Preparation method of graphite box plate for box-type graphitization furnace

Abstract

The invention discloses a preparation method of a graphite box plate for a box-type graphitization furnace, which comprises the following steps: dry materials and asphalt are weighed, and the dry materials comprise graphitized coke, pitch coke, dedusting powder and electrically calcined coal; wherein the graphitized coke accounts for 50-52% by weight, the pitch coke accounts for 10-12% by weight, the dedusting powder accounts for 10-12% by weight, the electrically calcined coal accounts for 5-7% by weight, and the pitch accounts for 20-22% by weight; the dry material and asphalt are mixed and kneaded into a paste material; adding the paste into a mold, carrying out mold pressing, and carrying out mold pressing vibration molding to obtain a graphite green body; demolding and cooling the graphite green body, and obtaining a graphite cooked blank through a ring type roasting furnace; and machining the graphite cooked blank to obtain the graphite box plate. Compared with the prior art, the preparation method has the following beneficial effects that the preparation method is simple and convenient to operate, the volume density of the prepared graphite box plate material is 1.62-1.65 g / cm < 3 >, the breaking strength is greater than 13 MPa, the compressive strength is greater than 45 MPa, the resistivity is 26-33 mu omega.m, and the requirement for thermal shock resistance of an electric load is met.

Description

Technical Field

[0001] The invention relates to the technical field of graphite products, and in particular to a method for preparing a graphite box plate for a box-type graphitization furnace. Background Art

[0002] Box-type graphitization furnace (also called box-type furnace) is a kind of equipment used in battery production, mainly used for graphitization of negative electrode materials of lithium-ion batteries to improve battery performance. Box-type furnace is a new type of furnace developed in recent years, mainly through the transformation of Acheson furnace. It has the advantages of high production capacity and low energy consumption. Therefore, large-capacity box-type furnace is the development trend of negative electrode graphitization furnace. In recent years, new projects are also mainly box-type furnaces.

[0003] All materials of the box body of the box furnace are basically graphitized plates. At present, graphitized plates are mainly made of calcined petroleum coke or a mixture of calcined petroleum coke and graphitized coke as raw materials, and are obtained by extrusion molding; however, the demand for graphitized coke extrusion molding asphalt is large, the molding is difficult, and the yield is low. Some graphitized plates are also obtained by extruding calcined petroleum coke and then graphitizing it. However, the cost of graphitization treatment in this way is high, resulting in high manufacturing costs of graphitized plates.

[0004] To solve the above problems, in the prior art, for example, in a patent with patent application number CN202210366183.3 and titled "A method for manufacturing a graphite box plate for a box-type graphitization furnace for negative electrode materials", graphitized coke is used as a raw material, asphalt is used as an adhesive, and the finished product is obtained through mixing, molding, firing, and machining.

[0005] In the above patent, due to the single raw material composition, which is only graphitized coke, the mechanical strength, resistivity, oxidation resistance and other properties of the obtained graphite box plate need to be improved. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing a graphite box plate for a box-type graphitization furnace. The prepared graphite box plate has a suitable volume density and has good mechanical strength and oxidation resistance.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for preparing a graphite box plate for a box-type graphitization furnace, comprising the following steps:

[0008] (1) Weighing dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal;

[0009] Among them, according to weight percentage, graphitized coke is 50-52%, asphalt coke is 10-12%, dust removal powder is 10-12%, electric calcined coal is 5-7%, and asphalt is 20-22%;

[0010] (2) mixing the dry material and asphalt in step (1) into a paste;

[0011] (3) adding the paste in step (2) into a mold, performing compression molding, and performing compression and vibration molding to obtain a graphite green body;

[0012] (4) demolding and cooling the graphite green body in step (3), and then passing through a ring-type roasting furnace to obtain a graphite cooked body;

[0013] (5) The graphite blank in step (4) is machined to obtain a graphite box plate.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The dry material (or raw material) of the present application includes graphitized coke, asphalt coke, dust removal powder, and electric calcined coal. The four powder materials have different particle size ranges. The present application adopts a multi-component synergistic design method to construct a mutual filling of large, medium, small and fine powder particles, which can effectively improve the volume density and mechanical strength of the graphite box plate material; at the same time, the coordinated construction of multi-stage graphitized coke can realize the filling between holes of different sizes in the graphite box plate material, and the formed pore structure is less than that of the previous box plate material, avoiding the box plate material from easily cracking due to excessive internal pressure in the box-type graphitization furnace, which leads to local furnace spraying.

[0016] 2. The lack of any one of the four powder materials in the raw materials of this application will lead to a significant decrease in the volume density of the graphite box plate material. In addition, the change in the proportion of particle sizes will also lead to a decrease in the volume density, and the volume density affects the thermal conductivity, strength and wear resistance of the graphite box plate material. For this reason, this application ensures that the volume density of the graphite box plate material meets the requirements through optimal design, and the graphite box plate material also has good mechanical strength.

[0017] 3. The electric calcined coal added to the raw materials of the present application can effectively improve the antioxidant properties of the graphitized box plate material and reduce the weight loss rate of the graphite box plate after one graphitization; at the same time, it can also indicate that the structure and performance of the graphitized box plate material of the present application are more stable, ensuring the long-term stable use of the graphitized box plate material; and, the smaller the weight loss rate, it also indicates that there are fewer impurities in the graphitized box plate material. For this reason, the resistivity of the graphitized box plate material of the present application is lower.

[0018] 4. The addition of dust removal powder in this application can appropriately reduce the amount of asphalt used, because the dust removal powder has a small particle size and can be effectively dispersed in the gaps of the dry material, playing a filling role, making the material stacking more compact. When the dry material and asphalt are combined, the packing density of the dry material increases and the gaps become smaller, so as not as much asphalt as before is needed to fill these gaps, thereby reducing the amount of asphalt used. At the same time, the dust removal powder is a spherical particle with a more regular shape, which makes the distribution of various substances in the graphitized box plate material more uniform, and can reduce the resistivity of the graphitized box plate material to a certain extent.

[0019] 5. The box board material prepared by the present invention has suitable hardness and is easy to cut and process, so that the box board material has good machinability.

[0020] 6. The present invention uses graphitized oil coke, asphalt coke and dust removal powder as raw materials. Graphitized coke can improve the overall thermal and electrical conductivity of the graphite box plate material due to its special watershed structure.

[0021] 7. The preparation method of the present invention is simple and easy to operate, and the volume density of the prepared graphite box plate material is 1.62-1.65g / cm 3 , flexural strength>13MPa, compressive strength>45MPa, resistivity 26-33μΩ·m, meeting the requirements of thermal shock resistance under electrical load.

[0022] Furthermore, in step (1), the graphitized coke is composed of graphitized coke materials of different particle sizes, and the proportion thereof is 70% of the powder with a particle size range of 0-2 mm and 30% of the powder with a particle size less than 0.075 mm;

[0023] The particle size of pitch coke ranges from 3 to 6 mm;

[0024] The dust removal powder includes the tail powder collected from the processes of electrode raw material block crushing, screening, transportation, batching and mechanical processing, and the dust removal powder also includes the tail powder collected from the graphitized coke screening process. The dust removal powder has a particle size range of 0.1-100μm;

[0025] The particle size range of electric calcined coal is 6-25mm.

[0026] Furthermore, graphitized coke with a particle size range of 0-2 mm meets the following indicators:

[0027] Ash content ≤0.5%, sulfur content ≤0.3%, true density ≥2.18g / cm3, powder resistivity ≤150μΩ·m.

[0028] Furthermore, the asphalt in step (2) meets the following indicators:

[0029] Ash content ≤ 0.3%, coking value ≥ 56%, softening point 106°C-112°C, toluene insoluble matter (TI) 28%-32%, quinoline insoluble matter (QI) 6%-12%.

[0030] Furthermore, the mixing of the raw material and asphalt in step (2) comprises the following steps:

[0031] Firstly, graphitized coke, dust removal powder, electric calcined coal and asphalt coke are dry mixed at a temperature of 140-150°C for 20-30 minutes to obtain a uniformly mixed dry material;

[0032] After the asphalt is heated and melted, it is allowed to stand still and the temperature is controlled at 160-180°C. The asphalt and dry material are wet mixed for 30-50 minutes so that the medium-temperature asphalt completely covers the surface of the raw materials to obtain a paste.

[0033] Furthermore, the asphalt is heated by the waste heat of the roasting furnace in step (4).

[0034] Furthermore, in step (3), a vertical molding device is used to pressurize the paste of a preset weight into a graphite green body of 2800 mm × 730 mm × 730 mm using a vertical molding process, the large cylinder pressure is 16-20 MPa, the pressure is maintained for 30-45 minutes, and after the pressure is released from the mold, it is placed in a cooling water pool for cooling for 7-8 hours to obtain a graphite green body.

[0035] Furthermore, in step (4), the graphite green body is placed in a ring-type roasting furnace, and the graphite green body is roasted in an air-tight condition by adopting a rapid temperature rise and variable temperature roasting method.

[0036] Furthermore, variable temperature calcination is performed according to the temperature rise curve, the temperature is gradually increased from room temperature to 1000-1200° C. according to the temperature rise curve, and then calcined at 1000-1200° C. for 3-4 hours.

[0037] Furthermore, metallurgical coke particles are laid at the bottom of the ring roasting furnace, and after the graphite green body is loaded, the gaps around the graphite green body and the top are filled with metallurgical coke particles so that the metallurgical coke particles completely surround the graphite green body, and the graphite green body is roasted under the protection of the protective medium. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0039] The present application provides a method for preparing a graphite box plate for a box-type graphitization furnace, and the method steps are as follows:

[0040] S1: Weigh dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal;

[0041] Among them, according to weight percentage, graphitized coke is 50-52%, asphalt coke is 10-12%, dust removal powder is 10-12%, electric calcined coal is 5-7%, and asphalt is 20-22%.

[0042] The ingredients of this application are prepared using graphitized coke, asphalt coke, dust removal powder, and electric calcined coal as raw materials, and asphalt as a binder. Among them, the graphitized coke is derived from the insulation material in the Acheson crucible furnace, and the graphitized coke is composed of powders of various particle sizes, among which the powders with a particle size range of 0-2mm account for 70%, and the powders with a particle size range of less than 0.075mm account for 30%. And the indicators of graphitized coke with a particle size range of 0-2mm are controlled as follows: ash content ≤0.5%, sulfur content ≤0.3%, true density ≥2.18g / cm 3 , powder resistivity ≤150μΩ·m.

[0043] Pitch coke has good mechanical strength and high wear resistance, with a particle size range of 3-6mm. The asphalt coke indicators are controlled as follows: ash content ≤0.3%, volatile matter ≤0.6%, and sulfur content ≤0.4%.

[0044] The dust removal powder is fine particles with a particle size range of 0.1-100 μm. The dust removal powder of this application is the tail powder collected from the processes of electrode raw material block crushing, screening, transportation, batching and mechanical processing, as well as the tail powder collected from the graphitized coke screening process. In the graphite processing process, especially cutting, a large amount of fine dust will be generated, and its particle size may be mainly concentrated in 0.1-1 μm.

[0045] Electric calcined coal is calcined at high temperature in an electric furnace. It has the characteristics of low ash, low sulfur, low phosphorus, high calorific value and high compressive strength. The particle size of electric calcined coal ranges from 6-25mm. Its true density is about 1.82g / cm 3 , the ash content is usually below 8.5% and the volatile matter is about 0.6±0.05%.

[0046] The asphalt of the present application has a high softening point, which makes the kneading temperature and molding temperature of the asphalt and the dry material high, which is beneficial to improve the uniformity of the paste and the briquette, thereby ensuring the uniformity of thermal expansion. Specifically, the asphalt indicators are ash content ≤ 0.3%, coking value ≥ 56%, softening point 106℃-112℃, toluene insoluble matter (TI) 28%-32%, and quinoline insoluble matter (QI) 6%-12%.

[0047] S2: The above four powders are mixed with asphalt according to the particle size formula and weight ratio to form a paste.

[0048] The kneading method is as follows: firstly, graphitized coke, asphalt coke, dust removal powder and electric calcined coal are dry-mixed, the dry-mixing temperature is controlled at 140-150°C, and the time is 20-30 minutes. After the dry-mixing is uniform, medium-temperature asphalt that has been completely melted and fully allowed to stand at a temperature of 160°C is added for wet mixing, the wet mixing temperature is 160-180°C, and the time is 30-50 minutes, so that the medium-temperature asphalt completely wraps the surface of the raw materials to obtain a paste.

[0049] S3: adding the paste into a mold and then performing compression molding, and then performing compression and vibration molding to obtain a graphite green body.

[0050] Specifically, the present application adopts vertical molding equipment and utilizes vertical molding process to pressurize the weighed paste into a 2800mm×730mm×730mm graphite green embryo, requiring a large cylinder pressure of 16-20Mpa and a pressure holding time of 30-45 minutes. After the pressure is removed from the mold, it is placed in a cooling water pool for cooling for 7-8 hours.

[0051] S4: After the graphite green body is demoulded and cooled, it is passed through a ring-type roasting furnace to obtain a graphite cooked body.

[0052] Metallurgical coke particles are laid at the bottom of the ring roasting furnace, and after the graphite green body is loaded, the gaps around the graphite green body and the top are covered with metallurgical coke particles, so that the metallurgical coke particles completely surround the graphite green body, and the graphite green body is protected by a protective medium and isolated from air. The temperature is raised to 1000-1200℃ according to the heating curve for 3-4 hours, and the temperature is lowered to 220℃ by program control, and then naturally cooled to room temperature to obtain a graphite cooked body. Among them, the roasting time is 20 days and the cooling time is about 20 days.

[0053] S5: The graphite blank is machined to obtain a graphite box plate material for a box-type graphitization furnace.

[0054] It is worth noting that: in order to save costs, the waste heat of the calcining workshop in this system is used for heating during the asphalt heating and melting process. Specifically, the waste heat generated by the tank calcining furnace in the calcining workshop is used as the heat source, and then the waste heat is transferred to the heat transfer oil in the form of radiation and convection through the heat pipe boiler. The heat transfer oil is circulated in the system through the circulation pump, and the heated high-temperature heat transfer oil is exchanged with the hot working medium asphalt in the heat exchange equipment, achieving the purpose of asphalt heating while reducing production costs.

[0055] The present application will demonstrate the various properties of the graphite box plate material of the present application through the following embodiments and comparative examples.

[0056] Example 1

[0057] S1: Weigh dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal;

[0058] Among them, according to weight percentage, graphitized coke is 51%, asphalt coke is 11%, dust removal powder is 11%, electric calcined coal is 6%, and asphalt is 21%.

[0059] S2: The above raw materials are kneaded into a paste with asphalt according to the particle size formula. The kneading method is to first dry-mix the graphitized coke, dust removal powder and other raw materials, the dry-mixing temperature is controlled at 150°C, the time is 30 minutes, after the dry-mixing is uniform, add the medium-temperature asphalt that has been completely melted and fully stood at a temperature of 160°C for wet mixing, the wet mixing temperature is 170°C, the time is 40 minutes, so that the medium-temperature asphalt completely covers the surface of the raw materials, thereby obtaining a paste.

[0060] S3: After the paste is added to the mold, it is molded and vibrated to obtain a graphite green body. Using vertical molding equipment and a vertical molding process, the weighed paste is pressed and molded into a 2800mm×730mm×730mm graphite green body, with a large cylinder pressure of 17Mpa and a holding time of 35 minutes. After the pressure is removed from the mold, it is placed in a cooling water pool for cooling for 8 hours.

[0061] S4: After the graphite green body is demoulded and cooled, a graphite cooked body is obtained by a ring-type roasting furnace. Metallurgical coke particles are laid at the bottom of the ring-type roasting furnace. After the graphite green body is loaded, the gaps around the graphite green body and the top are covered with metallurgical coke particles so that the metallurgical coke particles completely surround the graphite green body. The graphite green body is protected by a protective medium and isolated from air. The method of rapid temperature rise and temperature change roasting is adopted. The heating curve requirements are shown in Table 1. After the temperature is raised to 1100°C, it is roasted at a constant temperature for 4 hours at this temperature. After the temperature is lowered to 220°C by program control, it is naturally cooled to room temperature to obtain a graphite cooked body. The graphite cooked body is machined to obtain a graphite box plate material.

[0062] Table 1:

[0063]

[0064]

[0065] Example 2

[0066] S1: Weigh dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal;

[0067] Among them, according to weight percentage, graphitized coke is 51%, asphalt coke is 11%, dust removal powder is 12%, electric calcined coal is 6%, and asphalt is 20%.

[0068] S2: The above raw materials are kneaded with asphalt according to the particle size formula to form a paste. The kneading method is to first dry-mix the graphitized coke, dust removal powder and other raw materials, the dry-mixing temperature is controlled at 140°C, the time is 30 minutes, after the dry-mixing is uniform, add the medium-temperature asphalt that has been completely melted and fully stood at a temperature of 160°C for wet mixing, the wet mixing temperature is 160°C, the time is 45 minutes, so that the medium-temperature asphalt completely covers the surface of the raw materials, thereby obtaining a paste.

[0069] S3: After the paste is added to the mold, it is molded and vibrated to obtain a graphite green body. Using vertical molding equipment and a vertical molding process, the weighed paste is pressed and molded into a 2800mm×730mm×730mm graphite green body, requiring a large cylinder pressure of 16Mpa, a pressure holding time of 45 minutes, and after the pressure is removed from the mold, it is placed in a cooling water pool for cooling for 8 hours.

[0070] S4: After the graphite green body is demoulded and cooled, a graphite cooked body is obtained by a ring-type roasting furnace. Metallurgical coke particles are laid at the bottom of the ring-type roasting furnace. After the graphite green body is loaded, the gaps around the graphite green body and the top are covered with metallurgical coke particles so that the metallurgical coke particles completely surround the graphite green body. The graphite green body is protected by a protective medium and isolated from air. The method of rapid temperature rise and temperature change roasting is adopted. The heating curve requirements are shown in Table 2. After the temperature is raised to 1200°C, it is roasted at a constant temperature for 3 hours at this temperature. After the temperature is lowered to 220°C by program control, it is naturally cooled to room temperature to obtain a graphite cooked body. The graphite cooked body is machined to obtain a graphite box plate material.

[0071] Table 2:

[0072]

[0073]

[0074] Example 3

[0075] S1: Weigh dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal;

[0076] Among them, according to weight percentage, graphitized coke is 51%, asphalt coke is 11%, dust removal powder is 10%, electric calcined coal is 6%, and asphalt is 22%.

[0077] S2: The above raw materials are kneaded with asphalt according to the particle size formula to form a paste. The kneading method is to first dry-mix the graphitized coke, dust removal powder and other raw materials at a temperature of 140°C for 30 minutes, and after dry-mixing, add the completely melted and fully standing medium-temperature asphalt at a temperature of 160°C for wet mixing at a temperature of 180°C for 30 minutes, so that the medium-temperature asphalt completely covers the surface of the raw materials, thereby obtaining a paste.

[0078] S3: After the paste is added to the mold, it is molded and vibrated to obtain a graphite green body. Using vertical molding equipment and a vertical molding process, the weighed paste is pressed and molded into a 2800mm×730mm×730mm graphite green body, requiring a large cylinder pressure of 20Mpa, a pressure holding time of 45 minutes, and after the pressure is removed from the mold, it is placed in a cooling water pool for cooling for 8 hours.

[0079] S4: After the graphite green body is demoulded and cooled, a graphite cooked body is obtained by a ring-type roasting furnace. Metallurgical coke particles are laid at the bottom of the ring-type roasting furnace. After the graphite green body is loaded, the gaps around the graphite green body and the top are covered with metallurgical coke particles so that the metallurgical coke particles completely surround the graphite green body. The graphite green body is protected by a protective medium and isolated from air. The method of rapid temperature increase and temperature change roasting is adopted. The heating curve requirements are shown in Table 3. After the temperature is increased to 1000°C, it is roasted at a constant temperature for 4 hours at this temperature. After the temperature is reduced to 220°C by program control, it is naturally cooled to room temperature to obtain a graphite cooked body. The graphite cooked body is machined to obtain a graphite box plate material.

[0080] Table 3:

[0081]

[0082]

[0083] Comparative Example 1

[0084] This embodiment is the same as Embodiment 1, except that, among the raw materials, graphitized coke accounts for 51%, asphalt coke accounts for 11%, dust removal powder accounts for 17%, and no electric calcined coal is included.

[0085] Comparative Example 2

[0086] This embodiment is the same as Embodiment 1, except that, among the raw materials, graphitized coke accounts for 51%, asphalt coke accounts for 11%, and electric calcined coal accounts for 17%, and no dust removal powder is included.

[0087] Comparative Example 3

[0088] This embodiment is the same as Embodiment 1, except that, among the raw materials, graphitized coke accounts for 62%, dust removal powder accounts for 11%, electric calcined coal accounts for 6%, and no asphalt coke is contained.

[0089] Comparative Example 4

[0090] This embodiment is the same as Embodiment 1, except that, among the raw materials, asphalt coke accounts for 62%, dust removal powder accounts for 11%, electric calcined coal accounts for 6%, and no graphitized coke is contained.

[0091] Comparative Example 5

[0092] This embodiment is the same as Embodiment 1, except that, among the raw materials, graphitized coke accounts for 58%, asphalt coke accounts for 4%, dust removal powder accounts for 11%, and electric calcined coal accounts for 6%.

[0093] Comparative Example 6

[0094] This embodiment is the same as Embodiment 1, except that, among the raw materials, graphitized coke accounts for 51%, asphalt coke accounts for 11%, dust removal powder accounts for 9%, electric calcined coal accounts for 6%, and asphalt accounts for 23%.

[0095] The basic performance of the graphite box plate materials obtained in Examples 1-3 and Comparative Examples 1-5 was tested according to the test standard of GB / T 24533-2019, and the basic performance parameters are shown in Table 4.

[0096] Table 4:

[0097]

[0098]

[0099] It can be seen from the data of bulk density in Example 1 and Comparative Examples 1-4 that the four raw materials in the present invention are indispensable, and the lack of any one of them will lead to a significant decrease in bulk density. In addition, the change in the proportion of particle sizes will also lead to a decrease in bulk density.

[0100] From the data of flexural strength and compressive strength in Example 1 and Comparative Examples 4 and 5, it can be seen that the absence of graphitized coke and pitch coke in the raw materials will lead to a decrease in the mechanical strength of the graphite box plate material. At the same time, combined with the data of Comparative Examples 3 and 4, it can be seen that pitch coke has a greater impact on the mechanical strength of the graphite box plate material. It can be seen that the addition of pitch coke can make the graphite box plate material have better mechanical strength.

[0101] From the data of Example 1 and Comparative Example 6, it can be seen that the data difference between the two is not large, indicating that the graphite box plate material prepared by the raw material ratio in Comparative Example 6 also meets the requirements, but the application limits the amount of dust removal powder added in a cost-saving manner to reduce the amount of asphalt. Since the dust removal powder is a powdery residue (solid pollutant) in the production process, this ratio can reduce solid waste pollution while reducing raw material costs, and the quality of the prepared graphite box plate material is also effectively improved.

[0102] In the present application, the graphite box plates in Example 1 and Comparative Example 1 were graphitized once, respectively. The weight loss rate of the graphite box plates in Comparative Example 1 after the first graphitization was 4.6%, and the weight loss rate of the graphite box plates in Example 1 after the first graphitization was 1.8%. It can be seen that the addition of an appropriate amount of electric calcined coal can improve the antioxidant properties of the graphitized box plate material.

[0103] In this application, the graphite material produced is 2800mm×730mm×730mm in size. In the field of graphitization of negative electrode materials, graphite materials of this size can improve the utilization rate of graphite materials. In the past, the size of the graphite green billets produced was small. When loading the furnace, there would be extra space for two pieces and insufficient space for three pieces, which greatly wasted the remaining space of the roasting furnace and led to an increase in production costs. Now it can greatly improve the use efficiency of the roasting furnace, save production costs, and improve production efficiency.

[0104] In summary, we can get:

[0105] 1. The dry material (or raw material) of the present application includes graphitized coke, asphalt coke, dust removal powder, and electric calcined coal. The four powder materials have different particle size ranges. The present application adopts a multi-component synergistic design method to construct a mutual filling of large, medium, small and fine powder particles, which can effectively improve the volume density and mechanical strength of the graphite box plate material; at the same time, the coordinated construction of multi-stage graphitized coke can realize the filling between holes of different sizes in the graphite box plate material, and the formed pore structure is less than that of the previous box plate material, avoiding the box plate material from easily cracking due to excessive internal pressure in the box-type graphitization furnace, which leads to local furnace spraying.

[0106] 2. The lack of any one of the four powder materials in the raw materials of this application will lead to a significant decrease in the volume density of the graphite box plate material. In addition, the change in the proportion of particle sizes will also lead to a decrease in the volume density, and the volume density affects the thermal conductivity, strength and wear resistance of the graphite box plate material. For this reason, this application ensures that the volume density of the graphite box plate material meets the requirements through optimal design, and the graphite box plate material also has good mechanical strength.

[0107] 3. The electric calcined coal added to the raw materials of the present application can effectively improve the antioxidant properties of the graphitized box plate material and reduce the weight loss rate of the graphite box plate after one graphitization; at the same time, it can also indicate that the structure and performance of the graphitized box plate material of the present application are more stable, ensuring the long-term stable use of the graphitized box plate material; and, the smaller the weight loss rate, it also indicates that there are fewer impurities in the graphitized box plate material. For this reason, the resistivity of the graphitized box plate material of the present application is lower.

[0108] 4. The addition of dust removal powder in this application can appropriately reduce the amount of asphalt used, because the dust removal powder has a small particle size and can be effectively dispersed in the gaps of the dry material, playing a filling role, making the material stacking more compact. When the dry material and asphalt are combined, the packing density of the dry material increases and the gaps become smaller, so as not as much asphalt as before is needed to fill these gaps, thereby reducing the amount of asphalt used. At the same time, the dust removal powder is a spherical particle with a more regular shape, which makes the distribution of various substances in the graphitized box plate material more uniform, and can reduce the resistivity of the graphitized box plate material to a certain extent.

[0109] 5. The box board material prepared by the present invention has suitable hardness and is easy to cut and process, so that the box board material has good machinability.

[0110] 6. The present invention uses graphitized oil coke, asphalt coke and dust removal powder as raw materials. Graphitized coke can improve the overall thermal and electrical conductivity of the graphite box plate material due to its special watershed structure.

[0111] 7. The preparation method of the present invention is simple and easy to operate, and the volume density of the prepared graphite box plate material is 1.62-1.65g / cm 3 , flexural strength>13MPa, compressive strength>45MPa, resistivity 26-33μΩ·m, meeting the requirements of thermal shock resistance under electrical load.

[0112] 8. In this application, the manufacturing cost is greatly reduced under the condition that the physical and chemical properties of the product are basically the same. The cost of raw materials is reduced, and the cost is reduced by eliminating the graphitization treatment; the product quality is improved, and the finished product is qualified through unique molding formula, kneading and roasting process technologies.

[0113] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from all points of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims be included in the present invention. .

Claims

1. A method for preparing a graphite box plate for a box-type graphitization furnace, characterized in that: The steps include: (1) Weighing dry materials and asphalt, the dry materials include graphitized coke, asphalt coke, dust removal powder, and electric calcined coal; Among them, according to weight percentage, graphitized coke is 50-52%, asphalt coke is 10-12%, dust removal powder is 10-12%, electric calcined coal is 5-7%, and asphalt is 20-22%; (2) mixing the dry material and asphalt in step (1) into a paste; (3) adding the paste in step (2) into a mold, performing compression molding, and performing compression and vibration molding to obtain a graphite green body; (4) demolding and cooling the graphite green body in step (3), and then passing through a ring-type roasting furnace to obtain a graphite cooked body; (5) The graphite blank in step (4) is machined to obtain a graphite box plate.

2. The preparation method according to claim 1, characterized in that: In step (1), the graphitized coke is composed of graphitized coke materials of different particle sizes, wherein the powder with a particle size range of 0-2 mm accounts for 70% and the powder with a particle size less than 0.075 mm accounts for 30%; The particle size of pitch coke ranges from 3 to 6 mm; The dust removal powder includes the tail powder collected from the processes of electrode raw material block crushing, screening, transportation, batching and mechanical processing, and the dust removal powder also includes the tail powder collected from the graphitized coke screening process. The dust removal powder has a particle size range of 0.1-100μm; The particle size range of electric calcined coal is 6-25mm.

3. The preparation method according to claim 2, characterized in that: Graphitized coke with a particle size range of 0-2mm meets the following indicators: Ash content ≤0.5%, sulfur content ≤0.3%, true density ≥2.18g / cm3, powder resistivity ≤150μΩ·m.

4. The preparation method according to claim 1, characterized in that: The asphalt in step (2) meets the following indicators: Ash content ≤ 0.3%, coking value ≥ 56%, softening point 106°C-112°C, toluene insoluble matter (TI) 28%-32%, quinoline insoluble matter (QI) 6%-12%.

5. The preparation method according to claim 4, characterized in that: In step (2), the mixing of raw materials and asphalt comprises the following steps: Firstly, graphitized coke, dust removal powder, electric calcined coal and asphalt coke are dry mixed at a temperature of 140-150°C for 20-30 minutes to obtain a uniformly mixed dry material; After the asphalt is heated and melted, it is allowed to stand still and the temperature is controlled at 160-180°C. The asphalt and dry material are wet mixed for 30-50 minutes so that the medium-temperature asphalt completely covers the surface of the raw materials to obtain a paste.

6. The preparation method according to claim 5, characterized in that: The asphalt is heated by the waste heat from the roasting furnace in step (4).

7. The preparation method according to claim 1, characterized in that: In step (3), a vertical molding device is used to pressurize the paste of a preset weight into a graphite green body of 2800 mm × 730 mm × 730 mm using a vertical molding process. The large cylinder pressure is 16-20 MPa, the pressure is maintained for 30-45 minutes, and after the pressure is removed from the mold, it is placed in a cooling water pool for cooling for 7-8 hours to obtain a graphite green body.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In step (4), the graphite green body is placed in a ring-type roasting furnace, and the graphite green body is roasted in an air-tight condition by adopting a rapid temperature rise and variable temperature roasting method.

9. The preparation method according to claim 8, characterized in that: The variable temperature roasting is carried out according to the temperature rising curve, the temperature is gradually raised from room temperature to 1000-1200°C according to the temperature rising curve, and roasting is carried out at 1000-1200°C for 3-4h.

10. The preparation method according to claim 9, characterized in that: Metallurgical coke particles are laid at the bottom of the ring roasting furnace. After the graphite green body is loaded, the gaps around the graphite green body and the top are filled with metallurgical coke particles so that the metallurgical coke particles completely surround the graphite green body, and the graphite green body is roasted under the protection of the protective medium.

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