Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 273

Setting furnace conditions

Reading set values
(From Excel sheets)

Setting slab conditions

Setting combustion conditions

Other loops and other processing

Repeating overall convergence calculation (starting point)

Initializing parameters

Calculation of Heat Balance

Renewal of the temperature at
the furnace tail

Calculation of ton/h

Calculation of steel
temperature

Output of initial values

Calculation of air preheating
temperature

Repeat 1 to MXZ in the same zone

Heat taken away by a slab

Repeated calculation Heat loss by cooling water

Repeating calculation to find
convergence in the zone

Furnace body heat radiation

Exhaust gas heat loss

Calculation of furnace
temperature and time

Scale forming heat

Calculation of heat transfer
(finite-difference method)
(Column/ one-dimensional)
(Two-dimensional)

Combustion volume of fuel
gas

Heat balance at the non-
combustion zone

Renewal of temperature/
retained heat

Heat balance of RG heat
exchanger

Repeating convergence
calculation in the same zone
Output (to an Excel sheet)
of heating calculation

Calculation of the total of heat
balances

Average temperature
of retained heat

Output of heat balance
(to an Excel sheet)

Next NZ (Increase of the zone number)

If the convergence is not attained, calculate again

Judgment of overall
convergence

Convergence attained

To the next step

FIGURE 5.38 Processing flow of steel temperature calculation and heat balance model.

The kinds of fuel gas used were LPG, LNG, COG, and MixGas. MixGas has
three calorific values of 11.7, 8.4, and 7.3 MJ/ ( denotes the volumes at the
normal state), obtained by mixing COG and BFG with ingredients as shown in Table
5.14 . Note that the heat recovery rate differs depending on the calorific value, and
for this reason the heat recovery rates of a heat exchanger for each kind of fuel gas
are shown in Table 5.15 . In addition, facility and operating conditions are shown in
Tables 5.16 and 5.17 .
From the results obtained through the studies of Sections 5.1 and 5.2, the values
of fuel consumption are summarized as shown in Figure 5.48 , presuming that the

m 3 m 3