Environmental Engineering Reference
In-Depth Information
1.2 MW (A,Burner)
1.2 kW (A,B HiTAC)
760 MW (A,Burner)
760 kW (A,B HiTAC)
760 kW (C,D Burner)
760 kW (C,D,E,F HiTAC)
1.2 MW (A,B HiTAC,
enhanced mixture)
1.2 MW (A,B HiTAC,
forced circulation)
1.2 MW (A,Burner,
forced circulation)
80
75
70
Ordinary
combustion
65
60
Normal flames formed near skids
55
High-temperature air combustion
50
0
10
20
30
40
V
ion
, mV
FIGURE 5.25
Comparison of uniform heating performances of steel materials by the change
of mixture status near burner and the forced circulation of furnace gas.
3. Improvement in steel heating
Steel-heating tests using a model testing furnace of the lower part of a furnace
structure demonstrated several points. It was possible to obtain a uniform distribution
of furnace temperature even in a furnace space where heat-absorbing, water-cooled
supports exist, if combustion with high temperature air is adopted. The heating time
could be shortened by the improvement in the deviation of steel temperature made
possible by the high temperature air combustion. The steel temperature at the location
near the water-cooled skids could be raised by the flame volume increased from the
high temperature combustion, and the localized heating problem caused by the skids
could be improved. The locally cooled steel temperature could be raised by forming
normal flames near the skids, but combustion with high temperature air was better
in terms of obtaining a uniform heating of the whole steel. It was possible to
implement high temperature combustion, even with an enhanced mixture of fuel/air
nearer the burner by controlling the feeding method. The freedom of heating control
increased when a forced recirculation of furnace gas was added.
5.1.3.5 Furnace Width and Maximum Combustion Capacity
HiTAC has the characteristics of diluted slow combustion in low oxygen and, with
a narrower furnace width than the combustion space necessary to complete com-
bustion, the problem of ejection of unburned matter through discharge burner arises.
It is impossible to obtain the desired temperature distribution and heat transfer
quantity. Therefore, it is important to estimate specifically the relationship between
furnace width and suitable combustion capacity of burners.
Figure 5.26
,
with actual results and computational fluid dynamics (CFD) analysis
results, shows the relationship between furnace width and maximum combustion
capacity of burners to be considered to complete combustion in a furnace. This can
be used as a qualitative index to check the burner capacity derived from the heat
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