Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 335

where
V A m 3

= total airflow ( /h)

m 3 V E = total exhaust gas flow ( /h)

T Ai = inlet air temperature ( ˚ C)

T Ei = inlet exhaust gas temperature ( ˚ C)

T Ao = preheating (outlet) air temperature ( ˚ C)

C PAo = specific heat of preheating air (kJ/m 3 K)

C PAi = specific heat of inlet air (kJ/m 3 K)

C PEi = specific heat of inlet exhaust gas (kJ/m 3 K)

C PEa = specific heat of exhaust gas at inlet air temperature (kJ/m 3 K)

An energy saving of slightly more than 10% was achieved in the continuous
heating furnace group. The value is reasonable with respect to the unit fuel con-
sumption for this type of furnace, as it was already an energy efficient system.
An energy-saving ratio higher than 90% was achieved in the gas treatment
furnace group. The object to be heated in the gas treatment furnace itself is com-
bustible and fuel is required only for ignition. In other words, combustion of fuel
seldom occurs throughout the operation except during ignition. For this reason, the
energy-saving ratio of this group exceeded 90%.

100

H.P.I.F
Conventional F

80

60

40

20

0

FIGURE 5.85 Waste heat recovery rate.