A method and system for recycling waste wind turbine blades based on controlled pyrolysis and dissolution

Abstract

The present invention discloses a method and system for recycling waste wind turbine blades based on controlled pyrolysis and dissolution. The wind turbine blades are carbon fiber reinforced epoxy resin composite blades. The method comprises the following steps: (1) cutting the waste wind turbine blades after removing metal components into blocks; (2) placing the waste wind turbine blades cut into blocks in a pyrolysis furnace, using high-temperature flue gas from a coal-fired power plant as a heat source, the temperature of the high-temperature flue gas is 300°C to 320°C, the oxygen content is 3% to 6%, and pyrolysis is performed for 1h to 2h to obtain pyrolysis products; (3) immersing the pyrolysis products in a dissolving kettle with concentrated nitric acid, and after sufficient reaction, solid-liquid separation is performed to recover carbon fiber. The embodiment of the present invention achieves controlled pyrolysis of the waste wind turbine blades at a lower flue temperature and in a shorter time by precisely controlling the pyrolysis atmosphere, and then recovers carbon fiber by utilizing the dissolution reaction of carbon and concentrated nitric acid. The method of the present invention has low energy consumption, high recovered fiber quality and high recovery efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment, and relates to a technology for recycling waste wind turbine blades made of carbon fiber reinforced epoxy resin composite materials, and specifically to a method and system for recycling waste wind turbine blades made of carbon fiber reinforced epoxy resin composite materials based on controlled pyrolysis and dissolution. Background Art

[0002] Carbon fiber reinforced epoxy resin composite materials have low density, high strength and stiffness, and have broad application prospects in the manufacture of wind turbine blades. Due to the high price of carbon fiber, carbon fiber reinforced epoxy resin composite materials are currently only used in the manufacture of wind turbine blade main beams. With the vigorous development of offshore wind power, the demand for lightweight and high-strength large blades is increasing, and carbon fiber reinforced epoxy resin composite materials are likely to be used to manufacture full-size wind turbine blades. After retirement, the blades will become a high-value-added industrial solid waste. If they are not properly recycled, they will cause a lot of environmental pollution and waste of resources. Therefore, the recycling of waste blades, especially the recycling of carbon fiber reinforced epoxy resin composite blades, is becoming an industry problem in the field of wind power generation.

[0003] At present, the treatment processes for waste wind turbine blades include pyrolysis recovery technology and chemical solvent dissolution recovery technology. Pyrolysis recovery technology has high recovery efficiency, but the strength loss of the recovered fiber is large, and there are residues on the surface of the recovered fiber. The quality of the recovered fiber is poor and the energy consumption is also large; the chemical solvent dissolution recovery process has high recovered fiber quality and low energy consumption, but the recovery efficiency is low. Therefore, it is particularly important and necessary to develop a new carbon fiber reinforced composite material recycling technology to treat wind turbine blades. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems: the pyrolysis recovery technology has a high recovery efficiency, but the recovered fiber loses a lot of strength, and there are residues on the surface of the recovered fiber, the recovered fiber quality is poor, and the energy consumption is also high; the chemical solvent dissolution recovery process has a high recovered fiber quality and low energy consumption, but the recovery efficiency is low.

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the embodiment of the present invention proposes a method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution. The method of the embodiment of the present invention greatly reduces the recycling energy consumption with a lower reaction temperature. The method of the present invention has a short route, simple operation, low energy consumption, and a wide range of applications. It has broad application prospects in the field of recycling waste wind turbine blades made of carbon fiber reinforced epoxy resin composite materials.

[0006] To achieve the above object, an embodiment of the present invention provides a method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution, wherein the waste wind turbine blades are carbon fiber reinforced epoxy resin composite blades, and the method for recycling waste wind turbine blades comprises the following steps:

[0007] (1) Cutting the waste wind turbine blades into blocks after removing the metal components;

[0008] (2) placing the waste wind turbine blades cut into blocks in a pyrolysis furnace, using high-temperature flue gas from a coal-fired power plant as a heat source, wherein the temperature of the high-temperature flue gas is 300° C. to 320° C., the oxygen content is 3% to 6%, and pyrolysis is performed for 1 h to 2 h to obtain pyrolysis products;

[0009] (3) Immerse the pyrolysis product in a dissolving kettle containing concentrated nitric acid, and after sufficient reaction, separate the solid and liquid to recover the carbon fiber.

[0010] The embodiment of the present invention achieves controllable pyrolysis of waste wind turbine blades at a lower smoke temperature and in a shorter time by precisely controlling the pyrolysis atmosphere, thereby generating carbon fibers wrapped in cracked carbon. The pyrolysis carbon is then removed by a dissolution reaction of the carbon with concentrated nitric acid to obtain pure carbon fibers. The embodiment of the present invention has the technical advantages of low energy consumption, high quality of recycled fibers, and high recycling efficiency.

[0011] In some embodiments, the high-temperature flue gas further includes a dust removal step before entering the pyrolysis furnace to control the dust concentration of the flue gas to ≤5 mg / Nm 3 .

[0012] In some embodiments, the method for recycling waste wind turbine blades further includes: the pyrolysis exhaust gas in the pyrolysis furnace is sent to the furnace of the power plant boiler for combustion, and then purified together with the flue gas from the coal-fired power plant before being discharged.

[0013] In some embodiments, the method for recycling waste wind turbine blades also includes: step (3) the gas generated by the dissolution kettle is sent to the furnace of the power plant boiler for combustion, and then discharged together with the flue gas of the coal-fired power plant after purification, and the waste liquid after solid-liquid separation enters the wastewater treatment system of the coal-fired power plant.

[0014] In some embodiments, the molar concentration of the concentrated nitric acid is 10M to 12M.

[0015] In some embodiments, the reaction temperature of step (3) is 80°C to 90°C, and the reaction time is 1h to 2h.

[0016] In some embodiments, the size of the waste wind turbine blades cut into blocks is (20-30) cm×(10-15) cm.

[0017] In some embodiments, the pyrolysis furnace is horizontal and is provided with a rotary device with a rotation speed of 1 r / min to 5 r / min.

[0018] Another aspect of the present invention is to provide a waste wind turbine blade recycling system based on controlled pyrolysis and dissolution, the waste wind turbine blade recycling system comprising:

[0019] A cutting machine, wherein the cutting machine is used to cut waste wind turbine blades;

[0020] A pyrolysis furnace, wherein the pyrolysis furnace has a flue gas inlet, a first feed inlet, a first discharge port and a tail gas outlet; the flue gas inlet is connected to a high-temperature flue of a coal-fired power plant, the first feed inlet is used for feeding block-shaped waste wind turbine blades output by a cutting machine, the first discharge port is used for discharging pyrolysis products, and the tail gas outlet is connected to a tail gas pipeline;

[0021] A dissolving kettle, wherein the dissolving kettle has a second feed port, a second discharge port and an exhaust port; the second feed port is used for feeding the pyrolysis product, and the exhaust port is connected to the tail gas pipeline;

[0022] A solid-liquid separator, wherein the material inlet of the solid-liquid separator is connected to the second discharge port of the dissolving kettle, and the solid-liquid separator is used for separating the carbon fiber from the waste liquid;

[0023] The fan is arranged on the tail gas pipeline and is used to pump the gas in the tail gas pipeline to the furnace of the power plant boiler for combustion.

[0024] In some embodiments, the waste liquid outlet of the solid-liquid separator is connected to the wastewater treatment system of the coal-fired power plant.

[0025] In some embodiments, the pyrolysis furnace is horizontal and is provided with a rotating device.

[0026] In some embodiments, a dust cover is provided above the cutting machine, and a dust gas outlet is provided on the dust cover, and the dust gas outlet is connected to the exhaust gas duct.

[0027] Compared with the related art, the present invention has the following beneficial effects:

[0028] (1) The present invention achieves controlled pyrolysis of waste wind turbine blades at a lower smoke temperature and in a shorter time by precisely controlling the pyrolysis atmosphere, thereby generating carbon fibers wrapped in cracked carbon. The carbon is then removed by a dissolution reaction of the carbon with concentrated nitric acid to obtain pure carbon fibers.

[0029] (2) The method for recycling waste wind turbine blades of the present invention has the advantages of low energy consumption and high quality of recycled fibers compared to the traditional pyrolysis method; compared to the traditional (concentrated nitric acid) dissolution method, since the reaction activity of concentrated nitric acid with carbon is much higher than its reaction activity with epoxy resin, the time spent in the dissolution recovery process of the present invention is much less than that of the traditional dissolution method (usually taking dozens of hours), and has the advantage of high recovery efficiency. In short, the present invention skillfully combines the pyrolysis method with the dissolution method to recycle carbon fiber reinforced composite material wind turbine blades, and has the technical advantages of low energy consumption, high quality of recycled fibers, and high recovery efficiency.

[0030] (3) The controlled pyrolysis disclosed in the present invention is an innovation of the traditional pyrolysis technology, rather than a simple optimization of the pyrolysis process. Controlled pyrolysis can only be achieved in an atmosphere with an oxygen content of 3% to 6% and a temperature of 300°C to 320°C. If the oxygen content is too high or the temperature is too high, (carbon) oxidation reactions are very likely to occur, resulting in runaway reactions or even combustion; if the oxygen content is too low, the pyrolysis product (pyrolysis carbon wrapped carbon fiber) obtained will have a dense structure, which is not conducive to the subsequent dissolution reaction of concentrated nitric acid; if the temperature is too low, the composite material cannot be pyrolyzed.

[0031] (4) The fiber strength retention rate of the carbon fiber recycled by the method of the present invention reaches more than 90%, and the purity of the recycled fiber reaches more than 95%; the recycled carbon fiber has better performance and can be used in the production of carbon felt, reinforced resin to prepare carbon fiber composite materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0033] Figure 1 It is a schematic diagram of the waste wind turbine blade recycling system based on controlled pyrolysis and dissolution of the present invention.

[0034] Reference numerals:

[0035] 1 is a cutting machine, 2 is a pyrolysis furnace, 3 is a dissolving kettle, 4 is a solid-liquid separator, 5 is an exhaust gas pipeline, 6 is a fan, and 7 is a dust cover;

[0036] 201 is a flue gas inlet, 202 is a first feed inlet, 203 is a first discharge outlet, and 204 is a tail gas outlet;

[0037] 301 is a second feed port, 302 is a second discharge port, and 303 is an exhaust port. DETAILED DESCRIPTION

[0038] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0039] Unless otherwise specified, the raw materials and equipment in the embodiments of the present invention can be obtained through commercial channels.

[0040] The embodiment of the present invention provides a method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution. The waste wind turbine blades are carbon fiber reinforced epoxy resin composite blades. The method for recycling waste wind turbine blades includes the following steps:

[0041] (1) Cutting the waste wind turbine blades into blocks after removing the metal components;

[0042] (2) placing the waste wind turbine blades cut into blocks in a pyrolysis furnace, using high-temperature flue gas from a coal-fired power plant as a heat source, the high-temperature flue gas having a temperature of 300° C. to 320° C. and an oxygen content of 3% to 6%, and pyrolyzing for 1 h to 2 h to obtain pyrolysis products;

[0043] (3) Immerse the pyrolysis product in a dissolving kettle containing concentrated nitric acid, and after sufficient reaction, separate the solid and liquid to recover the carbon fiber.

[0044] The embodiment of the present invention achieves controllable pyrolysis of waste wind turbine blades at a relatively low flue gas temperature (300°C to 320°C) and in a relatively short time (1h to 2h) by precisely controlling the pyrolysis atmosphere (using high-temperature flue gas from a coal-fired power plant as a heat source, with a temperature of 300°C to 320°C and an oxygen content of 3% to 6%), thereby generating carbon fibers wrapped in cracked carbon. The pyrolytic carbon is then removed by a dissolution reaction of the carbon with concentrated nitric acid to obtain pure carbon fibers, which has the technical advantages of low energy consumption, high quality of recycled fibers, and high recycling efficiency.

[0045] In the embodiment of the present invention, the pyrolysis is controlled to be carried out in an atmosphere with an oxygen content of 3% to 6% and a temperature of 300°C to 320°C to ensure the best pyrolysis effect. If the oxygen content is too high and the temperature is too high, (carbon) oxidation reaction is very likely to occur, the reaction will be out of control, or even burn. If the oxygen content is too low, the obtained pyrolysis product (pyrolysis carbon wrapped carbon fiber) has a dense structure, which is not conducive to the subsequent dissolution reaction of concentrated nitric acid. If the temperature is too low, the composite material cannot be pyrolyzed.

[0046] Non-limiting examples are: the temperature of the high-temperature flue gas in step (2) can be 300°C, 305°C, 310°C, 315°C, 320°C, etc., the oxygen content can be 3%, 3.5%, 4.5%, 5%, 6%, etc., and the pyrolysis time can be 1h, 1.2h, 1.4h, 1.5h, 2h, etc.

[0047] In some embodiments, the high-temperature flue gas further includes a dust removal step before entering the pyrolysis furnace to control the dust concentration of the flue gas to ≤ 5 mg / Nm 3The main purpose of the dust removal step is that the high-temperature flue gas of a coal-fired power plant contains a large amount of fly ash, which can cause the tar (capillary condensation) produced during the pyrolysis of the blades to condense. The tar combines with the fly ash to form blocky slag, which not only affects the pyrolysis but also reduces the quality of the recovered fiber. Therefore, in the embodiment of the present invention, the dust concentration of the high-temperature flue gas is controlled before entering the pyrolysis furnace, which helps to improve the pyrolysis efficiency and the quality of the recovered fiber.

[0048] In some embodiments, the wind turbine blade recycling method also includes: the pyrolysis exhaust gas (carbon dioxide, polycyclic aromatic hydrocarbons and a small amount of nitrogen oxides) in the pyrolysis furnace is sent to the power plant boiler furnace for combustion, and then purified together with the flue gas from the coal-fired power plant before being discharged.

[0049] In some embodiments, the wind turbine blade recycling method also includes: step (3) the gas (carbon dioxide and nitrogen oxides) generated by the dissolution kettle is sent to the power plant boiler furnace for combustion, and then purified together with the flue gas of the coal-fired power plant and discharged, and the waste liquid after solid-liquid separation enters the wastewater treatment system of the coal-fired power plant.

[0050] In some embodiments, the molar concentration of concentrated nitric acid is 10 M to 12 M. For non-limiting example, the molar concentration of concentrated nitric acid can be 10 M, 10.5 M, 11 M, 11.5 M, 12 M, etc.

[0051] In some embodiments, the reaction temperature of step (3) is 80°C to 90°C, and the reaction time is 1h to 2h. Non-limiting examples include: the reaction temperature of step (3) can be 80°C, 82°C, 85°C, 87°C, 90°C, etc., and the reaction time can be 1h, 1.2h, 1.5h, 1.8h, 2h, etc.

[0052] In some embodiments, the size of the waste wind turbine blades cut into blocks is (20-30) cm×(10-15) cm. It is understandable that wind turbine blades are generally tens of meters long. In consideration of both processing cost and efficiency, cutting them into small blocks facilitates their full contact with high-temperature flue gas and facilitates pyrolysis.

[0053] For example, the size of the waste wind turbine blades can be cut into, for example, length×width=20cm×10cm, 20cm×15cm, 25cm×10cm, 25cm×15cm, 30cm×15cm, etc. It can be understood that in a specific example, the waste wind turbine blades cut into blocks can be any combination of one or more of the above multiple sizes.

[0054] In some embodiments, the pyrolysis furnace is horizontal and equipped with a rotary device with a rotation speed of 1 r / min to 5 r / min. Non-limiting examples include: the rotation speed can be 1 r / min, 2 r / min, 3 r / min, 4 r / min, 5 r / min, etc.

[0055] In some embodiments, the flow rate of the high temperature flue gas in the pyrolysis furnace is 5 m / s to 7 m / s. For example, the flow rate may be 5 m / s, 5.5 m / s, 6 m / s, 6.5 m / s, 7 m / s, etc.

[0056] The embodiment of the present invention also provides a waste wind turbine blade recycling system based on controlled pyrolysis and dissolution ( Figure 1 shown), including:

[0057] Cutting machine 1, cutting machine 1 is used for cutting waste wind turbine blades;

[0058] The pyrolysis furnace 2 has a flue gas inlet 201, a first feed inlet 202, a first discharge port 203 and an exhaust gas outlet 204; the flue gas inlet 201 is connected to the high-temperature flue of the coal-fired power plant, the first feed inlet 202 is used for feeding the block-shaped waste wind turbine blades output by the cutting machine, the first discharge port 203 is used for discharging the pyrolysis product, and the exhaust gas outlet 204 is connected to the exhaust gas pipeline 5;

[0059] The dissolving kettle 3 has a second feed port 301, a second discharge port 302 and an exhaust port 303; the second feed port 301 is used for feeding the pyrolysis product, and the exhaust port 303 is connected to the tail gas pipeline 5;

[0060] A solid-liquid separator 5, wherein the material inlet of the solid-liquid separator 5 is connected to the second discharge port 302 of the dissolving kettle 3, and the solid-liquid separator 5 is used for separating the carbon fiber from the waste liquid;

[0061] The fan 6 is arranged on the tail gas pipeline 5 and is used to pump the gas in the tail gas pipeline 5 to the furnace of the power plant boiler for combustion.

[0062] In some embodiments, the waste liquid outlet of the solid-liquid separator 5 is connected to the waste water treatment system of the coal-fired power plant. In a specific example, the solid-liquid separator 5 can be a plate-frame solid-liquid separator.

[0063] In some embodiments, the pyrolysis furnace 2 may be horizontal and provided with a rotating device.

[0064] In some embodiments, a dust cover 7 may be provided above the cutting machine 1 , and a dust gas outlet is provided on the dust cover 7 , and the dust gas outlet is connected to the exhaust gas duct 5 .

[0065] During operation, the waste wind turbine blades are cut into specified sizes by the cutting machine 1, and then enter the pyrolysis furnace 2 through the first feed port 202 of the pyrolysis furnace 2. After the pyrolysis is completed, the pyrolysis products are discharged through the first discharge port 203 of the pyrolysis furnace 2, and then enter the dissolution kettle 3 through the second feed port 301 of the dissolution kettle 3. The reaction products enter the solid-liquid (plate and frame) separator 5 through the second discharge port 302 on the dissolution kettle 3 for solid-liquid separation. The separated solid is chopped carbon fiber, and the separated waste liquid enters the wastewater treatment system of the coal-fired power plant for centralized treatment. The flue gas inlet 201 of the pyrolysis furnace 2 is connected to the high-temperature flue of the coal-fired power plant. Figure 1 The high-temperature flue gas is drawn into the pyrolysis furnace 2 under the action of the pyrolysis furnace 2 to pyrolyze the waste wind turbine blade blocks.

[0066] In a specific example, the tail gas outlet 204 on the pyrolysis furnace 2 is connected to the tail gas pipeline 5 through a first pipeline, the exhaust port 303 on the dissolving kettle 3 is connected to the tail gas pipeline 5 through a second pipeline, and the dust gas outlet on the dust cover 7 is connected to the tail gas pipeline 5 through a third pipeline. It can be understood that the first pipeline, the second pipeline, and the third pipeline are connected in parallel to the same tail gas pipeline 5.

[0067] During the operation, the dust gas generated during the cutting process of the cutting machine 1 is discharged through the dust gas outlet, the pyrolysis exhaust gas in the pyrolysis furnace 2 is discharged through the exhaust gas outlet 204, and the gas generated by the dissolving kettle 3 is discharged through the exhaust port 303. They all enter the same exhaust gas pipeline 5, are sent to the boiler furnace of the power plant for combustion through the fan 6, and are purified together with the coal-fired flue gas pollutants before being discharged.

[0068] A large amount of dust (mainly carbon fiber reinforced epoxy resin powder) will be generated when wind turbine blades are mechanically cut, causing secondary environmental pollution. The embodiment of the present invention uses the fan 6 to extract the dust and send it to the furnace of the power plant boiler for combustion, so as to achieve dust-free cutting of the blades. Air pollutants (mainly nitrogen oxides and high-boiling point compounds such as polycyclic aromatic hydrocarbons) will be generated during the pyrolysis of the blades, and carbides will also generate air pollutants (nitrogen oxides) during the acid dissolution process, both of which will cause secondary pollution. The present invention uses the fan 6 to directly extract the above pollutants to the furnace of the power plant boiler for combustion, so that the polycyclic aromatic hydrocarbons are further decomposed into small molecular gas pollutants, and then treated together with nitrogen oxides by the power plant pollutant purification system, effectively solving the secondary pollution problem in the blade recovery process.

[0069] The following are non-limiting examples and comparative examples of the present invention. It should be noted that the following comparative examples are not prior art and are only provided for comparison with the examples and are not intended to limit the present invention.

[0070] The recycling effects of Examples 1 to 7 of the present invention and Comparative Examples 1 to 3 were evaluated by the resin residual rate of the recycled fiber and the strength retention rate of the recycled fiber.

[0071] The resin content in the recycled carbon fiber was analyzed using a Mettler Toledo thermogravimetric analyzer. The lower the content, the more complete the resin degradation in the blade.

[0072] The tensile strength of carbon fiber was measured using an LLY-06E tensile testing machine. The ratio of the tensile strength of carbon fiber to the strength of the original fiber represents the strength retention rate of the recycled fiber. The greater the retention rate, the smaller the impact of the degradation process on the recycled fiber.

[0073] Example 1

[0074] A method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution, wherein the waste wind turbine blades are carbon fiber reinforced epoxy resin composite blades, and the method comprises the following steps:

[0075] (1) Cutting the waste wind turbine blades into blocks after removing the metal components;

[0076] (2) placing the waste wind turbine blades cut into blocks in a pyrolysis furnace, using the high-temperature flue gas of 300°C from a coal-fired power plant as a heat source, with an oxygen content of 5% in the flue gas, and pyrolyzing for 2 hours to obtain a pyrolysis product (carbon fiber wrapped in pyrolytic carbon);

[0077] (3) The pyrolysis product is immersed in a dissolving kettle with concentrated nitric acid with a molar concentration of 10 M. After fully reacting at 85° C. for 2 h, the pyrolytic carbon on the fiber surface is removed to finally obtain pure carbon fiber, which is then separated from the solid and liquid to recover the carbon fiber.

[0078] (4) The gas generated in the dissolving kettle in step (3) and the pyrolysis tail gas in the pyrolysis furnace are sent to the furnace of the power plant boiler for combustion, and are discharged after purification together with the flue gas of the power plant. The waste liquid after solid-liquid separation in step (3) enters the wastewater treatment system of the coal-fired power plant for treatment.

[0079] Before the high-temperature flue gas from a coal-fired power plant enters the pyrolysis furnace, it also includes a high-temperature dust removal step to control the dust concentration of the flue gas to ≤5mg / Nm 3 .

[0080] Embodiments 2 to 7

[0081] The preparation process of Examples 2 to 7 is the same as that of Example 1, but the preparation parameters are different from those of Example 1. The specific parameters and recovery effects are detailed in Table 1.

[0082] Table 1 Process parameters and recovery effects of Examples 1 to 7

[0083]

[0084] Comparative Examples 1 to 3

[0085] The preparation process of Comparative Examples 1 to 3 is the same as that of Example 1, but the preparation parameters are different from those of Example 1. The specific parameters and recovery effects are detailed in Table 2.

[0086] Table 2 Relevant process parameters and recovery effects of Example 1 and Comparative Examples 1 to 3

[0087]

[0088] From the comparison of Example 1 and Comparative Examples 1 to 3, it can be seen that the pyrolysis temperature is high and the oxygen content in the high-temperature flue gas is high, and the thermal damage of the recovered fiber is large, which is manifested in that the strength retention rate of the recovered fiber is significantly reduced. The oxygen content in the high-temperature flue gas is low, and the purity of the recovered fiber is low, which is manifested in that the resin residue is high.

[0089] Therefore, the embodiment of the present invention achieves controlled pyrolysis of waste wind turbine blades at a lower smoke temperature and in a shorter time by precisely controlling the pyrolysis atmosphere (3% to 6% oxygen content and a high temperature flue gas atmosphere of 300°C to 320°C), thereby generating carbon fibers wrapped in cracked carbon, and then removing the pyrolytic carbon to obtain pure carbon fibers by using the dissolution reaction of carbon with concentrated nitric acid. The fiber strength retention rate of the carbon fibers recycled by the method of the embodiment of the present invention reaches more than 90%, and the purity of the recycled fibers reaches more than 95%; the recycled carbon fibers have better performance. The method of the embodiment of the present invention has the technical advantages of low energy consumption, high quality of recycled fibers, and high recycling efficiency, and has great application value.

[0090] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0091] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0092] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0093] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0094] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction 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 described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution, characterized in that: The waste wind turbine blades are carbon fiber reinforced epoxy resin composite blades, and the waste wind turbine blade recycling method comprises the following steps: (1) Cutting the waste wind turbine blades into blocks after removing the metal components; (2) placing the waste wind turbine blades cut into blocks in a pyrolysis furnace, using high-temperature flue gas from a coal-fired power plant as a heat source, wherein the temperature of the high-temperature flue gas is 300°C to 320°C and the oxygen content is 3% to 6%, and pyrolyzing for 1h to 2h to obtain pyrolysis products; (3) The pyrolysis product is immersed in a dissolving kettle containing concentrated nitric acid. After sufficient reaction, the solid-liquid separation is performed to recover the carbon fiber.

2. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: Before the high-temperature flue gas enters the pyrolysis furnace, a dust removal step is also included to control the dust concentration of the flue gas to ≤5mg / Nm 3 .

3. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The waste wind turbine blade recycling method also includes: the pyrolysis tail gas in the pyrolysis furnace is sent to the furnace of the power plant boiler for combustion, and then purified together with the flue gas of the coal-fired power plant before being discharged.

4. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The method for recycling waste wind turbine blades also includes: in step (3), the gas generated in the dissolving kettle is sent to the furnace of the power plant boiler for combustion, and then discharged together with the flue gas of the coal-fired power plant after purification, and the waste liquid after solid-liquid separation enters the wastewater treatment system of the coal-fired power plant.

5. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The molar concentration of the concentrated nitric acid is 10M~12M.

6. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The reaction temperature of step (3) is 80°C to 90°C, and the reaction time is 1h to 2h.

7. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The size of the waste wind turbine blades cut into blocks is 20-30 cm×10-15 cm.

8. The method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to claim 1 is characterized in that: The pyrolysis furnace is horizontal and is provided with a rotary device with a rotation speed of 1 r / min to 5 r / min.

9. A waste wind turbine blade recycling system based on controlled pyrolysis and dissolution, characterized by: Used to implement a method for recycling waste wind turbine blades based on controlled pyrolysis and dissolution according to any one of claims 1 to 8, the waste wind turbine blade recycling system comprises: A cutting machine, wherein the cutting machine is used to cut waste wind turbine blades; A pyrolysis furnace, wherein the pyrolysis furnace has a flue gas inlet, a first feed inlet, a first discharge port and a tail gas outlet; the flue gas inlet is connected to a high-temperature flue of a coal-fired power plant, the first feed inlet is used for feeding block-shaped waste wind turbine blades output by a cutting machine, the first discharge port is used for discharging pyrolysis products, and the tail gas outlet is connected to a tail gas pipeline; A dissolving kettle, wherein the dissolving kettle has a second feed port, a second discharge port and an exhaust port; the second feed port is used for feeding the pyrolysis product, and the exhaust port is connected to the tail gas pipeline; A solid-liquid separator, wherein the material inlet of the solid-liquid separator is connected to the second discharge port of the dissolving kettle, and the solid-liquid separator is used for separating the carbon fiber from the waste liquid; A fan, the fan being arranged on the tail gas pipeline and used for pumping the gas in the tail gas pipeline to the furnace of the power plant boiler for combustion; The waste liquid outlet of the solid-liquid separator is connected to the waste water treatment system of the coal-fired power plant.

10. A waste wind turbine blade recycling system based on controlled pyrolysis and dissolution according to claim 9, characterized in that: A dust cover is arranged above the cutting machine, and a dust gas outlet is arranged on the dust cover, and the dust gas outlet is communicated with the exhaust gas pipeline.

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