Method for recycling carbon fiber waste through high-energy water ion normal-pressure pyrolysis and application

Abstract

The invention discloses a method for recycling carbon fiber waste through high-energy water ion normal-pressure pyrolysis, which comprises the following steps: S1, pretreatment: removing metal impurities in the carbon fiber waste to obtain metal-free carbon fiber waste; s2, step-by-step crushing, wherein the metal-free carbon fiber waste is sequentially subjected to coarse crushing (the tooth spacing is 5 mm) through a first crusher and fine crushing (the tooth spacing is 2 mm) through a second crusher, and crushed materials with the particle size smaller than or equal to 2 mm are obtained; s3, cracking: feeding the crushed material into a high-energy water ion cracking furnace, and carrying out directional cracking on a resin matrix through hydroxide ions under the conditions of normal pressure and 320-420 DEG C to generate carbon fibers and carbon-containing gas; the pollution is greatly reduced even if a small amount of pollution exists; in addition, a large amount of low-order activated carbon is contained in soft washing water after cracking, and some pollution during cracking can be recycled and utilized; the recycled carbon fiber can replace most of currently used new carbon fiber cut short filaments, so that the carbon fiber can be recycled.

Description

Technical Field

[0001] The present invention relates to the recycling of carbon fiber resin matrix composites, and particularly to a method and application for pyrolyzing carbon fiber waste by high-energy water ions under normal pressure. Background Art

[0002] Carbon fiber reinforced resin matrix composites are widely used in the fields of aerospace, automotive industry, sports equipment, etc. due to their excellent mechanical properties (such as high strength, high modulus, high temperature resistance, etc.). However, the problem of waste treatment is becoming increasingly serious. Existing recycling technologies mainly include mechanical method, solvent method and high-temperature pyrolysis method, but all have significant defects:

[0003] 1. Mechanical method: The performance of the recycled fiber deteriorates and can only be used as a filler.

[0004] 2. Solvent method: The chemical reagents cause great pollution, and the supercritical fluid technology has high costs.

[0005] 3. High-temperature pyrolysis method: The temperature control is difficult, the carbon fiber is easily damaged and the energy consumption is high. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a method for pyrolyzing carbon fiber waste by high-energy water ions, which can degrade the resin on the carbon fiber at a lower temperature and in a shorter time.

[0007] One of the purposes of the present invention is achieved by adopting the following technical solution: A method for pyrolyzing carbon fiber waste by high-energy water ions under normal pressure, comprising the following steps:

[0008] S1: Pretreatment: Remove metal impurities in the carbon fiber waste to obtain metal-free carbon fiber waste.

[0009] S2: Stepwise crushing: Pass the metal-free carbon fiber waste through a first crusher for coarse crushing (tooth pitch 5 mm) and a second crusher for fine crushing (tooth pitch 2 mm) in sequence to obtain crushed material with a particle size ≤ 2 mm.

[0010] S3: Pyrolysis: Feed the crushed material into a high-energy water ion pyrolysis furnace, and under normal pressure and at 320°C - 420°C, pyrolyze the resin matrix by hydroxyl ions in a directional manner to generate carbon fiber and carbon-containing gas.

[0011] S4: Cooling and cleaning: Inject water into the pyrolysis furnace to cool down to below 60°C, take out the carbon fiber and remove the residual carbon and tar on the surface through a cleaning machine.

[0012] S5: Dehydration and post-treatment: Dehydrate the cleaned carbon fiber to a moisture content ≤ 60%, and process it into short fibers with a length ≤ 8 mm through a shredder, and package it as a finished product.

[0013] Furthermore, the hydroxide ions are generated by electrolyzing water vapor, the water vapor concentration in the cracking furnace is 10% - 30% (volume fraction), and the electrolysis voltage is 5 - 15V.

[0014] Furthermore, the cracking temperature is 350°C - 380°C, and the cracking time is 4 - 8 hours.

[0015] Furthermore, in step S2, the stepwise crushing is carried out by a double-shaft crusher, and the crushing rate is 50 - 100 kg / h.

[0016] Furthermore, the moisture content of the finished product in step S5 is 55% - 60%, which is used to suppress the dust during the processing of carbon fiber.

[0017] Furthermore, the carbon-containing gas includes methane, carbon monoxide and carbon dioxide. After being separated by the gas treatment system, activated carbon is recovered, and the remaining gas is purified and discharged through an RCO (Regenerative Catalytic Oxidizer).

[0018] Furthermore, its single-filament tensile strength ≥ 1500 MPa, modulus ≥ 200 GPa, and there are no crack defects on the surface.

[0019] An application of high-energy water ion atmospheric pressure pyrolysis for recovering carbon fiber waste, which is used in the following fields:

[0020] (a) Blending and pelletizing with thermoplastic resins (PVC, PE) to prepare antistatic plastic products;

[0021] (b) As a reinforcing material incorporated into cement-based building materials to improve seismic and electromagnetic radiation resistance performance;

[0022] (c) Preparing short fiber reinforced composites for use in automotive parts or sports equipment.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The high-energy water ions in the present invention are mainly hydroxide ion technology. By breaking the structure of the resin through hydroxide ion bonds, the resin on the carbon fiber board is completely cracked, and the final products are only carbon fiber filaments and carbon. Also, because it uses cracking instead of combustion (oxidation), the pollution during the process is greatly reduced. Even if there is a small amount of pollution, it can be simply treated. In addition, after cracking and gentle washing, the water contains a large amount of low-grade activated carbon, which can also be recovered and used to treat some pollution during cracking.

[0025] (2) After the carbon fiber is recycled and processed, its carbon fiber filaments can be cut into a certain length according to customer needs, such as 2-3 mm. Its uses can include mixing with PVC / PE for pelletizing, and then extruding plastic products (such as safety helmets, explosion-proof barrels, antistatic boxes, etc.) through an extruder. It has the effects of improving toughness, antistatic property, and inhibiting EMI radiation, and can even be mixed with cement to build earthquake-resistant and EMI radiation-resistant houses. Therefore, the recycled carbon fiber can replace most of the current uses of newly cut short carbon fiber filaments, enabling the carbon fiber to be recycled.

[0026] The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given, and in conjunction with the accompanying drawings, the details are described as follows. Description of the Drawings

[0027] Figure 1 : Optical comparison diagram of carbon fiber waste before and after treatment (automobile front frame and fishing rod waste);

[0028] Figure 2 : SEM diagram of carbon fiber after treatment (no surface defects);

[0029] Figure 3 : Tensile mechanical property curve of recycled carbon fiber single filament (compared with commercial fiber);

[0030] Figure 4 : Process flow chart (covering waste gas and wastewater recycling treatment systems). Detailed Embodiments

[0031] Next, in combination with the accompanying drawings and specific embodiments, the present invention will be further described. It should be noted that on the premise of non-conflict, any combination of the following-described embodiments or technical features can form a new embodiment.

[0032] It should be noted that when a component is referred to as being "fixed to" another component, it can be directly on the other component or there can also be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component at the same time. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0034] Example 1:

[0035] Carbon fiber composite waste is obtained from carbon fiber automotive front frame waste. The carbon fiber is PAN-based fiber, and the morphology of the carbon fiber is short fiber, with the carbon fiber weight content being 60%. It is cut into a cuboid sample with a volume of 100mm * 60mm * 5mm, as shown in Figure 1 Figure (a) below. It is placed in a high-energy water ion cracking furnace, the temperature is set at 350°C, and the treatment time is 6h. After completion, it is cooled to room temperature with water. The recovered carbon fiber is shown in Figure 1 Figure (b) below with a smooth surface. As shown in Figure 2 No physical damages such as any defects or cracks are found on the surface of the scanning electron microscope (SEM) images of the carbon fiber waste after treatment. The tensile properties of single carbon fiber filaments are tested according to the GB / T31290 - 2014 standard. The tensile properties of the recovered carbon fiber and commercial carbon fiber are tested by a single fiber strength tester, and the results show that their tensile properties are comparable, as shown in Figure 3 Figures (a) and (b) below.

[0036] Example 2:

[0037] Carbon fiber composite waste is obtained from carbon fiber fishing rod waste. The carbon fiber is PAN-based fiber, and the morphology of the carbon fiber is short fiber, with the carbon fiber weight content being 60%. It is cut into a cylindrical sample with a diameter of 10mm and a length of 20mm, as shown in Figure 1 Figure (c) below. It is placed in a high-energy water ion cracking furnace, the temperature is set at 350°C, and the treatment time is 6h. After completion, it is cooled to room temperature with water. The recovered carbon fiber is shown in Figure 1 Figure (d) below with a smooth surface. As shown in Figure 2 No physical damages such as any defects or cracks are found on the surface of the scanning electron microscope (SEM) images of the carbon fiber waste after treatment. The tensile properties of single carbon fiber filaments are tested according to the GB / T31290 - 2014 standard. The tensile properties of the recovered carbon fiber and commercial carbon fiber are tested by a single fiber strength tester, and the results show that their tensile properties are comparable, as shown in Figure 3 Figures (c) and (d) below.

[0038] The above embodiments are only preferred embodiments of the present invention, and the scope of protection of the present invention cannot be limited thereby. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for recovering carbon fiber waste by atmospheric pressure pyrolysis of high-energy water ions, characterized in that, It includes the following steps: S1: Pretreatment: Remove metal impurities from carbon fiber waste to obtain metal-free carbon fiber waste; S2: Step-by-step crushing: Pass the metal-free carbon fiber waste through a first crusher for coarse crushing (tooth pitch 5 mm) and a second crusher for fine crushing (tooth pitch 2 mm) in sequence to obtain crushed material with a particle size ≤ 2 mm; S3: Pyrolysis: Feed the crushed material into a high-energy water ion pyrolysis furnace, and under normal pressure and at 320 °C–420 °C, pyrolyze the resin matrix by directional movement of hydroxide ions to generate carbon fibers and carbon-containing gases; S4: Cooling and cleaning: Inject water into the pyrolysis furnace to cool it down to below 60 °C, take out the carbon fibers and remove residual carbon and tar on the surface through a cleaning machine; S5: Dehydration and post-treatment: Dehydrate the cleaned carbon fibers to a moisture content ≤ 60%, process them through a shredder into short fibers with a length ≤ 8 mm, and package them as finished products.

2. The method according to claim 1, wherein The hydroxide ions are generated by electrolyzing water vapor, the water vapor concentration in the pyrolysis furnace is 10%–30% (volume fraction), and the electrolysis voltage is 5–15 V.

3. The method according to claim 1, characterized in that, The pyrolysis temperature is 350 °C–380 °C, and the pyrolysis time is 4–8 hours.

4. The method according to claim 1, characterized in that In step S2, the step-by-step crushing uses a double-shaft crusher, and the crushing rate is 50–100 kg / h.

5. The method according to claim 1, wherein In step S5, the moisture content of the finished product is 55%–60%, which is used to inhibit dust generation during the processing of carbon fibers.

6. The method according to claim 1, wherein The carbon-containing gases include methane, carbon monoxide and carbon dioxide. After being separated by a gas treatment system, activated carbon is recovered, and the remaining gases are purified and discharged through an RCO (regenerative catalytic oxidizer).

7. The carbon fiber recovered by the method according to claim 1, characterized in that, Its single-filament tensile strength ≥ 1500 MPa, modulus ≥ 200 GPa, and there are no crack defects on the surface.

8. Use of the carbon fiber recovered by the method according to claim 1, characterized in that It is used in the following fields: (a) Blending and pelletizing with thermoplastic resins (PVC, PE) to prepare antistatic plastic products; (b) As a reinforcing material incorporated into cement-based building materials to improve seismic resistance and electromagnetic radiation resistance; (c) Preparing short fiber reinforced composites for use in automotive parts or sports equipment.

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