A device and process for extracting helium from liquefied natural gas (BOG)

Abstract

The invention relates to a device and a process for extracting helium from liquefied natural gas (BOG), comprising a non-condensable gas separation device and a non-condensable gas refining device; the non-condensable gas separation device comprises a first buffer tank connected to the raw gas, and a first compressor, a first heat exchanger, a distillation tower, a first cooler, and a first gas-liquid separator connected in sequence after the first buffer tank; the non-condensable gas refining device comprises a second heat exchanger connected to the gas phase outlet of the first gas-liquid separator, and a membrane separation group, a Roots blower, a mixer, a catalytic oxidizer, a second cooler, a third heat exchanger, a second gas-liquid separator, a drying tower, a second compressor, and a low-temperature adsorption tower connected in sequence after the second heat exchanger; the device BOG is compressed without circulation, and methane and helium-containing light components in the BOG are separated at one time and the methane is returned to the LNG production device; the device has the advantages of reducing the energy consumption of the BOG compressor, improving the product utilization rate, operating economically and stably, being safe and easy to regulate, and being able to adapt to strong load fluctuations.

Description

Technical Field

[0001] The invention belongs to the technical field of extracting helium from liquefied natural gas (BOG), and specifically relates to a device and process for extracting helium from liquefied natural gas (BOG) which is economical and stable in operation, safe and easy to regulate, and adaptable to strong load fluctuations. Background Art

[0002] Helium is the element with the lowest known boiling point in nature. It is a rare gas with the characteristics of low density, low boiling point, good thermal conductivity, not easy to liquefy, good stability, strong diffusivity and low solubility. It mainly exists in natural gas, and its content in gas fields ranges from a few ten-thousandths to a few percent. It is widely used in high-tech fields such as aerospace, nuclear industry, national defense and military industry, and cryogenic science. It is a scarce strategic resource related to national security and the development of high-tech industries.

[0003] Although the helium content in natural gas in my country is generally low, my country is rich in helium-containing natural gas resources. A certain amount of BOG gas will be produced during the production, storage and transportation of liquefied natural gas. The helium content in non-condensable gas can reach 2%~9%, which has extremely high utilization value. However, due to the limitations of extraction and purification technology and economic issues, the current domestic treatment method for liquefied natural gas BOG is mainly cyclic pressurized liquefaction or use as combustion gas, and industrial extraction of helium in BOG has not been achieved. Summary of the invention

[0004] The present invention provides a device and a process for extracting helium from liquefied natural gas (BOG), which is economical and stable in operation, safe and easy to regulate, and suitable for use with liquefied natural gas (BOG) with strong load fluctuations.

[0005] A device for extracting helium from liquefied natural gas (BOG) comprises a non-condensable gas separation device and a non-condensable gas refining device.

[0006] The non-condensable gas separation device comprises a first buffer tank for feeding raw gas, wherein the outlet of the first buffer tank is connected to the inlet of the first compressor through a pipeline, the outlet of the first compressor is connected to the first inlet of the first heat exchanger through a pipeline, the first heat exchanger is provided with a first outlet and a second inlet, the first outlet is respectively connected to the second inlet and the inlet of the reboiler tube side at the bottom of the distillation tower through pipelines, the outlet of the reboiler tube side is connected to the second inlet of the first heat exchanger through a pipeline, the second outlet of the first heat exchanger is connected to the air inlet in the middle of the distillation tower through a pipeline; a liquid phase outlet is provided at the bottom of the distillation tower, the liquid phase outlet is connected to the third inlet of the first heat exchanger through a pipeline, the first heat exchanger is provided with a third outlet and a fourth inlet, the third outlet is connected to the fourth inlet through a pipeline, the fourth outlet of the first heat exchanger is connected to the second buffer tank through a pipeline; a gas phase outlet is provided at the top of the distillation tower, the gas phase outlet is connected to the inlet of the first cooler tube side through a pipeline, the outlet of the first cooler tube side is connected to the inlet of the first gas-liquid separator through a pipeline, and the liquid phase outlet at the bottom of the first gas-liquid separator is connected to the reflux liquid inlet at the top of the distillation tower through a pipeline.

[0007] The non-condensable gas refining device comprises a second heat exchanger, wherein the second heat exchanger is provided with a first inlet, the gas phase outlet at the top of the first gas-liquid separator is connected to the first inlet of the second heat exchanger through a pipeline, the first outlet of the second heat exchanger is connected to the inlet of the membrane separation group through a pipeline, the outlet of the membrane separation group is connected to the inlet of the Roots blower through a pipeline, the outlet of the Roots blower is connected to the raw gas inlet of the mixer through a pipeline, the outlet of the mixer is connected to the inlet of the catalytic oxidizer through a pipeline, the outlet of the catalytic oxidizer is connected to the inlet of the second cooler through a pipeline, the outlet of the second cooler is respectively connected to the first inlet of the third heat exchanger and the inlet of the Roots blower through pipelines, and the outlet of the third heat exchanger is connected to the first inlet of the third heat exchanger and the inlet of the Roots blower through pipelines. The first outlet is connected to the inlet of the second gas-liquid separator through a pipeline, the gas phase outlet of the second gas-liquid separator is connected to the inlet of the drying tower through a pipeline, the outlet of the drying tower is connected to the inlet of the second compressor through a pipeline, the outlet of the second compressor is connected to the second inlet of the second heat exchanger through a pipeline, the second outlet of the second heat exchanger is connected to the inlet of the low-temperature adsorption tower through a pipeline, the outlet of the low-temperature adsorption tower is connected to the third inlet of the second heat exchanger through a pipeline, the third outlet of the second heat exchanger is connected to the second inlet of the third heat exchanger through a pipeline, the second outlet of the third heat exchanger is connected to the inlet of the third compressor through a pipeline, and the outlet of the third compressor is connected to the inlet of the product storage tank through a pipeline.

[0008] The device for extracting helium from liquefied natural gas (BOG) comprises an oxygen storage tank, and an outlet of the oxygen storage tank is connected to an oxygen inlet of a mixer through a pipeline.

[0009] The device for extracting helium from liquefied natural gas (BOG) comprises a liquid nitrogen storage tank, and an outlet of the liquid nitrogen storage tank is connected to an inlet of a first cooler shell side through a pipeline.

[0010] In the device for extracting helium from liquefied natural gas (BOG), a first valve is provided on the pipeline between the outlet of the first buffer tank and the inlet of the first compressor, a second valve is provided on the pipeline between the outlet of the first compressor and the first inlet of the first heat exchanger, a third valve is provided on the pipeline between the first outlet and the second inlet of the first heat exchanger, a fourth valve is provided on the pipeline between the third outlet and the fourth inlet of the first heat exchanger, and a fifth valve is provided on the pipeline between the second outlet of the first heat exchanger and the air inlet in the middle of the distillation tower; a sixth valve is provided on the pipeline between the first outlet of the second heat exchanger and the inlet of the membrane separation group, a seventh valve is provided on the pipeline between the outlet of the membrane separation group and the inlet of the Roots blower, and an eighth valve is provided on the pipeline between the outlet of the Roots blower and the raw gas inlet of the mixer; a ninth valve is provided on the pipeline between the outlet of the catalytic oxidizer and the inlet of the second cooler, and a ninth valve is provided on the pipeline between the outlet of the second cooler and the first inlet of the third heat exchanger. A tenth valve is provided on the pipeline between the inlets, and an eleventh valve is provided on the pipeline between the outlet of the second cooler and the inlet of the Roots blower; a twelfth valve is provided on the pipeline between the gas phase outlet of the second gas-liquid separator and the inlet of the drying tower, and a thirteenth valve is provided on the pipeline between the outlet of the drying tower and the inlet of the second compressor; a fourteenth valve is provided on the pipeline between the second outlet of the second heat exchanger and the inlet of the low-temperature adsorption tower, and a fifteenth valve is provided on the pipeline between the outlet of the low-temperature adsorption tower and the third inlet of the second heat exchanger; a sixteenth valve is provided on the pipeline between the second outlet of the third heat exchanger and the inlet of the third compressor, and a seventeenth valve is provided on the pipeline between the outlet of the third compressor and the inlet of the product storage tank; an eighteenth valve is provided on the pipeline between the outlet of the oxygen storage tank and the oxygen inlet of the mixer; a nineteenth valve is provided on the pipeline between the outlet of the liquid nitrogen storage tank and the shell inlet of the first cooler.

[0011] A process for extracting helium from liquefied natural gas (BOG), the process comprising the following extraction steps.

[0012] Step 1: Allow the raw gas to enter the first buffer tank. The main components of the raw gas are: methane, nitrogen, hydrogen, and helium. The pressure is 0.003MPa and the temperature is room temperature.

[0013] Step 2: The raw gas in the first buffer tank enters the first compressor for compression. The temperature of the raw gas at the outlet of the first compressor is 35°C and the pressure is 2.5MPa.

[0014] Step 3: The raw gas at the outlet of the compressor enters the first inlet of the first heat exchanger, the reboiler at the bottom of the distillation tower, and the second inlet of the first heat exchanger in turn for heat exchange and cooling to -113°C, and then enters the distillation tower through the middle air inlet of the distillation tower for distillation. A bypass regulating pipeline is provided between the first outlet of the first heat exchanger and the second inlet of the first heat exchanger; the high-boiling-point components are enriched in the lower part of the distillation tower, and are successively passed through the third inlet of the first heat exchanger, the fourth valve, and the fourth inlet of the first heat exchanger to be decompressed and heated before going to the second buffer tank; the low-boiling-point components enter the first inlet of the distillation tower from the gas phase outlet of the distillation tower. After cooling in the first cooler tube, it enters the first gas-liquid separator, and the liquid phase at the bottom of the first gas-liquid separator returns to the distillation tower through the reflux liquid inlet at the top of the distillation tower; the temperature of the raw gas at the first outlet of the first heat exchanger is -98°C, the temperature of the raw gas at the outlet of the reboiler at the bottom of the distillation tower is -116°C, and the temperature of the raw gas at the air inlet in the middle of the distillation tower is -175°C; the temperature of the high boiling point component at the third outlet of the first heat exchanger is -172°C, and the temperature of the high boiling point component at the fourth inlet of the first heat exchanger is -176°C, and the pressure is 0 .03MPa, the high boiling point component at the inlet temperature of the second buffer tank is 27°C, the low boiling point component at the gas phase outlet temperature of the distillation tower is -176.5°C, and the low boiling point component at the outlet temperature of the first gas-liquid separator is -204°C; the high boiling point component is 86.8% methane and 13.2% nitrogen, and the low boiling point main components are 52.9% helium, 14.4% hydrogen and 32.7% nitrogen.

[0015] Step 4: Allow the mixed gas at the top of the first gas-liquid separator to enter the first inlet of the second heat exchanger, and the mixed gas at the first outlet of the second heat exchanger to enter the membrane separation group after being decompressed by the sixth valve; the temperature of the mixed gas at the first outlet of the second heat exchanger is 20°C, and the temperature of the mixed gas at the outlet of the membrane separation group is 28°C, and the pressure is 0.1MPa.

[0016] Step 5: The mixed gas at the outlet of the membrane separation group and the circulating gas returned from the outlet of the second cooler enter the Roots blower for pressurization. The mixed gas at the outlet of the Roots blower enters the mixer and mixes with the oxygen from the oxygen storage tank. The oxygen-carrying mixed gas enters the catalytic oxidizer to remove hydrogen. The mixed gas at the outlet of the catalytic oxidizer enters the second cooler for cooling and separation. The mixed gas at the outlet of the second cooler is divided into two paths, one path returns to the inlet of the Roots blower as circulating gas, and the other path enters the first inlet of the third heat exchanger. The ratio of circulating gas to the mixed gas at the first inlet of the third heat exchanger is 85:15. The temperature of the mixed gas at the outlet of the Roots blower is 64°C and the pressure is 0.15MPa. The temperature of the mixed gas at the outlet of the catalytic oxidizer is 450°C, and the temperature of the mixed gas at the outlet of the second cooler is 40°C.

[0017] Step 6: The mixed gas at the first outlet of the third heat exchanger enters the second gas-liquid separator, and the mixed gas at the second gas-liquid separator enters the drying tower for dehydration and drying. The mixed gas temperature at the first outlet of the third heat exchanger is 10°C.

[0018] Step 7: The mixed gas at the outlet of the drying tower enters the second compressor, and the mixed gas at the outlet of the second compressor enters the second inlet of the second heat exchanger. The mixed gas at the second outlet of the second heat exchanger enters the low-temperature adsorption tower to remove nitrogen and oxygen to obtain a helium product. The helium at the outlet of the low-temperature adsorption tower passes through the third inlet of the second heat exchanger, the second inlet of the third heat exchanger, and the third compressor in turn, and the helium enters the product storage tank after pressurization. The temperature of the mixed gas at the outlet of the second compressor is 40°C and the pressure is 2.5MPa; the inlet temperature of the low-temperature adsorption tower is -195°C; the third outlet temperature of the second heat exchanger is -117°C; the second outlet temperature of the third heat exchanger is 10°C; the outlet temperature of the third compressor is 45°C and the pressure is 20MPa.

[0019] The present invention is a skid-mounted design, and the device has the characteristics of low investment, simple operation, quick effect and high rate of return. It breaks through the technical barriers of high difficulty and high development cost of domestic helium extraction, realizes the localization application of low-cost helium extraction technology, and enables liquefied natural gas BOG to be fully extracted and utilized, with very high economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the device structure of the present invention. DETAILED DESCRIPTION

[0021] like Figure 1As shown, a device for extracting helium from liquefied natural gas (BOG) comprises a first buffer tank 1 for feeding raw gas, wherein the outlet of the first buffer tank 1 is connected to the inlet of a first compressor 2 through a pipeline, the outlet of the first compressor 2 is connected to the first inlet 35 of a first heat exchanger 3 through a pipeline, the first heat exchanger 3 is provided with a first outlet 4 and a second inlet 7, the first outlet 4 is respectively connected to the second inlet 7 and the tube-side inlet of a reboiler 6 at the bottom of a distillation tower 5 through a pipeline, the tube-side outlet of the reboiler 6 is connected to the second inlet 7 of the first heat exchanger 3 through a pipeline, the second outlet of the first heat exchanger 3 is connected to the gas inlet 8 at the middle of the distillation tower 5 through a pipeline; the bottom of the distillation tower 5 is provided with a liquid phase outlet 9, the liquid phase outlet 9 The first heat exchanger 3 is connected to the third inlet 10 of the first heat exchanger 3 through a pipeline, the first heat exchanger 3 is provided with a third outlet 11 and a fourth inlet 12, the third outlet 11 is connected to the fourth inlet 12 through a pipeline, and the fourth outlet of the first heat exchanger 3 is connected to the second buffer tank 13 through a pipeline; the top of the distillation tower 5 is provided with a gas phase outlet 14, the gas phase outlet 14 is connected to the pipe side inlet of the first cooler 15 through a pipeline, the pipe side outlet of the first cooler 15 is connected to the inlet of the first gas-liquid separator 16 through a pipeline, the liquid phase outlet at the bottom of the first gas-liquid separator 16 is connected to the reflux liquid inlet 17 of the upper part of the distillation tower 5 through a pipeline, and the gas phase outlet at the top of the first gas-liquid separator 16 is connected to the reflux liquid inlet 17 of the upper part of the distillation tower 5 through a pipeline. The first outlet of the second heat exchanger 18 is connected to the inlet of the membrane separation group 20 through a pipeline, the outlet of the membrane separation group 20 is connected to the inlet of the Roots blower 21 through a pipeline, the outlet of the Roots blower 21 is connected to the raw gas inlet 58 of the mixer 22 through a pipeline, the outlet of the mixer 22 is connected to the inlet of the catalytic oxidizer 23 through a pipeline, the outlet of the catalytic oxidizer 23 is connected to the inlet of the second cooler 24 through a pipeline, the outlet of the second cooler 24 is respectively connected to the first inlet 26 of the third heat exchanger 25 and the inlet of the Roots blower 21 through a pipeline, the first outlet of the third heat exchanger 25 is connected to the inlet of the second gas-liquid separator 27 through a pipeline, and the second gas The gas phase outlet of the liquid separator 27 is connected to the inlet of the drying tower 28 through a pipeline, the outlet of the drying tower 28 is connected to the inlet of the second compressor 29 through a pipeline, the outlet of the second compressor 29 is connected to the second inlet 30 of the second heat exchanger 18 through a pipeline, the second outlet of the second heat exchanger 18 is connected to the inlet of the low-temperature adsorption tower 31 through a pipeline, the outlet of the low-temperature adsorption tower 31 is connected to the third inlet 32 ​​of the second heat exchanger 18 through a pipeline, the third outlet of the second heat exchanger 18 is connected to the second inlet 33 of the third heat exchanger 25 through a pipeline, the second outlet of the third heat exchanger 25 is connected to the inlet of the third compressor 34 through a pipeline, and the outlet of the third compressor 34 is connected to the inlet of the product storage tank 57 through a pipeline.

[0022] The device for extracting helium from liquefied natural gas BOG comprises an oxygen storage tank 37, and the outlet of the oxygen storage tank 37 is connected to the oxygen inlet of the mixer 22 through a pipeline.

[0023] The device for extracting helium from liquefied natural gas BOG comprises a liquid nitrogen storage tank 36, and the outlet of the liquid nitrogen storage tank 36 is connected to the shell side inlet 38 of the first cooler 15 through a pipeline.

[0024] In the device for extracting helium from liquefied natural gas (BOG), a first valve 39 is provided on the pipeline between the outlet of the first buffer tank 1 and the inlet of the first compressor 2, a second valve 40 is provided on the pipeline between the outlet of the first compressor 2 and the first inlet 35 of the first heat exchanger 3, a third valve 41 is provided on the pipeline between the first outlet 4 and the second inlet 7 of the first heat exchanger 3, a fourth valve 42 is provided on the pipeline between the third outlet 11 and the fourth inlet 12 of the first heat exchanger 3, and a fifth valve 43 is provided on the pipeline between the second outlet of the first heat exchanger 3 and the middle air inlet 8 of the distillation tower 5; a sixth valve 44 is provided on the pipeline between the first outlet of the second heat exchanger 18 and the inlet of the membrane separation group 20, a seventh valve 45 is provided on the pipeline between the outlet of the membrane separation group 20 and the inlet of the Roots blower 21, and an eighth valve 46 is provided on the pipeline between the outlet of the Roots blower 21 and the raw gas inlet of the mixer 22; a ninth valve 47 is provided on the pipeline between the outlet of the catalytic oxidizer 23 and the inlet of the second cooler 24, and a ninth valve 48 is provided on the pipeline between the outlet of the second cooler 24 and the first inlet 2 6, a tenth valve 48 is provided on the pipeline between the outlet of the second cooler 24 and the inlet of the Roots blower 21; a twelfth valve 49 is provided on the pipeline between the gas phase outlet of the second gas-liquid separator 27 and the inlet of the drying tower 28, and a thirteenth valve 50 is provided on the pipeline between the outlet of the drying tower 28 and the inlet of the second compressor 29; a fourteenth valve 51 is provided on the pipeline between the second outlet 30 of the second heat exchanger 18 and the inlet of the low-temperature adsorption tower 31, and a fifteenth valve 52 is provided on the pipeline between the outlet of the low-temperature adsorption tower 31 and the third inlet 32 ​​of the second heat exchanger 18; a sixteenth valve 53 is provided on the pipeline between the second outlet of the third heat exchanger 25 and the inlet of the third compressor 34, and a seventeenth valve 54 is provided on the pipeline between the outlet of the third compressor 34 and the inlet of the product storage tank 35; an eighteenth valve 55 is provided on the pipeline between the outlet of the oxygen storage tank 37 and the oxygen inlet of the mixer 22; a nineteenth valve 56 is provided on the pipeline between the outlet of the liquid nitrogen storage tank 36 and the shell inlet 38 of the first cooler 15.

[0025] A process for extracting helium from liquefied natural gas (BOG) comprises the following extraction steps.

[0026] Step 1: allow the raw gas to enter the first buffer tank 1, the main components of the raw gas are: methane, nitrogen, hydrogen, helium, the pressure is 0.003MPa, and the temperature is room temperature.

[0027] Step 2: The raw gas in the first buffer tank 1 enters the first compressor 2 for compression. The temperature of the raw gas at the outlet of the first compressor 2 is 35° C. and the pressure is 2.5 MPa.

[0028] Step 3: The raw gas at the outlet of the compressor is sequentially introduced into the first inlet 35 of the first heat exchanger 3, the lower reboiler 6 of the distillation tower 5, and the second inlet 7 of the first heat exchanger 3 for heat exchange and cooling to -113°C, and then enters the distillation tower 5 for distillation through the middle air inlet 8 of the distillation tower 5, and a bypass regulating pipeline is provided between the first outlet of the first heat exchanger 3 and the second inlet 7 of the first heat exchanger 3; the high-boiling-point component is enriched in the lower part of the distillation tower 5, and sequentially passes through the third inlet 10 of the first heat exchanger 3, the fourth valve 42, and the fourth inlet 12 of the first heat exchanger 3 to be decompressed and heated, and then goes to the second buffer tank 13; the low-boiling-point component enters the first cooler 15 from the gas phase outlet 14 of the distillation tower 5, and then enters the first gas-liquid separator 16 for cooling, and the lower liquid phase of the first gas-liquid separator 16 returns to the distillation tower through the upper reflux liquid inlet 17 of the distillation tower 5; The temperature of the raw gas at the first outlet of the first heat exchanger 3 is -98°C, the temperature of the raw gas at the outlet of the reboiler 6 at the lower part of the distillation tower 5 is -116°C, and the temperature of the raw gas at the air inlet 8 in the middle of the distillation tower 5 is -175°C; the temperature of the high boiling point component at the third outlet 11 of the first heat exchanger 3 is -172°C, the temperature of the high boiling point component at the fourth inlet 12 of the first heat exchanger 3 is -176°C, the pressure is 0.03MPa, the inlet temperature of the high boiling point component at the second buffer tank 13 is 27°C, the temperature of the low boiling point component at the gas phase outlet 14 of the distillation tower 5 is -176.5°C, and the outlet temperature of the low boiling point component at the first gas-liquid separator 16 is -204°C; the high boiling point component is methane with a content of more than 99%, and the low boiling point main components are helium, hydrogen, and nitrogen.

[0029] Step 4: Allow the mixed gas at the top of the first gas-liquid separator 16 to enter the first inlet 19 of the second heat exchanger 18, and the mixed gas at the first outlet of the second heat exchanger 18 to enter the membrane separation group 20 after being decompressed by the sixth valve 44; the temperature of the mixed gas at the first outlet of the second heat exchanger 18 is 20°C, and the temperature of the mixed gas at the outlet of the membrane separation group 20 is 28°C, and the pressure is 0.1MPa.

[0030] Step 5: The mixed gas at the outlet of the membrane separation group 20 and the circulating gas returned from the outlet of the second cooler 24 enter the Roots blower 21 for pressurization, the mixed gas at the outlet of the Roots blower 21 enters the mixer 22 and mixes with the oxygen from the oxygen storage tank 37, the oxygen-carrying mixed gas enters the catalytic oxidizer 23 to remove hydrogen, the mixed gas at the outlet of the catalytic oxidizer 23 enters the second cooler 24 for cooling and separation, the mixed gas at the outlet of the second cooler 24 is divided into two paths, one path returns to the inlet of the Roots blower 21 as circulating gas, and the other path enters the first inlet 26 of the third heat exchanger 25, and the ratio of circulating gas to the mixed gas at the first inlet 26 of the third heat exchanger 25 is 85:15. The temperature of the mixed gas at the outlet of the Roots blower 21 is 64°C and the pressure is 0.15MPa, the temperature of the mixed gas at the outlet of the catalytic oxidizer 23 is 450°C, and the temperature of the mixed gas at the outlet of the second cooler 24 is 40°C.

[0031] Step 6: The mixed gas at the first outlet of the third heat exchanger 25 enters the second gas-liquid separator 27, and the mixed gas at the outlet of the second gas-liquid separator 27 enters the drying tower 28 for dehydration and drying. The temperature of the mixed gas at the first outlet of the third heat exchanger 25 is 10°C.

[0032] Step 7: The mixed gas at the outlet of the drying tower 28 enters the second compressor 29, and the mixed gas at the outlet of the second compressor 29 enters the second inlet 30 of the second heat exchanger 18. The mixed gas at the second outlet of the second heat exchanger 18 enters the low-temperature adsorption tower 31 to remove nitrogen and oxygen to obtain a helium product. The helium at the outlet of the low-temperature adsorption tower 31 passes through the third inlet 32 ​​of the second heat exchanger 18, the second inlet 33 of the third heat exchanger 25, and the third compressor 34 in sequence, and the pressurized helium enters the product storage tank 57. The temperature of the mixed gas at the outlet of the second compressor 29 is 40°C and the pressure is 2.5MPa; the inlet temperature of the low-temperature adsorption tower 31 is -195°C; the third outlet temperature of the second heat exchanger 18 is -117°C; the second outlet temperature of the third heat exchanger 25 is 10°C; the outlet temperature of the third compressor 34 is 45°C and the pressure is 20MPa.

[0033] The above is only a specific description of the feasible implementation mode of the present invention, and is not intended to limit the protection scope of the present invention. All equivalent implementation modes or improved modifications that do not deviate from the technical spirit of the present invention should be included in the protection scope of the present invention. It should be pointed out that the terms "first", "second", "third", etc. in this article are only used to distinguish each other, and do not indicate their importance and order. In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of simplifying the description of the present invention, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be noted that, unless otherwise clearly specified and limited, the terms "connection" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, an integrated connection, or a detachable connection; it can be a direct connection, or it can be a connection between two elements, or it can be connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Claims

1. A device for extracting helium from liquefied natural gas (BOG), comprising a non-condensable gas separation device and a non-condensable gas refining device, characterized in that: a. A non-condensable gas separation device: comprising a first buffer tank (1) for feeding raw gas, wherein the outlet of the first buffer tank (1) is connected to the inlet of a first compressor (2) through a pipeline, the outlet of the first compressor (2) is connected to the first inlet (35) of a first heat exchanger (3) through a pipeline, the first heat exchanger (3) is provided with a first outlet (4) and a second inlet (7), the first outlet (4) is respectively connected to the second inlet (7) and the tube-side inlet of a reboiler (6) at the bottom of a distillation tower (5) through a pipeline, the tube-side outlet of the reboiler (6) is connected to the second inlet (7) of the first heat exchanger (3) through a pipeline, the second outlet of the first heat exchanger (3) is connected to the middle air inlet (8) of the distillation tower (5) through a pipeline; the bottom of the distillation tower (5) is provided with a liquid phase outlet (9), the The liquid phase outlet (9) is connected to the third inlet (10) of the first heat exchanger (3) through a pipeline. The first heat exchanger (3) is provided with a third outlet (11) and a fourth inlet (12). The third outlet (11) is connected to the fourth inlet (12) through a pipeline. The fourth outlet of the first heat exchanger (3) is connected to the second buffer tank (13) through a pipeline. The top of the distillation tower (5) is provided with a gas phase outlet (14). The gas phase outlet (14) is connected to the tube side inlet of the first cooler (15) through a pipeline. The tube side outlet of the first cooler (15) is connected to the inlet of the first gas-liquid separator (16) through a pipeline. The liquid phase outlet at the bottom of the first gas-liquid separator (16) is connected to the reflux liquid inlet (17) at the top of the distillation tower (5) through a pipeline. b. A non-condensable gas refining device: comprising a second heat exchanger (18), wherein the second heat exchanger (18) is provided with a first inlet (19), wherein the gas phase outlet at the top of the first gas-liquid separator (16) is connected to the first inlet (19) of the second heat exchanger (18) through a pipeline, wherein the first outlet of the second heat exchanger (18) is connected to the inlet of a membrane separation group (20) through a pipeline, wherein the outlet of the membrane separation group (20) is connected to the inlet of a Roots blower (21) through a pipeline, wherein the outlet of the Roots blower (21) is connected to the raw gas inlet (59) of a mixer (22) through a pipeline, wherein the outlet of the mixer (22) is connected to the inlet of a catalytic oxidizer (23) through a pipeline, wherein the outlet of the catalytic oxidizer (23) is connected to the inlet of a second cooler (24) through a pipeline, wherein the outlet of the second cooler (24) is connected to the first inlet (26) of a third heat exchanger (25) and the inlet of the Roots blower (21) through pipelines, respectively, wherein the outlet of the third heat exchanger (25) is connected to the first inlet (26) of a third heat exchanger (25) and the inlet of the Roots blower (21) through pipelines ... 25) the first outlet is connected to the inlet of the second gas-liquid separator (27) through a pipeline, the gas phase outlet of the second gas-liquid separator (27) is connected to the inlet of the drying tower (28) through a pipeline, the outlet of the drying tower (28) is connected to the inlet of the second compressor (29) through a pipeline, the outlet of the second compressor (29) is connected to the second inlet (30) of the second heat exchanger (18) through a pipeline, the second outlet of the second heat exchanger (18) is connected to the inlet of the low-temperature adsorption tower (31) through a pipeline, the outlet of the low-temperature adsorption tower (31) is connected to the third inlet (32) of the second heat exchanger (18) through a pipeline, the third outlet of the second heat exchanger (18) is connected to the second inlet (33) of the third heat exchanger (25) through a pipeline, the second outlet of the third heat exchanger (25) is connected to the inlet of the third compressor (34) through a pipeline, and the outlet of the third compressor (34) is connected to the inlet of the product storage tank (57) through a pipeline; The device for extracting helium from liquefied natural gas (BOG) further comprises an oxygen storage tank (37), the outlet of the oxygen storage tank (37) being connected to the oxygen inlet of the mixer (22) via a pipeline; A first valve (39) is provided on the pipeline between the outlet of the first buffer tank (1) and the inlet of the first compressor (2), a second valve (40) is provided on the pipeline between the outlet of the first compressor (2) and the first inlet (35) of the first heat exchanger (3), a third valve (41) is provided on the pipeline between the first outlet (4) and the second inlet (7) of the first heat exchanger (3), a fourth valve (42) is provided on the pipeline between the third outlet (11) and the fourth inlet (12) of the first heat exchanger (3), and a fourth valve (43) is provided on the pipeline between the second outlet (11) and the fourth inlet (12) of the first heat exchanger (3). A fifth valve (43) is provided on the pipeline between the middle air inlet (8) of the distillation tower (5); a sixth valve (44) is provided on the pipeline between the first outlet of the second heat exchanger (18) and the inlet of the membrane separation group (20); a seventh valve (45) is provided on the pipeline between the outlet of the membrane separation group (20) and the inlet of the Roots blower (21); an eighth valve (46) is provided on the pipeline between the outlet of the Roots blower (21) and the raw gas inlet of the mixer (22); a first valve (47) is provided on the pipeline between the outlet of the catalytic oxidizer (23) and the inlet of the second cooler (24); a second valve (48) is provided on the pipeline between the outlet of the catalytic oxidizer (23) and the inlet of the second cooler (24); a first valve (49) is provided on the pipeline between the outlet of the membrane separation group (20) and the inlet of the Roots blower (21); and a second valve (41) is provided on the pipeline between the outlet of the catalytic oxidizer (23) and the inlet of the second cooler (24). A ninth valve (47) is provided on the pipeline between the outlet of the second cooler (24) and the first inlet (26) of the third heat exchanger (25); a tenth valve (48) is provided on the pipeline between the outlet of the second cooler (24) and the inlet of the Roots blower (21); a twelfth valve (49) is provided on the pipeline between the gas phase outlet of the second gas-liquid separator (27) and the inlet of the drying tower (28); a thirteenth valve (58) is provided on the pipeline between the outlet of the drying tower (28) and the inlet of the second compressor (29); 0); a fourteenth valve (51) is provided on the pipeline between the second outlet of the second heat exchanger (18) and the inlet of the low-temperature adsorption tower (31), and a fifteenth valve (52) is provided on the pipeline between the outlet of the low-temperature adsorption tower (31) and the third inlet (32) of the second heat exchanger (18); a sixteenth valve (53) is provided on the pipeline between the second outlet of the third heat exchanger (25) and the inlet of the third compressor (34), and a seventeenth valve (54) is provided on the pipeline between the outlet of the third compressor (34) and the inlet of the product storage tank (57).

2. The device for extracting helium from liquefied natural gas (BOG) according to claim 1, characterized in that: It comprises a liquid nitrogen storage tank (36), the outlet of the liquid nitrogen storage tank (36) is connected to the shell side inlet (38) of the first cooler (15) through a pipeline.

3. The device for extracting helium from liquefied natural gas (BOG) according to claim 1, characterized in that: An eighteenth valve (55) is provided on the pipeline between the outlet of the oxygen storage tank (37) and the oxygen inlet of the mixer (22).

4. The device for extracting helium from liquefied natural gas (BOG) according to claim 2, characterized in that: A nineteenth valve (56) is provided on the pipeline between the outlet of the liquid nitrogen storage tank (36) and the shell side inlet (38) of the first cooler (15).

5. A process for extracting helium from liquefied natural gas (BOG), applied to the device according to claim 1, characterized in that The extraction process includes the following steps: Step 1: allowing the raw material gas to enter the first buffer tank (1), wherein the raw material gas mainly comprises: methane, nitrogen, hydrogen, and helium, the pressure is 0.003 MPa, and the temperature is room temperature; Step 2: allowing the raw gas in the first buffer tank (1) to enter the first compressor (2) for compression, wherein the temperature of the raw gas at the outlet of the first compressor (2) is 35° C. and the pressure is 2.5 MPa; Step 3: The raw gas at the outlet of the compressor enters the first inlet (35) of the first heat exchanger (3), the tube side inlet of the lower reboiler (6) of the distillation tower (5), and the second inlet (7) of the first heat exchanger (3) in sequence. After heat exchange and cooling to -113°C, the raw gas enters the distillation tower (5) through the middle air inlet (8) of the distillation tower (5) for distillation. A bypass regulating pipeline is provided between the first outlet of the first heat exchanger (3) and the second inlet (7) of the first heat exchanger (3); the high boiling point component is discharged from the distillation tower (5) ) is enriched at the bottom, and is successively passed through the third inlet (10) of the first heat exchanger (3), the fourth valve (42), and the fourth inlet (12) of the first heat exchanger (3) to be decompressed and heated, and then goes to the second buffer tank (13); the low-boiling-point component enters the first cooler (15) from the gas phase outlet (14) of the distillation tower (5), is cooled in the pipe side, and then enters the first gas-liquid separator (16); the liquid phase at the bottom of the first gas-liquid separator (16) returns to the distillation tower through the reflux liquid inlet (17) at the top of the distillation tower (5) The temperature of the raw gas at the first outlet of the first heat exchanger (3) is -98°C, the temperature of the raw gas at the outlet of the reboiler (6) at the lower part of the distillation tower (5) is -116°C, and the temperature of the raw gas at the air inlet (8) in the middle of the distillation tower (5) is -175°C; the temperature of the high boiling point component at the third outlet (11) of the first heat exchanger (3) is -172°C, the temperature of the high boiling point component at the fourth inlet (12) of the first heat exchanger (3) is -176°C, and the pressure is 0 .03MPa, the inlet temperature of the high boiling point component in the second buffer tank (13) is 27°C, the temperature of the low boiling point component at the gas phase outlet (14) of the distillation tower (5) is -176.5°C, and the outlet temperature of the low boiling point component at the first gas-liquid separator (16) is -204°C; the high boiling point component is 86.8% methane and 13.2% nitrogen, and the low boiling point main component is 52.9% helium, 14.4% hydrogen and 32.7% nitrogen; Step 4: allowing the mixed gas at the top of the first gas-liquid separator (16) to enter the first inlet (19) of the second heat exchanger (18), and the mixed gas at the first outlet of the second heat exchanger (18) to enter the membrane separation group (20) after being decompressed by the sixth valve (44); the temperature of the mixed gas at the first outlet of the second heat exchanger (18) is 20° C., and the temperature of the mixed gas at the outlet of the membrane separation group (20) is 28° C., and the pressure is 0.1 MPa; Step 5: the mixed gas at the outlet of the membrane separation group (20) and the circulating gas returned from the outlet of the second cooler (24) are allowed to enter the Roots blower (21) for pressurization; the mixed gas at the outlet of the Roots blower (21) enters the mixer (22) to mix with the oxygen from the oxygen storage tank (37); the mixed gas with oxygen enters the catalytic oxidizer (23) to remove hydrogen; the mixed gas at the outlet of the catalytic oxidizer (23) enters the second cooler (24) for cooling and separation; the mixed gas at the outlet of the second cooler (24) is divided into two paths, one path is returned to the inlet of the Roots blower (21) as circulating gas, and the other path enters the first inlet (26) of the third heat exchanger (25); the ratio of the circulating gas to the mixed gas at the first inlet (26) of the third heat exchanger (25) is 85:15; the temperature of the mixed gas at the outlet of the Roots blower (21) is 64°C and the pressure is 0.15 MPa; the temperature of the mixed gas at the outlet of the catalytic oxidizer (23) is 450°C; and the temperature of the mixed gas at the outlet of the second cooler (24) is 40°C; Step 6: allowing the mixed gas at the first outlet of the third heat exchanger (25) to enter the second gas-liquid separator (27), and the mixed gas at the outlet of the second gas-liquid separator (27) to enter the drying tower (28) for dehydration and drying; the temperature of the mixed gas at the first outlet of the third heat exchanger (25) is 10° C.; Step 7: the mixed gas at the outlet of the drying tower (28) enters the second compressor (29), the mixed gas at the outlet of the second compressor (29) enters the second inlet (30) of the second heat exchanger (18), the mixed gas at the second outlet of the second heat exchanger (18) enters the low-temperature adsorption tower (31) to remove nitrogen and oxygen to obtain a helium product, the helium at the outlet of the low-temperature adsorption tower (31) passes through the third inlet (32) of the second heat exchanger (18), the second inlet (33) of the third heat exchanger (25), and the third compressor (34) in sequence, and the pressurized helium enters the product storage tank (57); the temperature of the mixed gas at the outlet of the second compressor (29) is 40°C and the pressure is 2.5 MPa; the inlet temperature of the low-temperature adsorption tower (31) is -195°C; the third outlet temperature of the second heat exchanger (18) is -117°C; the second outlet temperature of the third heat exchanger (25) is 10°C; the outlet temperature of the third compressor (34) is 45°C and the pressure is 20 MPa.

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