Carbon dioxide trapping device and method

Abstract

The invention relates to a carbon dioxide trapping device and method. The device comprises a first membrane separation unit, an adsorption unit, a desorption unit and a second membrane separation unit, wherein the first membrane separation unit is used for performing membrane separation treatment on flue gas to be treated; the adsorption unit is used for carrying out carbon dioxide adsorption treatment on the intercepted gas; the desorption unit is used for carrying out carbon dioxide removal treatment on the adsorbent adsorbed with carbon dioxide in the adsorption unit; and the second membrane separation unit is used for carrying out membrane separation treatment on the permeation desorption gas. The carbon dioxide trapping device / method provided by the embodiment of the invention has the characteristics of low energy consumption and high trapping rate, and can overcome the defects of high energy consumption and low trapping rate in the existing carbon dioxide trapping technologies of an adsorption method and a membrane separation method.

Description

Technical Field

[0001] The present invention relates to the capture of carbon dioxide, and in particular to a device and method for capturing carbon dioxide by coupling membrane treatment with adsorption. Background Art

[0002] In recent years, climate change has become a focus of public attention. The large amount of greenhouse gas emissions caused by human activities has 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. The huge flue gas flow and velocity of atmospheric flue gas in large-scale industries such as coal-fired power plants, steel metallurgy, cement building materials and petrochemicals have increased the cost and technical difficulty of operating large-scale CO2 capture systems. Existing separation technologies face 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] The adsorption method has certain advantages due to its simple equipment, easy automation, low corrosion, simple process amplification rules, etc. It is one of the most promising alternative technologies for capturing and separating CO2 gas for large-scale application. However, the adsorption method also has problems such as low separation rate, slow desorption rate, long cooling process, and high cost of capturing flue gas with low carbon dioxide content. 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 cost, low capture efficiency, and low purity of captured carbon dioxide. Summary of the invention

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

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

[0007] An adsorption unit, used for adsorbing carbon dioxide on the trapped gas to obtain trapped adsorbed gas;

[0008] a desorption unit, used for removing carbon dioxide from the adsorbent adsorbed with carbon dioxide in the adsorption unit to obtain permeate desorbed gas; and

[0009] A second membrane separation unit, used for performing membrane separation treatment on the permeate desorbed gas to obtain a second retentate gas and a carbon dioxide product;

[0010] The desorption unit is connected to the first membrane separation unit and the adsorption unit respectively, and the first permeate gas can enter the adsorption unit through the desorption unit to perform heat exchange with the adsorbent to heat the adsorbent; the retained gas includes the first retained gas and the second retained gas.

[0011] In a second aspect, an embodiment of the present invention provides a method for capturing carbon dioxide, comprising the following steps:

[0012] The flue gas to be treated is subjected to membrane separation treatment to obtain a first retentate gas and a first permeate gas;

[0013] Adsorbing carbon dioxide on the trapped gas after membrane separation by an adsorbent to obtain trapped adsorbed gas;

[0014] removing carbon dioxide from the adsorbent adsorbing carbon dioxide to obtain permeate desorbed gas; and

[0015] The permeate desorbed gas is subjected to membrane separation treatment to obtain a second retentate gas and a carbon dioxide product;

[0016] The trapped gas includes the first trapped gas and the second trapped gas; in the process of removing carbon dioxide, the adsorbent is heated by heat exchange between the first permeate gas and the adsorbent, so that the adsorbent removes carbon dioxide; the permeate-desorbed gas includes the first permeate gas and the removed carbon dioxide.

[0017] A carbon dioxide capture device / method according to one embodiment of the present invention has the characteristics of low energy consumption and high capture rate, and can overcome the defects of high energy consumption and low capture rate in existing adsorption and membrane separation carbon dioxide capture technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0019] Figure 1 A carbon dioxide capture device according to an embodiment of the present invention;

[0020] Figure 2 A process flow chart of a carbon dioxide capture method according to an embodiment of the present invention;

[0021] The following are the descriptions of the reference numerals:

[0022] 10. Feed pipeline; 11. First booster; 12. First heat exchanger; 13. Residual pressure recovery machine; 14. Second heat exchanger; 15. Third heat exchanger; 16. Gas-water separator; 20. First membrane separation device; 30. Adsorption tower; 40. Second membrane separation device; 41. Second booster; 42. Fourth heat exchanger; 51. First intercepted gas pipeline; 52. Second intercepted gas pipeline; 53. Intercepted adsorption gas pipeline; 61. Permeate gas pipeline; 62. Permeate desorption gas pipeline; 70. Gas outlet pipeline. DETAILED DESCRIPTION

[0023] 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.

[0024] Reference Figure 1 , 2 As shown, one embodiment of the present invention provides a carbon dioxide capture device, comprising a first membrane separation unit, an adsorption unit, a desorption unit, and a second membrane separation unit; wherein the first membrane separation unit is used to perform membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; the adsorption unit is used to perform carbon dioxide adsorption treatment on the retentate gas to obtain a retentate adsorbed gas; the desorption unit is used to perform a treatment of removing carbon dioxide from an adsorbent adsorbed with carbon dioxide in the adsorption unit to obtain a permeate desorbed gas; the second membrane separation unit is used to perform membrane separation treatment on the permeate desorbed gas to obtain a second retentate gas and a carbon dioxide product;

[0025] Among them, the desorption unit is connected to the first membrane separation unit and the adsorption unit respectively. The first permeate gas can enter the adsorption unit through the desorption unit to exchange heat with the adsorbent to heat the adsorbent, so as to facilitate the removal of carbon dioxide in the adsorbent. The permeate-desorption gas includes the first permeate gas and the removed carbon dioxide gas; the retained gas includes the first retained gas and the second retained gas.

[0026] In one embodiment, the carbon dioxide capture device further includes a flue gas pretreatment unit, which includes a feed pipeline 10 and a residual pressure recovery component. The feed pipeline 10 is connected to the first membrane separation unit, and the flue gas to be treated can enter the first membrane separation unit through the feed pipeline 10; a retained adsorbed gas pipeline 53 is arranged outside the adsorption unit, and both ends of the retained adsorbed gas pipeline 53 are connected to the adsorption unit, and the residual pressure recovery component is respectively connected to the feed pipeline 10 and the retained adsorbed gas pipeline 53; the retained adsorbed gas can expand and do work through the residual pressure recovery component to increase the pressure of the flue gas to be treated, and the temperature of the retained adsorbed gas is reduced. The retained adsorbed gas after cooling can enter the adsorption unit through the retained adsorbed gas pipeline 53.

[0027] In one embodiment, the residual pressure recovery component can be an existing device that achieves pressurization and / or cooling based on gas expansion work, which can be an existing residual pressure recovery machine 13 (or residual pressure recovery refrigerator), such as a blast furnace gas residual pressure recovery turbine power generation device (TRT for short).

[0028] In one embodiment, the flue gas pretreatment unit includes a first booster 11, a first heat exchanger 12, a residual pressure recovery machine 13, a second heat exchanger 14, a third heat exchanger 15 and a gas-water separator 16 which are sequentially arranged in the feed pipeline 10, and the above devices are arranged in sequence along the flow direction of the gas in the feed pipeline 10. Among them, the flue gas to be treated is firstly pressurized by the first booster 11, then pressurized by the residual pressure recovery machine 13, and cooled and dehumidified by the first heat exchanger 12, the second heat exchanger 14, the third heat exchanger 15 and the gas-water separator 16, so as to reach the temperature and pressure required for the membrane separation treatment of the first membrane separation unit.

[0029] In one embodiment, the adsorption unit comprises one or more adsorption towers 30, Figure 1 The device includes only one adsorption tower 30, which is divided into three descriptions in order to more clearly present the three process steps of the adsorption tower 30 during operation, namely, adsorption treatment, thermal desorption treatment (referred to as thermal desorption) and cold adsorption treatment (referred to as cold adsorption, also the second adsorption treatment).

[0030] In one embodiment, the adsorption unit may include three adsorption towers 30 , and the adsorption process, the thermal desorption process, and the cold adsorption process may be performed in the three adsorption towers 30 , respectively.

[0031] In one embodiment, the adsorption tower 30 includes a feed port and a discharge port, wherein the feed port is used for materials to enter the adsorption tower 30, and the discharge port is used to discharge the materials from the adsorption tower 30; further, the feed port may be located at the bottom of the adsorption tower 30, and the discharge port may be located at the top of the adsorption tower 30. An adsorbent for carbon dioxide is provided in the adsorption tower 30 to adsorb carbon dioxide from the gas introduced. Furthermore, the adsorbent provided in the adsorption tower 30 may be an existing adsorbent, preferably an adsorbent having better adsorption performance at low temperatures (e.g., -40°C to 10°C), such as activated carbon, molecular sieves, or adsorbents prepared from coal liquefaction asphalt residues. The adsorbent prepared from coal liquefaction asphalt residues has the best adsorption performance at low temperatures, especially at -10°C.

[0032] In one embodiment, the adsorption tower 30 is connected to the first membrane separation unit and the second membrane separation unit, respectively. Further, the feed port of the adsorption tower 30 is connected to the first membrane separation unit and the second membrane separation unit, respectively, so that the first retained gas and the second retained gas can enter the adsorption tower 30 and then the retained gas is treated by adsorption of carbon dioxide through the adsorbent.

[0033] In one embodiment, the first membrane separation unit includes a first membrane separation device 20, which can be an existing device used for membrane separation treatment to capture carbon dioxide, such as an existing carbon dioxide membrane separator, which can achieve carbon dioxide separation through the pressure difference driving force on both sides of the membrane in the device; further, the first membrane separation device 20 may include an air inlet, a first air outlet and a second air outlet, which is connected to the feed pipeline 10 through the air inlet so that the flue gas to be treated enters the first membrane separation device 20 for membrane separation treatment; the first air outlet and the second air outlet of the first membrane separation device 20 are both connected to the feed port of the adsorption tower 30.

[0034] In one embodiment, the first gas outlet of the first membrane separation device 20 is connected to the feed port of the adsorption tower 30 through the first retained gas pipeline 51, so that the first retained gas generated by the first membrane separation device 20 enters the adsorption tower 30 through the first retained gas pipeline 51, and is subjected to carbon dioxide adsorption treatment by the adsorbent to obtain retained adsorbed gas from which carbon dioxide is preliminarily removed.

[0035] In one embodiment, the retained adsorption gas pipeline 53 is respectively connected to the discharge port and the feed port of the adsorption tower 30, and the retained adsorption gas can re-enter the adsorption tower 30 through the retained adsorption gas pipeline 53 to be subjected to carbon dioxide adsorption treatment by the adsorbent; the first heat exchanger 12 is respectively connected to the feed pipeline 10 and the retained adsorption gas pipeline 53, so that the flue gas to be treated in the feed pipeline 10 can be heat exchanged with the retained adsorption gas in the retained adsorption gas pipeline 53 through the first heat exchanger 12, so as to cool the flue gas to be treated, thereby saving energy consumption.

[0036] Furthermore, the trapped adsorbed gas after the heat exchange treatment can work on the flue gas to be treated in the feed pipeline 10 through the residual pressure recovery machine 13, so that the flue gas to be treated is pressurized, and the trapped adsorbed gas is cooled and reduced in pressure. Specifically, the trapped adsorbed gas is compressed by expanding to increase the pressure of the flue gas to be treated, so as to meet the pressure requirement of the first membrane separation unit for the gas; while the trapped adsorbed gas expands and works, its own temperature drops, and the low-temperature trapped adsorbed gas enters the adsorption tower 30, which can achieve rapid cooling of the carbon dioxide adsorbent, which is conducive to the adsorption in the subsequent cycle, and can also achieve the re-adsorption of carbon dioxide in the trapped gas (second adsorption treatment), and the adsorption efficiency can be not less than 50%; after the adsorption tower 30 is cooled to a certain temperature, the entire cycle is completed. In addition, the adsorbent has a better adsorption effect at low temperature, which can further remove the remaining carbon dioxide in the trapped adsorbed gas, so that the gas meets the requirements of purified emission; the purified exhaust gas can be discharged from the adsorption tower 30 from the discharge port, and discharged from the device through the outlet pipe 70.

[0037] In one embodiment, the use of the residual pressure recovery machine 13 allows the retained adsorbed gas to expand and do work, thereby achieving compression of the flue gas to be treated and cooling of the retained adsorbed gas itself. The recovery energy consumption in the process is not less than 40% of the boosting energy consumption. The temperature of the retained adsorbed gas after cooling is not higher than 30°C, and can be reduced to -100°C at the lowest; the temperature of the retained adsorbed gas after cooling can be -100°C to 30°C, for example, -80°C, -50°C, -30°C, -20°C, -10°C, 0°C, 50°C, 10°C, 15°C, 20°C, and 25°C.

[0038] In one embodiment, the desorption unit includes a permeate gas pipeline 61, and the second gas outlet of the first membrane separation device 20 is connected to the feed port of the adsorption tower 30 through the permeate gas pipeline 61, and the first permeate gas generated by the first membrane separation device 20 can enter the adsorption tower 30 through the permeate gas pipeline 61; further, the second heat exchanger 14 located on the feed pipeline 10 is also connected to the permeate gas pipeline 61, so that the first permeate gas in the permeate gas pipeline 61 can be heat exchanged with the flue gas in the feed pipeline 10 through the second heat exchanger 14, so that the temperature of the flue gas is reduced to further meet the temperature requirement of the first membrane separation unit for the gas, and the temperature of the first permeate gas is increased; when the carbon dioxide in the adsorbent in the adsorption tower 30 reaches saturation, the first permeate gas is subjected to the above-mentioned heat exchange treatment with the flue gas in the feed pipeline 10, and then the first permeate gas is passed into the adsorption tower 30, the adsorbent is heated by the high-temperature first permeate gas, and a decompression operation is performed to achieve desorption of carbon dioxide, and a permeate-desorbed gas containing desorbed carbon dioxide is formed in the adsorption tower 30. The above-mentioned decompression may include natural pressure relief of the adsorption tower 30 , or may include using a low-pressure first permeate gas to enter the adsorption tower 30 .

[0039] In one embodiment, the discharge port of the adsorption tower 30 is connected to the second membrane separation unit through the permeation desorption gas pipeline 62, and the permeation desorption gas can enter the second membrane separation unit through the permeation desorption gas pipeline 62. The second membrane separation unit includes a second membrane separation device 40, and the second membrane separation device 40 can be an existing device for capturing carbon dioxide through membrane separation treatment, such as an existing carbon dioxide membrane separator; further, the second membrane separation device 40 may include a second air inlet, a third air outlet, and a fourth air outlet, which is connected to the permeation desorption gas pipeline 62 through the second air inlet, so that the permeation desorption gas enters the second membrane separation device 40 for membrane separation treatment to obtain a second retained gas and a second permeate gas; the second permeate gas is directly discharged from the second membrane separation device 40 through the third air outlet as a finished carbon dioxide product. The fourth gas outlet of the second membrane separation device 40 is connected to the feed port of the adsorption tower 30 through the second retained gas pipeline 52, so that the second retained gas can enter the adsorption tower 30 through the second retained gas pipeline 52, and then the first retained gas and the second retained gas are adsorbed by the adsorbent in the adsorption tower 30 to treat carbon dioxide.

[0040] In one embodiment, a second booster 41 and a fourth heat exchanger 42 may be further provided on the permeate-desorption gas pipeline 62, so that the gas in the pipeline can reach the temperature and pressure required for the membrane separation process of the second membrane separation unit through their functions.

[0041] In one embodiment, the discharge port of the adsorption tower 30 is connected to the gas outlet pipeline 70, and the fourth heat exchanger 42 located on the permeation desorption gas pipeline 62 is also connected to the gas outlet pipeline 70, so that the purified exhaust gas in the gas outlet pipeline 70 can be heat exchanged with the permeation desorption gas in the permeation desorption gas pipeline 62 through the fourth heat exchanger 42.

[0042] In one embodiment, on the feed pipeline 10, the third heat exchanger 15 and the gas-water separator 16 are located between the second heat exchanger 14 and the first membrane separation unit, so that the flue gas in the feed pipeline 10 treated by the second heat exchanger 14 is subjected to another heat exchange treatment by the third heat exchanger 15 to meet the temperature requirement of the first membrane separation unit for the intake air.

[0043] In one embodiment, the first supercharger 11 and the second supercharger 41 may both be blowers or compressors.

[0044] In one embodiment, the control system can be used to control the programmable valve of the adsorption tower 30 to achieve switching between different process steps in the tower; for example, after the carbon dioxide adsorption tower completes the desorption process, the feed passage can be switched to the cooled retained adsorption gas to enter the adsorption tower 30 through the switch valve at the inlet and outlet of the adsorption tower.

[0045] In one embodiment, the adsorption tower 30 can be an existing device, which can be used for the adsorption and desorption of carbon dioxide and the pressurization, decompression, vacuumization, heating, cooling and other operations required in the process. Among them, the feed port of the adsorption tower 30 can be connected to multiple pipelines such as the first trapped gas pipeline 51, the second trapped gas pipeline 52, the trapped adsorption gas pipeline 53, etc., and a connection control device can be set between the feed port and these pipelines to achieve the connection switching between different pipelines and the adsorption tower 30, so that only one pipeline is connected to the adsorption tower 30 during operation. Similarly, the discharge port of the adsorption tower 30 can be connected to multiple pipelines such as the trapped adsorption gas pipeline 53, the permeation desorption gas pipeline 62, and the gas outlet pipeline 70, respectively, and a connection control device can be set between the discharge port and these pipelines to achieve the connection switching between different pipelines and the adsorption tower 30.

[0046] In one embodiment, the carbon dioxide capture device further includes a flow meter, a temperature transmitter, a pressure transmitter, an electric switch valve, a control system, etc., which can be arranged on each pipeline. Among them, the flow meter, temperature transmitter, pressure transmitter, electric switch valve, etc. are used for flow control, pressure regulation, temperature control, etc.; the control system is used for centralized control of the overall process and equipment to achieve low energy consumption and high efficiency capture of carbon dioxide.

[0047] Reference Figure 2 As shown, one embodiment of the present invention provides a carbon dioxide capture method that can be implemented in the above-mentioned device, comprising the following steps:

[0048] The flue gas to be treated is subjected to membrane separation treatment to obtain a first retentate gas and a first permeate gas;

[0049] Adsorbing carbon dioxide on the trapped gas after membrane separation by an adsorbent to obtain trapped adsorbed gas;

[0050] performing a process for removing carbon dioxide from the adsorbent adsorbed with carbon dioxide (desorption process) to obtain a permeate desorbed gas; and

[0051] The permeate desorbed gas is subjected to membrane separation treatment to obtain a second retentate gas and a carbon dioxide product;

[0052] Among them, the above-mentioned trapped gas subjected to carbon dioxide adsorption treatment includes a first trapped gas and a second trapped gas; during the desorption process, the first permeate gas is heat exchanged with the adsorbent to heat the adsorbent, and high temperature conditions are more conducive to desorption; the permeate-desorbed gas includes the first permeate gas after heat exchange and the carbon dioxide gas removed by the adsorbent.

[0053] In one embodiment, the trapped adsorbed gas can be expanded to increase the pressure of the flue gas to be treated and reduce the temperature of the trapped adsorbed gas.

[0054] In one embodiment, the retained adsorbed gas is subjected to heat exchange treatment with the flue gas to be treated, and then the flue gas to be treated is pressurized by the retained adsorbed gas.

[0055] In one embodiment, the adsorbent is cooled by intercepting the adsorbed gas. The low temperature provided by the intercepted adsorbed gas is more conducive to the adsorption of carbon dioxide by the adsorbent. While cooling, the adsorbent can perform a second adsorption treatment of carbon dioxide on the intercepted adsorbed gas.

[0056] In one embodiment, the first permeate gas is subjected to heat exchange treatment with the flue gas to be treated after the pressurization treatment.

[0057] In one embodiment, the permeate desorption gas is first heat exchanged with the gas after the second adsorption treatment, and then membrane separation treatment is performed.

[0058] In one embodiment, the flue gas to be treated is pretreated before being subjected to membrane separation treatment. Furthermore, the pretreatment includes heat exchange treatment, pressurization treatment and gas-water separation treatment.

[0059] In one embodiment, the flue gas to be treated can be pressurized by the first booster 11 and the residual pressure recovery machine 13. After two stages of pressurization, the pressure of the flue gas to be treated can reach, for example, 0.1-2 MPa (A).

[0060] In one embodiment, the flue gas to be treated may be subjected to heat exchange treatment through the first heat exchanger 12, the second heat exchanger 14, and the third heat exchanger 15, so that the temperature of the flue gas to be treated reaches the temperature required for membrane separation treatment, for example, not higher than 40°C.

[0061] In one embodiment, the flue gas to be treated may be subjected to gas-water separation treatment by a gas-water separator 16 to remove moisture from the treated flue gas.

[0062] In one embodiment, the flue gas to be treated is first pressurized by the first booster 11, then pressurized by the residual pressure recovery machine 13, and cooled and dehumidified by three heat exchangers and a gas-water separator 16 to reach the temperature and pressure required for membrane separation treatment.

[0063] In one embodiment, membrane separation treatment can be performed by a first membrane separation device 20 and a second membrane separation device 40. The separation pressure in the membrane separation device can be 0.1-2 MPa (A), the trapped gas pressure drop can be no more than 20 kPa, and the membrane separation capture efficiency can be no less than 50%.

[0064] In one embodiment, the adsorption treatment of carbon dioxide can be performed by the adsorption tower 30; during the adsorption of the trapped gas in the adsorption tower 30, the adsorption pressure can be 0.1-2MPa(A), the resistance loss during the adsorption process can be no more than 20KPa, and the adsorption efficiency can be no less than 60%.

[0065] In one embodiment, during the desorption process, the desorption pressure may be 0-0.1 MPa(A), such as 0.05 MPa; the temperature may be 40-150°C, such as 50°C, 60°C, 80°C, 100°C, 120°C.

[0066] In one embodiment, the collection device includes a plurality of adsorption towers 30, and each adsorption tower 30 can perform adsorption treatment, thermal desorption treatment and cold adsorption treatment according to the situation to achieve continuous operation of the capture process.

[0067] 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.

[0068] One embodiment of the present invention makes full use of the pressure energy of the compressed flue gas to be treated. Specifically, membrane separation treatment is first performed, and then high-pressure adsorption, expansion work, and low-temperature adsorption are performed. Through one compression, multi-gradient utilization of energy is achieved, which saves equipment such as compressors and refrigerators and operating energy consumption compared to conventional processes.

[0069] One embodiment of the present invention uses a gas expansion cooling process to fully utilize the cooled trapped gas to cool the adsorbent, thereby simplifying the adsorbent cooling process of temperature swing adsorption, which can greatly reduce the cooling time and improve the efficiency of the overall device; at the same time, a low-temperature adsorbent is used to perform low-temperature adsorption on the trapped gas, thereby improving the capture rate. The capture rate of CO2 is greatly improved compared to traditional processes, and the capture rate can be increased by more than 5%.

[0070] In one embodiment of the present invention, a self-circulation of low-temperature adsorption-high-temperature desorption is achieved by exchanging heat between the first permeated gas and the compressed flue gas to be treated to recover heat, and using the first permeated gas to heat the adsorbent.

[0071] A carbon dioxide capture device / method according to one embodiment of the present invention can capture carbon dioxide in flue gas, especially low-concentration carbon dioxide flue gas, significantly reduce capture energy consumption, greatly improve capture efficiency, and obtain high-quality carbon dioxide products.

[0072] The carbon dioxide capture device / method of one embodiment of the present invention combines the characteristics and advantages of adsorption and membrane separation, couples the two processes and forms a 1+1 greater than 2 effect after coupling, which can improve the overall energy efficiency and capture efficiency of the process. For example, the capture rate of carbon dioxide can be no less than 90%, which is more than 10% higher than that of the secondary membrane treatment or secondary adsorption process.

[0073] A carbon dioxide capture device / method according to one embodiment of the present invention couples membrane separation with adsorption separation. The coupling is that the trapped gas generated by membrane separation can be used as a raw material for the adsorption process, the first permeate gas can be used as a desorption medium, and the exhaust air after adsorption (trapped adsorbed gas) is fed back to the pressurization of the gas required for membrane separation; at the same time, there are multiple heat and cold conversions between the membrane separation process and the adsorption process, that is, the two processes are fed back to each other, rather than the traditional series or parallel connection; and the coupled process can achieve a significant increase in the carbon dioxide capture rate and the purity of the captured carbon dioxide on the basis of reducing the total energy consumption, compared with secondary adsorption or secondary membrane separation.

[0074] A carbon dioxide capture device / method according to one embodiment of the present invention is used to capture carbon dioxide from power plant flue gas (carbon dioxide content of about 15%), with a capture efficiency of more than 90%, a capture energy consumption of less than 2.5 GJ / t-CO2, and a purity of more than 90% of the obtained carbon dioxide; and a carbon dioxide capture device / method is used to capture carbon dioxide from chemical plant tail gas (carbon dioxide content of about 50%), with a capture efficiency of more than 90%, a capture energy consumption of less than 1.5 GJ / t-CO2, and a purity of more than 95% of the obtained carbon dioxide.

[0075] Hereinafter, a carbon dioxide capture device / method according to an embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples. Wherein, unless otherwise specified, the raw materials used are all commercially available.

[0076] Example 1

[0077] S1: The flue gas to be treated is the flue gas from the desulfurization tower of the power plant, and the flue gas flow rate is 6000Nm 3 / h, the flue gas temperature is 40°C; the flue gas to be treated is introduced into the feed pipeline 10 from the feed port of the feed pipeline 10, and flows through the first booster 11, the first heat exchanger 12, the residual pressure recovery machine 13, the second heat exchanger 14, the third heat exchanger 15 and the gas-water separator 16 in sequence; wherein, the flue gas to be treated is pressurized to 200 kPa (the temperature rises to about 120°C) by the first booster 11, cooled by the first heat exchanger 12 (cooled to about 60°C), and then enters the residual pressure recovery machine 13 for secondary pressurization to reach 300 kPa (the temperature rises to about 140°C), and then enters the second heat exchanger 14 for heat exchange (cooled to about 80°C), the third heat exchanger 15 (cooled to about 40°C), and then enters the gas-water separator 16 for dehumidification, and the obtained flue gas (pretreated flue gas) has a pressure of 295 kPa and a temperature of 40°C.

[0078] 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 produce a first permeate gas and a first retentate gas rich in carbon dioxide gas; wherein the first retentate gas enters the adsorption tower 30 through the first retentate gas pipeline 51, and the adsorbent in the adsorption tower 30 adsorbs carbon dioxide on the first retentate gas to obtain a retentate adsorbed gas.

[0079] S3: The retained adsorbed gas is discharged from the adsorption tower 30 from the discharge port of the adsorption tower 30 and enters the retained adsorbed gas pipeline 53; in the retained adsorbed gas pipeline 53, the retained adsorbed gas exchanges heat with the flue gas to be treated in the feed pipeline 10 through the first heat exchanger 12, and works on the flue gas to be treated through the residual pressure recovery machine 13 to increase the pressure of the flue gas to be treated, while the retained adsorbed gas is cooled; the retained adsorbed gas after cooling re-enters the adsorption tower 30 to cool the adsorbent, and undergoes a second adsorption treatment (cold absorption) of carbon dioxide through the adsorbent to obtain purified exhaust gas; the purified exhaust gas is discharged from the adsorption tower 30 from the discharge port of the adsorption tower 30, and is discharged out of the device through the exhaust pipeline 70.

[0080] S4: The first permeate gas enters the permeate gas pipeline 61 from the second gas outlet of the first membrane separation device 20. In the permeate gas pipeline 61, the first permeate gas exchanges heat with the flue gas to be treated in the feed pipeline 10 through the second heat exchanger 14, so that the temperature of the flue gas to be treated is reduced, and at the same time the temperature of the first permeate gas is increased; the high-temperature first permeate gas enters the adsorption tower 30, and the saturated adsorbent is made to remove carbon dioxide under high temperature and reduced pressure conditions to obtain permeate-desorbed gas; wherein the permeate-desorbed gas includes the first permeate gas after heat exchange with the adsorbent and the desorbed carbon dioxide gas.

[0081] S5: The permeate desorption gas is discharged from the adsorption tower 30 from the discharge port of the adsorption tower 30 and enters the permeate desorption gas pipeline 62; in the permeate desorption gas pipeline 62, the permeate desorption gas is first pressurized by the second booster 41, and then heat exchanged with the purified exhaust gas in the gas outlet pipeline 70 through the fourth heat exchanger 42, and then the permeate desorption gas enters the second membrane separation device 40.

[0082] S6: After the permeate-desorbed gas is subjected to membrane separation treatment in the second membrane separation device 40, a second retentate gas and a second permeate gas are formed; the second retentate gas enters the adsorption tower 30 through the second retentate gas pipeline 52 and is adsorbed by the adsorbent together with the first retentate gas in step S2; the second permeate gas is directly discharged from the second membrane separation device 40 as a finished carbon dioxide product; wherein the mass concentration of carbon dioxide in the finished carbon dioxide product is 95.5%, and other parameters involved are shown in Table 1, and the test results are shown in Table 2.

[0083] Table 1

[0084] name Carbon dioxide mass content pressure temperature Flue gas to be treated 15％ 300KPa 40℃ First retentate gas 5％ 290KPa 40℃ First-stage purification exhaust air 2％ 280KPa 42℃ Secondary purification exhaust air 2％ 10KPa -30℃ Final purification of exhaust air 0.5％ 1KPa 15℃

[0085] Note: In Table 1, the first-stage purified exhaust air refers to the retained adsorbed gas, the second-stage purified exhaust air refers to the retained adsorbed gas after passing through the residual pressure recovery machine 13, and the final purified exhaust air refers to the gas discharged from the exhaust pipeline 70.

[0086] Comparative Example 1

[0087] The flue gas from the desulfurization tower of the power plant is used as the flue gas to be treated, and the flue gas flow rate is 6000Nm 3 / h, the flue gas temperature is 40℃, and the existing device is used to capture carbon dioxide. The specific process is as follows:

[0088] The flue gas to be treated is pressurized to 300 kPa by the first compressor, cooled by the heat exchanger, and dehumidified by the gas-water separator to obtain the flue gas to be adsorbed (pressure is 295 kPa, temperature is 40°C).

[0089] The flue gas to be adsorbed is passed through a primary membrane separation device, and after membrane separation treatment, a primary retentate gas and a primary permeate gas are obtained; wherein, the primary retentate gas enters the chimney for evacuation; the primary permeate gas rich in carbon dioxide gas is sucked by a vacuum pump and then enters the second compressor, and after heat exchange, enters the secondary membrane separation device for membrane separation treatment to obtain secondary retentate gas and secondary permeate gas; the primary retentate gas and the secondary retentate gas are combined and passed through the first compressor.

[0090] The secondary permeate gas is sucked into the third compressor through a vacuum pump, and enters the adsorption tower after heat exchange. After adsorption and desorption operations in the adsorption tower, the decarbonized gas produced is discharged, and the carbon dioxide gas desorbed by vacuum is the product gas. The mass concentration of the product gas can reach 95%.

[0091] Carbon dioxide in flue gas was captured according to Comparative Example 1, and the test results are shown in Table 2 below.

[0092] Table 2

[0093]

[0094] Note: In Table 2, the carbon dioxide capture rate refers to the mass percentage of captured carbon dioxide in the flue gas to be adsorbed.

[0095] In summary, it can be seen that the use of the carbon dioxide capture device / method of Example 1 of the present invention for flue gas treatment can significantly reduce energy consumption and improve the carbon dioxide capture rate, while taking into account a higher product gas concentration, compared with the carbon dioxide capture system of Comparative Example 1.

[0096] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0097] 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 device, comprising: A first membrane separation unit, used for performing membrane separation treatment on the flue gas to be treated to obtain a first retentate gas and a first permeate gas; An adsorption unit, used for adsorbing carbon dioxide on the trapped gas to obtain trapped adsorbed gas; A desorption unit, used for removing carbon dioxide from the adsorbent adsorbed with carbon dioxide in the adsorption unit to obtain permeate desorption gas; as well as A second membrane separation unit, used for performing membrane separation treatment on the permeate desorbed gas to obtain a second retentate gas and a carbon dioxide product; The desorption unit is connected to the first membrane separation unit and the adsorption unit respectively, and the first permeate gas can enter the adsorption unit through the desorption unit to perform heat exchange with the adsorbent to heat the adsorbent; the retained gas includes the first retained gas and the second retained gas.

2. The device according to claim 1 comprises a flue gas pretreatment unit, wherein the flue gas pretreatment unit comprises a feed pipeline and a residual pressure recovery component, wherein the feed pipeline is connected to the first membrane separation unit, and the flue gas to be treated can enter the first membrane separation unit through the feed pipeline; an intercepted adsorption gas pipeline is arranged outside the adsorption unit, and both ends of the intercepted adsorption gas pipeline are connected to the adsorption unit, and the residual pressure recovery component is respectively connected to the feed pipeline and the intercepted adsorption gas pipeline; The trapped adsorbed gas can expand and do work through the residual pressure recovery component to increase the pressure of the flue gas to be treated, and the temperature of the trapped adsorbed gas is reduced. The trapped adsorbed gas after cooling can enter the adsorption unit through the trapped adsorbed gas pipeline.

3. The device according to claim 2, wherein: The adsorption unit includes one or more adsorption towers, and the adsorption towers are respectively connected to the first membrane separation unit and the second membrane separation unit, so that the first retentate gas and the second retentate gas can enter the adsorption towers.

4. The device according to claim 3, wherein: The desorption unit comprises a permeate gas pipeline, the first membrane separation unit is connected to the adsorption tower through the permeate gas pipeline, and the first permeate gas can enter the adsorption tower through the permeate gas pipeline; The flue gas pretreatment unit comprises a second heat exchanger, which is arranged on the feed pipeline and is also connected to the permeate gas pipeline, so that the first permeate gas can exchange heat with the flue gas in the feed pipeline through the second heat exchanger; and / or, The adsorption tower is connected to the second membrane separation unit through a permeation-desorption gas pipeline, and the permeation-desorption gas can enter the second membrane separation unit through the permeation-desorption gas pipeline.

5. The device according to claim 4, wherein: A third heat exchanger and a gas-water separator are arranged on the feed pipeline, and the third heat exchanger and the gas-water separator are located between the second heat exchanger and the first membrane separation unit; and / or, An air outlet pipeline connected to the adsorption tower is arranged outside the adsorption tower, and a fourth heat exchanger is arranged on the permeation-desorption gas pipeline. The fourth heat exchanger is also connected to the air outlet pipeline. The gas in the air outlet pipeline can perform heat exchange with the gas in the permeation-desorption gas pipeline through the fourth heat exchanger.

6. The device according to claim 2, wherein: The flue gas pretreatment unit comprises a first heat exchanger, which is connected to the feed pipeline and the retained adsorbed gas pipeline respectively, and the flue gas to be treated and the retained adsorbed gas can exchange heat through the first heat exchanger.

7. A method for capturing carbon dioxide, comprising the following steps: The flue gas to be treated is subjected to membrane separation treatment to obtain a first retentate gas and a first permeate gas; Adsorbing carbon dioxide on the trapped gas after membrane separation by an adsorbent to obtain trapped adsorbed gas; The adsorbent adsorbing carbon dioxide is subjected to a treatment for removing carbon dioxide to obtain a permeate desorbed gas; as well as The permeate desorbed gas is subjected to membrane separation treatment to obtain a second retentate gas and a carbon dioxide product; wherein the trapped gas includes the first trapped gas and the second trapped gas; In the process of removing carbon dioxide, the temperature of the adsorbent is increased by heat exchange between the first permeate gas and the adsorbent, so that the adsorbent removes carbon dioxide; the permeate-desorbed gas includes the first permeate gas and the removed carbon dioxide.

8. The method according to claim 7, wherein: By expanding the trapped adsorbed gas to do work, the pressure of the flue gas to be treated is increased and the temperature of the trapped adsorbed gas is reduced; and / or, The method comprises pre-treating the flue gas to be treated and then performing the membrane separation treatment.

9. The method according to claim 8, wherein: The retained adsorbed gas is subjected to heat exchange treatment with the flue gas to be treated, and then the flue gas to be treated is subjected to pressurization treatment by the retained adsorbed gas; and / or, The adsorbent is subjected to a temperature reduction treatment by the retained adsorbed gas, and at the same time, the adsorbent performs a second adsorption treatment of carbon dioxide on the retained adsorbed gas.

10. The method according to claim 9, wherein: performing heat exchange treatment on the first permeate gas and the pressurized flue gas to be treated; and / or, Firstly, heat exchange is performed between the permeate desorption gas and the gas after the second adsorption treatment, and then the membrane separation treatment is performed; and / or, The pretreatment includes heat exchange treatment, pressurization treatment and gas-water separation treatment.

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