JPS627288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device for manufacturing carbon fibers in large quantities by heating fibers mainly made from organic synthetic fibers using microwaves.

Conventionally, infusible (flame-resistant) fibers made from organic synthetic fibers are heated at 1000 to 1500°C in an inert gas atmosphere.
When carbonizing by heating, heating methods include (a) heating by radiation heat transfer from an electric resistance heating element, (b) heating by heat exchange with high-temperature inert gas, and (c) heating by microwaves. is proposed. When heating method (a) is used, when heating a large group of fibers, an insulating material is heated, and heat transfer from the outer surface fibers to the inner fibers, which are heated first, is poor. Due to thermal insulation by gas between the fibers, and the large amount of surface radiation compared to the heat capacity of the fibers, the heat transfer rate is low, and it is difficult to uniformly heat the entire body, which takes a long time to heat. I have a problem that requires energy. In addition, the inside of the heating device should be heated to 1000 to 1500℃.
Because it must be kept in a temperature atmosphere of
In order to reduce the amount of heat dissipated from the device, the heat insulating material of the surrounding wall must be thickened, and high-temperature refractory materials, heat-resistant steel, etc. must be used, resulting in the problem that the device becomes large and expensive. When using the heating method (b), a heat exchanger for high temperature, a circulation blower, etc. are required, and the equipment becomes expensive, and there is a problem that heating above 800°C is difficult in practice. In the field of carbon fiber manufacturing technology, heating in (c) is only known in the field of carbon fiber manufacturing technology, in which the yarn is stretched under tension in a quartz tube and irradiated with microwaves. There was a problem that it could not be applied to the infusible version because it was too fragile. In addition, in this case, it is difficult to increase the size of equipment for mass production.
Currently, mass production is not carried out.

For this reason, this invention uses microwave heating to make coal-based pitch fibers infusible.Even the brittle raw material fibers remain tow-like, can be heat-treated with less energy, and can be mass-produced. The purpose of the present invention is to provide a heating device for carbon fiber production that is possible.

The present invention will be explained below based on one embodiment shown in the drawings. The heating device of this example was implemented in a carbon fiber manufacturing device, and the heating device includes a furnace body 1,
The carbon fiber manufacturing apparatus is composed of a conveyance device 2, a microwave irradiation device 3, and an inert gas distribution device 4, and in conjunction with these, a temperature control device 5, a cooling device 6, etc. are provided.

As shown in FIGS. 1 to 4, the furnace body 1 is formed into a horizontally long rectangular tube shape having an inlet 10 at one end and an outlet 11 at the other end, and the outer shell 12 is made of a material that reflects microwaves. It is made of heat-resistant steel plate. Inside the furnace body 1 are partition walls 13, 14, 15, 1
jet zone 18 divided by 6, 17, first
Heating zone 19, second heating zone 20, soaking zone 2
1. A cooling zone 22 and a jet zone 23 are formed. Each of the partition walls 13 to 17 is made of the same heat-resistant steel plate as the outer shell 12, and is provided with through holes 13a to 17a for transporting a container 31, which will be described later. The outer shell 12 is divided into the above-mentioned zones, and the zones are connected to each other by interposing a partition wall between flanges that connect the zones. There are sliding doors 2 made of steel plate that can be opened and closed at the entrance 10 and the exit 11 respectively.
4,25 are provided. All heating zones 2
6, that is, the inner surfaces of the furnace shell of the first and second heating zones 19 and 20 and the soaking zone 21 and the inner surface of the cooling zone 22 are lined with ceramic fiber-based heat insulating material 27, which is a fireproof heat insulating material through which microwaves can pass. There is. A number of nozzles each formed of punched metal 28 are opened in the spout zones 18 and 23, and an inert gas such as nitrogen gas is supplied through these nozzles.
and prevents air from flowing in from the outlet 11. The entire furnace body 1 is supported by a pedestal 30 via rollers 29 to allow expansion and contraction due to heat.

The conveying device 2 moves the inside of the furnace body 1 from the inlet 10 to the outlet 1.
It is a belt conveyor mainly composed of a mesh belt 32 made of heat-resistant steel. mesh belt 32
has a mesh size so that microwaves are not reflected, and is stretched by pulleys 33, 34, an in-furnace belt guide 35, and an outside belt guide 36. The in-furnace belt guide 35 is provided continuously along the entire length of the furnace, and in the jet zones 18 and 23, an outer shell (see FIG. 3) is used to support the entire width of the belt 32, and the heating zone 26 The cooling zone 22 is provided to protrude inward from the inner surface of the outer shell 12 so as to support both end edges of the belt 32, and as shown in FIG. Only the top and bottom are connected. Reference numeral 37 in FIG. 2 is a drive section for the mesh belt 32.

The container 31 is made of a fire-resistant material that transmits microwaves, such as ceramic wool.
It is box-shaped with a width of 500mm, a length of 1000mm, and a height of 150mm.
The bottom wall has many ventilation holes with a diameter of about 5 mm. This container 31 has a lid 38, which is also made of the same material, has many similar ventilation holes, and further has a 10 mm wide slit for detecting the internal temperature. The container 31 is connected to the belt 32 on the inlet 10 side.
Once placed on top, it is transported through the furnace body 1 by the transport device 2 and exits to the outlet 11 side.

The microwave irradiation device 3 includes a first heating zone 19,
One end of microwave waveguides 39 and 40 are opened from the upper and lower surfaces of each of the second heating zone 20 and the soaking zone 21, and the other end is connected to a microwave generator. Note that an isolator is provided between each waveguide and the magnetron for the microwaves reflected within the furnace body 1 and returned, and water is supplied into the isolator to be absorbed and discharged as heat. There is.

The inert gas distribution device 4 includes a nozzle 41 made of a tube having a large number of small holes arranged at the bottom of each of the first heating zone 19, the second heating zone 20, and the soaking zone 21 in the furnace body 1 on both sides. , each band 19, 20,
21, a damper 43 provided in the exhaust path, and piping for supplying inert gas to the nozzle 41. An appropriate amount of inert gas is supplied from the nozzle 41, and the internal pressure of the furnace body 1 is maintained at a positive pressure slightly higher than atmospheric pressure by adjusting the damper 43. Furthermore, while the inert gas flows from the bottom to the top, when the container 31 is on the mesh belt 32, the in-furnace belt guide 3
5, most of the air passes through the vent holes in the container 31 and lid 38.

As shown in FIG.
The fiber temperature is detected by a radiation type thermometer 44 installed on the ceiling of the containers 9, 20, and 21 and directed toward the raw material fibers inside through a slit in the lid 38 of the container 31 positioned on the mesh belt 32. , the microwave output in the corresponding band is adjusted by a separate control section. The temperature control is such that, for example, the temperature is raised to about 700°C in the first heating zone 19, the temperature is raised to a predetermined 1300°C in the second heating zone 20, and 1300°C is maintained in the soaking zone.

The cooling device 6 is for cooling the heat-treated carbon fibers and then taking them out of the furnace, and includes nozzles 41a and exhaust holes at the bottom of both sides, similar to the inert gas distribution device 4 in the first heating zone 19, etc. 42a, a damper 43a, and piping for the nozzle 41a. However, since the purpose is cooling, it is possible to flow a larger amount of inert gas than in the heating zone.

45 in FIG. 2 is a viewing window. Note that this viewing window, thermometer, and each exhaust port are equipped with measures to prevent or protect microwaves from leaking.

According to the carbon fiber manufacturing apparatus configured in this way, when raw material fibers are stored in the container 31 from the inlet 10 of the furnace body 1, the lid 38 is placed, and the raw material fibers are fed into the furnace, the raw material fibers are processed into carbon fibers. comes out from exit 11. For example, to explain the case where carbon fiber is made from infusible coal-based pitch fibers, first the raw material fibers are made into tows with a length of about 1 m, and then stacked to a thickness of 100 mm. It is housed in a container 31 at a packing density of about 50 kg/m ³ . A large number of such containers 31 are prepared and sequentially inserted into the furnace body. The transport device 2 operates intermittently. The container 31 that is first sent into the furnace body 1 is in the first heating zone 1.
9, and only the raw material fibers inside are heated by microwaves while being supplied with nitrogen gas. The supplied nitrogen gas passes through the inside of the container 31 and is discharged to the outside, replacing most of the air contained between the raw material fibers at the initial stage of heating, and then continues to circulate. The temperature of the raw material fiber reaches a predetermined temperature, for example 700° C., in a predetermined time t, and the container 31 is heated to the second heating zone 20.
transported to. Here, too, the raw material fibers are heated by microwaves while being supplied with nitrogen gas, and the temperature of the raw material fibers reaches a predetermined treatment temperature for the same predetermined time t as above, e.g.
When the temperature reaches 1300°C, the container 31 is transported to the soaking zone 21. Here, too, the container 31 is heated by microwaves while being supplied with nitrogen gas, and after the temperature of the raw fiber is maintained at the processing temperature of 1300° C. for a processing time t, the container 31 is conveyed to the cooling zone 22 . Here, a relatively large amount of nitrogen gas is supplied to cool the fibers in the container to about 300° C., and after a time t has elapsed, the fibers are transported outside. The above is the container 3 that was first sent into the furnace body 1.
1, the subsequent containers 31 are sequentially subjected to the same process and transported outside.

The carbon fibers produced in this manner had the same strength and yield as those produced by conventional radiant heating.

In the above-mentioned apparatus, inert gas is supplied and discharged for each zone, and this is caused by the partition walls 13,
The presence of elements 14, 15, 16, and 17 is effective, and a favorable state is maintained by adjusting the amount of inert gas supplied and the damper. Thereby, the oxygen concentration in each zone can be controlled to be below the specified value. Furthermore, in the flow of inert gas, the behavior from the state where the lower half of the furnace body 1 is filled, through the ventilation holes of the container 31, between the fibers, and into the upper space is due to the partitioning action of the guide 35. Therefore, when there is a gap between the containers that are continuously fed in one after another, a fin-like protrusion may be provided that protrudes along the bottom surface of the container 31 in the sense of the upper and lower divisions within the furnace body 1.

Furthermore, the presence of the partition walls 13 to 17 is also effective because the temperature of the fibers in the container in each zone becomes a prescribed temperature increase pattern. That is, in addition to the rectification effect of the inert gas, the rectification effect is also applied to the microwaves so that the microwaves irradiated to each zone 19, 20, and 21 of the heating zone 26 do not greatly affect the other bands. There is something like that.

In addition, the microwave heating in this device takes 1/5 to 1/5 of the heating time compared to conventional radiation heating methods.
It can be shortened to 1/6. While the conventional electric heater type device had a heating rate of 5° C./min, this device was able to heat at a rate of 30 to 45° C./min. Furthermore, when heating a fiber layer with a thickness of 100 mm, we measured the temperature distribution at the stage of exiting the second heating zone and found that it was ±20°C.
It was within

As described above, the carbon fiber manufacturing apparatus using this microwave heating apparatus for carbon fiber manufacturing can significantly shorten the heating time compared to the conventional method, and therefore can shorten the length of the furnace body. Furthermore, since microwave heating is used, only the fibers are heated without raising the atmosphere inside the furnace to a high temperature, so by covering the fibers with a fireproof material or fireproof insulation material that allows microwaves to pass through, less heat is dissipated and energy is reduced. Consumption can be significantly reduced compared to conventional methods. According to experiments, the specified processing amount, which conventionally required 318KW of power, could be processed using 50KW with this device. Furthermore, since this device can continuously process a large amount of fiber in tow form, the product cost is also low.

As described above, according to the present invention, it is possible to provide a microwave heating apparatus for producing carbon fibers that is small in size, capable of high-speed processing, has a large energy saving effect, and is extremely economical.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional plan view showing the general configuration of an embodiment of the present invention, Fig. 2 is a longitudinal sectional side view of the embodiment, Fig. 3 is an enlarged cross-sectional view taken along line B-B in Fig. 2, and Fig. 4 is Second
It is an enlarged cross-sectional view taken along line AA in the figure. 1...Furnace body, 2...Transfer device, 3...Microwave irradiation device, 4...Inert gas distribution device, 6...
Cooling device, 10...inlet, 11...outlet, 12...
... Outer shell, 13, 14, 15, 16, 17 ... Division wall, 18, 23 ... Jet zone, 26 ... Heating zone, 22 ... Cooling zone, 27 ... Heat insulation material, 31 ...
...Container, 32...Mesh belt, 38...Lid,
39, 40...Microwave waveguide, 41...Nozzle, 42...Exhaust hole, 43...Damper, 44...
Thermometer, 41a...nozzle, 42a...exhaust hole,
43a...Dumper.

Claims (1)

[Scope of Claims] 1. The outer shell is formed of a material that reflects microwaves and has an outlet and an inlet that can be opened and closed, and a heating zone is provided between the inlet and the outlet, and at least the outer shell of the heating zone is provided with a heating zone between the inlet and the outlet. A furnace body whose inside is insulated with a fireproof heat insulating material that allows microwaves to pass therethrough; a conveying device configured to transport a fireproof raw material fiber container that allows microwaves to pass from the inlet to the outlet; A microwave for manufacturing carbon fiber, comprising a microwave irradiation device having a microwave waveguide opening in the zone, and an inert gas distribution device installed in the heating zone so as to circulate an inert gas through the container. heating device. 2. The apparatus according to claim 1, wherein the heating zone in the furnace body is provided with a partition wall made of a microwave-reflecting material extending from the outer shell to near the conveyance path of the container. A microwave heating device for manufacturing carbon fiber, characterized in that the length in the path direction is divided into a plurality of sections.