Environmental Engineering Reference
In-Depth Information
2.2.1.2
Influence on NO
Emissions
x
The infl
-
sions was studied using LPG gas as the fuel. The CO emissions were found to be
less than 100 ppm within the combustion stability limits shown in
Figure 1.4
. The
results presented in
Figure 2.5
show a significant influence of the dilution gas
composition on NO
uence of both air temperature and gas chemical composition on NO
emis
x
emission le
vels. Much higher levels of NO
are obtained with
x
x
N
y degree of air preheating. This shows
the importance of gas chemical composition for controlling NO
as the dilution g
as compared to CO
at an
2
2
air combustion. Thus, in the combustion process, the use of burned gases (natural
products of combustion) can be more effective to control NO
in highly preheated
x
in addition to the
x
amount of oxygen in the combustion air.
High temperature and low O
ustion extended the flame size (both in
length and width) as shown in
Figure 2.2
.
The size of the flame has a direct effect
on the distribution of temperatures in the flame. Therefore, in higher temperature
air combustion it is possible to maintain the maximum combustion temperature,
similar to that achieved in the case of conventional normal air combustion or lower
than in the case of conventional combustion, depending upon the choice of air
preheating temperature and air chemical composition.
air comb
2
2.2.2
T
F
B
HERMAL
IELD
EHAVIOR
2.2.2.1
350 kW-Scale Combustion Test
ve of this study was to evaluate the effect of fuel-air nozzle
configuration as well as location of the exhaust gas exit in a large-scale furnace on
the combustion process. The physical dimensions of the 350-kW combustion test
facility were 1.0 m wide, 1.0 m high, and 3.8 m long. A schematic diagram of this
facility is shown in
Figure 2.6
.
The combustion air in this facility was preheated with
the high-cycle switched regenerator operating with a switching time of 30 s (i.e., same
as that used for the 1.3-kW facility). Town gas (13A) was used as the fuel. The firing
rate was maintained constant at 349 kW with a constant air ratio of 1.2.
The primary objecti
gurations modes were examined in the rig to determine their effect
on the distribution of temperatures in the furnace. The locations of 15 thermocouples
for temperature measurements are indicated in
Figure 2.7
.
Each thermocouple in the
furnace was positioned midway between the ceiling and the bottom. However,
provision existed to traverse the thermocouple within the furnace, if desired.
Three confi
2.2.2.2
Cold Flow Model Test
Flo
w visualization for the three configurations modes was made using a cold water
flow model as shown as
Figure 2.8
. This facility is a scaled down model test rig
made from transparent acrylic material and is 1/10 scale in length. A light scattering
technique was used for flow visualization. A sheet light beam formed using a 3W
argon ion laser allowed illumination of the desired cross section of the flow. Small-
size scatters were introduced to the flow to enhance the quality of flow pattern images
obtained. The facility provided information on the resulting flow patterns obtained
at various operational conditions.
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