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RIELLO
RIELLO
S.p.A. — BURNER DIVISION Combustion Research
Centre
RIELLO
BURNERS AND
BlO-FUEL
Synthesis of
the experiences with the bio-fuel
The
features and the effects of the bio-fuel used on heating plants are the
following:
1) Reduction of the polluting emissions of SO2 and other by-products of the sulphur combustion (unlike the gas-oils, this bio-fuel does
not have sulphur ).
2) Lower net calorific value (about 14%) than the light-oil net calorific value
with the necessity to increase the fuel volumetric output in order to have the
same burner output.
3) Higher density and viscosity than the light-oil; these Change the atomising features and involve, with the same pump pressure
adjustments),an increase of the volumetric burner output. (On average about
10%).
4) As general consequence of the points 2 and 3, according to the burner and
the adjustment, there are not significant changes of burner output (after all
higher output and lower net calorific value balance each other).
5) The different viscosity and density create also a compact and long flame
with probable problems due to less stability and probable smoke (Bacharach) and
CO presence on boilers with short combustion chamber.
6) Nitrile rubbers and some plastics soften after a
long contact with this fuel: therefore for the burners with standard materials,
the flexible oil pipes (intake and return), the seals of the oil valves, the
hydraulic jacks of the air dampers and the pump are at issue.
7) The solvent power of the bio-fuel involves the melting of residual products
and sludge inside the tanks. These materials remain in suspension in the fuel
and could wear the components (i.e. nozzles, pump gears, etc.).
According to the a.m. indications, Riello has developed
some relevant retrofit kits for two series of burners (Riello
40 and Press G burners) with flexible oil pipes, pumps, hydraulic jack, valve
assembly (required in certain models): theses kits make the burners suitable
for working with bio-fuel.
In case of other RIELLO burners, it is necessary to analyze each time the
modifications the burners need in order to make them suitable for the bio-fuel.
Regarding the RIELLO burners with retrofit kit, the precautions to follow are
the following:
a.) Insertion of a filter in the fuel intake line (filtering degree 40microns)
to verify and to clean periodically;
b.) Use of nozzles with atomization angle of 80° in order to have regular
ignitions (without pre-heater also for small output) and short flames.
c.)
Check
the Combustion adjustment with analyzer for burnt gas, considering that the
parameter like CO2 (and therefore air excess) and opacity are equivalent to
those of the traditional light oil.
d.) An annual check concerning the rubber conditions of the seals and flexible
pipes (anyway, it is advised an annual replacement of the flexible pipes,
component more “at risk”).
e.) A careful cleaning of the tanks and pipes before the first bio-fuel supply,
in order to reduce the quantities of residual products and sludge which could
be dissolved.
Paolo Bolognin
Combustion Research Centre Director