Solid calcium-based carbon dioxide trapping system and method applied to coal-fired boiler

Abstract

The invention discloses a solid calcium-based carbon dioxide trapping system and method applied to a coal-fired boiler, and relates to the technical field of environmental protection. According to the system, a fixed bed is adopted as a reactor for absorbing CO2, CaO solid is adopted as a CO2 adsorbent, a large amount of water does not need to be consumed, and meanwhile the problem that a liquid chemical reagent serves as the CO2 adsorbent can be effectively solved. The system provides high-temperature flue gas for the fixed bed assembly through the combustion chamber assembly. CaCO3 particles are stored in the fixed bed assembly, CO2 and CaO are decomposed under the action of high-temperature flue gas, and then the CO2 is sent to the carbon dioxide storage assembly; the carbon dioxide storage assembly provides fuel for the combustion chamber assembly. The boiler assembly sends generated flue gas containing CO2 to the fixed bed assembly, the flue gas reacts with CaO in the fixed bed assembly, and after CO2 in the flue gas is removed, the flue gas is sent to the waste heat utilization device for waste heat utilization. The method is suitable for efficiently capturing carbon dioxide in flue gas discharged by a coal-fired power plant.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a solid calcium-based carbon dioxide capture system applied to a coal-fired boiler. Background Art

[0002] Carbon dioxide capture technology is divided into pre-combustion capture, post-combustion capture, oxygen-enriched combustion, etc. Pre-combustion capture and oxygen-enriched combustion have great restrictions on the application of coal-fired boilers and are difficult to apply to operating boilers. Post-combustion capture has little impact on coal-fired units. Among them, liquid chemical absorption is one of the most mature and widely used technologies. It uses the chemical reaction between chemical reagents and CO2 to separate CO2 from flue gas. This technology is basically mature and has been demonstrated on a small scale. This technology generally has the problem of high energy consumption. The chemical absorption method requires more energy during the absorption and regeneration process, especially the regeneration process of the absorbent, which may lead to high overall energy consumption. Due to energy consumption and chemical use, the operating cost of the chemical absorption method is relatively high, which limits its economic feasibility on a larger scale. The absorbent may have a certain impact on the environment, such as the emission of volatile organic compounds and corrosion to equipment. Long-term operation may cause equipment corrosion and blockage problems, increase maintenance costs and operational complexity. Summary of the invention

[0003] The purpose of the present invention is to provide a solid calcium-based carbon dioxide capture system for coal-fired boilers. The system uses a fixed bed as a reactor for absorbing CO2, and the CO2 adsorbent uses CaO solid, which does not require the consumption of a large amount of water and can effectively avoid the problem of using liquid chemical reagents as CO2 adsorbents.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a solid calcium-based carbon dioxide capture system for use in a coal-fired boiler, the system comprising a combustion chamber assembly, a fixed bed assembly, a waste heat utilization device, a carbon dioxide storage assembly and a boiler assembly;

[0006] The combustion chamber assembly is used to provide high-temperature flue gas to the fixed bed assembly;

[0007] The fixed bed component is used to store CaCO3 particles, and after decomposing CO2 and CaO under the action of high-temperature flue gas, the CO2 is sent to the carbon dioxide storage component;

[0008] The carbon dioxide storage assembly is used to provide fuel to the combustor assembly;

[0009] The boiler assembly is used to send the generated flue gas containing CO2 to the fixed bed assembly to react with CaO in the fixed bed assembly, remove CO2 from the flue gas, and then send it to the waste heat utilization device for waste heat utilization.

[0010] Furthermore, in a preferred embodiment, the combustion chamber assembly comprises a natural gas combustion chamber and a natural gas burner;

[0011] The natural gas combustion chamber is used to generate high-temperature flue gas under the action of the natural gas burner and send it to the fixed bed assembly.

[0012] Furthermore, in a preferred embodiment, the fixed bed assembly comprises a first fixed bed reactor, a first cyclone dust collector, a second fixed bed reactor and a second cyclone dust collector;

[0013] The first fixed bed reactor and the second fixed bed reactor are both used to store CaCO3 particles;

[0014] The first cyclone dust collector is used to remove dust from the CO2 discharged from the first fixed bed reactor, and send the removed CO2 and fixed dust to the carbon dioxide storage component and the boiler component respectively;

[0015] The second cyclone dust collector is used to remove dust from the CO2 discharged from the second fixed bed reactor, and send the removed CO2 and fixed dust to the carbon dioxide storage component and the boiler component respectively.

[0016] Furthermore, there is a preferred embodiment, the carbon dioxide storage assembly comprises a carbon dioxide cooler, a buffer tank, a carbon dioxide pressurizing device and a carbon dioxide storage tank;

[0017] The carbon dioxide cooler is used to cool the CO2 after dust removal by the first cyclone dust collector or the second cyclone dust collector and store it in a buffer tank;

[0018] The CO2 booster is used to send CO2 from the buffer tank to the CO2 storage tank;

[0019] The CO2 tanks are used to fuel the natural gas combustion chambers.

[0020] Furthermore, in a preferred embodiment, the boiler assembly comprises a coal boiler, a dust collector and a desulfurization tower;

[0021] Coal-fired boilers are used to generate flue gas and send it to the dust collector;

[0022] The dust collector is used to remove dust from the flue gas and send it to the desulfurization tower;

[0023] The desulfurization tower is used to desulfurize the flue gas after dust removal and the fixed dust discharged from the first cyclone dust collector or the second cyclone dust collector and then send them to the first fixed bed reactor or the second fixed bed reactor.

[0024] Furthermore, in a preferred embodiment, the system is further provided with a plurality of valves.

[0025] Furthermore, there is a preferred embodiment in which carbon dioxide capture is achieved by opening and closing multiple valves.

[0026] Furthermore, there is a preferred embodiment in which the opening and closing of multiple valves are achieved through a control system.

[0027] The present invention also provides a carbon dioxide capture method implemented by a solid calcium-based carbon dioxide capture system applied to a coal-fired boiler based on any one of the above, the method comprising:

[0028] Step 1: Add solid CaCO3 particles into the first fixed bed reactor and the second fixed bed reactor respectively, and close all valves;

[0029] Step 2: Open the valves at the inlet and outlet of the first fixed bed reactor, the outlet of the first cyclone dust collector, between the carbon dioxide cooler and the natural gas combustion, and between the carbon dioxide storage tank and the natural gas combustion chamber, start the natural gas burner, and the carbon dioxide gas in the carbon dioxide storage tank adjusts the flue gas temperature in the natural gas combustion chamber to maintain the flue gas temperature at 0-1000°C, and then the high-temperature flue gas enters the first fixed bed reactor, heats the CaCO3 particles in the first fixed bed reactor, and decomposes them into CO2 and CaO. The CO2 is dedusted by the first cyclone dust collector, and the separated solid dust is sent to the desulfurization tower for utilization. The dedusted carbon dioxide enters the carbon dioxide cooler, and part of the cooled carbon dioxide is used to adjust the flue gas temperature in the natural gas combustion chamber, and the rest is sent to the buffer tank, which is then pressurized by the carbon dioxide booster and stored in the carbon dioxide storage tank;

[0030] Step 3: retain the valve between the carbon dioxide cooler and the natural gas combustion, close the valve opened in step 2, open the inlet and outlet of the second fixed bed reactor, the outlet of the second cyclone dust collector, the valve between the first fixed bed reactor and the desulfurization tower, and the valve between the first fixed bed reactor and the waste heat utilization device, the high-temperature flue gas in the natural gas combustion chamber enters the second fixed bed reactor, heats the CaCO3 particles in the second fixed bed reactor, and decomposes them into CO2 and CaO, CO2 is dedusted by the second cyclone dust collector, and the separated solid dust is sent to the desulfurization tower for utilization, the dedusted carbon dioxide enters the carbon dioxide cooler, the cooled carbon dioxide is partly used to adjust the flue gas temperature in the natural gas combustion chamber, and the rest is sent to the buffer tank, and then is pressurized by the carbon dioxide booster and stored in the carbon dioxide storage tank, at the same time, the flue gas discharged from the coal-fired boiler after dedusting and desulfurization enters the first fixed bed reactor, CO2 in the flue gas reacts with CaO to generate CaCO3, the flue gas after CO2 is removed enters the waste heat utilization device, and the clean flue gas without CO2 is discharged into the atmosphere;

[0031] Step 4: After the system runs normally and continuously, the first fixed bed reactor and the second fixed bed reactor are operated alternately through valve switching, one for absorbing CO2 in the flue gas, and the other for decomposing CaCO3 to generate CO2 and CaO, thereby achieving absorbent regeneration and carbon dioxide capture.

[0032] Furthermore, there is a preferred embodiment that uses natural gas or other liquid fuel as fuel and adopts a pure oxygen combustion method.

[0033] The beneficial effects of the present invention are:

[0034] 1. The present invention provides a solid calcium-based carbon dioxide capture system for coal-fired boilers, which has an independent high-temperature flue gas generator, uses natural gas as fuel, and uses pure oxygen combustion to provide heat for the high-temperature flue gas to decompose CaCO3 into CaO and CO2.

[0035] 2. The present invention provides a solid calcium-based carbon dioxide capture system for coal-fired boilers, which uses a fixed bed reactor as a reactor for CO2 absorption and CaO regeneration, thereby ensuring that CO2 is in full contact with CaO powder and the reaction efficiency can be guaranteed.

[0036] 3. The present invention provides a solid calcium-based carbon dioxide capture system for coal-fired boilers, which uses high-temperature flue gas with only CO2 and water components, and does not introduce other gas components, ensuring that there are no other gases in CO2 decomposed by CaCO3, and the purity of CO2 can be guaranteed.

[0037] 4. The present invention provides a solid calcium-based carbon dioxide capture system for coal-fired boilers. It utilizes part of the captured carbon dioxide, cools it down and uses it to adjust the temperature of high-temperature flue gas produced by pure oxygen combustion of natural gas, maintains safe and reliable operation of the system, does not introduce other gas components, and ensures effective measures for CO2 purity.

[0038] The technical solution provided by the present invention can realize the efficient capture of carbon dioxide in the flue gas discharged by coal-fired power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is a schematic diagram of a solid calcium-based carbon dioxide capture system for a coal-fired boiler according to the present invention. 1 represents a coal-fired boiler; 2 represents a dust collector; 3 represents a desulfurization tower; 4 represents a first fixed bed reactor; 5 represents a first cyclone dust collector; 6 represents a waste heat utilization device; 7 represents a second fixed bed reactor; 8 represents a second cyclone dust collector; 9 represents a carbon dioxide cooler; 10 represents a buffer tank; 11 represents a carbon dioxide booster device; 12 represents a carbon dioxide storage tank; 13 represents a natural gas combustion chamber; 14 represents a natural gas burner; 15-30 represent valves. DETAILED DESCRIPTION

[0041] 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.

[0042] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0043] Embodiment 1. This embodiment provides a solid calcium-based carbon dioxide capture system for coal-fired boilers, in which solid CaO is used as a CO2 adsorbent and a fixed bed reactor is used as a reactor for carbon dioxide capture and absorbent regeneration. The system includes a combustion chamber assembly, a fixed bed assembly, a waste heat utilization device 6, a carbon dioxide storage assembly and a boiler assembly;

[0044] The combustion chamber assembly is used to provide high-temperature flue gas to the fixed bed assembly;

[0045] The fixed bed component is used to store CaCO3 particles, and after decomposing CO2 and CaO under the action of high-temperature flue gas, the CO2 is sent to the carbon dioxide storage component;

[0046] The carbon dioxide storage assembly is used to provide fuel to the combustor assembly;

[0047] The boiler assembly is used to send the generated flue gas containing CO2 to the fixed bed assembly to react with CaO in the fixed bed assembly, remove CO2 from the flue gas, and then send it to the waste heat utilization device 6 for waste heat utilization.

[0048] Implementation Method 2: See Figure 1 This embodiment is described. This embodiment specifically describes a solid calcium-based carbon dioxide capture system applied to a coal-fired boiler described in Embodiment 1.

[0049] The combustion chamber assembly comprises a natural gas combustion chamber 13 and a natural gas burner 14;

[0050] The fixed bed assembly comprises a first fixed bed reactor 4, a first cyclone dust collector 5, a second fixed bed reactor 7 and a second cyclone dust collector 8;

[0051] The carbon dioxide storage assembly includes a carbon dioxide cooler 9, a buffer tank 10, a carbon dioxide booster 11 and a carbon dioxide storage tank 12;

[0052] The boiler assembly comprises a coal boiler 1, a dust collector 2 and a desulfurization tower 3;

[0053] like Figure 1 As shown, the specific structure of the carbon dioxide capture system is as follows:

[0054] The natural gas burner 14 is connected to the natural gas combustion chamber 13 and is used to provide combustion energy for the natural gas combustion chamber 13;

[0055] The carbon dioxide storage tank 12 is connected to the natural gas combustion chamber 13 to provide fuel for the natural gas combustion chamber 13;

[0056] The natural gas combustion chamber 13 is connected to the first fixed bed reactor 4 and the second fixed bed reactor 7 respectively, and is used to provide high-temperature flue gas;

[0057] The first cyclone dust collector 5 is connected to the first fixed bed reactor 4 and is used for dust removal of CO2 discharged from the first fixed bed reactor 4;

[0058] The second fixed bed reactor 7 is connected to the second cyclone dust collector 8, which is used to remove dust from the CO2 discharged from the second fixed bed reactor 7;

[0059] The first cyclone dust collector 5 and the second cyclone dust collector 8 are both connected to the carbon dioxide cooler 9, which is in turn connected to the buffer tank 10, the carbon dioxide booster 11, and the carbon dioxide storage tank 12. The dust-removed CO2 and the cooled carbon dioxide are partially used to adjust the flue gas temperature in the natural gas combustion chamber 13, and the rest is sent to the buffer tank 10, and then pressurized by the carbon dioxide booster 11 and stored in the carbon dioxide storage tank 12;

[0060] The coal boiler 1 is connected to the dust collector 2 and the desulfurization tower 3 in sequence, and the first cyclone dust collector 5 and the second cyclone dust collector 8 are both connected to the desulfurization tower 3; the first fixed bed reactor 4 and the second fixed bed reactor 7 are both connected to the waste heat utilization device 6; the solid dust separated by the cyclone dust collector is sent to the desulfurization tower for utilization, and at the same time, the flue gas discharged by the coal-fired boiler after dust removal and desulfurization enters the fixed bed reactor, and the CO2 in the flue gas reacts with CaO to generate CaCO3. The flue gas after removing CO2 enters the waste heat utilization device, and the clean flue gas without CO2 is discharged into the atmosphere.

[0061] Furthermore, the cooled carbon dioxide is partially used to adjust the flue gas temperature in the natural gas combustion chamber 13, so that it can be used to adjust the high-temperature flue gas temperature produced by the natural gas pure oxygen combustion after cooling, maintaining the safe and reliable operation of the system without introducing other gas components, ensuring the effective measure of CO2 purity.

[0062] The solid calcium-based carbon dioxide capture system applied to coal-fired boilers proposed in this embodiment has an independent high-temperature flue gas generator, natural gas as fuel, and pure oxygen combustion, and the high-temperature flue gas is used to provide heat for decomposing CaCO3 into CaO and CO2. Further, a fixed bed reactor is used as a reactor for CO2 absorption and CaO regeneration, which can ensure that CO2 is fully in contact with CaO powder, and the reaction efficiency can be guaranteed. At the same time, the high-temperature flue gas components are only CO2 and water, and no other gas components are introduced, which ensures that there are no other gases in the CO2 decomposed by CaCO3, and the purity of CO2 can be guaranteed.

[0063] Implementation method three, see Figure 1 The present embodiment is described as follows. On the basis of the above-mentioned embodiment, a plurality of valves are added to achieve carbon dioxide capture by controlling the opening of the valves.

[0064] like Figure 1 As shown, a valve 15 is provided between the natural gas combustion chamber 13 and the first fixed bed reactor 4; a valve 16 is provided between the first fixed bed reactor 4 and the first cyclone dust collector 5; a valve 17 is provided between the first cyclone dust collector 5 and the carbon dioxide cooler 9; a valve 18 is provided between the first cyclone dust collector 5 and the desulfurization tower 3; a valve 19 is provided between the desulfurization tower 3 and the second fixed bed reactor 7; a valve 20 is provided between the second fixed bed reactor 7 and the waste heat utilization device 6; a valve 21 is provided between the natural gas combustion chamber 13 and the second fixed bed reactor 7; a valve 22 is provided between the second fixed bed reactor 7 and the second cyclone dust collector 8 door 22; a valve 23 is set between the second cyclone dust collector 8 and the carbon dioxide cooler 9; a valve 24 is set between the second cyclone dust collector 8 and the desulfurization tower 3; a valve 25 is set between the carbon dioxide cooler 9 and the buffer tank 10; a valve 26 is set between the carbon dioxide cooler 9 and the natural gas combustion chamber 13; a valve 27 is set between the carbon dioxide storage tank 12 and the natural gas combustion chamber 13; a valve 28 is set between the carbon dioxide boosting device 11 and the carbon dioxide storage tank 12; a valve 29 is set between the desulfurization tower 3 and the first fixed bed reactor 4; a valve 30 is set between the first fixed bed reactor 4 and the waste heat utilization device 6.

[0065] Embodiment 4: This embodiment provides a carbon dioxide capture method implemented by a solid calcium-based carbon dioxide capture system applied to a coal-fired boiler based on any one of the above embodiments, and the method specifically comprises the following steps:

[0066] In order to prevent other gases from being introduced into the flue gas of depyrolyzing CaCO3, this embodiment uses natural gas or other liquid fuels as fuel and adopts a pure oxygen combustion method.

[0067] Step 1: Add sufficient solid CaCO3 particles to the first fixed bed reactor 4 and the second fixed bed reactor 7, respectively, and keep all valves in the system closed. Open valves 15, 16, 17, 26 and 27, start the natural gas burner 14, use the carbon dioxide gas in the carbon dioxide storage tank 12 to adjust the flue gas temperature in the natural gas combustion chamber 13, so that the flue gas temperature is maintained at 0-1000°C, and then the high-temperature flue gas enters the first fixed bed reactor 4, heats the CaCO3 particles in the first fixed bed reactor 4, and decomposes them into CO2 and CaO. CO2 is first dedusted by the first cyclone dust collector 5, and the separated solid dust is sent to the desulfurization system for use. The dedusted carbon dioxide enters the carbon dioxide cooler 9, and the cooled carbon dioxide is partly used to adjust the flue gas temperature in the natural gas combustion chamber 13, and the rest is sent to the buffer tank 10, and then pressurized by the carbon dioxide booster 11 and stored in the carbon dioxide storage tank 12.

[0068] Step 2: Close valves 15, 16, 17 and 27, and open valves 21, 22, 23, 29 and 30. At this time, the high-temperature flue gas in the natural gas combustion chamber 13 no longer passes through the first fixed bed reactor 4, but enters the second fixed bed reactor 7, heats the CaCO3 particles in the second fixed bed reactor 7, and decomposes them into CO2 and CaO. Similarly, CO2 is first dedusted by the second cyclone dust collector 8, and the separated solid dust is sent to the desulfurization system for utilization. The dedusted carbon dioxide enters the carbon dioxide cooler 9, and the cooled carbon dioxide is partly used to adjust the flue gas temperature in the natural gas combustion chamber 13, and the rest is sent to the buffer tank 10, and then pressurized by the carbon dioxide booster 11 and stored in the carbon dioxide storage tank 12. At the same time, the flue gas discharged from the coal-fired boiler after dedusting and desulfurization enters the first fixed bed reactor 4, and the CO2 in the flue gas reacts with CaO to generate CaCO3, and the flue gas after removing CO2 enters the waste heat utilization device 6. Finally, the clean flue gas without CO2 is discharged into the atmosphere.

[0069] Step 3: When the system is running normally and continuously, the first fixed bed reactor 4 and the second fixed bed reactor 7 are operated alternately through valve switching, one for absorbing CO2 in the flue gas, and the other for decomposing CaCO3 to generate CO2 and CaO, thereby achieving absorbent regeneration and carbon dioxide capture.

[0070] 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.

[0071] 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.

[0072] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0073] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0074] The above description is only the implementation mode of the present invention and is not limited to the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A solid calcium-based carbon dioxide capture system for coal-fired boilers, characterized in that: It includes a combustion chamber assembly, a fixed bed assembly, a waste heat utilization device (6), a carbon dioxide storage assembly and a boiler assembly; The combustion chamber assembly is used to provide high-temperature flue gas to the fixed bed assembly; The fixed bed component is used to store CaCO3 particles, and after decomposing CO2 and CaO under the action of high-temperature flue gas, the CO2 is sent to the carbon dioxide storage component; The carbon dioxide storage assembly is used to provide fuel to the combustor assembly; The boiler component is used to send the generated flue gas containing CO2 to the fixed bed component to react with CaO in the fixed bed component, remove CO2 from the flue gas, and then send it to the waste heat utilization device (6) for waste heat utilization.

2. A solid calcium-based carbon dioxide capture system for a coal-fired boiler according to claim 1, characterized in that: The combustion chamber assembly comprises a natural gas combustion chamber (13) and a natural gas burner (14); The natural gas combustion chamber (13) is used to generate high-temperature flue gas under the action of the natural gas burner (14) and send it to the fixed bed assembly.

3. A solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 2, characterized in that: The fixed bed assembly comprises a first fixed bed reactor (4), a first cyclone dust collector (5), a second fixed bed reactor (7) and a second cyclone dust collector (8); The first fixed bed reactor (4) and the second fixed bed reactor (7) are both used to store CaCO3 particles; The first cyclone dust collector (5) is used to remove dust from the CO2 discharged from the first fixed bed reactor (4), and send the removed CO2 and fixed dust to the carbon dioxide storage component and the boiler component respectively; The second cyclone dust collector (8) is used to remove dust from the CO2 emitted from the second fixed bed reactor (7), and to send the removed CO2 and fixed dust to the carbon dioxide storage component and the boiler component respectively.

4. A solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 3, characterized in that: The carbon dioxide storage assembly includes a carbon dioxide cooler (9), a buffer tank (10), a carbon dioxide pressurizing device (11) and a carbon dioxide storage tank (12); The carbon dioxide cooler (9) is used to cool the CO2 after dust removal by the first cyclone dust collector (5) or the second cyclone dust collector (8) and store it in a buffer tank (10); The carbon dioxide boosting device (11) is used to send CO2 in the buffer tank (10) to the carbon dioxide storage tank (12); The carbon dioxide storage tank (12) is used to provide fuel for the natural gas combustion chamber (13).

5. A solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 4, characterized in that: The boiler assembly comprises a coal boiler (1), a dust collector (2) and a desulfurization tower (3); A coal-fired boiler (1) is used to generate flue gas and send it to a dust collector (2); The dust collector (2) is used to remove dust from the flue gas and then send it to the desulfurization tower (3); The desulfurization tower (3) is used to desulfurize the flue gas after dust removal and the fixed dust discharged from the first cyclone dust collector (5) or the second cyclone dust collector (8) and then send them to the first fixed bed reactor (4) or the second fixed bed reactor (7).

6. A solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 5, characterized in that: The system also has multiple valves.

7. A solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 6, characterized in that: Carbon dioxide is captured by opening and closing multiple valves.

8. The solid calcium-based carbon dioxide capture system for coal-fired boilers according to claim 6, characterized in that: The opening and closing of multiple valves are achieved through the control system.

9. A method for capturing carbon dioxide using a solid calcium-based carbon dioxide capture system for a coal-fired boiler according to any one of claims 1 to 8, characterized in that: The method is: Step 1: Add solid CaCO3 particles into the first fixed bed reactor and the second fixed bed reactor respectively, and close all valves; Step 2: Open the valves at the inlet and outlet of the first fixed bed reactor, the outlet of the first cyclone dust collector, between the carbon dioxide cooler and the natural gas combustion, and between the carbon dioxide storage tank and the natural gas combustion chamber, start the natural gas burner, and the carbon dioxide gas in the carbon dioxide storage tank adjusts the flue gas temperature in the natural gas combustion chamber to maintain the flue gas temperature at 0-1000°C, and then the high-temperature flue gas enters the first fixed bed reactor, heats the CaCO3 particles in the first fixed bed reactor, and decomposes them into CO2 and CaO. The CO2 is dedusted by the first cyclone dust collector, and the separated solid dust is sent to the desulfurization tower for utilization. The dedusted carbon dioxide enters the carbon dioxide cooler, and part of the cooled carbon dioxide is used to adjust the flue gas temperature in the natural gas combustion chamber, and the rest is sent to the buffer tank, and then pressurized by the carbon dioxide booster equipment and stored in the carbon dioxide storage tank; Step 3: retain the valve between the carbon dioxide cooler and the natural gas combustion, close the valve opened in step 2, open the inlet and outlet of the second fixed bed reactor, the outlet of the second cyclone dust collector, the valve between the first fixed bed reactor and the desulfurization tower, and the valve between the first fixed bed reactor and the waste heat utilization device, the high-temperature flue gas in the natural gas combustion chamber enters the second fixed bed reactor, heats the CaCO3 particles in the second fixed bed reactor, and decomposes them into CO2 and CaO, CO2 is dedusted by the second cyclone dust collector, and the separated solid dust is sent to the desulfurization tower for utilization, the dedusted carbon dioxide enters the carbon dioxide cooler, the cooled carbon dioxide is partly used to adjust the flue gas temperature in the natural gas combustion chamber, and the rest is sent to the buffer tank, and then is pressurized by the carbon dioxide booster and stored in the carbon dioxide storage tank, at the same time, the flue gas discharged from the coal-fired boiler after dedusting and desulfurization enters the first fixed bed reactor, CO2 in the flue gas reacts with CaO to generate CaCO3, the flue gas after CO2 is removed enters the waste heat utilization device, and the clean flue gas without CO2 is discharged into the atmosphere; Step 4: After the system runs normally and continuously, the first fixed bed reactor and the second fixed bed reactor are operated alternately through valve switching, one for absorbing CO2 in the flue gas, and the other for decomposing CaCO3 to generate CO2 and CaO, thereby achieving absorbent regeneration and carbon dioxide capture.

10. The solid calcium-based carbon dioxide capture method for coal-fired boilers according to claim 1, characterized in that: It uses natural gas or other liquid fuel as fuel and adopts pure oxygen combustion method.

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