Temperature control method for processing graphite by double plasma sources

Abstract

The invention discloses a temperature control method for processing graphite by using double plasma sources, and relates to the technical field of plasma material processing, in particular to a temperature control method for processing graphite by using double plasma sources, which comprises the following steps: adopting a cylindrical reactor, and arranging a plasma source I and a plasma source II up and down along the axial direction on two sides of the cylindrical reactor, and an outlet of the powder feeding mechanism directly faces a core high-temperature area of the plasma source I, so that graphite powder directly enters a heating area. The two sources are connected in series up and down to construct a continuous relay type high-temperature path. The center distance between the powder feeding port and the source I is limited not to exceed half of the outlet diameter of the reactor, the center distance between the two sources is 1-2.5 times of the outlet diameter, and the center distance between the source II and the outlet is larger than 5 times of the diameter; the flow of the second source is 1.2-1.8 times that of the first source, the temperature of the core area is maintained to be 8000-10000 K by adjusting the flow ratio, and the total power does not exceed 100 kilowatts. The total retention time of the graphite powder in a two-source high-temperature area is longer than 0.2 second, the diameter of an outlet of the reactor is 100-400 mm, the reactor is made of high-temperature-resistant stainless steel or graphite, and accurate control over the graphite treatment temperature is achieved.

Description

Technical Field

[0001] This invention relates to the field of plasma material processing technology, specifically a temperature control method for processing graphite using dual plasma sources. Background Technology

[0002] Graphite powder, as a key functional material, is widely used in high-end fields such as lithium battery anodes, semiconductor heat sinks, and aerospace sealing materials. Among these, large-particle-size graphite powder (50–200 μm) is the preferred raw material due to its higher packing density, superior conductivity, and better mechanical strength. However, the actual industrial processing of large-particle-size graphite powder faces severe challenges, especially as existing single-plasma source technologies struggle to meet its processing requirements. Specifically, these challenges manifest in the following three core issues: First, the residence time in the high-temperature zone is severely insufficient. The length of the high-temperature zone in a single plasma source is typically only 50–100 mm, while the velocity of large-diameter graphite powder in the plasma flow is approximately 1–2 m / s, resulting in a residence time of only 0.05–0.1 s in the high-temperature zone. Due to the poor thermal conductivity of graphite powder, brief exposure to high temperatures only achieves surface melting, making it difficult to reach the thermal equilibrium time required for sufficient internal heating. Consequently, complete spheroidization of the particles and optimization of the internal structure cannot be achieved. For example, in the preparation of lithium-ion battery anode materials, insufficiently spheroidized graphite particles lead to uneven lithium-ion intercalation during charging and discharging, significantly reducing battery cycle life.

[0003] Secondly, the impurity purification effect is poor. Large-particle graphite powder often contains impurities such as argon, nitrogen, and hydrogen metal oxides, as well as volatiles. The melting points of these impurities are usually below 1500 °C, but their complete volatilization requires sufficient time to diffuse to the particle surface. The short residence time of a single plasma source prevents impurities from fully volatilizing, resulting in a purification rate generally below 85%. In addition, unvaporized impurities can form localized high-temperature points on the graphite particle surface, causing particle adhesion or localized overheating and decomposition, further reducing product quality. For example, high-purity graphite for semiconductors requires an impurity content of less than 1%, but graphite powder treated with a single source is unlikely to meet this standard.

[0004] Third, continuous production capacity is limited. To increase residence time, the powder flow rate needs to be significantly reduced during single-plasma source processing, which cannot meet the processing efficiency requirements of industrial continuous production. Low flow rate operation also leads to increased energy consumption and low equipment utilization, severely restricting the large-scale application of large-particle-size graphite powder in high-end fields.

[0005] While some existing technologies attempt to extend residence time by lengthening the reactor or adding auxiliary heating sources, these methods often introduce new problems. For example, simply extending the reactor can lead to unstable plasma flow fields and graphite powder accumulation in the low-temperature region; while auxiliary heating sources may cause uneven temperature distribution, exacerbating particle adhesion. Therefore, there is an urgent need for an innovative solution that can precisely control temperature distribution, extend residence time in the high-temperature region, and support continuous production. Summary of the Invention

[0006] The purpose of this invention is to provide a temperature control method for processing graphite using a dual plasma source. By setting up a removal component and a cleaning component, this method solves the problem mentioned in the background art where the depilation effect is poor and lint remains when processing textile fabrics, affecting subsequent processing.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a temperature control method for treating graphite using dual plasma sources, comprising a cylindrical reactor, wherein plasma source one and plasma source two are arranged vertically along the axial direction on both sides of the cylindrical reactor, and the outlet of the powder feeding mechanism is directly opposite the core high-temperature zone of plasma source one, ensuring that graphite powder directly enters the heating zone of plasma source one after being discharged from the powder feeding mechanism; the vertical arrangement forms a series high-temperature path, avoiding airflow interference caused by horizontal arrangement, and ensuring that graphite powder passes through the core zone of the dual plasma sources sequentially from bottom to top along the axial direction.

[0008] Furthermore, the axial distance L1 between the outlet of the powder feeding mechanism and the center of the plasma source does not exceed half the diameter D1 of the reactor outlet, to ensure that the graphite powder does not undergo significant cooling before entering the plasma core region, thus avoiding a temperature drop due to contact with the cold wall.

[0009] Furthermore, the axial distance L2 between the centers of plasma source one and plasma source two is set to 1 to 2.5 times the reactor outlet diameter D1, so that after the graphite powder leaves the high-temperature zone of plasma source one, it enters the core zone of plasma source two before it is completely cooled to the critical temperature (<7000K), thus maintaining a continuous high-temperature state.

[0010] Furthermore, the axial distance L3 between the center of the plasma source II and the reactor outlet is greater than 5 times the reactor outlet diameter D1 to ensure a uniform flow field at the reactor outlet and to prevent graphite powder from accumulating at the outlet, which would lead to temperature rise and particle adhesion.

[0011] Furthermore, the working gas flow rate m3 of the second plasma source is set to 1.2 to 1.8 times the flow rate m2 of the first plasma source, and the total gas flow rate ranges from 50 to 200 standard liters per minute. The flow rate ratio is used to supplement the energy consumed by the graphite powder after passing through the first plasma source, thereby maintaining the temperature balance of the dual-source core region.

[0012] Furthermore, by adjusting the flow rate ratio of plasma source one to plasma source two, the core region temperature of both is maintained at 8000 to 10000K, ensuring that the graphite powder is in the optimal heating state in both high-temperature regions, thereby achieving full melting of the internal structure and volatilization of impurities.

[0013] Furthermore, the graphite powder is continuously conveyed at a flow rate of 0–2 g / s and passes sequentially through the core high-temperature zones of plasma source one and plasma source two. The total residence time in the high-temperature zone is greater than 0.2 seconds, thereby completing the high sphericity (≥95%) and high purification (≥90%) processing.

[0014] Furthermore, the total power of plasma source one and plasma source two does not exceed 100 kilowatts, and the working gas is argon, nitrogen, hydrogen or a mixture thereof, wherein the volume percentage of hydrogen is 5%–15% to balance thermal efficiency and reactivity.

[0015] Furthermore, the outlet diameter D1 of the reactor is designed to be 100 to 400 mm, and the material is high-temperature resistant stainless steel or graphite to adapt to high-temperature environments and ensure structural stability.

[0016] Furthermore, the method is applicable to the continuous processing of graphite powder with a large particle size of 50–200 micrometers, which can meet the stringent requirements for particle sphericity and purity in high-end fields such as lithium battery anode materials and semiconductor graphite.

[0017] This invention provides a temperature control method for processing graphite using a dual plasma source, which has the following advantages: 1. Significantly improves the processing quality of large-particle-size graphite powder This method, through a dual-plasma source series design, extends the residence time of graphite powder in the optimal temperature range of 8000-10000K to over 0.2 seconds, solving the problem of insufficient internal heating caused by the short residence time in the high-temperature zone during single-plasma source processing. The graphite powder sequentially passes through the core high-temperature zones of the two plasma sources, forming a continuous heating path, allowing for thorough melting and reorganization of the internal structure of the particles and full volatilization of impurities. Ultimately, it achieves a spheroidization rate ≥95% and a purification rate ≥90% (impurity content <1%), significantly superior to single-source processes (spheroidization rate <90%, purification rate <85%), meeting the stringent requirements for graphite powder purity and spheroidization in high-end fields such as lithium-ion battery anode materials.

[0018] Optimize thermal field distribution and energy utilization efficiency By quantitatively controlling the distance between the two sources and the gas flow rate ratio, this invention achieves "relay-style" temperature maintenance. The higher flow rate of plasma source 2 compensates for the energy loss of graphite powder when passing through source 1, avoiding a sudden temperature drop and ensuring that the temperature in the core region of the two sources remains stable at 8000-10000K. Simultaneously, the design of the reactor outlet distance ensures flow field uniformity, preventing graphite powder accumulation or adhesion. This synergistic control reduces ineffective heat loss, enabling devices with a total power ≤100kW to support continuous feeding at 0-2g / s, improving energy utilization by more than 30% compared to single-source systems.

[0019] Support for continuous industrial production and large-scale application Traditional single-plasma sources require reduced powder flow rates to extend residence time, which is insufficient for industrial applications. This invention, through a dual-source series structure and parameter optimization, maintains a high-temperature residence time >0.2s while supporting continuous feeding at 0-2g / s, achieving a doubling of processing efficiency. The flexible design of the reactor diameter (D1=100-400mm) and total gas flow rate (50-200slm) adapts to different production lines, and the vertical arrangement avoids airflow interference between the two sources, ensuring long-term operational stability. This provides a reliable technical foundation for the mass production of large-particle-size graphite powder in semiconductor, aerospace, and other fields.

[0020] Enhance process controllability and operational flexibility The claims clearly define key parameters, forming a quantifiable temperature control logic. Operators can precisely control the core area temperature by adjusting the dual-source flow rate ratio to accommodate graphite powder with different particle sizes from 50-200μm. The close proximity design between the powder feeding mechanism and plasma source 1 avoids powder pre-cooling, while the flow rate enhancement strategy of plasma source 2 dynamically compensates for energy loss. This parameterized model reduces reliance on operational experience, improves process repeatability and yield, and provides a basic framework for equipment automation upgrades.

[0021] Breakthrough in high-end material performance bottlenecks and expand application scenarios To address the issue of "surface melting and internal unconverted" that easily occurs in single-source processing of large-particle graphite powder (50-200μm), a dual-source tandem design extends the high-temperature residence time, allowing heat to be fully conducted into the particle interior, achieving uniform spheroidization and deep purification. The resulting graphite powder possesses both high packing density (large particle size) and low impurity content, perfectly meeting the capacity and cycle stability requirements of lithium-ion battery anode materials, while also satisfying the stringent purity standards of semiconductor heat sinks. This method advances graphite powder processing technology from the laboratory level to the industrial level, providing a new paradigm for the application of high-temperature plasma technology in fields such as new material synthesis and waste treatment. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0024] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses consistent with some aspects of this disclosure as detailed in the appended claims.

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] How to use: 1. Equipment Configuration and Startup First, configure the cylindrical reactor 4, ensuring its outlet diameter D1 is within the range of 100 to 400 mm, and use high-temperature resistant stainless steel or graphite as the material. Arrange plasma source 1 and plasma source 2 vertically along the axial direction on both sides of the reactor 4, with a total power not exceeding 100 kW. The outlet of the powder feeding mechanism 3 should be directly aligned with the core high-temperature zone of plasma source 1, ensuring that the graphite powder directly enters the heating zone after discharge. Before startup, check the working gas supply system for the plasma sources (such as argon, nitrogen, hydrogen, or a mixture thereof, with hydrogen accounting for 5-15%).

[0027] Distance parameter settings The axial distance L1 between the outlet of the powder feeding mechanism 3 and the center of plasma source 1 is set to no more than half the outlet diameter D1 of reactor 4. The axial distance L2 between the centers of plasma source 1 and plasma source 2 is set to 1 to 2.5 times the outlet diameter D1 of reactor 4. The axial distance L3 between the center of plasma source 2 and the outlet of reactor 4 is set to be greater than 5 times the outlet diameter D1 of reactor 4. These distance parameters ensure that the graphite powder enters the high-temperature zone rapidly, avoids cooling, and maintains a stable flow field.

[0028] Gas flow and temperature control The working gas flow rate m2 of plasma source 1 is adjusted to be within the range of 20 to 80 standard liters per minute, and the flow rate m3 of plasma source 2 is set to 1.2 to 1.8 times that of m2. The total flow rate m2 plus m3 is controlled between 50 and 200 standard liters per minute. By adjusting the flow rate ratio, the core region temperature of plasma source 1 and source 2 is maintained at 8000 to 10000 K to compensate for energy consumption and maintain optimal heating.

[0029] Graphite powder processing operation The powder feeding mechanism 3 is activated to continuously deliver large-particle-size graphite powder (50-200 micrometers) at a flow rate of 0 to 2 grams per second. The graphite powder sequentially passes through the core high-temperature zones of plasma source 1 and source 2, with a total residence time greater than 0.2 seconds. During this process, the graphite powder achieves full spheroidization (spheroidization rate ≥95%) and purification (purification rate ≥90%, impurity content <1%), and is finally uniformly discharged from the outlet of reactor 4.

[0030] Monitoring and Adjustment Real-time monitoring of plasma temperature and working gas flow rate is crucial to ensure parameter stability. If the temperature deviates from the 8000-10000K range, the flow rate ratio should be adjusted promptly. The reactor outlet flow field should be checked to prevent graphite powder accumulation. This method is suitable for continuous production in high-end fields such as lithium-ion battery anode materials and semiconductor graphite.

[0031] Example: Example 1: Dual Plasma Source Series Arrangement and High-Temperature Path Construction This embodiment focuses on the structural design of a dual plasma source arranged in series, one above the other, and its effect on extending the high-temperature residence time of graphite powder. A cylindrical reactor 4 is configured with an outlet diameter within a reasonable range, and the material is selected as high-temperature resistant stainless steel or graphite. Plasma source 1 and plasma source 2 are arranged axially on both sides of the reactor 4, one above the other, with plasma source 1 located at the bottom and plasma source 2 at the top. The outlet of the powder feeding mechanism 3 is directly opposite the core high-temperature zone of plasma source 1, allowing the graphite powder to directly enter the high-temperature region after discharge. The series arrangement of plasma sources 1 and 2 forms a continuous relay heating path, with the graphite powder passing through the core high-temperature zones of both sources sequentially from bottom to top. By optimizing the distance between the two sources, it is ensured that the graphite powder enters the heating zone of plasma source 2 without significant cooling after leaving plasma source 1, thereby extending its total residence time in the optimal temperature zone. This method effectively solves the problems of short high-temperature zones and insufficient internal heating in single-plasma source processing, achieving sufficient spheroidization and purification of graphite powder.

[0032] Example 2: Optimization of key distance parameters and control of flow field stability This embodiment illustrates the impact of synergistic optimization of various axial distance parameters on the processing effect. The distance between the outlet of the powder feeding mechanism 3 and the center of the plasma source 1 is set within a reasonable range to ensure that the graphite powder quickly enters the core high-temperature zone and avoids premature cooling. The spacing between plasma source 1 and plasma source 2 is designed to be appropriately proportioned, so that the temperature of the graphite powder is maintained at a high level during transfer between them, preventing thermal interruption. The spacing between the center of plasma source 2 and the outlet of reactor 4 is set to a larger value to ensure a uniform and stable outlet flow field and avoid graphite powder accumulation or adhesion. Each distance parameter is designed proportionally based on the outlet diameter of reactor 4, collectively ensuring that the movement trajectory of the graphite powder in the high-temperature zone is controllable and the residence time is sufficient, while maintaining stable airflow inside the reactor, improving processing efficiency and product consistency.

[0033] Example 3: Coordinated Control of Working Gas Flow Ratio and Temperature This embodiment focuses on the crucial role of gas flow rate matching between the two plasma sources in temperature control. The working gases for plasma source 1 and plasma source 2 are argon, nitrogen, hydrogen, or a mixture thereof, with the hydrogen percentage controlled within an appropriate range. The flow rate of plasma source 2 is set to a reasonable multiple of the flow rate of plasma source 1, ensuring the total gas flow rate is within an applicable range. By adjusting the flow rate ratio, the core temperatures of both plasma sources 1 and 2 are maintained within the ideal high-temperature range. This design compensates for the temperature drop caused by energy absorption when graphite powder passes through plasma source 1, ensuring that plasma source 2 provides sufficient heat to keep the graphite powder in its optimal processing state in the second high-temperature zone. Precise control of the flow rate ratio is key to achieving dual-source temperature balance and extending the effective heating time.

[0034] Example 4: Continuous powder feeding and high-temperature residence time assurance This embodiment illustrates the coordinated design of graphite powder conveying and residence time in the high-temperature zone. The powder feeding mechanism 3 continuously conveys graphite powder, with the flow rate controlled within a reasonable range to support the needs of continuous industrial production. The graphite powder sequentially passes through the core high-temperature zones of plasma source 1 and plasma source 2, with a total residence time exceeding a critical value, ensuring sufficient internal heating of large-diameter particles. The total power of the dual plasma sources is limited to a reasonable level, controlling energy consumption while ensuring high-temperature processing. This method, by extending the residence time, allows impurities in the graphite powder to fully volatilize and achieves a highly spherical particle morphology. The final product's spheroidization rate and purification rate both meet the requirements of high-end applications, significantly outperforming the single-plasma source treatment effect.

[0035] Example 5: Overall process integration and processing effect verification This embodiment comprehensively describes the overall process flow and output effect of the dual-plasma source temperature control method. The structure of reactor 4, along with the synergistic effects of the dual-source arrangement, distance parameters, gas flow rate, and powder feeding rate, creates a stable high-temperature processing environment. Graphite powder undergoes dual-stage heating within reactor 4, achieving high levels of sphericity and purification, and significantly reducing impurity content. This method is suitable for high-end applications such as lithium-ion battery anode materials and semiconductor graphite, solving problems such as insufficient residence time and poor purification effect in single-plasma source processing of large-particle-size graphite powder, and achieving efficient, continuous, and stable industrial production.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A temperature control method for processing graphite using dual plasma sources, comprising a cylindrical reactor (4), characterized in that: The columnar reactor (4) has plasma source one (1) and plasma source two (2) arranged vertically along the axial direction on both sides. The outlet of the powder feeding mechanism (3) is directly opposite the core high-temperature zone of plasma source one (1), ensuring that the graphite powder directly enters the heating zone of plasma source one (1) after being discharged from the powder feeding mechanism (3).

2. The temperature control method for dual-plasma source processing of graphite according to claim 1, characterized in that: The plasma source one (1) and the plasma source two (2) are arranged in series to form a continuous relay high-temperature path.

3. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The axial distance L1 between the outlet of the powder feeding mechanism (3) and the center of the plasma source (1) does not exceed half the outlet diameter D1 of the reactor (4).

4. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The axial distance L2 between the centers of plasma source one (1) and plasma source two (2) is set to be 1 to 2.5 times the outlet diameter D1 of the reactor (4).

5. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The axial distance L3 between the center of the plasma source 2 (2) and the outlet of the reactor (4) is greater than 5 times the outlet diameter D1 of the reactor (4).

6. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The working gas flow rate m3 of plasma source two (2) is set to 1.2 to 1.8 times the flow rate m2 of plasma source one (1).

7. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: By adjusting the flow rate ratio of plasma source one (1) and plasma source two (2), the core temperature of both is maintained at 8000 to 10000K.

8. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The total residence time of the graphite powder in the high-temperature regions of plasma source one (1) and plasma source two (2) is greater than 0.2 seconds.

9. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The total power of plasma source one (1) and plasma source two (2) does not exceed 100 kilowatts.

10. The temperature control method for processing graphite using a dual plasma source according to claim 1, characterized in that: The outlet diameter D1 of the reactor (4) is designed to be 100 to 400 mm, and the material is high-temperature resistant stainless steel or graphite.

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