JPS6363649B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a carbon fiber manufacturing apparatus for continuously manufacturing carbon fiber with high production efficiency.

[Conventional technology]

Normally, to produce carbon fibers, organic polymers such as polyacrylonitrile fibers, recycled cellulose fibers, phenolic fibers, and pitch fibers are first made flame resistant at 200 to 300°C in an atmosphere of air or other oxidizing gas. This is then carbonized at 800 to 2000°C in an inert gas atmosphere such as nitrogen or argon. Furthermore, graphitization is performed at 1500 to 3000℃,
Carbon fibers with even higher Young's moduli are also produced.

However, the yarn treatment temperature in the above carbonization and graphitization steps is extremely high, especially at a treatment temperature of 1500
In the high-temperature heating equipment used in the graphitization process, which requires a temperature of ~3000°C, carbon or A cylindrical graphite material is often used, and a thread is passed through the cylindrical material to undergo high-temperature treatment. in this case,
It is well known that the above-mentioned heating elements made of carbon or graphite materials undergo a significant oxidation reaction in an oxidizing atmosphere at high temperatures, and wear out and deteriorate in an extremely short period of time, making them unusable. As a countermeasure, an inert gas such as nitrogen or argon is introduced into the high-temperature heating device to maintain an internal pressure slightly higher than atmospheric pressure, thereby controlling the atmosphere on the inner and outer surfaces of the heating element.

On the other hand, in order to make the heating element made of carbon or graphite exhibit its characteristics efficiently and safely at high temperatures, carbon or graphite particles or The structure is such that it is filled with powder and functions as an intermediate support material and a heat insulating material for the high-temperature heating element. Further, as the heating means of the above-mentioned high-temperature heating device, a Joule heating effect using the electric current of the heating element itself is generally used, such as a Tammann type or a high frequency induction type.

Next, the above-mentioned conventional device will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of a Tanmann type furnace conventionally commonly used in a carbonization or graphitization process to produce the above-mentioned carbon fibers. To explain the apparatus shown in FIG. 1 in particular as a graphitization furnace, a carbonized yarn 1 is continuously introduced into a graphitization furnace 10 from one end by a nip roller 2,
After being graphitized in the graphitization furnace 10, it can be continuously drawn out from the other end by a nip roller 3 as a graphitized fiber 1'. In the main furnace 10, a graphite heating element 4 configured in a cylindrical shape
is thermally supported by graphite powder 5 filled in the furnace as an intermediate support and heat insulating material, and the graphite heating element 4 generates heat by connecting a low-voltage, high-current power source to the water-cooled electrode 6 and directly energizing it. It is now possible to obtain high temperatures of 2500°C to 3000°C. The inside of the graphitization furnace 10 is replaced with nitrogen gas in advance, and even during operation, nitrogen gas is continuously introduced into the graphite heating element 4 from the nitrogen gas inlet provided in the graphitization furnace 10. It has a structure in which it is ventilated and flows out from the outlet 8.

[Problem that the invention seeks to solve]

However, in the conventional high-temperature heating device described above, the temperature of the heating element itself made of carbon or graphite is 1500 to 3000°C, despite the various devices mentioned above.
Because of this extremely high temperature, a reaction with the residual oxygen in the heating device or evaporation of carbonaceous material may occur, resulting in wear and tear in an extremely short period of time, making it necessary to frequently replace the heating element. Further, the above-mentioned evaporation phenomenon is thought to rapidly become more intense when the ambient temperature exceeds 2000°C, and the wear on the outer circumferential surface of the heating element is particularly significant. SUMMARY OF THE INVENTION However, it is an object of the present invention to provide a high temperature heating device which makes it possible to largely overcome the above-mentioned problems of the prior art.

[Means for solving problems]

The present invention includes a cylindrical heating element made of graphite or carbon, electrodes provided at both ends of the heating element, a heat insulating material provided on the outer periphery of the heating element, and a cylindrical heating element provided on one side of the heating element. In a carbon fiber manufacturing apparatus comprising an inert gas inlet communicating with the heating element and an inert gas outlet provided on the other side of the heating element and communicating with the inside of the cylinder, there is a space between the heat insulating material and the heating element. A pipe having an inner diameter larger than the outer diameter of the heating element and made of graphite or carbon is arranged so that the pipe is a sheath and the heating element is the core, and both ends of the pipe are sealed to both ends of the heating element. The gist of the present invention is an apparatus for manufacturing carbon fiber, which is characterized in that the pipe and the heating element are fixed to each other via a sealing material, and a gap is formed between the pipe and the heating element for sealing an inert gas.

Next, the apparatus of the present invention will be explained with reference to the drawings.

FIG. 3 shows the conventional graphitization furnace 10 shown in FIG.
FIG. 4 shows a schematic cross-sectional view of a graphitizing furnace 20 modified according to the present invention, and FIG. 4 shows a schematic vertical cross-sectional view of the central part of the graphitizing furnace 20.

The graphite heating element 4 of the present graphitization furnace 20 includes:
Six outer circumference grooves 2 forming clearance parts are cut along the axial direction of the outer circumference, and the six protrusions 23 with the grooves left uncut contact the pipe 21 made of graphite material or graphite felt. pipe 21
is a sheath in which a graphite heating element 4 is disposed and supported at a core position, and its outer periphery is filled with carbon powder 5. Further, both ends of the heating element 4 are partitioned by flange portions 26 provided at both ends of the pipe 31, and the contact portion between the flange portion 26 and the outer periphery of the graphite heating element 4 is sealed with refractory cement (for example, alumina cement) 27. The outer cylinder 25 is provided with an air vent 28. This 27 does not necessarily have to be cement, but may be ceramic such as alumina or boron nitrite.

Note that since the inner diameter of the pipe 21 is larger than the outer diameter of the graphite heating element 4, a clearance 22 is formed. As shown, water-cooled electrodes 6 are attached to both ends of the heating element 4, and the heating element 4 is heated by passing current from one electrode to the other electrode.

In the above device of the present invention, a case is shown in which a groove is cut on the outer periphery of the graphite heating element 4, but the fifth
The clearance 22 can also be created by a separate spacer 24, as shown in schematic longitudinal section.

Alternatively, carbon powder 5 serves as a heat insulator and support material in the device of the present invention.
Instead, some or all of the appropriate lightweight insulation materials, such as felt, can be used.
Since the weight of the heat insulating material applied to the innermost pipe 21 can be reduced, the number and arrangement of the protrusions 23 on the outer periphery of the graphite heating element 4 or the spacers 24 can be minimized. The convex portion 23 of the graphite heating element shown in FIG. 4 or the spacer 24 shown in FIG. 5 may be provided only at an appropriate location in the axial direction of the graphite heating element 4.

Furthermore, in the apparatus of the present invention, the clearance 22 is provided in the axial direction of the outer circumference of the graphite heating element 4, but it is not necessarily limited to the axial direction. It is also possible to form the clearance part 22 by supporting the light heating element 4. Note that in this case, the ring-shaped spacer 24 serves as a sealing material.

The clearance formed as described above is filled with an inert gas such as nitrogen in advance. In addition,
When the pipe 21 has ventilation, the air vent 2
8, and then supplying inert gas to replace the air, the clearance part 22
An inert gas may be filled in.

〔Example〕

By using the high-temperature heating device according to the present invention described above, surprising effects beyond expectations could be achieved as seen in the following examples.

Comparative Example 1 In the conventional graphitization furnace 10 shown in FIG.
When 99.999% nitrogen was set at a flow rate of 8/min and continuously operated day and night, the graphite heating element 4 became unusable after 17 days. Fig. 2 shows a schematic cross-sectional view of the graphite heating element 4 after use, and a markedly worn part 4' can be seen on the outer periphery near the highest temperature part, and the amount of wasted amount reaches 2 kg (approximately 15% of the total weight). was.

Example 1 Another graphitization furnace 20 according to the present invention shown in FIG.
After first sealing the yarn inlet and outlet, the air inside the graphitization furnace 20 (including the clearance part 22) was evacuated from the nitrogen flow ports 7 and 8 and the air vent 28, and the inside of the furnace was replaced with nitrogen gas. After that, close the air vent 28 and heat the highest temperature part of the graphite heating element 4 to 2500℃ and purity.
The flow rate of 99.999% nitrogen was set at 15/min, and the nitrogen was supplied from the inlet 7 and exhausted from the outlet 8 while being operated continuously day and night. Because the carbon vapor in the heating element was sealed, it reached a saturated vapor pressure, and the amount of wear and tear on the graphite heating element 4 was significantly reduced, extending its life to 60 days.

In the embodiments described above, the case of a Tammann furnace for producing graphitized fibers has been described, but the purpose of the high-temperature heating device is not necessarily limited, and the gist of the present invention can be widely applied. . Moreover, the heating means and apparatus can be widely applied as long as it is a high-temperature heating apparatus using carbon or graphite as a heating element.
Alternatively, the inert gas to be substituted is not limited to nitrogen, and can be appropriately selected depending on the purpose.

〔effect〕

As explained above, in the carbon fiber manufacturing apparatus of the present invention, a pipe having an inner diameter larger than the outer diameter of the heating element and made of graphite or carbon is inserted between the heat insulating material and the heating element. is a sheath and the heating element is the core, both ends of the pipe are fixed to both ends of the heating element via a sealing material, and there is a gap between the pipe and the heating element for sealing an inert gas. By filling the gap with an inert gas, it is possible to seal the atmosphere around the outer circumferential surface of the heating element and saturate the carbon vapor pressure, thereby preventing evaporation of the heating element. This significantly extends the life of the heating element, which was previously short-lived, and greatly contributes to improving the production efficiency of the heating equipment, which is the objective, and furthermore, to reducing the cost of the production items that are the objective. In addition, if the filling insulation material is carbon or graphite powder, the pipe that forms the clearance section supports it, so the heating element can be replaced without removing the powder. It became possible.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a conventionally used Tammann furnace for producing graphitized fibers, and Figure 2 shows the state of the graphite heating element 4 used in the Tammann furnace shown in Figure 1 after use. 3 is a schematic cross-sectional view showing an embodiment of the Tammann furnace shown in FIG. 1 modified according to the present invention; FIG. 4 is a schematic vertical cross-sectional view of the Tammann furnace shown in FIG. 3. side view,
FIG. 5 shows a schematic longitudinal sectional view of a different embodiment of the Tammann furnace shown in FIG. 1: Carbonized thread, 1': Graphitized thread, 2: Nippuro roller, 3: Nippuro roller, 4: Graphite heating element, 4': Graphite heating element wear part, 5: Carbon powder, 6: Water-cooled electrode, 7: Nitrogen inlet,
8: Nitrogen outlet, 9: Inside of graphite heating element,
10: Conventional graphitization furnace, 20: Modified graphitization furnace, 21: Pipe, 22: Clearance part, 2
3: Convex portion of graphite heating element, 24: Spacer, 25: Outer cylinder, 26: Flange, 27: Fireproof cement, 28: Air vent.

Claims (1)

[Claims] 1. A cylindrical heating element made of graphite or carbon, electrodes provided at both ends of the heating element, a heat insulating material provided around the outer periphery of the heating element, and a cylindrical heating element provided on one side of the heating element and communicating with the inside of the cylinder. an inert gas inlet;
In a carbon fiber manufacturing apparatus comprising an inert gas discharge port provided on the other side of the heating element and communicating with the inside of the cylinder, the space between the heat insulating material and the heating element has an inner diameter larger than the outer diameter of the heating element. , and a pipe made of graphite or carbon is arranged such that the pipe is a sheath and the heating element is a core, and both ends of the pipe are fixed to both ends of the heating element through a sealing material, and the pipe is made of graphite or carbon. A carbon fiber manufacturing apparatus characterized in that a gap is formed between a heating element and a heating element for sealing an inert gas.