Fused salt pyrolysis recovery system and method for phenolic resin composite material

Abstract

The invention relates to the technical field of molten salt pyrolysis, in particular to a molten salt pyrolysis recovery system and method for a phenolic resin composite material. The system comprises a first reaction tank used for mixing a to-be-treated phenolic resin composite material with a target fused salt so as to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis, and a second reaction tank used for mixing the to-be-treated phenolic resin composite material with a target fused salt, the mixing device is connected with the first reaction tank and used for mixing the fused salt floating on the top of the target fused salt liquid level after the pyrolytic reaction is completed with water to obtain a mixed solution; the second reaction tank is connected with the mixing device and is used for introducing carbon dioxide gas into the mixed solution until the pH value is 7-9 and separating out black solid phenolic substances; and the first recovery device is used for separating and recovering fibers in the mixed solution. According to the technical scheme, fused salt pyrolysis recovery of the phenolic resin composite material can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of molten salt pyrolysis, and in particular to a molten salt pyrolysis recovery system and method for a phenolic resin composite material. Background Art

[0002] Carbon fiber / phenolic resin composites are widely used in aerospace, wind power, automobile and other fields due to their excellent properties of light weight and high strength. However, composite materials will face abandonment after their service life expires. If they are not recycled, it will inevitably lead to a huge waste of resources. At present, the key bottleneck problem restricting the high-value recycling of composite materials is that the three-dimensional cross-linked structure of the resin is difficult to break and the decomposition process is difficult to control. First, the three-dimensional cross-linked structure during the thermal decomposition of the resin will make it difficult for the resin to depolymerize and decompose completely, and it is easy to produce residual carbon, which is mixed with the carbon fiber, significantly reducing the quality of the recycled fiber product. On the other hand, the thermal decomposition process of the resin is disordered, resulting in complex components of the resin decomposition products and low quality, making it difficult to recycle the production of phenolic resin.

[0003] Based on this, there is an urgent need for a molten salt pyrolysis recovery system and method for phenolic resin composite materials to solve the above technical problems. Summary of the invention

[0004] The embodiments of the present invention provide a molten salt pyrolysis and recovery system and method for a phenolic resin composite material, which can realize the molten salt pyrolysis and recovery of the phenolic resin composite material.

[0005] In a first aspect, an embodiment of the present invention provides a molten salt pyrolysis recovery system for a phenolic resin composite material, a first reaction tank, for mixing a phenolic resin composite material to be treated with a target molten salt, so as to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis;

[0006] A mixing device, connected to the first reaction tank, for mixing the molten salt floating on the top of the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution;

[0007] A second reaction tank is connected to the mixing device and is used to introduce carbon dioxide gas into the mixed solution until the pH is 7 to 9 and a phenolic substance is precipitated as a black solid;

[0008] The first recovery device is used to separate and recover the fibers in the mixed solution.

[0009] In a second aspect, an embodiment of the present invention provides a method for recovering a phenolic resin composite material by molten salt pyrolysis, comprising:

[0010] The phenolic resin composite material to be treated is mixed with a target molten salt to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis;

[0011] Mixing the molten salt floating on the top of the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution;

[0012] Passing carbon dioxide gas into the mixed solution until the pH is 7 to 9, and a phenolic substance is precipitated as a black solid;

[0013] The fibers in the mixed solution are separated and recovered.

[0014] The embodiment of the present invention provides a molten salt pyrolysis recovery system and method for phenolic resin composite materials. By using the target molten salt to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis, the three-dimensional cross-linked structure of the phenolic resin can be depolymerized, thereby promoting the cracking of the resin matrix, making the decomposed product components more homogeneous, and the molecular weight distribution more uniform, reducing the residual carbon rate of the resin, and improving the quality of the recycled fiber. At the same time, the skeleton structure of the phenolic substance can be effectively retained, and the phenolic substance can be captured in the molten salt system in time through the replacement reaction, which inhibits its further deep cracking into small molecular gases and increases the feasibility of reprocessing the resin decomposition products to produce resin. Therefore, the above technical scheme can realize the molten salt pyrolysis recovery of phenolic resin composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 is a system schematic diagram of a molten salt pyrolysis recovery system for a phenolic resin composite material provided by an embodiment of the present invention;

[0017] Figure 2 It is a schematic flow chart of a method for molten salt pyrolysis recovery of a phenolic resin composite material provided in an embodiment of the present invention.

[0018] Reference numerals:

[0019] 1-first reaction tank; 2-mixing device; 3-second reaction tank; 4-first recovery device; 5-cooling device; 6-second recovery device. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] like Figure 1 As shown, an embodiment of the present invention provides a molten salt pyrolysis recovery system for a phenolic resin composite material, comprising a first reaction tank 1, a mixing device 2, a second reaction tank 3 and a first recovery device 4, wherein:

[0022] The first reaction tank 1 is used to mix the phenolic resin composite material to be treated with the target molten salt, so as to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis;

[0023] The mixing device 2 is connected to the first reaction tank 1 and is used to mix the top molten salt floating on the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution;

[0024] The second reaction tank 3 is connected to the mixing device 2 and is used to introduce carbon dioxide gas into the mixed solution until the pH is 7 to 9 and a phenolic substance is precipitated as a black solid;

[0025] The first recovery device 4 is used to separate and recover the fibers in the mixed solution.

[0026] In the present embodiment, by using the target molten salt to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis, the three-dimensional cross-linked structure of the phenolic resin can be promoted to depolymerize, thereby promoting the cracking of the resin matrix, making the decomposed product components more homogeneous, and the molecular weight distribution more uniform, reducing the residual carbon rate of the resin, and improving the quality of the recycled fiber. At the same time, the skeleton structure of the phenolic substance can be effectively retained, and the phenolic substance can be captured in the molten salt system in time through the replacement reaction, which inhibits its further deep cracking into small molecular gases, and increases the feasibility of reprocessing the resin decomposition products to produce resin. Therefore, the above technical scheme can realize the molten salt pyrolysis recovery of the phenolic resin composite material.

[0027] In addition, electrolysis can further enhance the conversion reaction. The above technical solution can promote the decomposition rate of the resin pyrolysis process through the coupling of thermal field and electric field, and improve the conversion rate of phenolic substances produced by resin decomposition and the reaction of alkaline molten salt to form organic sodium salt. If excessive carbon dioxide gas is introduced, aromatic phenolic acid will be generated during the reaction, thereby affecting the purity of phenolic substances. If insufficient carbon dioxide gas is introduced, phenolic substances will not be completely precipitated, resulting in waste.

[0028] It should be noted that the top molten salt is soluble in water. After being dissolved in water, carbon dioxide is passed into the top molten salt, which can not only separate out phenols, but also capture carbon dioxide to improve carbon reduction potential. If other acidic gases such as sulfur dioxide and hydrogen chloride are passed into the mixed solution, these acidic gases and sodium phenolate will be complexed, which will affect the purity of phenols. Therefore, in the present invention, carbon dioxide is selected as the acidic gas for separating out phenols, and carbon dioxide can also be captured simultaneously.

[0029] It is understandable that the precipitated phenolic substance is pure phenol, which can be dissolved in an organic solvent (such as acetone, dichloromethane, etc.) to obtain a solution rich in phenolic substances, wherein the phenolic substances can be used for recycling to produce phenolic resins.

[0030] In some embodiments, a mixture containing fiber and sodium phenol salt is taken out from the top of the first reaction tank, and fiber is fished out therefrom and subjected to shaking and water washing to recover the fiber.

[0031] In one embodiment of the present invention, the target molten salt is sodium hydroxide and sodium carbonate, the heating temperature of the target molten salt is 350-500°C, and the electrolysis current density of the target molten salt is 150-250 mA / cm 2 , the electrode materials are all made of graphite materials.

[0032] In this embodiment, the three-dimensional cross-linked structure of the phenolic resin is depolymerized by the catalytic effect of alkali metal cations in the molten salt system, and the hydroxyl group on the phenol can be replaced with the sodium in the sodium salt by using alkaline sodium salt to obtain sodium phenolate. The organic component in the top molten salt is sodium phenolate, which is black. Since sodium phenolate does not dissolve in the molten salt and has a lower density than the molten salt, it floats on the upper liquid surface of the molten salt.

[0033] If the electrolysis parameters exceed the given range, carbon deposition may occur (CO 3 2- +4e - =C+3O 2- ). If the electrolysis parameters are less than the given range, the effect of promoting the decomposition of the resin may not be good. The temperature of the molten salt is controlled at 350-500°C. If the temperature is too high, the organic phenol sodium salt may condense to produce carbon. If the temperature is too low, the resin may not be fully cracked and the conversion of the phenol sodium salt generated by the reaction with the molten salt is limited. The molten salt reaction pool should be controlled to an inert atmosphere. If it is an oxidizing atmosphere, it may oxidize and damage the fiber.

[0034] It should be noted that, in the molten salt system of the present invention, sodium hydroxide is used as the main body, a small amount of sodium carbonate is added to reduce the fusing point of the molten salt, and by controlling the temperature and the molten salt system of the molten salt system, the three-dimensional structure of the phenolic resin can be destroyed, and the phenolic substance is captured in the system in time by the replacement reaction, i.e., the skeleton structure of the phenolic substance is retained, so that the feasibility of the resin decomposition product to reprocess the production resin is increased. However, conventional pyrolysis technology is usually used for the pyrolysis technology of phenolic resin composite materials at present, which not only destroys the three-dimensional structure of the phenolic resin, but also destroys the skeleton structure of the phenolic substance, i.e., further deep cracking into small molecule gas.

[0035] In one embodiment of the present invention, a molten salt pump (not shown in the figure) and a cooling device 5 are connected between the first reaction tank 1 and the mixing device 2. The molten salt pump is used to extract the top molten salt into the mixing device 2, and the cooling device 5 is used to cool the extracted top molten salt.

[0036] In this embodiment, the phenolic substances generated by the initial decomposition of the resin react with the alkaline molten salt to generate sodium phenolate, which floats on the surface of the molten salt, and the top molten salt is extracted by a molten salt pump. When the upper liquid surface is extracted by the molten salt pump, when there is no obvious black substance at the upper liquid surface, it can be said that the extraction is clean. Since the extracted top molten salt has a high temperature, directly dissolving it in water will cause the molten salt to splash out. Therefore, by cooling it to below 100°C, it is possible to prevent water from being added to the extracted top molten salt without causing the molten salt to splash out.

[0037] In one embodiment of the present invention, an atomizer (not shown) is provided in the second reaction tank 3, and the atomizer is used to atomize the mixed solution to obtain an atomized liquid, and the flow ratio of the atomized liquid to the carbon dioxide gas is 3:2 to 5:2.

[0038] In this embodiment, the remaining sodium phenolate is dissolved in water and then atomized, and carbon dioxide gas is introduced simultaneously to maintain a certain flow ratio between the atomized liquid and the carbon dioxide gas. On the one hand, the gas-liquid reaction can be changed to a gas-gas reaction, thereby increasing the contact time between the two. While ensuring that the replacement reaction can fully occur, the intake of carbon dioxide gas and solution is controlled, thereby preventing excessive acidification from generating impurities of aromatic phenolic acid.

[0039] In one embodiment of the present invention, a second recovery device 6 is further included, and the second recovery device 6 is used to sequentially dry, dehydrate and separate impurities from the gas generated by pyrolysis to obtain high-purity hydrogen.

[0040] In this embodiment, the hydrogen concentration in the gas product generated by resin decomposition is higher than 80%, and high-purity hydrogen can be obtained through further separation.

[0041] In one embodiment of the present invention, a density detector (not shown in the figure) is provided in the first reaction tank 1, and the density detector is used to detect the density of the target molten salt during the pyrolysis reaction;

[0042] When the density of the target molten salt exceeds the preset value, the target molten salt is discharged; wherein the preset value is 1.9-2g / cm 3 The discharged target molten salt is used to react with the introduced carbon dioxide gas to produce sodium carbonate.

[0043] In this embodiment, the density of the molten salt under the initial conditions is ≤1.781g / cm 3 During the reaction, NaOH is continuously consumed to generate sodium carbonate. When the density of the molten salt system is detected to be ≥1.95g / cm 3 This means that the molar amount of sodium carbonate is greater than or equal to 40%, and the activity of the molten salt system is not enough to react, so the waste molten salt is discharged. Carbon dioxide gas is further introduced into the discharged waste molten salt (i.e., sodium hydroxide and sodium carbonate), so that it is completely converted into sodium carbonate, so that the waste molten salt can be used to obtain pure sodium carbonate, and carbon dioxide gas can be further captured.

[0044] It should be pointed out that the specific structures of the above-mentioned entity devices are not shown in the embodiments of the present invention, but those skilled in the art can understand that the structures with the functions of the entity devices are within the protection scope of the present invention based on their functions, and the specific structures of the entity devices are not repeated here.

[0045] In addition, if Figure 2 As shown, the embodiment of the present invention also provides a molten salt pyrolysis recovery method of a phenolic resin composite material, comprising:

[0046] Step S1, mixing the phenolic resin composite material to be treated with the target molten salt, so as to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis;

[0047] Step S2, mixing the top molten salt floating on the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution;

[0048] Step S3, introducing carbon dioxide gas into the mixed solution until the pH value is 7-9, and a phenolic substance is precipitated as a black solid;

[0049] Step S4, separating and recovering the fibers in the mixed solution.

[0050] In one embodiment of the present invention, the target molten salt is sodium hydroxide and sodium carbonate, the heating temperature of the target molten salt is 350-500°C, and the electrolysis current density of the target molten salt is 150-250 mA / cm 2 .

[0051] In one embodiment of the present invention, step S2 may specifically include:

[0052] Extract the top molten salt floating on the target molten salt liquid surface after the pyrolysis reaction is completed, until there is no black matter on the upper liquid surface of the target molten salt;

[0053] Cooling the extracted molten salt;

[0054] The cooled molten salt is mixed with water.

[0055] In one embodiment of the present invention, step S3 may specifically include:

[0056] atomizing the mixed solution to obtain an atomized liquid;

[0057] Carbon dioxide gas is introduced into the atomized liquid; wherein the flow ratio of the atomized liquid to the carbon dioxide gas is 3:2 to 5:2.

[0058] In one embodiment of the present invention, the method further includes:

[0059] The gas produced by pyrolysis is dried, dehydrated and impurities separated in sequence to obtain high-purity hydrogen.

[0060] In one embodiment of the present invention, the method further includes:

[0061] Detecting the density of the target molten salt during the pyrolysis reaction;

[0062] When the density of the target molten salt exceeds the preset value, the target molten salt is discharged; wherein the preset value is 1.9-2g / cm 3 ;

[0063] Carbon dioxide gas is introduced into the discharged target molten salt to convert all the target molten salt into sodium carbonate.

[0064] It can be understood that the method embodiment and system embodiment provided by the present invention are based on the same inventive concept and have the same beneficial effects, and the beneficial effects of the method embodiment will not be elaborated herein.

[0065] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical factors in the process, method, article or device including the elements.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A molten salt pyrolysis recovery system for a phenolic resin composite material, characterized in that: A first reaction tank is used to mix the phenolic resin composite material to be treated with a target molten salt to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis; A mixing device, connected to the first reaction tank, for mixing the molten salt floating on the top of the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution; A second reaction tank is connected to the mixing device and is used to introduce carbon dioxide gas into the mixed solution until the pH is 7 to 9 and a phenolic substance is precipitated as a black solid; The first recovery device is used to separate and recover the fibers in the mixed solution.

2. The system according to claim 1, characterized in that The target molten salt is sodium hydroxide and sodium carbonate, the heating temperature of the target molten salt is 350-500°C, and the electrolysis current density of the target molten salt is 150-250 mA / cm 2 .

3. The system according to claim 1, characterized in that A molten salt pump and a cooling device are connected between the first reaction tank and the mixing device. The molten salt pump is used to extract the top molten salt into the mixing device, and the cooling device is used to cool the extracted top molten salt.

4. The system according to claim 1, characterized in that The second reaction tank is provided with an atomizer, and the atomizer is used to atomize the mixed solution to obtain an atomized liquid, and the flow ratio of the atomized liquid to the carbon dioxide gas is 3:2 to 5:

2.

5. The system according to any one of claims 1 to 4, characterized in that: It also includes a second recovery device, which is used to sequentially dry, dehydrate and separate impurities from the gas produced by pyrolysis to obtain high-purity hydrogen; and / or, A density detector is provided in the first reaction tank, and the density detector is used to detect the density of the target molten salt during the pyrolysis reaction; When the density of the target molten salt exceeds a preset value, the target molten salt is discharged; wherein the preset value is 1.9-2 g / cm 3 The discharged target molten salt is used to react with the introduced carbon dioxide gas to generate sodium carbonate.

6. A method for recovering a phenolic resin composite material by molten salt pyrolysis, characterized in that: include: The phenolic resin composite material to be treated is mixed with a target molten salt to pyrolyze the phenolic resin composite material under the external action of heating and electrolysis; Mixing the molten salt floating on the top of the target molten salt liquid surface after the pyrolysis reaction is completed with water to obtain a mixed solution; Passing carbon dioxide gas into the mixed solution until the pH is 7 to 9, and a phenolic substance is precipitated as a black solid; The fibers in the mixed solution are separated and recovered.

7. The method according to claim 6, characterized in that The target molten salt is sodium hydroxide and sodium carbonate, the heating temperature of the target molten salt is 350-500°C, and the electrolysis current density of the target molten salt is 150-250 mA / cm 2 .

8. The method according to claim 6, characterized in that The step of mixing the molten salt and water floating on the top of the target molten salt liquid surface after the pyrolysis reaction is completed comprises: Extracting the top molten salt floating on the target molten salt liquid surface after the pyrolysis reaction is completed, until there is no black matter at the upper liquid surface of the target molten salt; Cooling the extracted molten salt; The cooled molten salt is mixed with water.

9. The method according to claim 6, characterized in that The step of introducing carbon dioxide gas into the mixed solution comprises: Atomizing the mixed solution to obtain an atomized liquid; Carbon dioxide gas is introduced into the atomized liquid; wherein the flow ratio of the atomized liquid to the carbon dioxide gas is 3:2 to 5:

2.

10. The method according to any one of claims 6 to 9, characterized in that: Also includes: The gas produced by pyrolysis is dried, dehydrated and impurities separated in sequence to obtain high-purity hydrogen; and / or, Also includes: detecting the density of the target molten salt during the pyrolysis reaction; When the density of the target molten salt exceeds a preset value, the target molten salt is discharged; wherein the preset value is 1.9-2 g / cm 3 ; Carbon dioxide gas is introduced into the discharged target molten salt to convert all the target molten salt into sodium carbonate.

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