A method and apparatus for producing high purity, non-graphitizable, viscose-based carbon fiber felt

Abstract

The application discloses a high-purity and difficult-graphitization viscose-based carbon fiber felt preparation method and equipment, the high-purity and viscose-based carbon fiber felt has impurity element content ratio less than 50ppm, single fiber strength greater than 120Mpa, and graphitization degree less than 85% after 2650 DEG C treatment; the application also provides a high-purity, high-strength and difficult-graphitization viscose-based carbon fiber felt preparation equipment which is composed of a felt inlet air seal section, a heat treatment section, a cooling section, a felt outlet air seal section and a cooling section. The metal impurities in viscose fibers are removed through pickling, the viscose fibers are needled into a felt, impregnated with a catalyst, dried, and then subjected to catalytic dehydration in a micro-negative pressure inert atmosphere, and finally carbonization and graphitization are carried out to obtain the high-purity and high-strength viscose-based carbon fiber felt with low ash content and less tar pollution. The raw materials used in the application are rich, the preparation process is simple, the equipment corrosion is effectively controlled, the high-purity and high-strength product is prepared, and the product production efficiency is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber preparation technology, and in particular to a method and equipment for preparing high-purity, non-graphitized viscose-based carbon fiber felt. Background Technology

[0002] Carbon fiber felt, as a thermal insulation material for photovoltaic and semiconductor single-crystal silicon crystal pulling furnaces and semiconductor silicon carbide crystal growth furnaces, has a crucial impact on single crystal growth. With the development of photovoltaic N-type single crystal technology and the rise of the semiconductor industry, especially for silicon carbide crystal growth furnaces with higher operating temperatures and atmosphere purity requirements, higher demands are placed on carbon fiber insulation materials. In addition to high energy efficiency, they also need lower impurity (metal ions, even fiber clusters) emission, better oxidation resistance, and better material strength. This requires carbon fiber insulation materials to have higher purity and higher fiber strength.

[0003] Currently, domestic carbon fiber felt mainly uses polyacrylonitrile carbon fiber and viscose carbon fiber, which generally have high impurity content. In particular, the alkali metal impurity content in viscose carbon fiber can reach 1000-3000ppm, which not only has poor oxidation resistance, but also makes it easy for a large number of impurities to volatilize and escape into the pollutant material in a high-temperature atmosphere.

[0004] To produce high-purity carbon fiber felt, existing technologies generally involve secondary purification through subsequent chemical processing. For example, Chinese patent application number 202011297063.X discloses a method for preparing high-purity carbon fiber rigid felt, which uses purified gas and performs three-step purification at high temperature. Although the purification purpose is achieved, the defects left by the escape of impurities cannot be self-repaired, resulting in more surface defects in the obtained high-purity carbon fiber rigid felt, making it prone to flaking.

[0005] It is well known that if the raw materials for carbon fiber production can be controlled from the outset, high-purity carbon fiber felt and carbon fiber composite insulation materials with fewer defects and superior performance can be obtained. Current technical solutions are mainly limited to post-purification processes due to cost constraints.

[0006] Therefore, how to obtain a viscose-based carbon fiber felt with high initial purity and few defects is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method and equipment for preparing high-purity, high-strength, and graphitizable viscose-based carbon fiber felt.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing high-purity, high-strength, and graphitization-resistant viscose-based carbon fiber felt, wherein the impurity element content of the high-purity, high-strength viscose-based carbon fiber felt is less than 50 ppm and the single fiber strength is greater than 120 MPa.

[0010] Its preparation method includes the following steps:

[0011] S1. Viscose fibers are prepared by pickling, washing, and drying to remove metal ions and produce viscose fibers with an ash content of less than 100 ppm.

[0012] S2, demetallized viscose fiber needle-punched into felt;

[0013] S3. Mix organic carboxylic acid, crosslinking catalyst, ammonium sulfate, ammonium chloride, and nonionic surfactant in a mass percentage ratio of 2-6:0.1-1:0.1-1:0.1-1:0.01-0.02, add deionized water to prepare 100 parts, then add organic base to adjust the pH to 5-7 to obtain a catalyst with an effective concentration of 3-10%; impregnate viscose fiber felt with the catalyst for 20-120 min, remove and roll dry until the water-felt ratio is <0.8, repeat the impregnation-rolling process twice, and send it into a drying oven to dry at <140℃ until the water content is less than 5%;

[0014] S4. The impregnated and dried viscose fiber felt is sent into a special catalytic dehydration furnace. In a slightly negative pressure inert atmosphere with circulating air at -20 to -100 Pa, it is heated from room temperature to 200-210℃ in 20 min, to 220-230℃ in 20-60 min, to 230-240℃ in 15-60 min, to 250-260℃ in 15-60 min, and to 260-300℃ in 10-60 min to remove hydroxyl groups from the structured water.

[0015] S5. After cooling, viscose fiber catalytic dehydration felt is obtained;

[0016] S6. The viscose fiber catalytic dehydration felt is fed into a carbonization-graphitization furnace and heated to 800-1200℃ for 30-90 minutes. It is kept at the same temperature for 10-30 minutes, then heated to 1600-2400℃ for 30-60 minutes and kept at the same temperature for 3-10 minutes to remove non-carbon elements. The felt is then removed from the furnace and cooled to obtain high-purity, high-strength viscose-based carbon fiber graphite felt.

[0017] Preferably, in order to improve the pickling effect, the pickling in S1 uses 0.5-5% hydrochloric acid, acetic acid, aminosulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, citric acid and mixtures thereof.

[0018] Preferably, in order to effectively improve the degree of cross-linking of cellulose molecules, the organic carboxylic acid in S3 is a carboxylic acid with a boiling point >140℃, preferably citric acid or maleic anhydride; the cross-linking catalyst in S3 is p-toluenesulfonic acid, terephthalic acid, aminosulfonic acid, etc.

[0019] Preferably, in order to effectively promote catalyst dispersion and wetting, the nonionic surfactant in S3 is preferably a fluorocarbon surfactant, a fatty alcohol polyoxyethylene ether, a fatty amine polyoxyethylene ether, or a mixture of any two of the above.

[0020] Preferably, in order to adjust the pH value and avoid equipment corrosion, triethanolamine is used in particular, which can also slowly release sulfate and chloride ions at high temperature, effectively improve the high-temperature catalytic dehydration efficiency, increase the carbon yield of the product, and reduce microscopic defects in the product. The organic base in S3 is guanidine, guanidine carbonate, triethanolamine, triethylenetetramine, diethylenetriamine, ethylenediamine, or a mixture of any two of the above.

[0021] This invention also proposes a high-purity, high-strength, and graphitized viscose-based carbon fiber felt preparation equipment, which consists of a felt inlet gas seal section, a heat treatment section, a cooling section, a felt outlet gas seal section, and a cooling section. The felt inlet gas seal section is connected to the heat treatment section, which consists of 5-8 sections. The heat treatment section at the very end is connected to the cooling section, the cooling section is connected to the felt outlet gas seal section, and the felt outlet gas seal section is connected to the cooling section.

[0022] Preferably, to ensure the effectiveness of heat treatment, the heat treatment section consists of a muffle furnace with heating and transmission, a side coke discharge tank, a cyclone separator, a silicon carbide ceramic circulating fan, and a waste exhaust fan. The bottom of the muffle furnace with heating and transmission is connected to the side coke discharge tank, the top of the side coke discharge tank is connected to the waste exhaust fan and the cyclone separator, the cyclone separator is connected to the silicon carbide ceramic circulating fan, and the silicon carbide ceramic circulating fan is connected to the top of the muffle furnace with heating and transmission.

[0023] Preferably, in order to facilitate rapid cooling, the cooling section consists of a muffle furnace body without heating rods.

[0024] Preferably, in order to ensure the performance of the furnace body, the length of the muffle furnace body with heating and transmission is 2-5m and the width is 2-4m. The outer part is a metal cavity, the inner sides and bottom are refractory brick / cotton insulation layer, the top is a ceramic top plate, and the heating rod and transmission roller are made of ceramic material and penetrate through the inside of the furnace body cavity.

[0025] The beneficial effects of this invention are:

[0026] 1. Metal ions are directly removed from the raw materials to avoid structural defects caused by metal ions during the carbon fiber felt preparation process;

[0027] 2. The catalyst uses an organic base to adjust the pH value, which greatly reduces the corrosion of equipment during the product manufacturing process;

[0028] 3. The slightly negative pressure circulating air atmosphere ensures the rapid progress of the reaction process, especially the timely removal of tar, which greatly improves product strength and production efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a dedicated catalytic dehydration furnace for the preparation of high-purity, high-strength, and difficult-to-graphitize viscose-based carbon fiber felt proposed in this invention;

[0030] Figure 2 This is a structural diagram of the heat treatment section of a preparation equipment for high-purity, high-strength, and difficult-to-graphitize viscose-based carbon fiber felt proposed in this invention.

[0031] In the diagram: 1. Felt inlet gas seal section, 2. Heat treatment section, 2-1. Muffle furnace body with heating and transmission, 2-2. Side coke discharge tank, 2-3. Cyclone separator tower, 2-4. Silicon carbide ceramic circulating fan, 2-5. Waste exhaust fan, 3. Cooling section, 4. Felt outlet gas seal section, 5. Cooling section. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] This application provides a method for preparing high-purity, high-strength, and graphitizable viscose-based carbon fiber felt. The viscose-based carbon fiber felt obtained has an impurity element (ash content) content of less than 50 ppm and a single fiber strength of greater than 120 MPa.

[0034] Its preparation method includes the following steps:

[0035] S1. Viscose fibers are acid-washed, water-washed, and dried to prepare demetallized viscose fibers with an ash content of less than 100 ppm.

[0036] S2, demetallized viscose fiber needle-punched into felt;

[0037] S3. Mix organic carboxylic acid, crosslinking catalyst, ammonium sulfate, ammonium chloride, and nonionic surfactant in a mass percentage ratio of 2-6:0.1-1:0.1-1:0.1-1:0.01-0.02, add deionized water to prepare 100 parts, then add organic base to adjust the pH to 5-7 to obtain a catalyst with an effective concentration of 3-10%; impregnate viscose fiber felt with the catalyst for 20-120 min, remove and roll dry until the water-felt ratio is <0.8, repeat the impregnation-rolling process twice, and send it into a drying oven to dry at less than 140℃ until the water content is less than 5%;

[0038] S4. The impregnated and dried viscose fiber felt is sent into a special catalytic dehydration furnace and heated from room temperature to 200-210℃ in a slightly negative pressure inert atmosphere circulating air at -2 to -100Pa for 20 minutes, to 220-230℃ for 20-60 minutes, to 230-240℃ for 15-60 minutes, to 250-260℃ for 15-60 minutes, and to 260-300℃ for 10-60 minutes.

[0039] S5. After cooling, viscose fiber catalytic dehydration felt is obtained;

[0040] S6. The viscose fiber catalytic dehydration felt is fed into a carbonization-graphitization furnace and heated to 800-1200℃ for 30-90 minutes, held at that temperature for 10-30 minutes, and then heated to 1600-2400℃ for 30-60 minutes, held at that temperature for 3-10 minutes to remove non-carbon elements (removing tar, low-molecular-weight hydrocarbons, water, etc.). After cooling, high-purity, high-strength viscose-based carbon fiber graphite felt is obtained. High-temperature carbonization can be stably carried out by heating to 800-1200℃ and holding at that temperature, which is the process of further transforming the structure of carbon fiber into a disordered graphite structure or a graphite structure. The entire process will remove elements other than carbon, producing carbon fibers with a carbon content of more than 90%. Furthermore, by heating to 1600-2400℃, physical changes allow the hexagonal carbon atom planar network layer stacking structure to develop perfectly, transforming into graphitic carbon with a three-dimensional regular and ordered graphite structure. At the same time, rapid heating can effectively stabilize costs.

[0041] In this invention, the pickling in S1 uses 0.5-5% hydrochloric acid, acetic acid, aminosulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, citric acid, and a mixture of any two of the above. The use of the above materials or a mixture of any two of the above materials can fully ensure the controllability of the acid mass fraction used in pickling, and can fully remove oxide scale and rust.

[0042] In this invention, the organic carboxylic acid in S3 is preferably citric acid or maleic anhydride with a boiling point >140°C. By selecting citric acid and maleic anhydride, which have high boiling points, a cross-linked structure can be formed on the surface of cellulose fibers under the catalytic action of a cross-linking catalyst.

[0043] In this invention, the nonionic surfactant in S3 is preferably a fluorocarbon surfactant, a fatty alcohol polyoxyethylene ether, a fatty amine polyoxyethylene ether, or a mixture of any two of the above. The use of the above materials can effectively promote the penetration of inorganic catalysts. At the same time, the materials themselves have cross-linking properties and can undergo cross-linking reactions with viscose fibers to promote curing. Furthermore, the materials have good water solubility, which facilitates rapid dissolution and improves the uniformity of mixing.

[0044] In this invention, the organic base in S3 is guanidine, guanidine carbonate, triethanolamine, triethylenetetramine, diethylenetriamine, ethylenediamine, or a mixture of any two of the above. The above materials themselves, as well as after combining with ammonium salts, have high boiling points and high decomposition temperatures, which can further protect metal materials from corrosion in high-temperature environments.

[0045] Reference Figure 1 This invention also proposes a high-purity, high-strength, and graphitized viscose-based carbon fiber felt preparation equipment, which consists of a felt inlet gas seal section 1, a heat treatment section 2, a cooling section 3, a felt outlet gas seal section 4, and a cooling section 5. The felt inlet gas seal section 1 is connected to the heat treatment section 2, which has 5-8 segments to facilitate data determination based on actual conditions, ensuring efficient and high-quality heat treatment. The heat treatment section 2, located at the very end, is connected to the cooling section 3 for cooling treatment. The cooling section 3 is connected to the felt outlet gas seal section 4, which is also connected to the cooling section 5 for rapid cooling. This equipment enables streamlined operation, improving work efficiency and quality.

[0046] Reference Figure 2 The heat treatment section 2 consists of a muffle furnace body 2-1 with heating and transmission, a side coke discharge tank 2-2, a cyclone separator 2-3, a silicon carbide ceramic circulating fan 2-4, and a waste exhaust fan 2-5. The bottom of the muffle furnace body 2-1 with heating and transmission is connected to the side coke discharge tank 2-2 for rapid coke discharge. The top of the side coke discharge tank 2-2 is connected to both the waste exhaust fan 2-5 and the cyclone separator 2-3, enabling rapid extraction of waste gas. The waste gas is then separated by the cyclone separator 2-3 to remove impurities and harmful substances. The cyclone separator 2-3 is connected to the silicon carbide ceramic circulating fan 2-4 to facilitate directional airflow. The silicon carbide ceramic circulating fan 2-4 is connected to the top of the muffle furnace body 2-1 with heating and transmission, which can effectively realize the hot air circulation operation. It can allow the hot air after removing impurities and harmful substances to re-enter the muffle furnace body 2-1, realize the recycling of hot air, and help maintain the temperature inside the muffle furnace body 2-1.

[0047] In this invention, the cooling section 3 is composed of a muffle furnace body without heating rods, which facilitates rapid cooling of the product.

[0048] In this invention, the muffle furnace body 2-1 with heating and transmission is 2-5m long and 2-4m wide. The exterior is a metal cavity, the interior sides and bottom are refractory brick / cotton insulation layers, and the top is a ceramic top plate. The heating rod and transmission roller are made of ceramic material and penetrate through the furnace body cavity, which can well ensure the performance of the furnace body, ensure its refractory and insulation performance, and ensure heating efficiency and quality. Example 1

[0049] A method for preparing high-purity, high-strength, and graphitizable viscose-based carbon fiber felt.

[0050] The preparation steps are as follows:

[0051] Commercially available 2.5D viscose fiber is soaked in 1% hydrochloric acid for 10 hours, then rinsed with deionized water until the chlorine content is less than 0.01 mol / L, and dried at 120℃ to obtain demetallized viscose fiber with an ash content of 59 ppm.

[0052] Metal ion-free viscose fiber needle-punched into felt;

[0053] Citric acid, p-toluenesulfonic acid, ammonium sulfate, ammonium chloride, and AC-1210 were mixed in a mass percentage ratio of 2:0.1:0.6:0.2:0.01, and deionized water was added to prepare 100 parts. Triethanolamine was then added to adjust the pH to 5, resulting in a catalyst with an effective concentration of 3.1%. The catalyst was impregnated with viscose fiber felt for 60 minutes, then removed and rolled dry to a water-to-felt ratio of 0.6. This impregnation-rolling process was repeated twice, and the mixture was then placed in a drying oven and dried at 130°C until the water content reached 4.2%.

[0054] The impregnated and dried viscose fiber felt was fed into a dedicated catalytic dehydration furnace and heated from room temperature to 200°C for 20 min, to 230°C for 40 min, to 240°C for 20 min, to 260°C for 20 min, and to 280°C for 20 min in a circulating nitrogen atmosphere under a slight negative pressure of -60 Pa, to remove structural water (hydroxyl groups). After cooling, viscose fiber catalytic dehydration felt was obtained with a product yield of 51%.

[0055] Viscose fiber catalytic dehydration felt was fed into a carbonization-graphitization furnace, heated to 800℃ for 60 min, held at that temperature for 20 min, heated to 2200℃ for 40 min, and held at that temperature for 50 min to remove non-carbon elements (removing tar, low molecular weight hydrocarbons, water, etc.). After cooling, viscose-based carbon fiber graphite felt with ash content of 28 ppm and monofilament tensile strength of 135 MPa was obtained, with a product yield of 53%. Example 2

[0056] A method for preparing high-purity, high-strength, and graphitizable viscose-based carbon fiber felt.

[0057] The preparation steps are as follows:

[0058] Commercially available 1.5D viscose fiber is soaked in 1% acetic acid and 0.25% hydrochloric acid for 48 hours, then repeatedly rinsed with deionized water until the chlorine content is lower than 0.01 mol / L of washing water, and dried at 120℃ to obtain viscose fiber with demetallized ions and ash content of 35 ppm.

[0059] Metal ion-free viscose fiber needle-punched into felt;

[0060] Maleic anhydride, terephthalic acid, ammonium sulfate, ammonium chloride, and OP-10 were mixed in a mass percentage ratio of 4:0.3:0.2:0.2:0.01, and deionized water was added to prepare 100 parts. Guanidine was then added to adjust the pH value to 6.5 to obtain a catalyst with an effective concentration of 5.5%. The catalyst was impregnated with viscose fiber felt for 100 min, taken out and squeezed dry to a water-felt ratio of 0.6. The impregnation-squeezing process was repeated twice, and then the mixture was sent to a drying oven and dried at 130℃ to a water content of 4.5%.

[0061] The impregnated and dried viscose fiber felt was fed into a dedicated catalytic dehydration furnace. Under a -80Pa slightly negative pressure nitrogen atmosphere with circulating air, the temperature was increased from room temperature to 200℃ in 20 min, to 230℃ in 60 min, to 240℃ in 40 min, to 260℃ in 30 min, and to 270℃ in 20 min to remove structural water (hydroxyl groups). After cooling, viscose fiber catalytic dehydration felt was obtained with a product yield of 52%.

[0062] The viscose fiber catalytic dehydration felt was fed into a carbonization-graphitization furnace, heated to 1000℃ for 90 min, held at that temperature for 20 min, heated to 2350℃ for 40 min, and held at that temperature for 30 min to remove non-carbon elements (removing tar, low molecular weight hydrocarbons, water, etc.). After cooling, viscose-based carbon fiber graphite felt with ash content of 25 ppm and monofilament tensile strength of 205 MPa was obtained, with a product yield of 57%. Example 3

[0063] A method for preparing high-purity, high-strength, and graphitizable viscose-based carbon fiber felt.

[0064] The preparation steps are as follows:

[0065] Commercially available 3.3D viscose fiber is soaked in 1% citric acid and 2% aminosulfonic acid for 48 hours, then repeatedly rinsed with deionized water and dried at 120℃ to obtain demetallized viscose fiber with 80ppm ash content.

[0066] Metal ion-free viscose fiber needle-punched into felt;

[0067] Maleic anhydride, aminosulfonic acid, ammonium sulfate, ammonium chloride, and OP-10 were mixed in a mass ratio of 3:1:0.25:0.25:0.01, and deionized water was added to prepare 100 parts. Guanidine was then added to adjust the pH value to 5.5 to obtain a catalyst with an effective concentration of 5%. The catalyst was impregnated with viscose fiber felt for 100 minutes, taken out and squeezed dry to a water-felt ratio of 0.6. The impregnation-squeezing process was repeated twice, and the mixture was sent to a drying oven and dried at 130°C to a water content of 4.5%.

[0068] The impregnated and dried viscose fiber felt was fed into a dedicated catalytic dehydration furnace and heated from room temperature to 210°C for 20 min, then to 230°C for 20 min, then to 240°C for 60 min, then to 260°C for 30 min, and finally to 300°C for 20 min in a -80Pa slightly negative pressure nitrogen atmosphere with circulating air, to remove structural water (hydroxyl groups). After cooling, viscose fiber catalytic dehydration felt was obtained with a product yield of 48%.

[0069] The viscose fiber catalytic dehydration felt was fed into a carbonization-graphitization furnace, heated to 1000℃ for 90 min, held at that temperature for 20 min, heated to 2350℃ for 40 min, and held at that temperature for 30 min to remove non-carbon elements (removing tar, low molecular weight hydrocarbons, water, etc.). After cooling, viscose-based carbon fiber graphite felt with 35 ppm ash and 185 MPa monofilament tensile strength was obtained, with a product yield of 58%.

[0070] The product manufacturing quality is determined by the following methods: Ash content test method: GB / T 1429-2009 Determination of Ash Content in Carbon Materials; Monofilament Tensile Strength Test Method: GB / T 31290-2014 Determination of Tensile Properties of Carbon Fiber Monofilaments.

[0071] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity, difficult-to-graphitize viscose-based carbon fiber felt, characterized in that, The high-purity, non-graphitized viscose-based carbon fiber felt has an impurity element content of less than 50 ppm and a single fiber strength of greater than 120 MPa. Its preparation method includes the following steps: S1. Viscose fibers are prepared by pickling, washing, and drying to remove metal ions and produce viscose fibers with an ash content of less than 100 ppm. S2, demetallized viscose fiber needle-punched into felt; S3. Add organic carboxylic acids, cross-linking catalyst, ammonium sulfate, ammonium chloride, and nonionic surfactant in a mass percentage of 2-6: Mix 0.1-1:0.1-1:0.1-1:0.01-0.02, add deionized water to prepare 100 parts, then add organic base to adjust the pH to 5-7 to obtain a catalyst with an effective concentration of 3-10%; impregnate viscose fiber felt with the catalyst for 20-120 minutes, remove and roll dry until the water-felt ratio is <0.8, repeat the impregnation-rolling process twice, and send it to a drying oven to dry at <140℃ until the water content is less than 5%; The organic carboxylic acid is a carboxylic acid with a boiling point >140℃; the crosslinking catalyst is p-toluenesulfonic acid, terephthalic acid, or aminosulfonic acid; the nonionic surfactant is a fluorocarbon surfactant, fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, or a mixture thereof; the organic base is guanidine, guanidine carbonate, triethanolamine, triethylenetetramine, diethylenetriamine, ethylenediamine, or a mixture of any two of the above. S4. The impregnated and dried viscose fiber felt is sent into a special catalytic dehydration furnace and heated in a slightly negative pressure inert atmosphere of -20 to -100Pa for 20 minutes from room temperature to 200-210℃, 20-60 minutes to 220-230℃, 15-60 minutes to 230-240℃, 15-60 minutes to 250-260℃, and 10-60 minutes to 260-300℃. S5. After cooling, viscose fiber catalytic dehydration felt is obtained; S6. The viscose fiber catalytic dehydration felt is fed into a carbonization-graphitization furnace and heated to 800-1200℃ for 30-90 minutes, held at that temperature for 10-30 minutes, and then heated to 1600-2400℃ for 30-60 minutes, held at that temperature for 3-10 minutes to remove non-carbon elements. The felt is then removed from the furnace and cooled to obtain high-purity, difficult-to-graphitize viscose-based carbon fiber felt.

2. The method for preparing high-purity, non-graphitizable viscose-based carbon fiber felt according to claim 1, characterized in that: The pickling in S1 uses 0.5-5% hydrochloric acid, acetic acid, aminosulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, citric acid, or a mixture of any two of the above.

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