A microwave and hot air mixed heating type preoxidation furnace and a preoxidation process

Abstract

The application discloses a microwave and hot air mixed heating type preoxidation furnace and a preoxidation process, which comprises a furnace body, the inner cavity of the furnace body is divided into a middle wire running area and two side air inlet areas and air outlet areas by two groups of current homogenizers, a plurality of guide rollers are installed in the air inlet areas and the air outlet areas, the preoxidized wire is in a reciprocating and returning shape, the preoxidized wire runs around the guide rollers and returns to the wire running area direction, limit rollers are installed at the position close to the wire running area at the lower side of the guide rollers, the preoxidized wire runs around the limit rollers and forms an included angle a, the direction of the preoxidized wire running around the guide rollers is opposite to the direction of the preoxidized wire running around the limit rollers, and the polyacrylonitrile original wire is heated and preoxidized by using hot air and microwaves, the polyacrylonitrile original wire can be maintained at a certain heating temperature based on the hot air, the preoxidation efficiency is improved, the preoxidation time and the hot air temperature are shortened, and the preoxidation efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a carbon fiber pre-oxidation device, more particularly, to a microwave and hot air mixed heating type pre-oxidation furnace, and to a microwave and hot air mixed heating type pre-oxidation process. BACKGROUND

[0002] In the production of carbon fiber, the pre-oxidation furnace as a core device, its performance and energy utilization efficiency have an important influence on the final performance of carbon fiber and production cost.

[0003] The temperature of the pre-oxidation furnace is usually controlled between 200℃ and 300℃, and the polyacrylonitrile (PAN) fiber is blown by hot air to make the PAN fiber undergo cyclization, dehydrogenation, oxygen absorption and other reactions, forming a heat-resistant trapezoidal six-membered ring structure, which is beneficial to the subsequent oxidation process.

[0004] In the pre-oxidation furnace, the inner cavity of the pre-oxidation furnace is divided into a middle fiber running area and two side air inlet and outlet areas by two flow equalizers. In some pre-oxidation processes, a microwave device is usually installed in the fiber running area, which can heat the fiber in the fiber running area by microwave, forming a microwave and hot air mixed heating, which can improve the pre-oxidation efficiency of carbon fiber. However, in the two side air inlet and outlet areas, a microwave device cannot be installed, and the fiber cannot be heated by microwave in the two side air inlet and outlet areas, which leads to the pre-oxidation efficiency of the fiber cannot be further improved. Moreover, since the microwave device cannot be installed in the two side air inlet and outlet areas, the heating and oxidation states of the fiber in the middle fiber running area and the two side air inlet and outlet areas are greatly different, which is not conducive to the stability and uniformity of the fiber pre-oxidation.

[0005] Therefore, a new scheme is needed to solve this problem. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a microwave and hot air mixed heating type pre-oxidation furnace and process.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] The application discloses a microwave and hot air mixed heating type preoxidation furnace, which comprises a furnace body, an inner cavity of the furnace body is divided into a middle wire running area and two side air inlet areas and air outlet areas by two groups of current distributors, a plurality of guide rollers are arranged in the air inlet areas and the air outlet areas, the preoxidation wire is in a reciprocating and returning shape, the preoxidation wire runs from the wire running area, passes through the guide rollers and returns to the wire running area, limit rollers are arranged at positions close to the wire running area on the lower side of the guide rollers, the preoxidation wire passes through the limit rollers and forms an included angle a, the direction in which the preoxidation wire passes through the guide rollers is opposite to the direction in which the preoxidation wire passes through the limit rollers, a plurality of waveguide tubes one and waveguide tubes two are further arranged, the waveguide tubes one are arranged on the top surface or the bottom surface of the wire running area and are used for microwave heating of the preoxidation wire in the wire running area, the air inlet areas and the air outlet areas have opposite end surfaces, the waveguide tubes two are arranged on the end surfaces and are arranged in a plurality of rows, and the waveguide tubes two in each row are arranged along the up-down direction.

[0009] The application further provides that the guide rollers are arranged in parallel in the up-down direction, and each row of the waveguide tubes two is transversely opposite to each guide roller.

[0010] The application further provides that the waveguide tubes two comprise first ports and second ports, the first ports of the waveguide tubes two are connected with a microwave source, and the second ports of the waveguide tubes two are arranged on the end surfaces and are opposite to the guide rollers.

[0011] The application further provides that the limit rollers are arranged on the sides of the guide rollers which are away from the waveguide tubes two, the outer diameters of the limit rollers are smaller than those of the guide rollers, and the guide rollers can shield the waveguide tubes two.

[0012] The application further provides that the outer diameter of the limit rollers 6 is 1 / 3-3 / 4 of the outer diameter of the guide rollers 5, and the guide rollers and the limit rollers are stainless steel rollers.

[0013] The application further provides that the included angle a is 20-45 degrees.

[0014] The application further provides that the length of the preoxidation wire passing through the guide rollers is L1, the length of the preoxidation wire passing through the limit rollers is L2, and L2 is not less than 1 / 8 of L1.

[0015] The application further provides that the end surfaces are provided with feed openings, the second ports of the waveguide tubes two extend into the feed openings, the second ports of the waveguide tubes two are provided with wave penetrating plates, and the wave penetrating plates are made of fused quartz, high-purity aluminum oxide, hexagonal boron nitride or silicon nitride.

[0016] The application further provides that the furnace further comprises a heater for heating gas and a fan for conveying the gas, an air outlet of the fan is communicated with the air inlet areas and is used for conveying hot air to the air inlet areas, and an air inlet of the fan is communicated with the air outlet areas and is used for forming a hot air circulation between the furnace body and the heater.

[0017] The application also provides a microwave and hot air mixed heating type pre-oxidation process, which uses the pre-oxidation furnace in the above embodiment, and can use hot air and microwaves to pre-oxidize the pre-oxidation yarn.

[0018] In summary, the application has the following beneficial effects:

[0019] The polyacrylonitrile precursor yarn is heated and pre-oxidized by using hot air and microwaves, the polyacrylonitrile precursor yarn can be maintained at a certain heating temperature based on the hot air, and the pre-oxidation efficiency is improved by using microwaves for auxiliary pre-oxidation, the pre-oxidation time and the hot air temperature are shortened, and the pre-oxidation efficiency is greatly improved.

[0020] The waveguide pipes are also installed in the air inlet area and the air outlet area on both sides of the wire running area, the waveguide pipes can heat the end position of the pre-oxidation yarn, and the waveguide pipes can also heat the guide rollers, so that the pre-oxidation yarn can contact the guide rollers with higher temperature when passing through the guide rollers, and the pre-oxidation efficiency of the pre-oxidation yarn is improved; in addition, a limiting roller is arranged near the guide roller, the pre-oxidation yarn is reversely bent through the limiting roller, the pre-oxidation yarn is quickly reversely stressed, the stress and shrinkage of the inner and outer sides of the fiber yarn can be reversely compensated, the cortex states of the two sides of the pre-oxidation yarn can be quickly adjusted to a state close to uniformity. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a structure schematic diagram of a microwave and hot air mixed heating type pre-oxidation furnace in embodiment one;

[0022] Figure 2 It is a structure schematic diagram of the installation of waveguide pipe two in embodiment one;

[0023] Figure 3 It is a structure schematic diagram of the guide roller and the limiting roller in embodiment one;

[0024] Figure 4 It is a structure schematic diagram of the furnace body and the hot air channel in embodiment one;

[0025] Figure 5 It is a structure schematic diagram of the furnace body and the hot air channel in embodiment two;

[0026] Figure 6 It is a structure schematic diagram of the communication part of the hot air channel in embodiment two;

[0027] Figure 7 It is a structure schematic diagram of a microwave and hot air mixed heating type pre-oxidation furnace in embodiment three;

[0028] Figure 8 It is a state schematic diagram of the shielding cover in embodiment three;

[0029] Figure 9 This is a schematic diagram of another state of the shielding in Embodiment 3.

[0030] Reference numerals: Furnace body 1; Air inlet zone 101; Wire feeding zone 102; Air outlet zone 103; Flow equalizer 2; Waveguide 1 3; Waveguide 2 4; First port 41; Second port 42; Microwave source 43; Guide roller 5; Limiting roller 6; End face 7; Feed port 71; Wave-transparent plate 8; Hot air channel 9; Heater 91; Fan 92; Connecting part 93; Recessed cavity 931; Shielding cover 932; Through hole 933; Roller 934; Mesh sheet 935; Opening 936; Flow equalizer mesh plate 201; Flow equalizer cavity 202; Wire feeding through hole 203; Wire feeding tube 204; Wire feeding channel 205; Shielding cover 301; Air outlet side 302; First air outlet 303; Second air outlet 304; Shielding baffle 305. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment discloses a pre-oxidation furnace employing a microwave and hot air hybrid heating method, referring to... Figures 1-4 As shown, the furnace body 1 is divided into three chambers by two sets of flow equalizers 2: the middle wire feeding zone 102 and the air inlet zone 101 and air outlet zone 103 on both sides.

[0034] Reference Figure 1 As shown, the pre-oxidizing furnace in this embodiment also includes a heater 91 and a blower 92. The heater heats the gas, and the blower delivers the heated gas to form hot air. The blower's outlet is connected to the inlet zone 101, delivering hot air to the inlet zone 101. The blower's inlet is connected to the outlet zone 103, forming a hot air circulation between the furnace body 1 and the heater. The flow equalizer 2 is a perforated plate, which can evenly distribute the hot air, ensuring that the hot air is evenly distributed and parallel to the wire feeding direction.

[0035] Hot air enters from the inlet zone 101 and is evenly distributed by the flow equalizer 2. This heats the pre-oxidized yarn in the yarn feeding zone 102 before exiting from the outlet zone 103, where it is reheated by the heater, forming a hot air circulation heating process. During the hot air heating process, the temperature in the inlet zone 101 is maintained at 200-260 degrees Celsius. As the hot air flows from the inlet zone 101 to the outlet zone 103, the temperature decreases slightly. The temperature in the inlet zone 101 is higher than that in the outlet zone 103, with a temperature difference of 20-30 degrees Celsius.

[0036] Reference Figure 1 As shown, several guide rollers 5 are installed in both the air inlet zone 101 and the air outlet zone 103, so that the pre-oxidized wires are fed in a reciprocating folding motion, which can extend the length of the pre-oxidized wires in the wire feeding zone 102, so that the pre-oxidized wires have sufficient hot air heating length in the furnace body 1.

[0037] Several waveguides 3 are installed within the wire feeding zone 102 of the furnace body 1, and the waveguides 3 are mounted on the top surface of the wire feeding zone 102. The waveguides 3 are arranged in several rows, with each row of waveguides 3 distributed along the length of the wire feeding zone 102. Furthermore, within each row of the wire feeding zone 102, the waveguides 3 are evenly distributed along the width of the wire feeding zone 102. The waveguides 3 create a microwave heating area within the wire feeding zone 102, enabling mixed heating using hot air and microwaves, thus improving the heating and pre-oxidation effect on the pre-oxidized wire.

[0038] When the pre-oxidized yarn passes through the guide roller 5, it first passes through the through hole on the flow equalizer 2 from the yarn feeding zone 102, then goes around the guide roller 5, then turns back towards the yarn feeding zone 102, passes through the through hole on the flow equalizer 2, and flows back to the yarn feeding zone 102. The pre-oxidized yarn will form a wrap angle at a certain angle on the surface of the guide roller 5.

[0039] The air inlet zone 101 and the air outlet zone 103 have opposing end faces 7, which are the side walls of the front and rear sides of the furnace body 1. A second waveguide 4 is installed on the end face 7, allowing microwave heating of the pre-oxidized wire passing through the air inlet zone 101 and the air outlet zone 103. Furthermore, the microwaves emitted by the second waveguide 4 can also heat the guide roller 5. The guide roller 5 is made of stainless steel, which has higher microwave absorption efficiency and can reach higher temperatures. When the pre-oxidized wire contacts and wraps around the guide roller 5, it can come into contact with the higher-temperature guide roller 5, thus improving the pre-oxidation efficiency at the wrapping point.

[0040] A limiting roller 6 is installed on the lower side of the guide roller 5 near the yarn feeding area 102, and the limiting roller 6 is set in a one-to-one correspondence with the guide roller 5. The pre-oxidized yarn wraps around the limiting roller 6 and forms a wrap angle α, and the direction in which the pre-oxidized yarn wraps around the guide roller 5 is opposite to the direction in which it wraps around the limiting roller 6.

[0041] When the pre-oxidized fiber passes around the guide roller 5 and the limiting roller 6, it first passes around the guide roller 5 for auxiliary heating. When the pre-oxidized fiber passes around the guide roller 5, the fiber forms a certain angle of bending outside the guide roller 5. Because the fiber is bent, the inner and outer sides of the fiber surface will experience different degrees of stress and contraction. Under heating, the cortex on the surface will undergo different states of pre-oxidation denaturation, which may lead to deviation of internal stress on both sides of the pre-oxidized fiber, affecting the strength performance of the fiber. The pre-oxidized fiber then passes through the limiting roller 6 and bends in the opposite direction, which can quickly apply reverse force to the pre-oxidized fiber, so that the stress and contraction on the inner and outer sides of the fiber can be reversed to compensate for the stress and contraction, so as to maintain the cortex state on both sides of the pre-oxidized fiber and quickly adjust the state on both sides of the pre-oxidized fiber to a near-uniform state.

[0042] As the pre-oxidized fiber passes through each guide roller 5 and limiting roller 6, a certain tension is maintained on the pre-oxidized fiber. This ensures that the pressure between the pre-oxidized fiber and the corresponding roller is maintained as the fiber passes through these rollers, allowing for reverse bending compensation. In this embodiment, the tension of the pre-oxidized fiber is controlled at 6000-7000 cN.

[0043] Reference Figure 2 As shown, waveguide 2 4 is arranged in several rows, with each row of waveguide 2 4 arranged along the vertical direction. In a single row of waveguide 2 4, each waveguide 2 4 is evenly arranged along the axial direction of the guide roller 5. The structures of waveguide 1 3 and waveguide 2 4 are roughly the same. Waveguide 2 4 includes a first port 41 and a second port 42. The first port 41 of waveguide 2 4 is connected to a microwave source 43, and the second port 42 of waveguide 2 4 can emit microwaves, which can be directed towards the pre-oxidized wire and the guide roller 5 to perform microwave-assisted pre-oxidation treatment on the pre-oxidized wire, thereby improving the efficiency of the pre-oxidation treatment.

[0044] A feed port 71 is provided on end face 7, and the second port 42 of waveguide 4 extends into the feed port 71. Furthermore, a wave-transparent plate 8 is installed at the second port 42 of waveguide 4. The wave-transparent plate 8 is made of fused silica, high-purity alumina, hexagonal boron nitride, or silicon nitride. The wave-transparent plate 8 can form a shield at the feed port 71, preventing hot air leakage while allowing normal microwave irradiation into the furnace body 1.

[0045] Furthermore, the second port 42 of waveguide 2 4 is directly opposite to the guide roller 5. The guide rollers 5 are arranged vertically in parallel, and each row of waveguide 2 4 is laterally opposite to each guide roller 5. Each row of waveguide 2 4 can heat the guide roller 5, allowing it to maintain a relatively high temperature. The temperature of the guide roller 5 is 20-30 degrees Celsius higher than the surrounding hot air. The relatively high temperature of the guide roller 5 improves the heating and pre-oxidation efficiency at the passing point.

[0046] Normally, when the pre-oxidized fiber passes around the guide roller 5, the angle at which it passes outside the guide roller 5 is about 180°. Due to the reverse limiting action of the limiting roller 6, the limiting roller 6 guides the pre-oxidized fiber in the opposite direction and bends the pre-oxidized fiber in the opposite direction. Therefore, the angle at which it passes outside the guide roller 5 will be slightly greater than 180°.

[0047] Reference Figure 3 As shown, the outer diameter of the limiting roller 6 is 1 / 3 to 3 / 4 of the outer diameter of the guide roller 5, and the wrap angle α of the pre-oxidized wire outside the limiting roller 6 is 20° to 45°. Through a reverse bend of 20° to 45°, a certain reverse bend length is achieved. Specifically, the length of the pre-oxidized wire around the guide roller 5 is L1, and the length of the pre-oxidized wire around the limiting roller 6 is L2. L2 is not less than L1 / 8. Maintaining a certain reverse bend appropriately allows the properties of the two sides of the pre-oxidized wire to be more similar, resulting in more uniform strength properties.

[0048] Furthermore, the limiting roller 6 is located on the side of the guide roller 5 facing away from the second waveguide 4. The outer diameter of the limiting roller 6 is smaller than that of the guide roller 5, and the guide roller 5 can form a shield between the second waveguide 4 and the limiting roller 6. The guide roller 5 can shield the microwave irradiation from the second waveguide 4 towards the limiting roller 6, preventing the microwave from directly irradiating and heating the limiting roller 6. The limiting roller 6 mainly serves to bend the pre-oxidized filament in the opposite direction, preventing the temperature at the limiting roller 6 from becoming too high and affecting the cortical state on both sides of the pre-oxidized fiber.

[0049] This embodiment also discloses a pre-oxidation process using a microwave and hot air hybrid heating method. By using the pre-oxidation furnace as described in the above embodiment, hot air and microwave can be used to pre-oxidize the pre-oxidized filaments.

[0050] Example 2

[0051] This embodiment discloses a pre-oxidation furnace using a microwave and hot air hybrid heating method, which is based on Embodiment 1 and further refers to... Figure 5 , Figure 6 Please provide a detailed explanation.

[0052] The two ends of the hot air duct 9 are connected to the air inlet zone 101 and the air outlet zone 103, respectively. Since waveguide 4 is installed in the air inlet zone 101 and the air outlet zone 103, a microwave wave field exists within their internal spaces. During equipment operation, microwaves in the air inlet zone 101 and the air outlet zone 103 may leak from the connection points with the hot air duct 9. This leakage causes energy loss and, more seriously, damages other electrical components, affecting the overall lifespan of the equipment.

[0053] Reference Figure 5 , Figure 6As shown, a connecting portion 93 is formed at the end of the hot air passage 9 and in the side wall of the air inlet area 101 and the wire feeding area 102, which can connect the hot air passage 9 to the chamber of the furnace body 1. A recessed cavity 931 is formed on the inner side of the furnace wall at the connecting portion 93, and the recessed cavity 931 has an opening 936 facing the inner cavity of the furnace body 1.

[0054] A shielding cover 932 is installed on the upper side of the opening 936, which covers the opening 936. The shielding cover 932 has several through holes 933. The through holes 933 allow hot air to pass through and isolate microwaves from passing through.

[0055] Furthermore, a roller 934 is rotatably mounted within the recessed cavity 931, and a plurality of perforated sheets 935 are arranged in a row on the outer periphery of the roller 934. The inner cavity of the recessed cavity 931 forms an arc-shaped structure, and the circle of the inner wall of the arc coincides with the rotation center of the roller 934. During the rotation of the perforated sheets 935, a gap is formed between the edge of the perforated sheets 935 and the inner wall of the recessed cavity 931, forming a narrow slit. The perforations on the surface of the perforated sheets 935, and the gap between the perforated sheets 935 and the inner wall of the recessed cavity 931, all prevent microwave leakage.

[0056] Reference Figure 6 As shown, the hot air channel 9 is connected to the lower side of the recessed cavity 931, and the connection port is located at an eccentric position on the roller 934, roughly tangentially. Furthermore, the through-hole 933 on the shielding cover 932 is only opened at certain locations, directly above the connection port of the hot air channel 9. During the flow of hot air through the connecting part 93, the hot air channel 9 can drive the roller 934 and the mesh sheet 935 within the connecting part 93 to rotate. This allows for normal hot air flow while the multiple mesh sheets 935 within the recessed cavity 931 provide shielding, creating a barrier against microwaves and reducing microwave leakage.

[0057] At the connection between the hot air channel 9 and the furnace body 1, a structure with multiple microwave shielding and leakage prevention is formed. This ensures that the hot air can pass through normally while shielding and blocking the microwaves as much as possible, preventing leakage of microwaves from causing loss and avoiding damage to external electrical components.

[0058] Example 3

[0059] This embodiment discloses a pre-oxidation furnace using a microwave and hot air hybrid heating method, which is based on Embodiment 1 and further refers to... Figures 7-9 Please provide a detailed explanation.

[0060] In this embodiment, the flow equalizer 2 includes two layers of flow equalization mesh plates 201, which are arranged in parallel and have mesh openings for the passage of hot air. In each set of flow equalizers 2, a flow equalization cavity 202 is formed between the two layers of flow equalization mesh plates 201, that is, the inner cavity of the furnace body 1 forms five chambers from left to right, namely the air inlet zone 101, the first flow equalization cavity 202, the wire feeding zone 102, the second flow equalization cavity 202, and the air outlet zone 103.

[0061] Two shielding covers 301 are also installed inside the furnace body 1. The shielding covers 301 are located on the lower side of the flow equalizers 2 on both sides. The shielding cover 301 on the left side is located on the lower side of the air inlet zone 101 and the flow equalizer 202, and the shielding cover 301 on the right side is located on the lower side of the air outlet zone 103 and the flow equalizer 202.

[0062] In this embodiment, the air outlet (left end) of the hot air duct 9 is connected to the left-side shield 301, and the air return (right end) of the hot air duct 9 is connected to the right-side shield 301. An air outlet side 302 is formed on the upper side of the shield 301, and a first air outlet 303 and a second air outlet 304 are formed on the upper side of the air outlet side 302. The first air outlet 303 has a plurality of air outlet through holes, and the second air outlet 304 has a plurality of air outlet through holes.

[0063] In this embodiment, both flow equalization mesh plates 201 are metal mesh plates. The flow equalization mesh plates 201 are provided with wire feeding holes 203 for fiber filaments to pass through. In the same flow equalizer 2, the wire feeding holes 203 of the two flow equalization mesh plates 201 are parallel and opposite to each other. A plurality of wire feeding tubes 204 are fixedly connected between the two flow equalization mesh plates 201. The two ends of the wire feeding tubes 204 are respectively fixedly connected to the wire feeding holes 203 of the two flow equalization mesh plates 201, and a wire feeding channel 205 for fiber filaments to pass through is formed in the middle of the wire feeding tubes 204.

[0064] The wire feed tubes 204 are connected to the flow equalization mesh plates 201 at both ends, and both are made of metal. Heat can be conducted relatively efficiently between the wire feed tubes 204 and the flow equalization mesh plates 201, which can maintain the wire feed tubes 204 at a relatively uniform temperature.

[0065] In the left shield 301, the upper side of the first air outlet 303 is connected to the air inlet area 101, and the upper side of the second air outlet 304 is connected to the flow equalization cavity 202. Hot air can be delivered from the first air outlet 303 and the second air outlet 304 to the air inlet area 101 and the flow equalization cavity 202, respectively. The right shield 301 is roughly symmetrical to the left shield 301. In the right shield 301, the upper side of the first air outlet 303 is connected to the air outlet area 103, and the upper side of the second air outlet 304 is connected to the flow equalization cavity 202. Hot air can be delivered from the first air outlet 303 and the second air outlet 304 to the air outlet area 103 and the flow equalization cavity 202, respectively.

[0066] A shielding baffle 305 is also installed inside the shielding cover 301. The shielding baffle 305 can slide in the left and right direction inside the shielding cover 301 and can slide to the lower side of the first air outlet 303 or the second air outlet 304 to shield the air outlet holes of the first air outlet 303 or the second air outlet 304.

[0067] In this embodiment, during the circulation process, the hot air can switch between the first air outlet 303 and the second air outlet 304 by sliding the shielding baffle 305. When the shielding baffle 305 moves to the first air outlet 303, it can block and seal the first air outlet 303. During the flow process, the hot air can enter the left shielding cover 301 from the hot air channel 9, and then flow upward from the second air outlet 304 of the shielding cover 301. The hot air can enter between the flow equalization mesh plates 201 and enter the furnace body 1. It can flow from the left flow equalization cavity 202 to the middle wire feeding area 102, and then to the right flow equalization cavity 202. Finally, it flows out from the second air outlet 304 of the shielding cover 301 below the flow equalization cavity 202, and then enters the hot air channel 9 from the shielding cover 301. A hot air circulation can be formed between the hot air channel 9, the left shielding cover 301, the left flow equalization cavity 202, the wire feeding area 102, the right flow equalization cavity 202, the right shielding cover 301, and the hot air channel 9. During the hot air circulation heating process, the hot air entering the furnace body 1 first enters the flow equalization chamber 202. Since the flow equalization chamber 202 contains a fiber guide tube 204, the fiber filaments can pass through it, creating a separation between the hot air and the limiting wire. This prevents turbulence generated when the hot air first enters from affecting the fiber filaments and avoids uneven heating caused by uneven hot air. During circulation, the hot air avoids turbulent hot air directly blowing on the fiber filaments. Then, the hot air enters the fiber guide zone 102 from the flow equalization chamber 202. In the fiber guide zone 102, the hot air is in a uniform flow state, maintaining uniform heating of the fibers within the zone and preventing excessive turbulence from causing instability in the fiber filaments.

[0068] During the hot air circulation process, the shielding baffle 305 can be slidably adjusted to move to the second air outlet 304, closing the second air outlet 304 and opening the first air outlet 303. During the hot air purging process, the hot air can enter the air inlet area 101 from the first air outlet 303 on the upper side of the shielding cover 301. The hot air first enters the air inlet area 101, which can heat the ambient temperature in the air inlet area 101 to maintain a suitable temperature. Then, the hot air will move towards... The air flows from the right side, passes through the flow equalizer 2, and enters the yarn feeding zone 102, where it continuously and stably heats the fibers. Then, the hot air enters the right-side air outlet zone 103, flows out from the first air outlet 303 of the shield 301 below the air outlet zone 103, enters the shield 301, and then flows back through the hot air channel 9. When the hot air enters the air outlet zone 103, it can also heat the ambient temperature inside the air outlet zone 103 to maintain it at an appropriate heating temperature.

[0069] In addition, during the hot air circulation process, the shielding baffle 305 can be slidably adjusted to be positioned between the first air outlet 303 and the second air outlet 304, keeping both the first and second air outlets partially open and partially blocked. This allows for adjustment of the openness of the first and second air outlets 303 and 304, creating two hot air flow paths and splitting the hot air between them. This maintains the heat supply to the air inlet zone 101 and the air outlet zone 103 while preventing excessive hot air from directly causing instability and disturbance to the fiber filaments in the air inlet zone 101 and the air outlet zone 103. During the hot air circulation process, the shielding baffle 305 can be adjusted and switched to maintain the furnace body 1 within an appropriate overall range.

[0070] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A pre-oxidation furnace employing a microwave and hot air hybrid heating method, characterized in that, The furnace includes a furnace body (1). The inner cavity of the furnace body (1) is divided into a middle wire feeding zone (102) and two sides of air inlet zone (101) and air outlet zone (103) by two sets of flow equalizers (2). Several guide rollers (5) are installed in the air inlet zone (101) and the air outlet zone (103) to make the pre-oxidized wire feed in a reciprocating folding manner. The pre-oxidized wire passes around the guide roller (5) from the wire feeding zone (102) and then folds back towards the wire feeding zone (102). A limit roller (6) is installed on the lower side of the guide roller (5) near the wire feeding zone (102). The pre-oxidized wire passes around the limit roller (6) and forms a wrap angle a. The direction of the guide roller (5) is opposite to the direction of the guide roller (6); it also includes several waveguides 1 (3) and waveguides 2 (4). The waveguides 1 (3) are installed on the top or bottom surface of the wire feeding area (102) for microwave heating of the pre-oxidized filament in the wire feeding area (102). The air inlet area (101) and the air outlet area (103) have opposite end faces (7). The waveguides 2 (4) are installed on the end face (7) and are arranged in several columns. Each column of waveguides 2 (4) is arranged along the vertical direction. In a single column of waveguides 2 (4), each waveguide 2 (4) is evenly arranged along the axial direction of the guide roller (5).

2. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, Each guide roller (5) is arranged in parallel vertically, and each waveguide duct (4) is horizontally opposite to each guide roller (5).

3. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, The waveguide 2 (4) includes a first port (41) and a second port (42). The first port (41) of the waveguide 2 (4) is connected to a microwave source, and the second port (42) of the waveguide 2 (4) is installed on the end face (7) and is directly opposite to the guide roller (5).

4. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, The limiting roller (6) is located on the side of the guide roller (5) facing away from the waveguide duct 2 (4). The outer diameter of the limiting roller (6) is smaller than that of the guide roller (5). The guide roller (5) can shield the waveguide duct 2 (4).

5. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 4, characterized in that, The outer diameter of the limiting roller (6) is 1 / 3 to 3 / 4 of the outer diameter of the guide roller (5), and both the guide roller (5) and the limiting roller (6) are stainless steel rollers.

6. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, The wrap angle α is 20° to 45°.

7. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, The length of the pre-oxidized fiber passing over the guide roller (5) is L1, and the length of the pre-oxidized fiber passing over the limiting roller (6) is L2, where L2 is not less than L1 / 8.

8. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, The end face (7) is provided with a feed port (71), and the second port (42) of the second waveguide (4) extends into the feed port (71). A wave-transparent plate (8) is installed on the second port (42) of the second waveguide (4). The wave-transparent plate (8) is made of fused silica, high-purity alumina, hexagonal boron nitride, or silicon nitride.

9. The microwave and hot air hybrid heating pre-oxidation furnace according to claim 1, characterized in that, It also includes a heater for heating the gas and a fan for conveying the gas. The outlet of the fan is connected to the air inlet area (101) for conveying hot air to the air inlet area (101), and the air inlet of the fan is connected to the air outlet area (103) for forming a hot air circulation between the furnace body (1) and the heater.

10. A pre-oxidation process employing a combination of microwave and hot air heating, characterized in that, The microwave and hot air hybrid heating pre-oxidation furnace as described in any one of claims 1-9 can be used to pre-oxidize pre-oxidized fibers using hot air and microwave.

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