A device and method for continuous microwave thermal conversion of retired wind turbine blade recycled glass fibers

Abstract

This invention discloses a continuous microwave thermal conversion device and method for recovering glass fiber from decommissioned wind turbine blades, achieving efficient decomposition of organic components and clean recovery of inorganic fibers from decommissioned wind turbine blades. This invention utilizes the self-heating effect of materials and microwave absorbers under microwave action, significantly reducing reaction temperature and energy consumption. Uniform pyrolysis of materials is achieved in the microwave pyrolysis unit through a feeding hopper and a rake-type stirring device; the pyrolysis residue solids then enter the microwave oxidation unit for further oxidation and decomposition. The generated inorganic solids are separated by cyclone separation to obtain clean glass fiber, while the microwave absorber is sorted and returned to the system for recycling. The material residence time is controlled by adjusting the furnace inclination, and precise control and power optimization are achieved for different temperature zones using a multi-stage variable frequency microwave source. This enables continuous and efficient processing of large-size decommissioned wind turbine blades, effectively reducing secondary pollution and ensuring the quality of the recovered glass fiber while lowering the temperature and energy consumption of traditional heat recovery processes.

Description

Technical Field

[0001] This invention relates to the field of organic-inorganic composite material recycling technology, and in particular to a device and method for recycling glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion. Background Technology

[0002] For most organic solid wastes, thermal treatment is an effective means of resource recovery. However, with the large-scale generation of emerging organic solid wastes such as organic-inorganic composite materials in recent years, currently used thermal treatment technologies have certain limitations. For example, incineration easily produces harmful gases, and conventional pyrolysis methods suffer from limited heating rates, low thermal efficiency, and significant damage to the inorganic components. Traditional thermal treatment methods are no longer sufficient to meet the demands for efficient and targeted recycling, necessitating the development of novel thermal treatment methods adapted to the characteristics of these materials.

[0003] Microwaves typically refer to electromagnetic waves with frequencies between 0.3 and 300 GHz, with 2.45 GHz being the most common in industrial applications. Microwave thermal conversion, as an external field-enhanced heat treatment method, differs from traditional heating in its mechanism: this method utilizes the microwave responsiveness of specific components in the raw material to intensify microscopic particle vibration, achieving rapid heating from the material's interior. During this process, the energy and mass transfer direction within the system is consistent, thereby enhancing the thermal conversion process and improving thermal conversion efficiency. Currently emerging organic solid wastes, such as decommissioned wind turbine blades, photovoltaic panels, and batteries, are all organic-inorganic composite materials. Taking decommissioned wind turbine blades as an example, their main components are glass fiber and epoxy resin. Epoxy resin, due to its polar molecular structure, possesses excellent microwave responsiveness and can rapidly heat up in a microwave field, thus achieving selective and efficient thermal conversion of the organic components. Therefore, developing microwave thermal conversion methods to recycle emerging organic solid wastes, represented by wind turbine blades, provides a core basis for this approach.

[0004] Chinese invention patent CN 114963183 A discloses a microwave pyrolysis treatment system and method for treating blades. However, the batch operation process proposed requires adding the fan blades before the reaction starts and removing the glass fiber with a forklift after the reaction is complete. This makes it impossible to achieve continuous feeding and discharging, which hinders its large-scale industrial application.

[0005] Chinese invention patent CN 120137689 A discloses a continuous displacement pyrolysis device and its pyrolysis method. Through a continuous displacement system including a pulley device, a continuous material flow path of feeding-microwave pyrolysis-tar cracking-discharge is achieved, effectively reducing microwave leakage and improving production efficiency. However, because the material needs to be crushed (particle size 0.5-15 mm) before feeding, the length and integrity of the glass fibers are damaged, which is detrimental to their recycling.

[0006] Chinese invention patent CN 116515509 B discloses an apparatus and method for thermally converting and recycling glass fibers from waste wind turbine blades. This method involves connecting a pyrolysis unit and an oxidation unit in series, utilizing a feed hopper and a screw conveyor to completely separate the resin matrix and glass fibers from the waste wind turbine blades, thus recovering the glass fibers. The target pyrolysis temperature is 400-600 ℃ with a residence time of 15-30 min, while the target oxidation temperature is 300-500 ℃ with a residence time of 60-120 min. However, this method uses traditional heating methods, resulting in long decomposition times and high energy consumption.

[0007] In summary, current methods for large-scale disposal of decommissioned organic-inorganic composite materials still face several key challenges. Firstly, commonly used thermal treatment methods such as incineration and pyrolysis suffer from high energy consumption and significant pollution, and can cause substantial damage to the recovered fibers, hindering the high-value reuse of resources. Industrial-scale composite material recycling demands high economic and environmental benefits, and continuous operation is crucial for achieving both high efficiency and economic feasibility. However, existing continuous processing equipment often uses powder feeding, whose fine particles hinder precise prediction and control of sample movement during the reaction process and may cause deflagration at high temperatures, compromising industrial safety control. Especially for composite materials containing inorganic fibers, such as wind turbine blades, excessively small feed sizes can damage fiber length and integrity, severely reducing their recycling value. Therefore, developing novel thermal treatment processes that balance continuous operation with fiber structure protection has become an urgent need to promote the resource recovery of such solid waste. Summary of the Invention

[0008] To address the shortcomings and deficiencies of existing wind turbine blade recycling technologies, this paper provides a continuous microwave thermal conversion device and method for recycling glass fiber from decommissioned wind turbine blades. This method fundamentally solves the problems of fiber damage, environmental pollution, and industrial safety by addressing the drawbacks of existing methods, such as high pollution, low efficiency, and poor economic performance. At the same time, it utilizes microwave multi-stage frequency conversion and waste heat recovery design to minimize the operating costs of wind turbine blade recycling.

[0009] To achieve the objectives of this invention, the invention is implemented through the following technical solutions:

[0010] This invention discloses a continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades. It includes an inclined microwave pyrolysis unit, an inclined microwave oxidation unit located below the pyrolysis unit, and a material conveying mechanism connecting the bottom of the lower section of the microwave pyrolysis unit to the top of the upper section of the microwave oxidation unit. It also includes a feeding device connected to the top of the upper section of the microwave pyrolysis unit and a discharging device connected to the bottom of the lower section of the microwave oxidation unit. A lifting device and a gas path device are fixedly connected to the bottom of the upper sections of the microwave pyrolysis unit and the microwave oxidation unit. Both the microwave pyrolysis unit and the microwave oxidation unit include a furnace body, a raised cavity on the upper surface of the furnace body, a stirring rod fixed to the central axis of the furnace body, and a microwave source with a microwave source window located within the raised cavity. The gas path device includes a nitrogen inlet located on the upper front wall of the microwave pyrolysis unit furnace body, a pyrolysis gas outlet located on the upper rear wall of the microwave oxidation unit furnace body, an air inlet located on the upper rear wall of the microwave oxidation unit furnace body, and a tail gas outlet located on the upper rear wall of the microwave oxidation unit furnace body.

[0011] As a further improvement, the feeding device of the present invention includes a feeding hopper located at the front of the upper surface of the microwave pyrolysis unit furnace body, a transition chamber, a pneumatic hammer set on the side wall of the transition chamber, and a feeding port connected to the pipeline of the transition chamber. The material entering the feeding hopper is a block material with a size of 2-8cm.

[0012] As a further improvement, the discharge device of the present invention includes a discharge port opened from top to bottom and a cyclone separator connected to the discharge port; the inner wall of the furnace body is made of high-temperature resistant quartz, the outer wall is made of microwave-insulating metal, the stirring rod is connected to a motor, and at least three stirring blades are evenly distributed on the stirring rod.

[0013] As a further improvement, the protruding cavity described in this invention is located in the middle section of the upper surface of the furnace body. The protruding cavity is separated from the furnace body by a transparent quartz heat insulation and anti-fouling plate. The microwave source consists of at least two groups of microwave sources located on the same plane perpendicular to the furnace body. Each group includes two sources at the top and one source on each side. The window of each microwave source faces the protruding cavity and is located inside the protruding cavity.

[0014] As a further improvement, the microwave source group of the microwave pyrolysis unit of the present invention is set in a segmented frequency conversion configuration with a decreasing microwave power gradient from the front to the back, with the front end at 100-1500W and the back end at 100-600W, and the middle two at a decreasing frequency conversion configuration between the front and back ends; the microwave source group of the microwave oxidation unit is set in a segmented frequency conversion configuration with a decreasing microwave power gradient from the back to the front, with the last microwave source group at 100-1500W and the front end at 100-600W, and the middle two at a decreasing frequency conversion configuration between the back and front ends.

[0015] As a further improvement, the lifting device of the present invention includes a lifting column fixedly connected to the bottom of the furnace body, a lifting machine connected to the lifting column and controlling the lifting of the lifting column, adjusting the furnace body tilt angle to 0-10°, the stirring speed of the stirring rod to 0.2-10 r / min, and the pyrolysis gas discharge port being connected in sequence to the ethanol and saturated calcium hydroxide solution of the oil collection and gas washing unit, an external burner, and a flue pipe installed in the microwave oxidation unit via pipelines.

[0016] As a further improvement, the lifting mechanism of the present invention is preferably adjusted to a furnace body tilt angle of 0-5°, and the stirring speed of the stirring rod is preferably 2-3 r / min. The flue pipe in the microwave oxidation unit includes the outer part of the furnace body and the inner part of the furnace body located on the upper surface near the inner wall of the furnace body cavity. The rear section of the upper surface of the microwave oxidation unit is provided with a tail gas discharge port in front of the material conveying mechanism, and the front section is provided with a flue gas inlet near the front end. The high-temperature flue gas after passing through the external burner is introduced into the flue gas inlet and the flue pipe in the inner part of the furnace body through the external flue pipe and then discharged through the tail gas discharge port.

[0017] This invention discloses a method for recycling glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion, comprising:

[0018] Step 1: Introduce nitrogen gas into the furnace body of the microwave pyrolysis unit through the nitrogen gas inlet;

[0019] Step 2: Set the threshold values ​​for the pressure gauge and oxygen analyzer;

[0020] Step 3: Adjust the tilt angle of the two furnace bodies;

[0021] Step 4: Set the reaction temperature for both furnaces;

[0022] Step 5: Mix the material with the silicon carbide microwave absorber and place it into the feed hopper;

[0023] Step 6: The tar and pyrolysis gas discharged from the pyrolysis gas outlet pass through ethanol and saturated calcium hydroxide solution 12 in sequence.

[0024] Step 7: The tar is absorbed by ethanol. The pyrolysis gas is discharged from the oil collection and washing unit and then introduced into the external burner. Subsequently, the waste heat is recovered along the flue pipe and discharged from the exhaust gas outlet through the flue gas inlet.

[0025] Step 8: Introduce air into the furnace body of the microwave oxidation unit through the air inlet;

[0026] Step 9: The solid product is separated in a cyclone separator to obtain glass fiber and silicon carbide microwave absorbing agent;

[0027] Step 10: The recovered silicon carbide microwave absorbing agent is recycled again in step 5;

[0028] Step 11: The flue gas generated during the microwave oxidation process is discharged from the exhaust port.

[0029] As a further improvement, in step 1 of the present invention, the nitrogen flow meter outside the furnace is adjusted to 100-200 mL / min, and nitrogen is introduced into the furnace of the microwave pyrolysis unit for 20-60 minutes before the reaction is started; in step 3, the elevator is adjusted so that the furnace body tilt angle is 0-5°, and the stirring speed of the stirring rod is controlled to be 2-3 r / min.

[0030] As a further improvement, in step 4 of the present invention, the reaction temperature range in the furnace of the microwave pyrolysis unit is 200-600 ℃, and the microwave source power is set to 100-600 W; the reaction temperature in the furnace of the microwave oxidation unit is 200-600 ℃, and the microwave source power is set to 100-600 W. During the reaction process, the microwave power is automatically adjusted according to the temperature feedback from the thermocouple.

[0031] Compared with existing technologies, the method for recycling glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion provided by this invention has the following advantages:

[0032] (1) Balancing continuous production and fiber structure protection: By directly feeding the 2-8 cm wind turbine blade centimeter-sized block material mixed with silicon carbide wave absorber, the mechanical damage to the length and integrity of glass fiber caused by traditional powder feeding is avoided, ensuring the high value of recycled fiber; at the same time, the block material effectively eliminates the risk of deflagration of fine powder at high temperature, greatly improving the safety of industrial operation.

[0033] (2) High-quality fiber recycling achieved through two-stage microwave synergy: An innovative two-stage synergistic process of microwave pyrolysis and microwave oxidation is adopted. The first stage uses microwave selective heating to rapidly decompose the resin matrix in an oxygen-deficient environment, while the second stage uses microwave-assisted oxidation in an air atmosphere to thoroughly remove residual carbon. Efficient and clean separation of glass fibers can be achieved within relatively low temperatures (400-500℃ for the microwave pyrolysis unit and 450-500℃ for the microwave oxidation unit) and short time (15 min for microwave pyrolysis and 25 min for microwave oxidation), resulting in high purity and clean surface of the recovered fibers.

[0034] (3) Mild reaction conditions: The present invention can achieve complete decomposition of resin and cleaning of fiber in a short time (total processing time 40-60 min) under low temperature (400-500 ℃) and low microwave power (microwave pyrolysis power 400-500 W, microwave oxidation power 500-600 W), which significantly reduces the damage of thermal stress to fiber and system energy consumption compared with traditional pyrolysis method.

[0035] (4) Achieving efficient, continuous, uniform, and controllable large-scale processing: By connecting microwave pyrolysis and microwave oxidation units in series, the solid products after microwave pyrolysis can continuously and directly enter the microwave oxidation unit, thus forming a complete "pyrolysis-oxidation" continuous processing line, realizing uninterrupted operation of materials from feeding to discharging, which is particularly suitable for large-scale industrial recycling; Under this continuous framework, the tilt angle of the furnace body of the microwave pyrolysis unit and the microwave oxidation unit is adjusted by the motor, and the elevator is adjusted so that the furnace body tilt angle is 0-5°. Combined with the rake stirring mechanism, the material movement speed and residence time are controlled in coordination. The stirring speed of the stirring rod is 2-3 r / min, realizing precise control of the pyrolysis and oxidation process, thereby ensuring that the material is heated uniformly and reacts thoroughly.

[0036] (5) Significantly reduced microwave energy consumption: Both the microwave pyrolysis and microwave oxidation units adopt multi-zone independently controllable frequency conversion microwave sources. During initial setup, the reaction temperature range in the microwave pyrolysis unit furnace is 200-600 ℃, and the microwave source power is set to 100-600 W; the reaction temperature in the microwave oxidation unit furnace is 200-600 ℃, and the microwave source power is set to 100-600 W. During the reaction process, the thermocouples feed back the measured temperature to the computer, and the microwave power is automatically adjusted according to the temperature fed back by the thermocouples: when the temperature is higher than the set temperature, the power decreases, and vice versa, the power increases. This allows the power to be adjusted in real time with the temperature, maintaining a uniform and stable temperature field inside the furnace and avoiding energy waste.

[0037] (6) Recycling of microwave absorbing agent to reduce operating costs: The silicon carbide microwave absorbing agent is separated from the glass fiber by a cyclone separator, and the silicon carbide microwave absorbing agent is returned to the system for recycling, which greatly reduces the consumption of auxiliary materials and the generation of solid waste, and improves the economic efficiency and environmental friendliness of the process.

[0038] (7) By-product resource utilization to improve the efficiency of the whole process: The tar produced by microwave pyrolysis can be used as a chemical raw material for high-value utilization after being absorbed and purified by ethanol; the pyrolysis gas is discharged from the saturated calcium hydroxide solution and then fed into an external burner for combustion. The hot flue gas generated by the combustion of the pyrolysis gas is used to supplement the heat of the microwave oxidation unit. This process of returning to the furnace is equivalent to flue gas recirculation, which realizes the efficient recovery of the system's waste heat, further reduces the system's energy consumption, maximizes the recovery of retired blade resources, and improves the economic benefits of the overall process.

[0039] (8) Superior heat and mass transfer mechanism and high processing efficiency: Utilizing the excellent microwave response characteristics of organic resin itself, heat is generated from inside the material and diffuses outward, making the heat transfer and mass transfer directions consistent and mutually reinforcing, which greatly accelerates the pyrolysis process and improves the thermal conversion efficiency.

[0040] (9) Strong process scalability: This method is based on the microwave selective heating mechanism of organic components. It is not only applicable to retired wind turbine blades, but can also be extended to other organic and inorganic composite materials, such as waste photovoltaic panels and circuit boards. It has broad application prospects for high-value and high-efficiency recycling.

[0041] (10) Outstanding environmental benefits: The entire process is carried out in a closed system. The pyrolysis gas is washed and purified, and after heating the gas in the furnace, it is sprayed out from the tail gas outlet. In this process, it serves as a heat source to ensure the temperature in the furnace is maintained, and it is also convenient for subsequent carbon capture. The flue gas from the microwave oxidation process is discharged from the exhaust outlet and is treated to meet emission standards, effectively controlling secondary pollution and realizing the green and clean recycling of retired wind turbine blades. Attached Figure Description

[0042] Figure 1 This is a flowchart of the continuous microwave thermal conversion method for recycling glass fiber from decommissioned wind turbine blades according to the present invention.

[0043] Figure 2 This is a schematic diagram of the continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to the present invention.

[0044] Figure 3 This is a schematic diagram of the cross-sectional side view of the furnace body, microwave source, and protruding cavity.

[0045] 1-Nitrogen inlet, 2-Furnace body, 3-Motor, 4-Flue gas inlet, 5-Microwave source, 6-Material, 7-Silicon carbide microwave absorber, 8-Feed hopper, 9-Tar, 10-Pyrolysis gas, 11-Ethanol, 12-Saturated calcium hydroxide solution, 13-Material conveying mechanism, 14-Air inlet, 15-Discharge port, 16-Cyclone separator, 17-Glass fiber, 18-Pneumatic hammer, 19-Flue duct, 20-Raised cavity, 21-Stirring rod, 22-Pyrolysis gas discharge port, 23-Lifting column, 24-Thermocouple, 25-Transition chamber, 26-Flange, 27-Quartz heat insulation and anti-fouling plate, 28-Exhaust port, 29-Oxygen analyzer, 30-Pressure gauge, 31-Tail gas discharge port. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0047] Figure 2 This is a schematic diagram of the structure of the device for recycling glass fiber 17 from decommissioned wind turbine blades via continuous microwave thermal conversion according to the present invention. Figure 3This is a cross-sectional side view of the furnace body 2, microwave source 5, and protruding cavity. This invention discloses a continuous microwave thermal conversion device for recycling glass fiber 17 from decommissioned wind turbine blades. It includes an inclined microwave pyrolysis unit, an inclined microwave oxidation unit located below the microwave pyrolysis unit, and a material conveying mechanism 13 connecting the bottom of the lower section of the microwave pyrolysis unit and the top of the upper section of the microwave oxidation unit. It also includes a feeding device connected to the top of the upper section of the microwave pyrolysis unit, a discharging device connected to the bottom of the lower section of the microwave oxidation unit, and a lifting device and a gas path fixedly connected to the bottom of the upper sections of the microwave pyrolysis unit and the microwave oxidation unit. The apparatus includes a furnace body 2, a raised cavity 20 on the upper surface of the furnace body 2, a stirring rod 21 fixed on the central axis of the furnace body 2, and a microwave source 5 with its window set in the raised cavity 20. The gas path device includes a nitrogen inlet 1 on the upper front wall of the microwave pyrolysis unit furnace body 2, a pyrolysis gas outlet 22 on the upper rear wall, an air inlet 14 on the upper rear wall of the microwave oxidation unit furnace body 2, and a tail gas outlet 31 on the upper rear wall.

[0048] The device of the present invention mainly consists of a microwave pyrolysis unit and a microwave oxidation unit connected in series.

[0049] The microwave pyrolysis unit, with its core being the first continuous cascade microwave processing device, is used to microwave pyrolyze blocky wind turbine blade material 6 in an oxygen-deficient or oxygen-free environment. This unit includes a furnace body 2, a feeding device connected to the top of the upper section of the microwave pyrolysis unit and connected to the furnace body 2, a lifting device located at the bottom of the upper section of the microwave pyrolysis unit, and a gas path device mounted on the furnace body 2; a raised cavity 20 located on the upper surface of the furnace body 2, a stirring rod 21 fixed to the central axis of the furnace body 2, and evenly spaced stirring blades on the stirring rod 21. The stirring rod 21 is connected to a motor, and a microwave source 5 is located within the raised cavity 20. The lifting device includes a lifting column 23 fixedly connected to the bottom of the furnace body 2, and a lifting... The column 23 is connected to and controls the lifting of the column 23. The tilt angle of the furnace body 2 is adjusted to 0-10°. The rotation speed of the stirring rod 21 is 0.2-10 r / min and it is located near the front of the furnace body 2. The gas path device includes a nitrogen inlet 1 located on the upper part of the front wall of the microwave pyrolysis unit furnace body 2 and a pyrolysis gas outlet 22 located on the upper part of the rear wall. The feeding device includes a feeding hopper 8 located on the front part of the upper surface of the furnace body 2, which is opened from top to bottom, a transition chamber, and a pneumatic hammer 18 set on the side wall of the transition chamber. The material 6 entering the feeding hopper 8 is a block material 6 with a size of 2-8 cm, which does not need to be crushed into powder.

[0050] The feed hopper 8 is supported and connected to the transition chamber via flange 26, and the pneumatic hammer 18 is connected to the side of the transition chamber via small flange 26. The transition chamber has an opening at the bottom; material 6 is temporarily stored in the transition chamber by adjusting the size of the opening. When the opening of the transition chamber is blocked, the pneumatic hammer 18 strikes the transition chamber, causing the material 6 to continue falling from the opening into the furnace body 2 of the microwave pyrolysis unit.

[0051] The inner wall of the microwave pyrolysis unit furnace body 2 is made of high-temperature resistant quartz, and the outer wall is made of microwave-insulating metal. The stirring rod 21 contains seven stirring blades evenly distributed on the stirring rod 21, and the stirring rod 21 is rotated by a motor.

[0052] The protruding cavity 20 is located in the middle section of the upper surface of the furnace body 2. The protruding cavity 20 is separated from the furnace body 2 by a transparent quartz heat-insulating and anti-fouling plate to prevent the material 6 inside the furnace body 2 of the microwave pyrolysis unit from interfering with the use of the microwave source 5. The microwave source 5 consists of at least two groups of microwave sources 5 located on the same plane perpendicular to the furnace body 2. Each group includes two microwave sources at the top and one on each side. The window of each microwave source 5 faces the protruding cavity 20 and is located inside the protruding cavity 20. There are a total of sixteen microwave sources 5, located above and to the side of the protruding part in the middle of the furnace body 2. The eight microwave sources 5 at the top are arranged in four vertical rows.

[0053] The five microwave sources are configured with a segmented frequency conversion scheme, exhibiting a decreasing microwave power gradient from the front to the rear. The power of the first five microwave sources is 100-500 W, while the power of the last two is 100-200 W. The power of the middle two sources decreases between the front and rear ends. The power of the five microwave sources gradually decreases from the front to the rear of the microwave pyrolysis unit's furnace body 2, enabling segmented frequency conversion. This ensures that the microwave heating in the front of the furnace body 2 and the temperature in the rear of the microwave pyrolysis unit are self-sustaining. Furthermore, the operating time of each microwave source 5 can be individually adjusted, allowing for intermittent microwave release and reducing the system's microwave energy consumption.

[0054] The lifting mechanism adjusts the tilt angle of the microwave pyrolysis unit furnace body 2 to 0-10°. The tilt angle of the microwave pyrolysis unit furnace body 2 is changed by varying the length of the lifting column 23. The rotation speed of the stirring rod 21 is 0.2-10 r / min. Preferably, the tilt angle of the microwave pyrolysis unit furnace body 2 is 0-5°, and the rotation speed of the stirring rod 21 is preferably 2-3 r / min.

[0055] It also includes hot-wire couplers installed on the wall of the furnace body 2 of the microwave pyrolysis unit, offset from the plane of the stirring blades; flow meters installed on the air inlet pipes connected to the wall of the furnace body 2 of the microwave pyrolysis unit; an oxygen analyzer 29 located on the front wall of the furnace body 2; a pressure gauge 30 located on the upper surface of the furnace body 2; and a microwave leakage detection alarm device located near the feed hopper 8. The automatic shutdown device is controlled by computer feedback to ensure operational safety. All of the above components are connected to an external control computer. The pneumatic hammer 18, microwave source 5, stirring rod 21, and elevator are also connected to the external control computer. The start and stop of the microwave source 5, oxygen analyzer 29, and flow meters are synchronized with the start and stop of the entire microwave device. The oxygen analyzer 29 is located at the upper front of the furnace body 2, and the pressure gauge 30 is located above the rear section of the furnace body 2. It is used to detect the gas pressure inside the furnace. Thermocouples 24 are evenly distributed in the front, middle and rear of the furnace to measure the temperature of the material 6 at different travel positions. An external burner is located after the saturated calcium hydroxide solution and can burn the discharged pyrolysis gas 10. The gas then continues to enter the flue gas inlet 4 on the upper surface of the left section of the furnace chamber of the microwave oxidation unit through the pipeline and is discharged from the tail gas outlet 31 at its right end.

[0056] The pneumatic hammer 18, microwave source 5, stirring rod 21, elevator, oxygen analyzer 29, and flow meter can all be started and stopped and their parameters adjusted in the control cabinet computer, which is separate from the furnace body 2 of the microwave pyrolysis unit. The start and stop of the microwave source 5, oxygen analyzer 29, and flow meter are synchronized with the start and stop of the entire microwave device.

[0057] The microwave oxidation unit, at its core, is a second, structurally identical, continuous-stage microwave treatment device to the microwave pyrolysis unit, used for microwave-assisted oxidation of solid residues after pyrolysis in an air atmosphere. This unit also features an adjustable-angle microwave oxidation furnace body 2, a stirring mechanism, and independently controllable microwaves, and is equipped with an air inlet 14 and a flue gas exhaust pipe. Its function is to thoroughly remove residual carbon adhering to the surface of the glass fiber 17, achieving fiber cleaning. Unlike the microwave pyrolysis unit's furnace body 2, the microwave oxidation unit's furnace body 2 lacks a feeding device; the gas path device does not include a nitrogen inlet 1, but instead includes an air inlet 14 for the oxidation reaction; the flue gas inlet 4 on the upper left side of the microwave oxidation unit's furnace body 2 is used to introduce high-temperature flue gas discharged from the saturated calcium hydroxide solution and burned in the external burner, thereby heating the microwave oxidation unit's furnace body 2, reducing energy consumption, and finally discharging from the exhaust port 31; the leftmost group of microwave sources 5 has a frequency of 100-300 W, the rightmost group has a frequency of 100-600 W, and the two middle groups have progressively increasing frequency settings between the left and right values; the microwave oxidation unit's furnace body 2 is not equipped with an oxygen analyzer 29. The pyrolysis gas exhaust port 22 is connected in sequence via pipelines to the ethanol 11 and saturated calcium hydroxide solution of the oil collection and washing gas unit, the external burner, and the flue gas pipeline 19 located within the microwave oxidation unit. The flue pipe 19 in the microwave oxidation unit includes the outer part of the furnace body 2 and the inner part of the furnace body 2 located on the inner wall of the upper surface of the furnace body 2 cavity. The rear section of the upper surface of the microwave oxidation unit is provided with a tail gas discharge port 31 in front of the material conveying mechanism 13, and the front section is provided with a flue gas inlet 4 near the front end. The high-temperature flue gas after passing through the external burner enters the flue gas inlet 4 through the external flue pipe 19 and the flue pipe 19 of the inner part of the furnace body 2, and then exits through the tail gas discharge port 31.

[0058] The two units are connected end-to-end by a material conveying mechanism 13, allowing the solid products after microwave pyrolysis to continuously and directly enter the microwave oxidation unit, thus forming a complete continuous "pyrolysis-oxidation" processing line. This series-connected device design is the key to achieving continuous, efficient, and high-quality recycling of glass fiber 17 in this method.

[0059] This invention also discloses a method for recycling glass fiber 17 from decommissioned wind turbine blades via continuous microwave thermal conversion. Figure 1 This is a flowchart of the continuous microwave thermal conversion method for recycling glass fiber 17 from decommissioned wind turbine blades according to the present invention; specifically including:

[0060] Step 1: Introduce nitrogen into the furnace body 2 of the microwave pyrolysis unit through nitrogen inlet 1; in Step 1, adjust the nitrogen flow meter on the outside of the furnace body 2 to 100-200 mL / min, introduce nitrogen into the furnace body 2 of the microwave pyrolysis unit for 20-60 minutes, and then start the reaction.

[0061] Step 2: Set the threshold values ​​for pressure gauge 30 and oxygen analyzer 29;

[0062] Step 3: Adjust the tilt angle of the two furnace bodies 2; adjust the lifting mechanism so that the tilt angle of the furnace body 2 is 0-5°, and control the rotation speed of the stirring rod 21 to 2-3 r / min.

[0063] Step 4: Set the reaction temperatures of the two furnace bodies 2; set the reaction temperature of the microwave pyrolysis unit furnace body 2 to 400-500℃ and the reaction temperature of the microwave oxidation unit furnace body 2 to 400-550℃. Each microwave source 5 is equipped with circulating cooling water. The external cooling water pumps of the two furnace bodies 2 are activated via the control cabinet computer to prevent microwave sources 6 from malfunctioning due to overheating. Then, the microwave sources 5 are activated. During initial setup, the power of the four microwave sources in the first row on the left side of the microwave pyrolysis unit furnace body 2 is set to 400-600 W, the power of the four microwave sources in the second row on the left side is set to 300-600 W, the power of the four microwave sources in the third row on the left side is set to 200-600 W, and the power of the four microwave sources in the fourth row on the far right side is set to 100-600 W. Similarly, the power of the four microwave sources in the first row on the left side of the microwave oxidation unit furnace body 2 is set to 100-600 W, the power of the four microwave sources in the second row on the left side is set to 200-600 W, the power of the four microwave sources in the third row on the left side is set to 300-600 W, and the power of the four microwave sources in the fourth row on the far right side is set to 400-600 W. During the reaction, thermocouple 24 will feed back the measured temperature to the computer, and the microwave power will be automatically adjusted according to the temperature fed back by thermocouple 24: when the temperature is higher than the set temperature, the power decreases, and vice versa.

[0064] Step 5: Mix material 2 with silicon carbide microwave absorbing agent 7 and place it into feed hopper 8;

[0065] Step 6: The tar 9 and pyrolysis gas 10 discharged from the pyrolysis gas discharge port 22 pass through ethanol 11 and saturated calcium hydroxide solution 12 in sequence.

[0066] Step 7: Ethanol 11 is used to absorb tar 9. Pyrolysis gas 10 is discharged from the oil collection and washing unit and then introduced into the external burner. Subsequently, the residual heat is recovered along the flue pipe 19 and discharged from the flue gas inlet 4 into the exhaust outlet 5.

[0067] Step 8: Air is introduced into the furnace body 2 of the microwave oxidation unit through the air inlet 14;

[0068] Step 9: The solid product is separated in cyclone separator 16 to obtain glass fiber 17 and silicon carbide microwave absorbing agent 7.

[0069] Step 10: The recovered silicon carbide microwave absorbing agent 7 is recycled again in step 5;

[0070] Step 11: The flue gas generated during the microwave oxidation process is discharged from the exhaust port 28.

[0071] Example 1

[0072] Step 1: Connect the gas pipeline and check the airtightness. Adjust the nitrogen flow meter to 100 mL / min. Introduce nitrogen into the furnace body 2 of the microwave pyrolysis unit from the nitrogen inlet 1 for 20 minutes to ensure that the air in the system is completely discharged. Continue to introduce nitrogen during the reaction to maintain an oxygen-free pyrolysis environment.

[0073] Step 2: Set the threshold of pressure gauge 30 to below 0.6 MPa. The oxygen concentration measured by oxygen analyzer 29 must be stable below 2%. If the pressure exceeds 0.8 MPa and the oxygen value exceeds 3%, the microwave leakage detection alarm device will be activated and the power will be cut off.

[0074] Step 3: Adjust the tilt angle of the furnace body 2 of the microwave pyrolysis unit and the furnace body 2 of the microwave oxidation unit by the motor 3, adjust the elevator so that the tilt angle of the furnace body 2 is 5°, control the rotation speed of the stirring rod 21 to 2 r / min, and control the reaction time of the material 6 in the two furnaces to 15 min and 25 min respectively.

[0075] Step 4: Set the reaction temperature of furnace 2 in the microwave pyrolysis unit to 400 ℃ and the reaction temperature of furnace 2 in the microwave oxidation unit to 450 ℃. Each microwave source 5 is equipped with circulating cooling water. The external cooling water pumps of the two furnace bodies 2 are turned on by the computer in the control cabinet to prevent the microwave source 5 from failing due to excessive temperature. Then, the microwave source 5 is turned on. During the initial setup, the power of the microwave pyrolysis unit is set to a maximum of 400 W; the power of the microwave oxidation unit is set to a maximum of 500 W. During the reaction, the thermocouple 24 will feed back the measured temperature to the computer. The microwave power will automatically adjust according to the temperature fed back by the thermocouple 24: when the temperature is higher than the set temperature, the power decreases, and vice versa.

[0076] Step 5: Mix the 2-8 cm wind turbine blade block material 6 with the silicon carbide wave-absorbing agent 7 and place it into the feed hopper 8. The material 6 is fed into the transition chamber by controlling the pneumatic hammer 18 to strike it.

[0077] Step 6: The gas generated by microwave pyrolysis includes tar 9 and pyrolysis gas 10, which is introduced into the oil collection and gas washing unit from the exhaust port 28, and then passes through ethanol 11 and saturated calcium hydroxide solution in sequence to absorb organic gas and acid gas respectively.

[0078] Step 7: tar 9 is absorbed by ethanol 11, and then tar 9 is purified by dehydration, impurity removal, distillation and concentration, so that it can be used for subsequent quality improvement.

[0079] Step 8: After the pyrolysis gas 10 is discharged from the saturated calcium hydroxide solution, it is fed into the external burner for combustion. The flue gas after combustion flows through the flue pipe 19 installed in the furnace body 2 of the microwave oxidation unit from the flue gas inlet 4 at the left end of the furnace body 2 to the tail gas outlet 31 at the right end. This process of returning to the furnace is equivalent to flue gas recirculation. After heating the gas in the furnace, it is sprayed out from the tail gas outlet 31. In this process, it serves as a heat source to ensure the temperature in the furnace is maintained, and at the same time, it facilitates subsequent carbon capture.

[0080] Step 9: After pyrolysis, the residual solids produced enter the microwave oxidation unit through the material conveying mechanism 13. The air flow meter is adjusted to 100 mL / min, and air is introduced into the furnace body 2 of the microwave oxidation unit from the air inlet 14 to carry out the oxidation reaction.

[0081] Step 10: The solid product obtained after the oxidation reaction reaches the discharge port 15. Due to the difference in quality, the clean glass fiber 17 and silicon carbide microwave absorbing agent 7 can be separated in the cyclone separator 16.

[0082] Step 11: The recovered silicon carbide microwave absorbing agent 7 is mixed with the wind turbine blade material 6 in step 5 and then fed into the microwave pyrolysis unit to achieve recycling.

[0083] Step 12: The flue gas generated during the microwave oxidation process is discharged from the exhaust port 28 and is discharged after being treated to meet the standards.

[0084] Example 2

[0085] Unlike Example 1, in step 4, the microwave pyrolysis temperature was set to 500 °C for 15 min, and the microwave oxidation temperature was set to 400 °C for 40 min. The glass fiber 17 obtained in step 11 was a white, clean fiber.

[0086] Example 3

[0087] Unlike Example 1, in step 4, the microwave pyrolysis power was set to 500 W, the temperature to 450 °C, and the time to 15 min; the microwave oxidation power was set to 500 W, the temperature to 400 °C, and the time to 30 min. The glass fiber 17 obtained in step 11 was a white, clean fiber.

[0088] Comparative Example 1

[0089] The difference between the operation process of this comparative example and that of Example 1 is that the pyrolysis method in this comparative example is conventional pyrolysis, with a temperature of 600 ℃ and a time of 30 min, and the oxidation method is conventional oxidation, with a temperature of 500 ℃ and a time of 120 min. The data of this comparative example comes from Chinese invention patent CN 116515509 B, and the final product is white clean fiber.

[0090] Comparative Example 2

[0091] The difference between the operation process of this comparative example and that of Example 1 is that the pyrolysis method in this comparative example is microwave pyrolysis, with a microwave power of 500 W and a temperature of 500 °C, and the oxidation method is conventional oxidation, with a temperature of 500 °C and a time of 60 min. The final product is white and clean fiber.

[0092] Comparative Example 3

[0093] The difference between the operation process of this comparative example and Example 1 is that the pyrolysis method in this comparative example is microwave pyrolysis with a microwave power of 450 W, and the oxidation method is microwave oxidation with a microwave power of 300 W, a temperature of 400 °C, and a time of 60 min. The carbon on the fiber surface of the final product is not completely oxidized.

[0094] Comparative Example 4

[0095] The difference between the operation process of this comparative example and Example 1 is that the pyrolysis method in this comparative example is microwave pyrolysis, with a microwave power of 500 W and a temperature of 500 ℃, and the oxidation method is microwave oxidation, with a temperature of 600 ℃ and a time of 15 min. In the final product, the carbon on the fiber surface was not completely oxidized, and some fibers melted.

[0096] Comparative Example 5

[0097] The difference between the operation process of this comparative example and Example 1 is that the pyrolysis method in this comparative example is microwave pyrolysis, with a microwave power of 500 W, a temperature of 600 ℃, and a pyrolysis time of 20 min; the oxidation method is microwave oxidation, with a microwave power of 500 W, a temperature of 550 ℃, and a time of 30 min. The final product is white and clean fiber, but some fibers melted.

[0098] Table 1. Comparison of each embodiment and comparative example, their pyrolysis method, oxidation method, and products.

[0099] The comparison between Examples 1, 2, and 3 and Comparative Example 1 shows that the two-step heat treatment process of microwave pyrolysis coupled with microwave oxidation can achieve clean regeneration of waste fibers at a time cost far lower than that of conventional pyrolysis / oxidation processes. Although Comparative Example 1 ultimately obtained white clean fibers, its conventional oxidation process took as long as 120 minutes, while Examples 1, 2, and 3 could completely remove carbon from the fiber surface under microwave oxidation conditions of 25-40 minutes, and the processing efficiency was significantly improved.

[0100] The comparison between Examples 1, 2, and 3 and Comparative Example 2 shows that, under the condition that microwave pyrolysis is used in the pyrolysis stage, the subsequent oxidation method has a significant impact on the processing efficiency. Comparative Example 2 requires 60 minutes to obtain white and clean fibers using conventional oxidation, while Examples 1, 2, and 3 only require 25-40 minutes to achieve the same cleaning effect using microwave oxidation. This indicates that microwave oxidation can accelerate the oxidative removal kinetics of carbon deposited on the fiber surface by means of its bulk heating and hot spot effect.

[0101] The comparison between Examples 1, 2, and 3 and Comparative Example 3 shows that the power and temperature parameters during the microwave oxidation stage are the key control factors for achieving complete oxidation of carbon on the fiber surface. In Comparative Example 3, even with the microwave oxidation power reduced to 300W and the temperature maintained at 400℃, the carbon on the fiber surface could not be completely oxidized, even with the processing time extended to 60 min. This indicates that there is a critical threshold for the energy input of the oxidation atmosphere, and that a combination of too low power / temperature is insufficient to drive the complete conversion of carbon.

[0102] The comparison between Examples 1, 2, and 3 and Comparative Example 4 shows that higher temperatures during the microwave oxidation stage are not necessarily more beneficial. Excessively high oxidation temperatures will cause thermal damage to the fiber matrix. When the microwave oxidation temperature in Comparative Example 4 was increased to 600 °C, partial melting occurred before the carbon on the fiber surface was completely oxidized. However, Examples 1, 2, and 3 controlled the oxidation temperature within the range of 400-450 °C, which ensured the complete removal of carbon while preserving the microstructure and mechanical properties of the fiber.

[0103] A comparison of Examples 1, 2, and 3 with Comparative Example 5 shows that the risk of fiber melting damage exists not only in the microwave oxidation stage but is also limited by the upper limit of the microwave pyrolysis temperature threshold. Comparative Example 5 increased the microwave pyrolysis temperature to 600 ℃ and the microwave oxidation temperature to 550 ℃, and the carbon on the fiber surface was almost completely oxidized, but partial melting still occurred. In contrast, Examples 1, 2, and 3 controlled the microwave pyrolysis temperature within 400-500 ℃ and the microwave oxidation temperature within 400-450 ℃, thus achieving a balance between sufficient pyrolysis oxidation and avoiding melting damage.

[0104] As can be seen from Examples 1, 2, and 3, within the process window defined by this invention—microwave pyrolysis power of 400-500 W, temperature of 400-500 ℃, and time of 15-20 min, and microwave oxidation power of 500-600 W, temperature of 400-450 ℃, and time of 25-40 min—adjusting the combination of parameters can stably yield white, clean fibers with complete surface carbon oxidation and intact fiber morphology. This indicates that the two-step microwave heat treatment process has good parameter adaptability and repeatability.

[0105] The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments can be combined with each other to form new embodiments. The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the technical solutions of the present invention.

Claims

1. A device for recycling glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion, characterized in that, The system includes an inclined microwave pyrolysis unit, an inclined microwave oxidation unit located below the microwave pyrolysis unit, and a material conveying mechanism connecting the bottom of the lower section of the microwave pyrolysis unit to the top of the upper section of the microwave oxidation unit. It also includes a feeding device connected to the top of the upper section of the microwave pyrolysis unit and a discharging device connected to the bottom of the lower section of the microwave oxidation unit. A lifting device and a gas path device are fixedly connected to the bottom of the upper sections of the microwave pyrolysis unit and the microwave oxidation unit. Both the microwave pyrolysis unit and the microwave oxidation unit include a furnace body, a raised cavity on the upper surface of the furnace body, a stirring rod fixed to the central axis of the furnace body, and a microwave source with a microwave source window located within the raised cavity. The gas path device includes a nitrogen inlet located on the upper front wall of the microwave pyrolysis unit furnace body, a pyrolysis gas outlet located on the upper rear wall of the microwave oxidation unit furnace body, an air inlet located on the upper rear wall of the microwave oxidation unit furnace body, and a tail gas outlet located on the upper rear wall of the microwave oxidation unit furnace body.

2. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 1, characterized in that, The feeding device includes a feeding hopper located at the front of the upper surface of the microwave pyrolysis unit furnace body, a transition chamber, a pneumatic hammer set on the side wall of the transition chamber, and a feeding port connected to the pipeline of the transition chamber. The material entering the feeding hopper is a block material with a size of 2-8cm.

3. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 2, characterized in that, The discharge device includes a discharge port opened from top to bottom and a cyclone separator connected to the discharge port; the inner wall of the furnace body is made of high-temperature resistant quartz and the outer wall is made of microwave-insulating metal; the stirring rod is connected to a motor and at least three stirring blades are evenly distributed on the stirring rod.

4. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 1, 2, or 3, characterized in that, The protruding cavity is located in the middle section of the upper surface of the furnace body. The protruding cavity is separated from the furnace body by a transparent quartz heat insulation and anti-fouling plate. The microwave source consists of at least two groups of microwave sources located on the same plane perpendicular to the furnace body. Each group includes two sources at the top and one source on each side. The window of each microwave source faces the protruding cavity and is located inside the protruding cavity.

5. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 4, characterized in that, The microwave source group of the microwave pyrolysis unit is set in a segmented frequency conversion configuration with decreasing microwave power from the front to the back. The front end is 100-1500W and the back end is 100-600W, with the middle two showing a decreasing frequency conversion between the front and back ends. The microwave source group of the microwave oxidation unit is set in a segmented frequency conversion configuration with decreasing microwave power from the back to the front. The last microwave source group is 100-1500W and the front end is 100-600W, with the middle two showing a decreasing frequency conversion between the back and front ends.

6. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 5, characterized in that, The lifting device includes a lifting column fixedly connected to the bottom of the furnace body, a lifting machine connected to the lifting column and controlling the lifting of the lifting column, adjusting the furnace body tilt angle to 0-10°, and the stirring speed of the stirring rod to 0.2-10 r / min. The pyrolysis gas discharge port is connected in sequence to the ethanol and saturated calcium hydroxide solution of the oil collection and gas washing unit, the external burner, and the flue pipe set in the microwave oxidation unit through pipelines.

7. The continuous microwave thermal conversion device for recycling glass fiber from decommissioned wind turbine blades according to claim 6, characterized in that, The preferred angle of the furnace body adjustment mechanism is 0-5°, and the preferred rotation speed of the stirring rod is 2-3 r / min. The flue pipe in the microwave oxidation unit includes the outer part of the furnace body and the inner part of the furnace body located on the upper surface near the inner wall of the furnace body cavity. The rear section of the upper surface of the microwave oxidation unit is provided with a tail gas discharge port in front of the material conveying mechanism, and the front section is provided with a flue gas inlet near the front end. The high-temperature flue gas after passing through the external burner is introduced into the flue gas inlet and the flue pipe in the inner part of the furnace body through the external flue pipe, and then discharged through the tail gas discharge port.

8. A method for recycling glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion as described in claim 1, 2, 3, 5, 6, or 7, characterized in that: Step 1: Introduce nitrogen gas into the furnace body of the microwave pyrolysis unit through the nitrogen gas inlet; Step 2: Set the threshold values ​​for the pressure gauge and oxygen analyzer; Step 3: Adjust the tilt angle of the two furnace bodies; Step 4: Set the reaction temperature for both furnaces; Step 5: Mix the material with the silicon carbide microwave absorber and place it into the feed hopper; Step 6: The tar and pyrolysis gas discharged from the pyrolysis gas outlet pass through ethanol and saturated calcium hydroxide solution in sequence. Step 7: The tar is absorbed by ethanol. The pyrolysis gas is discharged from the oil collection and washing unit and then introduced into the external burner. Subsequently, the waste heat is recovered along the flue pipe and discharged from the exhaust gas outlet through the flue gas inlet. Step 8: Introduce air into the furnace body of the microwave oxidation unit through the air inlet; Step 9: The solid product is separated in a cyclone separator to obtain glass fiber and silicon carbide microwave absorbing agent; Step 10: The recovered silicon carbide microwave absorbing agent is recycled again in step 5; Step 11: The flue gas generated during the microwave oxidation process is discharged from the exhaust port.

9. The method for recovering glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion according to claim 8, characterized in that: In step 1, the nitrogen flow meter outside the furnace is adjusted to 100-200 mL / min, and nitrogen is introduced into the furnace of the microwave pyrolysis unit for 20-60 minutes before the reaction is started; in step 3, the elevator is adjusted so that the furnace body tilt angle is 0-5°, and the stirring speed of the stirring rod is controlled to be 2-3 r / min.

10. The method for recovering glass fiber from decommissioned wind turbine blades via continuous microwave thermal conversion according to claim 8, characterized in that: In step 4, the reaction temperature range in the microwave pyrolysis unit furnace is 200-600 ℃, and the microwave source power is set to 100-600 W; the reaction temperature in the microwave oxidation unit furnace is 200-600 ℃, and the microwave source power is set to 100-600 W. During the reaction, the microwave power is automatically adjusted according to the temperature feedback from the thermocouple.

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