Compressed carbon dioxide energy storage system, low-carbon emission coal-fired unit and working method thereof

Abstract

The invention discloses a compressed carbon dioxide energy storage system, a low-carbon-emission coal-fired unit and a working method of the low-carbon-emission coal-fired unit. The compressed carbon dioxide energy storage system comprises a low-pressure CO2 storage chamber, a high-pressure CO2 storage chamber, a second carbon dioxide cooling compression system and a heating expansion system. An outlet of the low-pressure CO2 storage chamber is communicated with an inlet of the second carbon dioxide cooling compression system through the heating expansion system, an outlet of the second carbon dioxide cooling compression system is communicated with an inlet of the low-pressure CO2 storage chamber and an inlet of the high-pressure CO2 storage chamber, and an outlet of the high-pressure CO2 storage chamber is communicated with an inlet of the heating expansion system. According to the unit and the working method thereof, mutual adjustment among the unit, the carbon capture system and the compressed carbon dioxide energy storage system can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and relates to a compressed carbon dioxide energy storage system, a low-carbon emission coal-fired unit and a working method thereof. Background Art

[0003] In the power industry, due to the rise and commercial application of carbon capture technology, the carbon dioxide extracted from flue gas can be reasonably utilized. The compressed carbon dioxide energy storage system is proposed based on the traditional compressed air energy storage technology, but there is little research on the mutual regulation between the unit, carbon capture system and compressed carbon dioxide energy storage system, as well as the design and system operation of the compressed carbon dioxide energy storage system. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a compressed carbon dioxide energy storage system, a low-carbon emission coal-fired unit and a working method thereof, which can achieve mutual regulation between the unit, the carbon capture system and the compressed carbon dioxide energy storage system.

[0005] To achieve the above object, the present invention discloses a compressed carbon dioxide energy storage system, including a low-pressure CO2 storage chamber, a high-pressure CO2 storage chamber, a second carbon dioxide cooling and compression system, and a heating and expansion system;

[0006] The outlet of the low-pressure CO2 storage chamber is connected to the inlet of the second carbon dioxide cooling and compression system via the heating expansion system, the outlet of the second carbon dioxide cooling and compression system is connected to the inlet of the low-pressure CO2 storage chamber and the inlet of the high-pressure CO2 storage chamber, and the outlet of the high-pressure CO2 storage chamber is connected to the inlet of the heating expansion system.

[0007] Furthermore, the heating and expansion system includes CO2 heater No. 1, CO2 expander No. 1, CO2 heater No. 2, CO2 expander No. 2, CO2 heater No. 3 and CO2 expander No. 3 which are connected in sequence, wherein the inlet of CO2 heater No. 1 is connected to the outlet of the low-pressure CO2 storage chamber, and the outlet of CO2 expander No. 3 is connected to the inlet of the second carbon dioxide cooling and compression system.

[0008] Furthermore, the second carbon dioxide cooling and compression system includes CO2 cooler No. 4, CO2 compressor No. 4, CO2 cooler No. 5, CO2 compressor No. 5, CO2 cooler No. 6, CO2 compressor No. 6 and CO2 cooler No. 7 which are connected in sequence, wherein the inlet of CO2 cooler No. 4 is connected to the outlet of the heating expansion system, and the outlet of CO2 cooler No. 7 is connected to the inlet of the low-pressure CO2 storage chamber and the inlet of the high-pressure CO2 storage chamber.

[0009] Furthermore, a first valve is provided between the outlet of the low-pressure CO2 storage chamber and the inlet of the heating and expansion system.

[0010] Furthermore, a second valve is provided between the outlet of the high-pressure CO2 storage chamber and the inlet of the heating and expansion system.

[0011] Furthermore, a third valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the low-pressure CO2 storage chamber.

[0012] Furthermore, a fourth valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the high-pressure CO2 storage chamber.

[0013] The present invention discloses a low-carbon emission coal-fired unit, comprising a coal-fired unit, a carbon capture system, a first carbon dioxide cooling and compression system, and a compressed carbon dioxide energy storage system;

[0014] The steam outlet of the boiler is connected to the inlet of the steam turbine, the exhaust port of the steam turbine is connected to the inlet of the boiler via the condenser and the regenerative heater in sequence, the steam extraction port of the steam turbine is connected to the steam inlet of the desorption tower, the flue gas outlet of the boiler is connected to the flue gas inlet of the absorption tower via the induced draft fan and the flue gas cooler in sequence, the outlet of the bottom slurry pool of the absorption tower is connected to the inlet of the desorption tower via the rich liquid pump and the rich liquid heater in sequence, and the lean liquid outlet of the desorption tower is connected to the inlet of the spray device in the absorption tower via the lean liquid cooler;

[0015] The carbon dioxide outlet at the top of the desorption tower is connected to the inlet of the low-pressure CO2 storage chamber in the compressed carbon dioxide energy storage system through the first carbon dioxide cooling and compression system.

[0016] Furthermore, the first carbon dioxide cooling and compression system includes CO2 compressor No. 1, CO2 cooler No. 1, CO2 compressor No. 2, CO2 cooler No. 2, CO2 compressor No. 3 and CO2 cooler No. 3 which are connected in sequence, wherein the inlet of CO2 compressor No. 1 is connected to the carbon dioxide outlet of the desorption tower, and the outlet of CO2 cooler No. 3 is connected to the inlet of the low-pressure CO2 storage chamber.

[0017] The present invention discloses a working method of a low-carbon emission coal-fired unit, comprising the following steps:

[0018] When the increase in the load of the power grid is less than the preset increase, the first valve and the third valve are opened, the second valve and the fourth valve are closed, and the low-pressure carbon dioxide in the low-pressure CO2 storage chamber is sent to the heating expansion system to do work; when the increase in the load of the power grid is greater than or equal to the preset increase, the second valve and the third valve are opened, the first valve and the fourth valve are closed, and then the high-pressure carbon dioxide in the high-pressure CO2 storage chamber is sent to the heating expansion system to do work. The preset increase can be 10%. During this process, the second carbon dioxide cooling and compression system is in a closed state;

[0019] When the reduction in the grid load is less than or equal to a preset reduction threshold, the surplus electric energy is used to provide energy, and then some compressors and coolers in the second carbon dioxide cooling and compression system are turned on, and the first valve and the third valve are opened at the same time, and the second valve and the fourth valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber is circulated and compressed by the compressors and coolers opened in the second carbon dioxide cooling and compression system to increase the gas pressure of the carbon dioxide in the low-pressure CO2 storage chamber; when the reduction in the grid load is greater than the preset reduction threshold, the surplus electric energy is used to provide energy, and then all compressors and coolers in the second carbon dioxide cooling and compression system are turned on, and the first valve and the fourth valve are opened at the same time, and the second valve and the third valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber is pressurized by the second carbon dioxide cooling and compression system and then stored in the high-pressure CO2 storage chamber. During this process, the heating expansion system is in a closed state.

[0020] The present invention has the following beneficial effects:

[0021] During specific operation of the compressed carbon dioxide energy storage system, the low-carbon emission coal-fired unit and the working method thereof described in the present invention, the outlet of the low-pressure CO2 storage chamber is connected to the inlet of the second carbon dioxide cooling and compression system via the heating and expansion system, the outlet of the second carbon dioxide cooling and compression system is connected to the inlet of the low-pressure CO2 storage chamber and the inlet of the high-pressure CO2 storage chamber, the outlet of the high-pressure CO2 storage chamber is connected to the inlet of the heating and expansion system, wherein the storage chamber adopts four flow paths, and when in use, the compressed carbon dioxide energy storage system cooperates with the load changes of the low-carbon emission coal-fired unit, and at the same time, the carbon dioxide in the flue gas discharged by the low-carbon emission coal-fired unit is obtained through the carbon capture system, and then sent to the compressed carbon dioxide energy storage system, so as to realize mutual regulation between the unit, the carbon capture system and the compressed carbon dioxide energy storage system, and the practicability is extremely strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 It is a structural diagram of the present invention.

[0024] Among them, 1 is a coal-fired unit, 2 is a carbon capture system, 3 is a compressed carbon dioxide energy storage system, 1-1 is a boiler, 1-2 is a steam turbine, 1-3 is a condenser, 1-4 is a heat recovery heater, 1-5 is a motor, 2-1 is an induced draft fan, 2-2 is a flue gas cooler, 2-3 is an absorption tower, 2-4 is a desorption tower, 2-5 is a rich liquid pump, 2-6 is a rich liquid heater, 2-7 is a lean liquid cooler; 3-1 is CO2 compressor No. 1, 3-2 is CO2 cooler No. 1, 3-3 is CO2 compressor No. 2, 3-4 is CO2 cooler No. 2, 3-5 is CO2 compressor No. 3, 3-6 is CO2 cooler No. 3 device, 3-7 is CO2 heater No. 1, 3-8 is CO2 expander No. 1, 3-9 is CO2 heater No. 2, 3-10 is CO2 expander No. 2, 3-11 is CO2 heater No. 3, 3-12 is CO2 expander No. 3, 3-13 is CO2 cooler No. 4, 3-14 is CO2 compressor No. 4, 3-15 is CO2 cooler No. 5, 3-16 is CO2 compressor No. 5, 3-17 is CO2 cooler No. 6, 3-18 is CO2 compressor No. 6, 3-19 is CO2 cooler No. 7, 3-20 is high-pressure CO2 storage room, and 3-21 is low-pressure CO2 storage room. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0027] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0028] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0029] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0030] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0033] Embodiment 1

[0034] refer to Figure 1 The compressed carbon dioxide energy storage system described in the present invention includes a low-pressure CO2 storage chamber 3-21, a high-pressure CO2 storage chamber 3-20, a second carbon dioxide cooling and compression system and a heating expansion system; the outlet of the low-pressure CO2 storage chamber 3-21 is connected to the inlet of the second carbon dioxide cooling and compression system via the heating expansion system, the outlet of the second carbon dioxide cooling and compression system is connected to the inlet of the low-pressure CO2 storage chamber 3-21 and the inlet of the high-pressure CO2 storage chamber 3-20, and the outlet of the high-pressure CO2 storage chamber 3-20 is connected to the inlet of the heating expansion system.

[0035] A first valve is provided between the outlet of the low-pressure CO2 storage chamber 3-21 and the inlet of the heating expansion system; a second valve is provided between the outlet of the high-pressure CO2 storage chamber 3-20 and the inlet of the heating expansion system; a third valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the low-pressure CO2 storage chamber 3-21; a fourth valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the high-pressure CO2 storage chamber 3-20.

[0036] Embodiment 2

[0037] refer to Figure 1 The low-carbon emission coal-fired unit of the present invention comprises a coal-fired unit 1, a carbon capture system 2 and a compressed carbon dioxide energy storage system 3; the coal-fired unit 1 comprises a boiler 1-1, a turbine 1-2, a condenser 1-2, a regenerative heater 1-4 and a motor 1-5; the carbon capture system 2 comprises an induced draft fan 2-1, a flue gas cooler 2-2, an absorption tower 2-3, a desorption tower 2-4, a rich liquid pump 2-5, a rich liquid heater 2-6 and a lean liquid cooler 2-7; the compressed carbon dioxide energy storage system 3 comprises a low-pressure CO2 storage chamber 3-21, a high-pressure CO2 storage chamber 3-20, a first carbon dioxide cooling and compression system, a second carbon dioxide cooling and compression system and a heating expansion system;

[0038] The steam outlet of the boiler 1-1 is connected to the inlet of the steam turbine 1-2, the exhaust port of the steam turbine 1-2 is connected to the inlet of the boiler 1-1 via the condenser 1-2 and the regenerative heater 1-4, the steam extraction port of the steam turbine 1-2 is connected to the steam inlet of the desorption tower 2-4, the flue gas outlet of the boiler 1-1 is connected to the flue gas inlet of the absorption tower 2-3 via the induced draft fan 2-1 and the flue gas cooler 2-2, the bottom slurry pool outlet of the absorption tower 2-3 is connected to the inlet of the desorption tower 2-4 via the rich liquid pump 2-5 and the rich liquid heater 2-6, and the lean liquid outlet of the desorption tower 2-4 is connected to the inlet of the spray device in the absorption tower 2-3 via the lean liquid cooler 2-7;

[0039] The carbon dioxide outlet at the top of the desorption tower 2-4 is connected to the inlet of the low-pressure CO2 storage chamber 3-21 via the first carbon dioxide cooling and compression system, the outlet of the low-pressure CO2 storage chamber 3-21 is connected to the inlet of the second carbon dioxide cooling and compression system via the heating expansion system, the outlet of the second carbon dioxide cooling and compression system is connected to the inlet of the low-pressure CO2 storage chamber 3-21 and the inlet of the high-pressure CO2 storage chamber 3-20, and the outlet of the high-pressure CO2 storage chamber 3-20 is connected to the outlet of the low-pressure CO2 storage chamber 3-21.

[0040] The first carbon dioxide cooling and compression system includes CO2 compressor No. 1 3-1, CO2 cooler No. 1 3-2, CO2 compressor No. 2 3-3, CO2 cooler No. 2 3-4, CO2 compressor No. 3 3-5 and CO2 cooler No. 3 3-6 which are connected in sequence, wherein the inlet of CO2 compressor No. 1 3-1 is connected to the carbon dioxide outlet of the desorption tower 2-4, and the outlet of CO2 cooler No. 3 3-6 is connected to the inlet of the low-pressure CO2 storage chamber 3-21.

[0041] The heating and expansion system includes CO2 heater No. 1 3-7, CO2 expander No. 1 3-8, CO2 heater No. 2 3-9, CO2 expander No. 2 3-10, CO2 heater No. 3 3-11 and CO2 expander No. 3 3-12 which are connected in sequence, wherein the inlet of CO2 heater No. 1 3-7 is connected to the outlet of the low-pressure CO2 storage chamber 3-21, and the outlet of CO2 expander No. 3 3-12 is connected to the inlet of the second carbon dioxide cooling and compression system.

[0042] The second carbon dioxide cooling and compression system includes CO2 cooler No. 4 3-13, CO2 compressor No. 4 3-14, CO2 cooler No. 5 3-15, CO2 compressor No. 5 3-16, CO2 cooler No. 6 3-17, CO2 compressor No. 6 3-18 and CO2 cooler No. 7 3-19 which are connected in sequence, wherein the inlet of CO2 cooler No. 4 3-13 is connected with the outlet of the heating expansion system, and the outlet of CO2 cooler No. 7 3-19 is connected with the inlet of the low-pressure CO2 storage chamber 3-21 and the inlet of the high-pressure CO2 storage chamber 3-20.

[0043] A first valve is provided between the outlet of the low-pressure CO2 storage chamber 3-21 and the inlet of the No. 1 CO2 heater 3-7, a second valve is provided between the outlet of the high-pressure CO2 storage chamber 3-20 and the inlet of the No. 1 CO2 heater 3-7, a third valve is provided between the outlet of the No. 7 CO2 cooler 3-19 and the inlet of the low-pressure CO2 storage chamber 3-21, and a fourth valve is provided between the outlet of the No. 7 CO2 cooler 3-19 and the inlet of the high-pressure CO2 storage chamber 3-20.

[0044] The working principle of the present invention is:

[0045] When the grid load increases, when the increase in the grid load is less than the preset increase, the first valve and the third valve are opened, the second valve and the fourth valve are closed, and the low-pressure carbon dioxide in the low-pressure CO2 storage chamber 3-21 is sent to the heating expansion system to do work. When the increase in the grid load is greater than or equal to the preset increase, the second valve and the third valve are opened, the first valve and the fourth valve are closed, and then the high-pressure carbon dioxide in the high-pressure CO2 storage chamber 3-20 is sent to the heating expansion system to do work. The preset increase can be 10%. During this process, the second carbon dioxide cooling and compression system is in a closed state.

[0046] When the grid load decreases and the reduction in grid load is less than or equal to the preset reduction threshold, the surplus electric energy is used to provide energy, and some compressors and coolers in the second carbon dioxide cooling and compression system are turned on, and the first valve and the third valve are opened at the same time, and the second valve and the fourth valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber 3-21 is circulated and compressed by the compressors and coolers opened in the second carbon dioxide cooling and compression system to increase the gas pressure of the carbon dioxide in the low-pressure CO2 storage chamber 3-21; when the reduction in grid load is greater than the preset reduction threshold, the surplus electric energy is used to provide energy, and all compressors and coolers in the second carbon dioxide cooling and compression system are turned on, and the first valve and the fourth valve are opened at the same time, and the second valve and the third valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber 3-21 is pressurized by the second carbon dioxide cooling and compression system and stored in the high-pressure CO2 storage chamber 3-20. During this process, the heating expansion system is in a closed state.

[0047] It should be noted that the present invention has the following characteristics:

[0048] 1) The carbon dioxide energy storage system of the present invention adopts a closed circulation system, so that the carbon dioxide energy storage system only exchanges energy with the outside world during its working process, but does not exchange substances.

[0049] 2) Make full use of the waste heat of the carbon capture system 2 and the compressed air energy storage system to achieve multi-level energy utilization.

[0050] 3) In the present invention, a high-pressure CO2 storage chamber 3-20 and a low-pressure CO2 storage chamber 3-21 are provided, and four flow paths are adopted to quickly respond to load changes.

[0051] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0052] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0053] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A compressed carbon dioxide energy storage system, characterized in that: It includes a low-pressure CO2 storage chamber (3-21), a high-pressure CO2 storage chamber (3-20), a second carbon dioxide cooling and compression system, and a heating and expansion system; The outlet of the low-pressure CO2 storage chamber (3-21) is connected to the inlet of the second carbon dioxide cooling and compression system via the heating expansion system, the outlet of the second carbon dioxide cooling and compression system is connected to the inlet of the low-pressure CO2 storage chamber (3-21) and the inlet of the high-pressure CO2 storage chamber (3-20), and the outlet of the high-pressure CO2 storage chamber (3-20) is connected to the inlet of the heating expansion system.

2. The compressed carbon dioxide energy storage system according to claim 1, characterized in that: The heating and expansion system comprises a CO2 heater No. 1 (3-7), a CO2 expander No. 1 (3-8), a CO2 heater No. 2 (3-9), a CO2 expander No. 2 (3-10), a CO2 heater No. 3 (3-11) and a CO2 expander No. 3 (3-12) which are connected in sequence, wherein the inlet of the CO2 heater No. 1 (3-7) is connected to the outlet of the low-pressure CO2 storage chamber (3-21), and the outlet of the CO2 expander No. 3 (3-12) is connected to the inlet of the second carbon dioxide cooling and compression system.

3. The compressed carbon dioxide energy storage system according to claim 1, characterized in that: The second carbon dioxide cooling and compression system includes CO2 cooler No. 4 (3-13), CO2 compressor No. 4 (3-14), CO2 cooler No. 5 (3-15), CO2 compressor No. 5 (3-16), CO2 cooler No. 6 (3-17), CO2 compressor No. 6 (3-18) and CO2 cooler No. 7 (3-19) which are connected in sequence, wherein the inlet of CO2 cooler No. 4 (3-13) is connected to the outlet of the heating expansion system, and the outlet of CO2 cooler No. 7 (3-19) is connected to the inlet of the low-pressure CO2 storage chamber (3-21) and the inlet of the high-pressure CO2 storage chamber (3-20).

4. The compressed carbon dioxide energy storage system according to claim 1, characterized in that: A first valve is provided between the outlet of the low-pressure CO2 storage chamber (3-21) and the inlet of the heating expansion system.

5. The compressed carbon dioxide energy storage system according to claim 4, characterized in that: A second valve is provided between the outlet of the high pressure CO2 storage chamber (3-20) and the inlet of the heating expansion system.

6. The compressed carbon dioxide energy storage system according to claim 5, characterized in that: A third valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the low-pressure CO2 storage chamber (3-21).

7. The compressed carbon dioxide energy storage system according to claim 6, characterized in that: A fourth valve is provided between the outlet of the second carbon dioxide cooling and compression system and the inlet of the high-pressure CO2 storage chamber (3-20).

8. A low-carbon emission coal-fired unit, characterized in that: It comprises a coal-fired unit (1), a carbon capture system (2), a first carbon dioxide cooling and compression system, and the compressed carbon dioxide energy storage system according to claim 7; The steam outlet of the boiler (1-1) is connected to the inlet of the steam turbine (1-2), the exhaust port of the steam turbine (1-2) is connected to the inlet of the boiler (1-1) via the condenser (1-2) and the regenerative heater (1-4), the steam extraction port of the steam turbine (1-2) is connected to the steam inlet of the desorption tower (2-4), the flue gas outlet of the boiler (1-1) is connected to the flue gas inlet of the absorption tower (2-3) via the induced draft fan (2-1) and the flue gas cooler (2-2), the bottom slurry pool outlet of the absorption tower (2-3) is connected to the inlet of the desorption tower (2-4) via the rich liquid pump (2-5) and the rich liquid heater (2-6), and the lean liquid outlet of the desorption tower (2-4) is connected to the inlet of the spray device in the absorption tower (2-3) via the lean liquid cooler (2-7); The carbon dioxide outlet at the top of the desorption tower (2-4) is connected to the inlet of the low-pressure CO2 storage chamber (3-21) in the compressed carbon dioxide energy storage system through the first carbon dioxide cooling and compression system.

9. The low-carbon emission coal-fired unit according to claim 8, characterized in that: The first carbon dioxide cooling and compression system comprises a CO2 compressor No. 1 (3-1), a CO2 cooler No. 1 (3-2), a CO2 compressor No. 2 (3-3), a CO2 cooler No. 2 (3-4), a CO2 compressor No. 3 (3-5) and a CO2 cooler No. 3 (3-6) which are connected in sequence, wherein the inlet of the CO2 compressor No. 1 (3-1) is connected to the carbon dioxide outlet of the desorption tower (2-4), and the outlet of the CO2 cooler No. 3 (3-6) is connected to the inlet of the low-pressure CO2 storage chamber (3-21).

10. An operating method of the low-carbon emission coal-fired unit according to claim 8, characterized in that: The following steps are involved: When the increase in the load of the power grid is less than the preset increase, the first valve and the third valve are opened, the second valve and the fourth valve are closed, and the low-pressure carbon dioxide in the low-pressure CO2 storage chamber (3-21) is sent to the heating expansion system to perform work. When the increase in the load of the power grid is greater than or equal to the preset increase, the second valve and the third valve are opened, the first valve and the fourth valve are closed, and then the high-pressure carbon dioxide in the high-pressure CO2 storage chamber (3-20) is sent to the heating expansion system to perform work. The preset increase can be 10%. During this process, the second carbon dioxide cooling and compression system is in a closed state. When the reduction range of the grid load is less than or equal to the preset reduction range threshold, the surplus electric energy is used to provide energy, and then some compressors and coolers in the second carbon dioxide cooling and compression system are opened, and the first valve and the third valve are opened at the same time, and the second valve and the fourth valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber (3-21) is circulated and compressed by the compressors and coolers opened in the second carbon dioxide cooling and compression system to increase the gas pressure of the carbon dioxide in the low-pressure CO2 storage chamber (3-21); when the reduction range of the grid load is greater than the preset reduction range threshold, the surplus electric energy is used to provide energy, and then all compressors and coolers in the second carbon dioxide cooling and compression system are opened, and the first valve and the fourth valve are opened at the same time, and the second valve and the third valve are closed. The low-pressure carbon dioxide in the low-pressure CO2 storage chamber (3-21) is pressurized by the second carbon dioxide cooling and compression system and then stored in the high-pressure CO2 storage chamber (3-20). During this process, the heating expansion system is in a closed state.

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