Self-sustained plasma-based sulfur hexafluoride degradation apparatus and method

Abstract

The present application relates to the technical field of SF6 degradation, and specifically provides a self-sustaining plasma-based sulfur hexafluoride degradation device and method, which comprises a sealed box, a plasma generation unit and a liquid-phase lye absorption device; the sealed box is filled with a constant amount of starting gas at normal pressure; the upper part of the sealed box is provided with an air inlet for inputting mixed gas with a molar ratio of water vapor to sulfur hexafluoride gas of 3:1; the plasma generation unit is arranged in the sealed box and located below the air inlet, and is used for plasmaizing the mixed gas to obtain acid cracking products; the acid cracking products react with lye in the liquid-phase lye absorption device; the lye absorption device is arranged at the lower part of the sealed box and is used for containing lye. The problems that the sulfur hexafluoride degradation device in the related art needs to continuously consume protective carrier gas, the discharge dithering arc extinguishing caused by the air pressure fluctuation of the sealed box, and the device cannot be continuously and stably operated for a long time are solved.

Description

Technical Field

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

[0002] Sulfur hexafluoride (SF6) is a highly stable synthetic specialty gas with excellent insulation and arc-quenching properties. It is widely used in industrial fields such as high-voltage power equipment, semiconductor etching, and precision metallurgy.

[0003] Currently, the mainstream SF6 waste gas treatment technologies in the industry mainly include high-temperature pyrolysis, catalytic degradation, and conventional plasma decomposition. Among them, the traditional high-temperature pyrolysis method has extremely high energy consumption, requires a high-temperature environment of over 1200℃, and has high equipment wear and tear and high operating costs; the catalytic degradation method is prone to catalyst poisoning and failure due to impurities in the waste gas, resulting in poor degradation stability and high maintenance costs; existing plasma treatment technologies mostly operate in a low-pressure vacuum environment, with complex equipment structures, stringent airtightness requirements, and generally require continuous introduction of protective gas and carrier gas to maintain the plasma discharge state, resulting in large gas consumption and cumbersome operating procedures throughout the process.

[0004] Meanwhile, existing technologies generally suffer from uncontrollable reaction ratios, and incomplete SF6 degradation easily generates various toxic byproducts containing fluorine and sulfur. Furthermore, the absorption and treatment processes for these byproducts are cumbersome and prone to causing secondary pollution. Current technologies cannot achieve low-cost, high-efficiency, harmless degradation of SF6 under normal pressure without continuous gas maintenance, exhibiting significant technological shortcomings and failing to meet the demands of large-scale industrial application. Summary of the Invention

[0005] The present invention provides a self-sustaining 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 self-sustaining plasma-based sulfur hexafluoride (SF6) degradation device, comprising: a sealed chamber, a plasma generating unit, and a liquid-phase alkaline solution absorption device; the sealed chamber is filled with a constant amount of ignition gas at atmospheric pressure, and an air inlet is provided at the upper part of the sealed chamber for inputting a mixture of SF6 gas and water vapor in a preset ratio, wherein the preset ratio is a molar ratio of water vapor to SF6 gas of 3:1; the plasma generating unit is located inside the sealed chamber and below the air inlet, and is configured to plasma-encode the mixture to obtain acidic pyrolysis products, which react with the alkaline solution of the liquid-phase alkaline solution absorption device; the alkaline solution absorption device is located at the lower part of the sealed chamber and is used to hold the alkaline solution.

[0007] As an optional solution, the ignition gas is argon, which is pre-filled into the sealed enclosure to maintain the continuous operation of the plasma generating unit.

[0008] As an optional solution, an argon gas inlet is also included, which is located on the upper part of the sealed housing and below the plasma generating unit.

[0009] As an alternative, an argon recovery device is also included, which is configured to extract argon gas through the argon inlet for purification and recovery when the degradation device is shut down.

[0010] As an optional solution, a waste heat vaporization device is also included, which includes a vaporization chamber and a water storage chamber. The vaporization chamber is connected to the water storage chamber and is disposed on the outer surface of the upper part of the sealed box and connected to the air inlet. It is configured to use the waste heat generated by the plasma generating unit to vaporize the liquid water flowing into the water storage chamber to obtain water vapor, which is then transmitted to the air inlet.

[0011] As an optional solution, a flow control valve is also provided between the vaporization chamber and the air inlet; the flow control valve is configured to output water vapor with a corresponding molar mass of 3 times the molar mass of the sulfur hexafluoride gas input into the air inlet.

[0012] As an optional solution, the plasma generating unit is located on the top of the sealed enclosure. The plasma generating unit is a normal pressure microwave plasma generating unit, a normal pressure dielectric barrier discharge plasma generating unit, or a normal pressure radio frequency plasma generating unit.

[0013] As an optional solution, the main frequency of the atmospheric pressure microwave plasma generating unit is 2.45 GHz, and the power is 0.5~3 kW; and / or, the input voltage of the atmospheric pressure dielectric barrier discharge plasma generating unit is AC220V, the output voltage is 20kV, the power is 0.1~1 kW, and the frequency is 10~12 kHz; and / or, the frequency of the atmospheric pressure radio frequency plasma generating unit is 13.56 MHz, the power is 0~50W, and the voltage is 7~11kV.

[0014] As an optional solution, the vertical distance between the discharge end face of the plasma generating unit and the liquid surface of the liquid phase alkaline solution absorption device is 5-20 mm, wherein the discharge end face is the lowest end face of the plasma generating region of the plasma generating unit.

[0015] 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.

[0016] As an optional solution, a temperature and humidity sensor is also installed inside the sealed enclosure; 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.

[0017] This invention also provides a self-sustaining plasma-based sulfur hexafluoride degradation method, comprising: after verifying the airtightness of the sealed chamber, introducing argon gas to ignite the plasma generating unit once and then shutting off the argon gas; mixing water vapor and sulfur hexafluoride gas at a molar ratio of 3:1 and then introducing the mixture into the plasma generating unit through the inlet; performing plasma pyrolysis on the sulfur hexafluoride gas through the plasma generating unit to generate acidic pyrolysis products, which fall into the bottom alkaline solution for neutralization; continuously introducing water vapor and sulfur hexafluoride gas, relying on the constant amount of argon gas in the sealed chamber for self-sustaining discharge, and continuously and stably degrading the sulfur hexafluoride.

[0018] As an optional approach, the method further includes: using the waste heat generated by plasma pyrolysis to heat the water body in situ to generate water vapor; and transferring the water vapor to the air inlet as the water vapor source for the air inlet.

[0019] As an optional approach, the method further includes: shutting down the plasma generating unit after the sulfur hexafluoride gas is stopped; and extracting and purifying argon gas through the argon gas inlet.

[0020] As an optional approach, the method further includes: real-time monitoring of the temperature and humidity inside the sealed enclosure; issuing an alarm when the temperature exceeds 50°C and / or the humidity exceeds 50%, and automatically controlling the introduction of sulfur hexafluoride gas and the shutdown of the plasma generating unit.

[0021] The self-sustaining plasma-based sulfur hexafluoride (SF6) degradation device provided by this invention adopts an atmospheric pressure, sealed, integrated, layered structure. It uses a constant amount of argon gas within a sealed chamber as an ionization substrate to achieve self-sustaining discharge. A precise 3:1 water vapor to SF6 stoichiometric ratio ensures complete pyrolysis. A top-down flow field allows acidic products to rapidly settle to the bottom for in-situ neutralization with alkaline solution. The entire process is sealed without continuous carrier gas supply or external exhaust gas treatment, achieving continuous degradation at atmospheric pressure, with low material consumption and no secondary pollution. It operates at atmospheric pressure, requiring no vacuum equipment; requires only a one-time argon purging, eliminating continuous gas consumables; degrades SF6 completely, leaving no toxic intermediates; integrates pyrolysis and neutralization, preventing secondary pollution; and provides long-term stable plasma discharge, enabling continuous industrial operation. This overcomes multiple shortcomings of existing SF6 treatment technologies, such as complex vacuum equipment, continuous carrier gas consumption, uncontrolled water vapor ratio leading to incomplete degradation, cumbersome byproduct handling resulting in secondary pollution, and unstable discharge preventing long-term continuous operation. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a schematic diagram of a self-sustaining plasma-based sulfur hexafluoride degradation device according to an embodiment of the present invention.

[0024] Figure 2 This is a flowchart of a self-sustaining plasma-based sulfur hexafluoride degradation method according to an embodiment of the present invention.

[0025] Figure 3(a) is a schematic diagram of the degradation detection results of Embodiment 1 of the present invention.

[0026] Figure 3(b) is a schematic diagram of the degradation detection results of Embodiment 2 of the present invention.

[0027] Figure 3(c) is a schematic diagram of the degradation detection results of Embodiment 3 of the present invention.

[0028] The reference numerals in the above figures are as follows: 1. Sealed enclosure; 2. Air inlet; 3. Argon gas inlet; 4. Plasma generation unit; 5. Alkali solution. Detailed Implementation

[0029] 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.

[0030] Example 1 like Figure 1 As shown, this embodiment provides a self-sustaining plasma-based sulfur hexafluoride degradation device, including: a sealed box 1, a plasma generating unit, and a liquid-phase alkaline solution absorption device; the sealed box is filled with a constant amount of ignition gas at atmospheric pressure, and an air inlet 2 is provided at the upper part of the sealed box for inputting a mixture of sulfur hexafluoride gas and water vapor in a preset ratio, wherein the preset ratio is a molar ratio of water vapor to sulfur hexafluoride gas of 3:1; the plasma generating unit 4 is located in the sealed box and below the air inlet, and is configured to plasma-encode the mixture to obtain acidic pyrolysis products, which react with the alkaline solution 5 of the liquid-phase alkaline solution absorption device; the alkaline solution absorption device is located at the lower part of the sealed box, and the alkaline solution 5 absorption device is used to hold the alkaline solution.

[0031] The aforementioned sealed chamber 1 can be a completely sealed reaction chamber that maintains a normal pressure sealed atmosphere, with no continuous gas venting / leakage channels. The internal pressure is maintained at standard normal pressure, eliminating the need for a vacuum unit. The internal pressure of the sealed chamber is equivalent to the external pressure, without vacuuming or high-pressure pressurization, unlike traditional vacuum plasma equipment.

[0032] Only plasma generation unit 4 is charged with a fixed amount of inert ignition gas during the startup phase. The total amount of ignition gas remains constant throughout the entire operation, is not consumed, and is not continuously replenished. Its function is to excite the plasma to ignite and ionize. The aforementioned ignition gas can be argon, nitrogen, etc.

[0033] The aforementioned plasma generating unit is a device capable of generating atmospheric pressure plasma, comprising three types of generators: microwave, dielectric barrier, and radio frequency, which rely on high-energy ionization to decompose SF6.

[0034] The aforementioned liquid-phase alkaline absorption device can be a container arranged at the bottom of a sealed box and filled with an alkaline aqueous solution, used to capture and neutralize the acidic gases generated by pyrolysis.

[0035] The acidic pyrolysis products generated by the complete reaction of SF6 and water vapor with plasma include two acidic gases: sulfur trioxide (SO3) and hydrogen fluoride (HF).

[0036] The molar ratio of water vapor to sulfur hexafluoride gas is 3:1, which is the theoretical stoichiometric ratio for the complete hydrolysis and degradation of SF6.

[0037] The aforementioned device consists of a sealed enclosure, a plasma generation unit, and a liquid-phase alkaline absorption device. It integrates plasma pyrolysis and tail gas neutralization absorption functions within the same sealed enclosure, forming a complete set of equipment. The pyrolysis reaction and acid-base neutralization are completed continuously within the same sealed space, and the gas flows downwards due to gravity, eliminating the need for an external tail gas treatment tower.

[0038] The equipment features high integration, a compact structure, and a small footprint, simplifying the entire process and reducing the need for auxiliary piping and equipment. It solves the problems of traditional plasma equipment that require multiple stages of spraying and adsorption towers, complex piping, and a large footprint due to the separation of the pyrolysis and tail gas absorption sections.

[0039] The aforementioned sealed chamber operates at atmospheric pressure and is filled with a constant amount of ignition gas. It operates entirely at atmospheric pressure, with a fixed amount of ignition argon gas pre-filled into the chamber. No additional gas is added during operation, and the total gas volume remains constant. This eliminates the need for a vacuum unit to create negative pressure, reducing the difficulty of sealing the equipment. Argon gas is chemically inert, does not participate in reactions, and is insoluble in alkaline solutions, continuously providing an ionization substrate for the sealed chamber. Plasma glow can be maintained long-term solely by the fixed argon gas within the sealed chamber, without the need for a continuous carrier gas supply.

[0040] Compared to traditional technologies, this method eliminates the need for a vacuum unit, reducing equipment manufacturing costs and airtightness maintenance requirements. Furthermore, the absence of continuous carrier gas consumption significantly lowers gas consumable operating costs. The stable gaseous environment within the sealed enclosure provides a foundation for long-term self-sustaining plasma discharge. This addresses the problems of existing plasma degradation equipment, which mostly operates under vacuum conditions, resulting in high costs and stringent sealing requirements for vacuum units; and the need for continuous argon / air carrier gas to maintain discharge, leading to high gas consumption and cumbersome maintenance procedures.

[0041] An air inlet is located at the top of the chamber, through which a mixture of water vapor and SF6 in a 3:1 molar ratio is introduced. This mixture is fed in from the top of the sealed chamber, with strict control over the molar ratio of water vapor and SF6. This ensures complete degradation of the main reaction under plasma conditions: SF6 + 3H2O (atmospheric pressure plasma) = SO3 + 6HF. 1 mol of SF6 consumes exactly 3 mol of water molecules. Achieving the correct ratio ensures complete breaking of the chemical bonds in SF6, preventing the formation of toxic intermediate byproducts such as SOF2 and SO2F2 due to insufficient water vapor.

[0042] This method ensures complete SF6 degradation, achieving a degradation rate close to 100%, with no toxic fluorine-containing sulfur intermediates generated. The reaction products are only two acidic gases, HF and SO3, and the byproducts are simple and easy to handle. It solves the problems of conventional processes that rely on the natural volatilization of alkaline solutions for water vapor supply, resulting in uncontrollable water vapor content, incomplete SF6 degradation, and the generation of various toxic fluorine-oxidized sulfur byproducts, which can easily lead to secondary pollution.

[0043] The aforementioned plasma generation unit is located below the air inlet, ionizing the mixed gas to generate acidic pyrolysis products. This allows the mixed gas to flow downwards through the plasma region, where high-energy plasma bombards SF6 molecules to complete their pyrolysis. The plasma generates a large number of high-energy electrons and reactive particles, breaking the highly stable chemical bonds of the SF6 molecules; water vapor provides an oxygen source, oxidizing S and F elements into acidic oxides.

[0044] SF6 cracking can be completed at ambient temperature and pressure, without the need for heating above 1200℃, and the energy consumption is far lower than that of high-temperature thermal decomposition. The equipment is flexible to start and stop and can continuously treat industrial waste gas. It solves the problems of extremely high energy consumption and severe furnace wear in high-temperature thermal decomposition; easy contamination by waste gas impurities in the catalytic degradation process; catalyst poisoning and failure; and poor degradation stability.

[0045] A liquid-phase alkali absorption device is installed at the bottom of the aforementioned sealed box, where acidic pyrolysis products are neutralized by the alkali solution.

[0046] Neutralization reaction: SO3 + 2OH- - =SO4 2- +H₂O;HF+OH - =F - +H2O; acidic gases are converted into stable water-soluble sulfates and fluorides, all fixed in the liquid phase. This allows SF6 cracking, neutralization, and detoxification to be completed in one step, with no acidic or harmful gases emitted, completely eliminating secondary pollution. Compared to traditional plasma processes that require complex post-cracking tail gas treatment equipment and where insufficient absorption of acidic tail gas can easily lead to environmental pollution, this embodiment eliminates the need for external multi-stage tail gas absorption devices.

[0047] The degradation device in this embodiment features an upper air intake, a middle plasma section, and a lower alkaline solution section. The air intake, plasma discharge zone, and alkaline solution absorption zone are arranged in layers from top to bottom, with the mixed gas flowing vertically downwards. The highly humid acidic products after pyrolysis rapidly settle into the bottom liquid phase due to gravity, preventing high-humidity water vapor from lingering in the plasma discharge region. Furthermore, it reduces the inhibitory effects of water molecules trapping electrons and electrode condensation creepage on ionization.

[0048] This ensures uniform and stable plasma discharge without jitter or arc extinguishing; the gas inside the sealed chamber is dynamically balanced with minimal pressure fluctuations, supporting long-term continuous automated operation.

[0049] The degradation device in this embodiment adopts an atmospheric pressure sealed integrated layered structure, using a constant amount of argon gas in the sealed box as an ionization substrate to achieve self-sustaining discharge; it precisely matches the 3:1 water vapor to SF6 metering ratio to complete the pyrolysis; it relies on the top-down flow field to make the acidic products settle rapidly to the bottom alkaline solution for in-situ neutralization; the entire process is sealed without continuous carrier gas supply and without external tail gas treatment, achieving continuous degradation at atmospheric pressure, with low material consumption and no secondary pollution.

[0050] It operates at atmospheric pressure and requires no vacuum equipment; requires only a one-time argon purging, eliminating the need for continuous gas consumables; completely degrades SF6 without producing toxic intermediates; integrates pyrolysis and neutralization, preventing secondary pollution; and ensures long-term stable plasma discharge for continuous industrial operation. It overcomes multiple shortcomings of existing SF6 treatment technologies, including complex vacuum equipment, continuous consumption of carrier gas, uncontrolled water-vapor ratio leading to incomplete degradation, cumbersome byproduct handling resulting in secondary pollution, and unstable discharge preventing long-term continuous operation.

[0051] As an optional embodiment, the ignition gas is argon, which is pre-filled into the sealed chamber to maintain the continuous operation of the plasma generating unit.

[0052] Argon is an inert rare gas with moderate ionization energy. It does not chemically react with water, SF6, HF, SO3, or alkaline solutions in the system and is insoluble in alkaline solutions. It is suitable as the ignition and self-sustaining base gas for atmospheric pressure plasma. Argon is selected as the ignition gas and is only injected into the sealed chamber once during the equipment startup phase. The plasma continues to self-sustain by relying on the argon gas remaining in the chamber, and no continuous gas replenishment is required during operation.

[0053] Argon gas is easily ionized to generate a large number of high-energy electrons, creating a stable discharge atmosphere; its chemical inertness means it is not consumed or produces impurities or byproducts throughout the process, and the sealed enclosure can be permanently recycled to serve as an ionization substrate.

[0054] Only one gas filling is required, with no argon gas consumed throughout the entire operation, significantly reducing the cost of carrier gas consumables; the discharge is stable and not prone to arc extinguishing or discharge jitter due to water vapor or trace amounts of acidic gases; and it does not generate nitrogen oxides (NOx). X It contains impurities and gases, but no additional pollutants.

[0055] Using nitrogen or air as carrier gas will participate in the discharge reaction to generate nitrogen oxides, increasing the consumption of alkali and causing secondary pollution; helium is too expensive and is not suitable for continuous industrial use; traditional solutions continuously supply carrier gas, resulting in large gas consumption and complex maintenance of gas supply pipelines.

[0056] As an optional embodiment, it also includes an argon gas inlet 3, which is located on the upper part of the sealed box and below the plasma generating unit 4.

[0057] Argon inlet 3 is an independent pipeline interface, used only for filling argon gas during equipment startup and closed during normal operation. An independent argon inlet is added to the enclosure; the inlet is located at the top of the enclosure, below the plasma generation unit.

[0058] Argon gas is denser than air, and the gas filling at the top can quickly diffuse downwards, rapidly filling the entire sealed gas phase space, establishing a full-domain ionized atmosphere in a short time, and quickly igniting the plasma.

[0059] It allows for uniform diffusion of argon gas during filling and rapid ignition; the interface is independent, preventing interference with SF6 and water vapor inlet pipelines and ensuring no contamination of the gas paths.

[0060] As an optional embodiment, it also includes an argon recovery device, which is configured to extract argon through an argon inlet for purification and recovery when the degradation device is shut down.

[0061] The aforementioned argon recovery equipment can be a complete set of recovery components consisting of a vacuum pump, a condensation and dehydration module, an impurity adsorption and purification column, and an argon storage tank.

[0062] The unit is equipped with argon recovery equipment. During equipment shutdown and maintenance, argon gas is extracted from the sealed chamber through the argon inlet, purified, and then stored for reuse. Before shutdown and opening the cover, the argon mixture inside the sealed chamber is extracted, condensed to remove moisture, and adsorbed to remove trace amounts of HF / SO3 impurities, resulting in high-purity argon gas for storage. The sealed chamber is then directly refilled upon the next startup.

[0063] Argon gas is not wasted during equipment maintenance and opening the cover for upkeep, and it can be recycled multiple times, further reducing long-term operating consumable costs. Compared to the method of directly venting argon gas from the sealed chamber when the machine is shut down and the cover is opened, this effectively avoids the waste of rare gases and the higher long-term operating costs.

[0064] As an optional embodiment, it also includes a waste heat vaporization device, which includes a vaporization chamber and a water storage chamber. The vaporization chamber is connected to the water storage chamber and is disposed on the outer surface of the upper part of the sealed box and connected to the air inlet. It is configured to use the waste heat generated by the plasma generating unit to vaporize the liquid water flowing into the water storage chamber to obtain water vapor, which is then transmitted to the air inlet.

[0065] The aforementioned waste heat vaporization device can be a water vapor generation unit consisting of a vaporization chamber and a water storage chamber; the vaporization chamber absorbs heat to vaporize pure water, and the water storage chamber stores liquid water and continuously supplies water to the vaporization chamber. An additional waste heat vaporization device is added, with the vaporization chamber connected to the water storage chamber; the vaporization chamber is attached to the upper outer wall of the housing, utilizing plasma waste heat to heat the liquid water to generate water vapor, which is then transported to the air inlet to participate in the reaction.

[0066] The plasma process releases low-temperature waste heat, eliminating the need for additional electric heating equipment. This waste heat is conducted to the vaporization chamber to heat pure water for vaporization. The generated water vapor is then directly supplied to the air inlet, forming a closed-loop water vapor supply. Waste heat can be recovered, eliminating the need for an external steam generator and electric heating device, significantly reducing overall energy consumption. The self-generated water vapor is clean and free of impurities, preventing external water vapor from introducing impurities that could interfere with the discharge process. The sealed enclosure further facilitates water vapor circulation, minimizing water resource loss.

[0067] This solution addresses the problems of traditional methods that rely on external electric heating steam equipment for water supply, resulting in additional power consumption, large equipment size, and the potential for external water vapor to introduce impurities, thus affecting the SF6 degradation effect.

[0068] As an optional embodiment, a flow control valve is also provided between the vaporization chamber and the air inlet; the flow control valve is configured to output water vapor with a corresponding molar mass of 3 times the molar mass of sulfur hexafluoride gas input into the air inlet.

[0069] The aforementioned flow control valve can be linked with the SF6 intake flow regulating valve to match the steam output in real time. A flow control valve is installed between the vaporization chamber and the intake port, thereby automatically outputting steam at a flow rate of 3 times the molar flow rate of SF6.

[0070] Relying on the 1:3 stoichiometric ratio of the SF6 complete degradation reaction for precise quantity control, the required amount of water vapor for the reaction is ensured to be just enough, with no excess water vapor. The ratio of water vapor to SF6 is accurate and stable over a long period, resulting in complete SF6 decomposition without toxic intermediate byproducts such as SOF2 and SO2F2. The water vapor content inside the sealed chamber is controllable, reducing high humidity and inhibiting plasma ionization.

[0071] It solves the problems of uncontrollable water vapor supply when there is no flow regulation, incomplete degradation due to insufficient water vapor, and excessive humidity in the sealed box due to excessive water vapor, as well as electrode condensation, creepage, and discharge instability.

[0072] As an optional embodiment, the plasma generating unit is located on the top of the sealed enclosure. The plasma generating unit is an atmospheric pressure microwave plasma generating unit, an atmospheric pressure dielectric barrier discharge plasma generating unit, or an atmospheric pressure radio frequency plasma generating unit.

[0073] The aforementioned atmospheric pressure microwave plasma unit, atmospheric pressure dielectric barrier discharge (DBD) unit, and atmospheric pressure radio frequency plasma unit are three types of discharge devices that do not require a vacuum and can stably generate plasma under atmospheric pressure. The plasma generation unit is installed on the top of the enclosure and can be configured with microwave, dielectric barrier discharge, or radio frequency atmospheric pressure plasma structures.

[0074] All three types of plasma can generate high-energy active particles under normal pressure, breaking the stable chemical bonds of SF6; different discharge forms are adapted to different exhaust gas flow rates and operating conditions. The plasma module can be flexibly replaced according to the on-site conditions: microwave is selected for large flow rates, DBD for medium and small flow rates, and radio frequency is selected for high-precision, low-impurity conditions, making it highly versatile.

[0075] As an optional embodiment, the main frequency of the atmospheric pressure microwave plasma generator is 2.45 GHz, and the power is 0.5~3 kW; and / or, the input voltage of the atmospheric pressure dielectric barrier discharge plasma generator is AC220V, the output voltage is 20kV, the power is 0.1~1 kW, and the frequency is 10~12 kHz; and / or, the frequency of the atmospheric pressure radio frequency plasma generator is 13.56 MHz, the power is 0~50W, and the voltage is 7~11kV.

[0076] Each parameter range represents the optimal window for stable self-sustaining discharge and efficient SF6 pyrolysis of the corresponding plasma. Too low a parameter results in insufficient pyrolysis efficiency, while too high a parameter leads to a significant increase in energy consumption. Locking in the optimal operating conditions for each plasma balances high degradation efficiency with low energy consumption, preventing parameter deviations that could lead to discharge failure and a decrease in degradation rate.

[0077] As an optional embodiment, the vertical distance between the discharge end face of the plasma generating unit and the liquid surface of the liquid phase alkaline solution absorption device is 5-20 mm, wherein the discharge end face is the lowest end face of the plasma generating region of the plasma generating unit.

[0078] The vertical distance between the lowest end face of the plasma discharge and the bottom alkaline solution surface is controlled at 5–20 mm. This is to reduce the gas-liquid gap, allowing the acidic products HF and SO3 generated by pyrolysis to quickly settle into the alkaline solution for neutralization, thus shortening the residence time of the acidic gas in the discharge zone; at the same time, controlling the gap avoids liquid splashing and contamination of the electrodes.

[0079] Acidic products are rapidly captured by the liquid phase, reducing the accumulation of acidic gases in the discharge zone and preventing corrosion of discharge components; the residence time of products in the gas phase is shortened, inhibiting reverse reactions and improving degradation efficiency. This solves the problems of acidic gases remaining in the discharge zone for extended periods when the spacing is too large, corroding electrodes and easily causing reverse reactions to regenerate fluorine-containing toxic gases; and of alkaline liquid splashing and adhering to electrodes when the spacing is too small, causing creepage and short circuits.

[0080] 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.

[0081] Sodium hydroxide aqueous solution is an alkaline neutralizing medium that provides OH-. -Neutralize HF and SO3 to form stable salts. Use a 5%–20% NaOH solution as the alkali; the liquid level should be 10–30 mm, and the total volume of the alkali solution ≤ 1 L. This concentration range provides sufficient neutralization while allowing for controllable water vapor evaporation; the low liquid level and small volume reduce excessive water vapor production from alkali evaporation, preventing excessive humidity inside the sealed enclosure from interfering with the discharge.

[0082] The alkali solution has sufficient neutralization capacity, allowing for continuous SF6 treatment over extended periods. The alkali solution exhibits low water vapor evaporation, making humidity control within the sealed chamber easy and reducing the risk of electrode condensation and creepage short circuits. This addresses the problems of insufficient neutralization capacity due to excessively low alkali concentration, leading to rapid saturation and failure; and excessively high concentration or liquid level, resulting in excessive water vapor evaporation, high humidity within the sealed chamber, inhibiting plasma ionization, and causing leakage faults.

[0083] As an optional embodiment, a temperature and humidity sensor is also installed inside the sealed enclosure; 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.

[0084] The aforementioned temperature and humidity sensor is a monitoring element that collects real-time data on the temperature and relative humidity inside the sealed enclosure; RH represents relative humidity. The sealed enclosure contains a built-in temperature and humidity sensor that monitors and controls the temperature inside the enclosure to not exceed 50℃ and the humidity to not exceed 50%RH.

[0085] High temperatures accelerate water vapor evaporation and exacerbate electrode corrosion; high humidity causes water molecules to capture electrons and condensation on the electrode surface, resulting in discharge jitter and creepage short circuits. Setting a threshold ensures a stable discharge environment.

[0086] Real-time monitoring of operating conditions triggers alarms / shutdowns when temperature or humidity exceeds limits, preventing short circuits and plasma arc extinguishing, thus improving equipment safety and stability. It solves the problems of uncontrolled temperature and humidity within the sealed enclosure, leading to unstable discharge, high-voltage short circuits, and equipment corrosion damage caused by high humidity and temperature, when no temperature and humidity monitoring is available.

[0087] Example 2 like Figure 2 As shown, this embodiment provides a self-sustaining plasma-based sulfur hexafluoride degradation method, including: Step S201: After verifying that the airtightness of the sealed enclosure is qualified, argon gas is introduced into the plasma generator unit once and then the argon gas is turned off.

[0088] In step S202, water vapor and sulfur hexafluoride gas are mixed in a molar ratio of 3:1 and then introduced into the plasma generating unit through the inlet.

[0089] In step S203, sulfur hexafluoride gas is subjected to plasma cracking through a plasma generation unit to generate acidic cracking products, which fall into the bottom alkaline solution for neutralization.

[0090] In step S204, water vapor and sulfur hexafluoride gas are continuously introduced, and the degradation is continuous and stable by relying on the constant amount of argon gas in the sealed box for self-sustaining discharge.

[0091] The above-mentioned airtightness test of the sealed enclosure can detect leaks in all welds, joints, and valves of the sealed enclosure, ensuring that there is no gas leakage in the sealed enclosure, maintaining a constant total amount of argon gas inside, and keeping it sealed at normal pressure throughout the process.

[0092] The operation procedure begins with leak detection of the sealed chamber to confirm that there is no leakage; a fixed amount of argon gas is then introduced through the argon gas inlet, the plasma power supply is started, and after a stable plasma glow appears in the sealed chamber, the argon gas inlet valve is closed.

[0093] Adequate airtightness is a prerequisite for achieving constant argon circulation. Leakage will cause argon loss and prevent self-sustaining discharge. Argon ionization energy should be moderate, as a small amount of argon is sufficient to break through the sealed chamber and establish plasma. Argon is chemically inert, does not participate in reactions, is insoluble in alkaline solutions, and remains permanently inside the sealed chamber after sealing.

[0094] Argon gas is consumed only once, and no continuous supply of carrier gas is required throughout the operation, which greatly reduces gas consumption. The total amount of argon gas inside the sealed chamber is constant, and the ionization atmosphere is stable, laying the foundation for long-term self-sustaining discharge.

[0095] Water vapor is generated by vaporizing waste heat from the plasma. A flow control valve is linked to the SF6 intake flow rate to automatically match a water vapor volume of 3 times the molar amount. The mixture is then introduced into the plasma discharge zone through the air inlet at the top of the chamber. Only when the water molecule ratio is met can the bonds be completely broken; insufficient ratio will generate toxic fluorine- and sulfur-containing intermediates such as SOF2 and SO2F2.

[0096] This allows SF6 to be fully decomposed, with a degradation rate of up to 100%, and no toxic or incomplete reaction byproducts; the water vapor supply is precisely controllable, and will not cause excessive humidity inside the sealed box.

[0097] The mixed gas passes through the plasma discharge zone from top to bottom. High-energy particles bombard and break the chemical bonds of SF6, generating SO3 and HF. The acidic gas settles to the bottom of the chamber by gravity and is directly neutralized by the liquid alkali solution.

[0098] The pyrolysis, harmless neutralization and decomposition are completed in one step within the same sealed enclosure, eliminating the need for an external multi-stage tail gas scrubbing tower; there is no external emission of acidic and harmful gases, completely eliminating secondary pollution; the vertical gas-liquid flow field shortens the residence time of acidic gases in the discharge zone, reducing electrode corrosion.

[0099] The solution addresses the problems of separating the pyrolysis section and the tail gas absorption section in traditional processes, which involves numerous supporting equipment and complex pipelines; insufficient absorption of acidic tail gas, which easily leads to external emission and environmental pollution; and the corrosion of plasma electrodes by acidic gases that remain in the discharge area for a long time.

[0100] The SF6 waste gas to be treated is continuously introduced, and water vapor is supplied simultaneously at a ratio of 3:1; the argon gas inside the sealed chamber is not consumed or lost, and the plasma discharge state is continuously maintained to achieve uninterrupted continuous degradation.

[0101] The sealed chamber is an atmospheric pressure closed-loop system with continuous input of SF6 and water vapor. All gaseous products after the reaction are absorbed by the liquid-phase alkaline solution, resulting in no gas accumulation and constant gas pressure throughout the process. Argon gas is uniformly filled into the sealed chamber at all times, continuously providing an ionization substrate. It can operate automatically and continuously for extended periods without manual adjustment of the carrier gas or pressure. The plasma operates without fluctuations or arc extinguishing conditions, exhibiting strong operational stability.

[0102] This addresses the problems of conventional plasma equipment where gas pressure fluctuates continuously with the intake and exhaust, easily leading to arc interruption and preventing long-term continuous operation; and the need for manual real-time adjustment of carrier gas flow and vacuum pressure, resulting in a large workload for maintenance.

[0103] As an optional embodiment, the method further includes: using the waste heat generated by plasma pyrolysis to heat the water body in situ to generate water vapor; and transferring the water vapor to the air inlet as a source of water vapor for the air inlet.

[0104] Waste heat is recovered and reused, eliminating the need for external electric heating steam equipment and significantly reducing the energy consumption of the entire unit. The self-produced water vapor is clean and free of impurities, and will not introduce external pollutants that may interfere with plasma discharge and SF6 degradation.

[0105] This solution addresses the problems of traditional solutions that rely on independent external steam generators for water supply, resulting in additional power consumption, large equipment size, and increased investment; and the fact that external water vapor can easily introduce impurities, leading to a decrease in degradation efficiency.

[0106] As an optional embodiment, the method further includes: shutting down the plasma generation unit after the sulfur hexafluoride gas is stopped; and extracting argon gas through the argon gas inlet for purification and recovery.

[0107] Argon gas is not directly vented and wasted during equipment opening for inspection and maintenance. Rare gas is reused, further reducing the cost of consumables during long-term operation. Direct argon gas emission avoids resource waste and the superposition of slight greenhouse gas emissions. Trace acidic impurities are purified and removed, so there will be no impurities interfering with the discharge during the next ignition.

[0108] This solves the problem that the original basic process only achieves self-circulation of argon gas within the sealed box during the operation phase, and the argon gas is directly vented when the equipment is opened for maintenance, resulting in the complete loss of the argon gas filled at one time and the high cost of argon gas procurement for long-term industrial use.

[0109] As an optional embodiment, the method further includes: real-time monitoring of the temperature and humidity inside the sealed enclosure; issuing an alarm when the temperature exceeds 50°C and / or the humidity exceeds 50%, and automatically controlling the introduction of sulfur hexafluoride gas and the shutdown of the plasma generation unit.

[0110] Real-time monitoring of internal operating conditions and immediate warning of abnormal situations eliminates the need for continuous manual monitoring; automatic shutdown when limits are exceeded prevents damage to plasma equipment from high-voltage creep, short circuits, and electrode corrosion, thus improving the safety of device operation; stable control of the total amount of water vapor inside the sealed chamber ensures continuous degradation of SF6 and prevents a decrease in degradation rate due to excessive humidity.

[0111] This addresses the issues of the lack of temperature and humidity control in basic processes, which can lead to problems such as overheating of the sealed enclosure, excessive evaporation of alkali solution, plasma discharge jitter and frequent arc extinction in high humidity and high temperature environments, and even high voltage short circuits that burn out the equipment. It also addresses the problem of the inability to monitor internal temperature and humidity in real time and the resulting delays in fault detection.

[0112] Example 3 This embodiment discloses a method for the self-sustaining, harmless degradation of SF6 waste gas using atmospheric pressure plasma, belonging to the field of industrial waste gas treatment technology. This method employs atmospheric pressure plasma (microwave, dielectric barrier discharge, or radio frequency plasma) to degrade sulfur hexafluoride (SF6) waste gas.

[0113] The core innovation lies in the fact that only a small amount of argon gas is introduced at the initial ignition, and no gas needs to be added after ignition. The argon gas is in constant quantity and consumed in the system. Combined with the closed-loop water vapor circulation and the full liquid phase absorption of reaction products, the gas pressure in the sealed reaction chamber remains constant throughout the process, and the plasma discharge is stable and self-sustaining in the long term.

[0114] During the process, the residual heat generated by the plasma operation is used to vaporize water vapor in situ. Through precise flow control, the water vapor is mixed with SF6 in a 3:1 molar ratio and enters the reaction zone, so that SF6 is completely decomposed into SO3 and HF. The by-products are then neutralized and absorbed by the alkaline aqueous solution and converted into harmless sulfates and fluorides.

[0115] This implementation method requires no continuous gas maintenance, no vacuum equipment, and no secondary pollution. It has significant advantages such as low energy consumption, low operating cost, 100% degradation rate, stable operation, and compatibility with multiple types of plasma. It can be widely used in the harmless treatment of SF6 waste gas in industries such as power, semiconductor, and metallurgy.

[0116] This implementation method relies on the core technologies of autonomous water vapor production from multiple types of plasma heat sources at atmospheric pressure, precise proportioning for degradation reaction, and initial argon ignition for self-sustaining discharge to achieve complete degradation of SF6 waste gas under atmospheric pressure without the need for continuous gas maintenance. Byproducts can be rapidly and harmlessly absorbed, significantly reducing equipment costs and operating energy consumption, improving SF6 waste gas degradation efficiency and treatment safety, and adapting to various industrial SF6 waste gas routine treatment scenarios.

[0117] This embodiment uses plasma technology under normal pressure to treat SF6 waste gas, and is compatible with three mainstream normal pressure plasma generation methods: microwave plasma, dielectric barrier discharge plasma, and radio frequency plasma. The microwave plasma source operates at a frequency of 2.45 GHz, with an adjustable power of 0.5~3 kW; the dual dielectric barrier discharge unit uses a dual dielectric plasma generator, operating at AC 220V, outputting 20 kV high voltage, with an adjustable power of 0.1-1kW and a frequency of 10-12 kHz; the radio frequency plasma operates at a frequency of 13.56 MHz, with a power of 0-50W and a voltage of 7-11kV.

[0118] The residual heat generated during plasma discharge is used to heat the water in the sealed enclosure at a low temperature, vaporizing it to generate trace amounts of water vapor. This water vapor is then mixed with the SF6 waste gas to be treated in a precise molar ratio of 3:1 and introduced into the plasma reaction zone to achieve the complete decomposition reaction of SF6.

[0119] The hydrogen fluoride and sulfuric acid gases generated in the reaction quickly neutralize with alkaline substances in the water, converting them into harmless salts and completely eliminating secondary pollution. The discharge device must be kept at a distance from the liquid surface. The liquid absorption system is located in an insulated container at the bottom of the tank, containing a 5%-20% sodium hydroxide aqueous solution, with the liquid level approximately 20 mm high. The gas inlet is located at the top of the tank; the gas outlet is located on the lower right side wall of the tank, 80 mm from the bottom.

[0120] Meanwhile, this implementation method adopts an argon-based initial ignition and subsequent self-sustaining discharge mode. Only a fixed amount of argon is introduced during the startup phase, and the argon supply remains constant throughout the operation with no consumption or loss. A closed-loop cycle is formed within the system: the water vapor generated by plasma heat evaporation participates in the reaction, and the final products all return to the water body. At the same time, the introduced SF6 and its reaction products are completely absorbed by the aqueous solution. The internal pressure of the entire sealed enclosure remains constant without pressure fluctuations, ensuring long-term extreme stability of the plasma discharge state. Normal operation requires no gas maintenance, achieving low-cost, high-stability continuous processing.

[0121] To ensure stable operation of the device over a long period and to guarantee discharge safety, the volume of NaOH solution contained in the insulating container shall not exceed 1L, and the liquid level shall not exceed 30mm; the concentration of the NaOH solution shall be 5%-20%, preferably 10%.

[0122] Temperature and humidity sensors are installed on the inner wall of the sealed chamber to monitor reaction environment parameters in real time. The temperature sensor's monitoring range is -30℃ to +100℃, and the humidity sensor's monitoring range is 0%-100%RH. The relative humidity of the gas inside the sealed chamber is controlled at ≤50%, preferably ≤30%, and the temperature must be controlled below 50 degrees Celsius. Excessive humidity and excessive alkali solution will increase the risk of creepage and short circuits. The monitoring range of the temperature and humidity sensors must cover the entire range of normal operation and abnormal alarms of the device to ensure timely detection and handling of abnormal conditions.

[0123] The detailed implementation steps of this invention are as follows: Step 1: Equipment Pretreatment and Initial Ignition. Perform an airtightness test on the atmospheric pressure plasma reaction chamber to ensure there are no air or water leaks. After passing the test, introduce only a small amount of argon gas into the plasma chamber, start the plasma power supply, and excite a stable atmospheric pressure plasma discharge field inside the chamber, completing the initial ignition. Argon gas is only used for initial discharge excitation; the argon gas supply can be shut off after ignition is complete, and continuous supply is not required throughout the process.

[0124] Step 2: In-situ generation of reactive water vapor. During the stable discharge of plasma, low-temperature waste heat will be continuously generated in the surrounding area. This waste heat is used to gently heat the aqueous solution in the water storage unit of the sealed box. No additional heating equipment is required. It will automatically vaporize to generate trace amounts of uniform water vapor, realizing the resource utilization of heat and reducing overall energy consumption.

[0125] Step 3: Precise mixing and reaction. The SF6 waste gas to be treated is continuously introduced into the plasma reaction sealed chamber. The molar ratio of water vapor to SF6 is precisely controlled to 3:1 using a flow control system, ensuring the mixed gas enters the high-temperature plasma reaction zone simultaneously. Under the bombardment and ionization of high-energy particles in the atmospheric pressure plasma, SF6 and water molecules undergo a complete oxidation-reduction reaction, resulting in the complete bond breaking and degradation of SF6 molecules, leaving no toxic intermediates.

[0126] Step 4: Rapid and Harmless Absorption of Byproducts. The fixed products of the reaction between SF6 and water vapor are two acidic gases: hydrogen fluoride (HF) and sulfur trioxide (SO3). An alkaline neutralizing agent (such as sodium hydroxide or calcium hydroxide) is pre-added to the aqueous solution in the sealed enclosure. The two acidic gases react instantly with the alkaline substances in the water, are rapidly and completely absorbed by the aqueous solution, and converted into stable and harmless water-soluble salts such as fluorides and sulfates, thus completely eliminating the emission of toxic and harmful gases.

[0127] Step 5: Self-sustaining continuous operation. After the initial argon ignition of the equipment, the plasma discharge state can be maintained autonomously. Only the continuous introduction of SF6 waste gas is needed to achieve continuous degradation treatment. There is no need to replenish argon or other protective gases or carrier gases. There is no gas maintenance operation throughout the process, and long-term stable continuous operation can be achieved.

[0128] The core chemical reaction equation for this implementation method is as follows: 1. Plasma-based primary degradation reaction (precise 3:1 ratio for complete reaction): SF6 + 3H2O (atmospheric pressure plasma) = SO3 + 6HF.

[0129] 2. Neutralization reaction for the harmless treatment of by-products: SO3 + 2OH - = SO4 2- + H2O; HF + OH - = F - + H2O.

[0130] This embodiment of the technical solution is compatible with three types of atmospheric pressure plasma generation methods, all of which can achieve self-sustaining discharge and precise degradation effects: Atmospheric pressure microwave plasma: stable discharge, high energy particle density, suitable for large-flow SF6 waste gas treatment scenarios; Atmospheric pressure dielectric barrier discharge plasma: uniform discharge, no electric arc, long equipment life, suitable for small and medium-sized routine waste gas treatment; Atmospheric pressure radio frequency plasma: controllable reaction temperature, extremely strong stability, suitable for high-precision, low-impurity waste gas treatment scenarios.

[0131] Compared with the prior art, this embodiment has the following advantages: 1. Unique constant argon gas ignition, zero-consumption self-sustaining operation, constant gas pressure in sealed enclosure, and ultra-stable discharge.

[0132] This invention completely breaks through the technical limitations of traditional plasma waste gas treatment, which requires continuous supply of protective gas and carrier gas. It only requires a fixed dose of argon gas to be introduced once during the equipment startup phase for plasma ignition. The total amount of argon gas remains constant throughout the entire operation of the equipment, with no consumption, no leakage, and no need for replenishment.

[0133] Meanwhile, the system forms a closed-loop steady-state cycle: the water vapor generated by the plasma waste heat vaporization participates in the SF6 degradation reaction and then condenses back into the water body with the products, realizing a closed-loop water vapor cycle; after the SF6 waste gas introduced into the sealed box undergoes complete reaction, all gaseous products are completely absorbed and fixed into liquid salts by the alkaline aqueous solution, and no gas remains inside the sealed box.

[0134] The entire reaction sealed chamber has no gas increment or gas loss, zero gas pressure fluctuation and absolutely constant operating conditions throughout the process, completely solving the problems of discharge jitter, arc extinguishing and unstable operating conditions caused by gas pressure fluctuations in traditional atmospheric pressure plasma, ensuring long-term stable self-sustaining discharge of plasma, and significantly reducing gas consumable costs and equipment maintenance procedures.

[0135] 2. Waste heat generates water vapor, and the precise 3:1 ratio ensures complete reaction.

[0136] No external heating device or water supply equipment is required. The residual heat generated during plasma operation is recovered and vaporized in situ to produce water vapor, realizing the resource utilization of waste heat and reducing energy consumption. Through precise flow control, a 3:1 molar ratio of water vapor to SF6 is achieved, ensuring complete degradation of SF6 with no incomplete reaction byproducts generated, and a degradation rate of up to 100%.

[0137] 3. Operates under normal pressure, with a simple equipment structure, and is suitable for industrial applications.

[0138] The entire reaction is completed under normal pressure, eliminating the need for a vacuum sealing system. It abandons the complex airtight structure and vacuum unit of traditional vacuum plasma equipment, making the equipment smaller, cheaper, and easier to operate. It can be adapted to various installation scenarios, including mobile and fixed installations in industrial sites.

[0139] 4. Byproducts are immediately rendered harmless in situ, without secondary pollution.

[0140] The hydrogen fluoride and sulfuric acid trioxide gases generated during degradation can immediately neutralize alkaline substances in the water and be rapidly absorbed and converted into stable and harmless salts. This eliminates the need for complex post-treatment equipment, achieving degradation and harmless treatment in one step and completely solving the problem of secondary pollution from SF6 treatment.

[0141] 5. Compatible with multiple plasma types, highly versatile.

[0142] The technical solution is compatible with three mainstream atmospheric pressure plasma technologies: microwave, dielectric barrier, and radio frequency. It can be flexibly selected according to the processing air volume and operating conditions, and is suitable for the SF6 waste gas treatment needs of different industries, concentrations, and flow rates. The technology has wide adaptability and strong scalability.

[0143] Compared with existing technologies, this implementation method has the following significant technical, economic, and environmental advantages: 1. Energy and cost advantages: The waste heat of plasma is recovered to produce water vapor, eliminating the need for an external heat source; there are no continuous gas consumables, significantly reducing operating costs; atmospheric pressure operation eliminates the need for vacuum equipment, and equipment investment and maintenance costs are significantly lower than traditional technologies.

[0144] 2. Advantages of treatment effect: The precise 3:1 ratio of SF6 to water ensures complete degradation of SF6 with no toxic intermediate residues, and thorough degradation; by-products are immediately rendered harmless, and exhaust gas emissions are zero-pollution, making the treatment extremely safe.

[0145] 3. Advantages of steady-state operation and maintenance: The equipment has a built-in constant pressure closed-loop reaction system with constant argon gas consumption, closed-loop water vapor circulation, and full liquid phase absorption of reaction products. The gas pressure in the sealed chamber is constant throughout the process, and the plasma has no arc extinguishing or discharge fluctuations, resulting in extremely strong operational stability. No gas maintenance or pressure control is required throughout the process. It is automated and continuous, with simple operation procedures and extremely low manual operation and maintenance costs, making it suitable for long-term, normalized, and stable operation in industrial settings.

[0146] 4. Application advantages: It is compatible with multiple plasma types and has strong adaptability to normal pressure conditions. It can be widely used in the treatment of SF6 waste gas in the power, semiconductor, chemical and other industries, and has extremely high industrial promotion value.

[0147] To demonstrate the technical effectiveness of this embodiment, three additional implementation methods are provided for comparison. Details are as follows.

[0148] Specific implementation case 1: Normal pressure microwave plasma working condition.

[0149] A 2.45 GHz, 1.5 kW atmospheric pressure microwave plasma was used to treat SF6 waste gas from the power industry. After the equipment's airtightness was tested, a small amount of argon gas was introduced to initiate the ignition, and then the argon supply was shut off. Water vapor and SF6 were mixed at a 3:1 molar ratio and introduced into the reaction zone through flow control. In the atmospheric pressure microwave field, the mixture was completely decomposed into SO3 and HF, which were then neutralized and absorbed by the alkaline solution to form sodium sulfate and sodium fluoride. The system features a closed-loop water vapor circulation, full liquid-phase absorption of products, and a constant gas pressure in the sealed chamber throughout the process, ensuring self-sustaining discharge. The results are shown in Figure 3(a). After one hour of operation, no gas replenishment was required, and the SF6 degradation rate in the exhaust gas was 94.8%.

[0150] Specific Implementation Case 2: Atmospheric Pressure Dielectric Barrier Discharge Plasma.

[0151] A dual-dielectric barrier discharge plasma system (AC 220V, 20 kV high voltage, 0.5 kW, 15 kHz) was used to treat SF6 waste gas from the high-voltage switchgear industry. Argon gas was introduced once before ignition and then cut off after ignition. The molar ratio of water vapor to SF6 was precisely controlled at 3:1. The mixed gas entered the discharge zone and was completely degraded into SO3 and HF, which were then neutralized in situ by alkaline solution into sulfates and fluorides. All reaction products were absorbed by the liquid phase, creating a closed-loop water vapor circulation system. The sealed chamber pressure remained stable, and the discharge was self-sustaining. The results are shown in Figure 3(b). After one hour of operation, no gas maintenance was required, and the SF6 degradation rate reached 96.2%.

[0152] Specific Implementation Case 3: Atmospheric Pressure Radio Frequency Plasma.

[0153] SF6-containing exhaust gas from the semiconductor industry was treated using atmospheric pressure radio frequency plasma at a frequency of 13.56 MHz and a power of 40 W. After initial ignition with argon gas, the argon gas was immediately shut off. Water vapor and SF6 were mixed in a 3:1 molar ratio and introduced into the reaction zone via flow control. SF6 was completely decomposed into SO3 and HF, which were immediately neutralized and absorbed by the alkaline solution as harmless salts. The system features closed-loop water vapor circulation, complete absorption of gaseous products, and a constant pressure within the sealed chamber, allowing for self-sustaining plasma operation. The results, shown in Figure 3(c), indicate that after one hour of operation, no gas replenishment was required, and the SF6 degradation rate reached 92.3%.

[0154] 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".

[0155] 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.

[0156] 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.

[0157] 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 self-sustaining plasma-based sulfur hexafluoride degradation device, characterized in that, include: Sealed enclosure, plasma generation unit, and liquid phase alkaline solution absorption device; The sealed enclosure is filled with a constant amount of ignition gas, which is argon, at atmospheric pressure. The argon is pre-filled into the sealed enclosure to maintain the continuous operation of the plasma generating unit. An argon gas inlet is provided at the top of the sealed enclosure, below the plasma generating unit. An air inlet is also provided at the top of the sealed enclosure for inputting a mixture of sulfur hexafluoride gas and water vapor in a preset ratio, wherein the preset ratio is a molar ratio of water vapor to sulfur hexafluoride gas of 3:

1. The plasma generating unit is located inside a sealed box and below the air inlet. It is configured to plasma-encode the mixed gas to obtain acidic pyrolysis products, which then react with the alkaline solution of the liquid-phase alkaline absorption device. The vertical distance between the discharge end face of the plasma generating unit and the liquid surface of the liquid phase alkaline solution absorption device is 5-20 mm, wherein the discharge end face is the lowest end face of the plasma generating region of the plasma generating unit. Waste heat vaporization device, the waste heat vaporization device includes a vaporization chamber and a water storage chamber; the vaporization chamber is connected to the water storage chamber, the vaporization chamber is disposed on the outer surface of the upper part of the sealed box and is connected to the air inlet, and is configured to use the waste heat generated by the plasma generating unit to vaporize the liquid water flowing into the water storage chamber to obtain water vapor, which is then transmitted to the air inlet. The liquid-phase alkali absorption device is located at the bottom of the sealed box and is used to hold the alkali solution.

2. The apparatus according to claim 1, characterized in that, It also includes an argon gas recovery device, which is configured to extract argon gas through the argon gas inlet for purification and recovery when the degradation device is shut down.

3. The apparatus according to claim 1, characterized in that, A flow control valve is also provided between the vaporization chamber and the air inlet; The flow control valve is configured to output water vapor in a corresponding molar ratio based on the mass of the sulfur hexafluoride gas input into the inlet.

4. The apparatus according to claim 1, characterized in that, The plasma generating unit is located on the top of the sealed enclosure. The plasma generating unit is a normal pressure microwave plasma generating unit, a normal pressure dielectric barrier discharge plasma generating unit, or a normal pressure radio frequency plasma generating unit.

5. The apparatus according to claim 4, characterized in that, The main frequency of the atmospheric pressure microwave plasma generator is 2.45 GHz, and the power is 0.5~3 kW; And / or, the input voltage of the atmospheric pressure dielectric barrier discharge plasma generating unit is AC220V, the output voltage is 20kV, the power is 0.1~1 kW, and the frequency is 10~12 kHz; And / or, the frequency of the atmospheric pressure radio frequency plasma generating unit is 13.56MHz and the voltage is 7~11kV.

6. The apparatus according to claim 1, characterized in that, The alkaline solution is an aqueous sodium hydroxide solution, and the mass concentration of the aqueous sodium hydroxide solution is 5% to 20%. 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 box is also equipped with a temperature and humidity sensor; The temperature and humidity sensor is used to monitor the temperature and humidity inside the chamber, ensuring that the temperature does not exceed 50°C and the humidity does not exceed 50% RH.

8. A self-sustaining plasma-based method for the degradation of sulfur hexafluoride, characterized in that, The method, applied to the self-sustaining plasma-based sulfur hexafluoride degradation device according to any one of claims 1 to 7, comprises: After the airtightness of the sealed enclosure is tested and found to be qualified, argon gas is introduced into the plasma generation unit to start the plasma generation unit and then the argon gas is turned off. After being mixed with water vapor and sulfur hexafluoride gas at a molar ratio of 3:1, the mixture is introduced into the plasma generating unit through the inlet. The plasma generating unit performs plasma pyrolysis on sulfur hexafluoride gas to generate acidic pyrolysis products, which fall into the bottom alkaline solution for neutralization. Water vapor and sulfur hexafluoride gas are continuously introduced, and the degradation is continuous and stable by relying on a constant amount of argon gas in the sealed box for self-sustaining discharge.

9. The method according to claim 8, characterized in that, The method further includes: The waste heat generated by plasma pyrolysis is used to heat water in situ to generate water vapor. The water vapor is transferred to the air inlet as a source of water vapor for the air inlet.

10. The method according to claim 8, characterized in that, The method further includes: After the sulfur hexafluoride gas is stopped, the plasma generating unit is shut down. Argon gas is extracted through the argon gas inlet for purification and recovery.

11. The method according to claim 9, characterized in that, The method further includes: Real-time monitoring of temperature and humidity inside the sealed enclosure; An alarm will be triggered if the temperature exceeds 50°C and / or the humidity exceeds 50%RH, and the introduction of sulfur hexafluoride gas and the shutdown of the plasma generation unit will be automatically controlled.

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