Design Guidelines for High Performance Industrial Furnaces - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 307

wide objects, axial flow heating burners are necessary to secure uniform temperature
distribution in the direction of the furnace width. However, with this combustion
system comprising high velocity air jet regenerative burners, the uniformity of
temperature distribution in the direction of the width is realized through a sideways
heating method. The use of the sideways heating method has made it possible for
the furnace to be designed as a simple boxlike unit. Furthermore, there is no noselike
section. Thus, the height of the furnace is reduced.
The furnace features the following improvements:
1. Maximized heat transfer : With flattened time-averaged temperature dis-
tribution and increased adiabatic flame temperature, the heat transfer effect
with respect to steel materials is maximized.
2. Uniform heating : With the in-furnace combustion gas stirred thoroughly,
uniform heating of steel materials is realized to the same degree as
achieved with conventional technology.
3. Minimized heat loss : With critical heat recovered by the regenerative
burners, heat loss is minimized.
By employing control methods based on the characteristics of regenerative burners
applied for heating control, furnace pressure control, and oxygen control, stable
operation is realized.
Refractory materials and a fiberlining structure are employed for the furnace
ceiling and walls to realize high energy savings and low heat inertia. In addition, a
ceramic fiber lining is employed for the in-furnace skid pipe to improve the thermal
insulation effect.
The facility building and foundation are also reduced in size. With the employ-
ment of regenerative burners, the recuperator used in a conventional furnace can be
dispensed. As the furnace length and height are reduced, the heights of the facility
building and foundation can also be reduced. As a result, the installation space for
the furnace and related equipment becomes smaller than that for a conventional
furnace.
Product quality and yield are improved. As a result of improved in-furnace heat
transfer capacity with the use of regenerative burners, the heating time required for
steel workpieces is reduced. This leads to a reduction of scale formation on the
surface of steel workpieces and also a reduction in decarburization.
5.4.3 H EAT T REATMENT F URNACE
A cross section of a semicontinuous heat treatment furnace (STC furnace), con-
sisting of a charging table, heating room, and discharging table, is shown in Figure
5.67 a s an example of a production heat treatment furnace. Materials for heat
treatment on the charging table are transferred into the furnace by driving rollers,
heat-treated and come to the end of the heat-treating process by being transferred
to the discharging table. The furnace is filled with atmospheric gas to prevent
oxidation, and carburization, decarburization, and radiant tubes are installed on
both the upper and lower sides of the heat-treating materials as well as under them.