Practical Combustion Methods Used in Industries - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 220

Representative examples of conventional combustion control systems for indus-
trial furnaces are shown in Figure 4.2 . From the figure, the general items to be
controlled are shown below.

1. Furnace temperature control
•Temperature in the zones
• Cascades in both the upper and lower zones
• Burner thinning
• Steel slab discharging and discharging temperature
2. Flow rate control
• Fuel flow
• Airflow
3. In-furnace oxygen control
4. Combustion safety control with shutdown conditions
• Fuel supply pressure-down
• Combustion air pressure-down
• Cooling water pressure-down
• Instrumentation fluid pressure-down
•Power breakdown
• Atomizing air pressure-down for heavy oil burning
5. In-furnace pressure control
6. Recuperator protection control
7. Discharging slab tracking with photo detector and ITV camera system

4.1.3 D EVELOPMENT OF H IGH P ERFORMANCE I NDUSTRIAL F URNACES

With the heating furnace for manufacturing steel materials as representative of
industrial furnaces, the results of the development of high performance industrial
furnaces are reviewed by tracing the changes in such heating furnaces since the end
of World War II.
Regarding the transition of the furnace shape, the focus of discussion was on the
burning technologies such as axial-flow burning, side burning, and top burning, to
ensure the uniformity of temperature in heating furnaces with wide widths. Table 4.3
shows the characteristics of these three types of burning. Taking the arrangement of
skids into consideration, side burning was to be adopted. However, a problem arose
with regard to the flame spreading to more than half the furnace width. If the flame
could not spread completely, axial-flow burning should be adopted and a fine control
at the final adjustment was to be carried out by top burning. The problem was which
type of burning should be adopted because the outer shape of the furnace might be
very different if this type of burning was adopted. Much discussion ensued regarding
which type of burner layout should be adopted because the dimensions of the furnace
might significantly affect combustion performance depending largely on the burner
layout.
On the basis of this concept, the length of flame is designed to be 6 to 7 m at
most in the case of a furnace having the burning capacity of about 3.48 MW (3

×
10 6 kcal/h). Some of the furnace shapes are shown in Figure 4.3, and the actual