Simulation Models for High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 209

3.4.2.6 Calculation on Wide Regenerative Furnace

To verify the performance of the numerical method described above, we carried out
a numerical experiment by using the code PROHEAT on one of the largest furnaces
in operation. The furnace has the dimensions of length 9.8 m, width 14 m, height
2.6 m, and has four sets of regenerative burners placed at equal distances in its upper
zone. It was assumed that there was a heat sink with a constant temperature of 1273
K at the bottom. The upper soaking zone was taken as the calculation domain. It
has no infow of gas from the upstream side, but some flow goes out downstream
from the gap between the partition of 1 m high and the steel slab.
Two cases were considered regarding the burner arrangement as shown in Table

3.4 .

1. Four sets, or eight units, of high-speed regenerative burners were placed
in a staggered arrangement.
2. Eight units of conventional preheated air burners were set. By comparing
furnace temperature distributions for the cases, we evaluated the effect of
the regenerative burners on the uniformity of temperature distribution in
furnaces.

Calculations use the code assuming the combustion heat value of κ = 2.0m -1 as
described above. The calculation under unsteady state condition was continued for
30 s by using temperatures calculated under steady state condition. The average
temperatures mentioned in the following section are obtained through the unsteady
calculation results.
Figure 3.21 shows the temperature distribution obtained in the furnace width
direction with the temperatures averaged both in the longitudinal and the vertical
(height) directions. For both burner arrangements, the temperature at the center of
the furnace width was lower than that in other regions.
While the maximum temperatures did not differ greatly in the two cases, 1479
K for the regenerative burner and 1483 K for the conventional burner, the minimum

TABLE 3.4
Calculation Conditions Regarding Upper Soaking
Zone of Wide Regenerative Furnace

Regenerative
Furnace

Conventional
Burner Furnace

Number of burners 4 sets 8 units 8 units

Burner combustion load (W) 1.50 × 10 6 0.75 × 10 6

Preheating air temperature (K) 1273 873

Air ratio 1.05 1.05

Pull-back ratio 0.8 —

Ejection velocity (m/s) 20 10