JPH0434072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electric vertical continuous heating furnace that can continuously heat treat materials housed in a heat-resistant container at high temperatures in a stationary state. The present invention relates to a heating furnace suitable as a high-temperature furnace for producing materials.

BACKGROUND ART In recent years, ceramic whiskers such as silicon carbide and silicon nitride have been attracting attention for use in fiber reinforcement materials. When producing ceramic whiskers by growing crystals in a raw material to be treated using a gas phase reaction, the raw material must be heated in a stationary state. In other words, when the raw material to be treated is in a fluid state, the product becomes powder, so conventionally,
Horizontal high-temperature heating furnaces, which allow the raw materials to be treated to remain stationary, have been widely used.

However, in such cases, high-temperature heat treatment of 1,300 to 2,000 degrees Celsius is performed, so if the raw materials to be treated contain substances that vaporize at low temperatures as impurities or additives, they may be heated during heating or at the target high temperature. During heat treatment, they volatilize or sublimate and are entrained in the atmospheric gas, and when they come into contact with the furnace wall in the low temperature range, they condense and precipitate to form furnace deposits (hereinafter simply referred to as deposits). There is a particular thing. When the amount of deposits increases, problems arise, such as the need to close the furnace wall space and shut down the furnace, or the deposits to be re-mixed into heat-treated products.

These situations are described, for example, in JP-A-58-172298, JP-A-58-213698, and JP-A-58-213698.
This is taught in Publication No. 502096, etc.
Although various measures have been taken, a sufficient solution has not yet been reached. Furthermore, in the case of a horizontal heating furnace, there are problems such as the need to provide an in-furnace conveyance mechanism for conveying the treated material under high temperature.

Problems to be Solved by the Invention The present invention provides an electric method capable of performing high-temperature heat treatment while storing an object to be heated (hereinafter simply referred to as the treatment material) in a heat-resistant container, which needs to be heat-treated in a stationary state. The purpose is to provide a vertical continuous heating furnace.

Specifically, the present invention provides a furnace that is suitable as a whisker manufacturing device that has the problems described above, but is not suitable for use as a whisker manufacturing device, for example, as seen in the manufacturing of molded bodies of ceramics, carbon materials, etc. A firing furnace for preforms made by mixing raw material powder with a binder, sintering aid, etc. and molding it by pressure molding or slurry casting, a firing furnace for metal powder preforms, or a furnace for ceramics and metals. It can also be applied to various uses such as a joining furnace with.

Means for Solving the Problems As illustrated in the longitudinal cross-sectional conceptual diagrams of FIGS. 1 and 2, the present invention provides a vertical heating furnace having an electrical heating section, in which A core tube 2 is provided through it, and cooling pipes 3, 3', an air supply pipe 7, and an exhaust pipe 7' are attached to the core tube 2 near both ends of the furnace body opening. A supply means 11 for the container 10 is provided at the lowest stage of the furnace tube 2.
This is a vertical continuous heating furnace in which supporting and carrying-out means 16 (a and 10b) are respectively disposed so that the processing material in a heat-resistant container can be continuously heat-treated.

The vertical furnace body 1 can be constructed with an appropriate fireproof and heat-insulating structure according to the operating temperature conditions, etc. by a conventional method. For example, when it is used as a heat treatment furnace up to about 2400°C, the center part is made of carbonaceous or graphite. The outer layer is made of high quality refractory material, the outer layer is made of silica-alumina insulating bricks or fiber-like insulating material, and the outermost shell is made of steel exterior material.

The energization heating parts 4, 4' arranged in the vertical furnace body 1 are as follows:
Although it is preferable to use direct current heating means from the viewpoint of thermal efficiency, indirect heating means may also be used.

That is, when the energization heating parts 4, 4' are used as direct energization heating treatment means, as illustrated in FIG.
The core tube 2 itself is manufactured from a resistance heating material, and the busbars 6 and 6' are connected and energized through cooling holders such as copper jacket type water cooling holders 5 and 5', thereby making the core tube 2 itself. It generates heat and raises the temperature. Resistance heating material is
An appropriate material can be used depending on the heat treatment temperature of the furnace. For example, when the heating temperature is 1000 to 2400°C, a heat-resistant material such as carbon silicon, carbon, or graphite is used. In addition, regarding its application, molds may be molded using only one of these types, molded from a mixture of two or more of these types, or molded from different materials with separate low-temperature and high-temperature areas. can take various forms. Furthermore, the bus bars 6, 6' can also be connected to the furnace core tube within the furnace body.

On the other hand, when the energizing heating parts 4, 4' are used as indirect heating means, as illustrated in FIG. The busbars 6 and 6' are connected to the cooling holders 5 and 5' as described above through the cooling holders 5 and 5', and electricity is applied to generate heat.
This indirectly raises the temperature of the furnace core tube 2. In this case, the furnace core tube 2 may be made of a material suitable for the heating temperature as long as it is heat resistant and has good thermal conductivity. For example, it may be made of silicon nitride, silicon carbide, carbon, or graphite. It is made from.

The furnace core tube 2 has a heat-resistant container 10 transferred therein.
As mentioned above, it can be made of any suitable material depending on the heating means applied, and in the case of an indirect heating method, it is divided into several parts in the longitudinal direction of the furnace. It can be assumed that It is also appropriate to form a coating layer of an oxidation-resistant or wear-resistant material such as oxide, carbide, or nitride on the exposed surface depending on the heating atmosphere or the like.

The coolers 3, 3' surround the entire circumference of the furnace tube 2,
It is installed to prevent oxidation and consumption of the part of the reactor core tube that comes into contact with the outside air and to cool the heat-resistant container.It is an appropriate type of cooling tube, such as one in which the cooling tube is wound in a spiral manner or a jacket type. things are applied.

The air supply pipe 7 and the exhaust pipe 7', which are ventilation pipes, are provided to adjust the atmosphere inside the furnace core tube 2, and are designed to prevent inert atmosphere (such as argon, nitrogen, carbon monoxide, etc.) inside the furnace. Depending on the purpose, such as forming and maintaining a gas atmosphere (gas atmosphere), removing gas produced by heating, and supplying reactive gas used in reaction sintering, etc., the gas supply source, gas suction device, and gas recovery/circulation device (all shown in the figure) are required. (not shown) etc.

As illustrated in the partially enlarged views of FIGS. 3 and 4, packing materials 9 and 9' are held at both ends of the core tube 2 to maintain airtightness within the core tube.
Guide tubes, for example graphite tube bodies 14 and 14', are connected to appropriately guide the heat-resistant containers into and out of the reactor core tube. The packing materials 9, 9' are made of raw rubber,
It is made of a flexible material such as silicone rubber or fluororesin and has a shape smaller in diameter than the outer diameter of the heat-resistant container, and is curved into close contact with the wall of the heat-resistant container during transportation to maintain sufficient airtightness.

The supply means 11 for the heat-resistant container 10 is for feeding the heat-resistant container into the reactor core tube from the uppermost stage of the reactor core tube 2, and is for transferring the heat-resistant container 10 containing the processing material on the holding table 12 to the upper part of the reactor core tube. Directional transfer machine 13
, a guide pipe 14 that guides the transferred heat-resistant container 10 to a fixed position, and a vertical transfer device 15 that forcibly moves the heat-resistant container 10 downward.

The support/unloading means 16 for the heat-resistant container 10 is for transporting the heat-resistant container inside the furnace core tube out of the system through the guide pipe 14' at the bottom of the furnace in cooperation with the supply means 11 at the upper stage of the furnace. A lifting device 17 that supports the heat-resistant container inside, a feeding device 18 that horizontally carries out the heat-resistant container that has come out of the furnace bottom by lowering the rod of the lifting device 17, and a cradle for the heat-resistant container to be carried out. It consists of a certain pedestal 19. At the tip of the rod of the lifting device 17 and the feeding device 18, a U-shaped curved portion 21 and a support plate portion 20 that can operate within the gap between the arm portions are connected in opposition to each other.

That is, in FIG. 5, the support plate part 20 is
7 side and the U-shaped arm portion 21 is disposed on the feeding device 18 side. However, if desired, as shown in FIG. It is also possible to arrange the prismatic arm portion 21' in an interlocking relationship. The aforementioned lateral transfer machine 1
3. The operating parts of the lateral transfer machine 15, the lifting device 17, and the feeding device 18 reciprocate rods such as piston-cylinder mechanisms operated by hydraulic pressure, air pressure, etc., or worm-worm gear mechanisms operated by electric motors. Any suitable mechanism can be used as long as it is capable of doing so.

The basic configuration of the vertical continuous heating furnace of the present invention has been described above, but means such as adding a conventional means for a furnace or replacing it with an appropriate equivalent means can be applied as appropriate.

For example, the furnace body 1 may be provided with a temperature gauge or a pressure gauge 22 to control the temperature and pressure inside the furnace core tube 2, or a viewing window (not shown) or a flexible bus bar may be installed inside the furnace. Conventional means such as interlocking control devices for various parts of the furnace may be provided. Further, the holding table 12 and the pedestal 19 may be not only a smooth horizontal fixed floor but also a smooth inclined fixed floor or a movable floor such as a belt conveyor or a roller conveyor. Furthermore, as illustrated in FIG. 2, the lateral transfer device 13 in the supply means 11 is replaced with a mechanism in which the rod simply reciprocates and feeds the container horizontally, and, for example, the heat-resistant container is held between both arms and moved away from the holding table surface. It is also possible to use a robot transfer device 23 that can directly transfer the robot onto the reactor core tube, or to replace the U-shaped arm 21 provided on the lifting device 17 or the feeding device 18 with a clamping device that can be opened and closed instead of a fixed type. can.

The heat-resistant container 10 is manufactured from an appropriate heat-resistant material in consideration of heat resistance, thermal conductivity, corrosion resistance, etc., depending on the processing conditions (temperature, atmosphere). For example, 1500
Silicon nitride, alumina,
It is manufactured from silica-alumina refractories, etc., and if the temperature reaches 2000℃ or higher, silicon carbide, carbon, graphite, etc. refractories are used.
For use at temperatures below 1000°C, a wider variety of conventional materials are applicable. In addition, the structure may be formed not only from a single material, but also from a stack of two or more materials.

The shape of the heat-resistant container 10 may be either an open type or a closed type, an example of which is shown in FIG. That is,
The heat-resistant container 10 is a simple cylindrical container (a), a container with a flow hole for the generated gas and the reaction gas (b), and a container with internal protrusions in series to improve heat transfer to the inside (c). , one with a perforated bottom to allow high-temperature gas to enter and exit the inside (d), one with a cage-like shape (e) that is applied when the material to be treated is a generated shape, or one with a lid to seal it. An appropriate shape such as a molded one (f) is used. In this case, it is also effective to use auxiliary means such as providing fitting uneven parts on the upper and lower surfaces of the heat-resistant containers to ensure stability in stacking the containers.

The outer diameter of the heat-resistant container 10 can be set as appropriate, but the narrower the clearance, the better the thermal efficiency is, and the more deposits can be scraped off when the container descends, so the clearance with the core tube is 2 to 4 mm. It is preferable that it be formed to a certain extent. In addition,
The inner diameter of the furnace core tube itself is not particularly limited, but when used as a whisker manufacturing furnace, it is 50 mm or more.
A diameter of around 500mm is often used.

Function Although the present heating furnace can be used in various ways, an example of the configuration furnace shown in FIGS. 1 and 5 will be shown.

a General-purpose embodiment While introducing an inert gas such as nitrogen gas from the air supply pipe 7', the inside of the reactor core tube 2 in which empty heat-resistant containers are stacked is replaced with an inert atmosphere, and the coolers 3, 3' and 5,
While passing water through 5', energize busbars 4 and 4',
Raise the temperature to a predetermined temperature.

Next, the vertical transfer device 15 and the lifting device 17 work together to extract the heat-resistant container 10a to the same level as the floor of the hearth bottom, and by advancing the rod of the feeding device 18, the tip of the container 10a is moved forward. The upper surface of the continuous U-shaped arm 21 receives the upper heat-resistant container 10b to prevent it from falling, and the front surface of the arm 21 grips the extracted heat-resistant container 10a and transports it sideways to the outside of the furnace bottom. Then, carry it out onto the rack floor 19. Next, the lifting device 1
After the support plate 20 connected to the tip of the rod 7 is raised through the gap of the U-shaped arm 21 to support the upper heat-resistant container 10b, the rod of the feeding device 18 is moved back. U-shaped arm portion 21
from the bottom of the hearth to its original position. By repeating the above cycle, the heat-resistant container 10 inside the furnace tube 2
can be carried out of the system from the bottom of the furnace.

On the other hand, in the upper part of the furnace, after the heat-resistant container 10a is pulled out from the bottom of the furnace, the heat-resistant container 10a is filled and stored with the processing material in advance by the supply means 11 at a quantitative supply position (not shown) or the like. is supplied into the furnace tube 2. That is, by advancing the rod of the lateral transfer device 13, the heat-resistant container 10 on the holding stand 12 is transferred laterally onto the core tube 2, and its alignment with the core tube is ensured by the guide tube 14. After that, the rod of the vertical transfer device 15 is lowered to feed the heat-resistant container 10 into the reactor core tube 2 from above.

By adjusting the speed of extraction of the heat-resistant container from the bottom of the furnace and supply from the top of the furnace, it is possible to maintain the desired maximum temperature range (e.g. 1000 to 2000°C) for a predetermined time (e.g. 30 minutes to 40 hours). Hold in a heat-resistant container 1
A predetermined high temperature heat treatment is performed on the processing material stored and filled in the container.

During this time, in order to adjust the atmosphere inside the reactor core tube, inert gas or reactive gas may be introduced from the air supply pipe 7, or generated gas may be sucked from the exhaust pipe 7', as appropriate. At this time, since the gas flow and the processing material flow are in a countercurrent state, it is extremely easy to control the atmosphere under heating, and the heat held by the gas is used for preheating, resulting in good energy efficiency.

In addition, even if volatile components in the treated material become deposits during the process of increasing the temperature of the treated material, since the gas flow and the heat-resistant container come into countercurrent contact, the volatile components will be deposited in the treated material in the target temperature range. No recontamination.
Even if deposits occur on the core tube wall, they will be scraped off by friction with the container wall as the heat-resistant container descends.
Since it is discharged through the guide pipe 14' at the bottom of the furnace, no operational trouble occurs.

Furthermore, during such high-temperature heat treatment, the treated material is stored in a heat-resistant container and heated to a high temperature statically without being subjected to vibration, so the treated material may be used as a preform with poor shape retention or as a raw material for producing whiskers. Even when the temperature is low, appropriate high-temperature heat treatment can be performed.

b. Specific usage mode This heating furnace can be applied to heat treatments in various temperature ranges up to about 2400°C, but an example of a specific usage mode when used as a whisker production furnace, which is a preferred example, will be shown.

1 Example of application to silicon carbide whisker production A treated material prepared by mixing fine carbon powder and fine silica powder has a bulk density of 0.100 g/cm ³ and a filling height of 100
Graphite cylindrical container with a depth of 150 mm (No. 6
The one shown in Figure b has a clearance of 3.
mm) and supplied to a graphite furnace tube with a length of 3 m and an inner diameter of 150 mm. When the heat treatment was carried out by moving the furnace at a speed that kept it heated at 1400 to 2000℃ for 30 minutes to 30 hours, it was found that the diameter was 0.1 to 1.0 mm and the length was 50 to 200μ.
Yield of β-type silicon carbide whiskers of m is 90-100%.
Obtained with.

Although production continued for 30 consecutive days, the inside of the reactor core tube was not clogged with deposits, and even though the introduction of inert gas was stopped during normal operation and heat treatment was performed, the graphite vessel and reactor core tube were not clogged with deposits. Almost no oxidative consumption was observed.

2 Example of application to the production of silicon nitride sintered bodies Silicon nitride-coated graphite core in which carbonized rice husks are filled in a graphite container with a porosity of 30% (the one shown in Figure 6 d), and nitrogen gas is then flowed. Supplied into the pipe,
Heat treatment was carried out while moving the inside of the furnace tube downward so as to maintain heating in a range of 1300 to 1400° C. for 5 to 20 hours.
As a result, silicon nitride with a diameter of 0.5 to 1 μm and a length of 50 to 300 μm was obtained, and the furnace could be operated continuously for 20 hours without any problem.

In addition to these uses, for example, sintering of aluminum powder preforms, heat treatment of small metal parts, bonding of ceramics and metal with brazing filler metal, carbonaceous products molded with coal tar pitch binder, etc. It can be widely applied to appropriate high-temperature heat treatments such as firing or graphitizing electrodes for electrolysis and electrodes for electrical discharge machining, or manufacturing silicon nitride sintered bodies by reacting metal silicon powder with nitrogen gas.

Effects of the Invention The present invention is a vertical continuous heating furnace in which the processing material is supplied from the upper stage of the furnace and carried out from the lower stage. 1. The processing material is heat-treated while being stored in a heat-resistant container,
Since the heat-resistant container is transported by its own weight, the material to be treated is subjected to high-temperature heat treatment as a stationary material, and there is no need for a transport device inside the furnace.

2. Even if deposits are generated, they are scraped off as the heat-resistant container descends, so there is no problem with shutdowns that occur with horizontal heating furnaces.

3. Since the gas flow and the flow of the processing material are in a countercurrent state, it is easy to prepare the atmosphere in the furnace, and the heat held by the gas is effectively used for preheating the processing material.

4 From the above effects, a furnace is provided which is particularly suitable as a manufacturing apparatus for whisker materials involving gas phase reactions, such as silicon carbide whiskers.

As it exhibits the following effects, it has remarkable industrial utility.

[Brief explanation of drawings]

FIG. 1 is a conceptual vertical cross-sectional view of a preferred embodiment of the present invention, and FIG. 2 is a conceptual vertical cross-sectional view of another embodiment. FIG. 3 shows a partially enlarged sectional view of the vicinity of the packing material in the upper stage of the furnace, and FIG. 4 shows a partially enlarged sectional view of the vicinity of the packing material in the lower stage of the furnace.
5 and 7 are plan views showing the positional relationship in the support and carry-out mechanism and other embodiments of the support and carry-out mechanism as seen from line A-A' in FIGS. 1 and 2, respectively, and FIG. It is a perspective view showing an embodiment of a heat-resistant container. 1... Vertical furnace body, 2... Furnace core tube, 3, 3'...
Cooler, 4, 4'... Current heating section, 7... Air pipe,
7'...Exhaust pipe, 9,9'...Packing material, 1
0, 10a, 10b...Heat-resistant container, 11...Supplying means, 16...Supporting and carrying out means, 20...Supporting plate portion, 21...U-shaped arm portion. 20'...concave groove support plate part, 21'...prismatic arm part.

Claims (1)

[Scope of Claims] 1. In a vertical heating furnace having an energized heating furnace, a core tube is provided in the center of the furnace body passing through it, and a cooler and a vent pipe are installed in the core tube near both ends of the furnace body opening. A heat-resistant container supply means is provided at the top of the reactor core tube, and a heat-resistant container support/export means is provided at the bottom of the reactor core tube to continuously heat-process the material in the heat-resistant container. A vertical continuous heating furnace characterized in that it is capable of heating. 2. The above-mentioned means for supporting and carrying out heat-resistant containers consists of a lifting device, a feeding device, and a platform, and a U-shaped arm and a gap between the U-shaped arm and the rod tip of the lifting device and the feeding device are provided. 2. The vertical continuous heating furnace according to claim 1, further comprising supporting plate portions which are arranged in a row to face each other.