A rapid separation and recovery device and method for SF6 / CF4 mixed gas

Abstract

This invention discloses a rapid separation and recovery device for SF6 / CF4 mixed gas, comprising a first solenoid valve, a first compressor, an alkaline solution tank, a first adsorption column, a second adsorption column, a second solenoid valve, and a third adsorption column connected in series. A normal temperature gas path and a cryogenic gas path are connected in parallel at the outlet of the third adsorption column. The normal temperature gas path includes a third compressor and a seventh solenoid valve connected in series. The cryogenic gas path includes a third solenoid valve, a cryogenic device, a second compressor, and a fifth solenoid valve. The seventh and fifth solenoid valves are combined at the discharge port. This invention uses an adsorbent to first adsorb a portion of the CF4 gas. Although the proportion of CF4 in the adsorbed gas is still high, the total amount of gas requiring refrigeration is significantly reduced, improving refrigeration efficiency. Compared to refrigerating the gas, heating the solid granular activated carbon is more efficient and consumes less energy.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, specifically to a device and method for rapid separation and recovery of SF6 / CF4 mixed gas. Background Technology

[0002] With the introduction of the "dual carbon" target, the State Grid Corporation of China is striving to promote the use of mixed gases to replace the highly greenhouse gas sulfur hexafluoride (SF6) in order to reduce its usage and emissions. Carbon tetrafluoride (CF4) and SF6 exhibit good synergistic properties; related studies have shown that, under certain proportions and pressures, their insulation and arc-extinguishing performance can meet the requirements of high-voltage circuit breakers. Furthermore, CF4 has an extremely low liquefaction temperature, making the mixture more difficult to liquefy than pure SF6. While SF6 / CF4 mixed gas electrical equipment is being widely deployed, the corresponding operation, maintenance, and repair technologies and equipment are severely lacking and urgently need improvement.

[0003] Electrical equipment containing SF6 / CF4 mixed gases may experience latent faults during long-term use, requiring maintenance. The first step in the maintenance process is to separate and recover the SF6 / CF4 mixture from the equipment. However, separating CF4 from SF6 remains a significant technical challenge in the industry. Current methods for separating SF6 and CF4 primarily employ cryogenic methods, utilizing the difficulty of liquefying CF4. The mixed gas is cooled to liquefy the SF6, and high-purity SF6 and CF4 are obtained by separating the liquid and gas phases. However, this method has inherent drawbacks such as long processing time and high energy consumption. Furthermore, adsorption methods commonly used in SF6 purification are unsuitable for CF4 separation because the CF4 molecule has a tetrahedral structure and stable physicochemical properties, resulting in poor adsorption performance of adsorbents. These methods can only achieve coarse separation, leaving the separated gas still containing a certain amount of the other component.

[0004] Therefore, there is an urgent need to find a separation and recovery method to achieve efficient and rapid separation and recovery of SF6 and CF4. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to solve the cost and speed issues of SF6 and CF4 separation.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A rapid separation and recovery device for SF6 / CF4 mixed gas includes a first solenoid valve, a first compressor, an alkali tank, a first adsorption column, a second adsorption column, a second solenoid valve, and a third adsorption column connected in series. The outlet end of the third adsorption column is connected in parallel to a normal temperature gas path and a cryogenic gas path. The normal temperature gas path includes a third compressor and a seventh solenoid valve connected in series. The cryogenic gas path includes a third solenoid valve, a cryogenic device, a second compressor, and a fifth solenoid valve. The seventh and fifth solenoid valves are combined at the discharge port.

[0008] The cryogenic equipment has a fourth solenoid valve, a storage tank, a liquid pump, and a sixth solenoid valve connected in series at its drain port.

[0009] A heating rod is installed inside the third adsorption column.

[0010] Furthermore, the cryogenic device includes a cryogenic tank, a refrigeration unit, a refrigeration coil, a second temperature sensor, and a pressure sensor; the refrigeration coil is located inside the cryogenic tank, and the refrigeration unit provides cooling to the refrigeration coil; the second temperature sensor and the pressure sensor are installed on the cryogenic tank and are used to detect the temperature and pressure of the cryogenic tank.

[0011] Furthermore, the third adsorption column is also equipped with a first temperature sensor.

[0012] Furthermore, the first adsorption column is filled with a desiccant.

[0013] Furthermore, the second adsorption column is filled with KD03 and 13X molecular sieves.

[0014] This invention also provides a method for rapid separation and recovery of SF6 / CF4 mixed gas, applied to the above-mentioned apparatus, characterized by comprising the following steps:

[0015] (1) Open the first solenoid valve, the second solenoid valve and the third solenoid valve. The SF6 / CF4 mixed gas to be separated and recovered is drawn into the device from the inlet by the first compressor. First, it passes through the alkaline pool to adsorb trace acidic gases such as SO2 and HF in the mixed gas. Then, it passes through the first adsorption column containing desiccant to adsorb moisture. The mixed gas then enters the second adsorption column to remove the main gaseous impurities such as CO, SO2 and F2. Finally, the mixed gas enters the cryogenic tank.

[0016] (2) The refrigeration unit controls the refrigeration coil to refrigerate the cryogenic tank, and the refrigeration temperature is set to -40℃; the second temperature sensor and pressure sensor monitor the temperature T and pressure P inside the tank. If T < 20℃ and P < 3.0MPa, the mixed gas continues to enter the cryogenic tank; as the temperature inside the tank gradually decreases and the pressure gradually increases, the SF6 gas begins to liquefy. When the liquid level gauge in the tank shows that the liquid level is higher than h1, the fourth solenoid valve is opened. Under the action of gravity, the SF6 liquid enters the storage tank through the pipeline. When the liquid level is lower than h2 (h1 > h2), the fourth solenoid valve is closed until it is higher than h1 again and then opened; during the period when the fourth solenoid valve is closed, the sixth solenoid valve is opened and the liquid pump is started to fill the SF6 liquid through the SF6 outlet.

[0017] (3) If T < 20℃ and P > 3.0MPa, close the first compressor and the third solenoid valve; if the liquid level is higher than h1, open the fourth solenoid valve and close the fourth solenoid valve when the liquid level is lower than h2; otherwise, no action is required; at this time, there is very little SF6 liquid in the cryogenic tank and the purity of CF4 in the tank is very high; the fifth solenoid valve is opened, the second compressor is started, the high-purity CF4 gas is extracted, pressurized and bottled, and stopped when the pressure in the cryogenic tank P < 0.1MPa, and the fifth solenoid valve and the second compressor are closed;

[0018] (4) Continue to open the first compressor and the third solenoid valve, and repeat steps (1) to (3) until all the mixed gas to be recovered is processed; at this time, only open the fifth solenoid valve and the sixth solenoid valve, and the liquid pump continues to work for 10 minutes to recover all the SF6 liquid in the storage tank. The second compressor recovers the gas in the cryogenic tank to 0.1MPa; then close all solenoid valves and compressors.

[0019] (5) After the recovery is completed, the CF4 adsorbed in the third adsorption column is desorbed, the seventh solenoid valve is opened, the third compressor is started, the heating rod is started to heat the adsorbent to 150°C, all the CF4 gas is desorbed and pressurized by the third compressor and bottled through the CF4 outlet, and then all solenoid valves and compressors are closed, and the separation and recovery work is completed.

[0020] The advantages of this invention are:

[0021] This invention employs an adsorbent to first adsorb a portion of the CF4 gas. Although the proportion of CF4 in the adsorbed gas remains high, the total amount of gas requiring refrigeration is significantly reduced, thus improving refrigeration efficiency. Compared to refrigerating the gas itself, heating the solid granular activated carbon is more efficient and consumes less energy. Therefore, compared to treating all the gas through cryogenic processes, this invention, using a method of partial cryogenic treatment followed by partial heating and desorption, significantly improves working efficiency, saves working time, and reduces energy consumption. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the overall structure of the device in an embodiment of the present invention.

[0023] 1. Inlet, 2. First solenoid valve, 3. First compressor, 4. Alkali tank, 5. First adsorption column, 6. Second adsorption column, 7. Second solenoid valve, 8. First temperature sensor, 9. Heating rod, 10. Third adsorption column, 11. Second temperature sensor and 12. Pressure sensor, 13. Third compressor, 14. Third solenoid valve, 15. Seventh solenoid valve, 16. Refrigeration unit, 17. Cryogenic tank, 18. Refrigeration coil, 20. Fourth solenoid valve, 21. Second compressor, 22. Fifth solenoid valve, 23. Outlet, 24. Liquid storage tank, 25. Liquid pump, 26. Sixth solenoid valve, 27. Outlet. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figure 1 As shown in the figure, this embodiment describes a rapid separation and recovery device for SF6 / CF4 mixed gas, including a first solenoid valve 2, a first compressor 3, an alkaline solution tank 4, a first adsorption column 5, a second adsorption column 6, a second solenoid valve 7, and a third adsorption column 10 connected in series. A normal temperature gas path and a cryogenic gas path are connected in parallel at the outlet end of the third adsorption column 10. The normal temperature gas path includes a third compressor 13 and a seventh solenoid valve 15 connected in series. The cryogenic gas path includes a third solenoid valve 14, a cryogenic device, a second compressor 21, and a fifth solenoid valve 22. The seventh solenoid valve 15 and the fifth solenoid valve 22 are combined to a discharge port 23. The discharge port of the cryogenic device is connected in series with a fourth solenoid valve 20, a storage tank 24, a liquid pump 25, and a sixth solenoid valve 26.

[0026] In this embodiment, the cryogenic device includes a cryogenic tank 17, a refrigeration unit 16, a refrigeration coil 18, a second temperature sensor 11, and a pressure sensor 12; the refrigeration coil 18 is located inside the cryogenic tank 17, and the refrigeration unit 16 provides cooling to the refrigeration coil 18; the second temperature sensor 11 and the pressure sensor 12 are disposed on the cryogenic tank 17 and are used to detect the temperature and pressure of the cryogenic tank 17.

[0027] The first adsorption column 5 is filled with a desiccant. The second adsorption column 6 is filled with KD03 and 13X molecular sieves. The third adsorption column 10 is also equipped with a first temperature sensor 8 and a heating rod 9.

[0028] Based on the above-described apparatus, the gas separation and collection method of this embodiment is as follows:

[0029] Step 1. Open the first solenoid valve 2, the second solenoid valve 7, and the third solenoid valve 14. The SF6 / CF4 mixed gas to be separated and recovered is drawn into the device from the inlet 1 by the first compressor 3. First, it passes through the alkaline solution tank 4 to adsorb trace acidic gases such as SO2 and HF in the mixed gas. Then, it passes through the first adsorption column 5 containing desiccant to adsorb moisture, so as to prevent the adsorbent in the later stage from reducing its adsorption capacity for other gaseous impurities due to water absorption. The mixed gas then enters the second adsorption column 6 containing KD03 and 13X molecular sieves to remove the main gaseous impurities such as CO, SO2, and F2 (thionyl fluoride). At this time, the mixed gas is purified. Finally, the mixed gas enters the cryogenic tank 17.

[0030] Step 2. The refrigeration unit 16 controls the refrigeration coil 18 to refrigerate the cryogenic tank, and the refrigeration temperature is set to -40℃. The second temperature sensor 11 and the pressure sensor 12 monitor the temperature T and pressure P inside the tank. If T < 20℃ and P < 3.0MPa, the mixed gas continues to enter the cryogenic tank. As the temperature inside the tank gradually decreases and the pressure gradually increases, the SF6 gas begins to liquefy. When the liquid level gauge in the tank shows that the liquid level is higher than h1, the fourth solenoid valve 20 is opened. Under the action of gravity, the SF6 liquid enters the storage tank 24 through the pipeline. When the liquid level is lower than h2 (h1 > h2), the fourth solenoid valve 20 is closed until it is higher than h1 again and then opened. During the period when the fourth solenoid valve 20 is closed, the sixth solenoid valve 26 is opened and the liquid pump 25 is started to fill the SF6 liquid into bottles through the SF6 outlet 27.

[0031] Step 3. If T < 20℃ and P > 3.0MPa, close the first compressor 3 and the third solenoid valve 14; if the liquid level is higher than h1, open the fourth solenoid valve 20, and close the fourth solenoid valve 20 when the liquid level is lower than h2; otherwise, no action is required; at this time, there is very little SF6 liquid in the cryogenic tank, and the purity of CF4 in the tank is extremely high; fifth, open the solenoid valve 22, start the second compressor 21, extract the high-purity CF4 gas, pressurize and fill the bottle, stop when the pressure in the cryogenic tank P < 0.1MPa, and close the fifth solenoid valve 22 and the second compressor 21;

[0032] Step 4. Continue to open the first compressor 3 and the third solenoid valve 14, and repeat steps 1 to 3 until all the mixed gas to be recovered is processed; at this time, only open the fifth solenoid valve 22 and the sixth solenoid valve 26, and the liquid pump 25 continues to work for 10 minutes to recover all the SF6 liquid in the liquid storage tank 24, and the second compressor 21 recovers the gas in the cryogenic tank 17 to 0.1 MPa; then close all solenoid valves and compressors.

[0033] Step 5. After the recovery is completed, the CF4 adsorbed in the third adsorption column 10 is desorbed, the seventh solenoid valve 15 is opened, the third compressor 13 is started, and the heating rod 9 is started to heat the adsorbent to 150°C. All the CF4 gas is desorbed and pressurized by the third compressor 13 and bottled through the CF4 outlet 23. Then all solenoid valves and compressors are closed, and the separation and recovery work is completed.

[0034] This method employs an adsorbent to first adsorb a portion of the CF4 gas. Although the proportion of CF4 in the adsorbed gas remains high, the total amount of gas requiring refrigeration is significantly reduced, thus improving refrigeration efficiency. Compared to refrigerating the gas, heating the solid granular activated carbon is more efficient and consumes less energy. Therefore, compared to treating all the gas through cryogenic processes, this invention uses a method of partial cryogenic treatment combined with partial heating and desorption, which significantly improves working efficiency, saves working time, and reduces energy consumption.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid separation and recovery device for SF6 / CF4 mixed gas, characterized in that, The system includes a first solenoid valve (2), a first compressor (3), an alkali tank (4), a first adsorption column (5), a second adsorption column (6), a second solenoid valve (7), and a third adsorption column (10) connected in series. The outlet of the third adsorption column (10) is provided with a normal temperature gas path and a cryogenic gas path in parallel. The normal temperature gas path includes a third compressor (13) and a seventh solenoid valve (15) connected in series. The cryogenic gas path includes a third solenoid valve (14), a cryogenic device, a second compressor (21), and a fifth solenoid valve (22). The seventh solenoid valve (15) and the fifth solenoid valve (22) are combined to the outlet (23). The cryogenic equipment has a fourth solenoid valve (20), a storage tank (24), a liquid pump (25), and a sixth solenoid valve (26) connected in series at its drain port. A heating rod (9) is provided inside the third adsorption column (10).

2. The SF6 / CF4 mixed gas rapid separation and recovery device according to claim 1, characterized in that, The cryogenic equipment includes a cryogenic tank (17), a refrigeration unit (16), a refrigeration coil (18), a second temperature sensor (11), and a pressure sensor (12); the refrigeration coil (18) is located inside the cryogenic tank (17), and the refrigeration unit (16) provides cooling to the refrigeration coil (18); the second temperature sensor (11) and the pressure sensor (12) are installed on the cryogenic tank (17) to detect the temperature and pressure of the cryogenic tank (17).

3. A rapid separation and recovery device for SF6 / CF4 mixed gas according to claim 1 or 2, characterized in that, The third adsorption column (10) is also equipped with a first temperature sensor (8).

4. A rapid separation and recovery device for SF6 / CF4 mixed gas according to claim 1 or 2, characterized in that, The first adsorption column (5) contains a desiccant.

5. A rapid separation and recovery device for SF6 / CF4 mixed gas according to claim 1 or 2, characterized in that, The second adsorption column (6) is filled with KD03 and 13X molecular sieves.

6. A method for rapid separation and recovery of SF6 / CF4 mixed gas, applied to the apparatus described in any one of claims 3 to 5, characterized in that, Includes the following steps: (1) Open the first solenoid valve (2), the second solenoid valve (7), and the third solenoid valve (14). The SF6 / CF4 mixed gas to be separated and recovered is drawn into the device from the inlet (1) by the first compressor (3). First, it passes through the alkaline tank (4) to adsorb trace amounts of acidic gas in the mixed gas. Then, it passes through the first adsorption column (5) containing desiccant to adsorb moisture. The mixed gas then enters the second adsorption column (6) to remove the main gas impurities. Finally, the mixed gas enters the cryogenic tank (17). (2) The refrigeration unit (16) controls the refrigeration coil (18) to refrigerate the cryogenic tank (17), and the refrigeration temperature is set to -40℃; the second temperature sensor (11) and the pressure sensor (12) monitor the temperature T and pressure P inside the tank. If T < 20℃ and P < 3.0MPa, the mixed gas continues to enter the cryogenic tank (17); as the temperature inside the tank gradually decreases and the pressure gradually increases, the SF6 gas begins to liquefy. When the liquid level gauge inside the tank shows that the liquid level is higher than h1, the fourth solenoid valve (20) is opened. Under the action of gravity, the SF6 liquid enters the storage tank (24) through the pipeline. When the liquid level is lower than h2, h1 > h2, the fourth solenoid valve (20) is closed until it is higher than h1 again and then opened; during the period when the fourth solenoid valve (20) is closed, the sixth solenoid valve (26) is opened and the liquid pump (25) is started to fill the SF6 liquid through the SF6 outlet (27) into bottles; (3) If T < 20℃ and P > 3.0MPa, close the first compressor (3) and the third solenoid valve (14); if the liquid level is higher than h1, open the fourth solenoid valve (20), and close the fourth solenoid valve (20) when the liquid level is lower than h2; otherwise, no action is required; at this time, there is very little SF6 liquid in the cryogenic tank and the purity of CF4 in the tank is very high; Open the fifth solenoid valve (22), start the second compressor (21), extract the high-purity CF4 gas, pressurize and fill the bottle, stop when the pressure in the cryogenic tank P < 0.1MPa, and close the fifth solenoid valve (22) and the second compressor (21). (4) Continue to open the first compressor (3) and the third solenoid valve (14), and repeat steps (1) to (3) until all the mixed gas to be recovered is processed; at this time, only open the fifth solenoid valve (22) and the sixth solenoid valve (26), and the liquid pump (25) continues to work for 10 minutes to recover all the SF6 liquid in the storage tank (24), and the second compressor (21) recovers the gas in the cryogenic tank (17) to 0.1MPa; then close all solenoid valves and compressors; (5) After the recovery is completed, the CF4 adsorbed in the third adsorption column (10) is desorbed, the seventh solenoid valve (15) is opened, the third compressor (13) is started, the heating rod (9) is started to heat the adsorbent to 150°C, all the CF4 gas is desorbed and pressurized by the third compressor (13) and bottled through the CF4 outlet (23), and then all solenoid valves and compressors are closed, and the separation and recovery work is completed.

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