6. Fuel
Specified fuel is dry chopped log fire wood, Ø 8O - 150 mm, at least two years old, moisture 12 %
to 20 %, caloric power 15 – 17 MJ.kg
-1
and log length 330 - 1000 mm as per boiler type. Fuel dimen-
sions are stated in section 3 „Technical Data“. It is also possible to burn large pieces of wood waste in
combination (max. 10 %) with crude logs.
Basic wood burning data
You can ensure maximum output and a long service life if you burn wood which has been left for
at least 2 years to dry. The following graph illustrates the relationship of moisture content to heating
capacity of the fuel. The energy content declines dramatically with increased water contents.
Example:
Wood with 20 % moisture contents has thermal power of 4 kWh /1 kg of wood
Wood with 60 % moisture contents has thermal power of 1.5 kWh /1 kg of wood
•
Example – spruce wood which has been stored for 1 year under shelter – see graph
The boilers maximum output with wet fuel
illustrated in the graph
kW
DC 15 E - 8
DC 18 S - 13
DC 22 S - 14
DC 25 S - 19
DC 32 S - 24
DC 40 S(E) - 31
DC 50 S(E) - 39
DC 75 S(E) - 53
The information is relevant to other gasifica-
tion boiler types.
Boilers are not suitable for burning wood with moisture content lower than 12 %.
Fuel heating capacity
Wood - type Heating capacity per 1 kg
kcal kJoule kWh
spruce
3900 16250 4,5
pine
3800 15800 4,4
birch
3750 15500 4,3
oak
3600 15100 4,2
beech
3450 14400 4,0
Raw wood does not burn easily, produces a lot of smoke and substantially decreases
the service life of your boiler and chimney. Boiler output drops as low as 50 % and fuel
consumption doubles.
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