A method for improving the baking yield of carbon products for aluminum

Abstract

The application relates to a method for improving the baking yield of carbon products for aluminum, and belongs to the technical field of baking of carbon products for aluminum. The method comprises the following steps: placing green blocks of carbon products for aluminum in a low-oxygen inert environment for baking treatment, wherein the baking treatment comprises a low-temperature section, a high-temperature section and a cooling section, wherein the environmental pressure of the environment where the green blocks of the carbon products for aluminum are located is controlled to be micro-negative pressure in the low-temperature section, and low-temperature baking intermediate products are obtained; the environmental pressure of the environment where the green blocks of the carbon products for aluminum are located is controlled to be micro-positive pressure in the high-temperature section, and high-temperature baking intermediate products are obtained; and the environmental pressure of the environment where the green blocks of the carbon products for aluminum are located is controlled to be increasing positive pressure in the cooling section, and finished products of the carbon products for aluminum are obtained.

Description

Technical Field

[0001] This application relates to the field of calcination technology for carbon products for aluminum, and in particular to a method for improving the yield of calcined carbon products for aluminum. Background Technology

[0002] Carbon products for aluminum are key raw materials in the production of electrolytic aluminum and are the most important consumables in the aluminum electrolysis process. The main production processes for carbon products for aluminum include mixing, molding, and calcination, among which the calcination process has a significant impact on the quality and yield of the carbon products. Traditional open calcination furnaces have poor sealing performance, and the pressure inside the furnace fluctuates randomly. The atmospheric pressure and unstable negative pressure environment causes two major problems: First, the pressure is out of control during the pyrolysis stage of the coal tar binder, and the volatile matter escapes irregularly. A large amount of coking coal tar binder macromolecules are lost with the waste gas, resulting in a low coking rate of the coal tar binder and poor adhesion of the carbon product matrix. Second, the furnace cannot maintain a stable pressure, and outside air can easily seep into the furnace. At high temperatures, the carbon matrix oxidizes and burns, further reducing the yield.

[0003] Currently, most optimization solutions in the industry are limited to adjusting the roasting temperature curve, ignoring the decisive influence of pressure on the coking and carbon oxidation of coal tar binders. They have not established a segmented pressure control process that matches the entire carbonization process of coal tar binders, and therefore cannot fundamentally improve the problem of low yield. Summary of the Invention

[0004] This application provides a method for improving the yield of calcination of carbon products for aluminum, in order to solve the following technical problem: how to improve the yield of calcination of carbon products for aluminum. This application provides a method for improving the calcination yield of carbon products for aluminum, the method comprising: The raw aluminum carbon products are placed in a low-oxygen, inert environment for calcination. The calcination process includes a low-temperature section, a high-temperature section, and a cooling section, wherein: The low-temperature section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to a slightly negative pressure, so as to regulate the escape rate of volatiles in the aluminum carbon product lumps and promote the pyrolysis and coking reaction of the coal tar pitch binder in the aluminum carbon product lumps to obtain a low-temperature roasting intermediate product. The high-temperature section controls the environmental pressure of the aluminum carbon product lumps to be slightly positive, so as to prevent external oxygen from penetrating into the environment of the low-temperature roasting intermediate product and inhibit the oxidation of the carbon matrix in the low-temperature roasting intermediate product, thereby obtaining the high-temperature roasting intermediate product. The cooling section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to be an increasing positive pressure, in order to compensate for the pressure loss caused by the decrease in gas temperature and volume shrinkage in the environment of the high-temperature roasting intermediate product, so as to obtain the finished aluminum carbon product.

[0005] Optionally, the low-temperature section heats the aluminum carbon product lumps from 30°C to 500°C and holds them at 500°C for 10-14 hours.

[0006] Optionally, controlling the ambient pressure of the environment where the aluminum carbon product briquettes are located in the low-temperature section to a slightly negative pressure includes: Within the temperature range of 30℃ to 350℃, the environmental pressure of the aluminum carbon product briquettes is -5Pa to 0Pa. During the temperature range of 350℃ to 500℃ and the heat preservation stage at 500℃, the environmental pressure of the raw aluminum carbon product is -3Pa to -1Pa.

[0007] Optionally, the high-temperature section raises the temperature of the low-temperature roasting intermediate product from 500°C to 1150°C and holds it at 1150°C for 8 to 12 hours.

[0008] Optionally, controlling the ambient pressure of the environment where the aluminum carbon product briquettes are located in the high-temperature section to be slightly positive includes: Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 3Pa. During the temperature range of 900℃ to 1150℃ and the holding stage at 1150℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 5Pa.

[0009] Optionally, the cooling section cools the high-temperature roasting intermediate product from 1150°C to 300°C and then naturally cools it to room temperature; the cooling section controls the ambient pressure of the environment where the aluminum carbon product lumps are located to be an increasing positive pressure, including controlling the ambient pressure of the high-temperature roasting intermediate product within the range of 5Pa to 10Pa, and gradually increasing the pressure as the cooling process proceeds.

[0010] Optionally, the bulk density of the aluminum carbon product lumps is ≥1.63 g / cm³. 3 The mass fraction of coal tar pitch binder in the raw aluminum carbon product blocks is 13.2% to 15.5%.

[0011] Optionally, the moisture content of the raw aluminum carbon product lumps is ≤0.3%.

[0012] Optionally, the low-oxygen inert environment can be constructed in the following ways: Aluminum carbon product raw blocks are placed in a sealed container, inert gas is introduced into the sealed container, and the air in the sealed container is replaced by vacuum circulation gas extraction, so that the oxygen volume fraction in the sealed container is reduced to 0.005% to 0.05%.

[0013] Optionally, the inert gas is nitrogen, and the purity of the nitrogen is ≥99.95wt%.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for improving the yield of calcination of aluminum carbon products. The method includes: placing green aluminum carbon products in a low-oxygen inert environment for calcination treatment. The calcination treatment includes a low-temperature section, a high-temperature section, and a cooling section. Specifically: in the low-temperature section, the environmental pressure of the environment where the green aluminum carbon products are located is controlled at a slightly negative pressure to regulate the escape rate of volatiles in the green aluminum carbon products and to promote the pyrolysis and coking reaction of the coal tar pitch binder in the green aluminum carbon products, obtaining a low-temperature calcination intermediate product; in the high-temperature section, the environmental pressure of the environment where the green aluminum carbon products are located is controlled at a slightly positive pressure to prevent external oxygen from penetrating into the environment of the low-temperature calcination intermediate product and to inhibit the oxidation of the carbon matrix in the low-temperature calcination intermediate product, obtaining a high-temperature calcination intermediate product; in the cooling section, the environmental pressure of the environment where the green aluminum carbon products are located is controlled at an incrementally positive pressure to compensate for the pressure loss caused by the decrease in gas temperature and volume shrinkage in the environment of the high-temperature calcination intermediate product, obtaining the finished aluminum carbon products. In this embodiment, the environmental pressure of the aluminum carbon product green block is controlled at a slightly negative pressure in the low-temperature section. Precise and controllable negative pressure suction is used to selectively separate the escaping volatile components, preferentially removing small, useless volatiles such as moisture and hydrogen sulfide. Meanwhile, large, coking components such as polycyclic aromatic hydrocarbons, due to their larger molecular size and higher boiling point, are less likely to be carried away under this negative pressure and are thus trapped inside the aluminum carbon product green block, undergoing a dehydrogenation and polycondensation reaction to transform into dense coke. This fundamentally solves the problem of low coking rate caused by the loss of effective components in the coal tar pitch binder. In the high-temperature section, the environment is switched to a slightly positive pressure environment, creating a physical gas seal barrier that prevents oxygen-containing air from entering the environment. This process cuts off the oxygen supply path. The slightly positive pressure environment, combined with the pre-existing low-oxygen inert environment, ensures that the carbon matrix in the low-temperature roasting intermediate is always protected by a non-oxidizing atmosphere throughout the high-temperature stage. This effectively inhibits the direct loss of carbon materials caused by the oxidation reaction between carbon and oxygen. In the cooling stage, the environmental pressure of the aluminum carbon product lumps is further controlled to be an increasing positive pressure, gradually increasing with the cooling process. By actively increasing the positive pressure value, the pressure loss caused by the decrease in gas temperature and volume contraction is compensated, ensuring that the environmental pressure remains higher than the external atmospheric pressure throughout the cooling process. This fundamentally eliminates the risk of secondary oxidation loss caused by the negative pressure backflow due to gas contraction. The low-temperature section with slight negative pressure, the high-temperature section with slight positive pressure, and the cooling section with incremental positive pressure achieve a smooth transition at the temperature junction, forming a complete protective chain throughout the entire roasting cycle. This maximizes the retention of effective materials through a dual mechanism that reduces the loss of effective components in the coal tar binder and prevents carbon oxidation loss, thereby significantly improving the roasting yield of carbon products for aluminum. Attached Figure Description The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating a method for improving the yield of carbon products for aluminum during calcination, as provided in an embodiment of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] The range descriptions used in this document, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, "content" in this document refers to mass content (mass percentage). Unless otherwise specified, the terms "including," "comprise," etc., used in this document mean "including but not limited to"; relational terms such as "first," "second," etc., are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," "at least one," etc., refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used in this document can all be obtained through commercial purchase or prepared using existing methods.

[0019] Figure 1 This is a flowchart illustrating a method for improving the yield of carbon products for aluminum during calcination, as provided in an embodiment of this application.

[0020] Please see Figure 1This application provides a method for improving the calcination yield of carbon products for aluminum, the method comprising: The raw aluminum carbon products are placed in a low-oxygen, inert environment for calcination. The calcination process includes at least a low-temperature section, a high-temperature section, and a cooling section, wherein: The low-temperature section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to a slightly negative pressure, so as to regulate the escape rate of volatiles in the aluminum carbon product lumps and promote the pyrolysis and coking reaction of the coal tar pitch binder in the aluminum carbon product lumps to obtain a low-temperature roasting intermediate product. The high-temperature section controls the environmental pressure of the aluminum carbon product lumps to be slightly positive, so as to prevent external oxygen from penetrating into the environment of the low-temperature roasting intermediate product and inhibit the oxidation of the carbon matrix in the low-temperature roasting intermediate product, thereby obtaining the high-temperature roasting intermediate product. The cooling section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to be an increasing positive pressure, in order to compensate for the pressure loss caused by the decrease in gas temperature and volume shrinkage in the environment of the high-temperature roasting intermediate product, so as to obtain the finished aluminum carbon product.

[0021] Aluminum carbon product blanks refer to aluminum carbon product blanks that have undergone pre-processing such as mixing and molding but have not yet been baked. These blanks contain coal tar pitch binder and also have a certain amount of moisture and volatile matter.

[0022] A low-oxygen inert environment refers to the external atmosphere in which raw aluminum carbon products are placed. In this environment, the oxygen content is controlled to a level significantly lower than that of normal air, and the atmosphere is primarily composed of chemically inert gases. The purpose of a low-oxygen inert environment is to reduce the opportunity for oxygen to come into contact with the carbon matrix during the calcination process, thereby inhibiting the occurrence of oxidation and burn-off reactions.

[0023] Ambient pressure refers to the pressure value of the external space in which the raw aluminum carbon products are located during each firing stage. In the embodiments of this application, the ambient pressure is expressed in gauge pressure, that is, with the ambient atmospheric pressure as the reference, values ​​higher than the ambient atmospheric pressure are recorded as positive values, and values ​​lower than the ambient atmospheric pressure are recorded as negative values.

[0024] The roasting process includes a low-temperature stage, a high-temperature stage, and a cooling stage. These three stages are sequential in time, forming a complete roasting process. The low-temperature stage comes first, followed by the high-temperature stage, and then the cooling stage. This sequence is determined by the material science changes in the raw aluminum carbon products during the roasting process: the low-temperature stage corresponds to the temperature window of pyrolysis of the coal tar binder and the large-scale release of volatiles; the high-temperature stage corresponds to the temperature window of carbonization of the coal tar binder and densification of the matrix; and the cooling stage corresponds to the temperature window of cooling and solidification of the product.

[0025] The low-temperature section controls the ambient pressure of the green aluminum carbon product briquettes to a slightly negative pressure. This operation regulates the volatile matter release behavior within the green briquettes. The slightly negative pressure environment allows volatile matter inside the green briquettes to be slowly and orderly released to the external environment driven by the internal and external pressure difference. The released volatile matter is neither too rapidly drawn away due to excessive negative pressure, thus losing its opportunity for sufficient reaction within the briquettes, nor too persistently retained due to insufficient negative pressure, affecting subsequent carbonization processes. The slightly negative pressure environment also selectively regulates the composition of the released volatile matter: small-molecule gaseous products such as moisture and hydrogen sulfide are preferentially released, while large-molecule coking components such as polycyclic aromatic hydrocarbons, due to their larger molecular size and slower diffusion rate, gain a longer residence time within the briquettes. During this residence period, these large-molecule components undergo dehydrogenation and condensation reactions, gradually transforming into a coke structure. The effect of slight negative pressure is ultimately to induce the pyrolysis and coking reaction of the coal tar binder in the green aluminum carbon products, generating a coke network that binds the carbon particles together, while preventing the rapid expansion of volatiles from causing cracks and pores inside the green lumps. After low-temperature roasting, the green aluminum carbon products are transformed into low-temperature roasting intermediate products.

[0026] The high-temperature stage controls the ambient pressure of the aluminum carbon product briquettes to a slightly positive pressure, creating a pressure barrier outside the environment of the low-temperature roasting intermediates. Under this slightly positive pressure, the internal pressure of the low-temperature roasting intermediates is higher than the external atmospheric pressure, preventing oxygen-containing air from seeping in through the sealed gaps. Even in the event of a minor leak, the gas flow is from the inside to the outside, not from the outside to the inside. This gas barrier effectively prevents external oxygen from contacting the carbon matrix in the low-temperature roasting intermediates under high-temperature conditions, thereby inhibiting the direct oxidation reaction of carbon with oxygen and the gasification reaction of carbon dioxide with carbon. After high-temperature roasting, the low-temperature roasting intermediates are transformed into high-temperature roasting intermediates.

[0027] The ambient pressure of the aluminum carbon product briquettes in the cooling stage is maintained at an incremental positive pressure. This operation actively compensates for the pressure drop caused by gas contraction during cooling. During cooling, the gas volume in the environment of the high-temperature roasting intermediate product shrinks significantly. Without active pressure compensation, the internal pressure will spontaneously decrease and fall below atmospheric pressure, creating a negative pressure backflow. The incremental positive pressure control method maintains the internal pressure above atmospheric pressure throughout the cooling process, and gradually increases the pressure setpoint as cooling progresses to dynamically match the increasing gas contraction due to temperature reduction. This operation ensures that there is no negative pressure window during the cooling stage, fundamentally eliminating the risk of outside air being drawn back into the environment of the high-temperature roasting intermediate product. After roasting in the cooling stage, the high-temperature roasting intermediate product is transformed into the finished aluminum carbon product.

[0028] In some embodiments, the low-temperature section heats the aluminum carbon product briquettes from 30°C to 500°C and holds them at 500°C for 10 to 14 hours.

[0029] In some embodiments, controlling the ambient pressure of the environment where the aluminum carbon product briquettes are located in the low-temperature section to be a slightly negative pressure includes: Within the temperature range of 30℃ to 350℃, the environmental pressure of the aluminum carbon product briquettes is -5Pa to 0Pa. During the temperature range of 350℃ to 500℃ and the heat preservation stage at 500℃, the environmental pressure of the raw aluminum carbon product is -3Pa to -1Pa.

[0030] Heating from 30℃ to 500℃ refers to the temperature change process of heating green aluminum carbon products from an initial temperature of 30℃ to a target temperature of 500℃ at a predetermined heating rate. 30℃ is a room temperature reference value, representing the initial temperature state of the green aluminum carbon products when entering the low-temperature stage; 500℃ is the target temperature of the low-temperature stage.

[0031] In aluminum carbon product briquettes, the coal tar binder begins to release volatiles after 200℃, with the amount of volatiles increasing continuously with rising temperature, reaching its peak in the 350℃ to 500℃ range. Setting the target temperature for the low-temperature section at 500℃ fully covers the temperature range where the pyrolysis and coking of the coal tar binder are most concentrated, allowing the coal tar binder to fully complete its structural transformation from aromatic compounds to high-boiling-point condensation aromatic compounds and carbonaceous matter within this range. The holding time range of 10h to 14h at 500℃ is determined based on the coking reaction kinetics of the coal tar binder. The dehydrogenation condensation reaction of the coal tar binder at 500℃ requires a certain amount of time to accumulate to reach the ideal conversion degree. The holding time range of 10h to 14h ensures the full progress of the coking reaction. If the holding time is less than 10h, the reaction kinetic time is insufficient, and the conversion of the coal tar binder is incomplete; if it exceeds 14h, the reaction has tended to equilibrium, and further extending the holding time has limited contribution to improving the coking rate, but instead increases energy consumption and production cycle.

[0032] Within the temperature range of 30℃ to 350℃, the escape of volatiles has just begun, and the internal pore network of the green aluminum carbon product briquettes has not yet been penetrated by a large amount of gaseous products, resulting in relatively high flow resistance for the volatiles. A lower negative pressure limit of -5Pa is sufficient to provide the driving force to overcome this flow resistance, allowing the volatiles to begin to escape in an orderly manner at a relatively low temperature. An upper limit of 0Pa ensures that a pressure level at least equal to ambient atmospheric pressure is maintained during this stage, preventing a positive pressure environment that could hinder the escape of volatiles. Simultaneously, the lower limit of -5Pa does not produce an excessively strong suction effect, thus protecting the structural integrity of the green aluminum carbon product briquettes in the initial stage of volatile escape.

[0033] Within the 350℃~500℃ range and during the 500℃ holding stage, the volatile matter escape rate reaches its peak, and the sensitivity to pressure fluctuations also reaches its highest level. A lower limit of -3Pa ensures sufficient negative pressure driving force to remove small, useless volatile molecules. Simultaneously, the absolute value of this negative pressure is less than the previous stage's -5Pa, reflecting the need to reduce suction force when a large amount of volatile matter escapes to prevent premature removal of large, coking components. An upper limit of -1Pa ensures that a slightly negative pressure environment of no less than -1Pa is maintained throughout the violent pyrolysis stage, preventing the pressure from approaching atmospheric pressure or becoming positive, which could lead to uncontrolled volatile matter escape.

[0034] In some embodiments, the high-temperature section raises the temperature of the low-temperature roasting intermediate product from 500°C to 1150°C and holds it at 1150°C for 8 to 12 hours.

[0035] In some embodiments, controlling the ambient pressure of the environment where the aluminum carbon product briquettes are located in the high-temperature section to be slightly positive includes: Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 3Pa. During the temperature range of 900℃ to 1150℃ and the holding stage at 1150℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 5Pa.

[0036] The high-temperature section is the intermediate stage of the roasting process. This stage receives the low-temperature roasting intermediate product output from the low-temperature section, and continues to heat the low-temperature roasting intermediate product from 500°C to 1150°C, and holds it at 1150°C for a predetermined time.

[0037] The coal tar binder in the raw aluminum carbon products has completed the main pyrolysis and coking reaction at 500℃, but the improvement of the carbonization structure and the enhancement of coke quality require further advancement at higher temperatures. Setting the target temperature for the high-temperature section at 1150℃ allows the remaining small amount of volatile matter to further escape during the temperature rise from 500℃ to 1150℃, and also allows the already formed coke to undergo ordered structural rearrangement under high temperature, ultimately transforming it into carbon products with sufficient mechanical strength and electrical conductivity.

[0038] Between 500℃ and 900℃, the temperature of the low-temperature roasting intermediate gradually increases, and the oxidation reactivity of the carbon matrix continuously enhances with rising temperature. This stage employs a micro-positive pressure control of 0Pa to 3Pa. Its core function is to establish an initial gas seal barrier. When the ambient pressure is 0Pa to 3Pa higher than the external atmospheric pressure, the internal gas pressure is higher than the external pressure, preventing outside air from permeating into the environment through furnace gaps. The carbon matrix in the low-temperature roasting intermediate thus gains protection against oxygen infiltration. 0Pa is the lower limit of the micro-positive pressure, representing the critical state where the ambient pressure is equal to the external atmospheric pressure. In this state, while there is no outward gas flow obstruction, there is also no inward pressure difference-driven air infiltration. 3Pa is the upper limit of the micro-positive pressure, representing the highest positive pressure value that can be used in this stage. The micro-positive pressure range of 0Pa to 3Pa is relatively low because the oxidation reactivity of the carbon matrix has not yet reached its peak between 500℃ and 900℃; a lower positive pressure is sufficient to form an effective gas seal, eliminating the need for higher positive pressure values.

[0039] In the 900℃ to 1150℃ range, the temperature of the low-temperature calcination intermediates is close to or has reached the maximum calcination temperature, and the oxidation reactivity of the carbon matrix reaches its peak. This stage employs a micro-positive pressure control of 0 Pa to 5 Pa, the core function of which is to maintain a stronger gas seal barrier. This 0 Pa to 5 Pa positive pressure range is numerically higher than the 0 Pa to 3 Pa range in the 500℃ to 900℃ range, reflecting a differentiated positive pressure strategy to address the increased temperature and oxidation risk. When the temperature rises above 900℃, the reactivity of the carbon matrix significantly increases; even trace amounts of oxygen infiltration are sufficient to trigger significant oxidation losses. Therefore, it is necessary to increase the positive pressure value to a higher range of 0 Pa to 5 Pa to provide stronger gas seal protection.

[0040] Holding at 1150℃ for 8 to 12 hours refers to maintaining the temperature at 1150℃ for 8 to 12 hours after the temperature of the low-temperature roasting intermediate product reaches 1150℃. The purpose of this holding operation is to ensure that the low-temperature roasting intermediate product receives sufficient isothermal treatment at its highest temperature point, ensuring uniformity of the internal temperature field, and providing sufficient reaction time for the final completion of the carbonization structure.

[0041] Maintaining a pressure range of 0 Pa to 5 Pa during the 1150℃ holding stage has a continuous effect. The 1150℃ holding stage is the period with the highest risk of carbon matrix oxidation. Maintaining a slight positive pressure of 0 Pa to 5 Pa ensures the continued effectiveness of the air seal barrier during the holding period, preventing the infiltration of outside air due to pressure fluctuations.

[0042] In some embodiments, the cooling section cools the high-temperature roasting intermediate product from 1150°C to 300°C and then naturally cools it to room temperature; the cooling section controls the ambient pressure of the environment where the aluminum carbon product lumps are located to be an increasing positive pressure, including controlling the ambient pressure of the high-temperature roasting intermediate product within the range of 5Pa to 10Pa, and gradually increasing the pressure as the cooling process proceeds.

[0043] When the temperature of the high-temperature roasting intermediate product drops to 300℃, the oxidation reaction rate of the carbon matrix decreases significantly, and even with trace amounts of oxygen contact, the oxidation loss is extremely limited. Simultaneously, the volume shrinkage effect of the gas below 300℃ is greatly reduced, and the pressure drop caused by gas shrinkage is significantly decreased. Therefore, below 300℃, active temperature control is discontinued, and subsequent cooling is completed by natural cooling, ensuring product quality while saving energy and equipment investment.

[0044] During the cooling phase, the ambient pressure of the intermediate product in the high-temperature roasting stage is 5 Pa to 10 Pa, higher than the -5 Pa to -1 Pa in the low-temperature phase and the 0 Pa to 5 Pa in the high-temperature phase. This is the stage with the highest pressure setting in the entire roasting process. The reason for this differential setting is that there is a special physical effect of gas volume contraction in the cooling phase. As the gas cools from 1150°C to room temperature, the volume contraction is significant. If sufficient positive pressure compensation is not applied, the ambient pressure will naturally drop to a negative pressure state. Therefore, the positive pressure value in the cooling phase needs to be further increased on the basis of the positive pressure in the high-temperature phase to reserve sufficient pressure margin to cope with the pressure loss caused by gas contraction.

[0045] During the cooling process, the gas temperature continues to decrease, and the gas volume continues to contract. If a fixed positive pressure value is used, as the temperature decreases and the gas continues to contract, the fixed positive pressure value will gradually be offset by the contraction effect, and it may eventually slip into the negative pressure range. Therefore, the positive pressure value must be increased synchronously with the cooling process, so that the rate of pressure increase matches the rate of gas contraction, ensuring that the ambient pressure remains in the positive pressure range throughout the entire cooling process.

[0046] In some embodiments, the bulk density of the aluminum carbon product lumps is ≥1.63 g / cm³. 3 The mass fraction of coal tar pitch binder in the raw aluminum carbon product blocks is 13.2% to 15.5%.

[0047] Bulk density refers to the mass per unit volume of green carbon products for aluminum, measured in grams per cubic centimeter. Bulk density is an important physical parameter reflecting the compactness of green carbon products for aluminum, determined by the pressure of the forming process and the composition of the green block's formula. A higher bulk density indicates a more compact packing of carbon particles and coal tar binder per unit volume, resulting in lower porosity within the green block. In the embodiments of this application, the bulk density of the green carbon products for aluminum is ≥1.63 g / cm³.3 .

[0048] The role of coal tar pitch binder in green aluminum carbon products is to bond carbon particles into a whole and form a coke network through pyrolysis and coking during the roasting process, thus giving the aluminum carbon products the necessary mechanical strength and structural integrity. In the embodiments of this application, the mass fraction of coal tar pitch in the green aluminum carbon products is 13.2% to 15.5%.

[0049] In some embodiments, the moisture content of the raw aluminum carbon product is ≤0.3%.

[0050] Moisture content refers to the percentage of water in the total mass of raw aluminum carbon products. After entering the low-temperature zone, as the temperature rises from 30°C, the moisture in the raw aluminum carbon products begins to evaporate and escape in large quantities around 100°C. Unlike the volatiles produced by the pyrolysis of coal tar pitch binders, the escape of moisture is a purely physical process. Its escape behavior is not controlled by the rate of temperature increase, nor is it affected by the progress of the coal tar pitch binder pyrolysis reaction. As soon as the temperature reaches the boiling point of water, moisture begins to vaporize and escape. This escape behavior occurs at the initial stage of the roasting process of the raw aluminum carbon products, that is, at the very beginning of the low-temperature zone.

[0051] When the moisture content in the raw aluminum carbon products is controlled at 0.3% or below, the total amount of water vapor escaping in the initial stage of the low-temperature section is extremely limited and will not significantly disturb the internal environment of the raw aluminum carbon products. At this time, the micro-negative pressure system can focus on controlling the volatiles generated by the pyrolysis of coal tar pitch binder, and precisely apply the suction force to the selective separation function.

[0052] In some embodiments, the oxygen volume fraction in the low-oxygen inert environment is 0.005% to 0.05%.

[0053] The volume fraction of oxygen in the low-oxygen inert environment is controlled at 0.005% to 0.05%. This operation continuously reduces the oxygen concentration in the environment where the raw aluminum carbon products are located throughout the entire temperature range of the calcination process. Oxygen is the fundamental cause of oxidation loss in aluminum carbon products during calcination. Under high-temperature conditions, the carbon elements in the carbon matrix react chemically with oxygen to generate carbon dioxide or carbon monoxide gas, resulting in a loss of mass in the carbon matrix.

[0054] Controlling the oxygen volume fraction to 0.005%–0.05% in a low-oxygen inert environment reduces the oxygen concentration in the environment where the green aluminum carbon products are located to an extremely low level. In the low-temperature range (30℃–500℃), the extremely low oxygen concentration reduces the opportunity for oxygen to come into contact with the surface of the green aluminum carbon products. This means that even under slight negative pressure conditions, the amount of oxygen introduced by minute air infiltration is extremely limited and will not cause any noticeable oxidation damage to the green aluminum carbon products.

[0055] In the high-temperature range (500℃~1150℃), the reaction rate between the carbon matrix and oxygen increases exponentially with increasing temperature. Above 900℃, even extremely low concentrations of oxygen can undergo significant oxidation reactions with the carbon matrix. A volume fraction range of 0.005%~0.05% keeps the oxygen concentration within a controllable range for the reaction rate at this temperature. When the oxygen volume fraction exceeds 0.05%, the oxidation loss of the carbon matrix in the high-temperature range will increase significantly. Even with a 0Pa~5Pa micro-positive pressure gas seal barrier to prevent continuous infiltration of external air, the initial residual oxygen in the environment where the aluminum carbon product lump is located, as well as the trace amounts of oxygen that infiltrate under incomplete sealing conditions, are sufficient to cause considerable carbon loss under high-temperature, long-term conditions.

[0056] During the cooling phase (1150℃~300℃), oxygen content control continues to play a protective role. Although a slightly positive pressure environment is maintained in the initial stage of the cooling phase, the contraction of ambient gas during cooling may cause instantaneous pressure fluctuations at the seal. At the moment of pressure fluctuation, the low-oxygen environment with an oxygen volume fraction of 0.005%~0.05% ensures that even under the most unfavorable pressure fluctuation conditions, the amount of oxygen that permeates is extremely limited and will not cause significant oxidation on the surface of the high-temperature carbon matrix.

[0057] In some embodiments, the low-oxygen inert environment is constructed in the following ways: Aluminum carbon product raw blocks are placed in a sealed container, inert gas is introduced into the sealed container, and the air in the sealed container is replaced by vacuum circulation gas extraction, so that the oxygen volume fraction in the sealed container is reduced to 0.005% to 0.05%.

[0058] In some embodiments, the inert gas is nitrogen, and the purity of the nitrogen is ≥99.95 wt%.

[0059] Inert gases are gases that are chemically inert and do not react with carbon products within the calcination temperature range for aluminum carbon products. The core characteristic of inert gases is that, as the primary filling gas in the environment, they do not react chemically with the carbon matrix or coal tar binder components in the raw aluminum carbon products, low-temperature calcination intermediates, or high-temperature calcination intermediates throughout the entire calcination cycle, thus ensuring the chemical stability of the low-oxygen inert environment. Nitrogen does not react with carbon materials within the calcination temperature range for aluminum carbon products and is one of the most commonly used inert protective gases in industry.

[0060] When the purity of nitrogen is below 99.95 wt%, the oxygen content in nitrogen may reach hundreds of ppm or even higher. This oxygen is introduced into the environment, which may make it difficult for the ambient oxygen content to reach the target range of 0.005% to 0.05%.

[0061] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0062] Example 1 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 15.5%, moisture content ≤ 0.3%) are placed on a horizontal carbonaceous carrier plate. The carbonaceous carrier plate carrying the raw aluminum carbon products is then placed into a sealed horizontal calcining furnace, and the furnace body is sealed. High-purity nitrogen gas (purity 99.95 wt%) is introduced into the sealed horizontal calcining furnace, and the air inside the furnace is replaced by a vacuum circulation gas extraction method. The specific steps of the vacuum circulation gas extraction operation are as follows: the vacuum system is started to extract the gas from the sealed horizontal calcining furnace, creating a negative pressure state inside the furnace. Then, high-purity nitrogen gas is introduced to atmospheric pressure, completing one cycle. The above operation is repeated three times to reduce the oxygen volume fraction inside the sealed horizontal calcining furnace to 0.05%, obtaining a low-oxygen inert environment.

[0063] The aluminum carbon product blocks in a low-oxygen inert environment are roasted according to the heating curve. The roasting process includes a low-temperature section, a high-temperature section, and a cooling section.

[0064] In the low-temperature section, the raw aluminum carbon products are heated from 30℃ to 500℃ at a rate of 5℃ / h, and then held at 500℃ for 12 hours. The environmental pressure of the raw aluminum carbon products in the low-temperature section is controlled to be slightly negative; specifically: within the temperature range of 30℃ to 350℃, the environmental pressure is -5Pa; within the temperature range of 350℃ to 500℃ and during the 500℃ holding period, the environmental pressure is -3Pa.

[0065] In the high-temperature section, the low-temperature roasting intermediate product is heated from 500℃ to 1150℃ and held at 1150℃ for 10 hours. The pressure of the environment where the low-temperature roasting intermediate product is located is controlled to be slightly positive pressure in the high-temperature section. Specifically, the environmental pressure of the low-temperature roasting intermediate product is 3 Pa in the temperature range of 500℃ to 900℃; and the environmental pressure of the low-temperature roasting intermediate product is 5 Pa in the temperature range of 900℃ to 1150℃ and during the 1150℃ holding stage.

[0066] The cooling section cools the high-temperature roasting intermediate product from 1150℃ to 300℃ at a rate of 50℃ / h, and then allows it to cool naturally to room temperature. The pressure of the environment in which the high-temperature roasting intermediate product is located in the cooling section is controlled as an increasing positive pressure, specifically: the environmental pressure of the high-temperature roasting intermediate product is 5Pa, and it gradually increases from 5Pa to 10Pa as the cooling process progresses.

[0067] After roasting, the finished aluminum carbon products were obtained, and the calculated yield reached 94.0%.

[0068] Example 2 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 14.0%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.05%, thereby obtaining a low-oxygen inert environment.

[0069] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. Within the temperature range of 30℃ to 350℃, the ambient pressure of the raw aluminum carbon products was -3Pa; within the temperature range of 350℃ to 500℃ and during the 500℃ holding stage, the ambient pressure of the raw aluminum carbon products was -3Pa.

[0070] In the high-temperature section, the temperature of the low-temperature calcination intermediate product is raised from 500℃ to 1150℃ and held at 1150℃ for 10 hours. The environmental pressure of the aluminum carbon product briquettes in the high-temperature section is controlled to be slightly positive. Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature calcination intermediate product is 3 Pa; within the temperature range of 900℃ to 1150℃ and during the 1150℃ holding stage, the environmental pressure of the low-temperature calcination intermediate product is 3 Pa.

[0071] In the cooling section, the high-temperature calcined intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the aluminum carbon product lumps in the cooling section is controlled to be an increasing positive pressure, and the ambient pressure of the high-temperature calcined intermediate product is 8Pa, which gradually increases to 10Pa as the cooling process progresses.

[0072] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 95.6%.

[0073] Example 3 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 13.2%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.01%, thereby obtaining a low-oxygen inert environment.

[0074] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. Within the temperature range of 30℃ to 350℃, the ambient pressure of the raw aluminum carbon products was -2Pa; within the temperature range of 350℃ to 500℃ and during the 500℃ holding stage, the ambient pressure of the raw aluminum carbon products was -2Pa.

[0075] In the high-temperature section, the temperature of the low-temperature calcination intermediate product is increased from 500℃ to 1150℃ and held at 1150℃ for 10 hours. The environmental pressure of the aluminum carbon product briquettes in the high-temperature section is controlled to be slightly positive. Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature calcination intermediate product is 2 Pa; within the temperature range of 900℃ to 1150℃ and during the 1150℃ holding stage, the environmental pressure of the low-temperature calcination intermediate product is 2 Pa.

[0076] In the cooling section, the high-temperature calcined intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the aluminum carbon product lumps in the cooling section is controlled as an increasing positive pressure, and the ambient pressure of the high-temperature calcined intermediate product is 6Pa, which gradually increases to 10Pa as the cooling process progresses.

[0077] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 95.6%.

[0078] Example 4 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 13.2%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.01%, thereby obtaining a low-oxygen inert environment.

[0079] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. Within the temperature range of 30℃ to 350℃, the ambient pressure of the raw aluminum carbon products was -1Pa; within the temperature range of 350℃ to 500℃ and during the 500℃ holding stage, the ambient pressure of the raw aluminum carbon products was -1Pa.

[0080] In the high-temperature section, the temperature of the low-temperature calcination intermediate product is increased from 500℃ to 1150℃ and held at 1150℃ for 10 hours. The environmental pressure of the aluminum carbon product briquettes in the high-temperature section is controlled to be slightly positive. Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature calcination intermediate product is 1 Pa; within the temperature range of 900℃ to 1150℃ and during the 1150℃ holding stage, the environmental pressure of the low-temperature calcination intermediate product is 1 Pa.

[0081] In the cooling section, the high-temperature calcination intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the aluminum carbon product lumps in the cooling section is controlled as an increasing positive pressure, and the ambient pressure of the high-temperature calcination intermediate product is 5Pa, which gradually increases to 10Pa as the cooling process progresses.

[0082] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 97.5%.

[0083] Comparative Example 1 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 15.5%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.01%, thereby obtaining a low-oxygen inert environment.

[0084] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. During the temperature range of 30℃ to 500℃ and the holding stage at 500℃, the ambient pressure of the raw aluminum carbon products was -0.5Pa.

[0085] In the high-temperature section, the temperature of the low-temperature roasting intermediate product is increased from 500℃ to 1150℃ and held at 1150℃ for 10 hours. The environmental pressure of the aluminum carbon product lumps in the high-temperature section is controlled to be slightly positive pressure. During the temperature range of 500℃ to 1150℃ and the holding stage at 1150℃, the environmental pressure of the low-temperature roasting intermediate product is 15Pa.

[0086] In the cooling section, the high-temperature roasting intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the high-temperature roasting intermediate product in the cooling section is 2Pa, and the pressure does not gradually increase during the cooling process.

[0087] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 90.6%.

[0088] Comparative Example 2 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 15.5%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.01%, thereby obtaining a low-oxygen inert environment.

[0089] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. During the temperature range of 30℃ to 500℃ and the holding stage at 500℃, the ambient pressure of the raw aluminum carbon products was -1 Pa.

[0090] In the high-temperature section, the low-temperature calcination intermediate product is heated from 500℃ to 1150℃ at a rate of increase, and then held at 1150℃ for 10 hours. The ambient pressure of the aluminum carbon product briquettes in the high-temperature section is controlled to be slightly positive. During the temperature range of 500℃ to 1150℃ and the holding period at 1150℃, the ambient pressure of the low-temperature calcination intermediate product is 8 Pa.

[0091] In the cooling section, the high-temperature roasting intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the high-temperature roasting intermediate product in the cooling section is 10Pa, and the pressure does not gradually increase during the cooling process.

[0092] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 85.2%.

[0093] Comparative Example 3 Raw aluminum carbon products (bulk density ≥ 1.63 g / cm³, coal tar binder mass fraction 15.5%, moisture content ≤ 0.3%) were placed in a closed horizontal calcining furnace. The air inside the furnace was replaced by vacuum circulation gas extraction in combination with high-purity nitrogen (purity 99.95 wt%). The vacuum circulation gas extraction was performed 3 times to reduce the oxygen volume fraction in the closed horizontal calcining furnace to 0.01%, thereby obtaining a low-oxygen inert environment.

[0094] The raw aluminum carbon products were calcined in a low-oxygen, inert environment according to a heating curve. In the low-temperature stage, the raw aluminum carbon products were heated from 30℃ to 500℃ at a heating rate of 5℃ / h, and held at 500℃ for 12 hours. The ambient pressure of the raw aluminum carbon products in the low-temperature stage was controlled to be slightly negative. During the temperature range of 30℃ to 500℃ and the holding stage at 500℃, the ambient pressure of the raw aluminum carbon products was -1 Pa.

[0095] In the high-temperature section, the intermediate product from low-temperature roasting is heated from 500℃ to 1150℃ at a rate of increase, and then held at 1150℃ for 10 hours. The ambient pressure of the aluminum carbon product briquettes in the high-temperature section is controlled to be slightly positive. During the temperature range of 500℃ to 1150℃ and the holding period at 1150℃, the ambient pressure of the intermediate product from low-temperature roasting is 5 Pa.

[0096] In the cooling section, the high-temperature roasting intermediate product is cooled from 1150℃ to 300℃ at a rate of 50℃ / h, and then naturally cooled to room temperature. The ambient pressure of the high-temperature roasting intermediate product in the cooling section is 15Pa, and the pressure does not gradually increase during the cooling process.

[0097] After roasting, the finished aluminum carbon products were obtained, and the calculated yield was 89.4%.

[0098] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: The pressure control parameters at each stage of the embodiments in this application are within the range that can be accurately achieved by conventional industrial pressure control instruments, and do not involve harsh conditions such as ultra-high pressure or ultra-vacuum. While achieving a high calcination yield, the embodiments in this application are characterized by a short process, simple operation, and low cost, demonstrating significant potential for industrial application and widespread adoption.

[0099] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for improving the calcination yield of carbon products for aluminum, characterized in that, The method includes: The raw aluminum carbon products are placed in a low-oxygen, inert environment for calcination. The calcination process includes a low-temperature section, a high-temperature section, and a cooling section, wherein: The low-temperature section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to a slightly negative pressure, so as to regulate the escape rate of volatiles in the aluminum carbon product lumps and promote the pyrolysis and coking reaction of the coal tar pitch binder in the aluminum carbon product lumps to obtain a low-temperature roasting intermediate product. The high-temperature section controls the environmental pressure of the aluminum carbon product lumps to be slightly positive, so as to prevent external oxygen from penetrating into the environment of the low-temperature roasting intermediate product and inhibit the oxidation of the carbon matrix in the low-temperature roasting intermediate product, thereby obtaining the high-temperature roasting intermediate product. The cooling section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to be an increasing positive pressure, in order to compensate for the pressure loss caused by the decrease in gas temperature and volume shrinkage in the environment of the high-temperature roasting intermediate product, so as to obtain the finished aluminum carbon product.

2. The method according to claim 1, characterized in that, The low-temperature section raises the temperature of the aluminum carbon product lumps from 30°C to 500°C and holds them at 500°C for 10 to 14 hours.

3. The method according to claim 1 or 2, characterized in that, The low-temperature section controls the ambient pressure of the environment in which the aluminum carbon product lumps are located to be slightly negative, including: Within the temperature range of 30℃ to 350℃, the environmental pressure of the aluminum carbon product briquettes is -5Pa to 0Pa. During the temperature range of 350℃ to 500℃ and the heat preservation stage at 500℃, the environmental pressure of the raw aluminum carbon product is -3Pa to -1Pa.

4. The method according to claim 1, characterized in that, The high-temperature section raises the temperature of the low-temperature roasting intermediate product from 500°C to 1150°C and holds it at 1150°C for 8 to 12 hours.

5. The method according to claim 1 or 4, characterized in that, The high-temperature section controls the ambient pressure of the environment in which the aluminum carbon product briquettes are located to be slightly positive pressure, including: Within the temperature range of 500℃ to 900℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 3Pa. During the temperature range of 900℃ to 1150℃ and the holding stage at 1150℃, the environmental pressure of the low-temperature roasting intermediate product is 0Pa to 5Pa.

6. The method according to claim 1, characterized in that, The cooling section cools the high-temperature roasting intermediate product from 1150°C to 300°C and then allows it to cool naturally to room temperature. The cooling section controls the ambient pressure of the aluminum carbon product lumps to be an increasing positive pressure, which includes controlling the ambient pressure of the high-temperature roasting intermediate product within the range of 5Pa to 10Pa, and gradually increasing the pressure as the cooling process progresses.

7. The method according to claim 1, characterized in that, The bulk density of the aluminum carbon product lumps is ≥1.63 g / cm³. 3 .

8. The method according to claim 1, characterized in that, The mass fraction of coal tar binder in the raw aluminum carbon product lumps is 13.2% to 15.5%; the moisture content of the raw aluminum carbon product lumps is ≤0.3%.

9. The method according to claim 1, characterized in that, The methods for constructing the low-oxygen inert environment include: Aluminum carbon product raw blocks are placed in a sealed container, inert gas is introduced into the sealed container, and the air in the sealed container is replaced by vacuum circulation gas extraction, so that the oxygen volume fraction in the sealed container is reduced to 0.005% to 0.05%.

10. The method according to claim 1 or 9, characterized in that, The inert gas is nitrogen, and the purity of the nitrogen is ≥99.95wt%.

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