Microwave heating device for cyclic oxidation of carbon fibers

Abstract

The invention discloses a microwave heating device for cyclic oxidation of carbon fibers. The microwave heating device comprises a front short-time staying area, a microwave heating cavity area, a rear short-time staying area and a ventilation system, the microwave heating cavity area comprises a microwave heating cavity, a microwave source, a microwave slot antenna, a mode stirrer, a belt and a belt roller; the microwave heating cavity is of a columnar hollow structure, one end of the microwave heating cavity is provided with a front short-time staying area, and the other end of the microwave heating cavity is provided with a rear short-time staying area; tow through holes are formed in the two end plates; a microwave source is arranged on the outer side surface of the microwave heating cavity, and a microwave slot antenna is arranged on the side surface of the microwave heating cavity; a mode stirrer is arranged in the microwave heating cavity; a belt is arranged in the middle of the microwave heating cavity and arranged on a belt roller in a sleeving mode. A driven roller, a driving roller and a thread rolling roller are arranged in the short-time staying area shell; and the ventilation system is arranged on the outer side of the microwave heating cavity. The microwave multi-cavity partition heating effect can be achieved only through one microwave heating cavity.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon fiber preparation, and in particular relates to a microwave heating device for cyclic oxidation of carbon fiber. Background Art

[0002] Carbon fiber composite materials are the most promising materials for various transportation tools in the current lightweight goal. The main component of carbon fiber composite materials is carbon fiber. The manufacturing process of carbon fiber mainly goes through four steps: spinning, pre-oxidation, carbonization and surface treatment. The pre-oxidation process is cumbersome, time-consuming and energy-intensive, which has a huge impact on the performance and manufacturing cost of the carbon fiber itself. At present, the pre-oxidation process of traditional carbon fiber is mainly achieved by means of resistance furnaces, etc. This method heats the carbon fiber from the surface to the inside through air convection conduction heat transfer. It is not only time-consuming and energy-intensive, but also easy to cause the carbon fiber to form skin-core structural defects, which has a significant impact on the performance of the carbon fiber. Microwave heating is a new heating method. It can directly heat from the inside of the carbon fiber to reduce the generation of the carbon fiber skin-core structure; at the same time, microwave heating does not release heat through air conduction, which can achieve faster heating, making the heating process more energy-efficient, and is conducive to reducing the cost and increasing the efficiency of the carbon fiber manufacturing process. On the other hand, in the existing carbon fiber microwave heating devices, most of them use multi-cavity partition heating. Multi-cavity partition heating requires the introduction of more equipment and its supporting facilities, which poses a huge challenge to the manufacture, control and placement of the equipment, and is not conducive to the basic research of carbon fiber pre-oxidation. Therefore, there is an urgent need for a small-scale microwave oxidation carbon fiber device that can carry out basic research. Summary of the invention

[0003] The purpose of the present invention is to provide a microwave heating device for cyclic oxidation of carbon fiber, so as to solve the problem that the current traditional carbon fiber pre-oxidation method mentioned in the background technology is time-consuming and energy-intensive, and easily causes the carbon fiber to form skin-core structural defects; and the existing carbon fiber microwave heating device has high requirements on the manufacture, control and placement of the equipment, which is not conducive to carrying out basic research on carbon fiber pre-oxidation.

[0004] To achieve the above object, the present invention provides a microwave heating device for carbon fiber cyclic oxidation, comprising a front short-time residence area, a microwave heating cavity area, a rear short-time residence area, and a ventilation system;

[0005] The microwave heating cavity area includes a microwave heating cavity, a microwave source, a microwave slit antenna, a mode stirrer, a belt, and a belt roller;

[0006] The microwave heating cavity is a horizontally placed centrally symmetrical cylindrical hollow structure, and a front short-time residence area is provided at one end thereof, and a rear short-time residence area is provided at the other end thereof; and filament bundle through holes are symmetrically provided on the two end plates of the microwave heating cavity, and the filament bundle through holes are used for the passage of filament bundles;

[0007] A plurality of microwave sources are evenly spaced around the outer surface of the microwave heating cavity, and microwave slit antennas are evenly spaced on the side of the microwave heating cavity. The microwave sources feed the generated microwaves into the interior of the microwave heating cavity through the microwave slit antennas; a mode stirrer is arranged at a position corresponding to the microwave slit antenna inside the microwave heating cavity;

[0008] A belt is symmetrically arranged in parallel in the middle of the microwave heating cavity, and the belt is sleeved on a belt roller; the belt is used to assist in the transmission of the tow and as an auxiliary heat source;

[0009] The front short-time stay area includes a front short-time stay area shell, and the rear short-time stay area includes a rear short-time stay area shell; the front short-time stay area shell and the rear short-time stay area shell are both provided with a passive roller, an active roller, and a winding roller; the winding roller is used for winding the wire bundle;

[0010] The ventilation system is arranged outside the microwave heating cavity, and the ventilation system is used for ventilating the microwave heating cavity.

[0011] In a specific embodiment, the cross-sectional shape of the columnar structure of the microwave heating cavity is circular, square or regular octagonal.

[0012] In a specific embodiment, both ends of the belt roller are arranged on the inner wall of the microwave heating cavity; the materials of the belt roller, the passive roller and the active roller are all wave-transmitting materials; the material of the belt is wave-absorbing, flexible and heat-resistant material.

[0013] In a specific embodiment, the materials of the belt roller, the passive roller and the active roller are ceramic, silicon nitride, glass or silicon carbide; the material of the belt is graphite fiber, polyamide, conductive polyurethane and modified rubber.

[0014] In a specific embodiment, the microwave heating cavity zone further includes a microwave suppressor; the microwave suppressor is arranged on the outside of the filament bundle through hole.

[0015] In a specific embodiment, the belt is a grid-shaped belt.

[0016] In a specific embodiment, power devices are provided on the outer side of the shell of the front short-time stay area corresponding to the active roller and the wire winding roller; power devices are also provided on the outer side of the shell of the rear short-time stay area corresponding to the active roller and the wire winding roller; and the active roller external power device is also provided with a torque sensor.

[0017] In a specific embodiment, the front short-time stay area housing and the rear short-time stay area housing are both provided with doors that are easy to open.

[0018] In a specific embodiment, the ventilation system includes an air purifier, an air intake channel, an exhaust channel, an exhaust pump, and an exhaust gas treatment device; the air purifier is arranged at the front end of the air intake channel, and the air purifier and the air intake channel are used to supply air to the microwave heating cavity; the exhaust pump is arranged on the exhaust channel, and the exhaust gas treatment device is arranged at the rear end of the exhaust channel, and the exhaust channel, the exhaust pump and the exhaust gas treatment device are used to extract the gas in the microwave heating cavity.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention uses microwave heating, thus avoiding the problems of low efficiency and easy skin-core defects caused by traditional heating.

[0021] The present invention uses a polyhedron cavity + a microwave mode stirrer to make the microwave field more uniform.

[0022] The present invention sets a short-time residence zone so that the carbon fiber can be heated by microwave circulation, realizes the effect of multi-cavity oxidation, and reduces equipment cost.

[0023] The present invention can achieve the effect of microwave multi-cavity zoned heating by using only one microwave heating cavity.

[0024] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention is further described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a schematic diagram of a cross-sectional structure in the main viewing direction of an embodiment of the present invention;

[0027] Figure 2 It is a schematic diagram of the cross-sectional structure of a microwave heating cavity viewed from the left according to an embodiment of the present invention.

[0028] Among them, 1. exhaust channel; 2. vacuum pump; 3. exhaust gas treatment device; 4. front short-time residence area; 5. microwave heating cavity; 6. rear short-time residence area; 8. belt; 9. belt roller; 12. microwave suppressor; 13. wire bundle; 14. mode agitator; 15. air simplifier; 16. air intake channel; 17. microwave slit antenna; 18. microwave source; 7-a. passive roller of the front area; 10-a. active roller of the front area; 11-a. wire winding roller of the front area; 7-b. passive roller of the rear area; 10-b. active roller of the rear area; 11-b. wire winding roller of the rear area. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Example 1

[0031] The present invention provides a microwave heating device for carbon fiber cyclic oxidation, comprising a front short-time residence area, a microwave heating cavity area, a rear short-time residence area, and a ventilation system;

[0032] The microwave heating cavity area includes a microwave heating cavity 5, a microwave source 18, a microwave slit antenna 17, a mode stirrer 14, a belt 8, and a belt roller 9;

[0033] The microwave heating cavity 5 is a horizontally placed, centrally symmetrical cylindrical hollow structure, and a front short-time residence area is provided at one end thereof, and a rear short-time residence area is provided at the other end thereof; and symmetrically arranged wire bundle through holes are provided on the two end plates of the microwave heating cavity 5, and the wire bundle through holes are used for allowing the wire bundle 13 to pass through; the two end plates of the microwave heating cavity 5 are connected to the microwave heating cavity 5 by means of screws and threaded holes, which is convenient for maintenance.

[0034] A plurality of microwave sources 18 are evenly spaced around the outer surface of the microwave heating cavity 5, and microwave slit antennas 17 are evenly spaced on the side of the microwave heating cavity 5. The microwave sources 18 feed the generated microwaves into the interior of the microwave heating cavity 5 through the microwave slit antennas 17; a mode stirrer 14 is arranged at a position corresponding to the microwave slit antenna 17 inside the microwave heating cavity 5; the materials of the microwave heating cavity 5 and the mode stirrer 14 are both stainless steel.

[0035] The mode stirrer 14 includes a stirring blade, a transmission support structure and a mode stirrer power device; the stirring blade is in a long strip shape and is provided with a rotating shaft along the length direction; both ends of the stirring blade are connected to the inner wall of the microwave heating cavity 5 through the transmission support structure, and the mode stirrer power device arranged outside the microwave heating cavity 5 drives the stirring blade to rotate through the transmission support structure. The microwave fed into the source is reflected and superimposed by the rotating stirring blade to provide a more uniform electric field distribution, and the microwave uniformity is better.

[0036] Two belts 8 are arranged in parallel and symmetrically in the middle of the microwave heating cavity 5, and each belt 8 is sleeved on two belt rollers 9; the belts 8 are used to assist in the transmission of the tow 13, and can also prevent the carbon fiber from breaking due to factors such as sliding, loosening or deviation; the belts 8 also serve as a heating component to provide auxiliary heat. The belts 8 are mesh-shaped belts. The belts are arranged in a mesh shape, which is conducive to microwave irradiation and air contact with the carbon fiber.

[0037] The two ends of the filament bundle are respectively wound on the winding rollers in the front short-time residence area and the rear short-time residence area.

[0038] The front short-time stay area includes a front short-time stay area shell 4, and the rear short-time stay area includes a rear short-time stay area shell 6; the front short-time stay area shell 4 and the rear short-time stay area shell 6 are both provided with a passive roller, an active roller, and a winding roller; the winding roller is used to wind the wire bundle 13; the front short-time stay area shell 4 and the rear short-time stay area shell 6 are both connected and arranged at the end of the microwave heating cavity 5 by a lock. The bottom of the front short-time stay area shell 4 and the rear short-time stay area shell 6 are also provided with rollers for easy movement.

[0039] In order to achieve the purpose of cyclic oxidation of carbon fiber, a front short-time residence area and a rear short-time residence area are set at the front and rear ends of the microwave heating cavity 5, so that the test section carbon fiber tow briefly enters the short-time residence area after the first stage heating in the microwave heating cavity is completed to wait for the microwave heating cavity to be heated to the second stage temperature. When the temperature in the microwave heating cavity rises to the second stage, the carbon fiber tow re-enters the microwave heating cavity for a slow oxidation process.

[0040] The ventilation system is arranged outside the microwave heating cavity 5 , and the ventilation system is used to ventilate the microwave heating cavity 5 .

[0041] The cross-sectional shape of the columnar structure of the microwave heating cavity 5 is circular, square or regular octagonal. A regular octagon is preferably used to form 8 faces, and 8 microwave sources 18 and 8 mode stirrers 14 are also provided.

[0042] Both ends of the belt roller 9 are arranged on the inner wall of the microwave heating cavity 5; the materials of the belt roller 9, the passive roller and the active roller are all wave-transmitting materials; the material of the belt 8 is a wave-absorbing, flexible and heat-resistant material.

[0043] The materials of the belt roller 9, the passive roller and the active roller are ceramic, silicon nitride, glass or silicon carbide; the material of the belt 8 is graphite fiber, polyamide, conductive polyurethane and modified rubber.

[0044] The microwave heating cavity area further includes a microwave suppressor 12; the microwave suppressor 12 is arranged outside the filament bundle through hole.

[0045] Power devices are provided on the outside of the front short-time stay area shell 4 corresponding to the front area active roller 10-a and the front area winding roller 11-a; power devices are provided on the outside of the rear short-time stay area shell 6 corresponding to the rear area active roller 10-b and the rear area winding roller 11-b; and the active roller external power device is also provided with a torque sensor. The active roller is provided to prevent the shrinkage of the carbon fiber during the oxidation process. The active roller external power device is also provided with a torque sensor to achieve the purpose of reducing the shrinkage by applying traction to stretch the carbon fiber.

[0046] The front short-time stay area housing 4 and the rear short-time stay area housing 6 are both provided with doors that are convenient to open.

[0047] The ventilation system includes an air purifier 15, an air inlet channel 16, an exhaust channel 1, an air pump 2, and an exhaust gas treatment device 3; the air purifier 15 is arranged at the front end of the air inlet channel 16, and the air purifier 15 and the air inlet channel 16 are used to supply air to the microwave heating cavity 5; the air pump 2 is arranged on the exhaust channel 1, and the exhaust gas treatment device 3 is arranged at the rear end of the exhaust channel 1, and the exhaust channel 1, the air pump 2 and the exhaust gas treatment device 3 are used to extract the gas in the microwave heating cavity 5; and the ventilation system keeps the microwave heating cavity 5 at a slight negative pressure. The function of maintaining a slight negative pressure is to make the exhaust gas generated by the reaction flow to the exhaust gas treatment device 3 without leaking out; at the same time, the gas flow speed can be slowed down so that the oxygen in the air and the carbon fiber precursor can fully react.

[0048] The air purifier 15 and the air inlet channel 16 are arranged at the upper part of the microwave heating cavity 5, and the exhaust channel 1, the vacuum pump 2 and the exhaust gas treatment device 3 are arranged at the lower part of the microwave heating cavity 5; they cooperate with each other to maintain a slight negative pressure inside the microwave heating cavity 5 and treat the generated exhaust gas.

[0049] When installing the tow, open the doors on the front short-time residence area shell 4 and the rear short-time residence area shell 6, first wind one end of the tow around the front area winding roller 11-a in the front short-time residence area, and then guide the tow outside to bypass the front area passive roller 7-a and the front area active roller 10-a in the front short-time residence area, change the forward direction of the tow and adjust the residence time; then use a thin and long stick to pull the tow through the tow through hole near the front short-time residence area, and make the tow in the microwave heating cavity 5 in two parallel arranged The belts are placed between the belts to make the filament bundle pass through the filament bundle through hole close to the rear short-time residence zone, and the slender stick used for traction is removed; the filament bundle continues to pass around the rear zone passive roller 7-b and the rear zone active roller 10-b in the rear short-time residence zone, and finally the other end of the filament bundle is wound around the rear zone winding roller 11-b in the rear short-time residence zone. The slackened filament bundle is tightened by adjusting the winding rollers at both ends, and the doors on the front short-time residence zone shell 4 and the rear short-time residence zone shell 6 are closed, and the experiment of microwave oxidation of carbon fiber filament bundle can be carried out.

[0050] Taking the treatment of polyacrylonitrile carbon fiber precursor as an example, before oxidation, the polyacrylonitrile carbon fiber material is first wound in the microwave heating device for carbon fiber cyclic oxidation of the present invention, the microwave source 18 is turned on, the microwave heating cavity 5 is heated to 180°C, and after the microwave heating cavity 5 reaches 180°C, the transmission device, i.e., the active roller and the winding roller, is turned on to transmit the test section of the carbon fiber tow to the microwave heating cavity 5. During the transmission process, a certain tension is applied to the carbon fiber by the active roller, and the carbon fiber is heated in the microwave heating cavity 5 for 20 minutes through slow feeding movement; after the heating in the microwave heating cavity 5 is completed, the test section of the carbon fiber tow is transmitted to the rear short-time residence area, and then the microwave heating cavity 5 is rapidly heated to 210°C, and then the test section of the carbon fiber tow is reversely transmitted to the microwave heating cavity 5 for heating for 20 minutes. After heating, it is transmitted to the front short-time residence area, and then the microwave heating cavity 5 is rapidly heated to 240°C... According to the above steps, cyclic oxidation is continuously performed. The temperature in the microwave heating cavity 5 is raised to 180°C, 210°C, 240°C, 270°C, and 300°C, and the single carbon fiber heating and oxidation time is set to 20 minutes. After the heating starts, the ventilation system is also turned on at the same time, and the microwave heating cavity 5 is kept at a slight negative pressure, and the gas is constantly flowing.

[0051] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A microwave heating device for cyclic oxidation of carbon fiber, characterized in that: It includes a front short-term residence area, a microwave heating cavity area, a rear short-term residence area, and a ventilation system; The microwave heating cavity area comprises a microwave heating cavity (5), a microwave source (18), a microwave slit antenna (17), a mode stirrer (14), a belt (8), and a belt roller (9); The microwave heating cavity (5) is a horizontally placed centrally symmetrical cylindrical hollow structure, and a front short-time residence area is provided at one end thereof, and a rear short-time residence area is provided at the other end thereof; and filament bundle through holes are symmetrically provided on the two end plates of the microwave heating cavity (5), and the filament bundle through holes are used for allowing the filament bundle (13) to pass through; A plurality of microwave sources (18) are evenly spaced around the outer surface of the microwave heating cavity (5); microwave slit antennas (17) are evenly spaced on the side of the microwave heating cavity (5); the microwave sources (18) feed the generated microwaves into the interior of the microwave heating cavity (5) through the microwave slit antennas (17); and a mode stirrer (14) is arranged at a position corresponding to the microwave slit antennas (17) inside the microwave heating cavity (5); A belt (8) is symmetrically arranged in parallel in the middle of the microwave heating cavity (5), and the belt (8) is sleeved on a belt roller (9); the belt (8) is used to assist in the transmission of the filament bundle (13) and as an auxiliary heat source; The front short-time stay area includes a front short-time stay area shell (4), and the rear short-time stay area includes a rear short-time stay area shell (6); a passive roller, an active roller, and a winding roller are arranged in the front short-time stay area shell (4) and the rear short-time stay area shell (6); the winding roller is used for winding the wire bundle (13); The ventilation system is arranged outside the microwave heating cavity (5), and the ventilation system is used to ventilate the microwave heating cavity (5).

2. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: The cross-sectional shape of the columnar structure of the microwave heating cavity (5) is circular, square or regular octagonal.

3. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: Both ends of the belt roller (9) are arranged on the inner wall of the microwave heating cavity (5); the materials of the belt roller (9), the passive roller and the active roller are all wave-transmitting materials; and the material of the belt (8) is a wave-absorbing, flexible and heat-resistant material.

4. The microwave heating device for cyclic oxidation of carbon fiber according to claim 3, characterized in that: The materials of the belt roller (9), the passive roller and the active roller are ceramic, silicon nitride, glass or silicon carbide; the material of the belt (8) is graphite fiber, polyamide, conductive polyurethane and modified rubber.

5. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: The microwave heating cavity area also includes a microwave suppressor (12); the microwave suppressor (12) is arranged outside the filament bundle through hole.

6. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: The belt (8) is a grid-shaped belt.

7. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: Power devices are provided on the outer side of the front short-time stay area shell (4) corresponding to the active roller and the winding roller; power devices are also provided on the outer side of the rear short-time stay area shell (6) corresponding to the active roller and the winding roller; and torque sensors are provided on the active rollers externally connected to the power devices.

8. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: The front short-time stay area housing (4) and the rear short-time stay area housing (6) are both provided with doors that are easy to open.

9. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, characterized in that: The ventilation system comprises an air purifier (15), an air intake channel (16), an exhaust channel (1), an air pump (2), and an exhaust gas treatment device (3); the air purifier (15) is arranged at the front end of the air intake channel (16), and the air purifier (15) and the air intake channel (16) are used to supply air to the microwave heating cavity (5); the air pump (2) is arranged on the exhaust channel (1), and the exhaust gas treatment device (3) is arranged at the rear end of the exhaust channel (1); the exhaust channel (1), the air pump (2), and the exhaust gas treatment device (3) are used to extract gas from the microwave heating cavity (5).

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