6 NIBE DOMESTIC BOILERS
1
2
3
4
What happens when
you burn wood?
Heating and evaporation
Wood heats up to approximately 100
o
C, evaporating
the moisture in it. There is no heating from the wood
at this point. This also explains why wood with high
moisture content is hard to ignite.
Gases start to burn and release heat
The wood solids start to break down, converting the
fuel into gases. The organic vapours start to react
with the oxygen and the combustion process begins.
Primary combustion
The process by which gases are released from wood
and burned is called primary combustion and it re-
sults in the release of a large amount of energy. The
main energy in the wood is released when fuel va-
pours containing 40% to 60% of the energy burn.
Secondary combustion
After the moisture has evaporated and the fuel va-
pours have been burned, only charcoal remains,
burning at high temperatures. At this point it would
be suitable to start cooking on your BBQ.
