Method and system for degrading sulfur hexafluoride based on tandem catalysis

Abstract

A method and system for degrading sulfur hexafluoride based on tandem catalysis, comprising: decomposing SF6 gas by means of a first treatment process; treating the decomposed gas by means of an alkali solution treatment; and treating the gas after alkali solution treatment by means of a second treatment process. After the second treatment process, the gas passes through a tail gas absorption tank, where most sulfur-containing and fluorine-containing gases are absorbed. The mixed gas finally discharged from the tail gas absorption tank comprises a carrier gas, N2, and other harmless gases, and can be directly discharged into the atmosphere. Thus, complete harmless degradation and emission of SF6 waste gas can be achieved.

Description

A method and system for the tandem catalytic degradation of sulfur hexafluoride Technical Field

[0001] This invention relates to the technical field of sulfur hexafluoride degradation, and more particularly to a method and system for sulfur hexafluoride degradation based on tandem catalytic degradation. Background Technology

[0002] SF6 is a synthetically produced inert gas widely used in industries such as power, semiconductors, and metal smelting due to its excellent arc-quenching ability and physicochemical properties. However, SF6 is a potent greenhouse gas, with a Global Warming Potential (GWP) 23,500 times that of carbon dioxide (CO2). For half a century, with the widespread application of gas-insulated equipment in the power industry, the consumption and emissions of SF6 have increased year by year. Statistics show that my country's power industry's SF6 consumption increased from 820 tons in 2001 to 5,000 tons in 2010, and continues to grow to this day, posing a significant potential threat to the atmospheric environment. In April 2021, General Secretary Xi Jinping incorporated "carbon peaking" and "carbon neutrality" into the overall framework of my country's ecological civilization construction; therefore, reducing SF6 emissions is now imperative.

[0003] Currently, from a resource perspective, recycling and purifying SF6 waste gas is the most environmentally friendly method. Through purification technology, impurities such as SF6 decomposition products, water, dust, and oil are removed from the SF6 waste gas to obtain pure SF6, thus completing the recycling and purification of SF6 waste gas. For example, there is a mixed gas purification, separation, and recovery system (publication number CN109850854A, June 7, 2019) and an environmentally friendly sulfur hexafluoride / nitrogen mixed gas separation and recovery device and method (publication number CN107413187A, December 1, 2017). However, the entire recycling and purification process is very complex and has high requirements for the process flow; more importantly, the recycling and purification devices are often large in size, only suitable for some large insulating equipment, and cannot be applied to some small gas insulating equipment, resulting in indiscriminate emissions and failing to fundamentally solve the problem of SF6 waste gas.

[0004] In recent years, scholars both domestically and internationally have proposed using degradation methods to treat SF6 waste gas generated from industrial applications, rendering it harmless. Currently, the most effective methods include pyrolysis, photolysis, and low-temperature plasma methods. Among these, the non-thermal plasma (NTP) method (Dielectiric barrier discharge, DBD) for SF6 degradation has the advantages of high degradation rate and high energy efficiency, making it suitable for widespread industrial application. For example, publications CN108273366A (July 13, 2018) on "Sulfur Hexafluoride Degradation Treatment Device and Method Based on [Method Name]" and CN112604465A (April 6, 2021) on "Gas Circulation Device and Method for Sulfur Hexafluoride Gas Discharge Degradation Treatment" effectively degrade SF6 waste gas to achieve emission reduction. Both publications mention using alkaline solutions such as sodium hydroxide to absorb and treat the products after SF6 decomposition. However, the paper "Study on Atmospheric Pressure and its Synergistic Catalytic Degradation of SF6 Gas" mentions that the main decomposition products of SF6 are five types: H2S, SOF2, SO2, SOF4, and SO2F2. In terms of properties, the first four gases can react with or be absorbed by alkaline solutions, while SO2F2 gas does not react with alkaline solutions and remains stable above 400℃. Inhalation of SO2 can cause pulmonary hemorrhage, therefore it cannot be directly emitted. This problem needs to be solved to better meet the requirements for the harmless degradation of SF6 waste gas. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned methods for the degradation of sulfur hexafluoride based on tandem catalytic degradation, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a method for the degradation of sulfur hexafluoride based on tandem catalytic degradation.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for the tandem catalytic degradation of sulfur hexafluoride, comprising,

[0008] The SF6 gas is decomposed through the first processing step;

[0009] The decomposed gases are treated with an alkaline solution; and...

[0010] The gas treated with alkali solution is then processed in a second processing step.

[0011] As a preferred embodiment of the method for the tandem catalytic degradation of sulfur hexafluoride described in this invention, the carrier gas is mixed with SF6 gas for dilution before the first treatment step.

[0012] As a preferred embodiment of the method for the degradation of sulfur hexafluoride based on tandem catalytic degradation of the present invention, wherein: the first treatment step is plasma electrolysis, and the SF6 is decomposed into gaseous products containing SO2F2, SOF2, SO2, SOF4 and SF6 through the first treatment step.

[0013] As a preferred embodiment of the method for the degradation of sulfur hexafluoride based on tandem catalytic degradation of the present invention, the alkaline treatment involves passing a gaseous product containing SO2F2, SOF2, SO2, SOF4, and SF6 into an alkaline liquid, through which SO2, SOF2, and SO2F2 are absorbed.

[0014] As a preferred embodiment of the method for the degradation of sulfur hexafluoride based on tandem catalytic degradation of the present invention, the second treatment step is plasma electrolysis, which decomposes the gaseous products after alkaline treatment into SOF2 and SO2.

[0015] The present invention also discloses a system for the tandem catalytic degradation of sulfur hexafluoride, applied to the above-mentioned method for the tandem catalytic degradation of sulfur hexafluoride; it includes a first reactor for performing a first treatment step; a second reactor for performing a second treatment step; and an alkaline tank connected to the first and second reactors for treating the gas discharged from the first reactor with alkaline solution and conveying the alkaline-treated gas to the second reactor.

[0016] As a preferred embodiment of the system for the tandem catalytic degradation of sulfur hexafluoride described in this invention, the first reactor and the second reactor have the same structure; both include an outer dielectric cylindrical tube, a metal outer mesh, an inner dielectric tube, and an inner electrode.

[0017] As a preferred embodiment of the system for the tandem catalytic degradation of sulfur hexafluoride described in this invention, it further includes a plasma power source for supplying power to the first reactor and the second reactor.

[0018] As a preferred embodiment of the system for the tandem catalytic degradation of sulfur hexafluoride described in this invention, it further includes a gas supply unit; which includes a carrier gas cylinder for loading gas to dilute SF6; and an exhaust gas cylinder for loading SF6 gas; both the carrier gas cylinder and the exhaust gas cylinder are connected to the first reactor via a pressure reducing valve and a flow meter.

[0019] As a preferred embodiment of the system for the tandem catalytic degradation of sulfur hexafluoride described in this invention, it further includes a tail gas reaction tank, which is connected to a second reactor.

[0020] The beneficial effects of this invention are as follows: After the gas from the second treatment process passes through the tail gas absorption tank, most of the sulfur-containing and fluorine-containing gases are absorbed. The final mixed gas discharged from the tail gas absorption tank is a carrier gas, N2 and other harmless gases, which can be directly discharged into the atmosphere. Thus, the complete harmless degradation and emission of SF6 waste gas is achieved. Attached Figure Description

[0021] 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:

[0022] Figure 1 is a comparison diagram of gas composition before and after alkaline treatment in this invention.

[0023] Figure 2 is a comparison diagram of gas composition before and after treatment by the exhaust gas absorption tank in this invention.

[0024] Figure 3 is a schematic diagram of the structure of the first reactor and the second reactor described in this invention.

[0025] Figure 4 is a schematic diagram of the overall system structure for the tandem catalytic degradation of sulfur hexafluoride in this invention. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] Secondly, the term "an 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 throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0029] 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.

[0030] Example 1

[0031] Referring to Figure 1, a method for the degradation of sulfur hexafluoride based on tandem catalytic degradation is provided, including:

[0032] S1. SF6 gas is decomposed through the first processing step;

[0033] Before the first processing step, the carrier gas is mixed with SF6 gas for dilution. The carrier gas can be air. In actual operation, since SF6 gas is a highly electronegative gas with a very strong arc-extinguishing ability, the carrier gas needs to be diluted before entering the reactor to make its concentration below 10% before entering the reaction area.

[0034] The first treatment process is plasma electrolysis. When the diluted SF6 waste gas begins the first treatment process, the main gas to be degraded is SF6 gas. At this time, the plasma power supply 400 needs to maintain a large power to achieve the initial degradation of most of the SF6 gas molecules in the first treatment process as much as possible.

[0035] After the first treatment process, most of the SF6 gas molecules are decomposed, except for the carrier gas, mainly forming four decomposition products: SO2F2, SOF2, SO2, and SOF4. It also includes a small amount of some impurity gases in the SF6 waste gas, such as CO and N2. Therefore, the types of gases after the first treatment process are relatively complex, but the content of SF6 gas is greatly reduced.

[0036] S2. Treat the decomposed gas with alkaline solution;

[0037] The gas enters the alkaline solution tank 300 for treatment to absorb a large amount of SO2, SOF2 and a small amount of SO2F2.

[0038] S3. The gas treated with alkali solution is processed through the second processing step.

[0039] The second treatment step is plasma electrolysis. After the gas remaining from the alkaline treatment enters this second step, from a molecular perspective, SF6, SO2F2, and SOF4 molecules are more prone to bond breaking and dissociation under the impact of high-energy particles. SOF4 molecules are inherently unstable and easily decompose, and under the influence of discharge, they dissociate to produce SO2F2 molecules. SO2F2 molecules, in turn, decompose under discharge to produce SOF2 and SO2. Therefore, after degradation in the second treatment step, besides the carrier gas, the main gas components are SOF2 and SO2. These gases can react with the alkaline solution and be fixed. Thus, after the second treatment step, the gas passes through the tail gas absorption tank, where most of the sulfur and fluorine-containing gases are absorbed. The final mixed gas discharged from the tail gas absorption tank consists of the carrier gas and harmless gases such as N2, which can be directly released into the atmosphere. This achieves the complete harmless degradation and emission of SF6 waste gas.

[0040] Example 2

[0041] Referring to Figures 3 and 4, this embodiment differs from the first embodiment in that: this embodiment also proposes a system based on tandem catalytic degradation of sulfur hexafluoride, applied to the method for tandem catalytic degradation of sulfur hexafluoride in Example 1; it includes a first reactor 100, which performs a first processing step; and a second reactor 200, which performs a second processing step; the first reactor 100 and the second reactor 200 have the same structure; both include an outer dielectric cylindrical tube, a metal outer mesh, an inner dielectric tube, and an inner electrode.

[0042] Two flange supports are fixed to both ends of the outer medium pipe, providing support for the outer medium pipe. Similarly, each flange support of the outer medium pipe has a terminal block at the bottom, which can be connected to the ground wire.

[0043] The alkali tank 300 is connected to the first reactor 100 and the second reactor 200. It is used to treat the gas discharged from the first reactor 100 with alkali and to transport the treated gas to the second reactor 200.

[0044] Both ends of the first reactor 100 and the second reactor 200 are respectively provided with air inlet and air outlet ports. That is, the gas enters the first reactor 100 through the air inlet port, and after the reaction is completed, it enters the alkali tank 300 through the air outlet port of the first reactor 100. The gas treated by the alkali tank 300 enters the second reactor 200 through the air inlet port, and is discharged from the second reactor 200 through the air outlet port.

[0045] In addition, silicone rubber is applied to all mechanical fixed connections in the system during the connection process to seal and prevent air leakage.

[0046] Specifically, this system based on the tandem catalytic degradation of sulfur hexafluoride also includes a plasma power supply 400, which supplies power to the first reactor 100 and the second reactor 200.

[0047] Based on the above, the metal outer mesh of the first reactor 100 and the metal outer mesh of the second reactor 200 serve as the outer electrodes of the two-stage discharge degradation system, respectively. The inner dielectric tube and the inner electrode are connected to the ground through a flange support, serving as the inner electrodes of the two-stage degradation system.

[0048] Two plasma power supplies 400 are connected to the metal mesh of the first reactor 100 and the metal mesh of the second reactor 200 respectively via high-voltage lines. After being powered on, they generate a high-frequency, high-voltage alternating electric field between the two metal meshes and the area covered by the inner electrodes, generating a variety of complex high-energy particles. These particles collide and dissociate with SF6 gas molecules that enter the reactor, causing the SF6 gas molecules to undergo bond breaking and recombination, thereby achieving the degradation of SF6 waste gas.

[0049] The rest of the structure is the same as in Example 1.

[0050] Example 3

[0051] Referring to Figures 3 and 4, this embodiment differs from the above embodiments in that: the system based on series catalytic degradation of sulfur hexafluoride further includes a gas supply unit 500; it includes a carrier gas cylinder 501 for loading gas to dilute SF6; and an exhaust gas cylinder 502 for loading SF6 gas; both the carrier gas cylinder 501 and the exhaust gas cylinder 502 are connected to the first reactor 100 through a pressure reducing valve 503 and a flow meter 504, wherein the flow meter 504 is used to control the SF6 content of the gas supplied to the first reactor 100, so that the gas with an SF6 concentration of less than 10% enters the interior of the first reactor 100.

[0052] Furthermore, it also includes an exhaust gas reaction tank 600, which is connected to the second reactor 200.

[0053] The gas discharged from the second reactor 200 passes through the tail gas absorption tank, where most of the sulfur- and fluorine-containing gases are absorbed. The final mixed gas discharged from the tail gas absorption tank consists of carrier gas, N2, and other harmless gases, which can be directly discharged into the atmosphere. Thus, the complete harmless degradation and emission of SF6 waste gas is achieved.

[0054] The rest of the structure is the same as in Example 2.

[0055] 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.

[0056] 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 best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0057] 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.

[0058] 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 method for the degradation of sulfur hexafluoride based on tandem catalytic degradation, characterized in that: include, The SF6 gas is decomposed through the first processing step; The decomposed gases are treated with an alkaline solution; and... The gas treated with alkali solution is then processed in a second processing step.

2. The method for the degradation of sulfur hexafluoride based on tandem catalytic degradation as described in claim 1, characterized in that: The carrier gas is mixed with SF6 gas for dilution before the first processing step.

3. The method for the degradation of sulfur hexafluoride based on tandem catalytic degradation as described in claim 2, characterized in that: The first processing step is plasma electrolysis, in which SF6 is decomposed into gaseous products containing SO2F2, SOF2, SO2, SOF4, and SF6.

4. The method for the degradation of sulfur hexafluoride based on tandem catalytic degradation as described in claim 3, characterized in that: The alkaline treatment involves passing a gaseous product containing SO2F2, SOF2, SO2, SOF4, and SF6 into an alkaline liquid, whereby the alkaline liquid absorbs SO2, SOF2, and SO2F2.

5. The method for the degradation of sulfur hexafluoride based on tandem catalytic degradation as described in claim 4, characterized in that: The second processing step is plasma electrolysis, which decomposes the gaseous products after alkaline treatment into SOF2 and SO2.

6. A system for the tandem catalytic degradation of sulfur hexafluoride, characterized in that: Applied to the method for the tandem catalytic degradation of sulfur hexafluoride as described in any one of claims 1 to 5; It includes, The first reactor (100) performs the first processing step; The second reactor (200) performs the second processing step; An alkaline tank (300) is connected to the first reactor (100) and the second reactor (200) for treating the gas discharged from the first reactor (100) with alkaline solution and transporting the alkaline-treated gas to the second reactor (200).

7. The system for the tandem catalytic degradation of sulfur hexafluoride as described in claim 6, characterized in that: The first reactor (100) and the second reactor (200) have the same structure; both include an outer dielectric cylindrical tube, a metal outer mesh, an inner dielectric tube, and an inner electrode.

8. The system for the tandem catalytic degradation of sulfur hexafluoride as described in claim 7, characterized in that: It also includes a plasma power supply (400) for supplying power to the first reactor (100) and the second reactor (200).

9. The system for the tandem catalytic degradation of sulfur hexafluoride as described in claim 8, characterized in that: It also includes a gas supply unit (500); which includes, Carrier gas cylinder (501) is used to hold gas for diluting SF6; Waste gas cylinder (502) is used to store SF6 gas; Both the carrier gas cylinder (501) and the waste gas cylinder (502) are connected to the first reactor (100) via a pressure reducing valve (503) and a flow meter (504).

10. The system based on tandem catalytic degradation of sulfur hexafluoride as described in claim 7, 8, or 9, characterized in that: It also includes an exhaust gas reaction tank (600), which is connected to the second reactor (200).

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