Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 333

between the types of combustion methods is also discussed in the report of “High
Performance Industrial Furnace Development Project.” Joint research activities
include the study and analysis of combustion methods.

5.5.3 C HARACTERISTIC A SPECTS OF THE 1998 F IELD T EST P ROJECT

The objectives, purposes, application methods, and effect of the introduction of high-
performance industrial furnace technologies with respect to the seven types of
furnaces were examined by taking typical cases in fiscal 1998 as examples.
With continuous heating furnaces, nine cases were considered. Among them,
four were high performance industrial furnaces modified by employing regenerative
burners only in the preheating zones or the heating zones corresponding to preheating
zones. They were all for blast-furnace makers, aiming to save energy, to reduce NO x
emissions, and to reduce size. In one case, a two-furnace operation was changed to
a one-furnace operation. In another case, a three-furnace operation was modified to
a two-furnace operation to realize a successful reduction of the facility by reducing
the heating time. Furthermore, with two electric furnace makers, the length of their
furnaces was reduced by more than one third. (One of the makers modified the
furnace by reducing the length by more than half and increasing the charging
temperature.)
For batch heating furnaces, as a result of the field test of high performance
industrial furnaces of this type, the energy-saving effect was seen to be the most
outstanding. Most of these furnaces were batch-type heating furnaces for forging,
in which waste heat recovery was rarely executed and heating and machining pro-
cesses were repeated resulting in very large unit fuel consumption. With these
furnaces transformed into high performance industrial furnaces, their energy con-
sumption of 2.0 to 25.1 GJ/t (500 to 6000 Mcal/t) prior to the modification was
reduced by 30 to 60%.
Ladle preheating (heat-retaining) units are designed for the purpose of saving
energy and uniform refractory heating. The applications in fiscal 1998 included five
ladle preheating units (including a ladle for heat-retaining purposes). The capacity
ranged from 40 to 200 t/ch. The energy-saving effect attained by high performance
industrial furnaces in these cases amounted to between 36 and 57%.
Continuous heat treatment furnaces consist of many furnace types, many mate-
rials, and many shapes of objects to be treated. Not only the workpieces to be treated
but also other objects, such as trays, are often heated in these furnaces, with the heat
capacity of such trays, etc. in some cases larger than the workpieces themselves.
Therefore, the energy-saving effect varies enormously from one case to another.
Nine cases of 11 used radiant tube burners. In particular, two cases aimed at drastic
energy savings by changing from electric heating to gas-fired heating with a resulting
reduction of energy consumption of more than 60%.
Batch heat treatment furnaces, as with continuous heat treatment furnaces, con-
sist of many furnace types, materials, and shapes of objects to be treated. Many of
those furnaces are used for processing automotive parts. Four cases of ten used
radiant tube burners. In these types, too, four electric heating furnaces were changed
to gas-fired furnaces with resulting achievement of an energy saving of 55 to 80%.