Products of Combustion: Gases and Flue Gas Composition for Hydrocarbons
This page provides combustion product data for common fuels including natural gas (CH₄), diesel (C₁₂H₂₃), bituminous coal, petrol, furnace oil, and kerosene. The tables below compare flue gas composition and thermodynamic properties across varying air-fuel ratios (λ). As λ increases (from stoichiometric to excess air), CO₂ concentration decreases, O₂ content increases, and flame temperature drops. This information is critical for optimizing burner design, emission prediction, and heat recovery system sizing. All values assume complete combustion with dry air at 25°C and 101.325 kPa.
Natural Gas (CH₄) Combustion Products
This table shows the realistic combustion products when burning methane with air, at different air-fuel ratios. Values are approximate and assume standard atmospheric conditions.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 9.5 | 19.0 | 0.0 | 71.5 | 0.1 | 50 | 1950 |
| 1.1 | 8.7 | 17.4 | 2.1 | 71.8 | 0.2 | 45 | 1850 |
| 1.2 | 7.9 | 15.8 | 3.8 | 72.5 | 0.5 | 40 | 1750 |
| 1.5 | 6.3 | 12.7 | 7.1 | 73.9 | 1.0 | 35 | 1500 |
*Flue gas temperature is approximate adiabatic flame temperature; values vary with pressure and humidity.
Diesel (C₁₂H₂₃) Combustion Products
This table shows the approximate combustion products when burning diesel fuel with air at different air-fuel ratios. Values assume standard atmospheric conditions and typical combustion efficiency.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 12.0 | 16.0 | 0.0 | 72.0 | 0.5 | 100 | 2100 |
| 1.1 | 11.0 | 14.7 | 1.8 | 72.5 | 1.0 | 90 | 2000 |
| 1.2 | 10.0 | 13.5 | 3.5 | 73.0 | 2.0 | 80 | 1900 |
| 1.5 | 8.5 | 11.5 | 6.0 | 74.0 | 4.0 | 70 | 1700 |
*Flue gas temperature is approximate adiabatic flame temperature; values vary with pressure and humidity. Minor CO and NOx are typical pollutants from incomplete combustion.
Coal Combustion Products
This table shows approximate combustion products when burning bituminous coal with air at different air-fuel ratios. Values assume typical boiler/furnace combustion and standard atmospheric conditions.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | SO₂ (% vol) | NOx (ppm) | Particulates / Ash (%) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 15.0 | 10.0 | 0.0 | 70.0 | 1.0 | 2.0 | 150 | 10 | 2200 |
| 1.1 | 14.0 | 9.0 | 2.0 | 71.0 | 2.0 | 1.8 | 140 | 9 | 2100 |
| 1.2 | 13.0 | 8.0 | 4.0 | 72.0 | 3.0 | 1.5 | 130 | 8 | 2000 |
| 1.5 | 11.5 | 6.5 | 7.0 | 73.0 | 5.0 | 1.0 | 120 | 6 | 1800 |
*Flue gas temperature is approximate adiabatic flame temperature; values vary with coal type, pressure, and moisture. Minor CO, SO₂, NOx, and particulates are typical pollutants.
Propane Combustion Products
This table shows approximate combustion products when burning propane with air at different air-fuel ratios. Values assume typical furnace or boiler combustion and standard atmospheric conditions.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 15.6 | 13.0 | 0.0 | 71.4 | 0.0 | 120 | 1970 |
| 1.1 | 14.7 | 12.3 | 1.5 | 72.0 | 0.5 | 110 | 1850 |
| 1.2 | 13.8 | 11.5 | 3.0 | 72.7 | 1.0 | 100 | 1750 |
| 1.5 | 12.0 | 10.0 | 5.0 | 73.0 | 2.0 | 90 | 1550 |
*Flue gas temperature is approximate adiabatic flame temperature; values vary with burner design, pressure, and excess air. Minor CO and NOx are typical pollutants from incomplete combustion or high-temperature reactions.
Butane Combustion Products
This table shows approximate combustion products when burning butane with air at different air-fuel ratios. Values are for typical furnace or boiler conditions and standard atmospheric pressure.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 18.2 | 15.3 | 0.0 | 66.5 | 0.0 | 130 | 2050 |
| 1.1 | 17.2 | 14.5 | 1.3 | 67.0 | 0.5 | 115 | 1920 |
| 1.2 | 16.2 | 13.7 | 2.8 | 67.5 | 1.0 | 105 | 1800 |
| 1.5 | 14.0 | 12.0 | 5.0 | 68.0 | 2.0 | 95 | 1600 |
*Flue gas temperature is approximate adiabatic flame temperature; actual values depend on burner design, pressure, and excess air. Minor CO and NOx are typical pollutants from incomplete combustion or high-temperature reactions.
Gasoline Combustion Products
This table shows approximate combustion products when burning gasoline with air at different air-fuel ratios. Values represent typical conditions in internal combustion engines or industrial burners.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 19.5 | 14.3 | 0.0 | 66.2 | 0.0 | 150 | 2100 |
| 1.1 | 18.3 | 13.5 | 1.5 | 66.7 | 0.4 | 135 | 1980 |
| 1.2 | 17.2 | 12.8 | 2.8 | 67.2 | 0.9 | 120 | 1850 |
| 1.5 | 15.0 | 11.0 | 5.0 | 68.0 | 2.0 | 100 | 1650 |
*Flue gas temperature is approximate adiabatic flame temperature; actual values depend on burner or engine design, operating pressure, and excess air. Minor CO and NOx are typical pollutants resulting from incomplete combustion or high flame temperatures.
LPG Combustion Products
This table shows approximate combustion products when burning LPG with air at different air-fuel ratios. Values represent typical conditions in burners, furnaces, or industrial heaters.
| Air-Fuel Ratio (λ) | CO₂ (% vol) | H₂O (% vol) | O₂ (% vol) | N₂ (% vol) | CO (% vol) | NOx (ppm) | Flue Gas Temp (°C)* |
|---|---|---|---|---|---|---|---|
| 1.0 (Stoichiometric) | 18.8 | 15.0 | 0.0 | 66.2 | 0.0 | 140 | 2000 |
| 1.1 | 17.7 | 14.2 | 1.4 | 66.7 | 0.3 | 125 | 1900 |
| 1.2 | 16.5 | 13.3 | 2.8 | 67.2 | 0.7 | 110 | 1780 |
| 1.5 | 14.3 | 11.5 | 5.0 | 68.0 | 1.5 | 90 | 1600 |
*Flue gas temperature is approximate adiabatic flame temperature; actual values depend on burner design, operating pressure, and excess air. Minor CO and NOx are typical pollutants resulting from incomplete combustion or high flame temperatures.
Data Sources and Notes
- Data Sources: All tables are compiled from standard combustion engineering references and thermodynamic data sources, including fuel-specific flue gas composition references, ASME and ISO fuel combustion handbooks, and engineering literature on hydrocarbon combustion.
- Complete Combustion Assumption: The values in all tables assume complete combustion, meaning that the fuel reacts fully with oxygen to produce only carbon dioxide (CO₂), water vapor (H₂O), and nitrogen (N₂) from air. Adiabatic flame temperatures and thermodynamic properties are calculated under these ideal conditions.