JPS5869390A - Furnace wall - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a furnace wall having a heat insulating structure used in a heating furnace or the like.

Generally, in heating furnaces, heat treatment furnaces, and other various types of furnaces,
In order to reduce the amount of heat dissipated from the furnace, a furnace wall with an insulating structure is used. This furnace wall is usually made of a steel plate furnace shell lined with fireproof insulation bricks or monolithic refractories, but it is easy to crack due to sudden heating or cooling of the furnace wall, and it does not have sufficient insulation performance. That's because you can't get it.

This invention has been made in view of the above points, and provides excellent heat insulation performance by enclosing a radiation shield in a hollow chamber formed inside a box-shaped furnace wall and reducing the pressure inside the hollow chamber. The aim is to provide a furnace wall that has a high degree of durability and is highly durable.

An embodiment in which the present invention is applied to a heating furnace will be described below with reference to FIGS. 1 to 3.

In the figure, 1 is a roller hearth type heating furnace, in which double-structured panel-shaped furnace walls 2a12b and 2c12d are connected to each other and in the longitudinal direction by bolts or welding.
The furnace body 3 is formed! 4 is a hearth roller that conveys the heated object W, and 5 is an electric heater that is a heat source. Furnace wall 2a~
2d have the same structure, so FIG. 2 shows an enlarged cross section of the furnace wall 2a as a representative. Reference numeral 6 denotes a box-shaped body having a closed structure, and its longitudinal dimension is determined by appropriately dividing the length of the furnace. The box-shaped body 6 is made of pressed or welded steel plates, and among its side plates 7 and 8 is a wall inside the furnace. It is preferable that the side plate 7 is made of stainless steel plate. Reference numeral 9 denotes a hollow chamber formed inside the box-like body 6, and a radiation shield lO is enclosed within this hollow chamber. The radiation shield 10 is made of a heat insulating material or heat retaining material having a thermal conductivity of about 0.1 kcal/mh'C or less, and may be a fibrous material such as ceramic fiber, rock wool, or glass wool.
Alternatively, a heat insulating board made of asbestos or calcium silicate may be used. The inner wall surfaces 11 and 12 of the hollow chamber 9 are subjected to a low-flow and weight-resistant treatment such as coating with aluminum foil, aluminum plating, or galvanizing.

13 is an exhaust port provided in the box-like body 6, 14 is an on-off valve connected to this exhaust port, and 15 is a pipe leading from this on-off valve to a vacuum pump (not shown). After the pressure inside the box-like body 6 is reduced to below atmospheric pressure by the vacuum pump, the reduced pressure state is maintained by closing the on-off valve 14.

Note that the pressure reduction using a vacuum pump may be performed periodically, or a containment method may be used in which the exhaust port and the like are sealed by welding or the like once the pressure is reduced. Moreover, the degree of depressurization inside the box-shaped body 6 is
It is most desirable to use a medium vacuum region with a pressure of 1 to 1 mmHg, but it may also be a low vacuum region with a pressure of 1 mmHg or more depending on the required heat insulation performance of the furnace wall.

When the heating furnace 1 using the furnace walls 2a to 2d having the above structure is operated, the inside of the hollow chamber 9 of the box-like body 6 is in a reduced pressure state, so the amount of heat transferred due to air convection and gas heat conduction inside this hollow chamber is reduced. The amount of heat transferred from the side plate 7 on the high temperature side to the side plate 8 on the low temperature side is reduced due to the presence of the radiation shield 10. The situation of reduction in the amount of heat transfer will be explained with reference to FIG. 8 in the case where glass wool is used as the radiation shield 10. In other words, the overall thermal conductivity λ of glass wool is composed of solid conduction, convection, radiation, and air conductivity, as shown in the figure.
In the present invention, air conduction and convective conduction, which are major factors, are greatly reduced by reducing the pressure inside the box-like body 6, and the thermal conductivity in absolute vacuum is approximated to λ' shown by the chain line in the figure. It is. Furthermore, the inner wall surface 11.1 of the hollow chamber 9
2 has undergone low radiation and weight resistance treatment, so its radiation blocking function is further strengthened. For example, the radiation rate of the oxidized surface of a steel plate that is not subjected to weight-resistant treatment is approximately ε' = 0.8, whereas that of aluminum paint is approximately ε = 0.4.
, ε = 0.1 for aluminum metal 00°C oxidized surface
1 to 0.19, ε= for galvanized 400℃ oxidized surface
Since the radiation rate drops significantly to 0.11, the amount of heat from the oven to the oven further decreases.

In addition, since the box-shaped body 6 is made of a steel plate or the like, no cracks will occur even when it is rapidly heated and cooled. Furthermore, since the inside of the hollow chamber 9 is depressurized and there is little oxygen, the inside of the box-shaped body 6 will be oxidized. Since there is little wear and tear, a highly durable furnace wall can be obtained.

Next, regarding the furnace wall of the above structure, the heat flux of the furnace wall when the pressure inside the box-shaped body 6 is set to atmospheric pressure and when the pressure is reduced. Furnace wall specifications. Hollow chamber thickness (L): 150. Temperature inside the furnace = 600°C. Outside the furnace. Temperature = 20°C Side plate 7: Stainless steel plate (4wtM thickness) Side plate 8: Ordinary steel plate (6wtM thickness) Radiation shielding material: Ceramic fiber (porosity 95.5%) Low flame vs. heavy treated aluminum sill/(-paint coating) Since the heat insulation property is considerably improved by reducing the pressure, the low-flow weight resistance treatment can be omitted for one or both of the inner wall surfaces 10 and 11.

Although the embodiment described above shows an example in which the furnace body was composed of only the furnace wall according to the present invention, as shown in FIGS. 2
The furnace body 3 may be configured by using the same with 0. In the figure, parts with the same symbols as in Figures 1 and 2 are shown in Figure 1.
The same or equivalent parts as in the figure and FIG. 2 are shown. Ceramic fiber (layer thickness 5Qffi) is used as the inner insulation material 20.
1, porosity 95.5%), and other specifications are the same as in the previous example (however, only with low flux weighting treatment), the measurement results of the furnace wall heat flux and the surface temperature of the side plate 7 are Shown in Table 2.

As explained above, according to the present invention, a furnace wall with excellent heat insulation performance and durability can be obtained by reducing the pressure inside the hollow chamber of a box-like body in which a radiation shield is enclosed, and furnace wall loss can be reduced. By reducing this, energy savings can be achieved, and by reducing the thickness of the furnace wall, it is possible to downsize the furnace and reduce heat storage loss. Furthermore, in the second aspect of the invention, in which the inner wall surface of the hollow chamber is subjected to a low-burden and weight-resistant treatment, it is possible to further improve the heat insulation performance.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a heating furnace showing an embodiment of the present invention;
FIG. 2 is an enlarged sectional view of the furnace wall 2a in FIG. 1, FIG. 3 is a diagram showing the constituent factors of the thermal conductivity of glass wool, and FIG. 4 is equivalent to FIG. 1 showing another embodiment of the present invention. Similarly, FIG. 5 is a diagram corresponding to FIG. 2. 2a to 2d... Furnace wall, 6... Box-shaped body, 9... Hollow chamber, 10... Radiation shield, 11... Inner wall surface, 12
...Inner wall surface, 18...Exhaust port, 14...Opening/closing valve. Applicant Daido Steel Co., Ltd. Agent Akira Inui

Claims (1)

[Scope of Claims] 1. A furnace wall formed by enclosing a radiation shield in a hollow chamber formed inside a box-shaped body and reducing the pressure in the hollow chamber. 2. A furnace wall formed by enclosing a radiation shielding material in a hollow chamber formed inside a box-like body, applying a low radiation weighting treatment to the inner wall surface of the hollow chamber, and reducing the pressure in the hollow chamber.