Flue gas purification and CO2 capture coupling system and carbon capture method

Abstract

The present invention proposes a flue gas purification and CO2 capture coupling system and a carbon capture method. The flue gas purification and CO2 capture coupling system includes a flue gas generating device, a flue gas purification device and a CO2 capture device. The CO2 capture device includes an absorption tower and a regeneration tower containing an absorbent solution. The absorbent rich liquid that captures CO2 in the absorption tower flows into the regeneration tower to be desorbed by heat to form a regeneration gas and a lean liquid. The regeneration gas and the lean liquid are discharged from the regeneration tower. A portion of the lean liquid discharged from the regeneration tower is used for heat exchange with the high-temperature flue gas that leaves the flue gas generating device but does not enter the CO2 capture device to form a superheated lean liquid and returns to the regeneration tower to provide steam and heat for the CO2 regeneration reaction. The superheated lean liquid specifically refers to a CO2 lean liquid that is maintained in a boiling state at a preset pressure. Therefore, the flue gas purification and CO2 capture coupling system of the embodiment of the present invention has the advantages of low energy consumption and capture cost as well as high operation stability and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture utilization and storage (CCUS), and in particular to a flue gas purification and CO2 capture coupling system and method. Background Art

[0002] Carbon capture, utilization and storage (CCUS) is an important means of large-scale low-carbon utilization of fossil energy, and plays an important role in ensuring national energy security and building an energy power. High energy consumption and high cost are the main obstacles to the large-scale promotion of CCUS technology, and the cost of carbon capture accounts for 75% of its full-chain cost. Reducing the cost of carbon capture is an international problem that urgently needs to be solved in the development of CCUS technology. The capture cost mainly lies in the steam consumption in the regeneration process, that is, the heat required for CO2 regeneration is usually provided by superheated steam extracted from the power plant generator set, which consumes a large amount of steam, resulting in high carbon capture costs. The proportion of steam cost to the total capture cost is about 50%. In addition, the extraction of steam will reduce the power generation efficiency of the power plant, increase the auxiliary load loss of the power plant, and further increase the capture cost. In addition, the access to the CO2 capture system requires a large number of modifications to the original equipment system, which will affect the flue gas purification treatment. Related technologies have also proposed using flue gas waste heat to replace the extraction of superheated steam to heat the carbon capture system, but there are still many problems such as insufficient heat utilization in the system, unreasonable temperature matching, and high energy consumption, which affect actual use, so there is a need for improvement. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, the present invention proposes a flue gas purification and CO2 capture coupling system. The flue gas purification and CO2 capture coupling system has the advantage of reducing capture energy consumption.

[0005] The flue gas purification and CO2 capture coupling system includes flue gas generating equipment, flue gas purification equipment and CO2 capture equipment.

[0006] The flue gas discharged from the flue gas generating device enters the CO2 capture device after being purified by the flue gas purification device, and is finally discharged after CO2 capture and decarbonization, while completing the separation and storage of CO2. The CO2 capture device includes an absorption tower and a regeneration tower. The rich liquid that captures CO2 in the absorption tower flows into the regeneration tower to be thermally desorbed into regeneration gas and lean liquid. The regeneration gas and the lean liquid are discharged from the regeneration tower respectively. It is characterized in that a part of the lean liquid discharged from the regeneration tower is heat-exchanged with the flue gas discharged from the flue gas generating device and not entering the CO2 capture device to become superheated lean liquid. The superheated lean liquid is returned to the regeneration tower to provide steam and heat for the desorption. The superheated lean liquid specifically refers to CO2 lean liquid maintained in a boiling state under a preset pressure.

[0007] In some embodiments, the flue gas generating device includes a boiler and an air preheater, and the flue gas exhausted by the boiler passes through the air preheater and exchanges heat with the portion of the lean liquid.

[0008] In some embodiments, the CO2 capture device includes a reboiler, and the flue gas generated by the flue gas generating device exchanges heat with the portion of lean liquid through the reboiler. After the heat exchange, the portion of lean liquid returns to the regeneration tower to provide heat for the regeneration reaction.

[0009] In some embodiments, the CO2 capture device also includes a lean-rich liquid heat exchanger, wherein the rich liquid discharged from the absorption tower enters the regeneration tower through the lean-rich liquid heat exchanger, and another part of the lean liquid discharged from the regeneration tower enters the lean-rich liquid heat exchanger to exchange heat with the rich liquid flowing through the lean-rich liquid heat exchanger before entering the absorption tower.

[0010] In some embodiments, the flue gas purification equipment includes a denitrification tower and a desulfurization tower. The flue gas discharged from the boiler passes through the denitrification tower, the air preheater and the desulfurization tower and enters the absorption tower. After CO2 capture and decarbonization, it becomes decarbonized flue gas and is discharged from the absorption tower.

[0011] In some embodiments, the CO2 capture device further comprises a pressure pump, wherein the pressure pump is disposed between the regeneration tower and the reboiler, and the pressure pump is used to pressurize the portion of the lean liquid to increase its boiling point.

[0012] In some embodiments, the CO2 capture device also includes a pressure reducing valve, which is arranged between the reboiler and the regeneration tower and adjacent to the regeneration tower, and is used to reduce the pressure of the superheated lean liquid after heat exchange with the flue gas through the reboiler to reduce the boiling point of the superheated lean liquid, wherein the decompressed superheated lean liquid returns to the regeneration tower and releases steam.

[0013] In some embodiments, the regeneration tower has a lean liquid inlet, wherein the decompressed superheated lean liquid returns to the regeneration tower through the lean liquid inlet, and the lean liquid inlet is lower than the packing in the regeneration tower and higher than the liquid level of the lean liquid pool at the bottom of the regeneration tower.

[0014] In some embodiments, the booster pump pressurizes the portion of lean liquid discharged from the regeneration tower to a pressure of 3-7 atmospheres.

[0015] In some embodiments, the pressure reducing valve reduces the pressure of the superheated lean liquid discharged from the reboiler to 1.2-2.0 atmospheres.

[0016] In some embodiments, in a portion of the lean liquid returned to the regeneration tower after decompression, the mass percentage of the vapor phase to the total returned lean liquid is 2%-15%.

[0017] In some embodiments, the portion of lean liquid accounts for 20%-60% by mass of the total lean liquid discharged from the regeneration tower.

[0018] In some embodiments, the CO2 capture device also includes a rich liquid preheater, and the rich liquid generated in the absorption tower passes through the rich liquid preheater and the lean-rich liquid heat exchanger in sequence and enters the regeneration tower, and the regeneration gas generated in the regeneration tower enters the rich liquid preheater to exchange heat with the rich liquid passing through the rich liquid preheater.

[0019] In some embodiments, the CO2 capture equipment also includes a flue gas reheater, and the other part of the lean liquid discharged from the regeneration tower passes through the lean-rich liquid heat exchanger and the flue gas reheater in sequence and enters the absorption tower, and the decarbonized flue gas discharged from the absorption tower enters the flue gas reheater to exchange heat with the lean liquid passing through the flue gas reheater and then is discharged externally.

[0020] In some embodiments, the CO2 capture device further comprises a flow control valve, and the flow control valve is used to control the ratio of the flue gas discharged from the desulfurization tower entering the flue gas reheater and the flue gas entering the absorption tower.

[0021] In some embodiments, a flow meter is provided in conjunction with the flow control valve to monitor the flow of flue gas entering the CO2 capture device.

[0022] In some embodiments, the flue gas purification equipment also includes two flow control valves and an induced draft fan, the induced draft fan is arranged between the desulfurization flue gas outlet of the desulfurization tower and the pre-wash tower, one of the control valves is arranged between the desulfurization flue gas outlet of the desulfurization tower and the air inlet of the flue gas reheater to control the amount of desulfurization flue gas discharged from the desulfurization tower entering the flue gas reheater, and the other control valve is arranged between the desulfurization flue gas outlet of the desulfurization tower and the induced draft fan to control the amount of flue gas entering the pre-wash tower from the desulfurization tower, and the two control valves are controlled in linkage.

[0023] In some embodiments, the flue gas purification equipment also includes a pre-wash tower, a dust collector, and a chimney; the CO2 capture equipment also includes a CO2 compressor, wherein the dust collector is arranged between the reboiler and the desulfurization tower, and is used to remove dust from the flue gas coming out of the reboiler, and the CO2 compressor is connected to the rich liquid preheater to compress the regenerated gas after heat exchange with the rich liquid in the rich liquid preheater.

[0024] The flue gas purification and CO2 capture coupling method of the embodiment of the present invention includes:

[0025] The flue gas discharged from the flue gas generating device is purified by the flue gas purification device and then enters the CO2 capture device. After CO2 capture and decarbonization, the flue gas is finally discharged to the outside, and the storage of CO2 is completed at the same time. The CO2 capture device includes an absorption tower and a regeneration tower. The rich liquid that captures CO2 in the absorption tower flows into the regeneration tower and is desorbed by heat to form regeneration gas and lean liquid. The regeneration gas and lean liquid are discharged from the regeneration tower respectively.

[0026] A portion of the lean liquid discharged from the regeneration tower is heat-exchanged with the flue gas discharged from the flue gas generating device before entering the CO2 capture device to become superheated lean liquid, and the superheated lean liquid is returned to the regeneration tower to provide steam and heat for the desorption.

[0027] In some embodiments, the flue gas purification and CO2 capture coupling method of the embodiment of the present invention also includes pressurizing a portion of the lean liquid discharged from the regeneration tower to increase its boiling point, wherein the pressurized portion of the lean liquid is heat exchanged with the flue gas discharged from the flue gas generating equipment and not entering the CO2 capture equipment.

[0028] In some embodiments, the flue gas purification and CO2 capture coupling method of the embodiment of the present invention further comprises decompressing the superheated lean liquid to reduce its boiling point, wherein the decompressed superheated lean liquid is returned to the regeneration tower.

[0029] In some embodiments, the decompressed superheated lean liquid is returned to below the packing in the regeneration tower.

[0030] In some embodiments, the rich liquid discharged from the absorption tower is sequentially heat-exchanged with the regeneration gas discharged from the regeneration tower and another portion of the lean liquid discharged from the regeneration tower before flowing into the regeneration tower.

[0031] In some embodiments, the flue gas purification and CO2 capture coupling method of the embodiment of the present invention also includes subjecting the flue gas discharged from the flue gas generating equipment to denitrification, preheated air, heat exchange with the portion of lean liquid discharged from the regeneration tower, dust removal and desulfurization in sequence; a portion of the desulfurized flue gas and the other portion of lean liquid discharged from the regeneration tower after heat exchange with the rich liquid are heat exchanged with the decarbonized flue gas discharged from the absorption tower; the other portion of lean liquid after heat exchange with the decarbonized flue gas flows into the absorption tower; the decarbonized flue gas after heat exchange with the portion of the flue gas after desulfurization and the other portion of lean liquid is discharged outwardly; and the other portion of the desulfurized flue gas enters the absorption tower.

[0032] In some embodiments, the ratio of the portion of desulfurized flue gas that exchanges heat with the decarbonized flue gas and the other portion of desulfurized flue gas that enters the absorption tower is controlled.

[0033] In some embodiments, the flue gas may come from power plant boilers, cement plant exhaust gas, steel plant exhaust gas and other places that generate high-temperature flue gas.

[0034] The present invention uses a part of the lean liquid discharged from the regeneration tower to exchange heat with the high-temperature flue gas that leaves the flue gas generating device but does not enter the CO2 capture device to form superheated lean liquid and returns it to the regeneration tower to provide steam and heat for the CO2 regeneration reaction. The superheated lean liquid is partially vaporized and returned to the regeneration tower, thereby promoting the desorption of CO2 in the regeneration tower. That is, the heat required for CO2 regeneration is provided by the high-temperature flue gas, and the flue gas is used to heat the lean liquid to form steam to participate in the regeneration process. It can partially or even completely replace the traditional steam from outside the system, thereby avoiding the consumption of high-value superheated steam, effectively reducing the energy consumption of the system, and reducing the capture cost of each ton of CO2 by 40%-50%.

[0035] At the same time, the use of the system of the present invention is conducive to adding additional equipment when renovating existing related equipment. Only the pipeline needs to be added, and the cost of system renovation is greatly reduced.

[0036] In addition, the present invention utilizes pressurized lean liquid to exchange heat with flue gas to form superheated lean liquid. Under the pressurized state, the superheated lean liquid will not be vaporized in large quantities in the reboiler, and the vibration or cavitation of the equipment caused by the gas hitting the heat exchange tube or heat exchange wall of the reboiler can be avoided. Therefore, the present invention has the advantages of improving the service life of the equipment and the operational stability and safety.

[0037] Therefore, the flue gas purification and CO2 capture coupling system of the embodiment of the present invention has the advantages of improving operation safety and reducing capture costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a flue gas purification and CO2 capture coupling system according to an embodiment of the present invention.

[0039] Figure 2 Schematic diagram of a flue gas purification and CO2 capture coupling system according to another embodiment of the present invention.

[0040] Reference numerals:

[0041] Boiler 1;

[0042] Denitrification tower 2;

[0043] Air preheater 3;

[0044] Reboiler 4;

[0045] Pressure reducing valve 5;

[0046] Regeneration tower 6;

[0047] Booster pump 7;

[0048] Lean liquid pump 8;

[0049] Lean and rich liquid heat exchanger 9;

[0050] Rich liquid preheater 10;

[0051] CO2 compressor 11;

[0052] Rich liquid pump 12;

[0053] Absorption tower 13;

[0054] Pre-wash tower 14;

[0055] induced draft fan 15;

[0056] Desulfurization tower 16;

[0057] Dust collector 17;

[0058] Reheater 18;

[0059] Chimney 19;

[0060] Flow control valve 20;

[0061] Flow meter 21. DETAILED DESCRIPTION

[0062] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0063] The flue gas purification and CO2 capture coupling system of an embodiment of the present invention is described below with reference to the accompanying drawings, wherein the flue gas comes from the power plant boiler 1. The coupling system specifically refers to the coupling of the flue gas treatment system and the CO2 capture system. The flue gas discharged from the boiler 1 is subjected to CO2 capture by a CO2 absorbent solution after desulfurization and denitrification, and the flue gas after carbon capture becomes decarbonized flue gas and is discharged to the outside. Commonly used CO2 absorbent solutions include, but are not limited to, organic amine solutions, amino acid salt alkaline solutions, inorganic salt alkaline solutions, ionic liquids, and metal organic framework solutions, etc.

[0064] like Figure 1 , Example 1, the flue gas purification and CO2 capture coupling system of the embodiment of the present invention includes a boiler 1, a denitrification tower 2, an air preheater 3, a reboiler 4, a dust collector 17, a desulfurization tower 16, a pre-washing tower 14, an absorption tower 13, a rich liquid preheater 10, a lean and rich liquid heat exchanger 9, a regeneration tower 6, a booster pump 7, a pressure reducing valve 5, a flue gas reheater 18, a chimney 19 and a CO2 compressor 11.

[0065] The flue gas discharged from the boiler 1 enters the denitrification tower 2 for denitrification. The denitrified flue gas passes through the air preheater 3 and the reboiler 4 in turn and enters the dust collector 17 for dust removal. The desulfurized flue gas is desulfurized in the flue gas desulfurization tower 16. The desulfurized flue gas is sent to the pre-washing tower 14 by the induced draft fan 15 for pre-washing. The pre-washed flue gas enters the absorption tower 13. The flue gas is subjected to CO2 capture by the absorbent solution (lean liquid) in the absorption tower 13 to become decarbonized flue gas. The absorbent solution captures CO2 in the absorption tower 13 and becomes rich liquid. The decarbonized flue gas is discharged from the top of the absorption tower 13 into the flue gas reheater 18, and is reheated in the flue gas reheater 18 and discharged into the chimney 19. The rich liquid in the absorption tower 13 is transported from the bottom of the absorption tower 13 by the rich liquid pump 12 and flows through the rich liquid preheater 10 and the lean and rich liquid heat exchanger 9 in sequence into the regeneration tower 6. The rich liquid is heated in the regeneration tower 6 for desorption and regeneration to obtain regenerated gas. The rich liquid is desorbed and regenerated to become lean liquid. The regenerated gas enters the CO2 compressor 11 for compression and storage, and the lean liquid flows back to the absorption tower 13 to be reused.

[0066] It is worth noting that the regeneration energy consumption and operating costs in the existing CO2 capture process are high. The rich liquid after the absorbent is loaded with CO2 is all sent to the regeneration tower 6 for heating and regeneration. Since the proportion of water in the absorbent is high (generally more than 70%), the heating and volatilization of water during the high-temperature desorption of CO2 will consume a lot of energy (about more than 50%). Therefore, changing the water environment of the regeneration process and reducing the participation of water in the regeneration process will be expected to maximize the use of steam heat and reduce regeneration energy consumption. In conventional technology, the heat required for regeneration is usually introduced from the outside, such as using the steam generated by the steam turbine of the power plant. This process requires matching equipment such as pipelines on the one hand, and consumes superheated steam on the other hand, which increases energy consumption. At the same time, the flue gas discharged from the boiler 1 has a higher temperature. Even if it is 350-400°C after passing through the denitrification tower 2, the temperature can still be maintained at 100-180°C after passing through the air preheater, which is suitable for providing the heat required for desorption of the rich liquid. Therefore, the rational use of this part of the heat to obtain the heat required for the absorbent regeneration process will be an important means to reduce the overall energy consumption of the system.

[0067] In this embodiment, the steam environment of the regeneration process is changed by extracting part of the lean liquid discharged from the regeneration tower 6 and exchanging heat with the flue gas of the boiler 1 to form a superheated liquid, thereby effectively reducing the overall energy consumption of the coupling system, wherein the superheated lean liquid specifically refers to the superheated CO2 lean liquid maintained in a boiling state under a preset pressure, and the preset pressure generally refers to a pressure superatmospheric pressure. Optionally, the flue gas can come from a variety of places that produce high-temperature flue gas, such as power plant boilers, cement plant exhaust gas, and steel plant exhaust gas.

[0068] Specifically, Figure 1 As shown, a part of the lean liquid discharged from the regeneration tower 6 enters one end of the reboiler 4, and the other orthogonal end of the reboiler 4 is connected to the boiler 1 through a pipeline, so that the part of the lean liquid exchanges heat with the flue gas passing through the reboiler 4 in the reboiler 4, and the temperature of the part of the lean liquid after the heat exchange rises to form a superheated lean liquid of mixed liquid steam, and the superheated lean liquid returns to the regeneration tower 6 along the pipeline, and the steam in the superheated lean liquid is released to provide the required heat for the regeneration process, so as to achieve efficient utilization of flue gas waste heat. It is worth noting that in this embodiment, the lean liquid is heated by flue gas to form a superheated lean liquid, and the steam in the superheated lean liquid participates in the regeneration process, which can partially or even completely replace the traditional steam from the steam turbine, thereby avoiding the consumption of high-value superheated steam. For example, the traditional CO2 rich liquid desorption requires steam extracted from the generator set to heat and desorb the rich liquid in the regeneration tower. Therefore, the present invention reduces the impact on the generator set and reduces the energy consumption and cost of carbon capture.

[0069] Another part of the lean liquid discharged from the regeneration tower 6 enters the lean-rich liquid heat exchanger 9 to exchange heat with the rich liquid flowing through the lean-rich liquid heat exchanger 9. After the heat exchange, the other part of the lean liquid enters the absorption tower 13 to capture and absorb CO2 in the flue gas in the absorption tower 13.

[0070] On the other hand, in the embodiment of the present invention, the flue gas generated by the boiler 1 of the power plant is first denitrated by the denitrification tower 2, and the temperature of the high-temperature flue gas at the outlet of the boiler 1 can be reduced from about 800-1000°C to about 350-400°C, and further cooled to about 100-180°C by the air preheater. This part of the flue gas still has a relatively high temperature at this time, and has a relatively high available energy (exergy), which can be used to supplement the regeneration process with the highest energy consumption, and can be used to supplement the regeneration of the absorbent with the highest energy consumption. Therefore, a reboiler 4 with a heat energy collection function is added, and a part of the lean liquid generated in the regeneration tower 6 is extracted into the reboiler 4 to exchange heat with the high-temperature flue gas after denitration to form a superheated lean liquid, and the superheated lean liquid enters the regeneration tower 6 and becomes a vapor-liquid two-state, wherein the vapor can flow upward in the regeneration tower 6, and the heat it carries is transferred to the packing layer to promote the desorption reaction of CO2 in the rich liquid, thereby realizing the effective utilization of the flue gas waste heat, and the liquid phase flows to the bottom of the tower for recycling. The temperature of the flue gas flowing through the reboiler 4 is generally between 100°C and 180°C, and the temperature of the lean liquid discharged from the regeneration tower 6 is generally between 80°C and 140°C. The heat exchange temperature difference between the two must be maintained at more than 5°C, so that the heat exchange between the two in the reboiler 4 has the advantage of reducing relative heat loss.

[0071] On the other hand, it is worth noting that in this embodiment, the transfer of flue gas waste heat is carried out by a part of the lean liquid drawn out of the regeneration tower 6. This part of the lean liquid is selected because, on the one hand, the temperature of the part of the lean liquid is more suitable, and on the other hand, the recycling of the lean liquid itself can reduce the additional equipment required for heat exchange, thereby reducing the difficulty of modifying existing equipment and reducing the modification cost. In addition, it is worth noting that there have been related technologies in the art that have proposed a scheme in which a part of the flue gas directly discharged from the boiler 1 is heated by the reboiler 4 with the rich liquid (45-65°C) discharged from the regeneration tower 6, and the rich liquid is circulated back to the regeneration tower 6 after heat exchange. However, the inventors of the present invention have found and realized through research that, due to the relatively high temperature of the flue gas from the boiler 1 (generally 800-1000°C), the above scheme will cause serious thermal degradation of the absorbent in the rich liquid, and the rich liquid is rich in absorbed CO2. After heat exchange with the high-temperature flue gas at normal pressure, the pipeline will be filled with desorbed CO2 gas, which will not only hit the pipeline to form noise and easily cause leakage, but also easily scale in the pipeline, resulting in blockage, affecting operation, and even causing major safety accidents. In comparison, the embodiment of the present invention utilizes the relatively low temperature and heat exchange between the lean liquid and the flue gas to utilize the waste heat of the flue gas to provide at least a portion of the heat required for absorbent regeneration. Since the lean liquid is not easy to desorb CO2 in the pipeline, the amount of CO2 gas in the pipeline is small.

[0072] At the same time, further, the pipeline at the bottom of the regeneration tower 6 is provided with a lean liquid pump 8 that can achieve pressurization, and the part of the lean liquid drawn out will first be pressurized to 3-7 atmospheres by the lean liquid pump 8. Preferably, the lean liquid pump 8 pressurizes the gas pressure of the lean liquid to 3-6 atmospheres, so that its boiling point is reduced after being heated by the reboiler 4, and the lean liquid that is pressurized and heated by heat exchange is not easy to vaporize, reducing the gas content in the lean liquid in this part of the pipeline, and the lean liquid fluid under a relatively high pressure absorbs the heat of the flue gas to form a superheated lean liquid, which carries the heat absorbed from the flue gas, and the temperature can reach the desorption temperature required by the regeneration process, thereby helping to achieve the smooth progress of the regeneration process. At the same time, further, before a part of the lean liquid after heat exchange re-enters the regeneration tower 6, a pressure reduction control valve is added to further reduce the pressure of the high-pressure superheated lean liquid with heat to 1-2 atmospheres to reduce its boiling point. Due to the reduction in boiling point, part of the lean liquid after decompression volatilizes part of the liquid in the superheated lean liquid and becomes hot steam, which returns to the regeneration tower 6 to participate in regeneration. Furthermore, in a portion of the lean liquid returned to the regeneration tower 6 after decompression, the mass percentage of the vapor phase to the total returned lean liquid is 2%-15%. If it exceeds 15%, it will cause excessive gas to overflow into the pipeline and cause problems such as gas hitting the pipeline. If it is less than 2%, the heat carried back to the regeneration tower 6 will be reduced, thereby reducing the waste heat utilization rate.

[0073] In another embodiment, the booster pump 7 is disposed adjacent to the lean liquid outlet of the regeneration tower 6, and the pressure reducing valve 5 is disposed adjacent to the lean liquid inlet of the regeneration tower 6, for example, the pressure reducing valve 5 can be installed at the lean liquid inlet of the regeneration tower 6. The lean liquid inlet of the regeneration tower 6 is located below the packing in the regeneration tower 6, for example, adjacent to the bottom surface of the packing. More preferably, the lean liquid inlet is higher than the lean liquid level at the bottom of the regeneration tower 6, thereby avoiding the superheated lean liquid returned to the regeneration tower 6 from first contacting and exchanging heat with the lean liquid below the regeneration tower 6, avoiding the problem of low desorption efficiency caused by failure to fully utilize the heat carried by the lean liquid for desorption of the rich liquid, and further improving the desorption efficiency of the rich liquid.

[0074] In another embodiment, the mass percentage of the portion of lean liquid to the total lean liquid discharged from the regeneration tower 6 is 20%-60%.

[0075] In another embodiment, the regeneration gas is discharged from the top of the regeneration tower 6. At this time, the temperature of the regeneration gas is above 60°C, that is, it still has a certain amount of heat. It is guided into the rich liquid preheater 10 to exchange heat with the rich liquid from the absorption tower 13. That is, the regeneration gas is used to heat the rich liquid flowing from the absorption tower 13 to the regeneration tower 6, thereby recovering the heat carried by the regeneration gas for adsorbent regeneration. The regeneration gas after heat exchange with the rich liquid finally enters the CO2 compressor 11 for compression and storage.

[0076] In another embodiment, the flue gas enters the reboiler 4 after denitrification and before dust removal, that is, the waste heat of the flue gas is utilized before dust removal after denitrification. Because it is relatively difficult for the dust collector 17 to handle high-temperature flue gas, the flue gas needs to be cooled to 90°C, while the temperature of the flue gas after denitrification can still be as high as 180°C. Therefore, it is relatively reasonable to set a reboiler 4 between the denitrification tower 2 and the dust collector 17 to utilize the waste heat of the flue gas.

[0077] In another embodiment, the decarbonized flue gas discharged from the absorption tower 13 is heated by the flue gas reheater 18 and then discharged into the chimney 19, thereby increasing the exhaust temperature of the chimney 19 (generally increasing the exhaust temperature to above 80°C) and reducing the "white smoke" phenomenon of the chimney 19.

[0078] The flue gas purification and CO2 capture coupling system of the embodiment of the present invention improves the efficiency of heat recycling in the system such as flue gas waste heat and heat carried by regenerated gas and lean liquid, fully reduces steam consumption, and CO2 capture costs can be reduced by 40%-50%. At the same time, the use of this system reduces the impact of steam extraction on the generator set and reduces additional equipment such as steam desuperheater and pressure reducer. In addition, the heat exchange mode of this system overcomes the problems of gas impact pipeline, pipeline leakage, impact vibration, and cavitation that are prone to occur in related technologies, and improves the operating performance and safety of the system.

[0079] Reference below Figure 2 A flue gas purification and CO2 capture coupling system according to another specific embodiment of the present invention is described.

[0080] and Figure 1 Compared with the embodiment shown, Figure 2 As shown, the flue gas purification and CO2 capture coupling system of another embodiment of the present invention further includes a flow control valve 20, which is used to control the ratio of the flue gas discharged from the desulfurization tower 16 entering the flue gas reheater 18 and the flue gas entering the absorption tower 13, that is, the flue gas flow entering the CO2 capture can be controlled. In addition, a part of the lean liquid discharged from the regeneration tower 6 is not directly returned to the absorption tower 13 after heat exchange with the rich liquid discharged from the absorption tower 13 in the lean-rich liquid heat exchanger 9, but enters the flue gas reheater 18 and exchanges heat with the decarbonized flue gas before returning to the absorption tower 13, that is, the heat of this part of the lean liquid is used again to supplement the temperature of the discharged flue gas.

[0081] The flue gas purification and CO2 capture coupling system of the embodiment of the present invention can control the flue gas volume entering the pre-wash tower 14 and the absorption tower 13 from the desulfurization tower 16 and the flue gas volume entering the flue gas reheater 18 from the desulfurization tower 16 through the flow control valve 20, thereby flexibly adjusting the flue gas volume entering the absorption tower 13 for carbon capture according to the carbon capture load capacity of the coupling system, for example, it can be achieved that carbon capture does not require the consumption of high-value superheated steam, for example, it is completely unnecessary to extract steam from the generator set, further reducing the energy consumption and cost of carbon capture, avoiding the impact on the generator set, reducing the difficulty and cost of modifying the existing generator set, and improving the coupling performance of flue gas purification and CO2 capture. On the other hand, when a fault occurs in the carbon capture process, the flue gas can all enter the flue gas reheater 18 and then be discharged through the chimney 19, which will not affect the emission of the purified flue gas and the operation of the generator set.

[0082] In addition, a portion of the lean liquid discharged from the regeneration tower 6 enters the flue gas reheater 18 after passing through the lean-rich liquid heat exchanger 9 to exchange heat with the decarbonized flue gas, thereby utilizing the heat contained in the lean liquid to heat the decarbonized flue gas, which can reduce the heat supplied to the flue gas reheater 18 through other heat sources, further reduce energy consumption, and reduce the "white smoke" phenomenon emitted from the chimney 19. Moreover, by controlling a portion of the desulfurized flue gas to enter the flue gas reheater 18 through the flow control valve 20, the temperature of the decarbonized flue gas can be further increased, and the "white smoke" phenomenon emitted from the chimney 19 can be better avoided.

[0083] For example, Figure 2 As shown, the flue gas purification and CO2 capture coupling system of the embodiment of the present invention also includes a flow meter 21 supporting the flow control valve to monitor the flow of flue gas entering the CO2 capture device. The flow meter 21 is arranged between the flow control valve and the induced draft fan 15. Furthermore, the flow control valve 20 can also be a three-way valve, and the inlet of the three-way valve is connected to the desulfurized flue gas outlet of the desulfurization tower 16. One outlet of the three-way valve is connected to the induced draft fan 15 for supplying desulfurized flue gas to the pre-wash tower 14, and the other outlet of the three-way valve is connected to the air inlet of the flue gas reheater 18. The decarbonized flue gas outlet in the absorption tower 13 is also connected to the air inlet of the flue gas reheater 18. The flow meter 21 is arranged between the flow control valve and the induced draft fan 15. The induced draft fan 15 can introduce the flue gas at the outlet of the desulfurization tower 16 into the pre-wash tower 14.

[0084] Alternatively, in other embodiments, the flow control valve 20 may also be two separately arranged control valves. For example, one control valve is arranged between the desulfurized flue gas outlet of the desulfurization tower 16 and the air inlet of the flue gas reheater 18 to control the amount of desulfurized flue gas discharged from the desulfurization tower 16 entering the flue gas reheater 18, and the other control valve is arranged between the desulfurized flue gas outlet of the desulfurization tower 16 and the induced draft fan 15 to control the amount of flue gas entering the pre-wash tower 14 from the desulfurization tower 16. Of course, the two control valves need to be controlled in linkage.

[0085] Figure 2 The embodiment of the present invention shown is Figure 1 The remaining aspects of the illustrated embodiments may be the same and will not be described in detail here.

[0086] The following describes the corresponding flue gas purification and CO2 capture coupling method of the embodiment of the present invention in conjunction with Example 1.

[0087] The flue gas purification and CO2 capture coupling method of the embodiment of the present invention includes:

[0088] The flue gas discharged from the flue gas generating device is purified by the flue gas purification device and then enters the CO2 capture device. After CO2 capture and decarbonization, the flue gas is finally discharged to the outside, and the CO2 storage is completed at the same time. The CO2 capture device includes an absorption tower 13 and a regeneration tower 6. The rich liquid that captures CO2 in the absorption tower 13 flows into the regeneration tower 6 and is desorbed by heat to form regeneration gas and lean liquid. The regeneration gas and lean liquid are discharged from the regeneration tower 6 respectively.

[0089] A portion of the lean liquid discharged from the regeneration tower 6 is heat-exchanged with the flue gas discharged from the flue gas generating device before entering the CO2 capture device to become superheated lean liquid, and the superheated lean liquid is returned to the regeneration tower to provide steam and heat for desorption.

[0090] The flue gas purification and CO2 capture coupling method of the embodiment of the present invention, by allowing a portion of the lean liquid discharged from the regeneration tower 6 to enter the reboiler 4 for heat exchange with the flue gas passing through the reboiler 4, a portion of the lean liquid after the heat exchange is returned to the regeneration tower 6, that is, the portion of the lean liquid is heated in the reboiler 4 by using the waste heat of the flue gas, thereby using the waste heat of the flue gas to regenerate the absorbent, which can partially or even completely replace traditional steam heating, thereby avoiding the consumption of high-value superheated steam, such as steam heating extracted from the generator set, thereby reducing the impact on the generator set and reducing the energy consumption and cost of carbon capture.

[0091] In addition, compared with the related art that utilizes the waste heat of flue gas by heat exchange between the rich liquid in the regeneration tower 6 and the flue gas, the embodiment of the present invention utilizes the lean liquid with relatively low temperature and low CO2 content and the flue gas to exchange heat and utilize the waste heat of flue gas to provide at least a part of the heat required for absorbent regeneration. Since the lean liquid is not easy to vaporize in the pipeline, the amount of gas in the pipeline is small, so that the gas will not hit the pipeline or the wall, the risk of leakage is reduced, the vibration is reduced, the cavitation is reduced, the operating performance is good, and the safety is high, thus overcoming the defects caused by heat exchange between the rich liquid and the flue gas in the related art. Moreover, the temperature difference between the temperature of the lean liquid discharged from the regeneration tower 6 and the temperature of the flue gas flowing through the reboiler 4 is small, so the heat exchange between the two in the reboiler 4 has the advantage of reducing relative heat loss.

[0092] The following describes a coupling method for flue gas purification and CO2 capture in accordance with a specific embodiment of the present invention, which comprises: the flue gas discharged from the boiler 1 passes through the denitrification tower 2, the air preheater 3, the reboiler 4, the dust collector 17, the desulfurization tower 16, and the pre-washing tower 14 in sequence and enters the absorption tower 13, wherein the CO2 of the flue gas is captured by using an absorbent solution in the absorption tower 13, and the flue gas becomes decarbonized flue gas and is discharged from the top of the absorption tower 13 into the flue gas reheater 18, and then enters the chimney 19 from the flue gas reheater 18 and is discharged to the outside.

[0093] The absorbent solution becomes rich liquid after capturing CO2 in the absorption tower 13. The rich liquid enters the rich liquid preheater 10, then enters the lean-rich liquid heat exchanger 9 from the rich liquid preheater 10, and then enters the regeneration tower 6 for desorption and regeneration to generate regeneration gas, and the absorbent solution becomes lean liquid.

[0094] The regenerated gas is discharged from the top of the regeneration tower 6 and enters the rich liquid preheater 10 to exchange heat with the rich liquid from the absorption tower 13. The regenerated gas after heat exchange is compressed and stored.

[0095] A portion of the lean liquid in the regeneration tower 6 is discharged from the bottom of the regeneration tower 6 and enters the lean-rich liquid heat exchanger 9, and then enters the absorption tower 13 after heat exchange with the rich liquid from the rich liquid preheater 10, for absorption and capture of CO2. A portion of the lean liquid in the regeneration tower 6 is discharged from the bottom of the regeneration tower 6, and then enters the reboiler 4 after pressurization, and then exchanges heat with the flue gas after denitration through the reboiler 4 to form superheated lean liquid. After decompression, the superheated lean liquid returns to the bottom of the packing in the regeneration tower 6, and the gas therein flows upward through the packing to provide steam and heat for the desorption of the rich liquid in the regeneration tower 6.

[0096] The flue gas purification and CO2 capture coupling method of the embodiment of the present invention utilizes part of the lean liquid discharged from the regeneration tower 6 to exchange heat with the flue gas after denitration and then returns to the regeneration tower 6, thereby utilizing the waste heat of the flue gas for desorption and regeneration of the absorbent, and utilizing the regeneration gas to exchange heat with the rich liquid discharged from the absorption tower 13, further utilizing the heat carried by the regeneration gas, and improving the heat recycling of the system. Thus, it can partially or even completely replace the traditional steam heating, thereby avoiding the consumption of high-value superheated steam and significantly reducing the cost of CO2 capture.

[0097] Moreover, compared with the related art of using the rich liquid in the regeneration tower 6 for heat exchange with the flue gas, the lean liquid is not easy to vaporize and desorb the absorbed CO2 in the pipeline, and the amount of gas in the pipeline is small, which will not cause the gas to hit the pipeline or the wall, reducing the risk of pipeline leakage, reducing the vibration caused by the impact, reducing cavitation, and having good operating performance and high safety. Moreover, the lean liquid is discharged from the regeneration tower 6, first pressurized, then heat-exchanged with the flue gas, and then decompressed and returned to the regeneration tower 6, which can better reduce the problems of the lean liquid vaporizing or desorbing CO2 in the pipeline and the impact, vibration, cavitation and other problems caused thereby, and at the same time, can better utilize the flue gas waste heat carried by the lean liquid and exchanged with the flue gas.

[0098] The decarbonized flue gas passes through the flue gas reheater 18 and enters the chimney 19 for discharge, thereby reducing the phenomenon of "white smoke" emitted from the chimney 19.

[0099] The following describes a flue gas purification and CO2 capture coupling method according to another specific embodiment of the present invention.

[0100] Compared with the above embodiment, in this other specific embodiment, a part of the lean liquid discharged from the regeneration tower 6 enters the flue gas reheater 18 after heat exchange with the rich liquid in the lean-rich liquid heat exchanger 9 and then returns to the absorption tower 13 after heat exchange with the decarbonized flue gas, instead of directly returning to the absorption tower 13, so that the heat carried by the part of the lean liquid can be better utilized, the heat recycling rate in the system is improved, and the chimney 19 is better prevented from emitting "white smoke", and the heat supply to the flue gas reheater 18 through other heat sources is reduced. On the other hand, the ratio of the desulfurized flue gas entering the absorption tower 13 and the flue gas reheater 18 is controlled, so that the amount of flue gas entering the absorption tower 13 for carbon capture can be flexibly adjusted according to the carbon capture load capacity of the coupled system, for example, it can be achieved that carbon capture does not need to consume high-value superheated steam, for example, it is completely unnecessary to extract steam from the generator set, further reducing the energy consumption and cost of carbon capture, avoiding the impact on the generator set, reducing the difficulty and cost of modifying the existing generator set, and improving the coupling performance of flue gas purification and carbon capture. On the other hand, when a failure occurs in the carbon capture process, all the flue gas can enter the flue gas reheater 18 and be discharged through the chimney 19, which will not affect the emission of the purified flue gas and the operation of the generator set.

[0101] The flue gas purification and CO2 capture coupling method of another embodiment of the present invention may be the same as the flue gas purification and CO2 capture coupling method of the above embodiment in other aspects, which will not be repeated here.

[0102] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0103] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0104] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0105] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in 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 obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0106] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0107] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A flue gas purification and CO2 capture coupling system, comprising: A flue gas generating device, a flue gas purification device and a CO2 capture device, wherein the flue gas discharged from the flue gas generating device enters the CO2 capture device after being purified by the flue gas purification device, and is finally discharged to the outside after CO2 capture and decarbonization, while completing the separation and storage of CO2, wherein the CO2 capture device comprises an absorption tower and a regeneration tower, wherein the rich liquid having captured CO2 in the absorption tower flows into the regeneration tower to be thermally desorbed into regeneration gas and lean liquid, and the regeneration gas and the lean liquid are respectively discharged from the regeneration tower, and is characterized in that a part of the lean liquid discharged from the bottom of the regeneration tower is heat-exchanged with the flue gas discharged from the flue gas generating device but not entering the CO2 capture device to become superheated lean liquid, and the superheated lean liquid is returned to the regeneration tower to provide steam and heat for the desorption, The regeneration tower has a lean liquid inlet and a lean liquid outlet located at the bottom of the regeneration tower, the lean liquid inlet is lower than the packing in the regeneration tower and higher than the liquid level of the lean liquid pool at the bottom of the regeneration tower, the CO2 capture equipment includes a reboiler, a pressure pump and a pressure reducing valve, the pressure boosting pump is arranged between the regeneration tower and the reboiler and is adjacent to the lean liquid outlet of the regeneration tower, the pressure reducing valve is arranged between the reboiler and the regeneration tower and is adjacent to the lean liquid inlet of the regeneration tower, the flue gas generated by the flue gas generating equipment exchanges heat with the part of the lean liquid through the reboiler, the pressure boosting pump is used to pressurize the part of the lean liquid to increase its boiling point, and the pressure reducing valve is used to reduce the pressure of the superheated lean liquid after the heat exchange with the flue gas through the reboiler to reduce the boiling point of the superheated lean liquid, wherein the superheated lean liquid after pressure reduction returns to the regeneration tower through the lean liquid inlet and releases steam.

2. The flue gas purification and CO2 capture coupling system according to claim 1, characterized in that: The flue gas generating equipment comprises a boiler and an air preheater. The flue gas discharged from the boiler exchanges heat with the portion of lean liquid after passing through the air preheater.

3. The flue gas purification and CO2 capture coupling system according to claim 2, characterized in that: The CO2 capture device further comprises a lean-rich liquid heat exchanger, wherein the rich liquid discharged from the absorption tower passes through the lean-rich liquid heat exchanger and enters the regeneration tower, and another portion of the lean liquid discharged from the regeneration tower enters the lean-rich liquid heat exchanger to exchange heat with the rich liquid flowing through the lean-rich liquid heat exchanger before entering the absorption tower; And / or, the flue gas purification equipment includes a denitrification tower and a desulfurization tower. The flue gas discharged from the boiler passes through the denitrification tower, the air preheater and the desulfurization tower and enters the absorption tower. After CO2 capture and decarbonization, it becomes decarbonized flue gas and is discharged from the absorption tower.

4. The flue gas purification and CO2 capture coupling system according to claim 3, characterized in that: The booster pump pressurizes the portion of lean liquid discharged from the regeneration tower to 3-7 atmospheres; and / or, the pressure reducing valve reduces the pressure of the superheated lean liquid discharged from the reboiler to 1.2-2.0 atmospheres; and / or, in a portion of the lean liquid returned to the regeneration tower after decompression, the mass percentage of the vapor phase to the total lean liquid returned is 2%-15%; And / or, the mass percentage of the portion of lean liquid to the total lean liquid discharged from the regeneration tower is 20%-60%.

5. The flue gas purification and CO2 capture coupling system according to any one of claims 3-4, characterized in that: The CO2 capture equipment further comprises a rich liquid preheater, the rich liquid generated in the absorption tower sequentially passes through the rich liquid preheater and the lean-rich liquid heat exchanger into the regeneration tower, and the regeneration gas generated in the regeneration tower enters the rich liquid preheater to exchange heat with the rich liquid passing through the rich liquid preheater; And / or, the CO2 capture equipment also includes a flue gas reheater, and the other part of the lean liquid discharged from the regeneration tower passes through the lean-rich liquid heat exchanger and the flue gas reheater in sequence and enters the absorption tower, and the decarbonized flue gas discharged from the absorption tower enters the flue gas reheater to exchange heat with the lean liquid passing through the flue gas reheater and then is discharged externally.

6. The flue gas purification and CO2 capture coupling system according to claim 5, characterized in that: The CO2 capture device also includes a flow control valve, which is used to control the ratio of the flue gas discharged from the desulfurization tower entering the flue gas reheater and the flue gas entering the absorption tower; and / or, a flow meter matching the flow control valve is also provided.

7. The flue gas purification and CO2 capture coupling system according to claim 5, characterized in that: The flue gas purification equipment further includes a pre-wash tower, a dust collector and a chimney; the CO2 capture equipment further includes a CO2 compressor, wherein the dust collector is arranged between the reboiler and the desulfurization tower, and is used to remove dust from the flue gas coming out of the reboiler, and the CO2 compressor is connected to the rich liquid preheater to compress the regenerated gas after heat exchange with the rich liquid in the rich liquid preheater; And / or, the flue gas purification equipment also includes two flow control valves and an induced draft fan, the induced draft fan is arranged between the desulfurization flue gas outlet of the desulfurization tower and the pre-washing tower, one of the control valves is arranged between the desulfurization flue gas outlet of the desulfurization tower and the air inlet of the flue gas reheater to control the amount of desulfurization flue gas discharged from the desulfurization tower entering the flue gas reheater, and the other control valve is arranged between the desulfurization flue gas outlet of the desulfurization tower and the induced draft fan to control the amount of flue gas entering the pre-washing tower from the desulfurization tower, and the two control valves are controlled in linkage.

8. A flue gas purification and CO2 capture coupling method, characterized in that: The flue gas purification and CO2 capture coupling system according to any one of claims 1 to 7 is adopted, and the flue gas purification and CO2 capture coupling method comprises: The flue gas discharged from the flue gas generating device is purified by the flue gas purification device and then enters the CO2 capture device. After CO2 capture and decarbonization, the flue gas is finally discharged to the outside, and the storage of CO2 is completed at the same time. The CO2 capture device includes an absorption tower and a regeneration tower. The rich liquid that captures CO2 in the absorption tower flows into the regeneration tower and is desorbed by heat to form regeneration gas and lean liquid. The regeneration gas and lean liquid are discharged from the regeneration tower respectively. A portion of the lean liquid discharged from the bottom of the regeneration tower is heat-exchanged with the flue gas discharged from the flue gas generating device before entering the CO2 capture device to become a superheated lean liquid, and the superheated lean liquid is returned to the regeneration tower to provide steam and heat for the desorption, wherein the flue gas discharged from the flue gas generating device before entering the CO2 capture device passes through the reboiler of the CO2 capture device to exchange heat with the portion of the lean liquid; pressurizing a portion of the lean liquid discharged from the regeneration tower to increase its boiling point, wherein the pressurized portion of the lean liquid is heat exchanged with the flue gas discharged from the flue gas generating device and not entering the CO2 capture device; The superheated lean liquid is decompressed to reduce its boiling point, and the decompressed superheated lean liquid is returned to below the packing in the regeneration tower.

9. The flue gas purification and CO2 capture coupling method according to claim 8, characterized in that: A portion of the lean liquid discharged from the regeneration tower is pressurized to increase its boiling point, wherein the pressurized portion of the lean liquid is heat exchanged with the flue gas discharged from the flue gas generating device and not entering the CO2 capture device; the superheated lean liquid is decompressed to lower its boiling point, wherein the decompressed superheated lean liquid is returned to the regeneration tower.

10. The flue gas purification and CO2 capture coupling method according to claim 9, characterized in that: The rich liquid discharged from the absorption tower is sequentially heat-exchanged with the regeneration gas discharged from the regeneration tower and another part of the lean liquid discharged from the regeneration tower and then flows into the regeneration tower.

11. The flue gas purification and CO2 capture coupling method according to claim 10, characterized in that: It also includes subjecting the flue gas discharged from the flue gas generating equipment to denitrification, preheated air, heat exchange with the portion of lean liquid discharged from the regeneration tower, dust removal and desulfurization in sequence; a portion of the desulfurized flue gas and the other portion of lean liquid discharged from the regeneration tower after heat exchange with the rich liquid are heat exchanged with the decarbonized flue gas discharged from the absorption tower; the other portion of lean liquid after heat exchange with the decarbonized flue gas flows into the absorption tower; the decarbonized flue gas after heat exchange with the portion of the flue gas after desulfurization and the other portion of the lean liquid is discharged outwardly; and the other portion of the desulfurized flue gas enters the absorption tower.

12. The flue gas purification and CO2 capture coupling method according to claim 11, characterized in that: The ratio of the part of the desulfurized flue gas that exchanges heat with the decarbonized flue gas and the other part of the desulfurized flue gas that enters the absorption tower is controlled.

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