Microwave hot air mixed heating type preoxidation furnace using waveguide

Abstract

The utility model discloses a kind of microwave hot air mixed heating type preoxidation furnace of waveguide tube, including furnace body, heater, fan and microwave heating device, wire area is formed inside furnace body, wire area width is W, microwave heating device includes microwave source and waveguide tube, waveguide tube includes first port and second port, the first port of waveguide tube is connected microwave source, the second port of waveguide tube is distributed in the top surface and / or bottom surface of wire area, the narrow side of the second port of waveguide tube is parallel with wire area width direction, the long side of the second port of waveguide tube is parallel with wire area length direction, the quantity of waveguide tube is at least one column, single column waveguide tube is evenly arranged along wire area width direction.The utility model can reduce reaction time and reaction temperature.

Description

Technical Field

[0001] This utility model relates to the field of pre-oxidation furnaces, and more specifically, to a microwave hot air hybrid heating pre-oxidation furnace using a waveguide. Background Technology

[0002] Currently, the oxidation furnace is the core equipment in carbon fiber production, and the pre-oxidation of precursor fibers plays a crucial role in the process, directly affecting the final performance of carbon fibers.

[0003] Pre-oxidation is a crucial step in the preparation of polyacrylonitrile (PAN)-based carbon fibers. In a pre-oxidation furnace at 200℃–300℃, PAN precursor fibers undergo cyclization, dehydrogenation, and oxygen absorption reactions, transforming the linear molecular chains into heat-resistant trapezoidal six-membered ring structures. The color of the PAN fibers changes from white to golden yellow, then brown, and finally black, ensuring that PAN-based carbon fiber products do not melt or burn during high-temperature carbonization. In the industrial production of carbon fibers, the pre-oxidation furnace heats the gas via electric heating tubes and then the fiber bundle via hot air, resulting in low energy efficiency. The entire process uses four to six pre-oxidation furnaces with gradient heating, and the pre-oxidation time is typically 60-90 minutes, accounting for approximately 90% of the entire carbon fiber production process. These multiple pre-oxidation furnaces consume about 65% of the total power of the production line.

[0004] Polyacrylonitrile (PAN) precursor fibers have very low dielectric constants and loss factors, making microwave heating of the fibers inefficient. Current research involves coating the surface of PAN precursor fibers with a highly stable microwave-absorbing coating, followed by microwave heating for pre-oxidation. For example, patent CN111691012A discloses an electrically controlled microwave pre-oxidation process for PAN precursor fibers, which involves coating the fiber surface with a carbon black coating for microwave pre-oxidation. The coating process often employs an impregnation and drying process, with the PAN precursor fibers impregnated for 20 minutes or using multiple short impregnations, increasing production line investment and subsequent production costs. Due to the inherent characteristics of microwaves, a distinct microwave field distribution exists within the cavity. Directly heating the microwave-absorbing coating for pre-oxidation places extremely high demands on the temperature detection and control of the fiber bundle within the furnace. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microwave-hot-air hybrid heating pre-oxidation furnace using a waveguide. By heating with both hot air and microwaves, the pre-oxidation reaction process can be accelerated, the reaction time and temperature reduced, and lower energy consumption achieved.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A microwave hot air hybrid heating pre-oxidation furnace employing a waveguide includes a furnace body, a heater for heating gas, a fan for conveying gas, and a microwave heating device. A wire-feeding zone is formed inside the furnace body, the wire-feeding zone having a length of L and a width of W. The furnace body includes an air inlet, an air outlet, a wire bundle inlet, and a wire bundle outlet. The wire-feeding zone is located between the wire bundle inlet and the wire bundle outlet and connects the wire bundle inlet and the wire bundle outlet. The wire-feeding zone is also located between the air inlet and the air outlet and connects the air inlet and the air outlet. The fan... The delivery gas enters from the air inlet and exits from the air outlet. The microwave heating device includes a microwave source and a waveguide. The waveguide includes a first port and a second port. The first port of the waveguide is connected to the microwave source. The second ports of the waveguide are distributed on the top and / or bottom surfaces of the wire-feeding area. The narrow side of the second port of the waveguide is parallel to the width direction of the wire-feeding area, and the long side of the second port of the waveguide is parallel to the length direction of the wire-feeding area. The number of waveguides is at least one row, and the single row of waveguides is uniformly arranged along the width direction of the wire-feeding area.

[0008] As a further setting, the center distance between single-row waveguides satisfies d≤2.25*λ^0.845, where λ is the microwave wavelength.

[0009] As a further setting, the number of single-row waveguides is n = floor(W / d), where d is the center distance between the single-row waveguides.

[0010] As a further setting, when the microwave power deviation fed into each waveguide of a single-row waveguide is out-of-order deviation, the deviation value is less than or equal to 9%.

[0011] As a further setting, when the microwave power deviation of each waveguide in a single-row waveguide is positive or negative, the deviation value is less than or equal to 30%.

[0012] As a further configuration, each waveguide in a single-row waveguide is either in phase or differs by 2n*pi.

[0013] As a further setting, when the phase of each waveguide in a single-row waveguide is symmetrically deviated, the phase deviation of each waveguide in a single-row waveguide is ≤3° or differs by 2n*pi on this basis.

[0014] As a further configuration, the frequency of the microwave source is 915MHz and / or 2450MHz. The wavelength λ corresponding to the frequency of 915MHz is 328mm, the wavelength λ corresponding to the frequency of 2450MHz is 122mm, the opening cross-sectional size of the second port of the waveguide corresponding to the frequency of 915MHz is 248mm x 124mm, and the opening cross-sectional size of the second port of the waveguide corresponding to the frequency of 2450MHz is a rectangle of 86mm x 43mm.

[0015] As a further configuration, the waveguides are arranged in multiple rows and simultaneously distributed on the top or bottom surface of the wire-running area. Each row of waveguides has the same frequency, the center distance d between individual rows of waveguides is the same, the phase is the same or not, and the power is the same or not.

[0016] As a further configuration, the waveguides are in multiple rows, with at least one row distributed on the top surface of the wire-running area and at least one row distributed on the bottom surface of the wire-running area. The single-row waveguides located on the top surface of the wire-running area and the single-row waveguides located on the bottom surface of the wire-running area may have the same or different frequencies, the center distance d between the single-row waveguides may be the same or different, the phase may be the same or different, and the power may be the same or different.

[0017] As a further configuration, the single-row waveguide is offset to one side in the width direction of the wire-feeding zone, with an eccentricity distance P≤0.005*λ^1.592, where λ is the microwave wavelength.

[0018] As a further feature, the furnace body is provided with a feed port on the top and / or bottom surface of the wire feeding zone. The feed port corresponds one-to-one with the waveguide, and the projection of the feed port at the second port of the waveguide falls within the range of the second port of the waveguide.

[0019] As a further configuration, the feed opening can be circular, oval, elliptical, or rectangular in shape.

[0020] As a further configuration, the elliptical feed port, the waist-shaped feed port, and the rectangular feed port are deflected at a certain angle relative to the waveguide.

[0021] As a further feature, the two ends of the wire feeding zone along its length are defined by perforated plates, the distance between the two perforated plates at both ends of the wire feeding zone is L, and the perforated plates are provided with through holes that pass through both ends.

[0022] As a further feature, the perforated plate has at least two perforated plates at each end of the wire feeding zone along its length, and the through holes of the multiple perforated plates at the same end are arranged in a staggered manner.

[0023] As a further feature, the diameter of the through hole is less than or equal to 0.25*λ, where λ is the microwave wavelength.

[0024] As a further setting, the spacing between multiple perforated plates at the same end is less than or equal to λ, where λ is the microwave wavelength.

[0025] As a further feature, a wave-transparent plate is provided at the connection between the waveguide and the feed port. The wave-transparent plate is made of fused silica, high-purity alumina, hexagonal boron nitride, or silicon nitride.

[0026] In summary, this invention has the following advantages: without any treatment of the polyacrylonitrile precursor fiber, the microwaves form a uniform electric field distribution in the direction perpendicular to the fiber bundle's movement within the fiber-carrying zone through hot air microwave coupling technology, ensuring uniform pre-oxidation of the fiber bundle during operation; the microwave-enhanced acceleration of the pre-oxidation process can shorten the pre-oxidation time and reduce the reaction temperature, significantly improving production efficiency and thus reducing the production cost of the carbon fiber pre-oxidation process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an embodiment;

[0028] Figure 2 for Figure 1 Sectional view along the middle AA direction;

[0029] Figure 3 for Figure 1 Sectional view along the BB direction;

[0030] Figure 4 This is a schematic diagram showing the distribution of the perforated plate in an embodiment;

[0031] Figure 5 This is a partial top view of an embodiment;

[0032] Figure 6 Simulation diagram showing that the center of the elliptical feed port does not coincide with the center of the waveguide;

[0033] Figure 7 Simulation diagram showing the center of the circular feed port coinciding with the center of the waveguide;

[0034] Figure 8 Simulation diagram of a waist-shaped feed port deflected at a certain angle;

[0035] Figure 9 A simulation diagram of a rectangular feed port deflected at a certain angle;

[0036] Figure 10 Simulation diagram of an elliptical feed port deflected at a certain angle;

[0037] Figure 11 The simulation diagram shows the distribution of an array with a wavelength of 328 mm and a diameter of 300 mm when rotated by 90 degrees.

[0038] Figure 12 The simulation diagram shows the distribution of an array with a wavelength of 122mm and a d of 100mm when rotated 90 degrees.

[0039] Figure 13 The simulation diagram shows the center distance d deviating from the uniform distribution by ±4mm.

[0040] Figure 14 The simulation diagram shows the center distance d deviating from the uniform distribution by ±2mm.

[0041] Figure 15 The simulation diagram is for a frequency of 2450MHz and d=130mm;

[0042] Figure 16 The simulation diagram is for a frequency of 2450MHz and d = 135mm;

[0043] Figure 17 The simulation diagram is for a frequency of 2450MHz and d = 128mm;

[0044] Figure 18 The simulation diagram is for a frequency of 915MHz and d = 300mm;

[0045] Figure 19 The simulation diagram is for a frequency of 915MHz and d = 298mm;

[0046] Figure 20 The simulation diagram is for a frequency of 915MHz and d = 302mm;

[0047] Figure 21 The simulation diagram is for a frequency of 915MHz and d = 304mm;

[0048] Figure 22 The simulation diagram is for a frequency of 915MHz and d = 360mm;

[0049] Figure 23 The simulation diagram is for a frequency of 915MHz, d=360mm, and n=4.

[0050] Figure 24 The simulation diagram is for a frequency of 915MHz, d=360mm, and n=3.

[0051] Figure 25 The simulation diagram is for a frequency of 2450MHz, d=100mm, and n=5.

[0052] Figure 26 The simulation diagram is for a frequency of 2450MHz, d=100mm, and n=4.

[0053] Figure 27 Simulation diagrams for microwave powers of 500, 495, 500, 505, and 500.

[0054] Figure 28 Simulation diagrams for microwave powers of 500, 495, 505, 500, and 495.

[0055] Figure 29 Simulation diagrams for microwave powers of 475, 525, 500, 500, and 475.

[0056] Figure 30 Simulation diagrams for microwave powers of 455, 500, 500, 545, and 455.

[0057] Figure 31 Simulation diagrams for microwave powers of 500, 450, 550, 500, and 450.

[0058] Figure 32 Simulation diagrams for microwave powers of 500, 450, 500, 550, and 500.

[0059] Figure 33 Simulation diagrams for microwave powers of 500, 400, 500, 600, and 500.

[0060] Figure 34 Simulation diagrams for microwave powers of 650, 500, 500, 500, and 350.

[0061] Figure 35 Simulation diagrams for microwave powers of 500, 675, 500, 325, and 500.

[0062] Figure 36 Simulation diagrams for microwave powers of 725, 500, 500, 500, and 275.

[0063] Figure 37 Simulation diagrams for microwave powers of 500, 900, 500, 100, and 500.

[0064] Figure 38 Simulation diagrams for microwave powers of 1000, 700, 1000, 1300, 700, 1000, 1300, and 1000.

[0065] Figure 39 Simulation diagrams for microwave powers of 1000, 600, 1000, 1400, 600, 1000, 1400, and 1000.

[0066] Figure 40 Simulation diagrams for phase values ​​of 0, -pi / 180, pi / 180, -pi / 180, and 0;

[0067] Figure 41 Simulation diagrams for phases of 0, -pi / 180, 0, pi / 180, 0;

[0068] Figure 42 Simulation diagrams for phases 0, -pi / 60, 0, pi / 60, 0;

[0069] Figure 43 Simulation diagrams for phases 0, -pi / 36, 0, pi / 36, 0;

[0070] Figure 44 Simulation diagrams for phases 0, -pi / 18, 0, pi / 18, 0;

[0071] Figure 45 Simulation diagrams for phases 0, -pi / 2, 0, pi / 2, 0;

[0072] Figure 46 Simulation diagrams for phases 0, pi / 60, 0, -pi / 60, pi / 60, 0, -pi / 60, 0;

[0073] Figure 47 Simulation diagrams for phases 0, pi / 36, 0, -pi / 36, pi / 36, 0, -pi / 36, 0;

[0074] Figure 48 Simulation diagram of two waveguides with a d-d difference of 10mm;

[0075] Figure 49 Simulation diagram of two waveguides with a d-d difference of 1mm;

[0076] Figure 50 Simulation diagrams of waveguides distributed on the top and bottom surfaces of the wire-feeding area;

[0077] Figure 51 The simulation diagram is for a frequency of 2450MHz, a wavelength of 122mm, and an eccentricity of 10mm.

[0078] Figure 52 The simulation diagram is for a frequency of 2450MHz, a wavelength of 122mm, and an eccentricity of 12mm.

[0079] Figure 53 The simulation diagram is for a frequency of 915MHz, a wavelength of 122mm, and an eccentricity of 40mm.

[0080] Figure 54 The simulation diagram is for a frequency of 915MHz, a wavelength of 122mm, and an eccentricity of 50mm.

[0081] Figure 55 The simulation diagram is for a frequency of 915MHz, a wavelength of 122mm, and an eccentricity of 55mm.

[0082] Figure labels: 1. Fan, 2. Heater, 3. Furnace body, 31. Air inlet, 32. Air outlet, 33. Wire bundle inlet, 34. Wire bundle outlet, 4. Feed port, 5. Waveguide, 6. Microwave source, 7. Mesh plate, 71. Through hole, 8. Transparent plate. Detailed Implementation

[0083] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0084] Reference Figures 1-5 As shown, this embodiment discloses a microwave hot air hybrid heating pre-oxidation furnace using a waveguide, referring to... Figure 1 It includes a furnace body 3, a heater 2 for heating the gas, a blower 1 for conveying the gas, and a microwave heating device. A fiber feeding zone is formed inside the furnace body 3. The fiber feeding zone is distributed along the length of the furnace body 3 and serves as a space for fiber pre-oxidation treatment. The length of the fiber feeding zone is L and the width is W.

[0085] Reference Figure 1 The furnace body 3 includes an air inlet 31, an air outlet 32, a filament inlet 33, and a filament outlet 34. The filament feeding zone is located between the filament inlet 33 and the filament outlet 34 and the filament feeding zone connects the filament inlet 33 and the filament outlet 34. The filament enters from the filament inlet 33, and after being heated by hot air and microwaves in the filament feeding zone, it leaves from the filament outlet 34.

[0086] Reference Figure 1 The wire feeding zone is located between the air inlet 31 and the air outlet 32, and the wire feeding zone connects the air inlet 31 and the air outlet 32. The blower 1 delivers gas from the air inlet 31 and exhausts it from the air outlet 32. The heater 2 heats the gas in the furnace body 3 so that the gas temperature reaches the temperature required for the pre-oxidation reaction. The blower 1 blows the heated gas into the air inlet 31 and heats the wire bundle in the wire feeding zone. The gas is finally discharged from the air outlet 32 ​​and is heated again and blown into the air inlet 31 by the blower 1. This cycle continues.

[0087] Reference Figure 2 , Figure 4 The wire feeding zone is defined at both ends by perforated plates 7 located within the furnace body 3. The distance between the two perforated plates 7 at both ends of the wire feeding zone is L. The perforated plates 7 have through holes 71 extending through both ends. The diameter of the through holes 71 is less than or equal to 0.25*λ, where λ is the microwave wavelength. The perforated plates 7 are made of metal and are used to evenly distribute hot air, ensuring that the hot air is evenly distributed and blown into the wire feeding zone parallel to the wire feeding direction. At the same time, the perforated plates 7 shield microwave energy from entering other areas through the through holes 71, thus protecting the normal operation of components such as the fan 1 and heater 2.

[0088] Reference Figure 2 , Figure 4At least two perforated plates 7 are provided at each end of the wire feeding zone along its length, and the through holes 71 of multiple perforated plates 7 at the same end are arranged in a staggered manner. Figure 4 The through-holes 71 with dark solid lines and those with light solid lines represent two staggered mesh plates 7. The spacing between multiple mesh plates 7 at the same end is less than or equal to λ. By setting multiple mesh plates 7 at the same end, the hot air distribution and microwave shielding functions can be better achieved.

[0089] The microwave heating device includes a microwave source 6 and a waveguide 5. The waveguide 5 is connected to the microwave source 6 and is a purchased component. The waveguide 5 includes a first port and a second port. The first port and the second port are formed at both ends of the waveguide 5 along its length. The first port of the waveguide 5 is connected to the microwave source 6. The second port of the waveguide 5 is distributed on the top and / or bottom surface of the wire-walking area. The microwaves fed by the microwave source 6 enter from the first port of the waveguide 5 and exit from the second port of the waveguide 5 before being fed into the wire-walking area. The opening of the second port of the waveguide 5 is rectangular. The frequency of the microwave source 6 is 915MHz and / or 2450MHz. The wavelength λ corresponding to the frequency 915MHz is 328mm, and the wavelength λ corresponding to the frequency 2450MHz is 122mm. The cross-sectional dimensions of the opening of the second port of the waveguide 5 corresponding to the frequency 915MHz are 248mm x 124mm, and the cross-sectional dimensions of the opening of the second port of the waveguide 5 corresponding to the frequency 2450MHz are 86mm x 43mm. These cross-sectional dimensions are standard models corresponding to the frequencies.

[0090] The fiber-carrying zone is the working area of ​​the microwave heating device. Microwaves create a uniform electric field distribution perpendicular to the fiber-carrying plane, ensuring uniform pre-oxidation of the fiber during its movement. Since the fiber-carrying plane is horizontal, microwaves are fed into the top and bottom surfaces of the zone to ensure the microwave electric field is perpendicular to the fiber-carrying plane. Microwaves assist in heating the precursor fiber and accelerate the pre-oxidation reaction, shortening the reaction time and lowering the reaction temperature.

[0091] Reference Figure 2 , Figure 3 The furnace body 3 is provided with a feed port 4 on the top and / or bottom surface of the wire feeding area. The feed port 4 corresponds one-to-one with the waveguide 5, that is, the feed port 4 and the opening of the second port of the waveguide 5 are directly opposite each other. The microwave of the waveguide 5 is fed into the wire feeding area through the feed port 4.

[0092] The projection of feed port 4 onto waveguide 5 falls within the area where waveguide 5 is located. The center of feed port 4 and the center of waveguide 5 may or may not coincide. (Refer to...) Figure 6 The feed port 4 is elliptical in shape, and its center does not coincide with the center of the waveguide 5. The electric field intensity along the width of the same column is consistent, meeting the requirements. (Refer to...) Figure 7The feed port 4 is circular, and its center coincides with the center of the waveguide 5. The electric field strength in the same width direction is consistent, which meets the requirements. The size of the feed port 4 is smaller than the opening cross-sectional size of the second port of the waveguide 5 and does not exceed the opening cross-sectional range of the second port of the waveguide 5.

[0093] The feed port 4 is circular, elliptical, waist-shaped, or rectangular. The circular, waist-shaped, elliptical, or rectangular feed port 4 is located within the range defined by the rectangular opening of the second port of the waveguide 5 and does not exceed its defined range.

[0094] Waist-shaped feed opening 4 ( Figure 8 ), rectangular feed opening 4 ( Figure 9 ), elliptical feed port 4 ( Figure 10 The feed port 4 is deflected by a certain angle relative to the waveguide 5. Specifically, the center of the elliptical feed port 4, the waist-shaped feed port 4, and the rectangular feed port 4 are aligned with the center of the rectangular opening of the second port of the waveguide 5 and deflected by a certain angle, while not exceeding the range defined by the rectangular opening of the second port of the waveguide 5.

[0095] Reference Figure 2 , Figure 3 A wave-transparent plate 8 is provided at the connection between the waveguide 5 and the feed port 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 ensures microwave feed while preventing hot air from entering the waveguide 5.

[0096] The furnace body 3, where the waveguide 5 and feed port 4 are located, is detachably connected for easy maintenance. Alternatively, the furnace body 3, where the waveguide 5 and feed port 4 are located, is welded together for reliable connection.

[0097] Multiple waveguides 5 are connected to a single microwave source 6 via a power divider, meaning one microwave source 6 inputs microwaves to the corresponding multiple waveguides 5. Alternatively, each waveguide 5 is connected to a microwave source 6, meaning one microwave source 6 inputs microwaves to the corresponding waveguide 5. The microwave source 6 is a solid-state microwave source, each equipped with its own phase-locked loop (PLL), which ensures the consistency of each solid-state microwave source.

[0098] The narrow side of the second port of waveguide 5 is parallel to the width direction of the wire-feeding region, and the long side of the second port of waveguide 5 is parallel to the length direction of the wire-feeding region. (Refer to...) Figure 11 (wavelength 328mm, center distance d is 300mm) Figure 12(Wavelength 122mm, center distance d = 100mm), the horizontal axis represents the length of the furnace body, and the vertical axis represents the width of the furnace body. This figure shows the electric field distribution of the furnace body on a plane at a certain height. The different colors of the legend on the far right indicate the magnitude of the electric field intensity on this plane. In the microwave-enhanced pre-oxidation process, the uniformity of the electric field distribution directly affects the thermal oxidation reaction process of the filament bundles. Areas with higher electric field intensity have a higher degree of oxidation. Uneven electric field distribution will cause inconsistent pre-oxidation degrees of the filament bundles in different width directions, and may even cause filament breakage, seriously restricting the consistency control of the final product. Therefore, it is necessary to ensure the consistency of the electric field intensity in any "column" width direction on any plane at any height of the furnace body. Let the length of the furnace body be the X-coordinate, the width be the Y-coordinate, and the height be the Z-coordinate, that is, the electric field intensity on the line where the XY plane and the YZ plane intersect at any height of the furnace body must be consistent. Figure 12 The colored area is the wire-feeding region. When the narrow side of the second port of waveguide 5 is parallel to the length direction of the wire-feeding region, and the long side of the second port of waveguide 5 is parallel to the width direction of the wire-feeding region, that is, when the second port of waveguide 5 is rotated 90 degrees, refer to... Figure 11 It is an array with a wavelength of 328 mm and a center-to-center distance d between waveguides 5 of 300 mm; refer to Figure 12 It is an array with a wavelength of 122mm and a center distance d between waveguides 5 of 100mm, and it can be seen that the electric field strength is inconsistent.

[0099] The waveguides 5 are arranged in at least one row, with each row of waveguides 5 uniformly arranged along the width of the wire-running zone. (Refer to...) Figure 13 The center distance d between the five waveguides 5 deviates from a uniform distribution by ±4mm, meaning the center distance d between the five waveguides 5 is inconsistent, which does not meet the requirements. (Refer to...) Figure 14 The center distance d between the five waveguides 5 deviates from the uniform distribution by ±2mm, which does not meet the requirements.

[0100] The center-to-center distance between the single-row waveguides 5 satisfies d ≤ 2.25 * λ^0.845. When the frequency is 2450 MHz and the wavelength is 122 mm, d ≤ 130 mm. Figure 15 The center distance d = 130mm, which meets the requirements. Figure 3 , Figure 5 This is reflected in the text.

[0101] Reference Figure 16 When the frequency is 2450MHz and d is 135mm, the electric field strength in the same column width direction is inconsistent, which does not meet the requirements.

[0102] Reference Figure 17 When the frequency is 2450MHz and the diameter (d) is 128mm, the requirements are met.

[0103] When the frequency is 915MHz and the wavelength is 328mm, d≤300mm. Figure 18 The diameter d = 300mm, which meets the requirements.

[0104] When the frequency is 915MHz and d = 298mm, refer to Figure 19 The requirements are met.

[0105] When the frequency is 915MHz and d = 302mm, refer to Figure 20 At this point, the consistency of the electric field strength has begun to deviate and does not meet the requirements.

[0106] When the frequency is 915MHz and d = 304mm, refer to Figure 21 This does not meet the requirements.

[0107] When the frequency is 915MHz and d = 360mm, refer to Figure 22 This does not meet the requirements.

[0108] The number of single-row waveguides 5 is n = floor(W / d), which is the floor of W / d. With a frequency of 915MHz, d = 300mm, and a furnace width W of 1200mm, we get n = 4. (Refer to...) Figure 23 The requirements are met.

[0109] The frequency is 915MHz, d = 300mm, the furnace width W is 1200mm, and n is reduced to 3, referencing... Figure 24 This does not meet the requirements.

[0110] With a frequency of 2450MHz, d = 100mm, and furnace width W = 500mm, we get n = 5. (Refer to...) Figure 25 The requirements are met.

[0111] The frequency is 2450MHz, d = 100mm, furnace width W is 500mm, and n is reduced to 4, refer to Figure 26 This does not meet the requirements.

[0112] When the microwave power deviation of each waveguide 5 in a single-row waveguide 5 is out of order, the deviation value is less than or equal to 9%; when the microwave power deviation of each waveguide 5 in a single-row waveguide 5 is positive or negative, i.e. symmetrically distributed, the deviation value is less than or equal to 30%.

[0113] Reference Figure 27 The main microwave power port is 500W, and the deviation ports have a deviation of 1%, namely 495W and 505W. The positive and negative deviations of the five ports are symmetrical, namely 500, 495, 500, 505 and 500 respectively, which meets the requirements.

[0114] Reference Figure 28The main microwave power port is 500W, and the deviation ports have a deviation of 1%, namely 495W and 505W. The positive and negative deviations of the five ports are asymmetrical, namely 500, 495, 505, 500, and 495, which meets the requirements.

[0115] Reference Figure 29 The main microwave power port is 500W, and the deviation ports have a deviation of 5%, namely 475W and 525W. The positive and negative deviations of the five ports are asymmetrical, namely 475, 525, 500, 500 and 475 respectively, which meets the requirements.

[0116] Reference Figure 30 The main microwave power port is 500W, and the deviation ports have a deviation of 9%, namely 455W and 545W. The positive and negative deviations of the five ports are asymmetrical, namely 455, 500, 500, 545, and 455, which meets the requirements.

[0117] Reference Figure 31 The main microwave power port is 500W, and the deviation ports have a deviation of 10%, namely 450W and 550W. The positive and negative deviations of the five ports are asymmetrical, namely 500, 450, 550, 500, and 450 respectively. The electric field strength on the same column width has begun to be inconsistent, which does not meet the requirements.

[0118] Reference Figure 32 The main microwave power port is 500W, and the deviation ports have a deviation of 10%, namely 450W and 550W. The positive and negative deviations of the five ports are symmetrical, namely 500, 450, 500, 550 and 500 respectively, which meets the requirements.

[0119] Reference Figure 33 The main microwave power port is 500W, and the deviation ports have a deviation of 20%, namely 400W and 600W. The positive and negative deviations of the five ports are symmetrical, namely 500, 400, 500, 600 and 500 respectively, which meets the requirements.

[0120] Reference Figure 34 The main microwave power port is 500W, and the deviation ports have a deviation of 30%, namely 350W and 650W. The positive and negative deviations of the five ports are symmetrical, namely 650, 500, 500, 500 and 350 respectively, which meets the requirements.

[0121] Reference Figure 35 The main microwave power port is 500W, and the deviation ports have a deviation of 35%, namely 325W and 675W. The positive and negative deviations of the five ports are symmetrical, namely 500, 675, 500, 325, and 500 respectively. The electric field strength on the same column width has begun to be inconsistent, although only slightly, which does not meet the requirements.

[0122] Reference Figure 36The main microwave power port is 500W, and the deviation ports have a deviation of 40%, namely 300W and 700W. The positive and negative deviations of the five ports are symmetrical, namely 700, 500, 500, 500 and 300 respectively, which does not meet the requirements.

[0123] Reference Figure 37 The main microwave power port is 500W, and the deviation ports have an 80% deviation, namely 100W and 900W. The positive and negative deviations of the five ports are symmetrical, namely 500, 900, 500, 100, and 500 respectively, which does not meet the requirements.

[0124] Reference Figure 38 The frequency is 915MHz, the number of single-row waveguides 5 is even, the main microwave power is 1000W, the deviation port has a deviation of 30%, namely 700W and 1300W, the positive and negative deviations of the 8 ports are symmetrical, namely 1000, 700, 1000, 1300, 700, 1000, 1300, 1000, which meets the requirements.

[0125] Reference Figure 39 The frequency is 915MHz, the number of single-row waveguides 5 is even, the main microwave power is 1000W, the deviation port has a deviation of 40%, namely 600W and 1400W, the positive and negative deviations of the 8 ports are symmetrical, namely 1000, 600, 1000, 1400, 600, 1000, 1400, 1000, which does not meet the requirements.

[0126] Each waveguide 5 in a single-row waveguide 5 is fed with the same phase, and can be 2n*pi out of phase.

[0127] Reference Figure 40 The phase has an irregular deviation, with the main phase aperture being 0 and the deviation being pi / 180, or 1°. The five apertures are 0, -pi / 180, pi / 180, -pi / 180, and 0, which does not meet the requirements.

[0128] When the phase is symmetrically deviated, the phase deviation fed into each waveguide 5 of the single-row waveguide 5 is ≤3°, and on this basis, the phase difference can be 2n*pi.

[0129] Reference Figure 41 The phase has a symmetrical deviation, the main phase aperture is 0, the deviation aperture is pi / 180, i.e. 1°, and the five apertures are 0, -pi / 180, 0, pi / 180, and 0 respectively, which meets the requirements.

[0130] Reference Figure 42 The phase has a symmetrical deviation, the main phase aperture is 0, the deviation aperture is pi / 60, i.e. 3°, and the five apertures are 0, -pi / 60, 0, pi / 60, and 0 respectively, which meets the requirements.

[0131] Reference Figure 43 The phase is symmetrically deviated, with the main phase aperture being 0 and the deviation aperture being pi / 36, i.e., 5°. The five apertures are 0, -pi / 36, 0, pi / 36, and 0, respectively. The consistency of the electric field intensity on the same column width has begun to shift, although only slightly, which does not meet the requirements.

[0132] Reference Figure 44 The phase has a symmetrical deviation, the main phase aperture is 0, the deviation aperture is pi / 18, i.e. 10°, and the five apertures are 0, -pi / 18, 0, pi / 18, and 0 respectively, which does not meet the requirements.

[0133] Reference Figure 45 The phase has a symmetrical deviation, the main phase aperture is 0, the deviation aperture is pi / 2, i.e. 90°, and the five apertures are 0, -pi / 2, 0, pi / 2, and 0 respectively, which does not meet the requirements.

[0134] Reference Figure 46 The frequency is 915MHz, the number of single-row waveguides 5 is even, the phase is symmetrically deviated, the main phase aperture is 0, the deviation aperture is pi / 60, i.e. 3°, and the 8 apertures are 0, pi / 60, 0, -pi / 60, pi / 60, 0, -pi / 60, 0, which meets the requirements.

[0135] Reference Figure 47 The frequency is 915MHz, the number of single-row waveguides 5 is even, the phase is symmetrically deviated, the main phase aperture is 0, the deviation aperture deviation is pi / 36, i.e. 5°, the 8 apertures are 0, pi / 36, 0, -pi / 36, pi / 36, 0, -pi / 36, 0, and the consistency of the electric field intensity on the same row width has begun to deviate, which does not meet the requirements.

[0136] The waveguides 5 are arranged in multiple rows and are simultaneously distributed on the top or bottom surface of the wire-walking area. Each row of waveguides 5 has the same frequency, the same center distance d, the same or different phase, and the same or different power.

[0137] When the center distance d of the two waveguides 5 on the same side is not consistent, refer to Figure 48 The center distance d difference is 10mm (d = 100mm and 90mm respectively), which does not meet the requirements. The center distance d difference is 1mm (d = 100mm and 99mm respectively), refer to... Figure 49 This does not meet the requirements.

[0138] The waveguides 5 are arranged in multiple rows, with at least one row located on the top surface of the wire-walking zone and at least one row located on the bottom surface of the wire-walking zone. The single row of waveguides 5 located on the top surface of the wire-walking zone and the single row of waveguides 5 located on the bottom surface of the wire-walking zone may or may not have the same frequency, center distance d, phase, or power. (Refer to...) Figure 50The waveguides 5 distributed on different surfaces have different frequencies, different center distances d, different phases, and different powers, which meets the requirements.

[0139] The single-row waveguide 5 is offset to one side along the width of the wire-feeding zone, with an eccentricity P ≤ 0.005*λ^1.592. The eccentricity P is within... Figure 5 As shown in the diagram, if the single-row waveguide 5 is centered with its center point n, and now the entire waveguide is shifted upwards, causing its center point to become m, the distance P between m and n is the eccentricity distance.

[0140] Reference Figure 51 The frequency is 2450MHz, the wavelength is 122mm, and the eccentricity is 10mm, which meets the requirements.

[0141] Reference Figure 52 With a frequency of 2450 MHz, a wavelength of 122 mm, and an eccentricity of 12 mm, the uniformity of the electric field intensity across the same column width has begun to shift, albeit only slightly, and does not meet the requirements.

[0142] Reference Figure 53 The frequency is 915MHz, the wavelength is 328mm, and the eccentricity is 40mm, which meets the requirements.

[0143] Reference Figure 54 The frequency is 915MHz, the wavelength is 328mm, and the eccentricity is 50mm, which meets the requirements.

[0144] Reference Figure 55 With a frequency of 915MHz, a wavelength of 328mm, and an eccentricity of 55mm, the consistency of the electric field intensity across the same column width has begun to shift, failing to meet the requirements.

[0145] Example 1

[0146] 12k polyacrylonitrile precursor fibers were tensioned at both ends and passed through a pre-oxidation furnace at a temperature of 220℃. The air velocity in the fiber-carrying zone was 3 m / s. A microwave heating device was in operation, with waveguides 5 arranged in a row on the top surface of the fiber-carrying zone at a frequency of 915 MHz and a center-to-center distance d of 300 mm. The microwave power was 1000 W, with consistent phase, and a residence time of 10 minutes. The fiber bundle was brown in color, and the bulk density of the prepared fiber was 1.246 g / cm³. 3 .

[0147] Comparative Example 1

[0148] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and passed through a pre-oxidation furnace at a temperature of 220℃. The air velocity in the fiber-carrying zone was 3m / s. Microwave heating was not used; only hot air heating was employed. The residence time was 10 minutes. The resulting fiber bundle was golden yellow in color, and the bulk density of the prepared fibers was 1.228g / cm³. 3Compared to Example 1, the pre-oxidation degree of Comparative Example 1 was significantly insufficient, resulting in a yellow color in the filament bundle. Therefore, using a microwave heating device can accelerate the pre-oxidation process and improve production efficiency.

[0149] Example 2

[0150] 12k polyacrylonitrile precursor fibers were tensioned at both ends and passed through a pre-oxidation furnace at a temperature of 220℃. The air velocity in the fiber-carrying zone was 3 m / s. A microwave heating device was in operation, with two rows of waveguides (5) distributed on the top surface of the fiber-carrying zone. The frequency was 915 MHz, the center distance (d) was 298 mm, and the microwave power was 500 W. The positive and negative deviations were asymmetrical with a deviation of 5%, but the phases were consistent. The dwell time was 7 minutes. The fiber bundle was golden yellow, and the bulk density of the prepared fiber was 1.232 g / cm³. 3 .

[0151] Comparative Example 2

[0152] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and passed through a pre-oxidation furnace at a temperature of 220℃. The air velocity in the fiber-carrying zone was 3m / s. Microwave heating was not used; only hot air heating was employed. The residence time was 10 minutes. The resulting fiber bundle was golden yellow, and the bulk density of the prepared fibers was 1.230 g / cm³. 3 Compared to Example 2, the time required for the filaments to turn golden yellow during the pre-oxidation process in Comparative Example 2 was longer than that in Example 2. Therefore, using a microwave heating device can reduce the pre-oxidation time, increase the speed of the production line, and improve production efficiency.

[0153] Example 3

[0154] 12k polyacrylonitrile precursor fibers were tensioned at both ends and passed through a pre-oxidation furnace at a temperature of 240℃. The air velocity in the fiber-carrying zone was 3 m / s. A microwave heating device was in operation, with two rows of waveguides (5) distributed on the top surface of the fiber-carrying zone. The frequency was 2450MHz, the center distance (d) was 128mm, the microwave power was 800W, the phase was consistent, and the dwell time was 10 minutes. The fiber bundle was brownish-black, and the bulk density of the prepared fiber was 1.251 g / cm³. 3 .

[0155] Comparative Example 3

[0156] 12k polyacrylonitrile precursor fibers were tensioned at both ends and passed through a pre-oxidation furnace at room temperature without heating. The air velocity in the fiber-carrying zone was 3 m / s. A microwave heating device was in operation, with two rows of waveguides (5) distributed on the top surface of the fiber-carrying zone. The frequency was 2450 MHz, the center distance (d) was 128 mm, the microwave power was 800 W, the phase was consistent, and the residence time was 10 minutes. The fiber bundle color was predominantly white with a slight yellow tint, and the bulk density of the prepared fibers was 1.206 g / cm³. 3Compared to Example 3, the pre-oxidation process in Comparative Example 3 resulted in a predominantly white to slightly yellowish fiber bundle color, indicating that the effect of using only a microwave heating device without turning on the hot air is negligible in the pre-oxidation process.

[0157] Example 4

[0158] 12k polyacrylonitrile precursor fibers were tensioned at both ends and passed through a pre-oxidation furnace at a temperature of 230℃. The air velocity in the fiber-carrying zone was 3 m / s. A microwave heating device was in operation, with two rows of waveguides (5) distributed on the top surface of the fiber-carrying zone. The frequency was 2450MHz, the center distance (d) was 125mm, the microwave power was 1000W, the phase was consistent, and the residence time was 12 minutes. The fiber bundle was brownish-black, and the bulk density of the prepared fiber was 1.255 g / cm³. 3 .

[0159] Comparative Example 4

[0160] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and passed through a pre-oxidation furnace at a temperature of 240℃. The air velocity in the fiber-carrying zone was 3m / s, and the microwave heating device was not used. The residence time was 14 minutes. The fiber bundle was brownish-black in color, and the bulk density of the prepared fibers was 1.250g / cm³. 3 Compared to Example 4, Comparative Example 4 has a higher hot air temperature and a longer process time. Therefore, using a microwave heating device can significantly reduce the hot air temperature and energy consumption.

[0161] Example 5

[0162] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set to 220℃ / 230℃ / 240℃ / 250℃ / 260℃. The hot air velocity in the fiber-feeding zone was 2.5 m / s. A microwave heating device was activated, with waveguides 5 positioned on the top surface of the fiber-feeding zone at a frequency of 2450 MHz and a center-to-center distance d of 130 mm. The microwave power was 1200 W for all ports, with consistent phase. The dwell time in each pre-oxidation furnace was 7 minutes. The fiber bundle was black, and the bulk density of the prepared pre-oxidized fiber was 1.368 g / cm³. 3 .

[0163] Comparative Example 5

[0164] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set at 220℃ / 230℃ / 240℃ / 250℃ / 260℃. The hot air velocity in the fiber-carrying zone was 2.5 m / s. Microwave heating was not used; only hot air heating was employed. The residence time in each pre-oxidation furnace was 7 minutes. The resulting fiber bundle was black, and the bulk density of the prepared fiber was 1.342 g / cm³. 3Compared to Example 5, Comparative Example 5 had insufficient pre-oxidation time and a lower bulk density. Therefore, using a microwave heating device can reduce the pre-oxidation time, increase the speed of the production line, and improve production efficiency.

[0165] Example 6

[0166] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set to 220℃ / 230℃ / 240℃ / 250℃ / 260℃ respectively. The hot air velocity in the fiber-feeding zone was 3.0 m / s. A microwave heating device was activated, with waveguides 5 distributed on the top surface of the fiber-feeding zone at a frequency of 915MHz and a center-to-center distance d of 280mm. The microwave power was 900W across all ports, with consistent phase. The dwell time in each pre-oxidation furnace was 10 minutes. The fiber bundle was black, and the bulk density of the prepared pre-oxidized fiber was 1.391 g / cm³. 3 .

[0167] Comparative Example 6

[0168] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set at 230℃ / 240℃ / 250℃ / 260℃ / 270℃. The hot air velocity in the fiber-carrying zone was 3.0 m / s. Microwave heating was not used; only hot air heating was employed. The residence time in each pre-oxidation furnace was 10 minutes. The resulting fiber bundle was black, and the bulk density of the prepared fiber was 1.370 g / cm³. 3 Compared to Example 6, Comparative Example 6 has a higher hot air temperature, but the degree of pre-oxidation is significantly lower than that of Example 6. Therefore, using a microwave heating device can significantly reduce the hot air temperature and energy consumption.

[0169] Example 7

[0170] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set to 230℃ / 240℃ / 250℃ / 260℃ / 270℃ respectively. The hot air velocity in the fiber-feeding zone was 3.5 m / s. A microwave heating device was activated, with waveguides 5 distributed on the top surface of the fiber-feeding zone at a frequency of 915 MHz and a center-to-center distance d of 300 mm. The microwave power was 600 W for all ports, with consistent phase. The dwell time in each pre-oxidation furnace was 8 minutes. The fiber bundle was black, and the bulk density of the prepared pre-oxidized fiber was 1.379 g / cm³. 3 .

[0171] Comparative Example 7

[0172] 12k polyacrylonitrile precursor fibers were subjected to tension at both ends and pre-oxidized in five pre-oxidation furnaces at temperatures set at 235℃ / 245℃ / 255℃ / 265℃ / 275℃. The hot air velocity in the fiber-carrying zone was 3.5 m / s. Microwave heating was not used; only hot air heating was employed. The residence time in each pre-oxidation furnace was 12 minutes. The resulting fiber bundle was black, and the bulk density of the prepared fiber was 1.378 g / cm³. 3 Compared to Example 7, Comparative Example 7 has a higher hot air temperature and a longer process time. Therefore, using a microwave heating device can significantly reduce the hot air temperature and energy consumption.

[0173] As can be seen from the examples and comparative examples, the pre-oxidation furnace of this application has a significant strengthening effect compared with hot air pre-oxidation and microwave pre-oxidation alone. In the process of preparing polyacrylonitrile pre-oxidized fibers, it can reduce the pre-oxidation time and reduce the production cost of carbon fiber pre-oxidation process, which has important application value for the actual production process of carbon fiber.

[0174] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. A microwave hot air hybrid heating pre-oxidation furnace employing a waveguide, characterized in that, The system includes a furnace body (3), a heater (2) for heating gas, a fan (1) for conveying gas, and a microwave heating device. A wire feeding zone is formed inside the furnace body (3), with a length of L and a width of W. The furnace body (3) includes an air inlet (31), an air outlet (32), a wire bundle inlet (33), and a wire bundle outlet (34). The wire feeding zone is located between the wire bundle inlet (33) and the wire bundle outlet (34) and connects the wire bundle inlet (33) and the wire bundle outlet (34). The wire feeding zone is located between the air inlet (31) and the air outlet (32) and connects the air inlet (31) and the air outlet (32). The fan... (1) Gas is delivered from the air inlet (31) and discharged from the air outlet (32). The microwave heating device includes a microwave source (6) and a waveguide (5). The waveguide (5) includes a first port and a second port. The first port of the waveguide (5) is connected to the microwave source (6). The second port of the waveguide (5) is distributed on the top and / or bottom surface of the wire-feeding area. The narrow side of the second port of the waveguide (5) is parallel to the width direction of the wire-feeding area. The long side of the second port of the waveguide (5) is parallel to the length direction of the wire-feeding area. The number of waveguides (5) is at least one row. The single row of waveguides (5) is evenly arranged along the width direction of the wire-feeding area.

2. The microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The center distance between the single-row waveguides (5) satisfies d≤2.25*λ^0.845, where λ is the microwave wavelength.

3. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide as described in claim 1, characterized in that, The number of single-row waveguides (5) is n = floor(W / d), where d is the center distance between the single-row waveguides (5).

4. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide as described in claim 1, characterized in that, When the microwave power deviation of each waveguide (5) in a single-row waveguide (5) is out-of-order deviation, the deviation value is less than or equal to 9%.

5. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide as described in claim 1, characterized in that, When the microwave power deviation of each waveguide (5) of the single-row waveguide (5) is positive or negative, the deviation value is less than or equal to 30%.

6. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide as described in claim 1, characterized in that, Each waveguide (5) in a single-row waveguide (5) has the same phase or differs by 2n*pi.

7. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide as described in claim 1, characterized in that, When the phase of each waveguide (5) of the single-row waveguide (5) is symmetrically deviated, the phase deviation of each waveguide (5) of the single-row waveguide (5) is ≤3° or 2n*pi on this basis.

8. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The microwave source (6) has a frequency of 915MHz and / or 2450MHz. The wavelength λ corresponding to the frequency of 915MHz is 328mm, the wavelength λ corresponding to the frequency of 2450MHz is 122mm, the opening cross-sectional size of the second port of the waveguide (5) corresponding to the frequency of 915MHz is 248mm x 124mm, and the opening cross-sectional size of the second port of the waveguide (5) corresponding to the frequency of 2450MHz is a rectangle with an opening cross-sectional size of 86mm x 43mm.

9. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The waveguides (5) are arranged in multiple rows and simultaneously distributed on the top or bottom surface of the wire-running area. Each row of waveguides (5) has the same frequency, the center distance d between individual rows of waveguides (5) is the same, the phase is the same or not, and the power is the same or not.

10. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The waveguides (5) are in multiple rows, with at least one row distributed on the top surface of the wire-running area and at least one row distributed on the bottom surface of the wire-running area. The single-row waveguides (5) located on the top surface of the wire-running area and the single-row waveguides (5) located on the bottom surface of the wire-running area have the same or different frequencies, the center distance d between the single-row waveguides (5) is the same or different, the phase is the same or different, and the power is the same or different.

11. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The single-row waveguide (5) is offset as a whole to one side of the width direction of the wire-feeding area, and its eccentricity distance P≤0.005*λ^1.592, where λ is the microwave wavelength.

12. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The furnace body (3) has a feed port (4) on the top and / or bottom surface of the wire feeding area. The feed port (4) corresponds one-to-one with the waveguide (5). The projection of the feed port (4) at the second port of the waveguide (5) falls within the range of the second port of the waveguide (5).

13. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 12, characterized in that, The feed opening (4) is circular, waist-shaped, elliptical, or rectangular.

14. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 13, characterized in that, The elliptical feed port (4), the waist-shaped feed port (4), and the rectangular feed port (4) are deflected at a certain angle relative to the waveguide (5).

15. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 1, characterized in that, The two ends of the wire feeding area along its length are defined by a perforated plate (7), and the distance between the two perforated plates (7) at both ends of the wire feeding area is L. The perforated plate (7) is provided with through holes (71) that pass through both ends.

16. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 15, characterized in that, The perforated plate (7) has at least two perforated plates at each end of the wire feeding zone along its length, and the through holes (71) of the multiple perforated plates (7) at the same end are arranged in a staggered manner.

17. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 15, characterized in that, The diameter of the through hole (71) is less than or equal to 0.25*λ, where λ is the microwave wavelength.

18. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 16, characterized in that, The spacing between multiple perforated plates (7) at the same end is less than or equal to λ, where λ is the microwave wavelength.

19. A microwave hot air hybrid heating pre-oxidation furnace using a waveguide according to claim 12, characterized in that, A wave-transparent plate (8) is provided at the connection between the waveguide (5) and the feed port (4). The wave-transparent plate (8) is made of fused silica, high-purity alumina, hexagonal boron nitride, or silicon nitride.

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