JPS61122482A - High-frequency induction heating furnace - 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 the structure of a high frequency induction heating furnace incorporating a graphite heater.

(Prior Art) FIG. 6 shows nine typical examples of structures that have been adopted in conventional high-frequency induction heating furnaces. That is, a graphite container 1 and a bottom plate 2 are placed in the center of the furnace. It has a structure in which a graphite heater made up of an upper lid 3 is placed, and a high frequency work coil 13 is spirally surrounding the graphite heater. When a high-frequency current is passed through the work coil, an induced current is generated on the outer circumferential surface of the graphite heater, and the heater itself is heated. The object to be heated 9 and the jig 10 placed in the graphite heater are heated by thermal radiation and thermal conduction from the graphite heater. in this case.

Depending on the purpose of processing the object to be heated, gas 30 from each box is introduced into the graphite heater from its nozzle 6 through the introduction pipe 7, and exhaust gas 31 such as reaction gas or pyrolysis gas generated in the graphite heater is passed through the exhaust gas port. 8 and is discharged. In the figure, 5 is a nozzle protection tube. Generally, the gas introduced into the graphite heater is:

Air (especially oxygen) that can induce dangerous conditions such as combustion or explosion
Inert gas such as e Nx * He + Ar is often used for the purpose of expelling the gas from inside the graphite heater and preventing its intrusion.

On the other hand, the threshold space between the outer peripheral surface of the graphite heater and the work coil is filled with a filler powder 11 such as carbon powder to improve the thermal efficiency of the graphite heater, provide insulation to prevent overheating of the work coil, and prevent combustion of the graphite heater. The air is blocked.

Copper tubes are most often used as the material for work coils, but since their melting point is around 1000℃, they avoid deformation or breakage due to conduction heat from the filling powder and heat generated by electricity. For this purpose, water is passed through the pipe to cool it.

If this water were to leak outside, it would enter the stuffing 11 and evaporate rapidly, potentially causing a steam explosion in the stuffing. For this reason, the outer periphery of the work coil is further covered with heat-resistant cement 12.

Every effort has been made to prevent the work coil from breaking due to conduction heat from the stuffing powder.

In addition, the above structural members 11 and 12 and concrete foundation 1
A castable 14 is provided between 60 and 60.

Further, a heat insulating material 15 is disposed on the surface of the castable with which the heater support leg (made of graphite) 4 comes into contact to block heat conduction from the graphite heater to the foundation 16.

The above is the basic structure of a conventional high-frequency induction heating furnace.
Workers who operate and manage this furnace usually work on the floor 20. In this case, in order to ensure a safe distance from the high frequency current flowing through the work coil 13 and the heat transmitted from the graphite heater, the heat resistant cement 12
The outer part of the furnace is covered with a furnace wall 19 made of heat-resistant bricks or the like. Further, the exhaust gas 31 discharged from the exhaust gas port 8 has a high temperature.

If it contains a large amount of flammable thermal decomposition components, it will often burst into flames immediately after coming into contact with the surrounding air. Additionally, the above pyrolysis gas may contain harmful components.

Depending on the surrounding airflow conditions, this can be extremely dangerous for workers. For this reason, the heat-resistant cement 12 or the furnace wall 1
An exhaust gas hood 21, which can be attached to and removed from the upper end of the outer wall 12, is attached almost tightly to the upper end of the outer wall 12.
1 is sucked in as shown by the dotted arrow and forcibly discharged out of the furnace through an exhaust gas duct 218 using a blower or the like. If the exhaust gas contains harmful components, it is passed through an exhaust gas treatment device before being discharged into the outdoor atmosphere.

The conventional structure described above has the following three problems.

The first problem is the blockage of exhaust gas at the exhaust gas port 8. Although the state of blockage at the exhaust gas port 8 differs depending on the material of the object to be heated 9, the type of gas introduced, and the processing temperature, generally the exhaust gas contains a large amount of pyrolysis gas, so that it does not come into contact with the inner surface of the exhaust gas port 8. During this process, a large amount of deposits (such as soot) accumulate. If the exhaust gas port 8 is blocked, the pressure inside the graphite heater will increase, and there is a danger that the top lid 3 and the stuffing powder 11 thereon will be blown away. To avoid this situation, deposits deposited on the inner surface of the exhaust gas port 8 must be removed periodically during operation of the furnace. However, in the case of conventional furnaces, the exhaust gas
1 is placed on the upper end surface of the heat-resistant cement 12 or the furnace wall 19, it is not possible to constantly monitor the gas outflow condition (flame condition) from the exhaust gas port 8, and the frequency of blockage is predicted based on experience. There is no other choice. Further, in the operation of removing deposits from the exhaust gas port 8, it is necessary to remove the exhaust gas hood 21 each time, which is a dangerous operation in a high-temperature atmosphere.

The second problem is that depending on the type of introduced gas 30 or exhaust gas 31, it may contain components heavier than air, which may accumulate on the upper or lower side of the floor 20 without the operator's knowledge. This may lead to accidents such as suffocation. In particular, the bit 17 under the floor is used for inspection and repair at the bottom of the furnace.(When there is water intrusion from the outside or leakage from the work coil 13, water is allowed to flow down here to prevent large amounts of water from entering the powder filling section at the bottom of the furnace.) 1 Heavy gas tends to accumulate here.

Therefore, working with bit 17 requires special care.

The third problem is that a large amount of time is spent on the cooling process after the heating power is turned off. As described above, from the viewpoint of safety and thermal efficiency in the heating furnace, the structure is designed to minimize heat transfer from the graphite heater to the outside, so the cooling rate becomes extremely slow. Although water is passed through the inside of the work coil 13, it has almost no cooling effect on the graphite heater because of the insulation provided by the powder filling 11 and heat-resistant cement.

(Objective of the Invention) The object of the present invention is to provide a high-frequency induction heating furnace that solves the above nine problems and is easy and safe to manage the operation of the heating furnace, and at the same time shortens the time required for the cooling process. It is.

(Structure of the Invention) The present invention provides a high-frequency induction heating furnace having a structure in which a graphite heater is heated by high-frequency induction and a gas is introduced and discharged.Al! Above the heat-resistant cement outer wall containing the i-frequency work coil, there is an exhaust gas hood having a gas inlet with a cross section larger than the outer wall.

The exhaust gas port attached to the top lid of the graphite heater is placed with a space between it and the outer wall so that the upper end can be seen, and the outer wall is covered with a cylinder having a cross section of approximately the same shape and size as the inside of the gas suction of the exhaust gas hood. An annular space surrounding and communicating with the space below the work floor is provided, and a heat radiation block having a large number of heat transfer fins on the head and a plurality of sets of caps covering the head of the heat radiation block are attached to the upper lid of the graphite heater. The present invention relates to a high frequency induction heating furnace having a structure in which powder is placed on the upper surface of the cap and filled up to the upper end of the cap.

First, a solution to the blockage at the first exhaust gas port will be explained. In order to be able to constantly monitor the gas outflow situation (or flame situation) at the exhaust gas port, and to facilitate the work of removing deposits from the exhaust gas port when a tendency towards blockage is recognized, 9. A space was provided between the lower end of the hood and the upper end of the heat-resistant cement (the part covered with the high-frequency work coil). This space (distance H between the lower end surface of the exhaust gas hood and the upper end surface of the heat-resistant cement)
), the larger H makes it easier to monitor the exhaust gas port and remove deposits, but conversely, more air flows into the space from around the furnace, which increases the amount of gas sucked into the exhaust gas hood. and become economically disadvantageous.

From this.

Based on the overall length (L) of the exhaust gas port, the distance H is
It is preferable to select from the range =(0,5 to ZO)XL. Exhaust gas is normally forcibly sucked in by a blower, but in this case, the capacity of the exhaust gas blower is equivalent to the amount of gas sucked into the exhaust gas hood.

The flow velocity of the air flowing from the periphery of the furnace into the space through the outer periphery of the exhaust gas hood is selected to be greater than the maximum flow velocity of the air current generated around the furnace. This is to prevent the upward flow of exhaust gas (or flame) discharged from the exhaust gas port from being disturbed and flowing out to the outside of the hood. Although it depends on the environmental conditions at the location where the furnace is installed, the peripheral speed at the outer circumferential position of the exhaust gas hood in a normal indoor environment is 1 m/sec.
The above is preferable. Install one or more blind plates at appropriate locations on the outer periphery of the exhaust gas port that can be installed and removed while leaving only the space necessary for monitoring the exhaust gas port and removing deposits, and blinding other spaces. If you install one, you can reduce the amount of gas suction required.

The material of the exhaust gas hood may be any material as long as it receives high frequency induction, has a certain degree of heat resistance, and is resistant to combustibility, and aluminum alloy is preferred.

A flame-retardant plastic material may be used as long as it can suck a large amount of air and can be sufficiently cooled.

The second problem is a solution to the phenomenon of heavy gas accumulation near the work floor (including under the floor).

Regarding the problem of heavy gas accumulation on the upper surface of the work floor,
If the structure solves the first problem mentioned above, the surrounding gas above the work floor will be constantly ventilated, so this will be solved by itself. Therefore, the accumulation of heavy gas under the floor of one working floor becomes a problem. The present invention takes the following solution to this problem. That is, one work floor is not brought into complete contact with the outer circumferential surface of the heat-resistant cement containing the work coil, but an annular space is provided at approximately constant intervals through which air can pass without resistance.

To this end, this working floor is provided with a hole that is larger around the outer periphery of the heat-resistant cement.

Further, a cylinder having a cross section having approximately the same shape and size as this hole is provided on the working floor up to the upper end of the heat-resistant cement, and surrounds the entire outer periphery of the heat-resistant cement.

The material of this cylinder may be any material that is not susceptible to (or is not easily susceptible to) high-frequency induction and has a certain degree of flame retardancy and heat resistance, and aluminum alloy, asbestos, ceramic brick, etc. are generally used. If such a work floor and cylinder are provided and the structure is designed to address the first problem described above, the lower part of one work floor will be automatically ventilated to solve the problem of heavy gas accumulation. The above tube has a cross-sectional shape and size that are almost the same as the gas suction port of the exhaust gas hood.

In addition, the provision of the above-mentioned tube improves the safety of 9 operations.
Don't be a hindrance. Rather, it serves to protect workers from inadvertently approaching the work coil through which high-frequency current flows, and to prevent objects such as jigs and tools from falling under the work floor. Further, since an upward air flow is formed in the annular space between the tube and the outer periphery of the heat-resistant cement, the temperature of the tube does not rise due to this air cooling effect.

As a third problem, the present invention will be explained with regard to time reduction in the cooling process of the heating furnace.

When the heating power is turned off and the cooling process begins, the graphite heater that stores heat at the highest temperature in the high-frequency induction heating furnace (hereinafter referred to as the heating furnace) and the heat radiating path from the heated object inside it to the outside are as follows. There are three directions. That is, (
a) Heat transfers from the side of the graphite heater through packing powder such as graphite powder and coke powder to the heat-resistant cement and the work coil inside it, and finally rises and passes through the cooling water flowing inside the work coil and the outer circumferential surface of the heat-resistant cement. Side roux that is cooled and heat radiated by the air), (lower roux that transfers heat from the bottom plate of the lead heater to the caster through the padding and then to the concrete foundation), tc) From the top cover of the graphite heater, through the padding and onto the padding surface. This is the upward route where the air that comes into contact cools and radiates heat.

Among the above heat dissipation routes, the former two routes (a) and (b
), as mentioned above, the heating furnace is strictly insulated for safety reasons, so the cooling rate will increase even more.

Since this cannot be expected, we investigated a structure that increases the heat dissipation efficiency of the upper route (C) above. Normally, when stuffing the object to be heated inside the graphite heater into the furnace or taking it out from the furnace, the top lid of the graphite heater is
Leave the filling on top of the top lid temporarily removed. Therefore, in the present invention, after setting the graphite heater top cover in the furnace packing.

Before filling the upper filling powder, a plurality of sets of heat dissipation blocks having a large number of heat transfer fins on the head and caps covering the heads are placed on the surface of the graphite heater top lid.

Thereafter, the upper stuffing powder is packed up to the upper end of the cap so as not to leave any gaps between the heat radiation blocks. In addition,
Make sure that the lower end surface of the heat dissipation block and the upper lid surface of the graphite heater are in close contact with each other so that there is no gap between them.'! It is preferable to sieve to prevent tamed powder from entering. With the above configuration, the heating furnace starts operating and heats the object to be heated.

After heating is complete and the cooling process begins, the top filling is gradually removed while minimizing combustion due to air oxidation.
This powder removal work is carried out to the lower end of the cap. Afterwards, lift the cap to expose the head of the heat radiation block (heat transfer fins). At this time, the air flow formed above the furnace by the exhaust gas hood that sucks in a large amount of air due to the structure of the present invention for solving the above-mentioned first and second problems comes into contact with the above-mentioned exposed heat transfer fins.
It becomes possible to quickly remove heat from a high-temperature heater.

The material for the heat dissipation block and cap should be selected to have good thermal conductivity and heat resistance, and graphite is the most suitable among general industrial materials.

(Example) The contents of the present invention described above will be specifically explained with reference to FIGS. 1 to 5 showing nine embodiments of the present invention.

First, FIG. 1 shows a longitudinal section of a high-frequency induction heating furnace according to an embodiment of the present invention, taken from the outer periphery of a heat-resistant cement 12 containing a high-frequency work coil 13.

- The exhaust gas hood 27 having the gas inlet 27b with a large cross section was installed at a position higher than the upper end surface of the heat-resistant cement 12. Exhaust gas 3 discharged from the exhaust gas port 8 is located between the gas inlet 27b and the upper end surface of the heat-resistant cement 12.
The condition of No. 1 can be easily checked visually, and a space necessary for removing deposits inside the exhaust gas port is provided. Exhaust gas 7
- The door 27 can be installed by taking a support from the concrete floor 18, but in this embodiment.

In order to avoid hindrance to the above-mentioned work, a method was adopted in which the exhaust gas hood was suspended from above using lifting parts 22 attached to the upper surface of the exhaust gas hood at several locations. The material of the exhaust gas hood 27 is aluminum alloy (JISH4000, A3052
) was used.

The upper part of the exhaust gas hood 27 is connected to the duct 27a.

In addition, in order to compensate for the lack of capacity of the exhaust gas blower (not shown), only the space necessary for monitoring the exhaust gas port 8 and removing deposits is left, and 2/2 of the entire circumference is left along the outer peripheral surface of the gas inlet 427b. One blind plate 33 was attached over 3. This installation was done by tightening and fixing the port 34, making it possible to remove it.

Furthermore, a strip 25 having a cross section of approximately the same shape and size as the gas inlet 27b was surrounded by the outer circumferential surface of the heat-resistant cement 12 with the same gap provided around its entire circumference. The upper end of the cylinder 25 was set at approximately the same height as the upper end of the heat-resistant cement 12, and the lower end of the blind plate 33 was brought into contact therewith. On the other hand, the lower end 25a of the tube 25 has a seven-lung shape and is fixed to the work floor 24 via an insulating plate 26 by tightening bolts or the like.

In addition, a floor base 23 is provided below the work floor 24 for reinforcement purposes.
were installed on the concrete floor surface 18. In addition, the insulating plate 261 and the work floor surface 249. floor pace 23
In each case, a hole of a size matching the inner circumferential surface of the tube 25 was provided at the connection part with the tube 25. The material used in this example for these parts is blind plate 33. The cylinder 25 and the work floor 24 are made of aluminum alloy (JIS H4000, A3052),
The insulation board 26 is made of asbestos, and the floor base 23 is made of wood, both of which were selected in consideration of high frequency induction.

Next, ten sets of graphite heat dissipation blocks 28 and Φ pieces 29 were arranged on the upper surface of the upper lid 3 of the lead-free heater. At this time, the lower end surface of the heat radiation block 28 and the surface of the upper lid 3 are brought into close contact with each other.

Powder 11 was packed over these as shown in FIG. 1 so that no voids were left between the heat dissipation blocks 28 or the caps 29. FIG. 2 shows the structure of the portion above the upper lid 3 when the heating furnace is in heating operation. A large number of disc-shaped heat transfer fins 28a are provided at the head of the heat radiation block 2B. Furthermore, a collar 28b is provided at the bottom to further increase the area in contact with the surface of the upper lid 30. Further, a cap 29 was placed over the head of the heat radiation block to isolate all heat transfer fins 28a from the surrounding air. Two air vent holes 29a are provided in the upper end surface of the cap 29, so that when the heat radiation block 28 is heated to a high temperature, the air contained between the cap 29 and the heat radiation block 28 thermally expands, and the cap 29 and its This prevents the surrounding powder 11 from being blown away. Thereafter, the stuffing powder 11 was filled up to the upper end surface of the cap 29.

When the main heating furnace is heated and begins the cooling process as described above, while minimizing the combustion of the stuffing powder due to air oxidation, gradually remove the stuffing powder 11 from the top 9, and finally remove the stuffing powder 9 from the cap. Lower the surface of the stuffed powder at position 1 of the lower end 29b. At this time, the cap 29 was removed using the buckle of the lower end 29b, resulting in the state shown in FIG. 3. Here, the air flow 32 is forced into convection by the exhaust gas hood 27.

comes into contact with a large number of heat transfer fins 28a of the heat radiation block,
Heat is transferred directly from the upper lid 3.

FIGS. 4 and 5 show other embodiments of the heat dissipation block in the heating furnace according to the present invention, with FIG. 4 being a top view and FIG. 5 being a side view.

At the head of the heat dissipation block 350, there is a thin 8 in the axial direction.
A rod 35b is provided on the outer peripheral surface of these eight rods.

A large number of blade-shaped heat transfer fins 35a are provided radially to promote heat radiation.

As a result of operating the high frequency induction heating furnace of the example, the following items were confirmed.

(1) The outflow status of exhaust gas can be constantly monitored,
In addition, it becomes easy to check for signs of blockage in the exhaust gas port, and it is possible to safely and quickly remove deposits before blocking the exhaust gas port. It was possible to shorten the time to about 115 2 minutes.

By attaching a blind plate 33 as shown in FIG. 1, the capacity of the blower required for suctioning exhaust gas can be reduced to about 1/2 of that in the case where no blind plate is attached.

(2) When the furnace was operated with Cot gas intentionally accumulated in the space above and below the work floor, and the oxygen concentration in the same space was measured with an oxygen concentration meter, it was found that the oxygen concentration in normal air was within 2 minutes. concentration has returned.

(3) In the conventional high frequency induction heating furnace shown in Fig. 6, the outer diameter is 9.
A 00mm graphite heater was heated to 2500℃,
It took five days for the temperature of the heater to drop below 50°C after the power was turned off, but the same heater was used in the high-frequency induction heating furnace shown in Figure 1, which is an embodiment of the present invention. However, cooling was completed in three days.

(Effect of the invention) According to the invention, without removing the exhaust gas hood.

This makes it possible to monitor the blockage of exhaust gas ports and remove deposits, making operation work safer such as preventing heavy gas from accumulating on or under the work floor and having a negative impact on workers. The cooling time is shortened and the operating efficiency of the heating furnace is improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the entire high-frequency induction heating furnace according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a combination of the heat dissipation block and the cap in FIG. 1. FIG. 3 is a sectional view explaining the state of heat radiation of the heat radiation block of FIG. 2, FIGS. The top view and FIG. 5 are side views, and FIG. 6 is a sectional view of a typical conventional high frequency induction heating furnace. Explanation of symbols 1...Container 2...Bottom plate 3...Top lid 4...Heater support leg 5...Nozzle protection tube 6...Nozzle 7...Gas introduction tube 8...
Exhaust gas port 9...Heated object 10...Jig 11...Powder filling 12...Heat-resistant cement 1
3... High frequency work coil 14... Castable 1
5... Insulation material 16... Concrete foundation 17... Bit 18... Concrete floor surface 19... Furnace wall 20... Work floor 21
...Exhaust gas 7-de 22...Lifting lug 2
3... Floor pace 24... Working floor surface 25...
・Cylinder 26... Insulating plate 27... Exhaust gas 7-de 28... Heat radiation block 29... Cap 30... Introduced gas 31... Exhaust gas
32...Air 33...Blind plate 34...
・Mounting bolt 35...heat radiation block

Claims (1)

[Scope of Claims] 1. In a high-frequency induction heating furnace having a structure in which a graphite heater is heated by high-frequency induction and gas is introduced and discharged, a cross section that is one size larger than the outer wall is provided above the outer wall of heat-resistant cement that houses the high-frequency work coil. An exhaust gas hood with a gas inlet of A heat dissipation block having a large number of heat transfer fins on the head and a head of the heat dissipation block, which surrounds the outer wall with a cylinder having a cross section of the same size and has an annular space communicating with the space under the floor of the work floor. A high-frequency induction heating furnace has a structure in which a plurality of sets of caps are placed on the upper surface of the upper lid of a graphite heater, and powder is filled up to the upper end of the caps. 2. The high-frequency induction heating furnace according to claim 1, wherein one or more blind plates are partially attached between the lower end of the gas inlet of the exhaust gas hood and the upper end of the cylinder.