Graphitized carbon having uniform particle size and a method for producing the same

Abstract

The application discloses a kind of graphitized carbon with uniform granularity and its preparation method, which comprises: coal is broken into particles with particle size less than 10 mm, and is subjected to deashing and drying to obtain pretreated powder; the pretreated powder is added into a ball mill to be spheroidized to obtain spheroidized powder; the spheroidized powder is placed in an oxygen-free sealed environment and calcined at a temperature lower than 900 DEG C to obtain calcined powder; the calcined powder is added into an electric furnace for graphitization treatment; during spheroidization, a spheroidization aid is added into the pretreated powder, and the addition amount of the spheroidization aid is 0.3-1% of the mass of the pretreated powder; the spheroidization aid is prepared by free radical copolymerization of raw materials including the following components: 10-20 parts of unsaturated monomer containing long-chain alkyl; 8-15 parts of unsaturated dicarboxylic acid monomer; 1-5 parts of sulfonate type acrylic acid monomer. The application can effectively reduce the content of particles with excessively large or small particle size in the product, and improve the uniformity and stability of the performance of carbon particles.

Description

Technical Field

[0001] This application relates to the field of graphitized carbon, and in particular to a graphitized carbon with uniform particle size and a method for preparing the same. Background Technology

[0002] Carbon raisers play a crucial role in the steelmaking process, primarily by adding carbon to molten iron or steel. Under high-temperature smelting conditions, they undergo physicochemical reactions with the molten metal, dissolving, diffusing, and precipitating carbon atoms to uniformly integrate into the metal matrix. This allows for the adjustment and control of the carbon content in the final product, meeting specific material performance requirements.

[0003] Using coal as the main raw material to prepare carbon raisers has significant cost advantages and resource utilization value. Coal resources are abundant and relatively inexpensive, and it is rich in carbon, which can be converted into high-quality carbon raisers after appropriate processing. However, the particle size distribution of existing coal-based carbon raisers is generally wide, a characteristic that reveals certain limitations in specific applications. Specifically, under long-term smelting or process conditions with strict requirements for carbon distribution uniformity, fine particles (such as particles smaller than 1 mm) in coal-based carbon raisers have a large specific surface area, resulting in rapid dissolution and release, decreased uniformity of carbon distribution in the melt, and high oxygen loss. At the same time, fine particles easily generate a large amount of dust during use, which not only increases the difficulty of operation but may also cause environmental pollution and safety hazards. While coarse particles (such as particles larger than 5 mm) can slow down the carbon release rate and reduce oxidation loss to some extent, they are prone to settling and have low utilization rates. They may also accumulate on the melt surface, affecting heat transfer and stirring effects during the smelting process. Summary of the Invention

[0004] This application provides a graphitized carbon with uniform particle size and its preparation method, which can effectively alleviate the problems of wide particle size distribution and poor uniformity in the preparation process of coal-based graphitized carbon.

[0005] In a first aspect, this application provides a method for preparing graphitized carbon with uniform particle size, comprising the following steps:

[0006] The coal raw material is crushed to obtain particles with a particle size of less than 10mm. The crushed particles are deashed and then dried to obtain pretreated powder.

[0007] The pretreated powder is added to a ball mill for spheroidization to obtain spheroidized powder;

[0008] The spheroidized powder was placed in an oxygen-free sealed environment and calcined at a temperature below 900°C to obtain calcined powder.

[0009] The calcined powder is added to an electric calcining furnace for graphitization treatment. The feed temperature is 600-800℃ and the discharge temperature is 2300-2500℃.

[0010] During the spheroidizing process, a spheroidizing aid is added to the pretreated powder, and the amount of spheroidizing aid added is 0.3% to 1% of the mass of the pretreated powder; the spheroidizing aid is obtained by free radical copolymerization of raw materials comprising the following monomers in parts by mass:

[0011] 10-20 parts of unsaturated monomers containing long-chain alkyl groups;

[0012] 8-15 parts of unsaturated dicarboxylic acid monomers;

[0013] 1 to 5 parts of sulfonate-type acrylic monomer.

[0014] Preferably, the long-chain alkyl group of the unsaturated monomer containing the long-chain alkyl group is a straight-chain or branched alkane of C12 to C20.

[0015] Preferably, the long-chain alkyl-containing unsaturated monomer is selected from one or more of lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, and N-long-chain alkyl acrylamide.

[0016] Preferably, the unsaturated dicarboxylic acid monomer is selected from one or more of maleic acid, fumaric acid, and itaconic acid.

[0017] Preferably, the sulfonate-type acrylic monomer is selected from one or more of sodium allyl sulfonate, sodium 2-propene sulfonate, and sodium methpropylene sulfonate.

[0018] The crushing process effectively reduces coarse particles, controlling the raw material particle size to below 10mm. Deashing and drying remove most of the ash and moisture from the raw material. The spheroidizing process further reduces the particle size of coarse particles and transforms the particle shape into spherical shapes, removing irregular surfaces and improving the uniformity and stability of the recarburizer particle size. In the roasting process, high-temperature treatment in an oxygen-free environment further removes moisture from the raw material, promotes the volatilization and precipitation of volatiles, and creates a microporous structure on the particles. In the electric furnace graphitization process, carbon atoms in the coal-based raw material gradually grow to form graphitized crystals; the graphite-structured recarburizer exhibits excellent recarburizing effects.

[0019] The spheroidizing agent added in this application helps reduce the content of coarse and fine particles in the raw material after spheroidization. Specifically, the spheroidizing agent is obtained by free radical copolymerization of unsaturated reactive monomers, wherein the unsaturated monomers containing long-chain alkyl groups provide long-chain alkyl groups for the spheroidizing agent, the unsaturated dicarboxylic acid monomers provide abundant carboxyl groups, and the sulfonate-type acrylic monomers provide anionic charged groups.

[0020] During ball milling, numerous active sites are generated on the particle surface due to high-energy collisions. These active sites on the particle surface tend to cause particle aggregation, affecting the ball milling effect, increasing ball milling time, and increasing the content of fine particles in the product. Active sites generated at particle cracks hinder crack propagation and fracture, reducing the crushing effect of ball milling and increasing the content of coarse particles. The carboxyl groups in this spheroidizing aid allow it to bond to the active sites on the particles. The spheroidizing aid adsorbed on the particle surface can reduce the surface energy of the particles through its long-chain alkyl groups and enhance the surface charge density through its anionic sulfonic acid groups, effectively inhibiting the aggregation tendency. Simultaneously, the outwardly extending long-chain alkyl groups of the spheroidizing aid can form a lubricating film on the particle surface, improving its fluidity and preventing particles from requiring longer ball milling times due to frictional resistance, thus helping to reduce fine particles. When the spheroidizing aid is adsorbed at particle cracks, the steric hindrance of the long-chain alkyl groups and the charge repulsion of the anionic sulfonic acid groups both promote crack propagation and fracture, helping to reduce coarse particles and ensure the ball milling effect.

[0021] Preferably, the roasting is divided into a single roasting and a double roasting, specifically:

[0022] One-time roasting: The spheroidized powder is roasted in an oxygen-free sealed environment with a feed temperature of 80-120℃, a discharge temperature of 320-420℃, and a roasting time of 20-50 minutes.

[0023] Secondary calcination: The spheroidized powder is placed in an oxygen-free sealed environment for calcination. The feed temperature is 320-420℃, the discharge temperature is 750-900℃, and the time is 20-40 minutes.

[0024] Preferably, before graphitization, industrial white oil is added to the calcined powder and stirred and mixed, with the mass ratio of calcined powder to industrial white oil being 1:0.1 to 0.2.

[0025] Preferably, the industrial white oil has a kinematic viscosity of 10–40 cSt at 40°C.

[0026] Preferably, the mixing temperature is 60–95°C.

[0027] During roasting, the release of moisture and volatiles from coal particles creates microporous structures within the particles. These micropores become filled with air, which can lead to uneven internal temperatures during high-temperature graphitization, generating stress and increasing the risk of particle breakage. Industrial white oil, with its excellent fluidity and permeability, can penetrate these pores formed during roasting. Containing a large amount of saturated hydrocarbons, it cokes and carbonizes during high-temperature graphitization, sealing the pore structure. This improves the strength of the carbonizer, reduces breakage caused by temperature stress or external forces during storage and transportation, and helps reduce the generation of fine particles.

[0028] Preferably, the coal raw material is selected from one or more of bituminous coal, sub-bituminous coal, lignite, and bituminous coal.

[0029] Secondly, this application provides a graphitized carbon with uniform particle size, which is prepared by any of the above-mentioned preparation methods.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. This application involves spheroidizing coal-based raw materials and adding a spheroidizing aid obtained by copolymerizing unsaturated monomers containing long-chain alkyl groups, unsaturated dicarboxylic acid monomers, and sulfonate-type acrylic acid monomers during the spheroidizing process. This significantly inhibits the formation of coarse and fine particles, increases the content of carbon raisers with a particle size of 1-5 mm, and is beneficial to improving the uniformity of carbon concentration after melt smelting.

[0032] 2. In this application, before electric calcination after roasting, the addition of industrial white oil with a kinematic viscosity of 10-40 cSt (40°C) to the coal-based powder helps to improve the strength of the resulting carbon raiser, reduce particle breakage caused by temperature stress or external force, and reduce the fine particle content in the carbon raiser product. Detailed Implementation

[0033] Preparation examples of raw materials and / or intermediates

[0034] Preparation Example 1

[0035] The spheroidizing agent was prepared according to the following method:

[0036] Emulsion preparation: Dissolve sodium dodecyl sulfate in water to obtain a 2wt% emulsifier solution for later use; take 150g of octadecyl acrylate, 120g of maleic acid, and 23g of sodium allyl sulfonate, add them to 1000ml of emulsifier solution, and heat to 45℃; then add 3.6g of dicumyl peroxide, and heat to 80℃ and keep the reaction for 3h to obtain the spheroidizing aid.

[0037] Preparation Example 2

[0038] The spheroidizing agent was prepared according to the following method:

[0039] Emulsion preparation: Dissolve sodium dodecyl sulfate in water to obtain a 2wt% emulsifier solution for later use; take 120g of lauryl methacrylate, 90g of itaconic acid, and 40g of sodium allyl sulfonate and add them to 1000ml of emulsifier solution, and heat to 45℃; then add 3.3g of dicumyl peroxide, and heat to 82℃ and keep the reaction for 3h to obtain the spheroidizing aid.

[0040] Preparation Example 3

[0041] The spheroidizing agent was prepared according to the following method:

[0042] Emulsion preparation: Dissolve sodium dodecyl sulfate in water to obtain a 2wt% emulsifier solution for later use; take 180g of octadecyl acrylate, 150g of maleic acid, and 15g of sodium methyl methacrylate and add them to 1000ml of emulsifier solution, and heat to 45℃; then add 5g of dicumyl peroxide, and heat to 82℃ and keep the reaction for 3h to obtain the spheroidizing aid.

[0043] Preparation Example 4

[0044] The spheroidizing agent differs from that in Preparation Example 1 in that an equal amount of octadecyl acrylate is used instead of sodium allyl sulfonate.

[0045] Preparation Example 5

[0046] The spheroidizing agent differs from that in Preparation Example 1 in that an equal amount of sodium allyl sulfonate is used instead of octadecyl acrylate.

[0047] Preparation Example 6

[0048] The spheroidizing agent differs from that in Preparation Example 1 in that an equal amount of acrylic acid is used instead of maleic acid.

[0049] Example

[0050] Example 1

[0051] A graphitized carbon with uniform particle size is prepared according to the following steps:

[0052] Anthracite raw material is added to a crusher for cyclic crushing to obtain particles with a size of less than 10mm. The crushed particles are deashed using a density classification method. The deashed particles are then dried to remove moisture, resulting in pretreated powder with a moisture content of less than 5%.

[0053] The pretreated powder with a mass ratio of 100:0.6 and the spheroidizing agent obtained in Preparation Example 1 were added to a ball mill and spheroidized at a ball-to-powder ratio of 1:1 to obtain spheroidized powder.

[0054] The spheroidized powder was added to a primary calcining furnace purged with nitrogen at a feed temperature of 100±5℃, a calcination time of 30 min, and a discharge temperature of 390±5℃. Immediately after discharge, the powder was fed into a secondary calcining furnace purged with nitrogen at a calcination time of 30 min and a discharge temperature of 850±5℃. The powder was then cooled and discharged to obtain the calcined powder.

[0055] Take 1 kg of calcined powder and 0.16 kg of 30# industrial white oil and mix them evenly at 85℃. Then add them to an electric calcining furnace for graphitization treatment. The feed temperature is 800±5℃, and the temperature is increased to 2400±10℃ at a rate of 5℃ / min. Hold for 4 days. Cool and discharge to obtain graphitized carbon.

[0056] Example 2

[0057] A graphitized carbon with uniform particle size is prepared according to the following steps:

[0058] Anthracite raw material is added to a crusher for cyclic crushing to obtain particles with a size of less than 10mm. The crushed particles are deashed using a density classification method. The deashed particles are then dried to remove moisture, resulting in pretreated powder with a moisture content of less than 5%.

[0059] The pretreated powder with a mass ratio of 100:0.4 and the spheroidizing agent obtained in Preparation Example 2 were added to a ball mill and spheroidized at a ball-to-powder ratio of 1:1 to obtain spheroidized powder.

[0060] The spheroidized powder was added to a primary calcining furnace purged with nitrogen at a feed temperature of 110±5℃, a calcination time of 20 min, and a discharge temperature of 400±5℃. Immediately after discharge, the powder was fed into a secondary calcining furnace purged with nitrogen for a calcination time of 40 min and a discharge temperature of 800±5℃. The powder was then cooled and discharged to obtain the calcined powder.

[0061] Take 1 kg of calcined powder and 0.1 kg of No. 10 industrial white oil and mix them evenly at 60℃. Then add them to an electric calcining furnace for graphitization treatment. Heat the furnace at a rate of 5℃ / min to 2500±10℃ and hold for 4 days. Cool and discharge the material to obtain graphitized carbon.

[0062] Example 3

[0063] A graphitized carbon with uniform particle size is prepared according to the following steps:

[0064] Anthracite raw material is added to a crusher for cyclic crushing to obtain particles with a size of less than 10mm. The crushed particles are deashed using a density classification method. The deashed particles are then dried to remove moisture, resulting in pretreated powder with a moisture content of less than 5%.

[0065] The pretreated powder with a mass ratio of 100:0.9 and the spheroidizing agent obtained in Preparation Example 3 were added to a ball mill and spheroidized at a ball-to-powder ratio of 1:1 to obtain spheroidized powder.

[0066] The spheroidized powder was added to a primary calcining furnace purged with nitrogen at a feed temperature of 100±5℃, a calcination time of 40 min, and a discharge temperature of 350±5℃. Immediately after discharge, the powder was fed into a secondary calcining furnace purged with nitrogen at a calcination time of 40 min and a discharge temperature of 800±5℃. The powder was then cooled and discharged to obtain the calcined powder.

[0067] Take 1 kg of calcined powder and 0.2 kg of 40# industrial white oil and mix them evenly at 80℃. Then add them to an electric calcining furnace for graphitization treatment. The feed temperature is 800±5℃, and the temperature is increased to 2300±10℃ at a rate of 5℃ / min. Hold for 3 days. Cool and discharge to obtain graphitized carbon.

[0068] Example 4

[0069] A graphitized carbon with uniform particle size, which differs from Example 1 in that the calcined powder is not mixed with industrial white oil, but is directly added to an electric calcining furnace for graphitization treatment.

[0070] Comparative Example

[0071] Comparative Example 1

[0072] A graphitized carbon with uniform particle size, which differs from Example 1 in that the spheroidizing aid obtained in Example 4 is replaced with an equal amount of the spheroidizing aid obtained in Example 1 in the spheroidizing process.

[0073] Comparative Example 2

[0074] A graphitized carbon with uniform particle size, which differs from Example 1 in that the spheroidizing aid obtained in Example 5 is replaced with an equal amount of the spheroidizing aid obtained in Example 1 in the spheroidizing process.

[0075] Comparative Example 3

[0076] A graphitized carbon with uniform particle size, which differs from Example 1 in that the spheroidizing aid obtained in Example 6 is replaced with an equal amount of the spheroidizing aid obtained in Example 1 in the spheroidizing process.

[0077] Comparative Example 4

[0078] A graphitized carbon with uniform particle size, which differs from Example 1 in that no spheroidizing agent is added in the spheroidizing process.

[0079] Performance testing

[0080] Experiment 1: Basic Indicator Test

[0081] The ash content, fixed carbon content, moisture content, and volatile matter content of the recarburizer were tested in accordance with the provisions of YB T192-2015 "Carburizing Agents for Steelmaking".

[0082] Experiment 2: Determination of particle size distribution of graphitized carbon

[0083] The particle size of graphitized carbon was determined using a laser particle size analyzer.

[0084] Experiment 3: Mechanical Strength Test

[0085] The compressive strength of the carbon raiser was determined in accordance with the provisions of JB / T 8133.8-2013 "Test Methods for Physicochemical Properties of Electrocarbon Products - Part 8: Compressive Strength".

[0086] Table 1. Results of Basic Indicator Tests

[0087]

[0088]

[0089] Table 2. Results of particle size distribution and mechanical strength tests

[0090]

[0091] Results analysis:

[0092] As can be seen from Examples 1-4 and Comparative Examples 1-4, and in conjunction with Tables 1 and 2, this application employs a spheroidization process in the preparation of graphitized carbon. By adding a spheroidization aid, the content of graphitized carbon with a particle size of 1-5 mm is effectively increased, while the content of coarse particles (>5 mm) and fine particles (<1 mm) is reduced. This may be because, during ball milling, particles are fed from one end of the milling equipment and discharged from the other. During this process, high-energy collisions with the milling stone generate numerous active sites on the coal-based particles. These active sites on the particle surface cause a tendency for particle aggregation, increasing milling time and the content of fine particles. Conversely, active sites generated at particle cracks hinder crack propagation and fracture, reducing the crushing effect of the milling process and increasing the content of coarse particles in the product.

[0093] The carboxyl groups in this spheroidizing aid allow it to bond to the active sites of particles. Adsorbed on the particle surface, the spheroidizing aid reduces particle surface energy and increases steric hindrance through its long-chain alkyl groups; simultaneously, it enhances surface charge density through anionic sulfonic acid groups, effectively inhibiting agglomeration and reducing fine particles. Furthermore, the outwardly extending long-chain alkyl groups of the spheroidizing aid form a lubricating film on the particle surface, improving its fluidity and preventing increased ball milling time due to frictional resistance, further reducing fine particles. When the spheroidizing aid adsorbs at particle cracks, the steric hindrance of the long-chain alkyl groups and the charge repulsion of the anionic sulfonic acid groups both promote crack propagation and fracture, helping to reduce coarse particles and ensure effective ball milling.

[0094] Therefore, it can be seen that unsaturated monomers containing long-chain alkyl groups, unsaturated dicarboxylic acid monomers, and sulfonate-type acrylic monomers in the raw materials of spheroidizing aids all play an irreplaceable role as necessary reactive monomers for reducing coarse and fine particles.

[0095] (2) As can be seen from Examples 1 and 4 and Tables 1 and 2, adding industrial white oil to the powder before graphitization in this application helps reduce the content of fine particles in the graphitized carbon. This may be because the precipitation of moisture and volatiles within the coal particles during roasting creates microporous structures within the particles. These micropores are filled with air, which can easily lead to uneven internal temperatures during high-temperature graphitization, generating stress and increasing the risk of particle breakage. Industrial white oil, with its excellent fluidity and permeability, can penetrate into the pores formed during roasting. Containing a large amount of saturated hydrocarbons, it cokes and carbonizes during high-temperature graphitization, sealing the pore structure and improving the strength of the carbonizer. This reduces breakage caused by temperature stress or external forces during storage and transportation, thus reducing the generation of fine particles.

[0096] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing graphitized carbon with uniform particle size, characterized in that, Includes the following steps: The coal raw material is crushed to obtain particles with a particle size of less than 10mm. The crushed particles are deashed and then dried to obtain pretreated powder. The pretreated powder is added to a ball mill for spheroidization to obtain spheroidized powder; The spheroidized powder was placed in an oxygen-free sealed environment and calcined at a temperature below 900°C to obtain calcined powder. The calcined powder is added to an electric calcining furnace for graphitization treatment. The feed temperature is 600-800℃ and the discharge temperature is 2300-2500℃. During the spheroidizing process, a spheroidizing aid is added to the pretreated powder, and the amount of the spheroidizing aid added is 0.3% to 1% of the mass of the pretreated powder; the spheroidizing aid is obtained by free radical copolymerization of raw materials comprising the following monomers in parts by mass: 10-20 parts of unsaturated monomers containing long-chain alkyl groups; 8-15 parts of unsaturated dicarboxylic acid monomers; 1-5 parts of sulfonate-type acrylic monomer; The long-chain alkyl-containing unsaturated monomer is selected from one or more of lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, and N-long-chain alkyl acrylamide. The unsaturated dicarboxylic acid monomer is selected from one or more of maleic acid, fumaric acid and itaconic acid; The sulfonate-type acrylic monomer is selected from one or more of sodium allyl sulfonate, sodium 2-propene sulfonate, and sodium methpropylene sulfonate.

2. The method according to claim 1, characterized in that, The roasting process is divided into a single roasting and a double roasting, specifically as follows: One-time roasting: The spheroidized powder is roasted in an oxygen-free sealed environment with a feed temperature of 80-120℃, a discharge temperature of 320-420℃, and a roasting time of 20-50 minutes. Secondary calcination: The spheroidized powder is placed in an oxygen-free sealed environment for calcination. The feed temperature is 320-420℃, the discharge temperature is 750-900℃, and the time is 20-40 minutes.

3. The method according to claim 1, characterized in that, Before graphitization, industrial white oil is added to the calcined powder and stirred. The mass ratio of the calcined powder to the industrial white oil is 1:0.1 to 0.

2.

4. The method according to claim 3, characterized in that, The industrial white oil has a kinematic viscosity of 10–40 cSt at 40°C.

5. The method according to claim 3, characterized in that, The mixing temperature is 60–95°C.

6. The method according to claim 1, characterized in that, The coal raw material is selected from one or more of bituminous coal, sub-bituminous coal, lignite, and bituminous coal.

7. A graphitized carbon with uniform particle size, characterized in that, It is prepared by any one of the methods described in claims 1 to 6.

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