A greenhouse gas treatment device based on microwave plasma

Abstract

The present invention provides a greenhouse gas treatment device and method based on microwave plasma, comprising an electromagnetic wave input and transmission system, a microwave coupling cavity, an air intake system and an exhaust gas treatment system; the electromagnetic wave input and transmission system comprises two groups of microwave magnetrons and transmission waveguides, and the transmission waveguides are connected to the microwave coupling cavity; the air intake system comprises an Ar input pipeline, an O2 input pipeline, an SF6 input pipeline and a three-layer air intake sleeve; an automatic ignition device is arranged on the side of the three-layer air intake sleeve; the exhaust gas treatment system comprises a closed cavity, an exhaust gas delivery pipeline and a spray device; the microwave coupling cavity can not only improve the ionization effect of SF6 and the utilization rate of microwave power by power coupling, but also improve the ability to treat large flow SF6; the air intake device adopts a three-layer sleeve, which can effectively reduce the etching of the air intake pipe by ionized fluorine ions while improving the SF6 treatment flow, thereby improving the continuous working time.

Description

Technical Field

[0001] The present invention belongs to the field of gas degradation, and more specifically, relates to a greenhouse gas treatment device and method based on microwave plasma. Background Art

[0002] The chemical properties of SF6 are very stable and it is not easy to decompose under normal conditions. At the same time, SF6 has excellent arc extinguishing performance and good insulation performance, which makes it widely used in electrical equipment such as gas insulated switchgear (GIS), insulated transmission pipelines, transformers and insulated substations. The life cycle of SF6 reaches 3200 years and the GWP value is 8000, so the emission of SF6 has a great impact on the greenhouse effect. The SF6 emissions caused by gas leakage in the power industry and equipment maintenance and decommissioning account for about 70% of the total emissions; in addition, the emissions generated by the application of SF6 in the semiconductor manufacturing industry account for about 10% of the total. Therefore, effectively controlling the emission of SF6 in industry is also a very important task in promoting development.

[0003] In recent years, plasma waste gas treatment technology has been widely studied. Compared with traditional high-temperature pyrolysis, chemical catalysis and other methods, plasma technology has the characteristics of high degradation rate, high energy efficiency and simple operation. Thermal arc plasma has been widely studied and applied to the treatment of SF6 gas due to the high plasma temperature it produces. However, there are problems such as the service life of the electrode, and the consumption and waste of high electrical energy. In low-temperature plasma, dielectric barrier discharge is used to remove SF6 gas because it has a higher electron temperature. However, the reaction caused by the inelastic collision of its electrons can only occur within the pulse time, and in the entire afterglow it is mainly the collision between heavy particles. Therefore, as the concentration of SF6 gas increases, the removal efficiency decreases, and large flows of SF6 cannot be treated. The present invention aims to solve the above problems. Summary of the invention

[0004] The present invention provides a greenhouse gas treatment device and method based on microwave plasma, in view of the fact that traditional plasma has a relatively low ability to degrade SF6, cannot completely decompose SF6, and cannot process large flows of SF6, while thermal arc plasma has high power consumption and waste in degrading SF6.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A greenhouse gas processing device based on microwave plasma comprises an electromagnetic wave input and transmission system, a microwave coupling cavity, an air intake system and an exhaust gas processing system.

[0007] The electromagnetic wave input and transmission system comprises two groups of microwave magnetrons and a transmission waveguide, wherein the transmission waveguide is connected to the microwave coupling cavity and transmits the electromagnetic fields generated by the two groups of microwave magnetrons into the microwave coupling cavity respectively;

[0008] The air intake system comprises an Ar input pipeline, an O2 input pipeline, an SF6 input pipeline and a three-layer air intake sleeve, wherein the O2 input pipeline is divided into two groups by a three-way valve, the first group of O2 input pipelines is communicated with the outer layer of the three-layer air intake sleeve, the second group of O2 input pipelines is combined with the Ar input pipeline and communicated with the middle layer of the three-layer air intake sleeve, and the SF6 input pipeline is communicated with the inner layer of the three-layer air intake sleeve; the three-layer air intake sleeve runs through the microwave coupling cavity; an automatic ignition device is provided on the side of the three-layer air intake sleeve for initial excitation;

[0009] The exhaust gas treatment system includes a closed chamber, an exhaust gas conveying pipeline and a spray device; the closed chamber is connected to the three-layer air intake sleeve, the spray device uses an alkaline solution to absorb acidic gas products, and the exhaust gas conveying pipeline is connected to the closed chamber and is provided with an exhaust fan for exhausting exhaust gas.

[0010] Based on the above technical solution, the present application has also made the following improvements:

[0011] Furthermore, each of the transmission waveguides includes a stepped gradient part and a compression waveguide part, the overall wall thickness of the transmission waveguide is 5 mm, the stepped gradient part is a three-level gradient waveguide, wherein the first-level waveguide has the smallest height, width and length, the second-level waveguide has the second largest height, width and length, and the third-level waveguide has the largest height, width and length, the compression waveguide is connected to the third-level waveguide, and the compression waveguide compresses the height of the third-level waveguide to a predetermined size, and the two groups of the transmission waveguides are distributed in parallel up and down and are arranged at intervals.

[0012] Furthermore, the microwave coupling cavity is a rectangular parallelepiped with a hollow interior, the microwave coupling cavity is connected to two groups of transmission waveguides, and the microwave coupling cavity is provided with an opening of a predetermined radius at a predetermined position away from the transmission waveguide.

[0013] Furthermore, the outer layer of the three-layer air intake sleeve is made of quartz material, the middle layer is made of ceramic material, and the inner layer is made of metal material. The wall thickness of the three layers is equal and the tube diameter decreases stepwise from the outside to the inside. The outer layer and the middle layer are respectively provided with two air inlets.

[0014] Furthermore, the Ar gas pipeline and the second group of O2 input pipelines are connected to the middle layer of the three-layer air intake device in a 60° tangential manner.

[0015] Furthermore, the automatic ignition device includes an electromagnet and an ignition needle, and the material of the ignition needle is La0.8 Sr 0.2 CoO3.

[0016] Furthermore, the automatic ignition device is configured such that the ignition needle penetrates the three-layer air inlet sleeve to reach the bottom of the microwave coupling cavity when power is supplied, and is retracted when power is cut off.

[0017] Furthermore, the automatic ignition device and the three-layer air intake sleeve are sealed with rubber parts.

[0018] Furthermore, the tail gas generated by ionization of SF6 in the microwave coupling cavity is directly discharged into the closed cavity through the three-layer air inlet sleeve, and the closed cavity is made of quartz.

[0019] Furthermore, a groove is provided at the left end of the exhaust gas conveying pipe.

[0020] The greenhouse gas treatment device of atmospheric pressure microwave plasma provided by the present invention has at least the following advantages:

[0021] ① The coupling cavity can not only improve the ionization effect of SF6 and the utilization of microwave power through power coupling, but also improve the ability to handle large flow SF6;

[0022] ② The air intake device adopts a three-layer structure, with the outer tube made of quartz material, the middle tube made of ceramic material, and the innermost tube made of metal material. While increasing the SF6 flow rate, it can effectively reduce the etching of the intake pipe by the ionized fluorine ions and increase the continuous working time;

[0023] ③ An automatic ignition device is provided on the side of the three-layer air inlet sleeve, which does not require manual ignition, thus improving the simplicity of the device and allowing for re-energization when the plasma is quenched;

[0024] ④ The Ar input pipeline and the O2 input pipeline are connected to the three-layer gas inlet sleeve at a 60° angle, which can ensure that the carrier gas forms a vortex in the microwave coupling cavity and improve the stability of the plasma when processing the atmospheric gas SF6;

[0025] ⑤ A groove is provided at the left end of the exhaust gas conveying pipe, which can effectively prevent the ionized hot air flow from condensing and refluxing in the transmission pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of a greenhouse gas treatment device based on microwave plasma;

[0027] Figure 2 It is a schematic diagram of the structure of the waveguide and microwave coupling cavity;

[0028] Figure 3 It is a schematic diagram of the structure of a three-layer air intake sleeve;

[0029] Figure 4 This is a comparison diagram of the electromagnetic field intensity between the microwave coupled cavity and the double cavity superposition;

[0030] Figure 5 This is a simulation diagram of the gas flow pattern of the three-layer air intake sleeve. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention can be arbitrarily combined with each other to form a feasible technical solution. This combination is not subject to the constraints of the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] The present invention provides a greenhouse gas treatment device based on microwave plasma, comprising an electromagnetic wave input and transmission system 10, a microwave coupling cavity 20, an air intake system 30, and an exhaust gas treatment system 40.

[0033] The electromagnetic wave input and transmission system 10 includes two groups of microwave magnetrons and transmission waveguides. The transmission waveguides are connected to the microwave coupling cavity 20 to transmit the electromagnetic fields generated by the two groups of microwave magnetrons into the microwave coupling cavity 20 respectively.

[0034] The air intake system 30 includes an Ar input pipeline 31 , an O 2 input pipeline 32 , an SF 6 input pipeline 33 and a three-layer air intake sleeve 34 .

[0035] Among them, Ar is the initial excitation gas, O2 is the working gas, and SF6 is the greenhouse gas to be treated.

[0036] The O2 input pipeline 32 is divided into two groups by a three-way valve 301. The first group of O2 input pipelines 321 is connected to the outer layer 341 of the three-layer air intake sleeve 34. The second group of O2 input pipelines 322 is combined with the Ar input pipeline 31 and connected to the middle layer 341 of the three-layer air intake sleeve 34. The SF6 input pipeline 33 is connected to the inner layer 343 of the three-layer air intake sleeve 34. The three-layer air intake sleeve 34 runs through the microwave coupling cavity 20. An automatic ignition device 50 is provided on the side of the three-layer air intake sleeve 34 for initial excitation.

[0037] The exhaust gas treatment system 40 includes a closed chamber 41, an exhaust gas delivery pipeline 42 and a spray device 43; the closed chamber 41 is connected to the three-layer air intake sleeve 34, the spray device 43 uses an alkaline solution to absorb acidic gas products, and the exhaust gas delivery pipeline 42 is connected to the closed chamber 41 and is provided with an exhaust fan 44 for exhausting exhaust gas.

[0038] The two groups of microwave magnetrons 11a, 11b and the two groups of transmission waveguides 12a, 12b are connected to the microwave coupling cavity 20 in sequence. The schematic diagram of the connection structure of the transmission waveguide and the microwave coupling cavity 20 is shown in FIG. Figure 2 An opening is provided in the middle of the microwave coupling cavity 20, and a three-layer air intake sleeve 34 runs through the microwave coupling cavity 20; the O2 input pipeline 32 is divided into two at the three-way valve 301, and the first group of O2 input pipelines 321 and the Ar input pipeline 31 are combined at the second three-way valve 302 and connected to the air intake pipe of the middle layer 342 of the three-layer air intake sleeve 34, and the other group of O2 is connected to the air intake pipe of the outer layer 341 of the three-layer air intake sleeve, and the SF6 input pipeline 33 is connected to the inner layer 343 of the three-layer air intake sleeve. The automatic ignition device 50 is arranged on the left side of the three-layer air intake sleeve 34, see Figure 3 The sealed chamber 41 is connected to the three-layer air inlet sleeve, and the sealed chamber 41 , the exhaust gas delivery pipe 42 , and the spray device 43 are connected in sequence. A groove 421 is provided in the exhaust gas delivery pipe 42 , and an exhaust fan 44 is provided in the spray device 43 .

[0039] Its working principle is as follows: two groups of microwave magnetrons 11a, 11b generate electromagnetic waves, which are transmitted into the microwave coupling cavity 20 through transmission waveguides 12a, 12b, and Ar, O2, and SF6 are respectively input into the three-layer air intake sleeve 34 through corresponding transmission pipelines. The gas in the microwave coupling cavity 20 is ignited and ionized by the automatic ignition device 50 under the excitation of the electromagnetic wave to form plasma. SF6 is ionized and decomposed in the plasma, and the generated tail gas is discharged into the closed cavity 41, and is transmitted into the spray device 43 through the exhaust gas delivery pipeline 42, and is absorbed by the alkali solution in the spray device 13. In the embodiment of the present application, the alkali solution is preferably a saturated Ca(OH)2 solution.

[0040] Among them, see Figure 2The transmission waveguide includes a stepped gradient portion 121 and a compression waveguide portion 122. The overall wall thickness of the transmission waveguide is 5 mm. The stepped gradient portion 121 is a three-level gradient waveguide, wherein the first-level waveguide 1211 has the smallest height, width and length, the second-level waveguide 1212 has the second largest height, width and length, and the third-level waveguide 1213 has the largest height, width and length. The compression waveguide 122 is connected to the third-level waveguide 1213. The compression waveguide 122 compresses the height of the third-level waveguide 1213 to a predetermined size. The two groups of transmission waveguides are arranged in parallel up and down and are spaced apart.

[0041] In a specific implementation scheme; the first-level waveguide 1211 has a height of 53.18 mm, a width of 96.36 mm, and a length of 6 mm, the second-level waveguide 1212 has a height of 58.90 mm, a width of 107.79 mm, and a length of 39 mm, the third-level waveguide 1213 has a height of 64.61 mm, a width of 119.22 mm, and a length of 105 mm, the compression waveguide 122 is connected to the third-level waveguide 1213, and the height is compressed from 64.61 mm to 37.3 mm, the compression waveguide 122 has a length of 90 mm, and the spacing between the two groups of transmission waveguides is 22.21 mm.

[0042] The microwave coupling cavity 20 is a rectangular parallelepiped with a hollow interior. The microwave coupling cavity 20 is connected to two sets of transmission waveguides. The microwave coupling cavity 20 is provided with an opening of a predetermined radius at a predetermined position away from the transmission waveguide. In a specific embodiment, the microwave coupling cavity 20 is square, hollow inside, with a height of 130 mm, a width of 119.22 mm, a length of 100 mm, and a wall thickness of 5 mm. The microwave coupling cavity has an opening 53.5 mm away from the transmission waveguide, and the opening radius is 20 mm.

[0043] Among them, see Figure 3 In one embodiment of the present application, the outer layer 341 of the three-layer air inlet sleeve 34 is made of quartz material, the middle layer 342 is made of ceramic material, and the inner layer 343 is made of metal material. The wall thickness of the three layers is equal and the tube diameter decreases stepwise from the outside to the inside. The outer layer 341 and the middle layer 342 are respectively provided with two air inlets. Specifically, the outer layer 341 is made of quartz material, with a tube diameter of 40 mm and a wall thickness of 2 mm; the middle layer 342 is made of ceramic material, with a tube diameter of 30 mm and a wall thickness of 2 mm; the inner layer 343 is made of metal material, with a tube diameter of 14 mm and a wall thickness of 2 mm.

[0044] The Ar input pipeline and the O2 input pipeline are connected to the three-layer air inlet sleeve at a 60° angle. The outer layer 341 and the middle layer 342 have two air inlets respectively, and the diameter of the air inlet is 4 mm.

[0045] The automatic ignition device 50 includes an electromagnet and an ignition needle. The material of the ignition needle is La 0.8 Sr 0.2 CoO3, the automatic ignition device is configured so that when power is supplied, the ignition needle penetrates the three-layer air inlet sleeve to reach the bottom of the microwave coupling cavity, and is retracted when power is cut off.

[0046] Preferably, the automatic ignition device 50 and the three-layer air intake sleeve 34 are sealed with rubber parts.

[0047] The tail gas generated by ionization of SF6 in the microwave coupling cavity 20 is directly discharged into the sealed cavity 41 through the three-layer gas inlet sleeve 34. The sealed cavity 41 is made of quartz.

[0048] Figure 4 This is a comparison of the electromagnetic field intensity between the microwave coupled cavity and the double cavity superposition. The microwave frequency is 2.45 GHz and the microwave power is 3 kW. The solid line is the electromagnetic field intensity in the microwave coupled cavity, and the dotted line is the electromagnetic field intensity in the double cavity superposition. The ordinate in the figure is the electromagnetic field intensity E, and the abscissa is the longitudinal height. The comparison shows that the electromagnetic field in the microwave coupled cavity is more uniform than that in the double cavity superposition. The plasma ionized from this is theoretically more stable and has a higher utilization rate of microwave energy.

[0049] Figure 5 This is a simulation diagram of the gas flow state of the three-layer intake sleeve, in which the gas flow rate of the inner layer is set to 5 SLM, the gas flow rate of the middle layer is set to 30 SLM, and the gas flow rate of the outer layer is set to 20 SLM. As can be seen from the figure, the gas streamlines in the three-layer intake sleeve are clearly layered and transmitted in the device in a stable vortex spiral. This can effectively reduce the etching of the outer tube wall by the ionized fluorine ions, increase the working time, and also ensure the stability of the plasma in the atmospheric flow.

[0050] Specific implementation method:

[0051] The two groups of magnetrons output 1 kW power respectively, open the valve of the Ar input pipeline, adjust the input Ar flow rate of the middle layer 342 of the three-layer air inlet sleeve 34 to 10 SLM, start the automatic ignition device 50 to excite plasma and then turn it off.

[0052] Then, the O2 input pipeline valve is opened, and the O2 input flow rate of the middle layer 342 is adjusted to 10 SLM, and the O2 input flow rate of the outer layer is adjusted to 5 SLM, and then the Ar pipeline valve is closed. The output power of the magnetron is increased to 3 kW, and the O2 input flow rate of the middle layer 342 is adjusted to 30 SLM, and the O2 input flow rate of the outer layer 341 is adjusted to 20 SLM. After the plasma is stabilized, the SF6 input pipeline valve is opened, and 3 SLM of SF6 gas is introduced into the inner layer 343 of the three-layer gas inlet sleeve 34. The ionized gas is discharged and then transmitted to the spray device 43 to be absorbed by the saturated Ca(OH)2 solution. At the same time, by increasing the power supply of the magnetron to 6 kW, the O2 input flow rate of the outer layer 341 of the three-layer gas inlet sleeve 34 can be increased to 50 SLM, the O2 input flow rate of the middle layer 342 can be increased to 40 SLM, and the SF6 input flow rate of the inner layer 343 can be increased to 10 SLM.

[0053] The present invention provides a greenhouse gas treatment device using atmospheric pressure microwave plasma, which has the following beneficial effects:

[0054] 1. The microwave coupling cavity can not only improve the ionization effect of SF6 and the utilization of microwave power through power coupling, but also improve the ability to handle large flow SF6;

[0055] 2. The air intake device adopts a three-layer sleeve structure, with the outer tube made of quartz material, the middle tube made of ceramic material, and the innermost tube made of metal material. While increasing the SF6 flow rate, it can effectively reduce the etching of the intake pipe by the ionized fluorine ions and increase the continuous working time;

[0056] 3. An automatic ignition device 50 is provided on the side of the three-layer air inlet sleeve 34, which does not require manual ignition, thereby improving the simplicity of the device and allowing for re-energization when the plasma is quenched;

[0057] 4. The Ar gas pipeline and the O2 pipeline are connected to the three-layer gas inlet sleeve at a 60° angle, which can ensure the vortex of the carrier gas in the microwave coupling cavity and improve the stability of the plasma when processing the atmospheric gas SF6;

[0058] 5. A groove is provided at the left end of the exhaust gas delivery pipe, which can effectively prevent the ionized hot air flow from condensing and refluxing in the transmission pipe.

[0059] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0060] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A greenhouse gas treatment device based on microwave plasma, characterized in that: It includes electromagnetic wave input and transmission system, microwave coupling cavity, air intake system and exhaust gas treatment system; The electromagnetic wave input and transmission system comprises two groups of microwave magnetrons and a transmission waveguide, wherein the transmission waveguide is connected to the microwave coupling cavity and transmits the electromagnetic fields generated by the two groups of microwave magnetrons into the microwave coupling cavity respectively; The air intake system comprises an Ar input pipeline, an O2 input pipeline, an SF6 input pipeline and a three-layer air intake sleeve, wherein the O2 input pipeline is divided into two groups by a three-way valve, the first group of O2 input pipelines is communicated with the outer layer of the three-layer air intake sleeve, the second group of O2 input pipelines is combined with the Ar input pipeline and communicated with the middle layer of the three-layer air intake sleeve, and the SF6 input pipeline is communicated with the inner layer of the three-layer air intake sleeve; the three-layer air intake sleeve runs through the microwave coupling cavity; an automatic ignition device is provided on the side of the three-layer air intake sleeve for initial excitation; The exhaust gas treatment system includes a closed chamber, an exhaust gas delivery pipeline and a spray device, the closed chamber is connected to the three-layer air intake casing, the spray device uses an alkaline solution to absorb acidic gas products, and the exhaust gas delivery pipeline is connected to the closed chamber and is provided with an exhaust fan for exhaust gas extraction; The outer layer of the three-layer air intake sleeve is made of quartz material, the middle layer is made of ceramic material, and the inner layer is made of metal material. The wall thickness of the three layers is equal and the tube diameter decreases stepwise from the outside to the inside. The outer layer and the middle layer are respectively provided with two air inlets.

2. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: Each of the transmission waveguides includes a stepped gradient part and a compression waveguide part. The overall wall thickness of the transmission waveguide is 5 mm. The stepped gradient part is a three-level gradient waveguide, wherein the first-level waveguide has the smallest height, width and length, the second-level waveguide has the second largest height, width and length, and the third-level waveguide has the largest height, width and length. The compression waveguide is connected to the third-level waveguide, and the compression waveguide compresses the height of the third-level waveguide to a predetermined size. The two groups of transmission waveguides are distributed in parallel up and down and are arranged at intervals.

3. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: The microwave coupling cavity is a rectangular parallelepiped with a hollow interior. The microwave coupling cavity is connected to two groups of transmission waveguides. The microwave coupling cavity is provided with an opening with a predetermined radius at a predetermined position away from the transmission waveguide.

4. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: The Ar input pipeline and the O2 input pipeline are connected to the middle layer of the three-layer air intake sleeve in a 60° tangential manner.

5. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: The automatic ignition device includes an electromagnet and an ignition needle. The material of the ignition needle is La 0.8 Sr 0.2 CoO3.

6. The greenhouse gas treatment device based on microwave plasma according to claim 5, characterized in that: The automatic ignition device is configured such that the ignition needle penetrates the three-layer air inlet sleeve to reach the bottom of the microwave coupling cavity when power is supplied, and is retracted when power is cut off.

7. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: The automatic ignition device and the three-layer air intake sleeve are sealed with rubber parts.

8. The greenhouse gas treatment device based on microwave plasma according to claim 1, characterized in that: The tail gas generated by ionization of SF6 in the microwave coupling cavity is directly discharged into the closed cavity through the three-layer air inlet sleeve, and the closed cavity is made of quartz.

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