A dual-tower combined argon recovery and purification system and method

Abstract

This invention provides a dual-tower combined argon gas recovery and purification system and method. The system includes a cold box, an argon distillation unit, and a nitrogen distillation unit. The argon distillation unit is located inside the cold box and includes an argon distillation column, an argon condenser, and a liquid argon inlet. The argon condenser is located at the top of the inner cavity of the argon distillation column, and the liquid argon inlet is located at the top of the argon distillation column and communicates with the argon condenser. The nitrogen distillation unit is located inside the cold box and includes a nitrogen distillation column, a first conveying pipe, and a second conveying pipe. The nitrogen distillation column is connected to the inlet of the argon condenser through the first conveying pipe and to the outlet of the argon condenser through the second conveying pipe. The nitrogen introduced into the argon condenser can recover excess cold energy from the liquid argon to form liquid nitrogen. Finally, the liquid nitrogen is sent back to the nitrogen distillation column through the second conveying pipe. The recovered liquid nitrogen can be sold as a byproduct, increasing economic benefits and avoiding the waste of cold energy caused by the vaporization of liquid argon at room temperature.

Description

Technical Field

[0001] This invention relates to the field of gas purification and recovery technology, and in particular to a dual-tower combined argon gas recovery and purification system and method. Background Technology

[0002] The Czochralski method is the primary method for producing monocrystalline silicon, and the majority of monocrystalline silicon globally is produced using this method. The most commonly used Czochralski process for producing monocrystalline silicon employs a reduced-pressure crystal pulling process, which resembles both a vacuum process and a flowing atmosphere process. In this reduced-pressure process, high-purity argon gas is continuously and at a constant speed introduced into the furnace chamber during the silicon single-crystal pulling process, while a vacuum pump continuously pumps argon gas out of the furnace chamber, maintaining a stable vacuum level of approximately 20 Torr. This process combines the characteristics of both vacuum and flowing atmosphere processes. The vacuum pump in the reduced-pressure crystal pulling process typically uses a slide valve pump, a mechanical vacuum pump that uses oil to maintain a seal. The argon gas carries silicon oxides and volatile impurities generated during the high-temperature single-crystal pulling process and is discharged into the atmosphere through the vacuum pump. Analysis of the emitted argon gas reveals that the main impurities are dust, O2, N2, CO, CO2, CH4 and other alkanes, and liquid lubricating oil mist. Recycling and utilizing this argon gas has significant practical implications.

[0003] In existing technologies, common methods for argon gas recovery and purification are as follows: First, the argon gas recovered from the single crystal furnace undergoes rough oil removal, followed by high-precision oil and dust removal after compression and cooling. Next, high-temperature catalysis is used to react hydrocarbons such as methane and carbon monoxide with oxygen to produce water and carbon dioxide, ensuring an excess of oxygen during the catalytic reaction (adding oxygen if there is insufficient impurity oxygen). After cooling, the excess oxygen reacts with added hydrogen under the action of a catalyst to produce water, ensuring an excess of hydrogen. The impurity components in the treated argon gas are water, carbon dioxide, hydrogen, and nitrogen. Then, the water and carbon dioxide are adsorbed by an argon gas room-temperature adsorption unit to obtain crude argon gas containing only nitrogen and hydrogen as impurities. Finally, the crude argon gas is passed into an argon gas distillation column to separate hydrogen and nitrogen, yielding argon gas. Argon distillation columns typically require the addition of liquid argon to provide cooling. Since the general argon recovery rate is 92%, 8% of the liquid argon needs to be vaporized to compensate for the loss of argon. However, 2% of the liquid argon usually provides sufficient cooling for the argon distillation column, so about 6% of the liquid argon will be vaporized at room temperature to compensate for this loss of argon, resulting in a waste of cooling capacity. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a dual-tower combined argon recovery and purification system to solve the technical problem in the prior art where, when liquid argon is added to the argon distillation tower to compensate for argon loss, part of the cold energy of the liquid argon is consumed by vaporization at room temperature, resulting in a waste of cold energy.

[0005] This invention proposes a dual-tower combined argon gas recovery and purification system, comprising:

[0006] Cold box;

[0007] An argon distillation unit is provided inside the cold box. The argon distillation unit includes an argon distillation column, an argon condenser, and a liquid argon inlet. The argon condenser is located at the top of the inner cavity of the argon distillation column, and the liquid argon inlet is located at the top of the argon distillation column and communicates with the argon condenser. The liquid argon inlet is used to add liquid argon to the argon condenser.

[0008] A nitrogen distillation unit is provided inside the cold box. The nitrogen distillation unit includes a nitrogen distillation column, a first conveying pipe, and a second conveying pipe. The nitrogen distillation column is connected to the inlet end of the argon condenser through the first conveying pipe and to the outlet end of the argon condenser through the second conveying pipe.

[0009] Furthermore, the dual-tower combined argon recovery and purification system further includes an argon coarse filtration unit and a nitrogen coarse filtration unit located outside the cold box, as well as a first main heat exchanger and a second main heat exchanger located inside the cold box. The argon coarse filtration unit is used to recover waste argon from the single crystal furnace and filter it into crude argon containing only nitrogen and hydrogen. The first main heat exchanger is used to receive the crude argon from the argon coarse filtration unit and cool it before sending it into the argon distillation tower to produce pure argon.

[0010] The nitrogen coarse filtration unit is used to extract air and remove carbon dioxide and water from it. The second main heat exchanger is used to receive air from the nitrogen coarse filtration unit, cool the air, and send it into the nitrogen distillation column to produce nitrogen.

[0011] Furthermore, in the dual-tower combined argon gas recovery and purification system, the first main heat exchanger and the second main heat exchanger are combined into one.

[0012] Furthermore, in the dual-tower combined argon recovery and purification system, the argon coarse filtration unit includes a first molecular sieve and a first argon delivery pipeline. One end of the first argon delivery pipeline is connected to the outlet end of the first molecular sieve, and the other end is sequentially connected to the first main heat exchanger and the argon distillation tower.

[0013] The cold box is equipped with an expander. A third conveying pipe is connected to the first conveying pipe. The third conveying pipe is used to send the nitrogen produced in the nitrogen distillation column into the second main heat exchanger for reheating. Then, the reheated nitrogen is sent into the expander for expansion to generate cooling capacity. Then, the expanded nitrogen is sent back to the cold end of the second main heat exchanger for the second main heat exchanger to recover the cooling capacity. Finally, the nitrogen is sent out of the second main heat exchanger as purge gas and enters the first molecular sieve. The first conveying pipe is equipped with a first throttling valve for controlling the nitrogen entering the argon condenser. The third conveying pipe is equipped with a molecular sieve regeneration heater for heating the purge gas about to enter the first molecular sieve.

[0014] Furthermore, in the dual-tower combined argon recovery and purification system, a reboiler is provided at the bottom of the inner cavity of the argon distillation tower, the end of the first argon delivery pipe away from the first molecular sieve is connected to the inlet end of the reboiler, the outlet end of the reboiler is provided with a first reflux pipe connected to the middle of the argon distillation tower, the bottom of the argon distillation tower is provided with a second reflux pipe connected to the argon condenser, a second throttling valve is provided on the first reflux pipe, and a third throttling valve is provided on the second reflux pipe.

[0015] Furthermore, in the dual-tower combined argon gas recovery and purification system, the top of the argon distillation tower is provided with a waste gas discharge pipe and a pure argon gas discharge pipe. The waste gas discharge pipe passes through the first main heat exchanger and connects to the first molecular sieve. The pure argon gas discharge pipe passes through the first main heat exchanger and extends out of the cold box. The end of the pure argon gas discharge pipe is connected to a pure argon gas compressor.

[0016] Furthermore, in the dual-tower combined argon gas recovery and purification system, the argon coarse filtration unit further includes a second argon gas delivery pipeline. One end of the second argon gas delivery pipeline is connected to the inlet of the first molecular sieve, and the other end is connected to a dust filter. A dual-membrane gas holder system, a crude argon gas compressor, a water cooler, a high-precision oil removal system, a regenerator, a crude argon gas heater, a carbon monoxide removal reactor, a deoxygenation reactor, and a crude argon gas cooler are sequentially arranged on the second argon gas delivery pipeline after the dust filter.

[0017] Furthermore, in the dual-tower combined argon recovery and purification system, the nitrogen coarse filtration unit further includes an air delivery pipeline. One end of the air delivery pipeline passes through the second main heat exchanger and connects to the nitrogen distillation tower, while the other end is connected to an air filter. An air compressor, an air cooling unit, and a second molecular sieve are sequentially arranged on the air delivery pipeline after the air filter.

[0018] The top of the nitrogen distillation column is equipped with a nitrogen delivery pipe and a liquid nitrogen discharge pipe. The nitrogen delivery pipe passes through the second main heat exchanger and connects to the second molecular sieve. The liquid nitrogen discharge pipe extends out of the cold box and is equipped with a liquid nitrogen valve for controlling the discharge of liquid nitrogen.

[0019] Furthermore, in the dual-tower combined argon recovery and purification system, the bottom of the nitrogen distillation tower is provided with a third reflux pipe connected to its top, and the third reflux pipe is provided with a fourth throttling valve.

[0020] In another aspect, the present invention also proposes a dual-tower combined argon recovery and purification method for use in the dual-tower combined argon recovery and purification system described in the above technical solution, the method comprising the following steps:

[0021] a) Purification of waste argon gas: The waste argon gas from the single crystal furnace is filtered to obtain crude argon gas containing only nitrogen and hydrogen as impurities.

[0022] b) Crude argon gas distillation: Crude argon gas is passed into an argon distillation column and separated according to the different boiling points of argon, nitrogen and hydrogen. Liquid argon is obtained at the bottom of the argon distillation column and distillation waste gas is discharged at the top of the argon distillation column. The distillation waste gas includes hydrogen and nitrogen.

[0023] c) Cold energy recovery: A portion of the nitrogen in the nitrogen distillation column is transferred to the argon distillation column through the first conveying pipeline to recover the excess cold energy of the liquid argon in the argon distillation column to form liquid nitrogen, which is then sent back to the nitrogen distillation column through the second conveying pipeline.

[0024] d) Production of pure argon: Liquid argon is extracted from the argon distillation column and reheated to generate pure argon.

[0025] The aforementioned dual-tower combined argon recovery and purification system and method, by combining an argon distillation unit and a nitrogen distillation unit, allows the cooling capacity of liquid argon added to the argon condenser to be fully utilized. Specifically, when the user adds liquid argon to the argon condenser through the liquid argon inlet, the nitrogen distillation tower can send a portion of nitrogen into the argon condenser through the first delivery pipe. The nitrogen introduced into the argon condenser can recover the excess cooling capacity of the liquid argon to form liquid nitrogen. Finally, the liquid nitrogen is sent back to the nitrogen distillation tower through the second delivery pipe. The recovered liquid nitrogen can be sold as a by-product, increasing economic benefits and avoiding the waste of cooling capacity caused by the vaporization of liquid argon at room temperature. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the argon recovery and purification system in this invention;

[0027] Figure 2 This is a flowchart of the argon gas recovery and purification method in this invention;

[0028] Explanation of key component symbols:

[0029] 101. Dust filter; 102. Dual-membrane gas holder system; 103. Crude argon compressor; 104. Water cooler; 105. High-precision oil removal system; 106. Regenerator; 107. Crude argon heater; 108. Carbon monoxide removal reactor; 109. Deoxygenation reactor; 110. Crude argon cooler; 111. First molecular sieve; 112. First main heat exchanger; 113. Argon distillation column; 114. Pure argon compressor; 201. Air filter; 202. Air compressor; 203. Air cooling unit; 204. Second molecular sieve; 205. Second main heat exchanger; 206. Nitrogen distillation column; 300. Cold box; 11. Argon 12. Liquid argon inlet; 13. First argon delivery pipeline; 14. Expander; 15. Third delivery pipeline; 16. First throttle valve; 17. Molecular sieve regeneration heater; 18. Reboiler; 19. First reflux pipe; 20. Second reflux pipe; 21. Second throttle valve; 22. Third throttle valve; 23. Waste gas discharge pipe; 24. Pure argon gas discharge pipe; 25. Second argon delivery pipeline; 26. First delivery pipeline; 27. Second delivery pipeline; 31. Air delivery pipeline; 32. Nitrogen delivery pipeline; 33. Liquid nitrogen discharge pipe; 34. Liquid nitrogen valve; 35. Third reflux pipe; 36. Fourth throttle valve; 400. Analyzer.

[0030] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Please see Figure 1 The first embodiment of the present invention provides a dual-tower combined argon recovery and purification system, including a cold box 300 and an argon distillation unit and a nitrogen distillation unit disposed within the cold box 300.

[0034] The aforementioned argon distillation unit includes an argon distillation column 113, an argon condenser 11, and a liquid argon inlet 12. The argon condenser 11 is located at the top of the inner cavity of the argon distillation column 113, and the liquid argon inlet 12 is located at the top of the argon distillation column 113 and communicates with the argon condenser 11. The liquid argon inlet 12 is used to add liquid argon to the argon condenser 11, which serves two purposes: firstly, to provide cooling to the argon condenser 11, and secondly, to compensate for argon loss during the distillation process and improve the argon recovery rate.

[0035] It should be explained that the reason for adding liquid argon to the argon condenser 11 is that there is a certain loss of argon during the distillation process. In this embodiment, the argon recovery rate is about 92%, and 8% liquid argon needs to be added for vaporization to make up for the loss of argon. However, the 2% liquid argon provided by the argon distillation column 113 is usually sufficient for cooling, so about 6% of the liquid argon needs to be vaporized at room temperature to make up for this part of the lost argon. This leads to a waste of cooling capacity. In order to reasonably recover this part of the cooling capacity of liquid argon, we have integrated a nitrogen distillation unit on the basis of the argon distillation unit.

[0036] Specifically, the nitrogen distillation unit includes a nitrogen distillation column 206, a first conveying pipe 26, and a second conveying pipe 27. The nitrogen distillation column 206 is connected to the inlet of the argon condenser 11 via the first conveying pipe 26 and to the outlet of the argon condenser 11 via the second conveying pipe 27. In practical applications, the nitrogen distillation column 206 can feed a portion of nitrogen into the argon condenser 11 via the first conveying pipe 26. Specifically, the flow rate of the nitrogen can be controlled by the first throttle valve 16. After the nitrogen enters the argon condenser 11, the excess cooling capacity of the liquid argon can be recovered to form liquid nitrogen, which is then sent back to the nitrogen distillation column 206 via the second conveying pipe 27. The recovered liquid nitrogen can be sold as a byproduct, increasing economic benefits and avoiding the waste of cooling capacity caused by the vaporization of liquid argon at room temperature.

[0037] Specifically, in this embodiment, the dual-tower combined argon recovery and purification system also includes an argon coarse filtration unit and a nitrogen coarse filtration unit located outside the cold box 300, as well as a first main heat exchanger 112 and a second main heat exchanger 205 located inside the cold box 300.

[0038] The argon coarse filtration unit is used to recover waste argon from the single crystal furnace and filter it into crude argon containing only nitrogen and hydrogen. The first main heat exchanger 112 is used to receive the crude argon from the argon coarse filtration unit and cool the crude argon before sending it into the argon distillation column 113 to produce pure argon.

[0039] In another embodiment, the first main heat exchanger 112 and the second main heat exchanger 205 can also be combined into one.

[0040] The nitrogen coarse filtration unit is used to extract air and remove carbon dioxide and water from it. The second main heat exchanger 205 is used to receive air from the nitrogen coarse filtration unit, cool the air, and send it into the nitrogen distillation column 206 to produce nitrogen.

[0041] Specifically, the argon coarse filtration unit includes a first molecular sieve 111 and a first argon delivery pipe 13. One end of the first argon delivery pipe 13 is connected to the outlet end of the first molecular sieve 111, and the other end is connected in sequence to the first main heat exchanger 112 and the argon distillation column 113.

[0042] In this embodiment, the first molecular sieve 111 may consist of two adsorbers. When one adsorber is performing adsorption, the other adsorber is regenerated. The regeneration steps include depressurization, heating, cooling, and displacement. The two adsorbers are automatically switched between operation by a time program controller.

[0043] The purge gas (nitrogen) used for the regeneration of the first molecular sieve 111 is mainly supplied through a nitrogen distillation column 206. It should be noted that by introducing nitrogen, it competes with the argon on the adsorbent for adsorption, gradually displacing the argon. Subsequently, the nitrogen and the argon are collected and processed together, while the adsorbent is ready for the next round of adsorption. The choice of these regeneration methods depends on the design of the adsorber and the application scenario. The purpose of adsorber regeneration is to ensure that the adsorber can continuously and efficiently recover argon and that the adsorbent can be recycled, reducing argon waste and costs.

[0044] In practical applications, nitrogen leaving the nitrogen distillation column 206 typically has a pressure of 4.0 barg or higher, but nitrogen in the first molecular sieve 111 generally only needs a pressure of 0.1 to 0.2 barg. Therefore, if nitrogen is directly sent to the first molecular sieve 111, a large amount of work will be wasted. To prevent this work waste, in this embodiment, an expander 14 is installed in the cold box 300 to recover this portion of cold energy.

[0045] Specifically, a third conveying pipe 15 is connected to the first conveying pipe 26. The third conveying pipe 15 is used to send the nitrogen produced in the nitrogen distillation column 206 into the second main heat exchanger 205 to be reheated to -150°C. Then, the reheated nitrogen is sent into the expander 14 to expand and generate cooling capacity. Then, the expanded nitrogen is sent back to the cold end of the second main heat exchanger 205 for the second main heat exchanger 205 to recover the cooling capacity. Finally, the nitrogen is sent out of the second main heat exchanger 205 as purge gas and enters the first molecular sieve 111. The first conveying pipe 26 is equipped with a first throttle valve 16 for controlling the nitrogen to enter the argon condenser 11. The third conveying pipe 15 is equipped with a molecular sieve regeneration heater 17, which is used to heat the purge gas about to enter the first molecular sieve 111. Therefore, in this embodiment, the nitrogen in the nitrogen distillation column 206 is mainly transported to the first molecular sieve 111 as a purge gas through the third conveying pipeline 15.

[0046] Specifically, a reboiler 18 is provided at the bottom of the inner cavity of the argon distillation column 113. The end of the first argon delivery pipe 13 away from the first molecular sieve 111 is connected to the inlet end of the reboiler 18. The outlet end of the reboiler 18 is provided with a first reflux pipe 19 connected to the middle of the argon distillation column 113. The bottom of the argon distillation column 113 is provided with a second reflux pipe 20 connected to the argon condenser 11. A second throttling valve 21 is provided on the first reflux pipe 19, and a third throttling valve 22 is provided on the second reflux pipe 20. In this embodiment, the heat source of the reboiler 18 comes from the crude argon gas transported by the first argon gas delivery pipe 13. After entering the reboiler 18, the crude argon gas is condensed into liquid by liquid argon with a lower pressure. The cold source of the argon condenser 11 comes from the cold energy generated by the vaporization of liquid argon under low pressure. Specifically, a portion of the liquid argon can be added from the liquid argon inlet 12, and another portion of the liquid argon can be returned to the argon condenser 11 through the second reflux pipe 20 to provide cold energy for the condensation of the rising crude argon gas in the tower. When the returned liquid argon is vaporized by the steam recovery of cold energy, it is discharged to the outside through the pure argon gas outlet pipe 24.

[0047] In this embodiment, in order to further improve the purity of liquid argon at the bottom of the argon distillation column 113, the reboiler 18 is used to reheat and boil the liquid argon at the bottom of the argon distillation column 113. The liquid argon will be converted into gaseous form and rise to the middle of the argon distillation column 113 through the first reflux pipe 19 to continue to participate in the distillation process of the argon condenser 11, further improving the separation effect of liquid argon.

[0048] Furthermore, the top of the argon distillation column 113 is provided with a waste gas discharge pipe 23 and a pure argon gas discharge pipe 24. The waste gas discharge pipe 23 passes through the first main heat exchanger 112 and connects to the first molecular sieve 111. The pure argon gas discharge pipe 24 passes through the first main heat exchanger 112 and extends out of the cold box 300. The end of the pure argon gas discharge pipe 24 is connected to a pure argon gas compressor 114. It can be understood that in this embodiment, the non-condensable gas at the top of the argon distillation column 113 is distillation waste gas, which mainly contains nitrogen, hydrogen, and a small amount of argon. It can be discharged into the first molecular sieve 111 through the waste gas discharge pipe 23 as a replacement gas. Specifically, after the first molecular sieve 111 has finished regenerating, replacement gas (nitrogen, hydrogen, and argon) is supplied to the first molecular sieve 111 through the waste gas discharge pipe 23 to completely remove the remaining argon on the adsorber. The refluxed liquid argon can be sent out of the cold box 300 through the pure argon exhaust pipe 24, and will be reheated and vaporized when passing through the first main heat exchanger 112. Finally, it is compressed by the pure argon compressor 114 and sent to the single crystal production workshop.

[0049] Specifically, the argon coarse filtration unit also includes a second argon delivery pipe 25. One end of the second argon delivery pipe 25 is connected to the inlet end of the first molecular sieve 111, and the other end is connected to a dust filter 101. The second argon delivery pipe 25 after the dust filter 101 is sequentially equipped with a dual-membrane gas holder system 102, a crude argon compressor 103, a water cooler 104, a high-precision oil removal system 105, a regenerator 106, a crude argon heater 107, a carbon monoxide removal reactor 108, a deoxygenation reactor 109, and a crude argon cooler 110. In practical applications, the argon coarse filtration process is as follows: First, waste argon gas from the single crystal furnace is passed through a dust filter 101 to remove dust, and then sent to a dual-membrane gas holder system 102. A crude argon gas compressor 103 draws crude argon gas from the dual-membrane gas holder system 102, and after compression and cooling, it is de-oiled. After being heated by a crude argon gas heater 107, it is sent to a carbon monoxide removal reactor 108 to remove hydrocarbons such as methane and carbon monoxide. During this process, excess oxygen is ensured. If oxygen is insufficient, air from a nitrogen distillation column 206 or oxygen-enriched air can be added to produce water and carbon dioxide. The crude argon gas, now free of hydrocarbons and carbon monoxide, is then passed through... After cooling, a slight excess of hydrogen is added and sent to the deoxygenation reactor 109 to remove oxygen, and water is produced in the reaction. After two catalytic reactions, the crude argon is sent to the first molecular sieve 111 to remove water and carbon dioxide. The adsorber of the first molecular sieve 111 can be regenerated by nitrogen transported by the third conveying pipe 15 and distillation waste gas transported by the waste gas discharge pipe 23. The main impurities in the crude argon leaving the first molecular sieve 111 are hydrogen and nitrogen. It is then sent to the argon distillation column 113 for distillation. At the top of the argon distillation column 113, distillation waste gas with high nitrogen and hydrogen content is separated, and pure liquid argon is obtained at the bottom.

[0050] In addition, in this embodiment, two analyzers 400 are also provided on the second argon gas delivery pipeline 25 to monitor the working status of the argon gas coarse filtration unit in order to prevent hydrocarbons from accumulating and causing an explosion.

[0051] Specifically, the nitrogen coarse filtration unit also includes an air delivery pipe 31. One end of the air delivery pipe 31 passes through the second main heat exchanger 205 and is connected to the nitrogen distillation column 206, and the other end is connected to an air filter 201. An air compressor 202, an air cooling unit 203 and a second molecular sieve 204 are sequentially arranged on the air delivery pipe 31 after the air filter 201.

[0052] The top of the nitrogen distillation column 206 is equipped with a nitrogen delivery pipe 32 and a liquid nitrogen discharge pipe 33. The nitrogen delivery pipe 32 passes through the second main heat exchanger 205 and connects to the second molecular sieve 204. The liquid nitrogen discharge pipe 33 extends outside the cold box 300 and is equipped with a liquid nitrogen valve 34 for controlling the discharge of liquid nitrogen. In practical applications, the nitrogen coarse filtration process is as follows: First, ambient air is passed through an air filter 201 to filter out dust and other impurities, and then sent to an air compressor 202 for compression to increase the air pressure and density. Then, it is passed through an air cooling unit 203 for cooling. The coolant in the air cooling unit 203 absorbs heat, causing the air to cool and condense into liquid. The cooled air-liquid enters the second molecular sieve 204 to remove water and carbon dioxide, and finally, it is sent to the nitrogen distillation column 206 for distillation. Based on the relationship between nitrogen and oxygen... Separation is achieved through the difference in boiling points. Specifically, pure nitrogen is separated at the top of the nitrogen distillation column 206, and crude liquid oxygen is separated at the bottom. The nitrogen distillation column 206 can send some nitrogen into the second molecular sieve 204 as a purging gas through the nitrogen delivery pipe 32 to remove or wash the adsorbed substances (oxygen, water, and carbon dioxide) on the second molecular sieve 204, ensuring the normal operation and adsorption performance of the second molecular sieve 204. The liquid nitrogen returned through the second delivery pipe 27 can be discharged from the nitrogen distillation column 206 through the liquid nitrogen discharge pipe 33.

[0053] It is important to note that the gas refluxed into the second molecular sieve 204 must be properly treated and controlled to ensure the normal operation and performance of the second molecular sieve 204. This includes controlling the flow rate, pressure, and temperature of the reflux gas, as well as regular molecular sieve regeneration operations.

[0054] Furthermore, the bottom of the nitrogen distillation column 206 is provided with a third reflux pipe 35 connected to its top, and a fourth throttling valve 36 is provided on the third reflux pipe 35. It can be understood that the third reflux pipe 35 is used to reflux crude liquid oxygen to the nitrogen condenser at the top of the nitrogen distillation column 206 to provide cooling for the condensation of the rising air in the column.

[0055] In summary, the dual-tower combined argon recovery and purification system of the present invention, by combining an argon distillation unit and a nitrogen distillation unit, allows the cooling capacity of liquid argon added to the argon condenser to be fully utilized. Specifically, when the user adds liquid argon to the argon condenser through the liquid argon inlet, the nitrogen distillation tower can send a portion of nitrogen into the argon condenser through the first delivery pipe. The nitrogen introduced into the argon condenser can recover the excess cooling capacity of the liquid argon to form liquid nitrogen. Finally, the liquid nitrogen is sent back to the nitrogen distillation tower through the second delivery pipe. The recovered liquid nitrogen can be sold as a by-product, increasing economic benefits and avoiding the waste of cooling capacity caused by the vaporization of liquid argon at room temperature.

[0056] Please refer to Figure 2 The image shows a dual-tower combined argon recovery and purification method according to a second embodiment of the present invention. The method includes the following steps:

[0057] Step S101, purification of waste argon gas: filter the waste argon gas from the single crystal furnace to obtain crude argon gas containing only nitrogen and hydrogen as impurities.

[0058] Step S102, crude argon gas distillation: crude argon gas is passed into an argon distillation column and separated according to the different boiling points of argon, nitrogen and hydrogen. Liquid argon is obtained at the bottom of the argon distillation column and distillation waste gas is discharged at the top of the argon distillation column. The distillation waste gas includes hydrogen and nitrogen.

[0059] Step S103, cold energy recovery: a portion of the nitrogen in the nitrogen distillation column is transferred to the argon distillation column through the first conveying pipeline to recover the excess cold energy of the liquid argon in the argon distillation column to form liquid nitrogen, which is then sent back to the nitrogen distillation column through the second conveying pipeline.

[0060] Step S104, preparation of pure argon: extract liquid argon from the argon distillation column and reheat it to generate pure argon.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A dual-tower combined argon gas recovery and purification system, characterized in that, include: Cold box; An argon distillation unit is provided inside the cold box. The argon distillation unit includes an argon distillation column, an argon condenser, and a liquid argon inlet. The argon condenser is located at the top of the inner cavity of the argon distillation column, and the liquid argon inlet is located at the top of the argon distillation column and communicates with the argon condenser. The liquid argon inlet is used to add liquid argon to the argon condenser. A nitrogen distillation unit is provided inside the cold box. The nitrogen distillation unit includes a nitrogen distillation column, a first conveying pipe, and a second conveying pipe. The nitrogen distillation column is connected to the inlet end of the argon condenser through the first conveying pipe and to the outlet end of the argon condenser through the second conveying pipe.

2. The dual-tower combined argon recovery and purification system according to claim 1, characterized in that, It also includes an argon coarse filtration unit and a nitrogen coarse filtration unit located outside the cold box, as well as a first main heat exchanger and a second main heat exchanger located inside the cold box. The argon coarse filtration unit is used to recover waste argon gas from the single crystal furnace and filter it into crude argon gas containing only nitrogen and hydrogen. The first main heat exchanger is used to receive the crude argon gas from the argon coarse filtration unit and cool the crude argon gas before sending it into the argon distillation column to produce pure argon gas. The nitrogen coarse filtration unit is used to extract air and remove carbon dioxide and water from it. The second main heat exchanger is used to receive air from the nitrogen coarse filtration unit, cool the air, and send it into the nitrogen distillation column to produce nitrogen.

3. The dual-tower combined argon recovery and purification system according to claim 2, characterized in that, The first main heat exchanger and the second main heat exchanger are combined into one.

4. The dual-tower combined argon recovery and purification system according to claim 2, characterized in that, The argon coarse filtration unit includes a first molecular sieve and a first argon delivery pipeline. One end of the first argon delivery pipeline is connected to the outlet end of the first molecular sieve, and the other end is connected in sequence to the first main heat exchanger and the argon distillation column. The cold box is equipped with an expander. A third conveying pipe is connected to the first conveying pipe. The third conveying pipe is used to send the nitrogen produced in the nitrogen distillation column into the second main heat exchanger for reheating. Then, the reheated nitrogen is sent into the expander for expansion to generate cooling capacity. Then, the expanded nitrogen is sent back to the cold end of the second main heat exchanger for the second main heat exchanger to recover the cooling capacity. Finally, the nitrogen is sent out of the second main heat exchanger as purge gas and enters the first molecular sieve. The first conveying pipe is equipped with a first throttling valve for controlling the nitrogen entering the argon condenser. The third conveying pipe is equipped with a molecular sieve regeneration heater for heating the purge gas about to enter the first molecular sieve.

5. The dual-tower combined argon recovery and purification system according to claim 4, characterized in that, The argon distillation column has a reboiler at the bottom of its inner cavity. The end of the first argon delivery pipe away from the first molecular sieve is connected to the inlet of the reboiler. The outlet of the reboiler is provided with a first reflux pipe connected to the middle of the argon distillation column. The bottom of the argon distillation column is provided with a second reflux pipe connected to the argon condenser. The first reflux pipe is provided with a second throttling valve, and the second reflux pipe is provided with a third throttling valve.

6. The dual-tower combined argon recovery and purification system according to claim 4, characterized in that, The top of the argon distillation column is provided with an exhaust gas discharge pipe and a pure argon gas discharge pipe. The exhaust gas discharge pipe passes through the first main heat exchanger and is connected to the first molecular sieve. The pure argon gas discharge pipe passes through the first main heat exchanger and extends out of the cold box. The end of the pure argon gas discharge pipe is connected to a pure argon gas compressor.

7. The dual-tower combined argon recovery and purification system according to claim 4, characterized in that, The argon coarse filtration unit also includes a second argon delivery pipeline. One end of the second argon delivery pipeline is connected to the inlet of the first molecular sieve, and the other end is connected to a dust filter. A dual-membrane gas holder system, a crude argon compressor, a water cooler, a high-precision oil removal system, a regenerator, a crude argon heater, a carbon monoxide removal reactor, a deoxygenation reactor, and a crude argon cooler are sequentially arranged on the second argon delivery pipeline after the dust filter.

8. The dual-tower combined argon recovery and purification system according to claim 2, characterized in that, The nitrogen coarse filtration unit also includes an air delivery pipe. One end of the air delivery pipe passes through the second main heat exchanger and is connected to the nitrogen distillation tower, and the other end is connected to an air filter. An air compressor, an air cooling unit, and a second molecular sieve are sequentially arranged on the air delivery pipe after the air filter. The top of the nitrogen distillation column is equipped with a nitrogen delivery pipe and a liquid nitrogen discharge pipe. The nitrogen delivery pipe passes through the second main heat exchanger and connects to the second molecular sieve. The liquid nitrogen discharge pipe extends out of the cold box and is equipped with a liquid nitrogen valve for controlling the discharge of liquid nitrogen.

9. The dual-tower combined argon recovery and purification system according to claim 1, characterized in that, The bottom of the nitrogen distillation column is equipped with a third reflux pipe connected to its top, and the third reflux pipe is equipped with a fourth throttle valve.

10. A dual-tower combined argon recovery and purification method, used in any one of the dual-tower combined argon recovery and purification systems according to claims 1 to 9, characterized in that, The method includes the following steps: a) Purification of waste argon gas: The waste argon gas from the single crystal furnace is filtered to obtain crude argon gas containing only nitrogen and hydrogen as impurities. b) Crude argon gas distillation: Crude argon gas is passed into an argon distillation column and separated according to the different boiling points of argon, nitrogen and hydrogen. Liquid argon is obtained at the bottom of the argon distillation column and distillation waste gas is discharged at the top of the argon distillation column. The distillation waste gas includes hydrogen and nitrogen. c) Cold energy recovery: A portion of the nitrogen in the nitrogen distillation column is transferred to the argon distillation column through the first conveying pipeline to recover the excess cold energy of the liquid argon in the argon distillation column to form liquid nitrogen, which is then sent back to the nitrogen distillation column through the second conveying pipeline. d) Production of pure argon: Liquid argon is extracted from the argon distillation column and reheated to generate pure argon.

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