To determine the excess air at which the combustion system will operate we have to start with the stoichiometric air-fuel ratio known as the perfect or ideal fuel ratio - or stoichiometric combustion. With stoichiometric combustion there is
In practice process heating equipment almost never runs stoichiometric. Even so-called "on-ratio" combustion, used in boilers and high temperature process furnaces incorporates a modest amount of excess air - 10 to 20% more than needed to burn the fuel completely.
If insufficient amount of air is supplied to the burner, unburned fuel, soot, smoke, and carbon monoxide are exhausted from the boiler. The results is heat transfer surface fouling, pollution, lower combustion efficiency, flame instability and a potential for explosion. To avoid inefficient and unsafe conditions, boilers normally operate at an excess air level. This excess air level also provides protection from insufficient oxygen conditions caused by variations in fuel composition and "operating slops" in the fuel-air control system.
Boiler house topics, fuels like oil, gas, coal, wood - chimneys, safety valves, tanks - combustion efficiency.
Heating, ventilation and air conditioning systems - design and dimensions.
Incomplete boiler combustion may generate carbon monoxide - CO - and re-ignition may cause disastrous effects on personnel and property.
Properties of alternative fuels like biodiesel, E85, CNG and more.
An overview of ASTM Section 5 - Petroleum Products, Lubricants, and Fossil Fuels - Volume 05.06 Gaseous Fuels, Coal and Coke.
Combustion gross and net calorific value.
Minimum area in a boiler room.
Classification of coal based on volatile matter and cooking power of clean material.
Exhaust and outlet temperatures fuels like natural gas, liquefied petroleum, diesel and more.
Environmental emission of carbon dioxide CO2 when combustion fuels like coal, oil, natural gas, LPG and bio energy.
Typical furnace combustion efficiencies in fireplaces, space heaters, boilers and more.
Flue gas dew point temperatures and condensation of water vapor.
Net (low) and gross (high) energy content in fossil and alternative fuels.
Fuels and their boiling points.
Combustion air and flue gas for common fuels - coke, oil, wood, natural gas and more.
Higher and lower calorific values (heating values) for fuels like coke, oil, wood, hydrogen and others.
Flue gas dew point temperatures for some fuels.
Chemical composition of gaseous fuels like coal gas, natural gas, propane and more.
Cost comparison formulas for heating fuels like Natural Gas, Propane LP Gas, Fuel Oil and Electricity.
Efficiency reduction due to intermittent boiler operation.
Emission of Nitrogen Oxides - NOx - with combustion of fuels like oil, coal, propane and more.
Properties like heat values, air/fuel ratios, flame speed, flame temperatures, ignition temperatures, flash points and flammability limits.
Stoichiometric combustion and excess air.
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