Coal-fired unit peak regulation power generation system coupled with carbon dioxide energy storage and operation method of coal-fired unit peak regulation power generation system

Abstract

The invention discloses a coal-fired unit peak regulation power generation system coupled with carbon dioxide energy storage and an operation method of the coal-fired unit peak regulation power generation system. The peak regulation power generation system of the coal-fired unit comprises the coal-fired unit, a carbon dioxide capturing device and a carbon dioxide energy storage device, wherein the coal-fired unit, the carbon dioxide capturing device and the carbon dioxide energy storage device are connected in sequence; the carbon dioxide capturing device captures carbon dioxide in flue gas discharged by the coal-fired unit by using electric power and steam generated by the coal-fired unit; the carbon dioxide energy storage device is used for performing compression energy storage on the carbon dioxide captured by the carbon dioxide capturing device by utilizing electric power generated by the coal-fired unit; the carbon dioxide energy storage device comprises a carbon dioxide compression device and a carbon dioxide expansion power generation device which operate independently. According to the invention, the peak regulation depth of the coal-fired unit can be effectively improved at the low power consumption ebb, and the consumption level of the power grid on off-peak electricity and new energy is enhanced; and the power generation peak capacity of the coal-fired unit can be effectively improved in the power utilization peak.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-fired unit power generation, and in particular is a peak-shaving power generation system of a coal-fired unit coupled with carbon dioxide energy storage and an operation method thereof. Background Art

[0003] Coal-fired units are often limited by their ultra-low load operation capabilities, which to some extent affects their peak load depth. At the same time, in order to reduce the carbon emissions of coal-fired units, coupling carbon capture systems has become one of the main routes for low-carbon transformation of coal-fired units. The carbon capture system consumes steam and electricity during operation. Although it can increase the peak load depth of coal-fired units to a certain extent, when the load of the coal-fired unit increases, the power consumed by the carbon capture system also needs to increase accordingly, which undoubtedly limits the peak capacity of the coal-fired unit.

[0004] At the same time, existing carbon dioxide energy storage devices often need to purchase industrial-grade carbon dioxide products as operating fluids, and the operating costs of the energy storage devices are high. Summary of the invention

[0005] In view of the problems of insufficient peak-shaving depth and peak capacity of existing coal-fired units and high operating costs of existing carbon dioxide energy storage devices, the present invention provides a coal-fired unit peak-shaving power generation system coupled with carbon dioxide energy storage and an operating method thereof, which couples the coal-fired unit, the carbon dioxide capture system and the carbon dioxide energy storage device for application, which can effectively improve the peak-shaving depth and peak capacity of the coal-fired unit, and reduce the cost of carbon sequestration and storage and transportation, as well as the operating cost of the carbon dioxide energy storage device.

[0006] To this end, the present invention adopts the following technical solution.

[0007] In a first aspect, the present invention provides a peak-shaving power generation system of a coal-fired unit coupled with a carbon dioxide energy storage, comprising a coal-fired unit, a carbon dioxide capture device and a carbon dioxide energy storage device, wherein the coal-fired unit, the carbon dioxide capture device and the carbon dioxide energy storage device are sequentially connected; the carbon dioxide capture device utilizes the electricity and steam generated by the coal-fired unit to capture carbon dioxide in the flue gas emitted by the coal-fired unit; the carbon dioxide energy storage device utilizes the electricity generated by the coal-fired unit to compress and store the carbon dioxide captured by the carbon dioxide capture device;

[0008] The carbon dioxide energy storage device includes a carbon dioxide compression device and a carbon dioxide expansion power generation device, which operate independently; when the power grid is under low load, the operation level of the carbon dioxide capture device is improved, and the captured carbon dioxide is sent to the carbon dioxide compression device for compression and energy storage using surplus electric energy; when the power grid is under high load, the operation levels of the carbon dioxide capture device and the carbon dioxide compression device are reduced, and the carbon dioxide expansion power generation device is used to expand the stored carbon dioxide to do work, thereby increasing the power generation power.

[0009] Furthermore, the carbon dioxide energy storage device includes a low-pressure gas storage bin, a compressor, a cooler, a high-pressure storage tank, a heater, an expander, a generator, a cold storage tank, a first working fluid pump, a second working fluid pump, a heat storage tank and a storage space;

[0010] The cold storage tank, the first working fluid pump, the cooler, the heat storage tank, the second working fluid pump and the heater are connected end to end in sequence to form a closed loop; the expander is connected to the generator; the high-pressure storage tank is connected to the storage space, and when the high-pressure storage tank reaches the maximum storage capacity, the excess carbon dioxide is stored in the storage space, and the storage space can provide carbon dioxide for carbon dioxide users;

[0011] The low-pressure gas storage warehouse and high-pressure storage tank are equipped with pressure detectors and leakage detection devices to ensure that the leakage rate is within a reasonable range;

[0012] During the energy storage stage, the carbon dioxide from the carbon dioxide capture device is first compressed by a compressor, cooled by a cooler, and then stored in a high-pressure storage tank. At the same time, the first working fluid pump drives the working fluid in the cold storage tank to absorb heat in the cooler and then enter the heat storage tank for storage. During the energy release stage, the carbon dioxide in the high-pressure storage tank is heated by the heater and then expanded by the expander to do work, driving the generator to generate electricity. The expanded carbon dioxide enters the low-pressure gas storage tank for storage. At the same time, the second working fluid pump drives the working fluid in the heat storage tank to enter the cold storage tank for storage after the heater releases heat.

[0013] Furthermore, the compression, cooling, heating and expansion are multi-stage processes.

[0014] Furthermore, the heat storage medium in the cold storage tank and the heat storage tank is water, heat transfer oil or molten salt.

[0015] In a second aspect, the present invention provides an operation method of the above-mentioned coal-fired unit peak load generation system, which comprises:

[0016] Step 1, determine whether the actual grid power of the coal-fired unit is greater than the grid power demand. If yes, proceed to step 2; if no, proceed to step 5;

[0017] Step 2, determine whether the power generation capacity of the coal-fired unit is higher than the minimum guaranteed power generation capacity, if yes, reduce the power generation capacity of the coal-fired unit; if no, execute step 3;

[0018] Step 3, determining whether the carbon dioxide capture device and the carbon dioxide compression device are at the highest operating level; if not, increasing the operating level of the carbon dioxide capture device and the carbon dioxide compression device;

[0019] Step 4, determining whether the high-pressure storage tank has reached the maximum storage capacity, if yes, storing the excess carbon dioxide in the storage space;

[0020] Step 5, determine whether the actual grid power of the coal-fired unit is less than the grid demand power, if yes, execute step 6;

[0021] Step 6, determine whether the coal-fired unit is in full load power generation state, if yes, execute step 7; if no, increase the power generation capacity of the coal-fired unit;

[0022] Step 7, determine whether the carbon dioxide capture device and the carbon dioxide compression device are at the lowest operating level. If yes, start the carbon dioxide expansion power generation device to start releasing energy; if no, reduce the operating level of the carbon dioxide capture device and the carbon dioxide compression device.

[0023] Furthermore, during the energy storage process, a maximum storage capacity is set in the high-pressure storage tank. When the carbon dioxide capacity in the high-pressure storage tank reaches the maximum storage capacity, the excess carbon dioxide needs to be stored in the storage space, and the storage space is used as a carbon dioxide storage area to provide carbon dioxide to external users.

[0024] Furthermore, during the energy storage stage, the mass flow rate of carbon dioxide of the compressor in the carbon dioxide energy storage device is controlled so that the power generation of the coal-fired unit is not lower than the minimum guaranteed power generation, and at the same time, the actual grid power of the coal-fired unit is equal to the power demanded by the grid.

[0025] Furthermore, the calculation formula for the mass flow rate of carbon dioxide in the compressor is:

[0026]

[0027] In the formula, m ch is the mass flow rate of carbon dioxide in the compressor, kg / s; P 2 is the current power generation of the coal-fired unit, kW; P 1 is the target grid-connected power of coal-fired units, kW; P 01 Power consumption of the carbon dioxide capture device, kW; h 2 is the enthalpy of carbon dioxide at the compressor outlet, kJ / kg; h 1 is the enthalpy of carbon dioxide at the compressor inlet, kJ / kg; η ch is the compressor efficiency, %.

[0028] In the carbon dioxide energy storage device, the calculation formula for the heat transfer fluid flow in the first working fluid pump is:

[0029]

[0030] In the formula, m c is the mass flow rate of the heat transfer fluid in the first working fluid pump, kg / s; h 20 is the enthalpy of carbon dioxide at the cooler outlet, kJ / kg; η ex1 is the heat transfer efficiency of the cooler, %; h 5is the enthalpy of the heat transfer fluid at the outlet of the first working fluid pump, kJ / kg; h 6 is the enthalpy of the heat transfer fluid at the cooler outlet, kJ / kg.

[0031] Furthermore, during the energy release phase, the mass flow rate of carbon dioxide in the expander in the carbon dioxide energy storage device is controlled so that the actual grid power of the coal-fired unit is equal to the grid demand power.

[0032] Furthermore, the calculation formula for the mass flow rate of carbon dioxide in the expander is:

[0033]

[0034] In the formula, m disch is the mass flow rate of carbon dioxide in the expander, kg / s; P 2 is the current power generation of the coal-fired unit, kW; P 1 is the target grid-connected power of coal-fired units, kW; P 02 The power consumed by the CO2 capture device and the CO2 compression device, kW; h 3 is the enthalpy of carbon dioxide at the expander inlet, kJ / kg; h 4 is the enthalpy of carbon dioxide at the expander outlet, kJ / kg; η disch is the expansion power generation efficiency, %;

[0035] In the carbon dioxide energy storage device, the calculation formula for the heat transfer fluid flow in the second working fluid pump is:

[0036]

[0037] In the formula, m h is the mass flow rate of the heat transfer fluid in the second working fluid pump, kg / s; h 30 is the enthalpy of carbon dioxide at the heater inlet, kJ / kg; η ex2 is the heat transfer efficiency of the heater, %; h 7 is the enthalpy of the heat transfer fluid at the outlet of the second working fluid pump, kJ / kg; h 8 is the enthalpy of the heat transfer fluid at the heater outlet, kJ / kg.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) In the past, coal-fired units faced the problem of limited peak-shaving depth and peak power generation capacity. The present invention couples the coal-fired unit with a carbon dioxide capture device and a carbon dioxide energy storage device. When electricity consumption is low, the operation level of the carbon dioxide capture device is improved. Further, the carbon dioxide compression device can be started to compress the captured carbon dioxide and store it, which can effectively improve the peak-shaving depth of the coal-fired unit and reduce its carbon emissions. When electricity consumption is peak, the operation levels of the carbon dioxide capture device and the carbon dioxide compression device are reduced. Further, the stored carbon dioxide can be used for expansion and work, which can effectively improve the peak power generation capacity of the coal-fired unit.

[0040] (2) In the past, coal-fired units often compressed and stored the captured carbon dioxide for other purposes, which increased the storage and transportation costs of carbon dioxide. In the past, carbon dioxide energy storage devices often purchased industrial-grade carbon dioxide products as the operating fluid of the device, which increased the construction and operation costs of the carbon dioxide energy storage device. The present invention couples the coal-fired unit with the carbon dioxide capture device and the carbon dioxide energy storage device, and directly uses the carbon dioxide captured from the coal-fired unit for the carbon dioxide energy storage system, enriching the utilization channels of the carbon dioxide captured by the coal-fired unit, while reducing the construction and operation costs of the carbon dioxide energy storage device. In addition, directly using the carbon dioxide energy storage device as a temporary storage site for carbon dioxide can reduce the storage and transportation costs of carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of a peak-shaving power generation system coupled with carbon dioxide energy storage according to the present invention;

[0042] In the figure: 1-coal-fired unit; 2-carbon dioxide capture device; 3-low-pressure gas storage tank; 4-compressor; 5-high-pressure storage tank; 6-expander; 7-storage space; 8-cooler; 9-first working fluid pump; 10-cold storage tank; 11-heater; 12-second working fluid pump; 13-heat storage tank; 14-carbon dioxide user; 15-generator.

[0043] Figure 2 The present invention is a flow chart of a method for operating a peak-shaving power generation system coupled with carbon dioxide energy storage. DETAILED DESCRIPTION

[0044] The following is an explanation and description of the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work are all within the protection scope of the present invention.

[0045] Example 1

[0046] This embodiment provides a peak-shaving power generation system of a coal-fired unit coupled with carbon dioxide energy storage, including a coal-fired unit, a carbon dioxide capture device and a carbon dioxide energy storage device.

[0047] like Figure 1 As shown, the coal-fired unit, the carbon dioxide capture device, and the carbon dioxide energy storage device are connected in sequence; the carbon dioxide capture device uses the electricity and steam generated by the coal-fired unit to capture the carbon dioxide in the flue gas emitted by the coal-fired unit; the carbon dioxide energy storage device uses the electricity generated by the coal-fired unit to compress and store the carbon dioxide captured by the carbon dioxide capture device.

[0048] When the grid is under low load, the operating level of the carbon dioxide capture device is improved, and the surplus electricity is used to send the captured carbon dioxide to the carbon dioxide compression device for compression and energy storage; when the grid is under high load, the operating levels of the carbon dioxide capture device and the carbon dioxide compression device are reduced, and the carbon dioxide expansion power generation device is used to expand the stored carbon dioxide to do work, thereby increasing the power generation capacity.

[0049] The carbon dioxide energy storage device includes a carbon dioxide compression device and a carbon dioxide expansion power generation device, both of which can operate independently; the carbon dioxide energy storage device specifically includes a low-pressure gas storage tank 3, a compressor 4, a cooler 8, a high-pressure storage tank 5, a heater 11, an expander 6, a generator 15, a cold storage tank 10, a first working fluid pump 9, a second working fluid pump 12, a heat storage tank 13 and a storage space 7. The cold storage tank 10, the first working fluid pump 9, the cooler 8, the heat storage tank 13, the second working fluid pump 12 and the heater 11 are connected end to end in sequence to form a closed loop; the expander 6 is connected to the generator 15; the high-pressure storage tank 5 is connected to the storage space 7, and when the high-pressure storage tank 5 reaches the maximum storage capacity, the excess carbon dioxide can be stored in the storage space 7. The storage space 7 can provide carbon dioxide for the carbon dioxide user 14.

[0050] The low-pressure gas storage warehouse 3 and the high-pressure storage tank 5 need to be equipped with a pressure detector and a leakage detection device to ensure that the leakage rate is within a reasonable range.

[0051] In the energy storage stage, the carbon dioxide from the carbon dioxide capture device 2 is first compressed by the compressor 4, cooled by the cooler 8, and then stored in the high-pressure storage tank 5. At the same time, the first working fluid pump 9 drives the working fluid in the cold storage tank 10 to absorb heat in the cooler 8 and then enter the heat storage tank 13 for storage. In the energy release stage, the carbon dioxide in the high-pressure storage tank 5 is heated by the heater 11 and then expanded by the expander 6 to drive the generator 15 to generate electricity. The expanded carbon dioxide enters the low-pressure gas storage tank 3 for storage. At the same time, the second working fluid pump 12 drives the working fluid in the heat storage tank 13 to enter the cold storage tank 10 for storage after the heater 11 releases heat.

[0052] Specifically, the compression, cooling, heating and expansion may be a multi-stage process; the heat storage medium in the cold storage tank 10 and the heat storage tank 13 may be water, heat transfer oil, molten salt and other materials.

[0053] Example 2

[0054] This embodiment provides an operation method of a coal-fired unit peak-shaving power generation system, which adopts a coal-fired unit peak-shaving power generation system coupled with carbon dioxide energy storage as described in Example 1, such as Figure 2 As shown, the following steps are included:

[0055] Step 1: Determine whether the actual grid power of the coal-fired unit is greater than the grid power demand. If yes, proceed to step 2; if no, proceed to step 5;

[0056] Step 2: Determine whether the power generation capacity of the coal-fired unit is higher than the minimum guaranteed power generation capacity. If yes, reduce the power generation capacity of the coal-fired unit; if no, proceed to step 3;

[0057] Step 3: Determine whether the CO2 capture device and the CO2 compression device are at the highest operating level; if not, increase the operating level of the CO2 capture device and the CO2 compression device;

[0058] Step 4: Determine whether the high-pressure storage tank has reached its maximum storage capacity, if yes, store the excess carbon dioxide in the storage space;

[0059] Step 5: Determine whether the actual grid power of the coal-fired unit is less than the grid demand power. If yes, proceed to step 6;

[0060] Step 6: Determine whether the coal-fired unit is in full load power generation state. If yes, execute step 7; if no, increase the power generation capacity of the coal-fired unit;

[0061] Step 7: Determine whether the carbon dioxide capture device and the carbon dioxide compression device are at the lowest operating level. If yes, start the carbon dioxide expansion power generation device to start releasing energy; if no, reduce the operating level of the carbon dioxide capture device and the carbon dioxide compression device.

[0062] During the energy storage process, the high-pressure storage tank is set with a maximum storage capacity. When the carbon dioxide capacity in the high-pressure storage tank reaches the maximum storage capacity, the excess carbon dioxide needs to be stored in the storage space. The storage space can provide carbon dioxide to external carbon dioxide users as a carbon dioxide storage site.

[0063] During the energy storage stage, the mass flow rate of carbon dioxide in the compressor of the carbon dioxide energy storage system is controlled so that the power generation capacity of the coal-fired unit is not lower than the minimum guaranteed power generation capacity, and the actual grid power of the coal-fired unit is equal to the power demanded by the grid.

[0064] Specifically, the calculation formula for the mass flow rate of carbon dioxide in the compressor is:

[0065]

[0066] In the formula, m ch is the mass flow rate of carbon dioxide in the compressor, kg / s; P 2 is the current power generation of the coal-fired unit, kW; P 1 is the target grid-connected power of coal-fired units, kW; P 01 Power consumption of the carbon dioxide capture device, kW; h 2 is the enthalpy of carbon dioxide at the compressor outlet, kJ / kg; h 1 is the enthalpy of carbon dioxide at the compressor inlet, kJ / kg; η ch is the compressor efficiency, %.

[0067] Specifically, the calculation formula for the heat transfer fluid flow rate in the first working fluid pump is:

[0068]

[0069] In the formula, m c is the mass flow rate of the heat transfer fluid in the first working fluid pump, kg / s; h 20 is the enthalpy of carbon dioxide at the cooler outlet, kJ / kg; η ex1 is the heat transfer efficiency of the cooler, %; h 5 is the enthalpy of the heat transfer fluid at the outlet of the first working fluid pump, kJ / kg; h 6 is the enthalpy of the heat transfer fluid at the cooler outlet, kJ / kg.

[0070] During the energy release stage, the mass flow rate of carbon dioxide in the expander of the carbon dioxide energy storage system is controlled so that the actual grid power of the coal-fired unit is equal to the power demanded by the grid.

[0071] Specifically, the calculation formula for the mass flow rate of carbon dioxide in the expander is:

[0072]

[0073] In the formula, m disch is the mass flow rate of carbon dioxide in the expander, kg / s; P 2 is the current power generation of the coal-fired unit, kW; P 1 is the target grid-connected power of coal-fired units, kW; P 02 The power consumed by the CO2 capture device and the CO2 compression device, kW; h 3 is the enthalpy of carbon dioxide at the expander inlet, kJ / kg; h 4 is the enthalpy of carbon dioxide at the expander outlet, kJ / kg; η disch is the expansion power generation efficiency, %.

[0074] Specifically, the calculation formula for the heat transfer fluid flow rate in the second working fluid pump is:

[0075]

[0076] In the formula, m h is the mass flow rate of the heat transfer fluid in the second working fluid pump, kg / s; h 30 is the enthalpy of carbon dioxide at the heater inlet, kJ / kg; η ex2 is the heat transfer efficiency of the heater, %; h 7 is the enthalpy of the heat transfer fluid at the outlet of the second working fluid pump, kJ / kg; h 8 is the enthalpy of the heat transfer fluid at the heater outlet, kJ / kg.

[0077] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A peak-shaving power generation system of a coal-fired unit coupled with carbon dioxide energy storage, characterized in that: The invention comprises a coal-fired unit, a carbon dioxide capture device and a carbon dioxide energy storage device, wherein the coal-fired unit, the carbon dioxide capture device and the carbon dioxide energy storage device are connected in sequence; the carbon dioxide capture device uses the electricity and steam generated by the coal-fired unit to capture carbon dioxide in the flue gas emitted by the coal-fired unit; the carbon dioxide energy storage device uses the electricity generated by the coal-fired unit to compress and store the carbon dioxide captured by the carbon dioxide capture device; The carbon dioxide energy storage device includes a carbon dioxide compression device and a carbon dioxide expansion power generation device, which operate independently; when the power grid is under low load, the operation level of the carbon dioxide capture device is improved, and the captured carbon dioxide is sent to the carbon dioxide compression device for compression and energy storage using surplus electric energy; when the power grid is under high load, the operation levels of the carbon dioxide capture device and the carbon dioxide compression device are reduced, and the carbon dioxide expansion power generation device is used to expand the stored carbon dioxide to do work, thereby increasing the power generation power.

2. The peak-shaving power generation system of a coal-fired unit according to claim 1, characterized in that: The carbon dioxide energy storage device comprises a low-pressure gas storage bin (3), a compressor (4), a cooler (8), a high-pressure storage tank (5), a heater (11), an expander (6), a generator (15), a cold storage tank (10), a first working fluid pump (9), a second working fluid pump (12), a heat storage tank (13) and a storage space (7); The cold storage tank (10), the first working fluid pump (9), the cooler (8), the heat storage tank (13), the second working fluid pump (12) and the heater (11) are connected end to end in sequence to form a closed loop; the expander (6) is connected to the generator (15); the high-pressure storage tank (5) is connected to the storage space (7); when the high-pressure storage tank (5) reaches the maximum storage capacity, the excess carbon dioxide is stored in the storage space (7); The low-pressure gas storage bin (3) and the high-pressure storage tank (5) are equipped with a pressure detector and a leakage detection device; In the energy storage stage, the carbon dioxide from the carbon dioxide capture device (2) is first compressed by the compressor (4), cooled by the cooler (8) and then stored in the high-pressure storage tank (5). At the same time, the first working fluid pump (9) drives the working fluid in the cold storage tank (10) to absorb heat in the cooler (8) and then enter the heat storage tank (13) for storage. In the energy release stage, the carbon dioxide in the high-pressure storage tank (5) is heated by the heater (11) and then expanded by the expander (6) to perform work, thereby driving the generator (15) to generate electricity. The expanded carbon dioxide enters the low-pressure gas storage tank (3) for storage. At the same time, the second working fluid pump (12) drives the working fluid in the heat storage tank (13) to enter the cold storage tank (10) for storage after the heater (11) releases heat.

3. The peak-shaving power generation system of a coal-fired unit according to claim 2, characterized in that: The compression, cooling, heating and expansion are multi-stage processes.

4. The peak-shaving power generation system of a coal-fired unit according to claim 2, characterized in that: The heat storage medium in the cold storage tank (10) and the heat storage tank (13) is water, heat transfer oil or molten salt.

5. The method for operating the peak-shaving power generation system of a coal-fired unit according to any one of claims 1 to 4, characterized in that: include: Step 1, determine whether the actual grid power of the coal-fired unit is greater than the grid demand power, if yes, proceed to step 2; If no, proceed to step 5. Step 2, determine whether the power generation capacity of the coal-fired unit is higher than the minimum guaranteed power generation capacity, if yes, reduce the power generation capacity of the coal-fired unit; if no, execute step 3; Step 3, determining whether the carbon dioxide capture device and the carbon dioxide compression device are at the highest operating level; if not, increasing the operating level of the carbon dioxide capture device and the carbon dioxide compression device; Step 4, determining whether the high-pressure storage tank has reached the maximum storage capacity, if yes, storing the excess carbon dioxide in the storage space; Step 5, determine whether the actual grid power of the coal-fired unit is less than the grid demand power, if yes, execute step 6; Step 6, determine whether the coal-fired unit is in full load power generation state, if yes, execute step 7; No, increase the power generation capacity of coal-fired units; Step 7, determine whether the carbon dioxide capture device and the carbon dioxide compression device are at the lowest operating level. If yes, start the carbon dioxide expansion power generation device to start releasing energy; if no, reduce the operating level of the carbon dioxide capture device and the carbon dioxide compression device.

6. The operating method according to claim 5, characterized in that: During the energy storage process, the high-pressure storage tank is set with a maximum storage capacity. When the carbon dioxide capacity in the high-pressure storage tank reaches the maximum storage capacity, the excess carbon dioxide needs to be stored in the storage space, which is used as a carbon dioxide storage area to provide carbon dioxide to external users.

7. The operating method according to claim 5, characterized in that: During the energy storage stage, the mass flow rate of carbon dioxide of the compressor in the carbon dioxide energy storage device is controlled so that the power generation power of the coal-fired unit is not lower than the minimum guaranteed power generation power, and the actual grid power of the coal-fired unit is equal to the power demanded by the grid.

8. The operating method according to claim 7, characterized in that: The calculation formula for the mass flow rate of carbon dioxide in the compressor is: In the formula, m ch is the mass flow rate of carbon dioxide in the compressor, kg / s; P2 is the current power generation power of the coal-fired unit, kW; P1 is the target grid-connected power of the coal-fired unit, kW; P 01 is the power consumption of the carbon dioxide capture device, kW; h2 is the enthalpy of carbon dioxide at the compressor outlet, kJ / kg; h1 is the enthalpy of carbon dioxide at the compressor inlet, kJ / kg; η ch is the compressor efficiency, %; In the carbon dioxide energy storage device, the calculation formula for the heat transfer fluid flow in the first working fluid pump is: In the formula, m c is the mass flow rate of the heat transfer fluid in the first working fluid pump, kg / s; h 20 is the enthalpy of carbon dioxide at the cooler outlet, kJ / kg; η ex1 is the heat exchange efficiency of the cooler, %; h5 is the enthalpy value of the heat transfer fluid at the outlet of the first working fluid pump, kJ / kg; h6 is the enthalpy value of the heat transfer fluid at the outlet of the cooler, kJ / kg.

9. The operating method according to claim 5, characterized in that: During the energy release stage, the mass flow rate of carbon dioxide in the expander in the carbon dioxide energy storage device is controlled so that the actual grid power of the coal-fired unit is equal to the power demanded by the grid.

10. The operating method according to claim 9, characterized in that: The calculation formula for the mass flow rate of carbon dioxide in the expander is: In the formula, m disch is the mass flow rate of carbon dioxide in the expander, kg / s; P2 is the current power generation power of the coal-fired unit, kW; P1 is the target grid-connected power of the coal-fired unit, kW; P 02 is the power consumed by the CO2 capture device and the CO2 compression device, kW; h3 is the enthalpy of CO2 at the inlet of the expander, kJ / kg; h4 is the enthalpy of CO2 at the outlet of the expander, kJ / kg; η disch is the expansion power generation efficiency, %; In the carbon dioxide energy storage device, the calculation formula for the heat transfer fluid flow in the second working fluid pump is: In the formula, m h is the mass flow rate of the heat transfer fluid in the second working fluid pump, kg / s; h 30 is the enthalpy of carbon dioxide at the heater inlet, kJ / kg; η ex2 is the heat exchange efficiency of the heater, %; h7 is the enthalpy value of the heat transfer fluid at the outlet of the second working fluid pump, kJ / kg; h8 is the enthalpy value of the heat transfer fluid at the outlet of the heater, kJ / kg.

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