Cascade cycle refrigeration crude helium extraction device

Abstract

The utility model relates to the technical field of crude helium extraction from natural gas, in particular to a cascade cycle refrigeration crude helium extraction device. Comprising a first heat exchanger, a first helium extraction tower, a second heat exchanger and a second helium extraction tower which are sequentially connected, a propane / propylene refrigeration unit, an ethylene / ethane refrigeration system and a nitrogen-methane refrigeration system which are respectively connected with the first heat exchanger, and a nitrogen refrigeration system connected with the second heat exchanger, the first heat exchanger is connected with the second heat exchanger. According to the utility model, the pressure loss of the raw material natural gas after helium extraction is small, tail gas is not required to be output to a compressor, the power consumption is reduced, the yield is improved, the operation energy consumption is low, and the system stability is strong.

Description

Technical Field

[0001] The utility model relates to the technical field of natural gas helium extraction, specifically, it is a cascade cycle refrigeration helium extraction device. Background Art

[0002] The essence of natural gas helium extraction is the separation of helium-containing mixed gas. Generally speaking, natural gas helium extraction processes are divided into two categories: cryogenic method and non-cryogenic method. The cryogenic method cools natural gas step by step through low-temperature liquefaction to condensate various hydrocarbons and obtain concentrated helium gas. This method can obtain crude helium with a purity of 50% - 90%, and the required cooling capacity is generally provided by liquid methane and liquid nitrogen. Due to its advantages of high yield and high purity, the cryogenic method is still the mainstream technology choice for industrial helium production at present. At present, more than 80% of helium extraction devices adopt the cryogenic process. However, although the cryogenic process is technically mature and widely used, it has the disadvantage of high energy consumption, which increases the cost of helium extraction. Content of the Utility Model

[0003] The purpose of the utility model is to provide a cascade cycle refrigeration helium extraction device. By setting a propane / propylene refrigeration unit, an ethylene / ethane refrigeration system, a nitrogen-methane refrigeration system, and a nitrogen refrigeration system, an external refrigeration method of cascade cycle is realized. After the raw material natural gas is subjected to helium extraction, the pressure loss is small, and there is no need for a tail gas external transmission compressor; the crude helium extraction process reduces the power consumption, the recovery rate is ≥98%, the operation energy consumption is low, and the system stability is strong.

[0004] The utility model is realized through the following technical solutions:

[0005] A cascade cycle refrigeration helium extraction device includes a first heat exchanger, a first helium extraction tower, a second heat exchanger, and a second helium extraction tower connected in sequence, a propane / propylene refrigeration unit, an ethylene / ethane refrigeration system, and a nitrogen-methane refrigeration system respectively connected to the first heat exchanger, and a nitrogen refrigeration system connected to the second heat exchanger; the first heat exchanger is connected to the second heat exchanger.

[0006] Furthermore, in order to better realize the utility model and effectively realize the connection between the first heat exchanger and the propane / propylene refrigeration unit, the ethylene / ethane refrigeration system, the nitrogen-methane refrigeration system, the first helium extraction tower, and the second heat exchanger;

[0007] Inside the first heat exchanger, there are a first pipeline connected to a propane / propylene refrigeration unit, a second pipeline connected to an ethylene / ethane refrigeration system, a third pipeline connected to the first helium extraction tower and serving as an exhaust gas output pipeline, a fourth pipeline with one end connected to the input end of a nitrogen-methane refrigeration system and the other end connected to the first helium extraction tower, a fifth pipeline with one end connected to the output end of the nitrogen-methane refrigeration system and the other end connected to the first helium extraction tower, and a sixth pipeline with one end connected to the first helium extraction tower and serving as a helium-containing natural gas input pipeline; the third pipeline is connected to the second heat exchanger.

[0008] Further, to better implement the present utility model and effectively connect the propane / propylene refrigeration unit to the first heat exchanger;

[0009] The propane / propylene refrigeration unit includes a propane / propylene refrigeration system and a first buffer tank connected to both the propane / propylene refrigeration system and the first pipeline.

[0010] Further, to better implement the present utility model and effectively connect the ethylene / ethane refrigeration system to the first heat exchanger;

[0011] The second pipeline includes a pipeline A located inside the first heat exchanger and connected to the input end of the ethylene / ethane refrigeration system, a pipeline B located inside the first heat exchanger and connected to the output end of the ethylene / ethane refrigeration system, and a pipeline C located outside the first heat exchanger and used to connect pipeline A and pipeline B.

[0012] Further, to better implement the present utility model and effectively connect the first helium extraction tower to the first heat exchanger and the second heat exchanger;

[0013] The first helium extraction tower includes a first top section, a first middle section, and a first bottom section connected in sequence, a first condenser located in the first top section and connected to the fifth pipeline and the fourth pipeline respectively, and a first reboiler located in the first bottom section and connected to the sixth pipeline; the first middle section is connected to the sixth pipeline; the first bottom section is connected to the third pipeline.

[0014] Further, to better implement the present utility model,

[0015] A pipeline six is provided at the output end of the sixth pipeline; the pipeline six is connected to the output end of the first reboiler; a pipeline seven is provided between the input end of the sixth pipeline and the first reboiler.

[0016] Further, to better implement the present utility model and effectively connect the second heat exchanger to the first heat exchanger, the first helium extraction tower, the second helium extraction tower, and the nitrogen refrigeration system;

[0017] The second heat exchanger includes a seventh pipeline connected to the third pipeline, an eighth pipeline connected to the input end of the nitrogen refrigeration system, a ninth pipeline connected to the first top section, a tenth pipeline connected to the output end of the nitrogen refrigeration system, and an eleventh pipeline connected to the second helium extraction tower.

[0018] Further, in order to better implement the present invention,

[0019] The second helium extraction tower includes a second top section, a second middle section, and a second bottom section connected in sequence, a second condenser located at the top and connected to the eighth pipeline and the eleventh pipeline respectively, and a first reboiler located at the first bottom section and connected to the tenth pipeline and the eleventh pipeline respectively; the second middle section is connected to the ninth pipeline; the second bottom section is connected to the seventh pipeline.

[0020] Further, in order to better implement the present invention,

[0021] Flow control valves are respectively arranged on the pipeline six and on the connecting pipeline between the ninth pipeline and the second middle section; level control valves are respectively arranged on the connecting pipeline between the first bottom section and the third pipeline and on the connecting pipeline between the seventh pipeline and the second bottom section; a temperature control valve is arranged on the pipeline seven;

[0022] J-T valves are respectively arranged on the output pipeline of the propane / propylene refrigeration system, pipeline C, the pipeline connecting the fifth pipeline and the first condenser, and the connecting pipeline between the eleventh pipeline and the second condenser.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] The present invention realizes two-stage rectification by setting a first helium extraction tower and a second helium extraction tower, and realizes cascade cycle refrigeration through the cooperation of a propane / propylene refrigeration unit, an ethylene / ethane refrigeration system, a nitrogen-methane refrigeration system, and a nitrogen refrigeration system; to process low-helium raw natural gas, so that the He concentration in the natural gas is gradually increased, and finally crude helium with a purity of 54% can be obtained;

[0025] The present invention can make the pressure loss of the raw natural gas small after helium extraction, no longer requires a tail gas export compressor, reduces power consumption, improves the recovery rate, has low operating energy consumption, and strong system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a structural schematic diagram of the present invention;

[0027] Among them, 1 is the first heat exchanger, 11 is the first pipeline, 12 is the second pipeline, 121 is pipeline A, 122 is pipeline B, 123 is pipeline C, 13 is the third pipeline, 14 is the fourth pipeline, 15 is the fifth pipeline, 16 is the sixth pipeline, 2 is the first helium extraction tower, 21 is the first condenser, 22 is the first reboiler, 23 is pipeline six, 24 is pipeline seven, 3 is the second heat exchanger, 31 is the seventh pipeline, 32 is the eighth pipeline, 33 is the ninth pipeline, 34 is the tenth pipeline, 35 is the eleventh pipeline, 4 is the second helium extraction tower, 41 is the second condenser, 42 is the second reboiler, 5 is the propylene / propane refrigeration unit, 6 is the ethylene / ethane refrigeration system, 7 is the nitrogen / methane refrigeration system, 8 is the nitrogen refrigeration system, 9 is the J-T valve, 10 is the flow regulating valve, 20 is the temperature control valve, and 100 is the liquid level control valve. Detailed implementation manners

[0028] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as a limitation to the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0030] In the present invention, unless otherwise clearly specified and defined, the terms "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] As Figure 1 shown:

[0032] A cascaded cycle refrigeration helium extraction device for crude helium, comprising a first heat exchanger 1, a first helium extraction tower 2, a second heat exchanger 3, and a second helium extraction tower 4 connected in sequence, a propane / propylene refrigeration unit 5, an ethylene / ethane refrigeration system 6, and a nitrogen-methane refrigeration system 7 respectively connected to the first heat exchanger 1, and a nitrogen refrigeration system 8 connected to the second heat exchanger 3; the first heat exchanger 1 is connected to the second heat exchanger 3.

[0033] During use, the cooling capacity of the first helium extraction tower 2 is provided by the propane / propylene refrigeration unit 5, the ethylene / ethane refrigeration system 6, and the nitrogen-methane refrigeration system 7; the propane / propylene refrigeration unit 5 precools natural gas, ethylene / ethane, and nitrogen-methane, and the ethylene / ethane refrigeration system 6 precools natural gas and nitrogen-methane, thus forming a cascaded cycle refrigeration; the cooling capacity of the second helium extraction tower 4 is provided by the nitrogen refrigeration system 8;

[0034] The refrigerant of the propane / propylene refrigeration unit 5 can be propane or propylene;

[0035] The refrigerant of the ethylene / ethane refrigeration system 6 is ethylene or ethane;

[0036] Furthermore, in order to better implement the present utility model and effectively achieve the connection of the first heat exchanger 1 with the propane / propylene refrigeration unit 5, the ethylene / ethane refrigeration system 6, the nitrogen-methane refrigeration system 7, the first helium extraction tower 2, and the second heat exchanger 3;

[0037] In the first heat exchanger 1, there are provided a first pipeline 11 connected to the propane / propylene refrigeration unit 5 and forming a cycle refrigeration pipeline, a second pipeline 12 connected to the ethylene / ethane refrigeration system 6 and forming a cycle refrigeration pipeline, a third pipeline 13 connected to the first helium extraction tower 2 and serving as an exhaust gas output pipeline, a fourth pipeline 14 with one end connected to the input end of the nitrogen-methane refrigeration system 7 and the other end connected to the first helium extraction tower 2, a fifth pipeline 15 with one end connected to the output end of the nitrogen-methane refrigeration system 7 and the other end connected to the first helium extraction tower 2, and a sixth pipeline 16 with one end connected to the first helium extraction tower 2 and serving as a helium-containing natural gas input pipeline; the third pipeline 13 is connected to the second heat exchanger 3.

[0038] The first helium extraction tower 2, the fourth pipeline 14, the fifth pipeline 15, and the nitrogen-methane refrigeration system 7 cooperate to form a cycle refrigeration pipeline;

[0039] Furthermore, in order to better implement the present utility model and effectively achieve the connection of the propane / propylene refrigeration unit 5 with the first heat exchanger 1; the propane / propylene refrigeration unit 5 includes a propane / propylene refrigeration system and a first buffer tank connected to the propane / propylene refrigeration system and the first pipeline 11;

[0040] Specifically, the output pipeline of the propane / propylene refrigeration system is connected to an input port of the first buffer tank. An output port of the first buffer tank is connected to the first pipeline 11, and its other output port is connected to the input end of the propane / propylene refrigeration system. The other input port of the first buffer tank is connected to the output end of the first pipeline 11. A J-T valve 9 is provided on the output pipeline of the propane / propylene refrigeration system.

[0041] After being evaporated by the first heat exchanger 1, the propane / propylene with a temperature of -31°C and a pressure of 0.12 MPa enters the first buffer tank through the first pipeline 11, then enters the propane / propylene refrigeration system, is pressurized to 1.4 MPa by the first booster in the propane / propylene refrigeration system, passes through the J-T valve 9 on the output pipeline of the propane / propylene refrigeration system and is depressurized to about 0.14 MPa with the temperature dropping to -35°C, and then enters the first pipeline 11 of the first heat exchanger 1 to provide cooling capacity for precooling natural gas, ethylene, and nitrogen-methane.

[0042] Furthermore, to better implement the present utility model and effectively realize the connection between the ethylene / ethane refrigeration system 6 and the first heat exchanger 1;

[0043] The second pipeline 12 includes a pipeline A121 located inside the first heat exchanger 1 and connected to the input end of the ethylene / ethane refrigeration system 6, a pipeline B122 located inside the first heat exchanger 1 and connected to the output end of the ethylene / ethane refrigeration system 6, and a pipeline C123 located outside the first heat exchanger 1 and used to connect the pipeline A121 and the pipeline B122. A J-T valve 9 is provided on the pipeline C123.

[0044] Furthermore, to better implement the present utility model and effectively realize the connection between the first helium extraction tower 2 and the first heat exchanger 1 and the second heat exchanger 3;

[0045] The first helium extraction tower 2 includes a first top section, a first middle section, and a first bottom section connected in sequence, a first condenser 21 located in the first top section and connected to the fifth pipeline 15 and the fourth pipeline 14 respectively, a first reboiler 22 located in the first bottom section and connected to the sixth pipeline 16. The first middle section is connected to the sixth pipeline 16. The first bottom section is connected to the third pipeline 13. A pipeline six 23 is provided at the output end of the sixth pipeline 16. The pipeline six 23 is connected to the output end of the first reboiler 22. A pipeline seven 24 is provided between the input end of the sixth pipeline 16 and the first reboiler 22, and the connection point of the pipeline seven 24 and the sixth pipeline 16 is set between the output port and the output port of the sixth pipeline 16. The other end of the pipeline six 23 is connected to the first middle section;

[0046] Further, to better implement the present utility model and effectively realize the connection of the second heat exchanger 3 with the first heat exchanger 1, the first helium extraction tower 2, the second helium extraction tower 4, and the nitrogen refrigeration system 8;

[0047] The second heat exchanger 3 includes a seventh pipeline 31 connected to the third pipeline 13, an eighth pipeline 32 connected to the input end of the nitrogen refrigeration system 8, a ninth pipeline 33 connected to the first top section and the second helium extraction tower 2, a tenth pipeline 34 connected to the output end of the nitrogen refrigeration system 8 and the second helium extraction tower 2, and an eleventh pipeline 35 connected to the second helium extraction tower 4.

[0048] Further, to better implement the present utility model and effectively realize the coordinated use of the second helium extraction tower 4 with the second heat exchanger 3 and the nitrogen refrigeration system 8; the second helium extraction tower 4 includes a second top section, a second middle section, and a second bottom section connected in sequence; a second condenser 41 located in the second top section and connected to the eighth pipeline 32 and the eleventh pipeline 35 respectively; a second reboiler 42 located in the second bottom section and connected to the tenth pipeline 34 and the eleventh pipeline 35 respectively; the second middle section is connected to the ninth pipeline 33; the second bottom section is connected to the seventh pipeline 31.

[0049] Further, to better implement the present utility model, flow control valves 10 are respectively provided on the pipeline six 23 and on the connecting pipeline between the ninth pipeline 33 and the second middle section;

[0050] Level control valves 100 are respectively provided on the connecting pipeline between the first bottom section and the third pipeline 13 and on the connecting pipeline between the seventh pipeline 31 and the second bottom section;

[0051] A temperature control valve 20 is provided on the pipeline seven 24;

[0052] J-T valves 9 are respectively provided on the pipeline connecting the fifth pipeline 15 and the first condenser 21 and on the pipeline connecting the eleventh pipeline 35 and the second condenser 41.

[0053] The flow regulating valve 10 provided on the pipeline six 23 is located between the connection point of the pipeline six 23 and the first reboiler 22 and the connection point of the pipeline six 23 and the first middle section.

[0054] After the natural gas is pretreated, with a helium content of 0.04 mol%, a temperature of 40 °C, and a pressure of 3.5 MPa, it enters the sixth pipeline 16 of the first heat exchanger 1 and is cooled to -103 °C, and then enters the first helium extraction tower 2 after passing through the temperature control valve 20 on the pipeline seven 24. After rectification in the first helium extraction tower 2, a first-stage crude helium with a temperature of -145 °C is obtained, and at this time, the helium content is 1.17%, and the helium content is concentrated by 29 times.

[0055] The helium concentration in the liquid phase at the first bottom section of the first helium extraction column 2 is already very low. After passing through the liquid level control valve 100 installed on the connecting pipeline between the first bottom section and the third pipeline 13, the pressure is reduced to 3.0 MPa and the temperature is -106 °C. After recovering the cold energy through the third pipeline 13 that returns to the first heat exchanger 1, it is then transported out.

[0056] In order to meet the energy balance of the first helium extraction column 2, heat needs to be generated at the bottom of the column (the first bottom section) and condensation needs to be carried out at the top of the column (the first top section). The heat source for heat generation at the bottom comes from the raw natural gas. When the raw natural gas (helium-containing natural gas) is cooled to -100 °C through the sixth pipeline 16 of the first heat exchanger 1, a stream of about 15% of the gas is extracted and enters the first reboiler 22 to provide heat for the first helium extraction column 2. Then, the gas separated by the first reboiler 22 will converge with the remaining 85% of the gas and enter the first middle section of the first helium extraction column 2.

[0057] Condensation at the top of the column (the first top section) uses three refrigeration cycles, namely the propane / propylene refrigeration unit 5, the ethylene / ethane refrigeration system 6, and the nitrogen-methane refrigeration system 7, to provide cooling capacity for the condenser. The propane / propylene refrigeration unit 5 precools the natural gas, ethylene / ethane, and nitrogen-methane. The ethylene / ethane precools the natural gas and nitrogen-methane. In this way, a cascaded cycle refrigeration is formed.

[0058] In the propane refrigeration cycle: After evaporation in the first heat exchanger 1, the propane / propylene with a temperature of -31 °C and a pressure of 0.12 MPa enters the first buffer tank through the first pipeline 11, and then enters the propane / propylene refrigeration system. It is pressurized to 1.4 MPa by the first booster in the propane / propylene refrigeration system, and is decompressed to about 0.14 MPa and the temperature drops to -35 °C by the J-T valve 9 on the output pipeline of the propane / propylene refrigeration system. Then it enters the first pipeline 11 of the first heat exchanger 1 to provide cooling capacity for precooling the natural gas, ethylene, and nitrogen-methane.

[0059] In the ethylene / ethane refrigeration cycle: Specifically, after evaporation in the first heat exchanger 1, the ethylene / ethane with a temperature of -33 °C and a pressure of 0.12 MPa is pressurized to 1.8 MPa by the second booster in the ethylene / ethane refrigeration system 6, enters the pipeline B122 of the first heat exchanger 1 and is precooled to -95 °C, and then is decompressed to about 0.14 MPa by the J-T valve 9 on the pipeline C123, and the temperature drops to -98 °C and returns to the pipeline A121 of the first heat exchanger 1 to provide cooling capacity for precooling the natural gas and nitrogen-methane.

[0060] In the nitrogen-methane refrigeration cycle: The nitrogen-methane refrigerant is pressurized to about 4.0 MPa by the third booster in the nitrogen-methane refrigeration system 7 and then enters the fifth pipeline 15 of the first heat exchanger 1. After being cooled to -150 °C, it passes through the J-T valve 9 on the connecting pipeline between the fifth pipeline 15 and the first condenser 21, and is depressurized to 0.1 MPa, with the temperature dropping to -162 °C. It enters the first condenser 21 of the first helium extraction tower 2 to provide cooling capacity, and then returns to the fourth pipeline 14 of the first heat exchanger 1 to recover the cooling capacity, and then enters the third booster to continue compression; The energy of the entire first helium extraction tower 2 can be adjusted through three refrigeration cycles, achieving the effective and cascaded utilization of energy.

[0061] The primary crude helium separated by the first helium extraction tower 2 continues to enter the ninth pipeline 33 of the second heat exchanger 3, where it is cooled to -165 °C and depressurized to 2.88 MPa, and then enters the second middle section of the second helium extraction tower 4 to separate components such as methane and nitrogen. After rectification in the second helium extraction tower 4, secondary crude helium with a temperature of -180 °C is obtained at the top of the tower (the second top section), and the helium content is 54% at this time.

[0062] The liquid phase at the bottom (the second bottom section) of the second helium extraction tower 4 with a temperature of -147 °C returns to the seventh pipeline 31 of the second heat exchanger 3 to recover the cooling capacity, and then after converging with the liquid phase at the bottom of the first helium extraction tower 2, it returns to the third pipeline 13 of the first heat exchanger 1 to recover the cooling capacity and then is exported.

[0063] The heat and cooling capacity of the second helium extraction tower 4 are also provided by the nitrogen refrigeration system 8. Specifically: Nitrogen with a pressure of 2.5 MPa from the nitrogen refrigeration system 8 first enters the tenth pipeline 34 of the second heat exchanger 3, is cooled to -135 °C, and then enters the second reboiler 42 of the second helium extraction tower 4 to provide heat. After being cooled to -147 °C by the liquid phase at the bottom (the second bottom section) of the tower, it returns to the eleventh pipeline 35 of the second heat exchanger 3 to continue cooling, and is depressurized to 0.22 MPa through the J-T valve 9, with a temperature of -188 °C. It enters the second condenser 41 at the top of the second helium extraction tower 4 to provide cooling capacity, and then returns to the eighth pipeline 32 of the second heat exchanger 3 to recover the cooling capacity, and then returns to the fourth booster of the nitrogen refrigeration system 8 to continue compression to complete the cycle.

[0064] The present utility model realizes two-stage rectification by setting the first helium extraction tower 2 and the second helium extraction tower 4, and realizes cascaded cycle refrigeration through the cooperation of the propane / propylene refrigeration unit 5, the ethylene / ethane refrigeration system 6, the nitrogen-methane refrigeration system 7, and the nitrogen refrigeration system 8. The formed cascaded cycle refrigeration system gradually provides the required cooling capacity for liquefying each component in the natural gas. The refrigeration temperature gradients are about -30 °C, -90 °C, -160 °C, and -180 °C respectively, and it is particularly suitable for the light hydrocarbon separation of raw natural gas with a large processing volume and a large amount of heavy hydrocarbons, the production of LNG, and the helium extraction occasion.

[0065] The utility model is used to process natural gas with low helium content. Through a cascading cycle refrigeration system, each component in the raw natural gas is gradually condensed and separated, so that the helium concentration in the natural gas is gradually increased. Finally, crude helium with a purity of 54% can be obtained. The crude helium can be further purified by technologies such as pressure swing adsorption or membrane separation to produce high-purity helium.

[0066] By adopting the utility model, the pressure loss of the raw natural gas (helium-containing natural gas) after helium extraction is only about 300 kPa, and there is no need for a tail gas export compressor anymore.

[0067] The utility model reduces the power consumption of the crude helium extraction process by about 15%, the recovery rate is ≥98%, the operating energy consumption is low, and the system stability is strong.

[0068] The following further describes the utility model in detail with reference to the embodiments, but the implementation manners of the utility model are not limited thereto.

[0069] As described above, it is only a preferred embodiment of the utility model, and does not impose any form of limitation on the utility model. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the utility model falls within the protection scope of the utility model.

Claims

1. A cascaded cycle refrigeration helium extraction device for crude helium, characterized in that: It includes a first heat exchanger, a first helium extraction column, a second heat exchanger, and a second helium extraction column connected in sequence, a propane / propylene refrigeration unit, an ethylene / ethane refrigeration system, and a nitrogen-methane refrigeration system respectively connected to the first heat exchanger, and a nitrogen refrigeration system connected to the second heat exchanger; the first heat exchanger is connected to the second heat exchanger.

2. The cascade cycle refrigeration crude helium extraction device according to claim 1, wherein: In the first heat exchanger, there are provided a first pipeline connected to the propane / propylene refrigeration unit, a second pipeline connected to the ethylene / ethane refrigeration system, a third pipeline connected to the first helium extraction column and serving as a tail gas output pipeline, a fourth pipeline with one end connected to the input end of the nitrogen-methane refrigeration system and the other end connected to the first helium extraction column, a fifth pipeline with one end connected to the output end of the nitrogen-methane refrigeration system and the other end connected to the first helium extraction column, and a sixth pipeline with one end connected to the first helium extraction column and serving as a helium-containing natural gas input pipeline; the third pipeline is connected to the second heat exchanger.

3. The cascaded cycle refrigeration crude helium extraction device according to claim 2, characterized in that: The propane / propylene refrigeration unit includes a propane / propylene refrigeration system and a first buffer tank connected to the propane / propylene refrigeration system and the first pipeline.

4. A cascaded cycle refrigeration crude helium extraction device according to claim 2 or 3, characterized in that: The second pipeline includes a pipeline A located in the first heat exchanger and connected to the input end of the ethylene / ethane refrigeration system, a pipeline B located in the first heat exchanger and connected to the output end of the ethylene / ethane refrigeration system, and a pipeline C located outside the first heat exchanger and used to connect pipeline A and pipeline B.

5. The cascade cycle refrigeration crude helium extraction device according to claim 4, characterized in that: The first helium extraction column includes a first top section, a first middle section, and a first bottom section connected in sequence, a first condenser located in the first top section and connected to the fifth pipeline and the fourth pipeline respectively, and a first reboiler located in the first bottom section and connected to the sixth pipeline. The first middle section is connected to the sixth pipeline; the first bottom section is connected to the third pipeline.

6. The cascade cycle refrigeration crude helium extraction device according to claim 5, characterized in that: A pipeline six is provided at the output end of the sixth pipeline; the pipeline six is connected to the output end of the first reboiler; a pipeline seven is provided between the sixth pipeline and the input end of the first reboiler.

7. The cascade cycle refrigeration crude helium extraction device according to claim 6, characterized in that: The second heat exchanger includes a seventh pipeline connected to the third pipeline, an eighth pipeline connected to the input end of the nitrogen refrigeration system, a ninth pipeline connected to the first top section and the second helium extraction column, a tenth pipeline connected to the output end of the nitrogen refrigeration system, and an eleventh pipeline connected to the second helium extraction column.

8. The cascade cycle refrigeration crude helium extraction device according to claim 7, characterized in that: The second helium extraction column includes a second top section, a second middle section, and a second bottom section connected in sequence; a second condenser located at the top and connected to the eighth pipeline and the eleventh pipeline respectively; a second reboiler located in the second bottom section and connected to the tenth pipeline and the eleventh pipeline respectively; the second middle section is connected to the ninth pipeline; the second bottom section is connected to the seventh pipeline.

9. The cascade cycle refrigeration crude helium extraction device according to claim 8, wherein: Flow control valves are respectively provided on the pipeline six and on the connecting pipeline between the ninth pipeline and the second middle section; level control valves are respectively provided on the connecting pipeline between the first bottom section and the third pipeline and on the connecting pipeline between the seventh pipeline and the second bottom section; a temperature control valve is provided on the pipeline seven.

10. The cascaded cycle refrigeration crude helium extraction device according to claim 9, characterized in that: J-T valves are respectively provided on the output pipeline of the propane / propylene refrigeration system, pipeline C, the pipeline connecting the fifth pipeline and the first condenser, and the connecting pipeline between the eleventh pipeline and the second condenser.

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