A microwave heating device for cyclic oxidation of carbon fiber

Abstract

The present invention discloses a microwave heating device for cyclic oxidation of carbon fiber, which comprises a pre-stage short residence area, a microwave heating cavity area, a post-stage short residence area, and a ventilation system; the microwave heating cavity area includes 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 in a columnar hollow structure, with a pre-stage short residence area provided at one end and a post-stage short residence area provided at the other end; and through holes for fiber bundles are provided on both end plates thereof; a microwave source is provided on the outer side surface of the microwave heating cavity, and a microwave slot antenna is provided on the side surface of the microwave heating cavity; a mode stirrer is provided inside the microwave heating cavity; a belt is provided in the middle of the microwave heating cavity, and the belt is sleeved on the belt roller; passive rollers, active rollers, and wire winding rollers are all provided inside the short residence area housing; the ventilation system is provided outside the microwave heating cavity. The present invention can achieve the effect of multi-cavity zone heating by microwave only with one microwave heating cavity.

Description

Technical Field

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

[0002] Carbon fiber composites are the most potential materials for various transportation tools to achieve lightweight goals at present. The main component of carbon fiber composites is carbon fiber. The manufacturing process of carbon fiber mainly goes through four steps: spinning, pre-oxidation, carbonization, and surface treatment. Among them, the pre-oxidation process is cumbersome, time-consuming, and energy-consuming, which has a huge impact on the performance and manufacturing cost of carbon fiber itself. At present, the pre-oxidation process of traditional carbon fiber is mainly realized by means of resistance furnaces, etc. This method conducts heat transfer through air convection, heating the carbon fiber from the surface to the inside. It not only takes a long time and consumes a lot of energy, but also easily forms skin-core structure defects in the carbon fiber, having 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, reducing the generation of skin-core structure in the carbon fiber. At the same time, microwave heating does not release heat through air conduction, and can achieve faster heating, making the heating process more energy-efficient, which is conducive to reducing costs and increasing efficiency in the manufacturing process of carbon fiber. On the other hand, in the existing carbon fiber microwave heating devices, most adopt multi-cavity partition heating. Multi-cavity partition heating requires the introduction of more equipment and its supporting facilities, posing huge challenges to the manufacturing, control, and placement sites of the equipment, which is not conducive to carrying out basic research on 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 at present. Summary of the Invention

[0003] The purpose of the present invention is to provide a microwave heating device for cyclic oxidation of carbon fiber to solve the problems in the background art that the current pre-oxidation method of traditional carbon fiber is time-consuming and energy-consuming, and easily forms skin-core structure defects in the carbon fiber; while the existing carbon fiber microwave heating devices have high requirements for the manufacturing, control, and placement sites of the equipment, which is not conducive to carrying out basic research on carbon fiber pre-oxidation.

[0004] To achieve the above purpose, the present invention provides a microwave heating device for cyclic oxidation of carbon fiber, including a pre-stage short residence area, a microwave heating cavity area, a post-stage short residence area, and a ventilation system;

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

[0006] The microwave heating cavity is a horizontally placed columnar hollow structure with central symmetry, and a pre-stage short residence area is arranged at one end and a post-stage short residence area is arranged at the other end; and wire bundle through holes are symmetrically arranged on both end plates of the microwave heating cavity, and the wire bundle through holes are used for the wire bundle to pass through;

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

[0008] A belt is symmetrically arranged in parallel in the middle of the microwave heating cavity. 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 pre-stage short residence area includes a pre-stage short residence area housing, and the post-stage short residence area includes a post-stage short residence area housing; passive rollers, driving rollers, and wire winding rollers are arranged in both the pre-stage short residence area housing and the post-stage short residence area housing; the wire winding rollers are used to wind the tow;

[0010] The ventilation system is arranged outside the microwave heating cavity, and the ventilation system is used to ventilate the inside of 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 octagon.

[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 driving roller are all wave-transparent materials; the material of the belt is an absorbent, flexible, and heat-resistant material.

[0013] In a specific embodiment, the materials of the belt roller, the passive roller, and the driving roller are ceramics, 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 area further includes a microwave suppressor; the microwave suppressor is arranged outside the tow through-hole.

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

[0016] In a specific embodiment, power devices are arranged corresponding to the driving rollers and the wire winding rollers on the outer side of the pre-stage short residence area housing; power devices are also arranged corresponding to the driving rollers and the wire winding rollers on the outer side of the post-stage short residence area housing; and the driving rollers are externally connected to the power devices and are all provided with torque sensors.

[0017] In a specific embodiment, doors that are convenient to open are arranged on both the pre-stage short residence area housing and the post-stage short residence area housing.

[0018] In a specific embodiment, the ventilation system includes an air purifier, an intake passage, an exhaust passage, an air extraction pump, and an exhaust gas treatment device; the air purifier is arranged at the front end of the intake passage, and the air purifier and the intake passage are used to supply air to the microwave heating cavity; the air extraction pump is arranged on the exhaust passage, and the exhaust gas treatment device is arranged at the rear end of the exhaust passage. The exhaust passage, the air extraction 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, avoiding the problems of low traditional heating efficiency and easy occurrence of skin-core defects.

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

[0022] The present invention sets a short residence area so that the carbon fiber can be circularly heated by microwaves, achieving the effect of multi-chamber oxidation and reducing the equipment cost.

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

[0024] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following provides a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0027] Figure 2 is a schematic cross-sectional structure view of the microwave heating cavity in the left view direction of an embodiment of the present invention.

[0028] Wherein, 1. Exhaust passage; 2. Air extraction pump; 3. Exhaust gas treatment device; 4. Front short residence area; 5. Microwave heating cavity; 6. Rear short residence area; 8. Belt; 9. Belt roller; 12. Microwave suppressor; 13. Tow; 14. Mode stirrer; 15. Air simplifier; 16. Intake passage; 17. Microwave slot antenna; 18. Microwave source; 7-a. Front area passive roller; 10-a. Front area driving roller; 11-a. Front area winding roller; 7-b. Rear area passive roller; 10-b. Rear area driving roller; 11-b. Rear area winding roller. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following is a detailed description of the embodiments of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1

[0031] The present invention provides a microwave heating device for cyclic oxidation of carbon fiber, including a pre - short residence area, a microwave heating cavity area, a post - short residence area, and a ventilation system;

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

[0033] The microwave heating cavity 5 is a columnar hollow structure with central symmetry placed horizontally. One end of it is provided with a pre - short residence area, and the other end is provided with a post - short residence area. Both end plates of the microwave heating cavity 5 are symmetrically provided with tow through - holes for the tow 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 side surface of the microwave heating cavity 5. Microwave slot antennas 17 are evenly spaced on the side surface of the microwave heating cavity 5. The microwave source 18 feeds the generated microwaves into the interior of the microwave heating cavity 5 through the microwave slot antenna 17. A mode stirrer 14 is arranged at the position corresponding to the microwave slot antenna 17 inside the microwave heating cavity 5. The materials of both the microwave heating cavity 5 and the mode stirrer 14 are stainless steel.

[0035] The mode stirrer 14 includes stirring blades, a transmission support structure, and a mode stirrer power device. The stirring blades are strip - shaped and are provided with a rotating shaft along the length direction. Both ends of the stirring blades are connected to the inner wall of the microwave heating cavity 5 through the transmission support structure. The mode stirrer power device arranged outside the microwave heating cavity 5 drives the stirring blades to rotate through the transmission support structure. By rotating the stirring blades, the microwaves fed into the source are reflected and superposed to provide a more uniform electric field distribution, and the microwave uniformity is better.

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

[0037] Both ends of the tow are respectively wound on the winding rollers in the pre - short residence area and the post - short residence area.

[0038] The front short residence area includes the front short residence area housing 4, and the rear short residence area includes the rear short residence area housing 6; a passive roller, an active roller, and a wire winding roller are arranged in both the front short residence area housing 4 and the rear short residence area housing 6; the wire winding roller is used for winding the fiber bundle 13; both the front short residence area housing 4 and the rear short residence area housing 6 are connected and arranged at the end of the microwave heating cavity 5 by means of a buckle. Rollers are also arranged at the bottoms of the front short residence area housing 4 and the rear short residence area housing 6 to facilitate movement.

[0039] To achieve the purpose of carbon fiber cyclic oxidation, a front short residence area and a rear short residence area are arranged at the front and rear ends of the microwave heating cavity 5, so that after the first-stage heating of the test section carbon fiber bundle in the microwave heating cavity is completed, it briefly enters the short residence area to wait for the temperature in the microwave heating cavity to reach the second-stage temperature. When the temperature in the microwave heating cavity rises to the second stage, the carbon fiber bundle 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 inside of 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 octagon. Preferably, a regular octagon is adopted, forming 8 faces, with 8 microwave sources 18 arranged, and 8 mode stirrers 14 are also arranged.

[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-transparent materials; the material of the belt 8 is an absorbent, flexible and heat-resistant material.

[0043] The materials of the belt roller 9, the passive roller and the active roller are ceramics, 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 fiber bundle through hole.

[0045] Power devices are arranged outside the front short residence area housing 4 corresponding to the front area active roller 10-a and the front area wire winding roller 11-a; power devices are also arranged outside the rear short residence area housing 6 corresponding to the rear area active roller 10-b and the rear area wire winding roller 11-b; and the active rollers are externally connected to power devices and are all provided with torque sensors. The active rollers are provided to prevent the shrinkage of carbon fibers during the oxidation process. The active rollers are externally connected to power devices and are provided with torque sensors to achieve the purpose of stretching the carbon fibers by applying traction force to reduce shrinkage.

[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 located at the front end of the air inlet channel 16. 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 located on the exhaust channel 1, and the exhaust gas treatment device 3 is located 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. The ventilation system maintains a slight negative pressure in the microwave heating cavity 5. The purpose of maintaining a slight negative pressure is to direct the exhaust gas generated by the reaction to the exhaust gas treatment device 3, preventing it from leaking out. At the same time, it slows the gas flow rate, allowing oxygen in the air to fully react with the carbon fiber precursors.

[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 to treat the generated exhaust gas.

[0049] When installing the tow, open the doors on the front short-term residence area shell 4 and the rear short-term residence area shell 6, first wind one end of the tow around the front area winding roller 11-a in the front short-term 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-term residence area, change the forward direction of the tow and adjust the residence time; then use a thin long stick to pull the tow through the tow through hole near the front short-term residence area, and make the tow be in two parallel arranged in the microwave heating cavity 5. The belts are placed between the belts to make the filament bundle pass through the filament bundle through hole near the rear short-time residence area, and the slender stick used for traction is removed; the filament bundle continues to pass around the rear area passive roller 7-b and the rear area active roller 10-b in the rear short-time residence area, and finally the other end of the filament bundle is wound on the rear area winding roller 11-b in the rear short-time residence area. By adjusting the winding rollers at both ends, the loose filament bundle is tightened, and the doors on the front short-time residence area shell 4 and the rear short-time residence area 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 inside the microwave heating device for cyclic oxidation of carbon fiber of the present invention. Then, the microwave source 18 is turned on to heat up the microwave heating cavity 5, and the temperature is set to 180°C. After the microwave heating cavity 5 reaches 180°C, the conveying device, namely the driving roller and the winding roller, is turned on to convey the carbon fiber tow in the test section into the microwave heating cavity 5. During the conveying process, a certain tension is applied to the carbon fiber by the driving 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 carbon fiber tow in the test section is conveyed to the rear short-time residence area. Subsequently, the microwave heating cavity 5 is quickly heated to 210°C, and then the carbon fiber tow in the test section is conveyed back into the microwave heating cavity 5 for heating for 20 minutes in the reverse direction. After the heating is completed, it is conveyed to the front short-time residence area, and then the temperature in the microwave heating cavity 5 is quickly raised to 240°C... The cyclic oxidation is continuously carried out according to the above steps. The heat preservation temperature in the microwave heating cavity 5 is increased in sequence as 180°C, 210°C, 240°C, 270°C, and 300°C, and the single-time carbon fiber heating and oxidation time is set to 20 minutes. After the heating starts, the ventilation system should also be turned on at the same time, and the microwave heating cavity 5 is kept at a slightly negative pressure, and the gas is constantly flowing.

[0051] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, which should all 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 pre - short residence area, a microwave heating cavity area, a post - short residence area, and a ventilation system; The microwave heating cavity area includes a microwave heating cavity (5), a microwave source (18), a microwave slot antenna (17), a mode stirrer (14), a belt (8), and a belt roller (9); The microwave heating cavity (5) is a horizontally placed columnar hollow structure with central symmetry, and a pre - short residence area is provided at one end and a post - short residence area is provided at the other end; and through - holes for the tow (13) are symmetrically arranged on both end plates of the microwave heating cavity (5). A plurality of microwave sources (18) are evenly spaced around the outer side surface of the microwave heating cavity (5), and microwave slot antennas (17) are evenly spaced on the side surface 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 slot antennas (17); a mode stirrer (14) is arranged at a position corresponding to the microwave slot antenna (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 the belt roller (9); the belt (8) is used to assist in the conveyance of the tow (13) and as an auxiliary heat source. The pre - short residence area includes a pre - short residence area housing (4), and the post - short residence area includes a post - short residence area housing (6); passive rollers, active rollers, and winding rollers are arranged in both the pre - short residence area housing (4) and the post - short residence area housing (6); the winding rollers are used for winding the tow (13). The ventilation system is arranged outside the microwave heating cavity (5), and the ventilation system is used to ventilate the inside of the microwave heating cavity (5); the materials of the belt roller (9), passive rollers, and active rollers are all wave - transmitting materials; the material of the belt (8) is an absorbing - wave flexible heat - resistant material.

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 octagon.

3. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, wherein Both ends of the belt roller (9) are arranged on the inner wall of the microwave heating cavity (5).

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), passive rollers, and active rollers are ceramics, 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 further includes a microwave suppressor (12); the microwave suppressor (12) is arranged outside the through - hole for the tow.

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

7. The microwave heating device for cyclic oxidation of carbon fiber according to claim 1, wherein Power devices are arranged outside the pre - short residence area housing (4) corresponding to the active rollers and winding rollers; power devices are also arranged outside the post - short residence area housing (6) corresponding to the active rollers and winding rollers; and torque sensors are arranged 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, Doors that are convenient to open are arranged on both the pre - short residence area housing (4) and the post - short residence area housing (6).

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

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