Burner Firing Rate According To Air Density; Test Boiler - Riello RL 190/M Installation, Use And Maintenance Instructions

4.6.1

Burner firing rate according to air density

It may be that a burner has to operate with combustive air at a
higher temperature and/or higher altitudes.
The heating of the air and the increase in altitude produce the
same effect: the expansion of the air volume (i.e. the reduction of
its density).
The delivery of the burner fan remains essentially the same, but
the oxygen per cubic meter of air, and the thrust (discharge head)
of the fan are reduced.
It is therefore important to know if the maximum output requested
from the burner at a determinate combustion chamber pressure
remains within the firing rate of the burner even with the changed
temperature and altitude conditions.
Proceed as follows:
1 Find the correction factor F in the Tab. D for the plant's air
temperature and altitude.
2 Divide the burner's delivery Q by F in order to obtain the
equivalent delivery Qe:
Qe = Q : F (kg/h)
3 In the firing rate range of the burner (Fig. 4), indicate the
work point defined by:
Qe = equivalent delivery
H1 = combustion chamber pressure
The resulting point A must remain within the firing rate
range.
4 Trace a vertical line from point A, (Fig. 4), and find the maxi-
mum pressure H2 of the firing rate.
5 Multiply H2 by F to obtain the maximum lowered pressure
H3 of the firing rate
H3 = H2 : F (mbar)
Average
m
barometric
a.s.l.
pressure
M mbar
0 1013
100 1000
200 989
300 978
400 966
500 955
600 944
700 932
800 921
900 910
1000 898
1200 878
1400 856
1600 836
1800 815
2000 794
4.6.2

Test boiler

The firing rate was set in relation to special test boilers in accord-
ance with the methods defined in EN 267 standards.
Fig. 5 indicates the diameter and length of the test combustion
chamber.
Example:
delivery 200 kg/hour: diameter = 80 cm; length = 3,5 m.
Whenever the burner is operated in a much smaller commercial-
ly-available combustion chamber, a preliminary test should be
performed.
Technical description of the burner
0 5
1.087 1.068 1.049
1.073 1.054 1.035
1.061 1.042 1.024
1.050 1.031 1.013
1.037 1.018 1.000
1.025 1.007 0.989
1.013 0.995 0.977
1.000 0.982 0.965
0.988 0.971 0.954
0.977 0.959 0.942
0.964 0.946 0.930
0.942 0.925 0.909
0.919 0.902 0.886
0.897 0.881 0.866
0.875 0.859 0.844
0.852 0.837 0.822
If H3 is greater than H1, as in Fig. 4, the burner can produce the
delivery requested.
If H3 is lower than H1, the burner's delivery must be reduced. A
reduction in delivery is accompanied by a reduction of the pres-
sure in the combustion chamber:
Qr = reduced delivery
H1r = reduced pressure
( )
Qr
H1r = H1 x
Example, a 5% delivery reduction:
Qr = Q x 0.95
H1r = H1 x (0.95)
With the new values - Qr and H1r - repeat steps 2 - 5.
The combustion head must be adjusted in respect
to the equivalent delivery Qe.
WARNING
mbar
D388
F
Air °C
10 15 20
1.031 1.013
1.017 1.000
1.006 0.989
0.995 0.978
0.983 0.966
0.972 0.955
0.960 0.944
0.948 0.932
0.937 0.921
0.926 0.910
0.914 0.898
0.893 0.878
0.871 0.856
0.851 0.836
0.829 0.815
0.808 0.794
11
GB
2
Q
2
Qe
25 30
0.996 0.980
0.983 0.967
0.972 0.956
0.962 0.946
0.950 0.934
0.939 0.923
0.913
0.928
0.916 0.901
0.906 0.891
0.895 0.880
0.883 0.868
0.863 0.849
0.842 0.828
0.822 0.808
0.801 0.788
0.781 0.768
kg/h
Fig. 4
40
0.948
0.936
0.926
0.916
0.904
0.894
0.884
0.872
0.862
0.852
0.841
0.822
0.801
0.783
0.763
0.743
Tab. D
D688
Fig. 5
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