Nitrogen-containing methane gas denitrogenation liquefaction cold box and system
Patent Information
- Application Number
- CN202522014814.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-19
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2035-09-19
AI Technical Summary
Existing technologies are insufficient to effectively separate nitrogen and methane in high-nitrogen methane gas, and conventional methods such as pressure swing adsorption and membrane separation are not very effective.
A low-temperature separation method is adopted, in which nitrogen-containing methane gas is deeply cooled to below the boiling point of methane through a low-temperature denitrification tower and a low-temperature heat exchanger. The difference in boiling points between nitrogen and methane is used for separation to obtain high-purity methane product and nitrogen-rich tail gas.
It achieves efficient separation of nitrogen and methane, can handle high-nitrogen methane gas, reduces nitrogen content from 15% to below 1%, and produces high-quality products with high energy utilization efficiency.
Smart Images
Figure CN224933097U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to cold boxes, and more specifically, to a nitrogen-containing methane gas denitrification and liquefaction cold box and system. Background Technology
[0002] In the natural gas liquefaction process, denitrification of high-nitrogen methane gas is a crucial step. Nitrogen-containing methane gas refers to gas whose main components are methane and nitrogen, but it can also contain other hydrocarbon gases or other non-condensable gases such as carbon monoxide, hydrogen, and helium. Common nitrogen-containing methane gases used in industrial production include liquefied natural gas (LNG) flash gas (BOG), nitrogen-enriched wellhead natural gas, associated gas from nitrogen injection, and coke oven gas from the coal chemical industry.
[0003] Because methane and nitrogen have similar molecular weights, similar molecular polarities, and similar membrane permeabilities, conventional separation methods such as pressure swing adsorption and membrane separation are difficult to use for separating nitrogen and methane.
[0004] How to effectively separate high-nitrogen methane gas has become an urgent problem to be solved in the industry. Utility Model Content
[0005] To address the aforementioned problems, this utility model provides a nitrogen-containing methane gas denitrification and liquefaction cold box, which can process both low-nitrogen and high-nitrogen-content nitrogen-containing methane gas.
[0006] In the field of cryogenic separation, the difference in boiling points of different components is utilized for component separation. Methane has a boiling point of -161℃, while nitrogen has a boiling point of -196℃. This invention employs a cryogenic separation method to separate nitrogen and methane. Nitrogen-containing methane gas under a certain pressure is first cryogenically cooled to below the boiling point of methane at the corresponding pressure using a heat exchanger. Then, it enters a nitrogen flash tank or cryogenic distillation column to separate the nitrogen, yielding a high-purity methane product and nitrogen-rich tail gas. The high-purity methane gas can be further cryogenically cooled to produce LNG or reheated to room temperature to produce natural gas. The separated nitrogen-rich tail gas can be used to produce nitrogen products.
[0007] A nitrogen-containing methane gas denitrification and liquefaction cold box includes a low-temperature denitrification tower and a low-temperature heat exchanger. The low-temperature denitrification tower has a top condenser, a top separator, and a bottom reboiler. The low-temperature heat exchanger is provided with a first inlet, a first outlet, a second inlet, a second outlet, a third inlet, and a third outlet. The first inlet is connected to the first outlet, the second inlet is connected to the second outlet, and the third inlet is connected to the third outlet. The first inlet is connected to a first pipe, the first outlet is connected to a third pipe, and the other end of the third pipe is connected to the bottom reboiler. The second inlet is connected to a fourth pipe, and the other end of the fourth pipe is connected to the bottom reboiler. The second outlet is connected to a fifth pipe, on which a throttling valve V3 is installed. The other end of the fifth pipe is connected to the low-temperature denitrification tower. The third inlet is connected to a second pipe, the other end of which is connected to the bottom of the low-temperature denitrification tower. The third outlet is connected to a sixth pipe. The top condenser is connected to a seventh pipe, the other end of which is connected to the top of the low-temperature denitrification tower and communicates with the inner cavity of the tower. The top separator is connected to an eighth pipe.
[0008] Optionally, the fifth pipe is connected to the middle of the low-temperature denitrification tower.
[0009] Optionally, a switch valve V is installed on the second pipeline. 10 The third pipeline is equipped with a switch valve V7, the fourth pipeline is equipped with a switch valve V9, and the fifth pipeline is also equipped with a switch valve V. 11 The nitrogen-containing methane gas denitrification liquefaction cold box also includes a first connecting pipe and a second connecting pipe. One end of the first connecting pipe is connected to a third pipe, and the other end is connected to a fourth pipe. The second connecting pipe is connected to a fifth pipe, and the other end is connected to the second pipe. A switch valve V8 is installed on the first connecting pipe, and a switch valve V is installed on the second connecting pipe. 12 .
[0010] Optionally, the cryogenic heat exchanger is further provided with a fourth inlet and a fourth outlet. The fourth inlet is connected to an eighth pipe, and the fourth inlet is connected to the fourth outlet. The fourth outlet is connected to a ninth pipe, which is used to transport nitrogen-rich tail gas after heat exchange by the cryogenic heat exchanger. The eighth pipe is equipped with a throttling valve V5.
[0011] Optionally, the first inlet is located at the top of the low-temperature heat exchanger, the first outlet is located in the middle of the low-temperature heat exchanger, the second inlet is located in the middle of the low-temperature heat exchanger, the second outlet is located at the bottom of the low-temperature heat exchanger, the third inlet is located in the middle of the low-temperature heat exchanger, the third outlet is located at the bottom of the low-temperature heat exchanger, the fourth inlet is located at the bottom of the low-temperature heat exchanger, the fourth outlet is located at the top of the low-temperature heat exchanger, the first outlet is located above the second inlet, and the third inlet is located between the second inlet and the second outlet.
[0012] Optionally, the low-temperature heat exchanger is further provided with a fifth inlet, a fifth outlet, a sixth inlet, and a sixth outlet. The fifth inlet is connected to the fifth outlet, and the sixth inlet is connected to the sixth outlet. The fifth inlet is connected to a tenth pipe, and the fifth outlet is connected to an eleventh pipe. The eleventh pipe is also connected to a twelfth pipe and a thirteenth pipe. A throttling valve V2 is installed on the twelfth pipe, and a throttling valve V4 is installed on the thirteenth pipe. The other end of the thirteenth pipe is connected to the top condenser of the tower. The sixth inlet is connected to a fourteenth pipe, and the top condenser of the tower is also connected to a fifteenth pipe. The fifteenth pipe is connected to the fourteenth pipe, and the other end of the twelfth pipe is connected to the fourteenth pipe. The sixth outlet is connected to a sixteenth pipe.
[0013] Optionally, the fifth inlet is located at the top of the cryogenic heat exchanger, the fifth outlet is located at the bottom of the cryogenic heat exchanger, the sixth inlet is located at the bottom of the cryogenic heat exchanger, and the sixth outlet is located at the top of the cryogenic heat exchanger.
[0014] Optionally, the low-temperature heat exchanger is further provided with a seventh inlet, a seventh outlet and an eighth inlet. The seventh inlet is connected to the seventh outlet, the eighth inlet is connected to the sixth outlet, the seventh outlet is connected to a seventeenth pipe, the seventh outlet is connected to an eighteenth pipe, the other end of the eighteenth pipe is connected to the eighth inlet, and a throttling valve V1 is installed on the eighteenth pipe.
[0015] Optionally, the seventh inlet is located at the top of the cryogenic heat exchanger, the seventh outlet is located in the middle of the cryogenic heat exchanger, the eighth inlet is located in the middle of the cryogenic heat exchanger, and the seventh outlet is located above the eighth inlet.
[0016] This invention also provides a nitrogen-containing methane gas denitrification and liquefaction system.
[0017] A nitrogen-containing methane gas denitrification and liquefaction system includes a cold box and an LNG storage tank. The cold box is the aforementioned nitrogen-containing methane gas denitrification and liquefaction cold box, and the other end of a sixth pipeline is connected to the LNG storage tank.
[0018] Compared with the prior art, the principle and beneficial effects of this utility model are as follows:
[0019] In this invention, nitrogen-containing methane gas at room temperature and high pressure is cryogenically cooled (-40 to -120°C) by a low-temperature heat exchanger and then passes through a reboiler at the bottom of the denitrification tower to provide a reboiler heat source for the tower, further condensing and cooling itself. The condensed nitrogen-containing methane gas (liquid phase) is further subcooled by the low-temperature heat exchanger and then enters the low-temperature denitrification tower for low-temperature distillation separation, resulting in a nitrogen-rich tail gas at the top and a high-purity methane liquid stream at the bottom. The liquid methane stream at the bottom can be subcooled by the low-temperature heat exchanger and stored as LNG in LNG storage tanks, or it can be reheated by the low-temperature heat exchanger to obtain room-temperature methane gas for external export. The nitrogen-rich tail gas obtained at the top of the tower is reheated by the low-temperature heat exchanger to obtain room-temperature nitrogen gas. The cold source for the condenser at the top of the denitrification tower comes from the high-pressure gaseous refrigerant, which is cryogenically cooled (-120 to -180°C) by the low-temperature heat exchanger and then reduced to low pressure by a throttling valve. The cooling capacity of the top condenser of the low-temperature denitrification tower comes from the refrigerant of the entire liquefaction system. After the low-temperature refrigerant is throttled and depressurized, its temperature can be lower than -160℃, thus providing a lower cooling capacity to the top condenser and ensuring the denitrification accuracy of the denitrification tower. It can process nitrogen-rich methane gas containing 15% nitrogen as the feed gas to reduce the nitrogen content in the product methane gas to less than 1%. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the overall structure of this utility model;
[0022] Figure 2 This is a schematic diagram of the inlet and outlet positions of the low-temperature heat exchanger of this utility model.
[0023] Explanation of reference numerals in the attached diagram: 1. Cryogenic denitrification tower; 2. Cryogenic heat exchanger; 3. Top condenser; 4. Top separator; 5. Bottom reboiler; 6. LNG storage tank; 7. Second pipeline; 8. First pipeline; 9. Third pipeline; 10. Fourth pipeline; 11. First inlet; 12. Fifth inlet; 13. Seventh inlet; 14. Eighth inlet; 15. Second inlet; 16. Third inlet; 17. Sixth pipeline; 18. Fourth inlet; 19. Sixth inlet; 20. Fifth pipeline; 21. Fourth... Export, 22, Sixth Export, 23, Seventh Export, 24, First Export, 25, Third Export, 26, Fifth Export, 27, Second Export, 28, Seventh Pipe, 29, Eighth Pipe, 30, Ninth Pipe, 31, First Connecting Pipe, 32, Second Connecting Pipe, 33, Tenth Pipe, 34, Eleventh Pipe, 35, Twelfth Pipe, 36, Thirteenth Pipe, 37, Fourteenth Pipe, 38, Fifteenth Pipe, 39, Sixteenth Pipe, 40, Seventeenth Pipe, 41, Eighteenth Pipe. Detailed Implementation
[0024] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0025] In the description of this utility model, it should be understood that the terms "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In the description of this utility model, "a plurality of" means two or more, unless otherwise precisely specified.
[0026] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] The technical solution of this utility model will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.
[0029] Figure 1 This is a schematic diagram of the overall structure of this utility model. Figure 2 This is a schematic diagram of the inlet and outlet positions of the low-temperature heat exchanger of this utility model.
[0030] Please refer to Figure 1A nitrogen-containing methane gas denitrification and liquefaction cold box includes a low-temperature denitrification tower 1 and a low-temperature heat exchanger 2. The low-temperature denitrification tower 1 has a top condenser 3, a top separator 4, and a bottom reboiler 5. The low-temperature heat exchanger 2 is provided with a first inlet 11, a first outlet 24, a second inlet 15, a second outlet 27, a third inlet 16, and a third outlet 25. The first inlet 11 is connected to the first outlet 24, the second inlet 15 is connected to the second outlet 27, and the third inlet 16 is connected to the third outlet 25. The first inlet is connected to a first pipe 8, and the first outlet 24 is connected to a third pipe 9. The other end of the third pipe 9 is connected to the bottom reboiler 5. Next, the second inlet 15 is connected to the fourth pipe 10, and the other end of the fourth pipe 10 is connected to the reboiler 5 at the bottom of the tower. The second outlet 27 is connected to the fifth pipe 20, and a throttling valve V3 is installed on the fifth pipe 20. The other end of the fifth pipe 20 is connected to the low-temperature denitrification tower 1. The third inlet 16 is connected to the second pipe 7, and the other end of the second pipe 7 is connected to the bottom of the low-temperature denitrification tower 1. The third outlet 25 is connected to the sixth pipe 17. The top condenser 3 is connected to the seventh pipe 28, and the other end of the seventh pipe 28 is connected to the top of the low-temperature denitrification tower 1 and communicates with the inner cavity of the tower. The top separator 4 is connected to the eighth pipe 29.
[0031] Pipeline 8 is used to transport nitrogen-containing methane feed gas (temperature 20℃~40℃, atmospheric pressure); Pipeline 9 is used to transport nitrogen-containing methane feed gas cooled by low-temperature heat exchanger 2 (temperature -40℃~-120℃); Pipeline 10 is used to transport nitrogen-containing methane feed gas after heat exchange in reboiler 5; Pipeline 20 is used to transport nitrogen-containing methane feed gas cooled again by low-temperature heat exchanger 2; Pipeline 7 is used to transport high-purity methane liquid phase stream; Pipeline 17 is used to transport high-purity methane liquid phase stream after heat exchange in low-temperature heat exchanger 2; Pipeline 28 is used to transport the light components after distillation in the tower out of low-temperature denitrification tower 1; Pipeline 29 is used to transport the light components (nitrogen-rich tail gas) separated by the top separator 4.
[0032] In one or more specific embodiments of this utility model, in order to utilize heat energy more effectively, the low-temperature heat exchanger 2 is also provided with a fourth inlet 18 and a fourth outlet 21. The fourth inlet 18 is connected to the eighth pipe 29 and the fourth outlet 21 is connected to the fourth outlet 21. The fourth outlet 21 is connected to a ninth pipe 30. The ninth pipe 30 is used to transport nitrogen-rich tail gas after heat exchange by the low-temperature heat exchanger 2. The eighth pipe 29 is equipped with a throttling valve V5.
[0033] In one or more specific embodiments of this utility model, in order to achieve better separation effect, the fifth pipe 20 is connected to the middle of the low temperature denitrification tower 1.
[0034] In one or more specific embodiments of this utility model, in order to achieve better separation effect and efficient energy utilization, the first inlet 11 is located at the top of the low-temperature heat exchanger 2, the first outlet 24 is located in the middle of the low-temperature heat exchanger 2, the second inlet 15 is located in the middle of the low-temperature heat exchanger 2, the second outlet 27 is located at the bottom of the low-temperature heat exchanger 2, the third inlet 16 is located in the middle of the low-temperature heat exchanger 2, the third outlet 25 is located at the bottom of the low-temperature heat exchanger 2, the fourth inlet 18 is located at the bottom of the low-temperature heat exchanger 2, the fourth outlet 21 is located at the top of the low-temperature heat exchanger 2, the first outlet 24 is located above the second inlet 15, and the third inlet 16 is located between the second inlet 15 and the second outlet 27.
[0035] In one or more specific embodiments of this utility model, in order to handle both high-nitrogen-content gas (nitrogen content not less than 2%) and low-nitrogen-content gas (nitrogen content < 2%), a switch valve V is installed on the second pipeline 7. 10 A switch valve V7 is installed on the third pipe 9, a switch valve V9 is installed on the fourth pipe 10, and a switch valve V is also installed on the fifth pipe 20. 11 The nitrogen-containing methane gas denitrification liquefaction cold box also includes a first connecting pipe 31 and a second connecting pipe 32. One end of the first connecting pipe 31 is connected to the third pipe 9, and the other end is connected to the fourth pipe 10. The second connecting pipe 32 is connected to the fifth pipe 20, and the other end is connected to the second pipe 7. A switch valve V8 is installed on the first connecting pipe 31, and a switch valve V is installed on the second connecting pipe 32. 12 When processing nitrogen-containing methane gas with a nitrogen content of not less than 2%, V8 and V 12 Close, V7, V9, V 10 and V 11 Turn on; when processing nitrogen-containing methane gas with a nitrogen content of less than 2%, V8 and V 12 Enabled, V7, V9, V 10 and V 11 closure.
[0036] In one or more specific embodiments of this utility model, in order to achieve better separation effect and efficient energy utilization, the low-temperature heat exchanger 2 is also provided with a fifth inlet 12, a fifth outlet 26, a sixth inlet 19, and a sixth outlet 22. The fifth inlet 12 is connected to the fifth outlet 26, and the sixth inlet 19 is connected to the sixth outlet 22. The fifth inlet 12 is connected to a tenth pipe 33, and the fifth outlet 26 is connected to an eleventh pipe 34. The eleventh pipe 34 is also connected to a twelfth pipe 35 and a thirteenth pipe 36, respectively. A throttling valve V2 is installed on the twelfth pipe 35, and a throttling valve V4 is installed on the thirteenth pipe 36. The other end of the thirteenth pipe 36 is connected to the top condenser 3. The sixth inlet 19 is connected to a fourteenth pipe 37, and the top condenser 3 is also connected to a fifteenth pipe 38. The fifteenth pipe 38 is connected to the fourteenth pipe 37, and the other end of the twelfth pipe 35 is connected to the fourteenth pipe 37. The sixth outlet 22 is connected to a sixteenth pipe 39.
[0037] Pipeline 33 (10th) is used to transport gaseous refrigerant (temperature 20℃~40℃, pressure 20-30 atm). Pipeline 34 (11th) is used to transport the fluid after the gaseous refrigerant has been heated by the cryogenic heat exchanger 2. Throttling valves V2 and V4 convert high-pressure gas into low-pressure gas. Pipeline 38 (15th) is used to transport the fluid after the fluid in pipeline 36 has been heated by the condenser. Pipeline 39 (16th) is used to transport the return refrigerant after the fluid has been heated by the cryogenic heat exchanger 2. During operation, the gaseous refrigerant transported by pipeline 33 enters pipeline 37 after being heated by the cryogenic heat exchanger 2. Then, most of it enters pipeline 35, is pressurized by throttling valve V2, and then enters pipeline 37 again. The other part enters pipeline 36 and is transported to the top condenser 3 for heat exchange. After heat exchange, it enters pipeline 38 and then pipeline 37. The fluid in pipeline 37 enters pipeline 39 after being heated by the cryogenic heat exchanger 2.
[0038] In one or more specific embodiments of this utility model, in order to achieve better separation effect and efficient energy utilization, the fifth inlet 12 is located at the top of the low-temperature heat exchanger 2, the fifth outlet 26 is located at the bottom of the low-temperature heat exchanger 2, the sixth inlet 19 is located at the bottom of the low-temperature heat exchanger 2, and the sixth outlet 22 is located at the top of the low-temperature heat exchanger 2.
[0039] In one or more specific embodiments of this utility model, in order to achieve better separation effect and efficient energy utilization, the low-temperature heat exchanger 2 is also provided with a seventh inlet 13, a seventh outlet 23 and an eighth inlet 14. The seventh inlet 13 is connected to the seventh outlet 23, the eighth inlet 14 is connected to the sixth outlet 22, the seventh outlet 23 is connected to the seventeenth pipe 40, the seventh outlet 23 is connected to the eighteenth pipe 41, the other end of the eighteenth pipe 41 is connected to the eighth inlet 14, and a throttling valve V1 is installed on the eighteenth pipe 41.
[0040] The seventeenth tube 40 is used to transport liquid refrigerant (temperature 20℃~40℃, pressure 20 atm~30 atm), and the eighteenth tube 41 is used to transport fluid after heat exchange in the low-temperature heat exchanger 2. After the fluid is depressurized in the eighteenth tube 41, it returns to the low-temperature heat exchanger 2 for heat exchange and is discharged from the sixteenth tube 39.
[0041] In one or more specific embodiments of this utility model, in order to achieve better separation effect and efficient energy utilization, the seventh inlet 13 is located at the top of the low-temperature heat exchanger 2, the seventh outlet 23 is located in the middle of the low-temperature heat exchanger 2, the eighth inlet 14 is located in the middle of the low-temperature heat exchanger 2, and the seventh outlet 23 is located above the eighth inlet 14.
[0042] Please refer to this again. Figure 1 This utility model also provides a nitrogen-containing methane gas denitrification and liquefaction system, which includes a cold box and an LNG storage tank 6. The cold box is... Figure 1 The cold box in the middle, the other end of the sixth pipe 17 is connected to the LNG storage tank 6.
[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.
Claims
1. A nitrogen-containing methane gas denitrification liquefaction cold box, comprising a low-temperature denitrification tower (1) and a low-temperature heat exchanger (2), wherein the low-temperature denitrification tower (1) is equipped with a top condenser (3), a top separator (4), and a bottom reboiler (5), characterized in that, The low-temperature heat exchanger (2) is provided with a first inlet (11), a first outlet (24), a second inlet (15), a second outlet (27), a third inlet (16), and a third outlet (25). The first inlet (11) is connected to the first outlet (24), the second inlet (15) is connected to the second outlet (27), and the third inlet (16) is connected to the third outlet (25). The first inlet is connected to a first pipe (8), and the first outlet (24) is connected to a third pipe (9). The other end of the third pipe (9) is connected to the bottom reboiler (5). The second inlet (15) is connected to a fourth pipe (10), and the other end of the fourth pipe (10) is connected to the third outlet (25). The first end is connected to the reboiler (5) at the bottom of the tower, the second outlet (27) is connected to the fifth pipe (20), the fifth pipe (20) is equipped with a throttle valve V3, the other end of the fifth pipe (20) is connected to the low temperature denitrification tower (1), the third inlet (16) is connected to the second pipe (7), the other end of the second pipe (7) is connected to the bottom of the low temperature denitrification tower (1), the third outlet (25) is connected to the sixth pipe (17), the top condenser (3) is connected to the seventh pipe (28), the other end of the seventh pipe (28) is connected to the top of the low temperature denitrification tower (1) and communicates with the inner cavity of the tower; the top separator (4) is connected to the eighth pipe (29).
2. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 1, characterized in that, The fifth pipe (20) is connected to the middle of the low-temperature denitrification tower (1).
3. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 1, characterized in that, A switch valve V is installed on the second pipeline (7). 10 A switch valve V7 is installed on the third pipe (9), a switch valve V9 is installed on the fourth pipe (10), and a switch valve V is also installed on the fifth pipe (20). 11 The nitrogen-containing methane gas denitrification liquefaction cold box also includes a first connecting pipe (31) and a second connecting pipe (32). One end of the first connecting pipe (31) is connected to the third pipe (9), and the other end is connected to the fourth pipe (10). The second connecting pipe (32) is connected to the fifth pipe (20), and the other end is connected to the second pipe (7). A switch valve V8 is installed on the first connecting pipe (31), and a switch valve V is installed on the second connecting pipe (32). 12 .
4. The nitrogen-containing methane gas denitrification and liquefaction cold box according to any one of claims 1-3, characterized in that, The low-temperature heat exchanger (2) is also provided with a fourth inlet (18) and a fourth outlet (21). The fourth inlet (18) is connected to the eighth pipe (29), and the fourth inlet (18) is connected to the fourth outlet (21). The fourth outlet (21) is connected to the ninth pipe (30). The ninth pipe (30) is used to transport nitrogen-rich tail gas after heat exchange by the low-temperature heat exchanger (2). The eighth pipe (29) is equipped with a throttle valve V5.
5. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 4, characterized in that, The first inlet (11) is located at the top of the low-temperature heat exchanger (2), the first outlet (24) is located in the middle of the low-temperature heat exchanger (2), the second inlet (15) is located in the middle of the low-temperature heat exchanger (2), the second outlet (27) is located at the bottom of the low-temperature heat exchanger (2), the third inlet (16) is located in the middle of the low-temperature heat exchanger (2), the third outlet (25) is located at the bottom of the low-temperature heat exchanger (2), the fourth inlet (18) is located at the bottom of the low-temperature heat exchanger (2), the fourth outlet (21) is located at the top of the low-temperature heat exchanger (2), the first outlet (24) is located above the second inlet (15), and the third inlet (16) is located between the second inlet (15) and the second outlet (27).
6. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 4, characterized in that, The low-temperature heat exchanger (2) is also provided with a fifth inlet (12), a fifth outlet (26), a sixth inlet (19), and a sixth outlet (22). The fifth inlet (12) is connected to the fifth outlet (26), and the sixth inlet (19) is connected to the sixth outlet (22). The fifth inlet (12) is connected to a tenth pipe (33), and the fifth outlet (26) is connected to an eleventh pipe (34). The eleventh pipe (34) is also connected to the twelfth pipe (35) and the thirteenth pipe (36), respectively. A throttle valve V2 is installed on the second pipe (35), a throttle valve V4 is installed on the thirteenth pipe (36), the other end of the thirteenth pipe (36) is connected to the top condenser (3), the sixth inlet (19) is connected to the fourteenth pipe (37), the top condenser (3) is also connected to the fifteenth pipe (38), the fifteenth pipe (38) is connected to the fourteenth pipe (37), the other end of the twelfth pipe (35) is connected to the fourteenth pipe (37), and the sixth outlet (22) is connected to the sixteenth pipe (39).
7. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 6, characterized in that, The fifth inlet (12) is located at the top of the low-temperature heat exchanger (2), the fifth outlet (26) is located at the bottom of the low-temperature heat exchanger (2), the sixth inlet (19) is located at the bottom of the low-temperature heat exchanger (2), and the sixth outlet (22) is located at the top of the low-temperature heat exchanger (2).
8. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 6, characterized in that, The low-temperature heat exchanger (2) is also provided with a seventh inlet (13), a seventh outlet (23) and an eighth inlet (14). The seventh inlet (13) is connected to the seventh outlet (23), and the eighth inlet (14) is connected to the sixth outlet (22). The seventh outlet (23) is connected to the seventeenth pipe (40), and the seventh outlet (23) is connected to the eighteenth pipe (41). The other end of the eighteenth pipe (41) is connected to the eighth inlet (14), and a throttling valve V1 is installed on the eighteenth pipe (41).
9. The nitrogen-containing methane gas denitrification and liquefaction cold box according to claim 8, characterized in that, The seventh inlet (13) is located at the top of the low-temperature heat exchanger (2), the seventh outlet (23) is located in the middle of the low-temperature heat exchanger (2), the eighth inlet (14) is located in the middle of the low-temperature heat exchanger (2), and the seventh outlet (23) is located above the eighth inlet (14).
10. A nitrogen-containing methane gas denitrification and liquefaction system, comprising a cold box and an LNG storage tank (6), characterized in that, The cold box is a nitrogen-containing methane gas denitrification liquefaction cold box as described in any one of claims 1-9, and the other end of the sixth pipeline (17) is connected to the LNG storage tank (6).