A microwave plasma reactor

Abstract

The application discloses a microwave plasma reaction device and relates to the technical field of microwave plasma reaction, which comprises a reaction tube, a reaction cavity with an outlet formed in the reaction tube, an arc leading and protective gas branch pipe, a working gas branch pipe and a microwave inlet window. The arc leading and protective gas branch pipe is communicated with the reaction cavity in a tangential and inclined state towards the outlet, and the communication position is located on the side of the microwave inlet window away from the outlet. The working gas branch pipe is located on the side of the arc leading and protective gas branch pipe close to the outlet, and the end of the working gas branch pipe close to the metal waveguide torch part of the reaction tube is arranged close to the end face of the outlet. The end of the working gas branch pipe communicated with the reaction cavity is arranged away from the outlet than the other end, and the working gas is inputted into the middle part of the reaction cavity in an inclined state. In the application, the arc leading and protective gas branch pipe and the working gas branch pipe are designed in a partitioned mode, the countercurrent motion of the two, the tangential rotation of the arc leading and protective gas forms a continuous hollow annular gas flow sheath, and the working gas is constrained in the plasma high-temperature area. Therefore, the internal reaction efficiency can be improved, and the production quality can be improved as a whole.

Description

Technical Field

[0001] This invention relates to the field of microwave plasma reaction technology, and in particular to a microwave plasma reaction device. Background Technology

[0002] Microwave plasma torches possess significant advantages such as concentrated high-temperature areas, high electron density, no electrode contamination, and controllable atmosphere, making them a core technological route for the gas-phase cracking of methane to produce high-quality graphene powder. However, the microwave plasma torches known to the applicant generally employ an integrated, solid quartz reaction tube structure, which presents a series of insurmountable technical defects during actual industrial operation. First, the working gas tends to flow close to the quartz tube wall, preventing most of the raw materials from entering the high-temperature plasma core area in the center of the cavity. Instead, incomplete pyrolysis occurs only in the low-temperature area of ​​the tube wall, resulting in a large amount of amorphous carbon impurities. The overall pyrolysis rate is low, and the raw material utilization rate is poor.

[0003] Secondly, the products or intermediates produced by pyrolysis are very easy to deposit on the inner wall of the quartz cavity, forming a continuous deposition layer. The deposition layer will absorb, reflect and interfere with microwave energy, causing the microwave reflection power to rise continuously, the plasma flame core to shrink and vibrate. The equipment can only run continuously for tens of minutes before it must be stopped for cleaning, making it impossible to achieve continuous large-scale production.

[0004] Third, the conventional cavity airflow distribution is disordered, and the axial or rotary airflow of the working gas can easily directly impact the plasma flame root region, causing frequent fluctuations in plasma density, continuous changes in microwave load impedance, high tuning difficulty, and a high risk of plasma flameout.

[0005] Fourth, the swirling cavity of the microwave plasma torch only has a single swirling gas path, and the protective gas flow cannot be separated from the working gas flow. The swirling gas flow easily disperses the working gas flow, resulting in uneven material dispersion and poor product nucleation consistency.

[0006] In summary, existing microwave plasma working gas pyrolysis reaction chambers suffer from problems such as low pyrolysis efficiency, severe wall deposition, poor product quality control, complex sealing structure, and poor equipment stability, making it difficult to meet the needs of large-scale preparation of high-quality materials.

[0007] Therefore, there is an urgent need for a microwave plasma reaction device that has high internal reaction efficiency, enables continuous large-scale production, has controllable internal airflow, and produces high-quality products. Summary of the Invention

[0008] The purpose of this invention is to provide a microwave plasma reaction device to solve the problems existing in the prior art. It utilizes a tangentially spiraling arc-initiating and protective gas to form a continuous hollow annular airflow sheath, confining the working gas within the high-temperature plasma region. Furthermore, the working gas and the arc-initiating and protective gas flow in countercurrent, increasing the working gas density and residence time at the flare center, improving internal reaction efficiency, reducing deposition on the inner wall of the reaction tube, enabling continuous large-scale production, and allowing for the control of the working gas and the arc-initiating and protective gas to regulate the internal airflow, thereby improving overall production quality.

[0009] To achieve the above objectives, the present invention provides the following solution: The present invention provides a microwave plasma reaction apparatus, comprising: A reaction tube, wherein a reaction chamber with an outlet is formed inside the reaction tube; An arc-starting and protective gas branch pipe is connected to the reaction chamber in a tangential and inclined manner toward the outlet, with the connection point located on the side of the microwave incident window away from the outlet. The working gas branch pipe is located on the side of the arc-starting and protective gas branch pipe near the outlet. The working gas branch pipe is located on the end face of the metal waveguide torch portion of the reaction tube near the outlet. The end of the working gas branch pipe that communicates with the reaction chamber is located further away from the outlet than the other end. The working gas is introduced at an angle toward the middle of the reaction chamber.

[0010] In one embodiment, the working gas branch pipe is positioned toward the central axis of the reaction chamber.

[0011] In one embodiment, the working gas branch pipe is disposed in the region between 10 mm away from the outlet and 50 mm away from the outlet on the end face of the metal waveguide torch section near the outlet.

[0012] In one embodiment, the angle between the working gas branch pipe and the radial surface of the reaction chamber is 5°-30°.

[0013] In one embodiment, multiple working gas branches are provided, and the distances of the multiple working gas branches from the outlet may be the same or different.

[0014] In one embodiment, the angle between the arc-starting and protective gas branch pipe and the radial surface of the reaction chamber is 50°-80°.

[0015] In one embodiment, multiple arc-initiating and protective gas branch pipes are provided, and the multiple arc-initiating and protective gas branch pipes are evenly distributed along the axial direction of the reaction chamber and rotate in the same direction.

[0016] In one embodiment, the microwave plasma reaction apparatus further includes an auxiliary and cooling gas branch pipe, which is connected to the reaction chamber in a tangential and inclined manner away from the outlet, and is disposed on the side of the working gas branch pipe near the outlet.

[0017] In one embodiment, the angle between the auxiliary and cooling gas branch pipe and the radial surface of the reaction chamber is 10°-50°.

[0018] In one embodiment, the end of the reaction tube furthest from the outlet is a sealed blind end.

[0019] The present invention achieves the following main technical effects compared to the prior art: The reaction tube is divided into sections: an arc-starting and protective gas branch pipe and a working gas branch pipe. The two actually move in opposite directions. The tangentially spiraling arc-starting and protective gas form a continuous hollow annular airflow sleeve, while the working gas is confined within the high-temperature plasma region. This increases the working gas density and residence time at the flare center, improves internal reaction efficiency, reduces deposition on the inner wall of the reaction tube, and enables continuous large-scale production. The internal airflow can be controlled by adjusting the working gas and the arc-starting and protective gas through gas pressure, thereby improving overall production quality. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the microwave plasma reaction device in an embodiment of the present invention; Figure 2 The image shows the Raman spectrum of the conventional device in the comparative experimental data of this invention. Figure 3 The image shows the Raman spectrum of this device in the comparative experimental data of this invention embodiment; The components are: 1. Reaction tube; 2. Metal waveguide torch section; 3. Metal short-circuit end face or short-circuit piston; 4. Flame core area; 5. Arc ignition and protective gas branch pipe; 6. Working gas branch pipe; 7. Auxiliary and cooling gas branch pipe; 8. Outlet; 9. Sealed blind end. Detailed Implementation

[0022] 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.

[0023] The purpose of this invention is to provide a microwave plasma reaction device to solve the problems existing in the prior art. It utilizes a tangentially spiraling arc-starting gas and a protective gas to form a continuous hollow annular airflow sheath. The working gas is confined within the high-temperature plasma region, and the working gas and the arc-starting and protective gas are in countercurrent flow. This increases the working gas density and residence time at the flare center, improves the internal reaction efficiency, reduces the deposition phenomenon on the inner wall of the reaction tube, and enables continuous large-scale production. The working gas and the arc-starting and protective gas can be adjusted to regulate the internal airflow, thereby improving the overall production quality.

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Please refer to the following: Figure 1 As shown, a microwave plasma reaction apparatus is provided, including: a reaction tube 1, an arc-starting and protective gas branch pipe 5, and a working gas branch pipe 6. A reaction chamber with an outlet 8 is formed within the reaction tube 1. A metal waveguide torch portion 2 and a metal short-circuit end face or short-circuit piston 3 are disposed on the reaction tube 1. The arc-starting and protective gas branch pipe 5 is tangentially connected to the reaction chamber and inclined towards the outlet 8, with the connection point located on the side of the microwave incident window away from the outlet 8. The working gas branch pipe 6 is located on the side of the arc-starting and protective gas branch pipe 5 near the outlet 8, and is disposed near the end face of the metal waveguide torch portion 2 of the reaction tube 1 near the outlet 8. This refers to the working gas branch pipe 6 being disposed near the end face of the metal waveguide torch portion 2 of the reaction tube 1 near the outlet 8. The end of the working gas branch pipe 6 that connects to the reaction chamber is positioned further away from the outlet 8 than the other end. The working gas (such as methane or ethanol used in graphene production) is introduced at an angle toward the middle of the reaction chamber. The reaction tube 1 is divided into arc-starting and protective gas branch pipes 5 and working gas branch pipes 6, which actually move in opposite directions. The tangentially spiraling arc-starting and protective gas forms a continuous hollow annular airflow sleeve, confining the working gas within the high-temperature plasma region. This increases the working gas density and residence time at the center of the torch, improves internal reaction efficiency, reduces deposition on the inner wall of the reaction tube 1, and enables continuous large-scale production. The internal airflow can be controlled by adjusting the working gas and the arc-starting and protective gas through gas pressure, thereby improving the overall production quality.

[0026] The inner diameter of the overall reaction tube 1 can be designed to be 50mm-100mm. The distance between the outlet 8 of the reaction tube 1 and the flame core zone 4 is more than 1000mm and it is sealed to the external components. Because it is far from the core zone and the temperature is low, it can ensure that the sealing ring operates stably for a long time.

[0027] In one embodiment, the working gas branch pipe 6 is positioned toward the central axis of the reaction chamber. Compared to a design that deviates from the central axis, being positioned toward the central axis can improve the converging effect of the working gas.

[0028] In one embodiment, the working gas branch pipe 6 is located in the region between 810 mm away from the outlet 8 and 850 mm away from the outlet 8 on the end face of the metal waveguide torch section 2 near the outlet 8, so as to ensure that the working gas can enter the center of the torch while preventing the working gas from impacting the plasma flame root region.

[0029] In one embodiment, the angle between the working gas branch pipe 6 and the radial surface of the reaction chamber is 5°-30°. The specific angle can be determined according to the actual working conditions, which mainly include the reaction temperature, the type of working gas, and the design of output and quality.

[0030] In one embodiment, multiple working gas branch pipes 6 are provided, and the distances of the multiple working gas branch pipes 6 from the outlet 8 may be the same or different. The multiple working gas branch pipes 6 can be located at different positions (position refers to the annular area at a certain distance from the outlet 8), or all located at the same position, or dispersed at different positions. However, two or more working gas branch pipes 6 are located at the same position (multiple working gas branch pipes 6 in the same annular area can be evenly distributed). The adjustment can be made according to the actual working conditions (reaction temperature, working gas type, production and quality design). For example, if a high production is required, multiple working gas branch pipes 6 at different positions can be designed to achieve adjustment. Feedback adjustment can also be made based on the results. For example, if the working gas cracking rate is low, the number of working gas branch pipes 6 can be reduced and the tilt angle can be lowered. If the production is insufficient, the number of working gas branch pipes 6 can be increased and the angle can be lowered.

[0031] In one embodiment, the angle between the arc-starting and protective gas branch pipe 5 and the radial surface of the reaction chamber is 50°-80° to provide a strong continuous hollow annular airflow sheath.

[0032] In one embodiment, multiple arc-initiating and protective gas branch pipes 5 are provided. The multiple arc-initiating and protective gas branch pipes 5 are evenly distributed along the axial direction of the reaction chamber and have the same rotation direction (the rotation direction refers to the direction of the swirling flow generated in the reaction chamber), which further enhances the stable formation of the continuous hollow annular airflow sheath.

[0033] In one embodiment, the microwave plasma reactor further includes an auxiliary and cooling gas branch pipe 7. The auxiliary and cooling gas branch pipe 7 is connected to the reaction chamber in a tangential and inclined state away from the outlet 8. The auxiliary and cooling gas branch pipe 7 is located on the side of the working gas branch pipe 6 near the outlet 8. By designing the auxiliary and cooling gas branch pipe 7, swirling cooling auxiliary gas can be supplied into the reaction chamber. The supply of cooling auxiliary gas is determined according to the cooling rate and nodule density requirements of the process. At the same time, after the cooling auxiliary gas is supplied, the temperature gradient in the reaction tube 1 can be effectively controlled.

[0034] In one embodiment, the angle between the auxiliary and cooling gas branch pipe 7 and the radial surface of the reaction chamber is 10°-50°, which can play a cooling role without significantly affecting the overall internal flow state of the reaction chamber.

[0035] In one embodiment, the end of the reaction tube 1 furthest from the outlet 8 is a sealed blind end 9. The overall reaction tube 1 is a quartz reaction tube 1. The sealed blind end 9 can be integrally set with the reaction tube 1, without segmented flange connection structure, which greatly reduces the number of high-temperature sealing points.

[0036] In this invention, the arc-starting and protective gas branch pipe 5, the working gas branch pipe 6, and the auxiliary and cooling gas branch pipe 7 are each connected to an independent pressure control system to achieve independent control of pressure and flow rate. The pipe openings of the three branches are flush with the inner wall of the reaction tube 1, and there is no protruding structure into the reaction chamber to avoid interfering with the microwave electric field distribution. When actually supplying gas, the pressure and flow rate of the swirling gas supplied by the arc-starting and protective gas branch pipe 5 must ensure that the airflow of the working gas branch pipe 6 is not significantly disturbed, and ensure that the plasma operates normally, and ensure that there are no deposits or only a small amount of deposits on the quartz tube wall in the microwave feed area.

[0037] In actual use, the arc ignition and protective gas branch pipe 5 introduces protective gas, forming a continuous hollow annular airflow sheath on the inner wall of the reaction tube 1. The working gas branch pipe 6 introduces working gas or mixed working gas, which is constrained within the high-temperature plasma region along the central axis of the cavity by pressure difference, and will not be dispersed by the surrounding swirling airflow. At the same time, it relies on counter-current inertia to increase the density and residence time of the working gas at the center of the flare. The auxiliary and cooling gas branch pipe 7 introduces cooling or dilution gas according to the cooling rate and nodule density requirements of the process.

[0038] The following is a set of actual comparative experimental data: In the graphene production process, this device was compared with a traditional straight-through quartz tube torch. The arc ignition and protective gas branch pipe 5 was supplied with 0.2 MPa gas at a flow rate of 17 m³ / s. 3 The arc-starting and protective gas (nitrogen) is supplied at a pressure of 0.2 MPa and a flow rate of 2.1 m³ / h through working gas branch pipe 6. 3 The methane output per hour is 11%, and its methane-graphene production is 11% higher than that of a traditional straight-through quartz tube flare.

[0039] By introducing 17℃, 10m³ / h gas into the auxiliary and cooling gas branch pipe 7 3 Cooling nitrogen gas at a rate of / h, detected by Raman spectroscopy, showed an average number of 3-7 layers (e.g., ...). Figure 2 (As shown) Upgrade to level 1-5 (e.g.) Figure 3 (As shown).

[0040] The sealing effect of the outer quartz sealing ring was compared under the same operating conditions: After the two torches were started up simultaneously for 5 hours, 0.4 MPa of nitrogen gas was introduced into the torch to create a positive pressure environment of 0.4 MPa. The ultrasonic leak detector was used for testing. The results showed that there was no obvious leak point in this device, while the upper part of the quartz tube near the torch in the traditional design had a leak of N+7 dB.

[0041] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0042] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0043] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A microwave plasma reaction apparatus, characterized in that, include: A reaction tube, wherein a reaction chamber with an outlet is formed inside the reaction tube; An arc-starting and protective gas branch pipe is connected to the reaction chamber in a tangential and inclined manner toward the outlet, with the connection point located on the side of the microwave incident window away from the outlet. The working gas branch pipe is located on the side of the arc-starting and protective gas branch pipe near the outlet. The working gas branch pipe is located on the end face of the metal waveguide torch portion of the reaction tube near the outlet. The end of the working gas branch pipe that communicates with the reaction chamber is located further away from the outlet than the other end. The working gas is introduced at an angle toward the middle of the reaction chamber.

2. The microwave plasma reaction apparatus according to claim 1, characterized in that, The working gas branch pipe is positioned toward the central axis of the reaction chamber.

3. The microwave plasma reaction apparatus according to claim 1, characterized in that, The working gas branch pipe is located in the area between 10 mm away from the outlet and 50 mm away from the outlet on the end face of the metal waveguide torch section near the outlet.

4. The microwave plasma reaction apparatus according to claim 1, characterized in that, The angle between the working gas branch pipe and the radial surface of the reaction chamber is 5°-30°.

5. The microwave plasma reaction apparatus according to claim 1, characterized in that, Multiple working gas branch pipes are provided, and the distances of the multiple working gas branch pipes from the outlet may be the same or different.

6. The microwave plasma reaction apparatus according to claim 1, characterized in that, The angle between the arc-starting and protective gas branch pipe and the radial surface of the reaction chamber is 50°-80°.

7. The microwave plasma reaction apparatus according to claim 1, characterized in that, Multiple arc-initiating and protective gas branch pipes are provided, and the multiple arc-initiating and protective gas branch pipes are evenly distributed along the axial direction of the reaction chamber and have the same rotation direction.

8. The microwave plasma reaction apparatus according to claim 1, characterized in that, The microwave plasma reaction apparatus further includes an auxiliary and cooling gas branch pipe, which is connected to the reaction chamber in a tangential and inclined manner away from the outlet. The auxiliary and cooling gas branch pipe is located on the side of the working gas branch pipe near the outlet.

9. The microwave plasma reaction apparatus according to claim 8, characterized in that, The angle between the auxiliary and cooling gas branch pipe and the radial surface of the reaction chamber is 10°-50°.

10. The microwave plasma reaction apparatus according to claim 1, characterized in that, The end of the reaction tube furthest from the outlet is a sealed blind end.

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