A method for recovering fibers and phenolic oils through humid air atmosphere heat treatment.

Abstract

This invention relates to a method for recovering fibers and phenolic oils through heat treatment in a humid air atmosphere, comprising the following steps: S1, mechanically cutting retired wind turbine blades, sorting out lightweight core materials, and then cutting the fiber composite into blocks; S2, placing the block-shaped composite obtained in step S1 in a thermal reactor, and performing heat treatment in a humid air atmosphere, wherein the reaction atmosphere is a humid air mixture of air and water vapor at a ratio of 3 to 1:1, the reaction temperature is 500 to 550°C, the reaction time is 0.5 to 2 hours, and after the reaction, it can be cooled and separated to obtain clean, coke-free fibers and recovered phenolic oils; this method solves the problem that existing conventional inert atmosphere and oxidizing atmosphere treatments of wind turbine blades result in unclean and defective fiber surfaces, leading to poor mechanical properties and affecting their high-value utilization.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a method for recovering fibers and phenolic oils through humid air atmosphere heat treatment. Background Technology

[0002] With the rapid development of wind power technology, wind power has become an important part of the power supply system. Along with the rapid expansion of global wind power installed capacity, the deployment of wind turbine blades continues to climb. However, limited by a design life of 20-25 years, the amount of composite material waste from retired blades has also increased year by year in recent years. This serious situation highlights the urgency of developing efficient resource recovery technologies. Wind turbine blades are mainly composed of fiber-reinforced polymer composites (FRPs) and lightweight core materials (balsa wood / foam), among which FRPs have significant recycling value due to their excellent mechanical properties. Current traditional disposal methods such as mechanical cutting, landfilling, or incineration not only waste this high-performance engineering material but also lead to the economic loss of potentially recoverable capital.

[0003] Pyrolysis technology, as an efficient waste resource recovery method, has attracted widespread attention due to its ability to transform organic waste into high-value-added products and recycle fibers. Conventional pyrolysis involves heating wind turbine blades under an inert atmosphere, causing the epoxy organic matter to decompose and volatilize into pyrolysis gas and pyrolysis oil, composed of alkanes and olefins, leaving solid products such as fibers and coke. Because the organic components in the pyrolysis products are complex and difficult to selectively control, the residual coke on the surface of the obtained recycled fibers affects the fiber's mechanical properties to some extent, requiring separation and post-processing. However, excessively high temperatures significantly damage fiber properties and reduce the yield of phenolic components in the pyrolysis oil. Furthermore, excessively high oxygen concentrations in an oxidizing atmosphere can cause surface defects in the fibers, leading to a decrease in tensile strength, thus limiting the high-value utilization of the fibers. Therefore, developing efficient fiber-reinforced composite recycling technology has become a crucial issue urgently needing to be addressed to achieve sustainable development in the wind power industry. Summary of the Invention

[0004] In view of this, in order to solve the problem that the existing conventional inert atmosphere and oxidizing atmosphere treatment of wind turbine blades results in unclean and defective surfaces of the regenerated fibers after treatment, leading to poor mechanical properties and affecting their high-value utilization, the present invention provides a method for recovering fibers and phenolic oils through humid air atmosphere heat treatment. This method can achieve efficient decarbonization and fiber recovery under mild heat treatment conditions, and recover high-grade oil. This method is applicable to fiber composites of epoxy resins such as decommissioned wind turbine blades.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for recovering fibers and phenolic oils through heat treatment in a humid air atmosphere includes the following steps:

[0007] S1. Mechanically cut the retired wind turbine blades, sort out the lightweight core material, and then cut the fiber composite material into blocks;

[0008] S2. The blocky composite material obtained in step S1 is placed in a thermal reactor and heat-treated in a humid air atmosphere. The reaction atmosphere is a humid air mixture of air and water vapor at a ratio of 3 to 1:1. The thermal reaction temperature is 500 to 550°C, and the reaction time is 0.5 to 2 hours. After the reaction, the material is cooled and separated to obtain clean, coke-free fibers and high-value phenolic oil. The introduction of a humid air atmosphere can promote the removal of residual carbon and recover regenerated fibers with a smooth surface and good mechanical properties. The oil phase product is a phenolic compound with a bisphenol A content of more than 50%, a residual carbon yield of less than 1%, and a phenol content of more than 20%. This achieves comprehensive control of bisphenol A content and residual carbon yield on the fiber surface.

[0009] Furthermore, in step S1, the wind turbine blade cutting and sorting process should remove all auxiliary materials and sandwich materials except for fiber-reinforced epoxy composite materials. The auxiliary materials include foam and balsa wood, and the sandwich materials include metal materials.

[0010] Furthermore, the size of the fiber composite material after being cut into blocks in step S1 is (10~15)*(10~15)*(60~80)mm.

[0011] Furthermore, the thermal reactor in step S2 is a fixed-bed heater.

[0012] Furthermore, in step S2, the total carrier gas flow rate for the air and water vapor reaction is 200~400 ml / min, wherein the steam flow rate is calculated based on the actual reaction temperature and the ideal gas law to determine the water injection volume.

[0013] Further, the regenerated fibers after cooling and separation in step S2 are placed in a muffle furnace and calcined at 600°C for 1 hour, and the residual char rate is calculated based on the mass difference before and after calcination.

[0014] Furthermore, the oil phase condensed in step S2 is collected by dissolving it in dichloromethane / anhydrous ethanol at a ratio of 4:1.

[0015] Furthermore, in step S2, the reaction atmosphere is a humid air mixture of air and water vapor in a 3:1 ratio, the thermal reaction temperature is 550℃, the reaction time is 1h, and after the reaction is completed, the bisphenol A content obtained by cooling and separation is 58.51%, with only 0.35% carbon residue at 500℃, resulting in a phenol content of 24.29%.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The method for recovering fibers and phenol-rich oils through humid air atmosphere heat treatment disclosed in this invention utilizes a humid air atmosphere to perform thermal oxidation treatment on decommissioned wind turbine blades. This promotes the oxidative gasification reaction of heat treatment residues, removing carbon residues from the surface of the recovered fibers and achieving clean recovery of the regenerated fibers. Furthermore, by promoting the oxidative breakage of the organic carbon structure, it drives the conversion of the product into lighter components, yielding high-grade oil rich in phenols. Experimental results show that complete decarbonization can be achieved under reaction conditions of 550℃ (75% Air / 25% H2O) in a humid air atmosphere, while retaining 58.51% of the bisphenol A content. When this mixing ratio is maintained, the residual carbon rate is only 0.35% at 500℃, and 24.29% of the phenol content is collected. Compared with existing technologies, the beneficial effects of this invention are as follows: by using wet air heat treatment technology and adjusting the heat treatment process parameters, the fiber is cleanly recycled under mild conditions, while the epoxy organic polymer is converted into high-value-added products such as fuel or chemical raw materials. This achieves the resource recycling of retired wind turbine blades in a cleaner and more environmentally friendly way, avoiding the inefficiency and environmental pollution caused by traditional landfill and incineration.

[0018] 2. The method for recovering fibers and phenolic oils by humid air atmosphere heat treatment disclosed in this invention effectively inhibits the carbonization reaction of intermediate species in heat treatment by controlling the appropriate mixing concentration ratio of air and water vapor in the humid air to 3~1:1, promotes the conversion of products into light oils, and enhances the gasification of coke through oxidation synergy in the later stage of heat treatment. It can solve the technical pain point that traditional pyrolysis cannot achieve complete removal of coke, as well as the problem that excessive oxygen concentration causes fiber surface defects that lead to damage to the mechanical properties of regenerated fibers.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a flowchart illustrating the process of recovering fibers and phenolic oils through humid air atmosphere heat treatment according to the present invention.

[0022] Figure labels: 1 is N2 gas cylinder, 2 is air compressor, 3 is steam generator, 4 is mass flow meter, 5 is gas path, 6 is thermal reactor, 7 is reaction tube, 8 is temperature display and control instrument, 9 is block composite material, 10 is liquid phase product collection device, 11 is gas phase product collection device, 12 is cold trap, 13 is cryogenic cooling circulation pump. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] The materials used in the examples were prepared using existing methods or purchased directly from the market. The examples used the residual char of the regenerated fibers and the relative content of phenolic components in the tar as performance evaluation indicators. Gas chromatography-mass spectrometry (GC / MS) was used for qualitative and quantitative analysis of the characteristic components of the oil phase. The relevant calculation formulas for the organic conversion rate of the product components are as follows:

[0025] (1)

[0026] (2)

[0027] Where, m o For tar quality; m c For coke quality; m w For sample mass; m f For fiber quality.

[0028] The heat treatment experiments in this embodiment were conducted in a fixed-bed heat treatment experimental system, as shown in the schematic diagram below. Figure 1 As shown, but not limited to, the specific process is as follows: The pre-cut (10~15)*(10~15)*(70~100)mm blocks of composite material 9 are weighed (29~31g each time) and placed in the reaction tube 7, then placed in the thermal reactor 6. During the experiment, steam is injected into the thermal reactor 6 through the steam generator 3, and air is injected into the thermal reactor 6 through the air compressor 2. The oxygen concentration in the thermal reactor 6 is adjusted through the N2 gas cylinder 1. A mass flow meter 4 is installed on the pipe connecting the N2 gas cylinder 1, the air compressor 2, and the thermal reactor 6, and the amount of gas entering the thermal reactor 6 is controlled by the mass flow meter 4. The temperature control and time setting program is set through the temperature display and control instrument 8 connected to the thermal reactor 6 to conduct the heat treatment experiment.

[0029] The blocky composite material 9 undergoes a depolymerization reaction with a reactive atmosphere at high temperature, releasing volatiles that rapidly evaporate. The gas flows through the pipeline to the liquid-phase product collection device 10 within the cold trap 12, where it is cooled into tar. Non-condensable gases are collected via a gas path into the gas-phase product collection device 11. After the reaction process is complete, the solid products in the reaction tube 7 are recovered, and the solid residue and liquid products are weighed. The solid residue is further subjected to oxidative calcination in a muffle furnace, heated from room temperature to 600°C at a rate of 15°C / min and held for 1 hour to remove residual coke. The residue rate is then calculated by weighing.

[0030] Example 1

[0031] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 75%Air / 25%Steam mixing atmosphere ratio, set the Air and Steam flow rates to 150ml / min and 50ml / min, respectively. Set the reaction time to 60min and continuously introduce the gas until the reaction is complete. After the reaction is complete and cooled to room temperature, collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS analysis on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0032] Example 2

[0033] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 50%Air / 50%Steam mixing atmosphere ratio, set the Air and Steam flow rates to 100ml / min and 100ml / min respectively. The reaction time is 60min. During the reaction, the gas is continuously introduced until the reaction is completed. After the reaction is completed, allow it to cool to room temperature. Collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS detection on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0034] Example 3

[0035] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 500℃ and the total reaction gas flow rate to 400ml / min. Based on the 75%Air / 25%Steam mixing atmosphere ratio, set the Air and Steam flow rates to 300ml / min and 100ml / min, respectively. The reaction time is 60min. During the reaction, the gas is continuously introduced until the reaction is completed. After the reaction is completed, allow it to cool to room temperature. Collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS detection on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0036] Example 4

[0037] Approximately 30g of the 10*10*70mm cut composite block was weighed and placed into the thermal reactor. The target temperature was set to 500℃, and the total reaction gas flow rate was set to 400ml / min. Based on the 50%Air / 50%Steam mixing atmosphere ratio, the Air and Steam flow rates were set to 200ml / min and 200ml / min, respectively. The reaction time was 60min, and the gas was continuously introduced during the reaction until the reaction was completed. After the reaction was completed, the mixture was cooled to room temperature, and the gas, liquid, and solid three-phase products were collected sequentially. The solid residue and liquid product were weighed, and then the liquid product was analyzed by GC / MS. The solid residue was oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0038] Comparative Example 1

[0039] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 100% Air / 0% Steam mixing atmosphere ratio, the Air and Steam flow rates are set to 200ml / min and 0ml / min, respectively. The reaction time is 60min. During the reaction, the gas is continuously introduced until the reaction is completed. After the reaction is completed, allow it to cool to room temperature. Collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS detection on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0040] Comparative Example 2

[0041] Approximately 30g of the 10*10*70mm cut composite block was weighed and placed into the thermal reactor. The target temperature was set to 550℃, and the total reaction gas flow rate was set to 200ml / min. Based on the mixing atmosphere ratio of 25%Air / 75%Steam, the flow rates of Air and Steam were set to 50ml / min and 150ml / min, respectively. The reaction time was 60min. During the reaction, the gas was continuously introduced until the reaction was completed. After the reaction was completed, the mixture was cooled to room temperature. The gas, liquid, and solid phase products were collected sequentially, and the solid residue and liquid product were weighed. The liquid product was then analyzed by GC / MS. The solid residue was oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0042] Comparative Example 3

[0043] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 0%Air / 100%Steam mixing atmosphere ratio, set the Air and Steam flow rates to 0ml / min and 200ml / min, respectively. Set the reaction time to 60min and continuously introduce the gas during the reaction until the reaction is complete. After the reaction is complete, allow the mixture to cool to room temperature. Collect the gas, liquid, and solid phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS analysis on the liquid product. The solid residue is calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1 hour.

[0044] Comparative Example 4

[0045] Approximately 30g of the 10*10*70mm cut composite block was weighed and placed into a thermal reactor. The target temperature was set to 550℃, the total reaction gas flow rate was set to 200ml / min, the reaction atmosphere was N2, and the reaction time was 60min. During the reaction, the gas was continuously introduced until the reaction was completed. After the reaction was completed, the mixture was cooled to room temperature. The gas, liquid, and solid phase products were collected sequentially, and the solid residue and liquid product were weighed. The liquid product was then analyzed by GC / MS. The solid residue was oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at a rate of 15℃ / min and holding it for 1 hour.

[0046] Comparative Example 5

[0047] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 5% O2 oxygen concentration, set the Air and N2 flow rates to 50ml / min and 150ml / min, respectively. Set the reaction time to 60min and continuously introduce the gas until the reaction is complete. After the reaction is complete, allow it to cool to room temperature. Collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS analysis on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1 hour.

[0048] Comparative Example 6

[0049] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 10% O2 oxygen concentration, set the Air and N2 flow rates to 100ml / min and 100ml / min respectively. The reaction time is 60min. During the reaction, the gas is continuously introduced until the reaction is completed. After the reaction is completed, allow it to cool to room temperature. Collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS detection on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1h.

[0050] Comparative Example 7

[0051] Weigh approximately 30g of the 10*10*70mm cut composite block and place it into the thermal reactor. Set the target temperature to 550℃ and the total reaction gas flow rate to 200ml / min. Based on the 15% O2 oxygen concentration, set the Air and N2 flow rates to 150ml / min and 50ml / min, respectively. Set the reaction time to 60min and continuously introduce the gas until the reaction is complete. After the reaction is complete and cooled to room temperature, collect the gas, liquid, and solid three-phase products sequentially and weigh the solid residue and liquid product. Then, perform GC / MS analysis on the liquid product. The solid residue is oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at 15℃ / min and holding it for 1 hour.

[0052] Comparative Example 8

[0053] Approximately 30g of the 10*10*70mm cut composite block was weighed and placed into a thermal reactor. The target temperature was set to 500℃, the total reaction gas flow rate was set to 400ml / min, the reaction atmosphere was Air, and the reaction time was 60min. During the reaction, the gas was continuously introduced until the reaction was completed. After the reaction was completed, the mixture was cooled to room temperature. The gas, liquid, and solid phase products were collected sequentially, and the solid residue and liquid product were weighed. The liquid product was then analyzed by GC / MS. The solid residue was oxidized and calcined by heating it in a muffle furnace from room temperature to 600℃ at a rate of 15℃ / min and holding it for 1 hour.

[0054] The residual carbon yield and the distribution of phenol and bisphenol A yields in the liquid phase were obtained by conducting heat treatment experiments based on the relevant heat treatment process parameters in Examples 1-4 and Comparative Examples 1-8, as shown in Table 1.

[0055] Table 1. Residual carbon, phenol and bisphenol A yields of the examples.

[0056]

[0057] A comparative analysis of the experimental results from Examples 1-3 and Comparative Examples 1-8 shows that the decarbonization effect is better when the mixed atmosphere ratio is 75% Air / 25% Steam than that of pure Air atmosphere. A comparative analysis of the experimental results from Examples 2-4 and Comparative Example 6 shows that the addition of Steam significantly reduces the residual carbon rate, achieving carbon residue below 550℃ even at 500℃. Based on the results in Table 1, it is shown that the method proposed in this invention for recovering fibers and phenolic oils through humid air atmosphere heat treatment can achieve a synergistic enhancement of oxidative decarbonization. The reaction conditions at 550℃ (75% Air / 25% H2O) in a humid air atmosphere can achieve complete decarbonization to obtain clean regenerated fibers, while retaining 58.51% of the bisphenol A content. At temperatures lower than 500℃, only 0.35% carbon residue can be achieved, and 24.29% of phenol can be collected. These results demonstrate that the method proposed in this invention has excellent fiber and phenolic oil recovery effects.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for recovering fibers and phenolic oils through humid air atmosphere heat treatment, characterized in that, Includes the following steps: S1. Mechanically cut the retired wind turbine blades, sort out the lightweight core material, and then cut the fiber composite material into blocks; S2. The blocky composite material obtained in step S1 is placed in a thermal reactor and heat-treated in a humid air atmosphere. The reaction atmosphere is a humid air mixture of air and water vapor at a ratio of 3 to 1:

1. The thermal reaction temperature is 500 to 550°C, and the reaction time is 0.5 to 2 hours. After the reaction, the material is cooled and separated to obtain clean, coke-free fibers and high-value phenolic oil. The introduction of a humid air atmosphere can promote the removal of residual carbon and recover regenerated fibers with a smooth surface and good mechanical properties. The oil phase product is a phenolic compound rich in bisphenol A and phenol, achieving comprehensive control of phenolic content and residual carbon yield on the fiber surface.

2. The method for recovering fibers and phenolic oils as described in claim 1, characterized in that, Step S1, the wind turbine blade cutting and sorting process, should remove all auxiliary materials and sandwich materials except for fiber-reinforced epoxy composites. Auxiliary materials include foam and balsa wood, and sandwich materials include metal materials.

3. The method for recovering fibers and phenolic oils as described in claim 1, characterized in that, The thermal reactor in step S2 is a fixed-bed heating furnace.

4. The method for recovering fibers and phenolic oils as described in claim 1, characterized in that, In step S2, the total carrier gas flow rate for the air and water vapor reaction is 200~400 ml / min, where the steam flow rate is calculated based on the actual reaction temperature and the ideal gas law to determine the water injection volume.

5. The method for recovering fibers and phenolic oils as described in claim 4, characterized in that, The regenerated fibers after cooling and separation in step S2 are placed in a muffle furnace and heated from room temperature to 600°C at 15°C / min for oxidative calcination for 1 hour. The residual carbon rate is calculated based on the mass difference before and after calcination.

6. The method for recovering fibers and phenolic oils as described in claim 5, characterized in that, The oil phase condensed in step S2 was collected by dissolving it in dichloromethane and anhydrous ethanol at a ratio of 4:

1.

7. The method for recovering fibers and phenolic oils as described in claim 1, characterized in that, In step S2, the reaction atmosphere was a humid air mixture of air and water vapor in a 3:1 ratio. The thermal reaction temperature was 550℃, and the reaction time was 1 hour. After the reaction was completed, cooling and separation were performed to completely remove the residual carbon. The bisphenol A content obtained was 58.51 wt%.

8. The method for recovering fibers and phenolic oils as described in claim 1, characterized in that, In step S2, the reaction atmosphere was a humid air mixture of air and water vapor in a 3:1 ratio, and the reaction time was 1 hour. At a thermal reaction temperature of 500°C, only 0.35 wt% carbon residue was observed, resulting in a phenol content of 24.29 wt%.

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