reports, 6(Suppl. 3), 36–45 (2020). DOI: 10.1016/j.egyr.2019.10.016.

Frequently asked questions

What must the fuel percentages add up to?

The page checks C + H + N + O + S + W + M against 100%. A mismatch triggers a warning.

Why is λ important?

The excess-air coefficient appears in the real-flue-gas equation. At λ = 1 the real and stoichiometric gas-volume equations coincide for the same input set.

Does this estimate NOx, CO or incomplete-combustion products?

No. The implemented equations are limited to the species and total volumes present in the cited source model.

ENGINEERING GUIDES

Learn combustion air and flue-gas calculations

Use these guides to understand the equations, assumptions and units behind this calculator.

View all engineering guides →