Device and method for thermally degrading SF6 waste gas by using stainless steel

Abstract

The invention relates to the technical field of SF6 waste gas treatment, and particularly discloses a device and a method for thermal degradation of SF6 waste gas by stainless steel, the device comprises a gas supply system, the gas supply system comprises a gas distribution unit and a gas-water mixing unit, the gas distribution unit simultaneously supplies SF6 gas and reaction gas according to a required proportion, the mixing unit is communicated with the gas distribution unit, and the gas-water mixing unit is communicated with the gas distribution unit; mixing the generated water vapor with supplied SF6 gas and reaction gas to form a gas-water mixture; the degradation system comprises a reaction unit and an absorption unit, the gas inlet end of the reaction unit receives the gas-water mixture conveyed from the gas-water mixing unit, and the gas-water mixture passes through the absorption unit after being reacted and degraded by the reaction unit; the SF6 waste gas is converted into SO2 and SiF4 through stainless steel thermal degradation, subsequent treatment is more convenient compared with a gas-phase product obtained after SF6 conversion, harmless degradation of SF6 is achieved, meanwhile, the concentration of SF6 is diluted through water and gas mixing, gas consumption is effectively reduced, and cost waste is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of SF6 waste gas treatment, and in particular to a device and method for thermally degrading SF6 waste gas using stainless steel. Background Art

[0002] SF6 is a synthetic gas. The central sulfur atom and the surrounding six fluorine atoms are stably connected by covalent bonds, forming an octahedral configuration. SF6 gas itself is colorless, odorless, non-toxic, non-flammable and slightly soluble in water. It has very stable chemical properties and strong electron affinity. It can undergo a self-recovery process after bond breaking, so it has excellent insulation and arc extinguishing properties.

[0003] SF6 is widely used in the power industry as an excellent gas insulation material. It is also used as a protective gas in semiconductor processing and ore smelting. Although SF6 has many excellent properties, its efficient absorption of infrared radiation in the 915-960cm-1 band will lead to a serious greenhouse effect. It is listed as one of the six restrictive gases in the Kyoto Protocol. Its greenhouse effect potential is 23,500 times that of CO2, far exceeding other greenhouse gases.

[0004] SF6 can exist stably in the atmosphere for up to 3,200 years and only slowly decomposes under ultraviolet light. Therefore, large-scale emissions of SF6 waste gas pose a serious threat to the atmospheric environment. For the discharge treatment process of SF6, the mainstream method is to use dielectric barrier discharge, microwave discharge, etc. to form a plasma area in a designated reactor to decompose the SF6 gas. In 2017, Zhang Xiaoxing et al. of Wuhan University published "Experimental and Simulation Research on Degradation of SF6 by Dielectric Barrier Discharge Plasma" in the "Proceedings of the CSEE". A quartz glass reactor was used to achieve DBD discharge treatment of SF6 waste gas. During the treatment process, SF6 needs to be diluted. The dilution gas is usually nitrogen, air, etc., and ultimately a degradation effect of more than 90% can be achieved.

[0005] However, in this method, SF6 gas is degraded in a static environment, and the products are mainly acidic and toxic gases, which have limited emissions. Other scholars also need to dilute SF6 gas in the electrolysis process of SF6 waste gas. Too high a concentration of SF6 gas will inhibit the discharge process and weaken the treatment effect. In this way, a large amount of gas needs to be consumed in the dilution process, resulting in gas waste. This problem needs to be solved. Summary of the invention

[0006] In view of the problems existing in the above-mentioned existing devices and methods for thermally degrading SF6 waste gas with stainless steel, the present invention is proposed.

[0007] Therefore, the object of the present invention is to provide a device and method for thermally degrading SF6 waste gas with stainless steel.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a device for thermally degrading SF6 waste gas with stainless steel, comprising:

[0009] A gas supply system, comprising a gas distribution unit and a gas-water mixing unit, wherein the gas distribution unit simultaneously supplies SF6 gas and reaction gas according to a required ratio, and the mixing unit is connected to the gas distribution unit to form a gas-water mixture by mixing the generated water vapor with the supplied SF6 gas and reaction gas;

[0010] The degradation system includes a reaction unit and an absorption unit. The gas inlet end of the reaction unit receives the gas-water mixture delivered from the gas-water mixing unit. The gas-water mixture is degraded by the reaction unit and then passes through the absorption unit.

[0011] The circulation system is used to transport the gas with SF6 concentration that does not meet the standard after degradation back to the gas-water mixing unit for re-degradation treatment.

[0012] As a preferred solution of the device for thermally degrading SF6 waste gas with stainless steel of the present invention, the gas distribution unit comprises a reaction gas tank, an SF6 gas tank and a gas supply main for outputting the reaction gas and SF6 gas.

[0013] As a preferred solution of the device for thermally degrading SF6 waste gas with stainless steel of the present invention, the reaction gas tank is filled with N2.

[0014] As a preferred solution of the device for thermally degrading SF6 waste gas with stainless steel of the present invention, the mixing unit comprises a gas mixing tank, the gas inlet end of the gas mixing tank is connected to the gas supply main pipe for introducing SF6 gas and reaction gas, and an ultrasonic atomizer is arranged at the bottom of the gas mixing tank;

[0015] The ultrasonic atomizer is connected to the gas mixing tank to pass the generated water vapor into the gas mixing tank to mix with the SF6 gas and the reaction gas.

[0016] As a preferred solution of the device for thermal degradation of SF6 waste gas by stainless steel of the present invention, the reaction unit comprises a heating reaction furnace, a quartz tube, a 304 stainless steel mesh, and filter cotton;

[0017] The heating reaction furnace heats the quartz tube so that the internal 304 stainless steel mesh and filter cotton are heated, which is used to thermally degrade the passing gas-water mixture.

[0018] As a preferred solution of the device for thermally degrading SF6 waste gas with stainless steel of the present invention, the absorption unit adopts a washing absorption tower, and the washing liquid in the washing absorption tower adopts a saturated calcium hydroxide solution.

[0019] As a preferred solution of the device for thermal degradation of SF6 waste gas by stainless steel of the present invention, the circulation system includes a concentration sensor and a circulation pipe, the concentration sensor is installed in the exhaust pipe to detect the concentration of SF6, and the two ends of the circulation pipe are respectively connected to the mixing tank and the exhaust pipe.

[0020] As a preferred solution of the device for thermal degradation of SF6 waste gas by stainless steel of the present invention, the circulation system further comprises a heat exchange component which is installed on the exhaust pipe and used for cooling the high temperature gas inside the exhaust pipe.

[0021] A method for thermally degrading SF6 waste gas with stainless steel, which is applied to the above-mentioned device for thermally degrading SF6 waste gas with stainless steel, comprises:

[0022] S1. N2 and SF6 gases are transported to a gas mixing tank, and then the water mist generated by the ultrasonic atomizer is mixed with the SF6 gas and N2 in the gas mixing tank to form a gas-water mixture;

[0023] S2, the gas-water mixture enters the quartz tube of the heated reaction furnace, and is filtered and degraded by the high-temperature 304 stainless steel mesh and filter cotton to generate gas phase products and solid phase products;

[0024] S3, the generated gas phase products and solid phase products are detected by the concentration sensor, and after reaching the standard, they enter the absorption unit for washing to achieve harmless degradation of SF6;

[0025] S4. If the SF6 concentration in the discharged gas phase product exceeds the standard, it will be transported back through the circulation pipe to the gas-water mixing unit for re-degradation treatment.

[0026] As a preferred embodiment of the method for thermal degradation of SF6 waste gas by stainless steel of the present invention, the gas phase products are SO2 and SiF4, the solid phase products are related to the initial concentration of SF6, the solid phase products of the degradation reaction under low concentration conditions are FeF2 and FeS, and the degradation products under high concentration conditions are FeF and elemental S.

[0027] Beneficial effects of the present invention: The present invention converts SF6 waste gas into SO2 and SiF4 through thermal degradation of stainless steel. Compared with the gas phase product after SF6 conversion, it is more convenient for subsequent treatment, and the harmless degradation of SF6 is achieved. At the same time, the concentration of SF6 is diluted by water-gas mixture, which effectively reduces gas consumption and reduces cost waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0029] Figure 1 It is a schematic diagram of the overall process framework structure of the device for thermal degradation of SF6 waste gas by stainless steel of the present invention.

[0030] Figure 2 It is a schematic diagram of the framework of the gas supply system in the device for thermal degradation of SF6 waste gas by stainless steel of the present invention.

[0031] Figure 3 The schematic diagram of the framework of the reaction unit in the device for thermal degradation of SF6 waste gas by stainless steel of the present invention.

[0032] Figure 4 It is a schematic diagram of the framework of the circulation system in the device for thermal degradation of SF6 waste gas by stainless steel of the present invention.

[0033] Figure 5 This is a graph showing the SF6 degradation rate of 304 stainless steel meshes with different apertures in an experimental example of the method for thermally degrading SF6 waste gas using stainless steel of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0038] Example 1

[0039] Reference Figure 1-3 , provides a stainless steel thermal degradation SF6 waste gas device, comprising:

[0040] The gas supply system 100 includes a gas distribution unit 101 and a gas-water mixing unit 102. The gas distribution unit 101 simultaneously supplies SF6 gas and reaction gas according to a required ratio. The mixing unit 102 is connected to the gas distribution unit 101 to generate water vapor and mix it with the supplied SF6 gas and reaction gas to form a gas-water mixture.

[0041] The degradation system 200 includes a reaction unit 201 and an absorption unit 202 . The air inlet end of the reaction unit 201 receives the gas-water mixture delivered from the gas-water mixing unit 102 . The gas-water mixture is degraded by the reaction unit 201 and then passes through the absorption unit 202 .

[0042] Furthermore, the gas distribution unit 101 includes a reaction gas tank 101a, a SF6 gas tank 101b, and a gas supply main pipe 101c for outputting the reaction gas and SF6 gas.

[0043] Specifically, two gas supply pipes 101c are provided, and electromagnetic flowmeters are installed on the two gas supply pipes 101c. The electromagnetic flowmeters are used to control the gas output of N2 and SF6 to complete the preparation of SF6 with different initial concentrations.

[0044] Furthermore, the reaction gas tank 101a is filled with N 2， N2 is a low-cost gas and mixing it with SF6 can reduce the overall cost, especially in situations where a large amount of SF6 is required.

[0045] Furthermore, the mixing unit 102 includes a gas mixing tank 102a, the gas inlet end of the gas mixing tank 102a is connected to the gas supply main 101c for introducing SF6 gas and reaction gas, and an ultrasonic atomizer 102b is provided at the bottom of the gas mixing tank 102a;

[0046] The ultrasonic atomizer 102b is connected to the gas mixing tank 102a, and is used to pass the generated water vapor into the gas mixing tank 102a to mix with the SF6 gas and the reaction gas.

[0047] Specifically, the gas outlet end of the gas supply main 101c is connected to the gas mixing tank 102a, and is used to deliver the SF6 with a configured concentration to the gas mixing tank 102a. At this time, the ultrasonic atomizer 102b works to generate a large amount of water mist, which rises into the gas mixing tank 102a. The water mist entering the gas mixing tank 102a mixes with the flowing SF6 gas to form a mixture of water mist and gas. Mixing water mist and gas has the following advantages:

[0048] First, SF6 is a potent greenhouse gas, and its decomposition products may be toxic. During the treatment process, mixing with water mist can reduce the toxicity and reactivity of SF6 and its decomposition products, reducing the harm to the environment and human health;

[0049] Second, water mist can act as a medium to participate in the degradation reaction, helping to convert SF6 into less harmful byproducts, such as SO2 and SiF4, while almost no SO2F2 and SOF2 are generated, which is beneficial to the subsequent treatment of products;

[0050] Third, the decomposition of SF6 may produce fluorine-containing compounds, which are highly corrosive. By mixing with water mist, the impact of these corrosive substances on processing equipment can be reduced and the service life of the equipment can be extended.

[0051] Furthermore, the reaction unit 201 includes a heating reaction furnace 201a, a quartz tube 201b, a 304 stainless steel mesh 201c, and a filter cotton 201d;

[0052] Specifically, the 304 stainless steel mesh 201c is any one of a plain weave mesh, a twill mesh, a multi-layer mesh, a foam structure, and a mesh fiber structure, and the pore size of the 304 stainless steel mesh 201c is 0.1-0.5 mm;

[0053] The heating reaction furnace 201a heats the quartz tube 201b so that the internal 304 stainless steel mesh 201c and filter cotton 201d are heated to thermally degrade the passing gas-water mixture;

[0054] Specifically, the quartz tube 201b is installed in the heating reaction furnace 201a, and the two ends of the quartz tube 201b are respectively installed with an air inlet pipe and an exhaust pipe for conveying the gas-water mixture. The 304 stainless steel mesh 201c and the filter cotton 201d are installed in the quartz tube 201b for high-temperature filtration and degradation of the gas-water mixture being conveyed.

[0055] The quartz tube 201b has a length of 1000 mm, an outer diameter of 30 mm, and a wall thickness of 2 mm. The quartz tube 201b has high heat resistance and can work for a long time at 1400°C, and has high safety.

[0056] Specifically, the absorption unit 202 uses a washing absorption tower, which is connected to the exhaust pipe of the quartz tube 201b. The byproducts that have been degraded by high temperature inside the quartz tube 201b will enter the washing absorption tower for washing and absorption. The washing liquid in the washing absorption tower uses a saturated calcium hydroxide solution, which has a good cleaning effect on the byproducts after thermal degradation.

[0057] SO2 reacts with calcium hydroxide to produce calcium sulfite precipitate and water, effectively removing SO2. The reaction formula is as follows:

[0058] SO2+Ca(OH)2→CaSO3↓+H2O

[0059] SiF4 reacts with calcium hydroxide to generate silicic acid and calcium fluoride, effectively removing SiF4. The reaction formula is as follows:

[0060] SiF4+2Ca(OH)2→Si(OH)4+2CaF2

[0061] SiF4 is a toxic gas, and its safety risk in industrial applications can be reduced by reacting with calcium hydroxide.

[0062] Example 2

[0063] Reference Figure 4 , this embodiment is different from the first embodiment in that it also includes:

[0064] The circulation system 300 is used to transport the gas with SF6 concentration that does not meet the standard after degradation back to the gas-water mixing unit 102 for re-degradation treatment;

[0065] The circulation system 300 includes a concentration sensor 301 and a circulation pipe 302. The concentration sensor 301 is installed in the exhaust pipe to detect the concentration of SF6. The two ends of the circulation pipe 302 are respectively connected to the mixing tank 102a and the exhaust pipe.

[0066] Specifically, the other end of the circulation pipe 302 is connected to the exhaust pipe of the quartz tube 201b. A one-way valve and an electronic valve 1 are installed at both ends of the circulation pipe 302, and an electronic valve 2 is installed at the rear section of the exhaust pipe located at the connection of the circulation pipe 302. The one-way valve is used to prevent the mixed gas in the mixing tank 102a from directly entering the circulation pipe 302. Usually, the electronic valve 1 is in a normally closed state, and the electronic valve 2 is in a normally open state. The gas discharged after thermal degradation is transported through the exhaust pipe. The concentration sensor 301 monitors the SF6 concentration in the exhaust gas. If the concentration is qualified, it is directly passed into the washing absorption tower for treatment. If the concentration is unqualified, the electronic valve 2 will be controlled to close and the electronic valve 1 will be opened. The gas will return to the mixing tank 102a through the circulation pipe 302, and then be treated twice by the reaction unit 201, effectively improving the overall degradation effect.

[0067] The circulation system 300 further includes a heat exchange component 303 , which is installed on the exhaust pipe and is used to cool down the high-temperature gas inside the exhaust pipe.

[0068] Specifically, the heat exchange component 303 includes a heat exchange copper tube 303a and a water tank 303b. The heat exchange copper tube 303a is a multi-bend structure, which is installed on the exhaust pipe. Both ends are connected to the exhaust pipe respectively, so that the exhaust pipe forms a passage through the heat exchange copper tube 303a. The water tank 303b is installed on the outside of the heat exchange copper tube 303a, and the water source flows inside. The high-temperature gas that has undergone thermal degradation will be heat-conducted after entering the heat exchange copper tube 303a. The heat exchange copper tube 303a after heat conduction will be heat-exchanged by the flowing cold water, so that the temperature of the high-temperature gas passing through is quickly reduced, thereby preventing the high-temperature gas from directly entering the concentration sensor 301, which may easily cause problems with the concentration sensor 301.

[0069] The rest of the structure is the same as that of Example 1.

[0070] Example 3

[0071] Reference Figure 2 , this embodiment is different from the above embodiments in that: this embodiment discloses a method for thermally degrading SF6 waste gas with stainless steel, which is applied to the device for thermally degrading SF6 waste gas with stainless steel in Embodiment 1-Embodiment 2, and the method comprises:

[0072] S1, transporting N2 and SF6 gases to the gas mixing tank 102a, and then mixing the water mist generated by the ultrasonic atomizer 102b with the SF6 gas and N2 in the gas mixing tank 102a to form a gas-water mixture;

[0073] Specifically, the gas output of N2 and SF6 is controlled by adjusting the electromagnetic flowmeter, and the gas output flow rate is 50-500 mL / min.

[0074] S2, the gas-water mixture enters the quartz tube 201b through the heating reaction furnace 201a, and is filtered and degraded by the high-temperature 304 stainless steel mesh 201c and filter cotton 201d to generate gas phase products and solid phase products;

[0075] The temperature of the heating reaction furnace 201a is controlled at 800°C.

[0076] The gas phase products are SO2 and SiF4, and the solid phase products are related to the initial concentration of SF6. Under low concentration conditions, the solid phase products of the degradation reaction are FeF2 and FeS, while under high concentration conditions, the degradation products are FeF and elemental S.

[0077] S3, the generated gas phase products and solid phase products are detected by the concentration sensor 301, and after reaching the standard, they enter the absorption unit 202 for washing to achieve harmless degradation of SF6;

[0078] S4. If the SF6 concentration in the discharged gas phase product exceeds the standard, it is reversely transported to the gas-water mixing unit 102 through the circulation pipe 302 for re-degradation treatment.

[0079] Test example:

[0080] The structure of stainless steel mesh usually includes the following types, and the pore size and surface area corresponding to different structures are also different:

[0081] Plain woven mesh:

[0082] Aperture: Usually between 0.1mm and 1mm.

[0083] Surface area: Flat weave mesh has a larger surface area and is suitable for improving the efficiency of gas-solid contact.

[0084] Twill mesh:

[0085] Pore ​​diameter: generally 0.2mm to 0.5mm, providing better strength and air permeability.

[0086] Surface area: Relatively large, which can increase the resistance to gas passage and improve reaction efficiency.

[0087] Multi-layer network:

[0088] Aperture: It can be designed into different levels, with the outer layer having a larger aperture (such as 0.5mm) and the inner layer having a smaller aperture (such as 0.1mm).

[0089] Surface area: Multi-layer mesh can provide a larger surface area, suitable for complex reaction processes.

[0090] Foam Structure:

[0091] Aperture: Generally between 1mm and 5mm.

[0092] Surface area: The foam structure provides a large specific surface area, which helps the diffusion of gas during the reaction process.

[0093] Reticular fiber structure:

[0094] Pore ​​size: Usually small, about 0.01mm to 0.1mm.

[0095] Surface area: extremely high specific surface area, suitable for catalytic and adsorption reactions.

[0096] In this experiment, multi-layer mesh 304 stainless steel was used to thermally degrade SF6 waste gas, and the effect of 304 stainless steel with different pore sizes (0.1, 0.2, 0.3, 0.4, 0.5 mm) on the degradation rate of SF6 waste gas was explored;

[0097] like Figure 5 As shown in the experiment, it is found that the 0.3mm pore size stainless steel mesh can achieve complete degradation of SF6 waste gas under the conditions of SF6 initial concentration of 1500ppm, mixed gas flow rate of 150mL / min, and reaction temperature of 800℃;

[0098] The 0.3mm pore size stainless steel mesh maintains good gas fluidity while providing sufficient reaction surface area, which helps to improve the reaction rate and degradation efficiency.

[0099] The rest of the structure is the same as that of Example 2.

[0100] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0101] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0102] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0103] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A device for thermal degradation of SF6 waste gas using stainless steel, characterized in that: include: A gas supply system (100) comprises a gas distribution unit (101) and a gas-water mixing unit (102), wherein the gas distribution unit (101) simultaneously supplies SF6 gas and reaction gas according to a required ratio, and the mixing unit (102) is connected to the gas distribution unit (101) to generate water vapor and mix it with the supplied SF6 gas and reaction gas to form a gas-water mixture; The degradation system (200) comprises a reaction unit (201) and an absorption unit (202), wherein the gas inlet end of the reaction unit (201) receives the gas-water mixture delivered from the gas-water mixing unit (102), and the gas-water mixture is degraded by the reaction unit (201) and then passes through the absorption unit (202); The circulation system (300) is used to transport the gas whose SF6 concentration does not meet the standard after degradation back to the gas-water mixing unit (102) for re-degradation treatment.

2. The device for thermal degradation of SF6 waste gas by stainless steel according to claim 1, characterized in that: The gas distribution unit (101) comprises a reaction gas tank (101a), a SF6 gas tank (101b) and a gas supply main pipe (101c) for outputting the reaction gas and SF6 gas.

3. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 2, characterized in that: The reaction gas tank (101a) is filled with N2.

4. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 3, characterized in that: The mixing unit (102) comprises a gas mixing tank (102a), the gas inlet end of the gas mixing tank (102a) is connected to the gas supply main pipe (101c) for introducing SF6 gas and reaction gas, and an ultrasonic atomizer (102b) is arranged at the bottom of the gas mixing tank (102a); The ultrasonic atomizer (102b) is connected to the gas mixing tank (102a) and is used to pass the generated water vapor into the gas mixing tank (102a) to mix with the SF6 gas and the reaction gas.

5. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 4, characterized in that: The reaction unit (201) comprises a heating reaction furnace (201a), a quartz tube (201b), a 304 stainless steel mesh (201c), and filter cotton (201d); The heating reaction furnace (201a) heats the quartz tube (201b) so that the internal 304 stainless steel mesh (201c) and filter cotton (201d) are heated, so as to thermally degrade the gas-water mixture passing through.

6. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 5, characterized in that: The absorption unit (202) adopts a washing absorption tower, and the washing liquid in the washing absorption tower adopts a saturated calcium hydroxide solution.

7. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 6, characterized in that: The circulation system (300) comprises a concentration sensor (301) and a circulation pipe (302). The concentration sensor (301) is installed in the exhaust pipe to detect the concentration of SF6. The two ends of the circulation pipe (302) are respectively connected to the gas mixing tank (102a) and the exhaust pipe.

8. The device for thermal degradation of SF6 waste gas by stainless steel as claimed in claim 7, characterized in that: The circulation system (300) further comprises a heat exchange component (303), which is installed on the exhaust pipe and is used to cool down the high-temperature gas inside the exhaust pipe.

9. A method for thermal degradation of SF6 waste gas by stainless steel, characterized in that: The device for thermally degrading SF6 waste gas with stainless steel according to any one of claims 1 to 8 comprises: S1, transporting N2 and SF6 gases to a gas mixing tank (102a), and then mixing water mist generated by an ultrasonic atomizer (102b) with the SF6 gas and N2 in the gas mixing tank (102a) to form a gas-water mixture; S2, the gas-water mixture enters the quartz tube (201b) through the heating reaction furnace (201a), and is filtered and degraded by the high-temperature 304 stainless steel mesh (201c) and filter cotton (201d) to generate gas phase products and solid phase products; S3, the generated gas phase products and solid phase products are detected by the concentration sensor (301), and after reaching the standard, they enter the absorption unit (202) for washing to achieve harmless degradation of SF6; S4. If the SF6 concentration in the discharged gas phase product exceeds the standard, it is reversely transported to the gas-water mixing unit (102) through the circulation pipe (302) for re-degradation treatment.

10. The method for thermal degradation of SF6 waste gas by stainless steel according to claim 9, characterized in that: The gas phase products are SO2 and SiF4, and the solid phase products are related to the initial concentration of SF6. Under low concentration conditions, the solid phase products of the degradation reaction are FeF2 and FeS, and under high concentration conditions, the degradation products are FeF and elemental S.

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