Riello PRESS 2G - Combustion Characteristics; Emissions into the Atmosphere

33
20140894
GB
Start-up, calibration and operation of the burner
7.4 Combustion characteristics
The burner delivery in the 2nd stage must not exceed the rated
delivery for the boiler, and should be adjusted in relation to the
user's effective heating requirements and selected within the
MAX firing rates (See page 10). A lower setting of the boiler pro-
vides for a lower flue gas fume temperature, thus increasing com-
bustion efficiency and saving fuel.
The burner's delivery in the 1st stage is usually 50% of the de-
livery in the 2nd stage and must be contained in the MIN. values
range listed above the firing rates on page 10. The burner's 1st
stage delivery can even be lower than 50% of the 2nd stage de-
livery whenever it does not cause the formation of too much con-
densate in the stack. It may also be higher than 50% when
required by the reasons listed on page 17 in the "Choice of noz-
zles for 1st and 2nd stage" paragraph.
7.5 Emissions into the atmosphere
Test boilers UNI-DIN (Fig. 6 on page 12): emissions of Bacha-
rach-CO
2
-CO-CxHy-NOx obtained in laboratory tests with our
burners proved to be lower than the limits defined by EC Norms
EN 267 under the operating conditions established by these
standards, see (Tab. M).
Tab. M
Commercial boilers: emissions of Bacharach-CO
2
-CO-CxHy-
NOx must not exceed the limits imposed by locally-applicable
regulations for burner installations. In particular, the CO
2
level
should not be higher than 13.5% in order to prevent variations in
the draught and air temperature or dirty burner conditions from
causing polluting combustion.
An insufficient CO
2
level must also be avoided, since, in addition
to raising costs and falling short of the established range, this can
also be the cause for the generation of a dangerous quantity of
uncombusted hydrocarbons in the flue gas (yellow Bacharach)
and the detachment of the flame upon ignition.
The combustion values measured may be considered reliable
only if there are no entries of air between the burner and the stack
flue gas sampling point. Check for penetration of outside air by
placing a column of smoke near the suspected leak in the seal: if
the smoke column is drawn towards the seal there must be an en-
try of air.
EN 267 (5-91)
Stage 1° 2°
Bacharach n° < 2 < 1
CO
2
% > 11.3 > 12.3÷12.7 (15÷100 kg/h)
> 12.7 (> 100 kg/h)
CO ppm < 100 < 100
CxHy ppm < 10 < 10
NOx (3% O
2
)
mg/Nm
3
< 150 < 150
N.B. Excess air % = CO
2
max : CO
2
measured
CO
2
max = 15,2%
Example CO
2
measured = 13,5%
Excess air = 15,2 : 13,5 = 1,13 = 13%