Stages of Combustion
Stages of Combustion
In order for combustion to occur, the fuel must pass through three stages, which
are shown in Figure 13.
• Drying
• Gasification and combustion
• Charcoal burnout
When wood is heated, water begins evaporating from the surface of the wood.
Hence two things occur:
Gasification occurs at the wood surface - pyrolysis (the heating of a fuel without the introduction of gasification medium, i.e. oxygen
and water, is termed pyrolysis) - and the temperature deeper inside the wood will increase resulting in evaporation of moisture from the interior of the wood. As the water evaporates and is passed away, the area that is pyrolysed spreads into the wood.
The gas thus produced is ignited above the fuel and transfers heat to the ongoing evaporation and pyrolysis. The combustion process is continuous. The
gasified wood becomes glowing charcoal, transformed by oxygen, until only ash is left.
