©
HDG Bavaria GmbH 07/2008
HDG Compact 99 - 200 - Version 1 - en
3 Mode of operation – Fuel quality requirements
27
W
OOD
CHIPS
Regarding the origin of the wood, a distinction is made between ca-
tegory A1 and A2. For A1 the wood comes from trunk wood and che-
mically untreated wood residue; for category A2 the wood of the
entire tree and forestry waste can be used. Wood from both category
A1 and A2 can be used in HDG boilers.
Essential criteria are the particle size, moisture content and ash con-
tent of the fuel.
P
ARTICLE
SIZE
In accordance with DIN EN 14961-4, the fuel specifications for wood
chips are separated into
•
P31.5
Wood chips with a typical particle size smaller than 31.5 (P31.5) are a
machine-compatible material suitable primarily for small systems.
Oversized pieces (end pieces) could lead to malfunctions during
system operation. Higher proportions of finer content (dust) can lead
to high emissions and ejection of glowing particles.
Wood chips from category P31.5 can be used as fuel in all HDG wood
chip boilers. For P31.5 wood chips, at least 75% of the wood chips (by
weight) must be between 8 mm and 31.5 mm. The fine content
(<31.5 mm) may not exceed a max. of 8 % by weight. A max. of 6% by
weight of the wood chips may be longer than 45 mm; lengths gre-
ater than 120 mm are not allowed. The numeric value of the P class
refers to the size of the wood chips in mm, which fit through a round
opening with the indicated sieve opening size. The cross-section of
the outsized particles must be smaller than 2 cm
2
.
•
P45
Medium wood chips with a particle size of up to 45 mm (P45) are
used in larger systems, but can however, depending on the diameter
of the conveyor auger, also still be suitable for small systems.
Wood chips from category 45 can be used as fuel in all HDG HDG
Compact 99 - 200 wood chip boilers. For P45 wood chips at least 75%
by weight of the wood chips must measure between 8 mm and 45
mm. The fine content (<31.5 mm) may not exceed a max. of 8 % by
weight. A max. of 6% by weight of the wood chips may be more than
63 mm and 3.5% by weight may be over 100 mm. Lengths greater
than 120 mm are not permissible. The numeric value of the P cate-
gory refers to the size of the wood chips in mm, which fit through a
round opening with the indicated sieve size. The cross-section of the
outsized particles must be smaller than 5 cm
2
.
W
ATER
CONTENT
When selecting fuel, note that the heating value of the wood is pri-
marily dependent on the water content. The more water contained
in the wood, the smaller the thermal value since the water vaporises
in the course of the burning process and thereby consumes heat.
With regard to the quality standards for wood chips, DIN EN 14961-
4 "Solid biofuels - fuel specifications and classes - wood chips for
non-industrial use" applies
