A cogeneration system and method for a thermal power plant coupled with compressed carbon dioxide energy storage

Abstract

The present invention relates to the fields of thermal power generation and energy storage, and particularly relates to a cogeneration system and method for a thermal power plant coupled with compressed carbon dioxide energy storage. It includes: a low-pressure cylinder is connected to a first generator, the outlet of the medium-pressure cylinder is connected to a user end, the outlet of the user end is connected to a deaerator; the inlet and outlet of an intermediate cooler group are respectively connected to the outlet of a condenser and the inlet of the user end, a motor is connected to the first generator, and the outlet of the intermediate cooler group is also connected to a high-pressure carbon dioxide storage tank; the inlet and outlet of a preheater group are respectively connected to the outlet of the medium-pressure cylinder and the inlet of a low-pressure heater group, the outlet of an expansion unit is also connected to a low-pressure carbon dioxide storage tank, the outlet of the low-pressure carbon dioxide storage tank is connected to the inlet of a compressor unit, and the outlet of the high-pressure carbon dioxide storage tank is connected to the inlet of the preheater group. The present invention provides a cogeneration system and method for a thermal power plant coupled with compressed carbon dioxide energy storage, which has a simple structure and low cost.

Description

Technical Field

[0001] The present invention relates to the fields of thermal power generation and energy storage, and particularly relates to a cogeneration system and method for a thermal power plant coupled with compressed carbon dioxide energy storage. Background Art

[0002] The coordinated operation of a cogeneration unit and a large-scale energy storage system can improve the flexibility of the power system. Large-scale energy storage systems mainly include pumped storage systems, compressed air energy storage systems, and fuel cell energy storage systems, etc. Among them, the pumped storage system is restricted by geography, and the energy conversion efficiency of fuel cell energy storage systems is generally low. Only the compressed air energy storage system is considered the most applicable energy storage system due to its advantages such as low pollution, high efficiency, and long lifespan. However, traditional compressed air energy storage technology relies on fossil fuels, adiabatic compressed air energy storage technology requires a huge gas storage cavern, and liquid air energy storage technology is restricted by the too low critical temperature of air (about -140.6°C).

[0003] Compared with air, carbon dioxide has good thermal properties, with critical parameters of 31°C and 7.377 MPa, which can be easily achieved by existing technologies. At the same time, a cycle power system with supercritical carbon dioxide as the working medium has received increasing attention in recent years due to its compact system, good thermal performance, and safety performance. However, the research on applying compressed carbon dioxide energy storage technology to the power supply side, especially for peak shaving in coordination with the power grid, is still very scarce. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the complex structure and high cost of the coupling system between compressed carbon dioxide and the power grid in the prior art, and thus provide a cogeneration system and method for a thermal power plant coupled with compressed carbon dioxide energy storage with a simple structure and low cost.

[0005] To solve the above technical problem, the present invention provides a cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage, including:

[0006] A cogeneration device, including a boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a low-pressure heater group, a deaerator, and a high-pressure heater group that are connected in a cycle. The low-pressure cylinder is connected to a first generator, the outlet of the intermediate-pressure cylinder is connected to a user end, and the outlet of the user end is connected to the inlet of the deaerator;

[0007] An energy storage device, including an intercooler group, a compressor unit, and a motor that are connected in sequence. The inlet and outlet of the intercooler group are respectively connected to the outlet of the condenser and the inlet of the user end. The motor is connected to the first generator, and the outlet of the intercooler group is also connected to a high-pressure carbon dioxide storage tank;

[0008] The energy release device includes a preheater group, an expansion unit, and a second generator connected in sequence. The inlet and outlet of the preheater group are respectively connected to the outlet of the intermediate-pressure cylinder and the inlet of the low-pressure heater group. The outlet of the expansion unit is also connected to a low-pressure carbon dioxide storage tank. The outlet of the low-pressure carbon dioxide storage tank is connected to the inlet of the compression unit, and the outlet of the high-pressure carbon dioxide storage tank is connected to the inlet of the preheater group.

[0009] Optionally, it further includes a first pressure stabilizing valve respectively arranged between the outlet of the low-pressure carbon dioxide storage tank and the inlet of the compression unit, and a second pressure stabilizing valve between the outlet of the high-pressure carbon dioxide storage tank and the inlet of the preheater group.

[0010] Optionally, it further includes a condensate pump arranged between the condenser and the intermediate cooler group.

[0011] Optionally, a first cooler is arranged between the condensate pump and the low-pressure heater group, and a second cooler is arranged between the expansion unit and the low-pressure carbon dioxide storage tank.

[0012] Optionally, a deaerator is arranged between the low-pressure heater group and the high-pressure heater group, and the outlet of the user end is connected to the inlet of the deaerator.

[0013] Optionally, the outlet of the intermediate-pressure cylinder is also connected to a steam turbine for a water pump. A main feed water pump and a booster pump are arranged in sequence between the steam turbine for the water pump and the deaerator, and the steam turbine for the water pump is also connected to the condenser.

[0014] Optionally, it further includes a return water pump arranged between the user end and the deaerator.

[0015] There is also provided a cogeneration method for a thermal power plant with coupled compressed carbon dioxide energy storage, using the described system for cogeneration, including the following steps:

[0016] The boiler feed water absorbs heat in the boiler and then enters the high-pressure cylinder to expand and do work. Subsequently, it flows back to the boiler for reheating. The reheated steam enters the intermediate-pressure cylinder to expand and do work. A part of the exhaust steam from the intermediate-pressure cylinder flows into the user end for heating, and the return water after heating returns to the deaerator; another part enters the low-pressure cylinder to continue expanding and doing work, and drives the first generator to generate electricity. The exhaust steam enters the condenser and condenses into liquid. After being heated by the low-pressure heater group, it enters the high-pressure heater group for heating, and finally returns to the boiler to complete the thermal cycle.

[0017] When the electricity load demand at the user end is low and the heat load is relatively high at night, after the carbon dioxide in the low-pressure carbon dioxide storage tank is depressurized, the first generator supplies power to the motor, and the motor drives the compression unit to compress the depressurized carbon dioxide. The compressed high-pressure carbon dioxide is stored in the high-pressure carbon dioxide storage tank. The compression heat generated during the compression process is absorbed by the intermediate cooler group, and the condensate water in the intermediate cooler group absorbs the compression heat and then flows to the user end for heating.

[0018] When the electrical load demand of the user is high and the heat load demand is low during the day, after the carbon dioxide in the high-pressure carbon dioxide storage tank is depressurized, it is heated by the preheater group and then sent into the expansion unit to expand and do work, driving the second generator to generate electricity. The expanded low-pressure carbon dioxide is stored in the low-pressure carbon dioxide storage tank, and the heating extraction steam of the preheater group returns to the low-pressure heater group after heat exchange.

[0019] Optionally, it further includes that the condensate in the condenser is pumped out by the condensate pump, heated by the low-pressure heater group and then enters the deaerator, and is successively pressurized by the booster pump and the main feed water pump and then enters the high-pressure heater group for heating up.

[0020] Optionally, the carbon dioxide in the low-pressure carbon dioxide storage tank and the high-pressure carbon dioxide storage tank is depressurized through the first pressure stabilizing valve and the second pressure stabilizing valve respectively.

[0021] The technical solution of the present invention has the following advantages:

[0022] 1. The cogeneration system of a thermal power plant with coupled compressed carbon dioxide energy storage provided by the present invention significantly improves the peak shaving capacity of traditional cogeneration units and the thermal electrolysis decoupling capacity of the carbon dioxide energy storage system by coupling the compressed carbon dioxide energy storage device with the cogeneration device of the thermal power plant. While the cogeneration device supplies excess electric energy to the compressed carbon dioxide energy storage device, it also uses the heating extraction steam to provide the heating heat source for the energy release process, collects the compression heat during the energy storage process by using the condensate water, eliminates the heat storage equipment, reduces the complexity of the energy storage system, and saves costs.

[0023] 2. For the cogeneration system of a thermal power plant with coupled compressed carbon dioxide energy storage provided by the present invention, the setting of the first pressure stabilizing valve and the second pressure stabilizing valve ensures the safety of carbon dioxide during compression. Description of the Drawings

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic diagram of the cogeneration system of a thermal power plant with coupled compressed carbon dioxide energy storage provided by the present invention.

[0026] Description of the Reference Numerals:

[0027] 1. First-stage high-pressure heater; 2. Second-stage high-pressure heater; 3. Third-stage high-pressure heater; 4. Deaerator; 5. First-stage low-pressure heater; 6. Second-stage low-pressure heater; 7. Third-stage low-pressure heater; 8. Fourth-stage low-pressure heater; 9. Boiler; 10. High-pressure cylinder; 11. Intermediate-pressure cylinder; 12. Low-pressure cylinder; 13. Condenser; 14. Condensate pump; 15. First cooler; 16. Booster pump; 17. Main feed water pump; 18. Feed water turbine; 19. First generator; 20. Motor; 21. Compressor unit; 22. Intercooler unit; 23. High-pressure carbon dioxide storage tank; 24. Second pressure stabilizing valve; 25. Preheater unit; 26. Expansion unit; 27. Second generator; 28. Second cooler; 29. Low-pressure carbon dioxide storage tank; 30. First pressure stabilizing valve; 31. User end; 32. Return water pump. Detailed implementation manners

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] As Figure 1 shown in a specific implementation manner of a cogeneration system for a thermal power plant with coupled compressed carbon dioxide energy storage, which includes a cogeneration device, an energy storage device, and an energy release device.

[0031] The cogeneration device includes a boiler 9, a high-pressure cylinder 10, an intermediate-pressure cylinder 11, a low-pressure cylinder 12, a condenser 13, a condensate pump 14, a first cooler 15, a low-pressure heater group, and a high-pressure heater group that are connected in a cycle. The low-pressure cylinder 12 is connected to a first generator 19. The outlet of the intermediate-pressure cylinder 11 is connected to a user end 31. The outlet of the user end 31 is sequentially connected to a return water pump 32, a deaerator 4, a booster pump 16, a main feed water pump 17, and the high-pressure heater group. A feed water turbine 18 is also provided between the intermediate-pressure cylinder 11 and the main feed water pump 17.

[0032] The high-pressure heater group includes a first-stage high-pressure heater 1, a second-stage high-pressure heater 2, and a third-stage high-pressure heater 3. Among them, the outlet of the high-pressure cylinder 10 is connected to the shell-side inlet of the first-stage high-pressure heater 1; the shell-side inlet of the second-stage high-pressure heater 2 is connected to the pipeline between the outlet of the high-pressure cylinder 10 and the inlet of the reheater of the boiler 9; the outlet of the intermediate-pressure cylinder 11 is respectively connected to the shell-side inlet of the third-stage high-pressure heater 3, the inlet of the deaerator 4, and the inlet of the user end 31; the shell-side outlet of the first-stage high-pressure heater 1 is successively connected to the shell-side of the second-stage high-pressure heater 2, the shell-side of the third-stage high-pressure heater 3, and the inlet of the deaerator 4; the outlet of the deaerator 4 is successively connected to the tube-side of the third-stage high-pressure heater 3, the tube-side of the second-stage high-pressure heater 2, the tube-side of the first-stage high-pressure heater 1, and the inlet of the boiler 9.

[0033] The low-pressure heater group includes a first-stage low-pressure heater 5, a second-stage low-pressure heater 6, a third-stage low-pressure heater 7, and a fourth-stage low-pressure heater 8. Among them, the outlet of the low-pressure cylinder 12 is respectively connected to the shell-side inlet of the first-stage low-pressure heater 5, the shell-side inlet of the second-stage low-pressure heater 6, the shell-side inlet of the third-stage low-pressure heater 7, and the shell-side inlet of the fourth-stage low-pressure heater 8; the shell-side outlet of the first-stage low-pressure heater 5 is successively connected to the shell-side of the second-stage low-pressure heater 6, the shell-side of the third-stage low-pressure heater 7, the shell-side of the fourth-stage low-pressure heater 8, and the inlet of the condenser 13; the outlet of the condenser 13 is successively connected to the condensate pump 14, the tube-side of the first cooler 15, the tube-side of the fourth-stage low-pressure heater 8, the tube-side of the third-stage low-pressure heater 7, the tube-side of the second-stage low-pressure heater 6, the tube-side of the first-stage low-pressure heater 5, and the inlet of the deaerator 4.

[0034] The energy storage device includes an intermediate cooler group 22, a compressor group 21, and a motor 20 connected in sequence. The motor 20 is connected to the compressor group 21 through a transmission shaft. The inlet and outlet of the intermediate cooler group 22 are respectively connected to the tube-side inlet of the first cooler 15 and the inlet of the user end 31. The motor 20 is connected to the first generator 19 through a circuit. The outlet of the intermediate cooler group 22 is also connected to a high-pressure carbon dioxide storage tank 23.

[0035] The energy release device includes a preheater group 25, an expansion unit 26, and a second generator 27 connected in sequence. The second generator 27 is connected to the expansion unit 26 through a transmission shaft. The inlet and outlet of the preheater group 25 are respectively connected to the outlet of the intermediate-pressure cylinder 11 and the inlet of the low-pressure heater group. The outlet of the expansion unit 26 is also connected to a low-pressure carbon dioxide storage tank 29 through a second cooler 28. The outlet of the low-pressure carbon dioxide storage tank 29 is connected to the inlet of the compressor group 21 through a first pressure stabilizing valve 30. The outlet of the high-pressure carbon dioxide storage tank 23 is connected to the inlet of the preheater group 25 through a second pressure stabilizing valve 24.

[0036] The boiler 9 and the outlet of its reheater are respectively connected to the inlets of the high-pressure cylinder 10 and the intermediate-pressure cylinder 11. The outlet of the high-pressure cylinder 10 is connected to the inlet of the reheater of the boiler 9. At the same time, two sections of high-pressure extraction steam are respectively connected to the first-stage high-pressure heater 1 and the second-stage high-pressure heater 2. The outlet of the intermediate-pressure cylinder 11 is connected to the inlet of the low-pressure cylinder 12. At the same time, two sections of extraction steam are respectively connected to the third-stage high-pressure heater 3, the deaerator 4, and the feed water turbine 18. The feed water turbine 18 drives the booster pump 16 and the main feed water pump 17 and is connected to the condenser 13. The outlet of the intermediate-pressure cylinder 11 is provided with heating extraction steam connected to the user end 31. The user end 31 is connected to the inlet of the deaerator 4 through the return water pump 32. The heating extraction steam also serves as the heating steam source for the carbon dioxide at the inlet of the expansion unit 26 and is connected to the preheater group 25. The outlet of the low-pressure cylinder 12 is connected to the inlet of the condenser 13. At the same time, four sections of low-pressure extraction steam are connected to the low-pressure heater group. The high-pressure cylinder 10, the intermediate-pressure cylinder 11, and the low-pressure cylinder 12 are coaxially connected to drive the first generator 19 to generate electricity. The inlet of the condensate pump 14 is connected to the hot well at the outlet of the condenser 13. The outlet of the condensate pump 14 is divided into two paths. One path is successively connected to the first cooler 15, the low-pressure heater group, the deaerator 4, the booster pump 16, the main feed water pump 17, the high-pressure heater group, and the inlet of the boiler 9. The other path is connected to the indirect cooler group 22, which is used to provide the compression heat generated during the compression process of the condensate water collection energy storage device.

[0037] The steam turbine unit has a total of eight non-adjustable extraction steam and one section of heating extraction steam. The heating extraction steam comes from the intermediate-pressure cylinder 11 and is supplied to the user end 31. The first-stage extraction steam and the second-stage extraction steam are extracted from the high-pressure cylinder 10 and are respectively supplied to the first-stage high-pressure heater 1 and the second-stage high-pressure heater 2. The third-stage extraction steam and the fourth-stage extraction steam are extracted from the intermediate-pressure cylinder 11 and are respectively supplied to the third-stage high-pressure heater 3 and the deaerator 4. The last four-stage extraction steam all comes from the low-pressure cylinder 12 and is supplied to the low-pressure heater group. The high-pressure cylinder 10, the intermediate-pressure cylinder 11, and the low-pressure cylinder 12 are coaxially connected to drive the first generator 19 to generate electricity. The steam source of the feed water turbine 18 is part of the fourth-stage extraction steam, which is used to drive the booster pump 16 and the main feed water pump 17, and the exhaust steam is connected into the condenser 13. The cold source of the condenser 13 is the circulating water from the cooling water tower.

[0038] The number of stages of the compressor unit 21 is set to multiple stages according to the energy storage pressure and the energy release pressure, and it is driven by the motor 20. The condensate water from the condensate pump 14 absorbs the compression heat in the intercooler after each stage of the compressor and then is supplied to the inlet of the user end 31 to jointly supply heat with the extraction steam for heating. The outlet of the tube side of the intercooler group 22 is connected to the inlet of the high-pressure carbon dioxide storage tank 23. The high-pressure carbon dioxide storage tank 23 is connected to the expansion unit 26 through the second pressure stabilizing valve 24. The number of stages of the expansion unit 26 is set to multiple stages. The expansion unit 26 drives the second generator 27 to generate electricity. The extraction steam for heating from the low-pressure cylinder 12 heats the carbon dioxide in the preheater before each stage of the expander and then returns the water to the drain cooler corresponding to a certain stage of the low-pressure heater. The outlet of the expansion unit 26 is connected to the inlet of the low-pressure carbon dioxide storage tank 29 through the second cooler 28. The outlet of the low-pressure carbon dioxide storage tank 29 is connected to the inlet of the compressor unit 21 through the first pressure stabilizing valve 30.

[0039] A cogeneration method for a thermal power plant with coupled compressed carbon dioxide energy storage includes the following steps:

[0040] The boiler feed water absorbs the heat released by the fuel combustion in the boiler 9 to become superheated steam, enters the high-pressure cylinder 10 to expand and do work, then returns to the boiler reheater. The reheated reheat steam enters the intermediate-pressure cylinder 11 to expand and do work. A part of the exhaust steam from the intermediate-pressure cylinder 11 flows into the user end 31 as the extraction steam for heating to supply heat, and after heating, the water returns to the deaerator 4; another part enters the low-pressure cylinder 12 to continue expanding and doing work, and drives the first generator 19 to generate electricity. The exhaust steam enters the condenser 13 to be condensed into liquid and converges in the hot well, is pumped out by the condensate pump 14, is heated up by the low-pressure heater group and then enters the deaerator 4, and is successively boosted by the booster pump 16 and the main feed water pump 17 and then enters the high-pressure heater group to be heated up, and finally returns to the boiler 9 to complete the thermal cycle.

[0041] When the electricity load demand at the user end is low and the heat load is relatively high at night, the enhanced heating energy storage mode is turned on. The carbon dioxide in the low-pressure carbon dioxide storage tank 29 is depressurized by the first pressure stabilizing valve 30. The first generator 19 supplies power to the motor 20, and the motor 20 drives the compressor unit 21 to compress the depressurized carbon dioxide. The compressed high-pressure carbon dioxide is stored in the high-pressure carbon dioxide storage tank 23. The compression heat generated during the compression process is absorbed by the intercooler group 22. The cold source of the intercooler group 22 is the condensate water at the outlet of the condensate pump 14 of the cogeneration device. The condensate water in the intercooler group 22 absorbs the compression heat and then flows to the user end 31 to jointly supply heat with the extraction steam for heating.

[0042] When the electrical load demand of the user is high and the heat load demand is low during the day, the enhanced power supply and energy release mode is turned on. The carbon dioxide in the high-pressure carbon dioxide storage tank 23 is depressurized by the second pressure stabilizing valve 24, heated by the preheater group 25, and then sent into the expansion unit 26 to expand and do work, driving the second generator 27 to generate electricity. The expanded low-pressure carbon dioxide is stored in the low-pressure carbon dioxide storage tank 29. The heating extraction steam of the preheater group 25 returns the water to the drain cooler corresponding to the low-pressure heater group after heat exchange.

[0043] The cogeneration device absorbs the heat generated by coal combustion, supplies heat to the user side and drives the first generator to output electric energy. At the same time, it provides condensate water for collecting compression heat and heating extraction steam for preheating carbon dioxide to the compressed carbon dioxide energy storage system; the energy storage device stores the excess electric energy of the cogeneration device during the low electricity consumption period, and the generated compression heat and heating extraction steam jointly supply heat to the heat users, and output electric energy during the high electricity consumption period to improve the peak shaving capacity of the unit.

[0044] Obviously, the above embodiments are only examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage, characterized in that, Comprising: A combined heat and power generation device, including a boiler (9), a high-pressure cylinder (10), an intermediate-pressure cylinder (11), a low-pressure cylinder (12), a condenser (13), a low-pressure heater group, a deaerator (4) and a high-pressure heater group which are connected in a cycle. The low-pressure cylinder (12) is connected with a first generator (19). The outlet of the intermediate-pressure cylinder (11) is connected with a user end (31). The outlet of the user end (31) is connected with the inlet of the deaerator (4). An energy storage device, including an air-cooled cooler group (22), a compressor unit (21) and a motor (20) which are connected in sequence. The inlet and outlet of the air-cooled cooler group (22) are respectively connected with the outlet of the condenser (13) and the inlet of the user end (31). The motor (20) is connected with the first generator (19). The outlet of the air-cooled cooler group (22) is also connected with a high-pressure carbon dioxide storage tank (23). An energy release device, including a preheater group (25), an expansion unit (26) and a second generator (27) which are connected in sequence. The inlet and outlet of the preheater group (25) are respectively connected with the outlet of the intermediate-pressure cylinder (11) and the inlet of the low-pressure heater group. The outlet of the expansion unit (26) is also connected with a low-pressure carbon dioxide storage tank (29). The outlet of the low-pressure carbon dioxide storage tank (29) is connected with the inlet of the compressor unit (21). The outlet of the high-pressure carbon dioxide storage tank (23) is connected with the inlet of the preheater group (25). The outlet of the intermediate-pressure cylinder (11) is provided with a heating extraction steam which is connected with the user end (31), and the heating extraction steam is also used as a heating steam source for the carbon dioxide at the inlet of the expansion unit (26) and is connected with the preheater group (25).

2. The cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 1, characterized in that, It also includes a first pressure stabilizing valve (30) respectively arranged between the outlet of the low-pressure carbon dioxide storage tank (29) and the inlet of the compressor unit (21), and a second pressure stabilizing valve (24) between the outlet of the high-pressure carbon dioxide storage tank (23) and the inlet of the preheater group (25).

3. The cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 2, characterized in that, It also includes a condensate pump (14) arranged between the condenser (13) and the air-cooled cooler group (22).

4. The cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 3, characterized in that, A first cooler (15) is arranged between the condensate pump (14) and the low-pressure heater group, and a second cooler (28) is arranged between the expansion unit (26) and the low-pressure carbon dioxide storage tank (29).

5. The cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage according to any one of claims 1-4, characterized in that, The outlet of the intermediate-pressure cylinder (11) is also connected with a water pump steam turbine (18). A main feed water pump (17) and a booster pump (16) are arranged in sequence between the water pump steam turbine (18) and the deaerator (4). The water pump steam turbine (18) is also connected with the condenser (13).

6. The cogeneration system for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 5, characterized in that, It also includes a return water pump (32) arranged between the user end (31) and the deaerator (4).

7. A cogeneration method for a thermal power plant coupled with compressed carbon dioxide energy storage, characterized in that, Using the system according to any one of claims 1-6 for combined production, including the following steps: The boiler feed water absorbs heat in the boiler (9) and then enters the high-pressure cylinder (10) to expand and do work. Subsequently, it flows back to the boiler (9) for reheating. The reheated steam enters the intermediate-pressure cylinder (11) to expand and do work. Part of the exhaust steam from the intermediate-pressure cylinder (11) flows into the user end (31) for heating, and the water returns to the deaerator (4) after heating; the other part enters the low-pressure cylinder (12) to continue expanding and doing work, and drives the first generator (19) to generate electricity. The exhaust steam enters the condenser (13) and condenses into liquid. After being heated by the low-pressure heater group, it enters the high-pressure heater group for heating, and finally returns to the boiler (9) to complete the thermodynamic cycle; When the electrical load demand at the user end is low and the heat load is relatively high at night, after the carbon dioxide in the low-pressure carbon dioxide storage tank (29) is depressurized, the first generator (19) supplies power to the motor (20), and the motor (20) drives the compressor unit (21) to compress the depressurized carbon dioxide. The compressed high-pressure carbon dioxide is stored in the high-pressure carbon dioxide storage tank (23). The compression heat generated during the compression process is absorbed by the intermediate cooler group (22). The condensate water in the intermediate cooler group (22) absorbs the compression heat and then flows to the user end (31) for heating; When the electrical load demand of users is high and the heat load demand is low during the day, after the carbon dioxide in the high-pressure carbon dioxide storage tank (23) is depressurized, it is heated by the preheater group (25) and then sent into the expansion unit (26) to expand and do work, and drives the second generator (27) to generate electricity. The expanded low-pressure carbon dioxide is stored in the low-pressure carbon dioxide storage tank (29). After the heating extraction steam of the preheater group (25) exchanges heat, the water returns to the low-pressure heater group.

8. The cogeneration method for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 7, characterized in that, It also includes that the condensate in the condenser (13) is pumped out by the condensate pump (14), enters the deaerator (4) after being heated by the low-pressure heater group, and is successively pressurized by the booster pump (16) and the main feed water pump (17) and then enters the high-pressure heater group for heating.

9. The cogeneration method for a thermal power plant coupled with compressed carbon dioxide energy storage according to claim 8, characterized in that, The carbon dioxide in the low-pressure carbon dioxide storage tank (29) and the high-pressure carbon dioxide storage tank (23) is depressurized respectively through the first pressure stabilizing valve (30) and the second pressure stabilizing valve (24).

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