Practical Combustion Methods Used in Industries - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 241

FIGURE 4.22 Example of data on NO x generation measurement.
Figure 4.22 shows an example of measurement data on NO x generation in the
combustion tests conducted using large-scale combustion equipment. The horizontal
axis shows the combustion air temperature, and the vertical axis shows the NO x
generation equivalent to 11% O 2 . In addition, Types A, B, and C in the figure
correspond to those burner types shown in Figure 4.21 . All data were obtained from
use of the diluted and high temperature air combustion burner.
LNG or LPG was used as fuel. By using the diluted combustion burner, the
concentration of NO x is suppressed to a level of 60 ppm even at a combustion air
temperature as high as 1273 K and 30 ppm at 973 K, whereas with the conventional
burner, it is 70 ppm at the same temperature of 973 K. As stated above, the degree
of reduction in NO x generation with this combustion has been verified. Furthermore,
it is easily estimated from this figure that combustion with the diluted combustion
burner does not exist in the extended line of that of conventional combustion burners,
and that a completely different combustion phenomenon occurs in HiTAC.
Based on the achievements described above, the construction of continuous
reheating furnaces, incorporating the new concept of high temperature air combus-
tion system, has been steadily increasing. NO x generation data in actual operations
are beginning to be collected as well ( Table 4.5 ) . According to these data collected,
the total NO x generation for an operation temperature of 1323 to 1623 K is in a
range of 30 to 90 ppm (equivalent to 11% O 2 ). It is assumed that the test data from
the combustion laboratory equipment are valid.
Furthermore, this fact shows that the application of the diluted and high tem-
perature air combustion technology to industrial furnaces can greatly contribute to
reducing NO x generation.