Prebaked anode and method for producing the same

Abstract

The application discloses a prebaked anode, characterized in that the raw material for preparing the prebaked anode comprises aggregate and binder, wherein the aggregate comprises calcined petroleum coke and / or coal-based coke, and the binder comprises low-ash high-caking bituminous coal. The prebaked anode product prepared according to the application has better homogeneity and better product performance, the raw material source of the prebaked anode is expanded, and the dependence of the prebaked anode raw material on petroleum coke and coal pitch is reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon material preparation technology, specifically to a prebaked anode and its preparation method. Background Technology

[0002] Electrolytic aluminum is a crucial basic industry, and its production capacity has shown a steady growth trend over the past decade or so. Prebaked anodes are one of the main materials consumed in the electrolytic aluminum process, and their demand has increased proportionally year by year. However, the raw materials used in the production of prebaked anodes (aggregates and binders) have been decreasing year by year. Among these aggregates, the main raw material is petroleum coke. In the past two or three decades, with the annual increase in my country's oil imports and the continuous improvement of oil processing technology, refineries have focused on increasing the yield of light oil products. More petroleum asphalt is being used to convert into light oil products, resulting in a year-on-year decline in petroleum coke production. Moreover, the sulfur content and impurity content of petroleum coke are increasing. These changes have not only compressed the selection space for raw materials for prebaked anodes but also increased the production cost of prebaked anodes and affected the product quality. Regarding the binder for prebaked anodes, the binder mainly comes from high-temperature coal tar pitch. In recent years, with the implementation of a series of measures such as eliminating outdated production capacity and controlling total production capacity in the coking industry, the coking industry's production capacity has reached its peak, and the production capacity of high-temperature coal tar pitch is also in a period of slow decline, resulting in a decreasing supply of prebaked anode binders that cannot meet the needs of the electrolytic aluminum industry.

[0003] To address the increasingly tight supply of prebaked anode raw materials, researchers have begun searching for alternatives to aggregates and binders. However, there has been relatively little work on the development and application of new binders; only patent application CN113603488A proposes using phenolic resin as a binder for prebaked anode preparation. Clearly, the source and price of phenolic resin remain highly uncertain. In the search for new aggregate raw materials, coal is initially considered as a substitute for petroleum coke, as its molecular structure and carbon content are very similar. From a supply perspective, coal can fully meet the needs of prebaked anode preparation. However, coal cannot directly replace petroleum coke in prebaked anode preparation because its skeletal structure and properties differ significantly from petroleum coke. For example, coal has a high ash content (but low nickel and vanadium content), low true and apparent density, and high resistivity, all of which affect the performance indicators of prebaked anode products. Extensive experimental research has shown that selecting suitable coal types (such as anthracite and high-rank bituminous coal) and undergoing appropriate pretreatment (such as deashing and calcination) can partially replace petroleum coke. Besides coal, people have also used carbon-rich materials such as natural graphite and carbon black to partially replace petroleum coke, and this has achieved certain results.

[0004] Patent CN101225530B selects low-ash anthracite, bamboo charcoal, wood charcoal and recycled plastic and rubber pyrolysis carbon as auxiliary raw materials after calcination, and mixes them with calcined petroleum coke as aggregate for prebaked anodes, wherein the amount of auxiliary raw materials mixed in the aggregate does not exceed 25%.

[0005] Patent applications CN101343751A, CN103741168A, and CN112725837A describe methods for calcining anthracite to improve its density, strength, and conductivity, followed by acid washing and deashing. The calcination temperature needs to reach a maximum of 1800-2200℃. Anthracite treated in this way is then mixed with petroleum coke in a certain proportion as aggregate for prebaked anodes, which can alleviate the growing shortage of petroleum coke.

[0006] Patent CN103484896B uses a mixture of 50-60% deashed carbonized rice husks, 15-20% high-temperature calcined deashed anthracite, 12-16% petroleum coke, and 12-16% artificial graphite as aggregate, and a mixture of 60-70% modified phenolic resin and 30-40% modified asphalt as binder. Furthermore, 80-85% of the aggregate and 15-20% of the binder are mixed to prepare the prebaked anode. This reduces the dependence on petroleum coke and lowers the material cost of the prebaked anode.

[0007] Patent CN106283117B uses a certain proportion of anthracite and lean coal mixture to replace petroleum coke after calcination and deashing, and introduces furfuryl alcohol resin into the asphalt binder to improve the performance of the binder, which can prepare prebaked anodes with better antioxidant properties.

[0008] Patent CN112831805B describes the use of a mixture of low-rank bituminous coal (0.3% ≤ maximum average reflectance of vitrinite ≤ 0.6%) and high-rank bituminous coal (1.5% < maximum average reflectance of vitrinite ≤ 3.5%) as aggregate, mixed with asphalt binder, and then roasted twice at 1000-1100℃ and 1800-2000℃ to prepare a prebaked anode. To avoid the "furnace spraying" phenomenon during heating, this patent selects a blend of high-rank and low-rank bituminous coal, controlling the volatile matter content of the high-rank bituminous coal to be 15-25% and the caking index to be 50-70, while the volatile matter content of the low-rank bituminous coal is 28-37% and the caking index to be 5-30.

[0009] The aforementioned patents all propose different methods for processing bituminous coal and anthracite to replace or partially replace petroleum coke. However, due to the low true density of coal (bituminous coal has a true density of 1.3-1.4 g / cm³), these patents are not suitable for replacing petroleum coke. 3 The true density of anthracite is 1.4-1.8 g / cm³. 3 Its apparent density is much lower than that of petroleum coke (the true density of calcined petroleum coke is 2.0-2.1 g / cm³). 3Even with high-temperature calcination up to 2000℃, it is difficult to make the true density of coal meet the requirements of prebaked anodes (prebaked anodes require a true density of not less than 2.05 g / cm³). 3 Therefore, without changing the coal skeleton structure, coal is not an ideal aggregate raw material. It can only be mixed with an appropriate proportion of coal as aggregate when the technical indicators such as the true density and apparent density of the prebaked anode are sufficient. Summary of the Invention

[0010] The purpose of this invention is to overcome the defects of the prior art and provide a prebaked anode, wherein the raw materials for preparing the prebaked anode include aggregate and binder, wherein the aggregate includes calcined petroleum coke and / or coal-based coke, and the binder includes low-ash, high-caking bituminous coal.

[0011] Preferably, the mass ratio of the aggregate to the binder is in the range of 3 / 7 to 8 / 2.

[0012] Preferably, the calcined petroleum coke is low-volatile coke obtained by calcining petroleum coke at 1250-1350℃, and the particle size of the calcined petroleum coke particles is less than 60mm. The coal-based coke is produced by high-temperature coking of low-ash, high-caking bituminous coal, with the high temperature being 600-1300℃.

[0013] Preferably, the low-ash, high-caking bituminous coal has a caking index greater than 50, an ash content of no more than 1%, and a particle size of less than 1 mm; the low-ash, high-caking bituminous coal includes one or more of the following: deashed gas coal, gas-rich coal, 1 / 3 coking coal, fat coal, coking coal, and lean coal.

[0014] This invention provides a method for preparing the prebaked anode, comprising the following steps: 1) Mixing: Mix the raw materials of the prebaked anode evenly to obtain a mixture; 2) Molding: The mixture is loaded into the mold, the mold is sealed, and a vacuum system is connected to evacuate the mold. The mixture inside the mold is heated to a temperature of 380-430℃. The vacuuming is stopped, and the cracking gas generated by the mixture changes the vacuum state inside the mold to normal pressure. The temperature is then raised to a range of 450-500℃. Finally, the mixture is cooled and demolded to obtain the shaped carbon block. 3) Calcination: The shaped carbon blocks are placed in a calcination furnace and heated and calcined. After cooling, prebaked anode blanks are obtained and then processed into prebaked anodes according to the dimensions of the prebaked anodes.

[0015] Preferably, in step 2), the vacuum degree is controlled at 0-0.08 MPa, the heating rate is controlled at 1-50℃ / h, the temperature is raised to 450-500℃, and the temperature is held for 2-24 hours.

[0016] Preferably, in step 3), the charcoal blocks are heated and roasted at a heating rate of 1-50℃ / h, and the temperature is raised to the range of 1200-1300℃ and kept constant for 8-16 hours.

[0017] Preferably, in step 1), when the aggregate in the raw material of the prebaked anode is coal-based coke, the specific method for preparing the aggregate includes the following steps: Low-ash, high-caking bituminous coal is used as raw material. A certain amount of raw coal is weighed and placed into a mold, the mold is sealed, and a vacuum system is connected to evacuate the mold. The raw coal inside the mold is heated. When the temperature reaches the range of 380-430℃, the vacuuming is stopped, and the pyrolysis gas generated by the mold itself changes the vacuum state inside the mold to a normal pressure state. The temperature is continued to rise to the final temperature range of 600-1300℃. The temperature is kept constant, cooled, demolded, and crushed to obtain coal-based coke aggregate.

[0018] Preferably, the vacuum degree is controlled at 0-0.08 MPa, the heating rate is controlled at 1-50℃ / h, the temperature is raised to the final temperature at 600-1300℃, and the temperature is held for 2-8 hours.

[0019] Preferably, if the bulk density and / or mechanical strength of the prebaked anode are low, step 4) is also included: impregnation: the impregnation process adopts a conventional carbon block impregnation process, which is a conventional technical means in the field.

[0020] Compared with the prior art, the advantages of the present invention are: (1) Using low-ash, high-caking bituminous coal as a binder instead of coal tar pitch expands the source of binders and increases the coking value of the binder (the coking value of coal tar pitch binders is below 60%, while the coking value of low-ash, high-caking bituminous coal is around 85%). (2) Aggregates prepared using low-ash, high-caking bituminous coal as raw material and the technology of this invention expand the source of prebaked anode aggregates and also increase the true density of the aggregates. This results in aggregates prepared by this invention having a density as high as 2.00-2.08 g / cm³. 3 This invention solves the problems of low true density and low bulk density of prebaked anodes when using coal as aggregate in existing patents. The prebaked anode products prepared according to this invention have better homogeneity and superior performance, expand the raw material sources for prebaked anodes, and reduce the dependence of prebaked anode raw materials on petroleum coke and coal tar pitch. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation of a prebaked anode for electrolytic aluminum according to the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0023] Specifically, this invention proposes a method for preparing prebaked anodes for electrolytic aluminum, comprising: (1) selecting raw materials; (2) a process for preparing aggregates; (3) a process for preparing binders; and (4) a process for preparing prebaked anodes.

[0024] (1) Selecting raw materials The raw materials used in this invention include calcined petroleum coke and / or low-ash, high-caking bituminous coal. The coal-based coke is obtained by coking low-ash, high-caking bituminous coal at a high temperature of 600-1300℃. Aggregates and binders are prepared from these two raw materials, and finally, prebaked anode products are produced.

[0025] The calcined petroleum coke mentioned above is the low-volatile coke obtained by calcining commonly used petroleum coke at 1250-1350℃.

[0026] The low-ash, high-caking bituminous coal refers to various bituminous coals whose ash content has been reduced to below 1.0% (the optimal solution is less than 0.5%) and whose caking index is greater than 50 (preferably greater than 65) after deashing. According to the national coal classification standard (GB / T5751), the selected bituminous coals include some gas coal, gas-fat coal, 1 / 3 coking coal, fat coal, coking coal, and some lean coal.

[0027] (2) Process for preparing aggregate Calcined petroleum coke aggregate: Calcined petroleum coke is crushed into particles smaller than 60 mm and used as aggregate according to different particle size distributions in this invention, or it is crushed into fine particles with a particle size smaller than 1 mm and used as calcined petroleum coke aggregate in this invention.

[0028] Coal-based coke aggregate: Select one or more of the aforementioned low-ash, high-caking bituminous coals as raw coal. Crush the raw coal into fine particles with a particle size of less than 1 mm, weigh a certain amount, and load it into a mold. Vibrate appropriately to ensure the powder is packed as densely as possible. Seal the mold and connect it to a vacuum system to create a vacuum, placing the inside of the mold under negative pressure. The vacuum degree should be controlled within the range of 0-0.08 MPa, with an optimal range of 0-0.05 MPa. When the Gibbs freeness of the raw coal is low, a higher vacuum degree can be used; when the Gibbs freeness of the raw coal is high, a lower vacuum degree can be used, or even atmospheric pressure can be used.

[0029] Once the vacuum level inside the mold stabilizes, the raw coal inside the mold is heated at a rate controlled between 1-50℃ / h, with an optimal rate of 3-20℃ / h. When the temperature reaches above 300℃, cracked gas or tar will be generated. The extracted gas can be processed and used as fuel gas and tar products. When the temperature reaches 380-430℃, vacuuming is stopped, and the cracked gas generated by the mold itself changes the vacuum state to atmospheric pressure. The cracked gas is then transported to the gas processing system by its own pressure. Heating continues until the final temperature is reached, and the mixture is held at that temperature for 2-8 hours to obtain aggregate char blocks.

[0030] The endpoint temperature is selected within the range of 600-1300℃. Using a higher endpoint temperature is beneficial for increasing the true density of the aggregate and the bulk density of the prebaked anode. The endpoint temperature depends on the properties of the raw coal. For high-rank bituminous coal (e.g., lean coal, some coking coal), a lower endpoint temperature can be used, while for low-rank bituminous coal (e.g., gas coal), a higher endpoint temperature can be used. If the endpoint temperature is selected around 600℃, the temperature is directly raised to the endpoint temperature, held constant, then cooled and demolded to obtain aggregate char blocks. If a higher endpoint temperature is selected, the temperature is raised to 600℃, then cooled and demolded to obtain semi-finished char blocks. These semi-finished char blocks are then placed in a high-temperature roasting furnace and heated to the endpoint temperature at the original heating rate, held constant, and then cooled to obtain aggregate char blocks.

[0031] Finally, the aggregate char blocks are crushed into fine particles with a particle size of less than 1 mm to obtain the coal-based coke aggregate described in this invention.

[0032] The aggregates described in this invention: the calcined petroleum coke aggregates and coal-based coke aggregates prepared above can be used alone as the aggregates of this invention, or they can be mixed in any proportion as the aggregates of this invention.

[0033] (3) Process for preparing adhesive The raw materials selected are low-ash, high-caking bituminous coals, including deashed gas coal, gas-rich coal, 1 / 3 coking coal, coking coal, and some lean coal. Each of these coals can be used as a binder raw material, or two or more of them can be mixed together. Mixing these coals helps to compensate for the performance deficiencies exhibited when certain coal types are used alone. For example, using gas coal as a binder raw material results in products with low compressive and flexural strength, but mixing in some coking coal significantly improves both. Selecting one or more of the above-mentioned coals or mixed coals as the binder raw material and crushing them into fine particles with a particle size of less than 1 mm yields the binder described in this invention.

[0034] (4) Process for preparing prebaked anodes The process of preparing a prebaked anode using aggregates and binders involves the following steps: Preparation of the mixture: Mix the above-mentioned aggregates and binder in a certain proportion until homogeneous to obtain the mixture. The aggregates can be the above-mentioned calcined petroleum coke aggregates or coal-based coke aggregates, or a mixture of them in any proportion. The mass ratio of aggregates to binder ranges from 3 / 7 to 8 / 2, with the optimal mass ratio range being 4 / 6 to 7 / 3.

[0035] Molding: The above mixture is loaded into a mold (the three-dimensional shape of the mold should be close to the shape of the prebaked anode to be prepared. Considering the shrinkage of carbon block volume during high-temperature roasting, the size of the mold should be appropriately larger than the size of the prebaked anode to be prepared) and vibrated appropriately to make the mixture as dense as possible.

[0036] After the mixture is loaded into the mold, the mold is sealed, and a vacuum system is connected to evacuate the mold, placing the mixture inside under negative pressure. This negative pressure helps increase the apparent density of the prebaked anode. The vacuum level is controlled within the range of 0-0.08 MPa, with an optimal range of 0-0.05 MPa. The vacuum level can be adjusted based on the maximum Gibbs free flow of the binder. When the maximum Gibbs free flow of the binder is low, a higher vacuum level can be used; when the maximum Gibbs free flow of the binder is high, a lower vacuum level can be used, or even molding can be performed under normal pressure.

[0037] Once the vacuum level inside the mold stabilizes, the mixture inside the mold can be heated at a rate controlled within the range of 1-50℃ / h, with an optimal rate of 3-20℃ / h. When the temperature reaches above 300℃, cracked gas or tar will be generated. The extracted gas can be processed and used as fuel gas and tar. When the temperature reaches the range of 380-430℃, vacuuming is stopped, and the cracked gas generated by the mold itself changes the vacuum state inside the mold to atmospheric pressure. Then, the cracked gas is transported to the gas treatment system by its own pressure. The temperature is then increased to the range of 450-500℃ and held for 2-24 hours. Finally, the temperature is lowered and the mold is removed to obtain the formed carbon block.

[0038] Calcination: The shaped carbon blocks are placed in a calcination furnace and heated at a rate of 1-50℃ / h, with the optimal heating rate controlled within the range of 3-20℃ / h. The temperature is raised to 1200-1300℃ and held for 8-16 hours. After cooling, the carbon blocks are processed according to the dimensions of the prebaked anode to obtain the prebaked anode product. The fragments generated during processing can be crushed and incorporated into the aggregate for recycling.

[0039] Impregnation: If the target product is a high-density, high-strength carbon block, the carbon block after roasting can be further impregnated and roasted.

[0040] Example 1: Preparation of Aggregate A Aggregate preparation: A raw material for calcined petroleum coke as aggregate was selected. Its composition and properties are listed in Table 1. The calcined petroleum coke was crushed into fine particles with a particle size of less than 1 mm using a crusher. This material was then named aggregate A.

[0041] Table 1. Composition and properties of aggregates

[0042] Example 2: Preparation of Aggregate B A type of deashed coking coal (ash content of 0.42%) was selected as the raw material for preparing aggregate. Its composition and properties are listed in Table 2. The selected coking coal was crushed into fine particles with a particle size of less than 1 mm using a crusher.

[0043] Weigh approximately 3000g of the above-mentioned fine coking coal particles and pack them into a stainless steel mold with internal dimensions of 150mm in length, 120mm in width, and 220mm in height. Place the mold on a high-frequency vibrator and vibrate for 1 minute. Then, seal the mold and place it into a heating furnace. Connect the mold outlet to a vacuum system.

[0044] The vacuum system was activated to slowly increase the vacuum level inside the mold and stabilize it at 0.05 MPa. The heating furnace was started, and the temperature was raised to 300°C at a rate of 50°C / h, and held at that temperature for 2 hours. Then, the temperature was increased at a rate of 10°C / h until it reached 420°C. The vacuum system was then disconnected, and the vacuum process was stopped. As the temperature continued to rise, the generated gas caused the vacuum level inside the mold to gradually decrease until it reached atmospheric pressure. The temperature was then increased at a rate of 10°C / h until it reached the final temperature of 600°C, held at that temperature for 2 hours, and then cooled to obtain aggregate char blocks. The aggregate char blocks were crushed into fine particles with a particle size of less than 1 mm using a crusher, thus producing an aggregate, named Aggregate B.

[0045] Table 2 Composition and properties of low-ash, high-caking bituminous coal

[0046] Example 3: Preparation of aggregate C A deashed coking coal (ash content of 0.39%) was selected as the raw material for preparing aggregate. Its composition and properties are listed in Table 2. The selected coking coal was crushed into fine particles with a particle size of less than 1 mm using a crusher.

[0047] Weigh approximately 3000g of the above-mentioned fine coking coal particles and pack them into a stainless steel mold with internal dimensions of 150mm in length, 120mm in width, and 220mm in height. Place the mold on a high-frequency vibrator and vibrate for 1 minute. Then, seal the mold and place it into a heating furnace. Connect the mold outlet to a vacuum system.

[0048] The vacuum system was activated to slowly increase the vacuum level inside the mold and stabilize it at 0.03 MPa. The heating furnace was started, and the temperature was raised to 300℃ at a rate of 40℃ / h, and held at that temperature for 4 hours. Then, the temperature was raised further at a rate of 10℃ / h. When the temperature reached 400℃, the vacuum system was disconnected, and the vacuum process was stopped. As the temperature continued to rise, the generated gas caused the vacuum level inside the mold to gradually decrease, eventually reaching atmospheric pressure. The temperature was then raised to the final temperature of 1250℃ at a rate of 10℃ / h and held for 3 hours. Cooling was then initiated to obtain aggregate char blocks. The aggregate char blocks were crushed into fine particles with a particle size of less than 1 mm using a crusher, thus producing an aggregate, named Aggregate C.

[0049] Example 4: Preparation of Aggregate D Lean coal (ash content 0.28%) and gas coal (ash content 0.45%) after deashing were selected as raw materials for preparing aggregates. The composition and properties of the two raw coals are listed in Table 2. The two raw coals were crushed into fine particles with a particle size of less than 1 mm using a crusher.

[0050] Approximately 1500g of the aforementioned lean coal fine particles and 1500g of the aforementioned gas coal fine particles were placed together in a sealed rotating drum and mixed for 5 minutes to ensure thorough and uniform mixing of the two raw coal materials. The mixture was then poured into a stainless steel mold with internal dimensions of 150mm (length), 120mm (width), and 220mm (height), and the mold was placed on a high-frequency vibrator and vibrated for 1 minute. The mold was then sealed and placed into a heating furnace, with the mold outlet connected to a vacuum system.

[0051] The subsequent working procedures and conditions are the same as in Example 3, and the resulting aggregate is named Aggregate D.

[0052] Example 5: Preparation of prebaked anode A Aggregate: Aggregate A is selected. Binder preparation: A deashed coking coal (ash content of 0.42%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. The deashed coking coal was crushed into fine particles with a particle size of less than 1 mm using a crusher as the binder.

[0053] Mixing: Approximately 1200g of aggregate and 1800g of binder (aggregate / binder = 4 / 6) are placed in a sealed rotating drum and mixed for 5 minutes to ensure thorough and uniform mixing. Then, the mixture is poured into a stainless steel mold with internal dimensions of 150mm (length) x 120mm (width) x 220mm (height) and the mold is placed on a high-frequency vibrator and vibrated for 1 minute. Finally, the mold is sealed and placed in a heating furnace, with the mold outlet connected to a vacuum system.

[0054] Molding: Activate the vacuum system to slowly increase the vacuum level inside the mold and maintain it at 0.05 MPa. Start the heating furnace and control the heating rate to 300℃ at 50℃ / h, hold at that temperature for 2 hours to ensure uniform temperature inside and outside the carbon block. Then, continue heating at a rate of 10℃ / h. When the temperature reaches 420℃, disconnect the vacuum system and stop vacuuming. As the temperature continues to rise, the generated gas causes the vacuum level inside the mold to gradually decrease, eventually reaching atmospheric pressure. Maintain the original heating rate and raise the temperature to the maximum of 500℃, hold at that temperature for 2 hours, then cool and demold. Molding is complete, yielding the shaped carbon block.

[0055] Calcination: The shaped carbon blocks are loaded into a calcination furnace and calcined at high temperature under the protection of coke powder and inert gas. First, the temperature is raised to 400℃ at a rate of 50℃ / h and held for 2 hours. Then, the temperature is raised to 1250℃ at a rate of 5℃ / h and held for 8 hours before cooling is started to complete the calcination. Prebaked anode sample A is obtained. The performance of the calcined sample is tested, and the results are listed in Table 3.

[0056] Table 3 Performance Indicators of Roasted Charcoal Blocks

[0057] Example 6: Preparation of prebaked anode B Aggregate: Aggregate A is selected.

[0058] Binder preparation: The difference from Example 5 is that a deashed 1 / 3 coking coal (ash content of 0.50%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. Other aspects are the same as in Example 5.

[0059] The mixing, molding, and calcination processes and conditions are the same as in Example 5. The performance indicators of the calcined carbon block (i.e., prebaked anode B) are listed in Table 3.

[0060] Example 7: Preparation of prebaked anode C Aggregate: Aggregate A is selected.

[0061] Binder preparation: Unlike Example 5, a deashed coking coal (ash content of 0.38%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. Other aspects are the same as in Example 5.

[0062] Mixture: The difference from Example 5 is that the mixing ratio of aggregate and binder in this example is 7 / 3, that is, about 2100g of aggregate and 900g of binder are mixed. The rest is the same as in Example 5.

[0063] Molding: Activate the vacuum system to slowly increase the vacuum level inside the mold and maintain it at 0.03 MPa. Start the heating furnace and control the heating rate to 300℃ at 45℃ / h, holding it at that temperature for 6 hours to ensure uniform temperature inside and outside the carbon block. Then, continue heating at a rate of 15℃ / h. When the temperature reaches 400℃, disconnect the vacuum system and stop vacuuming. As the temperature continues to rise, the generated gas causes the vacuum level inside the mold to gradually decrease, eventually reaching atmospheric pressure. Maintain the original heating rate and raise the temperature to the maximum of 480℃, holding it at that temperature for 5 hours. Cool down, demold, and the molding process is complete, yielding the molded carbon block.

[0064] Calcination: Same as in Example 5, the performance indicators of the calcined carbon block (i.e., prebaked anode C) are listed in Table 3.

[0065] Example 8: Preparation of prebaked anode D Aggregate: Aggregate A is selected.

[0066] Binder preparation: The difference from Example 5 is that a deashed gas-rich coal (ash content of 0.39%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. Other aspects are the same as in Example 5.

[0067] Mixture: The difference from Example 5 is that the mixing ratio of aggregate and binder in this example is 6 / 4, that is, about 1800g of aggregate and 1200g of binder are mixed, and the rest is the same as in Example 5.

[0068] Molding: Same as in Example 7.

[0069] Calcination: Same as in Example 5, the performance indicators of the calcined carbon block (i.e., prebaked anode sample D) are listed in Table 3.

[0070] Example 9: Preparation of prebaked anode E The difference between this embodiment and Embodiment 8 is that no vacuum is applied during the initial molding stage, and molding is performed under normal pressure. Other processes and conditions are the same as in Embodiment 8. The final performance indicators of the calcined carbon block (i.e., the prebaked anode sample E) are listed in Table 3.

[0071] Example 10: Preparation of prebaked anode F Aggregate: Aggregate A is selected.

[0072] Binder preparation: Unlike Example 5, a type of deashed lean coal (ash content of 0.28%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. Other aspects are the same as in Example 5.

[0073] Mixture: Same as in Example 5 (aggregate / binder = 4 / 6).

[0074] Molding: Same as in Example 5. Calcination: The difference from Example 5 is that the maximum calcination temperature was increased to 1300℃, otherwise it was the same as Example 5. The performance indicators of the calcined carbon block (i.e., the prebaked anode sample F) are listed in Table 3.

[0075] Example 11: Preparation of prebaked anode G Aggregate: Aggregate A is selected.

[0076] Binder preparation: Unlike Example 5, a deashed coal gas (ash content of 0.45%) was selected as the raw material for the binder. Its composition and properties are listed in Table 2. Other aspects are the same as in Example 5.

[0077] Mixture: Same as in Example 8 (aggregate / binder = 6 / 4).

[0078] Molding: Same as in Example 7.

[0079] Calcination: Same as in Example 10. The final performance indicators of the calcined carbon block (i.e., the prebaked anode sample G) are listed in Table 3.

[0080] Example 12: Preparation of prebaked anode H Aggregate: Aggregate A is selected.

[0081] Binder preparation: The difference from Example 5 is that a mixture of two types of coal was used as the raw material for the binder. One type is deashed gas coal, and the other is deashed coking coal. The composition and properties of the two types of coal are listed in Table 2, and the ratio of the two types of coal is 50 / 50. Other procedures are the same as in Example 5.

[0082] Mixture: The difference from Example 5 is that the mixing ratio of aggregate and binder in this example is 5 / 5, that is, about 1500g of aggregate and 1500g of binder are mixed, and the rest is the same as in Example 5.

[0083] Molding: Same as in Example 7.

[0084] Calcination: Same as in Example 10. The final performance indicators of the calcined carbon block (i.e., the prebaked anode H sample) are listed in Table 3.

[0085] Example 13: Preparation of prebaked anode I Aggregate: Aggregate B is selected.

[0086] Binder preparation: A deashed coking coal (ash content of 0.42%) was selected as the raw material for preparing the binder. Its composition and properties are listed in Table 4. The selected coking coal was crushed into fine particles with a particle size of less than 1 mm using a crusher, thus preparing the binder.

[0087] Mixture: Approximately 1200g of aggregate B and 1800g of the binder (aggregate / binder = 4 / 6) are placed into a sealed rotating drum and mixed for 5 minutes to ensure thorough and uniform mixing. The mixture is then poured into a stainless steel mold with internal dimensions of 150mm (length) x 120mm (width) x 220mm (height), and the mold is placed on a high-frequency vibrator and vibrated for 1 minute. Finally, the mold is sealed and placed in a heating furnace, with the mold outlet connected to a vacuum system.

[0088] Molding: Activate the vacuum system to slowly increase the vacuum level inside the mold and maintain it at 0.05 MPa. Start the heating furnace and control the heating rate to 300℃ at 40℃ / h, holding it at that temperature for 4 hours. Then, continue heating at a rate of 15℃ / h. When the temperature reaches 420℃, disconnect the vacuum system from the mold. As the temperature continues to rise, the generated gas causes the vacuum level inside the mold to gradually decrease, eventually reaching atmospheric pressure. Then, continue heating at the original rate to 500℃ and hold it at that temperature for 5 hours. Begin cooling; molding is now complete.

[0089] Calcination: After cooling and demolding, the carbon blocks are loaded into the calcination furnace and calcined at high temperature under the protection of coke powder and inert gas. First, the temperature is raised to 400℃ at a rate of 40℃ / h and held for 6 hours. Then, the temperature is raised to 1250℃ at a rate of 5℃ / h and held for 10 hours. Cooling is then started to complete the calcination, and the prebaked anode I sample is obtained. The performance of the calcined sample is tested, and the results are listed in Table 4.

[0090] Table 4 Performance Indicators of Roasted Charcoal Blocks

[0091] Example 14: Preparation of prebaked anode J Aggregate: Select aggregate C Binder preparation: A mixture of 1 / 3 deashed coking coal (ash content of 0.50%) and deashed gas coal (ash content of 0.45%) was selected as the raw material for preparing the binder. Its composition and properties are listed in Table 2. The two raw coals were crushed into fine particles with a particle size of less than 1 mm using a crusher. Then, they were mixed evenly in a mass ratio of 1:1 to prepare the binder.

[0092] Mixture: The difference from Example 13 is that approximately 1800g of aggregate C is mixed with 1200g of the binder of this example (aggregate / binder = 6 / 4), otherwise the same as in Example 13.

[0093] Molding: Activate the vacuum system to slowly increase the vacuum level inside the mold and maintain it at 0.03 MPa. Start the heating furnace and raise the temperature to 300℃ at a rate of 35℃ / h, holding it at that temperature for 7 hours to ensure uniform temperature inside and outside the charcoal block. Then, raise the temperature to 400℃ at a rate of 20℃ / h, disconnect the vacuum system from the mold, and as the temperature continues to rise, the vacuum level inside the mold gradually decreases until it reaches atmospheric pressure. Continue heating to 480℃ and hold it at that temperature for 5 hours. Then begin cooling, completing the molding process.

[0094] Calcination: The difference from Example 13 is that the final calcination temperature is 1300℃, otherwise it is the same as Example 13. The performance indicators of the calcined carbon block (i.e., the prebaked anode J sample) are listed in Table 4.

[0095] Example 15: Preparation of prebaked anode K Aggregate: Selected aggregate D Binder preparation: A deashed coking coal (ash content of 0.38%) was selected as the raw material for preparing the binder. Its composition and properties are listed in Table 2. The selected coking coal was crushed into fine particles with a particle size of less than 1 mm using a crusher, thus preparing the binder.

[0096] Mixture: The difference from Example 13 is that approximately 1500g of aggregate D is mixed with 1500g of the binder of this example (aggregate / binder = 5 / 5), otherwise the same as in Example 13.

[0097] Molding: Same as in Example 14.

[0098] Calcination: Same as in Example 14. The final performance indicators of the calcined carbon block (i.e., the prebaked anode K sample) are listed in Table 4.

[0099] Example 16: Preparation of prebaked anode L, a comparative example of Example 15 The difference between this embodiment and Embodiment 15 is that no vacuum was applied at the beginning of the molding process; it was carried out under normal pressure. Otherwise, it is the same as Embodiment 15. The performance indicators of the calcined carbon block (i.e., the prebaked anode sample L) are listed in Table 4.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A prebaked anode, characterized in that, The prebaked anode is prepared from aggregate and binder. The aggregate is calcined petroleum coke or coal-based coke, and the coal-based coke is obtained by coking low-ash, high-caking bituminous coal at 600-1300℃. The binder is low-ash, highly adhesive bituminous coal; The mass ratio of the aggregate to the binder is in the range of 3 / 7 to 8 / 2. The low-ash, high-caking bituminous coal is bituminous coal with a caking index greater than 50 and an ash content of no more than 1%.

2. The prebaked anode according to claim 1, characterized in that, The calcined petroleum coke is a low-volatile coke obtained by calcining petroleum coke at 1250-1350℃, and the particle size of the calcined petroleum coke particles is less than 60mm.

3. The prebaked anode according to claim 1, characterized in that, The particle size of the low-ash, high-caking bituminous coal is less than 1 mm.

4. The prebaked anode according to claim 1, characterized in that, The low-ash, high-caking bituminous coal is a bituminous coal with a caking index greater than 65, an ash content of no more than 0.5%, and a particle size of less than 1 mm.

5. The prebaked anode according to claim 3 or 4, characterized in that, The low-ash, high-caking bituminous coal includes one or more of the following: deashed gas coal, gas-rich coal, 1 / 3 coking coal, fat coal, coking coal, and lean coal.

6. A method for preparing a prebaked anode, comprising the following steps: 1) Mixing: Mix the aggregates and binder evenly to obtain a mixture; The aggregate is calcined petroleum coke or coal-based coke, and the coal-based coke is obtained by coking low-ash, high-caking bituminous coal at 600-1300℃. The binder is low-ash, highly adhesive bituminous coal; The mass ratio of the aggregate to the binder is in the range of 3 / 7 to 8 / 2. The low-ash, high-caking bituminous coal is bituminous coal with a caking index greater than 50 and an ash content of no more than 1%. 2) Molding: The mixture is loaded into the mold, the mold is sealed, and a vacuum system is connected to evacuate the mold. The mixture inside the mold is heated to a temperature of 380-430℃. The vacuuming is stopped, and the cracking gas generated by the mixture changes the vacuum state inside the mold to normal pressure. The temperature is then raised to a temperature of 450-500℃. Finally, the mixture is cooled and demolded to obtain the shaped carbon block. 3) Calcination: The shaped carbon blocks are placed in a calcination furnace and heated and calcined. After cooling, prebaked anode blanks are obtained and then processed into prebaked anodes according to the dimensions of the prebaked anodes.

7. The preparation method according to claim 6, characterized in that, In step 2), the vacuum degree is controlled at 0-0.08 MPa, the heating rate is controlled at 1-50℃ / h, the temperature is raised to 450-500℃, and the temperature is held for 2-24 hours.

8. The preparation method according to claim 6, characterized in that, In step 3), the charcoal blocks are heated and roasted at a heating rate of 1-50℃ / h, and the temperature is kept constant for 8-16 hours when the temperature reaches the range of 1200-1300℃.

9. The preparation method according to claim 6, characterized in that, In step 1), the method for preparing coal-based coke includes the following steps: The low-ash, high-caking bituminous coal is used as raw coal. A certain amount of the raw coal is weighed and placed into a mold. The mold is sealed and connected to a vacuum system to evacuate the mold. The raw coal inside the mold is heated. When the temperature reaches the range of 380-430℃, the vacuuming is stopped. The pyrolysis gas generated by the coal itself changes the vacuum state inside the mold to a normal pressure state. The temperature is then raised to the final temperature range of 600-1300℃. The temperature is kept constant, cooled, demolded, and crushed to obtain coal-based coke.

10. The preparation method according to claim 9, characterized in that, In the preparation method of coal-based coke, the vacuum degree is controlled at 0-0.08 MPa, the heating rate is controlled at 1-50℃ / h, the temperature is raised to the final temperature of 600-1300℃, and the temperature is held for 2-8 hours.

11. The preparation method according to claim 6, characterized in that, When the bulk density and / or mechanical strength of the prebaked anode are low, step 4) is also included, which involves impregnation.

12. The preparation method according to claim 6, characterized in that, In step 1), the calcined petroleum coke is low-volatile coke obtained by calcining petroleum coke at 1250-1350℃, and the particle size of the calcined petroleum coke particles is less than 60mm.

13. The preparation method according to claim 6, characterized in that, In step 1), the particle size of the low-ash, high-caking bituminous coal is less than 1 mm.

14. The preparation method according to claim 6, characterized in that, The low-ash, high-caking bituminous coal is a bituminous coal with a caking index greater than 65, an ash content of no more than 0.5%, and a particle size of less than 1 mm.

15. The preparation method according to claim 13 or 14, characterized in that, The low-ash, high-caking bituminous coal includes one or more of the following: deashed gas coal, gas-rich coal, 1 / 3 coking coal, fat coal, coking coal, and lean coal.

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