JPH02203299A - Method for cooling batch operated external heat type electric furnace of globe box connection - Google Patents

Abstract

PURPOSE:To shorten the cooling time for a treating object by passing air from the outside of an inside vessel and a cooling gas in the inside vessel as well to cool the treating object and further, cooling the high-temp. gas emitted from a furnace by a heat exchange and recycling the gas to the inside of the inside vessel as well. CONSTITUTION:While the cooling gas is supplied from a piping 33 for supplying the gas by closing valves 14, 15 and 30 and opening valves 24 and 31 upon ending of heating of the treating object 1 in the inside vessel 1, the gas is passed into the vessel 2 by a pump 34 to cool the treating object 1. The gas which is made into the high temp. in the vessel 2 and is emitted from the vessel is cooled by the heat exchanger 27 and is circulated again as the cooling gas into the inside vessel 2. The air in the atm. is simultaneously passed by a pump 18 to the outside space 20 of the vessel 2 and the air heated to the high temp. by the heat exchanger 19 is released to the atm. and the vessel 2 is cooled from the outside to accelerate the cooling of the treating object 1. The treating object is cooled form the inside and outside of the vessel 2 in such a manner, by which the cooling rate is increased and the cooling gas in the vessel 2 is recycled into the vessel. The cost of the gas is thus reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises 1. This invention relates to a cooling method for a batch type external heating electric furnace connected to a glove box.

[Conventional technology]

In general, electric furnaces are divided into continuous furnaces and batch furnaces depending on their operation mode. A continuous furnace is a furnace with an inlet and an outlet, and the material to be treated is placed on plywood made of metal such as molybdenum, loaded into the furnace from the artificial side, and the plywood is moved inside the furnace using belts, chains, pushers, etc. This method heats the material and takes it out from the outlet after cooling, making it suitable for mass production on the scale of ceramics and semiconductors. On the other hand, in a batch furnace, a continuous furnace always maintains a constant temperature and the material to be processed moves inside.
The furnace itself is heated and cooled each time the material to be processed is loaded, and although it is not suitable for mass production, it allows fine control over the material to be processed and is highly efficient. Processing under special conditions such as under vacuum or under pressure is only possible in a batch furnace.

Further, electric furnaces are classified based on the heating method into external heating furnaces in which the heating element is located outside the airtight container, and internal heating furnaces in which the heating element is located inside the airtight container. External heat furnaces have a simple inner container structure, and if parts such as the heating element or heat reflector are damaged, they can be easily replaced by simply removing the outer casing or insulation material, making them highly maintainable. , many (
It is used in the field of When heating nuclear material such as plutonium in such an electric furnace, it is possible to connect the heating furnace to a glove box, take the nuclear material in and take it out from the glove box, and process it in isolation from the outside world. It is being said.

Among these electric furnaces, the present invention is directed to batch type external heat type electric furnaces.

Figure 2 is a diagram showing a conventional batch type external heating electric furnace connected to a glove box, and Figure 3 is a diagram showing temperature changes of the processed material due to various cooling methods. In the figure, 1 is the processed material, and 2 is the inner container. ,3
is a heating element, 4 is a heat reflector, 5 is a heat insulator, 6 is a casing, 7 is a water cooling pipe, 8 is a lid, 9 is a glove box, 1
0% 11 is the opening, 12.13.16.17.25.
26 is piping, 14.15.24 is a valve, 18.23 is a pump, 19.27 is a heat exchanger, 20 is an outside space, 21
is a filter, and 22 is a blower.

In the diagram, a glove box-connected batch type externally heated electric furnace has an airtight inner container 2 that heats the processed material 1 in the center of the furnace, and a heat generating part that heats the processed material 1 on the outside. body 3, heat reflective plate (reflector) 4 to prevent heat radiation
, a heat insulating material 5, a casing 6, a water cooling pipe 7, etc., in this order.

In this case, the heating element is usually made of nichrome, kanthal, or the like. The heat reflector is 0. It is a multilayer combination of 1 to 0.3 m metal plates, and is attached to the outside of the heating element or near the lid, and is used to prevent heat radiation and at the same time to protect against heat loss and heat. The insulation material is alumina brick,
Silica bricks, asbestos, etc. are used.

The glove box 9 is connected to one side of the furnace via a flange (not shown), and the inner container 2 has a lid 8 attached to the flange through which the processed material 1 is taken in and taken out. Openings 10 and 11 are provided on the side surface of the lid 8 and the inner container 2 opposite thereto.
pipes 12 and 13 for vacuuming the inside or for introducing a predetermined gas, and valves 14 connected to the pipes 12 and 13, respectively.
and 15 are provided in the openings 10 and 11, respectively. Further, the valve 15 is connected to a vacuum system (not shown).

Two openings for flowing air during cooling into the outer space 20 of the inner container 2 are provided in the casing 6 through the heat reflecting plate 4 and the heat insulating material 5, and air pressure is supplied to one opening through the piping 16. A pump 18 for feeding is attached to the other opening, and a heat exchanger 19 is attached to the other opening via piping 17.

Since the glove box 9 handles radioactive materials in the furnace, a filter 21 and a blower 22 are installed to maintain the inside at a negative pressure of about 30 mmAq with respect to the outside air. This is to prevent the nuclear material inside from leaking out of the glove box 9.

The material to be processed 1 is loaded onto a pedestal within the inner container 2 and sealed with a lid 8. The inner container 2 loaded with the material to be treated 1 is evacuated with a vacuum system through the valve 15, or a predetermined gas, for example, a hydrogen-nitrogen mixed gas, is flowed into the inner container 2 with a pump 23 through the piping 12 and the valve 14. Heat. When heating gas while flowing into the inner container 2, the gas and the processed material 1 may react or decomposed products are released from the processed material, resulting in deterioration of the composition and purity. is cooled by a heat exchanger 27 via a pipe 25 connected to the pipe 13, and then exhausted to the glove box 9 via a pipe 26 again. Due to the release of this exhaust gas, the negative pressure within the glove box 9 is disturbed. This disturbance in the negative pressure is absorbed by discharging the exhaust gas into the atmosphere by the blower 22 via the filter 21, thereby maintaining a normal negative pressure.

After the prescribed heating is completed, the furnace cools the processed material 1 using the following cooling method.
It is cooled to about 50 to 60°C, at which point it does not oxidize, and then taken out of the furnace.

The cooling method for Ca5el is to cool the inner container 2 by flowing air into the outer space 20 of the inner container 2 with a pump 18 in a sealed state during heating, and releasing it into the atmosphere via a heat exchanger 19.

The cooling method for Ca5e2 is to fill the interior of the inner container 2 with helium gas, etc., which has good thermal conductivity and does not react with the processed material 1, and seal it, and cool it by flowing air into the outer space 20 of the inner container 2, similar to Ca5el. It's a method.

(The cooling method for ase3 is to cool it by flowing air into the outer space 20 of the inner container 2 as described above, and also to flow nitrogen gas, etc., which does not react with the processed material 1 inside the inner container with the pump 23, for heat exchange. Nitrogen gas is discharged into the glove box 9 through a container 27, and nitrogen gas is discharged into the atmosphere through a filter 21 and a blower 22 while maintaining an appropriate negative pressure in the glove box 9 to cool the processed material 1. It's a method.

[Problem to be solved by the invention]

In this way, an external heat type electric furnace has an inner container between the heating element and the processed material, and there is no water cooling pipe near this area that contributes most to cooling, so cooling takes a long time, especially when processing capacity If the furnace is large in size, the heat capacity of the processed material and the inner container will be large, making it extremely difficult to cool it. Therefore, there is a drawback that the operating time of the furnace becomes long, and the influence not only on the preceding and succeeding processes but also on the entire process becomes large.

Under the same conditions for the processed material and inner container, etc., Ca5e1-3
The cooling rate when cooling was performed using the method described above was simulated on a computer, and the results shown in FIG. 3 were obtained. In Figure 3, the temperature at which the processed material is taken out is 50 to 6.
Ca5e 1 takes about 45 hours to reach 0°C.
e2 requires approximately 30 hours.

On the other hand, in the case of Ca5e3, it is around 10 hours,
It can be seen that the cooling rate has been significantly improved. However, if Ca5e3 is used as a one-time method in which the cooling gas inside the inner vessel is discarded as it is, the cost of cooling gas will be enormous, and in reactors that process nuclear materials including plutonium, exhaust gas is It must be vented into the box, but in this case, a large amount of gas exits the glove box, so the negative pressure in the glove box fluctuates greatly, just as when heating with gas flowing, and normal negative pressure must be maintained. Therefore, the complicated work of controlling the pressure with a blower via a filter is required.

The present invention is intended to solve the above-mentioned problems, and is capable of significantly increasing the cooling rate, reducing the cost of cooling gas, and relieving the glove box of negative pressure fluctuations caused by exhaust gas. The purpose of the present invention is to provide a cooling method for a batch type external heat type electric furnace.

[Means to solve the problem]

To that end, the present invention is a batch type external heating type that heats the processed material in an inner container connected to a negative pressure controlled glove box and surrounded by a heating element, a heat reflector, a heat insulating material, and a cooling pipe. In an electric furnace, cooling air is passed outside the inner container, and the hot air that comes out from the outside of the inner container is removed by a heat exchanger and released into the atmosphere. The gas which reaches high temperature and comes out of the inner container is cooled by a heat exchanger, and then passed through the inner container again as cooling gas.

[Effect]

The present invention is a batch type external heat type electric furnace, in which air is flowed outside the inner container to cool the processed material from the outside, and cooling gas is also flowed inside the inner container, so that the material is heated to a high temperature and is removed from the inner container. By cooling the emitted gas in a heat exchanger and recycling it back into the inner container as cooling gas, the cooling rate of the processed material in the inner container is increased, and the cost of cooling gas is significantly reduced. Since the helicycle gas inside the glove box is not released, the burden of negative pressure management inside the glove box can be significantly reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing an embodiment of the cooling method for a glove box-connected batch type external heating electric furnace of the present invention.
The same numbers as in the figure indicate the same contents. In addition, 30.3
1 is a valve, 32, 33 is a pipe, and 34 is a pump.

In the glove box connected batch type external heating electric furnace shown in the figure, the pump 18, the heat exchanger 19 and the connecting piping 16.1
7, etc., a cooling air supply/exhaust system for the outer space 20 of the inner container 2, a pump 23 for supplying and exhausting vacuum or gas to the inner container 2 when heating the processed material 1, a heat exchanger 27, and The structure of the glove box 9, which is equipped with an air supply and exhaust system consisting of pipes 12, 13, 25, 26, valves 14, 15, 24, etc. connected to these, and a filter 21 and a blower 22, is the same as that shown in Fig. 2. It is.

In this embodiment, a valve 30 provided at the open end of the pipe 26, a valve 31 between the heat exchanger 27 and the lid 8, and a pipe 32 opening into the inner container 2 are added, and cooling gas is supplied to the pipe 32. A supply pipe 33 and a pump 34 for circulating cooling gas are provided.

In such a furnace, the material to be treated 1 is loaded onto the frame inside the inner container 2 and sealed with the lid 8, and then the valves 14, 24 and 31 are closed, and the inner container 2 is maintained in a vacuum state using the vacuum system from the valve 15. to heat-treat the material 1, or to heat the material 1
1 is closed, valves 14, 24 and 30 are opened, and hydrogen-nitrogen mixed gas, etc. is allowed to flow into the inner container 2 from the pump 23 while being exhausted to the glove box 9 via the heat exchanger 27 for processing. Heat treat the material. Negative pressure management within the glove box 9 at this time is the same as described above.

After the predetermined VA is completed, the gas supply pipe 33 is opened with the valves 14, 15 and 30 in the closed state and the valves 24 and 31 in the open state.
pump 34 while supplying cooling gas such as nitrogen gas from
The processed material 1 is cooled by flowing into the inner container 2. The gas that reaches a high temperature in the inner container 2 and exits from the inner container 2 is cooled by a heat exchanger 27 and flfffl into the inner container 2 again as cooling gas.

Simultaneously with the cooling of the cooling gas inside the inner container 2, air from the atmosphere is caused to flow into the outer space 20 of the inner container 2 by the pump 18, and the high temperature air is cooled through the heat exchanger 19 and released into the atmosphere. Then, the inner container 2 is cooled from the outside to promote cooling of the processed material 1.

In this way, by cooling from the inside and outside of the inner container, the cooling rate is increased, and at the same time, the cooling gas inside the inner container is recycled and used inside the inner container, reducing gas costs and negative pressure in the glove box. Management burden can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, the processed material is cooled by flowing air from the outside of the inner container, cooling gas is also flowed inside the inner container at the same time, and the high temperature gas discharged from the furnace is further cooled by heat exchange. By recycling the cooling gas into the inner container, the cooling time for the processed material can be shortened.In addition, by recycling the cooling gas, gas costs can be significantly reduced, and the one-through type glove Management of negative pressure by disposable inside the box! ! can be destroyed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the cooling method for a glove box-connected batch type external heat type electric furnace of the present invention, and FIG.
The figure is a diagram showing the cooling rate of the processed material by various cooling methods.

Claims (1)

[Claims] (1) In a batch type external heating electric furnace that heats the processed material in an inner container connected to a negative pressure controlled glove box and surrounded by a heating element, a heat reflector, a heat insulator, and a cooling pipe, Cooling air is flowed outside the inner container, and the high temperature air that comes out from the outside of the inner container is removed by a heat exchanger and released into the atmosphere. At the same time, cooling gas is flowed inside the inner container to reduce the high temperature. A cooling method for a batch type external heating type electric furnace connected to a glove box, characterized in that the gas discharged from the inner container is cooled by a heat exchanger and then circulated back into the inner container as cooling gas.