CN115646155A - Oil-cooled sulfur hexafluoride degradation device and method based on sliding arc discharge - Google Patents

Abstract

The invention discloses an oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge, which includes a plasma spray gun, a metal electrode, a ceramic reaction tube, an oil cooling box and an exhaust gas absorption pool, and the oil cooling box is a semi-closed structure , the ceramic reaction tube can be completely inserted into it, and several heat dissipation fans are arranged on the top of the oil cooling box; a temperature sensor is arranged at a certain distance from the bottom surface of the oil cooling box side. Also disclosed its degradation method. The invention can not only degrade SF ₆ waste gas with relatively higher concentration and gas flow rate, but also maintain the reaction working temperature below 200°C for a long time, effectively solving the problem of low energy efficiency of sliding arc discharge treatment gas.

Description

An oil-cooled sulfur hexafluoride degradation device and degradation method based on sliding arc discharge

technical field

The invention relates to the technical field of sulfur hexafluoride degradation, in particular to an oil-cooled sulfur hexafluoride degradation device and degradation method based on sliding arc discharge.

Background technique

In industries such as electric power and smelting, sulfur hexafluoride (SF ₆ ) gas has been widely used year by year due to its excellent insulation and stability, and its emissions are also increasing year by year. However, SF ₆ itself is also a greenhouse gas, and its Global Warming Potential (GWP) is 23,500 times that of CO ₂ . Indiscriminate emission poses a huge threat to the atmospheric environment. At the same time, with the proposal of the "double carbon" goal in our country, the treatment of SF ₆ is imminent.

From the perspective of SF ₆ gas before use, in recent years, some scholars have proposed to replace SF ₆ with a gas that can meet the insulation requirements and have a low GWP value, reduce the use of SF ₆ , thereby reducing its emissions, and gradually get rid of current status quo. However, due to safety and other reasons, it is currently impossible to replace SF ₆ on a large scale with alternative gases, so it is still in the stage of research and small-scale use. As for the used SF ₆ gas, due to the influence of the power industry environment, after a certain period of use, SF ₆ will be decomposed to form SO ₂ F ₂ , SO ₂ , SOF ₂ and other decomposition gases, and it will also be mixed with air, dust, Impurities such as water and gas reduce the concentration of SF ₆ until it cannot meet the requirements of insulation, which is called SF ₆ waste gas. At this time, new SF ₆ gas needs to be refilled to meet the needs of gas insulation equipment.

For the treatment of SF ₆ waste gas, scholars at home and abroad have proposed many methods. In addition to alternative gases, recycling purification and degradation treatment are currently the two most likely methods to change the status quo. Recovery and purification is to improve the purity of SF ₆ in the gas by absorbing, adsorbing, precipitating, standing and other means of impurities other than SF ₆ in the SF ₆ waste gas, so that it can meet the needs of insulation again, thus completing the recovery and purification . For example: a sulfur hexafluoride gas separation and recovery device with publication number CN113701047A on November 26, 2021, and a rectification and purification system for sulfur hexafluoride recovery gas with publication number CN113877228A on January 4, 2022. Both are combined through distillation, filtration, separation, low-temperature liquefaction and other modules to form a complete sulfur hexafluoride separation and recovery device, which can realize the recovery and purification of sulfur hexafluoride. However, the entire recovery and purification process is very complicated, with strict requirements on the process, and requires multiple cycles to reach the target level; at the same time, the device is too large and expensive, making it only suitable for one-to-one large-scale gas insulation The use of equipment is difficult to take into account some small insulation equipment, let alone some insulation equipment serving in remote areas, so recovery and purification methods have not fundamentally solved the problem of SF ₆ waste gas.

Degradation treatment is a method that has been widely used in the treatment of pollutant gases in recent years. Plasma is generated by means of high temperature and discharge, which collides with and dissociates molecules of pollutant gases, causing them to break bonds and decompose to form Other gases, so as to achieve the purpose of harmless degradation. Using dielectric barrier discharge to degrade sulfur hexafluoride is a relatively effective method. On March 16, 2021, Dong Xiaohu et al. published "H ₂ O concentration on the degradation of SF ₆ in packed bed reactors" published in "High Voltage Electrical Appliances". In the "Experimental Research on the Impact", by adding H ₂ O into the SF ₆ degradation system, the degradation rate can reach more than 90%. However, this treatment method requires the gas flow and concentration of SF ₆ to be kept at a low level, which limits its treatment efficiency and still needs to be improved to a certain extent.

Using sliding arc discharge to generate plasma to degrade pollutant gases is a very potential means, for example: a plasma sterilization device, a preparation method of sterilization gas and a sterilization method published on July 13, 2021 with the publication number CN113101389A, A plasma reaction device based on sliding arc discharge is introduced, which uses the active substances in the generated gas to eliminate germs; the publication number is CN106268217A on January 4, 2017, a kind of NaOH synergistic gas-liquid two-phase sliding arc discharge to remove SO ₂ method, mix the flue gas to be treated with the vaporized NaOH solution evenly, and pass it into the sliding arc reactor for discharge treatment, so as to achieve the purpose of desulfurization. The above two gas treatment devices based on sliding arc discharge can both produce good effects on the corresponding treatment objects. However, during the use of sliding arc discharge, due to the long-term discharge of the arc, the gas temperature will rise sharply, which can reach above 600°C in general, and the temperature will be higher for long-term use, which may cause potential damage to equipment and potential safety hazards And other problems, this is a major disadvantage that the sliding arc discharge method cannot be ignored compared with the dielectric barrier discharge and other methods. For the degradation of SF ₆ , during the discharge reaction process, the rise of the reactor temperature means more energy loss, resulting in lower energy efficiency of SF ₆ degradation, and cannot produce a good degradation effect on SF ₆ exhaust gas.

Contents of the invention

The purpose of the present invention is to provide an oil-cooled sulfur hexafluoride degradation device and degradation method based on sliding arc discharge, which can not only degrade SF ₆ waste gas with relatively higher concentration and gas flow rate, but also maintain the reaction working temperature at Below 200°C, it effectively solves the problem of low energy efficiency of sliding arc discharge treatment gas.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

The present invention is an oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge, comprising a plasma spray gun, a metal electrode, a ceramic reaction tube, an oil cooling box and an exhaust gas absorption pool; the tail of the plasma spray gun is connected with a power line, Ground wire and air pipe, the power wire is used for the plasma power supply to supply power to the spray gun, the ground wire grounds the shell of the plasma spray gun to ensure the safety and reliability of the equipment, and the air pipe is used to allow SF6 waste gas to enter the plasma spray gun to generate Degradation reaction; the inner wall of the ceramic reaction tube is provided with a metal inner mesh, and the center of the ceramic reaction tube is also provided with the metal electrode, and the peripheral surface of the metal electrode is threaded, and the metal electrode is close to the plasma spray gun during the discharge process The end will discharge with the metal inner net, and the arc will gradually extend forward along the thread on the surface of the metal electrode, and the reaction area will be gradually elongated; the other end of the ceramic reaction tube is connected with a quick-plug interface through a flange, and is introduced through the connecting air pipe. In the exhaust absorption pool; the ceramic reaction tube is completely placed in the oil cooling box, the oil cooling box is a semi-closed structure, and several cooling fans are arranged on the top of the oil cooling box; the side of the oil cooling box A temperature sensor is arranged at a certain distance from the bottom surface so as to display the oil temperature inside the oil cooling box in real time.

Further, four cooling fans are arranged on the top of the oil cooling box.

Further, a temperature sensor is provided on the side of the oil cooler box 20 cm away from the bottom surface.

Further, an inspection window is provided on half of the side of the exhaust gas absorption pool, so that the capacity and turbid state of the metal alkali solution inside the absorption pool can be observed.

Further, a display screen for displaying the real-time temperature monitored by the temperature sensor is provided on one side of the oil cooling box.

A method for degrading an oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge, comprising the steps of:

Step 1, preparation before degradation: first according to the mechanism diagram of the oil-cooled SF6 degradation device based on sliding arc discharge according to the present invention, the circuit and the gas path are connected respectively, and the circuit includes a high-voltage line (plasma power supply-plasma spray gun), ground wire (Earth-plasma spray gun), oil cooling box power line (cooling fan, temperature sensor) and plasma power supply related wiring, gas path includes air inlet pipe, air outlet pipe (reactor-exhaust gas absorption pool, exhaust gas absorption pool-atmosphere) , to ensure that the connection is stable and reliable; check the liquid level of the transformer oil in the oil cooler to ensure that the liquid level is between 1/2 and 2/3; then observe the liquid level and According to this, it is judged whether it is necessary to add or replace the metal alkali solution. It is also necessary to observe the amount of precipitation at the bottom of the exhaust gas absorption tank. If there is a lot of precipitation, it needs to be cleaned. Widely present in nature, so it can be discarded directly;

Step 2. Start the degradation device: first open the carrier gas valve, adjust the gas flow meter to maintain a constant and stable gas flow rate, then turn on the cooling fan of the oil cooling box, and start the plasma power supply. Under normal conditions, it can be observed that The arc is extended and slides inside the ceramic reaction tube; if no obvious arc is observed after turning on the power supply, the plasma power supply needs to be checked. After the arc can slide normally, open the SF6 waste gas valve, adjust the flow rate to an appropriate level, and start the degradation reaction; after one hour of continuous operation, it is necessary to start to observe the temperature of the oil cooler. It should exceed 250°C. If the temperature exceeds 250°C, it indicates that the operating temperature of the reactor is too high, and the device needs to be closed for natural cooling;

Step 3. Close the degradation device: first close the SF ₆ waste gas valve, the SF ₆ waste gas flow rate will gradually decrease, and when the flow rate of the SF ₆ gas source drops to 0, the plasma power supply will be turned off after the device continues to work for one minute. During this period, the load must be kept Continuous gas blowing, on the one hand, can ensure that most of the SF ₆ waste gas in the reactor is degraded, and the degraded tail gas is blown into the tail gas absorption pool; on the other hand, it can dissipate heat to a certain extent inside the reaction tube. After the carrier gas is blown for one minute, the carrier gas valve can be closed to complete the degradation. After the transformer oil in the oil cooling box is cooled, the machine can be turned on again.

Compared with prior art, beneficial technical effect of the present invention:

1. The present invention degrades SF ₆ waste gas based on sliding arc discharge method. By setting an oil cooler, the temperature rise in the discharge process is greatly reduced, so that more energy is used to degrade SF 6 waste gas, which improves the degradation rate and energy efficiency;

2. Degrading SF ₆ waste gas by sliding arc discharge in oil cooling mode can decompose SF 6 more thoroughly, further react SO ₂ F ₂ in SF 6 decomposition products, and decompose SO ₂ F ₂ that is difficult to be absorbed by lye to form SO2, SOF2 and other gases that are easily absorbed by the metal alkali solution are conducive to harmless treatment;

3. In order to combine the heat dissipation with oil cooling more conveniently, the present invention makes improvements on the basis of the conventional sliding arc discharge spiral electrode, adopts a cylindrical electrode, and sets threads on it, compared with the conventional spiral electrode, It is more conducive to the development and extension of the arc;

4. The present invention achieves the purpose of enhancing heat dissipation by setting a metal inner net on the inner wall of the reaction tube. At the same time, the metal inner net can also effectively promote the development and derivation of the arc, improving the degradation rate and energy efficiency;

5. The top of the oil cooling box of the present invention is also equipped with a cooling fan, which can dissipate heat from the transformer oil in the oil cooling box, so that the degradation process can maintain a long-term and stable and reliable operation;

6. In the present invention, the ceramic reaction tube and the nozzle of the plasma spray gun are embedded and connected with each other through threads, which can be disassembled and inspected, and can be replaced when necessary, ensuring the reliability of equipment operation.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Fig. 1 shows the structural representation of oil-cooled sulfur hexafluoride based on sliding arc discharge according to the present invention;

Fig. 2 shows the oil-cooled SF degrading device mechanism diagram based on sliding arc discharge of the present invention;

Fig. 3 shows the metal electrode schematic diagram of the present invention;

In the figure: 1-cable wire, 2-plasma spray gun, 3-oil cold box, 4-special reaction tube, 5-gas outlet, 6-metal inner net, 7-metal electrode, 8-transformer oil.

Detailed ways

An oil-cooled sulfur hexafluoride structure based on sliding arc discharge, as shown in Figure 1, shows the structural diagram of its plasma torch and reaction tube. As shown in Figure 2, based on the above oil-cooled SF6 structure, an oil-cooled sliding arc discharge SF ₆ waste gas degradation device is formed, which mainly includes a plasma spray gun, metal electrodes, metal inner mesh, ceramic reaction There are five parts of the pipe and the exhaust gas absorption pool.

The oil-cooled SF ₆ degradation device based on sliding arc discharge of the present invention is shown in Figures 1 to 3 . Cable 1 is at the tail of the plasma spray gun, which includes the power line, grounding line and air intake pipe. The power line brings energy to the plasma spray gun, and the grounding line is connected to the earth to maintain stable and reliable equipment. The air intake pipe is connected to SF ₆ waste gas and carrier gas. The gas source is to send SF ₆ waste gas into the plasma spray gun for degradation reaction.

The plasma torch 2 has a high-voltage electrode and a low-voltage electrode inside, the high-voltage electrode is connected to the high-voltage line 8 introduced from the cable 1 , and the low-voltage electrode is connected to the cable also introduced from the power line 1 . High-frequency high-voltage alternating current is provided by the plasma power supply, and a high-frequency and high-voltage alternating electric field is formed inside the plasma spray gun 2, so that the gas in it is ionized, free electrons are generated, and various types of complex high-energy particles are formed. As the free electrons become more and more The more, an arc will form between the high voltage electrode and the low voltage electrode. The arc will be stretched under the blowing of the SF ₆ mixed gas entering from the air intake pipe. At this time, the SF ₆ gas molecules will collide with the high-energy active particles in the arc, break bonds, dissociate, etc., making the SF ₆ Gas molecules break bonds to form SFx ⁺ free radicals and F ^- ions. SFx ⁺ free radicals will combine with other anions, such as OH ^- ions, etc., to form relatively stable molecules, such as SO ₂ , SO ₂ F ₂ , SOF _{2 ,} etc., thereby achieving the degradation of SF ₆ .

The nozzle of the plasma torch 2 and the connection part of the ceramic reaction tube 4 are the main parts of the discharge reaction. The arc will gradually extend under the blowing of the SF ₆ mixed gas, the arc length will gradually become longer, and the area where the SF ₆ degradation reaction will gradually becomes larger, but the discharge loss that occurs at the same time also gradually increases. When the arc length reaches a certain length, the energy provided by the plasma power supply can no longer maintain the arc to extend forward, so the arc will be extinguished under the blowing of the SF ₆ gas flow, and at the same time, it will be re-formed at the shortest point between the high-voltage electrode and the low-voltage electrode. The arc is extended forward again under the blowing of the SF ₆ mixed gas flow, and the above process is repeated. The stainless steel spiral electrode 4 can assist the electric arc to extend forward, so that the electric arc can be stretched longer, thereby increasing the area where the SF ₆ gas molecules degrade. During the generation and extension of the arc, it will cause energy loss, manifested as luminescence and heat generation, and the temperature can be kept above 600°C during normal use, which will cause serious energy loss and reduce the energy efficiency of SF ₆ degradation. As shown in Figures 1 and 2, by placing the part of the reaction tube where the degradation reaction occurs in a semi-closed oil cooler box 3, where two-thirds of the transformer oil is placed in the oil cooler box 3, it is possible to ensure that the reaction tube part is completely submerged . Four cooling fans are also arranged on the top of the oil cooling box, which can effectively and timely dissipate heat from the transformer oil in the oil cooling box 3 . Under the effect of heat dissipation by the fan of the oil cooling box, it can ensure that the working temperature of the reaction tube does not exceed 200°C during the discharge reaction, so that more energy is used for the degradation of SF ₆ gas, and the energy efficiency of SF ₆ waste gas degradation is greatly improved.

The gas degraded by the sliding arc discharge passes through the remaining part of the reaction tube, and flows out from the gas outlet quick-connect port 5 into the exhaust gas absorption pool. The decomposition products of SF ₆ mainly include SO ₂ F ₂ , SOF ₂ , SO ₂ , HF and other substances, and the plasma generated by sliding arc discharge has the advantages of high intensity and high density, which can degrade SF ₆ more fully and make some decomposition products Further decomposition can occur, _for example _SO2F2 and _SOF2 can be further decomposed into _SO2 and HF. However, SOF ₂ , SO ₂ and HF are all acidic gases, which can react with metal alkali solution and be fixed. Therefore, the toxic gas after SF ₆ discharge degradation will be completely absorbed after passing through the tail gas absorption tank, so that the gas finally discharged into the atmosphere Completely harmless, so as to realize the harmless treatment of SF ₆ waste gas.

Fig. 2 is the mechanism diagram of the oil-cooled SF ₆ degradation device based on the sliding arc discharge of the present invention. The specific operation method of using the oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge in the present invention is as follows: firstly connect the gas circuit and circuit of the device in sequence according to the mechanism diagram of the device to ensure that the gas pipe connection is stable and air-tight, The relevant circuit connections are stable and reliable; check whether the transformer oil in the oil cooler is between 1/2 and 2/3 of the capacity; then observe the capacity and turbidity of the metal alkali solution in the side inspection window of the exhaust gas absorption, and judge accordingly Whether it is necessary to add or replace lye; after the inspection, first turn on the carrier gas valve and cooling fan, then start the plasma power supply, and observe whether the plasma spray gun can generate an arc normally; after the arc is normal, turn on the sulfur hexafluoride exhaust gas valve to start degradation reaction; after working for a long time, it is necessary to observe the temperature of the oil cooler box, if the temperature exceeds 250 ° C, it indicates that the temperature is too high, and the device needs to be shut down to cool down; when the device is ready to stop, first turn off the SF ₆ gas After the flow rate of the _SF6 gas source is 0, turn off the plasma power supply, and keep the carrier gas blowing at this time. One is to ensure that the toxic gas generated by the decomposition of SF6 is completely discharged into the exhaust gas absorption pool. Heat dissipation; the carrier gas can be blown for about one minute, then it can be turned off, that is, the entire degradation process is over, and after the transformer oil in the oil cooling box is cooled, it can be turned on again.

The main innovation of this invention is that it combines the characteristics of sliding arc discharge, proposes an oil-cooled heat dissipation method and improves the specific structure and function details, and changes the structure of the sliding arc electrode, optimizes the metal electrode, and adds a special The metal inner mesh on the inner wall of the reaction tube can better meet the characteristics of degrading SF6 by oil-cooled sliding arc discharge. It can solve the problem of excessive temperature mentioned in the background technology, and at the same time, it can also promote the improvement of degradation rate and energy efficiency, which has relatively good creativity.

The above-mentioned embodiments are only to describe the preferred mode of the present invention, not to limit the scope of the present invention. Without departing from the design spirit of the present invention, those skilled in the art may make various Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (5)

1. A kind of oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge, it is characterized in that, comprises plasma torch, metal electrode, ceramic reaction tube, oil cooling box and tail gas absorption pool; Described plasma torch tail is connected There are power lines, grounding lines and air pipes. The power lines are used for the plasma power supply to supply power to the spray gun. The ground line grounds the shell of the plasma spray gun to ensure the safety and reliability of the equipment. The air pipe is used to allow SF6 waste gas to enter The plasma spray gun undergoes a degradation reaction; the inner wall of the ceramic reaction tube is provided with a metal inner net, and the center of the ceramic reaction tube is also provided with the metal electrode, and the peripheral surface of the metal electrode is threaded. Near the end of the plasma torch, it will discharge with the metal inner grid, and the arc will gradually extend forward along the thread on the surface of the metal electrode, and the reaction area will be gradually elongated; the other end of the ceramic reaction tube is connected with a quick-plug interface through a flange, and Introduced into the exhaust gas absorption pool by connecting the air pipe; the ceramic reaction tube is completely placed in the oil cooling box, the oil cooling box is a semi-closed structure, and several cooling fans are arranged on the top of the oil cooling box; A temperature sensor is arranged at a certain distance from the side of the oil cooling box to the bottom surface so as to display the oil temperature inside the oil cooling box in real time. 2. The oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge according to claim 1, characterized in that four cooling fans are arranged on the top of the oil-cooled box. 3. The oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge according to claim 1, characterized in that, a temperature sensor is provided at a place 20 cm from the bottom surface of the oil-cooled box side. 4. The oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge according to claim 1, characterized in that, half of the side of the tail gas absorption pool is provided with an inspection window, and the capacity of the metal alkali solution inside the absorption pool can be observed and cloudy state. 5. the degradation method of the oil-cooled sulfur hexafluoride degradation device based on sliding arc discharge according to claim 1, is characterized in that, comprises the steps: Step 1. Preparation before degradation: First, connect the circuit and gas circuit respectively according to the mechanism diagram of the oil-cooled SF6 degradation device based on sliding arc discharge; check the liquid level of the transformer oil in the oil-cooled box to ensure that the liquid level is at half Between one and two-thirds; then observe the liquid level and turbid state of the metal alkali solution from the side inspection window of the tail gas absorption tank, and judge whether it is necessary to add or replace the metal alkali solution, and also need to observe the tail gas absorption tank If there is a lot of sediment at the bottom, it needs to be cleaned. Since the sediment is common sulfate, which exists widely in nature, it can be discarded directly; Step 2. Start the degradation device: first open the carrier gas valve, adjust the gas flow meter to maintain a constant and stable gas flow rate, then turn on the cooling fan of the oil cooling box, and start the plasma power supply. Under normal conditions, it can be observed that The arc is extended and slides inside the ceramic reaction tube; if no obvious arc is observed after turning on the power supply, the plasma power supply needs to be checked. After the arc can slide normally, open the SF6 waste gas valve, adjust the flow rate to an appropriate level, and start the degradation reaction; after one hour of continuous operation, it is necessary to start to observe the temperature of the oil cooler. It should exceed 250°C. If the temperature exceeds 250°C, it indicates that the operating temperature of the reactor is too high, and the device needs to be closed for natural cooling; Step 3. Close the degradation device: first close the SF ₆ waste gas valve, the SF ₆ waste gas flow rate will gradually decrease, and when the flow rate of the SF ₆ gas source drops to 0, the plasma power supply will be turned off after the device continues to work for one minute. During this period, the load must be kept Continuous gas blowing, on the one hand, can ensure that most of the SF ₆ waste gas in the reactor is degraded, and the degraded tail gas is blown into the tail gas absorption pool; on the other hand, it can dissipate heat to a certain extent inside the reaction tube. After the carrier gas is blown for one minute, the carrier gas valve can be closed to complete the degradation. After the transformer oil in the oil cooling box is cooled, the machine can be turned on again.

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