Continuous discharging system for preparing single-walled carbon nanotubes by electric arc method and preparation method

Abstract

The invention discloses a continuous discharging system for preparing single-walled carbon nanotubes by an electric arc method and a preparation method. The system comprises a growth unit, a purging unit, a vortex unit and a collection unit, the growth unit is provided with a growth tube cavity, and an arc generator is arranged in the growth tube cavity and used for forming a plasma arc; the purging unit is arranged at the first end and used for inputting purging gas into the growth tube cavity, and the purging gas surrounds the arc generator; the vortex unit is arranged at the second end, is provided with an airflow arrangement structure and is used for limiting vortex formed by the floating mixed gas in the vortex unit; and the collecting unit is communicated with the vortex unit and is used for collecting the carbon nanotubes. According to the system provided by the invention, a bottom discharging mode is adopted, so that products are prevented from being accumulated around plasma arcs, the difficulty that a traditional electric arc furnace system has the advantage of efficiently preparing high-crystallinity single-walled carbon nanotubes but cannot continuously discharge is overcome, and the system has great commercial value and significance.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a continuous discharge system and preparation method for preparing single-walled carbon nanotubes by electric arc method. Background Technology

[0002] Carbon is one of the most fundamental elements in nature, and carbon materials possess almost all the properties that matter should have. Therefore, the 21st century is also known as the "super-carbon era." Among the many carbon materials, carbon nanotubes are widely recognized as the most promising one-dimensional nanomaterials of the 21st century due to their excellent performance in electrical, mechanical, and thermal aspects.

[0003] Carbon nanotubes can be viewed as hollow columnar structures formed by the curling of graphene layers. They are classified into single-walled (monolayer) carbon nanotubes and multi-walled (multilayer) carbon nanotubes based on the number of curled layers. Single-walled carbon nanotubes, in particular, have long been a focus of research due to their ability to achieve excellent physicochemical properties with extremely low concentrations. However, the more demanding preparation conditions for single-walled carbon nanotubes, such as their small diameter, large surface curvature, and high reaction barriers, have limited their mass production to a single company globally—Ocsial in Russia—demonstrating the high technological barriers involved in their fabrication.

[0004] Among numerous methods for preparing single-walled carbon nanotubes, the plasma-arc method holds great potential for large-scale preparation of highly crystalline single-walled carbon nanotubes due to its ability to provide extremely high temperatures and ionize high-energy particles, thus offering greater energy to overcome the reaction barrier. However, the eddies generated by current conventional plasma-arc furnace structures lead to extremely turbulent airflow, causing the generated carbon nanotubes to become entangled and stacked, resulting in problems such as blockages and inability to discharge the material promptly and effectively, hindering continuous preparation. Therefore, designing a novel plasma-arc furnace system that can rapidly and continuously discharge material without interruption is a key approach to solving this problem. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a continuous discharge system and preparation method for preparing single-walled carbon nanotubes by electric arc method.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] In a first aspect, the present invention provides a continuous discharge system for preparing single-walled carbon nanotubes by electric arc method, which includes a growth unit, a purging unit, a vortex unit and a collection unit arranged in combination.

[0008] The growth unit has a growth cavity, and an arc generator is provided in the growth cavity to form a plasma arc, which is used to convert the growth medium into carbon nanotubes.

[0009] The purging unit is disposed at the first end of the growth cavity and is used to input purging gas into the growth cavity. When the purging gas moves in the growth cavity, it surrounds the arc generator and mixes with at least the carbon nanotubes to form a floating mixed gas that moves toward the second end of the growth cavity.

[0010] The vortex unit is disposed at the second end and has an airflow sorting structure, which is used to confine the vortex formed by the floating mixed gas at the second end in the vortex unit.

[0011] The collection unit is connected to the vortex unit for collecting carbon nanotubes in the floating mixed gas.

[0012] Secondly, the present invention also provides an arc method for preparing single-walled carbon nanotubes, comprising:

[0013] Using the above-mentioned continuous discharge system, growth medium is injected into the growth chamber and purge gas is input into the growth chamber by the self-purge unit. The plasma arc generated by the arc generator acts on the growth medium to form single-walled carbon nanotubes.

[0014] Single-walled carbon nanotubes are collected from the collection unit.

[0015] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0016] The system provided by this invention employs a bottom discharge method to avoid product accumulation around the plasma arc; it confines the plasma arc to the growth unit, avoiding the drawback of easy blockage caused by the growth zone also being the material accumulation zone in traditional electric arc furnace systems; the top downward blowing airflow utilizes the characteristic that direct current is more conducive to material discharge, quickly carrying the product to the bottom, avoiding the airflow turbulence and product entanglement problems caused by the eddies in traditional electric arc furnace systems; more importantly, the downward airflow at the bottom has an arc-shaped airflow organizing structure in the eddy current unit, which can form a controlled bottom eddy current, preventing the phenomenon of some products moving in the opposite direction to the growth unit caused by the large airflow disturbance generated by the upper blowing airflow and the gas backflow caused by the temperature gradient here. Thus, it overcomes the difficulty of the traditional electric arc furnace system, which has the advantage of high efficiency in preparing high-crystallinity single-walled carbon nanotubes but cannot continuously discharge, and has significant commercial value and significance.

[0017] In addition, the downward cold purge airflow has a partial cooling effect, which increases the temperature gradient around the electric arc and hinders the further growth of catalyst particles, which is conducive to the formation of single-walled carbon nanotubes. The direct current is hydrodynamically conducive to the formation of the cap end of carbon nanotubes, thus benefiting the nucleation kinetics of carbon nanotubes.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of a continuous discharge system for preparing single-walled carbon nanotubes by electric arc method, provided for some typical implementation examples of the invention;

[0020] Figure 2 A scanning electron microscope image of the prepared product provided as a typical embodiment of the present invention;

[0021] Figure 3 Raman spectrum of the prepared product provided in a typical embodiment of the present invention;

[0022] Figure 4 Scanning electron microscope image of the prepared product provided as another typical embodiment of the present invention;

[0023] Figure 5 Raman spectrum of the prepared product provided as another typical embodiment of the present invention;

[0024] Figure 6 A scanning electron microscope image of the prepared product provided as another typical embodiment of the present invention;

[0025] Figure 7 The Raman spectrum of the prepared product is provided as another typical embodiment of the present invention.

[0026] Explanation of reference numerals in the attached diagram: 1. Feeding unit; 2. Growth unit; 3. Purging unit; 4. Electrode gun; 5. Graphite crucible; 6. Graphite base; 7. Eddy current unit; 8. Collection tank; 9. Air pump; 10. Discharge port; 11. Exhaust gas outlet; 12. Filter screen. Detailed Implementation

[0027] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0029] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component or method step from another that has the same name, and do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0030] This invention provides a continuous discharge system for preparing single-walled carbon nanotubes using an electric arc method. The system includes a growth unit, a purging unit, a vortex unit, and a collection unit arranged in a coordinated manner. The growth unit has a growth cavity, within which an arc generator is installed to form a plasma arc, which converts the growth medium into carbon nanotubes. The purging unit is located at a first end of the growth cavity and is used to input purging gas into the cavity. As the purging gas moves within the cavity, it surrounds the arc generator and mixes with at least the carbon nanotubes to form a floating mixed gas that moves towards a second end of the cavity. The vortex unit is located at the second end and has an airflow regulating structure to confine the vortex formed by the floating mixed gas at the second end within the vortex unit. The collection unit is connected to the vortex unit and is used to collect the carbon nanotubes from the floating mixed gas.

[0031] In some embodiments, the arc generator includes a first electrode, a second electrode, and a material input channel disposed opposite to each other, wherein the plasma arc is formed between the first electrode and the second electrode, and the material input channel is used to deliver the growth medium into the plasma arc.

[0032] In some embodiments, the material input channel is located inside the first electrode and / or the second electrode.

[0033] In some embodiments, the first electrode extends from the first end into the growth cavity along the axial direction of the growth cavity, and the second electrode extends from the eddy current unit into the growth cavity along the axial direction of the growth cavity and in the direction from the second end to the first end.

[0034] In some embodiments, the first electrode includes a cathode electrode gun, and the second electrode includes a graphite base and a graphite crucible. The bottom end of the graphite base is fixed to the end face of the eddy current unit, and the top end abuts against the graphite crucible. The graphite crucible faces the cathode electrode gun, and the height of the graphite base is more than 5 times the height of the graphite crucible.

[0035] In some embodiments, the purging unit includes a purging gas input channel for inputting the purging gas, the purging gas input channel being disposed at the first end and forming a rotationally symmetrical gas outlet structure with the first electrode as the axis of symmetry.

[0036] In some embodiments, the airflow sorting structure includes a curved cavity and an extension cavity arranged sequentially along the direction from the first end to the second segment, wherein the inlet of the curved cavity is connected to the outlet of the growth cavity, and the outlet of the curved cavity is connected to the inlet of the extension cavity.

[0037] The extended cavity is coaxial with the growth cavity, and the inner diameter of the extended cavity is larger than that of the growth cavity. At the junction of the curved cavity and the growth cavity, the inner walls of the curved cavity and the growth cavity form an edge, and the curvature center of the curved cavity is located inside the vortex unit.

[0038] Regarding specific dimensional characteristics, in some implementations, the ratio of the inner diameter of the growth cavity to the inner diameter of the extension cavity is 1:1.2-1.5. In the following specific embodiment, this value is specifically 1:1.37. The curvature radius of the curved cavity is adaptively set, mainly to ensure that the edges are acute-angled edges with an included angle of less than 90° to prevent the airflow from having an upward tendency, and to ensure that the joint between the curved cavity and the extension cavity has a relatively smooth transition.

[0039] In some embodiments, the bottom end face of the growth cavity is closed, and the outlet of the growth cavity is located on the side wall of the growth cavity near the bottom end face; the inlet of the collection unit is connected to the outlet of the growth cavity.

[0040] In some embodiments, the collection unit includes a collection tank, a filter screen, and a vacuum pump. One end of the vacuum tank has an inlet on its side wall that communicates with the outlet of the growth chamber, and an outlet is provided on the side wall opposite to the inlet. The other end of the vacuum tank is provided with a tail gas discharge port. The filter screen is disposed inside the vacuum tank to block the product and allow the gas to pass through. The vacuum pump is disposed on the side wall of the vacuum tank to create a pressure difference between the growth chamber and the collection tank.

[0041] A second aspect of this invention also provides an arc method for preparing single-walled carbon nanotubes, comprising:

[0042] The continuous discharge system provided by any of the above embodiments injects growth medium into the growth chamber and a self-blowing unit inputs purge gas into the growth chamber. The plasma arc generated by the arc generator acts on the growth medium to form single-walled carbon nanotubes.

[0043] Single-walled carbon nanotubes are collected from the collection unit.

[0044] See Figure 1As shown, an embodiment of the present invention exemplarily provides a continuous discharge system and process for preparing single-walled carbon nanotubes by an electric arc method. The system includes a feeding unit 1, a growth unit 2, a purging unit 3, a vortex unit 7, and a collection unit. The feeding unit 1 is used to deliver the catalyst into the plasma arc region using a carrier gas. The carrier gas can be argon or helium, but is not limited to these. The growth unit 2 has a growth cavity containing a device for generating a plasma arc, providing reaction conditions for the catalyst and mixed gas to grow carbon nanotubes. The purging unit 3 is used to rapidly and vertically carry the generated carbon nanotube product to the bottom, achieving partial cooling, increasing the temperature gradient around the plasma arc, and reducing further growth of catalyst particles, which is beneficial for the formation of single-walled carbon nanotubes; it also contributes to the nucleation kinetics of the carbon nanotube cap. The vortex unit 7 utilizes the characteristic that the downward airflow can form vortices in the arc-shaped region to prevent excessive purging airflow and temperature gradient, which could cause some product to move upwards to the growth unit 2. The collection unit is used to store carbon nanotube products and to collect the discharged materials.

[0045] The growth unit 2 may specifically include: a cathode electrode gun 4, an anode graphite crucible 5, and a graphite base 6. The center of the graphite crucible 5 coincides with the center of the electric arc furnace growth unit 2. The electrode gun 4 is suspended 5-30 cm above the anode graphite crucible 5. The height of the graphite base 6 is more than 5 times the height of the graphite crucible 5, serving both to support the graphite crucible 5 and to provide current to it.

[0046] The purging unit 3 consists of at least four air inlets arranged in a centrally symmetrical array. Each air inlet is a cylindrical inlet of equal diameter with its lower end connected to the upper surface of the growth unit 2. The gas introduced into each air inlet is an inert gas, and the gas intake is 0.5-3 times the gas intake at the electrode gun 4 (i.e., the gas flow rate of the growth medium). The inert gas includes argon or helium.

[0047] The upper end of the vortex unit 7 is an arc-shaped wall, and its upper end is connected to the lower end of the straight growth unit 2.

[0048] The collection unit includes: a collection tank 8, a filter screen 12, an exhaust port 11, a discharge port 10, and a vacuum pump 9. The left end of the collection tank 8 is connected to the bottom of the right end of the vortex unit 7 via a pipe. The filter screen 12 is located in the upper part of the collection tank 8. The exhaust port 11 is located at the uppermost right end of the collection tank 8. The discharge port 10 is located at the lowest center of the collection tank 8. The vacuum pump 9 is located in the collection tank 8 near the upper end of the connection between the collection pipe and the vortex unit 7. The right end of the feeding unit 1 is connected to the left end of the growth unit 2.

[0049] Regarding the specific process method, the mixed gas is typically hydrogen, a carbon source, and an inert gas. The carbon source is methane, ethylene, propylene, or acetylene, and the inert gas is argon or helium. Furthermore, the mixed gas enters through a channel in the electrode gun 4. Further, the inlet flow rates of hydrogen, carbon source, and inert gas in the mixed gas can be 3-6 L / min, 6-10 L / min, and 20-40 L / min, respectively.

[0050] The electrode gun 4 is a plasma electrode gun 4, and the power of the plasma electrode gun 4 is greater than 10kW.

[0051] Raman characterization of single-walled carbon nanotubes prepared by the above-described system and method using the continuous discharge system for single-walled carbon nanotube preparation by the electric arc method. G / I D The ratio is greater than 50, and it can continuously discharge material without clogging.

[0052] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0053] Example 1

[0054] Adopting such Figure 1 The illustrated continuous discharge system for preparing single-walled carbon nanotubes using the electric arc method first purges the growth unit with argon gas at a flow rate of 20 L / min from the electrode gun. Then, the power supply of the plasma arc furnace is set to 20 kW, and an arc discharge is initiated at a distance of 5 cm from the graphite crucible to form plasma. Next, when the temperature rises to 2200℃, the catalyst is introduced through the feed inlet, and hydrogen, methane, and argon are introduced through the electrode gun at flow rates of 4 L / min, 8 L / min, and 20 L / min, respectively, to generate the product. Simultaneously, argon gas is introduced through the four inlets of the purging unit at a flow rate of 16 L / min to carry the generated product to the bottom, where it flows into the collection tank, enabling continuous preparation. Figure 2 The image shown is a scanning electron microscope image of the product prepared in Example 1 of this invention. Figure 3 The image shown is the Raman spectrum of the product prepared in Example 1 of this invention. The horizontal axis of the spectrum is 100-300 cm⁻¹. 1 The spectrum shows characteristic RBM peaks unique to single-walled carbon nanotubes, particularly at 1350 cm⁻¹. 1 and 1590cm- 1 I can be calculated from the corresponding D and G peak values ​​in the vicinity. G / I D A value of 51 indicates that the product has high crystallinity.

[0055] Example 2

[0056] Adopting such Figure 1 The illustrated continuous discharge system for preparing single-walled carbon nanotubes using the electric arc method first purges the growth unit with argon gas at a flow rate of 20 L / min from the electrode gun. Then, the power supply of the plasma arc furnace is set to 20 kW, and an arc discharge is initiated at a distance of 7 cm from the graphite crucible to form plasma. Next, when the temperature reaches 2400℃, a catalyst is introduced through the feed inlet, and hydrogen, methane, and argon are introduced through the electrode gun at flow rates of 6 L / min, 8 L / min, and 20 L / min, respectively, to generate the product. Simultaneously, argon gas is introduced through the four inlets of the purging unit at a flow rate of 18 L / min to carry the generated product to the bottom, where it flows into the collection tank, enabling continuous production. Figure 4 The image shown is a scanning electron microscope image of the product prepared in Example 1 of this invention. Figure 5 The image shows the Raman spectrum of the product prepared in Example 1 of this invention. The horizontal axis of the spectrum is 100-300 cm⁻¹. -1 The spectrum shows characteristic RBM peaks unique to single-walled carbon nanotubes, with the peak at 1350 cm⁻¹. -1 and 1590cm -1 I can be calculated from the corresponding D and G peak values ​​in the vicinity. G / I D A value of 59 indicates that the product has high crystallinity.

[0057] Example 3

[0058] Adopting such Figure 1 The illustrated continuous discharge system for preparing single-walled carbon nanotubes using the electric arc method first purges the growth unit with argon gas at a flow rate of 20 L / min from the electrode gun. Then, the power of the plasma arc furnace is set to 15 kW, and an arc discharge is initiated at a distance of 7 cm from the graphite crucible to form plasma. Next, when the temperature reaches 2200℃, a catalyst is introduced through the feed inlet, and hydrogen, methane, and argon are introduced through the electrode gun at flow rates of 4 L / min, 10 L / min, and 25 L / min, respectively, to generate the product. Simultaneously, argon gas is introduced through the four inlets of the purging unit at a flow rate of 20 L / min to carry the generated product to the bottom, where it flows into the collection tank, enabling continuous production. Figure 6 The image shown is a scanning electron microscope image of the product prepared in Example 1 of this invention. Figure 7 The image shows the Raman spectrum of the product prepared in Example 1 of this invention. The horizontal axis of the spectrum is 100-300 cm⁻¹. -1 The spectrum shows characteristic RBM peaks unique to single-walled carbon nanotubes, with the peak at 1350 cm⁻¹. -1 and 1590cm -1I can be calculated from the corresponding D and G peak values ​​in the vicinity. G / I D A value of 52 indicates that the product has high crystallinity.

[0059] Example 4

[0060] Adopting such Figure 1 The illustrated continuous feed system for preparing single-walled carbon nanotubes using the electric arc method first purges the growth unit with argon gas at a flow rate of 20 L / min through the electrode gun. Then, the power supply of the plasma arc furnace is set to 25 kW, and an arc discharge is initiated at a distance of 5 cm from the graphite crucible to form plasma. Next, when the temperature reaches 2400 °C, the catalyst is introduced through the feed inlet, and hydrogen, methane, and argon are introduced through the electrode gun at flow rates of 6 L / min, 8 L / min, and 25 L / min, respectively, to generate the product. Simultaneously, argon gas is introduced through the four inlets of the purging unit at a flow rate of 20 L / min to carry the generated product to the bottom, where it flows into the collection tank, enabling continuous production. The calculated Raman spectroscopy results for the product are shown. G / I D A value of 55 indicates that the product has high crystallinity.

[0061] Comparative Example 1

[0062] This comparative example is largely the same as Example 1, with the main difference being:

[0063] Instead of using a vortex unit, the bottom sidewall of the growth unit is directly connected laterally to the collection tank.

[0064] Because there is no eddy current unit to regulate the process, the product at the bottom will return to the plasma region, affecting continuous preparation and significantly shortening the time for continuous and stable operation of the equipment.

[0065] Comparative Example 2

[0066] This comparative example is largely the same as Example 1, with the main difference being:

[0067] The curved surface segment of the vortex element is modified into a flat, frustum-shaped cone, connecting pipe segments of different diameters at the top and bottom.

[0068] Because the cross-sectional shape has been changed to a non-curved surface, the eddy current rectification effect is also lost, and the product backflow phenomenon will occur, resulting in the loss of long-term continuous preparation capability.

[0069] Based on the above embodiments, it is clear that the embodiments of the present invention provide a continuous discharge system and method for preparing single-walled carbon nanotubes by electric arc method, belonging to the field of new materials technology. The system includes a feeding unit, a growth unit, a purging unit, a vortex unit, and a collection unit. The feeding unit and the electrode gun respectively feed the catalyst and mixed gas into the electric arc growth unit for carbon nanotube growth. The purging ports, centrally symmetrically distributed at the top of the growth unit, carry the product directly downwards into the vortex unit, and finally into the collection unit. This invention utilizes fluid dynamics design, not only achieving continuous and smooth discharge of carbon nanotube products, but also the downward cold purging gas helps to increase the temperature gradient around the electric arc and inhibit catalyst particle growth, thereby promoting the formation of high-quality single-walled carbon nanotubes. This overcomes the problem that traditional electric arc furnace systems, while having the advantage of high-efficiency preparation of high-crystallinity single-walled carbon nanotubes, cannot continuously discharge the product, and has significant commercial value and significance.

[0070] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A continuous discharge system for preparing single-walled carbon nanotubes by electric arc method, characterized in that, It includes a growth unit, a purging unit, a vortex unit, and a collection unit that are configured in a coordinated manner; The growth unit has a growth cavity, and an arc generator is provided in the growth cavity to form a plasma arc, which is used to convert the growth medium into carbon nanotubes. The purging unit is disposed at the first end of the growth cavity and is used to input purging gas into the growth cavity. When the purging gas moves in the growth cavity, it surrounds the arc generator and mixes with at least the carbon nanotubes to form a floating mixed gas that moves toward the second end of the growth cavity. The vortex unit is disposed at the second end and has an airflow sorting structure, which is used to confine the vortex formed by the floating mixed gas at the second end in the vortex unit. The collection unit is connected to the vortex unit for collecting carbon nanotubes in the floating mixed gas.

2. The continuous discharge system according to claim 1, characterized in that, The arc generator includes a first electrode, a second electrode, and a material input channel arranged opposite to each other. The plasma arc is formed between the first electrode and the second electrode, and the material input channel is used to deliver the growth medium into the plasma arc.

3. The continuous discharge system according to claim 2, characterized in that, The material input channel is located inside the first electrode and / or the second electrode.

4. The continuous discharge system according to claim 2 or 3, characterized in that, The first electrode extends from the first end into the growth cavity along the axial direction of the growth cavity, and the second electrode extends from the eddy current unit into the growth cavity along the axial direction of the growth cavity and in the direction from the second end to the first end.

5. The continuous discharge system according to claim 4, characterized in that, The first electrode includes a cathode electrode gun, and the second electrode includes a graphite base and a graphite crucible. The bottom end of the graphite base is fixed to the end face of the eddy current unit, and the top end abuts against the graphite crucible. The graphite crucible is directly opposite the cathode electrode gun, and the height of the graphite base is more than 5 times the height of the graphite crucible.

6. The continuous discharge system according to claim 4, characterized in that, The purging unit includes a purging gas input channel for inputting the purging gas. The purging gas input channel is located at the first end and forms a rotationally symmetrical gas outlet structure with the first electrode as the axis of symmetry.

7. The continuous discharge system according to claim 1, characterized in that, The airflow sorting structure includes a curved cavity and an extension cavity arranged sequentially along the direction from the first end to the second segment. The inlet of the curved cavity is connected to the outlet of the growth cavity, and the outlet of the curved cavity is connected to the inlet of the extension cavity. The extended cavity is coaxial with the growth cavity, and the inner diameter of the extended cavity is larger than that of the growth cavity. At the junction of the curved cavity and the growth cavity, the inner walls of the curved cavity and the growth cavity form an edge, and the curvature center of the curved cavity is located inside the vortex unit.

8. The continuous discharge system according to claim 7, characterized in that, The bottom end face of the growth cavity is closed, and the outlet of the growth cavity is located on the side wall of the growth cavity near the bottom end face. The inlet of the collection unit is connected to the outlet of the growth cavity.

9. The continuous discharge system according to claim 7, characterized in that, The collection unit includes a collection tank, a filter screen, and a vacuum pump. One end of the vacuum tank has an inlet on its side wall that communicates with the outlet of the growth chamber, and an outlet is provided on the side wall opposite to the inlet. The other end of the vacuum tank is provided with a tail gas discharge port. The filter screen is located inside the vacuum tank to block the product and allow the gas to pass through. The vacuum pump is located on the side wall of the vacuum tank to create a pressure difference between the growth chamber and the collection tank.

10. A method for preparing single-walled carbon nanotubes by electric arc method, characterized in that, include: Using the continuous discharge system described in any one of claims 1-9, growth medium is injected into the growth chamber and a self-blowing unit inputs purge gas into the growth chamber, and the plasma arc generated by the arc generator acts on the growth medium to form single-walled carbon nanotubes. Single-walled carbon nanotubes are collected from the collection unit.

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