Method and system for harmless degradation of SF 6 based on catalyst

Abstract

Disclosed in the present invention are a method and a system for the harmless degradation of SF6 based on a catalyst. The method comprises introducing SF6 and a protective gas, which are proportioned, into a reactor loaded with a catalyst to perform a reaction, and breaking the S-F bond of SF6 to generate SO2. In the present invention, by degrading SF6 into SO2 and utilizing the characteristic that SO2 is convenient to treat, the problems of a limited degradation rate and a poor degradation effect of SF6 can be effectively solved.

Description

A catalyst-based method and system for the harmless degradation of SF6 Technical Field

[0001] This invention relates to the technical field of SF6 treatment, and in particular to a catalyst-based method and system for the harmless degradation of SF6. Background Technology

[0002] SF6 is a synthetic industrial gas with excellent electrical insulation and arc-quenching properties, primarily used in electrical insulation, semiconductor processing, and metal smelting industries. Approximately 80% of SF6 is used in the electrical sector. With technological advancements and increasing demand, SF6 usage and emissions are increasing annually. However, due to its difficulty in degradation, atmospheric SF6 concentrations are rising. According to IPCC / TEAP statistics, in 1998, the atmospheric concentration of SF6 was 3.9 × 10⁻¹² L / L, increasing at a rate of approximately 5% per year. Data from 2008 to 2013 showed an average SF6 concentration of approximately 6.9 × 10⁻¹² L / L, further increasing at a rate of 0.28 × 10⁻¹² L / L per year. SF6's strong greenhouse effect has already damaged the atmosphere, and given the recent call for dual-carbon development, SF6 degradation has become inevitable.

[0003] In recent years, to reduce the damage of SF6 to the atmosphere, various emission reduction methods have been implemented, including SF6 waste adsorption and purification, SF6 substitute gases, and SF6 waste degradation and conversion. Among these, discharge degradation technology can achieve high degradation rates and low energy consumption. Low-temperature plasma technology has been widely used in waste gas treatment, featuring simple structure, low power consumption, high efficiency, and ease of control. Furthermore, there are already relevant case studies in SF6 waste gas treatment with excellent results.

[0004] Currently, many scholars have conducted experiments on SF6 waste gas treatment. For example, the patent "Sulfur hexafluoride degradation treatment device based on dielectric barrier discharge" published on June 7, 2019, and the patent "A confirmation method for efficient and harmless degradation of SF6 waste gas by dielectric barrier discharge" published on June 18, 2021, mainly dilute the SF6 waste gas and introduce it into a dielectric barrier reactor (200) for degradation. At this time, the SF6 degradation rate is limited and the product selectivity is poor.

[0005] The degradation of SF6 is mainly achieved through dielectric barrier discharge (DBD). Zhang Xiaoxing et al. from Wuhan University conducted experiments using DBD to degrade SF6, exploring the effects of various factors on SF6 degradation by changing input voltage, frequency, dielectric type, background gas, and external gas. They found that the presence of an appropriate amount of H2O in the reaction improves the degradation rate and energy efficiency, with 0.5% water vapor as the external gas showing the best results. However, even with this method, the SF6 degradation rate is limited, the degradation effect is poor, and the products contain various toxic substances such as SO2F2 and SOF2, which remains to be addressed. Summary of the Invention

[0006] In view of the problem that SF6 is difficult to degrade in the existing technology, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to provide a catalyst-based method for the harmless degradation of SF6.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a catalyst-based method for the harmless degradation of SF6, comprising;

[0009] The properly proportioned SF6 and protective gas are introduced into a reactor loaded with a catalyst to react. SF6 breaks the SF bonds to generate SO2.

[0010] As a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the catalyst is Fe@ZSM-5.

[0011] As a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the catalyst Fe@ZSM-5 is prepared before the properly proportioned SF6 and protective gas are introduced into the reactor containing the catalyst for reaction. This preparation includes: dissolving Fe(NO3)3·9H2O in water; placing ZSM-5 in the solution; evaporating the solution to dryness in a water bath to obtain the evaporated catalyst; drying the evaporated catalyst to completely evaporate the moisture; and calcining the catalyst to complete the preparation of the catalyst Fe@ZSM-5.

[0012] As a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the ratio of Fe(NO3)3·9H2O to water is 3.1g of Fe(NO3)3·9H2O per 100ml of water, and 70g of ZSM-5 per 100ml of water.

[0013] As a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the water bath evaporation temperature is 90°C; the drying temperature is 120°C and the drying time is 12 hours; the calcination temperature is 550°C and the calcination time is 4 hours.

[0014] In a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the protective gas is Ar.

[0015] As a preferred embodiment of the catalyst-based harmless degradation method for SF6 described in this invention, the ratio of Ar to SF6 is 49:1.

[0016] This invention also proposes a catalyst-based SF6 harmless degradation system, the aforementioned catalyst-based SF6 harmless degradation method; it includes,

[0017] Gas mixing mechanism, used to mix SF6 and protective gas in the correct proportions;

[0018] A reactor, which is internally loaded with a catalyst, has an inlet and an outlet, the inlet being connected to a gas distribution mechanism;

[0019] The processing unit is connected to the output end of the reactor;

[0020] The power supply mechanism is used to provide electrical energy to the reactor;

[0021] The gas mixing mechanism sends the properly proportioned SF6 and protective gas into the reactor from the input end. Under the action of the catalyst and power discharge, the SF6 breaks the SF bond to generate SO2. The processing mechanism can process the SO2.

[0022] As a preferred embodiment of the catalyst-based SF6 harmless degradation system of the present invention, the gas distribution mechanism includes:

[0023] A gas storage tank is used to store the SF6 and protective gas separately.

[0024] The gas distributor is connected to the gas storage tank and the input end of the reactor.

[0025] As a preferred embodiment of the catalyst-based SF6 harmless degradation system of the present invention, the power supply mechanism includes:

[0026] power supply;

[0027] A transformer is used to regulate the input voltage and power of a power supply.

[0028] The low-voltage electrode is connected to the power supply and is located inside the reactor.

[0029] High-voltage electrodes are connected to a power source and are located outside the reactor.

[0030] The catalyst is filled inside the reactor and located between the low-pressure electrode and the high-pressure electrode.

[0031] The beneficial effects of this invention are: by degrading SF6 into SO2, and taking advantage of the easy-to-process characteristics of SO2, the problem of limited degradation rate and poor degradation effect of SF6 can be effectively solved. Attached Figure Description

[0032] 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:

[0033] Figure 1 is a data graph of the air tube experimental group in Embodiment 1 of the present invention.

[0034] Figure 2 is a data graph of the experimental group in Example 1 of the present invention, in which ZSM-5 is used as a catalyst.

[0035] Figure 3 is a data graph of the experimental group of ZSM-5 with 1 wt% Fe content as catalyst in Example 1 of the present invention.

[0036] Figure 4 shows the experimental data of ZSM-5 with a 3 wt% Fe content as a catalyst in Example 1 of the present invention.

[0037] Figure 5 shows the experimental data of ZSM-5 with a 5 wt% Fe content as a catalyst in Example 1 of the present invention.

[0038] Figure 6 is a comparison chart of five sets of experimental data in Embodiment 1 of the present invention.

[0039] Figure 7 is a system configuration diagram of embodiments 2 and 3 of the present invention.

[0040] Figure 8 is a detailed diagram of the system in embodiments 2 and 3 of the present invention. Detailed Implementation

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Example 1

[0046] A catalyst-based method for the harmless degradation of SF6 is provided, firstly by preparing the catalyst Fe@ZSM-5;

[0047] Fe@ZSM-5 was added as a catalyst into reactor 200;

[0048] The properly proportioned SF6 and protective gas are introduced into reactor 200, which is loaded with catalyst, to react. SF6 breaks the SF bond and generates SO2.

[0049] Compared to SF6, SO2 is easier to remove and degrade, thus solving the problem of SF6's difficulty in degradation.

[0050] Preferably, the reactor 200 has a power supply structure that can provide electrical energy to the reactor 200. When SF6 is introduced into the reactor 200, under the dual action of electrolysis and catalyst Fe@ZSM-5, SF6 breaks the SF bond and reacts with ZSM-5 silicon oxide to generate SO2.

[0051] Furthermore, the power supply structure is a plasma power supply 401. Under the synergistic catalysis of plasma and ZSM-5@Fe, the porous structure of ZSM-5 provides more adsorption sites, increases the residence time of SF6 in the discharge region, and has microporous discharge and surface discharge, which promotes the full decomposition of SF6. Under the catalysis of Fe modification, the activation energy of SF6 decomposition is reduced and the degradation rate of SF6 is improved.

[0052] Preferredly, SO2 can be treated with alkaline solutions. By passing SO2 into an alkaline solution, CaSO4 precipitate is formed, thus rendering SF6 harmless. This prevents SF6 from being released into the atmosphere and polluting the environment.

[0053] Furthermore, the protective gas is Ar, and the ratio of Ar to SF6 is 49:1. After the SF6 degradation tail gas is treated with alkaline solution, the main component is Ar. The degradation tail gas is then collected after drying and reused to improve the economic efficiency of SF6 degradation.

[0054] The preparation of Fe@ZSM-5 as a catalyst includes the following steps:

[0055] S1. Dissolve Fe(NO3)3·9H2O in water;

[0056] The ratio of Fe(NO3)3·9H2O to water is 3.1g per 100ml of water. Add Fe(NO3)3·9H2O to the water and stir to fully dissolve Fe(NO3)3·9H2O in the water to obtain Fe(NO3)3·9H2O solution.

[0057] S2. Place ZSM-5 in the solution;

[0058] When adding ZSM-5, add 70g of ZSM-5 for every 100ml of water in the solution;

[0059] S3. Evaporate the solution to dryness using a water bath to obtain the evaporated catalyst;

[0060] The water bath evaporation temperature is 90℃. During evaporation, the water in the solution is evaporated, and ferric nitrate will adhere to the outer surface of ZSM-5. During the water bath evaporation process, it is necessary to stir continuously to make the ferric nitrate adhere more evenly.

[0061] S4. Dry the evaporated catalyst completely to remove all moisture.

[0062] The drying temperature is 120℃ and the drying time is 12 hours, which can completely evaporate the moisture.

[0063] S5. The catalyst is calcined to complete the preparation of catalyst Fe@ZSM-5.

[0064] The calcination temperature was 550℃ and the calcination time was 4h. During the calcination process, the ferric nitrate adhering to the outer surface of ZSM-5 was reduced to Fe2O3, thereby completing the coating of ZSM-5 with Fe2O3 and producing Fe@ZSM-5 catalyst.

[0065] In this embodiment, ZSM-5 catalysts modified with different Fe contents (1, 3, 5 wt%) were prepared by impregnation method. The ZSM-5 catalysts had a diameter of 2.5 mm and a composition of [Na+n(H2O)]. 16 ][AInSi 96 -nO 192 ]-MFI.

[0066] First, a certain amount of Fe(NO3)3·9H2O was dissolved in 100ml of H2O solution to ensure complete dissolution. Then, 70g of ZSM-5 was placed in the solution and evaporated to dryness in a 90℃ water bath while continuously stirring to ensure uniform adhesion. The evaporated catalyst was then placed in an oven at 120℃ for 12 hours to completely evaporate the moisture. After that, it was placed in a tube furnace and calcined at 550℃ in air for 4 hours. The catalyst preparation was then complete. Fe@ZSM-5 catalysts with different Fe contents were prepared using Fe(NO3)3·9H2O solutions of varying concentrations: 1 wt%, 3 wt%, and 5 wt%. The ZSM-5 catalysts with these different Fe contents (1, 3, and 5 wt%) were then used in SF6 degradation experiments. For comparison, two sets of comparative experiments were also conducted. The five experimental sets were: 1) empty tube experiment; 2) tube with ZSM-5 as catalyst; 3) tube with ZSM-5 containing 1 wt% Fe as catalyst; 4) tube with ZSM-5 containing 3 wt% Fe as catalyst; and 5) tube with ZSM-5 containing 5 wt% Fe as catalyst.

[0067] For specific experimental data, refer to Figures 1 to 5 and Figure 6. By comparing the five groups of experiments, we can see that the degradation effect of SF6 in the experimental group with Fe-containing ZSM-5 as the catalyst is significantly better than that in the empty tube experimental group and the experimental group with Fe-free ZSM-5 as the catalyst.

[0068] In the experimental groups where ZSM-5 with 1wt%, 3wt%, and 5wt% Fe content was used as catalyst, there was no significant difference in the degradation effect of SF6 when the input power reached 100W.

[0069] Example 2

[0070] Referring to Figures 7 and 8, this embodiment differs from the first embodiment in that: this embodiment proposes a catalyst-based SF6 harmless degradation system, applied to the catalyst-based SF6 harmless degradation method in the above embodiment; it includes a gas mixing mechanism 100, used to mix SF6 and protective gas in a specific ratio, the gas mixing mechanism 100 being able to properly mix the protective gas and SF6.

[0071] The system also includes a reactor 200, which is loaded with a catalyst and has an input end 201 and an output end 202. The input end 201 is connected to the gas distribution mechanism 100. When applied to the method in Example 1, Fe@ZSM-5 is loaded as a catalyst inside the reactor 200. The protective gas and SF6 that are proportioned in the gas distribution mechanism 100 can enter the interior of the reactor 200 through the input end 201.

[0072] The system also includes a processing unit 300, which is connected to the output end 202 of the reactor 200. The processing unit 300 is mainly used to process the degradation products. When applied to the method in Example 1, it is mainly used to decompose SO2.

[0073] The system also includes a power supply mechanism 400, which provides electrical energy to the reactor 200. When applied to the method in Example 1, the power supply mechanism 400 may be a plasma power supply 401.

[0074] The gas distribution mechanism 100 sends the properly proportioned SF6 and protective gas into the reactor 200 from the input end 201. Under the action of the catalyst and the power supply 401 discharge, the SF6 breaks the SF bond and generates SO2. The processing mechanism 300 can complete the processing of SO2.

[0075] The rest of the structure is the same as in Example 1.

[0076] Example 3

[0077] Referring to Figures 7 and 8, this embodiment differs from the previous embodiments in that: the gas distribution mechanism 100 includes a gas storage tank 101, which stores SF6 and protective gas separately; and a gas distributor 102, which is connected to the gas storage tank 101 and to the input terminal 201 of the reactor 200. In this embodiment, there are two gas storage tanks 101, which are respectively filled with Ar gas and SF6 gas. The gas distributor 102 can mix Ar gas and SF6 gas as needed and deliver them to the interior of the reactor 200 through the input terminal 201.

[0078] Furthermore, the power supply mechanism 400 includes a power supply 401; a transformer 402 for regulating the input voltage and power of the power supply 401; a low-voltage electrode 403 connected to the power supply 401 and disposed inside the reactor 200; a high-voltage electrode 404 connected to the power supply 401 and disposed outside the reactor 200; and a catalyst filled inside the reactor 200 and located between the low-voltage electrode 403 and the high-voltage electrode 404.

[0079] As shown in the figure, the entire reactor 200 is a medium-barrier reactor 200 with a tubular structure. The low-pressure electrode 403 is located inside the reactor 200 and has a long column structure. The high-pressure electrode 404 is a wire mesh that covers the outside of the reactor 200. The Fe@ZSM-5 filler 500 is located inside the reactor 200 and wraps around the low-pressure electrode 403.

[0080] In this embodiment, the processing unit 300 includes an alkali tank 301, a drying chamber 302, and a collection tank 303. The alkali tank 301 is filled with alkali solution. The output end 202 of the reactor 200 is connected to a discharge pipe. The end of the discharge pipe away from the reactor 200 extends into the alkali solution in the alkali tank 301. The generated SO2 gas will reach the alkali solution through the discharge pipe and be decomposed. After the SF6 degradation tail gas is treated by the alkali solution, the main component is Ar. After the degradation tail gas is treated by the drying chamber 302, it is transported to the inside of the collection tank 303 for collection. The Ar gas can be reused, improving the economic efficiency of SF6 degradation.

[0081] The rest of the structure is the same as in Example 2.

[0082] 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 without substantially departing from the novel teachings and advantages of the subject matter described in this application (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc., installation arrangement, use of materials, color, orientation, etc.)). 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 exemplary embodiments without departing from the scope of the invention. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0083] 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.

[0084] 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.

[0085] 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 catalyst-based method for the harmless degradation of SF6, characterized in that: include; The properly proportioned SF6 and protective gas are introduced into a reactor (200) containing a catalyst to react. SF6 breaks the SF bond to generate SO2.

2. The catalyst-based method for the harmless degradation of SF6 as described in claim 1, characterized in that: The catalyst is Fe@ZSM-5.

3. The SF6 harmless degradation method based on a catalyst as described in claim 2, characterized in that: Before the properly proportioned SF6 and protective gas are introduced into the reactor (200) containing the catalyst for reaction, the catalyst Fe@ZSM-5 is prepared, which includes: Dissolve Fe(NO3)3·9H2O in water; Place ZSM-5 in the solution; The solution was evaporated to dryness in a water bath to obtain the evaporated catalyst; The catalyst, after being evaporated, is dried to completely remove moisture. The catalyst was calcined to complete the preparation of catalyst Fe@ZSM-5.

4. The catalyst-based method for the harmless degradation of SF6 as described in claim 3, characterized in that: The ratio of Fe(NO3)3·9H2O to water is 3.1g of Fe(NO3)3·9H2O per 100ml of water, and 70g of ZSM-5 per 100ml of water.

5. The catalyst-based method for the harmless degradation of SF6 as described in claim 3 or 4, characterized in that: The temperature for drying in the water bath is 90°C; The drying temperature is 120℃ and the drying time is 12 hours. The calcination temperature is 550℃ and the calcination time is 4 hours.

6. The catalyst-based method for the harmless degradation of SF6 as described in claim 1, 2, 3, or 4, characterized in that: The protective gas is Ar.

7. The catalyst-based method for the harmless degradation of SF6 as described in claim 6, characterized in that: The ratio of Ar to SF6 is 49:

1.

8. A catalyst-based SF6 harmless degradation system, characterized in that: Applied to the catalyst-based harmless degradation method of SF6 as described in claim 1; It includes, Gas distribution mechanism (100) for mixing SF6 and protective gas; The reactor (200), which is internally loaded with a catalyst, has an input end (201) and an output end (202), the input end (201) being connected to a gas distribution mechanism (100); The processing unit (300) is connected to the output end (202) of the reactor (200); A power supply mechanism (400) is used to provide electrical energy to the reactor (200); The gas mixing mechanism (100) sends the SF6 and protective gas, which have been properly mixed, into the reactor (200) from the input end (201). Under the action of the catalyst and the power supply (401) discharge, the SF6 breaks the SF bond and generates SO2. The processing mechanism (300) can complete the processing of SO2.

9. The catalyst-based SF6 harmless degradation system as described in claim 8, characterized in that: The gas distribution mechanism (100) includes, A gas storage tank (101) is used to store the SF6 and protective gas separately. The gas distributor (102) is connected to the gas storage tank (101) and to the input terminal (201) of the reactor (200).

10. The catalyst-based SF6 harmless degradation system as described in claim 9, characterized in that: The power supply mechanism (400) includes, Power supply (401); Transformer (402) is used to regulate the input voltage and power of power supply (401); A low-voltage electrode (403) is connected to a power supply (401) and is located inside the reactor (200); A high-voltage electrode (404) is connected to a power supply (401) and is located outside the reactor (200); The catalyst is filled inside the reactor (200) and located between the low-pressure electrode (403) and the high-pressure electrode (404).

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