Calcium-based CO2 capturing method and system coupled with power station boiler

Abstract

The invention discloses a method and a system for capturing calcium-based CO2 coupled with a power station boiler, belongs to the technical field of energy conservation and emission reduction of power station boilers, and solves the problems that the existing power station boiler CO2 removal technology has certain defects in energy consumption, equipment corrosion, material cost and separation effect. The system is composed of two reaction units, the structures of the two reaction units are the same, and each unit comprises a reactor, a flue gas booster fan, a flue gas heater, a separation device, a booster fan, a cooler, a flue gas cooler and a circulating fan. When one reaction unit executes a CO2 capturing process, the other reaction unit executes a CO2 calcining and removing process, and the two reaction units alternately run in a reciprocating manner. The method is suitable for power station boiler energy conservation and emission reduction application scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of energy conservation and emission reduction of power station boilers, and specifically relates to a low-energy consumption CO2 removal technology. Background Art

[0002] As one of the main sources of carbon emissions, power plant boilers emit a large amount of flue gas containing low-concentration CO2. How to efficiently and economically remove this CO2 has become a key research direction in the energy field. At present, a variety of technical means have been developed for the removal of CO2 from power plant boiler flue gas, but there are still some technical problems.

[0003] From the perspective of physical absorption, although commonly used physical absorbents such as methanol and polyethylene glycol dimethyl ether have a certain absorption capacity for CO2, this method has the problem of high energy consumption for absorbent regeneration. After absorbing CO2, in order to realize the recycling of the absorbent, the rich liquid needs to be desorbed, and this process often consumes a lot of heat energy. For example, in some industrial applications, the steam consumption in the desorption process is large, resulting in a significant increase in production costs. In addition, the absorption performance of the desorbed absorbent will gradually decrease during repeated use, affecting the stability of the CO2 removal effect.

[0004] Chemical absorption is also a common method of CO2 removal, using chemical absorbents such as alcohol amine solutions (MEA, DEA, etc.). However, this type of method has the disadvantage of serious equipment corrosion. In the process of absorbing CO2, alcohol amine solutions will react chemically with the equipment material, accelerating the corrosion of the equipment. After long-term operation, the wall thickness of the equipment will decrease and the risk of leakage will increase, which will not only increase the equipment maintenance cost, but also extend the shutdown and maintenance time of the device, affecting the normal operation efficiency of the power station boiler. In addition, the degradation problem of chemical absorbents cannot be ignored. Under high temperature and high CO2 load conditions, the absorbent is prone to degradation and needs to be regularly replenished or replaced, further increasing the operating cost.

[0005] There are also studies on calcium-based CO2 capture in the world. Although the energy consumption is slightly lower than other methods, there are still many problems. The cyclic stability of calcium-based adsorbents is poor. During multiple cycles of adsorption-desorption, the activity and structure of the adsorbent will change, resulting in a gradual decrease in its ability to capture CO2. The adsorbent needs to be replaced frequently, which undoubtedly increases the operating cost. Moreover, the existing calcium-based CO2 capture technology is not perfect in terms of heat recovery and utilization. It fails to fully utilize the heat in the chemical reaction process and the waste heat of the boiler itself, resulting in low energy utilization. The overall operating cost is still very high, making it difficult to promote and apply on a large scale in the commercial field.

[0006] In summary, the existing power plant boiler CO2 removal technology has defects to varying degrees in terms of energy consumption, equipment corrosion, material cost, separation effect, etc. An innovative technology is urgently needed to solve these problems and achieve low-energy consumption, low-cost, efficient and stable CO2 removal. Summary of the invention

[0007] The present invention proposes a calcium-based CO2 capture method and system coupled with a power station boiler, the purpose of which is to solve the problem that the existing power station boiler CO2 removal technology has certain defects in energy consumption, equipment corrosion, material cost and separation effect.

[0008] The calcium-based CO2 capture system coupled with a power plant boiler proposed in the present invention is composed of two reaction units, the two reaction units have the same structure, and each unit includes a reactor, a flue gas booster fan, a flue gas heater, a separation device, a booster fan, a cooler, a flue gas cooler, and a circulation fan;

[0009] The reactor is used to carry out a decomposition reaction of CaCO3 or a chemical reaction of CaO and CO2;

[0010] The flue gas booster fan is used to boost the flue gas pressure;

[0011] The flue gas heater is used to heat the flue gas pressurized by the flue gas booster;

[0012] The cooler is used to cool the high-temperature CO2 and circulating water vapor generated by the reactor;

[0013] The booster fan is used to pressurize the cooled CO2 and the circulating water vapor;

[0014] The separation device is used to separate the pressurized CO2 and the circulating water vapor;

[0015] The flue gas cooler is used to cool the hot flue gas released by the reactor;

[0016] The circulating fan is used to transport the cooled flue gas to the boiler.

[0017] Furthermore, a preferred solution is provided: when one reaction unit performs a CO2 capture process, the other unit performs a CO2 calcination removal process, and the two units operate alternately and reciprocally.

[0018] Furthermore, a preferred solution is provided: the flue gas pressurized by the flue gas booster fan is taken from the flue gas after the desulfurization tower.

[0019] Furthermore, a preferred solution is provided: a plurality of heat exchange tubes are provided in the reactor, and the CaO particles are placed outside the plurality of heat exchange tubes.

[0020] Furthermore, a preferred solution is provided: when the reaction unit is performing CO2 capture, there is no medium in the heat exchange tube, and when the flue gas flows through the reactor, it only contacts and reacts with the CaO outside the tube.

[0021] Furthermore, a preferred solution is provided: the reactor is of a fixed bed type, and after the flue gas flows through the medium, the CaO particles remain stationary.

[0022] Furthermore, a preferred solution is provided: the heat source of the flue gas heater is taken from the high-temperature CO2 generated by calcination of another reaction unit.

[0023] Furthermore, a preferred solution is provided: after CO2 is removed from the flue gas of the reactor, the hot flue gas whose temperature rises to 650-670°C is directly sent to the tail flue of the boiler, and is discharged from the boiler to achieve heat recovery after heat exchange with the heating surface of the boiler.

[0024] Furthermore, a preferred solution is provided: the system uses hot flue gas from a boiler as a calcination heat source for the reactor.

[0025] The present invention also proposes a calcium-based CO2 capture method coupled with a power plant boiler, the method is implemented based on a calcium-based CO2 capture system coupled with a power plant boiler described in any one or more of the above schemes, and the method comprises the following steps:

[0026] CO2 capture steps: The flue gas from the boiler desulfurization tower is pressurized by the flue gas booster fan, sent to the flue gas heater for heating, and then sent to the reactor to react with CaO in the reactor to remove CO2 from the flue gas. The reaction exothermicity causes the medium temperature to rise to 650-670℃. The high-temperature flue gas with CO2 removed is directly sent back to the tail flue of the boiler and discharged from the boiler after heat exchange with the tail heating surface;

[0027] CO2 separation step: When no less than 2 / 3 of the CaO in the reactor is converted into CaCO3, low-pressure circulating steam is introduced, and the hot flue gas from the boiler is introduced into the heat exchange tube of the reactor to calcine and decompose the CaCO3. The decomposed CO2 enters the cooler together with the water vapor for cooling, and then enters the separation device after being pressurized by the booster fan. The separated water vapor returns to the reactor, and the CO2 enters the flue gas heater of another reaction unit. After the decomposition of the CaCO3 in the reactor is completed, the CO2 capture step is re-entered.

[0028] The present invention has the following advantages:

[0029] The present invention proposes a new calcium-based CO2 capture method, which utilizes the same principle of heat absorption of CaCO3→CaO+CO2 and heat release of CaCO3→CaO+CO2, and uses heat taken from the flue gas side of the boiler body as the calcination heat of the reactor to decompose CaCO3 into CaO and CO2. The heat will be released in the reaction process of capturing CO2, that is, CaO reacts with CO2 to generate CaCO3 and release heat. The released heat will heat the flue gas from which CO2 has been removed to 650-670°C, and the flue gas is returned to the boiler for heat recovery. The heat loss in the remaining process is further recovered to the boiler using reheated steam and boiler cold air, thereby significantly reducing energy consumption and operating costs.

[0030] The present invention is applicable to the application scenario of energy conservation and emission reduction of power station boilers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic structural diagram of a calcium-based CO2 capture system coupled with a power plant boiler according to a specific embodiment of the present invention, wherein 1 is a power plant boiler, 2 and 3 are reactors, 4 and 5 are flue gas booster fans, 6 and 7 are flue gas heaters, 8 and 9 are separation devices, 10 and 11 are booster fans, 12 and 13 are coolers, 14 and 15 are flue gas coolers, and 16 and 17 are circulating fans;

[0033] Figure 2 It is a longitudinal cross-sectional schematic diagram of a reactor of a calcium-based CO2 capture system coupled to a power plant boiler according to a specific embodiment of the present invention, wherein 18 is a heat exchange tube, 19 is a water vapor inlet, 20 is a water vapor / CO2 outlet, 21 is a heat source flue gas inlet, 22 is a heat source flue gas outlet, 23 is a shell, and 24 is a reaction particle;

[0034] Figure 3 This is a schematic cross-sectional view of a reactor of a calcium-based CO2 capture system coupled to a power plant boiler according to a first specific embodiment of the present invention. DETAILED DESCRIPTION

[0035] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0036] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0037] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific implementation methods disclosed below.

[0040] Implementation method 1:

[0041] Reference Figure 1 , Figure 2 , Figure 3 This embodiment will be described.

[0042] This embodiment proposes a calcium-based CO2 capture system coupled with a power plant boiler, which uses heat from the flue gas side of the boiler body as the calcination heat of the reactor to decompose CaCO3 into CaO and CO2. The heat will be released in the reaction process of capturing CO2, that is, CaO reacts with CO2 to generate CaCO3 and release heat. The released heat will heat the flue gas from which CO2 has been removed to 650-670°C, and the flue gas is sent back to the boiler 1 for heat recovery. The heat loss in the remaining process is further recovered to the boiler using reheated steam or the primary and secondary air of the boiler, thereby significantly reducing energy consumption and operating costs.

[0043] Specifically: the system consists of two reaction units, the two reaction units have the same structure, when one reaction unit performs the CO2 capture process, the other unit performs the CO2 calcination removal process, and the two units operate alternately; the system uses hot flue gas from the boiler (1) as the calcination heat source of the reactor.

[0044] Furthermore, each unit includes a reactor, a flue gas booster fan, a flue gas heater, a separation device, a booster fan, a cooler, a flue gas cooler, and a circulation fan;

[0045] The reactor is used to carry out a decomposition reaction of CaCO3 or a chemical reaction of CaO and CO2;

[0046] Further: Figure 2 , Figure 3 As shown: Several heat exchange tubes 18 are arranged vertically in the reactor, and the material thereof is stainless steel. Reaction particles 24 (CaO / CaCO3) are placed outside the several heat exchange tubes. The water vapor inlet 19 and the water vapor / CO2 outlet 20 are respectively located on the side of the reactor, for the introduction of water vapor and the discharge of the mixed gas of water vapor and CO2 after the reaction; the heat source flue gas inlet (21) and the heat source flue gas outlet (22) are respectively located at the upper and lower ends of the reactor, for the inflow and outflow of the heat source flue gas. When the reaction unit is performing CO2 capture, there is no medium in the heat exchange tube, and when the flue gas flows through the reactor, it only contacts and reacts with the CaO outside the tube. The reactor is a fixed bed type, and the CaO particles remain stationary after the flue gas passes through the medium. After the CO2 is removed from the flue gas passing through the reactor, the hot flue gas with a temperature of 650-670°C is directly sent to the tail flue of the boiler (1), and is discharged from the boiler after heat exchange with the boiler heating surface to achieve heat recovery.

[0047] When executing the calcination process, in order to reduce the calcination reaction temperature, the partial pressure of CO2 is reduced by introducing low-pressure circulating steam, so that the partial pressure of CO2 after decarburization is reduced to about 25KPa, and the calcination reaction temperature is reduced from about 900°C to about 800°C. The hot flue gas at about 900°C from the boiler body is used as the calcination heat source. The hot flue gas is introduced into the heat exchange tube of the reactor 2 or 3 to transfer heat to the CaCO3 outside the tube. The flue gas temperature is reduced to about 750°C and discharged from the reactor. It is reduced to below 450°C by the flue gas cooler 14 or 15 and enters the circulating fan 16 or 17, and then sent back to the tail flue of the boiler 1.

[0048] The flue gas booster fan is used to boost the flue gas pressure; the flue gas boosted by the flue gas booster fan is taken from the flue gas at about 50°C after the desulfurization tower;

[0049] The flue gas heater is used to heat the flue gas after being pressurized by the flue gas booster, and the temperature of the heated flue gas is about 120°C; the heat source of the flue gas heater is taken from the high-temperature CO2 generated by calcination of another reaction unit;

[0050] The cooler is used to cool the high-temperature CO2 and circulating water vapor generated by the reactor;

[0051] The booster fan is used to pressurize the cooled CO2 and the circulating water vapor;

[0052] The separation device is used to separate the pressurized CO2 and the circulating water vapor; the device adopts the density difference separation principle, the water vapor is discharged from the upper part, sent to the reactor 2, 3 to continue to participate in the reaction, and the high-temperature CO2 is discharged from the lower part, sent to the flue gas cooler 6 or 7 to heat the flue gas, and then discharged from the system.

[0053] The flue gas cooler is used to cool the hot flue gas released by the reactor;

[0054] The circulating fan is used to transport the cooled flue gas to the boiler.

[0055] like Figure 1As shown, taking reaction unit 1 as an example, reaction unit 1 is composed of 1, 2, 4, 6, 8, 10, 12, 14, and 16. When the unit performs the CO2 capture process, the flue gas at 50°C from the boiler desulfurization tower is pressurized by the booster fan 4 and sent to the heat exchanger 6 (the heat source of the heat exchanger comes from the high-temperature CO2 calcined by another unit) to heat the flue gas temperature to about 120°C, and then sent to the reactor 2. A large number of heat exchange tubes are arranged in the reactor 2, and CaO is installed outside the tube. The flue gas directly reacts with the CaO outside the reactor tube to remove CO2 from the flue gas, and the CaO in the reactor becomes CaCO3. This reaction is an exothermic reaction, which can heat the medium to about 650-670°C. The high-temperature flue gas with CO2 removed is directly sent back to the tail flue of the boiler 1, and is discharged from the boiler after heat exchange with the tail heating surface to achieve heat recovery. When most of the CaO in the reactor becomes CaCO3, the decarbonization reaction stops, and the reactor is converted from the carbon capture process to the calcination decarbonization process.

[0056] After entering the decarbonization process, the temperature of CaCO3 in the reactor is about 650-670°C. If directly calcined, the reaction temperature is about 900°C due to the excessively high CO2 partial pressure. In order to lower the reaction temperature, the final CO2 partial pressure is controlled at about 25KPa by introducing low-pressure steam. The low pressure of about 400°C from the CO2 / steam separator 8 is directly introduced into the reactor and mixed with the CaCO3 particles, and the reaction state is still a fixed bed.

[0057] The calcination heat source comes from the boiler body 1. The flue gas at about 900°C is extracted from the boiler body and directly sent to the heat exchange tube in the reactor 2, raising the reactor temperature to above 800°C to calcine and decompose CaCO3. The flue gas releases heat to about 750°C, which is cooled to about 450°C by the flue gas cooler 14 and sent back to the boiler through the circulating fan 16 to achieve heat recovery. The cooling medium of the cooler uses the cold end reheat steam from the steam turbine. The reheat steam after absorbing heat is directly sent to the low-temperature reheater of the boiler to achieve heat recovery.

[0058] The decomposed CO2 and water vapor enter the cooler 12 together, and the temperature is reduced to about 400°C. The cooling medium uses the primary cold air from the boiler to achieve heat recovery. The cooled medium is pressurized by the booster fan 10 and then enters the CO2 / water vapor separation device 8. The device adopts the density separation principle. The water vapor with low density is discharged from the upper part and re-enters the reactor for circulation. The CO2 with high density is discharged from the lower part and enters the flue gas heater 7 of another reaction unit to heat the flue gas from the desulfurization tower.

[0059] When the CaCO3 in the reactor is basically decomposed, the calcination reaction ends and the carbon capture process re-enters.

[0060] Reaction unit 2 is composed of 1, 3, 5, 7, 9, 11, 13, 15, and 17, and its function is the same as that of reaction unit 1. The two operate alternately and will not be described in detail here.

[0061] The system proposed in this embodiment makes full use of the heat of chemical reactions and boiler waste heat to achieve efficient heat recovery and utilization. By taking heat from the flue gas side of the boiler body as the calcination heat of the reactor, CaCO3 is decomposed, and the heat absorbed by the reaction is released when CaO captures CO2. The flue gas with CO2 removed is heated to 650-670℃ and sent back to the boiler to achieve heat circulation. The remaining process heat loss is further recovered through reheated steam or primary and secondary air of the boiler. Compared with the existing method of separately supplying energy for the reaction and treating waste heat, the energy consumption is significantly reduced.

[0062] The system operation cost of this embodiment is reduced. At the same time, due to the reasonable design of the system, the service life of the equipment is extended, and the equipment maintenance and replacement costs are reduced. In addition, the calcium-based materials used in this embodiment are widely available and low in cost, which solves the problem of high cost caused by the use of special absorbents or membrane materials in the prior art, further reduces the overall operation cost, and improves the feasibility of commercial promotion.

[0063] The two reaction units described in this embodiment adopt an alternating operation mode, so that the CO2 capture and separation process can be carried out continuously, thereby improving the overall reaction efficiency of the system.

[0064] In terms of reactor design, this embodiment adopts a fixed bed structure so that the CaO particles are in full contact with the flue gas, which is conducive to the full reaction of CaO and CO2, and can more efficiently capture CO2 in the flue gas, thereby improving the removal effect of CO2. At the same time, the stainless steel heat exchange tubes arranged in the reactor provide a stable environment for the reaction. In addition, the cyclic reaction between CaO and CaCO3 is relatively stable. With the guarantee of measures such as the introduction of low-pressure circulating steam, the calcination reaction temperature is effectively controlled, the operating stability of the entire system is enhanced, and the operating failures caused by fluctuations in reaction conditions are reduced, ensuring the continuous and stable progress of CO2 capture.

[0065] Implementation method 2:

[0066] This embodiment proposes a calcium-based CO2 capture method coupled with a power plant boiler. The method is implemented based on a calcium-based CO2 capture system coupled with a power plant boiler described in Embodiment 1. The method includes the following steps:

[0067] CO2 capture steps: The flue gas from the boiler desulfurization tower is pressurized by the flue gas booster fan, sent to the flue gas heater for heating, and then sent to the reactor to react with CaO in the reactor to remove CO2 from the flue gas. The reaction exothermicity causes the medium temperature to rise to 650-670℃. The high-temperature flue gas with CO2 removed is directly sent back to the tail flue of the boiler and discharged from the boiler after heat exchange with the tail heating surface;

[0068] CO2 separation step: When no less than 2 / 3 of the CaO in the reactor is converted into CaCO3, low-pressure circulating steam is introduced, and the hot flue gas from the boiler is introduced into the heat exchange tube of the reactor to calcine and decompose the CaCO3. The decomposed CO2 enters the cooler together with the water vapor for cooling, and then enters the separation device after being pressurized by the booster fan. The separated water vapor returns to the reactor, and the CO2 enters the flue gas heater of another reaction unit. After the decomposition of the CaCO3 in the reactor is completed, the CO2 capture step is re-entered.

[0069] Those skilled in the art will appreciate that the above are only preferred embodiments of the present invention, and the various embodiments of the present disclosure and / or the features described in the claims may be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. It is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments, or perform equivalent substitutions on some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

[0070] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0071] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0072] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present disclosure rather than to limit its protection scope. Although the present disclosure has been described in detail with reference to the above implementation modes, ordinary technicians in the relevant field should understand that after reading the present disclosure, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation modes of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the disclosed claims to be approved.

Claims

1. A calcium-based CO2 capture system coupled to a power plant boiler, characterized in that: The system is composed of two reaction units, the two reaction units have the same structure, and each unit includes a reactor, a flue gas booster fan, a flue gas heater, a separation device, a booster fan, a cooler, a flue gas cooler, and a circulation fan; The reactor is used to carry out a decomposition reaction of CaCO3 or a chemical reaction of CaO and CO2; The flue gas booster fan is used to boost the flue gas pressure; The flue gas heater is used to heat the flue gas pressurized by the flue gas booster; The cooler is used to cool the high-temperature CO2 and circulating water vapor generated by the reactor; The booster fan is used to pressurize the cooled CO2 and the circulating water vapor; The separation device is used to separate the pressurized CO2 and the circulating water vapor; The flue gas cooler is used to cool the hot flue gas released by the reactor; The circulating fan is used to transport the cooled flue gas to the boiler.

2. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: When one reaction unit performs the CO2 capture process, the other unit performs the CO2 calcination removal process, and the two units operate alternately back and forth.

3. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: The flue gas pressurized by the flue gas booster fan is taken from the flue gas after the desulfurization tower.

4. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: The reactor is provided with a plurality of heat exchange tubes, and the CaO particles are placed outside the plurality of heat exchange tubes.

5. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 4, characterized in that: When the reaction unit is capturing CO2, there is no medium in the heat exchange tubes, and when the flue gas flows through the reactor, it only comes into contact and reacts with the CaO outside the tubes.

6. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 4, characterized in that: The reactor is of fixed bed type, and after the flue gas flows through the medium, the CaO particles remain stationary.

7. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: The heat source of the flue gas heater is taken from the high-temperature CO2 generated by calcination of another reaction unit.

8. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: After CO2 is removed from the flue gas of the reactor, the hot flue gas, which has a temperature of 650-670°C, is directly fed into the tail flue of the boiler (1), and is discharged from the boiler after heat exchange with the boiler heating surface to achieve heat recovery.

9. A calcium-based CO2 capture system coupled to a power plant boiler according to claim 1, characterized in that: The system uses hot flue gas from a boiler (1) as a calcination heat source for the reactor.

10. A calcium-based CO2 capture method coupled with a power plant boiler, characterized in that: The method is implemented by using a calcium-based CO2 capture system coupled to a power plant boiler according to any one of claims 1 to 7, and the method comprises: CO2 capture step: the flue gas from the boiler desulfurization tower is pressurized by the flue gas booster fan, sent to the flue gas heater for heating, and then sent to the reactor to react with CaO in the reactor to remove CO2 from the flue gas. The reaction releases heat to raise the medium temperature to 650-670°C. The high-temperature flue gas from which CO2 has been removed is directly sent back to the tail flue of the boiler (1), and is discharged from the boiler after heat exchange with the tail heating surface; CO2 separation step: When no less than 2 / 3 of the CaO in the reactor is converted into CaCO3, low-pressure circulating steam is introduced, and the hot flue gas from the boiler (1) is introduced into the heat exchange tube of the reactor to calcine and decompose the CaCO3. The decomposed CO2 and water vapor enter the cooler together for cooling, and then enter the separation device after being pressurized by the booster fan. The separated water vapor returns to the reactor, and the CO2 enters the flue gas heater of another reaction unit. After the decomposition of the CaCO3 in the reactor is completed, the CO2 capture step is re-entered.

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