Wide-concentration adaptive natural gas deep decarbonization membrane separation-membrane absorption device and method

Abstract

The invention discloses a wide-concentration adaptive natural gas deep decarbonization membrane separation-membrane absorption device and method. The device comprises a natural gas pretreatment unit, a membrane separation unit, a membrane absorption unit and a membrane regeneration unit which are communicated in sequence, the method comprises the following steps: reducing the heavy hydrocarbon content of natural gas through the pretreatment unit, then feeding the natural gas into the membrane separation unit, primarily and selectively removing CO2 by using a hollow fiber dense membrane, then feeding the natural gas into a tube pass of the membrane absorption unit, and absorbing CO2 in a hydrophobic hollow fiber porous membrane by an absorption liquid reversely flowing in a shell pass for deep removal; the CO2-enriched absorption liquid releases absorbed CO2 in the membrane regeneration unit after being preheated, and the regenerated barren solution is circulated back to the membrane absorption unit for cyclic utilization. A double-membrane sequential coupling process is adopted, the problems that a single-membrane technology is narrow in decarburization range and insufficient in decarburization depth are solved, adaptability is high, natural gas with the CO2 concentration being 0.5%-80% can be treated, and CO2 after decarburization is smaller than or equal to 0.005%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of natural gas purification, and particularly relates to a wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device and method. BACKGROUND

[0002] With the increasing demand for clean energy and the increasingly stringent environmental protection regulations worldwide, as a relatively clean fossil fuel, the purification treatment of natural gas, especially the removal of CO2, is increasingly demanding. Deep removal of CO2 is not only a key step to meet the pipeline gas quality standard, but also a necessary prerequisite for the subsequent natural gas liquefaction process (which requires the CO2 content to be reduced to 0.005%).

[0003] At present, the mainstream natural gas decarburization technology in industry mainly includes chemical absorption method (such as tower absorption) and physical separation method (such as membrane separation). The tower absorption method is mature in technology, has high decarburization depth, and has certain adaptability to CO2 concentration fluctuations of raw gas. However, it has poor adaptability to complex working conditions, and in the working conditions of limited space and swinging on offshore platforms, the stable operation of large tower equipment, liquid level control, solvent entrainment and other problems are more prominent, and the safety risk is increased. The membrane separation method utilizes the selective difference of dense membranes for CO2 and other components in natural gas to realize CO2 removal under the driving of pressure difference, and has simple and compact process flow, light equipment and easy modularization. However, it cannot remove CO2 in natural gas to less than 0.005%.

[0004] Although some researches have tried to couple membrane separation with other technologies (such as tower absorption) to overcome their respective shortcomings, the existing schemes often have the following problems: the integration method is complex, the process is not optimized, and the synergistic advantages of the two technologies cannot be fully utilized. The adaptability to a wide range of CO2 concentrations is insufficient, and the system robustness is poor. The guarantee capacity for deep decarburization is limited. There is insufficient design consideration for the stable, efficient and compact operation requirements under severe working conditions such as offshore swinging. Therefore, there is an urgent need in the field to develop a new decarburization technology and device that has both deep decarburization and wide concentration adaptability, and can efficiently and stably process natural gas raw materials with a wide range of CO2 concentration changes. SUMMARY

[0005] The application is proposed to solve the problems in the prior art, and aims to provide a wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device and method.

[0006] The application is realized by the following technical scheme: The application discloses a natural gas deep decarburization membrane separation-membrane absorption device with wide concentration adaptability, which comprises a pretreatment unit, a membrane separation unit, a membrane absorption unit and a membrane regeneration unit which are sequentially connected through pipelines; the pretreatment unit comprises a refrigeration device and a filter which are sequentially connected through pipelines; the membrane separation unit comprises a preheater and a membrane separation assembly which are sequentially connected through pipelines; the membrane absorption unit comprises a membrane absorption assembly, a lean amine liquid storage tank and a gas-liquid separation tank; a liquid outlet of the lean amine liquid storage tank is communicated with an shell inlet of the membrane absorption assembly through a pipeline and a lean amine liquid pump, a shell outlet of the membrane absorption assembly is communicated with the membrane regeneration unit, an end outlet of the membrane absorption assembly is communicated with the gas-liquid separation tank through a pipeline, and a gas outlet of the gas-liquid separation tank is communicated with a gas collecting device; the membrane regeneration unit comprises a flash tank, a heater, a membrane regeneration assembly and a condenser which are sequentially communicated through pipelines; and the condenser outlet is communicated with the lean amine liquid storage tank.

[0007] In the technical scheme, the refrigeration device is at least one of a throttle expansion valve, a refrigeration heat exchanger or a turbine expander; and the filter is at least one of a polyseptum filter, a Y-type filter or a molecular sieve filter.

[0008] In the technical scheme, the membrane absorption assembly comprises an outer shell and a hydrophobic hollow fiber porous membrane arranged in the outer shell; a gap between the hydrophobic hollow fiber porous membrane and the outer shell is a shell passage, and the shell passage constitutes an absorption liquid flow channel; and an inner cavity of the hydrophobic hollow fiber porous membrane constitutes a natural gas flow channel.

[0009] In the technical scheme, a first back pressure valve is arranged at the top of the lean amine liquid storage tank; a second back pressure valve is arranged on a pipeline between the shell outlet of the membrane absorption assembly and the membrane regeneration unit; and a third back pressure valve is arranged at the top of the flash tank.

[0010] In the technical scheme, the membrane absorption unit further comprises an absorption liquid flow meter arranged on a pipeline between the lean amine liquid pump and the shell inlet of the membrane absorption assembly.

[0011] In the technical scheme, a natural gas pressure meter and a natural gas flow meter are arranged on a pipeline between the membrane separation unit and the membrane absorption unit.

[0012] A method for deeply removing CO2 in natural gas with wide concentration by using the device, comprising the following steps: S1, configuring a lean amine liquid solution and transferring the lean amine liquid solution into a lean amine liquid storage tank, and setting a back pressure pressure of a first back pressure valve; S2, setting temperatures of a refrigeration device, a preheater, a heater and a condenser and a back pressure pressure of a third back pressure valve; S3, inputting natural gas to be decarburized from an inlet of the refrigeration device in the pretreatment unit; S4, according to the natural gas pressure, the back pressure of the second back pressure valve is set; the lean amine liquid pump is started, and the operating frequency of the lean amine liquid pump is adjusted according to the natural gas flow to adjust the absorption liquid flow; S5, collecting the treated natural gas from the gas outlet of the gas-liquid separation tank of the membrane absorption unit.

[0013] In the technical scheme, the absorption liquid comprises the following components and mass fractions: Piperazine 5%~13%; N-methyldiethanolamine 35%~43%; Deionized water balance.

[0014] In the technical scheme, the back pressure of the first back pressure valve is set to 0.02MPa~0.04MPa.

[0015] In the technical scheme, the temperature of the refrigeration device is set to 5℃~10℃; the temperature of the preheater is set to 35℃~50℃; the temperature of the heater is set to 93℃~105℃; the temperature of the condenser is set to 20℃~30℃; the back pressure of the third back pressure valve is set to 0.10MPa~0.15MPa; the back pressure of the second back pressure valve 37 is higher than the natural gas pressure by 0.01MPa~0.04MPa; and the absorption liquid flow is 0.002 times to 0.003 times of the natural gas flow.

[0016] The present application has the following advantages: The present application provides a wide concentration adaptive natural gas deep decarburization membrane separation-membrane absorption device and method, which is suitable for natural gas liquefaction plants, and especially for CO2 natural gas raw materials with a wide concentration range and complex working conditions such as offshore swing; The present application has wide concentration CO2 adaptability: the membrane separation as a pre-treatment unit of the membrane absorption has high efficiency and large flux under high CO2 partial pressure, which can significantly reduce the CO2 load and volume entering the membrane absorption unit; the membrane absorption unit uses the membrane contactor to strengthen the mass transfer efficiency of the absorption liquid phase and CO2, which can realize deep removal of low concentration CO2 and ensure that the final product gas meets the deep purification requirements; The present application is highly compact and adopts modular design: the membrane separation unit and the membrane absorption unit are compact and have high modular degree, and the occupied area is much smaller than that of the large tower of the traditional amine method such as the absorption tower and the regeneration tower; at the same time, the energy consumption is low, the membrane absorption assembly can be linearly enlarged, and the design is convenient and easy to implement industrialization.

[0017] The application adopts a double-membrane sequential coupling process, breaks through the problem of insufficient decarburization depth of single-membrane technology, is strong in adaptability, can treat natural gas with a CO2 concentration of 0.5% to 80%, and has CO2≤0.005% after decarburization, is suitable for a natural gas liquefaction plant, meanwhile, the whole system is free of moving parts, is of a modular structure and is resistant to swing vibration, and is particularly suitable for a swing working condition at sea. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic view of a wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device of the application.

[0019] wherein: 1, a pretreatment unit; 11, a refrigeration device; 12, a filter; 2, a membrane separation unit; 21, a preheater; 22, a membrane separation assembly; 3, a membrane absorption unit; 31, a membrane absorption assembly; 32, a lean amine liquid storage tank; 33, a lean amine liquid pump; 34, a gas-liquid separation tank; 35, a gas collection device; 36, a first back pressure valve; 37, a second back pressure valve; 38, an absorption liquid flow meter; 4, a membrane regeneration unit; 41, a flash tank; 42, a heater; 43, a membrane regeneration assembly; 44, a condenser; 45, a third back pressure valve; 5, a natural gas pressure gauge; 6, a natural gas flow meter.

[0020] For those skilled in the art, other related drawings can be obtained according to the above drawings without creative labor. DETAILED DESCRIPTION

[0021] In order to enable personnel in the art to better understand the technical solutions of the application, the technical solutions of the application are further described below by specific embodiments in combination with the drawings of the specification.

[0022] As shown in Figure 1 a wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device, comprising a pretreatment unit 1, a membrane separation unit 2, a membrane absorption unit 3 and a regeneration unit 4 connected in sequence through pipelines; The pretreatment unit 1 is used to reduce the heavy hydrocarbon content of natural gas; The pretreatment unit 1 comprises a refrigeration device 11 and a filter 12 connected in sequence through pipelines; The refrigeration device 11 is at least one of a throttle expansion valve, a refrigeration heat exchanger or a turbo expander, and the temperature of natural gas treated by the refrigeration device 11 is ≤10℃; The filter 12 is at least one of a polyseptum filter, a Y-type filter or a molecular sieve filter, and the content of non-gaseous components in the treated natural gas is ≤0.01% in mass fraction. The membrane separation unit 2 is used for preliminary removal of CO2 in natural gas; The membrane separation unit 2 comprises a preheater 21 and a membrane separation assembly 22 connected in sequence through pipelines; The inlet of the preheater 21 is communicated with the outlet of the filter 12; the outlet of the preheater 21 is communicated with the end inlet of the membrane separation assembly 22; the temperature of the preheater is set to 35-50℃; The membrane separation assembly 22 is a hollow fiber dense membrane assembly, which is prepared by the method described in the patent “A Hollow Fiber Gas Separation Inner Membrane and Its Spinning Forming Process (Publication No. CN117732268A)”; The membrane absorption unit 3 is used for deep removal of CO2 in natural gas; The membrane absorption unit 3 comprises a membrane absorption assembly 31, a lean amine liquid storage tank 32 and a gas-liquid separation tank 34; The membrane absorption assembly 31 comprises a shell and a hydrophobic hollow fiber porous membrane (trade name: Sartorius 11806-47-N) arranged in the shell; the gap between the hydrophobic hollow fiber porous membrane and the shell is the shell side, which constitutes an absorption liquid flow channel; the inner cavity of the hydrophobic hollow fiber porous membrane constitutes a natural gas flow channel; The lean amine liquid storage tank 32 stores absorption liquid; the liquid outlet of the lean amine liquid storage tank 32 is communicated with the shell side inlet of the membrane absorption assembly 31 through a pipeline and a lean amine liquid pump 33; the shell side outlet of the membrane absorption assembly 31 is communicated with the membrane regeneration unit 4 through a pipeline, forming an absorption liquid circulation loop, and a second back pressure valve 37 is arranged on the pipeline between the shell side outlet of the membrane absorption assembly 31 and the membrane regeneration unit 4; A first back pressure valve 36 is arranged on the top of the lean amine liquid storage tank 32; The membrane absorption unit 3 further comprises an absorption liquid flow meter 38 arranged on the pipeline between the lean amine liquid pump 33 and the shell side inlet of the membrane absorption assembly 31; A natural gas pressure meter 5 and a natural gas flow meter 6 are arranged on the pipeline between the membrane separation unit 2 and the membrane absorption unit 3; The end inlet of the membrane absorption assembly 31 is communicated with the end outlet of the membrane separation assembly 22 through a pipeline; the end outlet of the membrane absorption assembly 31 is communicated with the gas-liquid separation tank 34 through a pipeline; The gas outlet of the gas-liquid separation tank 34 is communicated with a gas collecting device 35; the liquid outlet of the gas-liquid separation tank 34 is connected with the membrane regeneration unit 4; The membrane regeneration unit 4 is used for releasing the absorbed CO2 after preheating of the absorption liquid enriched with CO2, so as to realize regeneration of the absorption liquid; The membrane regeneration unit 4 is communicated with the liquid outlet of the gas-liquid separation tank 34 through a pipeline; The membrane regeneration unit 4 includes a flash tank 41, a heater 42, a membrane regeneration assembly 43 (trade name: Sartorius 11807-47-N), and a condenser 44 connected in sequence by pipelines; The outlet of the condenser 44 is connected to the lean amine solution tank 32 by a pipeline to realize recycling of the absorption solution. A third back pressure valve 45 is arranged at the top of the flash tank 41.

[0023] A method for deep removal of CO2 in wide concentration natural gas by using a wide concentration adaptive natural gas deep decarburization membrane separation-membrane absorption device, comprising the following steps: S1, configuring a lean amine solution and transferring it to the lean amine solution tank 32, and setting the back pressure of the first back pressure valve 32; The absorption solution comprises the following components and mass fractions: Piperazine 5%~13%; N-methyldiethanolamine 35%~43%; Deionized water balance; The back pressure of the first back pressure valve is set to 0.02MPa~0.04MPa; S2, setting the temperature of the refrigeration device 11, the preheater 21, the heater 42, and the condenser 44, and the back pressure of the third back pressure valve 45; The setting temperature of the refrigeration device is 5℃~10℃; the setting temperature of the preheater is 35℃~50℃; the setting temperature of the heater is 93℃~105℃; the setting temperature of the condenser is 20℃~30℃; and the back pressure of the third back pressure valve is set to 0.10MPa~0.15MPa; S3, passing the natural gas to be decarburized from the refrigeration device inlet in the pretreatment unit; S4, setting the back pressure of the second back pressure valve 37 according to the pressure of the natural gas passed in; starting the lean amine solution pump 33, and adjusting the flow rate of the absorption solution according to the flow rate of the natural gas passed in by adjusting the operating frequency of the lean amine solution pump 33; The back pressure of the second back pressure valve 37 is 0.01MPa~0.04MPa higher than the pressure of the natural gas; The flow rate of the absorption solution is 0.002 times~0.003 times the flow rate of the natural gas; S5, collecting the treated natural gas from the gas outlet of the gas-liquid separation tank 34 of the membrane absorption unit 3.

[0024] Example 1 A method for deep removal of CO2 in wide concentration natural gas by using a wide concentration adaptive natural gas deep decarburization membrane separation-membrane absorption device, comprising the following steps: S1, configure lean amine liquid solution and transfer to lean amine liquid storage tank 32, set the back pressure pressure of the first back pressure valve 32 to 0.02 MPa; The absorption liquid includes the following components and mass fractions of each component: Piperazine 10%; N-methyldiethanolamine 35%; Deionized water balance; S2, set the temperature of the refrigeration device to 5℃, the temperature of the preheater to 40℃, the temperature of the heater to 98℃, the temperature of the condenser to 20℃, and the back pressure pressure of the third back pressure valve 45 to 0.10 MPa; S3, pass the natural gas to be decarburized from the refrigeration device inlet in the pretreatment unit; the refrigeration device inlet passes through a pressure of 3.0 MPa, a flow rate of 10 m 3 / h, and the CO2 content of the natural gas to be decarburized is 78.6969%; S4, set the back pressure pressure of the second back pressure valve 37 to 3.01 MPa; start the lean amine liquid pump and adjust the absorption liquid flow rate to 25 L / h; S5, collect the treated natural gas from the gas outlet of the gas-liquid separation tank 34 of the membrane absorption unit 3.

[0025] After the above operations are completed, after stable operation for 12 h, natural gas samples are taken from the sampling ports of the membrane separation unit and the membrane absorption unit for testing, gas chromatography is used to perform GB / T 13610-2020 test analysis, the CO2 content in the natural gas treated by the membrane separation unit is reduced to 4.5322%, and the CO2 content in the natural gas treated by the membrane absorption unit is reduced to 0.0023%.

[0026] In this embodiment, the CO2 in the natural gas is preliminarily removed by using the selective difference of the dense membrane in the membrane separation unit, and then the CO2 in the natural gas is deeply removed by using the different solubility and absorption saturation of CO2 and other components in the lean amine liquid in the membrane absorption unit, so that the CO2 content in the natural gas with a CO2 content of 78.6969% is reduced to 0.0023%, and the requirement for the CO2 content before natural gas liquefaction is met.

[0027] Example 2 A wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device is used for a method for deep removal of CO2 in wide-concentration natural gas, which includes the following steps: S1, configure lean amine liquid solution and transfer to lean amine liquid storage tank 32, set the back pressure pressure of the first back pressure valve 32 to 0.02 MPa; The absorption liquid includes the following components and mass fractions of each component: Piperazine 10%; N-methyldiethanolamine 40%; Deionized water balance; S2, set the temperature of the refrigeration device to 5℃, the temperature of the preheater to 50℃, the temperature of the heater to 105℃, the temperature of the condenser to 20℃, and the back pressure pressure of the third back pressure valve to 0.15MPa; S3, the pressure of the refrigeration device inlet in the pretreatment unit is 3.0MPa, the flow rate is 10m 3 / h, and the CO2 content of the natural gas is 12.3562%; S4, set the back pressure pressure of the second back pressure valve to 3.01MPa; start the lean amine liquid pump and adjust the absorption liquid flow rate to 25L / h; S5, collect the treated natural gas from the gas outlet of the gas-liquid separation tank 34 of the membrane absorption unit 3.

[0028] After the above operation is completed, after stable operation for 12h, natural gas samples are taken from the sampling ports of the membrane separation unit and the membrane absorption unit for testing, gas chromatography is used to perform GB / T 13610-2020 test analysis, the CO2 content in the natural gas treated by the membrane separation is reduced to 2.7156%, and the CO2 content in the natural gas treated by the membrane absorption is reduced to 0.0014%.

[0029] In this embodiment, the CO2 in the natural gas is preliminarily removed by the selective difference of the dense membrane in the membrane separation, and then the CO2 in the natural gas is deeply removed by the different solubility and absorption saturation of CO2 and other components in the lean amine liquid in the membrane absorption unit, so that the CO2 content in the natural gas with a CO2 content of 12.3562% is reduced to 0.0014%, and the requirement for the CO2 content before natural gas liquefaction is met.

[0030] Example 3 A wide-concentration-adapted natural gas deep decarburization membrane separation-membrane absorption device for a method for deep removal of CO2 in wide-concentration natural gas, comprising the following steps: S1, configure a lean amine liquid solution and transfer it to a lean amine liquid storage tank 32, and set the back pressure pressure of the first back pressure valve 32 to 0.04MPa; The absorption liquid comprises the following components and mass fractions of each component: Piperazine 10%; N-methyldiethanolamine 35%; Deionized water balance; S2, set the temperature of the refrigeration device to 10℃, the temperature of the preheater to 40℃, the temperature of the heater to 98℃, the temperature of the condenser to 30℃, and the back pressure pressure of the third back pressure valve to 0.15MPa; S3, the pressure of the refrigeration device inlet in the pretreatment unit is 3.0 MPa, and the flow rate is 50 m 3 / h, and the CO2 content of the natural gas is 78.6969%; S4, the second back pressure valve is set to a back pressure of 3.04 MPa; the lean amine liquid pump is started, and the absorption liquid flow rate is adjusted to 100 L / h; S5, the treated natural gas is collected from the gas outlet of the gas-liquid separation tank 34 of the membrane absorption unit 3.

[0031] After the above operation is completed, after stable operation for 12 h, natural gas samples are taken from the sampling ports of the membrane separation unit and the membrane absorption unit for testing, gas chromatography is used to perform GB / T 13610-2020 test analysis, the CO2 content in the natural gas treated by the membrane separation unit is reduced to 6.2418%, and the CO2 content in the natural gas treated by the membrane absorption unit is reduced to 0.0043%.

[0032] In this embodiment, the CO2 in the natural gas is preliminarily removed by using the selective difference of the dense membrane in the membrane separation unit, and then the CO2 in the natural gas is deeply removed by using the different solubility and absorption saturation of CO2 and other components in the lean amine liquid in the membrane absorption unit, so that the CO2 content in the natural gas with a CO2 content of 78.6969% is reduced to 0.0043%, and the requirement for the CO2 content before liquefaction of the natural gas is met.

[0033] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A wide-concentration-adaptive deep decarbonization membrane separation-membrane absorption device for natural gas, characterized in that: The system includes a pretreatment unit (1), a membrane separation unit (2), a membrane absorption unit (3), and a membrane regeneration unit (4) connected sequentially via pipelines. The pretreatment unit (1) includes a refrigeration device (11) and a filter (12) connected sequentially via pipelines. The membrane separation unit (2) includes a preheater (21) and a membrane separation assembly (22) connected sequentially via pipelines. The membrane absorption unit (3) includes a membrane absorption assembly (31), a lean amine liquid storage tank (32), and a gas-liquid separator (34). The outlet of the lean amine liquid storage tank (32) is connected to the lean amine liquid via pipelines. The liquid pump (33) is connected to the shell-side inlet of the membrane absorption assembly (31), and the shell-side outlet of the membrane absorption assembly (31) is connected to the membrane regeneration unit (4); the end outlet of the membrane absorption assembly (31) is connected to the gas-liquid separator (34) through a pipeline; the gas outlet of the gas-liquid separator (34) is connected to the gas collection device (35); the membrane regeneration unit (4) includes a flash tank (41), a heater (42), a membrane regeneration assembly (43) and a condenser (44) connected in sequence through pipelines; the outlet of the condenser (44) is connected to the lean amine liquid storage tank (32).

2. The wide-concentration-adaptive natural gas deep decarbonization membrane separation-membrane absorption device according to claim 1, characterized in that: The refrigeration device (11) is at least one of a throttling expansion valve, a refrigeration heat exchanger, or a turbine expander; the filter (12) is at least one of a polymer filter, a Y-type filter, or a molecular sieve filter.

3. The wide-concentration-adaptive natural gas deep decarbonization membrane separation-membrane absorption device according to claim 1, characterized in that: The membrane absorption assembly (31) includes a shell and a hydrophobic hollow fiber porous membrane disposed inside the shell. The gap between the hydrophobic hollow fiber porous membrane and the shell is the shell side, which constitutes the absorbent liquid flow channel. The inner cavity of the hydrophobic hollow fiber porous membrane constitutes the natural gas flow channel.

4. The wide-concentration-adaptive natural gas deep decarbonization membrane separation-membrane absorption device according to claim 1, characterized in that: A first back pressure valve (36) is provided at the top of the lean amine storage tank (32); a second back pressure valve (37) is provided on the pipeline between the shell-side outlet of the membrane absorption assembly (31) and the membrane regeneration unit (4); and a third back pressure valve (45) is provided at the top of the flash tank (41).

5. The wide-concentration-adaptive natural gas deep decarbonization membrane separation-membrane absorption device according to claim 1, characterized in that: The membrane absorption unit (3) also includes an absorbent flow meter (38) installed on the pipeline between the lean amine pump (33) and the shell-side inlet of the membrane absorption assembly (31).

6. The wide-concentration-adaptive natural gas deep decarbonization membrane separation-membrane absorption device according to claim 1, characterized in that: A natural gas pressure gauge (5) and a natural gas flow meter (6) are installed on the pipeline between the membrane separation unit (2) and the membrane absorption unit (3).

7. A method for deep removal of CO2 from wide-concentration natural gas using the apparatus described in any one of claims 1 to 6, characterized in that: Includes the following steps: S1. Prepare the lean amine solution and transfer it to the lean amine storage tank, and set the back pressure of the first back pressure valve. S2. Set the temperature of the refrigeration unit, preheater, heater and condenser and the back pressure of the third back pressure valve; S3. Introduce the natural gas to be decarbonized from the inlet of the refrigeration unit in the pretreatment unit; S4. Set the back pressure of the second back pressure valve according to the pressure of the incoming natural gas; start the lean amine liquid pump and adjust the absorption liquid flow rate by adjusting the operating frequency of the lean amine liquid pump according to the flow rate of the incoming natural gas. S5. Collect the processed natural gas from the gas outlet of the gas-liquid separator in the membrane absorption unit.

8. The method for deep CO2 removal from natural gas of wide concentration according to claim 7, characterized in that: The absorbent liquid comprises the following components and the mass fraction of each component: Piperazine 5%~13%; N-Methyldiethanolamine 35%~43%; Deionized water balance.

9. The method for deep CO2 removal from natural gas of wide concentration according to claim 7, characterized in that: The back pressure of the first back pressure valve is set to 0.02MPa~0.04MPa.

10. The method for deep CO2 removal from natural gas of wide concentration according to claim 7, characterized in that: The refrigeration device is set to a temperature of 5℃~10℃; the preheater is set to a temperature of 35℃~50℃; the heater is set to a temperature of 93℃~105℃; the condenser is set to a temperature of 20℃~30℃; the back pressure of the third back pressure valve is set to 0.10MPa~0.15MPa; the back pressure of the second back pressure valve 37 is 0.01MPa~0.04MPa higher than the natural gas pressure; and the absorption liquid flow rate is 0.002 times~0.003 times the natural gas flow rate.

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