Coal-fired unit flue gas side coupling compressed air energy storage system and method

Abstract

The invention relates to the technical field of thermal power generation, in particular to a coal-fired unit flue gas side coupling compressed air energy storage system and method. In the energy storage stage, a first valve is opened, a second valve is closed, a motor drives a first air compressor and a second air compressor to compress air, generated high-pressure air flows through a first heat exchanger and a second heat exchanger and then enters an air storage tank, compression heat in the process is recycled into a steam turbine regenerative system, and more extracted steam is saved to do work in a steam turbine; and the third valve and the fourth valve are opened, the fifth valve and the sixth valve are closed, low-temperature heat conduction oil in the cold heat conduction oil storage tank is used for absorbing flue gas waste heat and steam heat and then storing the flue gas waste heat and the steam heat in the hot heat conduction oil storage tank, and high-temperature steam obtained after heat exchange enters the steam energy accumulator to be stored. The total efficiency of the coupling compressed air energy storage system on the flue gas side of the coal-fired unit can be improved, and meanwhile rapid and flexible peak regulation of the unit is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal power generation technology, in particular to a coal-fired unit flue gas side coupled compressed air energy storage system and method. BACKGROUND

[0002] Electric energy storage technology is considered to be an effective way to ensure safe and stable operation of the power grid and to greatly accommodate renewable energy, and therefore has attracted widespread attention. Compressed air energy storage (CAES) technology has the advantages of large energy storage capacity, long energy storage period, high system efficiency, long service life, and small investment, and is considered to be one of the most promising large-scale energy storage technologies.

[0003] At present, the coupling of the steam turbine side of the coal-fired unit and the compressed air energy storage system not only eliminates the combustion supplement link of the compressed air energy storage system, effectively improving the efficiency of the system, but also helps to improve the operation flexibility of the coal-fired unit, but during the energy release stage, part of the steam needs to be extracted from the coal-fired unit to heat the high-pressure air, which will reduce the climbing rate of the unit and affect the operation of the unit.

[0004] Therefore, there is an urgent need for a coal-fired unit flue gas side coupled compressed air energy storage system and method to solve the technical problem of how to improve the overall efficiency of the coal-fired unit flue gas side coupled compressed air energy storage system and the rapid and flexible peak regulation of the unit. SUMMARY

[0005] In order to solve the technical problem of how to improve the overall efficiency of the coal-fired unit flue gas side coupled compressed air energy storage system, the present application provides a coal-fired unit flue gas side coupled compressed air energy storage system and method.

[0006] In a first aspect, the present application provides a coal-fired unit flue gas side coupled compressed air energy storage system, comprising a coal-fired unit subsystem, a compressed air energy storage subsystem, and a steam energy storage subsystem connected in sequence. The coal-fired unit subsystem comprises a coal-fired boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a first generator, a condenser, a condensate pump, a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, a fourth low-pressure heater, a deaerator, a high-pressure feed pump, a first high-pressure heater, a second high-pressure heater, a third high-pressure heater, and a heat medium heat exchanger; the heat medium heat exchanger is used to absorb the waste heat on the flue gas side of the coal-fired boiler; The compressed air energy storage subsystem comprises a first compressor, a second compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a first expander, a second expander, a gas storage tank, a second generator, a motor, a first valve, and a second valve; The steam energy storage subsystem comprises a steam heat transfer oil heat exchanger, a steam accumulator, a hot heat transfer oil storage tank, a cold heat transfer oil storage tank, a hot heat transfer oil pump, a cold heat transfer oil pump, a third valve, a fourth valve, a fifth valve and a sixth valve.

[0007] In a second aspect, the embodiment of the present application provides a coal-fired unit flue gas side coupled compressed air energy storage method, which is applied to the coal-fired unit flue gas side coupled compressed air energy storage system and comprises the following steps. When the coal-fired unit is in low load operation or load reduction, the first valve, the third valve and the fourth valve are controlled to be opened, and the second valve, the fifth valve and the sixth valve are controlled to be closed. When the coal-fired unit is in load increase, the first valve, the third valve and the fourth valve are controlled to be closed, and the second valve, the fifth valve and the sixth valve are controlled to be opened.

[0008] The embodiment of the present application provides a coal-fired unit flue gas side coupled compressed air energy storage system, the coal-fired unit flue gas side coupled compressed air energy storage system of the present application comprises a coal-fired unit subsystem, a compressed air energy storage subsystem and a steam energy storage subsystem which are connected in sequence; the coal-fired unit subsystem comprises a coal-fired boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a first generator, a condenser, a condensate pump, a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, a fourth low-pressure heater, a deaerator, a high-pressure feed pump, a first high-pressure heater, a second high-pressure heater, a third high-pressure heater and a heat medium heat exchanger; the heat medium heat exchanger is used for absorbing waste heat on the flue gas side of the coal-fired boiler; the compressed air energy storage subsystem comprises a first air compressor, a second air compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a first expander, a second expander, an air tank, a second generator, a motor, a first valve and a second valve; the steam energy storage subsystem comprises a steam heat conduction oil heat exchanger, a steam accumulator, a hot heat conduction oil tank, a cold heat conduction oil tank, a hot heat conduction oil pump, a cold heat conduction oil pump, a third valve, a fourth valve, a fifth valve and a sixth valve. When the coal-fired unit flue gas side coupled compressed air energy storage system is in an energy storage stage, the first valve is opened, the second valve is closed, the motor drives the first air compressor and the second air compressor to compress air, high-pressure air generated is led into the air tank after passing through the first heat exchanger and the second heat exchanger, and the compression heat in the process is recovered into a steam turbine heat recovery system, thereby saving more steam extraction to do work in the steam turbine; the third valve and the fourth valve are opened, the fifth valve and the sixth valve are closed, low-temperature heat conduction oil in the cold heat conduction oil tank is used to absorb waste heat of flue gas and steam heat, and then is stored into the hot heat conduction oil tank, and high-temperature steam after heat exchange is led into the steam accumulator for storage; the total efficiency of the coal-fired unit flue gas side coupled compressed air energy storage system is improved, and rapid load reduction of the unit is realized; when the coal-fired unit flue gas side coupled compressed air energy storage system is in an energy release stage, the second valve is opened, the first valve is closed, high-pressure air in the air tank is heated after passing through the third heat exchanger and the fourth heat exchanger, and then is led into the first expander and the second expander to do work; the fifth valve and the sixth valve are opened, the third valve and the fourth valve are closed, high-pressure air is heated by using high-temperature heat conduction oil in the hot heat conduction oil tank, and steam in the steam accumulator is released as heating steam of the deaerator, so that the total efficiency of the coal-fired unit flue gas side coupled compressed air energy storage system and the load variation rate of the unit are improved. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, below the drawings needed to be used in the embodiments or prior art description will be briefly introduced, obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0010] Figure 1A structural diagram of a coal-fired unit flue gas side coupled compressed air energy storage system according to one embodiment is shown. Figure 2 A flow chart of a coal-fired unit flue gas side coupled compressed air energy storage method is shown.

[0011] Reference signs: 1-coal-fired boiler; 2-high pressure cylinder; 3-medium pressure cylinder; 4-low pressure cylinder; 5-first generator; 6-steam condenser; 7-condensate pump; 8-first high pressure heater; 9-second high pressure heater; 10-third high pressure heater; 11-deaerator; 12-high pressure feed water pump; 13-first low pressure heater; 14-second low pressure heater; 15-third low pressure heater; 16-fourth low pressure heater; 17-heat medium heat exchanger; 18-first compressor; 19-first heat exchanger; 20-second compressor; 21-second heat exchanger; 22-motor; 23-gas storage tank; 24-third heat exchanger; 25-first expander; 26-fourth heat exchanger; 27-second expander; 28-second generator; 29-first valve; 30-second valve; 31-third valve; 32-fourth valve; 33-steam heat conducting oil heat exchanger; 34-steam accumulator; 35-heat conducting oil storage tank; 36-fifth valve; 37-heat conducting oil pump; 38-cold conducting oil storage tank; 39-cold conducting oil pump; 40-sixth valve. DETAILED DESCRIPTION

[0012] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0013] For reference Figure 1 The embodiments of the present application provide a coal-fired unit flue gas side coupled compressed air energy storage system, which comprises a coal-fired unit subsystem, a compressed air energy storage subsystem and a steam energy storage subsystem connected in sequence. The coal-fired unit subsystem comprises a coal-fired boiler 1, a high pressure cylinder 2, a medium pressure cylinder 3, a low pressure cylinder 4, a first generator 5, a steam condenser 6, a condensate pump 7, a first low pressure heater 13, a second low pressure heater 14, a third low pressure heater 15, a fourth low pressure heater 16, a deaerator 11, a high pressure feed water pump 12, a first high pressure heater 8, a second high pressure heater 9, a third high pressure heater 10 and a heat medium heat exchanger 17; the heat medium heat exchanger 17 is used for absorbing waste heat on the flue gas side of the coal-fired boiler. The compressed air energy storage subsystem includes a first compressor 18, a second compressor 20, a first heat exchanger 19, a second heat exchanger 21, a third heat exchanger 24, a fourth heat exchanger 26, a first expander 25, a second expander 27, an air storage tank, a second generator 28, an electric motor 22, a first valve 29, and a second valve 30. The steam energy storage subsystem includes a steam heat exchanger 33, a steam accumulator 34, a thermal oil storage tank 35, a cold oil storage tank 38, a thermal oil pump 37, a cold oil pump 39, a third valve 31, a fourth valve 32, a fifth valve 36, and a sixth valve 40.

[0014] In this embodiment, the flue gas-coupled compressed air energy storage system of the coal-fired unit includes a coal-fired unit subsystem, a compressed air energy storage subsystem, and a steam energy storage subsystem connected in sequence. The coal-fired unit subsystem includes a coal-fired boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a first generator 5, a condenser 6, a condensate pump 7, a first low-pressure heater 13, a second low-pressure heater 14, a third low-pressure heater 15, a fourth low-pressure heater 16, a deaerator 11, a high-pressure feedwater pump 12, a first high-pressure heater 8, a second high-pressure heater 9, and a third high-pressure heater 10. The compressed air energy storage subsystem includes a first compressor 18, a second high-pressure heater 9, a third high-pressure heater 10, a third high-pressure heater 10, a fourth low-pressure heater 11, a fifth high-pressure heater 12, a sixth high-pressure heater 13, a seventh high-pressure heater 14, a eleventh high-pressure heater 15, a eleventh high-pressure heater 16, a eleventh low-pressure heater 17, a eleventh low-pressure heater 18, a eleventh high-pressure heater 19, a eleventh high-pressure heater 10, a eleventh high-pressure heater 10, a eleventh high-pressure heater 10, a eleventh high-pressure heater 11, a eleventh high-pressure heater 12, a eleventh high-pressure heater 13, a eleventh high-pressure heater 14, a eleventh high-pressure heater 15, a eleventh low-pressure heater 16, a seventh low-pressure heater 17, a eleventh low-pressure heater 18, a eleventh high-pressure heater 19, a eleventh high The system includes a second compressor 20, a first heat exchanger 19, a second heat exchanger 21, a third heat exchanger 24, a fourth heat exchanger 26, a first expander 25, a second expander 27, a gas storage tank, a second generator 28, an electric motor 22, a first valve 29, a second valve 30, and a heat medium heat exchanger 17. The heat medium heat exchanger 17 is used to absorb waste heat from the flue gas side of the coal-fired boiler 1. The steam energy storage subsystem includes a steam thermal oil heat exchanger 33, a steam energy storage tank 34, a thermal thermal oil storage tank 35, a cold thermal oil storage tank 38, a thermal thermal oil pump 37, a cold thermal oil pump 39, a third valve 31, a fourth valve 32, a fifth valve 36, and a sixth valve 40. When the flue gas-side coupled compressed air energy storage system of the coal-fired unit is in the energy storage stage, the first valve 29 is opened and the second valve 30 is closed. The motor 22 drives the first compressor 18 and the second compressor 20 to compress air. The high-pressure air generated flows through the first heat exchanger 19 and the second heat exchanger 21 and then enters the storage tank. The heat of compression during the process is recovered into the turbine regenerative system, saving more extraction steam to do work in the turbine. The third valve 31 and the fourth valve 32 are opened and the fifth valve 36 and the sixth valve 40 are closed. The low-temperature heat transfer oil in the cold heat transfer oil storage tank 38 absorbs the waste heat of the flue gas and the heat of the steam and stores it in the hot heat transfer oil storage tank 35. The high-temperature steam after heat exchange enters the steam accumulator 34 for storage, thereby improving the efficiency of the coal-fired unit's flue gas energy storage. The overall efficiency of the gas-side coupled compressed air energy storage system is improved, and the unit can quickly reduce its load. When the gas-side coupled compressed air energy storage system of the coal-fired unit is in the energy release stage, the second valve 30 is opened and the first valve 29 is closed. The high-pressure air in the storage tank is heated by the third heat exchanger 24 and the fourth heat exchanger 26 and then enters the first expander 25 and the second expander 27 to expand and do work. The fifth valve 36 and the sixth valve 40 are opened and the third valve 31 and the fourth valve 32 are closed. The high-temperature heat transfer oil in the thermal oil storage tank 35 is used to heat the high-pressure air and release the steam in the steam accumulator 34 as the heating steam for the deaerator 11, thereby improving the overall efficiency of the gas-side coupled compressed air energy storage system of the coal-fired unit and the unit's load change rate.

[0015] In one embodiment of the present invention, the main steam extraction from the outlet of the coal-fired boiler 1 is connected to the high-pressure cylinder 2; the first stage steam extraction from the high-pressure cylinder 2 is connected to the steam side of the first high-pressure heater 8; the exhaust steam from the high-pressure cylinder 2 is connected to the steam side of the coal-fired boiler 1 and the second high-pressure heater 9 respectively; the reheat steam extraction from the outlet of the coal-fired unit is connected to the intermediate-pressure cylinder 3; the first stage steam extraction from the intermediate-pressure cylinder 3 is connected to the steam side of the third high-pressure heater 10; and the second stage steam extraction from the intermediate-pressure cylinder 3 is connected to the steam side of the deaerator 11.

[0016] like Figure 1 As shown, in this embodiment, the first-stage extraction steam from the high-pressure cylinder 2 is connected to the steam-side inlet of the first high-pressure heater 8 via an extraction steam pipeline, utilizing the waste heat of the steam to preheat the boiler feedwater and achieve cascade utilization of thermal energy. The exhaust steam from the high-pressure cylinder 2 is connected via pipelines to the reheater inlet of the coal-fired boiler 1 and the steam side of the second high-pressure heater 9, respectively, where the exhaust steam waste heat is further recovered by the second high-pressure heater 9 to increase the feedwater temperature and reduce boiler fuel consumption. Simultaneously, the reheated steam from the reheater outlet of the coal-fired boiler is transported via a high-temperature pipeline to the steam inlet of the intermediate-pressure cylinder 3 of the turbine to complete secondary energy conversion. The first-stage extraction steam drawn out during the power operation of the intermediate-pressure cylinder 3 is connected to the steam side of the third high-pressure heater 10 to participate in the feedwater preheating cycle. The second-stage extraction steam from the intermediate-pressure cylinder 3 is connected to the steam-side inlet of the deaerator 11 via an insulated pipeline, utilizing the thermal energy and pressure of the steam to remove dissolved oxygen from the feedwater, preventing oxygen corrosion of thermal equipment and ensuring long-term stable operation of the unit.

[0017] In one embodiment of the present invention, the exhaust steam of the intermediate-pressure cylinder 3 is connected to the steam side of the low-pressure cylinder 4 and the first low-pressure heater 13 respectively; the first stage extraction steam of the low-pressure cylinder 4 is connected to the steam side of the second low-pressure heater 14; the second stage extraction steam of the low-pressure cylinder 4 is connected to the steam side of the third low-pressure heater 15; the third stage extraction steam of the low-pressure cylinder 4 is connected to the steam side of the fourth low-pressure heater 16; the exhaust steam of the low-pressure cylinder 4 is connected to the condenser 6; the condensate at the outlet of the condenser 6 enters the fourth low-pressure heater 16, the third low-pressure heater 15, the second low-pressure heater 14, and the first low-pressure heater 13 in sequence via the condensate pump 7 and is connected to the deaerator 11; the feedwater at the outlet of the deaerator 11 enters the third high-pressure heater 10, the second high-pressure heater 9, and the first high-pressure heater 8 in sequence via the high-pressure water pump and is connected to the coal-fired boiler 1; the high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4 are coaxially connected to the first generator 5.

[0018] like Figure 1As shown, in this embodiment, the first-stage extraction steam is connected to the steam side of the second low-pressure heater 14 through an insulated extraction steam pipe. The second-stage extraction steam is connected to the steam side of the third low-pressure heater 15, and the third-stage extraction steam is connected to the steam side of the fourth low-pressure heater 16. Through the stepped preheating design of the four-stage low-pressure heaters, the waste heat of the steam is maximized, and the condensate temperature is increased to reduce system energy consumption. The final exhaust steam from the low-pressure cylinder 4 is connected to the condenser 6. The condensate formed after cooling and condensation is powered by the condensate pump 7 and flows sequentially through the fourth low-pressure heater 16, the third low-pressure heater 15, the second low-pressure heater 14, and the first low-pressure heater 13 to complete the step-by-step temperature increase. Then it is sent to the deaerator 11 for deep deoxygenation treatment to avoid corrosion of thermal equipment by dissolved oxygen in the water. The qualified feedwater from the outlet of the deaerator 11 is pressurized by a high-pressure water pump and then sequentially enters the third high-pressure heater 10, the second high-pressure heater 9, and the first high-pressure heater 8 to be further heated to the boiler's required temperature, and finally delivered to the coal-fired boiler 1 to participate in the steam-water circulation.

[0019] In one embodiment of the present invention, the condensate from the outlet of the condenser 6 enters the second heat exchanger 21 and the first heat exchanger 19 via the condensate pump 7 and the first valve 29, and is then connected to the water side of the deaerator 11; air from the atmosphere enters the first compressor 18, the first heat exchanger 19, the second compressor 20, and the second heat exchanger 21 in sequence and is connected to the air storage tank; the first compressor 18 and the second compressor 20 are coaxially connected to the motor 22; the air from the outlet of the air storage tank enters the third heat exchanger 24, the first expander 25, the fourth heat exchanger 26, and the second expander 27 in sequence via the second valve 30 and is connected to the atmosphere; the outlet of the thermal oil pump 37 enters the fourth heat exchanger 26 and the third heat exchanger 24 via the sixth valve 40 and is then connected to the inlet of the cold thermal oil storage tank 38; the first expander 25 and the second expander 27 are coaxially connected to the second generator 28.

[0020] like Figure 1As shown, in this embodiment, air from the atmosphere enters the first compressor 18, the first heat exchanger 19, the second compressor 20, and the second heat exchanger 21 sequentially through the air intake channel. After two stages of compression to increase pressure and temperature, heat energy exchange is completed in the heat exchanger, and finally, the high-pressure air is stored in the air tank for later use. The first compressor 18 and the second compressor 20 are coaxially connected by a rigid coupling and driven by an electric motor 22 to ensure synchronous speed and stable pressure increase during the two-stage compression process. The high-pressure air from the outlet of the gas storage tank, after its flow rate is regulated by the second valve 30, flows sequentially through the third heat exchanger 24, the first expander 25, the fourth heat exchanger 26, and the second expander 27. During the expansion process, it releases energy and cools and depressurizes before finally being discharged into the atmosphere. At the same time, the high-temperature heat transfer oil from the outlet of the heat transfer oil pump 37 is diverted by the sixth valve 40 and flows into the hot oil channels of the fourth heat exchanger 26 and the third heat exchanger 24 respectively, providing thermal energy support for the expansion process of the high-pressure air. The low-temperature heat transfer oil after heat exchange is then collected into the cold heat transfer oil storage tank 38 for recycling.

[0021] In one embodiment of the present invention, the outlet of the heat transfer medium heat exchanger 17 is connected to the heat transfer oil side inlet of the steam heat transfer oil heat exchanger 33, the heat transfer oil side outlet of the steam heat transfer oil heat exchanger 33 is connected to the inlet of the hot heat transfer oil storage tank 35, the outlet of the cold heat transfer oil storage tank 38 is connected to the inlet of the cold heat transfer oil pump 39, the outlet of the cold heat transfer oil pump 39 is connected to the heat transfer oil side of the heat transfer medium heat exchanger 17 via the fourth valve 32, the high-temperature steam of the coal-fired boiler 1 is connected to the steam side inlet of the steam heat transfer oil heat exchanger 33 via the third valve 31, the steam side outlet of the steam heat transfer oil heat exchanger 33 is connected to the inlet of the steam accumulator 34, the outlet of the steam accumulator 34 is connected to the steam side inlet of the deaerator 11 via the fifth valve 36, and the outlet of the hot heat transfer oil storage tank 35 is connected to the inlet of the hot heat transfer oil pump 37.

[0022] like Figure 1 As shown, in this embodiment, the low-temperature heat transfer oil at the outlet of the cold heat transfer oil storage tank 38 is drawn out by the cold heat transfer oil pump 39. After the flow and pressure are regulated by the fourth valve 32 connected in series, it is connected to the heat transfer oil side inlet of the heat medium heat exchanger 17. In the heat exchanger, it absorbs heat to complete the temperature rise, ensuring a stable energy supply for the heat transfer oil system. At the same time, the high-temperature and high-pressure steam generated by the coal-fired boiler 1 is introduced into the steam side inlet of the steam heat transfer oil heat exchanger 33 after the flow is controlled by the third valve 31. It serves as the heat source for heating the heat transfer oil. The steam with a lower temperature after heat exchange is transported to the steam accumulator 34 through the outlet pipe to realize the temporary storage and buffering of steam energy, avoiding energy waste caused by direct steam discharge.

[0023] In one embodiment of the present invention, a coal-fired boiler 1 is used to heat high-pressure feedwater into steam or to heat the first-stage extraction steam of the high-pressure cylinder 2 into reheat steam; the high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 are used to convert the received steam thermal energy into mechanical energy; a first generator 5 is used to convert the received mechanical energy into electrical energy; a condenser 6 is used to condense the exhaust steam discharged from the low-pressure cylinder 4 into condensate; a condensate pump 7 is used to pressurize the condensate into low-pressure feedwater; a first low-pressure heater 13, a second low-pressure heater 14, a third low-pressure heater 15, and a fourth low-pressure heater 16 are also included. The low-pressure heater 16 is used to utilize the waste heat from the exhaust steam of the intermediate-pressure cylinder 3, the first stage extraction steam of the low-pressure cylinder 4, the second stage extraction steam, and the third stage extraction steam to heat the low-pressure feedwater; the deaerator 11 is used to use the second stage extraction steam of the intermediate-pressure cylinder 3 to heat and remove dissolved oxygen from the low-pressure feedwater; the high-pressure feedwater pump 12 is used to pressurize the low-pressure feedwater at the outlet of the deaerator 11 to high-pressure feedwater; the first high-pressure heater 8, the second high-pressure heater 9, and the third high-pressure heater 10 respectively utilize the first stage extraction steam and exhaust steam of the high-pressure cylinder 2, and the waste heat from the first stage extraction steam of the low-pressure cylinder 4 to heat the high-pressure feedwater.

[0024] In one embodiment of the present invention, an electric motor 22 is used to drive a first compressor 18 and a second compressor 20 to convert electrical energy into mechanical energy; the first compressor 18 and the second compressor 20 are used to compress air to convert mechanical energy into air internal energy; a first heat exchanger 19 and a second heat exchanger 21 are used to recover the heat of air compression to heat low-pressure feedwater; an air storage tank 23 is used to store high-pressure air; a third heat exchanger 24 and a fourth heat exchanger 26 are used to convert the heat energy of heat transfer oil to heat high-pressure air; a first expander 25 and a second expander 27 are used to expand high-pressure air to do work and convert the air internal energy into mechanical energy; a second generator 28 is used to convert the received mechanical energy into electrical energy; a heat transfer medium heat exchanger 17 is used to absorb the waste heat of flue gas using heat transfer oil; a first valve 29 is used to control the flow of low-pressure feedwater in the coal-fired unit subsystem into the first heat exchanger 19 and the second heat exchanger 21; and a second valve 30 is used to control the flow of high-pressure air in the air storage tank into the third heat exchanger 24.

[0025] In one embodiment of the present invention, a steam thermal oil heat exchanger 33 is used to heat thermal oil using high-temperature steam from a coal-fired boiler 1; a steam accumulator 34 is used to store the high-temperature steam after heat exchange; a hot thermal oil storage tank 35 is used to store high-temperature thermal oil; a cold thermal oil storage tank 38 is used to store low-temperature thermal oil; a hot thermal oil pump 37 is used to transport high-temperature thermal oil; and a cold thermal oil pump 39 is used to transport low-temperature thermal oil.

[0026] In one embodiment of the present invention, the third valve 31 is used to control the flow of high-temperature steam generated by the coal-fired boiler 1 into the steam heat transfer oil heat exchanger 33; the fourth valve 32 is used to control the flow of low-temperature heat transfer oil in the cold heat transfer oil storage tank 38 into the heat medium heat exchanger 17; the fifth valve 36 is used to control the flow of steam in the steam accumulator 34 into the deaerator 11; and the sixth valve 40 is used to control the flow of high-temperature heat transfer oil in the hot heat transfer oil storage tank 35 into the fourth heat exchanger 26 and the third heat exchanger 24.

[0027] Secondly, such as Figure 2 As shown, this embodiment of the invention also provides a method for coupled compressed air energy storage on the flue gas side of a coal-fired power unit, applied to the coupled compressed air energy storage system on the flue gas side of a coal-fired power unit mentioned in the above embodiments. The method includes: S1: When the coal-fired unit is operating at low load or reducing load, control the first valve 29, the third valve 31 and the fourth valve 32 to open, and the second valve 30, the fifth valve 36 and the sixth valve 40 to close. S2: When the coal-fired unit increases its load, control the first valve 29, the third valve 31 and the fourth valve 32 to close, and the second valve 30, the fifth valve 36 and the sixth valve 40 to open.

[0028] In this embodiment, when the flue gas-side coupled compressed air energy storage system of the coal-fired unit is in the energy storage stage, the first valve 29 is opened and the second valve 30 is closed. The motor 22 drives the first compressor 18 and the second compressor 20 to compress air. The generated high-pressure air flows through the first heat exchanger 19 and the second heat exchanger 21 and then enters the air storage tank. The heat of compression during the process is recovered into the turbine regenerative system, saving more extraction steam to do work in the turbine. The third valve 31 and the fourth valve 32 are opened and the fifth valve 36 and the sixth valve 40 are closed. The low-temperature heat transfer oil in the cold heat transfer oil storage tank 38 absorbs the waste heat of the flue gas and the heat of the steam and stores it in the hot heat transfer oil storage tank 35. The high-temperature steam after heat exchange enters the steam accumulator 34 for storage, thereby improving the efficiency of coal-fired power generation. The overall efficiency of the unit's flue gas-side coupled compressed air energy storage system is improved, while simultaneously enabling rapid load reduction of the unit. When the coal-fired unit's flue gas-side coupled compressed air energy storage system is in the energy release phase, the second valve 30 is opened and the first valve 29 is closed. The high-pressure air in the storage tank is heated by the third heat exchanger 24 and the fourth heat exchanger 26, and then enters the first expander 25 and the second expander 27 to expand and do work. The fifth valve 36 and the sixth valve 40 are opened and the third valve 31 and the fourth valve 32 are closed. The high-temperature heat transfer oil in the thermal oil storage tank 35 is used to heat the high-pressure air, and the steam in the steam accumulator 34 is released as heating steam for the deaerator 11, thereby improving the overall efficiency of the coal-fired unit's flue gas-side coupled compressed air energy storage system and the unit's load change rate.

[0029] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A flue gas-coupled compressed air energy storage system for a coal-fired power unit, characterized in that, It includes a coal-fired power unit subsystem, a compressed air energy storage subsystem, and a steam energy storage subsystem connected in sequence; The coal-fired unit subsystem includes a coal-fired boiler, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a first generator, a condenser, a condensate pump, a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, a fourth low-pressure heater, a deaerator, a high-pressure feedwater pump, a first high-pressure heater, a second high-pressure heater, a third high-pressure heater, and a heat exchanger; the heat exchanger is used to absorb waste heat from the flue gas side of the coal-fired boiler. The compressed air energy storage subsystem includes a first compressor, a second compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a first expander, a second expander, an air storage tank, a second generator, an electric motor, a first valve, and a second valve; The steam energy storage subsystem includes a steam heat exchanger, a steam accumulator, a thermal oil storage tank, a cold thermal oil storage tank, a thermal oil pump, a cold thermal oil pump, a third valve, a fourth valve, a fifth valve, and a sixth valve.

2. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 1, characterized in that, The main steam extraction from the coal-fired boiler outlet is connected to the high-pressure cylinder; the first-stage steam extraction from the high-pressure cylinder is connected to the steam side of the first high-pressure heater; the exhaust steam from the high-pressure cylinder is connected to the steam sides of both the coal-fired boiler and the second high-pressure heater; the reheat steam extraction from the coal-fired unit outlet is connected to the intermediate-pressure cylinder; the first-stage steam extraction from the intermediate-pressure cylinder is connected to the steam side of the third high-pressure heater; and the second-stage steam extraction from the intermediate-pressure cylinder is connected to the steam side of the deaerator.

3. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 2, characterized in that, The exhaust steam from the intermediate-pressure cylinder is connected to the steam side of the low-pressure cylinder and the first low-pressure heater, respectively; the first-stage extraction steam from the low-pressure cylinder is connected to the steam side of the second low-pressure heater; the second-stage extraction steam from the low-pressure cylinder is connected to the steam side of the third low-pressure heater; the third-stage extraction steam from the low-pressure cylinder is connected to the steam side of the fourth low-pressure heater; the exhaust steam from the low-pressure cylinder is connected to the condenser; the condensate from the condenser outlet is pumped sequentially into the fourth low-pressure heater, the third low-pressure heater, the second low-pressure heater, and the first low-pressure heater, and connected to the deaerator; the feedwater from the deaerator outlet is pumped sequentially into the third high-pressure heater, the second high-pressure heater, and the first high-pressure heater, and connected to the coal-fired boiler; the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder are coaxially connected to the first generator.

4. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 3, characterized in that, The condensate from the condenser outlet enters the second heat exchanger via the condensate pump and the first valve, and is then connected to the water side of the deaerator. Atmospheric air sequentially enters the first compressor, the first heat exchanger, the second compressor, and the second heat exchanger, and is connected to the air storage tank. The first compressor and the second compressor are coaxially connected to the electric motor. The air from the air storage tank outlet enters the third heat exchanger, the first expander, the fourth heat exchanger, and the second expander sequentially via the second valve, and is connected to the atmosphere. The outlet of the thermal oil pump enters the fourth heat exchanger and the third heat exchanger via the sixth valve, and is then connected to the inlet of the cold thermal oil storage tank. The first expander and the second expander are coaxially connected to the second generator.

5. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 4, characterized in that, The outlet of the heat transfer medium heat exchanger is connected to the inlet of the heat transfer oil side of the steam heat transfer oil heat exchanger. The outlet of the heat transfer oil side of the steam heat transfer oil heat exchanger is connected to the inlet of the hot heat transfer oil storage tank. The outlet of the cold heat transfer oil storage tank is connected to the inlet of the cold heat transfer oil pump. The outlet of the cold heat transfer oil pump is connected to the heat transfer oil side of the heat transfer medium heat exchanger via the fourth valve. The high-temperature steam from the coal-fired boiler is connected to the steam side inlet of the steam heat transfer oil heat exchanger via the third valve. The steam side outlet of the steam heat transfer oil heat exchanger is connected to the inlet of the steam accumulator. The outlet of the steam accumulator is connected to the steam side inlet of the deaerator via the fifth valve. The outlet of the hot heat transfer oil storage tank is connected to the inlet of the hot heat transfer oil pump.

6. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 5, characterized in that, The coal-fired boiler is used to heat high-pressure feedwater into steam or to heat the first-stage extraction steam of the high-pressure cylinder into reheat steam; the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder are used to convert the received steam heat energy into mechanical energy; the first generator is used to convert the received mechanical energy into electrical energy; the condenser is used to condense the exhaust steam discharged from the low-pressure cylinder into condensate; the condensate pump is used to pressurize the condensate into low-pressure feedwater; the first low-pressure heater, the second low-pressure heater, the third low-pressure heater, and the fourth low-pressure heater are respectively used to utilize the exhaust steam of the intermediate-pressure cylinder, the first-stage extraction steam of the low-pressure cylinder, the second-stage extraction steam, and the third-stage extraction steam waste heat to low-pressure feedwater; the deaerator is used to use the second-stage extraction steam of the intermediate-pressure cylinder to heat and remove dissolved oxygen from the low-pressure feedwater; the high-pressure feedwater pump is used to pressurize the low-pressure feedwater at the deaerator outlet into high-pressure feedwater; the first high-pressure heater, the second high-pressure heater, and the third high-pressure heater respectively utilize the first-stage extraction steam and exhaust steam of the high-pressure cylinder, and the waste heat of the first-stage extraction steam of the low-pressure cylinder to heat the high-pressure feedwater.

7. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 6, characterized in that, The electric motor drives the first and second compressors to convert electrical energy into mechanical energy; the first and second compressors compress air to convert mechanical energy into air internal energy; the first and second heat exchangers recover the heat of air compression to heat low-pressure feedwater; the air storage tank stores high-pressure air; the third and fourth heat exchangers convert the heat energy of the heat transfer oil to heat the high-pressure air; the first and second expanders expand the high-pressure air to convert its internal energy into mechanical energy; the second generator converts the received mechanical energy into electrical energy; the heat transfer medium heat exchanger absorbs waste heat from the flue gas using the heat transfer oil; the first valve controls the flow of low-pressure feedwater from the coal-fired unit subsystem into the first and second heat exchangers; the second valve controls the flow of high-pressure air from the air storage tank into the third heat exchanger.

8. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 7, characterized in that, The steam-heated thermal oil heat exchanger is used to heat the thermal oil using high-temperature steam from the coal-fired boiler; the steam accumulator is used to store the high-temperature steam after heat exchange; the hot thermal oil storage tank is used to store the high-temperature thermal oil; the cold thermal oil storage tank is used to recover the low-temperature thermal oil; the hot thermal oil pump is used to transport the high-temperature thermal oil; and the cold thermal oil pump is used to transport the low-temperature thermal oil.

9. The flue gas-side coupled compressed air energy storage system for coal-fired power units according to claim 8, characterized in that, The third valve is used to control the flow of high-temperature steam generated by the coal-fired boiler into the steam heat transfer oil heat exchanger; the fourth valve is used to control the flow of low-temperature heat transfer oil in the cold heat transfer oil storage tank into the heat medium heat exchanger; the fifth valve is used to control the flow of steam in the steam accumulator into the deaerator; and the sixth valve is used to control the flow of high-temperature heat transfer oil in the hot heat transfer oil storage tank into the fourth heat exchanger and the third heat exchanger.

10. A method for coupled compressed air energy storage on the flue gas side of a coal-fired power unit, characterized in that, The flue gas-side coupled compressed air energy storage system applied to any one of claims 1-9 of a coal-fired power unit comprises: When the coal-fired power unit is operating at low load or reducing load, the first valve, the third valve, and the fourth valve are opened, while the second valve, the fifth valve, and the sixth valve are closed. When the coal-fired power unit increases its load, the first valve, the third valve, and the fourth valve are closed, while the second valve, the fifth valve, and the sixth valve are opened.

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