Plasma-based sulfur hexafluoride degradation apparatus and method

Abstract

The application relates to the technical field of SF6 degradation, and particularly provides a sulfur hexafluoride degradation device and method based on plasma, which comprises a sealed box body, a plasma generating device and a liquid-phase lye absorption device; the upper portion of the sealed box body is provided with an air inlet, the plasma generating device is arranged in the sealed box body and located below the air inlet; the lower portion of the sealed box body is provided with the liquid-phase lye absorption device and an air outlet; the plasma generating device degrades the mixed gas of the carrier gas and the sulfur hexafluoride input through the air inlet to obtain an acidic byproduct which reacts with the lye of the liquid-phase lye absorption device. In the related art, the ionization and degradation equipment of the sulfur hexafluoride degradation device are separated from each other, the intermediate product of ionization is strongly acidic, the structure and equipment are easily corroded, and the service life is low.

Description

Technical Field

[0001] This invention relates to the field of sulfur hexafluoride degradation technology, and in particular to a plasma-based sulfur hexafluoride degradation device and method. Background Technology

[0002] Sulfur hexafluoride (SF6) is widely used in the power, semiconductor and other industries due to its excellent insulation and arc-quenching properties.

[0003] Plasma technology has attracted attention due to its high reactivity and rapid start-up and shutdown capabilities. Dielectric barrier discharge (DBD) and microwave plasma are two commonly used methods for gas degradation. However, in the gas-phase degradation of SF6, conventional DBD suffers from low energy utilization due to the low density of gas molecules and the limited probability of electron-molecule collisions. Furthermore, the electrode surface is prone to corrosion by fluorine-containing products during discharge, leading to the generation of toxic and difficult-to-hydrolyze byproducts such as SOF2 and SO2F2, causing secondary pollution.

[0004] While microwave plasma can generate higher electron energy and active particle concentrations, its equipment is expensive, and its energy coupling efficiency is greatly affected by the type and pressure of the gas. When treating SF6 alone, it often requires extremely high input power to achieve the desired degradation rate. Furthermore, it also faces the problems of acidic gas corrosion and incomplete absorption of byproducts. Both DBD and microwave plasma technologies lack the ability to absorb and neutralize reaction products in situ, resulting in short equipment lifespans and high operating costs. Summary of the Invention

[0005] The present invention provides a plasma-based sulfur hexafluoride degradation device and method, which at least solves the problem in related technologies that the ionization and degradation equipment are separated, and the intermediate products of ionization are strongly acidic, which easily corrode the structure and equipment, resulting in a short service life.

[0006] This invention provides a plasma-based sulfur hexafluoride (SF6) degradation device, comprising: a sealed enclosure, a plasma generator, and a liquid-phase alkaline solution absorption device; an air inlet is provided at the upper part of the sealed enclosure, and the plasma generator is disposed inside the sealed enclosure and located below the air inlet; the liquid-phase alkaline solution absorption device and an air outlet are provided at the lower part of the sealed enclosure; the plasma generator is configured to electromagnetically excite and form a plasma zone within the sealed enclosure, degrading a mixture of carrier gas and SF6 input through the air inlet to obtain acidic byproducts, which react with the alkaline solution of the liquid-phase alkaline solution absorption device; the ratio of the carrier gas to SF6 input through the air inlet is within a preset range to stabilize the reaction rate of the acidic byproducts with the liquid-phase alkaline solution absorption device within a preset range; the liquid-phase alkaline solution absorption device is used to hold the alkaline solution, the total neutralization capacity of which satisfies the neutralization equivalent of not less than 8 mol of sodium hydroxide for 1 mol of SF6; the internal humidity of the sealed enclosure does not exceed a preset humidity threshold to ensure stable plasma discharge.

[0007] As an alternative, the plasma generator is a microwave plasma source or a dual dielectric barrier discharge plasma device.

[0008] As an optional solution, the dual dielectric barrier discharge plasma device includes a high-voltage power supply, an electrode assembly, an insulating shell, and multiple magnesium oxide discharge tubes; the high-voltage power supply inputs AC220V, outputs a high voltage of 20kV, has an adjustable power of 0.1–1kW, and a frequency of 10–12kHz; the magnesium oxide discharge tubes are arranged parallel to each other inside the insulating shell, with both ends fixed to the insulating shell, and the tube cavities are interconnected to form gas flow channels; the electrode assembly includes a high-voltage electrode and a grounding electrode, the high-voltage electrode is located on the inner or outer side of the magnesium oxide discharge tube, the grounding electrode is located on the inner wall of the insulating shell, and the tube wall of the magnesium oxide discharge tube serves as a dual dielectric barrier layer, separating the high-voltage electrode and the grounding electrode to form a discharge gap; the plasma region is formed below the magnesium oxide discharge tubes.

[0009] As an optional solution, the microwave plasma source includes a 2.45 GHz microwave generating module, a waveguide, and a plasma discharge tube; the power of the microwave generating module is adjustable from 0.5 to 3 kW, and the microwave energy is coupled into the sealed box through the waveguide to form the plasma region below the plasma discharge tube; the plasma discharge tube is preferably made of magnesium oxide.

[0010] As an optional solution, the vertical distance between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline solution absorption device is greater than 70 mm, wherein the discharge end face is the lowest end face of the plasma generation region of the plasma generator.

[0011] As an optional solution, a perforated insulating partition is provided between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline absorber. The insulating partition is installed on the inner wall of the sealed box and is made of polypropylene or polytetrafluoroethylene with a thickness of 3-5mm. The insulating partition has multiple vent holes with a diameter of 2-3mm, a hole spacing of 10-15mm, and an opening rate of 2%-4%.

[0012] As an optional solution, the vertical distance between the insulating partition and the liquid surface is 20mm-30mm, and the vertical distance between the insulating partition and the discharge end face is not less than 40mm.

[0013] As an optional solution, the alkaline solution is an aqueous sodium hydroxide solution with a mass concentration of 5% to 20%; the liquid level of the liquid phase alkaline solution absorption device is 10 mm to 30 mm, and the volume of the alkaline solution does not exceed 1 L.

[0014] As an optional solution, the sealed enclosure is also equipped with a temperature and humidity sensor and a circulating fan; the temperature and humidity sensor is used to monitor the temperature and humidity inside the enclosure, ensuring that the temperature does not exceed 50°C and the humidity does not exceed 50% RH; the circulating fan is used to ensure uniform airflow inside the enclosure.

[0015] As an optional solution, the sealed enclosure is grounded, the plasma generator is equipped with overheat protection and overcurrent protection devices, and the liquid phase alkali absorption device includes a polypropylene insulated container.

[0016] This invention also provides a plasma-based method for the degradation of sulfur hexafluoride, comprising: preparing a sodium hydroxide absorbent of a set concentration and injecting it into a polypropylene insulating container; adjusting the vertical distance between the discharge end face of the plasma generator and the liquid surface to be greater than 70 mm; continuously purging the interior of the sealed chamber with carrier gas for 5-10 minutes to replace residual air and reduce the relative humidity inside the chamber to below 50%RH; uniformly mixing sulfur hexafluoride with the carrier gas and introducing it into the chamber through the air inlet at the top of the sealed chamber; turning on the plasma generator to form a plasma zone, allowing the mixed gas to undergo a degradation reaction in the plasma zone; neutralizing the acidic byproducts generated by degradation in situ with alkali in the liquid-phase alkali absorbent below; and discharging the treated gas through the air outlet at the bottom of the sealed chamber.

[0017] As an alternative, the carrier gas is selected from one or more of the following: argon, nitrogen, and dry air; the carrier gas also contains 10%-30% oxygen by volume, and the volume ratio of argon to air is 3:1 to 5:1.

[0018] As an alternative, after the reaction is complete, the plasma power supply is turned off first, and the carrier gas is continued to purge the sealed chamber for 10-20 minutes to remove residual gas.

[0019] As an alternative, Fourier transform infrared spectroscopy is used to monitor the residual sulfur hexafluoride concentration at the outlet.

[0020] The plasma-based sulfur hexafluoride degradation device provided by this invention employs an integrated sealed enclosure, integrating the plasma pyrolysis unit and the alkaline absorption unit within the same sealed space. The inlet is located at the top of the enclosure, and the outlet at the bottom. The mixed gas passes sequentially from top to bottom through the plasma reaction zone and the liquid-phase alkaline zone. The acidic and toxic products such as HF and sulfuric acid generated from the pyrolysis of sulfur hexafluoride are directly captured and neutralized by the alkaline solution below at the moment of generation, eliminating the need for external structures such as independent absorption towers and pipelines. The entire process operates in a closed loop, completely preventing the leakage of toxic acidic gases, eliminating secondary pollution at its source, and ensuring compliant exhaust emissions.

[0021] A high-energy plasma zone is created within a sealed chamber using a plasma generator. High-energy electrons and reactive free radicals break the stable molecular chemical bonds of sulfur hexafluoride (SF6), achieving highly efficient pyrolysis. Simultaneously, the ratio of carrier gas to SF6 is controlled to ensure the gas concentration remains within a reasonable range, allowing for sufficient contact and reaction between the gas and the high-energy reactive particles. This significantly improves the SF6 pyrolysis and degradation efficiency. The stable and controllable gas ratio avoids incomplete pyrolysis due to excessively high SF6 concentration or energy waste due to excessively low concentration, ensuring a continuous and stable reaction.

[0022] Strictly limit the alkaline solution neutralization capacity, and prepare the alkaline solution according to the stoichiometric relationship of 1 mol sulfur hexafluoride to no less than 8 mol sodium hydroxide to ensure that all acidic degradation products are completely neutralized and the acidic atmosphere inside the chamber is completely eliminated. This significantly reduces the corrosion and wear of the plasma electrodes, discharge components, and internal components of the chamber by the acidic medium, significantly extends the continuous operating life of the equipment, and reduces maintenance costs and the frequency of component replacement.

[0023] By utilizing a sealed enclosure, the internal atmosphere is controlled, limiting the humidity inside the enclosure to a preset threshold. This suppresses condensation of water vapor on the surface of high-voltage discharge components, avoiding leakage and short-circuit problems in high-humidity environments, and ensuring uniform and continuous plasma discharge. The plasma can discharge stably for a long time without abnormal phenomena such as flickering, arc interruption, or localized arcing. High-voltage components operate safely, the probability of equipment failure is greatly reduced, and it can support long-term continuous operation.

[0024] By limiting three core parameters—the ratio of carrier gas to sulfur hexafluoride, the alkali neutralization equivalent, and the humidity inside the chamber—a standardized and controllable reaction environment is constructed, ensuring that the cracking and neutralization reactions remain within a stable operating range. This results in stable sulfur hexafluoride degradation rates and byproduct neutralization effects, good equipment operational consistency, strong resistance to operating condition fluctuations, and reliable overall processing performance. Attached Figure Description

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a plasma-based sulfur hexafluoride degradation device according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the DBD discharge module according to an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of a microwave plasma source according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the insulating partition mounting structure according to an embodiment of the present invention.

[0030] Figure 5 This is a flowchart of a plasma-based sulfur hexafluoride degradation method according to an embodiment of the present invention.

[0031] Figure 6(a) is a schematic diagram of the degradation detection results of Embodiment 1 of the present invention.

[0032] Figure 6(b) is a schematic diagram of the degradation detection results of Embodiment 2 of the present invention.

[0033] Figure 6(c) is a schematic diagram of the degradation detection results of Embodiment 3 of the present invention.

[0034] Figure 6(d) is a schematic diagram of the degradation detection results of Embodiment 4 of the present invention.

[0035] Figure 6(e) is a schematic diagram of the degradation detection results of Embodiment 5 of the present invention.

[0036] Figure 6(f) is a schematic diagram of the degradation detection results of Embodiment 6 of the present invention.

[0037] The reference numerals in the above figures are as follows: 1. Sealed enclosure; 2. Air inlet; 3. Air outlet; 4. Circulating fan; 5. Temperature and humidity sensor; 6. Insulating container; 7. Magnesium oxide discharge tube; 8. Insulating shell; 9. Microwave generator module; 10. Waveguide; 11. Plasma discharge tube; 12. Insulating partition; 13. Air vent. Detailed Implementation

[0038] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0039] Example 1 like Figures 1-4 As shown, this embodiment provides a plasma-based sulfur hexafluoride degradation device, including: a sealed box 1, a plasma generating device, and a liquid-phase alkaline solution absorption device; an air inlet 2 is provided at the upper part of the sealed box 1, and the plasma generating device is located inside the sealed box 1 and below the air inlet 2; a liquid-phase alkaline solution absorption device and an air outlet 3 are provided at the lower part of the sealed box 1.

[0040] The plasma generator is configured to form a plasma zone by electromagnetic excitation within a sealed enclosure. The mixed gas of carrier gas and sulfur hexafluoride input through inlet 2 is degraded to obtain acidic byproducts, which then react with the alkaline solution in the liquid-phase alkaline absorption device.

[0041] The ratio of carrier gas to sulfur hexafluoride input through inlet 2 is within a preset range to ensure that the reaction rate of acidic byproducts with the liquid-phase alkaline absorption device remains stable within a preset range. The liquid-phase alkaline absorption device is used to hold alkaline solution, and the total neutralization capacity of the alkaline solution meets the neutralization equivalent of not less than 8 mol of sodium hydroxide for 1 mol of sulfur hexafluoride. The internal humidity of the sealed chamber does not exceed a preset humidity threshold to ensure stable plasma discharge.

[0042] The aforementioned plasma-based sulfur hexafluoride (SF6) degradation device is an integrated unit that utilizes gas-phase plasma pyrolysis and in-situ liquid-phase absorption. Its core technology involves using high-energy electrons from plasma to pyrolyze SF6 molecules, while simultaneously neutralizing acidic byproducts such as hydrogen fluoride (HF) and SO2F2 with an alkaline solution within the same sealed chamber. This simultaneous pyrolysis and absorption avoids the problem of excessive flow and transport of acidic byproducts causing corrosion and shortening the lifespan of the system equipment.

[0043] The aforementioned sealed enclosure 1 provides a closed and controllable atmosphere for the entire reaction, preventing the leakage of SF6 and acidic byproducts, while facilitating stable control of humidity, pressure, and temperature. The preferred material is corrosion-resistant stainless steel or polypropylene.

[0044] An air inlet 2 is provided at the top of the sealed enclosure 1, serving as the inlet for the carrier gas and SF6 mixture. Its location at the top of the sealed enclosure 1 ensures that the mixture and ionized active fragments can flow downwards through the plasma zone. Specifically, a gas distributor can be installed to ensure the mixture enters the plasma zone uniformly, preventing excessively high local concentrations.

[0045] The plasma generator is the core reaction unit of the degradation device. Through electromagnetic excitation, such as the action of a high-voltage electric field or microwave, the mixture of carrier gas and SF6 is ionized to form a high-energy plasma region, which is responsible for breaking down stable SF6 molecules into active fragments. The active fragments combine with each other to form acidic byproducts.

[0046] The plasma generator is located below inlet 2. After the mixed gas enters, it first flows through the plasma zone to ensure that all SF6 molecules undergo high-energy cracking. Specifically, multi-stage plasma units can be configured to improve the cracking rate; or a different approach can be used. Figure 2 The multi-tube array DBD structure shown expands the reaction area.

[0047] The aforementioned liquid-phase alkaline solution absorption device is located at the bottom of the tank. It holds the alkaline solution and absorbs HF and SO4 generated by plasma degradation in situ through an acid-base neutralization reaction. 2- Acidic byproducts are treated to achieve harmless disposal.

[0048] Alkaline solutions can be aqueous solutions of alkaline substances such as potassium hydroxide (KOH), sodium hydroxide (NaOH), and magnesium hydroxide (MgOH).

[0049] The sealed chamber 1 is equipped with a liquid-phase alkaline solution absorption device and an outlet 3 at its lower part. The pyrolysis gas and active substances flow downwards, come into contact with the alkaline solution, and are neutralized. The remaining neutral gas after treatment is discharged from the bottom. An exhaust gas filter / online monitoring module can be added to the outlet 3 to detect the residual SF6 concentration. The alkaline solution device can also be equipped with a liquid level sensor to achieve automatic liquid replenishment.

[0050] The aforementioned plasma generator forms a plasma region through electromagnetic excitation and uses a high-voltage electric field or microwave energy to ionize the mixed gas, creating a plasma atmosphere containing high-energy electrons, ions, and free radicals. Specifically, it can be a dual dielectric barrier discharge (DBD) or microwave plasma source.

[0051] During the degradation of the carrier gas mixed with SF6, high-energy electrons collide with SF6 molecules, breaking their chemical bonds and disintegrating stable SF6 into reactive fragments. The carrier gas can be argon (Ar), nitrogen (N2), or dry air, preferably a mixture containing a small amount of oxygen (O2) to promote the generation of reactive free radicals.

[0052] The ratio of carrier gas to SF6 is kept within a preset range to control the SF6 concentration and carrier gas flow rate, avoiding incomplete cracking due to excessively high concentration or affecting processing efficiency due to excessively low concentration. Preferably, the SF6 volume concentration is 1-5 vol%, and the volume ratio of carrier gas to SF6 is 20:1 to 50:1.

[0053] The neutralization equivalent of the alkali solution should be ≥8 mol NaOH / 1 mol SF6 to ensure that the alkali solution has sufficient capacity to neutralize all acidic byproducts and avoid incomplete neutralization that could lead to equipment corrosion or excessive exhaust gas. The concentration of the NaOH aqueous solution should be 5-20 wt%, preferably 10 wt%; the liquid level should be 10-30 mm, and the volume should be ≤1 L.

[0054] It should be noted that the neutralization equivalent is related to different alkaline substances. For aqueous solutions of other alkaline substances, the corresponding alkaline neutralization equivalent can be obtained by conversion. The limitation here is only based on sodium hydroxide as an example to limit the corresponding alkaline neutralization equivalent to ensure neutralization efficiency.

[0055] Maintaining the humidity level inside the chamber within a preset threshold can prevent excessive humidity from causing unstable plasma discharge, electrode corrosion, or creepage short circuits. In this embodiment, the humidity is ≤50% RH, preferably ≤30% RH; closed-loop control can be achieved through the circulating fan 4 and the temperature and humidity sensor 5.

[0056] In practice, first inject a 10wt% NaOH aqueous solution into the liquid-phase alkaline absorption device, controlling the liquid level at 20mm (volume approximately 0.8L, neutralization equivalent ≥8mol NaOH / 1mol SF6); install... Figure 2 The multi-tube array DBD device shown connects the gas inlet of the magnesium oxide discharge tube 7 to the air inlet 2 at the top of the chamber, and maintains a vertical distance of 80mm (>70mm) between the discharge end face and the liquid surface; dry carrier gas is introduced to purge the chamber for 10 minutes to reduce the internal humidity to ≤30% RH.

[0057] SF6 is mixed with argon (Ar) / air carrier gas at a volume ratio of 1:30, resulting in an SF6 concentration of approximately 3 vol%. This mixture is then introduced into the chamber through inlet 2. The DBD high-voltage power supply is turned on, outputting 20 kV / 11 kHz / 0.5 kW, creating a uniform plasma region within the magnesium oxide discharge tube 7. The mixed gas flows downwards through the plasma region, where SF6 is decomposed into SF6 by high-energy electrons. X F - Active fragments; the gas after pyrolysis flows downwards and comes into contact with NaOH alkaline solution, HF, SO42- The acidic byproducts are neutralized into NaF and Na2SO4, and the harmlessly treated gas is discharged from the lower outlet 3.

[0058] Temperature and humidity sensor 5 monitors the humidity inside the chamber in real time. If the RH exceeds 50%, the circulating fan 4 is activated and the humidity of the carrier gas is reduced. The NaOH neutralization equivalent is calculated based on the initial concentration and volume. The pH value of the alkali solution is checked periodically. When the pH drops below 10, the alkali solution is replaced to ensure sufficient neutralization capacity.

[0059] Utilizing high-energy electrons (1-10 eV) from plasma, the strong chemical bonds of SF6 molecules are broken through collisions, achieving efficient pyrolysis. An integrated structure combining gas-phase pyrolysis and in-situ liquid-phase absorption is employed, allowing pyrolysis products to be directly neutralized by the alkaline solution below, preventing leakage and corrosion. A sealed enclosure 1 and humidity control effectively suppress water vapor ionization and condensation on the electrode surfaces, ensuring uniform and stable discharge. By limiting the NaOH neutralization equivalent to ≥8 mol / 1 mol SF6, complete neutralization of all acidic byproducts is ensured, extending equipment lifespan. The gas inlet 2 is located at the top, with the plasma zone situated in the gas path, ensuring that all mixed gas flows through the plasma zone, improving the degradation rate.

[0060] As an optional embodiment, the plasma generator is a microwave plasma source or a dual dielectric barrier discharge plasma device.

[0061] The dual dielectric barrier discharge plasma device (DBD) can adopt a high-voltage discharge structure adapted to mains power, featuring a compact overall structure, rapid start-up and shutdown, and low operating noise. The device consists of a high-voltage power supply, electrode components, and a magnesium oxide dielectric discharge tube / dielectric layer. It relies on the high-voltage electric field to break down the gas, forming a uniform streamer discharge that generates a large number of high-energy electrons and active particles. It is suitable for treating small to medium flow rates of waste gas, mobile on-site equipment, and laboratory conditions, and can operate continuously for extended periods.

[0062] The microwave plasma source consists of a standard 2.45GHz microwave generator module 9, a waveguide 10, and a plasma discharge tube 11. It relies on microwave energy to couple and ionize gas, exhibiting high electron energy, high plasma density, and strong reactivity. It is suitable for applications requiring high concentrations of sulfur hexafluoride waste gas and high pyrolysis depth, with a faster overall reaction rate.

[0063] Both devices work in conjunction with the liquid-phase alkaline absorption device at the bottom of the chamber. The pyrolysis products are uniformly neutralized in situ by sodium hydroxide alkaline solution, and both must meet basic constraints such as chamber humidity control, gas ratio, and alkaline neutralization equivalent.

[0064] As an optional embodiment, the dual dielectric barrier discharge plasma device includes a high-voltage power supply, an electrode assembly, an insulating housing 8, and multiple magnesium oxide discharge tubes 7; the high-voltage power supply inputs AC220V, outputs a high voltage of 20kV, has an adjustable power of 0.1–1kW, and a frequency of 10–12kHz; the magnesium oxide discharge tubes 7 are arranged in parallel inside the insulating housing 8, with both ends fixed to the insulating housing 8, and the tube cavities are interconnected to form gas flow channels; the electrode assembly includes a high-voltage electrode and a grounding electrode, with the high-voltage electrode located inside or outside the magnesium oxide discharge tubes 7, and the grounding electrode located on the inner wall of the insulating housing 8; the tube wall of the magnesium oxide discharge tubes 7 serves as a dual dielectric barrier layer, separating the high-voltage electrode and the grounding electrode to form a discharge gap; a plasma region is formed below the magnesium oxide discharge tubes 7.

[0065] The insulating shell 8 serves as the main supporting structure. Multiple magnesium oxide discharge tubes 7 are arranged in a parallel array inside the insulating shell 8. The two ends of the discharge tubes are sealed and fixed on the insulating shell 8, and the tube cavities are interconnected to form a channel for the flow of mixed gas. The entire discharge unit is installed in the sealed box 1, with the lower end of the discharge tube facing the alkaline liquid surface at the bottom of the box, forming a plasma reaction zone below the discharge tube.

[0066] Multiple magnesium oxide discharge tubes are arranged in parallel to effectively expand the discharge reaction area and increase the gas treatment throughput, which can be matched with sulfur hexafluoride waste gas of different flow rates; the tube cavity is connected to form a regular gas flow channel, allowing the mixed gas to flow evenly through the discharge area, and the mixed gas to fully contact the plasma, avoiding the problems of local gas stagnation and insufficient cracking, and ensuring the overall degradation uniformity.

[0067] Moreover, magnesium oxide is chemically stable and can withstand long-term corrosion from acidic gases such as hydrofluoric acid and sulfuric acid. Unlike quartz and ordinary glass, it does not experience cracking, powdering, or performance degradation, thus significantly extending the service life of discharge components and reducing equipment maintenance and replacement costs.

[0068] The high-voltage electrode is arranged on the inner or outer wall of the magnesium oxide discharge tube 7, and the grounding electrode is fixed on the inner wall of the insulating shell 8. The wall of the magnesium oxide discharge tube 7 serves as a dielectric barrier layer to separate the high-voltage electrode and the grounding electrode, forming a stable discharge gap between them.

[0069] Using the wall of the magnesium oxide discharge tube 7 as a dielectric barrier layer simplifies the equipment structure and eliminates the need for an additional independent dielectric plate. The electrodes are arranged on the discharge tube and the insulating shell 8 respectively, resulting in a compact layout and high space utilization. This design is compatible with the integrated design of the sealed enclosure 1 and avoids direct contact between the electrodes and corrosive gases and water vapor, thus improving structural safety.

[0070] The high-voltage power supply is connected to the civilian AC220V mains power, compatible with general civilian / industrial power supply conditions, and does not require the configuration of dedicated high-voltage power supply equipment. The equipment is simple to install and wire, and is suitable for most application scenarios such as substations, laboratories, and production workshops, reducing the equipment deployment threshold and usage costs.

[0071] It outputs 20kV at a frequency of 10~12kHz. This voltage and frequency combination can form a continuous and uniform streamer discharge within the discharge gap, which not only ensures reliable breakdown and ionization of the gas, but also avoids arc discharge and local overheating caused by excessive voltage, and reduces the generation of toxic byproducts; the 10~12kHz operating range can reduce power supply electromagnetic loss and interference, resulting in higher energy utilization.

[0072] Power adjustable from 0.1 to 1kW, covering small, medium and large waste gas treatment conditions: low power is suitable for laboratory micro-waste gas treatment, medium and high power meet the conventional flow treatment needs of industrial sites; power is continuously adjustable, and can be flexibly matched to the working conditions according to sulfur hexafluoride concentration and gas flow rate to achieve a balance between energy consumption and degradation efficiency.

[0073] The carrier gas and sulfur hexafluoride mixture enter through the inlet 2 and flow sequentially through the cavities of each magnesium oxide discharge tube 7. After the high-voltage power supply is turned on, the electric field between the electrodes breaks down the gas inside the tube to generate uniform streamer discharge, forming a plasma region. The sulfur hexafluoride completes the cracking under the action of high-energy particles, and the cracking products enter the liquid phase alkaline region and are neutralized in situ.

[0074] The plasma zone is located below the magnesium oxide discharge tube 7. The products after pyrolysis can quickly diffuse downwards to the liquid phase alkaline absorption area, and the acidic byproducts are neutralized in time. This shortens the residence time of corrosive gases around the discharge unit, further protecting the electrodes and discharge tube, while completely avoiding secondary pollution.

[0075] As an optional embodiment, the microwave plasma source includes a 2.45 GHz microwave generating module 9, a waveguide 10, and a plasma discharge tube 11; the power of the microwave generating module 9 is adjustable from 0.5 to 3 kW, and the microwave energy is coupled into the sealed box through the waveguide 10 to form a plasma region below the plasma discharge tube 11; the plasma discharge tube 11 is preferably made of magnesium oxide.

[0076] The microwave plasma source consists of three parts: a 2.45GHz microwave generating module 9, a waveguide 10, and a plasma discharge tube 11. These three parts are assembled sequentially and integrated into a sealed enclosure 1. The microwave generating module 9 serves as the energy core, outputting microwave energy at a fixed frequency of 2.45GHz, with the output power continuously adjustable within the range of 0.5~3kW. The microwave energy is directionally conducted through the waveguide 10 and coupled into the plasma discharge tube 11 inside the sealed enclosure 1.

[0077] The 2.45GHz fixed microwave frequency is a standard industrial microwave frequency. The supporting components are mature, the procurement cost is low, the electromagnetic compatibility is good, and it is not likely to interfere with other electrical equipment on site. At the same time, this frequency has a high degree of matching with the gas ionization characteristics, high microwave energy coupling efficiency, and can stably excite high-density plasma to ensure the continuous cracking of sulfur hexafluoride.

[0078] Waveguide 10 enables directional microwave transmission and shielding. On the one hand, it efficiently concentrates microwave energy to the discharge tube area, reducing energy loss and improving energy utilization. On the other hand, it isolates microwave leakage, avoids electromagnetic radiation risks, and improves the safety of equipment use.

[0079] With a wide power range of 0.5~3kW, it can adapt to various application scenarios. Low power (0.5~1kW): suitable for treating small flow and low concentration sulfur hexafluoride waste gas in laboratories, with lower energy consumption; Medium-high power (1~3kW): can treat medium-high flow and high concentration waste gas, significantly improving plasma electron energy and the number of active particles, enhancing the cracking ability of stable sulfur hexafluoride molecules, and further improving the degradation rate; the power is continuously adjustable, and the operating conditions can be flexibly matched according to the waste gas concentration and inlet flow rate to achieve the optimal balance between degradation effect and operating energy consumption.

[0080] The carrier gas and sulfur hexafluoride mixture flow into the plasma discharge tube 11 through the upper inlet 2. Microwave energy ionizes the gas inside the tube, forming a high-energy plasma region below the plasma discharge tube 11, thus completing the sulfur hexafluoride cracking reaction. The plasma discharge tube 11 is preferably made of magnesium oxide, which is suitable for working conditions with fluorine-containing acidic atmospheres due to its corrosion resistance and discharge performance advantages.

[0081] Magnesium oxide can withstand long-term corrosion from acidic gases such as HF and sulfuric acid produced during decomposition. Compared with traditional quartz tubes, it does not suffer from tube wall cracking or corrosion failure, significantly extending the service life of the discharge tube and reducing maintenance costs. Magnesium oxide has a high dielectric constant and secondary electron emission coefficient, which can improve plasma density and uniformity, enhance ionization effect, and achieve better degradation ability under the same microwave power.

[0082] The acidic byproducts produced by pyrolysis diffuse downwards and are neutralized in situ by the sodium hydroxide solution at the bottom, adhering to the constraints of the above-mentioned gas ratio, alkali neutralization equivalent, and humidity control inside the chamber throughout the process.

[0083] The plasma zone is located below the discharge tube, allowing the acidic byproducts after pyrolysis to flow rapidly to the bottom liquid alkaline zone and be neutralized immediately. This not only shortens the residence time of corrosive gases around the discharge tube, protecting core components, but also achieves harmless treatment of the products and eliminates secondary pollution.

[0084] As an optional embodiment, the vertical distance between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline solution absorption device is greater than 70 mm, wherein the discharge end face is the lowest end face of the plasma generation area of ​​the plasma generator.

[0085] The discharge end face specifically refers to the lowest end face of the plasma region, i.e., the lowest position of the high-energy active particle distribution area. During installation and commissioning, ensure that the vertical distance between this discharge end face and the alkaline solution surface inside the liquid phase alkaline solution absorption device is always greater than 70mm.

[0086] The entire plasma generator is installed in the upper part of the sealed box 1, and the alkaline solution is contained in the insulating container 6 at the bottom of the box. After the arrangement is completed, the vertical distance is re-measured to ensure that it is not less than 70mm. When the device is working normally, the gas flows from top to bottom through the plasma zone and then enters the alkaline solution zone to complete the neutralization reaction. The safe distance is maintained throughout the process.

[0087] This size needs to be used in conjunction with conditions such as humidity control inside the enclosure and insulation structure to ensure a stable discharge environment.

[0088] During the degradation of sulfur hexafluoride, the alkaline solution will evaporate and produce water vapor. The flow of carrier gas and airflow disturbances can also easily cause alkaline solution droplets to splash. The high-voltage plasma discharge region is highly sensitive to water vapor and conductive droplets.

[0089] When the distance between the discharge end face and the liquid surface is too small, on the one hand, the splashed droplets are easy to contact the high-voltage discharge components, directly causing creepage, leakage, and short circuit faults; on the other hand, the local humidity above the liquid surface is too high, which will change the dielectric properties of the gas, causing discharge deviation, frequent arcing, and reduced discharge uniformity.

[0090] By strictly controlling the vertical distance to be greater than 70mm, a buffer isolation space can be formed: on the one hand, it prevents alkaline droplets from splashing upwards into the plasma area; on the other hand, it dilutes and disperses the water vapor volatilized from the liquid surface, reduces the local humidity around the discharge end face, and avoids the abnormal discharge problems caused by high humidity and droplets from the spatial structure.

[0091] As an optional embodiment, a perforated insulating partition 12 is provided between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline absorber. The insulating partition 12 is installed on the inner wall of the sealed box 1 and is made of polypropylene or polytetrafluoroethylene with a thickness of 3-5mm. The insulating partition 12 has multiple vent holes 13 with a diameter of 2-3mm, a hole spacing of 10-15mm, and an opening rate of 2%-4%.

[0092] An insulating partition 12 is horizontally mounted on the inner wall of the sealed enclosure 1, located between the plasma discharge end face and the alkaline solution surface, serving as an isolation component between the two stages. It is made entirely of polypropylene or polytetrafluoroethylene, both materials possessing insulating, hydrofluoric acid resistant, and sulfuric acid resistant properties, making it suitable for acidic operating conditions within the device.

[0093] The thickness of the partition is controlled at 3-5mm to balance mechanical structural strength and insulation performance, preventing deformation, breakdown, and leakage due to long-term airflow impact. Circular ventilation holes 13 are evenly distributed on the board surface, with a single hole diameter of 2-3mm and a center-to-center distance of 10-15mm between adjacent holes, maintaining an overall opening rate of 2%-4%.

[0094] Mixed gas, plasma active particles, and acidic byproducts of degradation flow downwards only through vent 13; the baffle prevents alkaline liquid from splashing upwards while not blocking the gas path, and when used in conjunction with a vertical spacing of 70mm or more, it provides double protection for the discharge environment.

[0095] The flow of carrier gas can disturb the surface of the alkaline solution, causing droplet splashing and water vapor to rise; acidic corrosive gases and high humidity environments can threaten the safety and stability of the high-voltage discharge unit.

[0096] Polypropylene / polytetrafluoroethylene is an insulating and corrosion-resistant material. The plate can physically block alkaline droplets from directly impacting the discharge area. The design of low porosity and small-diameter vent holes 13 significantly reduces liquid surface disturbance and inhibits upward diffusion of water vapor while ensuring normal gas flow, thereby reducing local humidity in the discharge area.

[0097] Meanwhile, the partition itself is an insulating component, which will not change the electric field distribution or cause abnormal discharge. Combined with the distance restriction mentioned above, it forms a dual protection structure of spatial distance and physical partition, solving the hidden dangers of high humidity, droplets, corrosion and other hazards.

[0098] As an optional embodiment, the vertical distance between the insulating partition 12 and the liquid surface is 20mm-30mm, and the vertical distance between the insulating partition 12 and the discharge end face is not less than 40mm.

[0099] That is, the vertical distance between the lower surface of the horizontally installed insulating partition 12 and the alkaline liquid surface is controlled at 20mm to 30mm; the vertical distance between the upper surface of the partition and the plasma discharge end face is not less than 40mm.

[0100] During the equipment assembly and commissioning phases, the two distances are precisely calibrated; during the operation of the device, the alkali liquid level remains stable, ensuring that the vertical distance between the baffles is always within the set range, and working together with the baffles' own structure and materials to play a protective role.

[0101] The mixed gas and pyrolysis products in the plasma zone first pass through the buffer space above the partition, then through the vent hole 13, and finally through the area between the partition and the liquid surface, and finally come into full contact with the alkali solution to complete the neutralization reaction.

[0102] Combining the baffle structure and segmented spacing design, the space is functionally divided into zones: the baffle and liquid surface area (20~30mm): serving as a liquid-gas buffer zone, reserving space to accommodate small fluctuations in the liquid surface and minor droplet splashes, while allowing volatile water vapor to diffuse and dilute in this area first, preventing water vapor from rapidly rising into the discharge area. The height of this zone should not be too large, otherwise it will increase the residence time of corrosive gases; nor should it be too small, as it will not be able to accommodate liquid surface disturbances.

[0103] The area between the partition and the discharge end face (≥40mm): As a high-voltage safety isolation zone, the sufficient space is used in conjunction with the insulating partition 12 to completely isolate residual droplets and high-humidity water vapor, preventing them from contacting the high-voltage discharge components; at the same time, it ensures that the high-energy active particles generated by the plasma have sufficient diffusion space, and will not cause electric field distortion or discharge disorder due to the narrow space.

[0104] By using 12 segments of insulating partitions to limit movement, a complete protective system is formed inside the sealed enclosure 1, taking into account core requirements such as splash prevention, humidity control, and stable electric field.

[0105] As an optional embodiment, the alkaline solution is an aqueous sodium hydroxide solution with a mass concentration of 5% to 20%; the liquid level in the liquid phase alkaline solution absorption device is 10 mm to 30 mm, and the volume of the alkaline solution does not exceed 1 L.

[0106] In this embodiment, sodium hydroxide aqueous solution is preferably used as the absorption and neutralization solution. The mass concentration of the sodium hydroxide aqueous solution is strictly controlled between 5% and 20%. Under normal operating conditions, the concentration in the middle range is preferred. Under high load conditions, the concentration can be appropriately increased, and under low load conditions, a low concentration is selected. After the filling is completed, ensure that the height of the alkali solution relative to the bottom of the tank is maintained at 10mm to 30mm to avoid the liquid level being too high or too low.

[0107] The total volume of alkali solution added in a single batch shall not exceed 1L. After adding the alkali solution, the liquid level shall be verified before starting the equipment. When the alkali solution is consumed to the point where the neutralization capacity is insufficient, it shall be replaced with new solution. This set of parameters is linked with the safe distance of the discharge end face and the structure of the insulating partition 12, and together with the humidity control inside the chamber, it ensures stable discharge and sufficient neutralization reaction.

[0108] SF6 degradation ultimately produces two strong acids, HF and H2SO4. Sodium hydroxide is a strong alkaline reagent that can quickly undergo an acid-base neutralization reaction, converting toxic acidic byproducts into harmless salts and achieving in-situ detoxification. At the same time, NaOH aqueous solution is readily available and has a fast reaction rate, making it suitable for continuous waste gas treatment scenarios.

[0109] Based on stoichiometry, 1 mol of SF6 requires 8 mol of NaOH for neutralization. If the concentration is too low, the neutralization capacity of the alkali solution is insufficient, and acidic byproducts cannot be completely absorbed, easily leading to excessive exhaust gas and equipment corrosion. If the concentration is too high, the solution's volatility increases, resulting in more water vapor and alkaline mist inside the chamber, which raises humidity in the discharge area, causing creepage and unstable discharge. Simultaneously, high concentrations of strong alkali exacerbate corrosion of the chamber and components, increasing safety risks during use.

[0110] With a liquid level of 10-30mm and a total volume of ≤1L, the total amount of alkali solution is controlled. This allows for miniaturization and integrated positioning of the device, preventing excessive liquid from increasing its weight and pressure on the tank. On the other hand, limiting the liquid level height, combined with the aforementioned safety distance of over 70mm and the insulating partition 12, reduces the range of droplet splashing caused by airflow disturbance from the source, reduces the amount of water vapor rising, and balances the gas-liquid contact area with high-voltage discharge safety.

[0111] As an optional embodiment, the sealed enclosure 1 is also equipped with a temperature and humidity sensor 5 and a circulating fan 4; the temperature and humidity sensor 5 is used to monitor the temperature and humidity inside the enclosure, ensuring that the temperature does not exceed 50°C and the humidity does not exceed 50% RH; the circulating fan 4 is used to ensure that the gas inside the enclosure flows evenly.

[0112] Temperature and humidity sensor 5 and circulating fan 4 are both fixed inside the sealed enclosure 1. The sensors are arranged at key monitoring points such as the periphery of the plasma area and the middle of the enclosure. The circulating fan 4 is reasonably arranged to ensure uniform gas disturbance throughout the entire area.

[0113] During equipment operation, temperature and humidity sensor 5 collects data from inside the chamber in real time, and manages the operating conditions in a closed loop: internal temperature ≤50℃, relative humidity ≤50%RH; once the threshold is exceeded, an alarm can be triggered or the fan can be activated to strengthen airflow circulation until the parameters return to the qualified range.

[0114] The circulating fan 4 is always on or can be turned on and off according to humidity and temperature data to promote the circulation of air inside the chamber and balance the airflow, temperature and humidity distribution throughout the chamber.

[0115] This monitoring and temperature / humidity control system, together with the alkaline solution system, insulating partition 12, and safety spacing, maintains stable operating conditions inside the chamber, ensuring normal plasma discharge and continuous neutralization reaction.

[0116] As an optional embodiment, the sealed enclosure 1 is grounded, the plasma generator is equipped with overheat protection and overcurrent protection devices; the liquid phase alkali absorption device includes a polypropylene insulating container 6.

[0117] The sealed metal enclosure 1 is reliably connected to the ground to form a safe grounding circuit for the equipment. After the entire machine is assembled, the grounding line is tested for continuity to ensure that the grounding is effective.

[0118] Overheat protection and overcurrent protection devices are integrated into the power supply circuit of the plasma generator. The protection module is linked with the power supply and discharge components to monitor the operating current and component temperature throughout the process.

[0119] The liquid phase alkaline solution absorption device uses a polypropylene insulated container 6, which is placed separately at the bottom of the sealed box 1 to hold sodium hydroxide aqueous solution. The container is isolated from the box, electrodes and other components.

[0120] When the equipment is working normally, the grounding system, protection devices, and insulation container 6 work together. When faults such as abnormal current or overheating of components occur, the protection devices will automatically activate and cut off the power supply to ensure the safety of the equipment and the site.

[0121] Example 2 like Figure 5 As shown, this embodiment provides a plasma-based sulfur hexafluoride degradation method, including: Step S501: Prepare a sodium hydroxide absorbent solution of a set concentration, inject it into a polypropylene insulating container 6, and adjust the vertical distance between the discharge end face of the plasma generator and the liquid surface to be greater than 70 mm. Step S502: Introduce carrier gas to continuously purge the inside of the sealed chamber 1 for 5-10 minutes to replace the residual air and reduce the relative humidity inside the chamber to below 50%RH. Step S503: After the sulfur hexafluoride is mixed evenly with the carrier gas, it is introduced into the box through the air inlet 2 at the top of the sealed box 1. Step S504: Turn on the plasma generator to form a plasma zone, and allow the mixed gas to undergo a degradation reaction in the plasma zone; In step S505, the acidic byproducts generated during degradation are neutralized in situ by the alkali solution in the liquid phase alkali absorption device below. In step S506, the treated gas is discharged from the outlet 3 at the bottom of the sealed box 1.

[0122] Pre-prepared sodium hydroxide absorbent solution and proper installation and calibration of the distance between the discharge end face and the liquid surface (>70mm) are ensured. Relying on physical distance and polypropylene insulating container 6, the alkaline solution is prevented from contacting high-voltage components from the source, thus preventing creepage, short circuits and leakage.

[0123] Carrier gas is introduced in advance to purge the sealed chamber 1, replace the internal air and control the humidity to within 50% RH, eliminate the interference of water vapor and impurities on plasma discharge, and create a stable ionization environment.

[0124] Sulfur hexafluoride is mixed with the carrier gas and enters the plasma region from top to bottom. It is cracked by breaking stable molecular bonds with high-energy particles. The generated acidic byproducts such as hydrofluoric acid and sulfuric acid are directly neutralized in situ by the bottom alkaline solution, avoiding the diffusion of corrosive and toxic gases.

[0125] The entire process involves continuous pyrolysis, neutralization, and venting within a sealed enclosure, achieving a closed-loop process.

[0126] As an optional embodiment, the carrier gas is selected from one or more of the following mixed gases: argon, nitrogen, and dry air; the carrier gas also contains 10%-30% oxygen by volume, and the volume ratio of argon to air is 3:1 to 5:1.

[0127] Argon, nitrogen, and dry air are selected as carrier gases. Inert gases are used to stabilize the airflow and protect the discharge components. Adding 10% to 30% oxygen can generate highly oxidizing active groups in the plasma environment, which can help break the chemical bonds of sulfur hexafluoride and promote the complete oxidation and decomposition of intermediates. The volume ratio of argon to air is limited to 3:1 to 5:1 to precisely control the oxygen content ratio, which ensures that the oxidation reaction is sufficient and avoids that the oxygen content is too high, which may change the discharge characteristics and cause plasma instability.

[0128] As an optional embodiment, after the reaction is complete, the plasma power supply is turned off first, and the carrier gas is continued to purge the sealed chamber for 110-20 minutes to remove residual gas.

[0129] After the reaction is completed, the power is cut off first, and then the carrier gas is continuously purged for 10-20 minutes: After the plasma stops working, unreacted sulfur hexafluoride and acidic toxic products remain in the chamber. With the help of forced replacement by carrier gas, all the residual harmful gases in the sealed chamber 1 are carried out and absorbed by alkaline solution, so as to avoid gas retention and corrosion of equipment, and at the same time prevent toxic gases from leaking out when the cover is opened for maintenance.

[0130] As an optional embodiment, the residual sulfur hexafluoride concentration at the outlet 3 is monitored using a Fourier transform infrared spectrometer.

[0131] Fourier transform infrared spectroscopy (FTIR) is used to detect the gas at outlet 3 in real time. By utilizing the characteristic infrared absorption peak of sulfur hexafluoride, the residual concentration in the tail gas can be accurately quantified, and the degradation reaction can be directly judged to determine whether it meets the standard, and problems such as decreased degradation efficiency and abnormal operating conditions can be detected in a timely manner.

[0132] Example 3 This embodiment discloses a plasma-based sulfur hexafluoride (SF6) waste gas degradation system and method, belonging to the field of waste gas treatment technology. It addresses the problems of low energy efficiency and the easy generation of toxic fluorine-containing byproducts in existing gas-phase plasma degradation of SF6.

[0133] This embodiment proposes to pass sulfur hexafluoride into a closed reactor containing an alkaline absorbent solution of sodium hydroxide. High-energy active particles are excited using microwave plasma or dual-dielectric barrier discharge plasma to degrade the sulfur hexafluoride, with byproducts absorbed by the alkaline solution. This embodiment has advantages such as high degradation efficiency, no secondary pollution, minimal equipment corrosion, and long-term stable operation, making it suitable for the treatment of sulfur hexafluoride waste gas.

[0134] The system includes a sealed reaction chamber 1, a plasma generator, and a liquid-phase absorption system located at the bottom of the chamber. The top of the chamber has an interface for the plasma generator, the sides have an inlet 2 and an outlet 3, and the bottom has an insulating container 6.

[0135] There are two independent implementation methods for the plasma generator: one is a microwave plasma source with a working frequency of 2.45 GHz and an adjustable power of 0.5~3 kW; the other is a dual dielectric barrier discharge unit, which uses a dual dielectric plasma generator with a working voltage of AC 220V, an output voltage of 20 kV, an adjustable power of 0.1-1kW, a frequency of 10-12 kHz, and a discharge tube made of magnesium oxide, with the discharge tube maintaining a distance from the liquid surface.

[0136] The liquid absorption system is located in an insulating container 6 at the bottom of the chamber, containing a 5%-20% sodium hydroxide aqueous solution, with the liquid level approximately 20 mm high. The air inlet 2 is located at the top of the chamber; the air outlet 3 is located below the right side wall of the chamber, 80 mm from the bottom.

[0137] This embodiment is based on the following chemical reaction principle: SF6 first decomposes under the influence of high-energy electrons in plasma: SF6+e - →SF5+F+e - (1) Further pyrolysis produces intermediates such as SF4 and SF2, which are eventually completely oxidized in the presence of oxygen and water. SF6 + 3H2O → SO3 + 6HF (2) SO3 + H2O → H2SO4 (3) Overall reaction: SF6 + 4H2O → H2SO4 + 6HF (4) The generated HF and H2SO4 then neutralize with NaOH: HF + NaOH → NaF + H2O (5) H2SO4+2NaOH→Na2SO4+2H2O (6) As shown in reaction formula (4), the complete degradation of 1 mol SF6 requires the consumption of 4 mol H2O, producing 6 mol HF and 1 mol H2SO4. According to the law of conservation of atoms, neutralizing 6 mol HF requires 6 mol NaOH, and neutralizing 1 mol H2SO4 requires 2 mol NaOH, for a total of 8 mol NaOH. Therefore, theoretically, the degradation of 1 mol SF6 requires the consumption of 8 mol NaOH. If the volume of the absorbent is V (L) and the NaOH concentration is C (mol / L), then the maximum amount of SF6 that can be treated is CV / 8 (mol). This embodiment designs the initial concentration and volume of the alkali solution based on this precise stoichiometric relationship to ensure that the absorbent solution is not wasted or saturated prematurely.

[0138] To ensure stable operation of the device over a long period and to guarantee discharge safety, this embodiment establishes the following parameter control ranges: The volume of the NaOH solution contained in the insulating container 6 shall not exceed 1L, and the liquid level shall not exceed 30mm; the concentration of the NaOH solution shall be 5%-20%, preferably 10%.

[0139] Temperature and humidity sensors are installed on the inner wall of the sealed chamber 1 to monitor the reaction environment parameters in real time. The temperature sensor has a monitoring range of -30℃ to +100℃, and the humidity sensor has a monitoring range of 0%-100%RH. The relative humidity of the gas inside the sealed chamber 1 is controlled at ≤50%, preferably ≤30%, and the temperature needs to be controlled below 50 degrees Celsius.

[0140] The above parameter ranges are set based on the following principles: excessive humidity and excessive alkali solution will increase the risk of creepage and short circuit; the monitoring range of the temperature sensor and humidity sensor must cover the entire range of normal operation and abnormal alarm of the device to ensure timely detection and handling of abnormal operating conditions.

[0141] The plasma degradation method for sulfur hexafluoride in this embodiment includes the following steps: Prepare a sodium hydroxide absorbent solution of a set concentration and inject it into the insulating container 6 at the bottom of the reactor. Accurately calibrate the liquid level and adjust the vertical distance between the end face of the discharge unit and the liquid surface to ensure that the distance is greater than 70 mm to prevent the influence of liquid phase disturbance on discharge stability.

[0142] The reaction chamber 1 is sealed, and a carrier gas is continuously introduced into the system through the air inlet 2. The carrier gas is selected from argon, nitrogen, dry air, or a mixture of two to three of these components. The inside of the sealed chamber 1 is continuously purged for 5 to 10 minutes to replace the residual air and establish a controllable atmosphere. At the same time, the relative humidity inside the sealed chamber 1 is monitored. After it stabilizes, the next step is performed.

[0143] Turn on the plasma power supply and gradually adjust the output power to 0.1~3 kW to generate a uniform and stable plasma region from the microwave plasma source or the dual dielectric barrier discharge unit. A high-energy active atmosphere is formed between the discharge end face and the liquid surface, and characteristic glow or uniform streamer discharge phenomenon is observed near the discharge tube.

[0144] After the sulfur hexafluoride gas is mixed evenly with the carrier gas, it is introduced into the sealed chamber 1. The sulfur hexafluoride undergoes efficient dissociation and oxidation reactions in the high-energy electron region of the plasma, and the generated acidic byproducts (hydrofluoric acid and sulfuric acid) are immediately captured and neutralized in situ by the alkaline absorbent liquid at the liquid surface.

[0145] The treated exhaust gas is discharged through outlet 3, and the residual sulfur hexafluoride concentration can be monitored using a Fourier transform infrared spectrometer. After the reaction is complete, the plasma power supply is first turned off, and the sealed chamber is continuously purged with carrier gas for 110-20 minutes to remove residual gas.

[0146] To demonstrate the technical effectiveness of this embodiment, six other implementation methods are provided for comparison. Details are as follows: Implementation method 1 uses microwave plasma + argon carrier gas + quartz discharge tube.

[0147] This embodiment 1 uses a microwave plasma device with a microwave frequency of 2.45 GHz and an output power that is continuously adjustable from 0 to 1000 W. The discharge tube is made of quartz, with an outer diameter of 20 mm and an inner diameter of 16 mm. The reaction sealed chamber 1 is made of polypropylene, with internal dimensions of 300 mm in length, 200 mm in width, and 250 mm in height. A polypropylene box containing 500 mL of 0.5 mol / L sodium hydroxide solution is placed at the bottom of the sealed chamber 1. The lower end of the discharge tube is 120 mm above the liquid surface. Pure argon is used as the carrier gas at a flow rate of 1.5 L / min. Before the experiment, the sealed chamber is purged with carrier gas for 110 minutes to reduce the internal relative humidity to below 50%. The microwave power supply is turned on, and the power is adjusted to 800 W. After the discharge stabilizes, 0.01 mol of pure sulfur hexafluoride gas is injected through the gas inlet 2 using a gas-tight syringe. After 30 minutes of treatment, the residual SF6 concentration in the exhaust gas was detected by FTIR, and the degradation rate was calculated to be 78.2%. The FTIR image is shown in Figure 6(a). A small amount of SO2 was also detected in the exhaust gas.

[0148] Implementation method 2 uses microwave plasma + air carrier gas + quartz discharge tube.

[0149] The difference between Embodiment 2 and Embodiment 1 is that the carrier gas is changed from pure argon to air, with a flow rate maintained at 1.5 L / min. All other conditions remain the same. After 30 min of treatment, FTIR analysis showed that the SF6 degradation rate in the exhaust gas was 84.5%, as shown in Figure 6(b). The results indicate that oxygen in the air participates in the reaction, promoting the oxidative decomposition of sulfur hexafluoride, and the degradation efficiency is improved compared to the pure argon condition.

[0150] Implementation method 3 uses microwave plasma + argon carrier gas + magnesium oxide discharge tube 7.

[0151] The difference between Embodiment 3 and Embodiment 1 is that the quartz discharge tube is replaced with a magnesium oxide discharge tube 7. All other conditions remain the same. After 30 minutes of treatment, FTIR analysis showed an SF6 degradation rate of 92.3%, as shown in Figure 6(c). The SO2 concentration in the exhaust gas was approximately 30 ppm, and the HF concentration was approximately 15 ppm. The degradation rate is improved compared to Embodiment 1. Analysis suggests that the magnesium oxide coating has a high secondary electron emission coefficient, enhancing plasma density and the yield of active species. Simultaneously, magnesium oxide itself participates in the fluorine fixation reaction, reducing the escape of hydrogen fluoride gas.

[0152] Implementation method 4 uses dielectric barrier discharge + magnesium oxide discharge tube 7 + argon carrier gas.

[0153] This embodiment 4 uses a flat-plate dielectric barrier discharge module with a discharge area of ​​200mm × 100mm. The discharge dielectric layer is a magnesium oxide ceramic plate with a thickness of 2mm and a dielectric constant of 10.5. The discharge gap between the high-voltage electrode and the ground electrode is 4mm. The reaction sealing chamber 1 is the same as in Example 1. A polypropylene box containing 800mL of 0.4mol / L sodium hydroxide solution is placed at the bottom. The discharge module is 120mm above the liquid surface. Pure argon is used as the carrier gas with a flow rate of 2L / min. The high-voltage power supply parameters are: peak-to-peak output voltage 18kV, frequency 11kHz, and output power 1.2kW. 0.02mol of pure sulfur hexafluoride gas is injected using a syringe. After 30min of treatment, the FTIR detection showed that the SF6 degradation rate was 88.2%, and the FTIR image is shown in Figure 6(d).

[0154] Implementation method 5 uses dielectric barrier discharge + quartz discharge tube + argon carrier gas.

[0155] In Embodiment 5, the fixed dielectric barrier discharge conditions are the same as in Embodiment 4, using a common glass discharge tube and all other conditions being identical: argon carrier gas, injection of 0.02 mol of sulfur hexafluoride, and treatment for 30 minutes. The experimental results are as follows: the degradation rate of the common glass discharge tube was 73.5%, as shown in Figure 6(e). The degradation rate of the magnesium oxide discharge tube 7 was significantly higher than that of the glass tube. Analysis suggests that magnesium oxide, with its high dielectric constant (9.6–11.2) and high secondary electron emission coefficient, can significantly reduce the discharge initiation voltage (measured reduction of approximately 30%) and increase the plasma density (measured increase of approximately 2 times), thereby enhancing the cracking efficiency of sulfur hexafluoride.

[0156] Implementation method 6 uses dielectric barrier discharge + magnesium oxide discharge tube 7 + argon and air mixed carrier gas.

[0157] This embodiment 6 aims to investigate the effect of carrier gas composition on degradation efficiency. The dielectric barrier discharge conditions were the same as in embodiment 4 (magnesium oxide discharge tube 7), and a mixture of argon and air at a volume ratio of 4:1 was introduced. 0.02 mol of sulfur hexafluoride was injected, and the treatment lasted for 30 minutes. The experimental results are as follows: the degradation rate under the argon / air mixed gas condition was 94.5%, as shown in Figure 6(f), which is significantly higher than that under pure argon. The results indicate that adding an appropriate amount of air can significantly improve the degradation efficiency.

[0158] It should be noted that the term "comprising" and its variations used in the embodiments of the present invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of the present invention are illustrative and not restrictive, and those skilled in the art should understand that unless explicitly indicated otherwise in the context, they should be understood as "one or more".

[0159] The steps described in the method embodiments provided by the present invention can be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0160] The term "embodiment" in this specification refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply independence or alternativeity from other embodiments. The various embodiments in this specification are described in a related manner, with reference to each other for similar or identical parts. In particular, for apparatus, device, and system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, and relevant details are referred to in the description of the method embodiments.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A plasma-based sulfur hexafluoride degradation device, characterized in that, include: Sealed enclosure, plasma generator, and liquid-phase alkaline solution absorption device; An air inlet is provided at the upper part of the sealed box, and the plasma generator is located inside the sealed box and below the air inlet; The lower part of the sealed box is equipped with a liquid phase alkaline solution absorption device and an air outlet. The plasma generator is configured to form a plasma region by electromagnetic excitation within the sealed enclosure, and to degrade the mixed gas of carrier gas and sulfur hexafluoride input through the inlet to obtain acidic byproducts, which then react with the alkaline solution of the liquid-phase alkaline absorption device. The ratio of the carrier gas input through the air inlet to the sulfur hexafluoride is within a preset range, so that the reaction rate of the acidic byproduct with the liquid-phase alkaline solution absorption device is stabilized within a preset range. The liquid-phase alkaline solution absorption device is used to hold alkaline solution, and the total neutralization capacity of the alkaline solution meets the neutralization equivalent of not less than 8 mol of sodium hydroxide for 1 mol of sulfur hexafluoride. The internal humidity of the sealed enclosure does not exceed a preset humidity threshold to ensure stable plasma discharge. The plasma generating device is a microwave plasma source or a dual dielectric barrier discharge plasma device. The dual dielectric barrier discharge plasma device includes a high-voltage power supply, electrode assembly, insulating shell, and multiple magnesium oxide discharge tubes. The microwave plasma source includes a 2.45GHz microwave generating module, a waveguide, and a plasma discharge tube; the plasma discharge tube is made of magnesium oxide. A perforated insulating partition is also provided between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline solution absorption device. The vertical distance between the discharge end face of the plasma generator and the liquid surface of the liquid phase alkaline solution absorption device is greater than 70 mm, wherein the discharge end face is the lowest end face of the plasma generation area of ​​the plasma generator.

2. The apparatus according to claim 1, characterized in that, The high-voltage power supply has an input of AC220V, an output of 20kV, adjustable power of 0.1–1kW, and a frequency of 10–12kHz. The magnesium oxide discharge tubes are arranged in parallel inside the insulating shell, with both ends fixed to the insulating shell, and the tube cavity is through to form a gas flow channel; The electrode assembly includes a high-voltage electrode and a grounding electrode. The high-voltage electrode is located inside the magnesium oxide discharge tube, and the grounding electrode is located on the inner wall of the insulating shell. The tube wall of the magnesium oxide discharge tube serves as a double dielectric barrier layer, separating the high-voltage electrode and the grounding electrode to form a discharge gap. The plasma region is formed below the magnesium oxide discharge tube.

3. The apparatus according to claim 1, characterized in that, The power of the microwave generator module is adjustable from 0.5 to 3 kW. The microwave energy is coupled into the sealed box through the waveguide to form the plasma region below the plasma discharge tube.

4. The apparatus according to claim 1, characterized in that, The insulating partition is installed on the inner wall of the sealed box and is made of polypropylene or polytetrafluoroethylene with a thickness of 3-5mm. The insulating partition has multiple vent holes with a diameter of 2-3 mm, a spacing of 10-15 mm, and an opening rate of 2%-4%.

5. The apparatus according to claim 4, characterized in that, The vertical distance between the insulating partition and the liquid surface is 20mm-30mm, and the vertical distance between the insulating partition and the discharge end face is not less than 40mm.

6. The apparatus according to claim 1, characterized in that, The alkaline solution is an aqueous solution of sodium hydroxide; The liquid level in the liquid phase alkali absorption device is 10mm to 30mm, and the volume of the alkali solution does not exceed 1L.

7. The apparatus according to claim 1, characterized in that, The sealed enclosure is also equipped with a temperature and humidity sensor and a circulating fan; The temperature and humidity sensor is used to monitor the temperature and humidity inside the chamber, ensuring that the temperature does not exceed 50℃ and the humidity does not exceed 50% RH; the circulating fan is used to ensure that the gas inside the chamber flows evenly.

8. The apparatus according to claim 1, characterized in that, The sealed enclosure is grounded, and the plasma generator is equipped with overheat protection and overcurrent protection devices; the liquid phase alkali absorption device includes a polypropylene insulating container.

9. A plasma-based method for the degradation of sulfur hexafluoride, characterized in that, Applied to a plasma-based sulfur hexafluoride degradation apparatus as described in any one of claims 1 to 8, the method comprises: Prepare a sodium hydroxide absorbent solution of a set concentration, inject it into a polypropylene insulating container, and adjust the vertical distance between the discharge end face of the plasma generator and the liquid surface to be greater than 70 mm. Introduce carrier gas to continuously purge the inside of the sealed chamber for 5-10 minutes to replace the residual air and reduce the relative humidity inside the chamber to below 50%RH. After the sulfur hexafluoride is mixed evenly with the carrier gas, it is introduced into the box through the air inlet at the top of the sealed box. Turn on the plasma generator to form a plasma zone, and allow the mixed gas to undergo a degradation reaction in the plasma zone; The acidic byproducts generated during degradation are neutralized in situ by the alkali solution in the liquid phase alkali absorption device below; The treated gas is discharged from the outlet at the bottom of the sealed chamber.

10. The method according to claim 9, characterized in that, The carrier gas is selected from one or more of the following: argon, nitrogen, and dry air.

11. The method according to claim 9, characterized in that, After the reaction is complete, first turn off the plasma power supply, then continue to purge the sealed chamber with carrier gas for 10-20 minutes to remove residual gas.

12. The method according to claim 9, characterized in that, The residual sulfur hexafluoride concentration at the outlet was monitored using Fourier transform infrared spectroscopy.

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