Device and method for thermal degradation of SF 6 waste gas using stainless steel

Abstract

The present invention relates to the technical field of SF6 waste gas treatment, and specifically disclosed are a device and method for the thermal degradation of SF6 waste gas using stainless steel. The device includes: 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 a reactive gas at a required ratio, and the mixing unit is in communication with the gas distribution unit, and generates water vapor and mixes same with the supplied SF6 gas and reactive gas to form a gas-water mixture; and a degradation system, comprising a reaction unit and an absorption unit, wherein a 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 having been reacted and degraded in the reaction unit. The present invention enables the conversion of SF6 waste gas into SO2 and SiF4 by means of thermal degradation using stainless steel. Compared to gaseous products converted from SF6, the resulting products are easier to process in subsequent treatments, achieving the harmless degradation of SF6. At the same time, the dilution of SF6 concentration by means of mixing water and gas effectively reduces gas consumption and the wasting of cost.

Description

An apparatus and method for the thermal degradation of SF6 waste gas from stainless steel. Technical Field

[0001] This invention relates to the technical field of SF6 waste gas treatment, and in particular to an apparatus and method for the thermal degradation of SF6 waste gas from stainless steel. Background Technology

[0002] SF6 is a synthetic gas in which the central sulfur atom is stably connected to the six surrounding fluorine atoms by covalent bonds, forming an octahedral configuration. SF6 gas itself is colorless, odorless, non-toxic, non-flammable, and slightly soluble in water. It is chemically very stable, has strong electron affinity, and can undergo a self-restoration process after bond breakage, thus possessing excellent insulation and arc-quenching properties.

[0003] SF6 is widely used in the power industry as an excellent gaseous insulating material, and 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 915-960 cm-1 band will lead to a serious greenhouse effect. It is listed as one of the six limiting gases in the Kyoto Protocol. Its greenhouse potential is 23,500 times that of CO2, far exceeding other greenhouse gases.

[0004] SF6 can exist stably in the atmosphere for up to 3200 years, decomposing slowly only under ultraviolet light. Therefore, the large-scale emission of SF6 waste gas poses a serious threat to the atmospheric environment. For the discharge treatment of SF6, the mainstream method is to use dielectric barrier discharge, microwave discharge, etc., to form a plasma region in a designated reactor to decompose the SF6 gas. In the "Experimental and Simulation Study on Degradation of SF6 by Dielectric Barrier Discharge Plasma" published in the Proceedings of the Chinese Society for Electrical Engineering in 2017, Zhang Xiaoxing et al. of Wuhan University used a quartz glass reactor to achieve DBD discharge treatment of SF6 waste gas. During the treatment process, SF6 needs to be diluted, and nitrogen and air are commonly used as dilution gases. Ultimately, a degradation effect of more than 90% can be achieved.

[0005] However, in this method, SF6 gas degrades under static conditions, and the products are mainly acidic and toxic gases, which limits the emission. Other studies on the electrolysis process of SF6 waste gas also require dilution of the SF6 gas. Excessively high concentrations of SF6 gas will inhibit the discharge process and weaken the treatment effect. As a result, a large amount of gas needs to be consumed in the dilution process, leading to gas waste. This problem needs to be solved. Summary of the Invention

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

[0007] Therefore, the purpose of this invention is to provide an apparatus and method for the thermal degradation of SF6 waste gas from stainless steel.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an apparatus for the thermal degradation of SF6 waste gas from stainless steel, comprising:

[0009] The gas supply system includes a gas distribution unit and a gas-water mixing unit. The gas distribution unit simultaneously supplies SF6 gas and reactant gas according to the required ratio. The mixing unit is connected to the gas distribution unit and generates water vapor to mix with the supplied SF6 gas and reactant gas to form a gas-water mixture.

[0010] The degradation system includes a reaction unit and an absorption unit. The air inlet of the reaction unit receives a 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 reverse the flow of gases with substandard SF6 concentrations after degradation to the gas-water mixing unit for re-degradation treatment.

[0012] As a preferred embodiment of the apparatus for the thermal degradation of SF6 waste gas by stainless steel according to the present invention, the gas distribution unit includes a reaction gas tank, an SF6 gas tank, and a gas supply main pipe for outputting the reaction gas and SF6 gas.

[0013] In a preferred embodiment of the apparatus for the thermal degradation of SF6 waste gas from stainless steel according to the present invention, the reaction gas tank is filled with N2.

[0014] As a preferred embodiment of the device for the thermal degradation of SF6 waste gas of stainless steel according to the present invention, the mixing unit includes a mixing tank, the inlet end of the mixing tank is connected to the gas supply pipe for introducing SF6 gas and reaction gas, and an ultrasonic atomizer is provided at the bottom of the mixing tank.

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

[0016] As a preferred embodiment of the apparatus for the thermal degradation of SF6 waste gas by stainless steel according to the present invention, the reaction unit includes a heating reactor, a quartz tube, a 304 stainless steel mesh, and filter cotton.

[0017] The heating reactor heats the quartz tube, which in turn heats the internal 304 stainless steel mesh and filter cotton, thus thermally degrading the passing gas-water mixture.

[0018] As a preferred embodiment of the device for the thermal degradation of SF6 waste gas by stainless steel according to the present invention, the absorption unit adopts a scrubbing absorption tower, and the scrubbing liquid in the scrubbing absorption tower adopts a saturated calcium hydroxide solution.

[0019] As a preferred embodiment of the device for the thermal degradation of SF6 waste gas by stainless steel according to 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 embodiment of the device for the thermal degradation of SF6 waste gas by stainless steel according to the present invention, the circulation system further includes a heat exchange component, which is installed on the exhaust pipe for cooling the high-temperature gas inside the exhaust pipe.

[0021] A method for the thermal degradation of SF6 waste gas from stainless steel, applied to the aforementioned apparatus for the thermal degradation of SF6 waste gas from stainless steel, the method comprising:

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

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

[0024] S3. The generated gaseous and solid products are detected by concentration sensors. Once they meet the standards, they enter the absorption unit for washing, thus achieving the harmless degradation of SF6.

[0025] S4. If the SF6 concentration in the discharged gaseous products exceeds the standard, it will be reversed through the circulation pipe and transported 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 according to the present invention, 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.

[0027] The beneficial effects of this invention are as follows: This invention converts SF6 waste gas into SO2 and SiF4 through the thermal degradation of stainless steel. Compared with the gaseous products after SF6 conversion, these are easier to process in subsequent treatment, achieving the harmless degradation of SF6. At the same time, the dilution of SF6 concentration by water-gas mixing effectively reduces gas consumption and cost waste. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of 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. Wherein:

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

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

[0031] Figure 3 is a schematic diagram of the reaction unit in the apparatus for the thermal degradation of SF6 waste gas by stainless steel according to the present invention.

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

[0033] Figure 5 shows the SF6 degradation rate of 304 stainless steel mesh with different apertures in an experimental example of the method for thermal degradation of SF6 waste gas by stainless steel according to the present invention. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] 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 those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the 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 phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0038] Example 1

[0039] Referring to Figures 1-3, an apparatus for the thermal degradation of SF6 waste gas using stainless steel is provided, 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 reactant gas according to the required ratio. The mixing unit 102 is connected to the gas distribution unit 101 and generates water vapor to mix with the supplied SF6 gas and reactant 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 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, an SF6 gas tank 101b, and a gas supply main 101c for outputting the reaction gas and SF6 gas.

[0043] Specifically, there are two gas supply pipes 101c, and each of the two gas supply pipes 101c is equipped with an electromagnetic flow meter. The electromagnetic flow meter is used to control the output of N2 and SF6 in order to prepare SF6 with different initial concentrations.

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

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

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

[0047] Specifically, the outlet of the gas supply main pipe 101c is connected to the mixing tank 102a to deliver SF6 of the prepared concentration into the mixing tank 102a. At this time, the ultrasonic nebulizer 102b operates to generate a large amount of water mist. The water mist rises and enters the mixing tank 102a, where it 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] Firstly, SF6 is a potent greenhouse gas, and its decomposition products may be toxic. During the treatment process, mixing it with water mist can reduce the toxicity and reactivity of SF6 and its decomposition products, thereby reducing harm to the environment and human health.

[0049] Secondly, 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 generating almost no SO2F2 and SOF2, which is beneficial for the subsequent treatment of the products.

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

[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, 304 stainless steel mesh 201c can be made of any one of the following: plain weave, twill weave, multi-layer mesh, foam structure, and mesh fiber structure, and the aperture of 304 stainless steel mesh 201c is 0.1-0.5mm.

[0053] The heating reactor 201a heats the quartz tube 201b, which in turn heats the internal 304 stainless steel mesh 201c and filter cotton 201d, for thermal degradation of the passing gas-water mixture.

[0054] Specifically, quartz tube 201b is installed in heating reactor 201a, and inlet pipe and outlet pipe are installed at both ends of quartz tube 201b respectively for conveying gas-water mixture. 304 stainless steel mesh 201c and filter cotton 201d are installed in quartz tube 201b for high-temperature filtration and degradation of the conveyed gas-water mixture.

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

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

[0057] SO2 reacts with calcium hydroxide in an acid-base neutralization reaction, producing 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 produce 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, but its safety risks in industrial applications can be reduced by reacting it with calcium hydroxide.

[0062] Example 2

[0063] Referring to Figure 4, this embodiment differs from the first embodiment in that it further includes:

[0064] The circulation system 300 is used to reverse the flow of gas with substandard SF6 concentration after degradation 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 connected to the mixing tank 102a and the exhaust pipe, respectively.

[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 end of the exhaust pipe where the circulation pipe 302 is connected. The one-way valve is used to prevent the mixed gas in the mixing tank 102a from directly entering the circulation pipe 302. Normally, 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 discharged gas. If the concentration is qualified, it is directly fed into the washing and absorption tower for treatment. If the concentration is not qualified, it will control the electronic valve 2 to close and open the electronic valve 1. The gas will return to the mixing tank 102a through the circulation pipe 302 and then be treated again by the reaction unit 201, which effectively improves the overall degradation effect.

[0067] The circulation system 300 also includes a heat exchange component 303, which is installed on the exhaust pipe to cool 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 has a multi-bend structure and is installed on the exhaust pipe. Both ends are connected to the exhaust pipe, so that the exhaust pipe forms a passage through the heat exchange copper tube 303a. The water tank 303b is installed outside the heat exchange copper tube 303a and the water inside flows. After the high-temperature gas undergoes thermal degradation, it enters the heat exchange copper tube 303a and is heated. The heated heat exchange copper tube 303a is then heated by the flowing cold water, which causes the temperature of the high-temperature gas to drop rapidly and prevents the high-temperature gas from directly entering the concentration sensor 301, which could easily cause problems with the concentration sensor 301.

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

[0070] Example 3

[0071] Referring to Figure 2, this embodiment differs from the previous embodiments in that: this embodiment discloses a method for the thermal degradation of SF6 waste gas from stainless steel, applied to the apparatus for the thermal degradation of SF6 waste gas from stainless steel in Embodiments 1-2, the method comprising:

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

[0073] Specifically, the output of N2 and SF6 is controlled by adjusting the electromagnetic flow meter, with an output flow rate of 50–500 mL / min.

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

[0075] The temperature of the heating reactor 201a is controlled at 800℃.

[0076] The gaseous products are SO2 and SiF4, while the solid products are related to the initial concentration of SF6. Under low concentration conditions, the solid 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 gaseous and solid products are detected by the concentration sensor 301. After meeting the standards, they enter the absorption unit 202 for washing, thus achieving the harmless degradation of SF6.

[0078] S4. If the SF6 concentration in the discharged gaseous products exceeds the standard, it will be reversed through the circulation pipe 302 and transported to the gas-water mixing unit 102 for re-degradation treatment.

[0079] Experimental example:

[0080] Stainless steel mesh typically comes in several structural types, with different structures corresponding to different aperture sizes and surface areas:

[0081] Flat weave netting:

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

[0083] Surface area: Flat woven mesh has a large surface area, making it suitable for improving the efficiency of gas-solid contact.

[0084] Twill mesh:

[0085] Aperture: typically 0.2mm to 0.5mm, providing good strength and air permeability.

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

[0087] Multilayer network:

[0088] Aperture: It can be designed in different layers, with the outer layer having a larger aperture (e.g., 0.5 mm) and the inner layer having a smaller aperture (e.g., 0.1 mm).

[0089] Surface area: Multilayer networks can provide a larger surface area, making them 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 gas diffuse during the reaction process.

[0093] Reticulated fiber structure:

[0094] Aperture: Typically small, approximately 0.01 mm to 0.1 mm.

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

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

[0097] As shown in Figure 5, the experiment shows that a 0.3 mm aperture stainless steel mesh can achieve complete degradation of SF6 waste gas under the conditions of an initial SF6 concentration of 1500 ppm, a mixed gas flow rate of 150 mL / min, and a reaction temperature of 800℃.

[0098] The 0.3mm aperture stainless steel mesh maintains good gas flow 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 in Example 2.

[0100] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.

[0101] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the currently considered best mode for carrying out the invention, or those features that are not relevant to implementing the invention) may be omitted.

[0102] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0103] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A device for the thermal degradation of SF6 waste gas using stainless steel, characterized in that: include: 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 reactive gas according to the required ratio. The mixing unit (102) is connected to the gas distribution unit (101) and generates water vapor to mix with the supplied SF6 gas and reactive gas to form a gas-water mixture. The degradation system (200) includes a reaction unit (201) and an absorption unit (202). The air inlet of the reaction unit (201) receives a 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). The circulation system (300) is used to reverse the flow of gas with substandard SF6 concentration after degradation to the gas-water mixing unit (102) for re-degradation treatment.

2. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 1, characterized in that: The gas distribution unit (101) includes a reaction gas tank (101a), an SF6 gas tank (101b), and a gas supply main (101c) for outputting the reaction gas and SF6 gas.

3. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 2, characterized in that: The reaction gas container (101a) is filled with N2.

4. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 3, characterized in that: The mixing unit (102) includes a mixing tank (102a), the inlet of which is connected to a gas supply pipe (101c) for introducing SF6 gas and reaction gas, and an ultrasonic atomizer (102b) is provided at the bottom of the mixing tank (102a). The ultrasonic atomizer (102b) is connected to the mixing tank (102a) and is used to introduce the generated water vapor into the mixing tank (102a) to mix with SF6 gas and reactant gas.

5. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 4, characterized in that: The reaction unit (201) includes a heating reaction furnace (201a), a quartz tube (201b), a 304 stainless steel mesh (201c), and filter cotton (201d); The heating reactor (201a) heats the quartz tube (201b), which in turn heats the internal 304 stainless steel mesh (201c) and filter cotton (201d) to thermally degrade the passing gas-water mixture.

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

7. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 6, characterized in that: 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 connected to the mixing tank (102a) and the exhaust pipe, respectively.

8. The apparatus for the thermal degradation of SF6 waste gas from stainless steel as described in claim 7, characterized in that: The circulation system (300) also includes a heat exchange component (303), which is installed on the exhaust pipe to cool the high-temperature gas inside the exhaust pipe.

9. A method for the thermal degradation of SF6 waste gas from stainless steel, characterized in that: An apparatus for the thermal degradation of SF6 waste gas from stainless steel according to any one of claims 1-8, the method comprising: S1. N2 and SF6 gases are delivered to the mixing tank (102a), and then the water mist generated by the ultrasonic atomizer (102b) is mixed with the SF6 gas and N2 in the mixing tank (102a) to form a gas-water mixture; S2. The gas-water mixture enters the quartz tube (201b) of the heated reaction furnace (201a), and is filtered and degraded by the high-temperature 304 stainless steel mesh (201c) and filter cotton (201d) to generate gaseous products and solid products. S3. The generated gaseous and solid products are detected by the concentration sensor (301). After meeting the standards, they enter the absorption unit (202) for washing, thereby achieving the harmless degradation of SF6. S4. If the concentration of SF6 in the discharged gaseous products exceeds the standard, it is reversed through the circulation pipe (302) and transported to the gas-water mixing unit (102) for re-degradation treatment.

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

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