Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 263

8000

Approximate
Actual1
Actual2
Actual3
Imaginary Cap.
CFD

7000

6000

5000

4000

3000

2000

1000

0

0 2 4 6 8 10 12 14

Furnace width, m

FIGURE 5.26 The relationship between furnace width and maximum combustion capacity.

balance model. Further, when selecting larger-capacity burners than this index to a
given furnace width such as the point of Actual3 in Figure 5.26 , counter-measures
can be adopted to avoid the problem as the burner design concept is changed.

5.2 HEAT BALANCE AND PERFORMANCE
ESTIMATION WITH SIMULATION PROGRAM

5.2.1 O UTLINE OF S IMULATION P ROGRAM

Recently, many high performance industrial furnaces (regenerative furnaces) that use
regenerative heating exchangers have been developed. These furnaces are replacing
conventional reheating furnaces that use recuperators (conventional furnaces). Com-
parison between the high performance industrial furnaces and the conventional fur-
naces in the case of continuous reheating furnaces for semifinished steel (billets, slabs,
etc.) shows a big difference not only in combustion air and the flow of exhaust gas,
but also in heat patterns and the rising temperature curves of semifinished steel ( Figure
5.27 ) . There may also be a difference in the characteristics of thermal efficiency. If
this is true, future designs for saving energy will have to be reconsidered.
For this purpose, it is necessary to make a comparative evaluation of high
performance furnaces with regenerative heating exchangers and conventional fur-
naces with recuperators ( Figure 5.28 ) . It then becomes necessary to quantify the
relationship among factors including fuel consumption and heat recovery rates,
discharging temperatures, processing mass capacities (ton/h), size of steels to be
reheated, and charging temperatures. Therefore, a simulator was developed to eval-
uate the performance of the two types of reheating furnaces: those with regenerative
heat exchangers and recuperators. This would also be useful when drawing up basic
plans for the furnaces.