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5797 137 - 01
Vitoflex 300-UF Technical Data
Wood Fuel Requirements
(continued)
If fuel does not comply with these limits, there is a risk
of corrosion within the heat exchanger and early sintering
and melting of the ash which leads to:
- Shortened life of the heat exchanger
- Increased maintenance costs (firing, combustion
chamber door)
The maintenance instructions need to be complied with
in order to avoid a process, which will increasingly cause
damage to the boiler.
If maintenance instructions are not complied with the
following process may occur:
- Cinders change the airflow
- Temperature peaks
- More slag is produced
- More cinder builds up and changes the airflow more
This process leads to damage by overheating and may
affect refractory materials.
Additives in remnant and used wood have to be free of
heavy metals and halogen compounds.
Content limits for non-combustible substances
- No wood fuels may contain any foreign bodies, such as
pieces of metal, stones, masonry remnants or plastics.
Substance
Limit
Comparative value untreated forest wood
Chlorine (Cl)
max. 300 ppm (300 mg/kg)
10 ppm (10 mg/kg)
Sulphur (S)
max. 1000 ppm (1000 mg/kg)
120 ppm (120 mg/kg)
Total Cl, S
max. 1000 ppm (1000 mg/kg)
130 ppm (130 mg/kg)
Ash content, total
max. 0.25 oz/lb (15.0 g/kg)
0.08 oz/lb (5.0 g/kg)
Alkali oxides in the ash (K2O and Na2O) max. 0.016 oz/lb (1.0 g/kg)
0.006 oz/lb (0.35 g/kg)
Sintering point of the ash
min. 1800°F (1000°C)
approx. 2200°F (1200°C)
General Information
Other information
- Ash and cleaning:
Untreated wood without bark produces less than 0.5%
ash of the fuel mass supplied. All the specifications
regarding cleaning are based on untreated wood with
bark attached with an ash amount of 0.8% of the fuel
mass.
If the ash content is higher and/or the ash melting
point is lower, increased maintenance and/or cleaning
are
required.
- Changing fuels:
A substantial change in fuel quality, such as bulk
density, water content, dust proportion or ash content
might require a manual correction of the firing
parameters (see Operating section).
The following limits (per mg/kg of dry fuel) of contained non-combustible substances apply [ash analyzed at a
temperature of 1500°F (815°C)]:
