eta TWIN 20 kW, Операция

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Low-emission operation
12 Low-emission operation
Notes on complying with limit values in Germany
after 1 January 2015
In accordance with the provisions of "BImSchV," lower
limit values for the emission measurement in Germany
apply to all new heating system installations starting
1 January 2015. In particular, compliance with the new
dust limit value of 20 mg/m³ can lead to problems in
practice.
It was determined under laboratory conditions in
testing centres that the ETA boiler complies with the
new limit values. To be fair, however, it should be noted
that high-quality fuels were used and the heating
system operated under optimal conditions. Things look
different in practice. Low-quality fuels are often used,
which represents a problem for the dust limit value.
Fuels used for testing
The following fuels were used as test fuel for emission
measurements and approval of the boiler:
• Pellets according to EN ISO 17225-2 with the
designation "D06 M10 A0.5"
The ash content of the fuel is an indicator for the
dust emission
According to the current state of science, dust
emissions from complete combustion are inorganic
components in the fuel, so-called aerosol formers.
Studies by renowned research institutes have clearly
demonstrated that the aerosol formers present in the
fuel (e.g., potassium, calcium, sulphur, chlorine,
sodium, zinc, silicon, phosphorous...) are released in
relatively fixed proportions. Accordingly, the level of
dust emissions is determined by the proportions of
these aerosol formers in the fuel.
The situation is made difficult by the fact that the
percentage of aerosol formers in the wood depends on
many factors (tree species, soil condition, season…).
Even different parts of the tree (trunk, branches, core/
sapwood) can demonstrate stark fluctuations.
In practice, the ash content of the fuel has proven to be
a good indicator of the percentage of aerosol formers.
In order to operate the system with the lowest possible
dust emissions, a properly maintained condition as
well as high-quality fuels with the lowest possible ash
content (barks, impurities, leaves, needles...) are indis-
pensable.