Method for converting composite materials from waste wind turbine blades into silicon carbide

Abstract

This invention discloses a method for converting waste wind turbine blade composite materials into silicon carbide, comprising the following steps: mixing waste wind turbine blade composite material powder with a conductive agent to obtain a mixture, wherein the waste wind turbine blade composite material contains silicon and carbon elements; and subjecting the mixture to flash Joule heat treatment to obtain silicon carbide. This method requires no pretreatment of the waste wind turbine blade composite material powder, such as pyrolysis. In the presence of the conductive agent, only one step of flash Joule heat treatment is needed to convert the waste wind turbine blade composite material into high-value-added silicon carbide. The process is simple, and flash Joule heat treatment is a rapid, high-temperature electrothermal pulse treatment method, thus requiring very little time, being energy-efficient, environmentally friendly, and highly effective.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, specifically to a method for converting waste wind turbine blade composite materials into silicon carbide. Background Technology

[0002] Wind power, as a representative of new energy sources, has significant advantages. However, with the arrival of the decommissioning wave of wind turbines, the recycling of these decommissioned equipment faces enormous challenges. With the trend towards larger wind turbines, blades are becoming longer, towers are becoming taller, and individual units are becoming larger, leading to a simultaneous increase in the weight and overall proportion of the blade hub. Wind turbine blades and related fiberglass products are the most difficult parts of the turbine and its supporting facilities to recycle, further increasing the difficulty of recycling. Although industry and academia are exploring diversified recycling technologies, effective methods have not yet been established in practice. Currently, the most common treatment methods are landfilling, incineration, pyrolysis, or dissolution, but these methods suffer from environmental pollution, high carbon emissions, resource waste, and complex processes. Therefore, developing a simple, energy-efficient, and environmentally friendly treatment technology can not only achieve the resource recovery and harmless disposal of waste wind turbine blade composite materials but also promote the sustainable development of the industry. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the objective of this invention is to propose a method for converting waste wind turbine blade composite materials into silicon carbide, a method that is simple, energy-efficient, and environmentally friendly.

[0004] Specifically, the present invention provides a method for converting waste wind turbine blade composite materials into silicon carbide, comprising the following steps:

[0005] The waste wind turbine blade composite material powder is mixed with a conductive agent to obtain a mixture, wherein the waste wind turbine blade composite material contains silicon and carbon elements;

[0006] The mixture was subjected to flash Joule heat treatment to obtain silicon carbide.

[0007] The method of this invention does not require any pretreatment of the waste wind turbine blade composite material powder, such as pyrolysis. In the presence of a conductive agent, only one step of flash Joule heat treatment is needed to convert the waste wind turbine blade composite material into silicon carbide with high added value. The process steps are simple. At the same time, flash Joule heat treatment is a rapid high-temperature electrothermal pulse treatment method, which is very time-saving, energy-efficient and environmentally friendly.

[0008] Compared with traditional treatment methods, the method of this invention can significantly reduce energy consumption, greenhouse gas emissions, and solvent use, and simplify the process. This method can recycle and upgrade waste wind turbine blade composite materials into high-value-added silicon carbide materials, reducing production costs while promoting the green development of the industry, and has significant application prospects. Therefore, this invention provides a feasible approach for the sustainable utilization of waste wind turbine blade composite materials, contributing to the development of cleaner production and a circular economy.

[0009] According to some embodiments of the present invention, the waste wind turbine blade composite material includes one or more of glass fiber reinforced plastic and glass fiber reinforced resin.

[0010] According to some embodiments of the present invention, the temperature of the flash Joule heat treatment is 1500℃-2500℃, and the total time of the flash Joule heat treatment is 0.5s-2min.

[0011] According to some embodiments of the present invention, the flash Joule heating treatment is performed using a capacitor pulse. The flash Joule heating treatment includes a first stage of flash Joule heating treatment and a second stage of flash Joule heating treatment. The voltage and discharge time of the first stage of flash Joule heating treatment are both less than those of the second stage of flash Joule heating treatment. Preferably, the voltage of the first stage of flash Joule heating treatment is 40V-60V, and the discharge time is 0.4s-1.0s; the voltage of the second stage of flash Joule heating treatment is 130V-150V, and the discharge time is 1s-3s.

[0012] According to some embodiments of the present invention, the flash Joule heat treatment is performed using a DC pulse. The flash Joule heat treatment includes a first stage of flash Joule heat treatment and a second stage of flash Joule heat treatment. The voltage, current, and discharge time of the first stage of flash Joule heat treatment are all less than those of the second stage of flash Joule heat treatment. Preferably, the voltage of the first stage of flash Joule heat treatment is 15V-25V, the current is 15A-25A, and the discharge time is 0.4s-1.0s; the voltage of the second stage of flash Joule heat treatment is 28V-35V, the current is 60A-70A, and the discharge time is 10s-20s.

[0013] According to some embodiments of the present invention, the flash Joule heat treatment is performed under vacuum or an inert atmosphere; preferably, the flash Joule heat treatment is performed under vacuum; preferably, the vacuum degree is below 10 Pa.

[0014] According to some embodiments of the present invention, the conductive agent includes one or more of conductive carbon black, graphite powder, graphene, carbon nanotubes, petroleum coke, metallurgical coke, coke, and carbon fiber; preferably, the conductive agent includes one or more of graphene and carbon nanotubes.

[0015] According to some embodiments of the present invention, the conductive agent accounts for 20%-50% by mass in the mixture.

[0016] According to some embodiments of the present invention, the mesh size of the waste wind turbine blade composite material powder is 100-500 mesh.

[0017] According to some embodiments of the present invention, the method further includes post-treatment of silicon carbide; the post-treatment includes purification treatment; the purification treatment includes: acid washing to remove metal impurities, and / or calcination to remove carbon.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of converting waste wind turbine blade composite materials into silicon carbide according to an embodiment of the present invention.

[0020] Figure 2 Images of coarse tailings produced during the production of wind turbine blades;

[0021] Figure 3 Images of the fine tailings produced during the production of wind turbine blades;

[0022] Figure 4 Image of the mixture of finely ground tailings and conductive carbon black in Example 1;

[0023] Figure 5 The image shows a mixture of ground fine tailings and conductive carbon black loaded into a quartz reaction tube in Example 1.

[0024] Figure 6 This is a temperature curve diagram of the mixture of finely ground tailings and conductive carbon black in Example 1 during the first stage of flash Joule heat treatment.

[0025] Figure 7 This is a temperature curve diagram of the mixture of finely ground tailings and conductive carbon black in Example 1 during the second stage of flash Joule heat treatment.

[0026] Figure 8 The image shows the mixture of finely ground tailings and conductive carbon black from Example 1 after undergoing two stages of flash Joule heat treatment.

[0027] Figure 9 The image shows the XRD pattern of the fine tailings produced during the wind turbine blade manufacturing process in Example 1.

[0028] Figure 10The XRD pattern of the mixture of fine tailings and conductive carbon black after grinding in Example 1, after two-stage flash Joule heat treatment;

[0029] Figure 11 The TGA spectrum of the fine tailings produced during the wind turbine blade manufacturing process in Example 1, measured in air atmosphere;

[0030] Figure 12 The image shows the C, H, and N elemental analysis spectrum of the fine tailings produced during the wind turbine blade manufacturing process in Example 1.

[0031] Figure 13 The XRF spectrum of the fine tailings produced during the wind turbine blade manufacturing process in Example 1;

[0032] Figure 14 The XRF spectrum of the product obtained by flash Joule heat treatment of the fine tailings and conductive carbon black after grinding in Example 1.

[0033] Figure 15 The XRF spectrum of the product in Example 1 after acid washing;

[0034] Figure 16 This is an image of a quartz tube containing a mixture of ground fine tailings and conductive carbon black, as shown in Example 2.

[0035] Figure 17 This is a temperature curve diagram of the mixture of ground fine tailings and conductive carbon black in Example 2 during the second stage of flash Joule heat treatment;

[0036] Figure 18 The image shows the mixture of finely ground tailings and conductive carbon black from Example 2 after undergoing two stages of flash Joule heat treatment.

[0037] Figure 19 The Raman spectrum of the product after two-stage flash Joule heat treatment of the mixture of finely ground tailings and conductive carbon black in Example 2.

[0038] Figure 20 The image shows the coarse material obtained after crushing the decommissioned wind turbine blades in Example 3.

[0039] Figure 21 Image of fine powder obtained after grinding decommissioned wind turbine blades in Example 3;

[0040] Figure 22 Image of the mixture of fine powder from decommissioned wind turbine blades and conductive carbon black in Example 3;

[0041] Figure 23 The image shows a mixture of fine powder from decommissioned wind turbine blades and conductive carbon black packed into a quartz tube in Example 3.

[0042] Figure 24This is a temperature curve diagram of the mixture of decommissioned wind turbine blade fine powder and conductive carbon black in Example 3 during the first stage of flash Joule heat treatment;

[0043] Figure 25 This is a temperature curve diagram of the mixture of decommissioned wind turbine blade powder and conductive carbon black in Example 3 after the second stage of flash Joule heat treatment.

[0044] Figure 26 The image shows a mixture of decommissioned wind turbine blade powder and conductive carbon black in Example 3, after undergoing two stages of flash Joule heat treatment.

[0045] Figure 27 The XRD pattern of the product after two-stage flash Joule heat treatment of the mixture of decommissioned wind turbine blade fine powder and conductive carbon black in Example 3.

[0046] Figure 28 The TGA spectrum of the fine powder from the decommissioned wind turbine blades in Example 3;

[0047] Figure 29 The image shows the XRF spectrum of the fine powder from the decommissioned wind turbine blades in Example 3.

[0048] Figure 30 The image shows the SEM image of the product after the reaction of the mixture of decommissioned wind turbine blade powder and conductive carbon black in Example 3.

[0049] Figure 31 This is a magnified SEM image of the product after the reaction of the mixture of decommissioned wind turbine blade powder and conductive carbon black in Example 3.

[0050] Figure 32 for Figure 30 The elemental distribution diagram of C in the corresponding region;

[0051] Figure 33 for Figure 30 Elemental distribution of Si in the corresponding region;

[0052] Figure 34 for Figure 31 The elemental distribution diagram of O in the corresponding region;

[0053] Figure 35 The image shows the XRD pattern of the product after calcination treatment of the reaction mixture of decommissioned wind turbine blade powder and conductive carbon black in Example 4. Detailed Implementation

[0054] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0055] Wind turbine blades are primarily made of glass fiber reinforced plastic (GFRP). GFRP boasts advantages such as light weight, good chemical stability, and excellent mechanical properties, and is now widely used in various fields including sporting goods, wind turbine blades, the automotive industry, and aerospace. Both the processing of GFRP products and their eventual decommissioning generate significant amounts of waste and tailings. Currently, the most common disposal methods are landfilling, incineration, pyrolysis, or dissolution, but these methods suffer from environmental pollution, high carbon emissions, resource waste, and complex processes. Therefore, developing a simple, energy-efficient, and environmentally friendly treatment technology can not only achieve the resource recovery and harmless disposal of waste wind turbine blade composite materials but also promote the sustainable development of the industry.

[0056] To address the aforementioned issues, this invention proposes a method for converting waste wind turbine blade composite materials into silicon carbide. This method eliminates the need for any pretreatment of the waste wind turbine blade composite material powder, such as pyrolysis. In the presence of a conductive agent, only one step of flash Joule heat treatment is required to convert the waste wind turbine blade composite material into high-value-added silicon carbide. The process is simple, and flash Joule heat treatment is a rapid high-temperature electrothermal pulse treatment method, which is therefore very time-efficient, energy-saving, and environmentally friendly.

[0057] Specifically, the present invention provides a method for converting waste wind turbine blade composite materials into silicon carbide, comprising the following steps:

[0058] The waste wind turbine blade composite material powder is mixed with a conductive agent to obtain a mixture, wherein the waste wind turbine blade composite material contains silicon and carbon elements;

[0059] The mixture was subjected to flash Joule heat treatment to obtain silicon carbide.

[0060] Because the composite material of waste wind turbine blades inherently contains silicon and carbon, meaning it contains both silicon and carbon sources, the conductive agent, heated by electric current during flash Joule heat treatment, generates high temperatures to rapidly heat the target material. This causes the silicon and carbon to react quickly, forming silicon carbide. This process requires no additional silicon or carbon sources; only the conductive agent is needed. It fully utilizes the carbon and silicon inherent in the waste wind turbine blade composite material, achieving efficient recycling of the waste material. Furthermore, this process requires no additional solvents or catalysts, achieving results that traditional treatment methods cannot.

[0061] Compared with traditional treatment methods, the method of this invention can significantly reduce energy consumption, greenhouse gas emissions, and solvent use, and simplify the process. This method can recycle and upgrade waste wind turbine blade composite materials into high-value-added silicon carbide materials, reducing production costs while promoting the green development of the industry, and has significant application prospects. Therefore, this invention provides a feasible approach for the sustainable utilization of waste wind turbine blade composite materials, contributing to the development of cleaner production and a circular economy.

[0062] In this invention, "waste wind turbine blade composite material" refers to composite materials from discarded or decommissioned wind turbine blades. "Wind turbine blade composite material" refers to a composite material that can be used to manufacture wind turbine blades, containing silicon and carbon elements. For example, wind turbine blade composite materials include composites of silicon dioxide and polymer materials. Polymer materials include plastics, resins, etc.

[0063] The waste wind turbine blade composite material can be of various types, such as excess or residual materials generated during the wind turbine blade production process due to cutting, processing, and other techniques. Figure 2 and 3 As shown, these are either wind turbine blade composite materials that have reached their service life and have been retired, or wind turbine blade composite materials that have not reached their retirement age but have been damaged or phased out during use.

[0064] In some embodiments, the waste wind turbine blade composite material includes one or more of glass fiber reinforced plastic and glass fiber reinforced resin. The main raw material for wind turbine blades is glass fiber reinforced plastic. Glass fiber reinforced plastic is a robust composite material that uses glass fiber (mainly SiO2) and its products as reinforcing materials and synthetic resin as the matrix material. The silicon element in the waste wind turbine blade composite material mainly comes from glass fiber, and the carbon element mainly comes from synthetic resin. The inventors discovered that when a conductive agent is heated to a high temperature by an electric current, the silicon element in the glass fiber and the carbon element in the synthetic resin (carbon element is mainly in a lower valence state, such as 0 and / or negative valence) can directly undergo a carbothermic reduction reaction to generate silicon carbide, without the need for pretreatment of the waste wind turbine blade composite material powder. For example, it is not necessary to pre-pyrolyze the composite material to form carbon element capable of reacting with silicon. The valence state of carbon element in the synthetic resin is even lower than that of carbon element in the synthetic resin, which is more conducive to the reaction, thereby simplifying the process and reducing costs.

[0065] In some embodiments, the waste wind turbine blade composite material powder can be obtained by physical operations such as cutting, crushing, and grinding the waste wind turbine blade composite material. These physical operations are all conventional in the art and are not specifically limited herein.

[0066] In some embodiments, the temperature of the flash Joule heat treatment can be 1500-2500°C, and the total time of the flash Joule heat treatment can be 0.5s-2min. The temperature can be rapidly reached to 1500-2500°C by adjusting the pulse heating parameters. Optimizing the temperature and time of the flash Joule heat treatment is beneficial for promoting the reaction between silicon and carbon elements and reducing side reactions. The flash Joule heat treatment of this invention is a rapid high-temperature treatment using pulse heating. The desired temperature can be quickly reached by adjusting the pulse heating parameters.

[0067] In some specific embodiments, the temperature of the flash Joule heat treatment can be 1500℃-2000℃, 2000℃-2500℃, 1700℃-2000℃, 2000℃-2200℃ or 1700℃-2200℃.

[0068] In some specific embodiments, the total time of the flash Joule heat treatment can be 0.5s, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, or 120s.

[0069] "Total time of flash Joule heat treatment" refers to the sum of all discharge times during the entire heat treatment process. For example, if two pulse discharges are performed during the entire heat treatment process, then the total time of flash Joule heat treatment is the sum of the times of the two discharges.

[0070] In some embodiments, the flash Joule heat treatment includes: loading a mixture of the waste wind turbine blade composite material powder and a conductive agent into a reactor, and placing the entire reactor in a vacuum or inert atmosphere; connecting electrodes to both ends of the reactor to connect to a pulsed current system; and applying a pulsed current to perform flash Joule heat treatment. The reactor may be made of various materials, such as quartz or mullite. The electrodes may be made of graphite. The pulsed current system can generate second-level, time-controllable, and current-controllable electrical pulses.

[0071] In some embodiments, the flash Joule heating treatment is performed using a capacitor pulse. The flash Joule heating treatment includes a first stage flash Joule heating treatment and a second stage flash Joule heating treatment. The voltage and discharge time of the first stage flash Joule heating treatment are both shorter than those of the second stage flash Joule heating treatment. Using segmented heat treatment, and controlling the voltage and discharge time of the first stage to be shorter than those of the second stage, improves the conversion rate of silicon carbide by more than 25% compared to using non-segmented heat treatment.

[0072] In this invention, the capacitor pulse is a pulse emitted by a capacitor, and the "voltage" here refers to the voltage of the capacitor.

[0073] In this invention, discharge time refers to the duration of releasing electrical energy in the form of pulses.

[0074] In some specific embodiments, the voltage of the first stage of flash Joule heat treatment is 40V-60V, and the discharge time is 0.4s-1.0s; the voltage of the second stage of flash Joule heat treatment is 130V-150V, and the discharge time is 1s-3s. Optimizing the voltage and discharge time of the first stage heat treatment and the second stage heat treatment is beneficial to further improve the conversion rate of silicon carbide. The higher the voltage and the higher the heat treatment temperature, the more complete the reaction. The first stage heat treatment is carried out at a lower temperature for pre-reaction, and the second stage heat treatment increases the temperature to allow the reaction to proceed fully.

[0075] In some specific embodiments, the first stage of flash Joule heat treatment includes: performing the treatment 1 to 4 times continuously with a voltage of 40V-60V and a discharge time of 0.4s-1.0s; the second stage of flash Joule heat treatment includes: performing the treatment 1 to 3 times continuously with a voltage of 130V-150V and a discharge time of 1s-3s.

[0076] In some specific embodiments, the voltage of the first stage of flash Joule heating treatment can be 40V, 45V, 50V, 55V, or 60V. The discharge time of the first stage of flash Joule heating treatment can be 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, or 1.0s. "Performing 1 to 4 consecutive treatments" means performing 1, 2, 3, or 4 pulse discharges on the mixture at a predetermined voltage and a predetermined discharge time.

[0077] In some specific embodiments, the voltage of the second stage of flash Joule heating treatment can be 130V, 135V, 140V, 145V, or 150V. The discharge time of the second stage of flash Joule heating treatment can be 1s, 1.5s, 2s, 2.5s, or 3s. "Performing 1 to 3 consecutive treatments" means performing 1, 2, or 3 pulse discharges on the mixture with a predetermined voltage and a predetermined discharge time.

[0078] In some embodiments, the flash Joule heat treatment is performed using DC pulses. The flash Joule heat treatment includes a first stage and a second stage, wherein the voltage, current, and discharge time of the first stage are all less than those of the second stage. Using segmented heat treatment, and controlling the voltage, current, and discharge time of the first stage to be less than those of the second stage, improves the conversion rate of silicon carbide by more than 25% compared to using non-segmented heat treatment.

[0079] In this invention, the DC pulse is a pulse formed by a DC power supply, and the voltage here refers to the power supply voltage.

[0080] In some specific embodiments, the voltage of the first stage of flash Joule heat treatment is 15V-25V, the current is 15A-25A, and the discharge time is 0.4s-1.0s; the voltage of the second stage of flash Joule heat treatment is 28V-35V, the current is 60A-70A, and the discharge time is 10s-20s. Optimizing the voltage, current, and discharge time of the first and second stages of heat treatment is beneficial to further improving the conversion rate of silicon carbide. Higher voltage and current, and higher heat treatment temperature, result in a more complete reaction. The first stage of heat treatment is carried out at a lower temperature for pre-reaction, while the second stage of heat treatment, with its higher temperature, allows the reaction to proceed fully.

[0081] In some specific embodiments, the voltage of the first stage of flash Joule heat treatment is 15V, 16V, 17V, 18V, 19V, 20V, 21V, 22V, 23V, 24V, or 25V. The current is 15A, 16A, 17A, 18A, 19A, 20A, 21A, 22A, 23A, 24A, or 25A. The discharge time is 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, or 1.0s.

[0082] In some specific embodiments, the voltage of the second stage of flash Joule heat treatment is 28V, 29V, 30V, 31V, 32V, 33V, 34V, or 35V. The current is 60A, 61A, 62A, 63A, 64A, 65A, 66A, 67A, 68A, 69A, or 70A. The discharge time is 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, or 20s.

[0083] In some specific embodiments, the first stage of flash Joule heat treatment includes: setting a discharge voltage of 15V-25V, a discharge current of 15A-25A, a discharge time of 0.4s-1.0s, and 1-4 discharge cycles; the second stage of flash Joule heat treatment includes: setting a discharge voltage of 28V-35V, a discharge current of 60A-65A, a discharge time of 10s-20s, and 1-2 discharge cycles. "1-4 discharge cycles" refers to subjecting the mixture to 1, 2, 3, or 4 pulse discharges with a predetermined voltage, predetermined current, and predetermined discharge time. "1-2 discharge cycles" refers to subjecting the mixture to 1 or 2 pulse discharges with a predetermined voltage, predetermined current, and predetermined discharge time.

[0084] In some embodiments, the flash Joule heat treatment is performed under a vacuum or inert atmosphere. The presence of oxygen affects the formation of silicon carbide and the progress of the reaction; by evacuating or filling with an inert atmosphere, the influence of oxygen can be reduced.

[0085] In some specific embodiments, the flash Joule heat treatment is performed under vacuum. A higher vacuum level is beneficial for promoting the reaction between silicon and carbon elements in the composite powder of waste wind turbine blades, thereby increasing the conversion rate of silicon carbide. Preferably, the vacuum level is below 10 Pa, for example, below 8 Pa or below 5 Pa.

[0086] In some specific embodiments, the inert atmosphere includes one or more of nitrogen, argon, etc.

[0087] In some embodiments, the conductive agent includes one or more of conductive carbon black, graphite powder, graphene, carbon nanotubes, petroleum coke, metallurgical coke, coke, and carbon fiber. Preferably, the conductive agent includes one or more of graphene and carbon nanotubes. Graphene and carbon nanotubes have better conductivity; better conductivity is more conducive to generating high temperatures through electric current heating, which helps to shorten the heating time. Conductive carbon black and graphite powder have good conductivity and low cost, and also have advantages in actual production.

[0088] In some embodiments, the purity of the conductive agent is 95%-99%, for example 95%, 96%, 97%, 98%, or 99%. High-purity conductive agents are beneficial in reducing the introduction of impurities.

[0089] In some embodiments, the conductive agent comprises 20%-50% by mass in the mixture. "The mass percentage of the conductive agent in the mixture" refers to the ratio of the mass of conductive carbon black to the total mass of the mixture. Optimizing the amount of conductive agent helps to shorten the reaction time and improve the conversion rate of silicon carbide. Insufficient conductive agent will result in insufficient contact with the waste wind turbine blade composite powder, uneven heat distribution, and some powder may fail to react.

[0090] In some specific embodiments, the conductive agent in the mixture comprises 20%, 25%, 30%, 35%, 40%, 45%, or 50% by mass.

[0091] In some embodiments, the particle size of the composite powder from the waste wind turbine blades is 100-500 mesh. Optimizing the particle size of the powder is beneficial for promoting the reaction; generally, the finer the powder, the more favorable the reaction.

[0092] In some specific embodiments, the mesh size of the waste wind turbine blade composite material powder is 100 mesh, 200 mesh, 300 mesh, 400 mesh, or 500 mesh.

[0093] In some embodiments, the method further includes post-processing the silicon carbide. The post-processing includes purification. The purification includes acid washing to remove metallic impurities and / or calcination to remove carbon. Post-processing may be performed selectively depending on the required purity of the silicon carbide product.

[0094] In some specific embodiments, the acid includes at least one of inorganic acids and organic acids. For example, the inorganic acid includes one or more of sulfuric acid, nitric acid, and hydrochloric acid. For example, the organic acid includes one or more of acetic acid and citric acid. Depending on the composition of the waste wind turbine blade composite material, the metallic impurities include calcium, aluminum, etc.

[0095] In some specific embodiments, the calcination temperature is 600℃-800℃, for example, 600℃, 650℃, 700℃, 750℃ or 800℃.

[0096] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0097] Example 1

[0098] The fine tailings generated during the production of wind turbine blades are converted into silicon carbide material through capacitor pulse discharge. The specific steps are as follows:

[0099] (1) Select the fine tailings generated during the wind turbine blade production process as raw materials, such as... Figure 3 As shown.

[0100] (2) Cut, crush and grind the fine tailings from step 1 to obtain waste wind turbine blade composite material powder with a mesh size of 300 mesh.

[0101] (3) Mix the powder from step 2 with the conductive carbon black evenly. Specifically, mix by manual grinding to obtain a mixture, such as... Figure 4 As shown in the figure, conductive carbon black accounts for 40% of the mass of the mixture.

[0102] (4) Using a quartz tube with an inner diameter of 8 mm and a length of 70 mm as the reaction tube, a conductive plug (graphite plug) is inserted into one end of the quartz tube, and 0.3 g of the powder from step 3 is inserted into the other end. Then, another conductive plug (graphite plug) is inserted to form a relatively closed reaction environment, such as... Figure 5 As shown. Finally, install the quartz tube on the tubular reaction stand (Taiyuan Saiyin New Material Technology Co., Ltd.), rotate the knob on the side of the tubular reaction stand to connect the mixture powder to the power supply, check the sample resistance, compress the reaction tube stand, and observe the resistance value at the same time. The required resistance value is achieved. The resistance value is 2.0Ω.

[0103] (5) Place the tubular reaction rack in the stainless steel vacuum chamber, aim the infrared temperature probe at the reactant in the quartz tube, close the stainless steel vacuum chamber, start the vacuum pump, and achieve the required vacuum level of less than 10 Pa.

[0104] (6) Connect electrodes to both ends of the quartz tube to connect to the capacitor pulse current system (Taiyuan Saiyin New Material Technology Co., Ltd.). Within the withstand voltage range, the charge of the capacitor is proportional to the capacitor voltage. The highest capacitor voltage of the instrument used in this experiment is 300V.

[0105] (7) A pulsed current is applied to perform flash Joule thermoelectric treatment. Specifically, a two-stage flash Joule thermoelectric treatment mode is adopted; the first stage: the voltage is set to 50V, the discharge time is 0.5s, and the treatment is performed 3 times consecutively; the second stage: the voltage is set to 140V, the discharge time is 2s, and the treatment is performed 2 times consecutively. Temperature measurement software is started simultaneously with the Joule thermoelectric reaction. After the reaction is completed, data acquisition and recording are stopped and the data is saved. The temperature curves of the two stages of flash Joule thermoelectric treatment are shown below. Figure 6 , Figure 7 As shown. After heat treatment, the products obtained from the reaction are as follows. Figure 8 As shown in the figure. According to the XRD results, the conversion rate of silicon carbide is over 90%.

[0106] (8) Characterization of the fine tailings raw materials and reaction products included: X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray fluorescence spectroscopy (XRF). XRD characterization showed that the main component of the fine tailings was amorphous silica (…). Figure 9 Fine tailings are converted into silicon carbide after rapid high-temperature processing. Figure 10 TGA characterization showed that the organic component epoxy resin accounted for approximately 20% of the mass of the fine tailings. Figure 11 Elemental analysis characterization showed that the carbon content in the fine tailings was approximately 15% by mass. Figure 12 XRF characterization showed that the fine tailings contained approximately 35% Ca and 35% Si, as well as other metallic elements. Figure 13 The elemental composition of the reaction products is as follows: Figure 14 As shown, the mass proportions of each component are as follows: Si accounts for approximately 39%, Ca accounts for approximately 29%, Al accounts for approximately 10%, Mg accounts for approximately 9%, and Y accounts for approximately 5%.

[0107] (9) Take out the product from step 7, grind it into a fine powder using a mortar and pestle, mix the powder with 40 mL of hydrochloric acid (concentration 1 mol / L), and heat in an oil bath at 80℃ for 2 hours. After acid washing, the mass percentage of Si is approximately 74%, the mass percentage of Ca is approximately 10%, and it also contains a small amount of other metal elements ( Figure 15).

[0108] Example 2

[0109] The fine tailings generated during the production of wind turbine blades are converted into silicon carbide material through DC pulse discharge. The specific steps are as follows:

[0110] Steps (1)-(5) are the same as steps (1)-(5) in Example 1. In step (4), the amount of the mixture in the quartz tube is 1.2g. Figure 16 As shown, the resistance of the mixture inside the tube after compression is 3.0Ω.

[0111] (6) Connect electrodes to both ends of the quartz tube to connect it to a DC pulse discharge system (Taiyuan Saiyin New Material Technology Co., Ltd.), with a maximum current of 83A and a maximum voltage of 36V.

[0112] (7) Set the experimental parameters and begin the Joule heating reaction. Specifically, a two-stage flash Joule heating mode is adopted; the first stage: set the voltage to 20V, the current to 20A, the discharge time to 0.5s, the interval time to 0.1s, and the number of discharges to 3; the second stage: set the voltage to 30V, the current to 65A, the discharge time to 15s, and the number of discharges to 1. Start the temperature acquisition software to record data, and control the system to charge and discharge according to the set process. At the same time, monitor the reaction current, voltage, and reaction temperature. After the reaction is completed, stop the data acquisition and recording in time and save the data. The temperature curve of the second stage flash Joule heating is shown below. Figure 17 As shown. The products after the reaction are as follows. Figure 18 As shown in the figure. According to the XRD results, the conversion rate of silicon carbide is over 90%.

[0113] (8) Raman spectroscopy characterization of the reaction products. Raman spectroscopy characterization showed that the fine tailings generated during the wind turbine blade production process were transformed into silicon carbide material after rapid high-temperature treatment, with graphene material being generated simultaneously, such as... Figure 19 As shown.

[0114] Example 3

[0115] Decommissioned wind turbine blades that have reached their service life are converted into silicon carbide material through capacitor pulse discharge. The specific steps are as follows:

[0116] (1) Select retired waste wind turbine blades as raw materials.

[0117] (2) The decommissioned wind turbine blades from step 1 are cut, crushed, and ground to obtain waste wind turbine blade composite material powder with a mesh size of 200 mesh. A photograph of the coarse material obtained after crushing is shown below. Figure 20 As shown in the image, the fine powder obtained after grinding from the decommissioned wind turbine blades is as follows: Figure 21 As shown.

[0118] Steps (3)-(7) are the same as steps (3)-(7) in Example 1. The photograph of the mixture of decommissioned wind turbine blade fine powder and conductive carbon black is shown below. Figure 22 As shown in the image. A photograph shows a mixture of fine powder from decommissioned wind turbine blades and conductive carbon black, packed into a quartz tube. Figure 23 As shown. The temperature curves of the two flash Joule heat treatments are as follows: Figure 24 , Figure 25 As shown. The products obtained after the reaction are as follows. Figure 26 As shown in the figure. According to the XRD results, the conversion rate of silicon carbide is over 90%.

[0119] (8) The products before and after the reaction were characterized by XRD, TGA, XRF, and SEM. XRD characterization showed that the fine powder from decommissioned wind turbine blades was successfully converted into silicon carbide material after rapid high-temperature treatment. Figure 27 TGA characterization showed that epoxy resin accounted for approximately 53% of the mass of the fine powder from decommissioned wind turbine blades. Figure 28 XRF characterization showed that the fine powder from decommissioned wind turbine blades contained approximately 42% Ca and 34% Si by mass, along with other metallic elements. Figure 29 SEM characterization showed that the silicon carbide material transformed from the fine powder of decommissioned wind turbine blades after rapid high-temperature treatment had a relatively fine powder structure. Figures 30-31 ), and elemental analysis also shows that the main components of the converted silicon carbide material are silicon and carbon, while the oxygen content is low. Figure 32 , Figure 33 , Figure 34 ).

[0120] Example 4

[0121] The product obtained in Example 3 was purified, and the specific steps are as follows:

[0122] The product obtained in Example 3 was placed in a muffle furnace for calcination to remove carbon at 800°C for 30 minutes. The sample was then removed. The product obtained in Example 3 contains graphene material, which can be calcined in a muffle furnace to obtain pure silicon carbide material. The process flow diagram for Example 4 is shown below. Figure 1 As shown.

[0123] The product after calcination was characterized. Pure silicon carbide materials, such as..., were obtained after calcination. Figure 35 As shown in the figure. According to the XRD characterization results, there were no other impurity peaks in the calcined silicon carbide.

[0124] Example 5

[0125] The method described in Example 1 was followed, except that in step (7), a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a two-stage flash Joule thermoelectric treatment mode was used; the first stage: the voltage was set to 40V, the discharge time was 0.6s, and the treatment was performed three times consecutively; the second stage: the voltage was set to 130V, the discharge time was 3s, and the treatment was performed twice consecutively. Temperature measurement software was started simultaneously with the Joule thermoelectric reaction. After the reaction was completed, data acquisition and recording were stopped and the data was saved. After the heat treatment, the product obtained from the reaction was similar to... Figure 8 According to the XRD results, the conversion rate of silicon carbide is over 92%.

[0126] Example 6

[0127] The method described in Example 1 was followed, except that in step (7), a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a two-stage flash Joule thermoelectric treatment mode was used; the first stage: the voltage was set to 60V, the discharge time was 0.4s, and the treatment was performed three times consecutively; the second stage: the voltage was set to 150V, the discharge time was 1s, and the treatment was performed twice consecutively. Temperature measurement software was started simultaneously with the Joule thermoelectric reaction. After the reaction was completed, data recording was stopped and the data was saved. After the heat treatment, the product obtained from the reaction was similar to... Figure 8 According to the XRD results, the conversion rate of silicon carbide is over 95%.

[0128] Example 7

[0129] The method described in Example 2 was followed, except that (7) experimental parameters were set and the Joule heating reaction was started. Specifically, a two-stage flash Joule heating mode was used; the first stage: voltage 15V, current 15A, discharge time 0.6s, interval time 0.1s, discharge times 3 times; the second stage: voltage 28V, current 60A, discharge time 20s, discharge times 1 time. Temperature acquisition software was started to record data, and the control system was set to charge and discharge according to the pre-defined process. At the same time, the reaction current, voltage and reaction temperature were monitored. After the reaction was completed, data acquisition and recording were stopped in time and the data was saved. According to the XRD results, the conversion rate of silicon carbide was over 92%.

[0130] Example 8

[0131] The method described in Example 2 was followed, except that (7) experimental parameters were set and the Joule heating reaction was started. Specifically, a two-stage flash Joule heating mode was used; the first stage: voltage 25V, current 25A, discharge time 0.4s, interval time 0.1s, discharge times 3 times; the second stage: voltage 35V, current 70A, discharge time 10s, discharge times 1 time. Temperature acquisition software was started to record data, and the control system was set to charge and discharge according to the pre-defined process. At the same time, the reaction current, voltage and reaction temperature were monitored. After the reaction was completed, data acquisition and recording were stopped in time and the data was saved. According to the XRD results, the conversion rate of silicon carbide was over 95%.

[0132] Example 9

[0133] The method described in Example 1 was followed, except that in step (7), a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a two-stage flash Joule thermoelectric treatment mode was used; the first stage: the voltage was set to 20V, the discharge time was 0.5s, and the treatment was performed three times consecutively; the second stage: the voltage was set to 80V, the discharge time was 2s, and the treatment was performed twice consecutively. While the Joule thermoelectric reaction was underway, temperature acquisition software was started to measure the temperature, with a maximum temperature of 1000℃. After the reaction was completed, data acquisition and recording were stopped and the data was saved. The conversion rate of silicon carbide was below 20%.

[0134] Example 10

[0135] The method described in Example 1 was followed, except that in step (7), a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a single-stage flash Joule thermoelectric treatment mode was used: the voltage was set to 50V, the discharge time to 0.5s, and the treatment was performed 11 times consecutively. Temperature measurement was performed simultaneously with the Joule thermoelectric reaction using temperature acquisition software. Once the reaction was complete, data acquisition and recording were stopped and the data saved. According to the XRD results, the silicon carbide conversion rate was below 30%.

[0136] Example 11

[0137] The method described in Example 1 was followed, except that in step (7), a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a single-stage flash Joule thermoelectric treatment mode was used: the voltage was set to 140V, the discharge time to 2s, and the treatment was performed twice consecutively. Temperature measurement was performed simultaneously with the Joule thermoelectric reaction using temperature acquisition software. Once the reaction was complete, data acquisition and recording were stopped and the data saved. According to the XRD results, the conversion rate of silicon carbide was below 60%.

[0138] Example 13

[0139] The method described in Example 1 was followed, except that (7) a pulsed current was applied to perform flash Joule thermoelectric treatment. Specifically, a two-stage flash Joule thermoelectric treatment mode was used; the first stage: the voltage was set to 140V, the discharge time was 2s, and the treatment was performed twice consecutively; the second stage: the voltage was set to 50V, the discharge time was 0.5s, and the treatment was performed three times consecutively. While the Joule thermoelectric reaction was underway, temperature acquisition software was started to measure the temperature. After the reaction was completed, data acquisition and recording were stopped in time and the data was saved. According to the XRD results, the conversion rate of silicon carbide was below 80%.

[0140] Example 14

[0141] The method described in Example 2 was followed, except that step (7) involved setting experimental parameters and initiating the Joule heating reaction. Specifically, a single-stage flash Joule heating mode was used: voltage set to 20V, current set to 20A, discharge time set to 0.5s, interval time set to 0.1s, and discharge cycles set to 33. Temperature acquisition software was activated to record data, and the control system was configured to charge and discharge according to the pre-set process. Simultaneously, the reaction current, voltage, and reaction temperature were monitored. Once the reaction was complete, data acquisition and recording were stopped immediately, and the data was saved. According to the XRD results, the silicon carbide conversion rate was below 50%.

[0142] Example 15

[0143] The method described in Example 2 was followed, except that step (7) involved setting experimental parameters and initiating the Joule heating reaction. Specifically, a single-stage flash Joule heating mode was used: voltage set to 30V, current set to 65A, discharge time set to 15s, and discharge frequency set to 1. Temperature acquisition software was activated to record data, and the control system was set to charge and discharge according to the pre-defined process. Simultaneously, the reaction current, voltage, and reaction temperature were monitored. Upon completion of the reaction, data acquisition and recording were stopped promptly, and the data was saved. According to the XRD results, the silicon carbide conversion rate was below 50%.

[0144] Example 16

[0145] The method described in Example 2 was followed, except that (7) experimental parameters were set and the Joule heating reaction was started. Specifically, a two-stage flash Joule heating mode was used; the first stage: voltage 30V, current 65A, discharge time 15s, discharge times 1; the second stage: voltage 20V, current 20A, discharge time 0.5s, interval time 0.1s, discharge times 3. Temperature acquisition software was started to record data, and the control system was controlled to charge and discharge according to the set process. At the same time, the reaction current, voltage and reaction temperature were monitored. After the reaction was completed, data acquisition and recording were stopped in time and the data was saved. According to the XRD results, the conversion rate of silicon carbide was below 80%.

[0146] Example 17

[0147] The procedure was carried out according to the method described in Example 1, except that the vacuum level in step (5) was 30 Pa. According to the XRD results, the silicon carbide conversion rate was below 85%.

[0148] Example 18

[0149] The method described in Example 1 was followed, except that graphene was used instead of conductive carbon black. According to XRD results, the silicon carbide conversion rate was over 95%.

[0150] Example 19

[0151] The method described in Example 1 was followed, except that carbon nanotubes were used instead of conductive carbon black. According to XRD results, the silicon carbide conversion rate was over 92%.

[0152] Example 20

[0153] The method described in Example 1 was followed, except that the conductive carbon black accounted for 20% of the mass of the mixture in step (3). According to the XRD results, the conversion rate of silicon carbide was over 90%.

[0154] Example 21

[0155] The method described in Example 1 was followed, except that the conductive carbon black accounted for 50% of the mass of the mixture in step (3). According to the XRD results, the silicon carbide conversion rate was over 95%.

[0156] Example 22

[0157] The method described in Example 1 was followed, except that the conductive carbon black accounted for 10% of the mass of the mixture in step (3). According to the XRD results, the silicon carbide conversion rate was less than 70%.

[0158] Example 23

[0159] The method described in Example 1 was followed, except that the conductive carbon black accounted for 60% of the mass of the mixture in step (3). According to the XRD results, the conversion rate of silicon carbide was 98%, but the carbon content in the product was relatively high.

[0160] Example 24

[0161] The method described in Example 1 was followed, except that the powder used in step (2) had a mesh size of 50. According to XRD results, the silicon carbide conversion rate was below 60%.

[0162] Comparative Example 1

[0163] The method described in Example 1 was followed, except that silicone rubber (Zhonghao Chenguang Chemical Research Institute Co., Ltd.) was used to replace the fine tailings generated during the wind turbine blade production process. According to XRD results, the silicon carbide conversion rate was below 30%. The low conversion rate when treating silicone rubber using the method of this invention is unclear, but it is speculated that it may be related to the form in which silicon exists.

[0164] By comparing the examples and comparative examples, it can be seen that the method of the present invention does not require any pretreatment of the waste wind turbine blade composite material powder, such as pyrolysis. In the presence of a conductive agent, only one step of flash Joule heat treatment is needed to convert the waste wind turbine blade composite material into silicon carbide with high added value. The process steps are simple. At the same time, flash Joule heat treatment is a rapid high-temperature electrothermal pulse treatment method, which is very time-saving, energy-efficient and environmentally friendly.

[0165] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0166] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0167] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for converting waste wind turbine blade composite materials into silicon carbide, characterized in that, Includes the following steps: The waste wind turbine blade composite material powder is mixed with a conductive agent to obtain a mixture, wherein the waste wind turbine blade composite material contains silicon and carbon elements; The mixture was subjected to flash Joule heat treatment to obtain silicon carbide; The flash Joule heat treatment is performed using either a capacitor pulse or a DC pulse, and includes a first stage of flash Joule heat treatment and a second stage of flash Joule heat treatment. When the flash Joule heat treatment is performed using a capacitor pulse, the voltage and discharge time of the first stage of flash Joule heat treatment are both less than those of the second stage of flash Joule heat treatment; the voltage of the first stage of flash Joule heat treatment is 40V-60V, and the discharge time is 0.4 s-1.0 s; the voltage of the second stage of flash Joule heat treatment is 130V-150V, and the discharge time is 1 s-3 s; When the flash Joule heat treatment is performed using DC pulses, the voltage, current, and discharge time of the first stage of flash Joule heat treatment are all less than those of the second stage; the voltage of the first stage of flash Joule heat treatment is 15 V-25 V, the current is 15 A-25 A, and the discharge time is 0.4 s-1.0 s; the voltage of the second stage of flash Joule heat treatment is 28 V-35 V, the current is 60 A-70 A, and the discharge time is 10 s-20 s. The conductive agent comprises 20%-50% by mass in the mixture; The particle size of the composite powder from the waste wind turbine blades is 100-500 mesh.

2. The method according to claim 1, characterized in that, The composite material of the waste wind turbine blades includes one or more of glass fiber reinforced plastic and glass fiber reinforced resin.

3. The method according to claim 1 or 2, characterized in that, The temperature of the flash Joule heat treatment is 1500℃-2500℃, and the total time of the flash Joule heat treatment is 0.5 s-2 min.

4. The method according to claim 1 or 2, characterized in that, The flash Joule heat treatment is performed under a vacuum or inert atmosphere.

5. The method according to claim 4, characterized in that, The vacuum level is below 10 Pa.

6. The method according to claim 1 or 2, characterized in that, The conductive agent includes one or more of the following: conductive carbon black, graphite powder, graphene, carbon nanotubes, petroleum coke, metallurgical coke, coke, and carbon fiber.

7. The method according to claim 1 or 2, characterized in that, The conductive agent includes one or more of graphene and carbon nanotubes.

8. The method according to claim 1 or 2, characterized in that, Also includes: The silicon carbide is post-processed; the post-processing includes purification. The purification process includes: acid washing to remove metallic impurities, and / or calcination to remove carbon.

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