Device and method for recovering ethane, extracting helium and co-producing liquefied natural gas

Abstract

The invention discloses an ethane recovery and helium extraction co-production liquefied natural gas device and method, and the device comprises an ethane recovery cold box, a demethanizer, a liquefaction cold box, a pre-concentration tower, a primary concentration tower, a helium extraction cold box, a secondary concentration tower, a propane refrigerant refrigeration cycle unit, a mixed refrigerant refrigeration cycle unit and a nitrogen refrigeration cycle unit which are combined and connected through pipelines. The device can produce natural gas condensate, liquefied natural gas and product natural gas at the same time in the helium extraction process, and product diversification is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas processing, and particularly relates to an ethane recovery, helium extraction and liquefied natural gas co-production device and method. Background Art

[0002] Methane accounts for the vast majority in natural gas, and there are also hydrocarbon components such as ethane, propane, butane, pentane, hexane, etc. A small amount of helium is contained in a few natural gas fields. Natural gas condensate recovery refers to separating components such as ethane, propane, butane, pentane, etc. from natural gas, and using the recovered condensate as chemical raw materials, which has good economic benefits. Natural gas liquefaction is to produce liquefied natural gas after the purified natural gas is cooled and liquefied at low temperature.

[0003] Helium is an extremely light, colorless, odorless and tasteless monatomic gas at room temperature, and has a wide range of uses in the medical, optical fiber, and superconducting fields. At present, natural gas containing helium is the only source for producing helium in industry. The helium content in natural gas is as low as only 0.05% at the lowest and can reach up to 8% at the highest.

[0004] Utilizing the difference in boiling points between helium and natural gas, the low-temperature rectification helium extraction technology is still the main method for extracting helium from natural gas. This technology uses one or two rectification towers at low temperature to enrich and concentrate helium in natural gas.

[0005] However, only a crude helium intermediate product is produced during the process of low-temperature separation and extraction of helium using a rectification tower, and it is impossible to recover ethane from natural gas containing helium, extract helium, and by-product liquefied natural gas products, and it is impossible to achieve product diversification. Summary of the Invention

[0006] In view of the above problems, embodiments of the present invention are provided to provide an ethane recovery, helium extraction and liquefied natural gas co-production device and method that overcome the above problems or at least partially solve the above problems.

[0007] In a first aspect, an embodiment of the present invention provides an ethane recovery, helium extraction and liquefied natural gas co-production device, including:

[0008] The ethane recovery cold box, the low-temperature separator, the demethanizer, the liquefaction cold box, the helium extraction cold box, the pre-concentration tower, the primary concentration tower, and the secondary concentration tower are connected by pipelines;

[0009] The ethane recovery cold box pre-cools the raw natural gas and transports the pre-cooled raw natural gas to the low-temperature separator through a pipeline;

[0010] The low-temperature separator is used to separate the gas phase and the liquid phase from different components in the raw natural gas. The gas phase returns to the ethane recovery cold box through a pipeline and enters the demethanizer through a pipeline, and the liquid phase enters the demethanizer through a pipeline;

[0011] The demethanizer is used to remove methane, and a pipeline is connected to the liquid phase outlet at the bottom to output natural gas condensate;

[0012] The liquefaction cold box is used to liquefy the mixed gas processed by the demethanizer, and is provided with a pipeline to output liquefied natural gas;

[0013] The pre-concentration tower, the first concentration tower, and the second concentration tower are connected by pipelines and are used for rectifying and concentrating the natural gas processed by the liquefaction cold box;

[0014] The helium extraction cold box is connected to the second concentration tower by a pipeline and is used to liquefy the natural gas concentrated by the second concentration tower, and is provided with a pipeline to output crude helium;

[0015] The natural gas output from the helium extraction cold box and the natural gas output from the liquid phase at the bottom of the pre-concentration tower are combined through the same pipeline and then input into the liquefaction cold box, and are connected to the pipeline for outputting product natural gas;

[0016] The output pipeline of the liquid phase of the pre-concentration tower is connected to the pipeline connecting the liquefaction cold box and the ethane recovery cold box and the pipeline for outputting product natural gas.

[0017] In one embodiment, the device further includes: a propane refrigerant refrigeration cycle unit;

[0018] The propane refrigerant refrigeration cycle unit includes a propane refrigerant compressor, a third cooler, and an eighth throttle valve connected in sequence;

[0019] The propane refrigerant refrigeration cycle unit is connected to the ethane recovery cold box and is used to provide cooling capacity for the ethane recovery cold box.

[0020] In one embodiment, the device further includes: a mixed refrigerant refrigeration cycle unit;

[0021] The mixed refrigerant refrigeration cycle unit includes a mixed refrigerant refrigeration compressor and a fourth cooler connected in sequence;

[0022] The mixed refrigerant refrigeration cycle unit is connected to the liquefaction cold box and is used to provide cooling capacity for the liquefaction cold box.

[0023] In one embodiment, the device further includes: a nitrogen refrigeration cycle unit;

[0024] The nitrogen refrigeration cycle unit includes a nitrogen refrigeration compressor and a fifth cooler connected in sequence;

[0025] The nitrogen refrigeration cycle unit is connected to the helium extraction cold box and is used to provide cooling capacity for the helium extraction cold box and the condenser of the second concentration tower.

[0026] In one embodiment, a reflux branch of natural gas is formed by connecting the demethanizer and the ethane recovery cold box through a pipeline.

[0027] In one embodiment, it further includes: a demethanizer reboiler;

[0028] The demethanizer reboiler is connected to the demethanizer through a reflux pipeline.

[0029] In one embodiment, the bottom liquid phase outlet of the pre-concentration tower is connected to the demethanizer through a pipeline, and a demethanizer reflux pump is provided on the pipeline between the bottom liquid phase outlet of the pre-concentration tower and the demethanizer.

[0030] In one embodiment, the bottom liquid phase outlet of the pre-concentration tower is connected to the liquefaction cold box through a pipeline, and a primary concentration tower condenser is provided on the pipeline between the bottom liquid phase outlet of the pre-concentration tower and the liquefaction cold box.

[0031] In one embodiment, the bottom liquid phase outlet of the primary concentration tower is connected to the liquefaction cold box through a pipeline and is communicated with the output pipeline of the liquefied natural gas of the liquefaction cold box.

[0032] In one embodiment, the top gas phase outlet of the secondary concentration tower is connected to the helium extraction cold box through a pipeline. The pipeline passes through the secondary concentration tower condenser and is communicated with the crude helium output pipeline of the helium extraction cold box.

[0033] Second, an embodiment of the present invention provides a method for ethane recovery, helium extraction and co-production of liquefied natural gas from raw natural gas using an ethane recovery, helium extraction and co-production of liquefied natural gas device as described above.

[0034] The beneficial effects of the above technical solutions provided by the embodiments of the present invention at least include:

[0035] An ethane recovery, helium extraction and co-production of liquefied natural gas device and method provided by an embodiment of the present invention connect an ethane recovery cold box, a demethanizer, a liquefaction cold box and a helium extraction cold box through pipelines, realizing processes such as ethane recovery in natural gas, crude helium extraction and co-production of liquefied natural gas, and can produce products such as natural gas condensate, liquefied natural gas and crude helium, achieving product diversification and solving the problem of single product in the process of helium extraction. Description of the Drawings

[0036] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0037] Figure 1 It is a schematic structural diagram of an ethane recovery, helium extraction and co-production of liquefied natural gas device in an embodiment of the present invention.

[0038] Description of the reference numerals:

[0039] 1 - Ethane recovery cold box; 2 - Low - temperature separator; 3 - Expansion unit; 4 - Demethanizer; 5 - First throttle valve; 6 - Second throttle valve; 7 - Demethanizer reboiler; 8 - Pre - extraction enrichment column reboiler; 9 - Liquefaction cold box; 10 - Third throttle valve; 11 - Pre - extraction enrichment column; 12 - Demethanizer reflux pump; 13 - Fourth throttle valve; 14 - First - stage extraction enrichment column condenser; 15 - First - stage extraction enrichment column; 16 - Fifth throttle valve; 17 - Second - stage extraction enrichment column reboiler; 18 - Helium extraction cold box; 19 - Sixth throttle valve; 20 - Second - stage extraction enrichment column; 21 - Second - stage extraction enrichment column condenser; 22 - Seventh throttle valve; 23 - Low - pressure natural gas compressor; 24 - First cooler; 25 - Product natural gas compressor; 26 - Second cooler; 27 - Propane refrigerant compressor; 28 - Third cooler; 29 - Eighth throttle valve; 30 - Mixed refrigerant refrigeration compressor; 31 - Fourth cooler; 32 - Ninth throttle valve; 33 - Nitrogen refrigeration compressor; 34 - Fifth cooler; 35 - Tenth throttle valve; 36 - First - stage extraction enrichment column reboiler. Detailed implementation mode

[0040] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0041] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "far", "near", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and 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 thus should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0042] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" 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 situations.

[0043] The inventors of the present invention have found that the prior art process of using a distillation tower to separate and extract helium at low temperature can only produce one product, crude helium. The product is too single and resources and equipment cannot be fully utilized, resulting in low production efficiency and low capacity utilization.

[0044] In view of the problems existing in the prior art, an embodiment of the present invention provides an ethane recovery and helium extraction co-production liquefied natural gas device and method.

[0045] The structure of an ethane recovery and helium extraction co-production liquefied natural gas device provided in an embodiment of the present invention is described in detail below in conjunction with the accompanying drawings:

[0046] refer to Figure 1 As shown, an embodiment of the present invention provides an ethane recovery and helium extraction co-production liquefied natural gas device, comprising:

[0047] The ethane recovery cold box 1, the low temperature separator 2, the demethanizer 4, the liquefaction cold box 9, the helium extraction cold box 18, the pre-extraction concentration tower 11, the primary concentration tower 15 and the secondary concentration tower 17 are connected by pipelines;

[0048] The ethane recovery cold box 1 precools the raw natural gas, and transports the precooled raw natural gas to the low-temperature separator 2 through a pipeline;

[0049] The low temperature separator 2 is used to separate the gas phase and the liquid phase from the different components in the raw natural gas. The gas phase flows back to the ethane recovery cold box 1 through a pipeline and enters the demethanizer 4 through a pipeline. The liquid phase enters the demethanizer 4 through a pipeline.

[0050] The demethanizer 4 is used to remove methane, and the bottom liquid phase outlet is connected to a pipeline to output natural gas condensate;

[0051] The liquefaction cold box 9 is used to liquefy the mixed gas after being treated by the demethanizer 4, and is provided with a pipeline to output liquefied natural gas;

[0052] The pre-concentration tower 11, the primary concentration tower 15, and the secondary concentration tower 20 are connected by pipelines and are used to distill and concentrate the natural gas after being treated by the liquefied cold box 9;

[0053] The helium extraction cold box 18 is connected to the secondary concentration tower 20 through a pipeline, and is used to liquefy the natural gas after being concentrated by the secondary concentration tower 20, and is provided with a pipeline to output the crude helium;

[0054] The natural gas output from the helium extraction cold box 18 and the natural gas output from the liquid phase at the bottom of the pre-extraction concentration tower 11 are combined through the same pipeline and then input into the liquefaction cold box 9, and are connected to the pipeline for outputting the product natural gas;

[0055] The output pipeline of the liquid phase of the pre-concentration tower 11 is connected to the pipeline connecting the liquefaction cold box 9 and the ethane recovery cold box 1 and the pipeline for outputting the product natural gas.

[0056] In one embodiment, the device further includes: a propane refrigerant refrigeration cycle unit;

[0057] The propane refrigerant refrigeration cycle unit includes a propane refrigerant compressor 27, a third cooler 28, and an eighth throttle valve 29 connected in sequence;

[0058] The propane refrigerant refrigeration cycle unit is connected to the ethane recovery cold box 1 and is used to provide cooling capacity for the ethane recovery cold box 1.

[0059] In one embodiment, the device further includes: a mixed refrigerant refrigeration cycle unit;

[0060] The mixed refrigerant refrigeration cycle unit includes a mixed refrigerant refrigeration compressor 30 and a fourth cooler 31 connected in sequence;

[0061] The mixed refrigerant refrigeration cycle unit is connected to the liquefaction cold box and is used to provide cooling capacity for the liquefaction cold box 9.

[0062] In one embodiment, the device further includes: a nitrogen refrigeration cycle unit;

[0063] The nitrogen refrigeration cycle unit includes a nitrogen refrigeration compressor 33 and a fifth cooler 34 connected in sequence;

[0064] The nitrogen refrigeration cycle unit is connected to the helium extraction cold box 18 and is used to provide cooling capacity for the helium extraction cold box 18 and the secondary concentration tower condenser 21.

[0065] In one embodiment, a natural gas reflux branch is formed by connecting the demethanizer 4 and the ethane recovery cold box 1 through a pipeline.

[0066] In one embodiment, it further includes: a demethanizer reboiler 12;

[0067] The demethanizer reboiler 12 is connected to the demethanizer 4 through a reflux pipeline.

[0068] In one embodiment, the bottom liquid phase outlet of the pre-concentration tower 11 is connected to the demethanizer 4 through a pipeline, and a demethanizer reflux pump 12 is provided on the pipeline between the bottom liquid phase outlet of the pre-concentration tower 11 and the demethanizer 4.

[0069] In one embodiment, the bottom liquid phase outlet of the pre-concentration tower 11 is connected to the liquefaction cold box 9 through a pipeline, and a primary concentration tower condenser 14 is provided on the pipeline between the bottom liquid phase outlet of the pre-concentration tower 11 and the liquefaction cold box 9.

[0070] In one embodiment, the liquid phase outlet at the bottom of the first concentration tower 15 is connected to the liquefaction cold box 9 through a pipeline and is communicated with the output pipeline of the liquefied natural gas in the liquefaction cold box 9.

[0071] In one embodiment, the gas phase outlet at the top of the second concentration tower 20 is connected to the helium extraction cold box 18 through a pipeline. The pipeline passes through the condenser 21 of the second concentration tower and is communicated with the output pipeline of the crude helium gas in the helium extraction cold box 18.

[0072] The following specific embodiments are given to illustrate the structure of the ethane recovery and helium extraction co-production liquefied natural gas device;

[0073] Reference Figure 1 As shown, an ethane recovery and helium extraction co-production liquefied natural gas device provided by an embodiment of the present invention includes:

[0074] Ethane recovery cold box 1, low-temperature separator 2, demethanizer 4, liquefaction cold box 9, helium extraction cold box 18, pre-concentration tower 11, first concentration tower 15, second concentration tower 20, propane refrigerant refrigeration cycle unit, mixed refrigerant refrigeration cycle unit and nitrogen refrigeration cycle unit.

[0075] In one embodiment, the inlet end of the first-stage precooling section in the ethane recovery cold box 1 is connected to the raw natural gas through a pipeline, and the outlet end of the first-stage precooling section in the ethane recovery cold box 1 is connected to the low-temperature separator 2 through a pipeline.

[0076] In one embodiment, the low-temperature separator 2 is provided with a bottom liquid phase outlet and a top gas phase outlet. The bottom liquid phase outlet is connected to the demethanizer 4 through a pipeline provided with a first throttle valve 5. The top gas phase outlet is divided into two paths. One path of the gas phase is connected to the inlet end of the second-stage precooling section in the ethane recovery cold box 1 through a pipeline. The outlet section of the second-stage precooling section in the ethane recovery cold box 1 is connected to the demethanizer 4 through a pipeline provided with a second throttle valve 6. The other path is expanded by an expansion unit 3 and then connected to the demethanizer 4 through a pipeline.

[0077] In one embodiment, the first-stage side line outlet at the lower part of the demethanizer 4 is connected to the inlet of the first-stage side line reheating end in the ethane recovery cold box 1 through a pipeline. The outlet of the first-stage side line reheating end in the ethane recovery cold box 1 is connected to the inlet of the first-stage side line at the lower part of the demethanizer 4 through a pipeline, forming a reflux passage between the ethane recovery cold box 1 and the demethanizer 4 through a pipeline. The second-stage side line liquid phase outlet at the lower part of the demethanizer 4 is connected to the inlet of the demethanizer reboiler 7 through a pipeline. The outlet of the demethanizer reboiler 7 is connected to the inlet of the second-stage side line at the lower part of the demethanizer 4 through a pipeline;

[0078] Among them, the demethanizer 4 is provided with a liquid phase outlet and a gas phase outlet;

[0079] The bottom liquid phase outlet of the demethanizer 4 is used as the natural gas condensate process through a pipeline. The natural gas condensate contains ethane, as well as propane, butane, etc., to complete the ethane recovery;

[0080] The gas phase at the top gas phase outlet of the demethanizer 4 is divided into two paths. One path enters the middle of the pre-concentration tower 11 after passing through the reboiler 36 of the primary concentration tower through a pipeline, and the other path is connected to the reboiler 8 at the bottom of the pre-concentration tower 11 through a pipeline. The reboiler 8 of the pre-concentration tower is connected to the inlet end of the cooling section in the liquefaction cold box 9 through a pipeline. The outlet end of the cooling section in the liquefaction cold box 9 is connected to the pre-concentration tower 15 through a pipeline provided with a third throttle valve 10.

[0081] In one embodiment, the pre-concentration tower 11 is provided with a liquid phase outlet and a gas phase outlet;

[0082] The bottom liquid phase outlet of the pre-concentration tower 11 is divided into three paths: Among them, the first path is sequentially connected to the demethanizer reflux pump 12 and the top inlet of the demethanizer 4 through a pipeline as the top reflux of the demethanizer 4;

[0083] The other two paths can be connected through a pipeline to form product natural gas to the subsequent process:

[0084] Among them, the second path is connected to the inlet end of the first-stage liquid phase reheating section in the liquefaction cold box 9 through a pipeline. The outlet end of the first-stage liquid phase reheating section in the liquefaction cold box 9 is connected to the inlet end of the reheating section in the ethane recovery cold box 1 through a pipeline. The outlet end of the reheating section in the ethane recovery cold box 1 is sequentially connected to the boost end of the expansion unit 3, the product natural gas compressor 25, and the second cooler 26 through a pipeline as product natural gas to the subsequent process;

[0085] The third path is connected to the cold end inlet of the primary concentration tower condenser 14 through a pipeline provided with a fourth throttle valve 13. The cold end outlet of the primary concentration tower condenser 14 is connected to the inlet end of the second-stage reheating section in the liquefaction cold box 9 through a pipeline. The outlet end of the reheating section in the liquefaction cold box 9 is sequentially connected to the low-pressure natural gas compressor 23, the first cooler 24, the product natural gas compressor 25, and the second cooler 26 through a pipeline as product natural gas to the subsequent process;

[0086] The top gas phase outlet of the pre-concentration tower 11 is connected to the lower inlet of the primary concentration tower 15 through a pipeline.

[0087] In one embodiment, the primary concentration tower 15 is provided with a liquid phase outlet and a gas phase outlet;

[0088] The gas phase at the top of the primary concentration tower 15 is cooled into a gas-liquid two-phase by the primary concentration tower condenser 14 and then divided into two paths. One path of the liquid phase is connected to the top of the primary concentration tower 15 through a pipeline for liquid phase reflux in the primary concentration tower 15. The other path of the gas phase is connected to the reboiler 17 at the bottom of the secondary concentration tower 20 through a pipeline. The reboiler 17 of the secondary concentration tower is connected to the inlet end of the cooling section in the helium extraction cold box 18 through a pipeline. The outlet end of the cooling section in the helium extraction cold box 18 is connected to the secondary concentration tower 20 through a pipeline provided with a sixth throttle valve 19;

[0089] The liquid phase outlet at the bottom of the primary concentration tower 15 is connected to the inlet end of the subcooling section in the liquefaction cold box 9 through a pipeline. The outlet end of the subcooling section in the liquefaction cold box 9 is used as liquefied natural gas product to the subsequent process through a pipeline provided with a fifth throttle valve 16.

[0090] In one embodiment, the secondary concentration tower 20 is provided with a liquid phase outlet and a gas phase outlet. Among them, the liquid phase outlet at the bottom can be connected through a pipeline to form product natural gas to the subsequent process, and the gas phase outlet at the top can be connected through a pipeline to form crude helium gas to the subsequent process;

[0091] The liquid phase outlet at the bottom of the secondary concentration tower 20 is connected to the inlet end of the liquid phase reheating section in the helium extraction cold box 18 through a pipeline provided with a seventh throttle valve 22. The outlet end of the liquid phase reheating section of the helium extraction cold box 18 is connected to the pipeline where the liquid phase at the bottom of the pre-concentration tower 11 enters the liquefaction cold box 9 through the primary concentration tower condenser 14. After reheating in the liquefaction cold box 9, it is sequentially connected to the low-pressure natural gas compressor 23, the first cooler 24, the product natural gas compressor 25, and the second cooler 26 through a pipeline as product natural gas to the subsequent process;

[0092] The gas phase outlet at the top of the secondary concentration tower 20 is connected to the secondary concentration tower condenser 21 through a pipeline. The gas phase at the top of the secondary concentration tower 20 is condensed into a gas-liquid two-phase by the secondary concentration tower condenser 21 and then divided into two paths. One path of the liquid phase is connected to the top of the secondary concentration tower 20 through a pipeline for liquid phase reflux in the secondary concentration tower 20. The other path of the gas phase is connected to the inlet end of the gas phase reheating section in the helium extraction cold box 18 through a pipeline. The outlet end of the gas phase reheating section in the helium extraction cold box 18 is used as crude helium gas to the subsequent process through a pipeline.

[0093] In one embodiment, the propane refrigerant refrigeration cycle unit is connected to the ethane recovery cold box 1 to provide cooling capacity for the ethane recovery cold box 1;

[0094] Reference Figure 1As shown, the propane refrigerant refrigeration cycle unit includes a third cooler 28, a propane refrigerant refrigeration compressor 27, and an eighth throttle valve 29. The eighth throttle valve 29 is connected to the inlet end of the corresponding propane refrigerant reheating section in the ethane recovery cold box. The outlet end of the corresponding propane refrigerant reheating section in the ethane recovery cold box is connected to the propane refrigerant refrigeration compressor 27 through a pipeline. A pipeline provided with the third cooler 28 is connected between the propane refrigerant refrigeration compressor 27 and the eighth throttle valve 29 to form a propane refrigerant refrigeration cycle loop.

[0095] In one embodiment, the mixed refrigerant refrigeration cycle unit is connected to the liquefaction cold box 9 to provide cooling capacity for the liquefaction cold box 9.

[0096] Reference Figure 1 As shown, the mixed refrigerant refrigeration cycle unit includes a fourth cooler 13 and a mixed refrigerant refrigeration compressor 30. The fourth cooler 31 is connected to the corresponding cooling section in the liquefaction cold box 9. The corresponding cooling section in the liquefaction cold box 9 is connected to the inlet end of the corresponding mixed refrigerant reheating section in the liquefaction cold box 9 through a pipeline provided with a ninth throttle valve 32. The outlet end of the mixed refrigerant reheating section in the liquefaction cold box 9 is connected to the mixed refrigerant refrigeration compressor 30 through a pipeline. The mixed refrigerant refrigeration compressor 30 is connected to the fourth cooler 31 to form a mixed refrigerant refrigeration cycle loop.

[0097] In one embodiment, the nitrogen refrigeration cycle unit is connected to the helium extraction cold box 18 to provide cooling capacity for the helium extraction cold box 18 and the secondary concentration tower condenser 21.

[0098] Reference Figure 1 As shown, the nitrogen refrigeration cycle unit includes a fifth cooler 34 and a nitrogen refrigeration compressor 33. The fifth cooler 34 is connected to the corresponding cooling section in the helium extraction cold box 18. The corresponding cooling section in the helium extraction cold box 18 is connected to the secondary concentration tower condenser 21 through a pipeline provided with a tenth throttle valve 35. The secondary concentration tower condenser 21 is connected to the inlet end of the refrigerant reheating section in the helium extraction cold box 18. The outlet end of the refrigerant reheating section in the helium extraction cold box 18 is connected to the nitrogen refrigeration compressor 33 through a pipeline. The nitrogen refrigerant compressor 33 is connected to the fifth cooler 34 to form a nitrogen refrigeration cycle loop.

[0099] The present invention also provides a process method for ethane recovery and helium extraction co-producing liquefied natural gas based on the above ethane recovery, helium extraction co-producing liquefied natural gas device. For easy understanding, some specific unit names are explained: among them, kiloPascal absolute pressure (kPa.a).

[0100] The specific process flow is as follows:

[0101] The raw natural gas (4000 kPa.a - 7000 kPa.a, 30°C - 50°C) after decarbonization and dehydration treatment enters the ethane recovery cold box 1 through a pipeline, is precooled to -50°C - -70°C, and then enters the low-temperature separator 2 for gas-liquid separation;

[0102] After gas-liquid separation, the liquid phase of the low-temperature separator 2 is throttled to 2000 kPa.a - 3500 kPa.a through the first throttle valve 5 and then enters the middle part of the demethanizer 4. The gas phase is divided into two paths. One path (content 10% - 30%) of the logistics enters the ethane recovery cold box 1, is cooled to -88°C - -100°C, enters the second throttle valve 6, is throttled to 2000 kPa.a - 3500 kPa.a, and then enters the upper part of the demethanizer 4. The other path (content 70 - 90%) of the logistics enters the expansion unit 3, is expanded to 2000 kPa.a - 3500 kPa.a, and then enters the middle-upper part of the demethanizer 4.

[0103] The liquid phase in the middle part of the demethanizer 4 enters the ethane recovery cold box 1, is heated, and then returns to the inlet of the middle part of the demethanizer 4 to recover the cold energy in the demethanizer 4. The liquid phase in the lower part of the demethanizer 4 enters the demethanizer reboiler 7, is heated, and then returns to the inlet of the lower part of the demethanizer 4 to control the methane content in the bottom liquid phase of the demethanizer 4. The bottom liquid phase of the demethanizer 4 enters the natural gas condensate process for treatment;

[0104] The gas phase at the top outlet of the demethanizer 4 is divided into two paths. One path (content 1% - 10%) of the logistics enters the primary concentration tower reboiler 36 through a pipeline and then enters the middle part of the pre-concentration tower 11. The other path (content 90 - 99%) enters the pre-concentration tower reboiler 8 through a pipeline, then passes through a pipeline, enters the liquefaction cold box 9, is precooled to -100°C - -110°C, and then is throttled to 1500 kPa.a - 3000 kPa.a through the third throttle valve 10 and enters the top of the pre-concentration tower 11.

[0105] The liquid-phase outlet at the bottom of the pre-concentration tower 11 is divided into three paths: one path (with a content of 5% - 20%) is pressurized to 2500 kPa.a - 4000 kPa.a by the demethanizer reflux pump 12 through a pipeline and enters the top of the demethanizer 4 as reflux; the second path (with a content of 60% - 85%) is sent through a pipeline to the liquefaction cold box 9 for reheating to -95°C - -115°C and then enters the ethane recovery cold box 1 for further reheating to 25°C - 35°C, and then successively passes through the boosting end of the expansion unit 3, the product natural gas compressor 25, and the second cooler 26 to be pressurized to 4100 kPa.a - 7100 kPa.a and cooled to 40 - 50°C as product natural gas to the subsequent process; the third path (10% - 20%) is throttled to 500 kPa.a - 1500 kPa.a by the fourth throttle valve 3 and enters the primary concentration tower condenser 14 for reheating to -115°C - -135°C, and then passes through the liquefaction cold box 9 for reheating to 25°C - 35°C and then through a pipeline successively passes through the low-pressure natural gas compressor 23, the first cooler 24, the product natural gas compressor 25, and the second cooler 26 to be pressurized to 4100 kPa.a - 7100 kPa.a and cooled to 40°C - 50°C as product natural gas to the subsequent process;

[0106] The crude helium gas rectified and concentrated by the pre-concentration tower 11 enters the lower part of the primary concentration tower 15 from the top of the tower. After the gas phase at the top of the primary concentration tower 15 is condensed into gas-liquid two phases by the primary concentration tower condenser 14, one path is the liquid phase entering the top of the primary concentration tower as reflux, and the other path is the gas phase entering the secondary concentration tower reboiler 17 through a pipeline, and then sent through a pipeline to the helium extraction cold box 18 for cooling to -150°C - -160°C, and then throttled to 1000 kPa.a - 2700 kPa.a by the sixth throttle valve 19 and enters the middle part of the secondary concentration tower 20; the liquid-phase outlet at the bottom of the primary concentration tower 15 enters the liquefaction cold box 9 through a pipeline for cooling to -150°C - -160°C, and then passes through a pipeline provided with the fifth throttle valve 16 as liquefied natural gas product to the subsequent process.

[0107] The liquid phase at the bottom of the secondary concentration tower 20 is throttled to 500 kPa.a - 1500 kPa.a by the seventh throttle valve 22 and enters the helium extraction cold box 18 for reheating to -130°C - -150°C, and then is connected through a pipeline to the pipeline after reheating the liquid phase at the bottom of the pre-concentration tower 11 by the primary concentration tower condenser 14, and then enters the liquefaction cold box 9 for reheating to 25°C - 35°C and then through a pipeline successively passes through the low-pressure natural gas compressor 23, the first cooler 24, the product natural gas compressor 25, and the second cooler 26 to be pressurized to 4100 kPa.a - 7100 kPa.a and cooled to 40°C - 50°C as product natural gas to the subsequent process;

[0108] The crude helium gas rectified and concentrated by the secondary concentration tower 20 enters the secondary concentration tower condenser 21 from the top of the tower and is condensed to -170°C to -185°C. The gas at the top of the secondary concentration tower 20 is condensed into a gas-liquid two-phase state by the secondary concentration tower condenser 21 and then divided into two paths. One path is the liquid phase that enters the top of the secondary concentration tower 20 as reflux, and the other path is the gas phase that enters the helium extraction cold box 18, is reheated to 25°C to 35°C, and then passes through the pipeline as crude helium gas to the subsequent process.

[0109] In the propane refrigerant refrigeration cycle loop, the propane refrigerant coming from the third cooler 28 is throttled to -38°C by the eighth throttle valve 29, enters the ethane recovery cold box 1, vaporizes, and then is pressurized to 1400 kPa.a to 1900 kPa.a by the propane refrigerant refrigeration compressor 27. After entering the third cooler 28 and being cooled to 30°C to 50°C, it is throttled by the eighth throttle valve 29 and then enters the ethane recovery cold box 1, forming a propane refrigerant refrigeration cycle to provide the required cooling capacity for the ethane recovery cold box 1.

[0110] In the mixed refrigerant refrigeration cycle loop, the mixed refrigerant coming from the fourth cooler 31 enters the liquefaction cold box 9 and is cooled to -150°C to -160°C. After being throttled to 300 kPa.a to 500 kPa.a by the ninth throttle valve 32 and entering the liquefaction cold box 9 for reheating to 25°C to 35°C, it enters the mixed refrigerant refrigeration compressor 30 and is pressurized to 3500 kPa.a to 4000 kPa.a. After entering the fourth cooler 31 and being cooled to 30°C to 50°C, it enters the liquefaction cold box 9, forming a mixed refrigerant refrigeration cycle to provide the required cooling capacity for the liquefaction cold box 9.

[0111] In the nitrogen refrigerant refrigeration cycle loop, the nitrogen refrigerant coming from the fifth cooler 34 enters the helium extraction cold box 18 and is cooled to -170 to -185°C. After being throttled to 200 kPa.a to 500 kPa.a by the tenth throttle valve 35, it enters the secondary concentration tower condenser 21 and is reheated to -170°C to -180°C. After passing through the pipeline and entering the helium extraction cold box 18 for further reheating to 20°C to 30°C, it enters the nitrogen refrigerant refrigeration compressor 33 and is pressurized to 800 kPa.a to 4000 kPa.a. After entering the fifth cooler 34 and being cooled to 30°C to 40°C, it enters the helium extraction cold box 18, forming a nitrogen refrigerant refrigeration cycle to provide the required cooling capacity for the secondary concentration tower condenser 21 and the helium extraction cold box 18.

[0112] An ethane recovery, helium extraction and co-production of liquefied natural gas device and method provided by an embodiment of the present invention realize product diversification in the natural gas extraction process through the ethane recovery, helium extraction and co-production of liquefied natural gas device, and set up multiple circulation paths to improve utilization rate and increase production efficiency.

[0113] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. An ethane recovery and helium extraction combined production liquefied natural gas device, characterized in that, Comprising: The ethane recovery cold box, low-temperature separator, demethanizer, liquefaction cold box, helium extraction cold box, pre-concentration tower, primary concentration tower, and secondary concentration tower are connected by pipelines; The ethane recovery cold box pre-cools the raw natural gas and transports the pre-cooled raw natural gas to the low-temperature separator through a pipeline; The low-temperature separator is used to separate the gas phase and liquid phase in different components of the raw natural gas. The gas phase returns to the ethane recovery cold box through a pipeline and enters the demethanizer through a pipeline, and the liquid phase enters the demethanizer through a pipeline; The demethanizer is used to remove methane, and a pipeline is connected to the bottom liquid outlet to output natural gas condensate; The liquefaction cold box is used to liquefy the mixed gas processed by the demethanizer, and a pipeline is provided to output liquefied natural gas; The pre-concentration tower, primary concentration tower, and secondary concentration tower are connected by pipelines and are used to rectify and concentrate the natural gas processed by the liquefaction cold box; The helium extraction cold box is connected to the secondary concentration tower by a pipeline and is used to liquefy the natural gas concentrated by the secondary concentration tower, and a pipeline is provided to output crude helium gas; The natural gas output by the helium extraction cold box and the natural gas output from the bottom liquid phase of the pre-concentration tower are merged through the same pipeline and then input into the liquefaction cold box, and are connected to the pipeline for outputting product natural gas; The pipeline for outputting the liquid phase of the pre-concentration tower is connected to the pipeline connecting the liquefaction cold box and the ethane recovery cold box and the pipeline for outputting product natural gas; 2. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 1, characterized in that, The device further includes: a propane refrigerant refrigeration cycle unit; The propane refrigerant refrigeration cycle unit includes a propane refrigerant compressor, a third cooler, and an eighth throttle valve connected in sequence; The propane refrigerant refrigeration cycle unit is connected to the ethane recovery cold box and is used to provide cooling capacity for the ethane recovery cold box; 3. The ethane recovery and helium extraction combined production of liquefied natural gas device according to claim 1, characterized in that, The device further includes: a mixed refrigerant refrigeration cycle unit; The mixed refrigerant refrigeration cycle unit includes a mixed refrigerant refrigeration compressor and a fourth cooler connected in sequence; The mixed refrigerant refrigeration cycle unit is connected to the liquefaction cold box and is used to provide cooling capacity for the liquefaction cold box; 4. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 1, characterized in that, The device further includes: a nitrogen refrigeration cycle unit; The nitrogen refrigeration cycle unit includes a nitrogen refrigeration compressor and a fifth cooler connected in sequence; The nitrogen refrigeration cycle unit is connected to the helium extraction cold box and is used to provide cooling capacity for the helium extraction cold box and the condenser of the secondary concentration tower; 5. The ethane recovery and helium extraction combined production of liquefied natural gas device according to claim 1, characterized in that, A natural gas reflux branch is formed by connecting the demethanizer and the ethane recovery cold box through a pipeline; 6. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 5, characterized in that, Further included: A demethanizer reboiler; The demethanizer reboiler is connected to the demethanizer through a reflux pipeline; 7. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 1, characterized in that, The bottom liquid outlet of the pre-concentration tower is connected to the demethanizer through a pipeline, and a demethanizer reflux pump is provided on the pipeline between the bottom liquid outlet of the pre-concentration tower and the demethanizer; 8. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 1, wherein The bottom liquid outlet of the pre-concentration tower is connected to the liquefaction cold box through a pipeline, and a primary concentration tower condenser is provided on the pipeline between the bottom liquid outlet of the pre-concentration tower and the liquefaction cold box; 9. The ethane recovery and helium extraction co-production liquefied natural gas device according to claim 1, characterized in that, The bottom liquid outlet of the primary concentration tower is connected to the liquefaction cold box through a pipeline and is connected to the pipeline for outputting liquefied natural gas of the liquefaction cold box; 10. The ethane recovery and helium extraction combined production of liquefied natural gas device according to claim 1, characterized in that, The gas-phase outlet at the top of the secondary concentration tower is connected to the helium extraction cold box through a pipeline. The pipeline passes through the condenser of the secondary concentration tower and is communicated with the crude helium gas output pipeline of the helium extraction cold box.

11. A method for ethane recovery, helium extraction and co-production of liquefied natural gas from raw natural gas using the ethane recovery and helium extraction co-production liquefied natural gas device according to any one of claims 1-10.

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