A combined cycle coupled compressed air heat storage peak shaving system and method

Abstract

The present invention relates to the field of power generation technology, and particularly to a combined cycle coupled compressed air heat storage peak-shaving system and method, wherein the heat storage peak-shaving system includes a first compressor, a first gas storage tank, a first heat exchanger, a second heat exchanger, a gas turbine, a waste heat boiler, a first molten salt tank, a second molten salt tank, a first steam turbine and a generator. During paid peak-shaving power generation, the gas turbine reduces the power generation load, and the excess hot flue gas generated is transported to the first molten salt tank for heat exchange, and another part of the waste heat enters the waste heat boiler. The waste heat boiler heats water into water vapor after heat exchange with the waste heat of the gas turbine. Part of the water vapor drives the steam turbine to operate, providing power for the rotation of the drive shaft, thereby driving the generator to operate; the excess water vapor generated in the paid peak-shaving power generation process is transported to the second molten salt tank, exchanges heat with the second molten salt, and stores the heat in the second molten salt tank, thereby reducing energy loss during start-up and shutdown and peak-shaving processes and saving energy.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a combined cycle coupled compressed air heat storage peak regulation system and method. Background Art

[0002] In daily life and production, there are huge peak-to-valley differences in electricity load demand. More and more renewable energy sources such as wind and solar energy are used to integrate with traditional dispatchable power for power generation. Due to the uncertainty and intermittency of wind and solar energy, renewable power and traditional dispatchable power are volatile when integrated into the power grid. Therefore, it is necessary to couple power with fast startup and efficient dispatchability capabilities to compensate for the shortcomings of wind and solar power production.

[0003] Power plants usually draw compressed air from renewable energy power plants or from the power grid during the night when electricity consumption is low. They combine this with a large gas-steam combined cycle system consisting of a gas turbine, waste heat boiler and steam turbine to perform peak regulation and provide effective support for the power shortage of the power grid.

[0004] In the existing technology, the long-term low-load operation of the combined cycle system during the start-up, shutdown and peak regulation process will release a large amount of gas containing heat and kinetic energy into the environment, causing energy loss, thereby leading to low system operation efficiency. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art that the start-up, shutdown and peak-shaving processes of the combined cycle system are time-consuming, a large amount of energy loss is released into the environment, and thus the system operation efficiency is low, thereby providing a combined cycle coupled compressed air heat storage peak-shaving system and method.

[0006] In order to solve the above problems, the present invention provides a combined cycle coupled compressed air heat storage peak shaving system, comprising:

[0007] a first compressor adapted to compress air;

[0008] a first air storage tank, connected to the first compressor and suitable for storing compressed air;

[0009] a first heat exchanger connected to the first gas storage tank;

[0010] a second heat exchanger connected to the first heat exchanger;

[0011] a gas turbine connected to the second heat exchanger, wherein the gas turbine is provided with a drive shaft;

[0012] a waste heat boiler connected to the gas turbine;

[0013] a first molten salt tank connected to the gas turbine and the second heat exchanger, wherein the first molten salt tank stores a first molten salt;

[0014] a second molten salt tank, forming a first circuit with the first heat exchanger, the second molten salt tank being sequentially connected to the first molten salt tank and the second heat exchanger, the second molten salt tank forming a second circuit with the waste heat boiler, the second molten salt tank storing second molten salt, and the temperature in the second molten salt tank being lower than the temperature in the first molten salt tank;

[0015] a first steam turbine mounted on the drive shaft, the first steam turbine being connected to the waste heat boiler;

[0016] A generator is connected to the drive shaft.

[0017] Furthermore, the combined cycle coupled compressed air heat storage peak shaving system further includes:

[0018] The first turbine is mounted on the driving shaft and connected to the first air storage tank.

[0019] Furthermore, in this combined cycle coupled compressed air heat storage peak shaving system, the gas turbine includes:

[0020] a compressor connected to the first air storage tank and adapted to input the compressed air into the compressor to become part of the air intake of the gas turbine;

[0021] a combustion chamber, connected to the second heat exchanger and the compressor, respectively, and adapted to input the compressed air storage into the combustion chamber to become part of the fuel gas;

[0022] The second turbine is installed on the drive shaft, connected to the combustion chamber, the first molten salt tank and the waste heat boiler, and is suitable for providing power to the drive shaft. The second turbine is also connected to the second heat exchanger and is suitable for inputting the compressed air into the second turbine to become part of the flue gas.

[0023] Furthermore, the combined cycle coupled compressed air heat storage peak shaving system further includes:

[0024] a communicating vessel connecting the second turbine and the waste heat boiler;

[0025] The damper is provided between the communicating vessel and the first molten salt tank, and is adapted to control the connection and disconnection between the communicating vessel and the first molten salt tank.

[0026] Furthermore, the combined cycle coupled compressed air heat storage peak shaving system further includes:

[0027] a second steam turbine and condenser;

[0028] The waste heat boiler includes: a high-pressure steam heat exchanger and a low-pressure steam heat exchanger, wherein the high-pressure steam heat exchanger is connected to the communicating vessel, the first steam turbine and the second molten salt tank;

[0029] The low-pressure steam heat exchanger is connected to the high-pressure steam heat exchanger, and forms a second loop with the second molten salt tank;

[0030] The second steam turbine is connected to the first steam turbine;

[0031] The condenser is connected to the low-pressure steam heat exchanger and the second steam turbine respectively.

[0032] Furthermore, in this combined cycle coupled compressed air heat storage and peak-shaving system, the outer walls of the first molten salt tank and the second molten salt tank are provided with a plurality of interconnected pipes in parallel, and the pipes on the outer wall of the first molten salt tank are connected to the communicating vessel.

[0033] Furthermore, the combined cycle coupled compressed air heat storage peak shaving system further includes:

[0034] a chimney, connected to the first molten salt tank and the low-pressure steam heat exchanger, and suitable for discharging flue gas;

[0035] a second compressor connected to the chimney;

[0036] a second gas storage tank connected to the first heat exchanger and the second compressor;

[0037] The collector is arranged between the chimney and the second compressor and is suitable for capturing carbon dioxide in the chimney.

[0038] Furthermore, in this combined cycle coupled compressed air heat storage peak shaving system, the first molten salt and / or the second molten salt comprises:

[0039] 53 wt% potassium nitrate, 7 wt% sodium nitrate and 40 wt% sodium nitrite.

[0040] The present invention also provides a combined cycle coupled compressed air heat storage peak regulation method, which adopts the above-mentioned combined cycle coupled compressed air heat storage peak regulation system.

[0041] Furthermore, the combined cycle coupled compressed air heat storage peak regulation method includes the following steps:

[0042] Step S1: When electricity consumption is low or clean energy electricity is sufficient, start the first compressor to compress air and store the compressed air in the first air storage tank;

[0043] Step S2: During peak power consumption or power shortage, the gas turbine is started to sequentially input the compressed air in the first gas storage tank into the first heat exchanger and the second heat exchanger for heating:

[0044] Step S3: The compressed air in the first air storage tank is input into the compressor for compression and then enters the combustion chamber for combustion, and the second turbine drives the drive shaft to drive the generator to generate electricity;

[0045] Step S4: inputting part of the flue gas from the second turbine in step S3 into the first molten salt tank to exchange heat with the first molten salt;

[0046] Step S5: inputting another portion of the flue gas from the second turbine in step S3 into the waste heat boiler for heat exchange, and the waste heat boiler heats the water working medium after heat exchange into water vapor, which is input into the second molten salt tank for heat exchange with the second molten salt;

[0047] Step S6: The first molten salt stored in the first molten salt tank in step S4 and the second molten salt stored in the second molten salt tank in step S5 are respectively transported to the second heat exchanger and the first heat exchanger to exchange heat with the compressed air in the first gas storage tank in step S2;

[0048] Step S7: the first molten salt and the second molten salt after heat exchange flow back into the first molten salt tank.

[0049] The present invention has the following advantages:

[0050] 1. The combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention comprises a first compressor which compresses air using electricity generated by renewable energy or surplus electricity during the nighttime electricity off-peak period and stores the air in a first air storage tank. During peak electricity consumption, the compressed air can be directly input into the compressor for compression, thereby enhancing the kinetic energy of the gas turbine, thereby enabling the drive shaft to drive the generator to operate and participate in paid peak-shaving power generation. The gas turbine reduces the power generation load, and the excess hot flue gas generated is transported to the first molten salt tank, heat-exchanged with the first molten salt, and stored in the first molten salt tank. Another part of the waste heat enters the waste heat boiler, which heats water into water vapor after heat exchange with the waste heat of the gas turbine. Part of the water vapor drives the steam turbine to operate, providing power for the drive shaft to rotate, thereby driving the generator to operate. The excess water vapor generated in the process of participating in paid peak-shaving power generation is transported to the second molten salt tank, heat-exchanged with the second molten salt, and stored in the second molten salt tank. This reduces energy loss during start-up and shutdown and peak-shaving processes and saves energy.

[0051] During peak-shaving power generation, the second molten salt in the second molten salt tank is transported to the first heat exchanger, and the heat stored in the second molten salt is used to heat the compressed air in the first heat exchanger. The second molten salt after heat exchange flows back to the second molten salt tank, and the heated compressed air is transported to the second heat exchanger. The first molten salt in the first molten salt tank is transported to the second heat exchanger, and the compressed air in the second heat exchanger is heated again by using the heat stored in the first molten salt. The first molten salt after heat exchange flows back to the second molten salt tank. The compressed air in the first gas storage tank is heated by the first heat exchanger and the second heat exchanger and then transported to the combustion chamber to participate in combustion, thereby increasing the temperature of the compressed air so that the compressed air meets the temperature required by the combustion chamber, thereby improving the flexibility of the coupling of gas, air and steam.

[0052] It realizes the use of electricity generated by renewable energy or surplus electricity during the night when electricity consumption is low to compress air, reducing the cost of electricity. The compressed air is then coupled with a large gas-steam combined cycle consisting of a gas turbine, a waste heat boiler and a steam turbine to participate in paid peak-shaving power generation. The generated electricity is sold at the peak electricity price, and profits are obtained from the peak-valley electricity price difference, which can significantly improve economic benefits.

[0053] 2. The combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention has a first turbine mounted on the drive shaft and connected to a first air storage tank. During peak-shaving power generation, compressed air in the first air storage tank can be directly fed into the first turbine. The first turbine drives the drive shaft to rotate, causing the generator to generate electricity, thereby increasing the driving force of the generator and improving the utilization rate of the compressed air.

[0054] 3. The combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention also includes a communicating vessel and a damper. The communicating vessel connects the second turbine and the waste heat boiler. The damper is arranged between the communicating vessel and the first molten salt tank and is suitable for controlling the connection and disconnection between the communicating vessel and the first molten salt tank.

[0055] By setting the damper, during the start-up and shutdown process of the combined cycle system, the gas turbine is in the initial load combined cycle. The damper is opened to allow the airflow discharged from the gas turbine to enter the first molten salt tank to store heat. After the gas turbine is fully started, the damper is closed to allow the airflow to enter the waste heat boiler. By controlling the opening and closing of the damper, the impact of drastic temperature changes on the pressure in the first molten salt tank is reduced, thereby increasing the safety of the system.

[0056] 4. The combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention also includes a second steam turbine and a condenser. The waste heat boiler includes a high-pressure steam heat exchanger and a low-pressure steam heat exchanger. The high-pressure steam heat exchanger is connected to the second turbine, the first steam turbine and the second molten salt tank. The low-pressure steam heat exchanger is connected to the high-pressure steam heat exchanger and forms a second loop with the second molten salt tank. The second steam turbine is connected to the first steam turbine, and the condenser is respectively connected to the low-pressure steam heat exchanger and the second steam turbine.

[0057] After the high-pressure steam heat exchanger exchanges heat with the flue gas output by the second turbine, the high-temperature and high-pressure water vapor is transported to the first steam turbine for power generation. The high-temperature and high-pressure water vapor can also be transported to the second molten salt tank to store heat. After the low-pressure steam heat exchanger exchanges heat with the flue gas output from the high-pressure steam heat exchanger, the low-temperature and low-pressure water vapor is transported to the second molten salt tank for heat exchange. The water vapor after heat exchange is cooled into liquid water and flows back to the low-pressure steam heat exchanger through the second circuit. The high-temperature and high-pressure water vapor drives the first steam turbine, and the low-temperature and low-pressure water vapor output again drives the second steam turbine to generate electricity. In this way, the high-temperature flue gas output by the gas turbine can be utilized multiple times, and part of the water vapor after heat exchange can be stored as energy in the second molten salt tank, thereby realizing the comprehensive utilization of energy and achieving the effect of energy saving and efficiency improvement.

[0058] 5. In the combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention, a plurality of interconnected pipes are arranged in parallel on the outer walls of the first molten salt tank and the second molten salt tank. The pipes on the outer wall of the first molten salt tank are connected to the gas turbine, and a second loop is formed between the pipes on the outer wall of the second molten salt tank and the low-pressure steam heat exchanger.

[0059] The pipes on the outer walls of the first molten salt tank and the second molten salt tank form a membrane wall. By inputting the flue gas generated by the gas turbine into the pipe on the outer wall of the first molten salt tank, the first molten salt in the first molten salt tank can be heated. By inputting the water vapor generated in the waste heat boiler into the pipe on the outer wall of the second molten salt tank, the second molten salt in the second molten salt tank can be heated. This can effectively solve the disadvantage that the first molten salt and the second molten salt are easily frozen, effectively improve the heat storage capacity of the phase change molten salt deposit in the melting container, and thus improve the heat exchange efficiency.

[0060] 6. The combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention also includes a chimney, a second compressor, a second gas storage tank, and a collector. The chimney is connected to the first molten salt tank and the low-pressure steam heat exchanger and is suitable for discharging flue gas. The second compressor is connected to the chimney, and the second gas storage tank is connected to the first heat exchanger and the second compressor. The collector is arranged between the chimney and the second compressor and is suitable for capturing carbon dioxide in the chimney.

[0061] The carbon dioxide captured in the collector is compressed in the second compressor and stored in the second gas storage tank. The liquefied carbon dioxide is then transported to the first heat exchanger for heat exchange. The heat-exchanged carbon dioxide gas can then be transported to the second turbine and the first turbine to perform work. Since the molecular weight of carbon dioxide is about twice that of air, its work capacity is also twice that of air. In addition, carbon dioxide is inert and non-toxic, so the thermal efficiency can be greatly improved.

[0062] 7. In the combined cycle coupled compressed air heat storage and peak-shaving system provided by the present invention, the first molten salt and / or the second molten salt include 53wt% potassium nitrate, 7wt% sodium nitrate and 40wt% sodium nitrite. The freezing point of this molten salt is 142°C. When heated to 450°C, it can be used as a heat transfer fluid in liquid form to transfer heat into or out of the molten salt tank, and has the advantages of low freezing point and good fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0064] Figure 1 Schematic diagram of the combined cycle coupled compressed air heat storage peak-shaving system provided in this embodiment.

[0065] Description of reference numerals:

[0066] 1. First compressor; 2. First gas storage tank; 3. First heat exchanger; 4. Second heat exchanger; 5. Gas turbine; 51. Compressor; 52. Combustion chamber; 53. Second turbine; 6. Waste heat boiler; 61. High-pressure steam heat exchanger; 62. Low-pressure steam heat exchanger; 7. First molten salt tank; 8. Second molten salt tank; 9. First circuit; 10. Second circuit; 11. First steam turbine; 12. Generator; 13. First turbine; 14. Connecting vessel; 15. Damper; 16. Second steam turbine; 17. Condenser; 18. Chimney; 19. Second compressor; 20. Second gas storage tank; 21. Collector; 22. First electric pump; 23. Second electric pump; 24. Controller. DETAILED DESCRIPTION

[0067] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0068] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0069] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0070] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0071] Example 1

[0072] like Figure 1 As shown, a combined cycle coupled compressed air heat storage peak shaving system provided by the present invention includes a first compressor 1, a first gas storage tank 2, a first heat exchanger 3, a second heat exchanger 4, a gas turbine 5, a waste heat boiler 6, a first molten salt tank 7, a second molten salt tank 8, a first steam turbine and a generator 12. The first compressor 1 is suitable for compressing air, the first gas storage tank 2 is connected to the first compressor 1, the first heat exchanger 3 is connected to the first gas storage tank 2, the second heat exchanger 4 is connected to the first heat exchanger 3, the gas turbine 5 is connected to the second heat exchanger 4, the gas turbine 5 is provided with a drive shaft, and the waste heat boiler 6 is connected to the gas The turbine 5 is connected, the first molten salt tank 7 is connected to the gas turbine 5 and the second heat exchanger 4, the first molten salt tank 7 stores the first molten salt, the second molten salt tank 8 and the first heat exchanger 3 form a first loop 9, the second molten salt tank 8 is connected to the first molten salt tank 7 and the second heat exchanger 4 in sequence, the second molten salt tank 8 and the waste heat boiler 6 form a second loop 10, the second molten salt tank 8 stores the second molten salt, and the temperature in the second molten salt tank 8 is lower than the temperature in the first molten salt tank 7, the first steam turbine 11 is installed on the drive shaft, the first steam turbine 11 is connected to the waste heat boiler 6, and the generator 12 is connected to the drive shaft.

[0073] This embodiment does not specifically limit the first compressor 1. To conform to actual conditions, in this embodiment, the first compressor 1 can perform 2-4 stages of air compression, and the compressed air pressure after compression is 6-14 MPa. An interstage cooler is installed between the first compressor 1 and the first air storage tank 2 to ensure that the temperature of the compressed air stored in the first air storage tank 2 is not higher than 50°C.

[0074] This embodiment does not specifically limit the first gas storage tank 2. To meet the current situation, in this embodiment, the pressure in the first gas storage tank 2 is 8-12 MPa, the temperature is 30-50°C, and the compressed air flow rate at the outlet of the first gas storage tank 2 is 600-1800 t / h.

[0075] The present embodiment does not specifically limit the first molten salt tank 7 and the second molten salt tank 8. To conform to the actual situation, the first molten salt tank 7 and the second molten salt tank 8 in the present embodiment adopt a shell and tube heat exchange structure made of carbon steel.

[0076] The first compressor 1 uses the electricity generated by renewable energy or the surplus electricity during the night when electricity consumption is low to compress the air and store it in the first gas tank 2. During the peak electricity consumption, the compressed air in the first gas tank 2 is sequentially input into the first heat exchanger 3 and the second heat exchanger 4. The compressed air after heat exchange is input into the gas turbine 5 to become fuel gas or flue gas. The gas turbine 5 converts the heat energy into kinetic energy to drive the drive shaft to rotate, so that the drive shaft drives the generator 12 to operate and participate in paid peak-shaving power generation. The gas turbine 5 will generate flue gas of about 550°C when working, and part of the flue gas will be transported to the first molten salt tank 7 In the process, the first molten salt is heated to above 450°C and stored in the first molten salt tank 7. Another part of the flue gas enters the waste heat boiler 6. The waste heat boiler 6 exchanges heat with the waste heat of the gas turbine 5 to heat water into saturated steam with a temperature of about 420°C. Part of the water vapor drives the steam turbine to operate, providing power for the drive shaft to rotate, thereby driving the generator 12 to operate and participate in paid peak-shaving power generation. The other part of the water vapor is transported to the second molten salt tank 8, and the second molten salt is heated to above 400°C and stored in the second molten salt tank 8, which reduces the energy loss during the start-up and shutdown and peak-shaving processes and saves energy.

[0077] During peak-shaving power generation, the second molten salt in the second molten salt tank 8 is transported to the first heat exchanger 3, and the heat stored in the second molten salt is used to heat the compressed air in the first heat exchanger 3. The second molten salt after heat exchange flows back to the second molten salt tank 8, and the heated compressed air is transported to the second heat exchanger 4. The first molten salt in the first molten salt tank 7 is transported to the second heat exchanger 4, and the compressed air in the second heat exchanger 4 is heated again by using the heat stored in the first molten salt. After the heat exchange, the temperature of the first molten salt is reduced from 420°C to about 270°C and then flows back to the second molten salt tank 8. Then, the compressed air that is reheated to 350-500°C is transported to the gas turbine 5 for combustion, thereby improving the flexibility of the coupling of gas, air and steam.

[0078] The air is compressed by utilizing the electricity generated by renewable energy or the surplus electricity during the night when electricity consumption is low, thereby reducing the cost of electricity. The compressed air is then coupled to a large gas-steam combined cycle consisting of a gas turbine 5, a waste heat boiler 6 and a steam turbine to participate in paid peak-shaving power generation. The generated electricity is sold at the peak electricity price, and profits are obtained from the difference between peak and valley electricity prices, which significantly improves economic benefits, realizes the comprehensive utilization of energy, and achieves the effect of energy saving and efficiency improvement.

[0079] This embodiment does not specifically limit the renewable energy power. In this embodiment, the renewable energy power can come from solar energy, wind energy, ocean energy, etc.

[0080] In this embodiment, a first turbine 13 is also installed on the drive shaft. The first turbine 13 is connected to the first air tank 2. During peak-shaving power generation, the compressed air in the first air tank 2 can be directly input into the first turbine 13. The first turbine 13 drives the drive shaft to rotate so that the generator 12 generates electricity, thereby improving the driving force of the generator 12 and also improving the utilization rate of the compressed air.

[0081] This embodiment does not specifically limit the first turbine 13. To conform to the actual situation, the first turbine 13 in this embodiment is an air turbine.

[0082] In this embodiment, the gas turbine 5 includes a compressor 51, a combustion chamber 52, and a second turbine 53. The compressor 51 is connected to the first gas storage tank 2 and is suitable for pressurizing the air in the first gas storage tank 2. The combustion chamber 52 is connected to the second heat exchanger 4 and the compressor 51, respectively. The compressor 51 is equipped with an inlet filter, through which compressed air enters the combustion chamber 52 and is burned with natural gas. The second turbine 53 is installed on the drive shaft and is connected to the combustion chamber 52, the first molten salt tank 7, and the waste heat boiler 6. The expansion of the combusted gas in the combustion chamber 52 drives the second turbine 53 to operate and provide power for the drive shaft. Part of the flue gas output from the second turbine 53 is input into the waste heat boiler 6 through the exhaust pipe, and the remaining part is input into the first molten salt tank 7 through a bypass pipe for storage.

[0083] This embodiment does not impose any specific limitation on the second turbine 53. To comply with the actual situation, in this embodiment, the second turbine 53 is a gas turbine.

[0084] In this embodiment, a communicating vessel 14 is provided between the exhaust pipe and the bypass pipe. The communicating vessel 14 connects the second turbine 53 and the waste heat boiler 6. A damper 15 is provided on the bypass pipe between the communicating vessel 14 and the first molten salt tank 7, which is suitable for controlling the connection and disconnection between the communicating vessel 14 and the first molten salt tank 7.

[0085] The damper 15 is not specifically limited in this embodiment. To conform to the actual situation, the damper 15 in this embodiment adopts a knife-type damper 15, which is powered by a hydraulic system and can be set to three positions: fully open, partially cut off, and completely cut off the airflow.

[0086] By setting the damper 15, during the start-up and shutdown process of the combined cycle system, the gas turbine 5 is in the initial load combined cycle. The damper 15 is opened to allow the airflow discharged from the gas turbine 5 to enter the first molten salt tank 7 to store heat. After the gas turbine 5 is fully started, the damper 15 is closed to allow the airflow to enter the waste heat boiler 6. By controlling the opening and closing of the damper 15, the impact of drastic temperature changes on the pressure in the first molten salt tank 7 is reduced, thereby increasing the safety of the system.

[0087] In this embodiment, a second steam turbine 16 and a condenser 17 are also included. The waste heat boiler 6 includes a high-pressure steam heat exchanger 61 and a low-pressure steam heat exchanger 62. The high-pressure steam heat exchanger 61 is connected to the second turbine 53, the first steam turbine 11 and the second molten salt tank 8. The low-pressure steam heat exchanger 62 is connected to the high-pressure steam heat exchanger 61, and forms a second loop 10 with the second molten salt tank 8. The second steam turbine 16 is connected to the first steam turbine 11, and the condenser 17 is respectively connected to the low-pressure steam heat exchanger 62 and the second steam turbine 16.

[0088] After the high-pressure steam heat exchanger 61 exchanges heat with the flue gas output by the second turbine 53, the high-temperature and high-pressure water vapor with a temperature of 400°C is transported to the first steam turbine 11 to drive the drive shaft to generate electricity. The high-temperature and high-pressure water vapor can also be transported to the second molten salt tank 8 to exchange heat with the second molten salt and store the heat in the second molten salt tank 8. After the low-pressure steam heat exchanger 62 exchanges heat with the flue gas output from the high-pressure steam heat exchanger 61, the low-temperature and low-pressure water vapor is transported to the second molten salt tank 8 for heat exchange. The water vapor after heat exchange is cooled into liquid water and flows back to the low-pressure steam heat exchanger 62 through the second loop 10. The low-temperature and low-pressure water vapor output after the high-temperature and high-pressure water vapor drives the first steam turbine 11 again drives the second steam turbine 16 to generate electricity, so that the high-temperature flue gas output by the gas turbine 5 can be utilized multiple times, and part of the water vapor after heat exchange can be stored as energy in the second molten salt tank 8, thereby realizing the comprehensive utilization of energy and achieving the effect of energy saving and efficiency improvement.

[0089] In this embodiment, a plurality of interconnected pipes are arranged in parallel on the outer walls of the first molten salt tank 7 and the second molten salt tank 8 to form a membrane wall structure. The pipes on the outer wall of the first molten salt tank 7 are connected to the gas turbine 5, and a second loop 10 is formed between the pipes on the outer wall of the second molten salt tank 8 and the low-pressure steam heat exchanger 62.

[0090] During the shutdown of the combined cycle unit, the flue gas generated by the gas turbine 5 is input into the pipe on the outer wall of the first molten salt tank 7 to heat the first molten salt in the first molten salt tank 7, and the water vapor generated in the waste heat boiler 6 is input into the pipe on the outer wall of the second molten salt tank 8 to heat the second molten salt in the second molten salt tank 8. The water vapor after heat exchange forms hot water in the pipe and flows back to the low-pressure steam heat exchanger 62 through the second loop 10 to continue to serve as a feed water medium. This membrane wall structure can effectively solve the problem that the first molten salt and the second molten salt are easily frozen, effectively improve the ability of the phase change molten salt deposit in the melting container, thereby improving the heat exchange efficiency.

[0091] After heating, the first molten salt tank 7 and the second molten salt tank 8 enter the insulation state. When the stored heat is insufficient to continue operation or the electricity price is too low to economically release energy from the stored heat, the first molten salt tank 7 and the second molten salt tank 8 enter the standby mode and all the molten salt is transported to the first molten salt tank 7. When the combined cycle unit is started again, the first molten salt in the first molten salt tank 7 is heated by the flue gas of the gas turbine 5 and the first molten salt tank 7 and the second molten salt tank 8 enter the working mode.

[0092] During standby mode, as the temperature difference between the first and second molten salt tanks 7 and 8 and the environment decreases, the heat loss rate will decrease as the first and second molten salt tanks 7 and 8 cool down, and the heat loss rate is typically less than 1% per day.

[0093] The first molten salt tank 7 and the second molten salt tank 8 are also provided with a first electric pump 22 and a second electric pump 23, respectively. The control process of the first electric pump 22 and the second electric pump 23 is configured as follows: in the heat storage and recovery stage, the first molten salt and the first molten salt are pumped to the first molten salt tank 7 and the second molten salt tank 8 to absorb heat; in the heat release stage, the first molten salt and the second molten salt are pumped to the second heat exchanger 4 and the first heat exchanger 3, respectively, to heat the compressed air.

[0094] During low electricity consumption periods or when electricity costs are low, electricity can also be used as energy to heat the first molten salt tank 7 and the second molten salt tank 8 .

[0095] In this embodiment, a chimney 18 connected to the damper 15, the first molten salt tank 7 and the low-pressure steam heat exchanger 62 is further provided, which is suitable for discharging flue gas. By controlling the opening and closing of the damper 15, the flue gas after combustion in the gas turbine 5 can enter the waste heat boiler 6 or directly enter the chimney 18 for discharge. The flue gas after heat exchange with the first molten salt tank 7 can also enter the chimney 18 for discharge.

[0096] A collector 21 suitable for capturing carbon dioxide in the chimney 18 is provided at the outlet of the chimney 18. The carbon dioxide gas captured in the collector 21 is compressed and liquefied in the second compressor 19 and stored in the second gas storage tank 20. The liquefied carbon dioxide is then transported to the first heat exchanger 3 for heat exchange. The heat-exchanged carbon dioxide gas can then be transported to the second turbine 53 to perform work. Since the molecular weight of carbon dioxide is approximately twice that of air, the work capacity of carbon dioxide is also twice that of air. In addition, carbon dioxide is inert and non-toxic, so the thermal efficiency can be greatly improved.

[0097] In this embodiment, the components of the first molten salt and the second molten salt are: 53wt% potassium nitrate, 7wt% sodium nitrate and 40wt% sodium nitrite. The freezing point of this molten salt is 142°C. It can be used as a heat transfer fluid in liquid form to move heat into or out of the molten salt tank, and has the advantages of low freezing point and good fluidity.

[0098] In this embodiment, a controller 24 is further provided, which is signal-connected to the damper 15 , the first electric pump 22 and the second electric pump 23 , and is suitable for controlling the opening and closing of the damper 15 and the operation of the first electric pump 22 and the second electric pump 23 .

[0099] Example 2

[0100] The combined cycle coupled compressed air heat storage and peak-shaving method provided in this embodiment adopts the combined cycle coupled compressed air heat storage and peak-shaving system in Example 1.

[0101] The following steps are involved:

[0102] Step S1: When electricity consumption is low or clean energy electricity is sufficient, start the first compressor 1 to compress air and store the compressed air in the first air storage tank 2;

[0103] Step S2: During peak power consumption or power shortage, the gas turbine 5 is started to sequentially input the compressed air in the first gas storage tank 2 into the first heat exchanger 3 and the second heat exchanger 4 for heating;

[0104] Step S3: The heated compressed air is fed into the gas turbine 5 to be burned with natural gas, and the heat energy generated by the combustion is converted into mechanical energy to drive the drive shaft to rotate, and the drive shaft drives the generator 12 to generate electricity;

[0105] Step S4: The flue gas with a temperature of about 550° C. after combustion in step S3 is input into the first molten salt tank 7 , and the first molten salt is stored in the first molten salt tank 7 at a temperature of about 450° C. after heat exchange between the first molten salt and the flue gas;

[0106] Step S5: The remaining portion of the flue gas after combustion in step S3 is fed into the waste heat boiler 6 for heat exchange. The waste heat boiler 6 utilizes the waste heat of the flue gas to heat the water working medium into saturated water vapor at a temperature of approximately 420°C. A portion of the heat-exchanged water vapor is then fed into the second molten salt tank 8 to heat the second molten salt to 400°C for storage. The remaining portion of the saturated water vapor can drive the first steam turbine 11 to operate and generate electricity.

[0107] Step S6: The second molten salt at 450° C. stored in the first molten salt tank 7 in step S4 and the second molten salt at 400° C. stored in the second molten salt tank 8 in step S5 are respectively transported to the second heat exchanger 4 and the first heat exchanger 3, and the compressed air output from the first gas storage tank 2 in step S2 is heat-exchanged to 350-450° C. The heated compressed air is transported to the gas turbine 5 for combustion, thereby shortening the cold start time of the gas turbine 5;

[0108] Step S7: After heat exchange, the first molten salt and the second molten salt, whose temperature drops to about 220° C., flow back into the second molten salt tank 8 .

[0109] The combined cycle coupled with compressed air heat storage peak-shaving system in Example 1 is adopted. By setting the first molten salt tank 7 and the second molten salt tank 8, the heat generated in the peak-shaving process can be recovered and stored. During peak-shaving, the stored heat is coupled with compressed air to generate electricity, effectively absorbing the heat of the flue gas of the gas turbine 5 and reusing it, which can reduce fuel consumption and reduce flue gas emissions during startup, ensuring continuous and stable peak-shaving of the gas turbine 5, and achieving a relatively low-cost energy storage peak-shaving effect of the gas-steam cycle coupled with compressed air, thereby improving the overall power generation efficiency of the combined cycle power generation system and increasing profitability when participating in paid peak-shaving.

[0110] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A combined cycle coupled compressed air heat storage peak shaving system, characterized in that: include: A first compressor (1) adapted to compress air; a first air storage tank (2), connected to the first compressor (1), and suitable for storing compressed air; a first heat exchanger (3) connected to the first gas storage tank (2); a second heat exchanger (4), connected to the first heat exchanger (3); a gas turbine (5) connected to the second heat exchanger (4), wherein the gas turbine (5) is provided with a drive shaft; a waste heat boiler (6) connected to the gas turbine (5); a first molten salt tank (7) connected to the gas turbine (5) and the second heat exchanger (4), wherein the first molten salt tank (7) stores a first molten salt; a second molten salt tank (8) forming a first circuit (9) with the first heat exchanger (3); the second molten salt tank (8) being connected to the first molten salt tank (7) and the second heat exchanger (4) in sequence; the second molten salt tank (8) forming a second circuit (10) with the waste heat boiler (6); a second molten salt being stored in the second molten salt tank (8); and a temperature in the second molten salt tank (8) being lower than a temperature in the first molten salt tank (7); a first steam turbine (11) mounted on the drive shaft, the first steam turbine (11) being connected to the waste heat boiler (6); A generator (12) is connected to the drive shaft.

2. The combined cycle coupled compressed air heat storage peak shaving system according to claim 1, characterized in that: Also includes: A first turbine (13) is mounted on the drive shaft and connected to the first gas storage tank (2).

3. The combined cycle coupled compressed air heat storage peak shaving system according to claim 1 or 2, characterized in that: The gas turbine (5) comprises: A compressor (51) connected to the first air storage tank (2) and adapted to input the compressed air into the compressor (51) to become part of the air intake of the gas turbine (5); A combustion chamber (52) is connected to the second heat exchanger (4) and the compressor (51), respectively, and is suitable for inputting the compressed air storage into the combustion chamber (52) to become part of the fuel gas; The second turbine (53) is installed on the drive shaft and is connected to the combustion chamber (52), the first molten salt tank (7) and the waste heat boiler (6), and is suitable for providing power for the drive shaft. The second turbine (53) is also connected to the second heat exchanger (4) and is suitable for inputting the compressed air into the second turbine (53) to become part of the flue gas.

4. The combined cycle coupled compressed air heat storage peak shaving system according to claim 3, characterized in that: Also includes: a communicating vessel (14) connecting the second turbine (53) and the waste heat boiler (6); The damper (15) is arranged between the communicating vessel (14) and the first molten salt tank (7), and is suitable for controlling the connection and disconnection between the communicating vessel (14) and the first molten salt tank (7).

5. The combined cycle coupled compressed air heat storage peak shaving system according to claim 4, characterized in that: Also includes: a second steam turbine (16) and a condenser (17); The waste heat boiler (6) comprises: a high-pressure steam heat exchanger (61) and a low-pressure steam heat exchanger (62), wherein the high-pressure steam heat exchanger (61) is connected to the communicating vessel (14), the first steam turbine (11) and the second molten salt tank (8); The low-pressure steam heat exchanger (62) is connected to the high-pressure steam heat exchanger (61), and forms a second loop (10) with the second molten salt tank (8); The second steam turbine (16) is connected to the first steam turbine (11); The condenser (17) is connected to the low-pressure steam heat exchanger (62) and the second steam turbine (16), respectively.

6. The combined cycle coupled compressed air heat storage peak shaving system according to claim 5, characterized in that: The outer walls of the first molten salt tank (7) and the second molten salt tank (8) are provided with a plurality of mutually communicating pipes in parallel, and the pipes on the outer wall of the first molten salt tank (7) are connected to the communicating vessel (14).

7. The combined cycle coupled compressed air heat storage peak shaving system according to claim 6, characterized in that: Also includes: a chimney (18), connected to the first molten salt tank (7) and the low-pressure steam heat exchanger (62), and adapted to discharge flue gas; a second compressor (19) connected to the chimney (18); a second gas storage tank (20) connected to the first heat exchanger (3) and the second compressor (19); The collector (21) is arranged between the chimney (18) and the second compressor (19) and is suitable for capturing carbon dioxide in the chimney (18).

8. The combined cycle coupled compressed air heat storage peak shaving system according to claim 7, characterized in that: The first molten salt and / or the second molten salt include: 53 wt% potassium nitrate, 7 wt% sodium nitrate and 40 wt% sodium nitrite.

9. A combined cycle coupled compressed air heat storage peak shaving method, characterized in that: A combined cycle coupled compressed air heat storage and peak-shaving system according to any one of claims 3 to 8 is adopted.

10. The combined cycle coupled compressed air heat storage peak shaving method according to claim 9, characterized in that: The following steps are involved: Step S1: When electricity consumption is low or clean energy electricity is sufficient, starting the first compressor (1) to compress air, and storing the compressed air in the first air storage tank (2); Step S2: During peak power consumption or power shortage, the gas turbine (5) is started, and the compressed air in the first gas storage tank (2) is sequentially input into the first heat exchanger (3) and the second heat exchanger (4) for heating: Step S3: The compressed air in the first air storage tank (2) is input into the compressor (51) for compression and then enters the combustion chamber (52) for combustion, and the second turbine (53) drives the drive shaft to drive the generator (12) to generate electricity; Step S4: inputting part of the flue gas from the second turbine (53) in step S3 into the first molten salt tank (7) to exchange heat with the first molten salt; Step S5: another portion of the flue gas from the second turbine (53) in step S3 is input into the waste heat boiler (6) for heat exchange, and the waste heat boiler (6) heats the water working medium after heat exchange into water vapor, which is input into the second molten salt tank (8) for heat exchange with the second molten salt; Step S6: The first molten salt stored in the first molten salt tank (7) in step S4 and the second molten salt stored in the second molten salt tank (8) in step S5 are respectively transported to the second heat exchanger (4) and the first heat exchanger (3) to exchange heat with the compressed air in the first gas storage tank (2) in step S2; Step S7: the first molten salt and the second molten salt after heat exchange flow back into the first molten salt tank (7).

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