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5.9.1
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.
Maximum allowed pipe length (considering smooth steel pipes) is
specified for every burner and pipe diameter.
To prepare the Tab. L a flue gas maximum temperature of 260°C
was considered.
FGR pipe
RLS 810/E FGR
To account for the flow resistance at 90° elbows of the flue gas
circuit, the following equivalent straight pipe length values can be
considered, and shall be deducted from the maximum pipe length
values indicated in Tab. L to obtain the maximum length of FGR
pipe development in the considered instance:
Diameter
8"
5.10
Combustion head adjustment
In order to optimise performance, the burner is equipped with a
variable geometry combustion head which operates on the basis
of the delivered output.
According to the same rotation of the air servomotor, it is possible
to change the combustion head opening by moving the
lever 2)(Fig. 18) on the holes (1-2-3-4-5-6), after loosening the
screw 1). The choice of the hole (1-2-3-4-5-6) to use is based on
the following table, according to the required output.
These output values may not match with the actual values as the
combustion conditions change according to the plant.
The factory regulation corresponds to the minimum output (cou-
pling position: 1).
Coupling position
6 - GAS
6 - OIL
20171988
Diameter
Length (m)
8"
61
Pipe fittings
90° elbow (m)
45° elbow (m)
6.1
3.3
Output (kW)
1080
1650
Installation
5.9.2
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
Tab. L
Where:
(CO
) is the percentage of CO
2 R
coupling
(CO
) is the percentage of CO
2 f
Tab. M
20162133
Tab. N
22
GB
)/(CO
) x 100.
2 R
2 f
measured at the burner
2
measured at the stack
2
2
1
0
Fig. 18
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