Expansion Noises; The Chemistry Of Wood; Contribution To Environmental Protection; Evaluating The Combustion Quality - HASE Luno Mode D'emploi

Burn-off
fi g. 6

19.4 Expansion Noises

Steel expands upon heating and contracts as it cools. These
movements occur during the warming up and cooling down
phases, as well as when adding fuel. They can cause your
stove to emit audible expansion sounds. However, the design
and construction of your stove takes this into account and
prevents this physical process from damaging the stove.

20. The Chemistry of Wood

Wood predominantly consists of the elements carbon,
hydrogen, and oxygen. It contains virtually no environmental-
ly hazardous substances such as sulphur, chloride and heavy
metals. As a result, complete wood combustion produces
mainly carbon dioxide and water vapour as the primary
gaseous products as well as a small quantity of wood ash as
the solid combustion residue. On the other hand, incomplete
combustion can generate a number of pollutant substances,
such as carbon monoxide, acetic acid, phenols, methanol,
formaldehyde, soot, and tar.
62

21. Contribution to Environmental Protection

Whether your Luno burns in an environmentally-friendly or
environmentally hazardous manner depends to a large extent
on how you operate it and the type of fuel you use (see
Degasifi cation
Section 9, „The Right Fuel").
Therefore, use only dry wood; hardwoods such as birch and
beech are most suitable.
Only use small pieces of wood to light the fi re. They burn
faster than large logs and as a result, the temperature required
Drying
for complete combustion is reached more quickly.
For continuous heating, adding smaller quantities of wood
more frequently is more effi cient and more ecological.

22. Evaluating the Combustion Quality

The following characteristics can help you easily evaluate the
quality of the combustion:
– Colour and composition of the ash
If the combustion process is clean and effi cient, the
result is a fi ne white ash. Dark colouration indicates that
the ash contains charcoal residue; in this case, the burn-
off phase was incomplete.
– The colour of the fl ue gases emitted at the chimney pot
Here, the following applies: the more invisible the fl ue
gases exiting the chimney, the better the combustion
quality.
During the transitional seasons (spring/autumn), outdoor
temperatures above 16°C can impair the chimney draught. If
a draught cannot be created at these temperatures by rapidly
burning paper or thin wood shavings (quick fi re), you should
refrain from lighting the stove.
23. Wood Moisture Content and Calorifi c Value
Rule of thumb: the more damp the wood, the lower the
calorifi c value.
The calorifi c value of the wood depends largely on the wood
moisture content. The more
moisture the wood contains, the more energy expended to
evaporate it during the combustion
phase; this energy is then lost. The more damp the wood, the
lower its calorifi c value.
An example: freshly cut wood has a moisture content of
approx. 50% and a calorifi c value of around 2.3 kWh/kg;
in contrast, wood which has been effi ciently air-dried has
a moisture content of approx. 15% and a calorifi c value of
around 4.3 kWh/kg.
Accordingly, if you burn very moist wood, you will have about
half the thermal output with the same quantity of wood.
Furthermore, burning moist wood results in substantial soot
build-up on the fi re box window. Moreover, when moist wood
is burned, the resultant water vapour can condense in the fl ue
pipe or chimney, which can lead to a build up of shiny soot
on the chimney or chimney creosote. Chimney creosote can
cause unpleasant odours and damage brick chimneys, while
shiny soot poses a fi re hazard (chimney fi re). In addition,
if the wood has a high moisture content, the combustion
temperature decreases, which prevents complete combu-
stion of all the wood components and causes considerable
environmental pollution.
You can use a wood moisture meter to determine the residual
moisture content of your fi rewood.