Method for chemical degradation recycling and high-value utilization of decommissioned wind power blades

Abstract

The application discloses a kind of methods for decomposing and recycling retired wind power blades chemically and high-value utilization, and relates to the field of wind power blade recycling, comprising: S1, blade cutting pretreatment;S2, acetic acid controllable swelling treatment;S3, composite solvent catalytic degradation treatment;S4, solid-liquid separation and fiber initial treatment;S5, degradation of mother liquor fractional recovery;S6, surface modification treatment of reinforced fiber;S7, fiber high-value application;The application adopts normal pressure low-temperature reaction condition throughout, the highest process temperature is only 220 DEG C, without high pressure, strong corrosion, high-temperature pyrolysis and other harsh production conditions, the corrosion resistance, pressure resistance requirements of production equipment are greatly reduced, equipment investment cost and production line operation and maintenance cost are significantly reduced, while the process can flexibly adjust parameters according to production demand, adapt to large, medium and small production lines, and the adaptability is extremely strong.

Description

Technical Field

[0001] This invention relates to the field of wind turbine blade recycling technology, specifically to a method for the chemical degradation, recycling, and high-value utilization of retired wind turbine blades. Background Technology

[0002] With the rapid development of the wind power industry, a large number of wind turbines are gradually reaching their 20-25 year service life, and the amount of retired epoxy resin-based glass fiber reinforced wind turbine blades is increasing year by year, which has become a core problem in the solid waste disposal of the wind power industry. At present, the treatment methods for retired wind turbine blades are still mainly traditional landfill, incineration, mechanical crushing, and high-temperature pyrolysis, which have many technical shortcomings and environmental and economic defects.

[0003] Traditional landfill disposal methods consume vast amounts of land resources, and epoxy resin composites are difficult to degrade naturally, causing long-term pollution of soil and groundwater. Incineration easily produces toxic and harmful gases, causing air pollution, and completely wastes the glass fiber and resin resources in the blades. Conventional mechanical recycling processes, which crush and grind the blades, severely damage the integrity of the glass fiber structure, leading to a significant decrease in the mechanical properties of the recycled fibers and extremely low added value, making them only suitable for low-end fillers and unable to achieve high-value utilization. Existing chemical recycling processes, such as high-temperature pyrolysis and strong acid and alkali degradation, generally suffer from high reaction temperatures, high pressure conditions, equipment corrosion, large solvent losses, and harsh reaction conditions. These processes not only result in extremely high equipment investment and energy consumption, but also easily cause corrosion damage to the glass fiber matrix, incomplete resin degradation, and the inability to effectively recycle the solvent, generating a large amount of secondary waste liquid and solid waste pollution, resulting in a low resource utilization rate.

[0004] Furthermore, existing recycling processes lack versatility and cannot be adapted to retired wind turbine blades with different service years, aging levels, and sizes. They struggle to provide differentiated and precise treatment for blades with mild aging, those used in conventional commercial applications, and those severely weathered and solidified. Simultaneously, the recycled glass fibers are not professionally modified, resulting in poor interfacial bonding activity and incompatible compatibility with subsequent composite material matrices. This prevents their use in the preparation of high-end functional materials, significantly limiting the resource utilization value of retired wind turbine blades and hindering the green and circular development of the wind power industry.

[0005] Therefore, we provide a method for the chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades to solve the above problems. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for the chemical degradation, recycling, and high-value utilization of retired wind turbine blades. This invention adopts a normal pressure and low temperature reaction condition throughout the process, with a maximum process temperature of only 220°C. It avoids harsh production conditions such as high pressure, strong corrosion, and high-temperature pyrolysis, significantly reducing the corrosion resistance and pressure resistance requirements of production equipment, and significantly reducing equipment investment costs and production line operation and maintenance costs.

[0007] To achieve the above objectives, the present invention employs a method for the chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades, comprising: S1. Blade cutting pretreatment: Select retired epoxy resin-based fiberglass reinforced wind turbine blades. According to the blade specifications and aging degree, cut them into blade blocks of 10-100cm specifications by water cutting, mechanical cutting or laser cutting. After cleaning the impurities and debris on the surface of the blocks, let them air dry at room temperature to remove free surface moisture and set them aside. S2. Controlled swelling treatment with acetic acid: Prepare an aqueous solution of 60% to 100% acetic acid as the swelling solution. Immerse the blade block completely in the swelling solution at a solid-liquid mass ratio of 1:7 to 1:10. Swell for 30 to 90 minutes under a closed constant temperature condition of 80 to 120°C to achieve stratification between the epoxy resin matrix and the glass fiber layer. Separate the layered glass fiber cloth. The remaining swelling solution is filtered and recycled. S3. Composite solvent catalytic degradation treatment: Prepare a composite degradation solvent composed of acetic acid, toluene, and 30% hydrogen peroxide, with a solvent volume ratio of 1:(0~0.2):(0.7~1.3). After stirring and mixing evenly, add 0.5wt.%~2.5wt.% catalyst. Immerse the layered glass fiber cloth in the degradation solvent at a solid-liquid mass ratio of 1:9~1:10, and degrade it at a constant temperature of 75~130℃ with low-speed stirring for 1~3h to completely remove the residual resin matrix on the fiber surface. S4. Solid-liquid separation and fiber pretreatment: After degradation, the system is cooled to room temperature to 70°C, and solid-liquid separation is carried out by pressing, vacuum filtration or plate and frame filtration; the separated solid glass fibers are washed with clean water and dried at 50 to 150°C to obtain clean glass fibers with a moisture content of ≤0.5%; S5. Graded recovery of degradation mother liquor: After the degradation mother liquor is recycled 10 to 20 times, toluene and acetic acid solvents are recovered by graded distillation. The purity of the recovered solvents is ≥94%, and they can be directly reused. The remaining resin degradation products at the bottom of the reactor are purified by vacuum or atmospheric distillation and used as industrial chemical raw materials, adhesives, and waterproof coating auxiliaries. S6. Surface modification treatment of reinforced fiber: Prepare a water-based wetting agent, which includes silane coupling agent, polyurethane / epoxy emulsion, polyethylene glycol and acetic acid. The proportion of each component can be adjusted to suit different process scenarios. After wetting the clean glass fiber at room temperature for 3 to 5 minutes, bake it at 120 to 220°C for 15 to 120 minutes to complete the cross-linking modification of the fiber surface. S7. High-value application of fibers: Modified glass fibers are cut into short fibers of 6-10 mm and added as reinforcing fillers to the denitrification catalyst preparation system to prepare plate-type or honeycomb-type denitrification catalysts.

[0008] As a further optimization of the above scheme, in step S1, a water cutting process with a water pressure of 35MPa and an accuracy of ±0.5cm is used for conventional wind turbine blades without severe aging. For small and medium-sized lightweight blades weighing ≤500kg, a mechanical cutting process with a rotation speed of 800r / min is adopted. For aged blades with long service life, severe weathering, and high degree of solidification, a laser cutting process with 1500W power and 20mm / s speed is adopted.

[0009] As a further optimization of the above scheme, in step S2, conventional leaves are swollen at 80%–90% acetic acid aqueous solution and 80–100℃. The lightweight blades were swollen at 80°C using a 60% low-concentration acetic acid aqueous solution. Severely aged and difficult-to-degrade leaves are treated with 100% pure acetic acid and high temperature at 120℃ for enhanced swelling.

[0010] As a further optimization of the above scheme, in step S3, the catalyst is a single zinc acetate, a single iron acetate, or a composite catalyst in which zinc acetate and manganese acetate, or iron acetate and manganese acetate are compounded in a 1:1 mass ratio. For small- and medium-scale low-energy production, 0.5 wt.% of a single catalyst is used; for conventional mass production, 1.2 wt.% of a single catalyst is used; and for enhanced degradation of aging leaves, 2.5 wt.% of a composite catalyst is used.

[0011] As a further optimization of the above scheme, in step S4, the solid-liquid separation pressing pressure is controlled at 0.2-0.5 MPa, and the vacuum degree of vacuum filtration is 0.08 MPa. Low-temperature drying temperature is 50-80℃, and rapid drying temperature is 100-150℃. After drying, the fiber moisture content is controlled at 0.3%-0.5%.

[0012] As a further optimization of the above scheme, in step S5, the distillation recovery temperature of toluene is 115-118℃, and the distillation recovery temperature of acetic acid is 120-128℃. The purification temperature of the resin degradation products is 170-200℃, the vacuum degree is 0.09-0.095MPa, and the purity of the purified products is ≥87%.

[0013] As a further optimization of the above scheme, in step S6, the preferred ratio of the water-based wetting agent is silane coupling agent: polyurethane emulsion: polyethylene glycol: acetic acid = (6-8):(20-80):(5-10):1, and the ratio of the total mass of each component to the volume of pure water is 1:3 to 1:10.

[0014] As a further optimization of the above scheme, in step S7, the amount of modified chopped glass fiber added to the denitrification catalyst matrix is ​​4% of the total mass.

[0015] The present invention provides a method for the chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades, which has the following beneficial effects: This invention discloses a method for the chemical degradation, recycling, and high-value utilization of retired wind turbine blades. The entire process adopts a normal pressure and low-temperature reaction condition, with a maximum process temperature of only 220°C. There are no harsh production conditions such as high pressure, strong corrosion, or high-temperature pyrolysis, which significantly reduces the requirements for corrosion resistance and pressure resistance of production equipment. The equipment investment cost and production line operation and maintenance cost are significantly reduced. At the same time, the process parameters can be flexibly adjusted according to production needs, making it suitable for large, medium, and small production lines with extremely high adaptability.

[0016] This invention sets up multi-gradient process parameters, which can be used to treat small and medium-sized lightweight blades, conventional commercial blades, and severely aged high-curing-degree blades. It is suitable for small and medium-sized low-energy-consumption batch production, as well as large-scale continuous industrial production lines and centralized treatment needs for non-degradable waste blades. It solves the problems of poor versatility and insufficient adaptability of traditional processes.

[0017] This invention achieves long-term solvent recycling by precisely proportioning the swelling solution and degradation solvent. The remaining swelling solution and degradation mother liquor can be recycled 10 to 20 times with extremely low solvent loss rate per cycle. The overall solvent recycling rate can reach over 90%. The mother liquor after the recycling period can be efficiently recovered by fractional distillation and vacuum distillation to achieve efficient recovery of toluene and acetic acid solvents. The recovered solvent has high purity and can be directly reused. All resin degradation products can be utilized as resources, with no solid waste or waste liquid discharge, completely avoiding the secondary pollution problems of traditional processes.

[0018] This invention first achieves gentle stratification of the resin matrix and glass fiber through controlled swelling of acetic acid, and then precisely degrades the surface resin through a composite catalytic system, avoiding damage to the glass fiber body caused by high temperature and strong corrosion processes, thus preserving the fiber's complete structure and mechanical properties to the greatest extent. Combined with a proprietary water-based wetting agent modification process, a uniform and dense modified layer is formed on the fiber surface, which greatly improves the fiber's interfacial activity and matrix compatibility, solving the industry pain points of poor performance and low added value of traditional recycled fibers.

[0019] The recycled and modified glass fibers of this invention can be used as high-end reinforcing fillers in the preparation of denitrification catalysts, significantly improving the catalyst's mechanical strength, wear resistance, and high-temperature resistance, while maintaining stable and excellent denitrification efficiency and greatly extending the catalyst's service life. Simultaneously, the resin degradation products can be purified into industrial adhesives, waterproof coatings, and raw materials for high-end composite materials, achieving full resource utilization of the blade components.

[0020] Specific embodiments of the present invention are disclosed in detail with reference to the following description and accompanying drawings, indicating how the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope as a result, and that the embodiments of the present invention include many changes, modifications and equivalents within the spirit and scope of the appended claims. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to the present invention; Figure 2 This is a schematic diagram of the structure of the blade block that swells at high temperature using an aqueous acetic acid solution according to the present invention; Figure 3 The diagram illustrates the specific implementation steps of the method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to the present invention.

[0022] In the diagram: CH3COOH is an aqueous solution of acetic acid. Detailed Implementation

[0023] Please refer to the instruction manual appendix. Figure 1-3 This invention provides a technical solution: a method for the chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades, comprising: The core processes of this invention are, in sequence, pretreatment of decommissioned wind turbine blades, controlled swelling of acetic acid, catalytic degradation by composite solvent, solid-liquid separation, graded recovery of degradation mother liquor, surface modification of reinforcing fibers, and high-value application of fibers.

[0024] Example 1 This embodiment provides the process ratio and operating parameters of the present invention. The specific operating steps are as follows: S1. Blade Cutting Pretreatment: Select conventional retired epoxy resin-based wind turbine blades (glass fiber reinforced wind turbine blades, 20 years of service life, natural aging without severe carbonization or damage), and perform cutting pretreatment using water jet cutting. The water jet cutting pressure is controlled at 35MPa, and the cutting accuracy is controlled at ±0.5cm. Finally, square blade blocks with dimensions of 50cm×50cm×3cm are cut, with the block size preferably within the range of 10-100cm. After cutting, remove dust, mud, oil, and other impurities attached to the surface of the blade blocks, and place them in a ventilated place at room temperature to air dry naturally for 2 hours to remove surface free moisture and avoid impurities and moisture affecting the accuracy of subsequent swelling and degradation reactions.

[0025] This embodiment uses water jet cutting technology, which can effectively avoid the high-temperature carbonization problem of laser cutting and the debris splashing and material loss problem of mechanical cutting, thus preserving the integrity of the blade substrate material to the greatest extent and ensuring the quality of the subsequent recycled products.

[0026] S2. Controlled swelling treatment with acetic acid: Prepare an aqueous solution of acetic acid with a concentration of 90% as the swelling solution. This concentration is the optimal intermediate concentration between high and low concentration ranges, which takes into account both swelling effect and solvent loss.

[0027] The pretreated blade blocks were completely immersed in acetic acid swelling solution with a solid-liquid mass ratio of 1:8 to ensure that the blade blocks were completely wetted and no part was exposed. The reaction system was placed in a sealed constant-temperature reactor and heated to 100°C for 60 minutes for constant-temperature immersion and swelling treatment. During the swelling process, acetic acid molecules slowly penetrated into the interior of the wind turbine blade composite material, disrupting the interfacial bonding between the epoxy resin matrix and the glass fiber layer, achieving initial stratification between the fiber layer and the resin matrix. Only a trace amount of epoxy resin (the total amount of swelling resin accounts for 1.2% of the total mass of the blade resin) dissolved into the acetic acid swelling solution during the entire swelling process, with almost no loss of effective components. After the swelling was completed, the layered blade material was removed and the complete layered glass fiber cloth could be obtained by manual peeling. The remaining swelling solution was filtered to remove trace resin impurities and could be directly recycled for the next batch of blade swelling treatment. Fresh acetic acid was added in real time according to the solvent loss to maintain the swelling solution concentration at 90%.

[0028] S3. Composite solvent catalytic degradation treatment: Prepare a special degradation solvent. In this embodiment, the degradation solvent is prepared by mixing acetic acid, toluene and 30% hydrogen peroxide in a volume ratio of 1:0.1:1.0, which has the best reaction stability.

[0029] Accurately measure 1000 mL of acetic acid, 100 mL of toluene, and 1000 mL of 30% hydrogen peroxide, and mix thoroughly for 15 min to ensure the three solvent systems are homogeneous and compatible, without stratification or precipitation. Then, add 1.5 wt.% of a composite catalyst to the mixed degradation solvent. The catalyst is a 1:1 mass ratio of zinc acetate and manganese acetate, which exhibits superior catalytic activity compared to a single catalyst. The total amount of catalyst added is 1.5% of the total mass of the degradation solvent.

[0030] The layered glass fiber cloth prepared by S2 was completely immersed in the prepared catalytic degradation solvent, with the solid-liquid mass ratio controlled at 1:10 to ensure that every part of the fiber cloth could be fully in contact with the degradation solvent. The reaction system was sealed and heated to 105℃, and the degradation reaction was carried out at a constant temperature for 2 hours. During the degradation process, the stirring was carried out at a low speed of 60 r / min to avoid fiber entanglement and accumulation, while accelerating the resin degradation reaction rate and ensuring that the resin matrix was completely peeled off from the fiber surface and degraded.

[0031] S4. Solid-liquid separation and fiber pretreatment: After the degradation reaction is completed, turn off the heating and stirring devices and wait for the reaction system to cool down to 60°C naturally (to avoid high-temperature solvent evaporation and loss). Use a combination of mechanical pressing and filtration to perform solid-liquid separation.

[0032] First, the degraded fiber material is subjected to slight mechanical pressing at a pressure of 0.3 MPa to remove most of the free degradation solution from the fiber surface. Then, a vacuum filtration device is used for deep solid-liquid separation at a vacuum degree of 0.08 MPa to completely separate the solid reinforcing fiber from the liquid degradation mother liquor. The separated solid glass fiber is repeatedly washed twice with room temperature water, soaking for 5 minutes each time, to thoroughly remove residual catalyst, degradation solvent, and small molecule impurities from resin degradation from the fiber surface.

[0033] After cleaning, the fibers are laid flat in a forced-air drying oven, the drying temperature is set to 100℃, and the drying is carried out at a constant temperature for 40 minutes until the fiber moisture content drops to below 0.5%, thus obtaining clean virgin glass fibers for later use.

[0034] S5. Graded recycling of degradation mother liquor: In this embodiment, the degradation mother liquor can be stably recycled 15 times. During the recycling process, the degradation efficiency does not decrease significantly, which meets the industrial low-cost recycling requirements.

[0035] After the mother liquor has been recycled 15 times, it is sent to a precision fractional distillation apparatus for component separation and recovery. First, taking advantage of the boiling point difference (toluene boiling point 110.6℃, acetic acid boiling point 117.9℃), the first-stage distillation temperature is set at 115℃ to recover toluene solvent, with a toluene recovery rate of up to 92.3%; the second-stage distillation temperature is 125℃ to recover acetic acid solvent, with an acetic acid recovery rate of up to 94.1%. The purity of the recovered toluene and acetic acid both reach over 95%, which can be directly reused in the preparation of degradation solvents, realizing solvent recycling.

[0036] After solvent recovery, the remaining bottom liquid is a high-concentration resin degradation product. It is then further purified by vacuum distillation at a vacuum of 0.09 MPa and a temperature of 180°C. The purified resin degradation product is a mixture of polyols and organic acid esters with a purity of 89.7%. It can be directly used as an industrial chemical raw material, a special adhesive for composite materials, and an auxiliary material for waterproof coatings, realizing the high-value utilization of resin components and eliminating solid waste and wastewater discharge.

[0037] S6. Surface modification treatment of reinforcing fibers: Prepare a special water-based wetting agent. In this embodiment, the mass ratio of each component of the wetting agent is silane coupling agent: polyurethane emulsion: polyethylene glycol: acetic acid = 6:50:8:1, and the volume ratio of the sum of each component to pure water is 1:6. The ratio is the optimal modification ratio.

[0038] Accurately weigh 6g of silane coupling agent, 50g of polyurethane emulsion, 8g of polyethylene glycol, and 1g of acetic acid, add them to 600mL of pure water, and stir at high speed for 20min at a stirring speed of 300r / min to prepare a uniform, stable, and non-agglomerated water-based wetting agent.

[0039] The clean glass fibers dried with S4 were completely immersed in the sizing agent and treated at room temperature for 4 minutes to ensure that the sizing agent evenly coated the fiber surface without any local leakage or accumulation. After immersion, the fibers were removed and excess sizing agent was naturally drained off. The fibers were then placed in a hot air baking oven and baked at 180℃ for 60 minutes to complete the cross-linking modification of the fiber surface. Finally, clean reinforced glass fibers with a uniformly coated modified layer and excellent interfacial activity were obtained.

[0040] S7. High-value processing and application of fibers: Modified reinforcing glass fibers are sheared using a high-speed shearing device, with the shearing length controlled at 8mm and the length uniformity error ≤±0.3mm. This length is suitable for the reinforcement requirements of denitrification catalysts. Modified chopped glass fibers are added as reinforcing fillers to the plate-type denitrification catalyst preparation system, with the fiber addition amount being 4% of the total mass of the catalyst matrix, to prepare honeycomb and plate-type denitrification catalyst products. Testing showed that the denitrification catalyst prepared from the recycled modified fibers in this embodiment exhibited a 28.6% increase in tensile strength and a 32.3% increase in compressive strength. The catalyst porosity was uniform, and the denitrification efficiency remained stable at 93.5%. Compared to ordinary catalysts without recycled fibers, the service life was increased by 1.8 times, realizing the high-value resource utilization of retired wind turbine blade fibers.

[0041] The overall process in this embodiment is mild, with a maximum reaction temperature of 180°C throughout. There are no harsh conditions such as high pressure or strong corrosion, the process is highly safe, the solvent recycling rate is over 90%, the overall solid waste resource utilization rate can reach 98.2%, there is no secondary pollution, and it meets the requirements of green industrial production.

[0042] Example 2 This embodiment employs low-temperature, low-toluene addition process parameters, suitable for the recycling of small and medium-sized lightweight wind turbine blades, reducing production energy consumption and solvent consumption. The specific operation steps are as follows: S1. Blade cutting pretreatment: Select small decommissioned wind turbine blades (single blade weight ≤ 500kg, fiberglass thin-layer composite structure), and cut them using mechanical cutting. The mechanical cutting speed is controlled at 800r / min to avoid high-speed cutting damaging the fiber structure. After cutting, small blade blocks with dimensions of 10cm×10cm×2cm are obtained, and the block size meets the requirement of 10~100cm.

[0043] After cutting, clean the surface of the blocks to remove impurities and debris, and air dry at room temperature for 3 hours to remove surface moisture and dust. The mechanical cutting process is simple to operate, has low equipment costs, and is suitable for batch pre-processing of small and medium-sized blades, making it ideal for small- to medium-scale recycling production lines.

[0044] S2. Acetic acid swelling treatment: 60% low-concentration acetic acid aqueous solution is selected as the swelling solution to reduce the corrosion loss and raw material cost of high-concentration acetic acid.

[0045] The blade block was immersed in the swelling solution with a solid-liquid mass ratio of 1:7, placed in a constant temperature reaction vessel, heated to 80℃, and subjected to constant temperature swelling treatment for 90 minutes.

[0046] Low-temperature, low-concentration acetic acid has a relatively slow swelling rate, which can achieve gentle stratification and effectively avoid the slight corrosive damage to the glass fiber body caused by high-temperature, high-concentration acetic acid.

[0047] After swelling is completed, the layered fiber cloth and the remaining swelling liquid are successfully separated. In this embodiment, the amount of resin dissolved during the swelling process is extremely low, accounting for only 0.8% of the total resin content. The remaining swelling liquid can be directly recycled after filtration, and the cumulative number of recycling times can reach 20 times. The solvent loss rate is extremely low, only 1.2% / time.

[0048] S3. Catalytic Degradation Treatment: The degradation solvent uses an ultra-low toluene ratio system of acetic acid, toluene, and 30% hydrogen peroxide in a volume ratio of 1:0:0.7, i.e., no toluene solvent is added, minimizing the amount of organic solvent used and reducing VOC emissions. 1000 mL of acetic acid and 700 mL of 30% hydrogen peroxide are precisely prepared, stirred evenly, and then 0.5 wt.% of a single zinc acetate catalyst is added. The catalytic system is mild and inexpensive.

[0049] The layered fiber cloth was immersed in the degradation solvent at a solid-liquid ratio of 1:9. The reaction system was sealed and heated to 75°C. The mixture was then stirred at a constant temperature and low speed for 3 hours to degrade the fiber cloth.

[0050] The low-temperature, long-lasting degradation mode can gradually decompose the epoxy resin matrix on the fiber surface. The reaction process is mild and controllable, with no violent exothermic reactions or solvent evaporation. The equipment has low requirements for pressure resistance and corrosion resistance, which greatly reduces equipment investment costs.

[0051] S4. Solid-liquid separation and fiber treatment: After degradation, the fiber is naturally cooled to room temperature. Solid-liquid separation is carried out by manual scooping combined with light pressing. The pressing pressure is 0.2MPa. The operation is simple and suitable for small production lines.

[0052] The separated fibers are washed once with clean water and soaked for 3 minutes to remove residual catalysts and degradation impurities on the surface. Then, they are placed in a forced-air drying oven and dried at a temperature of 50°C for 120 minutes. Low-temperature and slow drying can completely preserve the mechanical properties of the fiber itself and avoid fiber embrittlement and strength reduction caused by high-temperature drying, ultimately resulting in clean and intact glass fibers.

[0053] S5. Mother liquor recovery and treatment: This embodiment does not contain toluene. The main components of the degradation mother liquor are acetic acid, hydrogen peroxide decomposition products and resin degradation products. The mother liquor can be stably recycled 20 times, and the degradation performance does not decrease during the recycling process.

[0054] After the recycling period is over, the mother liquor is subjected to fractional distillation. The first distillation temperature is 120℃ to recover acetic acid solvent. The acetic acid recovery rate is 91.5%, and the purity of the recovered acetic acid is 94%, which can be directly reused.

[0055] The remaining resin degradation products are purified by atmospheric distillation at 170℃. The purity of the purified products reaches 87.2%, which can be used as low-end waterproof coating auxiliary materials and raw materials for general industrial adhesives, realizing low-cost resource utilization.

[0056] S6. Fiber Modification Treatment: A low-dosage sizing agent is prepared, with the components being silane coupling agent: epoxy emulsion: polyethylene glycol: acetic acid = 5:20:5:1. The components are mild and low-cost, and the volume ratio of the sum of the components to water is 1:3. The sizing agent concentration is low, which is suitable for the modification requirements of low-temperature degradable fibers.

[0057] The clean fiber is immersed in the sizing agent for 3 minutes, then removed and placed in a 120℃ constant temperature baking oven for 120 minutes. Low-temperature long-time baking can achieve slow cross-linking and curing of the sizing agent, forming a uniform and dense modified coating layer, avoiding the cracking and peeling of the modified layer caused by high-temperature baking, thus completing the surface modification of the fiber.

[0058] S7. High-value application: The modified fibers were cut into 6mm short fibers for reinforcement and modification of plate-type denitrification catalysts. Testing showed that the catalyst prepared from the recycled fibers in this embodiment exhibited stable mechanical properties, with a 22.1% increase in compressive strength and a stable denitrification efficiency of 90.2%, meeting the requirements for conventional industrial flue gas denitrification.

[0059] The process in this embodiment has low overall energy consumption, low solvent consumption, and low equipment threshold, making it suitable for batch production by small and medium-sized recycling enterprises, with a resource utilization rate of up to 95.7%.

[0060] Example 3 This embodiment employs an enhanced degradation process with high temperature, high hydrogen peroxide ratio, and high catalyst addition, suitable for severely aged, highly cured, and difficult-to-degrade retired wind turbine blades. This significantly improves degradation efficiency and shortens the production cycle. The specific operating steps are as follows: S1. Blade Cutting Pretreatment: Select retired wind turbine blades that have been in service for 25 years, have undergone long-term outdoor aging, have high resin matrix curing degree, and have severe surface weathering. Use laser cutting to perform cutting pretreatment. The laser cutting power is 1500W and the cutting speed is 20mm / s. Precisely cut to obtain large-size blade blocks of 100cm×100cm×4cm. Large-size blocks can reduce cutting steps and improve batch processing efficiency.

[0061] After cutting, clean the surface of weathered debris and carbonized impurities, and let it dry for later use.

[0062] Laser cutting offers high precision, meeting the cutting needs of aged and hardened blades without mechanical stress damage, thus ensuring the integrity of the block.

[0063] S2. Swelling Treatment: 100% pure acetic acid is used as the swelling solution, which is free of water and has the strongest swelling and penetration capabilities. The blade block is immersed in pure acetic acid at a solid-liquid mass ratio of 1:10, placed in a sealed reactor, and heated to 120℃ for high-temperature enhanced swelling for 30 minutes. This rapidly breaks down the interlayer bonding force of the aged resin matrix, achieving rapid separation of the fiber layers and solving the problem of difficult delamination in aged blades.

[0064] This high-temperature pure acetic acid swelling process is time-saving and highly efficient, achieving the swelling effect of conventional processes that take 60-90 minutes in just 30 minutes, making it suitable for the rapid pretreatment needs of aging leaves; the residual swelling liquid has low impurity content and can be recycled more than 18 times.

[0065] S3. Enhanced catalytic degradation treatment: The degradation solvent adopts a high ratio system of acetic acid, toluene, and 30% hydrogen peroxide in a volume ratio of 1:0.2:1.3. The amount of toluene and hydrogen peroxide added reaches the upper limit to enhance the oxidative degradation ability.

[0066] Prepare 1000mL of acetic acid, 200mL of toluene, and 1300mL of 30% hydrogen peroxide, and mix thoroughly.

[0067] Adding 2.5 wt.% of a composite catalyst, which is a mixture of ferric acetate and manganese acetate in a 1:1 mass ratio, results in excellent high-temperature catalytic activity and efficient degradation of high-curing-degree epoxy resin.

[0068] The layered fiber cloth is completely immersed in the degradation solvent with a solid-liquid ratio of 1:10. The reaction system is sealed and heated to 130°C for 1 hour of high-temperature enhanced degradation, which greatly shortens the degradation reaction cycle. The aging resin on the fiber surface can be completely degraded and peeled off in just 1 hour. The degradation efficiency is more than twice that of conventional processes.

[0069] S4. Solid-liquid separation and fiber treatment: After the degradation reaction is completed, the temperature is lowered to 70℃, and a plate and frame filter press is used for high-pressure solid-liquid separation. The filter pressure is 0.5MPa, which quickly achieves complete solid-liquid separation and is suitable for large-scale material processing.

[0070] The separated fibers are washed three times with clean water, soaking for 6 minutes each time, to thoroughly remove trace residual impurities produced by high-temperature degradation. They are then placed in a drying oven and dried at 150℃ for 15 minutes. High-temperature rapid drying can significantly shorten the drying cycle. After drying, the fiber moisture content is ≤0.3%, and the cleanliness is extremely high.

[0071] S5. High-efficiency recovery of mother liquor: The high-ratio solvent system in this embodiment has strong degradation ability, and the mother liquor can be recycled 12 times, which is suitable for the degradation of high-load aging leaves.

[0072] After the cycle period, fractional distillation was performed to recover the solvents. The first distillation was carried out at 118℃ to recover toluene with a recovery rate of 93.1%; the second distillation was carried out at 128℃ to recover acetic acid with a recovery rate of 95.2%. The purity of the recovered solvents was higher than 96% and they could be directly reused.

[0073] The remaining resin degradation products were purified by high-temperature vacuum distillation (0.095 MPa vacuum, 200℃), achieving a purity of 91.3%. The high-purity resin degradation products can be used as raw materials for high-end composite adhesives and industrial waterproof and anti-corrosion coatings, demonstrating significant value enhancement.

[0074] S6. High-temperature rapid modification treatment: Prepare a high-solids-content wetting agent with a component mass ratio of silane coupling agent: polyurethane emulsion: polyethylene glycol: acetic acid = 8:80:10:1, and the sum of each component and the volume ratio of water is 1:10. The wetting agent has a high solids content and a strong modification effect.

[0075] The clean fiber is immersed for 5 minutes to fully absorb the modified components. After being removed, it is placed in a 220°C high-temperature baking oven and baked rapidly for 15 minutes. The high temperature and rapid cross-linking and curing process forms a surface modified layer with high strength and high adhesion, which greatly improves the interfacial bonding force between the fiber and the denitrification catalyst matrix.

[0076] S7. High-value application: Modified fibers are cut into 10mm long short fibers to prepare a honeycomb denitrification catalyst. Testing showed that the catalyst modified with recycled fibers in this embodiment exhibited a 35.2% increase in tensile strength, a 38.7% increase in compressive strength, and significantly improved wear resistance and high-temperature resistance. The denitrification efficiency remained stable at 94.8%, making it suitable for high-dust, high-temperature, and high-load industrial flue gas denitrification scenarios, thus significantly increasing the product's added value.

[0077] This embodiment is specifically designed for aging and difficult-to-degrade wind turbine blades. It achieves thorough degradation, high production efficiency, and excellent product quality. It is suitable for centralized resource utilization of large quantities of waste and retired blades, with an overall resource utilization rate of up to 99.1%.

[0078] Example 4 This embodiment uses a single iron acetate catalyst and moderate gradient process parameters, balancing process stability and raw material costs. It is suitable for the standardized batch recycling of conventional commercial decommissioned wind turbine blades, and the process has strong versatility. The specific operating steps are as follows: S1. Blade Cutting Pre-treatment: Select conventional commercial decommissioned wind turbine blades and cut them into standard blocks of 30cm×30cm×3cm using water jet cutting. The dimensions are within the optimal range. After cutting, clean surface impurities and dry the material for later use. Water jet cutting is free of high temperatures and dust, ensuring good material integrity and making it suitable for standardized batch pre-treatment.

[0079] S2. Swelling treatment: 80% acetic acid aqueous solution was used as the swelling solution, the reaction temperature was 90℃, and the swelling was carried out at a constant temperature for 70 min. The solid-liquid mass ratio was 1:8.

[0080] This parameter is a medium gradient parameter, with a balanced swelling effect, which can stably achieve the separation of the fiber layer and the resin matrix. The resin loss during the swelling process is 1.0%, and the remaining swelling liquid can be stably recycled 18 times. It has low solvent loss and strong process stability.

[0081] S3. Degradation treatment: The degradation solvent ratio is acetic acid: toluene: 30% hydrogen peroxide = 1:0.15:0.9, which is a medium ratio system with balanced oxidative degradation ability.

[0082] After the solvent is mixed evenly, 1.2 wt.% of a single iron acetate catalyst is added, resulting in a simple catalytic system, convenient raw material procurement, and lower cost.

[0083] The layered fiber cloth was immersed in the solvent and degraded at a constant temperature of 110℃ for 1.5 hours with a stirring speed of 50 r / min. The reaction conditions were mild and stable with no parameter fluctuations, and the degradation was complete without damaging the mechanical properties of the glass fiber itself.

[0084] S4. Solid-liquid separation and drying: After degradation, the solid-liquid system is separated by vacuum filtration, washed twice with clean water for 4 minutes each time, and dried at a constant temperature of 80℃ for 60 minutes to obtain clean glass fiber with a moisture content of ≤0.4%. The fiber is intact without breakage or corrosion damage.

[0085] S5. Mother liquor recovery: The degradation mother liquor can be recycled 16 times. After the recycling period, toluene and acetic acid are recovered by fractional distillation with recovery rates of 91.8% and 93.5%, respectively. The recovered solvent can be directly reused. The resin degradation products can be purified and applied in a variety of fields such as chemical raw materials, adhesives, and waterproofing auxiliaries, making it extremely versatile.

[0086] S6. Fiber modification: The mass ratio of the sizing agent components is silane coupling agent: polyurethane emulsion: polyethylene glycol: acetic acid = 7:60:7:1, and the volume ratio of the components to water is 1:5. The sizing agent is impregnated at room temperature for 4 minutes and baked at 200℃ for 40 minutes. The modified layer is uniform and stable, and the fiber surface activity is excellent.

[0087] S7. Application Testing: The modified fiber was cut into 7mm short fibers and used in the preparation of plate denitration catalyst. The mechanical strength of the catalyst was increased by 29.5%, the denitration efficiency was stabilized at 92.7%, the product performance was balanced, and it was suitable for industrialized standardized mass production. The overall resource utilization rate could reach 97.6%.

[0088] Example 5 This embodiment focuses on long solvent circulation, low energy consumption, and ultra-low loss, making it suitable for long-term continuous industrial production lines, minimizing production costs and maximizing economic benefits. The specific operating steps are as follows: S1. Blade cutting pretreatment: Mechanical cutting is used to cut retired wind turbine blades into 80cm×80cm blocks, reducing cutting processes, improving continuous production efficiency, and cleaning surface impurities before use.

[0089] S2. Swelling treatment: Using 70% acetic acid aqueous solution, swelling at 95℃ for 80 minutes, with a solid-liquid ratio of 1:8.5, it is a mild and long-lasting swelling solution that maximizes the stability of the swelling solution components. The single loss of residual swelling solution is ≤0.9%, and it can be stably recycled more than 20 times, making it the solution with the longest solvent cycle life among all processes.

[0090] S3. Degradation treatment: The solvent ratio is acetic acid:toluene:30% hydrogen peroxide = 1:0.05:1.2, with a low toluene and high hydrogen peroxide ratio, which balances degradation effect and low VOC emissions. The catalyst is a single catalyst of 1.0 wt.% manganese acetate. The degradation is carried out at 100℃ for 2.5 hours. The reaction has low energy consumption, stable system, and is suitable for 24-hour continuous production. There are no side reactions and no violent solvent volatilization.

[0091] S4. Separation and Drying: The process involves filtration and separation, washing twice with clean water, and drying at 90℃ for 50 minutes. This ensures good fiber integrity and retains over 98% of mechanical properties.

[0092] S5. Mother liquor recycling: The mother liquor can be continuously recycled 20 times without performance degradation, with optimal cycle stability. The recovery rates of acetic acid and toluene by distillation both exceed 92%, and the purity of resin degradation products is 88.5%, making it suitable for general high-value utilization.

[0093] S6. Modification process: wetting agent ratio 6.5:40:9:1, water volume ratio 1:8, wetting for 3.5 min, baking at 150℃ for 90 min, medium and low temperature long-term modification, modified layer with strong adhesion and excellent aging resistance.

[0094] S7. Application Effects: The denitrification catalyst prepared by cutting 9mm short fibers has excellent weather resistance and stability, and low decay rate over long-term use. It is suitable for use with large-scale industrial denitrification equipment. The overall production cost is reduced by more than 35% compared with the existing process, and the industrialization economic benefits are significant.

[0095] Overall performance comparison and process adaptation description of each embodiment The above five sets of differentiated implementation examples fully verify that the chemical degradation, recycling, and high-value utilization method for retired wind turbine blades disclosed in this invention has highly adjustable process parameters and is widely applicable. It can achieve precise recycling and processing for retired wind turbine blades of different service years, aging degrees, and specifications. Compared with traditional existing technologies that involve high temperature, high pressure, long duration, and high cost degradation processes, all embodiments of this invention complete the reaction under normal pressure and medium-low temperature conditions, with a maximum process temperature of only 220°C. There are no harsh high-pressure conditions, resulting in low equipment investment costs and high production safety. At the same time, this invention achieves efficient solvent recycling, with solvent recycling times reaching 10 to 20 times. The overall resource utilization rate is higher than 95%, reaching a maximum of 99.1%, completely solving the resource waste and environmental pollution problems of traditional landfill and incineration processes.

[0096] Meanwhile, this invention significantly improves the interfacial activity and mechanical properties of recycled waste glass fiber through fiber surface modification technology, completely solving the industry pain points of fiber performance degradation and low added value in traditional mechanical recycling and pyrolysis recycling. It transforms low-value solid waste into high-end denitrification catalyst reinforcement materials, realizing the green, efficient, and high-value recycling of retired wind turbine blades. Each embodiment can be flexibly selected according to the actual production scenario: Embodiment 1 is the general optimal mass production solution; Embodiment 2 is suitable for small and medium-scale, low-energy consumption production; Embodiment 3 is suitable for aging and difficult-to-treat waste blades; Embodiment 4 is suitable for standardized batch production; Embodiment 5 is suitable for large-scale continuous industrial production lines. The process covers the needs of implementation in all scenarios and has extremely strong industrial promotion value.

Claims

1. A method for the chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades, characterized in that, include: S1. Blade cutting pretreatment: Select retired epoxy resin-based fiberglass reinforced wind turbine blades. According to the blade specifications and aging degree, cut them into blade blocks of 10-100cm specifications by water cutting, mechanical cutting or laser cutting. After cleaning the impurities and debris on the surface of the blocks, let them air dry at room temperature to remove free surface moisture and set them aside. S2. Controlled swelling treatment with acetic acid: Prepare an aqueous solution of 60% to 100% acetic acid as the swelling solution. Immerse the blade block completely in the swelling solution at a solid-liquid mass ratio of 1:7 to 1:

10. Swell for 30 to 90 minutes under a closed constant temperature condition of 80 to 120°C to achieve stratification between the epoxy resin matrix and the glass fiber layer. Separate the layered glass fiber cloth. The remaining swelling solution is filtered and recycled. S3. Composite solvent catalytic degradation treatment: Prepare a composite degradation solvent composed of acetic acid, toluene, and 30% hydrogen peroxide, with a solvent volume ratio of 1:(0~0.2):(0.7~1.3). After stirring and mixing evenly, add 0.5wt.%~2.5wt.% catalyst. Immerse the layered glass fiber cloth in the degradation solvent at a solid-liquid mass ratio of 1:9~1:10, and degrade it at a constant temperature of 75~130℃ with low-speed stirring for 1~3h to completely remove the residual resin matrix on the fiber surface. S4. Solid-liquid separation and fiber pretreatment: After degradation, the system is cooled to room temperature to 70°C, and solid-liquid separation is carried out by pressing, vacuum filtration or plate and frame filtration; the separated solid glass fibers are washed with clean water and dried at 50 to 150°C to obtain clean glass fibers with a moisture content of ≤0.5%; S5. Graded recovery of degradation mother liquor: After the degradation mother liquor is recycled 10 to 20 times, toluene and acetic acid solvents are recovered by graded distillation. The purity of the recovered solvents is ≥94%, and they can be directly reused. The remaining resin degradation products at the bottom of the reactor are purified by vacuum or atmospheric distillation and used as industrial chemical raw materials, adhesives, and waterproof coating auxiliaries. S6. Surface modification treatment of reinforced fiber: Prepare a water-based wetting agent, which includes silane coupling agent, polyurethane / epoxy emulsion, polyethylene glycol and acetic acid. The proportion of each component can be adjusted to suit different process scenarios. After wetting the clean glass fiber at room temperature for 3 to 5 minutes, bake it at 120 to 220°C for 15 to 120 minutes to complete the cross-linking modification of the fiber surface. S7. High-value application of fibers: Modified glass fibers are cut into short fibers of 6-10 mm and added as reinforcing fillers to the denitrification catalyst preparation system to prepare plate-type or honeycomb-type denitrification catalysts.

2. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S1, a water jet cutting process with a water pressure of 35MPa and an accuracy of ±0.5cm is used for conventional wind turbine blades without severe aging. For small and medium-sized lightweight blades weighing ≤500kg, a mechanical cutting process with a rotation speed of 800r / min is adopted. For aged blades with long service life, severe weathering, and high degree of solidification, a laser cutting process with 1500W power and 20mm / s speed is adopted.

3. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S2, conventional leaves are swollen at 80%–90% acetic acid aqueous solution and 80–100℃. The lightweight blades were swollen at 80°C using a 60% low-concentration acetic acid aqueous solution. Severely aged and difficult-to-degrade leaves are treated with 100% pure acetic acid and 120℃ high temperature for enhanced swelling.

4. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S3, the catalyst is a single zinc acetate, a single iron acetate, or a composite catalyst in which zinc acetate and manganese acetate, or iron acetate and manganese acetate are mixed in a 1:1 mass ratio. For small- and medium-scale low-energy production, 0.5 wt.% of a single catalyst is used; for conventional mass production, 1.2 wt.% of a single catalyst is used; and for enhanced degradation of aged leaves, 2.5 wt.% of a composite catalyst is used.

5. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S4, the solid-liquid separation pressing pressure is controlled at 0.2-0.5 MPa, and the vacuum degree of vacuum filtration is 0.08 MPa; Low-temperature drying temperature is 50-80℃, and rapid drying temperature is 100-150℃. After drying, the fiber moisture content is controlled at 0.3%-0.5%.

6. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S5, the distillation recovery temperature of toluene is 115–118°C, and the distillation recovery temperature of acetic acid is 120–128°C. The purification temperature of the resin degradation products is 170-200℃, the vacuum degree is 0.09-0.095MPa, and the purity of the purified products is ≥87%.

7. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S6, the preferred ratio of the water-based wetting agent is silane coupling agent: polyurethane emulsion: polyethylene glycol: acetic acid = (6-8):(20-80):(5-10):1, and the ratio of the total mass of each component to the volume of pure water is 1:3 to 1:

10.

8. The method for chemical degradation, recycling, and high-value utilization of decommissioned wind turbine blades according to claim 1, characterized in that: In step S7, the amount of modified chopped glass fiber added to the denitrification catalyst matrix is ​​4% of the total mass.

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