A kind of high purity carbon powder and preparation method thereof

Abstract

The present invention discloses a high-purity carbon powder and a preparation method thereof. The preparation method comprises the following steps: melting sugar crystals to obtain a sugar melt, passing the sugar melt through an atomizing nozzle, atomizing the sugar melt into droplets by an atomizing gas medium, and carbonizing the droplets into carbon powder under high temperature and high pressure in a protective atmosphere. According to the technical scheme of the present invention, when the nozzle aperture is constant, the carbon powder particle size decreases with the increase of the atomizing gas pressure. When the atomizing gas pressure is constant, the carbon powder particle size increases with the increase of the nozzle aperture. Therefore, the carbon powder particle size and its distribution can be controlled by adjusting the nozzle aperture and the atomizing gas pressure according to actual needs. The method of the present invention has a simple process, few operating steps, and the obtained carbon powder has high purity, and the carbon powder particle size and its distribution are controllable.

Description

Technical Field

[0001] The invention relates to high-purity carbon powder and a preparation method thereof, belonging to the technical field of high-purity carbon powder preparation. Background Art

[0002] Carbon is an important non-metallic element. Carbon materials have high temperature resistance, good electrical and thermal conductivity, thermal shock resistance and chemical stability. They are an important non-metallic material and are widely used in machinery, atomic energy, aerospace, semiconductors, new energy, automotive industry and other fields. The continuous development of science and technology in recent years has put forward newer and higher requirements for the development, production and application of carbon materials, especially high-purity carbon materials, and their purity usually needs to reach more than 99.999%.

[0003] At present, carbon materials are mainly purified by wet purification and dry purification processes, utilizing their high chemical stability, high melting point and boiling point, and the fact that they do not react with various strong acids, alkalis, oxidants and reducing agents, and various organic and inorganic solvents under normal conditions.

[0004] The wet purification method mainly uses the impurities in the carbon material to react with strong acids and strong bases at high temperatures to generate soluble salts, which are then removed by washing with water to improve the purity of the carbon material. This method uses a large amount of strong acids and strong bases, which easily causes water pollution and is not friendly to the environment. It has limited effect on improving the purity of the carbon material and is difficult to improve to above 4N.

[0005] Dry purification methods mainly include chlorination roasting method and high temperature method. The high temperature method uses the melting and boiling points of carbon materials to be much higher than the melting and boiling points of its impurities, and heats the carbon materials to above 2700°C, so that its impurities are first gasified and removed, thereby achieving the purpose of improving the purity of the carbon materials. This method is suitable for the purification of fine carbon powder with a purity greater than 99%. Since this method needs to be heated to above 2700°C, it consumes a lot of energy and has high costs. The chlorination roasting method has high requirements for equipment operation due to the toxicity and strong corrosiveness of chlorine gas, strict sealing is required, and the tail gas must be properly handled, so its promotion and application are limited to a certain extent.

[0006] In addition to the high-purity carbon materials obtained by purifying natural graphite powder as the raw material, people often use high-carbon-content tar, asphalt and other raw materials to heat and decompose to obtain tar and asphalt carbon and then make artificial graphite materials. However, due to the purity of the raw materials, the purity of the obtained carbon materials is generally not high.

[0007] In addition, the designer of Chinese patent CN104176725B proposed that water-soluble sugar substances are used as carbon source materials, acrylamide and N, N'-methylenebisacrylamide are used as gel materials to prepare aqueous solutions, and then gel solidification is performed to form a gel body, and then low-temperature pyrolysis pre-carbonization treatment and high-temperature carbonization and / or graphitization treatment are performed to obtain carbon and / or graphite materials. This method has a wide range of raw material sources, a simple and convenient process, and no environmental pollution problems. However, this method requires the use of ammonium persulfate or ammonium sulfite during the gel curing process, so that the sulfur content in the prepared carbon material is very high, and the purity can only reach 99.99%, which cannot reach more than 99.999%, and the prepared carbon material is a block material, which will further cause pollution after being crushed into powder, and its purity will be further reduced.

[0008] In Chinese patent CN110510597A, the designer proposed to prepare a sucrose solution using sucrose as a carbon source material, separate metal ion impurities such as Fe, Al, and Ca using ion exchange resin, obtain a pre-purified sucrose solution, and then dry to obtain sucrose crystals. The sucrose is ground into powder, and under the protection of inert gas, low-temperature stabilization treatment is carried out in a high-temperature energy-saving tubular furnace, and high-temperature carbonization purification treatment is carried out in a high-temperature carbon tube furnace. By controlling the temperature, reaction time, and pressure range, the impurities are gasified or gasified and decomposed, thereby obtaining a high-purity carbon material with a purity of 99.9995 to 99.9999%. This method has a wide range of raw materials, low cost, and is environmentally friendly. The process is simple and high-purity carbon materials can be obtained without complex chemical reactions. However, when sugar substances are heated and decomposed under normal pressure, a large amount of water and by-products such as carbon dioxide will be produced, which will cause serious uncontrollable foaming and great volume expansion, which will bring great inconvenience to the operation. At the same time, the production of by-products such as carbon dioxide makes the carbon yield very low, usually not exceeding 15%. At the same time, this method requires grinding the sugar crystals, which inevitably brings pollution, is difficult to reach above 6N, and the particle size of the carbon powder is difficult to control. Summary of the invention

[0009] In view of the above problems existing in the prior art, the first object of the present invention is to provide a method for preparing high-purity carbon powder.

[0010] The second object of the present invention is to provide a high-purity carbon powder prepared by the above preparation method. The purity of the pure carbon powder prepared by the preparation method of the present invention can reach above 6N, and the particle size is controllable.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is:

[0012] The invention discloses a method for preparing high-purity carbon powder, which comprises the steps of melting sugar crystals to obtain a sugar melt, passing the sugar melt through an atomizing nozzle, atomizing the sugar melt into droplets by an atomizing gas medium, and carbonizing the droplets into carbon powder under high temperature and high pressure in a protective atmosphere.

[0013] In a preferred embodiment, the sugar in the sugar crystals is selected from at least one of sucrose, glucose, fructose and maltose.

[0014] In a preferred embodiment, the sugar crystals are obtained by dissolving sugar in ultrapure water to obtain a sugar solution, passing the sugar solution through an ion exchange resin to obtain a purified sugar solution, and evaporating and crystallizing the purified sugar solution to obtain sugar crystals.

[0015] In the present invention, the sugar solution is purified by resin to remove iron, calcium, sodium, magnesium, aluminum, nickel, copper, chlorine, sulfate and other ions in the sugar solution, and then evaporated and crystallized to obtain ultra-high purity sugar crystals.

[0016] In a preferred solution, the molten sugar is placed in a tundish located above the atomizing nozzle, and the molten sugar flows out from the leak at the bottom of the tundish and passes through the atomizing nozzle.

[0017] In a preferred solution, the aperture of the atomizing nozzle is 0.3 to 2 mm, preferably 0.5 to 1 mm.

[0018] In the present invention, the aperture of the atomizing nozzle needs to be effectively controlled. If it is controlled within the above range, micron-sized carbon powder can be obtained in a controllable and efficient manner. If the aperture of the atomizing nozzle is too large, it is difficult to atomize into small droplets, and ultimately no carbon powder can be obtained.

[0019] In a preferred embodiment, the atomizing gas medium is selected from argon and / or nitrogen.

[0020] In a preferred solution, the pressure of the atomizing gas medium is 0.5-5 MPa. The inventors have found that if the pressure of the atomizing gas medium is controlled within the above range, the liquid can be atomized into small droplets stably and fully, while if the pressure is too low, the liquid cannot be atomized.

[0021] In a preferred embodiment, the protective atmosphere is selected from argon and / or nitrogen.

[0022] In a preferred embodiment, the carbonization temperature is 1000-2000° C., preferably 1200-1500° C., and the pressure is 10-50 MPa, preferably 15-20 MPa.

[0023] The inventors have found that by controlling the carbonization temperature and pressure within the above range, sufficient carbonization can be achieved. If the carbonization temperature is too low, it will lead to insufficient carbonization. If the pressure is too low, carbon dioxide will be produced during the carbonization process, resulting in a low carbon yield.

[0024] The present invention also provides a high-purity carbon powder prepared by the above preparation method, wherein the purity of the high-purity carbon powder is 6N and the particle size is 10-200 μm.

[0025] Beneficial Effects

[0026] The present invention first purifies sugar substances through resin, evaporates and crystallizes them, and then obtains ultra-high purity sugar crystals without impurity ions. The ultra-high purity sugar crystals are melted and atomized into fine droplets, and then carbonized into carbon powder at high temperature and high pressure, and the purity is as high as 6N.

[0027] According to the technical solution of the present invention, when the nozzle aperture is constant, the carbon powder particle size decreases as the atomizing gas pressure increases. When the atomizing gas pressure is constant, the carbon powder particle size increases as the nozzle aperture increases. Therefore, the carbon powder particle size and its distribution can be controlled by adjusting the nozzle aperture and the atomizing gas pressure according to actual needs. The method of the present invention has a simple process, a few operating steps, and the obtained carbon powder has high purity, and the carbon powder particle size and its distribution are controllable. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below by way of examples, which are not intended to further limit the content of the present invention. It should be understood by those skilled in the art that equivalent replacements made to the technical features of the present invention, or corresponding improvements, still fall within the scope of protection of the present invention.

[0029] Example 1

[0030] Sucrose is dissolved in ultrapure water to obtain a sucrose solution. The sucrose solution is passed through an ion exchange column, and the iron, calcium, sodium, magnesium, copper, aluminum, chlorine, sulfate and other ions in the solution are removed by using an ion exchange resin. The solution is then placed in an oven, heated to 105°C, part of the water in the solution is evaporated, and when sucrose crystals are precipitated, they are cooled to room temperature for crystallization, filtered, and ultra-high-purity sucrose crystals are obtained. Ultra-high-purity sucrose crystals are melted at 200°C and injected into a tundish. The sucrose melt flows out from the bottom of the tundish, and when it passes through a nozzle with an aperture of 0.5mm, it meets a high-speed high-purity argon gas flow of 0.5MPa, and is atomized into fine droplets in a carbonization chamber filled with high-purity argon gas. The atomized droplets are carbonized into carbon powder at 1200°C and 15MPa. After analysis by a glow discharge mass spectrometer GDMS, the purity of the carbon powder reaches 99.99993%. The carbon powder particle size D50 was found to be 85.8 μm by laser particle size analyzer.

[0031] Comparative Example 1

[0032] The other conditions were the same as those in Example 1, except that the sucrose was not purified by resin. The purity of the obtained carbon powder was only 99.994% after analysis by glow discharge mass spectrometer GDMS.

[0033] Comparative Example 2

[0034] The other conditions were the same as those in Example 1, except that a nozzle with an aperture of 3 mm was used for atomization. As a result, no carbon powder was obtained, but carbon particles with a diameter of more than 0.5 mm were obtained.

[0035] Comparative Example 3

[0036] The other conditions were the same as those in Example 1, except that the carbonization temperature was 800° C. The mass loss of the obtained powder was about 2% after being kept at 1000° C. for 2 h in an inert environment, indicating that the powder was not completely carbonized.

[0037] Example 2

[0038] Glucose is dissolved in ultrapure water to obtain a glucose solution. The glucose solution is passed through an ion exchange column, and the iron, calcium, sodium, magnesium, copper, aluminum, chlorine, sulfate and other ions in the solution are removed by using an ion exchange resin. The solution is then placed in an oven, heated to 105°C, part of the water in the solution is evaporated, and when glucose crystals are precipitated, they are cooled to room temperature for crystallization, filtered, and ultra-high-purity glucose crystals are obtained. The ultra-high-purity glucose crystals are melted at 180°C and injected into a tundish. The glucose melt flows out from the leak at the bottom of the tundish, and meets a 3Mpa high-speed high-purity nitrogen flow when passing through a nozzle with an aperture of 1mm. It is atomized into fine droplets in a carbonization chamber filled with high-purity nitrogen, and the atomized droplets are carbonized into carbon powder at 1500°C and 20MPa. After analysis by a glow discharge mass spectrometer GDMS, the purity of the carbon powder reaches 99.99991%. After inspection by a laser particle size analyzer, the particle size of the carbon powder is D50=41.4μm.

Claims

1. A method for preparing high-purity carbon powder, characterized in that: The sugar crystals are melted to obtain a sugar melt, and the sugar melt is passed through an atomizing nozzle, where the atomizing gas medium atomizes the sugar melt into droplets, and the droplets are carbonized into carbon powder under high temperature and high pressure in a protective atmosphere; The sugar crystals are obtained by dissolving sugar in ultrapure water to obtain a sugar solution, passing the sugar solution through an ion exchange resin to obtain a purified sugar solution, and evaporating and crystallizing the purified sugar solution to obtain sugar crystals; The pressure of the atomizing gas medium is 0.5~5MPa; The aperture of the atomizing nozzle is 0.3-2 mm; The carbonization temperature is 1000-2000°C and the pressure is 10-50MPa; The purity of the high-purity carbon powder is 6N, and the particle size is 10-200 μm.

2. The method for preparing high-purity carbon powder according to claim 1, characterized in that: The sugar in the sugar crystals is selected from at least one of sucrose, glucose, fructose and maltose.

3. The method for preparing high-purity carbon powder according to claim 1, characterized in that: The molten sugar is placed in a tundish located above the atomizing nozzle, and the molten sugar flows out from the leak at the bottom of the tundish and passes through the atomizing nozzle.

4. The method for preparing high-purity carbon powder according to claim 1, characterized in that: The atomizing gas medium is selected from argon and / or nitrogen.

5. The method for preparing high-purity carbon powder according to claim 1, characterized in that: The protective atmosphere is selected from argon and / or nitrogen.