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A prerequisite for approval is the express permission for such by the public authority responsible.
For claims to the warranty according to Section 11 of our General Terms and Conditions of Delivery,
wood fuels have to meet the following conditions. If those conditions are not met, then approval is
possible with restrictions (warranty, maintenance, operational safety) with a written statement by the
manufacturer in reference to the facility.
1) Non-combustible substances contained
No wood fuels may contain any foreign bodies, such as pieces of metal, stones, masonry remnants or plastics. Nor
must the following limits (per kg of dry fuel) for non-combustible substances contained (ash analysed at a
temperature of 815°C) be exceeded or fallen short of:
1.1) Chlorine Cl:
1.2) Sulphur S:
1.3) Total Cl, S:
1.4) Ash content, total:
1.5) Alkali oxides in the ash (K
1.6) Sintering point of the ash:
Consequence of substantial overstepping of limits (1.1, 1.2, 1.3, 1.5, 1.6):
a) Hot-gas corrosion in the heat exchanger
b) Early sintering and melting of the ash
If the maintenance instructions are not followed, a process will be created that builds up in a negative fashion with:
→ Cinders change the airflow → Temperature peaks → more slag → etc, until there is fast destruction of the
refractory materials Fireproof materials
1.7) Additives in remnant and used wood:
2) Superfines & dust (wood particles smaller than 1.0 mm as per ÖNORM M 7133)
2.1) Without pre-dryer, max. 10.0% of the total mass; consequence of substantial overstepping of limit:
Temperature peaks → Slag formation → Even higher temperature → etc, to the point of destruction; →
Special maintenance instructions for firing;
Elevated values are especially critical for remnant wood in combination with elevated values as per 1.1, 1.2
2.2) For forest wood chips with pre-dryer, max 4.0% of the total mass; consequence of substantial overstepping
of limit:
→ Moving the exhaust air lines → Special maintenance instructions for cleaning exhaust air line.
3) Origin and treatment
3.1) Forest wood and plantation wood (complete trees and trunk wood untreated)
Mature wood from trunks and branches, untreated, chopped as billet wood or chips.
3.2) Compressed wood, pellets (conforming to standards, such as: ÖNORM M 7135)
Untreated wood with limited bark content, compressed by machine and calibrated
3.3) Increased proportion of bark, tree cuttings from roadside trees (untreated)
Remnants from the forestry and sawmill industries or from conservation of the countryside (elevated
ashcontent).
3.4) Remnants from derived timber products
Normally a mixture of treated and untreated woods as shavings and from processing machines and
chippings from slow-running choppers. With an elevated dust content and/or limited storage volume, the
shavings from processing machines are compressed into briquettes.
3.5) Used wood
This is essentially untreated wood that has been used prior to its energetic utilisation (e.g. pallets). It is
reduced in size by shredders for thermal utilisation. The metal parts have to be removed afterwards (by
magnetic separators).
4) Particle size: adjustment of the conveyor augers
4.1) G30/G50 chips from untreated wood as per ÖNORM M 7133:
made by fast-running and cutting tools;
G 30
G 50
Required cross-sections of the loading: depends on the boiler output:
Conveyor auger
Drop cross-sectio A
Köb Holzheizsysteme GmbH, Flotzbachstr. 33, A-6922 Wolfurt, Tel. +43/5574/6770-0, Fax 65707, E-Mail: office@kob.cc
Spec Sheet
Wood fuels
Minimum requirements - notices
O and Na
O):
2
2
max. coarse fraction
of 20%
of 20%
up to 150 kW
D
min. 12 cm;
min. 175 cm
Subject to technical changes
Limit
max. 300 mg/kg
max. 1000 mg/kg
max. 1000 mg/kg
max. 15.0 g/kg
max. 1.0 g/kg
min. 1000°C
→ Special maintenance instructions for heat exchanger
→ Shortened service life of heat exchanger
→ Special maintenance instructions for firing,
→ Increased maintenance costs (firing, boiler door)
Free of heavy metals and halogen compounds
with cross-section
2
max. 3 cm
2
max. 5 cm
up to 500 kW
min. 15 cm;
2
min. 300 cm
1010-1
2009-03-01_GB
Comparison with untreated forest
wood
10 mg/kg
120 mg/kg
130 mg/kg
5,0 g/kg
0.35 g/kg
approx. 1200°C
and length
max. 8.5 cm;
max. 12 cm;
from 500 kW
min. 20 cm
2
min. 600 cm
2
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