Method and system for degrading sulfur hexafluoride based on tandem catalysis

Abstract

The invention relates to the technical field of sulfur hexafluoride degradation, in particular to a method and system for degrading sulfur hexafluoride based on tandem catalysis, and the method comprises the following steps: decomposing SF6 gas through a first treatment process; the decomposed gas is treated through alkali liquor treatment; and treating the gas treated by the alkali liquor through a second treatment process. After the gas after the second treatment process passes through a tail gas absorption tank, most of sulfur-containing and fluorine-containing gas is absorbed, and finally, mixed gas discharged from the tail gas absorption tank is harmless gas such as carrier gas, N2 and the like and can be directly discharged into the atmosphere, so that complete harmless degradation and emission of the SF6 waste gas are realized.

Description

Technical Field

[0001] The invention relates to the technical field of sulfur hexafluoride degradation, and in particular to a method and system for degrading sulfur hexafluoride based on series catalysis. Background Art

[0002] SF6 is an artificially synthesized inert gas. Because of its excellent arc extinguishing ability and physical and chemical properties, it is widely used in the power, semiconductor and metal smelting industries. However, SF6 is a strong greenhouse gas, and its global warming potential (GWP) is 23,500 times that of carbon dioxide (CO2). Over the past half century, with the promotion and application of gas-insulated equipment in the power industry, the use and emissions of SF6 have increased year by year. According to statistics, the use of SF6 gas in my country's power industry has increased from 820 tons in 2001 to 5,000 tons in 2010, and is still increasing to date. This situation will pose a very large potential threat to the atmospheric environment.

[0003] At present, from the perspective of resources, recycling and purifying SF6 waste gas is the most environmentally friendly means. Through purification technology, SF6 decomposition products, water, dust, oil and other impurities in SF6 waste gas are removed to obtain pure SF6, which completes the recycling and purification of SF6 waste gas. For example: a mixed gas purification, separation and recovery system with a publication number of CN109850854A on June 7, 2019, and an environmentally friendly sulfur hexafluoride / nitrogen mixed gas separation and recovery device and method with a publication number of CN107413187A on December 1, 2017. However, the entire process of recycling and purification is very complicated and has high requirements for the process flow; more importantly, the recycling and purification device is often large in size and is only suitable for some large insulating equipment, but not for some small gas-insulated equipment, resulting in the problem of arbitrary emissions, and does not fundamentally solve the problem of SF6 waste gas.

[0004] In recent years, scholars at home and abroad have proposed the use of degradation methods to treat SF6 waste gas generated by industrial applications to make it harmless. At present, the more effective methods mainly include pyrolysis, photolysis and low-temperature plasma methods. Among them, the (Dielectirc barrier discharge, DBD) low-temperature plasma method (Non-Thermal Plasma, NTP) discharge degradation of SF6 has the advantages of high degradation rate and high energy efficiency, and is suitable for promotion and application in industry. For example: "Sulfur hexafluoride degradation treatment device and treatment method based on" with publication number CN108273366A on July 13, 2018, and "Gas circulation device and method for sulfur hexafluoride gas discharge degradation treatment" with publication number CN112604465A on April 6, 2021, can effectively degrade SF6 waste gas through means to achieve the purpose of emission reduction. It is mentioned that the products after SF6 decomposition are absorbed and treated by alkaline solutions such as sodium hydroxide. However, the paper "Study on Atmospheric Pressure and Its Co-catalytic Degradation of SF6 Gas" mentioned that the decomposition products of SF6 are mainly H2S, SOF2, SO2, SOF4, and SO2F2. In terms of nature, the first four gases can react with or be absorbed by alkali solution, while SO2F2 gas does not react with alkali solution and remains stable above 400°C. Inhalation can cause pulmonary hemorrhage, so it cannot be discharged directly. In order to better meet the harmless degradation of SF6 waste gas, this problem needs to be solved. Summary of the invention

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

[0006] Therefore, the object of the present invention is to provide a method for degrading sulfur hexafluoride based on tandem catalysis.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for degrading sulfur hexafluoride based on tandem catalysis, comprising:

[0008] Decomposing SF6 gas through a first processing step;

[0009] Treatment of decomposed gases by alkaline treatment; and,

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

[0011] As a preferred embodiment of the method for catalytic degradation of sulfur hexafluoride based on series connection, the carrier gas is mixed with SF6 gas for dilution before the first treatment step.

[0012] As a preferred embodiment of the method for sulphur hexafluoride degradation based on series catalysis described in the present invention, the first treatment process is plasma electrolysis, and the SF6 is decomposed into gas products containing SO2F2, SOF2, SO2, SOF4, and SF6 through the first treatment process.

[0013] As a preferred embodiment of the method for catalytic degradation of sulfur hexafluoride based on series catalysis described in the present invention, the alkaline solution treatment is to pass the gas products containing SO2F2, SOF2, SO2, SOF4, and SF6 into alkaline liquid, and absorb SO2, SOF2, and SO2F2 through the alkaline solution.

[0014] As a preferred embodiment of the method for degradation of sulfur hexafluoride based on series catalysis described in the present invention, the second treatment process is plasma electrolysis to decompose the gas product after the alkaline solution treatment into SOF2 and SO2.

[0015] The present invention also discloses a system for catalytic degradation of sulfur hexafluoride based on series connection, which is applied to the above-mentioned method for catalytic degradation of sulfur hexafluoride; the system comprises a first reactor, which performs a first treatment process; a second reactor, which performs a second treatment process; and an alkali liquid pool, which is connected to the first reactor and the second reactor, and is used for treating the gas discharged from the first reactor with alkali liquid, and conveying the gas treated with alkali liquid to the second reactor.

[0016] As a preferred solution of the system based on serial catalytic degradation of sulfur hexafluoride described in the present invention, the first reactor has the same structure as the second reactor; both include an outer medium cylindrical tube, a metal outer mesh, an inner medium tube and an inner electrode.

[0017] As a preferred solution of the system based on serial catalytic degradation of sulfur hexafluoride described in the present invention, it further comprises a plasma power supply, and the plasma power supply is used to supply power to the first reactor and the second reactor.

[0018] As a preferred solution of the system based on series catalytic degradation of sulfur hexafluoride described in the present invention, it also includes a gas supply unit; it includes a carrier gas bottle for loading gas for diluting SF6; a waste gas bottle for loading SF6 gas; the carrier gas bottle and the waste gas bottle are both connected to the first reactor through a pressure reducing valve and a flow meter.

[0019] As a preferred solution of the system based on serial catalytic degradation of sulfur hexafluoride described in the present invention, it further includes a tail gas reaction pool, and the tail gas reaction pool is connected to the second reactor.

[0020] The beneficial effects of the present invention are as follows: after the gas after the second treatment process passes through the tail gas absorption tank, most of the sulfur-containing and fluorine-containing gases will be absorbed, and the mixed gas finally discharged from the tail gas absorption tank is harmless gases such as carrier gas and N2, which can be directly discharged into the atmosphere, thereby achieving complete harmless degradation and emission of SF6 waste gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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:

[0022] Figure 1 This is a comparison chart of gas composition before and after alkali solution treatment in the present invention.

[0023] Figure 2 This is a comparison diagram of gas composition before and after treatment in the tail gas absorption tank of the present invention.

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

[0025] Figure 4 The figure is a diagram showing the overall structure of the system based on the series catalytic degradation of sulfur hexafluoride in the present invention. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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 is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0029] 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.

[0030] Example 1

[0031] Reference Figure 1 , provides a method for degrading sulfur hexafluoride based on tandem catalysis, comprising,

[0032] S1. Decomposing SF6 gas through a first processing step;

[0033] Before the first treatment process, the carrier gas is mixed with SF6 gas for dilution, wherein the carrier gas can be air. In the actual working process, since SF6 gas is a strongly electronegative gas with a very strong arc extinguishing ability, the carrier gas needs to be diluted before entering the reactor to a concentration below 10% before entering the reaction area.

[0034] The first treatment process is plasma electrolysis. When the diluted SF6 waste gas starts 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 initially achieve the degradation of most SF6 gas molecules in the first treatment process as much as possible.

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

[0036] S2. treating the decomposed gas by alkali treatment;

[0037] The gas enters the alkali liquid pool 300 for treatment to absorb a large amount of SO2, SOF2 and a small amount of SO2F2.

[0038] S3, treating the gas treated with alkali solution through a second treatment process.

[0039] The second treatment process is plasma electrolysis. After the gas left over from the alkali treatment enters the second treatment process, from the perspective of gas molecules, SF6, SO2F2, and SOF4 molecules are relatively more likely to undergo bond breaking and dissociation under the impact of high-energy particles. SOF4 gas molecules themselves are unstable and easily decomposed, and dissociate under the action of discharge to produce SO2F2 molecules, while SO2F2 molecules decompose under the action of discharge to produce two gases, SOF2 and SO2. Therefore, after the degradation through the second treatment process, in addition to the carrier gas, the main components of the gas are SOF2, SO2, etc., which can react with the alkali solution and be fixed. Therefore, after the gas after the second treatment process passes through the tail gas absorption tank, most of the sulfur-containing and fluorine-containing gases will be absorbed, and the mixed gas discharged from the tail gas absorption tank is finally harmless gases such as carrier gas and N2, which can be directly discharged into the atmosphere, thus achieving complete harmless degradation and emission of SF6 waste gas.

[0040] Example 2

[0041] Reference Figure 3 and Figure 4 This embodiment is different from the first embodiment in that: this embodiment also proposes a system based on series catalytic degradation of sulfur hexafluoride, which is applied to the method for series catalytic degradation of sulfur hexafluoride in Example 1; it includes a first reactor 100, which performs a first treatment process; a second reactor 200, which performs a second treatment process; the first reactor 100 and the second reactor 200 have the same structure; both include an outer medium cylindrical tube, a metal outer mesh, an inner medium tube and an inner electrode.

[0042] The two flange brackets are respectively fixed at both ends of the outer medium pipe to support the outer medium pipe. Similarly, each outer medium pipe has a flange bracket with a terminal at the bottom to connect the ground wire.

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

[0044] Inlet and outlet interfaces are respectively provided at both ends of the first reactor 100 and the second reactor 200, that is, other gases enter the first reactor 100 through the inlet interface of the first reactor 100, and enter the alkali liquid pool 300 through the outlet interface of the first reactor 100 after the reaction is completed. The gas treated in the alkali liquid pool 300 enters the second reactor 200 through the inlet interface on the second reactor 200, and is discharged from the second reactor 200 through the outlet interface of the second reactor 200.

[0045] In addition, the mechanical fixed connection parts of the system are coated with silicone rubber during the connection process to play a role in sealing and preventing air leakage.

[0046] Specifically, the system based on serial catalytic degradation of sulfur hexafluoride further includes a plasma power supply 400 , which is used to supply power to the first reactor 100 and the second reactor 200 .

[0047] On the basis of the above, the metal outer mesh of the first reactor 100 and the metal outer mesh of the second reactor 200 are respectively used as the outer electrodes of the two-stage discharge degradation system, and the inner dielectric tube and the inner electrode are connected to the ground through the flange bracket as the inner electrode of the two-stage degradation system.

[0048] The two plasma power supplies 400 are respectively connected to the metal outer mesh of the first reactor 100 and the metal outer mesh of the second reactor 200 through high-voltage lines. After power is turned on, high-frequency and high-voltage alternating electric fields are generated between the two metal outer meshes and the areas covered by the inner electrodes, generating many types of complex high-energy particles, which collide and dissociate with the SF6 gas molecules entering therein, causing the SF6 and other gas molecules to break bonds and recombine, thereby achieving the degradation of SF6 waste gas.

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

[0050] Example 3

[0051] Reference Figure 3 and Figure 4 This embodiment is different from the above embodiments in that: the system based on series catalytic degradation of sulfur hexafluoride also includes a gas supply unit 500; it includes a carrier gas bottle 501 for loading gas for diluting SF6; a waste gas bottle 502 for loading SF6 gas; the carrier gas bottle 501 and the waste gas bottle 502 are both 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 delivered to the first reactor 100, so that the gas with an SF6 concentration below 10% enters the interior of the first reactor 100.

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

[0053] After the gas discharged from the second reactor 200 passes through the tail gas absorption tank, most of the sulfur-containing and fluorine-containing gases will be absorbed. Finally, the mixed gas discharged from the tail gas absorption tank is harmless gas such as carrier gas and N2, which can be directly discharged into the atmosphere, thus achieving complete harmless degradation and emission of SF6 waste gas.

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

[0055] 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, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, 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 described herein that performs the function, 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 several modifications still falling within the scope of the appended claims.

[0056] 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.

[0057] 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.

[0058] 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 method for degrading sulfur hexafluoride based on tandem catalysis, characterized in that: include, Decomposing SF6 gas through a first processing step; Treatment of decomposed gases by alkaline treatment; and, The gas treated with alkali solution is processed through a second processing step.

2. The method for degrading sulfur hexafluoride based on tandem catalysis according to claim 1, characterized in that: The carrier gas is mixed with SF6 gas for dilution before the first treatment step.

3. The method for degrading sulfur hexafluoride based on tandem catalysis as claimed in claim 2, characterized in that: The first treatment process is plasma electrolysis, and the SF6 is decomposed into gas products containing SO2F2, SOF2, SO2, SOF4, and SF6 through the first treatment process.

4. The method for degrading sulfur hexafluoride based on tandem catalysis as claimed in claim 3, characterized in that: The alkaline solution treatment is to pass the gas products containing SO2F2, SOF2, SO2, SOF4, and SF6 into alkaline liquid, and absorb SO2, SOF2, and SO2F2 through the alkaline liquid.

5. The method for degrading sulfur hexafluoride based on tandem catalysis as claimed in claim 4, characterized in that: The second treatment process is plasma electrolysis, which decomposes the gas product after the alkali solution treatment into SOF2 and SO2.

6. A system based on tandem catalytic degradation of sulfur hexafluoride, characterized in that: Applicable to the method for degrading sulfur hexafluoride based on tandem catalysis as described in any one of claims 1 to 5; These include, A first reactor (100) for performing a first treatment process; A second reactor (200) for performing a second treatment process; The alkali liquid pool (300) is connected to the first reactor (100) and the second reactor (200) and is used to treat the gas discharged from the first reactor (100) with alkali liquid and transport the gas treated with alkali liquid to the second reactor (200).

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

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

9. The system for catalytic degradation of sulfur hexafluoride according to claim 8, characterized in that: Also included is an air supply unit (500); which includes, A carrier gas bottle (501), used for carrying gas for diluting SF6; A waste gas bottle (502) for loading SF6 gas; The carrier gas bottle (501) and the waste gas bottle (502) are both connected to the first reactor (100) via a pressure reducing valve (503) and a flow meter (504).

10. The system for catalytic degradation of sulfur hexafluoride based on series connection as claimed in claim 7, 8 or 9, characterized in that: It also includes a tail gas reaction tank (600), and the tail gas reaction tank (600) is connected to the second reactor (200).

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