Method for recycling wind power blade through low-temperature non-catalytic oxidation

Abstract

The invention relates to the technical field of solid waste treatment, in particular to a method for recycling a wind power blade through low-temperature non-catalytic oxidation. The method comprises the following steps: placing the pretreated waste wind turbine blade in a polar mixed solvent, introducing oxidizing gas, and reacting at 20100 DEG C for 0.55 h, so that epoxy resin is subjected to oxidation chain scission; introducing pure oxygen or oxygen-rich gas, and continuously reacting at 20130 DEG C for 0.55 h to realize deep degradation of the resin; then separating out a fiber material, balsa wood and organic liquid through a gravity settling flotation combined process; purifying and drying the fibers to obtain high-purity and high-strength recycled fibers; after the organic liquid is evaporated and separated, light components are recycled as solvents, and heavy components and balsa wood are used as energy carriers. The method realizes efficient degradation and resource recovery of the wind turbine blade under mild conditions of no catalyst and no strong acid and strong alkali, has the advantages of low energy consumption, small fiber damage, environmental friendliness, simple process flow and the like, and is suitable for large-scale recovery treatment.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a method for low-temperature non-catalytic oxidation recovery of wind turbine blades. Background Technology

[0002] With the rapid development of the wind power industry, the number of retired wind turbine blades worldwide is experiencing explosive growth. It is estimated that between 2025 and 2030, the amount of retired wind turbine blades in China will reach more than 3 million tons. Wind turbine blades are usually made of epoxy resin (about 30%), glass fiber or carbon fiber (about 60%), and balsa wood (about 10%). Their cross-linked curing structure and strong interfacial bonding characteristics make recycling a huge challenge.

[0003] Currently, common recycling technologies mainly include the following three types: mechanical crushing, high-temperature pyrolysis, and chemical degradation. Each of these methods has significant limitations: Mechanical crushing is simple, but fibers are easily broken, leaving significant resin residue on the surface, resulting in low added value of the recycled fibers; resin debris can easily cause secondary pollution. High-temperature pyrolysis requires temperatures of 500-800℃, leading to high energy consumption; it easily produces pollutants such as tar and benzene compounds; high temperatures severely damage the fiber structure, reducing its recycling value. Chemical degradation often relies on strong acids, strong alkalis, or expensive metal catalysts; the reaction conditions are harsh, equipment corrosion is severe, and economic efficiency is poor.

[0004] For example, Chinese patent CN115636980B discloses a method for recycling wind turbine blades based on catalytic degradation. The recycling process requires catalytic degradation in a polar organic solvent containing 10%–15% catalyst and under an inert atmosphere at 250℃–280℃ for 4–6 hours, resulting in high energy consumption, serious secondary pollution, and poor economic efficiency in the recycling process.

[0005] Therefore, developing a wind turbine blade recycling technology with mild reaction conditions, low energy consumption, and environmental friendliness and economy, to achieve efficient recycling of fiber materials and efficient degradation of epoxy resin, has become an urgent need for the sustainable development of the wind power industry. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing wind turbine blade recycling technologies, such as high energy consumption, significant fiber damage, the need for catalysts or highly corrosive reagents, and the potential for secondary pollution, and to provide a method for low-temperature non-catalytic oxidation recycling of wind turbine blades.

[0007] To achieve the above objectives, the present invention provides a method for low-temperature non-catalytic oxidation recovery of wind turbine blades, comprising the following steps:

[0008] Step 1: Place the waste wind turbine blades in a polar mixed solvent, introduce oxidizing gas, and at 20°C... The reaction was carried out at 100℃ for 0.5 seconds. After 5 hours, the epoxy resin undergoes oxidative chain scission, forming a mixture containing organic matter and peroxide intermediates; Step 2: Pass pure oxygen or oxygen-enriched gas into the mixture obtained in Step 1, at 20°C. The reaction continued at 130℃ for 0.5 seconds. After 5 hours, the peroxide intermediate is further degraded to obtain a solid-liquid mixture of an organic liquid mixture and an independent fiber material. Step 3: Perform solid-liquid separation on the solid-liquid mixture obtained in Step 2, and collect the fiber material, balsa wood and organic liquid mixture separately; Step 4: Purify and dry the fiber material to obtain dried recycled fiber.

[0009] Through the above steps, this invention achieves efficient and selective degradation of epoxy resin at low temperatures via a step-by-step oxidation reaction without a catalyst. This process protects the integrity of the fiber structure while completely decomposing the matrix resin, laying the foundation for the subsequent recycling of high-value fibers. Using an oxidizing gas as a chain-severing oxidant, combined with a step-by-step oxidation reaction, achieves efficient and deep degradation of the resin, avoiding the introduction of traditional catalysts and reducing energy costs and environmental risks. Under the conditions of step 1, the cross-linked structure of bisphenol A epoxy resin (epoxy bonds and ether bonds, etc.) undergoes oxidative breakage, forming an organic mixture composed of aldehydes, ketones, acids, phenols, and peroxide intermediates. Under the conditions of step 2, the peroxide intermediates undergo further chain severing, achieving efficient and deep degradation of the epoxy resin. The fiber material, originally encapsulated by the resin, completely detaches and exists independently, ultimately forming a solid-liquid mixture of an organic liquid mixture and independent fiber material.

[0010] Preferably, the components of the waste wind turbine blades include epoxy resin, glass fiber or carbon fiber, and balsa wood.

[0011] Preferably, before step 1, a pretreatment step is included, in which the spent wind turbine blades after the removal of metal components are cut into blocks or sheets. This pretreatment operation helps to increase the reaction contact area, promotes full contact between the oxidant and the resin, and avoids the adverse effects of excessive crushing on fiber length and strength, thus ensuring efficient degradation and high-quality fiber recycling in the future.

[0012] Preferably, the polar mixed solvent is selected from C2. C9 organic acids, C2 C9 alcohols, C2 The polar mixed solvent comprises at least one of the esters of C9 and is mixed with pure water or hydrogen peroxide to form a mixed system; the mass ratio of the polar mixed solvent to the wind turbine blade is 1:1. 20:1.

[0013] This solvent system has good polarity and solubility, which can effectively swell epoxy resin and promote the penetration of oxidant into the resin, thereby significantly improving the degradation reaction rate and thoroughness.

[0014] Preferably, the organic acid is selected from at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, or citric acid; the alcohol is selected from at least one of ethanol, ethylene glycol, propanol, propylene glycol, butanol, or pentanol; and the ester is selected from at least one of methyl acetate, ethyl acetate, or propyl acetate.

[0015] The aforementioned specific types of organic acids, alcohols, and esters not only provide a suitable dissolution environment, but some components (such as organic acids) can also participate in or promote oxidative chain scission reactions, producing a synergistic effect with oxidizing gases, further reducing the energy required for the overall reaction.

[0016] Preferably, the concentration of the oxidizing gas is 10. 300 mg / L; the flow rate of the pure oxygen or oxygen-enriched gas is 0.05 mg / L. 50 L / min. The oxidizing gas is ozone gas.

[0017] By precisely controlling the concentration and flow rate of oxidizing gas, the oxidation reaction can be accurately regulated, avoiding excessive oxidation that could damage the fibers, while ensuring sufficient resin degradation and the economy of the reaction process.

[0018] Preferably, the solid-liquid separation in step 3 is performed by gravity sedimentation. The combined flotation process specifically includes: 31. Control the system temperature at 20°C. 60℃, let stand for 0.5 minutes 2 hours, allowing the system to naturally separate into layers; 32. Collect the light phase containing balsa wood from the upper layer; 33. Collect the lower layer containing fibrous material and extract the organic liquid mixture.

[0019] This separation process cleverly utilizes the significant density differences between balsa wood, fibrous materials, and the degradation liquid, achieving efficient and clean separation of the three components through simple settling. The operating temperature is controlled within a low range, avoiding solvent evaporation losses and potential thermal disturbances that could affect the separation effect. The process requires no complex mechanical equipment and has extremely low energy consumption.

[0020] Preferably, the purification and drying in step 4 includes drying at 40°C under an inert atmosphere or negative pressure. 0.2% treated at 130℃ 2h; the single fiber breaking strength of the recovered fiber is not less than 0.5GPa and the purity is not less than 98%.

[0021] Low-temperature drying under inert or negative pressure conditions can effectively prevent oxidation or thermal damage to recycled fibers during the final processing stage, ensuring their excellent mechanical properties and extremely high purity, thus meeting the requirements for direct reuse as reinforcing materials.

[0022] Preferably, the process further includes step 5: evaporating and separating the organic liquid mixture, with the light component being recycled as the polar mixed solvent, and the heavy component being mixed with the balsa wood to form a composite organic carrier or used separately as fuel. The distillation process separates the light and heavy components based on the differences in their boiling points.

[0023] This step enables a closed-loop circulation of the solvent within the reaction system, significantly reducing raw material consumption and processing costs. At the same time, it converts degradation products and balsa wood into energy carriers, achieving comprehensive resource utilization of waste. The entire process generates virtually no solid waste, resulting in significant environmental benefits.

[0024] Preferably, the gas introduced in steps 1 and 2 is dispersed in the liquid phase in the form of microbubbles, and the diameter of the microbubbles is 1. 20μm.

[0025] Microbubble technology greatly increases the contact area between the gas and liquid phases, enhances the mass transfer process, and allows oxidizing gases to act on the resin more quickly and evenly, thereby achieving efficient degradation at lower temperatures and in shorter times. At the same time, the gentle disturbance of microbubbles also helps to cleanly remove fibers and avoid mechanical damage.

[0026] Preferably, the method is carried out entirely under conditions without catalysts or strong acids and bases.

[0027] This characteristic fundamentally eliminates the problems of catalyst cost, recycling difficulties, severe equipment corrosion caused by strong acids and alkalis, and hazardous waste liquid treatment, making the entire process safer, more economical, and more environmentally friendly, and more suitable for large-scale industrial applications.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: The reaction conditions are extremely mild, significantly reducing energy consumption and costs: The entire process of this invention is carried out at a low temperature of 20-130℃, without the need for high-temperature and high-pressure equipment, and without relying on any catalysts or highly corrosive reagents, fundamentally reducing energy consumption, equipment investment and raw material costs.

[0029] The recycled fibers are of excellent quality and high value: through step-by-step oxidation and microbubble-enhanced mass transfer, the structural integrity of glass fibers or carbon fibers is protected to the greatest extent while efficiently degrading resins. The recycled fibers have high strength retention and high purity, and can be directly used for the preparation of high value-added composite materials.

[0030] The process is green and environmentally friendly with a high degree of resource utilization: the entire process has no harmful catalyst residues, no strong acid or alkali waste liquids, the solvent can be recycled, and the degradation products and balsa wood can be recovered as energy, realizing the resource utilization of almost all components of retired leaves, with outstanding environmental benefits.

[0031] The process is simple, efficient, and highly applicable: the method steps are clear, mainly utilizing physicochemical principles for degradation and separation, with relaxed requirements for raw material pretreatment, strong equipment versatility, and easy to achieve large-scale, continuous production, thus having broad application prospects. Attached Figure Description

[0032] Figure 1 This is a simplified process flow diagram of the low-temperature non-catalytic oxidation method for recovering wind turbine blades according to the present invention.

[0033] Figure 2 This is a scanning electron microscope image (50x magnification) of the recycled glass fiber material in Example 1 of the present invention.

[0034] Figure 3 This is a scanning electron microscope image (500x magnification) of the recycled glass fiber material in Example 1 of the present invention.

[0035] Figure 4 This is a graph showing the single-fiber breaking strength test curve of the recycled glass fiber material in Embodiment 1 of the present invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0037] In this invention, C2-C9 refers to organic compounds containing 2-9 carbon atoms. Specifically: C2-C9 organic acids refer to organic acids containing 2-9 carbon atoms, such as formic acid, acetic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, octanoic acid, geranic acid, citric acid, etc.; C2-C9 alcohols refer to organic alcohols containing 2-9 carbon atoms, such as ethanol, ethylene glycol, propanol, propylene glycol, butanol, pentanol, n-hexanol, cyclohexanol, n-heptanol, benzyl alcohol, etc.; C2-C9 esters refer to organic esters containing 2-9 carbon atoms, such as methyl ester, ethyl ester, propyl ester, ethyl acetate, n-propyl acetate, isopropyl acetate, ethyl formate, isoamyl acetate, etc.

[0038] This embodiment discloses a method for low-temperature non-catalytic oxidation recovery of wind turbine blades, combined with... Figure 1 As shown, the specific steps include: Step 1, Raw Material Pretreatment: The discarded wind turbine blades, after the metal components have been removed, are cut into blocks or sheets to reduce pretreatment energy consumption while preserving the integrity of the fibers. The components of the discarded wind turbine blades include epoxy resin, glass fiber or carbon fiber, and balsa wood.

[0039] Step 2: Pass the block or sheet-shaped wind turbine blade and polar mixed solvent into an oxidizing gas at 20°C. The reaction was carried out at 100℃ for 0.5 seconds. After 5 hours, a mixture containing an organic liquid and a peroxide intermediate is formed; wherein the polar mixed solvent is selected from at least one of C2-C9 organic acids, C2-C9 alcohols, and C2-C9 esters, and is mixed with pure water or hydrogen peroxide.

[0040] In this scheme, any one of the following—C2-C9 organic acids, C2-C9 alcohol solvents, and C2-C9 ester solvents—is used as a solvent in a single or mixed system with pure water or hydrogen peroxide.

[0041] In this invention, the diameter of the strong oxidizing microbubbles is 1-20 μm. Their specific surface area is more than 50 times greater than that of traditional bubble reactors (bubble diameter greater than 1 mm), significantly increasing the contact area between the oxidant and the wind turbine blade bulk material and the polar mixed solvent. This greatly enhances mass transfer efficiency, allowing the oxidation reaction to penetrate uniformly into the raw material, ensuring the complete degradation of the cross-linked structure (epoxy groups, isopropylidene groups, and ether bonds) of the bisphenol A epoxy resin, while simultaneously ensuring that the fiber material is fully freed from resin binding and maintains its intact morphology.

[0042] Among them, organic acids include at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, and citric acid; alcohols include one or a mixture of ethanol, ethylene glycol, propanol, propylene glycol, butanol, and pentanol; and C2-C9 esters are selected from at least one of methyl ester, ethyl ester, and propyl ester. Methyl esters are a collective term for ester compounds formed by the esterification reaction of methanol with various organic acids. Their general formula is R-COO-CH3. Ethyl ester: refers to a general term for ester compounds formed by the esterification reaction of ethanol with various organic acids. Its general formula is R-COO-C2H5.

[0043] Propyl ester: refers to a general term for ester compounds formed by the esterification reaction of propanol with various organic acids. Its general formula is R-COO-C3H7.

[0044] The mass ratio of the mixed solvent to the raw material for wind turbine blades is 1:1-20:1; The solvent system described above can not only improve the homogeneity of the reaction system, but also promote the degradation of epoxy resin and the dissolution of products.

[0045] In this invention, an oxidizing gas, such as ozone (concentration 10-300 mg / L), is selected as a chain-breaking oxidant. Combined with a step-by-step oxidation reaction, it achieves efficient and deep degradation of the resin, which avoids the introduction of traditional catalysts and reduces energy consumption costs and environmental risks.

[0046] Step 3: Pass pure oxygen or oxygen-enriched gas into the mixture obtained in Step 2, at 20°C. The reaction continued at 130℃ for 0.5 seconds. After 5 hours, the epoxy resin undergoes efficient and deep degradation. The fiber material, originally encapsulated by the resin, completely detaches and exists independently, ultimately forming a solid-liquid mixture of an organic liquid mixture and the independent fiber material. The flow rate of the pure oxygen or oxygen-enriched gas is 0.05%. 50L / min.

[0047] Step 4: Perform solid-liquid separation on the solid-liquid mixture obtained in Step 3, collecting the fiber material, balsa wood, and organic liquid mixture separately. Utilizing the significant density differences between balsa wood (density approximately 0.08-0.12 g / cm³), glass fiber (density approximately 2.5-2.7 g / cm³), carbon fiber (density approximately 1.5-2.0 g / cm³), and the organic liquid mixture (density approximately 0.8-1.0 g / cm³), a gravity sedimentation-flotation combined separation process is employed to achieve efficient separation of the three components. The specific operation is as follows: First, maintain the temperature inside the apparatus from Step 2 at 20-60℃ (to avoid solvent evaporation and the effect of temperature on density), and allow it to stand for 0.5-2 hours to allow the system to naturally separate into layers. Then, collect the upper layer of wet balsa wood through the controllable discharge port at the top of the apparatus. Next, collect the fiber concentrate through the filter device at the bottom of the apparatus, and discharge the organic liquid mixture through the discharge port for recycling.

[0048] Furthermore, this scheme also includes purifying and drying the fiber concentrate: blowing nitrogen or argon into a microbubble reactor (flow rate 0.5-5 L / min), or performing vacuum treatment (vacuum degree 10-5000 Pa), while heating at a low temperature of 40-130℃ for 0.2-2 h to remove the residual solvent on the fiber surface, thereby obtaining a dried fiber material with a single fiber breaking strength maintained above 0.5 GPa and a fiber purity of not less than 98%.

[0049] Furthermore, regarding solvent recovery: the organic liquid mixture and wet balsa wood obtained in step 3 are treated by methods such as atmospheric pressure drying or vacuum evaporation. The separated light components are directly returned to the microbubble reactor in step 1 and recycled as a polar mixed solvent. The obtained heavy components (organic mixtures with boiling points above 150 degrees Celsius, such as phenols and acids) and dry balsa wood can be directly mixed to form a composite organic carrier, which can be directly used as a heating energy source for combustion in industrial boilers. Dry balsa wood can also be used alone as a biomass energy reserve, realizing diversified utilization of resources.

[0050] To fully demonstrate the synergistic effect of temperature, oxidant, and solvent in this invention and its significant technical effects, the following examples were set up and analyzed in conjunction with product quality testing data (such as fiber strength, purity, etc.).

[0051] Example 1 (Low-temperature ozone + medium-temperature oxygen + organic acid system) This embodiment provides a method for low-temperature non-catalytic oxidation recovery of wind turbine blades, and the specific steps are as described in the detailed implementation method above. This embodiment focuses on disclosing parameter information.

[0052] The purpose of this embodiment is to verify the synergistic degradation effect of ozone and organic acid solvents under low-temperature conditions. The specific parameter information is shown in Table 1: Table 1 is a summary of parameter information for Example 1.

[0053] Example 2 (Medium-temperature ozone + medium-temperature oxygen + acid / alcohol mixture system) This embodiment provides a method for low-temperature non-catalytic oxidation recovery of wind turbine blades, and the specific steps are as described in the detailed implementation method above. This embodiment focuses on disclosing parameter information.

[0054] The purpose of this embodiment is to verify the degradation efficiency of a mixed solvent composed of ozone, pure oxygen, alcohols, and acids under medium-temperature conditions.

[0055] The specific parameter information is shown in Table 2: Table 2 is a summary of parameter information for Example 2.

[0056] Example 3 (Medium-temperature ozone + high-temperature oxygen + acid / ester mixed solvent system) This embodiment provides a method for low-temperature non-catalytic oxidation recovery of wind turbine blades, and the specific steps are as described in the detailed implementation method above. This embodiment focuses on disclosing parameter information.

[0057] The purpose of this embodiment is to verify the degradation ability under medium and high temperature conditions, as well as the compatibility with mixed solvents composed of acids and esters.

[0058] The specific parameter information is shown in Table 3: Table 3 is a summary of parameter information for Example 3.

[0059] The recycled fibers obtained in Examples 1-3 were subjected to quality testing: The specific testing methods are as follows: Single fiber strength is tested using a single fiber tensile tester to measure its breaking strength (F, unit N), combined with scanning electron microscopy (SEM) to measure its single fiber diameter (D, m), and then the breaking strength (σ, GPa) is calculated according to the following formula. Fiber purity is determined using the thermogravimetric method. The recovered glass fibers (M1, g) are calcined at 500℃ until a constant weight (M2, g) is reached, and the fiber purity (P) is calculated according to Formula 2. r ).

[0060]

[0061]

[0062] The test results are shown in Table 5: Table 5 summarizes the test data from Examples 1-3.

[0063] in, Figure 2 , Figure 3 These are scanning electron microscope (SEM) images of the recycled fiber material from Example 1 at different magnifications. Figure 2 It can be seen that the fibers are dispersed with no obvious agglomeration; the fiber surface is basically smooth with no obvious resin residue; the fiber length is well maintained with no obvious mechanical damage or breakage; and the boundaries between the overall fiber bundles are clear, indicating that the epoxy resin matrix has been effectively degraded and removed. This shows that the method of the present invention achieves complete degradation of the resin under mild conditions, while providing good protection for the fiber structure.

[0064] Figure 3 The individual fibers are clearly visible as smooth and clean, free of adhering particles or resin residue; the fiber diameter is uniform, with no corrosion pits or surface etching; the fiber cross-section is flat, without signs of melting or brittle fracture due to thermal damage; and there is no adhesion between fibers, indicating that the resin has been completely removed and the fibers are completely independent. This further proves that the step-by-step oxidation process used in this invention efficiently degrades the resin without damaging the microstructure of the fibers, resulting in excellent surface quality of the recovered fibers, which can be directly used for the reprocessing of composite materials.

[0065] Figure 4 In the test, the load-displacement curve exhibited typical linear elastic characteristics until fracture; the maximum breaking strength was 0.2122 N (based on actual data); combined with the fiber diameter measured by SEM (approximately 20 μm), the single-fiber breaking strength was calculated to be 0.68 GPa; the curve was smooth and without fluctuations, indicating that the fiber surface was free of defects and that there was no slippage or premature fracture during the test. These test results demonstrate that the recycled glass fiber of this invention possesses excellent mechanical properties, with a breaking strength reaching 0.68 GPa, exceeding the lower limit requirement of 0.5 GPa, thus meeting the performance standards for reuse as a reinforcing material.

[0066] In this scheme, a microbubble reactor can generate strong oxidizing microbubbles with a diameter of 1-20 μm, which significantly increases the contact area between the oxidant and the raw materials of wind turbine blade bulk materials and polar mixed solvents, greatly enhancing mass transfer efficiency. This allows the oxidation reaction to penetrate uniformly into the interior of the raw materials, ensuring the complete degradation of the cross-linked structure (epoxy groups, isopropylidene groups, and ether bonds) of the bisphenol A epoxy resin, while ensuring that the fiber material is fully freed from the resin and maintains its intact morphology. The microbubble reactor integrates strong oxidation reaction, deep oxidation reaction, and preliminary solid-liquid separation functions, simplifying the process flow, reducing equipment footprint, and lowering equipment investment costs.

[0067] In terms of process control, the reaction temperature is strictly controlled within a low-temperature range of 20-130℃, eliminating the need for heavy equipment such as high-temperature heating furnaces. Compared with traditional high-temperature degradation processes, energy consumption is significantly reduced. The entire process does not involve corrosive reagents such as strong acids and alkalis, greatly reducing the risk of equipment corrosion and maintenance costs. At the same time, no catalysts are required, avoiding secondary pollution problems caused by catalyst residues. The final products are only fiber materials, recyclable solvents, and organic energy carriers, with no harmful pollutant emissions, demonstrating outstanding environmental advantages.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recycling wind turbine blades, characterized in that, Includes the following steps: Step 1: Place the pretreated waste wind turbine blades in a polar mixed solvent, introduce oxidizing gas, and react at 20-100℃ for 0.5-5 hours to cause the epoxy resin to undergo oxidative chain scission, forming a mixture containing organic matter and peroxide intermediates. Step 2: Introduce pure oxygen or oxygen-enriched gas into the mixture obtained in Step 1, and continue the reaction at 20-130℃ for 0.5-5 hours to further degrade the peroxide intermediate in the mixture, thereby obtaining a solid-liquid mixture of organic liquid mixture and independent fiber material. Step 3: Perform solid-liquid separation on the solid-liquid mixture obtained in Step 2, and collect the fiber material, balsa wood and organic liquid mixture separately; Step 4: Purify and dry the fiber material to obtain dried recycled fiber.

2. The method for recycling wind turbine blades according to claim 1, characterized in that, In step 1, the pretreatment step is to cut the waste wind turbine blades after removing the metal components into blocks or sheets.

3. The method for recycling wind turbine blades according to claim 1, characterized in that, The polar mixed solvent is selected from at least one of C2-C9 organic acids, C2-C9 alcohols, and C2-C9 esters. The polar mixed solvent forms a mixed system with pure water; or, the polar mixed solvent forms a mixed system with hydrogen peroxide. The mass ratio of the polar mixed solvent to the wind turbine blade is 1:1 to 20:

1.

4. The method for recycling wind turbine blades according to claim 3, characterized in that, The organic acid is selected from at least one of acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, oxalic acid, malonic acid, succinic acid, or citric acid; The alcohols are selected from at least one of ethanol, ethylene glycol, propanol, propylene glycol, butanol, or pentanol; The esters are selected from at least one of methyl acetate, ethyl acetate, or propyl acetate.

5. The method for recycling wind turbine blades according to claim 1, characterized in that, The concentration of the oxidizing gas is 10-300 mg / L; the flow rate of the pure oxygen or oxygen-enriched gas is 0.05-50 L / min.

6. The method for recycling wind turbine blades according to claim 1, characterized in that, The solid-liquid separation in step 3 employs a combined gravity sedimentation-flotation process, specifically including: Step 31: Control the system temperature at 20-60℃ and let it stand for 0.5-2 hours to allow the system to naturally separate into layers; Step 32: Collect the upper light phase containing balsa wood; Step 33: Collect the lower layer of heavy phase containing fibrous material and extract the organic liquid mixture.

7. The method for recycling wind turbine blades according to claim 1, characterized in that, The purification and drying process in step 4 includes treatment at 40-130℃ for 0.2-2 hours under an inert atmosphere or negative pressure; the resulting recycled fibers have a single fiber breaking strength of not less than 0.5 GPa and a purity of not less than 98%.

8. The method for recycling wind turbine blades according to claim 1, characterized in that, The process also includes step 5: evaporating and separating the organic liquid mixture, recycling the light components as a polar mixed solvent, and mixing the heavy components with the balsa wood to form a composite organic carrier or using them separately as fuel.

9. The method for recycling wind turbine blades according to claim 1, characterized in that, The gas introduced in steps 1 and 2 is dispersed in the liquid phase in the form of microbubbles, the diameter of which is 1-20 μm.

10. The method for recycling wind turbine blades according to any one of claims 1-9, characterized in that, The method is carried out entirely under conditions without catalysts or strong acids and bases.

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