Coal-fired power generation and carnot cell energy storage coupling system and operation method thereof

Abstract

The application discloses a coal-fired power generation and Carnot battery energy storage coupling system and an operation method thereof, and relates to the technical fields of coal-fired power generation and thermal energy storage. The system comprises a coal-fired power generation coupling storage tank system, a Carnot battery energy storage system and a Carnot battery energy release system. During a low electricity consumption valley, a coal-fired power generating unit maintains existing load unchanged, and redundant electric energy is input into the Carnot battery energy storage system through a motor, and finally, the electric energy is converted into heat energy of a heat storage medium and stored in different storage tanks. When electricity consumption peaks, the heat load of a boiler remains unchanged, the heat of a bypass feed water, newly added feed water and condensate water is used for heating, the output of the unit is improved, and the Carnot battery energy release system also generates part of electric energy by using the heat of the storage tank, and finally, the combined electric energy meets the electric load demand. The system can be expanded in a variable load range, and the efficiency of the variable load process can be ensured, the purpose of high efficiency and flexibility is achieved, and the system is an effective method for consumption of new energy and suppression of power grid fluctuation.

Description

Technical Field

[0001] This invention relates to the fields of coal-fired power generation and energy storage technology, specifically to a coal-fired power generation and Carnot battery energy storage coupling system and its operation method. Background Technology

[0002] my country is accelerating the construction of a "clean, low-carbon, safe, and efficient" energy system, with the proportion of renewable energy gradually increasing. However, renewable energy power generation, such as wind and solar power, is mostly intermittent and volatile. Large-scale grid connection poses a significant challenge to the safety and stability of the power system, causing difficulties in the absorption of renewable energy power generation in my country, and resulting in serious wind and solar curtailment problems in some regions. Coal-fired power generating units are gradually shifting from being the main power source to a supporting and regulating power source, undertaking more peak-shaving and frequency regulation services. This leads to units operating under transient load changes for extended periods. How to achieve efficient and flexible coordination during load changes is a key issue that urgently needs to be addressed in the development of my country's power industry. The application of thermal energy storage technology can effectively support the innovation and breakthroughs in coal-fired power generation technology. Carnot battery energy storage technology, which uses heat pump cycles and power cycles to achieve value-added heating and thermoelectric conversion of electrical energy, is a highly promising high-efficiency large-scale thermal energy storage technology. Combining coal-fired power generation with Carnot battery energy storage technology is expected to achieve efficient and flexible coordination during load changes. However, there is currently a lack of design and operation control methods for the coupled configuration of coal-fired power generation and Carnot battery energy storage systems. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a coal-fired power generation and Carnot battery energy storage coupling system and its operation method. The system of the present invention can be extended to a variable load range and can ensure high efficiency during the variable load process, achieving the goal of high efficiency and flexible coordination. It is an effective method for absorbing new energy sources and smoothing grid fluctuations.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A coal-fired power generation and Carnot battery energy storage coupling system, characterized in that the coupling system comprises a coal-fired power generation coupling storage tank system, a Carnot battery energy storage system, and a Carnot battery energy release system; wherein...

[0006] The coal-fired power generation coupled storage tank system includes a boiler 1, a high-pressure cylinder 2, a medium and low-pressure cylinder 3, a coal-fired generator 4, a condenser 5, a low-pressure heater 6, a deaerator 7, a high-pressure heater 8, a molten salt storage tank 9, a thermal oil storage tank 10, a cold water storage tank 11, a multi-stage molten salt heat exchanger 12, a thermal oil-water heat exchanger 13, a condensate pump 14, a feed water pump 15, a molten salt pump #1 16, a thermal oil pump #1 17, a water pump #1 18, a first valve 19, a second valve 20, a third valve 21, a fourth valve 22, a fifth valve 23, a sixth valve 24, and a seventh valve. 25; In the coal-fired power generation coupled storage tank system, feedwater enters boiler 1, generates main steam, and then enters high-pressure cylinder 2. Part of the intermediate steam extraction from high-pressure cylinder 2 is used to heat the feedwater of high-pressure heater 8. The exhaust steam from high-pressure cylinder 2 returns to boiler 1 for reheating, generating reheat steam which then enters medium-low pressure cylinder 3. Part of the intermediate steam extraction from medium-low pressure cylinder 3 is used to heat the condensate in deaerator 7 and low-pressure heater 6. High-pressure cylinder 2 and medium-low pressure cylinder 3 are coaxially connected, transferring the generated mechanical energy to coal-fired generator 4 to generate electrical energy for output. The condensate from low-pressure heater 6 and the medium-low pressure cylinder... The exhaust steam from boiler 3 is incorporated into condenser 5, where it condenses to produce condensate. After passing through condensate pump 14, part of the condensate enters low-pressure heater 6 through second valve 20, while the other part enters heat transfer oil-water heat exchanger 13 through first valve 19. The two parts of condensate, along with condensate from high-pressure heater 8, then merge into deaerator 7, producing saturated feedwater. This feedwater is then pumped through feedwater pump 15. Part of the feedwater passes through fourth valve 22 into high-pressure heater 8 and finally into boiler 1, while the other part passes through third valve 21, multi-stage molten salt heat exchanger 12, and fifth valve 13. 23. After generating new steam, it merges with the main steam from boiler 1 and then enters high-pressure cylinder 2, repeating this process. At the same time, medium-temperature molten salt enters molten salt storage tank 9 through molten salt pump 16. Molten salt from the outlet of molten salt storage tank 9 enters multi-stage molten salt heat exchanger 12 after passing through valve 24. Low-temperature heat transfer oil enters heat transfer oil storage tank 10 through heat transfer oil pump 17. Heat transfer oil from the outlet of heat transfer oil storage tank 10 enters heat transfer oil-water heat exchanger 13 after passing through valve 25. Water enters cold water storage tank 11 through water pump 18, and the generated low-temperature cold water enters condenser 5.

[0007] The Carnot battery energy storage system includes an electric motor 30, a multi-stage charging compressor 31, a molten salt-working fluid heat exchanger 32, a thermal oil-working fluid heat exchanger 33, a charging expander 34, a water-working fluid heat exchanger 35, a molten salt pump 36, a thermal oil pump 37, and a water pump 38. In the Carnot battery energy storage system, externally input electricity generates mechanical energy in the electric motor 30, driving the multi-stage charging compressor 31. The ambient temperature, low-pressure working fluid passes through the multi-stage charging compressor 31, producing a high-temperature, high-pressure working fluid, which then enters the molten salt-working fluid heat exchanger 32 and the thermal oil-working fluid heat exchanger 33. The low-temperature, high-pressure working fluid at the outlet of the mass heat exchanger 33 continues to do work in the charging expander 34, producing a low-temperature, low-pressure working fluid. This fluid absorbs heat in the water-working fluid heat exchanger 35 and eventually returns to the ambient temperature, low-pressure working fluid, repeating this process. Simultaneously, the medium-temperature molten salt passes through the molten salt pump 36 and the molten salt-working fluid heat exchanger 32 before entering the molten salt storage tank 9 to form high-temperature molten salt. The low-temperature heat transfer oil passes through the heat transfer oil pump 37 and the heat transfer oil-working fluid heat exchanger 33 before entering the heat transfer oil storage tank 10 to form medium-temperature heat transfer oil. The ambient temperature water passes through the water pump 38 and the water-working fluid heat exchanger 35 before entering the cold water storage tank 11 to form low-temperature cold water.

[0008] The Carnot battery energy release system includes a molten salt storage tank 9, a thermal oil storage tank 10, a cold water storage tank 11, a molten salt-working fluid heat exchanger 32, a thermal oil-working fluid heat exchanger 33, a water-working fluid heat exchanger 35, a discharge compressor 39, a multi-stage discharge expander 40, a Carnot battery generator 41, a molten salt pump 42, a thermal oil pump 43, a water pump 44, and an auxiliary heat exchanger 45. In the Carnot battery energy release system, the low-temperature, low-pressure working fluid is converted into a room-temperature, high-pressure working fluid after passing through the discharge compressor 39. This working fluid then passes sequentially through the thermal oil-working fluid heat exchanger 33 and the molten salt-working fluid heat exchanger 32 to generate a high-temperature, high-pressure working fluid. Finally, it performs work in the multi-stage discharge expander 40, producing… Biomechanical energy is converted into electrical energy in the Carnot battery generator 41 and output to the outside; the ambient temperature low-pressure working fluid after passing through the multi-stage discharge expander 40 releases heat in the auxiliary heat exchanger 45, then enters the water-working fluid heat exchanger 35, and finally returns to the low temperature low-pressure working fluid, repeating this process; at the same time, the high temperature molten salt passes through the No. 3 molten salt pump 42 and the molten salt-working fluid heat exchanger 32 in sequence and enters the molten salt storage tank 9 to form medium temperature molten salt; the medium temperature heat transfer oil passes through the No. 3 heat transfer oil pump 43 and the heat transfer oil-working fluid heat exchanger 33 in sequence and enters the heat transfer oil storage tank 10 to form low temperature heat transfer oil; the low temperature cold water passes through the No. 3 water pump 44 and the water-working fluid heat exchanger 35 in sequence and enters the cold water storage tank 11 to form ambient temperature water.

[0009] Furthermore, the molten salt storage tank 9 uses a ternary molten salt, namely 30% LiNO3, 18% NaNO3 and 52% KNO3 by mass, as the heat storage medium, with an operating temperature range of 130 to 550°C; the heat transfer oil storage tank 10 uses a eutectic mixture, namely 26.5% biphenyl and 73.5% diphenyl ether by mass, as the heat storage medium, with an operating temperature range of 25 to 170°C; and the cold water storage tank 11 uses atmospheric pressure water as the heat storage medium, with an operating temperature range of 10 to 45°C.

[0010] Furthermore, the Carnot battery energy storage system and the Carnot battery energy release system use nitrogen as the working fluid, adopt the Brayton cycle, and have a maximum operating temperature of 550°C and a minimum operating temperature of 5°C.

[0011] Furthermore, the multi-stage charging compressor 31 consists of at least four stages of compressors, adopts centrifugal compressors, and has an inlet-outlet combined pressure ratio of 10.5; the multi-stage discharging expander 40 consists of at least three stages of expanders, adopts axial flow expanders, and has an inlet-outlet expansion ratio of 7.8.

[0012] Furthermore, the electric motor 30, the multi-stage charging compressor 31, and the charging expander 34 are coaxially connected; the discharging compressor 39, the multi-stage discharging expander 40, and the Carnot battery generator 41 are coaxially connected.

[0013] Furthermore, the molten salt storage tank 9, the heat transfer oil storage tank 10, and the cold water storage tank 11 are all thermocline tanks, with the upper part of the tank containing a high-temperature medium and the lower part containing a low-temperature medium; at the same time, all three tanks include two inlets and two outlets.

[0014] Furthermore, the multi-stage molten salt heat exchanger 12 includes three stages: a molten salt-feedwater heater, a molten salt-steam generator, and a molten salt-steam heater.

[0015] The operation method of the coal-fired power generation and Carnot battery energy storage coupling system is characterized by:

[0016] 1) During periods of low electricity demand, the coal-fired power generating unit maintains its existing load, while its coupled storage tank system temporarily shuts down. Most of the electrical energy output from the coal-fired power generating unit 4 is used as the input source for the motor 30 in the Carnot battery energy storage system. The Carnot battery energy storage system converts excess electrical energy into heat energy for storage. Specifically, the third valve 21 and the fifth valve 23 on the feedwater bypass leading to the multi-stage molten salt heat exchanger 12 are closed, the No. 1 molten salt pump 16 is shut down, and the sixth valve 24 on the molten salt entering the multi-stage molten salt heat exchanger 12 is closed. The first valve 19 on the condensate entering the heat transfer oil-water heat exchanger 13 is closed, and the No. 1 heat transfer oil pump is shut down. Pump 17 closes the seventh valve 25 on the branch of the heat transfer oil entering the heat transfer oil-water heat exchanger 13; the amount of coal entering the boiler 1 of the coal-fired generator set remains unchanged, and the turbine operating condition fluctuates only slightly, then remains at a high load to ensure high power generation efficiency. The exhaust steam of this coal-fired generator set is no longer cooled by a cooling tower, but is directly cooled by the cold water generated by the Carnot battery energy storage system; the motor 30 in the Carnot battery energy storage system drives the multi-stage charging compressor 31 to work, converting the excess electrical energy of the coal-fired power generation and Carnot battery energy storage coupling system into the thermal energy of three heat storage media, which are finally stored in the molten salt tank 9, the heat transfer oil tank 10 and the cold water tank 11 respectively;

[0017] 2) During peak electricity consumption, the coal-fired power generation coupled storage tank system and the Carnot battery energy release system operate normally. The third valve 21 and the fifth valve 23 on the feedwater bypass leading to the multi-stage molten salt heat exchanger 12 are opened, and the No. 1 molten salt pump 16 is started. The sixth valve 24 on the molten salt entering the multi-stage molten salt heat exchanger 12 is opened. At this time, the feedwater entering the high-pressure heater 8 of the coal-fired generator unit decreases, and the expelled steam returns to the high-pressure cylinder 2 to further perform work, increasing the turbine output. Simultaneously, the feedwater entering the boiler 1 remains unchanged. The increased feedwater volume due to the increased power of the feedwater pump 15 is heated through the multi-stage molten salt heat exchanger 12. The resulting new steam mixes with the steam at the boiler 1 outlet and enters the turbine to perform work, significantly increasing the turbine's power generation. The first valve 19 on the condensate entering the thermal oil-water heat exchanger 13 is opened, and the No. 1 thermal oil pump 1 is started. 7. Open the seventh valve 25 on the branch of the heat transfer oil-water heat exchanger 13. At this time, the amount of condensate entering the low-pressure heater 6 of the coal-fired generator set is reduced, and the exhaust steam returns to the intermediate and low-pressure cylinder 3 to do more work, increasing the output of the steam turbine. The exhaust steam of this coal-fired generator set is no longer cooled by the cooling tower, but is directly cooled by the cold water generated by the Carnot battery energy storage system. In the Carnot battery energy release system, the working fluid is pressurized by the discharge compressor 39. Then, the working fluid absorbs the heat storage medium in the heat transfer oil storage tank 10 and the molten salt storage tank 9 in the heat transfer oil-working fluid heat exchanger 33 and the molten salt-working fluid heat exchanger 32, respectively, to generate high temperature and high pressure working fluid. It does work in the multi-stage discharge expander 40 and generates mechanical energy, which is converted into electrical energy in the Carnot battery generator 41 and output to the outside. After being added with the electrical energy of the coal-fired generator 4, it meets the electrical load requirements.

[0018] Furthermore, when the Carnot battery energy storage system is running, the molten salt tank 9, the heat transfer oil tank 10, and the cold water tank 11 operate for 10 hours; when the Carnot battery energy release system is running, the molten salt tank 9, the heat transfer oil tank 10, and the cold water tank 11 operate for 5.5 hours.

[0019] Furthermore, during peak electricity consumption periods, to ensure higher efficiency of the coal-fired power generation and Carnot battery energy storage coupling system, 56% of the heat stored in molten salt tank 9 is used for the coal-fired power generation unit and 44% for the Carnot battery energy release system; 68% of the heat stored in thermal oil tank 10 is used for the coal-fired power generation unit and 32% for the Carnot battery energy release system; and 81% of the cold energy stored in cold water tank 11 is used for the coal-fired power generation unit and 19% for the Carnot battery energy release system.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) Because the Carnot battery energy storage system is used to absorb the excess power of the grid, the coal-fired generator set can always operate at a high load during the load change process, and the operating parameters of each equipment of the unit are close to the design value, thus ensuring the high efficiency of the coal-fired generator set.

[0022] (2) By integrating coal-fired power generation with Carnot battery energy storage, the range of load increase and decrease can be greatly expanded, and the peak shaving depth can be improved.

[0023] (3) The cold end of the coal-fired power generation unit is cooled by low-temperature water in a cold water storage tank, which reduces the investment in cooling towers or air-cooled islands, making it more technically and economically advantageous, and is not limited by geographical location. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a coal-fired power generation system and a Carnot battery energy storage system during off-peak electricity demand, along with their operating modes.

[0025] Figure 2 This is a schematic diagram of the coal-fired power generation system and the Carnot battery energy release system during peak electricity demand, as well as their operation modes. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] like Figure 1 and Figure 2 As shown, this invention provides a coal-fired power generation and Carnot battery energy storage coupling system, which includes a coal-fired power generation coupling tank system, a Carnot battery energy storage system, and a Carnot battery energy release system; wherein,

[0028] In the coal-fired power generation coupled storage tank system, feedwater enters boiler 1, generates main steam, and then enters high-pressure cylinder 2. Part of the intermediate steam extracted from high-pressure cylinder 2 is used to heat the feedwater of high-pressure heater 8. The exhaust steam from high-pressure cylinder 2 returns to boiler 1 for reheating, generating reheat steam which then enters medium-low pressure cylinder 3. Part of the intermediate steam extracted from medium-low pressure cylinder 3 is used to heat the condensate in deaerator 7 and low-pressure heater 6. High-pressure cylinder 2 and medium-low pressure cylinder 3 are coaxially connected, transferring the generated mechanical energy to coal-fired generator 4 to generate electrical energy for output. The condensate from low-pressure heater 6 and the exhaust steam from medium-low pressure cylinder 3 are combined into condenser 5, where condensate is produced. After passing through condensate pump 14, part of the condensate enters low-pressure heater 6 through second valve 20, and the other part enters heat transfer oil-water heat exchanger 13 through first valve 19. The two parts of condensate then combine with the steam from high-pressure heater 6... The condensate from heater 8 flows into deaerator 7, where it generates saturated feedwater. This feedwater is then pumped by feedwater pump 15. Part of the feedwater passes through fourth valve 22 into high-pressure heater 8, and finally into boiler 1. The other part passes through third valve 21, multi-stage molten salt heat exchanger 12, and fifth valve 23, generating new steam which merges with the main steam from boiler 1 before entering high-pressure cylinder 2. This process is repeated. Simultaneously, medium-temperature molten salt flows through molten salt pump 16 into molten salt storage tank 9. Molten salt from tank 9 exits through sixth valve 24 before entering multi-stage molten salt heat exchanger 12. Low-temperature thermal oil flows through thermal oil pump 17 into thermal oil storage tank 10. Thermal oil from tank 10 exits through seventh valve 25 before entering thermal oil-water heat exchanger 13. Water flows through water pump 18 into cold water storage tank 11, where the generated low-temperature cold water enters condenser 5.

[0029] In the Carnot battery energy storage system, externally input electricity generates mechanical energy in the motor 30, driving the multi-stage charging compressor 31. The ambient temperature, low-pressure working fluid passes through the multi-stage charging compressor 31, producing a high-temperature, high-pressure working fluid, which then enters the molten salt-working fluid heat exchanger 32 and the thermal oil-working fluid heat exchanger 33. The low-temperature, high-pressure working fluid at the outlet of the thermal oil-working fluid heat exchanger 33 continues to perform work in the charging expander 34, producing a low-temperature, low-pressure working fluid, which then enters the water-working fluid heat exchanger 35. The medium-temperature molten salt absorbs heat and eventually returns to the ambient temperature and low pressure working fluid, repeating this process. At the same time, the medium-temperature molten salt passes through the No. 2 molten salt pump 36 and the molten salt-working fluid heat exchanger 32 in sequence before entering the molten salt storage tank 9 to form high-temperature molten salt. The low-temperature heat transfer oil passes through the No. 2 heat transfer oil pump 37 and the heat transfer oil-working fluid heat exchanger 33 in sequence before entering the heat transfer oil storage tank 10 to form medium-temperature heat transfer oil. The ambient temperature water passes through the No. 2 water pump 38 and the water-working fluid heat exchanger 35 in sequence before entering the cold water storage tank 11 to form low-temperature cold water.

[0030] In the Carnot battery energy release system, the low-temperature, low-pressure working fluid is converted into a room-temperature, high-pressure working fluid after passing through the discharge compressor 39. This working fluid then sequentially passes through the heat transfer oil-working fluid heat exchanger 33 and the molten salt-working fluid heat exchanger 32 to generate a high-temperature, high-pressure working fluid. It then performs work in the multi-stage discharge expander 40, generating mechanical energy which is converted into electrical energy in the Carnot battery generator 41 and output externally. The room-temperature, low-pressure working fluid after passing through the multi-stage discharge expander 40 releases heat in the auxiliary heat exchanger 45, and then enters the water- The working fluid heat exchanger 35 eventually returns to the low-temperature, low-pressure working fluid, repeating this process; at the same time, the high-temperature molten salt passes through the molten salt pump 42 and the molten salt-working fluid heat exchanger 32 in sequence before entering the molten salt storage tank 9 to form medium-temperature molten salt; the medium-temperature heat transfer oil passes through the heat transfer oil pump 43 and the heat transfer oil-working fluid heat exchanger 33 in sequence before entering the heat transfer oil storage tank 10 to form low-temperature heat transfer oil; the low-temperature cold water passes through the water pump 44 and the water-working fluid heat exchanger 35 in sequence before entering the cold water storage tank 11 to form room-temperature water.

[0031] Furthermore, the molten salt storage tank 9 uses a ternary molten salt (30% LiNO3 + 18% NaNO3 + 52% KNO3 by mass) as the heat storage medium, with an operating temperature range of 130–550℃; the heat transfer oil storage tank 10 uses a eutectic mixture (26.5% biphenyl and 73.5% diphenyl ether by mass) as the heat storage medium, with an operating temperature range of 25–170℃; and the cold water storage tank 11 uses atmospheric pressure water as the heat storage medium, with an operating temperature range of 10–45℃. This fully utilizes the temperature characteristics of the heat storage medium, maximizing the initial temperature and thus improving the overall electro-electric efficiency.

[0032] Furthermore, the Carnot battery energy storage system and Carnot battery energy release system use nitrogen as the working fluid, employing a Brayton cycle, with a maximum operating temperature of 550°C and a minimum operating temperature of 5°C. This allows for full utilization of the heat storage temperature ranges of different heat storage media and enables temperature matching between the working fluid and the heat storage medium, resulting in the highest heat exchanger efficiency.

[0033] Furthermore, the multi-stage charging compressor 31 consists of at least four stages, employing a centrifugal compressor, with an inlet-outlet combined pressure ratio of up to 10.5; the multi-stage discharging expander 40 consists of at least three stages, employing an axial flow expander, with an inlet-outlet expansion ratio of up to 7.8. In this way, the efficiency of the Carnot battery energy storage system and the Carnot battery energy release system can be maximized.

[0034] Furthermore, the electric motor 30, the multi-stage charging compressor 31, and the charging expander 34 are coaxially connected; the discharging compressor 39, the multi-stage discharging expander 40, and the Carnot battery generator 41 are coaxially connected. This ensures that the Carnot battery energy storage system directly receives net input electrical energy from the outside, and the Carnot battery energy release system directly outputs net output electrical energy to the outside.

[0035] Furthermore, the molten salt storage tank 9, the heat transfer oil storage tank 10, and the cold water storage tank 11 are all thermocline tanks, with the upper part containing the high-temperature medium and the lower part containing the low-temperature medium; at the same time, all three tanks need to include two inlets and two outlets. This ensures that the Carnot battery energy storage system and the Carnot battery energy release system operate independently without interfering with each other.

[0036] Furthermore, the multi-stage molten salt heat exchanger 12 comprises three stages: a molten salt-feedwater heater, a molten salt-steam generator, and a molten salt-steam heater. This effectively matches the single-phase and phase change processes of feedwater generating steam, improving the energy efficiency of the heat exchanger.

[0037] An operation method for a coal-fired power generation and Carnot battery energy storage coupling system: 1) When the electricity demand is low, the coal-fired power generation unit maintains its existing load operation, and its coupled storage tank system temporarily stops working. Most of the electrical energy output by the coal-fired power generation unit through the coal-fired generator 4 is used as the input source of the motor 30 in the Carnot battery energy storage system. The Carnot battery energy storage system is used to convert the excess electrical energy into heat energy for storage. Specifically, the third valve 21 and the fifth valve 23 on the feedwater bypass entering the multi-stage molten salt heat exchanger 12 branch are closed, the No. 1 molten salt pump 16 is stopped, and the sixth valve 24 on the molten salt entering the multi-stage molten salt heat exchanger 12 branch is closed; the first valve on the condensate entering the heat transfer oil-water heat exchanger 13 branch is closed. Door 19, shut down No. 1 heat transfer oil pump 17, and close the seventh valve 25 on the branch line of heat transfer oil entering heat transfer oil-water heat exchanger 13; the amount of coal entering the boiler 1 of the coal-fired generator set does not change, and the turbine operating condition only fluctuates slightly, and then maintains a high load condition to ensure high power generation efficiency. The exhaust steam of this coal-fired generator set is no longer cooled by a cooling tower, but is directly cooled by the cold water generated by the Carnot battery energy storage system; in the Carnot battery energy storage system, the motor 30 drives the multi-stage charging compressor 31 to work, converting the excess electrical energy of the coal-fired power generation and Carnot battery energy storage coupling system into the thermal energy of three heat storage media, which are finally stored in the molten salt storage tank 9, the heat transfer oil storage tank 10 and the cold water storage tank 11 respectively;

[0038] 2) During peak electricity consumption, the coal-fired power generation coupled storage tank system and the Carnot battery energy release system operate normally. The third valve 21 and the fifth valve 23 on the feedwater bypass leading to the multi-stage molten salt heat exchanger 12 are opened, and the No. 1 molten salt pump 16 is started. The sixth valve 24 on the molten salt entering the multi-stage molten salt heat exchanger 12 is opened. At this time, the feedwater entering the high-pressure heater 8 of the coal-fired power generation unit decreases, and the expelled steam returns to the high-pressure cylinder 2 to further perform work, increasing the turbine output. Simultaneously, the feedwater entering the boiler 1 remains unchanged. The increased feedwater volume due to the increased power of the feedwater pump 15 is heated through the multi-stage molten salt heat exchanger 12. The resulting new steam mixes with the steam at the boiler 1 outlet and enters the turbine to perform work, significantly increasing the turbine's power generation. The first valve 19 on the condensate entering the thermal oil-water heat exchanger 13 is opened, and the No. 1 thermal oil pump is started. 17. Open the seventh valve 25 on the branch of the heat transfer oil-water heat exchanger 13. At this time, the amount of condensate entering the low-pressure heater 6 of the coal-fired generator set is reduced, and the exhaust steam returns to the intermediate and low-pressure cylinder 3 to do more work, increasing the output of the steam turbine. The exhaust steam of this coal-fired generator set is no longer cooled by the cooling tower, but is directly cooled by the cold water generated by the Carnot battery energy storage system. In the Carnot battery energy release system, the working fluid is pressurized by the discharge compressor 39. Then, the working fluid absorbs the heat storage medium in the heat transfer oil storage tank 10 and the molten salt storage tank 9 in the heat transfer oil-working fluid heat exchanger 33 and the molten salt-working fluid heat exchanger 32, respectively, to generate high temperature and high pressure working fluid. It does work in the multi-stage discharge expander 40 and generates mechanical energy, which is converted into electrical energy in the Carnot battery generator 41 and output to the outside. After being added with the electrical energy of the coal-fired generator 4, it meets the electrical load requirements.

[0039] Furthermore, during the operation of the Carnot battery energy storage system, the molten salt tank 9, the thermal oil tank 10, and the cold water tank 11 operate for 10 hours; during the operation of the Carnot battery energy release system, the molten salt tank 9, the thermal oil tank 10, and the cold water tank 11 operate for 5.5 hours. This ensures that within one heat storage-release cycle, the heat stored in the molten salt tank 9, the thermal oil tank 10, and the cold water tank 11 is sufficient for the Carnot battery energy release system to utilize, and can meet different rate requirements.

[0040] Furthermore, during peak electricity consumption periods, to ensure higher efficiency of the coal-fired power generation and Carnot battery energy storage coupling system, 56% of the heat stored in molten salt tank 9 is used for the coal-fired power generation unit and 44% for the Carnot battery energy release system; 68% of the heat stored in thermal oil tank 10 is used for the coal-fired power generation unit and 32% for the Carnot battery energy release system; and 81% of the cold energy stored in cold water tank 11 is used for the coal-fired power generation unit and 19% for the Carnot battery energy release system.

Claims

1. A coal-fired power generation and Carnot battery energy storage coupling system, characterized in that, The coupling system includes a coal-fired power generation coupled storage tank system, a Carnot battery energy storage system, and a Carnot battery energy release system; wherein, The coal-fired power generation coupled storage tank system includes a boiler (1), a high-pressure cylinder (2), a medium and low-pressure cylinder (3), a coal-fired generator (4), a condenser (5), a low-pressure heater (6), a deaerator (7), a high-pressure heater (8), a molten salt storage tank (9), a thermal oil storage tank (10), a cold water storage tank (11), a multi-stage molten salt heat exchanger (12), a thermal oil-water heat exchanger (13), a condensate pump (14), a feed water pump (15), a molten salt pump (16), a thermal oil pump (17), a water pump (18), a first valve (19), a second valve (20), a third valve (21), a fourth valve (22), and a fifth valve (23). The sixth valve (24) and the seventh valve (25); in the coal-fired power generation coupled storage tank system, feedwater enters the boiler (1), generates main steam, and then enters the high-pressure cylinder (2). Part of the intermediate steam extraction in the high-pressure cylinder (2) is used to heat the feedwater of the high-pressure heater (8). The exhaust steam of the high-pressure cylinder (2) returns to the boiler (1) for heating, generates reheat steam, and then enters the medium-low pressure cylinder (3). Part of the intermediate steam extraction in the medium-low pressure cylinder (3) is used to heat the condensate in the deaerator (7) and the low-pressure heater (6); the high-pressure cylinder (2) and the medium-low pressure cylinder (3) are coaxially connected, and the generated mechanical energy is transferred to the coal-fired generator (4) to generate electrical energy for output; the low-pressure heater (6) The condensate and exhaust steam from the low-pressure cylinder (3) are combined into the condenser (5), where condensate is generated. After passing through the condensate pump (14), part of the condensate enters the low-pressure heater (6) through the second valve (20), and the other part enters the heat transfer oil-water heat exchanger (13) through the first valve (19). Then, the two parts of condensate and the condensate from the high-pressure heater (8) are combined and enter the deaerator (7). After generating saturated feedwater, it is pumped through the feedwater pump (15). Part of the feedwater enters the high-pressure heater (8) through the fourth valve (22) and finally enters the boiler (1). The other part of the feedwater passes through the third valve (21), the multi-stage molten salt heat exchanger (12), and the third stage heat exchanger (13). After generating new steam, the five valves (23) combine with the main steam from the boiler (1) and then enter the high-pressure cylinder (2), repeating this process. At the same time, the medium-temperature molten salt enters the molten salt storage tank (9) through the molten salt pump (16), and the molten salt at the outlet of the molten salt storage tank (9) enters the multi-stage molten salt heat exchanger (12) after passing through the sixth valve (24). The low-temperature heat transfer oil enters the heat transfer oil storage tank (10) through the heat transfer oil pump (17), and the heat transfer oil at the outlet of the heat transfer oil storage tank (10) enters the heat transfer oil-water heat exchanger (13) after passing through the seventh valve (25). The water enters the cold water storage tank (11) after passing through the water pump (18), and the generated low-temperature cold water enters the condenser (5). The Carnot battery energy storage system includes an electric motor (30), a multi-stage charging compressor (31), a molten salt-working fluid heat exchanger (32), a thermal oil-working fluid heat exchanger (33), a charging expander (34), a water-working fluid heat exchanger (35), a molten salt pump (36), a thermal oil pump (37), and a water pump (38). In the Carnot battery energy storage system, externally input electricity generates mechanical energy in the electric motor (30), which drives the multi-stage charging compressor (31) to work. The low-pressure working fluid at room temperature passes through the multi-stage charging compressor (31) to generate a high-temperature and high-pressure working fluid, which then enters the molten salt-working fluid heat exchanger (32) and the thermal oil-working fluid heat exchanger (33). - The low-temperature, high-pressure working fluid at the outlet of the working fluid heat exchanger (33) continues to do work in the charging expander (34), producing a low-temperature, low-pressure working fluid. It absorbs heat in the water-working fluid heat exchanger (35) and eventually returns to the ambient temperature, low-pressure working fluid, repeating this process. Meanwhile, the medium-temperature molten salt passes through the No. 2 molten salt pump (36) and the molten salt-working fluid heat exchanger (32) in sequence and enters the molten salt storage tank (9) to form high-temperature molten salt. The low-temperature heat transfer oil passes through the No. 2 heat transfer oil pump (37) and the heat transfer oil-working fluid heat exchanger (33) in sequence and enters the heat transfer oil storage tank (10) to form medium-temperature heat transfer oil. The ambient temperature water passes through the No. 2 water pump (38) and the water-working fluid heat exchanger (35) in sequence and enters the cold water storage tank (11) to form low-temperature cold water. The Carnot battery energy release system includes a molten salt storage tank (9), a thermal oil storage tank (10), a cold water storage tank (11), a molten salt-working fluid heat exchanger (32), a thermal oil-working fluid heat exchanger (33), a water-working fluid heat exchanger (35), a discharge compressor (39), a multi-stage discharge expander (40), a Carnot battery generator (41), a No. 3 molten salt pump (42), a No. 3 thermal oil pump (43), a No. 3 water pump (44), and an auxiliary heat exchanger (45). In the Carnot battery energy release system, the low-temperature, low-pressure working fluid generates a room-temperature, high-pressure working fluid after passing through the discharge compressor (39), and then passes through the thermal oil-working fluid heat exchanger (33) and the molten salt-working fluid heat exchanger (32) in sequence to generate a high-temperature, high-pressure working fluid, which is then discharged in the multi-stage discharge expander (40). Work is done, and mechanical energy is generated and converted into electrical energy in the Carnot battery generator (41) and output to the outside. The ambient temperature low pressure working fluid after passing through the multi-stage discharge expander (40) releases heat in the auxiliary heat exchanger (45), and then enters the water-working fluid heat exchanger (35), and finally returns to the low temperature low pressure working fluid, repeating this process. At the same time, the high temperature molten salt passes through the No. 3 molten salt pump (42) and the molten salt-working fluid heat exchanger (32) in sequence and enters the molten salt storage tank (9) to form medium temperature molten salt. The medium temperature heat transfer oil passes through the No. 3 heat transfer oil pump (43) and the heat transfer oil-working fluid heat exchanger (33) in sequence and enters the heat transfer oil storage tank (10) to form low temperature heat transfer oil. The low temperature cold water passes through the No. 3 water pump (44) and the water-working fluid heat exchanger (35) in sequence and enters the cold water storage tank (11) to form ambient temperature water.

2. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: Molten salt storage tank (9) uses ternary molten salt, namely 30% LiNO3, 18% NaNO3 and 52% KNO3 by mass percentage, as the heat storage medium, with an operating temperature range of 130~550℃; heat transfer oil storage tank (10) uses a eutectic mixture, namely 26.5% biphenyl and 73.5% diphenyl ether by mass percentage, as the heat storage medium, with an operating temperature range of 25~170℃; cold water storage tank (11) uses atmospheric pressure water as the heat storage medium, with an operating temperature range of 10~45℃.

3. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: The Carnot battery energy storage system and Carnot battery energy release system use nitrogen as the working fluid and adopt the Brayton cycle. The maximum operating temperature is 550℃ and the minimum operating temperature is 5℃.

4. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: The multi-stage charging compressor (31) consists of at least four stages of compressors, using centrifugal compressors, with an inlet-outlet comprehensive pressure ratio of 10.5; the multi-stage discharging expander (40) consists of at least three stages of expanders, using axial flow expanders, with an inlet-outlet expansion ratio of 7.

8.

5. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: The electric motor (30), the multi-stage charging compressor (31) and the charging expander (34) are coaxially connected; the discharge compressor (39), the multi-stage discharge expander (40) and the Carnot battery generator (41) are coaxially connected.

6. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: Molten salt tank (9), heat transfer oil tank (10) and cold water tank (11) are all thermocline tanks, with high-temperature medium in the upper part and low-temperature medium in the lower part; at the same time, all three tanks include two inlets and two outlets.

7. The coal-fired power generation and Carnot battery energy storage coupling system according to claim 1, characterized in that: The multi-stage molten salt heat exchanger (12) consists of three stages: molten salt-feed water heater, molten salt-steam generator and molten salt-steam heater.

8. The operation method of a coal-fired power generation and Carnot battery energy storage coupling system according to any one of claims 1 to 7, characterized in that: 1) When the electricity demand is low, the coal-fired generator set maintains its existing load and its coupled storage tank system temporarily stops working. Most of the electrical energy output by the coal-fired generator (4) is used as the input source of the motor (30) in the Carnot battery energy storage system. The Carnot battery energy storage system is used to convert the excess electrical energy into heat energy for storage. Specifically, the third valve (21) and the fifth valve (23) on the feedwater bypass into the multi-stage molten salt heat exchanger (12) are closed, the No. 1 molten salt pump (16) is shut down, the sixth valve (24) on the molten salt into the multi-stage molten salt heat exchanger (12) is closed, the first valve (19) on the condensate into the heat transfer oil-water heat exchanger (13) is closed, and the No. 1 pump is shut down. The heat transfer oil pump (17) closes the seventh valve (25) on the branch of the heat transfer oil entering the heat transfer oil-water heat exchanger (13); the amount of coal entering the coal-fired generator boiler (1) remains unchanged, the turbine operating condition fluctuates, and then it is maintained at a high load condition to ensure high power generation efficiency. The exhaust steam of this coal-fired generator no longer uses a cooling tower for cooling, but directly uses the cold water generated by the Carnot battery energy storage system for cooling; the motor (30) in the Carnot battery energy storage system drives the multi-stage charging compressor (31) to work, converting the excess electrical energy of the coal-fired power generation and Carnot battery energy storage coupling system into the thermal energy of three heat storage media, which are finally stored in the molten salt tank (9), the heat transfer oil tank (10) and the cold water tank (11) respectively; 2) When the power consumption is at its peak, the coal-fired power generation coupled storage tank system and the Carnot battery energy release system are working normally. The third valve (21) and the fifth valve (23) on the feedwater bypass into the multi-stage molten salt heat exchanger (12) branch are opened, the 1# molten salt pump (16) is started, and the sixth valve (24) on the molten salt into the multi-stage molten salt heat exchanger (12) branch is opened. At this time, the feedwater into the high-pressure heater (8) of the coal-fired power generation unit is reduced, and the exhaust steam returns to the high-pressure cylinder (2) to do more work, increasing the turbine output. At the same time, the feedwater into the boiler (1) does not change. The increased feedwater pump (15) power causes the increased feedwater to be heated through the multi-stage molten salt heat exchanger (12). The new steam generated is mixed with the steam at the boiler (1) outlet and enters the turbine to do work, increasing the turbine power generation. The first valve (19) on the condensate into the heat transfer oil-water heat exchanger (13) branch is opened, and the 1# heat transfer oil pump ( 17) Open the seventh valve (25) on the branch of the heat transfer oil entering the heat transfer oil-water heat exchanger (13). At this time, the amount of condensate entering the low-pressure heater (6) of the coal-fired generator set is reduced, and the exhaust steam returns to the medium and low pressure cylinder (3) to do more work, increasing the output of the steam turbine. The exhaust steam of this coal-fired generator set is no longer cooled by the cooling tower, but is directly cooled by the cold water generated by the Carnot battery energy storage system. The Carnot battery energy release system uses the discharge compressor (39) to pressurize the working fluid. Then the working fluid absorbs the heat of the heat storage medium in the heat transfer oil tank (10) and the molten salt tank (9) in the heat transfer oil-working fluid heat exchanger (33) and the molten salt-working fluid heat exchanger (32) respectively, generating high temperature and high pressure working fluid. It does work in the multi-stage discharge expander (40) and generates mechanical energy which is converted into electrical energy in the Carnot battery generator (41) and output to the outside. After being added with the electrical energy of the coal-fired generator (4), it meets the electrical load requirements.

9. The operation method of a coal-fired power generation and Carnot battery energy storage coupling system according to claim 8, characterized in that: When the Carnot battery energy storage system is running, the molten salt tank (9), the heat transfer oil tank (10) and the cold water tank (11) run for 10 hours; when the Carnot battery energy release system is running, the molten salt tank (9), the heat transfer oil tank (10) and the cold water tank (11) run for 5.5 hours.

10. The operation method of a coal-fired power generation and Carnot battery energy storage coupling system according to claim 8, characterized in that: During peak electricity demand, in order to achieve higher efficiency in the coupling system of coal-fired power generation and Carnot battery energy storage, 56% of the heat stored in the molten salt tank (9) is used for the coal-fired power generation unit and 44% is used for the Carnot battery energy release system; 68% of the heat stored in the heat transfer oil tank (10) is used for the coal-fired power generation unit and 32% is used for the Carnot battery energy release system; and 81% of the cold energy stored in the cold water tank (11) is used for the coal-fired power generation unit and 19% is used for the Carnot battery energy release system.

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