HDG M299, Operation Manual

Page: 27 / 176

©
HDG Bavaria GmbH 07/2008 HDG M299/300/350/400 - Version 1 - en
3 Mode of operation – Fuel quality requirements
27
Wood chips from category P45 can be used as fuel in all HDG HDG
M299/300/350/400 wood chip boilers. For P45 wood chips, at least
75% of the wood chips (by weight) must be between 8 mm and 45
mm. The fine content (<3.15 mm) may not exceed a maximum of 8%
by weight. A maximum 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
category 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 calorific value of the wood is
primarily dependent on the water content. The more water
contained in the wood, the smaller the calorific value, since the water
vaporises in the course of the burning process and thereby
consumes heat. This results in lower efficiency and thereby leads to
greater wood consumption. Increasing moisture in the fuel material
also causes reduced efficiency, greater amounts of ash and smoke, as
well as making it increasingly unfit for storage.
The maximum permissible water content of the wood chips for the
HDG M299/300/350/400 is 30 % (M30).
For technical considerations, a representative calorific value is
selected depending on water content. For burning that is both
economical and low on emissions, the calorific value should not be
less than 4 kWh/kg.
A
SH CONTENT
The ash content for wood in category A2 is higher than that of
category A1 due to the higher proportion of bark, needles and
leaves.
The maximum permissible ash content of wood chips for the HDG
M299/300/350/400 is 1.5 % by weight (A1.5).
W
OOD PELLETS
Water content Moisture Calorific value
Relative wood
consumption
10.0 % 11.1 % 4.6 kWh/kg 87 %
20.0 % 25.0 % 4.0 kWh/kg 100 %
26.0 % 35.0 % 3.7 kWh/kg 110 %
30.0 % 42.9 % 3.4 kWh/kg 120 %
Table 3/3 - Calorific value depending on water content
With regard to the quality standards for wood pellets, DIN EN
14961-2 “Solid biofuels - fuel specifications and classes - wood
pellets for non-industrial use” applies.