Hase Ottawa - Manual (Page 40)

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10.2 Degasifi cation Phase
At temperatures between 100°C and 150°C, the
contents of the wood start - slowly at fi rst – to dis-
integrate and gasify and the wood begins its ther-
mal decomposition. At temperatures above 150°C,
the gas development accelerates. The proportion of
volatile components makes up around 80% of the
wood substance. The actual combustion begins at
a temperature of about 225°C (ignition temperature)
with the ignition of the resultant gases and the re-
lease of heat. There must be an adequate supply of
oxygen available for this purpose. The peak of the
combustion process is reached at approx. 300°C.
The reaction process is now so rapid that the largest
amount of heat is released at this point; fl ames can
reach temperatures of up to 1100°C.
10.3 Burn-off Phase
Glowing charcoal embers remain after the volatile
components 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 ope-
nings, so that at high temperatures, there is a good,
thorough mixing of the gases with the air. An impor-
tant 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.
fi g. 3
Degasifi cation
Drying
Burn-off
10.4 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 expansi-
on sounds. However, the design and construction of
your stove takes this into account and prevents this
physical process from damaging the stove.
11. The Chemistry of Wood
Wood predominantly consists of the elements car-
bon, hydrogen, and oxygen. It contains virtually no
environmentally hazardous substances such as sul-
phur, chloride and heavy metals. As a result, com-
plete 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.
12. Contribution to Environmental
Protection
Whether your stove burns in an environmentally
friendly or environmentally hazardous manner de-
pends 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 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 tem-
perature required for complete combustion is rea-
ched more quickly.
For continuous heating, adding smaller quantities
of wood more frequently is more effi cient and more
ecological.
13. 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 ef-
fi cient, the result is a fi ne white ash. Dark
colouration indicates that the ash contains