A brush wire for rotary air preheater brush seal structure and a preparation method thereof

Abstract

The application provides a brush wire preparation method for a rotary air preheater brush seal structure, and the method comprises the following steps: stretching and surface treating alloy wires, carbon fibers and silicon carbide fibers; synchronously coating the alloy wires, the carbon fibers and the silicon carbide fibers with a binder; adopting variable tension twisting to form a fiber bundle, and simultaneously adopting infrared heating to pre-solidify the binder; and segmentally heating the fiber bundle to completely solidify the binder, so as to obtain brush wires. The composite brush wires prepared by the method have the advantages of wear resistance and high-temperature resistance, can significantly prolong the service life of the brush wires, and can reduce the air leakage rate of a rotor.

Description

Technical Field

[0001] This application relates to the field of rotary air preheater accessories, and more particularly to a brush filament for a rotary air preheater brush seal structure and its preparation method. Background Technology

[0002] Rotary air preheaters, as heat exchange devices in large boilers, are widely used in power plant boilers. They utilize the heat from the flue gas discharged from the boiler to preheat the air required for combustion, thereby improving boiler efficiency. The main problem is air leakage. Increased leakage leads to higher exhaust gas temperature and lower flue gas temperature inside the furnace, increasing the power consumption of the forced and induced draft fans. If leakage is too great, exceeding the load capacity of the forced and induced draft fans, it will result in insufficient combustion air volume, thus affecting boiler efficiency, safety, and economy.

[0003] Currently, rotary air preheaters widely used in power plant boilers commonly suffer from air leakage problems caused by "mushroom-shaped deformation." To address this issue, various sealing technologies have emerged in the industry. The mainstream is the flexible sealing structure. While flexible sealing structures can adapt to deformation, sealing components such as hinges and spring plates wear quickly, resulting in unstable long-term sealing performance. Another option is the labyrinth sealing structure. Labyrinth sealing structures are non-contact, with no friction between the seal and the fan-shaped plates, but they have a relatively high leakage rate. Furthermore, after prolonged operation, dust easily clogs the labyrinth channels, leading to suboptimal sealing performance. Cleaning the labyrinth channels is also troublesome, time-consuming, and labor-intensive. Finally, there is the brush sealing structure. Brush sealing structures have a much lower leakage rate than labyrinth seals, significantly improving air preheater efficiency. However, air preheaters operate under harsh conditions with large temperature differences and high dust levels. The continuous friction between the brush bristles and the fan-shaped plates in the dusty flue gas environment exacerbates wear, leading to rapid deterioration of sealing performance and a shorter service life. Summary of the Invention

[0004] In view of this, this application proposes a wear-resistant and high-temperature resistant brush bristle for a rotary air preheater brush seal structure, which can improve the service life of the brush bristle and reduce the air leakage rate of the rotor.

[0005] This application also proposes a method for preparing brush filaments for a rotary air preheater brush seal structure to prevent the filaments from tangling during preparation and use.

[0006] A method for preparing brush filaments for a brush seal structure in a rotary air preheater includes: Stretching and surface treatment of alloy wires, carbon fibers, and silicon carbide fibers; The alloy wire, carbon fiber, and silicon carbide fiber are simultaneously coated with an adhesive; The alloy wire, carbon fiber, and silicon carbide fiber are twisted with variable tension to form fiber bundles, and infrared heating is used to pre-cure the binder. The fiber bundle is heated in segments to completely cure the binder, resulting in brush filaments.

[0007] The technical advantages of this application are as follows: In the brush filament preparation method of the rotary air preheater brush sealing structure of this application, the stretching and twisting processes are linked, so that the stress of the fiber bundle can be evenly distributed after composite; the pre-curing during the twisting process allows the binder to reach a gel state, thereby initially fixing the fiber bundle structure and preventing fiber misalignment during subsequent processing; segmented heating can completely cure the binder and improve the rigidity of the brush filaments, thereby improving the structural stability and anti-untangling ability of the brush filaments. Through the combined effect of the properties of the three filament materials themselves and the binder and preparation process, compared with the conventional twisting of the three filaments, the proportion of brush filament untangling is reduced by more than 80%.

[0008] The composite brush bristles prepared by the above method are wear-resistant and high-temperature resistant, which can significantly improve the service life of the brush bristles and reduce the air leakage rate of the rotor. Detailed Implementation

[0009] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0010] A method for preparing brush filaments for a brush seal structure in a rotary air preheater includes: Stretching and surface treatment of alloy wires, carbon fibers, and silicon carbide fibers: In a preferred embodiment, the alloy wire is preferably a nickel-chromium alloy or a cobalt-based alloy, which possesses excellent wear resistance and high-temperature resistance. Under high-temperature conditions, it maintains high hardness and strength, and is not prone to softening or deformation. Simultaneously, the alloy wire exhibits good rigidity, providing a stable support structure for the brush bristles, ensuring they maintain a certain shape and sealing gap during operation. When the brush bristles are subjected to external pressure, the alloy wire resists deformation, allowing them to quickly return to their original shape.

[0011] Carbon fiber possesses high strength, high modulus, and a low coefficient of friction. When combined with alloy wire, carbon fiber forms a lubricating layer on the brush bristle surface, reducing direct contact and friction between the bristles and the fan-shaped plate. Simultaneously, the high strength of carbon fiber can distribute the load borne by the alloy wire, reducing its wear rate. Furthermore, carbon fiber exhibits good elasticity and toughness, allowing it to deform under external force, absorb some energy, and quickly return to its original shape. This elastic compensation reduces fatigue damage caused by prolonged stress, extending the brush bristle's lifespan. Additionally, the elasticity of carbon fiber allows the bristles to better adapt to the surface shape of the fan-shaped plate, improving sealing. For example, when the fan-shaped plate surface is uneven, carbon fiber can cause slight deformation of the bristles, maintaining good contact between them.

[0012] Silicon carbide fibers possess excellent chemical corrosion resistance and react almost entirely with no acids or alkalis. Adding silicon carbide fibers to composite brush filaments allows them to maintain good performance even in corrosive environments. Although silicon carbide fibers themselves have relatively poor toughness, when combined with alloy wires and carbon fibers, they can work synergistically to improve the overall toughness of the brush filament. Silicon carbide fibers can form a mesh structure within the brush filament, enhancing its resistance to breakage. When the brush filament is subjected to significant impact, silicon carbide fibers can prevent crack propagation and avoid breakage.

[0013] During the wear process, silicon carbide fibers first come into contact with the friction surface, using their high hardness to resist wear. Simultaneously, the alloy wires and carbon fibers provide support and distribute the load, reducing the stress on the silicon carbide fibers and extending their service life. In corrosive environments, the chemical stability of silicon carbide and carbon fibers effectively prevents the intrusion of corrosive media, protecting the internal alloy wires from corrosion. The alloy wires, in turn, provide the necessary strength and rigidity for the brush bristles. Under load, the toughness of the alloy wires and carbon fibers absorbs some energy, reducing stress concentration in the brush bristles, while the high strength of the silicon carbide fibers ensures that the brush bristles are not easily broken under high loads. The synergistic properties of these three fibers allow the composite brush bristles to exhibit excellent performance under various working conditions.

[0014] Through the synergistic effect of the three components, the composite brush bristles can be used for a long time under harsh working conditions, greatly extending the service life of the brush bristles, reducing the air leakage rate of the air preheater, and improving the operating efficiency of the equipment.

[0015] This application uses a stretching step to make the molecular chains inside the yarn more aligned, thereby improving the strength and toughness of the yarn and reducing shrinkage and deformation during subsequent processing.

[0016] In a preferred embodiment, the alloy wire is hot-stretched with an elongation of 16-18%, and the surface of the alloy wire is sandblasted to achieve a roughness Ra of 1.0-1.5 μm.

[0017] In a preferred embodiment, the carbon fiber is subjected to low-temperature mechanical stretching with an elongation of 8-10%, and active groups are introduced by surface plasma etching.

[0018] In a preferred embodiment, the silicon carbide fiber is subjected to plasma stretching with an elongation of 4-5%, and its surface is coated with nano-titanium dioxide particles.

[0019] In a preferred embodiment, the diameter ratio of the alloy wire, carbon fiber, and silicon carbide fiber after stretching is preferably 2-2.1:1:1.2-1.3 to ensure uniform stress distribution during subsequent twisting. Surface modification treatment ensures that the contact angle between the wire and the binder is ≤30°, thereby improving interfacial bonding. The surface treatment of the stretched wire maintains high strength while optimizing the interface to ensure a strong bond with the binder, thus enhancing the overall stability of the brush filaments.

[0020] The alloy wire, carbon fiber, and silicon carbide fiber are simultaneously coated with an adhesive; the wires, after being stretched and surface-treated, can adhere evenly when coated with the adhesive, thereby effectively preventing the coating from peeling off due to interface defects.

[0021] In a preferred embodiment, the adhesive comprises 40-45 parts by weight of phenolic resin, 28-35 parts by weight of alumina ceramic micropowder, 13-15 parts by weight of polytetrafluoroethylene micropowder, 5-6 parts by weight of silane coupling agent, and 10-12 parts by weight of curing agent. The silane coupling agent is preferably KH560, and the curing agent is preferably hexamethylenetetramine.

[0022] The phenolic resin in the binder provides high-strength bonding properties, ensuring the stability of the bristle structure; Alumina ceramic micro powder can improve the wear resistance of brush bristles and reduce bristle wear; at the same time, alumina ceramic micro powder can fill the gaps between fibers, improve the density of brush bristles, and reduce the damage to the bristle structure caused by fluid erosion.

[0023] Polytetrafluoroethylene (PTFE) micro powder can reduce the friction coefficient of the brush bristles, reduce the friction between the brush bristles and the rotor surface, and prevent the brush bristles from tangling due to overheating from friction.

[0024] The silane coupling agent added to the binder can form chemical bonds on the fiber surface, significantly improving the interfacial bonding force between the binder and the fiber.

[0025] The three-dimensional network structure formed after the adhesive cures can tightly wrap the three types of fibers, effectively preventing relative slippage between the fibers and causing the brush bristles to untangle.

[0026] In a preferred embodiment, the above three types of yarns are coated by impregnation, and the solvent is removed by hot air drying after coating, so that the adhesive is uniformly attached to the fiber surface.

[0027] By employing variable tension twisting, the alloy wire, carbon fiber, and silicon carbide fiber are formed into fiber bundles. Simultaneously, infrared heating is used to pre-cure the adhesive. The fiber bundles bonded by variable tension experience more uniform stress during the pre-curing process, resulting in improved structural consistency and more wear-resistant brush bristles after curing.

[0028] In a preferred embodiment, right-hand twisting is used for bonding, with a twist pitch of 8-12 mm. Dynamic tension is applied according to the difference in fiber diameter, wherein the alloy wire is 20-21 N, the carbon fiber is 12-13 N, and the silicon carbide fiber is 8-9 N. During the twisting process, infrared heating is used to make the adhesive reach a gel state, preferably at a heating temperature of 150-160°C for 3-4 minutes, to initially fix the fiber bundle structure and prevent fiber misalignment during subsequent processing. The fiber bundle is heated in segments to completely cure the binder, resulting in brush filaments.

[0029] In a preferred embodiment, a two-stage temperature gradient heating process is employed to achieve complete curing of the adhesive: High-temperature curing section: The heating temperature is 250-270℃, which allows the binder to fully cross-link and form a high-strength three-dimensional network structure, while promoting the interfacial bonding between ceramic micro powder and organic matrix; Low-temperature stress relief section: The heating temperature is 70-80℃, and it is slowly cooled to room temperature. Through the thermal expansion and contraction effect, a small pre-tightening force is formed between the fibers to improve the overall rigidity of the brush bristles.

[0030] The stretching and twisting of this application can form a linkage, so that the stress distribution of the fiber bundle is uniform after composite; the pre-curing during the bonding process allows the adhesive to reach a gel state during twisting, initially fixing the fiber bundle structure and effectively preventing fiber misalignment during subsequent processing; segmented heating can completely cure the adhesive while improving the rigidity of the brush bristles, thereby improving the structural stability and anti-tangling ability of the brush bristles.

[0031] Through the combined effects of the properties of the three yarn materials, the binder, and the processing, the rate of unwinding of the brush yarn is reduced by more than 80% compared to the conventional twisting of the three yarns.

[0032] The effects of this application will be verified through the following examples and comparative examples. The examples in this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0033] Example 1 Thread treatment: Nickel-chromium alloy: hot drawn, elongation 17%, surface sandblasted; Carbon fiber: Low-temperature mechanical stretching, elongation 9%, surface plasma etching; Silicon carbide fiber: plasma stretched, elongation 4.5%, surface coated with nano titanium dioxide; The diameter ratio after stretching is: alloy wire: carbon fiber: silicon carbide fiber = 2:1:1.2; Adhesive coating: Simultaneous impregnation coating with phenolic resin-based adhesive (40 parts by weight of phenolic resin, 28 parts by weight of alumina ceramic micro powder, 13 parts by weight of polytetrafluoroethylene micro powder, 5 parts by weight of KH560 and 10 parts by weight of hexamethylenetetramine), followed by hot air drying; Twisting pre-curing: right twist, twist pitch 10mm, variable tension control, alloy wire 20.5N, carbon fiber 12.5N, silicon carbide fiber 8.5N, pre-curing by infrared heating at 155℃ for 3.5min; Segmented curing: Curing at 260℃ for 10 minutes, followed by stress release at 75℃ for 5 minutes, and then naturally cooling to room temperature; Example 2 The elongation of the alloy wire was adjusted to 16%, the elongation of the carbon fiber to 10%, and the elongation of the silicon carbide fiber to 5%. Adhesive coating: Simultaneous impregnation coating with phenolic resin-based adhesive (45 parts by weight of phenolic resin, 35 parts by weight of alumina ceramic micro powder, 15 parts by weight of polytetrafluoroethylene micro powder, 6 parts by weight of KH560 and 12 parts by weight of hexamethylenetetramine). The remaining processes are the same as in Example 1.

[0034] Example 3 The twist pitch is adjusted to 8mm, and the tension is adjusted to 21N for alloy wire, 13N for carbon fiber, and 9N for silicon carbide fiber. Pre-curing temperature: 160℃; High-temperature curing temperature: 270℃. The remaining processes are the same as in Example 1.

[0035] Comparative Example 1 Three types of fibers were twisted at a constant tension of 15N, and the rest of the process was the same as in Example 1.

[0036] Comparative Example 2 After twisting, segmented curing is performed directly, omitting the 155℃ infrared pre-curing step; The remaining processes are the same as in Example 1.

[0037] Comparative Example 3 The three fibers are coated with adhesive separately before being twisted together, rather than being coated simultaneously. The remaining processes are the same as in Example 1.

[0038] Comparative Example 4 A one-time curing process at 260℃ for 15 minutes replaces two-stage gradient heating. The remaining processes are the same as in Example 1.

[0039] Comparative Example 5 (Prior Art) Sample source: Stainless steel brush bristles; Conventional three-strand simply twisted bristles, without synchronous coating or pre-curing.

[0040] The anti-tangling performance of the bristles prepared in the above embodiments and comparative examples was tested: Static high temperature unwinding test: Conditions: 500℃ high-temperature chamber, wind speed 10m / s, continuous for 100 hours; Indicator: Unwound bristle ratio (the number of unwound bristles out of every 100 bristles); The unwinding rates of the brush filaments prepared in the examples and comparative examples are shown in Table 1.

[0041] Table 1: As can be seen from Example 1 and Comparative Example 1, the variable tension effect reduced the bristle unwinding rate from ≥18% to ≤6%, a reduction of 66.7%.

[0042] As can be seen from Example 1 and Comparative Example 1, the pre-curing effect reduced the unwinding rate from ≥15% to ≤6%, a reduction of 60%.

[0043] As can be seen from Example 1 and Comparative Example 3, synchronous coating reduced the unwinding rate from ≥12% to ≤6%, a reduction of 50%.

[0044] As can be seen from Example 1 and Comparative Example 4, segmented heating reduced the unwinding rate from ≥10% to ≤6%, a reduction of 40%.

[0045] As can be seen from Example 1 and Comparative Example 5, the unwinding rate of the brush bristles in this application is only 13.3% of that of conventionally twisted stainless steel brush bristles.

[0046] The above test results show that the composite brush filaments prepared by this application through the synergistic process of variable tension twisting, infrared pre-curing, synchronous coating, and segmented heating significantly reduce the unwinding rate and are significantly superior to the existing technology.

[0047] This application also verifies the performance of different brush filament simulated brush seal structures in the application environment of rotary air preheaters.

[0048] The experimental materials include: Single material bristles: Nickel-chromium alloy wire, 0.12mm in diameter; Carbon fiber brush filaments, 0.10mm in diameter; Silicon carbide fiber brush filaments, 0.09mm in diameter.

[0049] Two-component brush bristles: Nickel-chromium alloy-carbon fiber composite brush filaments, 0.11mm in diameter, with nickel-chromium alloy wire and carbon fiber twisted together at a diameter ratio of 2:1; Nickel-chromium alloy-silicon carbide fiber composite brush filaments, 0.105mm in diameter, with nickel-chromium alloy wire and silicon carbide fiber twisted together at a diameter ratio of 2:1.2; Carbon fiber-silicon carbide composite brush filaments, 0.095mm in diameter, are twisted together with silicon carbide fibers at a diameter ratio of 1:1.2.

[0050] The three-component composite brush bristles were prepared according to the method in Example 1. The diameter ratio of the alloy wire, carbon fiber, and silicon carbide fiber after stretching was 2:1:1.2, and the diameter was 0.11 mm.

[0051] Brush-type sealing structures commonly use stainless steel bristles with a diameter of 0.13mm.

[0052] A high-temperature test chamber was used to simulate the operating temperature range (300–800℃) of a rotary air preheater. The test chamber was equipped with a temperature control system, and the temperature fluctuation range was controlled within ±5℃.

[0053] A corrosive gas generator is installed inside the test chamber, through which a mixed gas containing acidic gases such as sulfur dioxide and nitrogen oxides is introduced to simulate the corrosive environment of flue gas. The gas concentration can be adjusted according to actual conditions; for example, the SO2 concentration can be 500–1000 ppm, and the NO concentration can be [missing information]. x The concentration is 300–600 ppm. At the same time, a certain amount of dust particles with a particle size of 10–50 μm are added to simulate the scouring and abrasion effect of dust on the brush bristles.

[0054] A friction and wear testing apparatus was designed, in which brush bristles were fixed on a test bench and subjected to contact friction with a simulated sector plate. The sector plate was rotated by a motor to simulate the rotation of an air preheater rotor, with the rotation speed controlled between 10 and 20 r / min. Simultaneously, a loading device applied a certain pressure to the brush bristles to simulate the sealing pressure between the brush bristles and the sector plate, with the pressure range being 0.5–2 N.

[0055] Different types of brush bristles were installed on a friction and wear testing apparatus and tested under set high temperature, corrosion, and friction conditions. After 500 hours, the brush bristles were weighed, and the wear amount was calculated. During the wear test, a laser displacement sensor was used to measure the deformation of the brush bristles in real time. The deformation of the brush bristles under different times and pressures was recorded. After the test, the brush bristles were removed and placed in a room temperature environment to observe whether they could return to their original shape, and the permanent deformation was measured.

[0056] The brush bristle samples were placed in a high-temperature corrosion test chamber and subjected to corrosion testing at the set temperature and corrosive gas concentration. After 500 hours, the brush bristles were weighed, and the corrosion amount was calculated.

[0057] The brush filaments, after undergoing abrasion and corrosion tests, were subjected to tensile tests. The breaking strength and elongation at break were measured using a universal testing machine. The tensile speed was controlled at 1 mm / min. The load and elongation at break were recorded, and the breaking strength and elongation at break were calculated. The results are shown in Table 2.

[0058] Table 2: In the abrasion performance test of the bristles: The wear of a single alloy wire brush filament is 0.13 mm after 500 hours, that of a single carbon fiber brush filament is 0.23 mm, and that of a single silicon carbide fiber brush filament is 0.06 mm.

[0059] The wear of the alloy-carbon fiber composite brush filament is 0.16mm, which is slightly higher than that of a single alloy brush filament, but much lower than that of a single carbon fiber brush filament. This indicates that the addition of the alloy wire effectively improves the poor wear resistance of the carbon fiber brush filament. At the same time, the carbon fiber also shares the wear of the alloy wire to a certain extent, and the two play a complementary role.

[0060] The wear rate of the alloy-silicon carbide fiber composite brush bristle is 0.09mm, which is between that of a single alloy wire and a silicon carbide fiber brush bristle. It utilizes the excellent wear resistance of silicon carbide fiber while ensuring the structural strength of the brush bristle through the alloy wire, thus achieving a balance between wear resistance and strength.

[0061] The wear of the three-component composite brush bristles is 0.08mm, which is only slightly higher than that of a single silicon carbide fiber brush bristle, but 38.5% lower than that of a single alloy wire brush bristle and 65.2% lower than that of a single carbon fiber brush bristle. This fully demonstrates the synergistic effect of the three fibers in terms of wear resistance. The three fibers work together to further reduce the wear of the brush bristles.

[0062] The wear of the stainless steel brush bristles is 0.15 mm, which is much higher than that of the composite brush bristles of the three types, indicating that the composite brush bristles of this application have a significant advantage in wear resistance.

[0063] In the corrosion performance test of the bristles: The corrosion loss rate of a single alloy wire brush filament after 500 hours is 8.5%, that of a single carbon fiber brush filament is 1.2%, and that of a single silicon carbide fiber brush filament is 0.01%.

[0064] The corrosion loss rate of the alloy-carbon fiber composite brush bristles was 4.2%, which was 50% lower than that of single alloy wire brush bristles. This indicates that the addition of carbon fiber significantly improved the corrosion resistance of the brush bristles, and the chemical stability of carbon fiber effectively prevented the corrosive media from eroding the alloy wires.

[0065] The corrosion loss rate of the three-component composite brush bristles is 0.2%, which is higher than that of single silicon carbide fiber brush bristles, but much lower than that of single alloy wire and carbon fiber brush bristles. The synergistic effect of the three fibers makes the brush bristles perform better in corrosive environments, giving full play to the extreme corrosion resistance of silicon carbide fibers and utilizing the other performance advantages of carbon fiber and alloy wire.

[0066] The corrosion rate of stainless steel brush filaments is much higher than that of the composite brush filaments in this application, indicating that the composite brush filaments have a significant improvement in corrosion resistance.

[0067] In mechanical performance testing of the bristles: The breaking strength of a single alloy wire brush is 1521 MPa, and the elongation at break is 5%; the breaking strength of a single carbon fiber brush is 2536 MPa, and the elongation at break is 1.5%; the breaking strength of a single silicon carbide fiber brush is 3584 MPa, and the elongation at break is 1%.

[0068] The alloy-carbon fiber composite brush filament has a breaking strength of 2163 MPa and a breaking elongation of 3%, which is between that of a single alloy filament and a carbon fiber filament. It ensures a certain strength while improving the toughness of the filament, thus avoiding the defects of a single material.

[0069] The alloy-silicon carbide fiber composite brush filament has a breaking strength of 2857 MPa and a breaking elongation of 1.8%. While maintaining high strength, the breaking elongation is appropriately increased, making the brush filament less prone to breakage when subjected to load.

[0070] The composite brush filament has a breaking strength of 2819 MPa and a breaking elongation of 2%. It combines the advantages of the three fibers and achieves a good balance between strength and toughness. It has high strength to ensure the structural stability of the brush filament, and a certain degree of toughness to adapt to the vibration and deformation during the operation of the air preheater.

[0071] The permanent deformation and fracture performance of stainless steel brush filaments are much lower than those of the composite brush filaments in this application, indicating that the composite brush filaments have significantly improved mechanical properties.

[0072] When the mechanical properties of the bristles are improved, the problem of reduced sealing caused by bristle deformation and breakage can be reduced during long-term use, thereby reducing the air leakage rate of the sealing structure.

[0073] Meanwhile, the test results in Table 1 demonstrate that the alloy wire possesses good rigidity and strength, providing a stable support structure for the brush bristles and ensuring they maintain a certain shape and sealing gap during operation. Carbon fiber exhibits excellent elasticity and toughness, allowing it to deform under external force, absorb some energy, and quickly return to its original shape, reducing fatigue damage caused by prolonged stress. Silicon carbide fiber possesses extremely high hardness and wear resistance, forming a hard protective layer on the bristle surface to resist erosion and wear from dust, particles, and other contaminants. When these three fibers are combined, they complement each other structurally, forming a more stable and complete whole, thereby improving the overall performance of the brush bristles.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing brush filaments for a brush seal structure in a rotary air preheater, characterized in that... include: Stretching and surface treatment of alloy wires, carbon fibers, and silicon carbide fibers; The alloy wire, carbon fiber, and silicon carbide fiber are simultaneously coated with an adhesive; The alloy wire, carbon fiber, and silicon carbide fiber are twisted together using variable tension to form fiber bundles, while infrared heating is used to pre-cure the binder. The fiber bundle is heated in segments to completely cure the binder, resulting in brush filaments.

2. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The alloy wire is hot-stretched with an elongation of 16-18%, and the surface of the alloy wire is sandblasted to achieve a roughness Ra of 1.0-1.5 μm.

3. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The carbon fiber is subjected to low-temperature mechanical stretching with an elongation of 8-10%, and active groups are introduced by surface plasma etching.

4. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The silicon carbide fiber is subjected to plasma stretching with an elongation of 4-5%, and its surface is coated with nano-titanium dioxide particles.

5. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The adhesive comprises 40-45 parts by weight of phenolic resin, 28-35 parts by weight of alumina ceramic micro powder, 13-15 parts by weight of polytetrafluoroethylene micro powder, 5-6 parts by weight of silane coupling agent, and 10-12 parts by weight of curing agent.

6. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The alloy wire, carbon fiber, and silicon carbide fiber are bonded together using a right-hand twist method with a twist pitch of 8–12 mm.

7. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: During the twisting process, the dynamic tension applied to the alloy wire is 20-21 N, the dynamic tension applied to the carbon fiber is 12-13 N, and the dynamic tension applied to the silicon carbide fiber is 8-9 N.

8. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: During the twisting process, the adhesive is heated to a gel state by infrared heating at a temperature of 150–160°C for 3–4 minutes.

9. The method for preparing brush filaments for a rotary air preheater brush seal structure as described in claim 1, characterized in that: The fiber bundle is heated using a two-stage temperature gradient, wherein: High-temperature curing section: heating temperature 250~270℃; Low-temperature stress relief section: The heating temperature is 70-80℃, and then it is naturally cooled to room temperature to obtain brush bristles.

10. A brush bristle for a brush seal structure in a rotary air preheater, characterized in that: It is prepared by the method of any one of claims 1 to 9.

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