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5.11.1 Flue gas recirculation line sizing
The Tab. L can be helpful to correctly size the FGR pipes taking
flue gases from boiler stack base up to the burner intake port.
NOTE:
The typical recirculation percentage is between 10% and
15%.
A low recirculation percentage might cause a high Nox level.
A high recirculation percentage might cause flame instabili-
ty and a CO level higher than normal.
5.11.2 Calculating the percentage of recirculated
flue gas
As a general rule, recirculated flue gas quantity must be adjusted
so as to recirculate the smallest quantity necessary to obtain the
required NOx rate.
Adjustment is carried out through the throttle valve located on
FGR pipe. It is necessary to consider that too high a quantity of
recirculated flue gas could lead to flame instability and excessive-
ly high CO rate.
To calculate the % of recirculated flue gas, use the formula be-
low: % IFGR= (CO
)/(CO
2 R
5.12
Closing the burner
Once the combustion head adjustment is completed:
reassemble the burner on the guides 3) at about 100 mm
from the pipe coupling 4) - burner in the position shown in
Fig. 27;
insert the electrode cables and then slide the burner up to
the pipe coupling;
connect the socket of the maximum gas pressure switch;
connect the connector of the fuel servomotor;
replace screws 2) and lifting rings on the two slide bars 3);
connect the light oil pipes by screwing in the two fittings 16);
connect the gas train pipe 15);
fix the burner to the pipe coupling with the screws 4).
20168262
) x 100.
2 f
Installation
Where:
–
(CO
) is the percentage of CO
2 R
coupling
–
(CO
) is the percentage of CO
2 f
Burner output
kW
350
400
450
500
550
600
650
700
750
810
When fitting the burner on the two slide bars, it is
advisable to gently draw out the high voltage ca-
ble and the flame detection probe cable until they
are slightly stretched.
WARNING
WARNING
4
3
2
20158835
24
GB
measured at the burner
2
measured at the stack
2
Flue gas pressure at test
point 6)(Fig. 26) - mbar
-0.8
-1.1
-1.3
-1.6
-1.8
-2.1
-2.4
-2.6
-2.9
-3.2
Tab. L
15
16
Fig. 27
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