Poor woodchips:
■ Frayed surface
■ More than 5 % outliers
■ Coarse percentage higher than 20 %
■ Greater than G50
1.3 Minimum wood fuel requirements
Content
When procuring wood for combustion, it is important to ensure that
foreign matter (e.g. stones, metal parts, brick fragments, plastics, etc.)
is avoided. These change the composition of the charge and therefore
the critical parameters of the combustion process.
The values must not exceed or fall below the following limits (per kg of
dry fuel) for the non-combustible contents (ash at an analysis temper-
ature of 815 °C):
Limit
Comparison with natural wood from forest
thinnings
Chlorine Cl
mg/kg
max. 300
10
Sulphur S
mg/kg
max. 1000
120
Total Cl, S
mg/kg
max. 1000
130
Ash content total
g/kg
max. 15.0
5.0
Alkali oxides in the ash (K
2
O and Na
2
O)
g/kg
max. 1.0
0.35
SB starting of ash sintering
°C
min. 1000
approx. 1200
A consequence of exceeding the above limits is a shortened combus-
tion chamber and wood boiler service life. This also means that the
maintenance work is increased and the servicing intervals are short-
ened.
The proportion of dust-like and fine-grain materials should also be
minimised (in accordance with ÖNORM M 7133).
Non-wood biomass fuels
Non-wood biomass fuels, such as needles, leaves, grain, straw, husks,
fruit kernels, etc., are generally unsuitable as a fuel for trouble-free
operation and therefore not permissible.
In some cases, the fuel properties (essential composition, ash sinter-
ing point, etc.) differ considerably from those of wood. Combustion in
a PYROTEC can lead to impairment of the combustion characteristics
and to greater stress on the fireclay lining and the heat exchanger sur-
faces. Warranty claims can therefore only be asserted when using
permissible fuels.
Wood fuel regulations and standards
Germany
1.BImSchV in the revised version dated 22.03.2010
Austria
FAV dated 18.11.1997 "Ordinance for Combustion Systems" § 3.(1) 3. Solid fuels
Switzerland
Clean air regulations LRV dated 16.12.1985 (as at 28.03.2000)
ÖNORM M 7133
Woodchips for energy purposes (1998)
EN 303-5
Boilers for solid fuels, table 8 "Test fuels"
CEN/TS 14961
Solid biofuels
Principles of wood combustion
(cont.)
6
PYROTEC
1
5822 511 GB
Summary of Contents for KOB PYROTEC
Page 86: ...86 PYROTEC ...
Page 87: ...PYROTEC 87 5822 511 GB ...
