Automatic preparation system of high-purity graphite saggar and anaerobic roasting-incineration integrated process thereof

Abstract

The invention discloses an automatic preparation system of a high-purity graphite sagger and an anaerobic roasting-incineration integrated process of the high-purity graphite sagger. The system comprises a raw material treatment unit, a mixing and kneading unit, a forming pretreatment unit and an anaerobic roasting-incineration integrated unit which are sequentially arranged in the material flowing direction, and the whole-process automatic operation of graphite powder from crushing, screening, mixing and kneading, cooling and forming to green body roasting is achieved. A closed kneading machine and resin are adopted for vacuum injection for mixing and kneading, a multi-layer crawler-type closed cooling machine is used for cooling before forming, green bodies are automatically put into bowls to be put into an electric heating kiln, combustible volatile organic compounds VOCs waste gas generated by cracking in the anaerobic roasting process is guided into an integrated natural gas incineration device for combustion, and the residence time is prolonged through a spoiler; the CO2 concentration is monitored in real time, the natural gas injection amount is adjusted, and air permeation is prevented through inert gas micro-positive pressure protection in the cooling stage, so that the high-purity graphite saggar is obtained, the product purity is remarkably improved, and environmental pollution and energy consumption are reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium battery anode material production technology, specifically an automated preparation system for high-purity graphite saggers and its integrated oxygen-free roasting-incineration process. Background Technology

[0002] Graphite saggers are crucial containers in the purification process of lithium-ion battery anode materials, and their purity directly affects the final quality of the anode material. However, traditional graphite sagger production methods have the following prominent problems: First, the production process generates significant VOC pollution, which is difficult to treat. Because phenolic resin is used as a binder, the resin decomposes during the calcination stage, producing large amounts of volatile organic compounds (VOCs). Traditional treatment methods require additional exhaust gas treatment systems, such as activated carbon adsorption devices, which not only increases equipment costs but also poses a risk of secondary pollution after adsorption saturation. Some companies choose to outsource incineration to third parties, but they also face high transportation costs and significant environmental compliance pressures.

[0003] Secondly, product purity is difficult to guarantee. Traditional production uses an open process, and graphite powder is easily contaminated by dust and metallic impurities in the air during transfer, mixing, and molding. At the same time, protective gases such as nitrogen are required during calcination to prevent oxidation. If the purity of the protective gas is insufficient or leakage occurs, impurities will be further introduced, resulting in the final ash content of the sagger generally being ≥300ppm, which cannot meet the production requirements of high-purity anode materials.

[0004] Furthermore, it is energy-intensive and has a low degree of automation. Conventional roasting processes rely on the continuous supply of protective gas, which accounts for more than 30% of the total energy consumption. In addition, key processes such as raw material preparation, green body loading, and kiln operation are mostly manual, which not only results in high labor intensity but also leads to poor product quality consistency, specifically density fluctuations of ±5% and dimensional deviations of ±1mm.

[0005] Finally, the traditional process cycle settings are not reasonable enough. The conventional calcination (30-35 hours) and cooling (30-36 hours) cycles fail to match the coking kinetics of phenolic resin, which can easily lead to problems such as incomplete resin pyrolysis (residual carbon causing increased ash content) or excessive pyrolysis (causing a decrease in crucible strength).

[0006] While existing technologies attempt to address these challenges by optimizing calcination temperatures or improving exhaust gas treatment methods, they have not yet systematically solved the problem from the perspective of the entire production process and integrated process and equipment. Therefore, it is difficult to achieve an effective balance between multiple requirements such as purity, environmental protection, energy consumption, and automation. Thus, those skilled in the art provide an automated preparation system for high-purity graphite crucibles and its integrated anaerobic calcination-incineration process to solve the problems mentioned in the background art. Summary of the Invention

[0007] The purpose of this invention is to provide an automated preparation system for high-purity graphite crucibles and its integrated oxygen-free roasting-incineration process to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: An automated preparation system for high-purity graphite crucibles includes a fully enclosed production chain arranged sequentially along the material flow direction: The raw material processing unit includes an electromagnetic impurity separation device, a grading and screening device, and a negative pressure material tank connected along the material flow direction; The mixing unit includes a computer-automated batching module and a closed kneader. The closed kneader has a built-in temperature control module and a resin vacuum injection module. The computer-automated batching module is connected to the negative pressure tank. The pre-forming processing unit includes a multi-layer tracked enclosed cooling machine, a crusher, a mold release agent mixing device, and a pre-compression molding machine connected along the material flow direction; The anaerobic roasting-incineration integrated unit includes an electrically heated kiln with an inert gas replacement interface and an integrated natural gas incineration device; the electrically heated kiln is equipped with an automatic track-mounted loading module, and the exhaust gas outlet of the electrically heated kiln is directly connected to the air inlet of the natural gas incineration device. The natural gas combustion device includes a high-temperature alloy combustion chamber, a natural gas injection array, thermocouple temperature sensors, and an emergency cooling system; the natural gas combustion device is also equipped with an infrared CO2 analyzer and a hydrogen flame ion detector.

[0009] As a further aspect of the present invention, the vacuum pressure of the closed kneader is not higher than -0.09MPa; the number of belt layers of the multi-layer track-type closed slab cooling machine is 3-5 layers.

[0010] As a further aspect of the present invention, the liquid nitrogen spraying rate of the emergency cooling system is 5-10 L / min, and the response time is no more than 10 s.

[0011] As a further aspect of the present invention, the electric heating kiln has an automatic positioning and loading function for green blanks, with a positioning accuracy of no more than ±2mm.

[0012] An integrated process for anaerobic roasting and incineration of high-purity graphite using the above-described system includes the following steps: S1. Raw material processing: The graphite raw material is crushed and ball-milled to control the particle size to D. 50 =15μm±2μm, and then pass through an electromagnetic impurity removal device to remove iron impurities, a grading and screening device to screen, and store the powders of different mesh sizes into a negative pressure tank. S2. Mixing and kneading: After the ingredients are mixed according to the preset ratio by the computer automatic batching module, they are sent into the closed kneader and 11wt%-13wt% phenolic resin is added. The mixture is then vacuum kneaded at 95℃-105℃ for 35min-45min. S3. Pre-forming treatment: The mixed sheet material is fed into a multi-layer conveyor-type closed sheet cooling machine, which is cooled to 22℃-28℃ by forced air cooling at 8℃-12℃. After being crushed and mixed with a release agent, it is pressed into a green blank by a pre-press molding machine. S4. Anaerobic roasting-incineration treatment: The green billets are automatically loaded into an electrically heated kiln via a track-mounted automatic loading module, roasted in an anaerobic environment, and the pyrolysis waste gas is treated in conjunction with a natural gas incineration unit. Specifically, this includes: S41. Heating stage: First, nitrogen is introduced through the inert gas replacement port to replace the air in the kiln until the oxygen content is ≤50ppm; then the temperature is increased from 25℃ to 590℃-610℃ at a heating rate of 35℃ / h-45℃ / h. During the heating process, nitrogen is continuously introduced to maintain a slight positive pressure in the kiln. After reaching the target temperature, the temperature is held for 13h-17h. S42. Pyrolysis stage: Maintain a constant temperature of 590℃-610℃ for 8h-12h, and continuously introduce nitrogen as a carrier gas to cause the phenolic resin to decompose and produce combustible volatile organic compounds (VOCs). S43, Incineration Stage: The exhaust gas from the electric kiln is introduced into the natural gas incineration unit, and the inlet gas temperature is monitored by thermocouple temperature sensors. When the combustion chamber temperature is ≥850℃, the natural gas injection array is automatically activated, and natural gas is injected and mixed for combustion at a volume ratio of natural gas:VOCs=1:(2.8-3.2) to control the combustion chamber temperature between 850℃ and 900℃, and the gas residence time is ≥2s. When the combustion chamber temperature is <850℃, cut off the exhaust gas passage and start the liquid nitrogen spray of the emergency cooling system; S5. Shutdown and Cooling: After combustion, shut down the electric kiln and combustion device, and allow it to cool naturally for 21-27 hours. During the cooling process, nitrogen is continuously introduced to maintain a slight positive pressure inside the kiln and to keep the oxygen content inside the kiln below 100 ppm in order to obtain high-purity graphite saggers.

[0013] As a further embodiment of the present invention, in step S1, the screening efficiency of the grading and screening device is ≥95%, and the iron removal rate of the electromagnetic impurity removal device is ≥99.9%.

[0014] As a further embodiment of the present invention, in step S4, the heating element of the electric heating kiln is a silicon molybdenum rod, and the heating uniformity is controlled within ±5℃.

[0015] As a further aspect of the present invention, in step S43, the CO2 concentration is monitored in real time by an infrared CO2 analyzer, and the natural gas injection volume is adjusted when the detected CO2 value is lower than 95% of the theoretical value.

[0016] As a further embodiment of the present invention, in step S43, the combustion chamber is provided with a baffle to make the gas residence time reach 2s-3s.

[0017] As a further embodiment of the present invention, in step S5, the nitrogen gas introduced during the cooling process has a purity of ≥99.99%, and the pressure inside the kiln is monitored in real time by a pressure sensor to ensure that the micro-positive pressure is stable at 50-100Pa.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The system adopts a fully enclosed production chain, which effectively isolates external pollution; the oxygen-free roasting process does not rely on protective gas. Combined with electromagnetic impurity removal and graded screening, the ash content of the final sagger is significantly reduced compared with the traditional process, which can fully meet the high purity purification requirements of lithium battery anode materials.

[0019] (2) Through the integrated design of anaerobic roasting and incineration, VOCs are directly introduced into the incineration device and completely decomposed into carbon dioxide and water at a high temperature of 850-900℃, achieving a removal rate of up to 99.8%, effectively reducing emissions and avoiding secondary pollution.

[0020] (3) There is no need to continuously supply protective gas during the high-temperature roasting stage, which greatly reduces gas costs; the high-temperature flue gas generated by incineration can be reused in the electric heating kiln, while optimizing the roasting and cooling cycle, significantly reducing overall energy consumption and improving energy utilization efficiency.

[0021] (4) Through PLC full-process automatic control, the entire process from raw material preparation, mixing, molding to green body filling and kiln operation is completed automatically, greatly reducing manual intervention and significantly improving product quality consistency and production efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an automated preparation system for high-purity graphite crucibles.

[0023] Figure 2 This is a schematic diagram of the integrated process of anaerobic roasting-incineration. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 Please see Figure 1 An automated preparation system for high-purity graphite crucibles includes a fully enclosed production chain arranged sequentially along the material flow direction, with each unit as follows: The raw material processing unit includes an electromagnetic impurity separation device, a grading and screening device, and a negative pressure tank connected along the material flow direction; the grading and screening device has screening grades of 50 mesh, 80 mesh, 100 mesh, and 120 mesh, with a screening efficiency of ≥95%; the electromagnetic impurity separation device has an iron removal rate of ≥99.9%; and the negative pressure tank has a vacuum degree of -5kPa. The mixing unit includes a computer-automated batching module and a closed kneader. The closed kneader has a built-in temperature control module with a temperature control range of 100℃±5℃ and is equipped with a resin vacuum injection module. The computer-automated batching module is connected to a negative pressure tank to realize automatic weighing and feeding. The vacuum degree of the closed kneader is ≥-0.09MPa. The pre-forming unit includes a multi-layer tracked enclosed cooling machine (cooling method is mechanical air cooling, target cooling temperature 25℃±3℃), a crusher, a mold release agent mixing device, and a pre-compression molding machine connected along the material flow direction; the multi-layer tracked enclosed cooling machine has 3-5 track layers. The anaerobic roasting-incineration integrated unit includes an electrically heated kiln with an inert gas replacement interface and an integrated natural gas incineration device; the electrically heated kiln is equipped with an automatic loading module with a track, including a servo motor-driven conveying track and a positioning sensor, with a loading accuracy of ≤±2mm; the exhaust gas outlet of the electrically heated kiln is directly connected to the air inlet of the natural gas incineration device. The natural gas combustion device includes a high-temperature alloy combustion chamber (lined with ceramic fiber), a natural gas injection array (nozzle diameter Φ0.5-1mm), a thermocouple temperature sensor (range 0-1200℃), and an emergency cooling system (including liquid nitrogen spray pipeline); the natural gas combustion device is also equipped with an infrared CO2 analyzer and a hydrogen flame ion detector. The heating element of the electric heating kiln uses silicon molybdenum rods, and the heating uniformity is ≤±5℃.

[0026] Example 2 Please see Figure 2 A high-purity graphite sagger anaerobic roasting-incineration integrated process is described, which uses the system described in Example 1 to prepare high-purity graphite saggers. The specific process steps are as follows: S1, Raw Material Processing Graphite raw materials (including waste materials) are crushed by a jaw crusher and then ball-milled to D. 50 =15μm±2μm; the powder is passed through an electromagnetic impurity removal device to remove iron and a grading and screening device to screen, and then stored in negative pressure tanks according to the screening mesh.

[0027] S2, Mixing The materials are automatically batched by a computer according to a preset ratio (80 mesh:100 mesh=7:3±0.2) and then fed into a closed kneader. The materials are fed into the closed kneader, and 11wt%-13wt% of phenolic resin is added. The kneader is then vacuum kneaded at 95℃-105℃ for 35min-45min.

[0028] S3, Pre-molding treatment The kneaded sheet material is fed into a multi-layer conveyor-type closed sheet cooling machine, where it is cooled to 22℃-28℃ by forced air cooling at 8℃-12℃. After being crushed and mixed with a release agent, it is pressed into a green blank by a pre-pressing molding machine.

[0029] S4, Anaerobic roasting-incineration treatment The green blanks are automatically loaded into the electrically heated kiln via a track-mounted automatic loading module. Inert gas (nitrogen is selected) is introduced through an inert gas replacement interface for calcination in an oxygen-free environment. Simultaneously, a natural gas incineration unit is activated to treat the pyrolysis waste gas. Specifically, this includes: S41. Heating Stage: First, introduce nitrogen through the inert gas replacement port to replace the air in the kiln (replacement time ≥30min, nitrogen flow rate 1-1.5 times the kiln volume / h) until the oxygen content in the kiln is ≤50ppm; then, raise the temperature from room temperature (25℃) to 590℃-610℃ at a rate of 35℃ / h-45℃ / h, continuously introducing nitrogen during the heating process (flow rate 20-30m³ / h). 3 Maintain a slight positive pressure (50-100Pa) inside the kiln for 13-17 hours after reaching the target temperature; S42, Pyrolysis Stage: Maintain a constant temperature of 590℃-610℃ for 8-12 hours, continuously introducing nitrogen gas (flow rate 15-25m³ / h). 3 / h) to decompose phenolic resin to produce combustible volatile organic compounds (VOCs, small molecule volatile organic compounds); at the same time, maintain the oxygen content in the kiln ≤50ppm; the main components of VOCs are C1-C6 alkanes, alkenes, and benzenes; S43, Incineration Stage: The exhaust gas from the electric kiln is introduced into the natural gas incineration unit, and the inlet gas temperature is monitored by thermocouple temperature sensors. When the combustion chamber temperature is ≥850℃, the natural gas injection array is automatically activated, and natural gas is injected and mixed for combustion at a volume ratio of natural gas:VOCs=1:(2.8-3.2) to control the combustion chamber temperature between 850℃ and 900℃, and the gas residence time is ≥2s. The mixed combustion reaction equation is: CH4 + VOCs (general formula nC) n H n (i.e., C1-C6 alkanes, alkenes, benzenes) → CO2 + H2O; When the combustion chamber temperature is <850℃, cut off the exhaust gas passage and start the liquid nitrogen spray of the emergency cooling system (spray time ≥1min, until the combustion chamber temperature ≤200℃). A baffle is installed in the combustion chamber to extend the gas residence time to 2-3 seconds; The infrared CO2 analyzer monitors the CO2 concentration in real time, and automatically adjusts the natural gas injection rate when the detected CO2 concentration is lower than 95% of the theoretical value.

[0030] S5, Furnace shutdown and cooling After incineration, the electric kiln and incineration device are shut down and allowed to cool naturally for 21-27 hours. During the cooling process, nitrogen gas with a purity of ≥99.99% is continuously introduced. The pressure inside the kiln is monitored in real time by a pressure sensor to ensure that the micro-positive pressure is stable at 50-100Pa and that the oxygen content inside the kiln is kept below 100ppm in order to obtain high-purity graphite saggers.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An automated preparation system for high-purity graphite saggers, characterized in that, This includes a fully enclosed production chain arranged sequentially along the material flow direction: The raw material processing unit includes an electromagnetic impurity separation device, a grading and screening device, and a negative pressure material tank connected along the material flow direction; The mixing unit includes a computer-automated batching module and a closed kneader. The closed kneader has a built-in temperature control module and a resin vacuum injection module. The computer-automated batching module is connected to the negative pressure tank. The pre-forming processing unit includes a multi-layer tracked enclosed cooling machine, a crusher, a mold release agent mixing device, and a pre-compression molding machine connected along the material flow direction; The anaerobic roasting-incineration integrated unit includes an electrically heated kiln with an inert gas replacement interface and an integrated natural gas incineration device; the electrically heated kiln is equipped with an automatic track-mounted loading module, and the exhaust gas outlet of the electrically heated kiln is directly connected to the air inlet of the natural gas incineration device. The natural gas combustion device includes a high-temperature alloy combustion chamber, a natural gas injection array, thermocouple temperature sensors, and an emergency cooling system; the natural gas combustion device is also equipped with an infrared CO2 analyzer and a hydrogen flame ion detector.

2. The automated preparation system for a high-purity graphite sagger according to claim 1, characterized in that, The vacuum pressure of the closed kneader is not higher than -0.09MPa; the number of belt layers of the multi-layer track-type closed slicing machine is 3-5 layers.

3. The automated preparation system for a high-purity graphite sagger according to claim 1, characterized in that, The liquid nitrogen spray rate of the emergency cooling system is 5-10 L / min, and the response time is no more than 10 s.

4. The automated preparation system for a high-purity graphite sagger according to claim 1, characterized in that, The electric heating kiln has an automatic green body positioning and loading function with a positioning accuracy of no more than ±2mm.

5. An integrated process for high-purity graphite crucible anaerobic roasting-incineration using the system described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Raw material processing: The graphite raw material is crushed and ball-milled to control the particle size to D. 50 =15μm±2μm, and then pass through an electromagnetic impurity removal device to remove iron impurities, a grading and screening device to screen, and store the powders of different mesh sizes into a negative pressure tank. S2. Mixing and kneading: After the ingredients are mixed according to the preset ratio by the computer automatic batching module, they are sent into the closed kneader and 11wt%-13wt% phenolic resin is added. The mixture is then vacuum kneaded at 95℃-105℃ for 35min-45min. S3. Pre-forming treatment: The mixed sheet material is fed into a multi-layer conveyor-type closed sheet cooling machine, which is cooled to 22℃-28℃ by forced air cooling at 8℃-12℃. After being crushed and mixed with a release agent, it is pressed into a green blank by a pre-press molding machine. S4. Anaerobic roasting-incineration treatment: The green billets are automatically loaded into an electrically heated kiln via a track-mounted automatic loading module, roasted in an anaerobic environment, and the pyrolysis waste gas is treated in conjunction with a natural gas incineration unit. Specifically, this includes: S41. Heating stage: First, nitrogen is introduced through the inert gas replacement port to replace the air in the kiln until the oxygen content is ≤50ppm; then the temperature is increased from 25℃ to 590℃-610℃ at a heating rate of 35℃ / h-45℃ / h. During the heating process, nitrogen is continuously introduced to maintain a slight positive pressure in the kiln. After reaching the target temperature, the temperature is held for 13h-17h. S42. Pyrolysis stage: Maintain a constant temperature of 590℃-610℃ for 8h-12h, and continuously introduce nitrogen as a carrier gas to cause the phenolic resin to decompose and produce combustible volatile organic compounds (VOCs). S43, Incineration Stage: The exhaust gas from the electric kiln is introduced into the natural gas incineration unit, and the inlet gas temperature is monitored by thermocouple temperature sensors. When the combustion chamber temperature is ≥850℃, the natural gas injection array is automatically activated, and natural gas is injected and mixed for combustion at a volume ratio of natural gas:VOCs=1:(2.8-3.2) to control the combustion chamber temperature between 850℃ and 900℃, and the gas residence time is ≥2s. When the combustion chamber temperature is <850℃, cut off the exhaust gas passage and start the liquid nitrogen spray of the emergency cooling system; S5. Shutdown and Cooling: After combustion, shut down the electric kiln and combustion device, and allow it to cool naturally for 21-27 hours. During the cooling process, nitrogen is continuously introduced to maintain a slight positive pressure inside the kiln and to keep the oxygen content inside the kiln below 100 ppm in order to obtain high-purity graphite saggers.

6. The integrated process for high-purity graphite crucible anaerobic roasting-incineration according to claim 5, characterized in that, In step S1, the screening efficiency of the grading and screening device is ≥95%, and the iron removal rate of the electromagnetic impurity removal device is ≥99.9%.

7. The integrated process for high-purity graphite crucible anaerobic roasting-incineration according to claim 5, characterized in that, In step S4, the heating element of the electric heating kiln is a silicon molybdenum rod, and the heating uniformity is controlled within ±5℃.

8. The integrated process for high-purity graphite crucible anaerobic roasting-incineration according to claim 5, characterized in that, In step S43, the CO2 concentration is monitored in real time using an infrared CO2 analyzer. When the detected CO2 value is lower than 95% of the theoretical value, the natural gas injection rate is adjusted.

9. The integrated process for high-purity graphite crucible anaerobic roasting-incineration according to claim 5, characterized in that, In step S43, the combustion chamber is equipped with a baffle to make the gas residence time reach 2s-3s.

10. The integrated process for anaerobic roasting and incineration of high-purity graphite in a sagger according to claim 5, characterized in that, In step S5, the nitrogen gas introduced during the cooling process has a purity of ≥99.99%, and the pressure inside the kiln is monitored in real time by a pressure sensor to ensure that the micro-positive pressure is stable at 50-100Pa.

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