Carbon dioxide trapping system and method

Abstract

The invention relates to a carbon dioxide trapping system and method. The system comprises a first membrane separation device and a first energy recovery device, the first membrane separation device is used for carrying out membrane separation treatment on flue gas to be treated to obtain first trapped gas and first permeated gas, and the first energy recovery device is used for carrying out pressure energy recovery on the first trapped gas; wherein the first trapped gas can expand to do work through the first energy recovery device, so that the first permeated gas leaves the first membrane separation device to enter the first energy recovery device under the action of negative pressure, and the first permeated gas leaves the first energy recovery device under the action of pressurization. According to the carbon dioxide trapping system / method provided by the embodiment of the invention, low-energy-consumption trapping of carbon dioxide can be realized, and the defect of high energy consumption in the prior art is overcome.

Description

Technical Field

[0001] The present invention relates to the capture of carbon dioxide, and in particular to a low-energy consumption carbon dioxide capture system and method. Background Art

[0002] In recent years, climate change has become a focus of public attention. The large-scale greenhouse gas emissions caused by human activities have brought irreversible and significant impacts to the global ecosystem. Among the many emission reduction technologies, carbon dioxide capture and storage (CCS) is considered to be the key technology to solve the carbon emission problem.

[0003] CO2 capture and storage technology has the potential to reduce costs and increase flexibility in achieving greenhouse gas emission reductions. In view of the huge flue gas flow of atmospheric flue gas in large-scale industries such as coal-fired power plants, steel metallurgy, cement building materials and petrochemicals, the existing separation technology faces many challenges. Whether it is to store CO2 or to utilize it as a resource, efficient and low-energy CO2 capture and separation technology is currently the main bottleneck.

[0004] Although the membrane separation method occupies a small area, has no phase change, and is easy to operate, it also has problems such as high energy consumption, high operating costs, low capture efficiency, and low purity of captured carbon dioxide. Therefore, it is of great significance to study a process technology and system that fully utilizes the characteristics and advantages of membrane separation, reduces operating energy consumption, and improves capture purity for CO2 capture and emission reduction. Summary of the invention

[0005] In order to overcome at least one of the defects of the prior art, in a first aspect, an embodiment of the present invention provides a carbon dioxide capture system, comprising:

[0006] A first membrane separation device, used for performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; and

[0007] a first energy recovery device, used for recovering energy from the first retentate gas;

[0008] The first retentate gas can expand and do work through the first energy recovery device, so that the first permeate gas leaves the first membrane separation device and enters the first energy recovery device under negative pressure, and leaves the first energy recovery device under increased pressure.

[0009] In a second aspect, an embodiment of the present invention provides a method for capturing carbon dioxide, comprising the following steps:

[0010] Performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; and

[0011] The first retentate gas is expanded through a first energy recovery device to perform work so that the first permeate gas enters the first energy recovery device under negative pressure, and the first permeate gas is pressurized in the first energy recovery device.

[0012] A carbon dioxide capture system / method according to one embodiment of the present invention can achieve low-energy capture of carbon dioxide, thus overcoming the disadvantage of high energy consumption in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0014] Figure 1 A schematic structural diagram of a carbon dioxide capture system according to an embodiment of the present invention;

[0015] The following are the descriptions of the reference numerals:

[0016] 10. Feed pipeline; 11. Booster; 12. First heat exchanger; 13. Cooler; 14. Gas-water separator; 20. First membrane separation device; 21. First permeate gas pipeline; 22. First retained gas pipeline; 23. Exhaust pipeline; 30. First energy recovery device; 40. Second membrane separation device; 41. Second permeate gas pipeline; 42. Second retained gas pipeline; 43. Second heat exchanger; 50. Second energy recovery device. DETAILED DESCRIPTION

[0017] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially for the purpose of illustration rather than for limiting the present invention. According to the description of the process flow, the part "connected" herein includes the meaning of being connected

[0018] Reference Figure 1 As shown, an embodiment of the present invention provides a carbon dioxide capture system, including a first membrane separation device 20 and a first energy recovery device 30; the first membrane separation device 20 is used to perform membrane separation treatment on the flue gas to be treated to obtain a first retained gas and a first permeate gas; the first energy recovery device 30 is used to recover energy from the first retained gas; wherein the first retained gas can expand and do work through the first energy recovery device 30 so that the first permeate gas enters the first energy recovery device 30 under the action of negative pressure, and in the first energy recovery device 30, the first permeate gas can be pressurized to push the first permeate gas out of the first energy recovery device 30.

[0019] In one embodiment, the first energy recovery device 30 includes a connected expander and a compressor. Both the expander and the compressor can be existing devices, and energy recovery can be performed through the combined action of the expander and the compressor.

[0020] In one embodiment, the expander includes a turbine, the compressor includes an impeller, and the turbine and the impeller are arranged on the same axis; the operating principle of the first energy recovery device 30 is: using the inertial impulse of the high-pressure gas (the first retained gas) to drive the turbine in the turbine chamber, and the turbine drives the coaxial impeller, the impeller sucks the first permeate gas, so that it is pressurized into the cylinder, and discharged at a pressurized level.

[0021] In one embodiment, the carbon dioxide capture system includes a feed pipeline 10, which is connected to a first membrane separation device 20, and the flue gas to be treated can enter the first membrane separation device 20 through the feed pipeline 10. Further, a booster 11, a first heat exchanger 12, a cooler 13, and a gas-water separator 14 are sequentially arranged on the feed pipeline 10 to perform pressurization treatment, temperature reduction treatment, and dehumidification treatment (or gas-liquid separation treatment) on the flue gas in the feed pipeline 10 to reach the temperature and pressure required for membrane separation treatment.

[0022] In one embodiment, the first membrane separation device 20 may be an existing device for capturing carbon dioxide by membrane separation, such as an existing carbon dioxide membrane separator, and the separation of carbon dioxide may be achieved by the pressure difference driving force on both sides of the membrane in the device. Further, the first membrane separation device 20 may include a first air inlet, a first air outlet, and a second air outlet, and the first air inlet is connected to the feed pipeline 10.

[0023] In one embodiment, the carbon dioxide capture system includes a first retentate gas pipeline 22, which is respectively connected to the first membrane separation device 20 and the first energy recovery device 30, and the first retentate gas discharged from the first membrane separation device 20 can enter the first energy recovery device 30 through the first retentate gas pipeline 22. Further, the first membrane separation device 20 is connected to the first retentate gas pipeline 22 through a first gas outlet.

[0024] In one embodiment, the first heat exchanger 12 is connected to the feed pipeline 10 and the first retentate gas pipeline 22, respectively. On the first retentate gas pipeline 22, the first heat exchanger 12 is arranged between the first membrane separation device 20 and the first energy recovery device 30; the first heat exchanger 12 is used to perform heat exchange between the first retentate gas in the first retentate gas pipeline 22 and the flue gas in the feed pipeline 10, so as to cool the flue gas to be treated by the first retentate gas; after the heat exchange, the temperature of the first retentate gas increases and becomes a gas with a higher temperature and pressure, which is conducive to energy recovery through the first energy recovery device 30.

[0025] In one embodiment, the first retentate gas can recover the heat of the compressed gas in the feed pipeline 10 through the first heat exchanger 12, and then enter the first energy recovery device 30 to perform work, which can realize the conversion of thermal energy and pressure energy into mechanical compression energy, and realize the recovery of more than 40% of the energy in the system.

[0026] In one embodiment, on the feed pipeline 10, the first heat exchanger 12 may be located between the booster 11 and the cooler 13. The first heat exchanger 12 may be an existing device, such as an existing gas-to-gas heat exchanger.

[0027] In one embodiment, the carbon dioxide capture system includes a first permeate gas pipeline 21, and the first membrane separation device 20 is connected to the first permeate gas pipeline 21 through the second gas outlet. Further, the first energy recovery device 30 is connected to the first permeate gas pipeline 21 and the first retentate gas pipeline 22, respectively, so that the energy recovered from the first retentate gas can be used for the first permeate gas.

[0028] In one embodiment, in the first retentate gas pipeline 22, the first retentate gas after heat exchange and temperature increase through the first heat exchanger 12 enters the first energy recovery device 30. At this time, the first retentate gas has a relatively high pressure and temperature, and can expand and do work in the first energy recovery device 30, that is, it drives the turbine on the driving side of the first energy recovery device 30 to rotate, thereby driving the compressor impeller on the other side connected thereto to rotate at the same time, and the compressor impeller forms a negative pressure, and the first permeate gas is sucked into the first energy recovery device 30 through the first permeate gas pipeline 21; in addition, the formation of negative pressure increases the pressure difference between the two sides of the membrane in the first membrane separation device 20, thereby increasing the permeability of carbon dioxide gas;

[0029] Furthermore, after the rotation and compression of the blades, the first permeate gas is pressurized, so that the high-pressure first permeate gas is discharged from the outlet of the first energy recovery device 30 and re-enters the first permeate gas pipeline 21. The energy of the first retentate gas is recovered and utilized by the first energy recovery device 30, so that a negative pressure condition can be formed to allow the first permeate gas to enter the first energy recovery device 30, and the first permeate gas can be further pressurized to push it into the subsequent operation device.

[0030] In one embodiment, the carbon dioxide capture system includes an exhaust pipeline 23, which is connected to the first energy recovery device 30. After the first trapped gas has expanded and performed work, it leaves the first energy recovery device 30 and is discharged out of the system through the exhaust pipeline 23 as purified exhaust gas.

[0031] In one embodiment, the carbon dioxide capture system includes a second membrane separation device 40, and the second membrane separation device 40 is used to perform membrane separation treatment on the first permeate gas to obtain a second retentate gas and a second permeate gas.

[0032] In one embodiment, the first permeate gas pipeline 21 is disposed between the first membrane separation device 20 and the second membrane separation device 40, and the first permeate gas pressurized by the first energy recovery device 30 can enter the second membrane separation device 40 for membrane separation treatment through the first permeate gas pipeline 21. The pressurization treatment by the first energy recovery device 30 can meet the pressure requirement of the second membrane separation device 40 for gas.

[0033] In one embodiment, by providing the first energy recovery device 30, a pressure difference driving force for secondary membrane treatment can be provided for the first permeate gas, so that energy consumption can be recovered more thoroughly, thereby greatly reducing the energy consumption of the system.

[0034] In one embodiment, the second membrane separation device 40 may be an existing device for capturing carbon dioxide by membrane separation, such as an existing carbon dioxide membrane separator, and the separation of carbon dioxide may be achieved through the pressure difference driving force on both sides of the membrane in the device. Further, the second membrane separation device 40 may include a second air inlet, a third air outlet, and a fourth air outlet, and the second air inlet is connected to the first permeate pipeline 21, so that the pressurized first permeate enters the second membrane separation device 40 for membrane separation treatment.

[0035] In one embodiment, the carbon dioxide capture system includes a second energy recovery device 50, which can be the same device as the first energy recovery device 30; the second retained gas can expand and do work through the second energy recovery device 50 so that the second permeate gas enters the second energy recovery device 50 under the action of negative pressure, and in the second energy recovery device 50, the second permeate gas can be pressurized to push the second permeate gas out of the second energy recovery device 50.

[0036] In one embodiment, a second permeate gas pipeline 41 and a second retained gas pipeline 42 respectively connected to the second membrane separation device 40 are provided outside the second membrane separation device 40. Further, the second permeate gas pipeline 41 is connected to the third gas outlet, and the second retained gas pipeline 42 is connected to the fourth gas outlet. After the membrane separation treatment is completed, the second permeate gas enters the second permeate gas pipeline 41 through the third gas outlet, and the second retained gas enters the second retained gas pipeline 42 through the fourth gas outlet.

[0037] In one embodiment, the second energy recovery device 50 is connected to the second permeate gas pipeline 41 and the second retentate gas pipeline 42, respectively. The second retentate gas discharged from the second membrane separation device 40 can enter the second energy recovery device 50 through the second retentate gas pipeline 42 to expand and do work. The specific process is as follows: the second retentate gas drives the turbine on the driving side of the second energy recovery device 50 to rotate, thereby driving the compressor impeller on the other side connected thereto to rotate at the same time, the compressor impeller forms a negative pressure, and the second permeate gas is sucked into the second energy recovery device 50 through the second permeate gas pipeline 41; further, the second permeate gas is pressurized after being compressed by the rotation of the blades, so that the high-pressure second permeate gas is discharged from the system as CO2 product (finished CO2) gas, and the CO2 product gas can enter the subsequent carbon dioxide refining process.

[0038] In one embodiment, a second heat exchanger 43 is provided on the first permeate gas pipeline 21, and the second heat exchanger 43 is provided between the first membrane separation device 20 and the second membrane separation device 40. The second retentate gas after expansion and work can be heat exchanged with the flue gas in the first permeate gas pipeline 21 through the second heat exchanger 43, so that the flue gas reaches the temperature required for membrane separation treatment. The second heat exchanger 43 can be an existing device, such as an existing gas-to-gas heat exchanger. Furthermore, the second retentate gas pipeline 42 is connected to the exhaust pipeline 23. After heat exchange treatment, the second retentate gas enters the exhaust pipeline 23 and is discharged from the system as purified exhaust gas.

[0039] In one embodiment, the carbon dioxide capture system includes a control system, which can be used to centrally control the entire system and process.

[0040] In one embodiment, the carbon dioxide capture system includes a flow meter, a temperature transmitter, a pressure transmitter, an electric switch valve, etc., which are used to regulate the flow, pressure regulation, temperature, etc. in the system; further, a flow meter, an electric switch valve, etc. can be set on each pipeline as needed.

[0041] In one embodiment, the booster 11 may be a blower or a compressor.

[0042] In one embodiment, the temperature of the flue gas can be reduced to the temperature required by the first membrane separation device 20, for example, not higher than 40° C., through the cooling treatment of the first heat exchanger 12 and the cooler 13. Similarly, the temperature of the flue gas in the first permeate gas pipeline 21 can be reduced to the temperature required by the second membrane separation device 40, for example, not higher than 40° C., through the cooling treatment of the second heat exchanger 43.

[0043] In one embodiment, the separation pressure of the first membrane separation device 20 and the second membrane separation device 40 can be 0.1-2 MPa (A), for example, 0.2 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa; and the retained gas pressure drop is not more than 20 kPa.

[0044] In one embodiment, the capture efficiency of the first membrane separation device 20 and the second membrane separation device 40 is not less than 50%.

[0045] In one embodiment, after the first retentate gas (or the second retentate gas) passes through the first energy recovery device 30 (or the second energy recovery device 50) to perform work, the temperature may drop to -100°C at the lowest.

[0046] One embodiment of the present invention provides a method for capturing carbon dioxide, which can be implemented by the aforementioned carbon dioxide capture, and the method comprises the following steps:

[0047] Performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; and

[0048] The first retentate gas is expanded through the first energy recovery device to do work so that the first permeate gas enters the first energy recovery device under negative pressure, and the first permeate gas is pressurized in the first energy recovery device.

[0049] In one embodiment, the first retentate gas is first subjected to heat exchange treatment with the flue gas to be treated, and then the first retentate gas after the heat exchange treatment is expanded to perform work.

[0050] In one embodiment, the first permeate gas is subjected to membrane separation treatment to obtain a second retained gas and a second permeate gas; thereafter, the second retained gas is expanded through a second energy recovery device to perform work so that the second permeate gas enters the second energy recovery device under negative pressure, and the second permeate gas is pressurized in the second energy recovery device.

[0051] In one embodiment, the second retentate gas after expansion and work is heat exchanged with the pressurized first permeate gas.

[0052] In one embodiment, the flue gas to be treated is pretreated before being subjected to membrane separation treatment, and the pretreatment includes pressurization treatment, heat exchange treatment and gas-liquid separation treatment.

[0053] In one embodiment, the pressure of the flue gas entering the first membrane separation device 20 can reach 0.1-2 MPa (A), such as 0.2 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, 1.5 MPa, and 1.8 MPa, through the pressurization treatment of the booster 11.

[0054] In one embodiment, the recovery energy of the first energy recovery device 30 or the second energy recovery device 50 is not less than 40% of the corresponding supercharging energy consumption.

[0055] In one embodiment, the flue gas to be treated may be flue gas containing carbon dioxide from power plants, cement plants, steel plants, metallurgical plants, chemical plants, etc.

[0056] A carbon dioxide capture system / method according to one embodiment of the present invention can achieve low-energy consumption and high-purity capture of carbon dioxide, overcoming the shortcomings of the prior art of high energy consumption and low capture purity.

[0057] A carbon dioxide capture system / method according to one embodiment of the present invention can capture carbon dioxide in flue gas, especially low-concentration (e.g., greater than or equal to 5 vol%) carbon dioxide flue gas, significantly reduce capture energy consumption, and obtain high-quality carbon dioxide.

[0058] A carbon dioxide capture system / method according to one embodiment of the present invention forms a vacuum (negative pressure) through the first energy recovery device 30 and the second energy recovery device 50, thereby increasing the driving force of the membrane separation process and greatly improving the separation effect.

[0059] In a carbon dioxide capture system / method according to one embodiment of the present invention, the compressed flue gas to be treated is cooled by a first heat exchanger 12, thereby significantly reducing the amount of cooling water used before the flue gas enters the first membrane separation device 20; further, the first permeate gas is cooled by a second heat exchanger 43, so that the flue gas does not need to be cooled by cooling water before entering the second membrane separation device 40.

[0060] The carbon dioxide capture system / method of one embodiment of the present invention makes full use of the pressure energy of the compressed flue gas; specifically, firstly, a primary membrane separation is performed, and then the pressure energy is recovered to form a vacuum and pressurization; then a secondary membrane separation is performed, and the pressure energy is further recovered to form a vacuum and pressurization, and the multi-gradient utilization of energy is achieved through one-time compression, which saves the primary vacuum pump, secondary compressor, secondary heat exchanger, secondary vacuum pump and other equipment and the corresponding operating energy consumption compared with the conventional membrane treatment process / device. Among them, the primary vacuum pump can be used to increase the osmotic pressure difference of the first membrane separation device 20; the secondary compressor can be used to pressurize the first permeate gas to reach the pressure of the membrane; the secondary heat exchanger can be used to cool the compressed first permeate gas; the secondary vacuum pump can be used to increase the osmotic pressure difference of the second membrane separation device 40.

[0061] Hereinafter, a carbon dioxide capture system and method according to an embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples.

[0062] Example 1

[0063] S1: The flow rate of flue gas to be treated is 6000Nm 3 / h, the pressure is 3KPa, the temperature is 40℃, and the carbon dioxide content is 14vol%; the flue gas to be treated is introduced into the feed pipeline 10, and flows through the booster 11, the first heat exchanger 12, the cooler 13, and the gas-water separator 14 in sequence for pressurization, cooling, and dehumidification to reach the temperature and pressure requirements required for membrane separation.

[0064] S2: The pretreated flue gas discharged from the feed pipeline 10 enters the first membrane separation device 20, and is separated by the separation membrane to form a first permeate gas and a first retentate gas rich in carbon dioxide gas; wherein the inlet pressure of the first membrane separation device 20 is 0.5 MPa and the temperature is 40°C.

[0065] S3: The first retained gas enters the first retained gas pipeline 22, and exchanges heat with the flue gas to be treated through the first heat exchanger 12 to recover heat, and the obtained high-temperature and high-pressure first retained gas enters the first energy recovery device 30; in the first energy recovery device 30, the first retained gas expands and performs work to drive the driving side turbine to rotate, thereby driving the compressor impeller on the other side connected thereto to rotate at the same time, and the compressor impeller forms a negative pressure, and the first permeated gas is forcibly sucked into the first energy recovery device 30 through the first permeated gas pipeline 12; further, the first permeated gas is pressurized after being compressed by the rotation of the blades, so that the high-pressure first permeated gas is discharged from the outlet of the first energy recovery device 30; in addition, the first retained gas after expansion and work is discharged from the system through the exhaust pipeline 23.

[0066] S4: The high-pressure first permeate gas discharged from the first energy recovery device 30 enters the second membrane separation device 40 after heat exchange treatment in the first permeate gas pipeline 21 through the second heat exchanger 43, and is separated by the separation membrane to form a second permeate gas and a second retained gas; wherein the inlet pressure of the second membrane separation device 40 is 0.5 MPa and the temperature is 40°C.

[0067] S5: The second retentate gas enters the second energy recovery device 50 through the second retentate gas pipeline 42, and the second permeate gas is forcibly sucked into the second energy recovery device 50 in the same manner as the first energy recovery device 30, and the second permeate gas is pressurized, and the pressurized second permeate gas is discharged from the system as CO2 product gas; the second retentate gas after expansion and work is heat exchanged with the flue gas in the first permeate gas pipeline 21 through the second heat exchanger 43, and then enters the exhaust pipeline 23, and is discharged from the system as purified exhaust gas;

[0068] Among them, the first energy recovery device 30 and the second energy recovery device 40 are both expansion machine and compressor combined devices; the carbon dioxide concentration involved in the process, the total energy consumption and the carbon dioxide capture rate, and the carbon dioxide concentration in the carbon dioxide product gas are shown in Table 1.

[0069] Example 2

[0070] This embodiment uses raw materials, devices, and process flow that are basically the same as those of Embodiment 1 to capture carbon dioxide, with the only difference being that the first energy recovery device 30 is replaced by TRT+vacuum pump+secondary compressor, and the second energy recovery device 40 is replaced by TRT+vacuum pump.

[0071] Among them, TRT is the existing blast furnace gas waste pressure turbine power generation device; the carbon dioxide concentration involved in the process, the total energy consumption and the carbon dioxide capture rate, and the carbon dioxide concentration in the carbon dioxide product gas are shown in Table 1.

[0072] Comparative Example

[0073] This example uses raw materials, equipment, and process flow that are basically the same as those of Example 1 to capture carbon dioxide, with the only differences being that: the first energy recovery device 30, the second energy recovery device 40, and the first retained gas pipeline 22, the second retained gas pipeline 42, etc. associated with the two recovery devices are not provided; a vacuum pump and a compressor are provided on the first permeate gas pipeline 21, and a vacuum pump is provided on the second permeate gas pipeline 41; and the first heat exchanger 12 and the second heat exchanger 43 both use external energy for heat exchange.

[0074] The carbon dioxide concentration involved in the process, the total energy consumption and the carbon dioxide capture rate, and the carbon dioxide concentration in the carbon dioxide product gas are shown in Table 1.

[0075] Table 1

[0076]

[0077] According to the description of Examples 1 and 2 of the present invention and the comparative example, when the carbon dioxide capture rate and the carbon dioxide concentration in the product gas are kept at a high level, Examples 1 and 2 can greatly reduce the energy consumption in the carbon dioxide capture process by setting the first energy recovery device 30 and the second energy recovery device 40. In addition, the first energy recovery device 30 and the second energy recovery device 40 use a compressor and an expander combined device, which can further reduce energy consumption compared to the use of TRT.

[0078] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0079] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A carbon dioxide capture system comprising: A first membrane separation device, used for performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; as well as a first energy recovery device, used for recovering energy from the first retentate gas; The first retentate gas can expand and do work through the first energy recovery device, so that the first permeate gas leaves the first membrane separation device and enters the first energy recovery device under negative pressure, and leaves the first energy recovery device under increased pressure.

2. The capture system according to claim 1, wherein: The first energy recovery device includes an expander and a compressor.

3. The capture system according to claim 1, comprising a first retentate gas pipeline, wherein the first retentate gas pipeline is connected to the first membrane separation device and the first energy recovery device respectively, and the first retentate gas can enter the first energy recovery device through the first retentate gas pipeline.

4. The capture system according to claim 3, comprising a first heat exchanger and a feed pipeline, wherein the feed pipeline is connected to the first membrane separation device, and the first heat exchanger is connected to the feed pipeline and the first retentate gas pipeline respectively; on the first retentate gas pipeline, the first heat exchanger is arranged between the first membrane separation device and the first energy recovery device; The flue gas to be treated can enter the first membrane separation device through the feed pipeline, and the first retentate gas can perform heat exchange with the flue gas in the feed pipeline through the first heat exchanger.

5. The capture system according to claim 1, comprising a second membrane separation device for performing membrane separation treatment on the first permeate gas to obtain a second retentate gas and a second permeate gas.

6. The capture system according to claim 5, comprising a second energy recovery device, wherein the second retentate gas can expand through the second energy recovery device to perform work so that the second permeate gas enters the second energy recovery device under negative pressure, and the second permeate gas leaves the second energy recovery device under increased pressure; and / or, The second energy recovery device includes an expander and a compressor.

7. The capture system according to claim 6, wherein: A first permeate gas pipeline is provided between the first membrane separation device and the second membrane separation device, and the first permeate gas discharged from the first energy recovery device can enter the second membrane separation device through the first permeate gas pipeline; a second heat exchanger is provided on the first permeate gas pipeline, and the second retentate gas after expansion work can exchange heat with the flue gas in the first permeate gas pipeline through the second heat exchanger; and / or, The second energy recovery device is connected to the second membrane separation device through a second permeate gas pipeline and a second retentate gas pipeline respectively.

8. A method for capturing carbon dioxide, comprising the following steps: Performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; and The first retentate gas is expanded through a first energy recovery device to perform work so that the first permeate gas enters the first energy recovery device under negative pressure, and the first permeate gas is pressurized in the first energy recovery device.

9. The capture method according to claim 8, wherein: Firstly, the first retentate gas and the flue gas to be treated are subjected to heat exchange treatment, and then the first retentate gas after the heat exchange treatment is expanded to perform work; and / or, The method comprises: subjecting the first permeate gas to membrane separation treatment to obtain a second retentate gas and a second permeate gas; as well as The second retentate gas is expanded through a second energy recovery device to perform work so that the second permeate gas enters the second energy recovery device under negative pressure, and the second permeate gas is pressurized in the second energy recovery device.

10. The capture method according to claim 9, wherein: exchanging heat between the second retentate gas after expansion and the first permeate gas after pressurization; and / or, The method comprises pre-treating the flue gas to be treated and then performing the membrane separation treatment, wherein the pre-treatment comprises pressurization treatment, heat exchange treatment and gas-liquid separation treatment.

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