JPH0933176A - Heat insulation structure of heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure energy saving and space saving in a heating furnace using a graphite heater used for high temperature heating by assembling into a first layer of a graphite heat insulation layer a tungsten plate or a molybdenum plate. SOLUTION: There is assembled into a first layer of a graphite heat insulation material a tungsten plate or a molybdenum plate having a lower emissivity and useable at high temperature. For example, in a heating furnace including an oil rotary pump 8, a vacuum pump of a diffusion pump 7, and a graphite heater 3, 0.5mm thick tungsten plate 1 is sticked to the first layer of the graphite heat insulation material 2, on the outside of which the graphite heat insulation material 2 is used. Hereby, there are ensured an energy saving effect in view of power consumption, a compact space saving effect, and inexpensive manufacture of the heating furnace, and in particular the present structure is effective in high temperature application fields at 2000 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating structure of a heating furnace in which a graphite heat insulating layer of a heating furnace using a graphite heating element is incorporated with a highly reflective tungsten plate or molybdenum plate.

[0002]

2. Description of the Related Art Conventionally, graphite oxidizes at 700 ° C. or higher in the atmosphere, but since its melting point is 3500 ° C. or higher, it is used in a vacuum or an inert atmosphere, and it is inexpensive and has good workability. Widely used as materials and structural materials. In a heating furnace using a graphite heating element, graphite is generally used for the heat insulation layer.

[0003]

By the way, since graphite has a high emissivity and absorbs light well, the graphite, which is a heat insulating material, absorbs heat well in a high temperature range where radiant heating is the main component. It has the property of being lost. There are three types of heat transfer: conduction, convection, and radiation. Generally, conduction, convection, and heat transfer have a large heating effect in the low temperature range, and radiative heat transfer is at an absolute temperature of 4
Since the energy increases in proportion to the power, it is effective for heat transfer heating in a high temperature range. Graphite insulation has a melting point of 350
Although it is a material that can withstand high temperatures of 0 ° C or higher, conversely, it has good heat absorption of light in the high temperature region where radiant heating is the main, so it is necessary to increase the thickness of the heat insulating layer and increase the equipment power. There was a problem. It is an object of the present invention to provide a heat insulating structure for a heating furnace that uses a graphite heating element used for high-temperature heating and that saves energy and space.

[0004]

That is, the heat insulating structure of the heating furnace of the present invention is characterized in that the first layer of the graphite heat insulating material is incorporated with a tungsten plate or a molybdenum plate which has a low emissivity and can be used at high temperature. And

[0005]

[Function] In a heating furnace using a graphite heating element, by using a tungsten plate or a molybdenum plate as the first layer of the graphite heat insulating material, most of the radiant energy emitted by the graphite heating element is reflected, and the heated object is efficiently processed. It can be heated well. Therefore, power consumption is small and energy saving can be achieved. Further, since the heat insulation can be performed efficiently, the heat insulation layer can be thinned and an inexpensive and compact heating furnace can be formed.

[0006]

EXAMPLES The present invention will be described with reference to examples. In FIG. 1, in an effective furnace internal size W200 × H200 × L300, in a heating furnace equipped with a vacuum pump such as an oil rotary pump, a diffusion pump, and a graphite heating element, the first layer of the graphite heat insulating material has a thickness of 0.5.
mm tungsten plates were stuck together, and a graphite heat insulating material was used on the outside thereof. Based on the examples, the calculated value and the measured value of the power when the tungsten plate is used and when it is not used will be compared. Since the graphite heating element is surrounded by a heat insulating material, its radiant heat quantity Q is expressed by the following equation. Q = φ ₁ → ₂ A ₁ σ (T ₁ ⁴ −T ₂ ⁴ ) −where A ₁ is the surface area of the heating element, φ ₁ → ₂ is the overall absorption rate,
T ₁ is the heating element surface temperature, T ₂ is the heat insulating material surface temperature, and σ is S
It is a tefan-Bolt2mun constant. The overall absorption rate φ ₁ → ₂ is represented by the following formula. 1 / φ ₁ → ₂ = 1 / ε ₁ + (A ₁ / A ₂ ) (1 / ε ₂ −1) − Here, A ₂ is the surface area of the heat insulating material, ε ₁ is the emissivity of the heating element,
ε ₂ is the heat insulating material emissivity. Here, the conditions shown in FIG. 1 are applied to the formula, and the electric powers when the tungsten plate is used as the first layer of the heat insulating layer and when it is not used are calculated as follows. a) Electric power when no tungsten plate is used Qw A ₁ = 0.182m ² A ₂ = 0.843m ² ε ₁ = 0.95 ε ₂ = 0.95 Further, T ₁ = 2000 ° C. (2273k) by data measurement.
T ₂ = 1950 ° C. (2223 k) at
Qw = 22.1Kw b) Electric power when using a tungsten plate Qc A ₁ = 0.182m ² A ₂ = 0.843m ² ε ₁ = 0.26 ε ₂ = 0.95 and T ₁ = T = 2000 ° C (2273k) T ₂ is assumed to be the same as i). {T ₂ = 1950 ° C
(2223k)}. Qc = 14.1Kw Therefore, (Qw−Qc) / Qw × 100 = 36, which is 3
Energy savings of 6% can be expected. Taking power consumption data from the heating furnace shown in FIG. 1, it was found that when the ambient temperature was 2000 ° C. and the tungsten plate was not used, it was 25.3.
18.5Kw when using Kw and tungsten plate
That's a 27% energy savings. The efficiency is lower than the calculated value because the loss from the heating element terminals is included. In all cases, the heat insulating structure of the heating furnace according to the present invention had a good result that the energy saving was about 30% as compared with the conventional one.

[0007]

[Embodiment 1] As described above, the heat insulating structure of the heating furnace according to the present invention enables an energy saving effect in terms of power consumption, a compact space saving effect, and an inexpensive heating furnace to be manufactured. Can be said to be very effective in the high temperature field.

[Brief description of drawings]

FIG. 1 is a heating furnace using a graphite heating element.

[Explanation of Codes] Tungsten plate 2. Graphite insulation 3. Graphite heating element 4. Insulating glass 5. Thermocouple 6. Vacuum sensor 7. Diffusion pump 8. Oil rotary pump

Claims (1)

[Claims] 1. A heat insulating structure for a heating furnace, wherein a tungsten plate or a molybdenum plate is incorporated in a first layer of the graphite heat insulating layer in a heating furnace using a graphite heating element.