JPS636384A - Heat treatment equipment - 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 (Field of Industrial Application) The present invention relates to an apparatus for heat treating a workpiece that generates harmful combustible substances during heat treatment in a non-oxidizing atmosphere. In more detail, a workpiece containing a large amount of combustible pyrolyzable substances in a base material such as sinter, ceramic, carbon, graphite, or felt or its binder is sintered, fired, or fired in a non-oxidizing atmosphere. This relates to a device that performs some kind of heat treatment such as drying.

(Prior art) For example, electrode plates for fuel cells are made by hardening carbon fiber as a base material with a binder resin such as phenol resin to form a plate-like object, and then placing the object to be processed in a high-purity non-oxidizing atmosphere. Temperature 10 at
Manufactured by firing at 00 to 3000°C.

At this time, it is necessary to take out the thermal decomposition substances generated from the binder resin outside the processing chamber. In the case of phenolic resin, this thermally decomposed substance is composed of combustible substances such as cresol, xylenol, hydrocarbons, and carbon oxides, and exhibits various forms ranging from gaseous to liquid at room temperature.

The problems that arise when heat treating such objects are:
First, the inside of the processing chamber, including the objects to be treated, must already have a high-purity non-oxidizing atmosphere.Second, this thermally decomposed substance is harmful to the natural world.Thirdly, this thermally decomposed substance must be harmful to the natural world. If it remains in the processing chamber, it will impair the quality and physical properties of the product.Fourthly, it contains flammable substances and there is a risk of explosion if it is mixed with oxidizing gases.Fifthly, the system together with the atmospheric gas If taken outside, high-boiling decomposable substances will accumulate or condense in the cold parts of the piping, quickly clogging the pipes and valves and interfering with smooth operations.

Regarding the first problem above, it is necessary to replace the inside of the processing chamber with a non-oxidizing atmosphere after the material to be processed is charged into the processing chamber. In the case of containing components, sufficient atmospheric purity cannot be ensured by replacement with gas flow, and it takes a long time to obtain a predetermined purity. Therefore, a method of evacuating the processing system and then replacing it with a predetermined gas is efficient, as is known, for example, from Japanese Patent Publication No. 19911/1983.

The second and subsequent problems relate to how the pyrolyzed material is treated, typically by thermal decomposition treatment in the presence of oxygen, or by cold trapping or water bubbling to recover it as tar.

First, in the conventional method of thermal decomposition, as is known, for example, from Japanese Patent Publication No. 50-40172, the generated thermal decomposition material is led out of the heat treatment apparatus without being cooled to below 200'C, and then it is decomposed in the presence of oxygen. It is important to thermally decompose it. Therefore, for example, JP-A-54-264
As shown in Publication No. 3 or Japanese Unexamined Patent Publication No. 57-31139, it is common to incinerate the thermally decomposed material by adding air or a gas containing oxygen immediately after it is taken out of the heat treatment apparatus. In these conventional methods, even if the heat treatment is performed in an oxidizing atmosphere, the generation of flammable thermal decomposition substances is small and is below the explosion limit, or even if the heat treatment is performed in a non-oxidizing atmosphere, the generation of flammable thermal decomposition substances during thermal decomposition is insufficient for the same reason. This should be limited to cases where there is no possibility of explosion due to the addition of oxygen.

(Problems to be Solved by the Invention) In other words, in the apparatus of the present invention for heat-treating a workpiece that generates a large amount of combustible thermal decomposition substances in a non-oxidizing atmosphere, the conventional example described above has the following problems. This will cause the inconvenience described below.

b) Since there is no means to separate the non-oxidizing atmosphere system containing the generated flammable gas (hereinafter referred to as the combustible gas atmosphere system) and the oxidizing atmosphere system of the exhaust gas treatment section, operating conditions, operational errors, and malfunctions may be affected. Due to problems such as malfunctions, the pressure relationship in the rain cloud enclosure system may reverse, causing oxidizing gas to flow back into the flammable atmosphere system, creating a mixture that exceeds the explosive limit, or causing damage to the product. That there is a possibility.

(1) It is not configured to handle rapid changes in the amount of decomposed gas generated due to changes in processing temperature and in the thermal expansion of the supplied gas, so there is a limit to maintaining the processing pressure within a certain range. Also, depending on the processing conditions, there is a risk that the gas pressure may rise beyond the withstand pressure of the processing chamber.

C) Even if the concentration of generated decomposed gas drops below the environmentally safe standard value when the processing temperature is raised or lowered or the plant is shut down, the exhaust gas always passes through the exhaust gas incinerator, so the exhaust gas It is necessary to operate the incinerator. If the engine is not operated, low concentrations of pyrolyzed substances will accumulate or condense in the cold parts of the exhaust system passages.

In view of the above-mentioned points, an object of the present invention is to improve the shortcomings of conventional apparatuses for heat-treating objects to be treated containing flammable pyrolyzed substances in a non-oxidizing atmosphere. It is an object of the present invention to provide a heat treatment apparatus that can safely and efficiently process substances even if a large amount of substances are generated.

(Means for Solving the Problems) A heat treatment apparatus of the present invention that achieves the above object has the following configuration.

That is, in an apparatus for heat-treating a workpiece that generates combustible thermal decomposition substances during heat treatment in a non-oxidizing atmosphere, the processing chamber is provided with a supply hole for non-oxidizing gas via an opening/closing means, and A heat-resistant opening/closing means and an exhaust gas incineration device having an air introduction hole are arranged in order from the processing chamber side in the exhaust pipe connected to the processing chamber, and an opening/closing valve of the exhaust device is interposed between the processing chamber and the heat-resistant opening/closing means. The heat treatment apparatus is characterized in that the combustible gas atmosphere system and the oxidizing atmosphere system are separated by the heat-resistant opening/closing means.

Further preferable embodiments of the present invention will become apparent in accordance with the following description.

Hereinafter, the heat treatment apparatus according to the present invention will be explained in more detail based on the drawings.

FIG. 1 is a schematic diagram showing a preferred embodiment of a heat treatment apparatus according to the present invention.

In FIG. 1, a heating furnace 1 that heats a workpiece 4 containing a flammable substance basically includes a processing chamber 5 and a heater 6.
．． 6', opening/closing means 9°10, throttle valves 13,1
4 via a non-oxidizing gas, e.g. N2, A, , H8,
Alternatively, a supply hole 7 for supplying these mixtures or the like is provided. Although not shown, suction holes for different non-oxidizing gases are provided through opening/closing means, so that the properties of the unprocessed material 4 can be adjusted.
A desired atmosphere can also be obtained by appropriately opening and closing the opening/closing means depending on conditions such as processing temperature.

The exhaust pipe 20 connected to the processing chamber 5 has a
In order from the side, a heat-resistant opening/closing means 50, an exhaust gas incineration device 3 having an air introduction hole 63, and, depending on the case, a suction fan 74 are arranged, and the processing chamber 5 and the heat-resistant opening/closing means 5
An exhaust device 40 is connected to the exhaust pipe between 0 and 0 via an opening/closing means 42, and the heat resistant opening/closing means 50 connects a flammable gas atmosphere system (the system on the left side of the heat resistant opening/closing means 50 in FIG. 1);
The structure is such that it is separated from the oxidizing atmosphere system (the system on the right side of the heat-resistant switching means 50 in FIG. 1).

Here, what is important for safe operation in the above configuration is that the flammable gas atmospheric pressure is maintained higher than the oxidizing atmospheric pressure, at least under operating conditions where flammable gas is generated. .

Therefore, as shown in FIG. 1, a suction fan 74 is placed behind the exhaust gas incinerator 3 to lower the oxidizing gas atmosphere pressure, or the supply pressure of the non-oxidizing gas supplied to the heating furnace 1 is increased. , take any action.

Furthermore, as described above, since it is necessary to replace the flammable gas atmosphere system with a non-oxidizing gas in advance, the exhaust system 4
0 and the opening/closing means 9 and 10.42° 50 are selected depending on the required atmospheric gas purity. - Generally, a vacuum pump is used as the exhaust device 40, and the opening/closing means 9.10
, 42, 50 and the processing chamber 5 preferably have the necessary vacuum resistance.

Next, although the exhaust gas incineration device 3 can be either a direct combustion type or a catalytic type, a catalytic type is shown as an example in FIG. Air necessary for combustion is introduced into the incineration chamber 64 through the air introduction hole 63 after its volume is adjusted by the damper 62 and preheated by the air heater 61 . The chamber 6
4, the mixture is mixed with exhaust gas containing thermally decomposed substances introduced from the exhaust pipe 20, and is incinerated at the catalyst 60. The air heater 61 is for obtaining the activation temperature of the catalyst 60.

The incinerated exhaust gas passes through the exhaust pipe 20 to the damper 7.
3, the flow rate is adjusted, and depending on the case, it is discharged to the atmosphere by a suction fan 74. At that time, if the exhaust temperature is high and the suction fan 74 has a heat resistance problem, it may be water-cooled or the
As shown in the figure, it is effective to lower the exhaust temperature by sucking atmospheric air through an air introduction hole 72 via a damper 71.

The actual operation of the above heat treatment apparatus will be explained below.

First, after storing the object to be processed 4 into the processing chamber 5, the opening/closing means 9, 10 and the heat-resistant opening/closing means 50 are closed, the exhaust valve 42 is opened, and the inside of the processing chamber 5 is brought to a predetermined degree of vacuum by the exhaust device 40. exhaust to.

Next, the exhaust valve 42 is also closed, and the opening/closing means 9 is opened from the non-oxidizing gas supply hole 7 to supply non-oxidizing gas until the inside of the processing chamber 5 reaches approximately normal pressure. At that time, in order to keep the oxygen concentration in the processing chamber 5 at a level that will not cause damage due to oxidation reaction when the object to be processed 4 is heat-treated, if necessary, the above-mentioned vacuum displacement operation is performed to keep the oxygen concentration below a predetermined concentration. Repeat until. Thereafter, while non-oxidizing gas is constantly supplied from the non-oxidizing gas supply hole 7, the object 4 to be processed is heated by the heater 6 according to a predetermined temperature increase pattern. The amount of gas supplied can be adjusted with a throttle valve 13.

The combustible gas generated by thermal decomposition from the object to be treated 4 passes through the exhaust pipe 20 and the heat-resistant opening/closing means 50 together with the non-oxidizing gas, and reaches the exhaust gas incinerator 3, where the combustible components are incinerated, and then the suction fan 74 to the atmosphere.

Here, when the pyrolysis gas is led out from the exhaust pipe 20, if high boiling point decomposable substances adhere and accumulate as solids or condense in the cold part of the pipe, heat retention means or heating means such as a heater may be used. 21 between the processing chamber 5 and the exhaust gas incinerator 3 of the exhaust pipe 20, the heat-resistant opening/closing means 50, and the throttle valve 5.
1 can be covered to prevent this.

It is important that the temperature at which the heat is kept or heated is higher than the boiling point of the thermally decomposed substance, and is usually preferably 200° C. or higher.

Alternatively, if the high-boiling decomposition material is to be condensed and drained when cooled, it may be configured as in the embodiment shown in FIG. 2.

FIG. 2 is a schematic diagram showing another preferred embodiment of the heat treatment apparatus according to the present invention. An exhaust gas cooling device 2 consisting of a cooling chamber 30 and a drain recovery container 32 is provided in the middle of the exhaust pipe 20 between the processing chamber 5 and the connection pipe 41 to the exhaust device, and the exhaust gas cooling device 2 is provided with a cooling chamber 30 and a drain recovery container 32. A part of the condensed drain is collected in the container 32 at the bottom,
It can be recovered by opening the valve 34. In the configuration shown in this figure,
The exhaust gas temperature reaching the heat-resistant opening/closing means 50 is controlled by the cooling device 2.
Since the heat-resistant opening/closing means 50 can be cooled by cooling, there is an advantage that a heat-resistant vacuum valve can be used as the heat-resistant opening/closing means 50. Therefore, in the configuration shown in FIG. 2, the processing chamber 5, the opening/closing means 9.
From the viewpoint of the purity of the processing gas, it is preferable to configure the parts 10, 42, and 50 with a vacuum-resistant structure. In this case, the purpose of the exhaust gas cooling device 2 is to cool the exhaust gas temperature to a temperature lower than the heat-resistant temperature of the heat-resistant opening/closing means 50 having vacuum resistance, and is not to convert the thermal decomposition substances into drains. The other configuration may be the same as the configuration explained using FIG. 1.

Next, the control system will be explained below using FIG. 2 as an example.

The temperature of the heating furnace 1 is controlled by a signal from a temperature sensor in the processing chamber 5, such as a thermocouple or a radiation thermometer, and a programmed temperature controller is configured to raise and lower the temperature of the heater 6 in a predetermined heat pattern.

Pressure control of the non-oxidizing gas atmosphere system including the processing chamber 5 is carried out by switches 45 and 46 that detect the lower and upper limits of the processing pressure, the on-off valve 9 for large flow rate supply of the non-oxidizing gas supply hole 7, and the small flow rate supply. When the pressure is lower than the set pressure of the upper limit switch 46, the detection signal of the upper limit switch 46 causes the large flow rate supply on-off valve 9 to be opened.
is opened to supply non-oxidizing gas.

The throttle valve 13.14 and the flow meter 15.16 are connected, for example to the second
With the configuration as shown in the figure, the processing pressure during steady operation is detected by the set pressure of the upper limit switch 46 and the lower limit switch 45,
By adjusting the throttle valves 13, 14.51, non-oxidizing gas is supplied at a flow rate from the small flow valve 10 during steady state, and a large flow flow is supplied only when the processing pressure drops to the lower limit. It is preferable to supply the water through the on-off valve 9.

When the processing pressure drops below the set pressure of the lower limit switch 45 due to some trouble, such as a stoppage of the supply gas,
In response to a detection signal from the processing pressure lower limit warning switch 47, which has a set pressure lower than the set pressure of the gas pressure lower limit switch 45 and higher than the oxidizing atmospheric pressure, the operation of the processing chamber heater 6 is held or stopped, and the heat-resistant vacuum The opening/closing means 50 is closed to prevent air from flowing back from the exhaust gas incineration device 3 to the combustible gas atmosphere system. At the same time, the emergency supply hole 1 has a gas source separate from the supply hole 7.
1, the on-off valve 12, which is in a closed state during normal operation, is connected to the switch 4.
It opens in response to the signal No. 7 to introduce non-oxidizing gas, restores the pressure of the combustible gas atmosphere system, and prevents atmospheric air from flowing into the processing chamber 5.

When the processing pressure recovers to the set pressure of the lower limit warning switch 47, the original steady operating state is restored. On the other hand, in case the processing pressure rises further than the set pressure of the upper limit switch due to some abnormality, the relief valve 44 maintains the processing pressure below the withstand pressure of the flammable gas atmosphere system.

It is preferable that the on-off valves 9, 10, 12, 42, 50 are of an electromagnetic type or a pneumatic type.

If it is known in advance that the exhaust gas incineration device 3 will start generating pyrolysis gas at a certain temperature or higher and will stop generating at a certain temperature or higher, the exhaust gas incineration device 3 will turn on the heat treatment chamber heater 6.
It is preferable to start operation when the temperature reaches a set value or higher based on a signal from the temperature controller for 6', and to stop the operation after the temperature has been generated. Of course, during operation, it is desirable to control the temperature of the preheater 61 while detecting the gas temperature at the outlet of the catalyst layer 60, so as to be able to maintain it at a predetermined catalyst activation temperature.

The configuration of the control system described above is also effective in the embodiment example described using FIG.

3 and 4 are schematic diagrams showing a more preferred embodiment of the heat treatment apparatus according to the present invention.

In the configuration shown in FIGS. 1 and 2, the flow rate on the exhaust side is uniquely determined by the throttle valve 51, and even when non-oxidizing gas is supplied by the small flow rate supply valve 10, the flow rate on the exhaust side is determined by the throttle valve 51. Thermal expansion due to temperature rise or decomposition gas generation rate is too high,
There is a possibility that the exhaust speed will not be able to follow.

Further, the heat generated when incinerating combustible gas components in the exhaust gas incinerator 3 is released into the atmosphere together with the exhaust gas.

Therefore, as shown in FIG. 3 as a configuration corresponding to FIG. 1, and as shown in FIG. 4 as a configuration corresponding to FIG. 57, a piping having a small exhaust throttle valve 58, and a piping having a bypass exhaust valve 55. Furthermore, a heat-resistant valve 5 is installed in the exhaust pipe just before the exhaust gas incineration device 3.
4 is provided, and a direct exhaust hole 53 is formed in the exhaust pipe 20 between the heat resistant switching means 50 and the heat resistant switching valve 52.

By configuring as described above, the follow-up range of the exhaust speed is widened, and the processing pressure does not rise above the withstand pressure of the non-oxidizing gas atmosphere system. Conversely, when the amount of pyrolysis gas generated is so small that it does not pose an environmental problem, or when the temperature is falling, the process pressure should not be made much higher than atmospheric pressure, and only the small-flow exhaust throttle valve 58 should be used on the exhaust side. Open direct exhaust valve 5
It is preferable to open 2 and exhaust the air directly from the viewpoint of gas and energy saving.

An example of a preferable processing pressure control method in the above configuration is described in the fifth section.
As shown in the figure.

That is, among the valves on the exhaust side, the small exhaust throttle valve arch 8 is always open, and the processing pressure control ranges P1 and P shown in FIG.
2, the degree of throttling of the throttle valves 57 and 58 is adjusted in advance so that the exhaust is exhausted by the throttle valve 58 and the steady exhaust valve 56. When the furnace pressure exceeds P3 due to a change in the amount of pyrolysis gas generated, etc., a control system is constructed in which the small flow rate supply valve 10 for non-oxidizing gas is closed and the bypass exhaust valve 55 on the exhaust side is opened. Conversely, when the furnace pressure drops below P2, the large flow valve 9 on the supply side is opened to restore the pressure. The small flow supply valve 10 is P2
You can leave it open or close it below. If the furnace pressure still decreases, it is likely that the gas supply has stopped, a gas leak has occurred, or some other abnormality has occurred, so if it decreases to Pl, the steady supply of non-oxidizing gas In order to simultaneously open the emergency supply valve 12 disposed in the piping of the supply hole 11 from a gas source different from the hole 7 to supply gas, and to block the backflow of gas containing oxygen from the oxidizing atmosphere system. It constitutes a control system that closes the heat-resistant opening/closing means 50 and the steady exhaust valve 56.

The steady state exhaust valve 56 may be configured to close at P2.

(Indicated by a broken line in the figure) When the exhaust gas incinerator 3 is operating, the incineration introduction valve 54
When directly exhausting the air, the direct exhaust valve 52 is controlled as shown in the figure.

Furthermore, as shown in FIGS. 3 and 4, the air necessary for incineration is directly introduced into the incineration chamber 64 from the introduction hole 63, without releasing the combustion heat generated in the exhaust gas incinerator 3 into the atmosphere. If the structure is such that it can be preheated using the combustion heat in the catalyst layer 60, or if a heat exchanger is installed to preheat the introduced air, exhaust heat energy can be used effectively. Furthermore, the air introduction hole 6
3 is provided with an orifice 65, and a differential pressure transmitter 66 detects the differential pressure before and after the orifice 65. When the differential pressure falls below a set value, the suction fan 74 is stopped, the catalyst layer 60 is clogged, etc. Since trouble is expected, it is best to stop the heater 61 of the incinerator using the signal from the differential pressure transmitter 66, close the incineration introduction valve 54, and open the direct exhaust valve 52 to switch to direct exhaust. Preferable for protection.

(Effects) As explained above, the heat treatment apparatus according to the present invention is a heat treatment apparatus that is particularly effective in heat treating a workpiece containing a large amount of combustible thermal decomposition substances in a non-oxidizing atmosphere. ,
This produces the effects described below.

In other words, the combustible gas atmosphere system including the processing chamber and the oxidizing atmosphere system including the exhaust gas incinerator are separated by heat resistance and closure means, so that problems such as operating conditions, operational errors, malfunctions, breakdowns, etc. By closing the heat-resistant opening/closing means, it is possible to prevent the combustible decomposed gas and the oxidizing atmosphere from coming into contact with each other, creating a mixture that exceeds the explosion limit, or damaging the product.

In addition, since the exhaust pipe from the processing chamber to the exhaust gas incineration device is equipped with heat retention means or heating means capable of maintaining the temperature above the boiling point of the pyrolyzed substance, high boiling point decomposition can be achieved by cooling the exhaust pipe midway. No harmful substances will accumulate or condense and block pipes and valves.

In addition, if the high boiling point decomposable substance condenses and becomes drain when cooled, an exhaust gas cooling device having a drain collection container is provided in the middle of the route to the exhaust gas incineration device in the exhaust pipe. - The pyrolyzed substances can be recovered as drain, and similarly there is no clogging of pipes or valves. Furthermore, in this case, since the exhaust gas leading to the heat-resistant opening/closing means is cooled, a heat-resistant vacuum opening/closing valve can be used as the opening/closing means, and the entire flammable gas atmosphere system including the processing chamber is configured with a vacuum-resistant structure. At the same time, by using a vacuum evacuation device as the evacuation device, a highly purified non-oxidizing atmosphere can be obtained after gas replacement.

In addition, in that case, almost the entire system including the exhaust gas incineration device would have to be vacuum-resistant, but by inserting the heat-resistant vacuum opening/closing means into the above-mentioned location of the exhaust pipe, heat-resistant vacuum opening/closing is possible. It suffices to configure only the upstream side of the means to have a vacuum-resistant structure.

Furthermore, the non-oxidizing gas supply hole is branched into a large flow valve and a small flow valve, each of which is configured to be detected by a lower limit and upper limit switch of the non-oxidizing gas pressure and opened/closed by the signal, so that the processing temperature can be controlled. In response to rapid changes in the amount of decomposed gas generated and the thermal expansion of the supplied gas due to changes in
It is also effective in terms of energy saving.

Furthermore, a heat-resistant valve was installed just before the incinerator, and a direct exhaust hole was installed so that the pyrolysis gas could be discharged without passing through the incinerator when it was not needed. It does not pollute the inside of the incinerator and also saves energy.

As described above, by using the present apparatus, it has become possible to safely and efficiently heat treat objects containing a large amount of harmful combustible thermal decomposition substances in a non-oxidizing atmosphere.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG. 2 is a schematic diagram showing another embodiment of the present invention. Figures 3 and 4 are the first
FIG. 3 is a schematic diagram showing another preferred embodiment of the present invention corresponding to FIGS. FIG. 5 is an operational diagram of each element showing an example of a processing pressure control method for the apparatus shown in FIGS. 3 and 4. FIG. Brief description of the drawings 1: Heating furnace 2: Exhaust gas cooling device 3: Exhaust gas incinerator 4: Processing object 5: Processing chamber 6: Heater 7: Non-oxidizing gas supply hole 11: Emergency gas supply hole 13.14, 57, 58: Throttle valve 15.16: Flow meter 20: Exhaust pipe 30: Cooling chamber 31: Cooling pipe 32: Drain collection container 33: Drain return 34: Valve 40: Exhaust device 41: Piping 42: Opening/closing valve 43: Exhaust hole 60: Catalyst layer 61: Air heater 62.71.73: Damper 63.72: Air introduction hole 64: Chamber 65 Niorifice 66: Differential pressure transmitter 74: Suction fan

Claims (5)

[Claims] (1) In an apparatus for heat-treating a workpiece that generates flammable thermal decomposition substances during heat treatment in a non-oxidizing atmosphere, the processing chamber is provided with a supply hole for a non-oxidizing gas via an opening/closing means, and A heat-resistant opening/closing means and an exhaust gas incineration device having an air introduction hole are arranged in the exhaust pipe connected to the processing chamber in order from the processing chamber side, and an exhaust device is arranged in the exhaust pipe between the processing chamber and the heat-resistant opening/closing means. A heat treatment apparatus, characterized in that the combustible gas atmosphere system on the processing chamber side and the oxidizing atmosphere system on the exhaust gas incinerator side are separated by the heat-resistant opening/closing means, which are connected through an on-off valve. (2) Claims characterized in that the exhaust pipe from the processing chamber to the exhaust gas incineration device is equipped with heat retention means or heating means capable of maintaining the temperature at a temperature equal to or higher than the boiling point of the pyrolyzed substance. The heat treatment apparatus according to item 1. (3) All opening/closing means constituting the processing chamber and the combustible gas atmosphere system have a vacuum-resistant structure, and the evacuation device is a vacuum evacuation device, and the connecting portion between the processing chamber and the evacuation device is 2. The heat treatment apparatus according to claim 1, further comprising an exhaust gas cooling device having a drain collection container in the middle of the exhaust pipe between the exhaust pipes. (4) A switch for detecting the lower and upper limits of the processing pressure is provided in the flammable gas atmosphere system including the processing chamber, and the non-oxidizing gas supply hole is equipped with a piping having an on-off valve for supplying a large flow rate and a small flow rate. The large flow valve opens when the pressure is below the set pressure of the lower limit switch, and the small flow valve opens when the pressure is below the set pressure of the upper limit switch to supply non-oxidizing gas. The heat treatment apparatus according to claim 1, characterized in that it comprises a control system. (5) A gas pressure lower limit alarm switch having a set pressure lower than the set pressure of the processing pressure lower limit switch and higher than the oxidizing atmosphere pressure is provided in the flammable gas atmosphere system including the processing chamber; An emergency non-oxidizing gas supply hole is attached to the flammable gas atmosphere system via an on-off valve, and the operation of the processing chamber heater is held or stopped below the set pressure of the lower limit alarm switch, and the heat-resistant opening/closing means 5. The heat treatment apparatus according to claim 4, further comprising a control system in which the emergency supply valve is closed and the emergency supply valve is opened.