Degasifi Cation Phase; Burn-Off Phase; Expansion Noises; The Chemistry Of Wood - HASE Como Mode D'emploi

19.3 Burn-off Phase

Glowing charcoal embers remain after the volatile compon-
ents have been burned off. These burn slowly, almost without
fl ames, at a temperature of approx. 800°C.
Crucial to a clean and effi cient combustion process is a
complete as possible chemical
reaction of the wood gases with the oxygen in the combustion
air. In your Hase stove, the combustion air is pre-heated and
guided into the fi re box via wide air inlet openings, so that at
high temperatures, there is a good, thorough mixing of the
gases with the air. An important variable in any combustion
phase is the amount of combustion air. Too little air leads
to an oxygen defi ciency and incomplete combustion, while
too much air reduces the fi re box temperature and thus the
effi ciency. Incomplete combustion can generate air pollutants
such as dust, carbon monoxide, and hydrocarbons.
Burn-off
fi g. 11

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.

21. Contribution to Environmental Protection

Degasifi cation
Whether your Como 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
Section 9, „The Right Fuel").
Therefore, use only dry wood; hardwoods such as birch and
Drying
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
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
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