Thermal power plant carbon capture method and system using flue gas waste heat and fused salt energy storage

Abstract

The invention relates to a thermal power plant carbon capture system utilizing flue gas waste heat and fused salt energy storage, which comprises a CO2 absorption-analysis module, a gas-water heat exchange module and a fused salt energy storage module, a composite reboiler of the CO2 absorption-analysis module comprises a first tube pass and a second tube pass, and is used for heating barren liquor; a steam generation side outlet of a gas-water heat exchanger in the gas-water heat exchange module is connected to a first tube pass inlet of the combined type reboiler, and a first tube pass outlet is connected with a water side inlet of the gas-water heat exchanger through a pipeline. The fused salt energy storage module comprises a low-temperature fused salt tank, a high-temperature fused salt tank and a fused salt heat absorber, a second tube pass outlet of the composite reboiler is connected with an inlet of the low-temperature fused salt tank, an outlet of the low-temperature fused salt tank is connected to an inlet of the high-temperature fused salt tank through the fused salt heat absorber, and an outlet of the high-temperature fused salt tank is connected to a second tube pass inlet through a pipeline. According to the invention, the problem of high energy consumption in the CO2 desorption link of coal-fired power generation is solved, and continuous high-efficiency and low-energy-consumption carbon capture work of a coal-fired unit is realized.

Description

Technical Field

[0001] This application relates to the field of CO2 capture technology, and in particular to a method and system for carbon capture in thermal power plants that utilizes waste heat from flue gas and molten salt energy storage. Background Technology

[0002] In the power industry, coal-fired power plants account for more than 70% of total CO2 emissions, making carbon capture in coal-fired power plants particularly important. Currently, the most widely used CO2 capture technology for flue gas conditions in coal-fired power plants is chemical absorption carbon capture, primarily employing organic amine solutions such as monoethanolamine (MEA), diethanolamine (DEA), and complex amines.

[0003] Organic amine solutions offer advantages such as rapid adsorption rates, large capacity, and suitability for ambient temperature and pressure conditions. However, they also suffer from drawbacks including high regeneration energy consumption, easy volatilization and degradation, and strong corrosiveness to equipment. Absorbent regeneration primarily utilizes steam extracted from a steam turbine as the heating source, and this technology is the most mature. However, energy consumption accounts for 60-85% of the total operating cost, making energy consumption in the regeneration process a major factor restricting the development of this technology. Therefore, researching how to reduce energy consumption in the CO2 desorption process has become a new research topic. Summary of the Invention

[0004] This application provides a method and system for carbon capture in thermal power plants that utilizes waste heat from flue gas and molten salt energy storage, in order to at least solve the problem of high energy consumption in the CO2 desorption stage of carbon capture processes in coal-fired power generation in related technologies.

[0005] In a first aspect, embodiments of this application provide a carbon capture system for thermal power plants that utilizes waste heat from flue gas and molten salt energy storage. The system includes: a CO2 absorption-desorption module, a gas-water heat exchange module, and a molten salt energy storage module. The CO2 absorption-desorption module includes an absorption tower 15, a desorption tower 19, and a combined reboiler 27. The shell side of the combined reboiler 27 is in cyclic communication with the bottom of the desorption tower 19 for heating the lean liquor from the desorption tower 19. The tube side of the combined reboiler 27 includes a first tube side for introducing steam and a second tube side for introducing molten salt. The gas-water heat exchange module includes a bypass flue 06 and a gas-water heat exchanger 09. The bypass flue 06 is connected to the economizer outlet flue 03 for diverting part of the flue gas. The gas-water heat exchanger 09 is installed on the bypass flue 06 for recovering waste heat from the flue gas. The steam generation side outlet of the gas-water heat exchanger 09 is connected to the first tube inlet of the composite reboiler 27 through a saturated steam pipe 30. The first tube outlet of the composite reboiler 27 is connected to the water side inlet of the gas-water heat exchanger 09 through a pipe, forming a water-steam circulating heating loop. The molten salt energy storage module includes a low-temperature molten salt tank 32, a high-temperature molten salt tank 36, a molten salt absorber 34, and an electric heating unit 35 that supplies power to the molten salt absorber 34. The outlet of the second tube side of the composite reboiler 27 is connected to the inlet of the low-temperature molten salt tank 32 through a pipe. The outlet of the low-temperature molten salt tank 32 is connected to the inlet of the high-temperature molten salt tank 36 through the molten salt absorber 34. The outlet of the high-temperature molten salt tank 36 is connected to the inlet of the second tube side of the composite reboiler 27 through a pipe, forming a molten salt circulating heating loop.

[0006] In some embodiments, the absorption tower 15 is connected to the downstream flue of the desulfurization unit 05 for absorbing CO2 in the flue gas. The analytical tower 19 is equipped with a rich liquid nozzle 20, a crusher 21 and a porous tray 22 from top to bottom, which are used to spray, crush and heat the rich liquid that has absorbed CO2 for analytical purposes. The internal shell side of the composite reboiler 27 carries a circulating lean liquor, while the first tube side and the second tube side are independently distributed and arranged in a uniformly cross pattern.

[0007] In some embodiments, both the crusher 21 and the porous tray 22 are fully welded to the wall of the analytical tower 19. The spatial structure of the fragment 21 is composed of a hemispherical structure and a planar mesh structure. The surface of the hemispherical structure is uniformly arranged with conical hollow protrusions, and mesh holes are uniformly opened on the hemispherical surface between the protrusions.

[0008] In some embodiments, the CO2 absorption-desorption module further includes: a rich liquid pump 16, a lean-rich liquid heat exchanger 17, a lean liquid pump 24, and a lean liquid circulation pump 26; The upstream of the rich liquid pump 16 is connected to the bottom of the absorption tower 15, and the downstream is connected to the rich liquid inlet of the lean-rich liquid heat exchanger 17, which is used to send the rich liquid at the bottom of the absorption tower 15 to the lean-rich liquid heat exchanger 17. The rich liquid outlet of the rich and lean liquid heat exchanger 17 is connected to the rich liquid nozzle 20 in the analytical tower 19 through the rich liquid pipeline 18 of the analytical tower, and the lean liquid outlet is connected to the analytical tower 15 through the lean liquid pipeline 25 of the absorption tower. The upstream of the lean liquid pump 24 is connected to the bottom of the analytical column 19, and the downstream is connected to the lean liquid inlet of the lean-rich liquid heat exchanger 17, which is used to send the lean liquid at the bottom of the analytical column 19 back to the absorption column 15 through the lean-rich liquid heat exchanger 17. The upstream of the lean liquid circulation pump 26 is connected to the lean liquid outlet of the compound reboiler 27, and the downstream is connected to the stripping column 19, for sending the lean liquid at the bottom of the stripping column 19 to the compound reboiler 27.

[0009] In some embodiments, the gas-water heat exchange module further includes a baffle gate 07 and an adjusting baffle 08 disposed on the bypass flue 06, wherein the baffle gate 07 is located upstream of the adjusting baffle 08; The baffle door 07 has two operating modes: fully open and fully closed. It can determine whether to open the bypass flue based on the heating status of the molten salt energy storage module and the operating temperature of the analytical tower 19. The regulating baffle 08 adjusts the bypass flue gas flow rate according to the coal-fired unit load and the heat exchange requirements of the gas-water heat exchanger 09.

[0010] In some embodiments, the gas-water heat exchanger 09 is a waste heat boiler, and the tube bundle is made of finned tubes; The flue gas inlet of the gas-water heat exchanger 09 is connected to the bypass flue 06, and the flue gas outlet is connected to the outlet flue 10 of the gas-water heat exchanger. The gas-water heat exchanger outlet flue 10 is connected to the air preheater outlet flue 12.

[0011] In some embodiments, the pipe between the second tube outlet of the composite reboiler 27 and the inlet of the cryogenic molten salt tank 32 is arranged such that molten salt can flow from the composite reboiler 27 to the cryogenic molten salt tank 32 by gravity. The electric heating unit 35 is powered by off-peak electricity from the power grid at night or by surplus electricity from wind and solar power generation. The electric heating unit 35 has an automatic judgment function and can switch the power supply according to time changes and wind and solar power generation conditions.

[0012] In some embodiments, the molten salt outlet of the composite reboiler 27 is connected to the inlet of the low-temperature molten salt tank 32 via a low-temperature molten salt tank inlet pipe 31; The outlet of the low-temperature molten salt tank 32 is connected to the inlet of the molten salt absorber 34 via the low-temperature molten salt pump 33, and the outlet of the molten salt absorber 34 is connected to the inlet of the high-temperature molten salt tank 36. The outlet of the high-temperature molten salt tank 36 is connected to the second tube inlet of the composite reboiler 27 via a high-temperature molten salt pump 37.

[0013] Secondly, embodiments of this application provide a carbon capture method for thermal power plants utilizing flue gas waste heat and molten salt energy storage. The method is applied to the carbon capture system for thermal power plants utilizing flue gas waste heat and molten salt energy storage described in the first aspect. The method includes: After desulfurization, the boiler flue gas enters the absorption tower 15 and comes into countercurrent contact with the lean organic amine solution in the tower to complete CO2 absorption; the rich solution at the bottom of the absorption tower 15 flows through the desorption tower 19, is heated and desorbs CO2 gas. The lean liquid flowing out from the bottom of the stripping column 19 is cooled and returned to the absorption column 15 for recycling, while the other path is sent to the shell side of the compound reboiler 27 for heating. The lean liquid in the composite reboiler 27 is heated by a gas-water heat exchange circuit and / or a molten salt energy storage circuit. The heating of the gas-water heat exchange circuit includes the gas-water heat exchanger 09 heating water into saturated steam using the waste heat of bypass flue gas. The steam enters the first tube side of the composite reboiler 27 through the saturated steam pipe 30 to release heat. The heating of the molten salt energy storage circuit includes the high-temperature molten salt in the high-temperature molten salt tank 36 entering the second tube side of the composite reboiler 27 to release heat. After the molten salt is heated, it flows into the low-temperature molten salt tank 32 for storage. During off-peak hours of the power grid or during periods of surplus wind and solar power generation, the electric heating unit 35 is activated to heat the molten salt in the low-temperature molten salt tank 32 through the molten salt heat absorber 34 and then store it in the high-temperature molten salt tank 36 to complete the energy storage.

[0014] In some embodiments, the lean liquor flowing out from the bottom of the desorption column 19 is cooled and returned to the absorber 15 for recycling, while the other path is sent to the shell side of the combined reboiler 27 for heating, including: The lean liquor flowing out from the bottom of the analytical column 19 is transported by the lean liquor pump 24, cooled by the lean and rich liquor heat exchanger 17, and then returned to the absorber 15 for recycling. The other route is transported by the lean liquor circulation pump 26 to the shell side of the compound reboiler 27 for heating.

[0015] Compared to related technologies, the carbon capture system for thermal power plants utilizing flue gas waste heat and molten salt energy storage provided in this application utilizes the flue gas waste heat from coal-fired power plants to generate low-pressure saturated steam via a gas-water heat exchanger, providing one heating source for the composite reboiler. By coupling molten salt energy storage, inexpensive electricity generated during off-peak hours or periods of surplus wind and solar power is used to heat and store the molten salt, which then serves as the primary heat source for the composite reboiler. This coupling of flue gas waste heat and molten salt energy storage enables coal-fired units to perform continuous, efficient, and low-energy carbon capture under different loads and with different renewable energy generation conditions, solving the problem of high energy consumption in the CO2 desorption process of coal-fired power generation. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of a carbon capture system for a thermal power plant that utilizes waste heat from flue gas and molten salt for energy storage, according to an embodiment of this application. Figure 2 This is a flowchart of a carbon capture method for thermal power plants that utilizes waste heat from flue gas and molten salt for energy storage, according to an embodiment of this application.

[0017] In the above figures, the meanings of the reference numerals are as follows: 01. Boiler; 02. Economizer; 03. Economizer outlet flue; 04. Denitrification inlet flue; 05. Denitrification unit; 06. Bypass flue; 07. Baffle gate; 08. Regulating baffle; 09. Gas-water heat exchanger; 10. Gas-water heat exchanger outlet flue; 11. Air preheater; 12. Air preheater outlet flue; 13. Dust removal unit; 14. Desulfurization unit; 15. Absorber tower; 16. Rich liquor pump; 17. Lean-rich liquor heat exchanger; 18. Rich liquor pipeline of stripping tower; 19. Stripping tower; 20. 21. Rich liquor nozzle; 22. Crusher; 23. Perforated tray; 24. Desorption tower exhaust pipe; 25. Lean liquor pump; 26. Absorber lean liquor pipe; 27. Lean liquor circulation pump; 28. Compound reboiler; 29. ​​Reboiler outlet pipe; 30. Circulating water pump; 31. Saturated steam pipe; 32. Low-temperature molten salt tank inlet pipe; 33. Low-temperature molten salt tank; 34. Low-temperature molten salt pump; 35. Molten salt absorber; 36. Electric heating unit; 37. High-temperature molten salt tank; 38. High-temperature molten salt pump. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0019] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0020] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0021] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0022] This embodiment provides a carbon capture system for thermal power plants that utilizes waste heat from flue gas and molten salt energy storage. As used below, the terms "module," "unit," "subunit," etc., can refer to a combination of software and / or hardware that performs a predetermined function. The apparatus described in the following embodiments can be implemented in software, hardware, or a combination of software and hardware.

[0023] Figure 1 This is a structural block diagram of a carbon capture system for thermal power plants utilizing waste heat from flue gas and molten salt energy storage, according to an embodiment of this application. Figure 1 As shown, the system includes: a CO2 absorption-desorption module, a gas-water heat exchange module, and a molten salt energy storage module. The CO2 absorption-desorption module includes an absorption tower 15, a desorption tower 19, and a combined reboiler 27. The shell side of the combined reboiler 27 is in circulation with the bottom of the desorption tower 19 and is used to heat the lean liquor from the desorption tower 19. The tube side of the combined reboiler 27 includes a first tube side for introducing steam and a second tube side for introducing molten salt.

[0024] In some embodiments, the absorption tower 15 is connected to the downstream flue of the desulfurization unit 05 and is used to absorb CO2 in the flue gas; the desorption tower 19 is provided with a rich liquid nozzle 20, a crusher 21 and a porous tray 22 from top to bottom, which are used to spray, crush and heat the rich liquid that has absorbed CO2; the shell side of the composite reboiler 27 is filled with circulating lean liquid, and the first tube side and the second tube side are independently distributed and arranged in a uniform cross pattern.

[0025] The stripping column is equipped with rich liquid nozzles, breakers, and porous trays from top to bottom, forming a multi-stage stripping structure of spraying-breakers-uniform distribution: the rich liquid nozzles atomize and spray the rich liquid, increasing the contact area between the rich liquid and the high-temperature environment inside the column, and prolonging the contact heat transfer time between the stripping steam and the rich liquid, thereby improving the CO2 stripping efficiency; the breakers can further break up the droplets, prevent droplet aggregation, and enhance the gas-liquid mass transfer effect; the porous trays have a certain liquid holding effect, which is conducive to the strong mass and heat transfer between the rising stripping steam and the rich liquid.

[0026] The shell side of the combined reboiler 27 carries circulating lean liquor, while the tube side is divided into two independent sections: one carrying low-pressure saturated steam and the other carrying high-temperature molten salt. These two independent tube sides are designed with a uniform, cross-arrangement. This independent and uniformly cross-arrangement of the first tube side (steam) and the second tube side (molten salt) ensures that heat from both heat sources is evenly transferred to the shell-side lean liquor, avoiding localized overheating or insufficient heat exchange, improving the uniformity of lean liquor heating, and guaranteeing the stable operation of the stripping column.

[0027] In some embodiments, the crusher 21 and the porous tray 22 are both fully welded to the wall of the analytical tower 19; the spatial structure of the crusher 21 is composed of a hemispherical structure and a planar mesh structure, and the surface of the hemispherical structure is uniformly arranged with conical hollow protrusions, and the hemispherical surface between the protrusions is uniformly opened with mesh holes.

[0028] The walls of the crusher 21 and the analytical tower 19 are fully welded together. The spatial structure is composed of a hemispherical structure and a planar mesh structure. Preferably, the vertical projection area ratio of the two structures is 3:1. Conical hollow protrusions are uniformly arranged on the surface of the hemispherical structure, and mesh holes are uniformly opened on the hemispherical surface between the protrusions. The porous tray 22 is fully welded to the walls of the analytical tower 19. Preferably, the opening rate is 25%~35%. Optionally, both the crusher 21 and the porous tray 22 are made of 316L stainless steel, and both the crusher 21 and the porous tray 22 can be arranged in multiple stages.

[0029] The decomposer is composed of a hemispherical structure and a planar mesh structure. The curved surface design of the hemispherical structure can change the flow direction of the rich liquid, and combined with the diversion effect of the planar mesh structure, it further breaks the atomized droplets into finer liquid films or droplets, significantly increasing the contact area between the rich liquid and the high-temperature gas in the tower. The uniformly arranged conical hollow protrusions on the hemispherical surface can both turbulentize the rising high-temperature gas flow, prolonging the contact time between the gas flow and the rich liquid, and increase the heat exchange area through the hollow structure; the mesh holes between the protrusions can achieve bidirectional penetration of gas and liquid, enhance the turbulent mixing of the gas and liquid phases, accelerate the desorption rate of CO2 in the rich liquid, and ultimately improve the CO2 desorption efficiency of the desorption tower.

[0030] In some embodiments, the CO2 absorption-desorption module further includes: a rich liquid pump 16, a lean-rich liquid heat exchanger 17, a lean liquid pump 24, and a lean liquid circulation pump 26; the upstream of the rich liquid pump 16 is connected to the bottom of the absorption tower 15, and the downstream is connected to the rich liquid inlet of the lean-rich liquid heat exchanger 17, for sending the rich liquid at the bottom of the absorption tower 15 to the lean-rich liquid heat exchanger 17; the rich liquid outlet of the lean-rich liquid heat exchanger 17 is connected to the rich liquid nozzle 20 in the desorption tower 19 through the rich liquid pipe 18 of the desorption tower. The lean liquid outlet is connected to the absorption tower 15 via the lean liquid pipeline 25; the upstream of the lean liquid pump 24 is connected to the bottom of the stripping tower 19, and the downstream is connected to the lean liquid inlet of the lean-rich liquid heat exchanger 17, which is used to send the lean liquid at the bottom of the stripping tower 19 back to the absorption tower 15 via the lean-rich liquid heat exchanger 17; the upstream of the lean liquid circulation pump 26 is connected to the lean liquid outlet of the compound reboiler 27, and the downstream is connected to the stripping tower 19, which is used to send the lean liquid at the bottom of the stripping tower 19 to the compound reboiler 27.

[0031] Specifically, the CO2 absorption-desorption module includes an absorption tower 15, a rich liquor pump 16, a lean-rich liquor heat exchanger 17, a rich liquor pipeline 18 for the desorption tower, a desorption tower 19, a rich liquor nozzle 20, a crusher 21, a porous tray 22, a desorption tower exhaust pipeline 23, a lean liquor pump 24, a lean liquor pipeline 25 for the absorption tower, a lean liquor circulation pump 26, and a composite reboiler 27. The absorption tower 15 is connected to the downstream flue of the desulfurization unit 05. The upstream of the rich liquor pump 16 is connected to the bottom of the absorption tower 15, and the downstream of the rich liquor pump 16 is connected to the rich liquor inlet of the lean-rich liquor heat exchanger 17. The rich liquor outlet of the lean-rich liquor heat exchanger 17 is connected to the rich liquor pipeline 18 for the desorption tower. The rich liquor pipeline 18 for the desorption tower is connected to the rich liquor nozzle 20 inside the desorption tower 19. The desorption tower 19 is located at the working level of the absorption tower 15. Downstream of the process, the rich liquor nozzle 20 is located at the top of the absorption tower 15, the crusher 21 is located at the bottom of the rich liquor nozzle 20, the porous tray 22 is located at the bottom of the crusher 21, the desorption tower exhaust pipe 23 is connected to the top of the desorption tower 19, the upstream of the lean liquor pump 24 is connected to the bottom of the desorption tower 19, the downstream of the lean liquor pump 24 is connected to the lean liquor inlet of the lean-rich liquor heat exchanger 17, the upstream of the absorption tower lean liquor pipe 25 is connected to the lean liquor outlet of the lean-rich liquor heat exchanger 17, the downstream of the absorption tower lean liquor pipe 25 is connected to the top of the absorption tower 15, the upstream of the lean liquor circulation pump 26 is connected to the lean liquor outlet of the compound reboiler 27, the downstream of the lean liquor circulation pump 26 is connected to the bottom of the desorption tower 19, and the lean liquor inlet of the compound reboiler 27 is connected to the bottom of the desorption tower 19.

[0032] The gas-water heat exchange module includes a bypass flue 06 and a gas-water heat exchanger 09. The bypass flue 06 is connected to the economizer outlet flue 03 to divert part of the flue gas. The gas-water heat exchanger 09 is installed on the bypass flue 06 to recover waste heat from the flue gas. The steam generation side outlet of the gas-water heat exchanger 09 is connected to the first tube inlet of the compound reboiler 27 through a saturated steam pipe 30. The first tube outlet of the compound reboiler 27 is connected to the water side inlet of the gas-water heat exchanger 09 through a pipe, forming a water-steam circulating heating loop.

[0033] The system diverts a portion of the flue gas from the economizer outlet through a bypass flue, recovers the waste heat from the flue gas using a gas-water heat exchanger to generate steam, and then feeds the steam into the first tube pass of the combined reboiler to heat the lean liquor in the desorption tower. After completing heat exchange in the first tube pass, the steam condenses into water and flows back to the gas-water heat exchanger, forming a closed loop.

[0034] In some embodiments, the gas-water heat exchange module further includes a baffle gate 07 and an adjusting baffle 08 disposed on the bypass flue 06. The baffle gate 07 is located upstream of the adjusting baffle 08. The baffle gate 07 has two operating modes: fully open and fully closed. It can determine whether to open the bypass flue based on the heating situation of the molten salt energy storage module and the operating temperature of the analytical tower 19. The adjusting baffle 08 adjusts the bypass flue gas flow rate according to the load of the coal-fired unit and the heat exchange requirements of the gas-water heat exchanger 09.

[0035] Preferably, the opening range of the regulating baffle 08 is 20%~80%, which can automatically adjust the bypass flue gas flow rate according to the load of the coal-fired unit and the heat exchange requirements of the gas-water heat exchanger 09. The flue gas flow rate of the bypass flue 06 shall not exceed 15% of the total flue gas volume.

[0036] The system operates in a fully open / fully closed mode, allowing for the activation of waste heat recovery from the bypass flue gas based on the heating status of the molten salt energy storage module and the operating temperature of the stripping tower 19. When the molten salt energy storage provides sufficient heating and the stripping tower temperature meets the standard, the damper can be closed to prevent waste heat. When the stripping tower requires additional heat, the damper can be opened to introduce waste heat from the flue gas, enabling on-demand switching of the heat source.

[0037] With an opening range of 20% to 80%, the bypass flue gas flow rate can be precisely adjusted according to changes in the coal-fired unit load (such as differences in flue gas volume and temperature at high / low loads) and the heat exchange requirements of the gas-water heat exchanger 09. Combined with the restriction that the bypass flue gas flow rate should not exceed 15% of the total flue gas volume, this ensures effective waste heat recovery without excessive extraction of main flue gas, thus avoiding interference with the operation of denitrification, dust removal, and other systems at the boiler tail end.

[0038] In some embodiments, the gas-water heat exchanger 09 is a waste heat boiler, and the tube bundle adopts finned tubes; the flue gas inlet of the gas-water heat exchanger 09 is connected to the bypass flue 06, and the flue gas outlet is connected to the gas-water heat exchanger outlet flue 10; the gas-water heat exchanger outlet flue 10 is connected to the air preheater outlet flue 12.

[0039] The tube bundle adopts a finned tube structure. The addition of fins expands the heat exchange area and enhances the convective heat transfer effect on the flue gas side, enabling efficient recovery of low-grade waste heat from the low-temperature flue gas at the economizer outlet. Even under conditions of low unit load and low flue gas temperature, it can stably generate steam that meets the desorption requirements, improving the stability and utilization rate of waste heat recovery.

[0040] The high-efficiency heat exchange characteristics of the waste heat boiler + finned tube complement the "on / off + flow" control logic of the upstream damper and regulating damper: when the regulating damper adjusts the bypass flue gas flow, the finned tube waste heat boiler can quickly respond to the flow change and output steam stably; when the damper is closed, no flue gas enters the waste heat boiler, which can be in a low-load standby state to avoid ineffective operating losses.

[0041] Specifically, the gas-water heat exchange module includes a bypass flue 06, a damper 07, a regulating damper 08, a gas-water heat exchanger 09, a gas-water heat exchanger outlet flue 10, a reboiler outlet water pipe 28, a circulating water pump 29, and a saturated steam pipe 30. The upstream of the bypass flue 06 is connected to the economizer outlet flue 03. The damper 07 is located on the bypass flue 06, and the regulating damper 08 is located on the bypass flue 06 and downstream of the damper 07. The flue gas inlet of the gas-water heat exchanger 09 is connected to the bypass flue 06, the flue gas outlet of the gas-water heat exchanger 09 is connected to the gas-water heat exchanger outlet flue 10, and the gas-water heat exchanger outlet flue 10 is connected to the air preheater outlet flue 12.

[0042] The molten salt energy storage module includes a low-temperature molten salt tank 32, a high-temperature molten salt tank 36, a molten salt absorber 34, and an electric heating unit 35 that supplies power to the molten salt absorber 34. The outlet of the second tube side of the compound reboiler 27 is connected to the inlet of the low-temperature molten salt tank 32 through a pipeline. The outlet of the low-temperature molten salt tank 32 is connected to the inlet of the high-temperature molten salt tank 36 through the molten salt absorber 34. The outlet of the high-temperature molten salt tank 36 is connected to the inlet of the second tube side of the compound reboiler 27 through a pipeline, forming a molten salt circulating heating loop.

[0043] The composite reboiler is equipped with a second tube pass, introducing a molten salt circulation heating loop as a supplementary heat source. This solves the intermittent and fluctuating problems of waste heat from the flue gas (for example, when the unit is operating at low load, the flue gas volume and temperature decrease, resulting in insufficient waste heat supply). When the waste heat from the flue gas is sufficient, the molten salt can be heated and stored normally in a high-temperature molten salt tank. When the waste heat from the flue gas is insufficient, the molten salt stored in the high-temperature molten salt tank is pumped into the composite reboiler to provide heat for the desorption process, achieving "peak shaving and valley filling" of the heat source. Molten salt has the characteristics of high energy storage density and good thermal stability, and can store heat for a long time with low loss, ensuring the stable operation of the CO2 absorption-desorption module and avoiding a decrease in carbon capture efficiency due to heat source fluctuations.

[0044] In some embodiments, the pipe between the second tube outlet of the composite reboiler 27 and the inlet of the low-temperature molten salt tank 32 is arranged in such a way that molten salt can flow from the composite reboiler 27 to the low-temperature molten salt tank 32 by gravity. The electric heating unit 35 is powered by off-peak electricity from the power grid at night or by surplus electricity from wind and solar power generation. The electric heating unit 35 has an automatic judgment function and can switch the power supply according to time changes and wind and solar power generation conditions.

[0045] The electric heating unit uses off-peak electricity from the power grid at night, when the grid price is low, which can significantly reduce the electricity cost of molten salt heating compared to peak electricity prices. At the same time, it can absorb the surplus electricity generated by wind and solar power, thus avoiding the waste of clean energy.

[0046] The electric heating unit has automatic judgment and power switching functions. It can automatically select the optimal power source based on time changes (distinguishing between off-peak and peak power periods) and wind and solar power output (determining whether there is excess power). It can achieve the cost-optimal operation strategy of molten salt heating, while flexibly adapting to the volatility of new energy power generation, ensuring stable heating of the molten salt energy storage module, forming an efficient complement to the flue gas waste heat recovery system, and further optimizing the energy consumption structure of the CO2 desorption process.

[0047] In some embodiments, the molten salt outlet of the compound reboiler 27 is connected to the inlet of the low-temperature molten salt tank 32 via the low-temperature molten salt tank inlet pipe 31; the outlet of the low-temperature molten salt tank 32 is connected to the inlet of the molten salt absorber 34 via the low-temperature molten salt pump 33, and the outlet of the molten salt absorber 34 is connected to the inlet of the high-temperature molten salt tank 36; the outlet of the high-temperature molten salt tank 36 is connected to the second tube inlet of the compound reboiler 27 via the high-temperature molten salt pump 37.

[0048] It should be noted that the molten salt heating method uses electric heating. Electric heating offers rapid start-up and shutdown response and precise adjustable heating power. It allows for real-time adjustment of the molten salt absorber's heating power based on the heat demand of the desorption tower, quickly matching any shortfall in waste heat supply and ensuring stable temperature during the desorption process. The electric heating unit can be deeply coupled with off-peak electricity from the power grid and surplus wind and solar power, storing heat during periods of low electricity prices or when renewable energy is being curtailed, and releasing heat during periods of high electricity prices or when waste heat is insufficient. This reduces the operating costs of molten salt heating while improving the system's energy efficiency and economic benefits.

[0049] Specifically, the molten salt energy storage module includes a low-temperature molten salt tank inlet pipe 31, a low-temperature molten salt tank 32, a low-temperature molten salt pump 33, a molten salt absorber 34, an electric heating unit 35, a high-temperature molten salt tank 36, and a high-temperature molten salt pump 37. One end of the low-temperature molten salt tank inlet pipe 31 is connected to the molten salt outlet of the compound reboiler 27, and the other end of the low-temperature molten salt tank inlet pipe 31 is connected to the inlet of the low-temperature molten salt tank 32. The outlet of the low-temperature molten salt tank 32 is connected to the low-temperature molten salt pump 33, the outlet of the low-temperature molten salt pump 33 is connected to the inlet of the molten salt absorber 34, the outlet of the molten salt absorber 34 is connected to the inlet of the high-temperature molten salt tank 36, the electric heating unit 35 is located on the side of the molten salt absorber 34, the outlet of the high-temperature molten salt tank 36 is connected to the inlet of the high-temperature molten salt pump 37, and the outlet of the high-temperature molten salt pump 37 is connected to the molten salt inlet of the compound reboiler 27.

[0050] The aforementioned system utilizes waste heat from coal-fired power plant flue gas to generate low-pressure saturated steam via a gas-water heat exchanger, providing a heating source for the composite reboiler. Optimizing the absorption tower structure, such as adding crushers and porous trays, increases the heat transfer surface area of ​​the rich liquid, extending the contact time between stripping steam and the rich liquid, thereby improving CO2 desorption efficiency. Coupled with molten salt energy storage, cheap electricity generated during off-peak hours or periods of surplus wind and solar power is used to heat and store the molten salt, serving as the primary heat source for the composite reboiler. This coupling of waste heat from flue gas and molten salt energy storage enables coal-fired units to perform continuous, efficient, and low-energy carbon capture under different loads and renewable energy generation conditions, solving the problem of high energy consumption in the CO2 desorption process of coal-fired power generation.

[0051] By coupling flue gas waste heat with molten salt energy storage in a coal-fired power plant carbon capture system, the problems of extracting steam from the power plant turbine and the resulting significant reduction in power generation efficiency can be directly avoided. The special structural design within the analyzer tower also provides crucial support for deep CO2 analysis, helping to improve the purity of the CO2 product gas and facilitating subsequent utilization. Furthermore, the system's adjustable bypass flue gas flow and the flexible peak-shaving capabilities of the molten salt energy storage system can, to a certain extent, improve the operational stability and economy of the coal-fired power plant carbon capture system.

[0052] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0053] This embodiment provides a carbon capture method for thermal power plants that utilizes waste heat from flue gas and molten salt energy storage. This method is applied to the aforementioned carbon capture system for thermal power plants that utilizes waste heat from flue gas and molten salt energy storage. Figure 2 This is a flowchart of a carbon capture method for thermal power plants utilizing waste heat from flue gas and molten salt energy storage, according to an embodiment of this application. Figure 2 As shown, the process includes the following steps: In step S201, the boiler flue gas enters the absorption tower 15 after desulfurization and comes into countercurrent contact with the lean organic amine solution in the tower to complete CO2 absorption; the rich solution at the bottom of the absorption tower 15 flows through the desorption tower 19, is heated and desorbs CO2 gas.

[0054] In step S202, the lean liquid flowing out from the bottom of the stripping column 19 is cooled and returned to the absorption column 15 for recycling, while the other path is sent to the shell side of the composite reboiler 27 for heating.

[0055] In some embodiments, the lean liquor flowing from the bottom of the stripping column 19 is cooled and returned to the absorber 15 for recycling, while the other path is sent to the shell side of the combined reboiler 27 for heating, including: The lean liquor flowing out from the bottom of the analytical column 19 is transported by the lean liquor pump 24, cooled by the lean and rich liquor heat exchanger 17, and then returned to the absorber 15 for recycling. The other route is transported by the lean liquor circulation pump 26 to the shell side of the compound reboiler 27 for heating.

[0056] Step S203: The lean liquid in the composite reboiler 27 is heated using a gas-water heat exchange circuit and / or a molten salt energy storage circuit. The heating of the gas-water heat exchange circuit includes the gas-water heat exchanger 09 heating water into saturated steam using the waste heat of the bypass flue gas. The steam enters the first tube side of the composite reboiler 27 through the saturated steam pipe 30 to release heat. The heating of the molten salt energy storage circuit includes the high-temperature molten salt in the high-temperature molten salt tank 36 entering the second tube side of the composite reboiler 27 to release heat.

[0057] In step S204, the molten salt after exothermic flows into the low-temperature molten salt tank 32 for storage. During off-peak hours of the power grid or during periods of surplus wind and solar power generation, the electric heating unit 35 is activated to heat the molten salt in the low-temperature molten salt tank 32 through the molten salt heat absorber 34 and then store it in the high-temperature molten salt tank 36 to complete energy storage.

[0058] Specifically, the flue gas from boiler 01 enters economizer 02, is led out from economizer outlet flue 03 and splits into two paths. One path flows to denitrification inlet flue 04 and then enters denitrification device 05. The other path is led out from bypass flue 06. The flue gas led out from bypass flue flows through damper 07 and regulating damper 08 in sequence, enters gas-water heat exchanger 09, flows out from gas-water heat exchanger outlet flue 10, and merges with air preheater outlet flue 12 downstream of air preheater 11 to enter dust removal device 13.

[0059] The flue gas drawn from the dust removal device 13 is treated by the desulfurization device 14 and then enters the absorption tower 15. After being absorbed by the lean organic amine solution in the absorption tower 15, the flue gas forms decarbonized flue gas, which is discharged from the top of the absorption tower 15. The rich solution that absorbs CO2 is drawn out by the rich solution pump 16 and enters the lean-rich solution heat exchanger 17. After being heated by heat absorption, it enters the desorption tower 19 through the rich solution pipe 18. The rich solution is atomized by the rich solution nozzle 20 to form dispersed droplets. The droplets move downward and collide with the crusher 20. Under the action of the protrusions on the surface of the crusher 20, the droplets form smaller droplets, which exchange heat with the upward stripping steam below the desorption tower 19 and rapidly undergo desorption. Some droplets continue to fall and, under the liquid holding action of the porous tray 22, undergo strong mass transfer and heat exchange with the rising stripping steam to achieve further desorption. The desorbed CO2 is drawn out from the top of the desorption tower 19 and enters the subsequent cooling, compression, and purification units.

[0060] The lean liquid at the bottom of the stripping tower 19 flows through two paths. One path is drawn out through the lean liquid pump 24 and enters the lean-rich liquid heat exchanger 17. After releasing heat and cooling down, it enters the absorption tower 15 through the lean liquid pipeline 25. The other path is drawn out through the lean liquid circulation pump 26 and enters the compound reboiler 27. After being heated by steam or molten salt, it enters the stripping tower 19, maintaining sufficient stripping steam and temperature gradient in the stripping tower 19. The steam side of the compound reboiler 27 releases heat and condenses to form saturated water, which is drawn out through the circulating water pump 29 and enters the gas-water heat exchanger 09. After absorbing heat from the flue gas, the saturated water forms low-pressure saturated steam. The steam enters the compound reboiler 27 along the saturated steam pipeline 30 to participate in the next heat exchange cycle.

[0061] The low-temperature molten salt at approximately 290°C drawn from the other tube of the composite reboiler 27 flows by gravity along the inlet pipe 31 of the low-temperature molten salt tank into the low-temperature molten salt tank 32 for storage. During off-peak electricity hours or periods of surplus wind and solar power generation, the low-temperature molten salt pump 33 is activated to transport the low-temperature molten salt in the low-temperature molten salt tank 32 to the molten salt absorber 34. Under the heating action of the electric heating unit 35, the temperature of the low-temperature molten salt rises to 565°C and flows into the high-temperature molten salt tank 36 for storage. Under the action of the high-temperature molten salt pump 37, the high-temperature molten salt enters the composite reboiler 27 to participate in heat exchange, thereby achieving a continuous replenishment of heat for the stripping tower 19.

[0062] The above method utilizes waste heat from flue gas in coal-fired power plants to generate low-pressure saturated steam via a gas-water heat exchanger, providing one heating source for the composite reboiler. By coupling molten salt energy storage, inexpensive electricity generated during off-peak hours or periods of surplus wind and solar power is used to heat and store the molten salt, which then serves as the primary heat source for the composite reboiler. This coupling of waste heat from flue gas and molten salt energy storage enables coal-fired units to perform continuous, efficient, and low-energy carbon capture under different loads and renewable energy generation conditions, solving the problem of high energy consumption in the CO2 desorption process of coal-fired power generation.

[0063] It should be noted that the steps shown in the above process or in the flowchart of the accompanying figures can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0064] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A carbon capture system for thermal power plants utilizing waste heat from flue gas and molten salt energy storage, characterized in that, The system includes: a CO2 absorption-desorption module, a gas-water heat exchange module, and a molten salt energy storage module. The CO2 absorption-desorption module includes an absorption tower (15), a desorption tower (19), and a composite reboiler (27). The shell side of the composite reboiler (27) is in cyclic communication with the bottom of the desorption tower (19) for heating lean liquor from the desorption tower (19). The tube side of the composite reboiler (27) includes a first tube side for introducing steam and a second tube side for introducing molten salt. The gas-water heat exchange module includes a bypass flue (06) and a gas-water heat exchanger (09). The bypass flue (06) is connected to the economizer outlet flue (03) for diverting part of the flue gas. The gas-water heat exchanger (09) is installed on the bypass flue (06) for recovering waste heat from the flue gas. The steam generation side outlet of the gas-water heat exchanger (09) is connected to the first tube inlet of the composite reboiler (27) through a saturated steam pipe (30). The first tube outlet of the composite reboiler (27) is connected to the water side inlet of the gas-water heat exchanger (09) through a pipe, forming a water-steam circulating heating loop. The molten salt energy storage module includes a low-temperature molten salt tank (32), a high-temperature molten salt tank (36), a molten salt absorber (34), and an electric heating unit (35) that supplies power to the molten salt absorber (34). The outlet of the second tube of the composite reboiler (27) is connected to the inlet of the low-temperature molten salt tank (32) through a pipe. The outlet of the low-temperature molten salt tank (32) is connected to the inlet of the high-temperature molten salt tank (36) through the molten salt absorber (34). The outlet of the high-temperature molten salt tank (36) is connected to the inlet of the second tube of the composite reboiler (27) through a pipe, thus forming a molten salt circulating heating loop.

2. The system according to claim 1, characterized in that, The absorption tower (15) is connected to the downstream flue of the desulfurization unit (05) and is used to absorb CO2 in the flue gas. The analytical tower (19) is equipped with a rich liquid nozzle (20), a crusher (21) and a porous tray (22) from top to bottom, which are used to spray, crush, heat and analyze the rich liquid that has absorbed CO2. The internal shell side of the composite reboiler (27) carries a lean liquid, while the first tube side and the second tube side are independently distributed and arranged in a uniform cross pattern.

3. The system according to claim 2, characterized in that, Both the crushed body (21) and the porous tray (22) are fully welded to the wall of the analytical tower (19); The spatial structure of the fragment (21) is formed by connecting a hemispherical structure and a planar mesh structure. The surface of the hemispherical structure is uniformly arranged with conical hollow protrusions, and mesh holes are uniformly opened on the hemispherical surface between the protrusions.

4. The system according to claim 1, characterized in that, The CO2 absorption-desorption module also includes: a rich liquid pump (16), a lean and rich liquid heat exchanger (17), a lean liquid pump (24), and a lean liquid circulation pump (26). The upstream of the rich liquid pump (16) is connected to the bottom of the absorption tower (15), and the downstream is connected to the rich liquid inlet of the lean-rich liquid heat exchanger (17), which is used to send the rich liquid at the bottom of the absorption tower (15) to the lean-rich liquid heat exchanger (17). The rich liquid outlet of the rich and lean liquid heat exchanger (17) is connected to the rich liquid nozzle (20) in the analytical tower (19) through the rich liquid pipeline (18) of the analytical tower, and the lean liquid outlet is connected to the absorption tower (15) through the lean liquid pipeline (25) of the absorption tower. The upstream of the lean liquid pump (24) is connected to the bottom of the analytical tower (19), and the downstream is connected to the lean liquid inlet of the lean-rich liquid heat exchanger (17), which is used to send the lean liquid at the bottom of the analytical tower (19) back to the absorption tower (15) through the lean-rich liquid heat exchanger (17). The upstream of the lean liquid circulation pump (26) is connected to the lean liquid outlet of the compound reboiler (27), and the downstream is connected to the stripping column (19), which is used to send the lean liquid at the bottom of the stripping column (19) to the compound reboiler (27).

5. The system according to claim 1, characterized in that, The gas-water heat exchange module also includes a baffle door (07) and an adjusting baffle (08) installed on the bypass flue (06), wherein the baffle door (07) is located upstream of the adjusting baffle (08); The baffle door (07) has two operating modes: fully open and fully closed. It can determine whether to open the bypass flue based on the heating situation of the molten salt energy storage module and the operating temperature of the analytical tower (19). The regulating baffle (08) adjusts the bypass flue gas flow rate according to the coal-fired unit load and the heat exchange requirements of the gas-water heat exchanger (09).

6. The system according to claim 1, characterized in that, The gas-water heat exchanger (09) is a waste heat boiler, and the tube bundle adopts finned tubes; The flue gas inlet of the gas-water heat exchanger (09) is connected to the bypass flue (06), and the flue gas outlet is connected to the outlet flue (10) of the gas-water heat exchanger. The outlet flue (10) of the gas-water heat exchanger is connected to the outlet flue (12) of the air preheater.

7. The system according to claim 1, characterized in that, The pipe between the second tube outlet of the composite reboiler (27) and the inlet of the low-temperature molten salt tank (32) is arranged in such a way that molten salt can flow from the composite reboiler (27) to the low-temperature molten salt tank (32) by gravity. The electric heating unit (35) is powered by off-peak electricity from the power grid at night or by surplus electricity from wind and solar power generation. The electric heating unit (35) has an automatic judgment function and can switch the power supply according to time changes and wind and solar power generation conditions.

8. The system according to claim 1, characterized in that, The molten salt outlet of the composite reboiler (27) is connected to the inlet of the low-temperature molten salt tank (32) through the inlet pipe (31) of the low-temperature molten salt tank; The outlet of the low-temperature molten salt tank (32) is connected to the inlet of the molten salt absorber (34) via a low-temperature molten salt pump (33), and the outlet of the molten salt absorber (34) is connected to the inlet of the high-temperature molten salt tank (36). The outlet of the high-temperature molten salt tank (36) is connected to the second tube inlet of the composite reboiler (27) via a high-temperature molten salt pump (37).

9. A method for carbon capture in thermal power plants utilizing waste heat from flue gas and molten salt energy storage, characterized in that, The method is applied to a carbon capture system in a thermal power plant that utilizes waste heat from flue gas and molten salt energy storage as described in any one of claims 1-8, and the method includes: After desulfurization, the boiler flue gas enters the absorption tower (15) and comes into countercurrent contact with the lean organic amine solution in the tower to complete CO2 absorption; the rich solution at the bottom of the absorption tower (15) flows through the desorption tower (19), is heated and desorbs CO2 gas. The lean liquid flowing out from the bottom of the analytical column (19) is cooled and returned to the absorption column (15) for recycling, while the other path is sent to the shell side of the compound reboiler (27) for heating; The lean liquid in the composite reboiler (27) is heated by a gas-water heat exchange circuit and / or a molten salt energy storage circuit. The heating of the gas-water heat exchange circuit includes the gas-water heat exchanger (09) heating water into saturated steam by using the waste heat of bypass flue gas. The steam enters the first tube side of the composite reboiler (27) through the saturated steam pipe (30) to release heat. The heating of the molten salt energy storage circuit includes the high-temperature molten salt in the high-temperature molten salt tank (36) entering the second tube side of the composite reboiler (27) to release heat. After the heat is released, the molten salt flows into the low-temperature molten salt tank (32) for storage. During off-peak hours of the power grid or during periods of surplus wind and solar power generation, the electric heating unit (35) is activated to heat the molten salt in the low-temperature molten salt tank (32) through the molten salt heat absorber (34) and then store it in the high-temperature molten salt tank (36) to complete the energy storage.

10. The method according to claim 9, characterized in that, The lean liquor flowing out from the bottom of the analytical column (19) is cooled and returned to the absorber (15) for recycling, while the other path is sent to the shell side of the compound reboiler (27) for heating, including: The lean liquid flowing out from the bottom of the analytical column (19) is transported by the lean liquid pump (24), cooled by the lean and rich liquid heat exchanger (17), and returned to the absorber (15) for recycling. The other path is transported by the lean liquid circulation pump (26) to the shell side of the compound reboiler (27) for heating.

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