Method and device for extracting helium and recovering carbon dioxide through low-temperature rectification

Abstract

The invention provides a method and a device for extracting helium and recovering carbon dioxide through low-temperature rectification. The device for extracting helium from natural gas comprises a primary concentration device, a secondary concentration device and a helium refining unit, the first-stage concentration device comprises a first-stage low-temperature cold box and a first-stage concentration tower which are communicated in sequence; the first-stage low-temperature cold box is communicated with a raw material natural gas pipeline; the second-stage concentration device comprises a second-stage low-temperature cold box and a second-stage concentration tower which are communicated in sequence, and a tower top discharge port of the first-stage concentration tower is communicated with a feed port of the second-stage low-temperature cold box; the helium refining unit comprises a crude helium dehydrogenation device and a helium purification device which are communicated in sequence, and the helium purification device outputs a helium product; and a tower top discharge port of the secondary concentration tower is communicated with a feed port of the crude helium dehydrogenation device. According to the scheme, by adjusting the separation sequence of ethane and helium components, the process of extracting helium first and then recovering ethane and co-producing LNG is innovatively provided, and the total energy consumption of the system is reduced by 15%.

Description

Technical Field

[0001] The present invention relates to but is not limited to the field of gas processing, and in particular to but is not limited to a method and device for extracting helium and recovering carbon dioxide through cryogenic distillation. Background Art

[0002] Helium is a colorless, odorless, rare and inert gas. It is widely used in high-tech fields such as clinical medicine, national defense, aerospace, nuclear industry, deep-sea diving, cryogenic superconductivity, and high-precision welding. It is an important scarce strategic resource related to national security and the development of high-tech industries. my country has few helium resources and low content, high consumption and high dependence on imports. The external dependence rate exceeds 95%, and the helium supply security is poor. Helium is a monatomic gas and cannot be synthesized through chemical reactions. The content of helium in the air is only 5 parts per million, which has no industrial extraction value. Separating and purifying helium from helium-containing natural gas is currently the only source of industrial production of helium.

[0003] Because the liquefaction temperature of helium is -269℃ (4K), it is the most difficult gas to liquefy in the world. Helium extraction from natural gas is a typical cryogenic process with the lowest refrigeration separation temperature in cryogenic processing. At present, the main method for extracting helium from natural gas in the world is cryogenic method, and about 90% of helium is extracted by cryogenic method. Cryogenic method uses the difference in critical temperature of each component in natural gas to separate helium, and the obtained product has high purity and yield. The system needs to adopt a multi-stage low-temperature distillation process. The refrigeration adopts mixed refrigerant, throttling, expansion and nitrogen circulation refrigeration to provide cooling capacity. It has high recovery rate, reliability and stability, but the system is complex. Among them, the commonly used indirect distillation process (i.e., the process of recovering ethane first and then extracting helium to produce LNG) involves two depressurization processes, and the natural gas needs to be pressurized three times. And first expansion refrigeration to recover ethane, and then expansion refrigeration again to recover helium and other components, the two repeated refrigerations cause waste of cooling capacity and increase in energy consumption. The reality that the cost of extracting helium from helium-poor natural gas reservoirs in my country is already high is undoubtedly worse. Summary of the invention

[0004] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0005] In an embodiment of the present disclosure, a device for extracting helium from natural gas is provided, the device comprising:

[0006] Primary enrichment device, secondary enrichment device and helium refining unit;

[0007] The primary concentration device comprises a primary low temperature cold box and a primary concentration tower which are connected in sequence; the primary low temperature cold box is connected to the raw natural gas pipeline;

[0008] The secondary concentration device comprises a secondary low-temperature cold box and a secondary concentration tower which are connected in sequence, and the top discharge port of the primary concentration tower is connected to the feed port of the secondary low-temperature cold box;

[0009] The helium refining unit comprises a crude helium dehydrogenation device and a helium purification device which are connected in sequence, and the helium purification device outputs a helium product; the top outlet of the secondary concentration tower is connected to the feed inlet of the crude helium dehydrogenation device.

[0010] In some embodiments provided by the present disclosure, the raw natural gas pipeline includes a raw natural gas pretreatment device,

[0011] The raw natural gas pretreatment device is configured to remove mercury, dehydrate, increase pressure and adjust temperature of the raw natural gas.

[0012] In some embodiments provided in the present disclosure, a first low-temperature separator is further provided between the first low-temperature cold box and the first concentration tower, the outlet of the first low-temperature cold box is connected to the inlet of the first low-temperature separator, and the gas phase outlet of the first low-temperature separator is connected to the reboiler heat source feed port of the reboiler provided at the bottom of the first concentration tower.

[0013] In some embodiments provided in the present disclosure, the liquid phase outlet of the first low-temperature separator is connected to the feed inlet of the demethanizer.

[0014] In some embodiments provided in the present disclosure, a reboiler heat source outlet of the reboiler device is connected to the second low-temperature separator, a liquid phase outlet of the second low-temperature separator is connected to the first (lower) feed port of the raw material of the first-level concentration tower, a gas phase outlet of the second low-temperature separator is connected to the second (upper) feed port of the raw material of the first-level concentration tower through an independent pipeline, an independent pipeline connecting the gas phase outlet of the second low-temperature separator and the second (upper) feed port of the raw material of the first-level concentration tower is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to cool the gas phase in the independent pipeline.

[0015] In some embodiments provided in the present disclosure, the bottom outlet of the primary concentration tower is connected to the feed inlet of the demethanizer tower.

[0016] In some embodiments provided by the present disclosure, the secondary concentration device further comprises a molecular sieve decarbonization device disposed between the secondary low-temperature cold box and the secondary concentration tower;

[0017] The discharge port of the secondary low-temperature cold box is connected to the feed port of the molecular sieve decarbonization device, and the discharge port of the molecular sieve decarbonization device is connected to the reboiler heat source feed port of the reboiler provided at the bottom of the secondary concentration tower;

[0018] The reboiling heat source outlet of the reboiling device arranged at the bottom of the secondary concentration tower is communicated with the feed port of the fourth low-temperature separator, the gas phase outlet of the fourth low-temperature separator is communicated with the first (lower) feed port of the secondary concentration tower, and the liquid phase outlet of the fourth low-temperature separator is communicated with the second (upper) feed port of the secondary concentration tower;

[0019] The discharge port of the molecular sieve decarbonization device is connected to the reboiling heat source feed port of the reboiling device arranged at the bottom of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the discharge port of the molecular sieve decarbonization device and the reboiling heat source feed port of the reboiling device arranged at the bottom of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is also configured to cool the gas phase in the pipeline;

[0020] The gas phase outlet of the fourth low-temperature separator is connected to the first (lower) feed inlet of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the gas phase outlet of the fourth low-temperature separator and the first (lower) feed inlet of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is also configured to cool the gas phase in the pipeline;

[0021] The liquid phase outlet of the fourth low-temperature separator is connected to the second (upper) feed port of the secondary concentration tower through an independent pipeline. The independent pipeline connecting the liquid phase outlet of the fourth low-temperature separator and the second (upper) feed port of the secondary concentration tower is at least partially located in the secondary low-temperature cold box. The secondary low-temperature cold box is also configured to cool the liquid phase in the independent pipeline.

[0022] In some embodiments provided by the present disclosure, the secondary cryogenic cold box is configured to reheat the gas phase output from the top outlet of the primary concentration tower;

[0023] In some embodiments provided in the present disclosure, the bottom discharge port of the secondary concentration tower is connected to a liquid natural gas transmission pipeline.

[0024] In some embodiments provided by the present disclosure, the top outlet of the secondary concentration tower is connected to the feed inlet of the crude helium dehydrogenation device through an independent pipeline, and the independent pipeline connecting the top outlet of the secondary concentration tower and the feed inlet of the crude helium dehydrogenation device is at least partially located in a secondary cryogenic cold box, and the secondary cryogenic cold box is also configured to reheat the gas phase in the pipeline.

[0025] In some embodiments provided in the present disclosure, the helium refining unit further includes a molecular sieve dehydration and decarbonization device, the discharge port of the crude helium dehydrogenation device is connected to the feed port of the molecular sieve dehydration and decarbonization device, and the discharge port of the molecular sieve dehydration and decarbonization device is connected to the helium cold box of the helium purification device.

[0026] In some embodiments provided by the present disclosure, the helium purification device comprises the helium cold box, the cryogenic distillation tower and the pressure swing adsorption unit which are connected in sequence;

[0027] The discharge port of the helium cold box is connected to the feed port of the cryogenic distillation tower, the first discharge port at the bottom of the cryogenic distillation tower is connected to the natural gas export pipeline through an independent pipeline, the independent pipeline connecting the first discharge port at the bottom of the cryogenic distillation tower and the natural gas export pipeline is at least partially located in the helium cold box, and the helium cold box is configured to perform heat exchange and temperature increase on the pipeline;

[0028] The second discharge port at the bottom of the cryogenic distillation tower is connected to the gas phase feed port at the bottom of the cryogenic distillation tower through an independent pipeline, and the independent pipeline connecting the second discharge port at the bottom of the cryogenic distillation tower and the gas phase feed port at the bottom of the cryogenic distillation tower is at least partially located in a helium cold box, and the helium cold box is further configured to heat the liquid phase in the pipeline;

[0029] The top discharge port of the cryogenic distillation tower is connected to the feed port of the pressure swing adsorption unit through an independent pipeline. The independent pipeline connecting the top discharge port of the cryogenic distillation tower and the feed port of the pressure swing adsorption unit is at least partially located in a helium cold box. The helium cold box is also configured to heat the gas phase in the pipeline.

[0030] In another aspect, the present disclosure provides a method for extracting helium from natural gas, using the above-mentioned device for extracting helium from natural gas, the method comprising:

[0031] The raw natural gas is subjected to mercury removal, dehydration, pressure increase and temperature adjustment processes.

[0032] In some embodiments provided herein, mercury removal to 10 ng / m 3 Below, dehydrate to below 0.1ppm.

[0033] In some embodiments provided by the present disclosure, the primary cryogenic cold box cools the temperature of the raw natural gas to -60°C to -75°C.

[0034] In some embodiments provided by the present disclosure, the bottom temperature of the primary concentration tower is -75°C to -90°C, and the top temperature of the primary concentration tower is -90°C to -105°C.

[0035] In some embodiments provided in the present disclosure, the gas phase is cooled to -70°C to -85°C by a reboiler provided at the bottom of the primary concentration tower.

[0036] In some embodiments provided in the present disclosure, the secondary cryogenic cold box is configured to reheat the temperature of the gas phase output from the top outlet of the primary concentration tower to 20°C to 50°C; the molecular sieve decarbonization device is configured to remove carbon dioxide from the reheated gas phase output from the top outlet of the primary concentration tower to below 10 ppm, and the secondary cryogenic cold box is further configured to cool the gas phase treated by the molecular sieve decarbonization device to -80°C to -95°C.

[0037] The reboiler provided at the bottom of the secondary concentration tower is configured to further cool the liquid phase cooled to -80°C to -95°C to -95°C.

[0038] The bottom temperature of the secondary concentration tower is -150°C to -155°C, and the top temperature of the secondary concentration tower is -155°C to -165°C;

[0039] In some embodiments provided by the present disclosure, the secondary low-temperature cold box is further configured to increase the temperature of the gas phase at the top outlet of the secondary concentration tower to 30° C. to 50° C.

[0040] In some embodiments provided by the present disclosure, the helium cold box is configured to cool the liquid phase output from the outlet of the molecular sieve dehydration and decarbonization device to -175°C to -185°C.

[0041] In some embodiments provided by the present disclosure, the top temperature of the cryogenic distillation tower (three-stage distillation tower) is -185°C to -195°C.

[0042] In some embodiments provided by the present disclosure, the pressure swing adsorption unit is pressurized to obtain a qualified helium product, and the qualified helium product is transported to a storage facility.

[0043] On the other hand, in some embodiments provided by the present disclosure, there is provided a device for extracting helium from natural gas while collecting carbon dioxide, the device comprising the above-mentioned device, and the device further comprising:

[0044] A third low-temperature separator, wherein the bottom discharge port of the first-stage concentration tower is connected to the feed port of the third low-temperature separator;

[0045] A demethanizer, wherein the gas phase outlet of the third low-temperature separator is connected to the second (upper) feed inlet of the demethanizer;

[0046] The liquid phase discharge port of the third low-temperature separator is communicated with the feed port of the low-temperature separator of the demethanizer, the gas phase discharge port of the low-temperature separator of the demethanizer is communicated with the second (upper) feed port of the demethanizer, and the liquid phase discharge port of the low-temperature separator of the demethanizer is communicated with the first (middle) feed port of the demethanizer;

[0047] The liquid phase discharge port of the third low-temperature separator is connected to the feed port of the low-temperature separator of the demethanizer through at least two independent pipelines, wherein one independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the top condenser of the first-level concentration tower, and the top condenser of the first-level concentration tower is configured to reheat the liquid phase in the pipeline; the other independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to reheat the liquid phase in the pipeline.

[0048] The top outlet of the demethanizer is communicated with a natural gas transmission pipeline.

[0049] In some embodiments provided by the present disclosure, the ratio of the flow rate of the liquid phase flowing through the top condenser of the primary concentration tower to the flow rate of the liquid phase flowing through the primary low-temperature cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time;

[0050] In some embodiments provided in the present disclosure, the top discharge port of the demethanizer is connected to the natural gas export pipeline through an independent pipeline, and at least a portion of the independent pipeline connecting the top discharge port of the demethanizer and the natural gas export pipeline is located in the first-level cryogenic cold box, and the first-level cryogenic cold box is also configured to reheat the pipeline.

[0051] In some embodiments provided in the present disclosure, the liquid phase discharge port at the bottom of the demethanizer is connected with the gas phase feed port at the bottom of the demethanizer through an independent pipeline, and the independent pipeline connecting the liquid phase discharge port at the bottom of the demethanizer and the gas phase feed port at the bottom of the demethanizer is at least partially located in the first-level cryogenic cold box, and the first-level cryogenic cold box is also configured to reboil the liquid phase in the pipeline, and optionally, the reboiling temperature is 20°C to 35°C; the liquid phase discharge port at the bottom of the demethanizer is also connected with the feed port of the deethanizer.

[0052] In some embodiments provided by the present disclosure, the ratio of the liquid phase flow rate entering the deethanizer to the liquid phase flow rate flowing through the primary cryogenic cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time; the top gas outlet of the deethanizer is connected to the feed inlet of the top condenser of the deethanizer, the gas phase outlet of the top condenser of the deethanizer is connected to the feed inlet of the ethaneamine decarbonization device, and the liquid phase outlet of the top condenser of the deethanizer is connected to the top reflux feed inlet of the deethanizer;

[0053] The bottom discharge port of the deethanizer is connected with the feed port of the liquefied gas tower, the top gas of the liquefied gas tower is connected with the liquefied petroleum gas export pipeline, and the bottom of the liquefied gas tower is connected with the stable light hydrocarbon export pipeline; the top discharge port of the deethanizer is connected with the bottom feed port of the ethaneamine decarbonization absorption tower; the top material outlet of the ethaneamine decarbonization absorption tower is connected with the ethane output pipeline, the bottom discharge port of the ethaneamine decarbonization absorption tower is connected with the feed port of the carbon dioxide absorption liquid (N-methyldiethanolamine solution, MDEA solution) regeneration device, and the carbon dioxide discharge port of the carbon dioxide absorption liquid regeneration device is connected with the carbon dioxide export pipeline.

[0054] The outlet condition of the first-stage concentration tower top is a flow rate of 50×10 4 m 3 / d to 100×10 4 m 3 / d, temperature is -90℃ to -105℃, pressure is 3.5MPa.g to 4.0MPa.g;

[0055] The outlet condition of the first-stage concentration tower bottom is a flow rate of 2.0×10 4 m 3 / d to 5.0×10 4 m 3 / d, temperature is -75℃ to -90℃, pressure is 3.5MPa.g to 4.0MPa.g;

[0056] The inlet condition of the bottom of the secondary concentration tower is 100×10 4 m 3 / d to 150×10 4 Nm 3 / d, temperature is -90℃ to -100℃, pressure is 3.5MPa.g to 4.0MPa.g;

[0057] The outlet conditions (LNG) of the bottom of the secondary concentration tower are as follows: flow rate of 15000kg / h to 20000kg / h, temperature of -160°C to -170°C, and pressure of 2000kPa.g to 2500kPa.g;

[0058] The top outlet condition of the secondary concentration tower (outlet crude helium) is 50000Nm 3 / d to 60000Nm 3 / d, temperature is 20℃ to 45℃, pressure is 2.0MPa.g to 2.5MPa.g;

[0059] The crude helium dehydrogenation unit has a flow rate of 50000 Nm 3 / d to 70000Nm 3 / d, temperature is 20℃ to 45℃, pressure is 2.0MPa.g to 2.5MPa.g;

[0060] The outlet condition of the crude helium dehydrogenation device is a flow rate of 50000Nm 3 / d to 70000Nm 3 / d, temperature is 20℃ to 45℃, pressure is 2.0MPa.g to 2.5MPa.g;

[0061] The inlet condition of the helium purification device is a flow rate of 50000Nm 3 / d to 70000Nm 3 / d, temperature is 20℃ to 45℃, pressure is 2.0MPa.g to 2.5MPa.g;

[0062] The outlet condition of the helium purification device is a flow rate of 10000 Nm 3 / d to 15000Nm 3 / d, the temperature is 20℃ to 45℃, and the pressure is 20MPa.g to 27MPa.g.

[0063] Other features and advantages of the present disclosure will be described in the following description, and partly become apparent from the description, or be understood by implementing the present disclosure. Other advantages of the present disclosure can be invented and obtained by the schemes described in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The accompanying drawings are used to provide an understanding of the technical solution of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the technical solution of the present disclosure and do not constitute a limitation on the technical solution of the present disclosure.

[0065] Figure 1 It is a schematic diagram of the process flow of the present invention (a schematic diagram of the process flow of the primary and secondary concentration towers).

[0066] Figure 2 The process flow chart of the present invention is shown in FIG.

[0067] Figure 3 It is a process principle flow chart of sequential distillation - extracting helium first and then recovering ethane (process principle flow chart of extracting helium first and then recovering ethane).

[0068] Figure 4 It is a process flow chart of cryogenic distillation + pressure swing adsorption purification (process flow chart of cryogenic distillation + pressure swing adsorption purification). DETAILED DESCRIPTION

[0069] To make the purpose, technical solution and advantages of the present disclosure more clear, the embodiments of the present disclosure are described in detail below. It should be noted that the embodiments and features in the embodiments of the present disclosure can be combined with each other arbitrarily without conflict.

[0070] In an embodiment of the present disclosure, a device for extracting helium from natural gas is exemplarily provided, the device comprising:

[0071] Primary enrichment device, secondary enrichment device and helium refining unit;

[0072] The primary concentration device comprises a primary low temperature cold box and a primary concentration tower which are connected in sequence; the primary low temperature cold box is connected to the raw natural gas pipeline;

[0073] The secondary concentration device comprises a secondary low-temperature cold box and a secondary concentration tower which are connected in sequence, and the top discharge port of the primary concentration tower is connected to the feed port of the secondary low-temperature cold box;

[0074] The helium refining unit comprises a crude helium dehydrogenation device and a helium purification device which are connected in sequence, and the helium purification device outputs a helium product; the top outlet of the secondary concentration tower is connected to the feed inlet of the crude helium dehydrogenation device.

[0075] Exemplarily, the raw natural gas pipeline includes a raw natural gas pretreatment device, which is configured to remove mercury, dehydrate, increase pressure and adjust temperature of the raw natural gas.

[0076] Exemplarily, a first low-temperature separator is further arranged between the first low-temperature cold box and the first concentration tower, the outlet of the first low-temperature cold box is connected to the inlet of the first low-temperature separator, and the gas phase outlet of the first low-temperature separator is connected to the reboiler heat source feed port of the reboiler arranged at the bottom of the first concentration tower.

[0077] Exemplarily, the liquid phase outlet of the first low-temperature separator is connected to the feed inlet of the demethanizer.

[0078] Exemplarily, the reboiler heat source outlet of the reboiler device is connected to the second low-temperature separator, the liquid phase outlet of the second low-temperature separator is connected to the first (lower) feed port of the raw material of the first-level concentration tower, the gas phase outlet of the second low-temperature separator is connected to the second (upper) feed port of the raw material of the first-level concentration tower through an independent pipeline, and the independent pipeline connecting the gas phase outlet of the second low-temperature separator and the second (upper) feed port of the raw material of the first-level concentration tower is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to cool the gas phase in the independent pipeline.

[0079] Exemplarily, the bottom outlet of the primary concentration tower is connected to the feed inlet of the demethanizer tower.

[0080] Exemplarily, the secondary concentration device further comprises a molecular sieve decarbonization device disposed between the secondary low-temperature cold box and the secondary concentration tower;

[0081] The discharge port of the secondary low-temperature cold box is connected to the feed port of the molecular sieve decarbonization device, and the discharge port of the molecular sieve decarbonization device is connected to the reboiler heat source feed port of the reboiler provided at the bottom of the secondary concentration tower;

[0082] The reboiling heat source outlet of the reboiling device arranged at the bottom of the secondary concentration tower is communicated with the feed port of the fourth low-temperature separator, the gas phase outlet of the fourth low-temperature separator is communicated with the first (lower) feed port of the secondary concentration tower, and the liquid phase outlet of the fourth low-temperature separator is communicated with the second (upper) feed port of the secondary concentration tower;

[0083] The discharge port of the molecular sieve decarbonization device is connected to the reboiling heat source feed port of the reboiling device arranged at the bottom of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the discharge port of the molecular sieve decarbonization device and the reboiling heat source feed port of the reboiling device arranged at the bottom of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is also configured to cool the gas phase in the pipeline;

[0084] The gas phase outlet of the fourth low-temperature separator is connected to the first (lower) feed inlet of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the gas phase outlet of the fourth low-temperature separator and the first (lower) feed inlet of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is also configured to cool the gas phase in the pipeline;

[0085] The liquid phase outlet of the fourth low-temperature separator is connected to the second (upper) feed port of the secondary concentration tower through an independent pipeline. The independent pipeline connecting the liquid phase outlet of the fourth low-temperature separator and the second (upper) feed port of the secondary concentration tower is at least partially located in the secondary low-temperature cold box. The secondary low-temperature cold box is also configured to cool the liquid phase in the independent pipeline.

[0086] Exemplarily, the secondary cryogenic cold box is configured to reheat the gas phase output from the top outlet of the primary concentration tower;

[0087] Exemplarily, the bottom outlet of the secondary concentration tower is connected to a liquid natural gas transmission pipeline.

[0088] Exemplarily, the top outlet of the secondary concentration tower is connected to the feed inlet of the crude helium dehydrogenation device through an independent pipeline, and the independent pipeline connecting the top outlet of the secondary concentration tower and the feed inlet of the crude helium dehydrogenation device is at least partially located in a secondary cryogenic cold box, and the secondary cryogenic cold box is also configured to reheat the gas phase in the pipeline.

[0089] Exemplarily, the helium refining unit further includes a molecular sieve dehydration and decarbonization device, the discharge port of the crude helium dehydrogenation device is connected to the feed port of the molecular sieve dehydration and decarbonization device, and the discharge port of the molecular sieve dehydration and decarbonization device is connected to the helium cold box of the helium purification device.

[0090] Exemplarily, the helium purification device comprises the helium cold box, the cryogenic distillation tower and the pressure swing adsorption unit which are connected in sequence;

[0091] The discharge port of the helium cold box is connected to the feed port of the cryogenic distillation tower, the first discharge port at the bottom of the cryogenic distillation tower is connected to the natural gas export pipeline through an independent pipeline, the independent pipeline connecting the first discharge port at the bottom of the cryogenic distillation tower and the natural gas export pipeline is at least partially located in the helium cold box, and the helium cold box is configured to perform heat exchange and temperature increase on the pipeline;

[0092] The second discharge port at the bottom of the cryogenic distillation tower is connected to the gas phase feed port at the bottom of the cryogenic distillation tower through an independent pipeline, and the independent pipeline connecting the second discharge port at the bottom of the cryogenic distillation tower and the gas phase feed port at the bottom of the cryogenic distillation tower is at least partially located in a helium cold box, and the helium cold box is further configured to heat the liquid phase in the pipeline;

[0093] The top discharge port of the cryogenic distillation tower is connected to the feed port of the pressure swing adsorption unit through an independent pipeline. The independent pipeline connecting the top discharge port of the cryogenic distillation tower and the feed port of the pressure swing adsorption unit is at least partially located in a helium cold box. The helium cold box is also configured to heat the gas phase in the pipeline.

[0094] In another aspect, the present disclosure exemplarily provides a method for extracting helium from natural gas, using the above-mentioned device for extracting helium from natural gas, the method comprising:

[0095] The raw natural gas is subjected to mercury removal, dehydration, pressure increase and temperature adjustment processes.

[0096] For example, mercury removal to 10 ng / m 3 Below, dehydrate to below 0.1ppm.

[0097] Exemplarily, the primary cryogenic cold box cools the temperature of the raw natural gas to -60°C to -75°C.

[0098] Illustratively, the bottom temperature of the primary concentration tower is -75°C to -90°C, and the top temperature of the primary concentration tower is -90°C to -105°C.

[0099] Exemplarily, the gas phase is cooled to -70°C to -85°C by a reboiler provided at the bottom of the primary concentration tower.

[0100] Exemplarily, the secondary cryogenic cold box is configured to reheat the temperature of the gas phase output from the top outlet of the first concentration tower to 20°C to 50°C; the molecular sieve decarbonization device is configured to remove carbon dioxide from the reheated gas phase output from the top outlet of the first concentration tower to below 10 ppm, and the secondary cryogenic cold box is also configured to cool the gas phase treated by the molecular sieve decarbonization device to -80°C to -95°C.

[0101] The reboiler provided at the bottom of the secondary concentration tower is configured to further cool the liquid phase cooled to -80°C to -95°C to -95°C;

[0102] The bottom temperature of the secondary concentration tower is -150°C to -155°C, and the top temperature of the secondary concentration tower is -155°C to -165°C.

[0103] Exemplarily, the secondary low-temperature cold box is also configured to heat the gas phase at the top outlet of the secondary concentration tower to 30°C to 50°C.

[0104] Exemplarily, the helium cold box is configured to cool the liquid phase output from the discharge port of the molecular sieve dehydration and decarbonization device to -175°C to -185°C.

[0105] Exemplarily, the top temperature of the cryogenic distillation tower (three-stage distillation tower) is -185°C to -195°C.

[0106] Exemplarily, the pressure swing adsorption unit is pressurized to obtain a qualified helium product, and the qualified helium product is transported to a storage facility.

[0107] In another aspect, some embodiments provided by the present disclosure exemplarily provide a device for extracting helium from natural gas while collecting carbon dioxide, the device comprising the above-mentioned device, and the device further comprising:

[0108] A third low-temperature separator, wherein the bottom discharge port of the first-stage concentration tower is connected to the feed port of the third low-temperature separator;

[0109] A demethanizer, wherein the gas phase outlet of the third low-temperature separator is connected to the second (upper) feed inlet of the demethanizer;

[0110] The liquid phase discharge port of the third low-temperature separator is communicated with the feed port of the low-temperature separator of the demethanizer, the gas phase discharge port of the low-temperature separator of the demethanizer is communicated with the second (upper) feed port of the demethanizer, and the liquid phase discharge port of the low-temperature separator of the demethanizer is communicated with the first (middle) feed port of the demethanizer;

[0111] The liquid phase discharge port of the third low-temperature separator is connected to the feed port of the low-temperature separator of the demethanizer through at least two independent pipelines, wherein one independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the top condenser of the first-level concentration tower, and the top condenser of the first-level concentration tower is configured to reheat the liquid phase in the pipeline; the other independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to reheat the liquid phase in the pipeline.

[0112] The top outlet of the demethanizer is communicated with a natural gas transmission pipeline.

[0113] Exemplarily, the ratio of the flow rate of the liquid phase flowing through the top condenser of the primary concentration tower to the flow rate of the liquid phase flowing through the primary low-temperature cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time;

[0114] Exemplarily, the top discharge port of the demethanizer is connected to the natural gas export pipeline through an independent pipeline, and at least part of the independent pipeline connecting the top discharge port of the demethanizer and the natural gas export pipeline is located in the first-level cryogenic cold box, and the first-level cryogenic cold box is also configured to reheat the pipeline.

[0115] Exemplarily, the liquid phase discharge port at the bottom of the demethanizer is connected to the gas phase feed port at the bottom of the demethanizer through an independent pipeline, and the independent pipeline connecting the liquid phase discharge port at the bottom of the demethanizer and the gas phase feed port at the bottom of the demethanizer is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to reboil the liquid phase in the pipeline, optionally, the reboiling temperature is 20°C to 35°C; the liquid phase discharge port at the bottom of the demethanizer is also connected to the feed port of the deethanizer.

[0116] Exemplarily, the ratio of the liquid phase flow entering the deethanizer to the liquid phase flow passing through the primary cryogenic cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time; the top gas outlet of the deethanizer is connected to the feed inlet of the top condenser of the deethanizer, the gas phase outlet of the top condenser of the deethanizer is connected to the feed inlet of the ethaneamine decarbonization device, and the liquid phase outlet of the top condenser of the deethanizer is connected to the top reflux feed inlet of the deethanizer;

[0117] The bottom discharge port of the deethanizer is connected with the feed port of the liquefied gas tower, the top gas of the liquefied gas tower is connected with the liquefied petroleum gas export pipeline, and the bottom of the liquefied gas tower is connected with the stable light hydrocarbon export pipeline; the top discharge port of the deethanizer is connected with the bottom feed port of the ethaneamine decarbonization absorption tower; the top material outlet of the ethaneamine decarbonization absorption tower is connected with the ethane output pipeline, the bottom discharge port of the ethaneamine decarbonization absorption tower is connected with the feed port of the carbon dioxide absorption liquid regeneration device, and the carbon dioxide discharge port of the carbon dioxide absorption liquid regeneration device is connected with the carbon dioxide export pipeline.

[0118] The sequential distillation helium extraction process (helium extraction first and then ethane recovery and LNG co-production process) proposed in the present disclosure can significantly reduce the investment and energy consumption of the system by changing the separation order of different components such as ethane and N2 (including helium and methane). At the same time, the first-stage concentration tower further widens the difference between the bubble point and dew point curves, making the operation of the entire tower more stable. In addition, the difficulty of operating the first-stage concentration tower is reduced. The top of the tower does not accurately control the CO2 content, and a large amount of CO2 is removed through low-temperature distillation, which simplifies the raw gas amine method CO2 removal unit. The obtained liquid CO2 can also be used for CCUS-EOR (carbon dioxide enhanced oil recovery), which improves product quality and oil field recovery.

[0119] The present invention discloses a method and device for extracting helium and recovering carbon dioxide by cryogenic distillation. The method adjusts the separation order of ethane and helium components and innovatively proposes a process for co-producing LNG by first extracting helium and then recovering ethane (see Appendix). Figure 2 ), the conventional indirect distillation process (recovering ethane first and then extracting helium to produce LNG) was reduced from two depressurization and three pressurization to one depressurization and two pressurization, reducing the total energy consumption of the system by 15%. + The raw gas of the components is rich in gas quality components, and the temperature difference of the primary concentration tower is about 8℃. Under the same working conditions, the temperature difference of the primary concentration tower using the indirect distillation process is about 3℃. If it is assumed that the operation of the primary concentration tower is disturbed only when the temperature of the sequential distillation primary concentration tower changes by 1℃, then the operation of the primary concentration tower may be disturbed when the temperature of the indirect distillation primary concentration tower changes by 0.3℃. Therefore, the sequential distillation process is superior to the indirect distillation process in terms of operation stability and reliability, which improves the operation stability of the primary concentration tower. At the same time, the CO2 is removed by using the cold capacity of low-temperature distillation, eliminating the amine decarbonization unit, and the recovered liquid CO2 can also be used for oil displacement to improve the oil field recovery rate.

[0120] The disclosed method proposes a process for producing LNG by first extracting helium and then recovering ethane, and performs distillation separation on nitrogen (containing hydrogen + helium), methane, and ethane (containing propane and heavy hydrocarbons) in order according to the boiling points of different components in the raw natural gas;

[0121] The first stage of concentration realizes the separation of nitrogen (including hydrogen + helium) and methane.

[0122] The demethanizer separates methane from ethane;

[0123] The secondary concentration tower realizes the separation of methane and helium; the tertiary concentration tower realizes the separation of nitrogen and helium, etc.

[0124] The helium is concentrated by two-stage cryogenic distillation. The helium concentration ratio is 380 times through the first and second stage cryogenic distillation, and the helium is concentrated to about 16%. The third stage cryogenic distillation concentrates the helium to about 80%. Then it is connected to the pressure swing adsorption unit to purify the helium product to 99.999%. The methane gas from the first concentration tower is first passed through the demethanizer to obtain ethane liquid phase and pure methane gas, and then pressurized to the natural gas pipeline network. Then the ethane gas phase and C3 + Liquid hydrocarbons and ethane gas phase pass through the amine decarbonization and dehydration device to obtain two types of products: liquid CO2 and liquid ethane. The main equipment of the whole process is the first-stage cryogenic cold box, the first-stage concentration tower, the demethanization tower, the first-stage cryogenic cold box and the second-stage concentration tower. See the attached Figure 1 and attached Figure 4 .

[0125] In combination with the attached embodiment of the present disclosure Figure 3 and attached Figure 4 , clearly and completely describe the technical solutions in the embodiments of the present disclosure.

[0126] The raw gas is commercial natural gas or gas from a gas gathering station, with gas composition and operating conditions (absolute pressure).

[0127] Raw gas processing scale: 3000×10 4 Nm 3 / d

[0128] Raw gas pressure: 4.5MPa

[0129] Station entry temperature: 20℃

[0130] External transmission pressure: ≥5.0MPa

[0131] Dew point of gas and water for external transmission: <-5℃

[0132] The composition of the raw gas is shown in Table 1.

[0133] Table 1 Raw gas composition (saturated with water)

[0134] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C4H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H 12 ]]> <![CDATA[C6]]> <![CDATA[C7 <!-- 9 -->]]> composition 93.4401 3.9234 0.6708 0.1185 0.1161 0.0543 0.0224 0.0438 0.0270 Components <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> CO2 He <![CDATA[H2]]> <![CDATA[C2H4]]> <![CDATA[H2S]]> composition 0.0070 0.0000 0.0000 0.5067 0.9908 0.0401 0.0156 0.0000 0.0002 Components <![CDATA[H2O]]> Cyclopentane Cyclohexane benzene Mcycoctane <![CDATA[O2]]> Ar neon Methanol composition 0.0000 0.0053 0.0005 0.0063 0.0086 0.0000 0.0000 0.0000 0.0009

[0135] like Figure 3 and Figure 4As shown, the present disclosure discloses a method and device for extracting helium and recovering carbon dioxide by cryogenic distillation. The specific process is as follows:

[0136] 1) Conditions for the discharge of helium-rich natural gas from the top of the first-stage concentration tower

[0137] Pressure: 3.65MPa.g;

[0138] Temperature: -92°C;

[0139] Flow rate: 71×10 4 m 3 / d

[0140] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C4H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H 12 ]]> <![CDATA[C6]]> <![CDATA[C7]]> composition 94.9519 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Components <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> <![CDATA[C2H4]]> <![CDATA[H2S]]>

[0141] composition 0 0.0000 0.0000 3.8707 0.0027 0.8602 0.3144 0.0000 0.0000 Components <![CDATA[H2O]]> Cyclopentane Cyclohexane benzene Mcycoctane <![CDATA[O2]]> Ar neon Methanol composition 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0142] 2) Conditions for the outlet of liquid methane from the bottom of the primary concentration tower

[0143] Pressure: 3.68MPa.g

[0144] Temperature: -86.70℃

[0145] Condensate flow rate: 3.456×10 4 m 3 / d(under working conditions)

[0146] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C4H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H 12 ]]> <![CDATA[C6]]> <![CDATA[C7]]> composition 94.8053 3.43 0.3614 0.0351 0.0255 0.0054 0.0016 0.0010 0.0002 Components <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> CO2 He <![CDATA[H2]]> <![CDATA[C2H4]]> <![CDATA[H2S]]> composition 0 0.0000 0.0000 0.3547 0.9777 0.0005 0.001 0.0000 0.0002 Components <![CDATA[H2O]]> Cyclopentane Cyclohexane benzene Mcycoctane <![CDATA[O2]]> Ar neon Methanol composition 0.0001 0.0001 0.0000 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000

[0147] The flow rate of helium-containing raw gas is 1500×10 4 Nm 3 / d, the helium content is 400ppm, and the carbon dioxide content is about 1%. The above natural gas enters the primary concentration device area after being treated with mercury removal, dehydration, pressurization and temperature adjustment. First, it enters the primary low-temperature cold box for precooling to -69°C. The gas and liquid phases enter the primary low-temperature cold box for supercooling and then enter the first low-temperature separator to remove the heavy components. The liquid phase goes directly to the downstream demethanizer. The gas phase goes to the bottom of the primary concentration tower as a reboiling heat source and is cooled to -76°C. Then it enters the second low-temperature separator for gas-liquid separation. After separation, the liquid phase directly enters the primary concentration tower through the first feed port (lower feed port). The gas phase enters the primary low-temperature cold box for supercooling to -92°C and then enters the primary concentration tower after throttling. The bottom temperature and top temperature of the primary concentration tower are controlled at above -83°C and -92°C respectively to avoid the formation of CO2 dry ice. After low-temperature distillation in the primary concentration tower, a helium feed gas rich in light components of N2 (3.8%), helium (0.86%), and hydrogen (0.3%) is obtained at the top of the tower, and most of the liquid methane, C2+, and carbon dioxide are separated at the bottom of the primary concentration tower. The light components rich in N2, helium, and hydrogen at the top of the primary concentration tower enter the secondary concentration device area for further treatment, and the output from the bottom of the primary concentration tower enters the demethanization unit for further treatment.

[0148] The natural gas rich in N2, H2, and He light components at the top of the primary concentration tower enters the secondary concentration device area, first enters the molecular sieve decarbonization device after reheating in the secondary low-temperature cold box to remove the carbon dioxide content to below 10ppm, and then enters the secondary concentration tower for low-temperature distillation and concentration, and the crude helium obtained at the top of the secondary concentration tower. The liquid methane at the bottom of the primary concentration tower is throttled to 2.7MPa.g and enters the third low-temperature separator at -95℃. The gas phase logistics of the third low-temperature separator directly enters the second (upper) feed port of the downstream demethanizer. 35% of the liquid phase of the liquid phase discharge of the low-temperature separation gas 3 enters the condenser at the top of the primary concentration tower to provide cold and reheat to -94℃, and 65% of the liquid phase enters the primary low-temperature cold box to recover cold and reheat to -93℃. After reheating, two liquid phases of different proportions enter the demethanizer feed low-temperature separator, and the gas phase and liquid phase of the demethanizer feed low-temperature separator enter the middle and upper part of the demethanizer separately.

[0149] In addition, a stream of product natural gas from the product gas booster is supercooled to -98℃ in the first-stage low-temperature cold box and liquefied, and then enters the demethanizer as the top reflux liquid of the demethanizer. In the middle of the demethanizer, the measuring line 1 (-94℃) is drawn into the first-stage low-temperature cold box to provide cold capacity, reheat to -90℃, and then returns to the middle of the demethanizer. The measuring line 2 (-90℃) is drawn into the first-stage low-temperature cold box to provide cold capacity, reheat to -76℃, and then returns to the middle of the demethanizer to provide heat for the evaporation of methane in the tower. The product natural gas (-98°C) flowing out of the top of the demethanizer enters the first-stage low-temperature cold box for reheating to 26°C, and then is pressurized and transmitted externally through the product gas booster device; the 8°C C2+ liquid hydrocarbons recovered at the bottom of the demethanizer are pressurized by the bottom booster pump and divided into two streams, one of which is 75% of the flow rate of C2+ liquid hydrocarbons and is sent to the first-stage low-temperature cold box for reboiling, and the gas-liquid two phases are reboiled to 22°C and returned to the gas phase space at the bottom of the demethanizer, and the other is 25% of the flow rate of C2+ liquid hydrocarbons and is sent to the downstream deethanizer.

[0150] The C2+ mixed hydrocarbons (temperature 8.6℃, pressure 3.1MPa.g) from the demethanizer of the liquid hydrocarbon recovery unit enter the deethanizer, and carbon-containing ethane gas is obtained at the top of the tower through distillation separation, and C3+ mixed hydrocarbons are obtained at the bottom of the tower. The top gas of the deethanizer is cooled by the top condenser and enters the reflux tank of the deethanizer to separate into gas and liquid phases. The liquid phase is pressurized by the top reflux pump and returns to the top of the deethanizer as reflux liquid, and the gas phase enters the downstream ethane decarbonization unit area. The C3+ mixed hydrocarbons obtained at the bottom of the deethanizer enter the liquefied gas tower and are separated by distillation to obtain liquefied petroleum gas at the top of the liquefied gas tower, and stable light hydrocarbons are obtained at the bottom of the liquefied gas tower. The liquefied petroleum gas is cooled to 50℃ by the top air cooler and is completely condensed and liquefied before entering the liquefied gas reflux tank. After being pressurized by the pump, a part of it returns to the top of the liquefied gas tower as reflux liquid, and the rest is further water-cooled to 40℃ and sent to the liquefied gas storage tank. The stabilized light hydrocarbons at the bottom of the liquefied gas tower are cooled to 40°C by air cooling and water cooling in turn to stabilize the light hydrocarbon storage tank.

[0151] The carbon-containing ethane (temperature -2°C) from the top of the deethane tower of the liquid hydrocarbon separation unit enters the gas-to-gas heat exchanger and exchanges heat with the wet ethane after decarbonization (temperature 40°C) to heat up and then enter the bottom of the ethane amine decarbonization absorption tower. In the ethane amine decarbonization absorption tower, the carbon-containing ethane first contacts with the lean amine liquid in countercurrent from bottom to top, and the CO2 in the ethane gas is deeply removed to less than 0.05%. The wet ethane obtained at the top of the absorption tower is cooled by the gas-to-gas heat exchanger, enters the wet ethane separator to separate free water, and then enters the subsequent dehydration device for output. The rich amine liquid flowing out from the bottom of the ethane amine decarbonization absorption tower is reduced in pressure to 0.50MPa and then enters the amine liquid flash tank and the amine liquid regeneration tower in turn to analyze the CO2 gas dissolved in the amine liquid, and the lean amine liquid is cooled and returned to the ethane amine decarbonization absorption tower for cyclic decarbonization. The 30℃, 2.6MPa.a ethane gas from the ethane decarbonization unit is divided into two paths after passing through the pre-filter (coalescing filter). The ethane gas and the regenerated dry gas are mixed and enter the ethane amine decarbonization adsorption tower from the top. The water content of the dry ethane gas at the bottom of the ethane amine decarbonization adsorption tower is ≤0.1ppm. The dry ethane gas is filtered by the post-filter and enters the downstream device. The carbon dioxide tail gas generated by the ethane decarbonization unit is pressurized to 2.4MPa.g, and then undergoes solid desulfurization and molecular sieve dehydration in turn, and is cooled to -20℃ for liquefaction before being transported out.

[0152] Secondary concentration device: mainly removes most of the methane, carbon dioxide and nitrogen through low-temperature distillation separation process to obtain crude helium.

[0153] 1) Parameters of natural gas for helium feedstock entering the device:

[0154] Temperature: -92°C;

[0155] Pressure: 3.65MPa.g;

[0156] Helium raw gas flow rate: 142×10 4 Nm 3 / d;

[0157] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C4H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H2]]> <![CDATA[C6 <!-- 11 -->]]> composition 94.9519 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Components <![CDATA[C7]]> <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> composition 0.0000 0.0000 0.0000 0.0000 3.8707 0.0000 0.8602 0.3144 Components <![CDATA[H2S]]> <![CDATA[H2O]]> Cyclopentane Cyclohexane Toluene Methylcyclohexane <![CDATA[O2]]> Ar composition 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0158] 2) Crude helium product from the device

[0159] Temperature: 37°C

[0160] Pressure: 2.45MPa.g;

[0161] Flow rate: 58000Nm 3 / d;

[0162] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C4H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H 12 ]]> <![CDATA[C6]]> composition 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Components <![CDATA[C7]]> <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> composition 0.0000 0.0000 0.0000 0.0000 71.2554 0.0000 21.0446 7.6899 Components <![CDATA[H2S]]> <![CDATA[H2O]]> Cyclopentane Cyclohexane Toluene Methylcyclohexane <![CDATA[O2]]> Ar composition 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0163] 3) LNG parameters of the outlet device

[0164] Temperature: -162°C;

[0165] Pressure: 2470 kPa.g;

[0166] Flow rate: 17676kg / h;

[0167] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[C3H8]]> <![CDATA[i-C a H 10 ]]> <![CDATA[n-C4H 10 ]]> <![CDATA[i-C5H 12 ]]> <![CDATA[n-C5H 12 ]]> <![CDATA[C6]]> composition 0.9900 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Components <![CDATA[C7]]> <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> composition 0.0000 0.0000 0.0000 0.0000 1.0000 0.0000 0.0000 0.0000 Components <![CDATA[H2S]]> <![CDATA[H2O]]> Cyclopentane Cyclohexane Toluene Methylcyclohexane <![CDATA[O2]]> Ar composition 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

[0168] The helium raw natural gas from the primary concentration tower at -92℃ first enters the secondary low-temperature cold box for reheating to 30℃, then enters the molecular sieve decarbonization device to remove CO2 to 1ppm, then enters the secondary low-temperature cold box to cool to -92℃, enters the reboiler at the bottom of the secondary concentration tower to cool to -95℃, and then enters the fourth low-temperature separator for gas-liquid two-phase separation. The liquid phase enters the secondary low-temperature cold box to be supercooled to -110℃ and enters the secondary concentration tower through the second feed port (upper feed port). The gas phase enters the secondary low-temperature cold box for supercooling and liquefaction, and enters the secondary concentration tower after being cooled to -140℃ in the secondary low-temperature cold box. The operating pressure of the secondary concentration tower is 2.5MPa.g. Crude helium with a helium concentration of 21% is obtained at the top of the secondary concentration tower through low-temperature distillation separation, and a logistics by-product LNG with methane as the main component is obtained at the bottom of the secondary concentration tower. The liquid methane enters the secondary low-temperature cold box to be supercooled to -160℃ and then enters the storage tank as an LNG product for storage. The crude helium is reheated to 37°C through a secondary cryogenic cold box and then enters the downstream crude helium dehydrogenation unit.

[0169] The top condenser of the secondary concentration tower requires a -159℃ cold source. A mixed refrigerant is used to provide low-temperature coldness for the condensation at the top of the secondary concentration tower, ensuring the reflux rate and distillation accuracy of the secondary concentration tower and improving the concentration of crude helium products. The solid state temperature of pure methane is -182.46℃. To prevent freezing of low-temperature methane, the top temperature of the tower is controlled at ≤-159℃ after process optimization. The methane content in the crude helium gas at the top of the tower is 136ppm, ensuring that there is no freezing of low-temperature methane. In addition, the helium-rich natural gas from the primary concentration tower is reheated and enters the molecular sieve decarbonization device to remove CO2, so that the CO2 content entering the secondary concentration device is far lower than the concentration of dry ice generated, ensuring the stable operation of the secondary concentration tower.

[0170] Crude helium dehydrogenation unit: The hydrogen content in the crude helium from the secondary concentration unit reaches 7.6%, which cannot meet the quality requirements of helium products and needs to be removed to below 0.1ppm.

[0171] 1) Parameters of crude helium entering the device

[0172] Temperature: 37°C

[0173] Pressure: 2.45MPa.g;

[0174] Flow rate: 6×10 4 Nm 3 / d;

[0175] Components <![CDATA[CH4]]> <![CDATA[C2H6]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> <![CDATA[O2]]> Ar composition 0.000102 0.000000 0.714166 0.000000 0.209237 0.076493 0.000000 0.000000

[0176] 2) Air parameters entering the device

[0177] Temperature: 40℃;

[0178] Pressure: 2.5MPa.g

[0179] Flow rate: 10836Nm 3 / d;

[0180] Components <![CDATA[N2]]> <![CDATA[CO2]]> <![CDATA[O2]]> Ar composition 78.1 0.032 20.9 0.939

[0181] 3) Parameters of crude helium out of the device

[0182] Temperature: 40℃;

[0183] Pressure: 2.42MPa.g;

[0184] Flow rate: 6.5×10 4 Nm 3 / d;

[0185] Components <![CDATA[CH4]]> <![CDATA[O2]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> <![CDATA[H2O]]> Ar composition 0.000090 0.000547 0.803151 0.000053 0.190737 0.000000 0.003859 0.001564

[0186] The hydrogen content in crude helium is 7.6%. In order to facilitate the control of reactor temperature, a four-stage catalytic oxidation dehydrogenation process is recommended. Each stage of the dehydrogenation device consists of an electric heater, a reactor, a water cooler and a separator. When put into production, the crude helium from the cryogenic rectification device is mixed with the supplementary air and enters the primary reactor (an electric heater is required to activate the catalyst during the first operation). The amount of oxygen introduced is controlled by detecting that the outlet temperature of the primary reactor is ≤200°C. Hydrogen reacts with oxygen inside the reactor to generate water. After the primary reaction, the hydrogen concentration in the crude helium is reduced from 7.6% to below 5.4%; then it enters the secondary reactor for reaction, and the hydrogen concentration in the crude helium is reduced from 5.4% to below 3.5% after the reaction; then it enters the tertiary reactor for reaction, and the hydrogen concentration in the crude helium is reduced from 3.5% to below 1.6% after the reaction; then it enters the quaternary reactor for reaction, and the hydrogen concentration in the crude helium is reduced from 1.6% to 0 (hydrogen content ≤1ppm) after the reaction. The amount of air introduced into the quaternary reaction is controlled by the outlet oxygen content (oxygen content ≤100ppm). Finally, the crude helium after dehydrogenation enters the water cooler for cooling and then enters the separator to separate the free water contained therein, and then the crude helium is transported to the downstream dehydration device. An online oxygen and hydrogen detection analyzer is installed at the outlet of the dehydrogenation device to monitor the dehydrogenation effect and oxygen content online.

[0187] Helium purification device: The crude helium after dehydrogenation contains impurity gases such as nitrogen, methane, water, oxygen, argon, carbon dioxide, etc. The above impurity gases need to be removed to achieve the product quality requirements of pure helium.

[0188] 1) Parameters of crude helium entering the device

[0189] Temperature: 40℃;

[0190] Pressure: 2.34MPa.g;

[0191] Flow rate: 6.6×10 4 Nm 3 / d;

[0192] Components <![CDATA[CH4]]> <![CDATA[O2]]> <![CDATA[N2]]> <![CDATA[CO2]]> He <![CDATA[H2]]> <![CDATA[H2O]]> Ar composition 0.000091 0.000053 0.804264 0.000053 0.189651 0.000000 0.003859 0.001555

[0193] 2) Parameters of pure helium out of the device

[0194] Temperature: 40℃;

[0195] Pressure: 25MPa.g;

[0196] Flow rate: 1.2×10 4 Nm 3 / d;

[0197] Helium concentration: 99.999%;

[0198] As attached Figure 4 As shown, this unit adopts the "cryogenic distillation + pressure swing adsorption" process to purify helium. The crude helium after dehydrogenation contains saturated water and carbon dioxide. The molecular sieve adsorption method is used for deep dehydration and decarbonization, and the water in the crude helium is removed to below 0.1ppm, and the carbon dioxide is removed to below 0.1ppm; the dehydrated crude helium enters the cryogenic distillation device to remove most of the impurity gases such as nitrogen, methane, oxygen, carbon dioxide, argon, etc., to obtain crude helium with a helium content of 82%; the crude helium is purified by the pressure swing adsorption unit to obtain a pure helium product (helium content 99.999%).

[0199] The molecular sieve dehydration and decarbonization adopts a three-tower process, 1 tower for adsorption, 1 tower for heating, and 1 tower for cold blowing. The operating status of each tower is switched every 8 hours. The crude helium from the dehydrogenation unit first passes through the filter to remove the droplets and solid particles entrained in the gas flow. The crude helium passes through the adsorption tower in the adsorption state from top to bottom. The water and carbon dioxide contained in the crude helium are adsorbed by the molecular sieve. The dehydrated crude helium passes through the dust filter and enters the downstream low-temperature distillation device. The molecular sieve regeneration gas uses nitrogen. The nitrogen enters the regeneration gas electric heater and is heated to 280°C. Then it enters the adsorption tower in the hot blowing state from bottom to top. The water adsorbed by the molecular sieve in the adsorption tower is analyzed and enters the regeneration gas water cooler and regeneration gas separator in sequence with the hot regeneration gas. The free water contained in the regeneration gas is separated, and the regeneration gas is pressurized and enters the external natural gas pipeline.

[0200] The subsequent cryogenic distillation unit will increase the crude helium concentration from 19% to 82%: the crude helium after dehydration and decarbonization enters the helium cold box and is cooled to -180°C, and is depressurized to 1.6MPa.g by the throttle valve and enters the three-stage distillation tower. The operating pressure of the three-stage distillation tower is 1.4MPa.g, and the helium temperature at the top of the three-stage distillation tower is -188.9°C. It enters the helium cold box and is reheated to 37°C to go to the pressure swing adsorption unit. A portion of the cryogenic liquid at the bottom of the three-stage distillation tower is diverted to -162°C, and is depressurized to 0.58MPa.g by the throttle valve and enters the helium cold box and is reheated to 37°C. It enters the molecular sieve dehydration and decarbonization device as regeneration gas, and then enters the nitrogen compressor to increase the pressure to 5.9MPa.g and returns to the natural gas for external transmission. Another portion of the cryogenic liquid at the bottom of the three-stage distillation tower is -162°C, and enters the helium cold box for partial gasification and returns to the bottom of the three-stage distillation tower to provide a heat source for the distillation tower. The cold source at the top of the three-stage distillation tower is low-temperature nitrogen. The nitrogen refrigerant is pressurized by 0.1MPa.g through the nitrogen refrigerant compressor, cooled to -163℃ in the helium cold box, and then reduced to 0.5MPa.g through the throttle valve after liquefaction. The temperature is reduced to -192℃ and then enters the top condenser of the three-stage distillation tower and the helium cold box to provide cooling capacity. The reheated low-pressure nitrogen returns to the nitrogen refrigerant compressor for pressurization, thus completing a refrigeration cycle.

[0201] Pressure swing adsorption process: Crude helium (82%) from the cryogenic distillation unit enters the pressure swing adsorption unit, and the impurity gas contained in the crude helium is adsorbed by the solid adsorbent, and a helium product with a concentration of 99.999% is obtained at the outlet of the adsorption tower. The helium product is pressurized and enters the downstream storage facility. The analytical gas generated during the depressurization and regeneration process of the adsorption tower is pressurized and returned to the dehydrogenation unit to circulate and recover the helium it contains.

Claims

1. A device for extracting helium from natural gas, characterized in that: The device comprises: Primary enrichment device, secondary enrichment device and helium refining unit; The primary concentration device comprises a primary low temperature cold box and a primary concentration tower which are connected in sequence; the primary low temperature cold box is connected to the raw natural gas pipeline; The secondary concentration device comprises a secondary low-temperature cold box and a secondary concentration tower which are connected in sequence, and the top discharge port of the primary concentration tower is connected to the feed port of the secondary low-temperature cold box; The helium refining unit comprises a crude helium dehydrogenation device and a helium purification device which are connected in sequence, and the helium purification device outputs a helium product; the top outlet of the secondary concentration tower is connected to the feed inlet of the crude helium dehydrogenation device.

2. The device for extracting helium from natural gas according to claim 1, characterized in that: The raw natural gas pipeline includes a raw natural gas pretreatment device, The raw natural gas pretreatment device is configured to remove mercury, dehydrate, increase pressure and adjust temperature of the raw natural gas.

3. The device for extracting helium from natural gas according to claim 1, characterized in that: A first low-temperature separator is further provided between the first low-temperature cold box and the first concentration tower, the outlet of the first low-temperature cold box is communicated with the inlet of the first low-temperature separator, and the gas phase outlet of the first low-temperature separator is communicated with the reboiler heat source feed port of the reboiler provided at the bottom of the first concentration tower; Optionally, the liquid phase discharge port of the first low-temperature separator is connected to the feed port of the demethanizer.

4. The device for extracting helium from natural gas according to claim 3, characterized in that: The reboiler heat source outlet of the reboiler is communicated with the second low-temperature separator, the liquid phase outlet of the second low-temperature separator is communicated with the first feed inlet of the raw material of the primary concentration tower, the gas phase outlet of the second low-temperature separator is communicated with the second feed inlet of the raw material of the primary concentration tower through an independent pipeline, and the independent pipeline connecting the gas phase outlet of the second low-temperature separator and the second feed inlet of the raw material of the primary concentration tower is at least partially located in the primary low-temperature cold box, and the primary low-temperature cold box is further configured to cool the gas phase in the independent pipeline; Optionally, the bottom outlet of the primary concentration tower is connected to the feed inlet of the demethanizer tower.

5. The device for extracting helium from natural gas according to claim 1, characterized in that: The secondary concentration device also includes a molecular sieve decarbonization device arranged between the secondary low-temperature cold box and the secondary concentration tower; The discharge port of the secondary low-temperature cold box is connected to the feed port of the molecular sieve decarbonization device, and the discharge port of the molecular sieve decarbonization device is connected to the reboiler heat source feed port of the reboiler provided at the bottom of the secondary concentration tower; The reboiling heat source outlet of the reboiling device at the bottom of the secondary concentration tower is connected to the feed port of the fourth low-temperature separator, the gas phase outlet of the fourth low-temperature separator is connected to the first feed port of the secondary concentration tower, and the liquid phase outlet of the fourth low-temperature separator is connected to the second feed port of the secondary concentration tower; The discharge port of the molecular sieve decarbonization device is connected to the reboiling heat source feed port of the reboiling device at the bottom of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the discharge port of the molecular sieve decarbonization device and the reboiling heat source feed port of the reboiling device at the bottom of the secondary concentration tower is at least partially located in a secondary low-temperature cold box, and the secondary low-temperature cold box is also configured to cool the gas phase in the pipeline; The gas phase outlet of the fourth low-temperature separator is connected to the first feed inlet of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the gas phase outlet of the fourth low-temperature separator and the first feed inlet of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is further configured to cool the gas phase in the pipeline; The liquid phase outlet of the fourth low-temperature separator is connected to the second feed inlet of the secondary concentration tower through an independent pipeline, and the independent pipeline connecting the liquid phase outlet of the fourth low-temperature separator and the second feed inlet of the secondary concentration tower is at least partially located in the secondary low-temperature cold box, and the secondary low-temperature cold box is further configured to cool the liquid phase in the independent pipeline; Optionally, the secondary cryogenic cold box is configured to reheat the gas phase output from the top outlet of the primary concentration tower; Optionally, the bottom discharge port of the secondary concentration tower is connected to a liquid natural gas transmission pipeline.

6. The device for extracting helium from natural gas according to claim 5, characterized in that: The top discharge port of the secondary concentration tower is connected to the feed port of the crude helium dehydrogenation device through an independent pipeline. The independent pipeline connecting the top discharge port of the secondary concentration tower and the feed port of the crude helium dehydrogenation device is at least partially located in a secondary low-temperature cold box. The secondary low-temperature cold box is also configured to reheat the gas phase in the pipeline.

7. The device for extracting helium from natural gas according to any one of claims 1 to 6, characterized in that: The helium refining unit also includes a molecular sieve dehydration and decarbonization device, the discharge port of the crude helium dehydrogenation device is connected to the feed port of the molecular sieve dehydration and decarbonization device, and the discharge port of the molecular sieve dehydration and decarbonization device is connected to the helium cold box of the helium purification device.

8. The device for extracting helium from natural gas according to claim 7, characterized in that: The helium purification device comprises the helium cold box, the cryogenic distillation tower and the pressure swing adsorption unit which are connected in sequence; The discharge port of the helium cold box is connected to the feed port of the cryogenic distillation tower, the first discharge port at the bottom of the cryogenic distillation tower is connected to the natural gas export pipeline through an independent pipeline, the independent pipeline connecting the first discharge port at the bottom of the cryogenic distillation tower and the natural gas export pipeline is at least partially located in the helium cold box, and the helium cold box is configured to perform heat exchange and temperature increase on the pipeline; The second discharge port at the bottom of the cryogenic distillation tower is connected to the gas phase feed port at the bottom of the cryogenic distillation tower through an independent pipeline, and the independent pipeline connecting the second discharge port at the bottom of the cryogenic distillation tower and the gas phase feed port at the bottom of the cryogenic distillation tower is at least partially located in a helium cold box, and the helium cold box is further configured to heat the liquid phase in the pipeline; The top discharge port of the cryogenic distillation tower is connected to the feed port of the pressure swing adsorption unit through an independent pipeline. The independent pipeline connecting the top discharge port of the cryogenic distillation tower and the feed port of the pressure swing adsorption unit is at least partially located in a helium cold box. The helium cold box is also configured to heat the gas phase in the pipeline.

9. A method for extracting helium from natural gas, characterized in that: Using the device for extracting helium from natural gas according to claim 8, the method comprises: The raw natural gas is subjected to mercury removal, dehydration, pressurization and temperature adjustment treatments; Optionally, mercury removal to 10 ng / m 3 Below, dehydrate to below 0.1ppm; Optionally, the primary cryogenic cold box cools the temperature of the raw natural gas to -60°C to -75°C; Optionally, the bottom temperature of the primary concentration tower is -75°C to -90°C, and the top temperature of the primary concentration tower is -90°C to -105°C; Optionally, the gas phase is cooled to -70°C to -85°C by a reboiler provided at the bottom of the primary concentration tower; Optionally, the secondary low-temperature cold box is configured to reheat the temperature of the gas phase output from the top outlet of the primary concentration tower to 20°C to 50°C; the molecular sieve decarbonization device is configured to remove carbon dioxide from the reheated gas phase output from the top outlet of the primary concentration tower to less than 10 ppm, and the secondary low-temperature cold box is further configured to cool the gas phase treated by the molecular sieve decarbonization device to -80°C to -95°C; The reboiler provided at the bottom of the secondary concentration tower is configured to further cool the liquid phase cooled to -80°C to -95°C to -95°C; The bottom temperature of the secondary concentration tower is -150°C to -155°C, and the top temperature of the secondary concentration tower is -155°C to -165°C; Optionally, the secondary low-temperature cold box is further configured to heat the gas phase at the top outlet of the secondary concentration tower to 30° C. to 50° C.; Optionally, the helium cold box is configured to cool the liquid phase output from the discharge port of the molecular sieve dehydration and decarbonization device to -175°C to -185°C; Optionally, the top temperature of the cryogenic distillation tower is -185°C to -195°C; Optionally, the pressure swing adsorption unit is pressurized to obtain a qualified helium product, and the qualified helium product is transported to a storage facility.

10. A device for extracting helium from natural gas and collecting carbon dioxide at the same time, characterized in that: The device comprises the device of claim 8, and further comprises: A third low-temperature separator, wherein the bottom discharge port of the first-stage concentration tower is connected to the feed port of the third low-temperature separator; A demethanizer, wherein the gas phase outlet of the third low-temperature separator is connected to the second feed inlet of the demethanizer; The liquid phase discharge port of the third low-temperature separator is communicated with the feed port of the low-temperature separator of the demethanizer, the gas phase discharge port of the low-temperature separator of the demethanizer is communicated with the second feed port of the demethanizer, and the liquid phase discharge port of the low-temperature separator of the demethanizer is communicated with the first feed port of the demethanizer; The liquid phase discharge port of the third low-temperature separator is connected to the feed port of the low-temperature separator of the demethanizer through at least two independent pipelines, wherein one independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the top condenser of the primary concentration tower, and the top condenser of the primary concentration tower is configured to reheat the liquid phase in the pipeline; another independent pipeline connecting the liquid phase discharge port of the third low-temperature separator and the feed port of the low-temperature separator of the demethanizer is at least partially located in the primary low-temperature cold box, and the primary low-temperature cold box is also configured to reheat the liquid phase in the pipeline; Optionally, the ratio of the flow rate of the liquid phase flowing through the top condenser of the primary concentration tower to the flow rate of the liquid phase flowing through the primary low-temperature cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time; The top outlet of the demethanizer is connected to a natural gas transmission pipeline; Optionally, the top discharge port of the demethanizer is connected to a natural gas export pipeline through an independent pipeline, and at least part of the independent pipeline connecting the top discharge port of the demethanizer and the independent pipeline of the natural gas export pipeline is located in the first-stage low-temperature cold box, and the first-stage low-temperature cold box is further configured to reheat the pipeline; The liquid phase discharge port at the bottom of the demethanizer is connected to the gas phase feed port at the bottom of the demethanizer through an independent pipeline, and the independent pipeline connecting the liquid phase discharge port at the bottom of the demethanizer and the gas phase feed port at the bottom of the demethanizer is at least partially located in the first-level low-temperature cold box, and the first-level low-temperature cold box is also configured to reboil the liquid phase in the pipeline, and optionally, the reboiling temperature is 20° C. to 35° C.; the liquid phase discharge port at the bottom of the demethanizer is also connected to the feed port of the deethanizer; Optionally, the flow ratio of the liquid phase entering the deethanizer to the liquid phase flowing through the primary cryogenic cold box is (0 to 80): (0 to 80), and the two do not take the value of 0 at the same time; the top gas outlet of the deethanizer is connected to the feed inlet of the top condenser of the deethanizer, the gas phase outlet of the top condenser of the deethanizer is connected to the feed inlet of the ethaneamine decarbonization device, and the liquid phase outlet of the top condenser of the deethanizer is connected to the top reflux feed inlet of the deethanizer; The bottom discharge port of the deethanizer is connected with the feed port of the liquefied gas tower, the top gas of the liquefied gas tower is connected with the liquefied petroleum gas export pipeline, and the bottom of the liquefied gas tower is connected with the stable light hydrocarbon export pipeline; the top discharge port of the deethanizer is connected with the bottom feed port of the ethaneamine decarbonization absorption tower; the top material outlet of the ethaneamine decarbonization absorption tower is connected with the ethane output pipeline, the bottom discharge port of the ethaneamine decarbonization absorption tower is connected with the feed port of the carbon dioxide absorption liquid regeneration device, and the carbon dioxide discharge port of the carbon dioxide absorption liquid regeneration device is connected with the carbon dioxide export pipeline.

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