Method for recycling waste glass fiber

Abstract

The application discloses a method for removing impurities from glass fiber solid waste. Specifically, the method comprises the following steps: firstly, mixing recycled glass fiber solid waste powder containing metal Al, Ca, Mg and other impurities with carbon powder to prepare a precursor; then, rapidly heating the precursor by using Joule heat as a heat source; and finally, obtaining high-purity and high-value SiC powder. Relying on the non-equilibrium reaction environment formed by the ultrafast heating rate, the ultrafast cooling rate and the short time holding, the carbon thermal reduction reaction of Al, Ca, Mg and other impurities occurs at a lower temperature, and the gaseous metal is converted and overflowed, so that the efficient removal of impurities is realized; at the same time, the SiO2 in the glass fiber reacts with the carbon powder to generate high-value high-purity SiC products, which can be widely applied in wear-resistant ceramics, new energy, semiconductors and other fields.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection materials technology, solid waste treatment, and chemical synthesis technology, specifically relating to a method for removing impurities and recycling glass fiber solid waste. Background Technology

[0002] Currently, my country's annual output of fiberglass products has reached tens of thousands of tons. Since the service life of fiberglass products is generally 20-25 years, the amount of fiberglass waste is increasing daily, causing a significant environmental burden and high solid waste treatment costs. Fiberglass products have excellent corrosion and chemical resistance, making them difficult to degrade under natural conditions and causing serious environmental pollution. Therefore, the treatment of fiberglass waste is urgently needed.

[0003] Traditional methods for treating fiberglass waste can be categorized into landfill, incineration, chemical treatment, and material recycling. Landfilling requires excessive land area and causes severe soil pollution. Incineration can utilize some heat energy, but its efficiency is low, and it also produces large amounts of toxic gases, causing secondary pollution. Chemical treatment uses chemical methods to decompose waste fiberglass and recycle it into usable oil, gas, etc., but this method is costly and difficult to promote on a large scale.

[0004] Against this backdrop, the transformation of waste glass fiber, whose main component is silicon dioxide, into high-value silicon carbide (SiC) materials has demonstrated significant advantages. SiC is a widely used industrial raw material, applied in various fields such as high-performance ceramic materials, new energy materials, and semiconductor materials. Converting solid waste glass fiber into high-value SiC through economically feasible methods can greatly improve its utilization value, realize the secondary use of glass fiber waste, and achieve comprehensive benefits of environmental protection and economic development. Summary of the Invention

[0005] To address the issues of secondary pollution or high cost and low efficiency in the treatment of glass fiber waste in existing technologies, this invention proposes a method for impurity removal and recycling of glass fiber solid waste. This invention utilizes Joule thermal shock, employing a non-equilibrium reaction environment created by ultra-fast heating, ultra-fast cooling, and short-term heat preservation. This environment induces carbothermic reduction reactions of impurities such as Al, Ca, and Mg at relatively low temperatures, converting them into gaseous metals that then escape, thus achieving efficient impurity removal. Simultaneously, SiO2 in the glass fiber reacts with carbon powder to generate high-value, high-purity SiC products, which can be widely used in wear-resistant ceramics, new energy, semiconductors, and other fields. The various crystalline SiC types prepared by this invention using rapid thermal shock technology possess both high purity and structural stability. Furthermore, the preparation method is simple, significantly reducing material production costs, adapting to the needs of large-scale industrial production, effectively improving production efficiency, and reducing energy consumption.

[0006] Specifically, the objective of this invention is achieved through the following technical solutions: (1) After crushing the glass fiber solid waste, mix it with carbon powder and grind it into powder; (2) Place the powder obtained in step (1) on a heated substrate and subject it to Joule thermal shock at a temperature of 1200~2000℃.

[0007] Furthermore, the molar ratio of glass fiber to carbon powder in the powder of step (1) is 1:1 to 1:15.

[0008] Furthermore, the heating substrate is an open graphite crucible.

[0009] Furthermore, the carbon powder is one or more of graphite, coke, and Ketjen carbon.

[0010] In step 2, the powder is spread evenly on the bottom of an open graphite crucible, and covered with carbon cloth and carbon felt on top.

[0011] Furthermore, the Joule thermal shock time is 5 to 90 seconds.

[0012] Furthermore, the heating and cooling rate of the Joule thermal shock is 100℃ / s to 1000℃ / s.

[0013] Preferably, the thermal shock heating and cooling rate is 100-400℃ / s.

[0014] Furthermore, the grinding method is to grind by hand using a planetary ball mill or an agate mortar.

[0015] Furthermore, the powder has a mesh size of 100 to 2000 mesh.

[0016] In some implementation examples, a method for removing impurities from glass fiber solid waste and recycling and generating high-value-added products includes the following steps: (1) Weigh out solid waste glass fiber and carbon powder, and grind them evenly using a ball mill; the molar ratio of glass fiber to carbon powder is 1:1~1:15; (2) The precursor is placed in an open graphite crucible, and the crucible is placed in a high-temperature thermal shock device under an argon atmosphere. It is then subjected to one-step heat treatment at different temperatures. After cooling, a high-purity SiC product with impurities removed is obtained.

[0017] The mechanism of this invention is as follows: Due to years of service, solid waste glass fiber loses elements such as Na and B, leaving only amorphous SiO2 and amorphous compounds formed by impurities such as Al, Ca, and Mg. By mixing the solid waste glass fiber with carbon powder and using a non-equilibrium reaction system provided by Joule heating through high-temperature thermal shock technology, Al, Ca, and Mg elements can be reduced to gaseous metallic states and released, thereby removing impurities. Simultaneously, the amorphous SiO2 can be transformed into high-value, high-purity SiC through a carbothermal reaction. The reaction process is shown below: CaO + C = Ca↑ + CO↑ Al₂O₃ + C = 2Al↑ + 3CO↑ MgO + C = Mg↑ + CO↑ SiO2 + 3C = SiC + 2CO↑ This invention achieves carbothermic reduction of solid waste glass fiber using a high-temperature thermal shock method. Using solid waste glass fiber as raw material, the invention combines rapid heating and cooling with short-term heat preservation in an open heating device to remove impurities and prepare high-purity SiC. This method features simple process steps, significantly reduces solid waste treatment costs, and produces high-purity SiC products, facilitating large-scale production.

[0018] The silicon carbide recovered by the above method can be used as wear-resistant ceramics, new energy materials or semiconductor materials.

[0019] The advantages of this invention are: This invention, based on the characteristics of SiO2 and impurities such as Al, Ca, and Mg contained in recycled glass fiber from solid waste, innovatively proposes a carbothermic reduction method using Joule heating-based high-temperature thermal shock technology to remove Al, Ca, and Mg impurities while simultaneously converting SiO2 into high-value, high-purity SiC. The glass fiber solid waste impurity removal method provided by this invention is highly efficient and practical, and can improve the purity of the product to 3N. Attached Figure Description

[0020] Figure 1 This is a graph showing the temperature variation during heat treatment using the high-temperature thermal shock technology employed in this invention. Figure 2 Transmission electron microscope (TEM) images and high-resolution TEM images of the high-purity SiC obtained by this invention. Figure 3 This is a distribution diagram of various elements in the high-purity SiC obtained by this invention; Figure 4 The XRD curve of the high-purity SiC obtained by this invention; Figure 5 SEM images of the high-purity SiC obtained in this invention; Figure 6 EDS image of high-purity SiC obtained in this invention; Figure 7 Raman curve of high-purity SiC obtained in this invention; Figure 8 This is an EDS image of overflowing impurities collected during the preparation process of this invention. Detailed Implementation

[0021] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0022] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0023] In this invention, the heating substrate is a conductive substrate used to generate Joule heat under energized conditions, thereby achieving rapid heating of the load material. The conductive substrate can be made of various conductive materials known in the art, as long as it can withstand the instantaneous high temperature during the Joule thermal shock process and has good conductivity and thermal stability.

[0024] Preferably, the heating substrate is a carbon-based substrate. Exemplarily, the carbon-based substrate may be selected from one or more of the following: carbon cloth, carbon felt, carbon paper, graphite crucible, graphite paper, carbon nanotube film, or graphene film. Carbon-based materials possess good high-temperature resistance and chemical stability, making them suitable for high-temperature Joule thermal shock environments.

[0025] As another preferred embodiment, the heating substrate is a metal substrate. Exemplarily, the metal substrate may be selected from one or more of the following: copper mesh, copper foam, copper foil, nickel mesh, nickel foam, stainless steel mesh, molybdenum sheet, or tungsten wire. Among these, copper mesh, due to its excellent three-dimensional network structure, high electrical conductivity, and high thermal conductivity, can serve as an ideal conductive and thermally conductive network, contributing to uniform and efficient Joule heating.

[0026] As another preferred embodiment, the heating substrate is a composite substrate. For example, it uses a metal or carbon material as a framework, and deposits or coats other functional materials on its surface to improve its conductivity, oxidation resistance, or interfacial bonding with the load material. In one specific embodiment, the heating substrate can be a composite conductive network formed by introducing carbon nanotubes (CNTs) based on a copper mesh, utilizing the high electrical and thermal conductivity properties of the copper mesh and carbon nanotubes to achieve efficient Joule heating.

[0027] When some carbon powder residue is present in the recovered silicon carbide, it can be removed by methods such as high-temperature treatment. Preferably, the high-temperature treatment temperature is 800 degrees Celsius.

[0028] The embodiments of the present invention will be further described below with reference to several examples.

[0029] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0030] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] Example 1 (1) Weigh solid waste glass fiber and carbon powder in a molar ratio of 1:1.5, mix them evenly in a mortar and grind them to 100 mesh to obtain the precursor; (2) Weigh 80 mg of the precursor and spread it evenly at the bottom of the cylindrical cavity of the special graphite crucible; (3) Cut carbon cloth and carbon felt of appropriate size, place one layer of carbon cloth and two layers of carbon felt on the top of the powder precursor in a special graphite crucible and press them tightly. (4) The sample was heat-treated using a high-temperature thermal shock device with a heating rate of 100℃ / s, a heat treatment temperature of 1600℃, and a holding time of 60s. After cooling to room temperature, high-purity SiC was obtained.

[0032] Figure 1 The diagram shows the temperature change of the high-temperature thermal shock technology used in this invention. The heating time is 20s, the heat treatment temperature is 1600℃, and the holding time is 60s. Figure 2 The images shown are transmission electron microscope (TEM) images and high-resolution TEM images of the high-purity SiC obtained in this invention, indicating that the material consists of nanoparticles with a particle size of about 100 nm, and the interplanar spacing measurements confirm that it is 6H-SiC. Figure 3 The image shows the elemental distribution of the high-purity SiC obtained by this invention, proving that Si and C elements are uniformly distributed in the sample. Figure 4 The XRD curve of the high-purity SiC obtained in this invention proves that it is a 6H-SiC phase and there are no other impurity phases. Figure 5 The image shows a SEM image of the high-purity SiC obtained in this invention, indicating that the material is composed of nanoparticles. Figure 6 The image shows an EDS image of the high-purity SiC obtained in this invention, indicating that the material is free of other impurities. Figure 7 The Raman curve of the high-purity SiC obtained in this invention confirms that it is a 6H-SiC phase; Figure 8 The image shows an EDS image of overflowing impurities collected during the preparation process of this invention, demonstrating that impurity elements Al, Ca, and Mg overflowed and adhered upon cooling.

[0033] The ICP test results of the sample showed that the purity of SiC was 99.86 at%.

[0034] Example 2 (1) Weigh solid waste glass fiber and carbon powder in a molar ratio of 1:1.5, mix them evenly in a mortar and grind them to 500 mesh to obtain the precursor; (2) Weigh 80 mg of the precursor and spread it evenly at the bottom of the cylindrical cavity of the special graphite crucible; (3) Cut carbon cloth and carbon felt of appropriate size, place one layer of carbon cloth and two layers of carbon felt on the top of the powder precursor in a special graphite crucible and press them tightly. (4) The sample was heat-treated using a high-temperature thermal shock device with a heating rate of 400℃ / s, a heat treatment temperature of 1800℃, and a holding time of 5s. After cooling to room temperature, high-purity 3C-SiC was obtained.

[0035] Characterization of its morphology and structure using scanning electron microscopy, transmission electron microscopy, and XRD revealed that high-purity SiC was successfully prepared. The high-purity SiC prepared in this example is composed of nanoparticles.

[0036] Example 3 (1) Weigh solid waste glass fiber and carbon powder in a 1:1 ratio, mix them evenly in a mortar and grind them to 300 mesh to obtain the precursor; (2) Weigh 80 mg of the precursor and spread it evenly at the bottom of the cylindrical cavity of the special graphite crucible; (3) Cut carbon cloth and carbon felt of appropriate size, place one layer of carbon cloth and two layers of carbon felt on the top of the powder precursor in a special graphite crucible and press them tightly. (4) The sample was heat-treated using a high-temperature thermal shock device with a heating rate of 100℃ / s, a heat treatment temperature of 1800℃, and a holding time of 90s. After cooling to room temperature, high-purity SiC was obtained.

[0037] Characterization of its morphology and structure using scanning electron microscopy, transmission electron microscopy, and XRD revealed that high-purity 3C-SiC was successfully prepared. The high-purity SiC prepared in this example is composed of nanoparticles.

[0038] Example 4 (1) Weigh solid waste glass fiber and carbon powder in a molar ratio of 1:15, mix them evenly in a mortar and grind them to 2000 mesh to obtain the precursor; (2) Weigh 80 mg of the precursor and spread it evenly at the bottom of the cylindrical cavity of the special graphite crucible; (3) Cut carbon cloth and carbon felt of appropriate size, place one layer of carbon cloth and two layers of carbon felt on the top of the powder precursor in a special graphite crucible and press them tightly. (4) The sample was heat-treated using a high-temperature thermal shock device with a heating rate of 100℃ / s, a heat treatment temperature of 2000℃, and a holding time of 5s. After cooling to room temperature, high-purity 3C-SiC was obtained.

[0039] Comparative Example 1 (1) Weigh solid waste glass fiber and carbon powder in a 1:1 molar ratio, and mix them evenly with a mortar and pestle to obtain the precursor; (2) Weigh 80mg of the precursor and insert it into the closed quartz tube; (3) Cut carbon cloth and carbon felt to the appropriate size, place one layer of carbon cloth and two layers of carbon felt on both sides and press them tightly; (4) The sample was heat-treated using a high-temperature thermal shock device with a heating time of 20s, a heat treatment temperature of 1600°C, and a holding time of 300s. After cooling to room temperature, SiC was obtained.

[0040] Characterization of its morphology and structure using scanning electron microscopy, transmission electron microscopy, and XRD revealed that the purity of the prepared SiC was approximately 75%. The low-purity SiC prepared in this example consisted of nanoparticles.

[0041] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A method for removing impurities and recycling glass fiber solid waste, characterized in that, It includes the following steps: (1) After crushing the glass fiber solid waste, mix it with carbon powder and grind it into powder; (2) Place the powder obtained in step (1) on a heated substrate and subject it to Joule thermal shock at a temperature of 1200~2000℃.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of glass fiber to carbon powder is 1:1 to 1:

15.

3. The method according to claim 1, characterized in that, The heating substrate is an open graphite crucible.

4. The method according to claim 1, characterized in that, The carbon powder is one or more of graphite, coke, and Ketjen carbon.

5. The method according to claim 1, characterized in that, The Joule thermal shock time is 5~90s.

6. The method according to claim 1, characterized in that, The heating rate of the Joule thermal shock is 100℃ / s to 1000℃ / s.

7. The method according to claim 1, characterized in that, The grinding method is ball milling or manual grinding.

8. The method according to claim 1, characterized in that, The powder has a mesh size of 100 to 2000.

9. A silicon carbide recovered by the method of claim 1.

10. An application of silicon carbide as described in claim 9 as a wear-resistant ceramic, new energy material, or semiconductor material.

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