Environmental Engineering Reference
In-Depth Information
tant to accumulate the basic knowledge not only in the combustion field but also in
the gas-generation and heat-dissolving processes.
2.5.3 E
MISSIONS
IN
S
OLID
F
UEL
F
LAMES
A pilot trial on high temperature air combustion
53,54
of coal, herein called HTAC99,
was carried out by the IFRF in July 1999. This section reports the results of this
trial on coal high temperature air combustion comparing them with the results
obtained in the previous trials with oil and natural gas. In the section, the high
temperature air combustion experiments carried out with natural gas and those with
light and heavy fuel oil will be referred to as HTAC97
55-57
and HTAC98,
58
respectively.
2.5.3.1 The Furnace Setup
The HTAC99 trial was carried out in the IFRF furnace No. 1, which consists of 11
water-cooled segments.
56
F
or each segment the wall temperatures are monitored using
thermocouples located on the top and the side of the furnace. The furnace heat
extraction is monitored measuring the volumetric flow rate and the temperature rise
of the cooling water circulating in each segment. The furnace has a 1-foot square
cross-section of 2 × 2 m for an internal length of 6.25 m. The furnace is refractory lined.
Measurements are carried out using the ports located on both sides of each
segment. A pressure transducer is mounted on segment five to monitor the furnace
pressure. To avoid air ingress, the furnace is kept in overpressure.
The regenerative air is simulated using a precombustor. The precombustor is
operated using natural gas (NG) as fuel. Oxygen is added to the precombustor flue
gas to keep the oxygen level to 21% vol wet. After the oxygen addition, the com-
burent is injected into the furnace. The temperature and composition of the combu-
rent are monitored using a suction pyrometer and a gas-sampling probe, respectively.
An endoscope with a video camera is mounted on the roof of the furnace at 30
cm from the front wall. The image is displayed on a monitor. Selected parts are
recorded on video to study the flame behavior.
A schematic of the burner block is shown in
Figure 2.99
.
It consists of a 124-
mm air channel located at the center of the burner block. The comburent is injected
with an axial velocity of ú 65 m/s, at a temperature of ~ 1350˚C. Two coal guns can
be located at three different distances from the centerline:
• At 280 mm (the same position of the NG guns and oil injectors in the
HTAC97 and HTAC98 trials)
• At 175 mm
•
At 385 mm
During the trial two different coal guns were tested:
1.
Low-velocity coal gun
2.
High-velocity coal gun
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