49
OPERATION
2.1 Fuels
In accordance with the First Ordinance
on the Implementation of the Federal
Emission Reduction Law, only fuels
which generate low quantities of smoke
may be used in stoves. For Hase stoves
these are exclusively:
- With open fire box doors only natu-
ral wood with bark, eg. in the form
of logs or bricks.
- With closed fire box doors in addition
to the fuel described above also
brown coal briquettes.
The following should f. e. NOT BE
BURNED:
- painted or plastic-coated wood
- wood treated with wood preserva-
tives
- domestic waste
- paper briquettes (pollutants: cad-
mium, lead, zinc)
- damp wood (residual moisture
content over 20%)
Fig.: The combustion process
If the above materials are burned they
not only generate unpleasant smells but
also emissions which damage the envi-
ronment and are harmful to the health.
Highly resinous kinds of wood (eg. spru-
ce, pine, fir) tend to give off large quan-
tities of sparks. These types of wood
should only be burned with the doors
closed. Twigs and sticks of wood should
only be used for lighting the fire.
2.2 The combustion process
The following conditions must be met
for burning solid fuels:
- The necessary supply of oxygen must
be available. This is generally taken
from the ambient air.
- The ignition temperature must be
achieved. This means the temperature
at which the fuel continues to burn
without interruption whilst giving off
large quantities of heat.
Steel expands very slightly on heating
and contracts again to the same degree
on cooling. The steel of which your
chimney stove is made also reacts to
fluctuations in temperature. Your stove
is however designed in such a way as to
allow the metal room to expand and
contract without damaging the stove.
During the firing process the internal
action in the steel produces a crackling
noise.
Wood combustion can be broken
down into three phases:
1. Drying phase
The moisture still contained in the air-
dried wood (approx. 15 - 20%) is evapo-
rated. This is done at temperatures of
approx. 100°C. The wood must be provi-
ded with heat during the warming
phase for this purpose, which can be
achieved by quick-burning wood.
2. Degasification phase
At temperatures of between 100°C and
150°C the contents of the wood start
(slowly at first) to decompose and gasify
and the wood begins its thermal decom-
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