Preparation method and application of waste fan blade regenerated fiber

Abstract

The invention discloses a preparation method and application of waste fan blade regenerated fibers, a composite process route of'precise cutting, controllable crushing, inert atmosphere pyrolysis and ultrasonic-assisted surface activation 'is adopted, the obtained regenerated fibers are excellent in mechanical property, and'active' bonding with a concrete matrix is realized through surface chemical modification; the reinforcing effect is far better than that of traditional recycled fibers. Compared with the prior art, the method provided by the invention systematically solves the problems of performance, interface and homogenization of recovered fibers, avoids expensive chemical solvents, realizes recycling of part of byproducts through gas recovery, is simple and controllable in overall process, and has remarkable industrial application potential and cost advantage. A key high-performance reinforcing material is provided for the high-seawater-corrosion-resistance all-solid-waste negative carbon concrete, the reliability and success rate of downstream concrete mix proportion design and component performance research are ensured, and a complete technical innovation chain from solid waste to high-performance products is formed.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and marine engineering construction materials technology, and in particular to a method for preparing and applying recycled fibers from waste wind turbine blades. Background Technology

[0002] The global energy transition is driving a large number of early wind turbines into retirement, generating a large amount of waste wind turbine blades made of glass fiber / carbon fiber reinforced composite materials. Traditional disposal methods (landfill and incineration) face dual environmental and economic pressures, making high-value resource utilization an urgent priority. Meanwhile, marine engineering construction has long been hampered by the cracking, brittleness, and insufficient durability of concrete due to seawater erosion. While fiber reinforcement is an effective approach, metal fibers (such as steel fibers) are prone to corrosion in the chloride-rich marine environment, and the expansion of corrosion products can damage the concrete structure. Synthetic fibers (such as polypropylene fibers) have low elastic modulus, are chemically inert to the cement matrix, and have weak interfacial adhesion, limiting their reinforcing and toughening effects. Therefore, recycling high-performance fibers from waste wind turbine blades and using them to reinforce marine concrete constitutes an ideal "waste-to-resource" technological path. However, the industrial application of this path still faces the following recycling technology bottlenecks:

[0003] 1. Performance degradation problem during fiber recycling

[0004] Mechanical recycling: This method mainly involves rough crushing, resulting in short-cut powder with extremely low fiber aspect ratio, which cannot effectively transfer load and loses its value as a reinforcing phase.

[0005] Air pyrolysis: High-temperature pyrolysis in air removes the resin, but the fibers (especially glass fibers) will experience a significant decrease in strength and modulus under high-temperature oxidation, and the fiber surface is smooth, resulting in poor adhesion to concrete.

[0006] 2. The compatibility problem of fiber-concrete interface

[0007] The recycled fiber surface is chemically inert, unlike the novel Cl-rich... - SO4 2- The alkaline environment and compatibility of hydration products in solid waste low-carbon concrete are unknown, which can easily form a weak interface transition zone, becoming a rapid channel for the penetration of corrosive media.

[0008] 3. Challenges in process standardization and industrialization

[0009] The properties of fibers produced by existing recycling processes fluctuate greatly, failing to meet the basic requirements of engineering materials for homogeneity and stability, and making it difficult to conduct reliable concrete mix design and performance prediction. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method for preparing and applying recycled fibers from waste wind turbine blades. This method is a standardized preparation method for high-performance, low-damage, and strong interfacial bonding recycled fibers from waste wind turbine blades.

[0011] To achieve this technical objective, the present invention adopts the following solution:

[0012] In a first aspect, the present invention provides a method for preparing recycled fibers from waste wind turbine blades, comprising the following steps: 1. Cutting: The waste wind turbine blades are cut using a high-pressure water jet cutting system; II. Crushing: A twin-shaft shear crusher is used to crush the cut fan blades; 3. Pyrolysis: The crushed material is placed in a pyrolysis furnace and pyrolyzed under the protection of high-purity nitrogen (purity ≥99.99%). IV. Surface activation: After pyrolysis, the product is cooled to <60°C under an inert atmosphere, and the solid product is removed and obtained by vibrating sieve. The regenerated fibers were impregnated in a 1.0-2.0 wt% γ-aminopropyltriethoxysilane (KH-550) ethanol solution, ultrasonically treated at 50-60℃ (300-500W) for 20-40 minutes, and then dried and cured at 105℃ for 2 hours to obtain the regenerated fibers of waste wind turbine blades.

[0013] Furthermore, the cutting path is optimized based on the main load-bearing direction of the blade, prioritizing cutting along the direction perpendicular to the fiber main axis to maximize the preservation of the original effective length of the fiber.

[0014] Furthermore, the water pressure is set to 300~400MPa, the jet diameter is 0.8~1.2mm, the cutting speed is controlled at 0.8~1.5m / min, and emulsion is used for cooling to effectively avoid resin carbonization and fiber performance damage caused by the heat-affected zone.

[0015] Furthermore, based on the thickness gradient (10~150mm) of different parts of the wind turbine blades, water jet cutting or diamond saw blades are used for segmented cutting, with the cutting speed controlled at 0.5~2.0m / min. The cooling medium is emulsion to avoid fiber thermal damage and resin carbonization.

[0016] Furthermore, the blades of the dual-shaft shear crusher are made of cemented carbide, which has high wear resistance.

[0017] Furthermore, the crushing particle size is strictly controlled within 10~20mm, the equipment rotation speed is 250~400rpm, and the crushing chamber is equipped with an air-cooled or liquid nitrogen-cooled system to ensure that the process temperature is below 60℃, effectively preventing resin softening and adhesion and fiber entanglement. The crushing step aims to obtain uniformly sized flake materials, laying the foundation for subsequent uniform pyrolysis.

[0018] Furthermore, the pyrolysis process is programmed to raise the temperature to 500-580°C at a rate of 8-12°C / min, preferably 550±10°C, and then maintains the temperature at this level for 1.5-2.5 hours.

[0019] The pyrolysis step utilizes an inert atmosphere to completely eliminate fiber oxidation; the optimized temperature window ensures that the resin is fully decomposed and volatilized (which can be verified by thermogravimetric analysis (TGA)) while avoiding softening of the fiber glass phase, thus achieving a balance between efficient resin exfoliation and maximum retention of fiber properties.

[0020] The volatile gases produced during the pyrolysis process can be recovered by a two-stage condensation system (first stage water cooling, second stage deep cooling to -10℃) to recover chemicals such as styrene and phenols, achieving greening and resource utilization throughout the entire process.

[0021] The surface activation step utilizes a silane coupling agent to form a chemical grafting layer on the fiber surface. Its organic functional group (-NH2) can form a stable chemical bond with cement hydration products (such as CSH gel), which greatly improves the interfacial bonding strength.

[0022] Furthermore, the regenerated fibers from discarded wind turbine blades have a fiber length distribution of 5-20 mm and an aspect ratio ≥50; the tensile strength of the monofilament fibers is ≥800 MPa, the elastic modulus is ≥40 GPa, and the strength retention rate is not less than 85% of the original fiber. FTIR analysis showed that Si-O-Si and Si-OC characteristic peaks could be detected on the fiber surface, proving that silane grafting was successful.

[0023] Secondly, this invention provides a method for applying the recycled fiber from waste wind turbine blades prepared according to the aforementioned method, for use in Cl-rich... - SO4 2- The reinforcing phase of all-solid waste low-carbon concrete, especially in marine environmental facing components (such as Twisted King Block and I-shaped slabs), is added at a dosage of 0.5% to 1.5% of the concrete volume.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Original innovation: It pioneered a composite process route of "precise cutting + controllable crushing + inert atmosphere pyrolysis + ultrasonic-assisted surface activation", which systematically solved the problems of performance, interface and homogenization of recycled fibers.

[0026] 2. Superior performance: The obtained recycled fibers not only have excellent mechanical properties, but also achieve "active" bonding with the concrete matrix through surface chemical modification. Their reinforcing effect far exceeds that of traditional recycled fibers and can even rival some commercial synthetic fibers.

[0027] 3. Technical, economic and environmental benefits: This process avoids expensive chemical solvents and realizes the resource utilization of some by-products through gas recovery. The overall process is simple and controllable, and has significant potential for industrial application and cost advantages.

[0028] 4. Targeted application: It provides key high-performance reinforcing materials for "high seawater erosion resistant solid waste negative carbon concrete", ensuring the reliability and success rate of downstream concrete mix design and component performance research, and forming a complete technological innovation chain from solid waste to high-performance products. Attached Figure Description

[0029] Figure 1 This is a process flow diagram in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0031] Unless otherwise specified, the experimental methods used in the embodiments and comparative examples of this invention are conventional methods. Unless otherwise specified, the materials and reagents used are commercially available.

[0032] The discarded wind turbine blades come from the expiration of their designed service life, the early retirement of wind power plants due to the "larger replacement of smaller ones" policy, and faulty parts generated during operation and maintenance.

[0033] The performance of the obtained recycled fibers from waste leaves was characterized in accordance with the "Test Methods for Performance of Glass Fiber Reinforced Cement" (GB / T 15231-2023).

[0034] Example 1

[0035] A high-pressure water jet cutting system is used to cut the waste wind turbine blades in a direction perpendicular to the fiber spindle. The water pressure is set to 350 MPa, the jet diameter is 1.0 mm, the cutting speed is controlled at 1.2 m / min, and an emulsion is used for cooling.

[0036] A twin-shaft shear crusher is used to crush the cut fan blades. The crushing particle size is strictly controlled within 10~20mm, the equipment speed is 300rpm, and the crushing chamber is equipped with a liquid nitrogen cooling system to ensure that the process temperature is below 60℃.

[0037] The crushed material was placed in a controlled atmosphere pyrolysis furnace and pyrolyzed under the protection of high-purity nitrogen (purity ≥99.99%). The temperature was programmed to rise to 550℃ at a rate of 10℃ / min and held at that temperature for 2 hours.

[0038] After pyrolysis, the product is cooled to <60°C under an inert atmosphere, the solid product is removed, and regenerated fibers are obtained by vibrating sieve. The regenerated fibers were impregnated in a 1.5wt% γ-aminopropyltriethoxysilane (KH-550) ethanol solution, ultrasonically treated at 50~60℃ (400W) for 30 minutes, and then dried and cured at 105℃ for 2 hours to obtain the regenerated fibers of waste wind turbine blades.

[0039] The properties of the obtained recycled fibers from waste leaves were characterized: The regenerated fibers from discarded wind turbine blades mainly ranged in length from 8 to 15 mm, with an average length of 11.2 mm. Their aspect ratio (length to diameter) was calculated to be an average of 58, and the aspect ratio of all tested samples was >50. The tensile strength of the monofilament fibers was ≥850 MPa, and the elastic modulus was ≥42 GPa, with a strength retention rate of approximately 88%–90% of the original fibers. FTIR analysis revealed Si-O-Si and Si-OC characteristic peaks on the fiber surface, confirming successful silane grafting.

[0040] The prepared recycled fibers were used as a reinforcing phase in all-solid-waste concrete. Performance test results are shown in Table 1.

[0041] The components and dosage (per cubic meter) of all-solid-waste concrete are as follows: Cementitious material system (450kg / m³): Slag powder (S95 grade): 225kg, accounting for 50%; Fly ash (Grade I): 135 kg, accounting for 30%; Desulfurized gypsum: 45kg, accounting for 10%; Steel slag powder: 45kg, accounting for 10%; Fine aggregate: recycled waste ceramic sand (0-4.75mm), 680kg; Coarse aggregate: recycled crushed stone from waste concrete (5-25mm), 1180kg; Additive: Polycarboxylate superplasticizer (20% solid content), 6.75 kg (1.5% of the adhesive material); Mixing water: Seawater (simulating a marine environment, Cl) - Concentration 19.5 g / L, SO4 2- (Concentration 2.7 g / L), 165 kg; Regenerated fiber (prepared in Example 1): volume fraction 1.0% (approximately 28 kg / m³).

[0042] Example 2

[0043] A high-pressure water jet cutting system is used to cut the waste wind turbine blades in a direction perpendicular to the fiber spindle. The water pressure is set to 300 MPa, the jet diameter is 0.8 mm, the cutting speed is controlled at 1.0 m / min, and an emulsion is used for cooling.

[0044] A twin-shaft shear crusher is used to crush the cut fan blades. The crushing particle size is strictly controlled within 10~20mm, the equipment speed is 400rpm, and the crushing chamber is equipped with a liquid nitrogen cooling system to ensure that the process temperature is below 60℃.

[0045] The crushed material was placed in a controlled atmosphere pyrolysis furnace and pyrolyzed under the protection of high-purity nitrogen (purity ≥99.99%). The temperature was programmed to rise to 570℃ at a rate of 8℃ / min and held at that temperature for 2 hours.

[0046] After pyrolysis, the product is cooled to <60°C under an inert atmosphere, the solid product is removed, and regenerated fibers are obtained by vibrating sieve. The regenerated fibers were impregnated in a 2.0 wt% γ-aminopropyltriethoxysilane (KH-550) ethanol solution, ultrasonically treated at 50~60℃ (350W) for 35 minutes, and then dried and cured at 105℃ for 2 hours to obtain the regenerated fibers of waste wind turbine blades.

[0047] The properties of the obtained recycled fibers from waste leaves were characterized: The fiber length of the recycled fibers from waste wind turbine blades is mainly distributed in the range of 6~12mm, with an average length of 9.5mm (slightly shorter than in Example 1 due to the increased crushing speed to 400rpm). The calculated average aspect ratio (length to diameter) is 54, and the aspect ratio of all test samples is >50. The tensile strength of the monofilament fiber is ≥820MPa, and the elastic modulus is ≥41GPa. Its strength retention rate is approximately 86%~88% of the original fiber (slightly lower than in Example 1 due to the increased pyrolysis temperature to 570℃ and increased crushing strength). FTIR analysis revealed obvious Si-O-Si and Si-OC characteristic peaks on the fiber surface, and the intensity of these peaks was enhanced compared to Example 1 (due to the increased silane concentration to 2.0wt% and the extended treatment time to 35min, resulting in more thorough surface modification).

[0048] The prepared recycled fibers were used as a reinforcing phase in all-solid-waste concrete. Performance test results are shown in Table 1.

[0049] This embodiment uses 1.3% volumetric admixture (approximately 36 kg / m³) of recycled fiber, and the amount of polycarboxylate superplasticizer added is 7.2 kg. The remaining components and dosages of the all-solid waste concrete are the same as in Example 1.

[0050] Comparative Example 1

[0051] This comparative example uses a traditional mechanical crushing + air pyrolysis method to recover fibers, which are then used as a reinforcing phase in all-solid waste concrete. Performance test results are shown in Table 1.

[0052] Except for the recycled fiber, the other components and dosages of the all-solid-waste concrete are the same as in Example 1.

[0053] Traditional methods of fiber recycling result in low aspect ratios, significant strength loss, and numerous surface inertness and defects, failing to form effective bridging in concrete. Not only is the reinforcing effect weak, but the thin fiber-matrix interface also becomes a stress concentration point and erosion channel, leading to a comprehensive deterioration in crack resistance and impermeability. This comparative example fully demonstrates that recycled fibers not treated with the "inert atmosphere pyrolysis + ultrasonic-assisted surface activation" process of this invention cannot meet the reinforcement requirements of marine engineering concrete, highlighting the necessity and advancement of the technical approach of this invention.

[0054] Comparative Example 2

[0055] This comparative example uses commercially available high-performance synthetic fiber—polyvinyl alcohol fiber (PVA fiber)—as a reinforcing phase in all-solid waste concrete. The remaining components and dosages of the all-solid waste concrete are the same as in Example 1. Performance test results are shown in Table 1.

[0056] While commercial PVA fibers possess high tensile strength, their low elastic modulus (30 GPa vs. 40 GPa), poor surface chemical inertness, and poor compatibility with seawater environments lead to difficulties in high-Cl4 concentrations. - SO4 2- In highly corrosive environments, the interfacial bonding strength is significantly lower than that of the silane-activated fibers of this invention. The chloride ion diffusion coefficient is 33% higher, posing a greater risk to long-term durability. Furthermore, the cost of PVA fiber is approximately 18-25 yuan / kg, while the estimated cost of the recycled fiber of this invention is only 5-8 yuan / kg (solid waste utilization + by-product recycling), demonstrating significant economic and environmental value. This invention achieves "treating waste with waste," and its technical and economic advantages comprehensively surpass those of commercially available synthetic fibers.

[0057] Table 1. Concrete performance test results

[0058]

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should all be considered to be within the protection scope of the present invention.

Claims

1. A method for preparing recycled fibers from waste wind turbine blades, characterized in that, Includes the following steps:

1. Cutting: The waste wind turbine blades are cut using a high-pressure water jet cutting system; II. Crushing: A twin-shaft shear crusher is used to crush the cut fan blades; III. Pyrolysis: The crushed material is placed in a pyrolysis furnace and pyrolyzed under the protection of high-purity nitrogen. IV. Surface activation: After pyrolysis, the product is cooled to <60°C under an inert atmosphere, and the solid product is removed and obtained by vibrating sieve. The regenerated fibers were impregnated in a 1.0-2.0 wt% γ-aminopropyltriethoxysilane ethanol solution, ultrasonically treated at 50-60°C for 20-40 minutes, and then dried and cured at 105°C for 2 hours to obtain the regenerated fibers of waste wind turbine blades.

2. The method for preparing recycled fibers from waste wind turbine blades according to claim 1, characterized in that, The cutting path is perpendicular to the fiber spindle, the water pressure is set to 300~400MPa, the jet diameter is 0.8~1.2mm, the cutting speed is controlled at 0.8~1.5m / min, and an emulsion is used for cooling.

3. The method for preparing recycled fibers from waste wind turbine blades according to claim 1, characterized in that, The crushing particle size is strictly controlled within 10~20mm, the equipment speed is 250~400rpm, and the crushing chamber is equipped with an air-cooled or liquid nitrogen cooling system to ensure that the process temperature is below 60℃.

4. The method for preparing recycled fibers from waste wind turbine blades according to claim 1, characterized in that, The pyrolysis process involves heating the temperature to 500-580°C at a rate of 8-12°C / min and maintaining it at that temperature for 1.5-2.5 hours.

5. The method for preparing recycled fibers from waste wind turbine blades according to claim 1, characterized in that, The fiber length of the recycled fiber from waste wind turbine blades is distributed between 5 and 20 mm, with an aspect ratio of ≥50; the tensile strength of the single filament fiber is ≥800 MPa, the elastic modulus is ≥40 GPa, and its strength retention rate is not less than 85% of the original fiber.

6. A method for applying the recycled fiber from waste wind turbine blades prepared by the method according to any one of claims 1-5, characterized in that, For Cl-rich - SO4 2- The reinforcing phase of all-solid waste low-carbon concrete is added at a dosage of 0.5% to 1.5% of the concrete volume.

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