Device for extracting crude helium from natural gas

Abstract

The utility model relates to the technical field of crude helium extraction from natural gas, in particular to a crude helium extraction device from natural gas. Comprising a first heat exchanger, a first helium extraction tower connected with the first heat exchanger, a second heat exchanger connected with the first helium extraction tower and the first heat exchanger, a second helium extraction tower connected with the second heat exchanger, a propane / propylene refrigerating system, an ethane / ethylene refrigerating system and a nitrogen-methane refrigerating system, and the crude helium refining and liquid nitrogen production system is connected with the second helium extraction tower. Compared with the prior art, the process flow of low-temperature helium extraction is optimized, and the heat exchange efficiency is improved, so that the helium extraction energy consumption is reduced; the crude helium refining and liquid nitrogen production system is used for producing a liquid nitrogen product, and the liquid nitrogen product is stored in a liquid nitrogen storage tank for subsequent crude helium purification and refined helium liquefaction.

Description

Technical Field

[0001] The utility model relates to the technical field of natural gas extraction of crude helium. Specifically, it is a device for extracting crude helium from natural gas. Background Technique

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

[0003] The purpose of the utility model is to provide a device for extracting crude helium from natural gas.

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

[0005] A device for extracting crude helium from natural gas includes a first heat exchanger, a first helium extraction tower connected to the first heat exchanger, a second heat exchanger respectively connected to the first helium extraction tower and the first heat exchanger, a second helium extraction tower connected to the second heat exchanger, a propane / propylene refrigeration system, an ethane / ethylene refrigeration system, and a nitrogen-methane refrigeration system respectively connected to the first heat exchanger, and a crude helium refining and liquid nitrogen production system connected to the second helium extraction tower.

[0006] In some possible implementation manners, the crude helium refining and liquid nitrogen production system includes a dehydrogenation and dehydration system, a flash condensation separation system, a nitrogen refrigeration system, a third heat exchanger, and a pressure swing adsorption system; wherein, the dehydrogenation and dehydration system is respectively connected to the top of the second helium extraction tower, the pressure swing adsorption system, and the third heat exchanger; the nitrogen refrigeration system is connected to the third heat exchanger.

[0007] In some possible implementation manners, the first heat exchanger includes a first pipeline connected to the propane / propylene refrigeration system and forming a circulation pipeline, a second pipeline connected to the ethane / ethylene refrigeration system and forming a circulation pipeline, a third pipeline respectively connected to the bottom of the first helium extraction tower and the second heat exchanger and serving as a tail gas export pipeline, a fourth pipeline respectively connected to the top condenser of the first helium extraction tower and the input end of the nitrogen-methane refrigeration system, a fifth pipeline respectively connected to the output end of the nitrogen-methane refrigeration system and the second heat exchanger, and a sixth pipeline serving as a helium-containing natural gas inlet pipe and connected to the first helium extraction tower; a liquid level control valve A is arranged on the pipeline where the third pipeline is connected to the bottom of the first helium extraction tower.

[0008] In some possible embodiments, a buffer tank is provided between the propane / propylene refrigeration system and the first pipeline;

[0009] One output port of the buffer tank is connected to the input end of the first pipeline; the other output opening of the buffer tank is connected to the input port of the propane / propylene refrigeration system;

[0010] The output end of the propane / propylene refrigeration system is connected to one input port of the buffer tank through an output pipeline, and the output end of the first pipeline is connected to the other input port of the buffer tank;

[0011] A J-T valve A is provided on the output pipeline.

[0012] In some possible embodiments, the second pipeline includes a first branch and a second branch located in the first heat exchanger, and outer pipelines located outside the first heat exchanger and connected to the first branch and the second branch respectively; the other end of the first branch is connected to the input end of the ethane / ethylene refrigeration system through an input pipeline, and the other end of the second branch is connected to the output end of the ethane / ethylene refrigeration system; a J-T valve B is provided on the outer pipeline.

[0013] In some possible embodiments, a pipeline six is provided between the output end of the sixth pipeline and the first helium extraction tower; a pipeline seven is provided between the sixth pipeline and the bottom reboiler of the first helium extraction tower;

[0014] The output end of the bottom reboiler of the first helium extraction tower is connected to the pipeline six;

[0015] The connection point of the pipeline seven and the sixth pipeline is arranged between the input port and the output port of the sixth pipeline;

[0016] A temperature control valve A is provided on the pipeline seven; a flow control valve A is provided on the pipeline six, and the flow control valve A is located between the connection point of the pipeline six and the first helium extraction tower and the connection point of the pipeline six and the output end of the bottom reboiler of the first helium extraction tower.

[0017] In some possible embodiments, the second heat exchanger includes a first heat exchange pipeline respectively connected to the third pipeline and the bottom of the second helium extraction tower, a second heat exchange pipeline respectively connected to the input end of the top condenser of the first helium extraction tower and the output end of the top condenser of the second helium extraction tower, a third heat exchange pipeline respectively connected to the fifth pipeline and the input end of the condenser of the second helium extraction tower, and a fourth heat exchange pipeline connected to the second helium extraction tower; the top of the first helium extraction tower is connected to the input end of the bottom reboiler of the second helium extraction tower;

[0018] A J-T valve C is provided on the connecting pipeline between the third heat exchange pipeline and the top condenser of the second helium extraction tower, and a liquid level control valve B is provided on the connecting pipeline between the bottom of the second helium extraction tower and the first heat exchange pipeline.

[0019] In some possible embodiments, the input end of the fourth heat exchange pipeline is connected to the output end of the bottom reboiler of the second helium extraction tower; a pipeline four is provided between the output end of the fourth heat exchange pipeline and the second helium extraction tower;

[0020] A pipeline five is provided between the top of the first helium extraction tower and the input end of the bottom reboiler of the second helium extraction tower;

[0021] A flow control valve C is provided on the pipeline four.

[0022] In some possible embodiments, the dehydrogenation and dehydration system includes a dehydrogenation system connected to the top of the second helium extraction tower, and a dehydration system connected to the dehydrogenation system and the third heat exchanger respectively; the pressure swing adsorption system is connected to the dehydrogenation system;

[0023] The flash condensation separation system includes a condensation separation system and a flash system respectively connected to the third heat exchanger; the condensation separation system is connected to the flash system.

[0024] In some possible embodiments, the third heat exchanger includes a pipeline one respectively connected to the dehydrogenation system and the flash system, a pipeline two respectively connected to the top of the pressure swing adsorption system and the condensation separation system, a pipeline three respectively connected to the dehydration system and the condensation separation system, a pipeline four connected to the input end of the nitrogen refrigeration system, and a pipeline five connected to the output end of the nitrogen refrigeration system through an external pipeline and connected to the pipeline four; a J-T valve D is provided on the external pipeline.

[0025] Compared with the prior art, the present utility model has the following advantages and beneficial effects:

[0026] The present utility model adopts a three-stage cascaded cycle refrigeration formed by a propane / propylene refrigeration system, an ethane / ethylene refrigeration system, and a nitrogen-methane refrigeration system, and two-stage low-temperature helium extraction formed by the first helium extraction tower and the second helium extraction tower. By using a two-stage rectification method to process low-helium-containing natural gas, the helium concentration in the natural gas is gradually increased, and finally crude helium with a purity of 28% can be obtained. The crude helium contains 69% nitrogen and about 300 ppm of methane; the crude helium separated by the second helium extraction tower is purified by a pressure swing adsorption system to produce high-purity helium. Compared with the prior art, the present invention optimizes the process flow of low-temperature helium extraction, improves the heat exchange efficiency, and thus reduces the helium extraction energy consumption;

[0027] In the present utility model, in order to maintain the nitrogen circulation, it can be supplemented by pressure swing adsorption nitrogen production; the crude helium purification and liquid nitrogen production system is used to produce liquid nitrogen products, which are stored in the liquid nitrogen storage tank for subsequent use in crude helium purification and refined helium liquefaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the present utility model;

[0029] Figure 2 is a schematic connection diagram of the dehydration system, the third heat exchanger, the nitrogen refrigeration system, the condensation separation system, the flash evaporation system, and the pressure swing adsorption system in the present utility model;

[0030] Wherein: 1 - the first heat exchanger, 11 - the first pipeline, 12 - the second pipeline, 121 - the first branch, 122 - the second branch, 123 - the outer pipeline, 13 - the third pipeline, 14 - the fourth pipeline, 15 - the fifth pipeline, 16 - the sixth pipeline, 2 - the first helium extraction tower, 21 - pipeline six, 22 - pipeline seven, 3 - the second heat exchanger, 31 - the first heat exchange pipeline, 32 - the second heat exchange pipeline, 33 - the third heat exchange pipeline, 34 - the fourth heat exchange pipeline, 35 - pipeline four, 36 - pipeline five, 4 - the second helium extraction tower, 5 - the propane / propylene refrigeration unit, 6 - the ethane / ethylene refrigeration system, 7 - the nitrogen-methane refrigeration system, 9 - the dehydrogenation system, 10 - the dehydration system, 20 - the third heat exchanger, 201 - pipeline one, 202 - pipeline two, 203 - pipeline three, 204 - pipeline four, 205 - pipeline five, 30 - the nitrogen refrigeration system, 40 - the condensation separation system, 50 - the flash evaporation system, 60 - the pressure swing adsorption system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present utility model, but should not be construed as limiting the present utility model.

[0032] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present utility model.

[0033] In the present utility model, unless otherwise clearly defined and limited, terms such as "installation", "connection", "linkage", "fixation", etc. shall 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 a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0034] The following further elaborates on the present utility model in conjunction with embodiments, but the implementation manners of the present utility model are not limited thereto.

[0035] Embodiment 1:

[0036] As Figure 1 - Figure 2 shown:

[0037] A crude helium extraction device for natural gas includes a first heat exchanger 1, a first helium extraction tower 2 connected to the first heat exchanger 1, a second heat exchanger 3 respectively connected to the first helium extraction tower 2 and the first heat exchanger 1, a second helium extraction tower 4 connected to the second heat exchanger 3, a propane / propylene refrigeration system 5, an ethane / ethylene refrigeration system 6, and a nitrogen-methane refrigeration system 7 respectively connected to the first heat exchanger 1, and a crude helium refining and liquid nitrogen production system connected to the second helium extraction tower 4;

[0038] Among them, the cooling capacity of the first helium extraction tower 2 and the second helium extraction tower 4 is provided by the nitrogen-methane gas refrigeration system 7. The propane / propylene refrigeration system 5 provides precooling for natural gas, ethane / ethylene, and nitrogen-methane. The ethane / ethylene refrigeration system 6 provides precooling for nitrogen-methane, forming a cascaded cycle refrigeration; and the first helium extraction tower 2 and the second helium extraction tower 4 are used in cooperation to achieve rectification, which can effectively process low-helium natural gas, gradually increasing the helium concentration in the helium-containing natural gas, and finally obtaining crude helium with a purity of 28%, where the crude helium also contains 69% nitrogen; and finally obtaining pure helium and liquid nitrogen with a purity of more than 99.5% through the crude helium refining and liquid nitrogen production system.

[0039] In some possible implementation manners, the crude helium refining and liquid nitrogen production system includes a dehydrogenation and dehydration system, a flash condensation and separation system, a nitrogen refrigeration system 30, a third heat exchanger 20, and a pressure swing adsorption system 60;

[0040] Among them, the dehydrogenation and dehydration system is respectively connected to the top of the second helium extraction tower 4, the pressure swing adsorption system 60, and the third heat exchanger 20; the nitrogen refrigeration system 30 is connected to the third heat exchanger 20.

[0041] The secondary crude helium separated by the second helium extraction tower 4 enters the dehydrogenation and dehydration system for dehydrogenation and dehydration treatment in sequence, then enters the third heat exchanger 20, and is cooled with the cooperation of the nitrogen refrigeration system 30, and then enters the flash condensation separation system for treatment to obtain liquid nitrogen, and the separated gas phase enters the pressure swing adsorption system 60 and the dehydrogenation and dehydration system through the third heat exchanger 20.

[0042] Furthermore, in order to effectively realize the dehydrogenation and dehydration of the secondary crude helium separated by the second helium extraction tower 4; the dehydrogenation and dehydration system includes a dehydrogenation system 9 connected to the top of the second helium extraction tower 4, and a dehydration system 10 connected to the dehydrogenation system 9 and the third heat exchanger 20 respectively; the pressure swing adsorption system 60 is connected to the dehydrogenation system 9;

[0043] In order to effectively separate the crude helium cooled by the third heat exchanger 20 and the nitrogen refrigeration system 30 to obtain liquid nitrogen and pure helium; the flash condensation separation system includes a condensation separation system 40 and a flash evaporation system 50 respectively connected to the third heat exchanger 20; the condensation separation system 40 is connected to the flash evaporation system 50.

[0044] The third heat exchanger 20 includes a pipeline 1 201 connected to the dehydrogenation system 9 and the flash system 50 respectively, a pipeline 2 202 connected to the pressure swing adsorption system 60 and the top of the condensation separation system 40 respectively, a pipeline 3 203 connected to the dehydration system 10 and the condensation separation system 40 respectively, a pipeline 4 204 connected to the input end of the nitrogen refrigeration system 30, and a pipeline 5 205 connected to the input end of the pipeline 4 204 through an external pipeline and connected to the output end of the nitrogen refrigeration system 30; a JT valve D is arranged on the external pipeline.

[0045] Specifically, the secondary crude helium after dehydration treatment by the dehydration system 10 enters the pipeline 3 203 of the third heat exchanger 20, is cooled with the cooperation of the nitrogen refrigeration system 30, and then enters the condensation separation system 40;

[0046] The gas phase separated by the condensation separation system 40 enters the pressure swing adsorption system 60 after passing through the pipeline 202 of the third heat exchanger 20, and finally obtains pure helium;

[0047] The liquid phase separated by the condensation separation system 40 enters the flash evaporation system 50 for further separation, and the separated liquid phase is liquid nitrogen. The separated gas phase passes through the pipeline 201 and is combined with the secondary crude helium and the desorbed gas output by the pressure swing adsorption system 60 and enters the dehydrogenation system 9 again;

[0048] The input end of the nitrogen refrigeration system 30 is connected to one end of the fourth pipeline 204. The fourth pipeline 204 is connected to the fifth pipeline 205 through an external pipeline. The other end of the fifth pipeline 205 is connected to the output end of the nitrogen refrigeration system 30. The nitrogen refrigeration system 30, the fourth pipeline 204, the fifth pipeline 205, and the external pipeline form a circulating pipeline; thereby realizing the cooling of the secondary crude helium entering the third pipeline 203.

[0049] In some possible implementation manners, the first heat exchanger 1 includes a first pipeline 11 connected to the propane / propylene refrigeration system 5 and forming a circulating pipeline, a second pipeline 12 connected to the ethane / ethylene refrigeration system 6 and forming a circulating pipeline, a third pipeline 13 respectively connected to the bottom of the first helium extraction tower 2 and the second heat exchanger 3 and serving as a tail gas export pipeline, a fourth pipeline 14 respectively connected to the output end of the top condenser of the first helium extraction tower 2 and the input end of the nitrogen-methane refrigeration system 7, a fifth pipeline 15 respectively connected to the output end of the nitrogen-methane refrigeration system 7 and the second heat exchanger 3, and a sixth pipeline 16 serving as a helium-containing natural gas inlet pipe and connected to the first helium extraction tower 2; a liquid level control valve A is arranged on the pipeline where the third pipeline 13 is connected to the bottom of the first helium extraction tower 2; a pipeline six 21 is arranged between the output end of the sixth pipeline 16 and the first helium extraction tower 2; a pipeline seven 22 is arranged between the sixth pipeline 16 and the bottom reboiler of the first helium extraction tower 2; the output end of the bottom reboiler of the first helium extraction tower 2 is connected to the pipeline six 21; the connection point of the pipeline seven 22 and the sixth pipeline 16 is arranged between the input port and the output port of the sixth pipeline 16;

[0050] A temperature control valve A is arranged on the pipeline seven 22; a flow control valve A is arranged on the pipeline six 21, and the flow control valve A is located between the connection point of the pipeline six 21 and the first helium extraction tower 2 and the connection point of the pipeline six 21 and the output end of the bottom reboiler of the first helium extraction tower 2.

[0051] After the helium-containing natural gas passes through the sixth pipeline 16, a part enters the first helium extraction tower 2 through the pipeline six 21; another part enters the bottom reboiler of the first helium extraction tower 2 through the pipeline seven 22, and after being separated by the reboiler, also enters the first helium extraction tower 2 through the pipeline six 21. The crude helium separated by the first helium extraction tower 2 enters the second heat exchanger 3;

[0052] In some possible embodiments, the second heat exchanger 3 includes a first heat exchange pipeline 31 respectively connected to the third pipeline 13 and the bottom of the second helium extraction tower 4, a second heat exchange pipeline 32 respectively connected to the input end of the top condenser of the first helium extraction tower 2 and the output end of the top condenser of the second helium extraction tower 4, a third heat exchange pipeline 33 respectively connected to the fifth pipeline 15 and the input end of the top condenser of the second helium extraction tower 4, and a fourth heat exchange pipeline 34 connected to the second helium extraction tower 4; the top of the first helium extraction tower 2 is connected to the input end of the bottom reboiler of the second helium extraction tower 4;

[0053] A J-T valve C is provided on the connecting pipeline between the third heat exchange pipeline 33 and the top condenser of the second helium extraction tower 2, and a liquid level control valve B is provided on the connecting pipeline between the bottom of the second helium extraction tower 4 and the first heat exchange pipeline 31.

[0054] In some possible embodiments, the input end of the fourth heat exchange pipeline 34 is connected to the output end of the bottom reboiler of the second helium extraction tower 4; a pipeline four 35 is provided between the output end of the fourth heat exchange pipeline 34 and the second helium extraction tower;

[0055] A pipeline five 36 is provided between the top of the first helium extraction tower 2 and the input end of the bottom reboiler of the second helium extraction tower 4;

[0056] A flow control valve C is provided on the pipeline four 34.

[0057] The primary crude helium separated by the first helium extraction tower 2 enters the bottom reboiler of the second helium extraction tower 4 through the pipeline five 36 for precooling, and then enters the fourth heat exchange pipeline 34 of the second heat exchanger 3 to be cooled again, and then enters the second helium extraction tower 4 through the pipeline four 35 to separate components such as methane and nitrogen therein. After rectification by the second helium extraction tower 3, secondary crude helium is obtained at the top, and the secondary crude nitrogen will enter the crude helium refining and liquid nitrogen production system;

[0058] The liquid phase at the bottom of the second helium extraction tower 4 returns to the first heat exchange pipeline 31 of the second heat exchanger 3 to recover the cold energy, and then converges with the liquid phase at the bottom of the first helium extraction tower 2, and returns to the third pipeline 14 of the first heat exchanger 1 to recover the cold energy and then is exported.

[0059] In some possible embodiments,

[0060] The nitrogen-methane refrigeration system 7 provides cold energy to the top condenser of the second helium extraction tower 4 through the fifth pipeline 15 and the third heat exchange pipeline 33, and then returns to the top condenser of the first helium extraction tower 2 through the second heat exchange pipeline 32, and then enters the nitrogen-methane refrigeration system 7 through the fourth pipeline 14 to form a cycle.

[0061] In some possible embodiments, a buffer tank is provided between the propane / propylene refrigeration system 5 and the first pipeline 11; one output port of the buffer tank is connected to the input end of the first pipeline 11; the other output opening of the buffer tank is connected to the input port of the propane / propylene refrigeration system 5;

[0062] The output end of the propane / propylene refrigeration system 5 is connected to one input port of the buffer tank through an output pipeline, and the output end of the first pipeline 11 is connected to the other input port of the buffer tank; a J-T valve A is provided on the output pipeline.

[0063] In some possible embodiments, the second pipeline 12 includes a branch one 121 and a branch two 122 located inside the first heat exchanger 1, and an outer pipeline 123 located outside the first heat exchanger 1 and connected to the branch one 121 and the branch two 122 respectively; the other end of the branch one 121 is connected to the input end of the ethane / ethylene refrigeration system 6 through an input pipeline, and the other end of the branch two 122 is connected to the output end of the ethane / ethylene refrigeration system 6; a J-T valve B is provided on the outer pipeline 123.

[0064] The process flow of the first helium extraction tower 2 is as Figure 1 shown; after the helium-containing natural gas is pretreated, the helium content is 0.32 mol%, the temperature is 40 °C, and the pressure is 3.5 MPa. It enters the sixth pipeline 16 of the first heat exchanger 1 and is cooled to -103 °C. After passing through the flow control valve A on the pipeline six 21, it enters the first helium extraction tower 2. After rectification in the first helium extraction tower 2, primary crude helium with a temperature of -113 °C is obtained at the top of the first helium extraction tower 2. At this time, the helium content is 3.19%, and the helium content is concentrated by 10 times. The helium concentration in the bottom liquid phase of the first helium extraction tower 2 is already very low. After slightly reducing the pressure to 3.0 MPa through a pressure reducing valve and the temperature is -102 °C, it returns to the first heat exchanger 1 to recover the cold energy and then is exported.

[0065] To meet the energy balance of the first helium extraction tower 2, heat needs to be generated at the bottom and condensed at the top; the heat source for heat generation at the bottom comes from the helium-containing natural gas. When the helium-containing natural gas is cooled to -100 °C by the first heat exchanger 1, a stream of about 15% of the gas is extracted and enters the reboiler provided at the bottom of the first helium extraction tower 2 through the pipeline seven 22 to provide heat for the first helium extraction tower 2. The separated gas phase after the treatment of the reboiler is combined with the gas entering the first helium extraction tower through the pipeline six 21 of the remaining about 85% of the gas and enters the first helium extraction tower 2;

[0066] The condensation at the top of the first helium extraction tower 2 uses a nitrogen-methane refrigeration cycle to provide cold energy. The propane / propylene refrigeration cycle precools the natural gas, the ethane / ethylene refrigeration cycle, and the nitrogen-methane refrigeration cycle. The ethane / ethylene precools the natural gas and the nitrogen-methane refrigeration cycle, thus forming a cascade cycle refrigeration.

[0067] The specific steps are as follows, propane / propylene refrigeration cycle:

[0068] After evaporation in the first heat exchanger 11, the propane / propylene with a temperature of -31 °C and a pressure of 0.02 MPa enters the buffer tank through the first pipeline 11, and then enters the propane / propylene refrigeration system 5. It is pressurized to 1.4 MPa by the booster in the propane / propylene refrigeration system 5, passes through the J-T valve A on the output pipeline of the propane / propylene / propylene refrigeration system 5 and is depressurized to about 0.14 MPa with the temperature dropping to -35 °C, and then enters the first pipeline 11 of the first heat exchanger 1 to provide cooling capacity for the precooling of natural gas, ethane / ethylene, and nitrogen-methane.

[0069] Ethane / ethylene refrigeration cycle:

[0070] After evaporation in the first heat exchanger 1, the ethane / ethylene with a temperature of -33 °C and a pressure of 0.02 MPa is pressurized to 1.8 MPa by the booster in the ethane / ethylene refrigeration system 6, enters the second branch 122 of the first heat exchanger 1 and is precooled to -95 °C, then passes through the J-T valve B on the external pipeline 123 and is depressurized to about 0.04 MPa with the temperature dropping to -98 °C, and returns to the first branch 121 of the first heat exchanger 1 to provide cooling capacity for the precooling of natural gas and nitrogen-methane.

[0071] Nitrogen-methane refrigeration cycle:

[0072] The nitrogen-methane refrigerant is pressurized to about 4.0 MPa by the booster in the nitrogen-methane refrigeration system and then enters the fifth pipeline 15 of the first heat exchanger 1. After being cooled to -105 °C, it continues to enter the third heat exchange pipeline 33 of the second heat exchanger 3. After passing through the J-T valve C, it is depressurized to 0.06 MPa with the temperature dropping to -163 °C, enters the top condenser of the second helium extraction tower 4 to provide cooling capacity, and then returns to the second heat exchanger 3 to recover part of the cooling capacity with the temperature becoming -141 °C. After passing through the second heat exchange pipeline 32, it enters the top condenser of the first helium extraction tower 2 to provide cooling capacity with the temperature becoming -125 °C. After entering the first heat exchanger 1 to recover the cooling capacity, it returns to the compressor in the nitrogen-methane refrigeration system through the fourth pipeline 14 for continued compression. The cooling capacity of the first heat exchanger 1 and the second heat exchanger 3 can be adjusted through three refrigeration cycles, realizing the effective and cascaded utilization of energy.

[0073] The primary crude helium separated by the first helium extraction tower 2 enters the bottom reboiler of the second helium extraction tower 4 through pipeline five 36 and is precooled to -123°C, and then enters the fourth heat exchange pipeline 34 of the second heat exchanger 3 and is cooled again to -130°C, and then enters the second helium extraction tower 4 through pipeline four 35 to separate components such as methane and nitrogen therein. After rectification in the second helium extraction tower 3, secondary crude helium with a temperature of -159°C is obtained at the top of the tower. At this time, the helium content is 28.6%, and it also contains about 69% nitrogen and 300 ppm methane; the secondary crude nitrogen will enter the crude helium refining and liquid nitrogen production system;

[0074] The liquid phase at the bottom of the second helium extraction tower 4 with a temperature of -125°C returns to the first heat exchange pipeline 31 of the second heat exchanger 3 to recover cold energy, and then converges with the liquid phase at the bottom of the first helium extraction tower 2, and returns to the third pipeline 14 of the first heat exchanger 1 to recover cold energy and then is exported.

[0075] As Figure 2 shown, the nitrogen content in the secondary crude helium separated by the second helium extraction tower 4 is relatively high (about 69%). After passing through the dehydrogenation system 9 and the dehydration system 10 in sequence, it enters the pipeline three 203 of the third heat exchanger 20 and is cooled to -180°C by cooperating with the nitrogen refrigeration system 30, and then enters the condensation separation system 40. The liquid phase separated by the condensation separation system 40 is depressurized to 0.1 MPa and enters the flash evaporation system 50 for flash evaporation to separate the non-condensable gas therein, and the liquid phase obtains liquid nitrogen with a relatively high purity (99.5%), which can be used by other units in the device; the gas phase separated by the condensation separation system 40 returns to the pipeline two 202, and then enters the pressure swing adsorption system 60 to generate pure helium.

[0076] Example 2:

[0077] The process flow of the first helium extraction tower 2 is as Figure 1 shown; the helium content of the natural gas containing helium is 0.04 mol% after pretreatment, and the temperature is 40°C and the pressure is 3.5 MPa. It enters the sixth pipeline 16 and is cooled to -103°C by the first heat exchanger 1, and then enters the first helium extraction tower 2 through pipeline six 21 after passing through the flow control valve A. After rectification in the first helium extraction tower 2, primary crude helium with a temperature of -127°C is obtained at the top of the tower. At this time, the helium content is 0.72%, and the helium content is concentrated 18 times; the helium concentration in the liquid phase at the bottom of the first helium extraction tower 2 is already very low, and it is slightly depressurized to 3.0 MPa and the temperature is -102°C, and then returns to the third pipeline 13 of the first heat exchanger 1 to recover cold energy and then is exported.

[0078] To meet the energy balance of the first helium extraction tower 2, heat needs to be generated at the bottom of the tower and condensation needs to be carried out at the top of the tower;

[0079] The heat source for bottom heating comes from the raw natural gas. When the helium-containing natural gas is cooled to -100 °C by the first heat exchanger 1, a stream of gas (about 15%) is withdrawn and enters the reboiler at the bottom of the first helium extraction tower 2 through pipeline seven 22, providing heat for the first helium extraction tower 2, and then converges with the remaining 85% of the gas in pipeline six 21 and enters the first helium extraction tower 2;

[0080] The condensation at the top of the first helium extraction tower 2 uses a nitrogen-methane refrigeration system to provide cooling capacity. The propane / propylene refrigeration cycle pre-cools the natural gas, ethane / ethylene refrigeration cycle, and nitrogen-methane refrigeration cycle. The ethane / ethylene pre-cools the natural gas and nitrogen-methane refrigeration cycle, thus forming a cascade cycle refrigeration.

[0081] The specific steps are as follows. Propane / propylene refrigeration cycle:

[0082] After evaporation in the first heat exchanger 11, the propane / propylene with a temperature of -31 °C and a pressure of 0.02 MPa enters the buffer tank through the first pipeline 11, and then enters the propane / propylene refrigeration system 5. It is pressurized to 1.4 MPa by the booster in the propane / propylene refrigeration system 5, passes through the J-T valve A on the output pipeline of the propane / propylene refrigeration system 5 and is depressurized to about 0.14 MPa with the temperature dropping to -35 °C, and then enters the first pipeline 11 of the first heat exchanger 1 to provide cooling capacity for the pre-cooling of natural gas, ethane / ethylene, and nitrogen-methane;

[0083] Ethane / ethylene refrigeration cycle: After evaporation in the first heat exchanger 1, the ethane / ethylene with a temperature of -33 °C and a pressure of 0.02 MPa is pressurized to 1.8 MPa by the booster in the ethane / ethylene refrigeration system 6, enters the second branch 122 of the first heat exchanger 1 and is pre-cooled to -95 °C, then passes through the J-T valve B on the external pipeline 123 and is depressurized to about 0.04 MPa with the temperature dropping to -98 °C, and returns to the first branch 121 of the first heat exchanger 1 to provide cooling capacity for the pre-cooling of natural gas and nitrogen-methane.

[0084] Nitrogen-methane refrigeration cycle:

[0085] The nitrogen-methane refrigerant is pressurized to about 4.0 MPa by a compressor and then enters the fifth pipeline 15 of the first heat exchanger 1, where it is cooled to -105 °C. Then it continues to enter the third heat exchange pipeline 33 of the second heat exchanger 3 and is cooled down to -153 °C. After passing through the J-T valve C, it is depressurized to 0.06 MPa and the temperature drops to -163 °C. It enters the top condenser of the second helium extraction tower 4 to provide cooling capacity. Subsequently, it returns to the second heat exchange pipeline 32 of the second heat exchanger 3 to recover part of the cooling capacity and the temperature becomes -135 °C. Then it enters the top condenser of the first helium extraction tower 2 to provide cooling capacity and the temperature becomes -125 °C. Finally, it enters the fourth pipeline 14 of the first heat exchanger 1 and returns to the compressor of the nitrogen-methane refrigeration system 7 to continue compression; the cooling capacity of the first heat exchanger 1 and the second heat exchanger 2 can be adjusted through three refrigeration cycles, achieving the effective and cascaded utilization of energy.

[0086] The primary crude helium separated by the first helium extraction tower 2 enters the bottom reboiler of the second helium extraction tower 4 through pipeline five 36 and is precooled to -130 °C. Then it enters the fourth heat exchange pipeline 34 of the second heat exchanger 3 and is cooled again to -158 °C. Then it enters the second helium extraction tower 4 through pipeline four 35 to separate components such as methane and nitrogen therein. After rectification in the second helium extraction tower 3, secondary crude helium with a temperature of -158 °C is obtained at the top. At this time, the helium content is 18%, and it also contains about 74% nitrogen and 300 ppm methane; the secondary crude nitrogen will enter the crude helium refining and liquid nitrogen production system;

[0087] The liquid phase at the bottom of the second helium extraction tower 4 with a temperature of -138 °C returns to the first heat exchange pipeline 31 of the second heat exchanger 3 to recover cooling capacity, and then converges with the liquid phase at the bottom of the first helium extraction tower 2 and returns to the third pipeline 14 of the first heat exchanger 1 to recover cooling capacity and then is exported.

[0088] As Figure 2 shown, the nitrogen content in the secondary crude helium separated by the second helium extraction tower 4 is relatively high (about 74%). After passing through the dehydrogenation system 9 with the function of palladium-catalyzed dehydrogenation and the dehydration system 10 with the function of molecular sieve dehydration in sequence, it enters the pipeline three 203 of the third heat exchanger 20 and is cooled to -180 °C by cooperating with the nitrogen refrigeration system 30 in a cycle. Then it enters the condensation separation system 40. The liquid phase separated by the condensation separation system 40 is depressurized to 0.1 MPa and enters the flash evaporation system 50 for flash evaporation to separate the non-condensable gas therein. The liquid phase obtains liquid nitrogen with a relatively high purity (99.5%), which can be used by other units in the device; the gas phase separated by the condensation separation system 40 returns to the pipeline two 202 and then enters the pressure swing adsorption system 60; the gas phase separated by the flash evaporation system 50 enters the pipeline one 201 and then enters the dehydrogenation system 9.

[0089] The above are only the preferred embodiments of the present utility model, and do not impose any form of limitation on the present utility model. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A device for extracting crude helium from natural gas, characterized in that: The invention comprises a first heat exchanger, a first helium extracting tower connected to the first heat exchanger, a second heat exchanger connected to the first helium extracting tower and the first heat exchanger respectively, a second helium extracting tower connected to the second heat exchanger, a propane / propylene refrigeration system, an ethane / ethylene refrigeration system and a nitrogen-methane refrigeration system respectively connected to the first heat exchanger, and a crude helium refining and liquid nitrogen production system connected to the second helium extracting tower.

2. The device for extracting crude helium from natural gas according to claim 1, characterized in that: The crude helium refining and liquid nitrogen production system includes a dehydrogenation and dehydration system, a flash condensation separation system, a nitrogen refrigeration system, a third heat exchanger and a pressure swing adsorption system; wherein the dehydrogenation and dehydration system is respectively connected to the top of the second helium extraction tower, the pressure swing adsorption system and the third heat exchanger; and the nitrogen refrigeration system is connected to the third heat exchanger.

3. The device for extracting crude helium from natural gas according to claim 2, characterized in that: The first heat exchanger includes a first pipeline connected to a propane / propylene refrigeration system and forming a circulation pipeline, a second pipeline connected to an ethane / ethylene refrigeration system and forming a circulation pipeline, a third pipeline connected to the bottom of the first helium extracting tower and the second heat exchanger respectively and serving as an exhaust gas transmission pipeline, a fourth pipeline connected to the condenser at the top of the first helium extracting tower and the input end of the nitrogen-methane refrigeration system respectively, a fifth pipeline connected to the output end of the nitrogen-methane refrigeration system and the second heat exchanger respectively, and a sixth pipeline serving as a helium-containing natural gas inlet pipe and connected to the first helium extracting tower; A liquid level control valve A is provided on the pipeline connecting the third pipeline and the bottom of the first helium extraction tower.

4. The device for extracting crude helium from natural gas according to claim 3, characterized in that: A buffer tank is provided between the propane / propylene refrigeration system and the first pipeline; One output port of the buffer tank is connected to the input end of the first pipeline; another output opening of the buffer tank is connected to the input port of the propane / propylene refrigeration system; The output end of the propane / propylene refrigeration system is connected to an input port of the buffer tank via an output pipeline, and the output end of the first pipeline is connected to another input port of the buffer tank; A JT valve A is arranged on the output pipeline.

5. The device for extracting crude helium from natural gas according to claim 3, characterized in that: The second pipeline includes an external pipeline which is connected to branch one and branch two located in the first heat exchanger and is located outside the first heat exchanger and is connected to branch one and branch two respectively; the other end of branch one is connected to the input end of the ethane / ethylene refrigeration system through an input pipeline, and the other end of branch two is connected to the output end of the ethane / ethylene refrigeration system; a JT valve B is arranged on the external pipeline.

6. The device for extracting crude helium from natural gas according to claim 3, characterized in that: A pipeline 6 is provided between the output end of the sixth pipeline and the first helium extraction tower; a pipeline 7 is provided between the sixth pipeline and the reboiler at the bottom of the first helium extraction tower; The output end of the reboiler at the bottom of the first helium extraction tower is connected to pipeline 6; The connection point between the pipeline 7 and the sixth pipeline is arranged between the input port and the output port of the sixth pipeline; A temperature control valve A is arranged on the pipeline 7; a flow control valve A is arranged on the pipeline 6, and the flow control valve A is located between the connection point between the pipeline 6 and the first helium stripping tower and the connection point between the pipeline 6 and the output end of the reboiler at the bottom of the first helium stripping tower.

7. The device for extracting crude helium from natural gas according to claim 3, characterized in that: The second heat exchanger comprises a first heat exchange pipeline respectively connected to the third pipeline and the bottom of the second helium extracting tower, a second heat exchange pipeline respectively connected to the input end of the first helium extracting tower top condenser and the output end of the second helium extracting tower top condenser, a third heat exchange pipeline respectively connected to the fifth pipeline and the input end of the condenser of the second helium extracting tower, and a fourth heat exchange pipeline connected to the second helium extracting tower; the top of the first helium extracting tower is connected to the input end of the reboiler at the bottom of the second helium extracting tower; A JT valve C is provided on the connecting pipeline between the third heat exchange pipeline and the top condenser of the second helium extraction tower, and a liquid level control valve B is provided on the connecting pipeline between the bottom of the second helium extraction tower and the first heat exchange pipeline.

8. The device for extracting crude helium from natural gas according to claim 7, characterized in that: The input end of the fourth heat exchange pipeline is connected to the output end of the reboiler at the bottom of the second helium extraction tower; a pipeline 4 is provided between the output end of the fourth heat exchange pipeline and the second helium extraction tower; A pipeline 5 is provided between the top of the first helium extraction tower and the input end of the reboiler at the bottom of the second helium extraction tower; A flow control valve C is provided on the pipeline 4.

9. The device for extracting crude helium from natural gas according to claim 2, characterized in that: The dehydrogenation and dehydration system includes a dehydrogenation system connected to the top of the second helium extraction tower, and a dehydration system connected to the dehydrogenation system and the third heat exchanger respectively; the pressure swing adsorption system is connected to the dehydrogenation system; The flash condensation separation system comprises a condensation separation system and a flash evaporation system respectively connected to the third heat exchanger; the condensation separation system is connected to the flash evaporation system.

10. The device for extracting crude helium from natural gas according to claim 9, characterized in that: The third heat exchanger includes pipeline 1 connected to the dehydrogenation system and the flash evaporation system respectively, pipeline 2 connected to the pressure swing adsorption system and the top of the condensation separation system respectively, pipeline 3 connected to the dehydration system and the condensation separation system respectively, pipeline 4 connected to the input end of the nitrogen refrigeration system, and pipeline 5 connected to pipeline 4 through an external pipeline and connected to the output end of the nitrogen refrigeration system; a JT valve D is arranged on the external pipeline.

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