Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 136

Pure Coal
Bunker

Small K-tron

Coal Transport line

Compressed Air

Burners

Distributor

Manometers

FIGURE 2.100 Coal feeding system for the HTAC99 experiment.

• Position of the coal guns
• Amount of the coal transport air
•Transport air velocity
•NO x level in the comburent from the precombustor

2.5.3.4 In-Flame Measurements

Detailed in-flame measurements were performed for a baseline flame, in which the
coal guns were positioned in the same configuration used for the oil and NG injectors.
In the baseline configuration the low velocity coal gun was used with 130 kg/h
transport air resulting in an air-coal ratio of 1.96 kg air /kg coal and an injection velocity
of 26 m/s. The air-coal ratio and the coal velocity injections have values typically
used in pulverized coal combustion applications. The furnace wall temperatures were
around 1250˚C (see Figure 2.101 ) .
The natural gas and light fuel oil flames examined in the HTAC97 and HTAC98
trials, respectively, were similar in appearance. Both types of flames were difficult
to distinguish from background radiation with no clear visible flame. 56,58 In contrast
to the NG and LFO flame, the HFO test revealed two luminous jets approximately
2 m in length. During the HTAC99 trial a visible flame was clearly distinguishable
from the background radiation. Figure 2.102 shows the flame for the baseline
configuration. It is similar to the HFO flame.
All the in-flame measurements were performed in the plane of the coal guns
and their results are tabulated in the appendices. In the following sections the main
results will be presented. Each graph consists of two parts: contour lines are plotted
on the left-hand side of the figure, whereas profiles are plotted on the right-hand
side. To facilitate visual understanding, an outline of the furnace and burner geometry
is drawn overlaying the measurements.