Method for synergistically recovering glass fibers and preparing hard carbon negative electrode material based on retired blades

Abstract

The invention belongs to the technical field of resource circulation, and mainly relates to a method for synergistically recovering glass fibers and preparing a hard carbon negative electrode material based on retired leaves. The method comprises the steps that the retired windmill blades are subjected to cleaning, mechanical crushing, subzero treatment and crushing and then graded, and blade recycling particles are obtained; stirring and mixing the blade recovery particles with a catalyst solution, and drying to obtain catalyst-loaded particles; the catalyst solution is any one or more of a soluble ferric salt solution, a zinc salt solution and a potassium hydroxide solution; carrying out heating carbonization treatment on the catalyst-loaded particles in an inert atmosphere, and carrying out multi-stage linkage separation to obtain glass fibers and an intermediate phase carbon source; and carrying out high-temperature graphitization treatment on the intermediate-phase carbon source, washing, drying and grading to obtain the hard carbon negative electrode material. According to the method, the glass fibers and the epoxy resin materials in the retired blades are recycled in a high-quality mode, the hard carbon material with excellent electrical properties is obtained, and the method is environmentally friendly and high in economic value.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology, and mainly relates to a method for the synergistic recycling of glass fiber from decommissioned blades and the preparation of hard carbon anode materials. Background Technology

[0002] With the rapid development of my country's wind power industry, a large number of wind turbines have reached their design lifespan, and the number of retired blades is increasing. Improper disposal of wind turbine blades not only wastes resources but also has adverse environmental impacts. Wind turbine blades are made of high-performance composite materials, such as fiberglass and epoxy resin, which still have high value after blade retirement. Through recycling and processing, these composite materials can be reused, reducing resource waste and contributing to the goal of a circular economy.

[0003] Current methods for recycling wind turbine blades include: First, cutting the blades into small, temporary shelters. While this temporarily houses the retired blades, it doesn't reuse their components, resulting in low economic efficiency. Second, sidewall cutting eliminates end-face closure after blade segmentation, allowing for successful recovery of glass fibers. However, this method only provides preliminary glass fiber recovery with low purity. Third, oxygen-enriched heat treatment of the blades, using pyrolysis and low-temperature oxidation processes, and utilizing the heat from pyrolysis gas and residual carbon combustion to provide energy for glass fiber recovery. However, this method doesn't treat and recover the resin components. Fourth, blending retired wind turbine blades with asphalt mixtures to obtain modified asphalt mixtures for direct use in highway construction. Fifth, using oscillating purging combined with pyrolysis under specific catalytic conditions to efficiently recover glass fibers from the blades while simultaneously converting organic matter into syngas products.

[0004] Currently, the recycling of retired wind turbine blades has formed a pattern of three parallel technical routes: mechanical, pyrolysis, and chemical. However, their maturity, economics, and scalability vary significantly. Mechanical recycling is the most mature, but the product purity is low; the recycled materials can be used as roadbeds, sound insulation boards, or plastic fillers. Pyrolysis technology offers high purity but produces limited products; pyrolysis of wind turbine blades can recover glass fiber or carbon fiber, with even higher purity glass fiber. Chemical solvent methods offer high precision but are less environmentally friendly and have high costs; they use ethylene glycol, nitric acid, or alkaline solutions to dissolve epoxy resin, making them suitable for manufacturing high-end composite materials.

[0005] Existing recycling technologies, such as mechanical crushing, produce low-value products; fluidized bed recycling, which is energy-intensive; and solvent decomposition, which is costly and complex, making large-scale application difficult. The core challenges lie in: first, how to efficiently and cleanly separate glass fibers from cross-linked epoxy resin; second, how to convert thermosetting epoxy resin into high-value-added products, rather than simple fuels or low-value fillers; and third, how to achieve economic feasibility and environmental friendliness throughout the entire recycling process. Summary of the Invention

[0006] To overcome the technical problems in recycling wind turbine blades in existing technologies, this invention combines a specific crushing process, a thermal pyrolysis method, and a multi-stage linkage separation technology to achieve the clean recycling of glass fiber and the high-value conversion of epoxy resin.

[0007] In this embodiment of the invention, a method for preparing hard carbon anode materials based on the synergistic recycling of glass fiber from decommissioned wind turbine blades is provided, the method comprising the following steps: S1. The retired wind turbine blades are cleaned, mechanically crushed, cryogenically treated and crushed, and then graded to obtain blade recycling particles. S2. The recovered leaf particles are stirred and mixed with the catalyst solution and then dried to obtain catalyst-supported particles; the catalyst solution is any one or more of soluble iron salt solution, zinc salt solution and potassium hydroxide solution; S3. The catalyst-supported particles are subjected to heating and carbonization treatment in an inert atmosphere, and then glass fiber and mesophase carbon source are obtained through multi-stage linkage separation. S4. The intermediate phase carbon source is subjected to high-temperature graphitization treatment, followed by impurity removal, washing, drying, and classification to obtain hard carbon anode material.

[0008] As an optional implementation, the cryogenic treatment and crushing in step S1 includes: The mechanically crushed material is cryogenically treated at -200~-180℃ for 40~60 minutes; The cryogenically treated material is subjected to impact crushing at a temperature of -60~-40℃ in an inert atmosphere.

[0009] As an optional implementation, the particle size of the recovered blade particles ranges from 0.2 mm to 2.0 mm.

[0010] As an optional implementation, in step S2, the concentration of the catalyst solution is 0.2~0.5 mol / L; the temperature during stirring and mixing is 25~65℃, and the stirring time is 3~5h; the mass ratio of the recovered blade particles to the catalyst solution is 1:1.5~3.

[0011] As an optional implementation, the drying temperature in step S2 is 75~90℃, and the drying time is 10~16h.

[0012] As an optional implementation, the heating heat treatment in step S3 includes: First stage: Heat to 200~220℃ and hold for 25~35 minutes; Second stage: Continue to raise the temperature to 390~420℃ and hold for 55~70 minutes; Third stage: Continue to heat to 600~640℃ and keep warm for 100~150 minutes.

[0013] As an optional implementation, the multi-stage linkage separation in step S3 includes: screening, airflow separation and electrostatic separation.

[0014] As an optional implementation, the high-temperature graphitization treatment in step S4 is as follows: heating to 1200~1400℃ and holding for 80~100 minutes.

[0015] As an optional implementation, the impurity removal, washing, and drying process in step S4 includes: The hard carbon material after high-temperature graphitization treatment is placed in a 1-3 mol / L hydrochloric acid solution and refluxed and stirred at 60-80℃ for 4-5 hours. It is then washed multiple times with water until the filtrate is neutral, and then vacuum dried.

[0016] As an optional implementation, the particle size of the hard carbon anode material in step S4 is 8~12μm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention solves the most challenging problems in composite material recycling: "component separation" and "reuse of each component," achieving synergistic high-value recycling of epoxy resin and glass fiber. For the epoxy resin component in retired wind turbine blades, while recycling glass fiber, it is prepared as a "high-quality precursor" for high-performance hard carbon. This invention utilizes the different physical properties of epoxy resin and glass fiber, employing cryogenic treatment and low-temperature crushing technology to achieve interface separation between glass fiber and epoxy resin. After screening, appropriately sized blade particles are mixed with a catalyst solution, and the epoxy resin is carbonized through pyrolysis. Then, through crushing and a multi-stage linkage separation system, glass fiber and mesophase carbon source are separated. Finally, the mesophase carbon source is graphitized and subjected to acid washing and other impurity removal processes to obtain hard carbon material. Through innovative cryogenic embrittlement crushing and grading processes, the length and strength of the fiber are maintained to the maximum extent, achieving a purity of over 97%. This high-quality recycled fiber can be reused as a reinforcing material in composite material products (such as automotive parts and building materials), realizing a closed-loop cycle.

[0018] (2) This invention does not simply carbonize epoxy resin, but incorporates a series of targeted processes to ensure the excellent electrochemical performance of the final hard carbon product. By adding transition metal salts such as Fe and Zn or potassium hydroxide as catalysts, the nano-metal particles formed by the decomposition of the catalyst precursors during pyrolysis can serve as active sites, effectively catalyzing the breaking and recombination of CH and CC bonds. The added catalyst promotes the formation of cross-linked structures, significantly increasing the carbon yield from 40% in direct pyrolysis to 65%-75%, greatly improving economic efficiency. In addition, the catalyst guides the pyrolysis path of epoxy resin towards the generation of carbon structures more conducive to sodium ion storage, such as the formation of richer nanopores, more suitable interlayer spacing, and a better conductive network, resulting in good electrochemical performance when the hard carbon material is applied to sodium-ion batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The TEM spectrum of the hard carbon material HC-C1 provided in Example 1 of this invention; Figure 2 The image shows the SEM pattern of the hard carbon material HC-C1 provided in Example 1 of this invention. Detailed Implementation

[0021] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0022] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] The retired wind turbine blades used in this invention are all made of glass fiber / epoxy resin composite material, and their main components are shown in Table 1.

[0025] Table 1. Composition and content of composite materials for wind turbine blades To separate and recycle the various components of the aforementioned decommissioned wind turbine blades, this invention provides a method for the synergistic recovery of glass fiber from decommissioned wind turbine blades and the preparation of hard carbon anode materials, comprising the following steps: S1. The waste wind turbine blades are crushed into blocks <50 mm using a twin-shaft shear crusher. The coarsely crushed material is then fed into a liquid nitrogen cryogenic chamber and treated at -200~-180℃ for 40-60 minutes to fully embrittle the epoxy resin while maintaining the toughness of the glass fiber. The cryogenically cooled material is then rapidly fed into a low-temperature (-60~-40℃) grinder, where it is crushed by the impact of high-speed rotating hammers. The difference between the brittleness of the epoxy resin and the toughness of the glass fiber is utilized to achieve separation at the interface. The crushed material is then conveyed by an airflow separator for classification, collecting blade particles with a particle size between 0.2 mm and 2.0 mm. This particle size range exhibits the highest degree of dissociation and maintains good glass fiber length, making it an ideal feed for subsequent heat treatment. Material with an excessively large particle size (>2.0 mm) is returned for re-crushing, while excessively fine powder (<0.2 mm) can be collected separately as filler.

[0026] S2. Select transition metal iron salts, Lewis acid zinc salts, and potassium hydroxide as catalysts, and prepare a catalyst solution of 0.2~0.5 mol / L. Mix the recovered blade particles with the catalyst solution at a mass ratio of 1:1.5~3, and heat and stir until homogeneous. The temperature is 25~65℃, and the stirring time is 3~5 hours (the purpose of heating is to reduce the solution viscosity, increase the molecular motion rate, thereby enhancing the mass transfer process and promoting Fe...). 3+ Ions fully penetrate the microstructure of the epoxy resin through diffusion and capillary action. (This step is crucial to ensure uniform catalyst distribution.) Afterward, the catalyst-loaded particles are dried at 75-90°C for 10-16 hours.

[0027] S3. Spread the catalyst-supported particles evenly inside a quartz boat, with a layer thickness not exceeding 40 mm. Then, connect the legs of the quartz boat to the constant temperature zone of a temperature-controlled tube furnace. Perform heat treatment in an inert atmosphere, following the specific procedure: Atmosphere control: From room temperature to the end of the reaction, high-purity inert gas is introduced at a flow rate of 1.2 L / min to create an absolutely inert reaction environment and to promptly remove small molecule gases generated by pyrolysis.

[0028] Programmable temperature rise and control: The first stage (drying and preheating): the temperature is increased to 200~220℃ at a rate of 10℃ / min, and held at this temperature for 25~35min. This stage is mainly used to remove physically adsorbed water and some small molecule volatiles.

[0029] The second stage (softening and catalytic decomposition): The heating rate is reduced to 3℃ / min, and the temperature is slowly increased to 390~420℃ and held for 55~70min. During this stage, the epoxy resin network begins to soften and undergoes preliminary depolymerization and cross-linking reactions under the catalysis of the catalyst. The catalyst melts at this temperature, forming a liquid phase that comes into full contact with the resin, significantly catalyzing the breaking and recombination of C-C and CH bonds, inhibiting the formation of small molecule volatiles, and greatly improving the carbon fixation rate.

[0030] The third stage (deep carbonization): The temperature is slowly increased to 600-640℃ at a rate of 2℃ / min and held for 100-150 minutes. This is the crucial stage for the deep carbonization of the resin's main structure. The continuous action of the catalyst enables the resin to be efficiently transformed into a solid carbon skeleton rich in nanopores, while the glass fibers are completely exfoliated.

[0031] After the thermal conversion is completed, the system is naturally cooled to below 80 °C under continuous N2 supply. The oil and gas generated in the above-mentioned heating heat treatment process are condensed and separated to obtain liquid chemical fuel and non-condensable gas, and the non-condensable gas is either recovered or used to provide heat energy for the heating heat treatment process.

[0032] The product was extracted; it was a mixture of glass fiber and hard carbon, with a loose structure that was extremely easy to crush. The aggregates were then lightly crushed using a mortar and pestle or a low-speed crusher.

[0033] The initially crushed mixture is fed into a multi-stage linkage separation system.

[0034] First, the glass fibers are sieved through an ultrasonic vibrating screen (40 mesh). Most of the glass fibers are retained due to their long size, while the fine powdery hard carbon passes through the screen.

[0035] Then, a controlled airflow separation is applied to the sieve material (rich in glass fiber), and the residual hard carbon particles are further separated by utilizing the density and shape differences between the glass fiber and the hard carbon particles.

[0036] Finally, the undersize material is subjected to high-voltage electrostatic separation (20 kV). Taking advantage of the significant difference in conductivity between the two materials, a very small amount of glass fiber powder is efficiently removed from the hard carbon product.

[0037] Through the above three separation steps, high-purity glass fiber and high-purity mesophase carbon source are finally obtained.

[0038] S4. Spread the mesophase carbon source evenly in a quartz boat, with a layer thickness not exceeding 40 mm. Then, push the quartz boat into the isothermal zone of a temperature-controlled tube furnace. Heating is performed in an inert atmosphere at a rate of 5 °C / min to 1200–1400 °C (preferably 1300 °C in this invention), and held for 80–100 min. This high-temperature stage aims to eliminate defects and heteroatoms (H, O, N) in the carbon material, promoting short-range ordering of the carbon layer structure (i.e., forming graphite microcrystals), thereby significantly improving the material's conductivity and electrochemical stability. After this stage, the carbon source is completely converted into hard carbon material. The high-temperature graphitized hard carbon material is then placed in a 1–3 mol / L hydrochloric acid solution and refluxed at 60–80 °C for 4–5 h. It is then washed multiple times with water until the filtrate is neutral, and then vacuum dried to obtain the hard carbon anode material. The wet hard carbon filter cake is loosely broken and evenly spread on a stainless steel tray with a thickness of approximately 2 cm. First stage drying: Push the material tray into the drying apparatus and close the chamber door. Start the vacuum pump to reduce the absolute pressure inside the chamber to 10 kPa. Start the heating system and raise the temperature to 50 °C at a rate of 3 °C / min, maintaining this temperature for 3 hours. Second stage drying: Switch to a high-vacuum molecular pump to reduce the absolute pressure inside the chamber to 0.5 kPa. Slowly raise the temperature to 70 °C and maintain this temperature for 6 hours. After drying, stop heating, fill the chamber with high-purity nitrogen to atmospheric pressure, and allow the temperature to cool naturally to 30 °C before removing the dried hard carbon material.

[0039] The dried hard carbon powder was classified using a centrifugal air classifier, and particles with a D50 of 8~12μm were collected as the final product to ensure that it has good electrode processing performance.

[0040] It should be understood that during the high-temperature carbonization and graphitization processes in steps S3 and S4, some pyrolysis oil and gas will be generated. This oil and gas can be extracted from the reactor and separated by a condenser. The condensed liquid tar can be collected as a chemical feedstock or fuel. Non-condensable gases (such as CO, CH4, H2, etc.) have high calorific values ​​and can be introduced into the combustion chamber for direct combustion, providing some or all of the heat energy to the pyrolysis reactor. This significantly reduces the external energy consumption of the entire process, achieving energy self-sufficiency and recycling.

[0041] To determine the electrical properties of the aforementioned hard carbon material, it was used as a negative electrode active material in sodium-ion batteries. The hard carbon material, conductive agent (acetylene black), and binder (sodium carboxymethyl cellulose CMC) were mixed in a certain ratio (8:1:1) to form a slurry, which was then coated onto a current collector (aluminum foil). After drying, rolling, and slicing, the sodium-ion battery negative electrode sheet was produced.

[0042] This invention utilizes a specific pulverization process to combine epoxy resin and glass fiber, and enhances carbon recovery through a catalytic carbonization process. A multi-stage separation method separates the glass fiber from the mesophase carbon source. Finally, graphitization and acid washing processes yield a hard carbon material with abundant nanopores, which can be applied to sodium-ion batteries. This invention achieves the separation and recovery of various components in wind turbine blades, provides high-performance materials for new energy applications, realizes resource recycling, and is environmentally friendly and highly economical.

[0043] The following is a further explanation using specific embodiments.

[0044] Example 1 S1. A high-pressure water jet cleaner, combined with a neutral, environmentally friendly cleaning agent, thoroughly rinses the blade surface. After cleaning, primary crushing is performed using a high-power twin-shaft shear crusher. This equipment uses two opposing rotating cutter shafts to shear, tear, and compress the material, breaking it into blocks smaller than 50 mm. The blocks are then placed in an intermittent liquid nitrogen cryogenic chamber (-196 ℃) and held for 60 minutes. Equipped with a precise temperature control system and internal stirring device, it ensures uniform cooling of the material. The cryogenically treated material is then rapidly transferred to a cryogenic grinder. In a sealed environment with continuous injection of cold nitrogen, this equipment uses high-speed rotating hammers or blades to impact-crush the brittle material. The crushed mixture is then graded using an airflow separator. By adjusting the airflow speed, the material is divided into three parts: fine powder (<0.2 mm): mainly composed of completely pulverized epoxy resin powder and extremely short fibers, which can be collected separately as filler. Target particles (0.2-2.0 mm): This portion of the material exhibits the highest degree of dissociation between epoxy resin and glass fiber, with well-preserved fiber length, making it an ideal raw material for subsequent catalytic impregnation and centrifugal separation. Coarse particles (>2.0 mm): These are mainly incompletely dissociated composite lumps, which are returned to the coarse crushing process for recycling.

[0045] S2. Ferric chloride hexahydrate (FeCl3·6H2O) was selected as the catalyst, and a 0.4 mol / L FeCl3 aqueous solution was prepared. The recovered blade particles and 1160 kg (mass ratio 1:2) of the catalyst solution were added to a large impregnation vessel equipped with a stirrer and stirred continuously at 60 °C for 3 hours. The impregnated material was transferred to a vacuum drying oven and dried at 80 °C and -0.1 MPa for 12 hours to obtain catalyst-supported particles. Calculations showed that iron (Fe) was successfully supported on the epoxy resin, with a mass percentage of approximately 3 wt% of the epoxy resin.

[0046] S3. Spread the dried catalyst-supported particles evenly inside a quartz boat, with a layer thickness not exceeding 40mm. Then, connect the legs of the quartz boat to the constant temperature zone of a temperature-controlled tube furnace. Perform heat treatment in an inert atmosphere, following the specific procedure: Atmosphere control: From room temperature to the end of the reaction, high-purity inert gas is introduced at a flow rate of 1.2 L / min to create an absolutely inert reaction environment and to promptly remove small molecule gases generated by pyrolysis.

[0047] First stage (drying and preheating): Heat to 200℃ at a rate of 10℃ / min and hold at this temperature for 30 min. Second stage (softening and catalytic decomposition): Reduce the heating rate to 3℃ / min, slowly heat to 400℃, and hold for 60 min. Third stage (deep carbonization): Slowly heat to 600℃ at a rate of 2℃ / min and hold for 120 min. Allow the system to cool naturally to below 80℃ under continuous N2 purging. The product, a mixture of glass fiber and mesophase carbon source, has a loose structure and is easily pulverized. Lightly crush the agglomerates using a mortar and pestle or a low-speed crusher.

[0048] The initially crushed mixture is fed into a multi-stage linkage separation system: First, it is sieved through an ultrasonic vibrating screen (40 mesh), where most of the glass fibers are retained due to their long size, while the fine powdery mesophase carbon source passes through the screen. Then, a controlled airflow separation is applied to the oversize material (rich in glass fibers), utilizing the density and shape differences between the glass fibers and the mesophase carbon source to further separate the remaining hard carbon particles. Finally, the undersize material undergoes high-voltage electrostatic separation (20 kV), utilizing the significant difference in conductivity between the two to efficiently remove a very small amount of glass fiber powder from the mesophase carbon source product. The final result is high-purity glass fibers and high-purity mesophase carbon source.

[0049] S4. Spread the mesophase carbon source evenly in a quartz boat, with a layer thickness not exceeding 40 mm. Then, push the quartz boat into the isothermal zone of a temperature-controlled tube furnace. Heating to 1300 °C at a rate of 5 °C / min under an inert atmosphere and holding for 90 min. Cool the system naturally to below 80 °C under continuous N2 purging, and remove the product. Place the product in a 0.1 mol / L hydrochloric acid solution and reflux at 80 °C with stirring for 4 hours to dissolve and remove catalyst residues and any possible inorganic impurities. Wash repeatedly with deionized water until the filtrate is neutral. Filter the neutralized hard carbon slurry to obtain a wet filter cake. Loosen and break the wet hard carbon filter cake, and spread it evenly on a stainless steel tray to a thickness of approximately 2 cm. Primary drying: Push the tray into the drying device and close the chamber door. Start the vacuum pump and evacuate the chamber to an absolute pressure of 10 kPa. The heating system was activated, and the temperature was increased to 50 °C at a rate of 3 °C / min, and maintained at this condition for 3 hours. Secondary drying: The high-vacuum molecular pump was switched to reduce the absolute pressure inside the chamber to 0.5 kPa. The temperature was slowly increased to 70 °C and maintained at this condition for 6 hours. After drying, heating was stopped, and high-purity nitrogen was introduced into the chamber to atmospheric pressure. After the temperature naturally cooled to 30 °C, the dried hard carbon material was removed. This material was a black, fluffy powder without lumps. A centrifugal air classifier was used to classify the dried hard carbon powder, and particles with a D50 of 10 ± 2 μm were collected as the final product HC-1 to ensure good electrode processing performance.

[0050] The final yield was 580 kg of glass fiber, which, according to XRF analysis, had a purity of 98.2%, a clean surface, and well-preserved mechanical properties, making it suitable for direct reuse in plastics or composite reinforcement. Hard carbon (HC-1): 84.6 kg of hard carbon powder was collected. Based on the total amount of epoxy resin input, the total carbon yield of this process reached 74.6%.

[0051] Example 2 S1. A high-pressure water jet cleaner, combined with a neutral, environmentally friendly cleaning agent, thoroughly rinses the blade surface. After cleaning, primary crushing is performed using a high-power twin-shaft shear crusher. This equipment uses two opposing rotating cutter shafts to shear, tear, and compress the material, breaking it into blocks smaller than 50 mm. The blocks are then placed in an intermittent liquid nitrogen cryogenic chamber (-196 ℃) and held for 60 minutes. Equipped with a precise temperature control system and internal stirring device, it ensures uniform cooling of the material. The cryogenically treated material is then rapidly transferred to a cryogenic grinder. In a sealed environment with continuous injection of cold nitrogen, this equipment uses high-speed rotating hammers or blades to impact-crush the brittle material. The crushed mixture is then graded using an airflow separator. By adjusting the airflow speed, the material is divided into three parts: fine powder (<0.2 mm): mainly composed of completely pulverized epoxy resin powder and extremely short fibers, which can be collected separately as filler. Target particles (0.2-2.0 mm): This portion of the material exhibits the highest degree of dissociation between epoxy resin and glass fiber, with well-preserved fiber length, making it an ideal raw material for subsequent catalytic impregnation and centrifugal separation. Coarse particles (>2.0 mm): These are mainly incompletely dissociated composite lumps, which are returned to the coarse crushing process for recycling.

[0052] S2. Zinc chloride (ZnCl2) was selected as the catalyst, and a 0.4 mol / L ZnCl2 aqueous solution was prepared. The recovered blade particles and 1160 kg (mass ratio 1:2) of the catalyst solution were added to a large impregnation vessel equipped with a stirrer, and stirred continuously at 60 °C for 3 hours. The impregnated material was transferred to a vacuum drying oven and dried at 80 °C and -0.1 MPa for 12 hours to obtain catalyst-supported particles. Calculations showed that iron (Fe) was successfully supported on the epoxy resin, with a mass percentage of approximately 3 wt% of the epoxy resin.

[0053] S3. Spread the dried catalyst-supported particles evenly inside a quartz boat, with a layer thickness not exceeding 40mm. Then, connect the legs of the quartz boat to the constant temperature zone of a temperature-controlled tube furnace. Perform heat treatment in an inert atmosphere, following the specific procedure: Atmosphere control: From room temperature to the end of the reaction, high-purity inert gas is introduced at a flow rate of 1.2 L / min to create an absolutely inert reaction environment and to promptly remove small molecule gases generated by pyrolysis.

[0054] First stage (drying and preheating): Heat to 200℃ at a rate of 10℃ / min and hold at this temperature for 30 min. Second stage (softening and catalytic decomposition): Reduce the heating rate to 3℃ / min, slowly heat to 400℃, and hold for 60 min. Third stage (deep carbonization): Slowly heat to 600℃ at a rate of 2℃ / min and hold for 120 min. Allow the system to cool naturally to below 80℃ under continuous N2 purging. The product, a mixture of glass fiber and mesophase carbon source, has a loose structure and is easily pulverized. Lightly crush the agglomerates using a mortar and pestle or a low-speed crusher.

[0055] The initially crushed mixture is fed into a multi-stage linkage separation system: First, it is sieved through an ultrasonic vibrating screen (40 mesh), where most of the glass fibers are retained due to their long size, while the fine powdery mesophase carbon source passes through the screen. Then, a controlled airflow separation is applied to the oversize material (rich in glass fibers), utilizing the density and shape differences between the glass fibers and the mesophase carbon source to further separate the remaining hard carbon particles. Finally, the undersize material undergoes high-voltage electrostatic separation (20 kV), utilizing the significant difference in conductivity between the two to efficiently remove a very small amount of glass fiber powder from the mesophase carbon source product. The final result is high-purity glass fibers and high-purity mesophase carbon source.

[0056] S4. Spread the mesophase carbon source evenly in a quartz boat, with a layer thickness not exceeding 40 mm. Then, push the quartz boat into the isothermal zone of a temperature-controlled tube furnace. Heating to 1300 °C at a rate of 5 °C / min under an inert atmosphere and holding for 90 min. Cool the system naturally to below 80 °C under continuous N2 purging, and remove the product. Place the product in a 0.1 mol / L hydrochloric acid solution and reflux at 80 °C with stirring for 4 hours to dissolve and remove catalyst residues and any possible inorganic impurities. Wash repeatedly with deionized water until the filtrate is neutral. Filter the neutralized hard carbon slurry to obtain a wet filter cake. Loosen and break the wet hard carbon filter cake, and spread it evenly on a stainless steel tray to a thickness of approximately 2 cm. Primary drying: Push the tray into the drying device and close the chamber door. Start the vacuum pump and evacuate the chamber to an absolute pressure of 10 kPa. The heating system was started, and the temperature was increased to 50 °C at a rate of 3 °C / min, and maintained at this condition for 3 hours. Secondary drying: The high-vacuum molecular pump was switched to reduce the absolute pressure inside the chamber to 0.5 kPa. The temperature was slowly increased to 70 °C and maintained at this condition for 6 hours. After drying, heating was stopped, and high-purity nitrogen was introduced into the chamber to atmospheric pressure. After the temperature naturally cooled to 30 °C, the dried hard carbon material was removed. The material was a black, fluffy powder without lumps. The dried hard carbon powder was classified using a centrifugal air classifier, and particles with a D50 of 10 ± 2 μm were collected as the final product HC-2 to ensure good electrode processing performance. The total carbon yield was determined to be 72.2%.

[0057] Example 3 S1. A high-pressure water jet cleaner, combined with a neutral, environmentally friendly cleaning agent, thoroughly rinses the blade surface. After cleaning, primary crushing is performed using a high-power twin-shaft shear crusher. This equipment uses two opposing rotating cutter shafts to shear, tear, and compress the material, breaking it into blocks smaller than 50 mm. The blocks are then placed in an intermittent liquid nitrogen cryogenic chamber (-196 ℃) and held for 60 minutes. Equipped with a precise temperature control system and internal stirring device, it ensures uniform cooling of the material. The cryogenically treated material is then rapidly transferred to a cryogenic grinder. In a sealed environment with continuous injection of cold nitrogen, this equipment uses high-speed rotating hammers or blades to impact-crush the brittle material. The crushed mixture is then graded using an airflow separator. By adjusting the airflow speed, the material is divided into three parts: fine powder (<0.2 mm): mainly composed of completely pulverized epoxy resin powder and extremely short fibers, which can be collected separately as filler. Target particles (0.2-2.0 mm): This portion of the material exhibits the highest degree of dissociation between epoxy resin and glass fiber, with well-preserved fiber length, making it an ideal raw material for subsequent catalytic impregnation and centrifugal separation. Coarse particles (>2.0 mm): These are mainly incompletely dissociated composite lumps, which are returned to the coarse crushing process for recycling.

[0058] S2. Potassium hydroxide (KOH) was selected as the catalyst, and a 0.4 mol / L KOH aqueous solution was prepared. The above-mentioned recovered blade particles and 1160 kg (mass ratio 1:2) of the catalyst solution were added to a large impregnation vessel equipped with a stirrer, and stirred continuously at 60°C for 3 hours. The impregnated material was transferred to a vacuum drying oven and dried at 80°C and -0.1 MPa for 12 hours to obtain catalyst-supported particles. Calculations showed that iron (Fe) was successfully supported on the epoxy resin, with a mass percentage of approximately 3 wt% of the epoxy resin.

[0059] S3. Spread the dried catalyst-supported particles evenly inside a quartz boat, with a layer thickness not exceeding 40mm. Then, connect the legs of the quartz boat to the constant temperature zone of a temperature-controlled tube furnace. Perform heat treatment in an inert atmosphere, following the specific procedure: Atmosphere control: From room temperature to the end of the reaction, high-purity inert gas is introduced at a flow rate of 1.2 L / min to create an absolutely inert reaction environment and to promptly remove small molecule gases generated by pyrolysis.

[0060] First stage (drying and preheating): Heat to 200℃ at a rate of 10℃ / min and hold at this temperature for 30 min. Second stage (softening and catalytic decomposition): Reduce the heating rate to 3℃ / min, slowly heat to 400℃, and hold for 60 min. Third stage (deep carbonization): Slowly heat to 600℃ at a rate of 2℃ / min and hold for 120 min. Allow the system to cool naturally to below 80℃ under continuous N2 purging. The product, a mixture of glass fiber and mesophase carbon source, has a loose structure and is easily pulverized. Lightly crush the agglomerates using a mortar and pestle or a low-speed crusher.

[0061] The initially crushed mixture is fed into a multi-stage linkage separation system: First, it is sieved through an ultrasonic vibrating screen (40 mesh), where most of the glass fibers are retained due to their long size, while the fine powdery mesophase carbon source passes through the screen. Then, a controlled airflow separation is applied to the oversize material (rich in glass fibers), utilizing the density and shape differences between the glass fibers and the mesophase carbon source to further separate the remaining hard carbon particles. Finally, the undersize material undergoes high-voltage electrostatic separation (20 kV), utilizing the significant difference in conductivity between the two to efficiently remove a very small amount of glass fiber powder from the mesophase carbon source product. The final result is high-purity glass fibers and high-purity mesophase carbon source.

[0062] S4. Spread the mesophase carbon source evenly in a quartz boat, with a layer thickness not exceeding 40 mm. Then, push the quartz boat into the isothermal zone of a temperature-controlled tube furnace. Heating to 1300 °C at a rate of 5 °C / min under an inert atmosphere and holding for 90 min. Cool the system naturally to below 80 °C under continuous N2 purging, and remove the product. Place the product in a 0.1 mol / L hydrochloric acid solution and reflux at 80 °C with stirring for 4 hours to dissolve and remove catalyst residues and any possible inorganic impurities. Wash repeatedly with deionized water until the filtrate is neutral. Filter the neutralized hard carbon slurry to obtain a wet filter cake. Loosen and break the wet hard carbon filter cake, and spread it evenly on a stainless steel tray to a thickness of approximately 2 cm. Primary drying: Push the tray into the drying device and close the chamber door. Start the vacuum pump and evacuate the chamber to an absolute pressure of 10 kPa. The heating system was activated, and the temperature was increased to 50 °C at a rate of 3 °C / min, and maintained at this condition for 3 hours. Secondary drying: The high-vacuum molecular pump was switched to reduce the absolute pressure inside the chamber to 0.5 kPa. The temperature was slowly increased to 70 °C and maintained at this condition for 6 hours. After drying, heating was stopped, and high-purity nitrogen was introduced into the chamber to atmospheric pressure. After the temperature naturally cooled to 30 °C, the dried hard carbon material was removed. This material was a black, fluffy powder without lumps. A centrifugal air classifier was used to classify the dried hard carbon powder, and particles with a D50 of 10 ± 2 μm were collected as the final product HC-3 to ensure good electrode processing performance. The total carbon recovery rate was 71.8%.

[0063] Comparative Example 1 Comparative Example 1 omits step S2, does not add a catalyst, and follows the same steps and conditions as Example 1. The resulting hard carbon material is denoted as HC-C1. The total carbon yield is 65.5%.

[0064] Testing and Characterization 1. Material structure characterization (1) XRD analysis: A Bruker D8 Advance diffractometer was used with Cu Kα radiation (λ=1.5406 Å), a scanning range of 10-80°, and a scanning speed of 5° / min. The results are as follows: HC-1 showed typical hard carbon diffraction broad peaks at 23.5° and 43.2°, and its graphite interlayer spacing d002 was calculated to be 0.38 nm; the XRD interlayer spacing d002 of HC-2 was... 002 0.39 nm, XRD interlayer spacing d of HC-3 002 : 0.40 nm.

[0065] (2) Raman spectroscopy: A Horiba LabRAM HR Evolution spectrometer was used with a laser wavelength of 532 nm. The ID / IG ratio of HC-1 was 1.08, which was significantly lower than that of HC-C1 (1.25), indicating that the catalyst promoted the increase in graphitization. The Raman ID / IG ratio of HC-2 was 1.12, and that of HC-3 was 1.15.

[0066] (3) TEM analysis: Using a JEM-2100F field emission transmission electron microscope, taking HC-1 obtained in Example 1 as an example, the hard carbon material is composed of highly disordered nanocrystalline regions, showing its typical disordered graphite structure. See details. Figure 1 .

[0067] (4) SEM analysis: A Hitachi SU8010 field emission scanning electron microscope was used. Taking HC-1 obtained in Example 1 as an example, see details... Figure 2 .

[0068] Electrochemical performance testing (1) Electrode preparation: The hard carbon material obtained in Examples 1-3 and Comparative Example 1, conductive carbon black (Super P), and binder (PVDF) were mixed in NMP solvent at a mass ratio of 8:1:1 to form a slurry, which was then coated onto an aluminum foil current collector and vacuum dried at 120 °C for 12 hours. The active material loading was approximately 2.5 mg / cm².

[0069] (2) Battery assembly: CR2032 button cells were assembled in an argon glove box (H2O<0.1 ppm, O2<0.1 ppm), with a sodium metal sheet as the counter electrode, a glass fiber diaphragm (Whatman GF / D), and an electrolyte of 1 M NaClO4 in EC / DEC (1:1 v / v) containing 5% FEC.

[0070] (3) Electrochemical testing: A Neware BTS-4008 testing system was used, with a voltage range of 0.01-3.0 V vs. Na / Na. + The first-cycle coulombic efficiency, cycle performance, and rate performance were measured. Taking the HC-1 battery as an example, its weekly coulombic efficiency was 85.6%. Cycling performance: at a current density of 100 mA / g, after 200 cycles, the capacity retention rate was 95.2%, with a capacity decay rate of only 0.024% / cycle. Rate performance: the reversible capacities at current densities of 20, 50, 100, 200, 500, and 1000 mA / g were 315, 305, 295, 280, 260, and 235 mAh / g, respectively. Long-term cycle performance: after 1000 cycles at a high current of 500 mA / g, the capacity retention rate still reached 88.5%.

[0071] The material properties and corresponding battery electrochemical properties of each embodiment are shown in Table 2.

[0072] Table 2 Material properties and corresponding battery electrochemical performance of each embodiment As shown in the table above, the present invention employs a heat treatment process involving a mixture of catalyst and epoxy resin, which not only improves the yield of hard carbon materials but also enhances the electrochemical performance of the hard carbon anode material. This achieves efficient recovery and application of various materials from the wind turbine blades.

[0073] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials, characterized in that, The method includes the following steps: S1. The retired wind turbine blades are cleaned, mechanically crushed, cryogenically treated and crushed, and then graded to obtain blade recycling particles. S2. The recovered leaf particles are stirred and mixed with the catalyst solution and then dried to obtain catalyst-supported particles; the catalyst solution is any one or more of soluble iron salt solution, zinc salt solution and potassium hydroxide solution; S3. The catalyst-supported particles are subjected to heating and carbonization treatment in an inert atmosphere, and then glass fiber and mesophase carbon source are obtained through multi-stage linkage separation. S4. The intermediate phase carbon source is subjected to high-temperature graphitization treatment, followed by impurity removal, washing, drying, and classification to obtain hard carbon anode material.

2. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The cryogenic treatment and crushing in step S1 includes: The mechanically crushed material is cryogenically treated at -200~-180℃ for 40~60 minutes; The cryogenically treated material is subjected to impact crushing at a temperature of -60~-40℃ in an inert atmosphere.

3. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The particle size range of the recovered blade particles is 0.2 mm to 2.0 mm.

4. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, In step S2, the concentration of the catalyst solution is 0.2~0.5 mol / L; the temperature during the stirring and mixing process is 25~65℃, and the stirring time is 3~5h; the mass ratio of the recovered blade particles to the catalyst solution is 1:1.5~3.

5. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The drying temperature in step S2 is 75~90℃, and the drying time is 10~16h.

6. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The heating carbonization process in step S3 includes: First stage: Heat to 200~220℃ and hold for 25~35 minutes; Second stage: Continue to raise the temperature to 390~420℃ and hold for 55~70 minutes; Third stage: Continue to heat to 600~640℃ and keep warm for 100~150 minutes.

7. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The multi-stage linkage separation in step S3 includes: screening, airflow separation and electrostatic separation.

8. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The high-temperature graphitization process in step S4 is as follows: heat to 1200~1400℃ and hold for 80~100 minutes.

9. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The impurity removal, washing, and drying process in step S4 includes: The hard carbon material after high-temperature graphitization treatment is placed in a 0.1~0.3mol / L hydrochloric acid solution and refluxed and stirred at 60~80℃ for 4~5h. Then it is washed with water multiple times until the filtrate is neutral, and then vacuum dried.

10. The method for synergistically recovering glass fiber from decommissioned wind turbine blades and preparing hard carbon anode materials according to claim 1, characterized in that, The particle size of the hard carbon anode material in step S4 is 8~12μm.

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