A Wind Turbine Blade Recycling Method Based on Low-Temperature Pyrolysis and Its Application

Abstract

The present invention discloses a method for recycling wind turbine blades based on low-temperature pyrolysis and its application. The recycling method includes soaking the wind turbine blades in a solution composed of a solvent and a pore-forming agent; draining the soaked wind turbine blades and then performing pyrolysis. In the method for recycling wind turbine blades based on low-temperature pyrolysis of the present invention, the wind turbine blades are swollen in a specific solution before pyrolysis, and at the same time, the pore-forming agent substance enters the swollen wind turbine blades. The former can reduce the interaction between the matrix resin and the reinforcing fibers, thereby reducing the pyrolysis temperature, and the latter (pore-forming agent) can effectively avoid the formation of a dense carbon layer during the pyrolysis of the blades, improve the oxygen permeability, and promote the low-temperature pyrolysis of the blades; the entire recycling method has the advantages of low energy consumption and little thermal damage to the recycled fibers.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment, and particularly relates to a method for recycling wind turbine blades based on low-temperature pyrolysis and its application. Background Art

[0002] In recent years, with the rapid increase in the installed capacity of wind power and the gradual retirement of the first batch of operating wind turbines, the number of waste wind turbine blades has been increasing, becoming a high-value industrial solid waste that urgently needs to be treated. Wind turbine blades are mainly fiber-reinforced resin-based composites. Pyrolysis is a common method for recycling composites. Usually, under specific atmosphere and high temperature (≥850 °C), the matrix resin of the composite is converted into gaseous small-molecule compounds to recover the high-value reinforcing fibers and achieve resource utilization. However, this method has disadvantages such as high energy consumption and large thermal damage to the recycled fibers when treating waste blades. Therefore, developing low-temperature pyrolysis technology is of great significance for the recycling of wind turbine blades. Summary of the Invention

[0003] In view of this, an object of the present invention is to propose a method for recycling wind turbine blades based on low-temperature pyrolysis. Before pyrolysis, the wind turbine blades are swollen in a specific solution composed of a solvent and a pore-forming agent, and at the same time, the pore-forming agent substance enters the swollen wind turbine blades. The former can reduce the interaction between the matrix resin and the reinforcing fibers, thereby reducing the pyrolysis temperature. The latter (pore-forming agent) can effectively avoid the formation of a dense carbon layer during the pyrolysis of the blades, improve the oxygen permeability, and promote the low-temperature pyrolysis of the blades; the entire recycling method has the advantages of low energy consumption and small thermal damage to the recycled fibers.

[0004] Another object of the present invention is to propose the application of the method for recycling wind turbine blades based on low-temperature pyrolysis.

[0005] To achieve the above object, an embodiment of the first aspect of the present invention proposes a method for recycling wind turbine blades based on low-temperature pyrolysis, including:

[0006] Soaking the wind turbine blades in a solution composed of a solvent and a pore-forming agent;

[0007] Draining the soaked wind turbine blades and then performing pyrolysis.

[0008] The method for recycling wind turbine blades based on low-temperature pyrolysis according to the embodiment of the present invention, before pyrolysis, the wind turbine blades are swollen in a specific solution composed of a solvent and a pore-forming agent, and at the same time, the pore-forming agent substance enters the swollen wind turbine blades. The former can reduce the interaction between the matrix resin and the reinforcing fibers, thereby reducing the pyrolysis temperature. The latter (pore-forming agent) can effectively avoid the formation of a dense carbon layer during the pyrolysis of the blades, improve the oxygen permeability, and promote the low-temperature pyrolysis of the blades; the entire recycling method has the advantages of low energy consumption and small thermal damage to the recycled fibers.

[0009] In some embodiments of the present invention, the content of the pore-forming agent in the solution is 5-10 wt%. The inventors found that when the content of the pore-forming agent in the solution is 5-10 wt%, the wind power blade can be rapidly pyrolyzed and oxidized at a relatively (conventional pyrolysis) low temperature, and high-quality reinforcing fibers can be recovered, that is, the pore-forming agent has an obvious promoting effect on the pyrolysis of the blade; while when the content of the pore-forming agent in the solution is less than 5 wt%, the promoting effect of the pore-forming agent on the pyrolysis of the blade is very small; when the content of the pore-forming agent in the solution is greater than 10 wt%, the promoting effect of the pore-forming agent on the pyrolysis of the blade hardly changes with the increase of its concentration, and too much pore-forming agent will increase the recovery cost of the blade.

[0010] In some embodiments of the present invention, the solvent is any one of tetrahydrofuran, chloroform, and acetone.

[0011] In some embodiments of the present invention, the soaking temperature is room temperature and the soaking time is 8-10 h.

[0012] In some embodiments of the present invention, the pore-forming agent is any one of polyethylene glycol, octadecyl vinyl imidazole bromide ionic liquid, and carboxymethyl cellulose.

[0013] The inventors surprisingly found that reducing the interaction between the resin and the fiber in the blade structure while preventing the formation of a dense carbon layer on the surface or between the fibers is the key to reducing the pyrolysis temperature of the blade. Only in a highly volatile polar solvent and an amphiphilic pore-forming agent, that is, the above-mentioned solvents and pore-forming agents disclosed in the present invention, can the wind power blade be effectively pretreated, significantly reduce the pyrolysis temperature, and achieve a reduction in the energy consumption of wind power blade recycling and a reduction in the thermal damage to the recycled fibers. When using conventional solvents such as ketones, alcohols, ethers, sulfones, acyls other than acetone, the swelling effect of the wind power blade at room temperature is poor, and it is even difficult to swell within a limited time; when using conventional pore-forming agents such as ammonium bicarbonate, polystyrene, lithium chloride, etc., the pore-forming agent is difficult to penetrate into the resin matrix and cannot effectively loosen the pyrolytic carbon layer.

[0014] In some embodiments of the present invention, the wind power blade soaked in the solution is a waste wind power blade cut into blocks after removing the metal components.

[0015] In some embodiments of the present invention, the pyrolysis temperature is 390-410 °C and the pyrolysis time is 1-2 h. The inventors found that when the pyrolysis temperature is between 390-410 °C, the quality of the recycled fibers is the best; while when the pyrolysis temperature is lower than 390 °C, the resin pyrolysis and oxidation are incomplete in a short time, and the purity of the recycled fibers is low. If the pyrolysis time is increased, the thermal damage to the recycled fibers increases; when the pyrolysis temperature is higher than 410 °C, the thermal damage to the recycled fibers is serious.

[0016] In some embodiments of the present invention, the pyrolysis atmosphere is a mixed gas of nitrogen and air, with a total flow rate of 10 - 20 L / min, and the volume content of oxygen in the mixed gas is 9 - 12%. The inventors found that when the volume content of oxygen in the mixed gas is between 9 - 12%, the recovered fibers have both high purity and strength; when the volume content of oxygen in the mixed gas is less than 9%, within a limited time, the residual carbon rate of the resin on the surface of the recovered fibers is relatively high and the fiber purity is low; when the volume content of oxygen in the mixed gas is greater than 12%, during the pyrolysis process, the combustion of pyrolytic carbon is likely to occur and significant heat is released, resulting in serious thermal damage to the recovered fibers.

[0017] In some embodiments of the present invention, the solution is added to the reaction kettle, and the soaked wind turbine blade is drained naturally or by drying, and the pyrolysis reaction is carried out in a pyrolysis furnace.

[0018] To achieve the above object, an embodiment of the second aspect of the present invention provides an application of the wind turbine blade recovery method based on low-temperature pyrolysis as described in the embodiments of the present invention in the fields of solid waste recovery and fiber preparation, using other fiberglass waste except wind turbine blades to replace wind turbine blades.

[0019] The application of the wind turbine blade recovery method based on low-temperature pyrolysis in the embodiments of the present invention has basically the same beneficial effects as the wind turbine blade recovery method based on low-temperature pyrolysis in the embodiments of the present invention, and will not be elaborated here.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the drawings, wherein:

[0022] Figure 1 Microscopic photograph of the glass fiber (i.e., reinforcing fiber) recovered in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The embodiments of the present invention will be described in detail below. The embodiments are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0024] The raw materials and equipment involved in the embodiments and comparative examples of the present invention, unless otherwise specified, are all materials that can be obtained through commercial channels; the methods involved in the embodiments and comparative examples of the present invention, unless otherwise specified, are all conventional methods.

[0025] I. Embodiments and Comparative Examples

[0026] Example 1

[0027] After removing the metal components from the waste wind turbine blade, it is cut into blocks (length × width = 10 cm × 10 cm) and placed in a reaction kettle containing a solution of tetrahydrofuran (500 ml) with polyethylene glycol (the polyethylene glycol in the solution is PEG-20000 and its content is 5.2 wt%). After soaking at room temperature for 10 h, it is taken out and the solution on the surface of the wind turbine blade is naturally drained. Then, the drained wind turbine blade is placed in a pyrolysis furnace and pyrolyzed at 400 °C for 1.5 h under a continuous nitrogen-air mixed atmosphere (total gas flow rate is 15 L / min, and the volume content of oxygen in the mixed atmosphere is 11%) to obtain pure reinforcing fibers( Figure 1 ), realizing blade recycling.

[0028] The wind turbine blade recycling method based on low-temperature pyrolysis in Examples 2-8 is basically the same as that in Example 1, except that: some specific process parameters involved in the recycling method are different.

[0029] The specific process parameters of Examples 2-8 are shown in Table 1.

[0030] Comparative Example 1

[0031] The wind turbine blade recycling method in this comparative example is basically the same as that in Example 1, except that: the wind turbine blade is directly pyrolyzed without any pretreatment.

[0032] Comparative Example 2

[0033] The wind turbine blade recycling method in this comparative example is basically the same as that in Example 2, except that: the wind turbine blade is only soaked in the solvent tetrahydrofuran (the soaking solution does not contain the pore-forming agent PEG) and directly pyrolyzed after soaking.

[0034] II. Effect Test

[0035] 1. Test Method for Properties of Recycled Fibers

[0036] (1) Fiber Purity

[0037] The content of resin in the recycled fibers is analyzed by a Mettler Toledo thermogravimetric analyzer. The lower the content, the more complete the pyrolysis of the resin in the blade and the higher the fiber purity.

[0038] (2) Fiber Strength Retention Rate

[0039] The tensile strength of the recycled fibers is measured by an LLY-06E tensile testing machine. The ratio of it to the strength of the original fibers represents the strength retention rate of the recycled fibers. The larger the retention rate, the smaller the damage to the recycled fibers during the pyrolysis process.

[0040] 2. Test Results

[0041] The fiber purity and fiber strength retention rate of the fibers obtained by the recovery methods of Examples 1-8 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1.

[0042] Table 1 Relevant process parameters and recovery effects of examples and comparative examples

[0043]

[0044] As can be seen from Table 1, pretreating the blades with an organic solution containing a pore-forming agent can significantly improve the pyrolysis effect of the blades. That is, at the same pyrolysis temperature and pyrolysis time, the fiber purity obtained by pyrolysis recovery after pretreatment is higher, indicating that the pretreatment can cause the matrix resin in the blades to be fully pyrolyzed. On the contrary, in Comparative Examples 1-2, since no pore-forming agent was added or even no pretreatment was carried out, the resin was not fully pyrolyzed and adhered to the surface of the recovered fibers, resulting in a low strength purity of the recovered fibers. At this time, the fiber strength retention rate actually characterizes the strength of the "fiber and its residual resin" mixture.

[0045] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0046] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill 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 recycling wind turbine blades based on low-temperature pyrolysis, characterized in that, Including: Soaking a wind power blade in a solution composed of a solvent and a pore-forming agent; Draining the soaked wind power blade and then performing pyrolysis; The content of the pore-forming agent in the solution is 5-10 wt%; The solvent is any one of tetrahydrofuran, chloroform, and acetone; The pore-forming agent is any one of polyethylene glycol, octadecyl vinyl imidazole bromide ionic liquid, and carboxymethyl cellulose; 2. The recovery method according to claim 1, characterized in that, The soaking time of the wind power blade in the solution is 8-10 h, and the soaking temperature is normal temperature; 3. The recovery method according to claim 1, wherein The wind power blade soaked in the solution is a waste wind power blade cut into blocks after removing metal components; 4. The recycling method according to claim 1, wherein The pyrolysis temperature is 390-410 °C, and the pyrolysis time is 1-2 h; 5. The recovery method according to claim 1, characterized in that, The pyrolysis atmosphere is a mixed gas of nitrogen and air, and the mixed gas continuously flows at a speed of 10-20 L / min, and the volume content of oxygen in the mixed gas is 9-12%; 6. The recycling method according to claim 1, characterized in that, The solution is added to a reaction kettle, and the drained soaked wind power blade is drained naturally or dried, and the pyrolysis reaction is carried out in a pyrolysis furnace; 7. Use of the low-temperature pyrolysis-based wind turbine blade recycling method according to any one of claims 1 to 6 in the field of solid waste recycling, characterized in that, Using other fiberglass waste except wind power blades to replace wind power blades.

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