An apparatus and method for producing hydrogen and co-producing LNG using low-temperature methane washing.

Abstract

This invention discloses an apparatus and method for producing hydrogen and co-producing LNG using cryogenic methane washing. The apparatus includes a main heat exchanger, a heavy hydrocarbon separator, a cryogenic flash tank, an MRC cryogenic separator, a cryogenic separator, a methane washing tower, a hydrogen stripping tower, a hydrogen stripping tower reboiler, a carbon monoxide / methane separation tower, a bottom reboiler, a reflux tank, a top condenser, a liquid methane pump, a nitrogen compression system, and a mixed refrigerant compressor system. This invention effectively recovers CO from hydrogen-rich gas, achieving a hydrogen purity of over 97%, effectively reducing the requirements for PSA hydrogen extraction and decreasing investment. Furthermore, the hydrogen stripping tower further recovers hydrogen from the methane-rich gas, achieving a hydrogen yield greater than 98%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature deep cooling liquefaction separation technology, in particular to a device and method for producing hydrogen and co-producing LNG by using low-temperature methane washing. BACKGROUND

[0002] Coke oven gas is one of the main by-products in the coking process of coal dry distillation into coke, and the main components are hydrogen, methane, CO, CO2, nitrogen and the like. The coke oven gas is used to produce LNG and co-produce glycol, which not only reduces the waste of resources and environmental pollution, but also brings very good economic benefits to the factory.

[0003] However, the existing process for producing hydrogen and co-producing LNG by using low-temperature methane has the disadvantages of complex process, high energy consumption, and low utilization of raw materials, so there is a need for a device and method for producing hydrogen and co-producing LNG by using low-temperature methane washing, which has the advantages of simple process, flexible adjustment, reliable work, easy operation, and low energy consumption. SUMMARY

[0004] The present application relates to the field of low-temperature deep cooling liquefaction separation technology, in particular to a device and method for producing hydrogen and co-producing LNG by using low-temperature methane washing.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] This invention provides an apparatus for co-producing hydrogen and LNG using low-temperature methane washing, comprising a main heat exchanger, a heavy hydrocarbon separator, a low-temperature flash tank, an MRC low-temperature separator, a low-temperature separator, a methane washing tower, a hydrogen stripping tower, a hydrogen stripping tower reboiler, a carbon monoxide / methane separation tower, a bottom reboiler, a reflux tank, a top condenser, a liquid methane pump, a nitrogen compression system, and a mixed refrigerant compressor system. The main heat exchanger is equipped with a flash vapor channel, a feed gas channel I, a high-pressure hydrogen channel, a medium-pressure hydrogen channel, a carbon monoxide-rich channel I, a high-pressure nitrogen channel I, a reflux low-pressure nitrogen channel I, a high-pressure gaseous refrigerant channel I, a reflux refrigerant channel, a high-pressure liquid refrigerant channel I, a feed gas channel II, a high-pressure gaseous refrigerant channel II, and a high-pressure... The tower includes a liquid refrigerant channel II, an LNG channel I, an LNG channel II, an LNG channel III, a methane-rich channel I, and a methane-rich channel II. The top condenser is equipped with a carbon monoxide-rich channel II and a reflux low-pressure nitrogen channel II. The inlet of the feed gas channel I is connected to an external purified feed gas pipeline, and the outlet of the feed gas channel I is connected to the inlet of the heavy hydrocarbon separator. The bottom liquid phase outlet of the heavy hydrocarbon separator is connected to the inlet of the cryogenic flash tank. The top gas phase outlet of the cryogenic flash tank is connected to the inlet of the flash vapor channel, and the outlet of the flash vapor channel is connected to an external flash vapor pipeline. The bottom liquid phase outlet of the cryogenic flash tank is connected to the inlet of LNG channel I, and the outlet of LNG channel I is connected to the external LN... The gas phase outlet at the top of the heavy hydrocarbon separator is connected to the inlet of feed gas channel II. The outlet of feed gas channel II is connected to the feed inlet of the cryogenic separator. The gas phase outlet at the top of the cryogenic separator is connected to the feed inlet of the methane scrubbing tower. The liquid phase outlet at the bottom of the cryogenic separator is connected to the inlet of methane-rich channel II. The outlet of methane-rich channel II is connected to the feed inlet of the hydrogen stripping tower. The gas phase outlet at the top of the methane scrubbing tower is connected to the inlet of the high-pressure hydrogen channel. The outlet of the high-pressure hydrogen channel is connected to an external high-pressure hydrogen pipeline. The liquid phase outlet at the bottom of the methane scrubbing tower is connected to the feed inlet of the hydrogen stripping tower. The gas phase outlet at the top of the hydrogen stripping tower is connected to the inlet of the medium-pressure hydrogen channel. The outlet of the channel is connected to an external medium-pressure hydrogen pipeline. The bottom liquid phase outlet pipeline of the hydrogen stripping tower is divided into a methane-rich pipeline I and a methane-rich pipeline II. The inlet of methane-rich channel I is connected to methane-rich pipeline I, and the outlet of methane-rich channel I is connected to the feed inlet of the carbon monoxide / methane separation tower. The methane-rich pipeline II is also connected to the feed inlet of the carbon monoxide / methane separation tower. The top gas phase outlet of the carbon monoxide / methane separation tower is connected to the inlet pipeline of the carbon monoxide-rich channel II of the tower top condenser. The outlet of carbon monoxide-rich channel II is connected to the feed inlet of the reflux tank. The bottom liquid phase outlet of the reflux tank is connected to the feed inlet of the carbon monoxide / methane separation tower, and the top gas phase outlet of the reflux tank is connected to the inlet of carbon monoxide-rich channel I.The outlet of the carbon monoxide-rich channel I is connected to an external carbon monoxide-rich pipeline. The bottom liquid phase outlet pipeline of the carbon monoxide / methane separation tower is divided into an LNG wash liquid pipeline and an LNG product pipeline I. The inlet of the liquid methane pump is connected to the LNG wash liquid pipeline. The outlet of the liquid methane pump is connected to the inlet of LNG channel III. The outlet of LNG channel III is divided into an LNG wash liquid to hydrogen stripping tower pipeline and an LNG wash liquid to methane washing tower pipeline. The LNG wash liquid to hydrogen stripping tower pipeline is connected to the feed inlet of the hydrogen stripping tower. The LNG wash liquid to methane washing tower pipeline is connected to the feed inlet of the methane washing tower. The high-pressure liquid phase mixed refrigerant pipeline of the mixed refrigerant compressor system is connected to the inlet of the high-pressure liquid phase refrigerant channel I. The outlet of the high-pressure liquid phase refrigerant channel I is connected to the first port of the reflux refrigerant channel. The high-pressure gas phase mixed refrigerant of the mixed refrigerant compressor system is connected to the inlet of the high-pressure gas phase refrigerant channel I. The outlet of the high-pressure gas phase refrigerant channel I... The system is connected to the feed inlet of the MRC cryogenic separator. The bottom liquid phase outlet of the MRC cryogenic separator is connected to the inlet of the high-pressure liquid phase refrigerant channel II. The outlet of the high-pressure liquid phase refrigerant channel II is connected to the inlet of the bottom reboiler. The outlet of the bottom reboiler is connected to the second port of the reflux refrigerant channel. The top gas phase outlet of the MRC cryogenic separator is connected to the inlet of the high-pressure gas phase refrigerant channel II. The outlet of the high-pressure gas phase refrigerant channel II is connected to the inlet of the hydrogen stripping tower reboiler. The outlet of the hydrogen stripping tower reboiler is connected to the third port of the reflux refrigerant channel. The outlet of the reflux refrigerant channel is connected to the inlet of the mixed refrigerant compressor system. The outlet of the nitrogen compression system is connected to the inlet of the high-pressure nitrogen channel I. The outlet of the high-pressure nitrogen channel I is connected to the inlet of the reflux low-pressure nitrogen channel I. The outlet of the reflux low-pressure nitrogen channel II is connected to the inlet of the reflux low-pressure nitrogen channel I. The outlet of the reflux low-pressure nitrogen channel I is connected to the inlet of the nitrogen compression system.

[0007] Furthermore, the methane washing tower, hydrogen stripping tower, and carbon monoxide / methane separation tower are packed towers or plate towers; the reboiler and bottom reboiler of the hydrogen stripping tower can be built-in or external.

[0008] Furthermore, a regulating valve a is installed on the pipeline at the first inlet of the reflux refrigerant channel, a regulating valve b is installed on the pipeline at the second inlet of the reflux refrigerant channel, and a regulating valve c is installed on the pipeline at the third inlet of the reflux refrigerant channel.

[0009] Furthermore, the gas phase outlet pipeline at the top of the cryogenic flash tank is equipped with a regulating valve d to regulate the pressure of the cryogenic flash tank; the liquid phase outlet pipeline at the bottom of the heavy hydrocarbon separator is equipped with a regulating valve e to control the liquid level at the bottom of the heavy hydrocarbon separator; and the liquid phase outlet pipeline at the bottom of the cryogenic separator is equipped with a regulating valve h to control the liquid level at the bottom of the cryogenic separator.

[0010] Furthermore, the LNG channel I outlet pipeline is equipped with a regulating valve f to control the liquid level at the bottom of the cryogenic flash tank; the LNG channel II outlet pipeline is equipped with a regulating valve g to control the liquid level at the bottom of the carbon monoxide / methane separator.

[0011] Furthermore, the gas phase outlet pipeline at the top of the methane scrubbing tower is equipped with a regulating valve i to control the liquid level at the bottom of the methane scrubbing tower; the feed inlet pipeline of the methane scrubbing tower is equipped with a regulating valve j to control the flow rate of subcooled LNG entering the methane scrubbing tower; and the liquid phase outlet at the bottom of the methane scrubbing tower is equipped with a regulating valve l to control the liquid level at the bottom of the methane scrubbing tower.

[0012] Furthermore, the feed inlet pipeline of the hydrogen stripping tower is equipped with a regulating valve k to control the flow rate of subcooled LNG washing liquid entering the hydrogen stripping tower; the methane-rich pipeline I at the bottom liquid phase outlet of the hydrogen stripping tower is equipped with a regulating valve n to control the flow rate of liquid from the bottom liquid phase to the methane-rich channel I; the methane-rich pipeline II at the bottom liquid phase outlet of the hydrogen stripping tower is equipped with a regulating valve o to control the liquid level at the bottom of the hydrogen stripping tower; and the gas phase outlet pipeline at the top of the hydrogen stripping tower is equipped with a regulating valve q to control the pressure of the hydrogen stripping tower.

[0013] Furthermore, a regulating valve m is installed between the inlet and outlet pipelines of the hydrogen stripping tower reboiler to control the temperature of LNG entering the hydrogen stripping tower bottom; a regulating valve p is installed between the inlet and outlet pipelines of the bottom reboiler to control the temperature of the carbon monoxide / methane separation tower bottom; a regulating valve r is installed on the top gas phase outlet pipeline of the reflux tank to control the pressure of the carbon monoxide / methane separation tower; a regulating valve s is installed on the inlet pipeline of the reflux low-pressure nitrogen channel II to control the temperature of carbon monoxide-rich gas exiting the carbon monoxide-rich channel II; and a regulating valve s is installed on the inlet and outlet pipelines of the reflux low-pressure nitrogen channel II to control the temperatures of LNG exiting the LNG channel III, feed gas exiting the feed gas channel II, and high-pressure nitrogen exiting the high-pressure nitrogen channel I.

[0014] A method for producing hydrogen and co-producing LNG using low-temperature methane washing includes the following steps:

[0015] S1. The purified feed gas containing hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane, and nitrogen enters feed gas channel I, where it is cooled and partially condensed by the reflux cold stream. It then enters the heavy hydrocarbon separator for heavy hydrocarbon separation. The heavy hydrocarbons obtained at the bottom of the heavy hydrocarbon separator are depressurized and enter the cryogenic flash tank. The flash vapor phase enters the flash vapor channel for reheating to room temperature and is sent to the boundary area. The liquid phase separated in the cryogenic flash tank enters LNG channel I for subcooling and is sent to the boundary area LNG storage tank after being throttled and depressurized by the liquid level regulating valve f. The gas phase at the top of the heavy hydrocarbon separator enters feed gas channel II again for cooling and enters the cryogenic separator for gas-liquid separation. The separated liquid enters the methane-rich channel II for reheating and enters the bottom of the hydrogen stripping tower for distillation. The gas separated at the top enters the methane scrubbing tower for cryogenic scrubbing.

[0016] S2. The washing liquid is pressurized by the liquid methane pump and then enters LNG channel III to be cooled and subcooled. It is divided into two parts. One part enters the top feed port of the methane washing tower through the flow regulating valve j, and the other part enters the top feed port of the hydrogen stripping tower through the flow regulating valve k.

[0017] S3. In the methane washing tower, the rising gas and the flowing liquid come into contact with the structured packing for heat and mass transfer. During the gas rise, N2 and CO are washed by the washing liquid, and the hydrogen content gradually increases. High-pressure hydrogen-rich gas is obtained at the top of the methane washing tower. After the pressure is regulated by the pressure regulating valve i, it is sent to the high-pressure hydrogen channel for reheating to room temperature and then exits the main heat exchanger of the cold box to the boundary area. The methane-rich liquid obtained at the bottom of the methane washing tower is then depressurized by the liquid level regulating valve l and enters the middle part of the hydrogen stripping tower for distillation.

[0018] S4. The bottom of the hydrogen stripping tower is equipped with a hydrogen stripping tower reboiler, which exchanges heat with the gaseous refrigerant after heat exchange and cooling separation. Inside the hydrogen stripping tower, the rising gas and the flowing liquid transfer heat and mass on the surface of the structured packing. During the ascent, the hydrogen content of the gas gradually increases. N2 and CO in the ascent process are washed by the washing liquid. Medium-pressure hydrogen-rich gas is obtained at the top of the hydrogen stripping tower. After being reheated to room temperature through the medium-pressure hydrogen channel via the pressure regulating valve q, it exits the main heat exchanger of the cold box and goes to the boundary area. The liquid at the bottom of the hydrogen stripping tower is divided into two parts. One part is regulated by the flow regulating valve n and enters the methane-rich channel I for reheating before entering the bottom of the carbon monoxide / methane separation tower. The other part is depressurized by the liquid level regulating valve o and enters the middle of the carbon monoxide / methane separation tower to participate in the rectification.

[0019] S5. The carbon monoxide / methane separator is equipped with a top condenser at the top, using throttled liquid nitrogen as a cold source; a bottom reboiler is located at the bottom of the separator, using the liquid refrigerant after heat exchange and cooling separation as a heat source to evaporate LNG into rising gas. Inside the carbon monoxide / methane separator, the rising gas and reflux liquid undergo heat and mass transfer on the surface of the structured packing. During the gas's ascent, the nitrogen and CO content gradually increases, while the methane content gradually decreases. At the top of the carbon monoxide / methane separator, CO-rich gas is obtained and enters the carbon monoxide-rich channel II, where it exchanges heat with liquid nitrogen after throttling and depressurization via regulating valve S. Nitrogen evaporates, and part of the CO-rich gas is liquefied and separated in the reflux tank. The separated liquid phase is used as the reflux liquid of the carbon monoxide / methane separation tower. The uncondensed CO-rich gas is returned to the carbon monoxide-rich channel I through the pressure regulating valve r, reheated to room temperature, and then exits the cold box to the boundary area. LNG is obtained by distillation at the bottom of the carbon monoxide / methane separation tower and divided into two parts. One part is pressurized by the liquid methane pump and then enters the LNG channel III for subcooling to -180°C to serve as the washing liquid for the methane washing tower and hydrogen stripping tower. The other part is sent to the LNG channel II for subcooling to -162°C and then sent to the boundary area LNG storage tank after being throttled and depressurized by the liquid level regulating valve g.

[0020] S6. The high-pressure liquid refrigerant from the mixed refrigerant compressor system is subcooled to -30~-70℃ in the high-pressure liquid refrigerant channel I of the main heat exchanger. After being throttled and depressurized by regulating valve a, it enters the first port of the return refrigerant channel. The high-pressure gaseous refrigerant from the mixed refrigerant compressor system is cooled to -30~-70℃ in the high-pressure gaseous refrigerant channel I of the main heat exchanger and then enters the MRC cryogenic separator for gas-liquid separation. The liquid separated at the bottom enters the high-pressure liquid refrigerant channel II and is subcooled to -130~-80℃ before entering the bottom reboiler to provide a heat source for the bottom of the carbon monoxide / methane separation tower, controlling the CO content of LNG in the bottom of the carbon monoxide / methane separation tower to be below 0.5%, which is then absorbed by the carbon monoxide / methane separation tower. The cryogenic liquid in the bottom of the methane separator is cooled to -145~-100℃. After being throttled and depressurized by regulating valve b, it enters the second port of the reflux refrigerant channel. The high-pressure gaseous refrigerant from the top of the MRC cryogenic separator enters the high-pressure gaseous refrigerant channel II, is cooled and condensed to about -150℃, and then enters the reboiler of the hydrogen stripping tower to provide a heat source for the bottom of the hydrogen stripping tower. The hydrogen content of the methane-rich liquid in the bottom of the hydrogen stripping tower is controlled to be less than 0.5%. After being throttled and depressurized by regulating valve c, it enters the third port of the reflux refrigerant channel. The mixed refrigerant entering the reflux refrigerant channel absorbs heat and evaporates. After being completely evaporated into gas and reheated to room temperature, it exits the main heat exchanger and then returns to the mixed refrigerant compressor system to complete the mixed refrigerant refrigeration cycle.

[0021] S7. High-pressure nitrogen from the nitrogen compression system is condensed and subcooled to approximately -175~-180℃ in high-pressure nitrogen channel I, turning into liquid nitrogen. It is divided into two parts. One part of the liquid nitrogen is throttled and depressurized through regulating valve S and enters the return low-pressure nitrogen channel II, controlling the temperature of CO-rich gas entering the reflux tank between -180~-170℃, providing a cold source for the separation of carbon monoxide and methane at the top of the carbon monoxide / methane separation tower. The other part of the liquid nitrogen is throttled and depressurized through regulating valve S and merges with the liquid nitrogen returning from the return low-pressure nitrogen channel II, then enters the return low-pressure nitrogen channel I. After being reheated to room temperature, it exits the main heat exchanger and then returns to the nitrogen compression system inlet to complete the nitrogen refrigeration cycle.

[0022] Furthermore, the liquid phase separated in the cryogenic flash tank in S1 mainly consists of ethane, ethylene, propane, and butane. The subcooling temperature in LNG channel I is -162°C, the cooling temperature in feed gas channel II is -180°C, and the rewarming temperature in methane-rich channel II is -163°C. The subcooling temperature in S2 is -180°C. The washing liquid in S3 and S4 is LNG cooled to -180°C, produced by bottom distillation of the carbon monoxide / methane separation tower. The condensation and liquefaction of feed gas and nitrogen, as well as the liquefaction and subcooling of LNG, are provided by a mixed refrigerant refrigeration cycle. The cryogenic separation of feed gas is provided by a nitrogen cycle.

[0023] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0024] (1) High hydrogen purity and yield: The low-temperature methane washing process effectively recovers CO from the hydrogen-rich gas, making the hydrogen purity in the hydrogen-rich gas reach more than 97%, which effectively reduces the requirement for PSA to extract hydrogen and reduces investment. In addition, a hydrogen stripping tower is set up to recover hydrogen from the methane-rich gas again, making the hydrogen yield greater than 98%.

[0025] (2) High CO yield: Since both the methane washing tower and the hydrogen stripping tower use low-temperature methane washing, the CO and nitrogen in the hydrogen-rich gas are washed to the carbon monoxide / methane separation tower to separate carbon monoxide and methane, so that the CO yield is greater than 94%.

[0026] (3) Low energy consumption: The condensation and liquefaction of raw gas and nitrogen, as well as the liquefaction and subcooling of LNG, are provided by the mixed refrigerant refrigeration cycle, that is, the MRC (mixed refrigerant refrigeration cycle) provides a temperature range of -162℃ for the precooling of raw gas and the subcooling of LNG. The cryogenic separation of raw gas is provided by the nitrogen cycle, that is, it provides a cold source in the temperature range of -182~-162℃, realizing the provision of different temperature ranges and different cooling capacities, which greatly reduces the energy consumption of the cryogenic separation device.

[0027] (4) Low BOG content: High-pressure MRC gas phase is used as the heat source of reboiler. Due to the large specific heat and large circulation volume of MRC, the temperature difference between hot and cold in reboiler is small, which is also conducive to sufficient heat exchange in reboiler. This results in low nitrogen and CO content in LNG, reducing the generation of BOG in LNG.

[0028] (5) In addition, the device has the advantages of convenient maintenance, reliable operation, safety and reliability, and wide applicability. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the main heat exchanger structure;

[0031] In the diagram: 1-Main heat exchanger, 2-Heavy hydrocarbon separator, 3-Cryogenic flash tank, 4-MRC cryogenic separator, 5-Cryogenic separator, 6-Methane scrubbing tower, 7-Hydrogen stripping tower, 8-Hydrogen stripping tower reboiler, 9-Carbon monoxide / methane separation tower, 10-Bottom reboiler, 11-Reflux tank, 12-Top condenser, 13-Liquid methane pump, 14-Nitrogen compression system, 15-Mixed refrigerant compressor system, 101-Control valve a, 102-Control valve b, 103-Control valve c, 104-Control valve d, 105-Control valve e, 106-Control valve f, 107-Control valve g, 108-Control valve h, 109-Control valve i, 110-Control valve j, 111-Control valve k, 112-Control valve l, 113-Control valve m, 114-Control valve n, 115-Control valve o, 1 16-Regulating valve p, 117-Regulating valve q, 118-Regulating valve r, 119-Regulating valve s; A1-Flash vapor channel, A2-Raw gas channel I, A3-High-pressure hydrogen channel, A4-Medium-pressure hydrogen channel, A5-Carbon monoxide-rich channel I, A6-High-pressure nitrogen channel I, A7-Return low-pressure nitrogen channel I, A8-High-pressure vapor refrigerant channel I, A9-Return refrigerant channel, A10-High-pressure liquid refrigerant channel I, A11-Raw gas channel II, A12-High-pressure vapor refrigerant channel II, A13-High-pressure liquid refrigerant channel II, A14-LNG channel I, A15-LNG channel II, A16-LNG channel III, A17-Methane-rich channel I, A18-Methane-rich channel II, B1-Carbon monoxide-rich channel II, B2-Return low-pressure nitrogen channel II. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0033] like Figure 1 , Figure 2As shown, this invention provides an apparatus for producing hydrogen and co-producing LNG using low-temperature methane washing, comprising a main heat exchanger 1, a heavy hydrocarbon separator 2, a low-temperature flash tank 3, an MRC low-temperature separator 4, a low-temperature separator 5, a methane washing tower 6, a hydrogen stripping tower 7, a hydrogen stripping tower reboiler 8, a carbon monoxide / methane separation tower 9, a bottom reboiler 10, a reflux tank 11, a top condenser 12, a liquid methane pump 13, a nitrogen compression system 14, and a mixed refrigerant compressor system 15. The main heat exchanger 1 is equipped with a flash vapor channel A1, a feed gas channel IA2, a high-pressure hydrogen channel A3, a medium-pressure hydrogen channel A4, a carbon monoxide-rich channel IA5, a high-pressure nitrogen channel IA6, a reflux low-pressure nitrogen channel IA7, and a high-pressure gaseous refrigerant channel IA8. The tower includes a reflux refrigerant channel A9, a high-pressure liquid refrigerant channel IA10, a feed gas channel IIA11, a high-pressure gas refrigerant channel IIA12, a high-pressure liquid refrigerant channel IIA13, an LNG channel IA14, an LNG channel IIA15, an LNG channel IIIA16, a methane-rich channel IA17, and a methane-rich channel IIA18. The top condenser 12 is equipped with a carbon monoxide-rich channel IIB1 and a reflux low-pressure nitrogen channel IIB2. The inlet of feed gas channel IA2 is connected to a purified feed gas pipeline, and the outlet of feed gas channel IA2 is connected to the inlet 2-A of the heavy hydrocarbon separator 2. The bottom liquid phase outlet 2-C of the heavy hydrocarbon separator 2 is connected to the inlet 3-A of the low-temperature flash tank 3. The top gas phase outlet 3-B of the cryogenic flash tank 3 is connected to the inlet of flash vapor channel A1, and the outlet of flash vapor channel A1 is connected to the external flash vapor pipeline. The bottom liquid phase outlet 3-C of the cryogenic flash tank 3 is connected to the inlet of LNG channel IA14, and the outlet of LNG channel IA14 is connected to the external LNG to storage unit pipeline. The top gas phase outlet 2-B of the heavy hydrocarbon separator 2 is connected to the inlet of feed gas channel IIA11, and the outlet of feed gas channel IIA11 is connected to the feed inlet 5-A of the cryogenic separator 5. The top gas phase outlet 5-B of the cryogenic separator 5 is connected to the feed inlet 6-A of the methane scrubbing tower 6, and the bottom liquid phase outlet 5-C of the cryogenic separator 5 is connected to the methane-rich channel IIA18. The methane-rich channel IIA18 outlet is connected to the feed inlet 7-A of the hydrogen stripping tower 7. The top gas phase outlet 6-B of the methane scrubbing tower 6 is connected to the inlet of the high-pressure hydrogen channel A3. The outlet of the high-pressure hydrogen channel A3 is connected to an external high-pressure hydrogen pipeline. The bottom liquid phase outlet 6-C of the methane scrubbing tower 6 is connected to the feed inlet 7-B of the hydrogen stripping tower 7. The top gas phase outlet 7-D of the hydrogen stripping tower 7 is connected to the inlet of the medium-pressure hydrogen channel A4. The outlet of the medium-pressure hydrogen channel A4 is connected to an external medium-pressure hydrogen pipeline. The bottom liquid phase outlet pipeline of the hydrogen stripping tower 7 is divided into a methane-rich pipeline I201 and a methane-rich pipeline II202. The inlet of the methane-rich channel IA17 is connected to the methane-rich pipeline I201.The outlet of the methane-rich channel IA17 is connected to the feed inlet 9-A of the carbon monoxide / methane separation tower 9; the methane-rich pipeline II202 is connected to the feed inlet 9-B of the carbon monoxide / methane separation tower 9; the top gas phase outlet 9-C of the carbon monoxide / methane separation tower 9 is connected to the inlet pipeline of the carbon monoxide-rich channel IIB1 of the top condenser 12; the outlet of the carbon monoxide-rich channel IIB1 is connected to the feed inlet 11-A of the reflux tank 11; the bottom liquid phase outlet 11-B of the reflux tank 11 is connected to the feed inlet 9-D of the carbon monoxide / methane separation tower 9; the top gas phase outlet 11-C of the reflux tank 11 is connected to the inlet of the carbon monoxide-rich channel IA5; and the outlet of the carbon monoxide-rich channel IA5 is connected to the external rich methane channel. The carbon monoxide pipeline is connected to the bottom liquid phase outlet pipeline of the carbon monoxide / methane separation tower 9, which is divided into LNG scrubbing liquid pipeline 203 and LNG product pipeline I204. The inlet of the liquid methane pump 13 is connected to the LNG scrubbing liquid pipeline 203, and the outlet of the liquid methane pump 13 is connected to the inlet of LNG channel IIIA16. The outlet of LNG channel IIIA16 is divided into LNG scrubbing liquid to hydrogen stripping tower pipeline 205 and LNG scrubbing liquid to methane scrubbing tower pipeline 206. The LNG scrubbing liquid to hydrogen stripping tower pipeline 205 is connected to the feed inlet 7-C of the hydrogen stripping tower 7, and the LNG scrubbing liquid to methane scrubbing tower pipeline 206 is connected to the feed inlet 6-D of the methane scrubbing tower 6. The mixed refrigerant... The high-pressure liquid-phase mixed refrigerant line of compressor system 15 is connected to the inlet of high-pressure liquid-phase refrigerant channel IA10. The outlet of high-pressure liquid-phase refrigerant channel IA10 is connected to the first port A9-A of reflux refrigerant channel A9. The high-pressure gas-phase mixed refrigerant of the mixed refrigerant compressor system 15 is connected to the inlet of high-pressure gas-phase refrigerant channel IA8. The outlet of high-pressure gas-phase refrigerant channel IA8 is connected to the feed port 4-A of MRC cryogenic separator 4. The bottom liquid-phase outlet 4-B of MRC cryogenic separator 4 is connected to the inlet of high-pressure liquid-phase refrigerant channel II channel A13. The outlet of high-pressure liquid-phase refrigerant channel II channel A13 is connected to the inlet of bottom reboiler 10. The outlet of bottom reboiler 10 is connected to reflux refrigerant channel A9. The second port A9-B is connected to the MRC cryogenic separator 4. The top gas phase outlet 4-C is connected to the inlet of the high-pressure gas phase refrigerant channel IIA12. The outlet of the high-pressure gas phase refrigerant channel IIA12 is connected to the inlet of the hydrogen stripping tower reboiler 8. The outlet of the hydrogen stripping tower reboiler 8 is connected to the third port A9-C of the reflux refrigerant channel A9. The outlet of the reflux refrigerant channel A9 is connected to the inlet of the mixed refrigerant compressor system 15. The outlet of the nitrogen compression system 14 is connected to the inlet of the high-pressure nitrogen channel IA6. The outlet of the high-pressure nitrogen channel IA6 is connected to the inlet of the reflux low-pressure nitrogen channel I channel B2. The outlet of the reflux low-pressure nitrogen channel IIB2 is connected to the inlet of the reflux low-pressure nitrogen channel IA7.The outlet of the reflux low-pressure nitrogen channel IA7 is connected to the inlet of the nitrogen compression system 14.

[0034] The methane washing tower 6, hydrogen stripping tower 7, and carbon monoxide / methane separation tower 9 are packed towers or plate towers; the hydrogen stripping tower reboiler 8 and the bottom reboiler 10 can be built-in or external.

[0035] A regulating valve a101 is installed on the pipeline at the first port A9-A inlet of the reflux refrigerant channel A9, a regulating valve b102 is installed on the pipeline at the second port A9-B inlet of the reflux refrigerant channel A9, and a regulating valve c103 is installed on the pipeline at the third port A9-C inlet of the reflux refrigerant channel A9.

[0036] The low-temperature flash tank 3 is equipped with a regulating valve d104 on the top gas phase outlet 3-B pipeline to regulate the pressure of the low-temperature flash tank 3; the heavy hydrocarbon separator 2 is equipped with a regulating valve e105 on the bottom liquid phase outlet 2-C pipeline to control the bottom liquid level of the heavy hydrocarbon separator 2; and the low-temperature separator 5 is equipped with a regulating valve h108 on the bottom liquid phase outlet 5-C pipeline to control the bottom liquid level of the low-temperature separator 5.

[0037] The LNG channel IA14 outlet pipeline is equipped with a regulating valve f106 to control the bottom liquid level of the cryogenic flash tank 3; the LNG channel IIA15 outlet pipeline is equipped with a regulating valve g107 to control the bottom liquid level of the carbon monoxide / methane separation tower 9.

[0038] A regulating valve i109 is installed on the top gas phase outlet 6-B pipeline of the methane scrubbing tower 6 to control the bottom liquid level of the methane scrubbing tower 6; a regulating valve j110 is installed on the feed inlet 6-D pipeline of the methane scrubbing tower 6 to control the flow rate of the supercooled LNG entering the methane scrubbing tower 6; and a regulating valve l112 is installed on the bottom liquid phase outlet 6-C of the methane scrubbing tower 6 to control the bottom liquid level of the methane scrubbing tower 6.

[0039] A regulating valve k111 is installed on the feed inlet 7-C line of the hydrogen stripping tower 7 to control the flow rate of subcooled LNG washing liquid entering the hydrogen stripping tower 7; a regulating valve n114 is installed on the methane-rich pipeline I201 at the bottom liquid outlet of the hydrogen stripping tower 7 to control the flow rate of liquid from the bottom of the hydrogen stripping tower 7 to the methane-rich channel IA17; a regulating valve o115 is installed on the methane-rich pipeline II202 at the bottom liquid outlet of the hydrogen stripping tower 7 to control the liquid level at the bottom of the hydrogen stripping tower 7; and a regulating valve q117 is installed on the gas phase outlet 7-D line at the top of the hydrogen stripping tower 7 to control the pressure of the hydrogen stripping tower 7.

[0040] A regulating valve m113 is installed between the inlet and outlet pipelines of the hydrogen stripping tower reboiler 8 to control the temperature of LNG entering the bottom of the hydrogen stripping tower 7; a regulating valve p116 is installed between the inlet and outlet pipelines of the bottom reboiler 10 to control the temperature of the bottom of the carbon monoxide / methane separation tower 9; a regulating valve r118 is installed on the top gas phase outlet 11-C pipeline of the reflux tank 11 to control the pressure of the carbon monoxide / methane separation tower 9; a regulating valve s119 is installed on the inlet pipeline of the reflux low-pressure nitrogen channel IIB2 to control the temperature of the carbon monoxide-rich gas exiting the carbon monoxide-rich channel IIB1; and a regulating valve s120 is installed on the inlet and outlet pipelines of the low-pressure nitrogen channel IIB2 to control the temperatures of LNG exiting the LNG channel IIIA16, feed gas exiting the feed gas channel IIA11, and high-pressure nitrogen exiting the high-pressure nitrogen channel IA6.

[0041] Example 1

[0042] S1. The purified feed gas containing hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane, and nitrogen enters the feed gas channel IA2, where it is cooled and partially condensed by the reflux cold stream. It then enters the heavy hydrocarbon separator 2 for heavy hydrocarbon separation. The heavy hydrocarbons obtained at the bottom of the separator are depressurized and enter the low-temperature flash tank 3. The flash vapor phase enters the flash vapor channel A1 for reheating to room temperature and is then sent to the boundary area. The liquid phase separated in the low-temperature flash tank 3 (mainly ethane, ethylene, propane, and butane) enters LN. G channel IA14 is subcooled to -162℃, and after being throttled and depressurized by the liquid level regulating valve f (106), it is sent to the boundary LNG storage tank; the gas phase at the top of the heavy hydrocarbon separator 2 is cooled to -180℃ again in the raw material gas channel IIA11 and enters the cryogenic separator 5 for gas-liquid separation. The separated liquid enters the methane-rich channel IIA18 for rewarming. After being rewarmed to -163℃, it enters the bottom of the hydrogen stripping tower 7 for distillation; the gas separated at the top enters the methane scrubbing tower 6 for cryogenic scrubbing.

[0043] The washing liquid from S2, methane washing tower 6, and hydrogen stripping tower 7 comes from LNG produced by bottom distillation of carbon monoxide / methane separation tower 9. It is first pressurized by liquid methane pump 13, and then enters LNG channel IIIA16 to be cooled and subcooled to -180°C. It is divided into two parts: one part enters the top feed port 6-D of methane washing tower 6 through flow regulating valve j110, and the other part enters the top feed port 7-C of hydrogen stripping tower 7 through flow regulating valve k111.

[0044] S3. In the methane scrubbing tower 6, the rising gas and the flowing liquid come into contact with the structured packing for heat and mass transfer. During the gas rise, N2 and CO are washed by LNG scrubbing liquid cooled to -180℃, and the hydrogen content gradually increases. High-pressure hydrogen-rich gas is obtained at the top of the methane scrubbing tower 6. After the pressure is regulated by the pressure regulating valve i109, it goes to the high-pressure hydrogen channel A3 for reheating to room temperature and then exits the main heat exchanger 1 of the cold box to the boundary area. The methane-rich liquid obtained at the bottom of the methane scrubbing tower 6 is then depressurized by the liquid level regulating valve l112 and enters the middle part of the hydrogen stripping tower 7 for distillation.

[0045] S4. The bottom of the hydrogen stripping tower 7 is equipped with a hydrogen stripping tower reboiler 8, which exchanges heat with the gaseous refrigerant after heat exchange and cooling separation. In the hydrogen stripping tower 7, the rising gas and the flowing liquid transfer heat and mass on the surface of the structured packing. During the rising process, the hydrogen content gradually increases. The N2 and CO in the rising process are washed by LNG washing liquid that is subcooled to -180℃. Medium-pressure hydrogen-rich gas is obtained at the top of the hydrogen stripping tower 7. After being reheated to room temperature through the medium-pressure hydrogen channel A4 via the pressure regulating valve q117, it exits the main heat exchanger 1 of the cold box and goes to the boundary area. The liquid at the bottom of the hydrogen stripping tower 7 is divided into two streams. One part is regulated by the flow regulating valve n114 and enters the methane-rich channel IA17 for reheating before entering the bottom of the carbon monoxide / methane separation tower 9. The other part is depressurized by the liquid level regulating valve o115 and enters the middle part of the carbon monoxide / methane separation tower 9 to participate in the rectification.

[0046] S5. The top of the carbon monoxide / methane separation tower 9 is equipped with a top condenser 12, using throttled liquid nitrogen as a cold source. At the bottom of the carbon monoxide / methane separation tower 9 is a bottom reboiler 10, which, together with the liquid refrigerant after heat exchange and cooling separation, serves as a heat source for LNG evaporation, creating rising gas. Inside the carbon monoxide / methane separation tower 9, the rising gas and reflux liquid undergo heat and mass transfer on the surface of the structured packing. During the gas's ascent, the nitrogen and CO content gradually increases, while the methane content gradually decreases. At the top of the carbon monoxide / methane separation tower 9, CO-rich gas is obtained and enters the carbon monoxide-rich channel IIB1, where it exchanges heat with liquid nitrogen after throttling and depressurization via regulating valve S119. The liquid nitrogen then evaporates. Part of the CO-rich gas is liquefied and separated in reflux tank 11. The separated liquid phase is used as reflux liquid in carbon monoxide / methane separation tower 9. The uncondensed CO-rich gas is returned to the carbon monoxide-rich channel IA5 through pressure regulating valve r118, reheated to room temperature, and exited the cold box to the boundary area. LNG is obtained by distillation at the bottom of carbon monoxide / methane separation tower 9 and divided into two parts. One part is pressurized by liquid methane pump 13 and then enters LNG channel IIIA16 to be subcooled to -180°C to serve as washing liquid for methane washing tower 6 and hydrogen stripping tower 7. The other part is sent to LNG channel IIA15 to be subcooled to -162°C and then sent to the boundary LNG storage tank after being throttled and depressurized by liquid level regulating valve g107.

[0047] S6. The condensation and liquefaction of raw gas and nitrogen, as well as the liquefaction and subcooling of LNG, are provided by a mixed refrigerant refrigeration cycle. First, the high-pressure liquid refrigerant from the mixed refrigerant compressor system 15 is subcooled to -30~-70℃ in the high-pressure liquid refrigerant channel IA10 of the main heat exchanger 1. After being throttled and depressurized by regulating valve a101, it enters the port A9-A of the return refrigerant channel A9. The high-pressure gaseous refrigerant from the mixed refrigerant compressor system 13 is cooled to -30~-70℃ in the high-pressure gaseous refrigerant channel I (A8) of the main heat exchanger 1, and then enters the MRC cryogenic separator 4 for gas-liquid separation. The liquid separated at the bottom enters the high-pressure liquid refrigerant channel II channel A13 and is subcooled to -130~-80℃ before entering the bottom reboiler 10 to provide a heat source for the bottom of the carbon monoxide / methane separation tower 9, controlling the CO content of the LNG in the bottom of the carbon monoxide / methane separation tower 9 to be below 0.5%, which is then controlled by carbon monoxide. The cryogenic liquid in the bottom of methane separator 9 is cooled to -145~-100℃ and then enters the reflux refrigerant channel A9 through port A9-B after being throttled and depressurized by regulating valve b102. The high-pressure gaseous refrigerant from the top of MRC cryogenic separator 4 enters the high-pressure gaseous refrigerant channel IIA12 and is cooled and condensed to about -150℃, and then enters the hydrogen stripping tower reboiler 8 to provide a heat source for the bottom of hydrogen stripping tower 7. The hydrogen content of the methane-rich liquid in the bottom of hydrogen stripping tower 7 is controlled to be less than 0.5%. The mixed refrigerant enters the reflux refrigerant channel A9 through port A9-C after being throttled and depressurized by regulating valve c103. The mixed refrigerant entering the reflux refrigerant channel A9 absorbs heat and evaporates. After evaporating into gas and being reheated to room temperature, it exits the main heat exchanger 1 and then returns to the mixed refrigerant compressor system 15 to complete the mixed refrigerant refrigeration cycle.

[0048] S7. The cryogenic separation of the raw gas is provided by the nitrogen circulation. First, the high-pressure nitrogen from the nitrogen compression system 14 is condensed and subcooled to about -175~-180℃ in the high-pressure nitrogen channel IA6. The nitrogen becomes liquid nitrogen and is divided into two parts. One part of the liquid nitrogen is throttled and depressurized by the regulating valve s119 and enters the return low-pressure nitrogen channel IIB2. The temperature of the CO-rich gas entering the reflux tank (11) is controlled between -180~-170℃, which provides a cold source for the separation of carbon monoxide and methane at the top of the carbon monoxide / methane separation tower 9. The other part of the liquid nitrogen is throttled and depressurized by the regulating valve s120 and merged with the return liquid nitrogen in the return low-pressure nitrogen channel IIB2. It then enters the return low-pressure nitrogen channel IA7, is reheated to room temperature and exits the main heat exchanger 1, and then returns to the inlet of the nitrogen compression system 14 to complete the nitrogen refrigeration cycle.

[0049] This embodiment can be implemented using the purified feed gas parameters shown in the table below. The parameters and compositions of the resulting high-pressure hydrogen-rich gas, medium-pressure hydrogen-rich gas, CO-rich gas, flash vapor, and LNG are shown in Table 1 below:

[0050] Table 1 Parameters and Components of Example 1

[0051]

Claims

1. A device for producing hydrogen co-producing LNG by low-temperature methane washing, characterized in that, The application relates to a main heat exchanger (1), a heavy hydrocarbon separator (2), a low-temperature flash tank (3), an MRC low-temperature separator (4), a low-temperature separator (5), a methane washing tower (6), a hydrogen stripping tower (7), a hydrogen stripping tower reboiler (8), a carbon monoxide / methane separation tower (9), a tower bottom reboiler (10), a reflux tank (11), a tower top condenser (12), a liquid methane pump (13), a nitrogen gas compression system (14), a mixed cold agent compressor system (15), wherein the main heat exchanger (1) is provided with a flash gas channel (A1), a raw material gas channel I (A2), a high-pressure hydrogen gas channel (A3), a medium-pressure hydrogen gas channel (A4), a carbon monoxide-rich channel I (A5), a high-pressure nitrogen gas channel I (A6), a reflux low-pressure nitrogen gas channel I (A7), a high-pressure gas-phase cold agent channel I (A8), a reflux cold agent channel (A9), a high-pressure liquid-phase cold agent channel I (A10), a raw material gas channel II (A11), a high-pressure gas-phase cold agent channel II (A12), a high-pressure liquid-phase cold agent channel II (A13), an LNG channel I (A14), an LNG channel II (A15), an LNG channel III (A16), a methane-rich channel I (A17) and a methane-rich channel II (A18), the tower top condenser (12) is provided with a carbon monoxide-rich channel II (B1) and a reflux low-pressure nitrogen gas channel II (B2), the inlet of the raw material gas channel I (A2) is connected with a raw material gas pipeline after purification, the outlet of the raw material gas channel I (A2) is connected with a heavy hydrocarbon separator (2) feeding port (2-A), the bottom liquid-phase outlet (2-C) of the heavy hydrocarbon separator (2) is connected with a low-temperature flash tank (3) feeding port (3-A), the top gas-phase outlet (3-B) of the low-temperature flash tank (3) is connected with the inlet of the flash gas channel (A1), the outlet of the flash gas channel (A1) is connected with a flash gas pipeline for external delivery, the bottom liquid-phase outlet (3-C) of the low-temperature flash tank (3) is connected with the inlet of the LNG channel I (A14), the outlet of the LNG channel I (A14) is connected with an LNG storage unit pipeline, the top gas-phase outlet (2-B) of the heavy hydrocarbon separator (2) is connected with the inlet of the raw material gas channel II (A11), the outlet of the raw material gas channel II (A11) is connected with a low-temperature separator (5) feeding port (5-A), the top gas-phase outlet (5-B) of the low-temperature separator (5) is connected with a methane washing tower (6) first feeding port (6-A), the bottom liquid-phase outlet (5-C) of the low-temperature separator (5) is connected with the inlet of the methane-rich channel II (A18), the outlet of the methane-rich channel II (A18) is connected with a hydrogen stripping tower (7) first feeding port (7-A), the top gas-phase outlet (6-B) of the methane washing tower (6) is connected with the inlet of the high-pressure hydrogen gas channel (A3), the outlet of the high-pressure hydrogen gas channel (A3) is connected with a high-pressure hydrogen gas pipeline, the bottom liquid-phase outlet (6-C) of the methane washing tower (6) is connected with a hydrogen stripping tower (7) second feeding port (7-B), and the like.The hydrogen stripping tower (7) top gas phase outlet (7-D) is connected with the medium pressure hydrogen passage (A4) inlet, the medium pressure hydrogen passage (A4) outlet is connected with the outside medium pressure hydrogen pipeline, the hydrogen stripping tower (7) bottom liquid phase outlet pipeline is divided into the rich methane pipeline I (201) and the rich methane pipeline II (202), the rich methane passage I (A17) inlet is connected with the rich methane pipeline I (201), the rich methane passage I (A17) outlet is connected with the carbon monoxide / methane separation tower (9) first feeding port (9-A), the rich methane pipeline II (202) is connected with the carbon monoxide / methane separation tower (9) second feeding port (9-B), the carbon monoxide / methane separation tower (9) top gas phase outlet (9-C) is connected with the rich carbon monoxide passage II (B1) inlet pipeline of the overhead condenser (12), the rich carbon monoxide passage II (B1) outlet is connected with the reflux tank (11) feeding port (11-A), the reflux tank (11) bottom liquid phase outlet (11-B) is connected with the carbon monoxide / methane separation tower (9) third feeding port (9-D), the reflux tank (11) top gas phase outlet (11-C) is connected with the rich carbon monoxide passage I (A5) inlet, the rich carbon monoxide passage I (A5) outlet is connected with the outside rich carbon monoxide pipeline, the carbon monoxide / methane separation tower (9) bottom liquid phase outlet pipeline is divided into the LNG washing liquid pipeline (203) and the LNG product pipeline I (204), the liquid methane pump (13) inlet is connected with the LNG washing liquid pipeline (203), the liquid methane pump (13) outlet is connected with the LNG passage III (A16) inlet, the LNG passage III (A16) outlet is divided into the LNG washing liquid hydrogen stripping tower pipeline (205) and the LNG washing liquid demethanizing tower pipeline (206), the LNG washing liquid hydrogen stripping tower pipeline (205) is connected with the hydrogen stripping tower (7) third feeding port (7-C), the LNG washing liquid demethanizing tower pipeline (206) is connected with the methane washing tower (6) second feeding port (6-D), the mixed refrigerant compressor system (15) high pressure liquid phase mixed refrigerant pipeline is connected with the high pressure liquid phase refrigerant passage I (A10) inlet, the high pressure liquid phase refrigerant passage I (A10) outlet is connected with the reflux refrigerant passage (A9) first pipe (A9-A), the mixed refrigerant compressor system (15) high pressure gas phase mixed refrigerant is connected with the high pressure gas phase refrigerant passage I (A8) inlet, the high pressure gas phase refrigerant passage I (A8) outlet is connected with the MRC cryogenic separator (4) feeding port (4-A), the MRC cryogenic separator (4) bottom liquid phase outlet (4-B) is connected with the high pressure liquid phase refrigerant passage II passage (A13) inlet, the high pressure liquid phase refrigerant passage II passage (A13) outlet is connected with the tower bottom reboiler (10) inlet, the tower bottom reboiler (10) outlet is connected with the reflux refrigerant passage (A9) second pipe (A9-B),The MRC low-temperature separator (4) top gas phase outlet (4-C) is connected with the high-pressure gas phase refrigerant passage II (A12) inlet, the high-pressure gas phase refrigerant passage II (A12) outlet is connected with the hydrogen stripping tower reboiler (8) inlet, the hydrogen stripping tower reboiler (8) outlet is connected with the third pipe orifice (A9-C) of the reflux refrigerant passage (A9), and the reflux refrigerant passage (A9) outlet is connected with the mixed refrigerant compressor system (15) inlet; the nitrogen gas compression system (14) outlet is connected with the high-pressure nitrogen gas passage I (A6) inlet, the high-pressure nitrogen gas passage I (A6) outlet is connected with the reflux low-pressure nitrogen gas passage II (B2) inlet, the reflux low-pressure nitrogen gas passage II (B2) outlet is connected with the reflux low-pressure nitrogen gas passage I (A7) inlet, and the reflux low-pressure nitrogen gas passage I (A7) outlet is connected with the nitrogen gas compression system (14) inlet.

2. The device for producing hydrogen and co-producing LNG by low-temperature methane washing according to claim 1, characterized in that, The methane washing column (6), the hydrogen stripping column (7) and the carbon monoxide / methane separation column (9) are packed columns or plate columns; the hydrogen stripping column reboiler (8) and the bottom reboiler (10) are arranged in the form of built-in or external.

3. The device for producing hydrogen and co-producing LNG by low-temperature methane washing according to claim 1, characterized in that, The pipeline of the first nozzle (A9-A) of the reflux refrigerant passage (A9) is provided with an adjusting valve a (101), the pipeline of the second nozzle (A9-B) of the reflux refrigerant passage (A9) is provided with an adjusting valve b (102), and the pipeline of the third nozzle (A9-C) of the reflux refrigerant passage (A9) is provided with an adjusting valve c (103).

4. The apparatus for co-producing hydrogen and LNG by low-temperature methane washing according to claim 1, characterized in that, The pipeline of the gas phase outlet (3-B) at the top of the low-temperature flash tank (3) is provided with an adjusting valve d (104) for adjusting the pressure of the low-temperature flash tank (3); the pipeline of the liquid phase outlet (2-C) at the bottom of the heavy hydrocarbon separator (2) is provided with an adjusting valve e (105) for controlling the liquid level at the bottom of the heavy hydrocarbon separator (2); and the pipeline of the liquid phase outlet (5-C) at the bottom of the low-temperature separator (5) is provided with an adjusting valve h (108) for controlling the liquid level at the bottom of the low-temperature separator (5).

5. The apparatus for co-producing hydrogen and LNG by cryogenic methane washing according to claim 1, wherein, The pipeline of the LNG passage I (A14) outlet is provided with an adjusting valve f (106) for controlling the liquid level at the bottom of the low-temperature flash tank (3); and the pipeline of the LNG passage II (A15) outlet is provided with an adjusting valve g (107) for controlling the liquid level at the bottom of the carbon monoxide / methane separation column (9).

6. The apparatus for co-producing hydrogen and LNG by cryogenic methane washing according to claim 1, wherein, The pipeline of the gas phase outlet (6-B) at the top of the methane washing column (6) is provided with an adjusting valve i (109) for controlling the liquid level at the bottom of the methane washing column (6); the pipeline of the second feed inlet (6-D) of the methane washing column (6) is provided with an adjusting valve j (110) for controlling the flow of the supercooled LNG of the washing liquid into the methane washing column (6); and the pipeline of the liquid phase outlet (6-C) at the bottom of the methane washing column (6) is provided with an adjusting valve l (112) for controlling the liquid level of the liquid phase at the bottom of the methane washing column (6).

7. The apparatus for co-producing hydrogen and LNG by cryogenic methane washing according to claim 1, wherein, The pipeline of the third feed inlet (7-C) of the hydrogen stripping column (7) is provided with an adjusting valve k (111) for controlling the flow of the supercooled LNG of the washing liquid into the hydrogen stripping column (7); the pipeline of the liquid phase outlet of the hydrogen stripping column (7) rich in methane pipeline I (201) is provided with an adjusting valve n (114) for controlling the flow of the liquid at the bottom of the hydrogen stripping column (7) to the methane-rich passage I (A17); the pipeline of the liquid phase outlet of the hydrogen stripping column (7) rich in methane pipeline II (202) is provided with an adjusting valve o (115) for controlling the liquid level at the bottom of the hydrogen stripping column (7); and the pipeline of the gas phase outlet (7-D) at the top of the hydrogen stripping column (7) is provided with an adjusting valve q (117) for controlling the pressure of the hydrogen stripping column (7).

8. The apparatus for co-producing hydrogen and LNG by cryogenic methane washing according to claim 1, wherein, The reboiler (8) of the hydrogen stripping tower is provided with a regulating valve m (113) between the inlet pipeline and the outlet pipeline, which is used for controlling the temperature of the LNG into the tower kettle of the hydrogen stripping tower (7); the bottom reboiler (10) is provided with a regulating valve p (116) between the inlet pipeline and the outlet pipeline, which is used for controlling the temperature of the tower kettle of the carbon monoxide / methane separation tower (9); the reflux tank (11) is provided with a regulating valve r (118) on the gas phase outlet (11-C) pipeline at the top, which is used for controlling the pressure of the carbon monoxide / methane separation tower (9); the inlet pipeline of the reflux low-pressure nitrogen channel II (B2) is provided with a regulating valve s (119), which is used for controlling the temperature of the carbon monoxide-rich gas out of the carbon monoxide-rich channel II (B1); and the inlet pipeline and the outlet pipeline of the reflux low-pressure nitrogen channel II (B2) are provided with regulating valves s (119), which are used for controlling the temperatures of the LNG out of the LNG channel III (A16), the raw gas out of the raw gas channel II (A11) and the high-pressure nitrogen out of the high-pressure nitrogen channel I (A6).

9. A method for co-production of hydrogen and LNG by low temperature methane wash, characterized in that, The method comprises the following steps: S1, the purified raw gas containing hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane and nitrogen enters the raw gas channel I (A2) and is cooled and partially condensed by the reflux cold stream, and then enters the heavy hydrocarbon separator (2) for heavy hydrocarbon separation, and heavy hydrocarbon is obtained at the bottom of the heavy hydrocarbon separator and enters the low-temperature flash tank (3) after being depressurized, and the gas phase is flashed into the flash gas channel (A1) for reheating to normal temperature and is sent to the boundary area, and the liquid phase separated by the low-temperature flash tank (3) enters the LNG channel I (A14) for subcooling and is sent to the boundary area LNG storage tank after being throttled and depressurized by the liquid level regulating valve f (106); the gas phase at the top of the heavy hydrocarbon separator (2) enters the raw gas channel II (A11) again and is cooled and enters the low-temperature separator (5) for gas-liquid separation, and the separated liquid enters the methane-rich channel II (A18) for rewarming and enters the bottom of the hydrogen stripping tower (7) for rectification; and the separated gas at the top enters the methane washing tower (6) for low-temperature washing; S2, the washing liquid is pressurized by the liquid methane pump (13) and then enters the LNG channel III (A16) and is cooled and subcooled, and is divided into two parts, one part enters the second feed inlet (6-D) of the methane washing tower (6) through the flow regulating valve j (110), and the other part enters the third feed inlet (7-C) at the top of the hydrogen stripping tower (7) through the flow regulating valve k (111); S3, the ascending gas in the methane washing tower (6) contacts the descending liquid on the structured packing for heat and mass transfer, N2 and CO are washed by the washing liquid in the process of the ascending gas, the hydrogen content gradually increases, high-pressure hydrogen-rich gas is obtained at the top of the methane washing tower (6), is pressure-adjusted by the pressure regulating valve i (109) and then enters the high-pressure hydrogen channel (A3) for reheating to normal temperature and is sent to the cold box main heat exchanger (1) to the boundary area; the methane-rich liquid obtained at the bottom of the methane washing tower (6) is depressurized by the liquid level regulating valve l (112) and then enters the middle part of the hydrogen stripping tower (7) for rectification. S4, the hydrogen stripping tower (7) is provided with a hydrogen stripping tower reboiler (8) at the bottom, which exchanges heat with the gas phase cold agent separated after heat exchange and cooling, and the rising gas and the downward liquid exchange heat and mass on the surface of the structured packing in the hydrogen stripping tower (7), the content of hydrogen in the rising gas gradually increases, N2 and CO in the rising process are washed by the washing liquid, and the medium-pressure hydrogen-rich gas is obtained at the top of the hydrogen stripping tower (7), which is heated to normal temperature through the pressure regulating valve q (117) and then discharged from the cold box main heat exchanger (1) to the boundary zone; the liquid at the bottom of the hydrogen stripping tower (7) is divided into two parts, one part is adjusted through the flow regulating valve n (114) and then enters the methane-rich channel I (A17) for reheating, enters the bottom of the carbon monoxide / methane separation tower (9), and the other part is reduced in pressure through the liquid level regulating valve o (115) and then enters the middle part of the carbon monoxide / methane separation tower (9) to participate in rectification; S5, the carbon monoxide / methane separation tower (9) is provided with a tower top condenser (12) at the top, and the throttled liquid nitrogen is used as a cold source; the tower bottom reboiler (10) is arranged at the bottom of the carbon monoxide / methane separation tower (9), and the liquid phase cold agent separated after heat exchange and cooling is used as a heat source to make LNG evaporate as rising gas, the rising gas and the reflux liquid exchange heat and mass on the surface of the structured packing in the carbon monoxide / methane separation tower (9), the content of nitrogen and CO in the rising gas gradually increases, and the content of methane gradually decreases, the CO-rich gas is obtained at the top of the carbon monoxide / methane separation tower (9), enters the carbon monoxide-rich channel II (B1) and exchanges heat with the liquid nitrogen throttled and reduced in pressure through the regulating valve s (119), the liquid nitrogen evaporates, part of the CO-rich gas is liquefied in the reflux tank (11) for separation, the separated liquid phase is used as the reflux liquid of the carbon monoxide / methane separation tower (9), the uncondensed CO-rich gas returns to the carbon monoxide-rich channel I (A5) through the pressure regulating valve r (118) and is reheated to normal temperature to discharge from the cold box to the boundary zone, and the LNG is obtained by rectification at the bottom of the carbon monoxide / methane separation tower (9) and is divided into two parts, one part is pressurized through the liquid methane pump (13) and then enters the LNG channel III (A16) to be supercooled to-180 DEG C, and is used as the washing liquid of the methane washing tower (6) and the hydrogen stripping tower (7), and the other part is sent to the LNG channel II (A15) to be supercooled to-162 DEG C, throttled and reduced in pressure through the liquid level regulating valve g (107) and then sent to the boundary zone LNG storage tank; S6, high pressure liquid phase refrigerant from the mixed refrigerant compressor system (15) is subcooled to -30~-70℃ in the main heat exchanger (1) high pressure liquid phase refrigerant channel I (A10), after pressure reduction by adjusting valve a (101), enters the first pipe opening (A9-A) of the reflux refrigerant channel (A9), the high pressure gas phase refrigerant of the mixed refrigerant compressor system (15) is cooled to -30~-70℃ in the main heat exchanger (1) high pressure gas phase refrigerant channel I (A8), then enters the MRC low temperature separator (4) for gas-liquid separation, the bottom separated liquid is subcooled to -130~-80℃ in the high pressure liquid phase refrigerant channel II channel (A13), then enters the tower bottom reboiler (10) to provide heat source for the carbon monoxide / methane separation column (9) tower kettle, control the CO content of LNG in the carbon monoxide / methane separation column (9) tower kettle to be less than 0.5%, the low temperature liquid in the carbon monoxide / methane separation column (9) tower kettle is cooled to -145~-100℃, after pressure reduction by adjusting valve b (102), enters the second pipe opening (A9-B) of the reflux refrigerant channel (A9); the high pressure gas phase refrigerant from the top of the MRC low temperature separator (4) enters the high pressure gas phase refrigerant channel II (A12) to be cooled and condensed to -150℃, then enters the hydrogen stripping column reboiler (8) to provide heat source for the hydrogen stripping column (7) tower kettle, control the hydrogen content of the rich methane liquid in the hydrogen stripping column (7) tower kettle to be less than 0.5%, control after pressure reduction by adjusting valve c (103), enters the third pipe opening (A9-C) of the reflux refrigerant channel (A9), the mixed refrigerant in the reflux refrigerant channel (A9) absorbs heat and evaporates, all evaporate into gas and are reheated to normal temperature, then exit the main heat exchanger (1), then return to the mixed refrigerant compressor system (15) to complete the mixed refrigerant refrigeration cycle; S7, the high pressure nitrogen from the nitrogen compression system (14) is condensed and subcooled to -175~-180℃ in the high pressure nitrogen channel I (A6), the nitrogen becomes liquid nitrogen, which is divided into two parts, one part of the liquid nitrogen, after pressure reduction by adjusting valve s (119), enters the reflux low pressure nitrogen channel II (B2), control the CO rich gas entering the reflux tank (11) temperature between -180~-170℃, to provide cold source for the carbon monoxide and methane separation at the top of the carbon monoxide / methane separation column (9); the other part of the liquid nitrogen, after pressure reduction by adjusting valve s (119), and the liquid nitrogen returned from the reflux low pressure nitrogen channel II (B2) are combined, then enter the reflux low pressure nitrogen channel I (A7), to be reheated to normal temperature, then exit the main heat exchanger (1), then return to the nitrogen compression system (14) inlet to complete the nitrogen refrigeration cycle.

10. The method for co-producing hydrogen and LNG by low-temperature methane washing according to claim 9, characterized in that, The liquid phase separated by the S1 low-temperature flash tank (3) is mainly ethane, ethylene, propane and butane, the subcooling temperature in the LNG channel I (A14) is -162℃, the cooling temperature in the raw material gas channel II (A11) is -180℃, and the rewarming temperature in the rich-methane channel II (A18) is -163℃; the subcooling temperature in the S2 is -180℃; the washing liquid in the S3 and S4 is the LNG cooled to -180℃ generated by rectification at the bottom of the carbon monoxide / methane separation tower (9); the condensation and liquefaction of the raw material gas and nitrogen and the liquefaction and subcooling of the LNG are provided with cold energy by a mixed refrigerant refrigeration cycle; and the cryogenic separation of the raw material gas is provided with cold energy by a nitrogen cycle.

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