Carbon dioxide capture system

Abstract

The present invention provides a carbon dioxide capture system, comprising: an absorption tower, further provided with a rich liquid supply pipeline connected to a first accommodating chamber; a desorption and regeneration tower, further provided with a lean liquid supply pipeline connected to a second accommodating chamber; and a compression and reheating device, comprising a first compression and reheating unit, the first compression and reheating unit comprising a first heat exchanger, a first compressor, and a second heat exchanger. The first heat exchanger is provided on the rich liquid supply pipeline and is used to heat the CO2-rich absorbent in the rich liquid supply pipeline. The second heat exchanger is provided on the lean liquid supply pipeline and is used to cool the lean CO2 absorbent in the lean liquid supply pipeline. The carbon dioxide capture system provided by the present invention aims to address the problems of high energy consumption, high amine consumption, and high-temperature degradation of traditional carbon capture technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and in particular to a carbon dioxide capture system. Background Art

[0002] Currently, CCUS (Carbon Capture, Utilization, and Storage) technology is considered the most economically viable method for large-scale greenhouse gas emissions reduction and mitigating global warming. The key technological path to achieving carbon neutrality is CO2 capture and conversion. Therefore, developing and improving CO2 capture technology is a top priority in this field.

[0003] Chemical absorption carbon capture is the only technical path that can capture CO2 on a large scale at this stage.

[0004] Traditional absorption-based carbon capture systems face limitations in industrial applications, such as high energy consumption, high amine consumption, and susceptibility to degradation at high temperatures. These limitations significantly restrict the large-scale application of chemical absorption, particularly alcoholamine-based carbon capture technology. Existing research on CO2 capture technology focuses on the mechanisms and efficiency of CO2 absorption and regeneration, such as CO2 solubility, CO2 absorption efficiency and enhancement, and CO2 absorbents. Current CO2 regeneration research advances, such as direct steam regeneration, heat-stable salt regeneration, vacuum regeneration, microchannel reactor regeneration, and non-aqueous alcoholamine solution regeneration, offer limited benefits in reducing energy consumption and have not broken through the bottlenecks of large-scale industrial application of alcoholamine-based carbon capture. While some research has focused on process optimization, these have only addressed the optimal allocation of liquid sensible heat and waste heat, resulting in limited energy savings. Summary of the Invention

[0005] The present invention provides a carbon dioxide capture system, which aims to solve the problems of high energy consumption, high amine consumption, and easy degradation at high temperature in traditional carbon capture technology.

[0006] In order to solve the problems existing in the prior art, an embodiment of the present invention provides a carbon dioxide capture system, comprising:

[0007] An absorption tower having a first accommodating chamber filled with an absorption liquid, a raw gas inlet and a degassing outlet connected to the first accommodating chamber, and a rich liquid supply pipeline connected to the first accommodating chamber;

[0008] A desorption and regeneration tower, wherein the desorption and regeneration tower has a second accommodating chamber, the second accommodating chamber is used to accommodate the absorption liquid, and a lean liquid supply pipeline connected to the second accommodating chamber is opened on the desorption and regeneration tower, the rich liquid supply pipeline is used to output the absorption liquid that has absorbed CO2 to the desorption and regeneration tower, and the lean liquid supply pipeline is used to return the absorption liquid that has precipitated CO2 to the absorption tower;

[0009] The compression and reheating device includes a first compression and reheating unit, which includes a first heat exchanger, a first compressor and a second heat exchanger. The first heat exchanger is arranged on the rich liquid supply pipeline and is used to heat the rich CO2 absorption liquid in the rich liquid supply pipeline. The second heat exchanger is arranged on the lean liquid supply pipeline and is used to cool the lean CO2 absorption liquid in the lean liquid supply pipeline.

[0010] According to a carbon dioxide capture system provided by the present invention, the desorption and regeneration tower is provided with an exhaust port connected to the second accommodating chamber, and the compression enthalpy increase device further includes a second compression enthalpy increase unit and a third compression enthalpy increase unit respectively connected to the exhaust port, the second compression enthalpy increase unit is provided with a first CO2 outlet, and the third compression enthalpy increase unit is provided with a second CO2 outlet;

[0011] The second compression enthalpy increase unit is arranged in the rich liquid supply pipeline and the second containing chamber, and is used to recover the waste heat of the gas discharged from the exhaust port to heat the CO2-rich absorption liquid in the rich liquid supply pipeline and the absorbent solution in the second containing chamber. The third compression enthalpy increase unit is partially arranged in the second containing chamber, and is used to heat the absorbent solution in the second containing chamber.

[0012] According to a carbon dioxide capture system provided by the present invention, the second compression enthalpy increase unit includes a second compressor connected to the exhaust port, a third heat exchanger, and a fourth heat exchanger, the third heat exchanger is arranged in the second accommodating chamber, the fourth heat exchanger is arranged on the rich liquid supply pipeline, and the first CO2 outlet is arranged on the fourth heat exchanger;

[0013] The second compressor is used to compress the mixture of CO2 and H2O (g) discharged from the exhaust port, and the third heat exchanger and the fourth heat exchanger are both used to cool the compressed mixture of CO2 and water vapor.

[0014] According to a carbon dioxide capture system provided by the present invention, the third compression enthalpy increase unit includes a fifth heat exchanger connected to the exhaust port, a sixth heat exchanger, and a third compressor, the second CO2 outlet is provided on the fifth heat exchanger, and the sixth heat exchanger is provided in the second accommodating chamber;

[0015] The fifth heat exchanger is used to cool the CO2 mixture discharged from the exhaust port, and the sixth heat exchanger is used to heat the absorbent solution in the second containing chamber.

[0016] According to a carbon dioxide capture system provided by the present invention, the rich liquid supply pipeline includes a first rich liquid supply branch and a second rich liquid supply branch, and the fourth heat exchanger and the first heat exchanger are sequentially arranged on the first rich liquid supply branch;

[0017] The compression enthalpy increase device also includes a seventh heat exchanger, which is arranged on the second rich liquid supply branch and the lean liquid supply pipeline, and is used to exchange heat between the lean CO2 absorption liquid in the lean liquid supply pipeline and the rich CO2 absorption liquid in the second rich liquid supply branch.

[0018] According to a carbon dioxide capture system provided by the present invention, a first valve is provided at the connection between the second compression enthalpy increase unit and the exhaust port, and a second valve is provided at the connection between the third compression enthalpy increase unit and the exhaust port.

[0019] According to a carbon dioxide capture system provided by the present invention, the absorption tower also includes a first self-circulating pipeline connected to the first containing chamber, one end of the first self-circulating pipeline is connected to the bottom of the absorption tower, and the other end is connected to the top of the absorption tower, which is used to pump the absorption liquid that has not absorbed enough CO2 back to the absorption tower.

[0020] According to a carbon dioxide capture system provided by the present invention, the desorption and regeneration tower also includes a second self-circulation pipeline connected to the second containing chamber, one end of the second self-circulation pipeline is connected to the bottom of the desorption and regeneration tower, and the other end is connected to the top of the desorption and regeneration tower, which is used to pump the absorption liquid that has not fully desorbed CO2 back to the desorption and regeneration tower.

[0021] According to a carbon dioxide capture system provided by the present invention, the circulating working fluid of the first compression and reheating unit includes 134a or CO2, the circulating working fluid of the second compression and reheating unit includes H2O (g) and CO2, and the circulating working fluid of the third compression and reheating unit includes 134a or CO2.

[0022] According to a carbon dioxide capture system provided by the present invention, when the temperature of the desorption and regeneration tower is higher than 80~85°C, the first valve is in an open state and the second valve is in a closed state; when the temperature of the desorption and regeneration tower is lower than 80~85°C, the first valve is in a closed state and the second valve is in an open state.

[0023] According to a carbon dioxide capture system provided by the present invention, when the temperature of the desorption regeneration tower is lower than 80-85°C, the circulating working fluid of the first compression enthalpy increase unit is 134a, the circulating working fluid evaporation temperature is 10-25°C, the heat exchange temperature difference of the second heat exchanger is 3-8°C, and the heat exchange temperature difference of the first heat exchanger is 3-8°C;

[0024] When the temperature of the desorption regeneration tower is higher than 80~85℃, the circulating working fluid of the first compression enthalpy increase unit is CO2, the evaporation temperature of the circulating working fluid is -15~5℃, the heat exchange temperature difference of the second heat exchanger is 25~40℃, and the heat exchange temperature difference of the first heat exchanger is 5~15℃.

[0025] According to a carbon dioxide capture system provided by the present invention, the heat transfer temperature difference of the third heat exchanger is 3-7°C, and the heat transfer temperature difference of the fourth heat exchanger is 2-5°C.

[0026] According to a carbon dioxide capture system provided by the present invention, when the circulating working fluid of the third compression enthalpy increase unit is 134a, the evaporation temperature of the circulating working fluid at the inlet of the third compressor is 20~30°C, and the heat transfer temperature difference of the sixth heat exchanger is 3~8°C.

[0027] The carbon dioxide capture system provided by the present invention realizes cooling of the lean CO2 absorption liquid in the lean liquid supply pipeline and heating of the rich CO2 absorption liquid in the rich liquid supply pipeline through the arrangement of the first compression enthalpy increase unit. Through the combined cooling and heating strategy of the first compression enthalpy increase unit, a low-temperature absorption environment for the absorption tower and a high-temperature regeneration environment for the desorption regeneration tower are simultaneously created, thereby improving the CO2 absorption and desorption efficiency, reducing energy consumption, and reducing absorbent loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is a schematic diagram of the system structure of the carbon dioxide capture system provided by the present invention.

[0030] Reference numerals:

[0031] DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0034] In the description of the embodiments of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present invention based on the specific circumstances.

[0035] In the embodiments of the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," or "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," or "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0036] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0037] The following combination Figure 1 A carbon dioxide capture system 1 of the present invention is described.

[0038] Chemical absorption carbon capture is the only technical approach that can capture CO2 on a large scale at this stage. Traditional absorption carbon capture systems have limitations in industrial applications, such as high energy consumption, high amine consumption, and easy degradation at high temperatures, which greatly restrict the large-scale promotion and application of chemical absorption methods, especially alcoholamine carbon capture technology. In view of this, the present invention provides a carbon dioxide capture system 1, comprising: an absorption tower 2, the absorption tower 2 having a first accommodating chamber 5, the first accommodating chamber 5 being filled with an absorption liquid, the absorption tower 2 being provided with a raw gas inlet 6 and a gas removal outlet 7 connected to the first accommodating chamber 5, the absorption tower 2 being further provided with a rich liquid supply pipeline 8 connected to the first accommodating chamber 5, the absorption tower 2 providing a countercurrent heat and mass exchange place for CO2 absorption, the raw gas rich in CO2 enters the bottom of the absorption tower 2 from the raw gas inlet 6 and flows upward, and is absorbed by the absorption liquid collected in the first accommodating chamber 5, and the absorption liquid that has absorbed CO2 will flow into the rich liquid supply pipeline 8 for the next step of desorption and regeneration;

[0039] The desorption and regeneration tower 3 has a second accommodating chamber 13, which is used to accommodate the absorption liquid. The desorption and regeneration tower 3 is provided with a lean liquid supply pipeline 14 connected to the second accommodating chamber 13. The rich liquid supply pipeline 8 is used to output the absorption liquid that has absorbed CO2 to the desorption and regeneration tower 3, and the lean liquid supply pipeline 14 is used to return the absorption liquid from which CO2 has been precipitated to the absorption tower 2; the desorption and regeneration tower 3 provides a countercurrent heat and mass exchange place for CO2 desorption and absorbent regeneration, and the CO2-rich absorbent solution in the rich liquid supply pipeline 8 enters from the top of the desorption and regeneration tower 3 and sprays downward, and is in direct countercurrent contact with the water vapor flowing upward in the second accommodating chamber 13 of the desorption and regeneration tower 3, thereby realizing the desorption of CO2 and the regeneration of the absorbent.

[0040] The carbon dioxide capture system 1 provided by the present invention also includes a compression and reheating device 4, which includes a first compression and reheating unit 18. The first compression and reheating unit 18 includes a first heat exchanger 19, a first compressor 20, and a second heat exchanger 21. The first heat exchanger 19 is provided on the rich liquid supply line 8 and is used to heat the CO2-rich absorbent in the rich liquid supply line 8. The second heat exchanger 21 is provided on the lean liquid supply line 14 and is used to cool the CO2-lean absorbent in the lean liquid supply line 14. The provision of the first compression and reheating unit 18 achieves cooling of the CO2-lean absorbent in the lean liquid supply line 14 and heating of the CO2-rich absorbent in the rich liquid supply line 8. The combined cooling and heating strategy of the first compression and reheating unit 18 simultaneously creates a low-temperature absorption environment in the absorption tower 2 and a high-temperature regeneration environment in the desorption and regeneration tower 3, thereby improving the CO2 absorption and desorption efficiency, reducing energy consumption, and reducing absorbent loss.

[0041] Furthermore, the desorption / regeneration tower 3 is provided with an exhaust port 15 connected to the second accommodating chamber 13. The compression / enthalpy increase device 4 also includes a second compression / enthalpy increase unit 22 and a third compression / enthalpy increase unit 28, each connected to the exhaust port 15. The second compression / enthalpy increase unit 22 is provided with a first CO2 outlet 26, and the third compression / enthalpy increase unit 28 is provided with a second CO2 outlet 32. The second compression / enthalpy increase unit 22 is separately provided in the rich liquid supply line 8 and the second accommodating chamber 13, and is used to recover waste heat from the gas discharged from the exhaust port 15 to heat the CO2-rich absorbent liquid in the rich liquid supply line 8 and the absorbent solution in the second accommodating chamber 13. The third compression / enthalpy increase unit 28 is partially provided in the second accommodating chamber 13, and is used to heat the absorbent solution in the second accommodating chamber 13. It should be noted that the second compression / enthalpy increase unit 22 and the third compression / enthalpy increase unit 28 are in parallel. In actual use, one of them will be activated based on the actual operating conditions of the desorption / regeneration tower 3.

[0042] Specifically, see Figure 1 The second compression and reheating unit 22 includes a second compressor 23, a third heat exchanger 24 and a fourth heat exchanger 25 connected to the exhaust port 15. The third heat exchanger 24 is arranged in the second accommodating chamber 13, the fourth heat exchanger 25 is arranged on the rich liquid supply pipeline 8, and the first CO2 outlet 26 is arranged on the fourth heat exchanger 25; the second compressor 23 is used to compress the water vapor and CO2 mixture discharged from the exhaust port 15, and the third heat exchanger 24 and the fourth heat exchanger 25 are both used to cool the compressed water vapor and CO2 mixture.

[0043] The low-temperature, low-pressure mixed gas (H2O (g) and CO2) generated at the exhaust port 15 at the top of the desorption and regeneration tower 3 is first compressed by the second compressor 23 to increase the enthalpy, and then enters the third heat exchanger 24 to condense and release heat. The released heat will cause the absorbent solution in the second accommodating chamber 13 to boil, allowing water vapor to continuously evaporate upward, thereby realizing the desorption of CO2 and the recycling regeneration of the absorbent; the cooled water vapor mixture will further enter the fourth heat exchanger 25, where it will be further condensed to produce condensed water and tail gas, which will be discharged through the first CO2 outlet 26 and collected as CO2 product, while the heat released by its condensation will further heat the CO2-rich absorbent in the rich liquid supply pipeline 8, thereby realizing the recovery and utilization of the waste heat of the desorption and regeneration tower 3.

[0044] Furthermore, the third compression and reheating unit 28 includes a fifth heat exchanger 29, a sixth heat exchanger 30, and a third compressor 31, all connected to the exhaust port 15. A second CO2 outlet 32 ​​is provided on the fifth heat exchanger 29, and the sixth heat exchanger 30 is provided within the second accommodating chamber 13. The fifth heat exchanger 29 is used to further cool the compressed CO2 and H2O(g) gas mixture discharged from the exhaust port 15, and the sixth heat exchanger 30 is used to heat the absorbent solution in the second accommodating chamber 13. The circulating working fluid within the third compression and reheating unit 28 evaporates in the fifth heat exchanger 29 and condenses in the sixth heat exchanger 30. The gas discharged from the exhaust port 15 of the desorption and regeneration tower is condensed in the fifth heat exchanger 29 to form condensed water and tail gas, and the tail gas is discharged from the second CO2 outlet 32 ​​and collected as a CO2 product; and the sixth heat exchanger 30 releases heat in the second accommodating chamber 13 to realize the evaporation and reboiling of the absorbent solution in the second accommodating chamber 13. Through the cold and heat supply strategy of the third compression enthalpy increase unit 28, the condensation of water vapor at the top of the desorption and regeneration tower 3 and the reboiling of the absorbent solution in the bottom of the tower are simultaneously created.

[0045] Furthermore, the rich liquid supply pipeline 8 includes a first rich liquid supply branch 10 and a second rich liquid supply branch 11, and the fourth heat exchanger 25 and the first heat exchanger 19 are sequentially arranged on the first rich liquid supply branch 10; the compression enthalpy increase device 4 also includes a seventh heat exchanger 34, and the seventh heat exchanger 34 is arranged on the second rich liquid supply branch 11 and the lean liquid supply pipeline 14, and is used to exchange heat between the lean CO2 absorption liquid in the lean liquid supply pipeline 14 and the rich CO2 absorption liquid in the second rich liquid supply branch 11. It should be noted that the rich liquid supply pipeline 8 is divided into two solutions, one is the first rich liquid supply branch 10, which is heated in turn through the fourth heat exchanger 25 and the first heat exchanger 19; the other is the second rich liquid supply branch 11, and the rich CO2 absorption liquid in the second rich liquid supply branch 11 exchanges heat with the high-temperature lean CO2 absorption liquid in the lean liquid supply pipeline 14 in the seventh heat exchanger 34, so that the rich CO2 absorption liquid is heated and the lean CO2 absorption liquid is cooled; the first rich liquid supply branch 10 and the second rich liquid supply branch 11 are then merged into the desorption regeneration tower 3 to realize the utilization of waste heat.

[0046] As previously mentioned, the second compression and reheating unit 22 and the third compression and reheating unit 28 are used alternately. Therefore, a first valve 27 is provided at the connection between the second compression and reheating unit 22 and the exhaust port 15, and a second valve 33 is provided at the connection between the third compression and reheating unit 28 and the exhaust port 15. When the temperature of the desorption and regeneration tower 3 is higher than 80-85°C, the first valve 27 is open and the second valve 33 is closed. When the temperature of the desorption and regeneration tower 3 is lower than 80-85°C, the first valve 27 is closed and the second valve 33 is open.

[0047] Furthermore, the absorption tower 2 further includes a first self-circulating pipeline 9 connected to the first accommodating chamber 5. One end of the first self-circulating pipeline 9 is connected to the bottom of the absorption tower 2, and the other end is connected to the top of the absorption tower 2, for pumping the absorption liquid that has not fully absorbed CO2 back to the absorption tower 2. Figure 1 The first circulation pump 12 will pump the absorption liquid in the absorption tower 2 into the first self-circulation pipeline 9. The absorption liquid that has not absorbed CO2 sufficiently will enter the absorption tower 2 again through the first self-circulation pipeline 9, and spray into the first containing chamber 5 from the top of the absorption tower 2 to absorb CO2 again; and the absorption liquid that has fully absorbed CO2 will flow from the rich liquid supply pipeline 8 to the desorption regeneration tower 3.

[0048] Similarly, the desorption regeneration tower 3 further includes a second self-circulating pipeline 16 connected to the second accommodating chamber 13. One end of the second self-circulating pipeline 16 is connected to the bottom of the desorption regeneration tower 3, and the other end is connected to the top of the desorption regeneration tower 3, for pumping the absorption liquid that has not fully desorbed CO2 back to the desorption regeneration tower 3. Figure 1 , the second circulation pump 17 will pump the absorption liquid in the desorption regeneration tower 3 into the second self-circulation pipeline 16. The absorption liquid that does not desorb CO2 sufficiently will enter the desorption regeneration tower 3 again through the second self-circulation pipeline 16, and spray into the second containing chamber 13 from the top of the desorption regeneration tower 3 to desorb CO2; and the absorption liquid that fully desorbs CO2 will flow from the lean liquid supply pipeline 14 to the absorption tower 2, and spray into the first containing chamber 5 from the top of the absorption tower 2 to continue absorbing CO2. In addition, it should be noted that valves are provided on the first self-circulation pipeline 9 and the second self-circulation pipeline 16. When the liquid CO2 absorption concentration in the rich liquid supply pipeline 8 does not meet the requirements, it is necessary to open the valve on the first self-circulation pipeline 9 so that the liquid can circulate multiple times to meet the requirements; when the liquid CO2 concentration in the lean liquid supply pipeline 14 is too high, it is necessary to open the valve on the second self-circulation pipeline 16 so that the liquid can circulate multiple times to meet the requirements.

[0049] The following will further define and explain the working parameters of this system:

[0050] The circulating working fluid of the first compression and enthalpy increase unit 18 includes 134a or CO2, and the circulating working fluid of the second compression and enthalpy increase unit 22 includes H2O g and CO2, the circulating working fluid of the third compression enthalpy increase unit 28 includes 134a or CO2.

[0051] When the temperature of the desorption and regeneration tower 3 is lower than 80~85℃, the circulating working fluid of the first compression and reheat increasing unit 18 is 134a, the evaporation temperature of the circulating working fluid is 10~25℃, the heat exchange temperature difference of the second heat exchanger 21 is 3~8℃, and the heat exchange temperature difference of the first heat exchanger 19 is 3~8℃; when the temperature of the desorption and regeneration tower 3 is higher than 80~85℃, the circulating working fluid of the first compression and reheat increasing unit 18 is CO2, the evaporation temperature of the circulating working fluid is -15~5℃, the heat exchange temperature difference of the second heat exchanger 21 is 25~40℃, and the heat exchange temperature difference of the first heat exchanger 19 is 5~15℃.

[0052] The heat transfer temperature difference of the third heat exchanger 24 is 3-7°C, and the heat transfer temperature difference of the fourth heat exchanger 25 is 2-5°C.

[0053] When the circulating medium of the third compression and reheating unit 28 is 134a, the evaporation temperature of the circulating medium at the inlet of the third compressor 31 is 20-30°C, and the heat transfer temperature difference of the sixth heat exchanger 30 is 3-8°C.

[0054] It should also be noted that the moisture content of the gas at the raw gas inlet 6 of the absorption tower 2 is controlled below 5%, and the temperature is controlled below 40°C. The CO2 content of the purified gas after decarbonization at the gas removal outlet 7 at the top of the absorption tower 2 should be lower than 2~3%. The temperature of the fourth heat exchanger 25 and the first CO2 outlet 26 and the second CO2 outlet 32 ​​of the fifth heat exchanger should be controlled below 40°C.

[0055] The following uses the flue gas carbon capture of a power plant as an example to provide the actual parameters of the carbon dioxide capture system 1:

[0056] The main components of power plant flue gas are CO2 content of 13~15%, O2 content of 3~5%, N2 content of 75%, H2O content of 6~8%, and trace SO2 content of 400mg / m3, NO X The content is 700 mg / m3, the purity of CO2 after capture is required to be above 99%, and the processing scale of captured CO2 is 1 ton / hour;

[0057] Due to the low CO2 content and complex gas composition of the power plant flue gas, the requirements for the content of the captured CO2 product are relatively high. The examples are as follows:

[0058] The circulating absorbent solution in the absorption tower 2 adopts an alcohol amine absorbent solution, and the absorbent is limited to monoethanolamine MEA or MEA composite solution. The composite solution can contain active amines, antioxidants and corrosion inhibitors.

[0059] The inlet flue gas flow rate of the raw gas inlet 6 of the absorption tower 2 is preferably 5000~7000m 3 / h, the absorption temperature is 25~35°C, and the diameter of the cylinder of the absorption tower 2 is preferably 1300~1500mm;

[0060] The flow rate of the first circulation pump 12 is preferably 40-50m 3 / h, motor power is 5.5kW;

[0061] The temperature of the CO2-rich absorbent solution in the desorption and regeneration tower is preferably 95-105°C, and the diameter of the cylinder of the desorption and regeneration tower is preferably 1300-1500 mm;

[0062] The flow rate of the second circulation pump 17 is preferably 40-50m 3 / h, motor power is 5.5kW;

[0063] The seventh heat exchanger 34 is preferably a plate heat exchanger, and the heat exchange area is preferably 120-150m 2 ;

[0064] The first compression enthalpy increasing unit 18 uses CO2 as the circulating working medium, and the working medium evaporation temperature is preferably between -5 and 5°C. The heat exchange area of ​​the second heat exchanger 21 is preferably 5 to 10m 2 The heat exchange area of ​​the first heat exchanger 19 is preferably 5 to 10 m 2 , the first compressor 20 is preferably a single screw type, with a motor power of 75kW;

[0065] The second compression enthalpy increasing unit 224, the second compressor 23 inlet pressure is preferably 1~1.5bar, the outlet pressure is preferably between 1.5~2.5bar, the compressor type is single screw type, the motor power is 185kW, the third heat exchanger 24 is preferably plate type or shell and tube type, and the heat exchange area is 80~100m 2 The fourth heat exchanger 25 is preferably a plate heat exchanger, and the heat exchange area is preferably 5~10 m 2 .

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A carbon dioxide capture system, characterized in that: include: An absorption tower having a first accommodating chamber filled with an absorption liquid, a raw gas inlet and a degassing outlet connected to the first accommodating chamber, and a rich liquid supply pipeline connected to the first accommodating chamber; A desorption and regeneration tower, wherein the desorption and regeneration tower has a second accommodating chamber, the second accommodating chamber is used to accommodate the absorption liquid, and a lean liquid supply pipeline connected to the second accommodating chamber is opened on the desorption and regeneration tower, the rich liquid supply pipeline is used to output the absorption liquid that has absorbed CO2 to the desorption and regeneration tower, and the lean liquid supply pipeline is used to return the absorption liquid that has precipitated CO2 to the absorption tower; The compression enthalpy increase device includes a first compression enthalpy increase unit, the first compression enthalpy increase unit includes a first heat exchanger, a first compressor and a second heat exchanger, the first heat exchanger is provided on the rich liquid supply pipeline, and is used to heat the CO2-rich absorption liquid in the rich liquid supply pipeline, and the second heat exchanger is provided on the lean liquid supply pipeline, and is used to cool the CO2-lean absorption liquid in the lean liquid supply pipeline; The desorption regeneration tower is provided with an exhaust port connected to the second accommodating chamber, and the compression enthalpy increase device further includes a second compression enthalpy increase unit and a third compression enthalpy increase unit respectively connected to the exhaust port, the second compression enthalpy increase unit is provided with a first CO2 outlet, and the third compression enthalpy increase unit is provided with a second CO2 outlet; The second compression enthalpy increase unit is provided in the rich liquid supply pipeline and the second accommodating chamber, and is used to recover the waste heat of the gas discharged from the exhaust port to heat the CO2-rich absorption liquid in the rich liquid supply pipeline and the absorbent solution in the second accommodating chamber. The third compression enthalpy increase unit is partially provided in the second accommodating chamber, and is used to heat the absorbent solution in the second accommodating chamber; A first valve is provided at the connection between the second compression and enthalpy increase unit and the exhaust port, and a second valve is provided at the connection between the third compression and enthalpy increase unit and the exhaust port; When the temperature of the desorption regeneration tower is higher than 80~85℃, the first valve is in the open state and the second valve is in the closed state. When the temperature of the desorption regeneration tower is lower than 80~85℃, the first valve is in the closed state and the second valve is in the open state.

2. The carbon dioxide capture system according to claim 1, characterized in that The second compression enthalpy increase unit includes a second compressor connected to the exhaust port, a third heat exchanger, and a fourth heat exchanger, the third heat exchanger is arranged in the second accommodating chamber, the fourth heat exchanger is arranged on the rich liquid supply pipeline, and the first CO2 outlet is arranged on the fourth heat exchanger; The second compressor is used to compress the mixture of CO2 and H2O (g) discharged from the exhaust port, and the third heat exchanger and the fourth heat exchanger are both used to cool the compressed mixture of CO2 and water vapor.

3. The carbon dioxide capture system according to claim 2, characterized in that The third compression enthalpy increase unit includes a fifth heat exchanger and a sixth heat exchanger connected to the exhaust port and a third compressor, the second CO2 outlet is provided on the fifth heat exchanger, and the sixth heat exchanger is provided in the second accommodating chamber; The fifth heat exchanger is used to cool the CO2 mixture discharged from the exhaust port, and the sixth heat exchanger is used to heat the absorbent solution in the second containing chamber.

4. The carbon dioxide capture system according to claim 3, characterized in that The rich liquid supply pipeline includes a first rich liquid supply branch and a second rich liquid supply branch, and the fourth heat exchanger and the first heat exchanger are sequentially arranged on the first rich liquid supply branch; The compression enthalpy increase device also includes a seventh heat exchanger, which is arranged on the second rich liquid supply branch and the lean liquid supply pipeline, and is used to exchange heat between the lean CO2 absorption liquid in the lean liquid supply pipeline and the rich CO2 absorption liquid in the second rich liquid supply branch.

5. The carbon dioxide capture system according to claim 4, characterized in that The absorption tower also includes a first self-circulating pipeline connected to the first containing chamber, one end of the first self-circulating pipeline is connected to the bottom of the absorption tower, and the other end is connected to the top of the absorption tower, which is used to pump the absorption liquid that has not absorbed enough CO2 back to the absorption tower.

6. The carbon dioxide capture system according to claim 4, characterized in that The desorption and regeneration tower also includes a second self-circulating pipeline connected to the second containing chamber, one end of the second self-circulating pipeline is connected to the bottom of the desorption and regeneration tower, and the other end is connected to the top of the desorption and regeneration tower, which is used to pump the absorption liquid that has not fully desorbed CO2 back to the desorption and regeneration tower.

7. The carbon dioxide capture system according to claim 4, characterized in that The circulating working fluid of the first compression and reheating unit includes 134a or CO2, the circulating working fluid of the second compression and reheating unit includes H2O(g) and CO2, and the circulating working fluid of the third compression and reheating unit includes 134a or CO2.

8. The carbon dioxide capture system according to claim 4, characterized in that When the temperature of the desorption regeneration tower is lower than 80-85°C, the circulating working fluid of the first compression enthalpy increase unit is 134a, the circulating working fluid evaporation temperature is 10-25°C, the heat exchange temperature difference of the second heat exchanger is 3-8°C, and the heat exchange temperature difference of the first heat exchanger is 3-8°C; When the temperature of the desorption regeneration tower is higher than 80~85℃, the circulating working fluid of the first compression enthalpy increase unit is CO2, the evaporation temperature of the circulating working fluid is -15~5℃, the heat exchange temperature difference of the second heat exchanger is 25~40℃, and the heat exchange temperature difference of the first heat exchanger is 5~15℃.

9. The carbon dioxide capture system according to claim 7, characterized in that The heat transfer temperature difference of the third heat exchanger is 3-7°C, and the heat transfer temperature difference of the fourth heat exchanger is 2-5°C.

10. The carbon dioxide capture system according to claim 7, wherein: When the circulating working medium of the third compression and reheating unit is 134a, the evaporation temperature of the circulating working medium at the inlet of the third compressor is 20-30°C, and the heat transfer temperature difference of the sixth heat exchanger is 3-8°C.

Images