Compressed air energy storage and coal-fired unit cooperative power generation system

Abstract

The invention relates to a compressed air energy storage and coal-fired unit cooperative power generation system which comprises a coal-fired power generation system and a compressed air energy storage system coupled with the coal-fired power generation system. In the energy storage process, condensed water of the coal-fired power generation system enters the compressed air energy storage system from the diverter valve to absorb compression heat and then returns to the unit from the mixing valve; in the energy release process, steam extracted by the fifth-stage steam turbine enters the compressed air energy storage system from the diverter valve to primarily heat high-pressure air and then returns to the unit from the mixing valve, and steam extracted by the third-stage steam turbine enters the compressed air energy storage system from the diverter valve to further heat the high-pressure air and returns to the unit from the mixing valve. And meanwhile, the waste heat recovery heat exchanger is adopted for recovering exhaust gas of the expansion machine, and high-pressure air is preheated. According to the method, the operation flexibility and peak regulation capacity of the unit are remarkably improved, good engineering adaptability and economical efficiency are achieved, and the method is suitable for the scene that the coal-fired unit is flexibly transformed under the high-proportion renewable energy access background.

Description

Technical Field

[0001] This invention belongs to the field of compressed air energy storage technology, and in particular relates to a collaborative power generation system that uses compressed air energy storage and coal-fired power units for efficient thermal coupling to improve peak-shaving capacity. Background Technology

[0002] Significant progress has been made in the development of renewable energy in recent years, but its volatility and unpredictability remain major challenges to current technological development. This not only leads to a decline in the efficiency of renewable energy utilization but may also affect the safe and stable operation of the power grid, thereby threatening the reliability of the entire power system. To adapt to the new changes brought about by the integration of renewable energy into the grid, maintain real-time power balance in the grid, and ensure the safety and stability of the power system, flexible and efficient regulation methods are urgently needed.

[0003] Coal-fired power generating units are my country's main source of electricity, accounting for more than half of the country's total power generation, and play a crucial role in power grid peak shaving and frequency regulation. When renewable energy generation is high, coal-fired units need to participate deeply in peak shaving to cope with grid fluctuations and ensure power supply stability. They also need to maintain stable operating parameters and equipment safety during frequent load changes. However, coal-fired units face multiple challenges under deep peak shaving conditions, including reduced economic efficiency, increased pollutant emissions, reduced utilization hours, accelerated wear and tear due to frequent power adjustments, and a significant decline in power generation efficiency due to long-term operation deviating from design conditions. Therefore, with the increasing proportion of renewable energy generation, accelerating the flexibility upgrades of existing coal-fired power plants to improve their peak shaving and frequency regulation capabilities has become a key measure to ensure the stable operation of the power system.

[0004] Energy storage systems can regulate power output when there is a mismatch between power supply and demand, balancing the supply and demand of power producers and consumers, and effectively mitigating the impact of renewable energy grid connection on the power grid. Adding an additional energy storage system to a coal-fired power unit is an effective way to improve the unit's operational flexibility. Among energy storage systems, compressed air energy storage technology has advantages such as large scale, low cost, long lifespan, and high operational flexibility, and has great potential for application in renewable energy grid connection and power system peak shaving, attracting widespread attention. Furthermore, the operating temperature range of medium- and low-temperature compressed air energy storage systems is 100℃ to 400℃, matching the working fluid temperatures on the feedwater and extraction sides of the regenerative system in a coal-fired power unit, demonstrating significant coupling potential. Deeply coupling the highly flexible compressed air energy storage system with a coal-fired power unit that has stable power generation but limited regulation capabilities can effectively broaden the operating range of the coal-fired power unit, accelerate the unit's response speed to load changes, improve the unit's operational flexibility and peak shaving capacity, and reduce the low-load operating time of the coal-fired power unit during peak shaving. Meanwhile, by rationally designing the coupling structure, efficient heat transfer and comprehensive utilization can be achieved, which not only helps to improve the overall energy efficiency of the system, but also effectively reduces the investment cost of equipment such as heat storage tanks in compressed air energy storage systems, thereby achieving synergistic optimization of technical performance and economic benefits. Summary of the Invention

[0005] To address the insufficient regulation capacity of existing coal-fired power generation systems during deep peak shaving, this paper proposes a coupled system optimization scheme integrating compressed air energy storage technology and coal-fired power generating units, aiming to significantly improve the peak shaving capacity and operational flexibility of the units. In the energy storage phase, the system utilizes surplus electricity from the coal-fired power units or grid electricity during off-peak hours to drive a multi-stage compressor, compressing air to a high-pressure, high-temperature state. The heat of compression is absorbed by the condensate from the coal-fired power unit, and the cooled high-pressure air is stored in a storage tank. In the energy release phase, the high-pressure air is preheated in stages using high-temperature steam extracted from the coal-fired power unit, significantly increasing its temperature before it enters the expander to perform work and generate electricity.

[0006] Under the premise of pressure matching and temperature matching coupling principles, the coupling structure of the system is initially designed. Then, the coupling structure of the coal-fired unit and the compressed air energy storage system is further optimized by adopting the energy cascade utilization method: In the energy release stage, the high-temperature steam extracted from the steam turbine is fully utilized to reheat the high-pressure air, so as to achieve the synergy between air temperature rise and system thermal energy; at the same time, a waste heat recovery heat exchanger is introduced to recover heat from the air at the outlet of the expander and use it to heat the high-pressure air after throttling, thereby significantly improving the overall thermal efficiency of the system and reducing energy loss.

[0007] The present invention is implemented as follows: a compressed air energy storage and coal-fired power generation system, comprising a coal-fired power generation system and a compressed air energy storage system coupled thereto;

[0008] The coal-fired power generation system includes a boiler 1, a high-pressure cylinder of a steam turbine 2, a diversion valve 3, an intermediate-pressure cylinder of a steam turbine 4, a low-pressure cylinder of a steam turbine 5, a generator 6, a condenser 7, a condensate pump 8, a diversion valve 9, low-pressure heaters 10, 11, 12, and 13, a diversion valve 14, a deaerator 15, a mixing valve 16, a feedwater pump 17, a diversion valve 18, high-pressure heaters 19, 20, and 21, a mixing valve 22, and a mixing valve 23.

[0009] The main steam outlet of boiler 1 is connected to the steam inlet of the high-pressure cylinder 2 of the steam turbine; the extraction steam outlet of the high-pressure cylinder 2 is connected to the extraction steam inlet of the high-pressure heater 21, and the steam outlet of the high-pressure cylinder 2 is connected to the inlet of the diversion valve 3; the diversion valve 3 divides the steam into two paths, one connected to the reheat steam inlet of boiler 1 and the other connected to the extraction steam inlet of the high-pressure heater 20; the reheat steam outlet of boiler 1 is connected to the steam inlet of the intermediate-pressure cylinder 4 of the steam turbine; the extraction steam outlet of the intermediate-pressure cylinder 4 is connected to the inlet of the deaerator 15 and the inlet of the diversion valve 18; the diversion valve 18 divides the steam into two paths, one connected to the compressed air storage... The inlet of the diversion valve 44 in the energy release process of the energy storage system is connected, and one path is connected to the inlet of the high-pressure heater 19; the steam outlet of the intermediate-pressure cylinder 4 of the steam turbine is connected to the steam inlet of the low-pressure cylinder 5 of the steam turbine; the extraction steam of the low-pressure cylinder 5 of the steam turbine is connected to the inlets of the low-pressure heaters 10, 11, and 12 and the inlet of the diversion valve 14; the diversion valve 14 divides the steam into two paths, one path is connected to the inlet of the diversion valve 40 in the energy release process of the compressed air energy storage system, and the other path is connected to the inlet of the low-pressure heater 13; the steam outlet of the low-pressure cylinder 5 of the steam turbine is connected to the steam inlet of the condenser 7; the condensate outlet of the condenser 7 is connected to the inlet of the condensate pump 8. The outlet of condensate pump 8 is connected to the inlet of diverter valve 9; diverter valve 9 divides the condensate into two paths, one connected to the inlet of diverter valve 29 in the compressed air energy storage system, and the other connected to the water inlet of low-pressure heater 10; the condensate outlet of low-pressure heater 10 is connected to the condensate inlet of condenser 7; the condensate outlet of low-pressure heater 13 is connected to the inlet of mixing valve 23, the other inlet of mixing valve 23 is connected to mixing valve 56 in the compressed air energy storage system's energy release process, and the outlet of mixing valve 23 is connected to the condensate inlet of low-pressure heater 12; the water inlet of low-pressure heater 13... The outlet of the deaerator 15 is connected to the water inlet of the deaerator 15; the water outlet of the deaerator 15 enters the inlet of the mixing valve 16; the outlet of the mixing valve 16 is connected to the inlet of the feed water pump 17; the outlet of the feed water pump 17 is connected to the water inlet of the high-pressure heater 19; the condensate outlet of the high-pressure heater 19 is connected to the inlet of the mixing valve 22, and the outlet of the mixing valve 22 is connected to the condensate inlet of the deaerator 15; the water outlet of the high-temperature heater 21 is connected to the feed water inlet of the boiler 1; the high-pressure cylinder 2, the intermediate-pressure cylinder 4, and the low-pressure cylinder 5 of the turbine are connected by a rotating shaft and jointly drive the generator 6 to output electrical power.

[0010] The energy storage circuit of the compressed air energy storage system includes mixing valves 24, 25, and 26, flow divider valves 27, 28, and 29, heat exchangers 30, 31, 32, and 33, electric motor 34, compressors 35, 36, 37, and 38, and air storage tank 39.

[0011] Air enters compressor 35, and the outlet of compressor 35 is connected to the heat source inlet of heat exchanger 30; the heat source outlet of heat exchanger 30 is connected to the inlet of compressor 36; the outlet of compressor 36 is connected to the heat source inlet of heat exchanger 31; the heat source outlet of heat exchanger 31 is connected to the inlet of compressor 37; the outlet of compressor 37 is connected to the heat source inlet of heat exchanger 32; the heat source outlet of heat exchanger 32 is connected to the inlet of compressor 38; the outlet of compressor 38 is connected to the heat source inlet of heat exchanger 33; the heat source outlet of heat exchanger 33 is connected to the inlet of air receiver 39; compressors 35, 36, 37, and 38 are connected via a rotating shaft and driven by motor 34; the outlet of flow divider valve 9 is connected to flow divider valve 2. 9 are connected; the diverter valve 29 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 33 and the other connected to the inlet of diverter valve 28; the diverter valve 28 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 32 and the other connected to the inlet of diverter valve 27; the diverter valve 27 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 31 and the other connected to the cold source inlet of heat exchanger 30; the cold source outlets of heat exchangers 30 and 31 are connected to the inlet of mixing valve 24; the cold source outlets of heat exchangers 32 and 33 are connected to the inlet of mixing valve 26; the outlets of mixing valves 24 and 26 are connected to the inlet of mixing valve 25, and the outlet of mixing valve 25 is connected to the inlet of mixing valve 16.

[0012] The energy release circuit of the compressed air energy storage system includes flow divider valves 40, 41, and 42; throttle valve 43; flow divider valves 44, 45, and 46; mixing valves 47, 48, and 49; high-temperature heat exchangers 50, 51, 52, and 53; mixing valves 54, 55, and 56; low-temperature heat exchangers 57, 58, 59, and 60; waste heat recovery heat exchanger 61; generator 62; and expanders 63, 64, 65, and 66.

[0013] The outlet of the gas storage tank 39 is connected to the inlet of the throttle valve 43, and the outlet of the throttle valve 43 is connected to the cold source inlet of the waste heat recovery heat exchanger 61; the cold source outlet of the waste heat recovery heat exchanger 61 is connected to the cold source outlet of the low-temperature heat exchanger 60; the cold source outlet of the low-temperature heat exchanger 60 is connected to the cold source inlet of the high-temperature heat exchanger 53; the cold source outlet of the high-temperature heat exchanger 53 is connected to the inlet of the expander 66; the outlet of the expander 66 is connected to the cold source inlet of the low-temperature heat exchanger 59, the cold source outlet of the low-temperature heat exchanger 59 is connected to the cold source inlet of the high-temperature heat exchanger 52, the cold source outlet of the high-temperature heat exchanger 52 is connected to the inlet of the expander 65; the outlet of the expander 65 is connected to the cold source inlet of the low-temperature heat exchanger 58, and the cold source outlet of the low-temperature heat exchanger 58 is connected to the cold source inlet of the high-temperature heat exchanger 51. The cold source inlet of the high-temperature heat exchanger 51 is connected to the cold source outlet of the expander 64; the outlet of the expander 64 is connected to the cold source inlet of the low-temperature heat exchanger 57, the cold source outlet of the low-temperature heat exchanger 57 is connected to the cold source inlet of the high-temperature heat exchanger 50, and the cold source outlet of the high-temperature heat exchanger 50 is connected to the inlet of the expander 63; the outlet of the expander 63 is connected to the heat source inlet of the waste heat recovery heat exchanger 61; the outlet of the diversion valve 14 is connected to the inlet of the diversion valve 40; the diversion valve 40 divides the extracted steam into two paths, one connected to the heat source inlet of the low-temperature heat exchanger 57 and the other connected to the inlet of the diversion valve 41; the diversion valve 41 divides the extracted steam into two paths, one connected to the heat source inlet of the low-temperature heat exchanger 58 and the other connected to the inlet of the diversion valve 42; the diversion valve 42 The extracted steam is divided into two paths: one connected to the heat source inlet of low-temperature heat exchanger 59, and the other connected to the heat source inlet of low-temperature heat exchanger 60; the heat source outlets of low-temperature heat exchangers 57 and 58 are connected to the inlet of mixing valve 54; the outlet of mixing valve 54 and the heat source outlet of low-temperature heat exchanger 59 are connected to the inlet of mixing valve 55; the outlet of mixing valve 55 and the heat source outlet of low-temperature heat exchanger 60 are connected to the inlet of mixing valve 56; the outlet of mixing valve 56 is connected to the inlet of mixing valve 23; the outlet of diverter valve 18 is connected to the inlet of diverter valve 44; diverter valve 44 divides the extracted steam into two paths: one connected to the heat source inlet of high-temperature heat exchanger 50, and the other connected to the inlet of diverter valve 45; diverter valve 45 divides the extracted steam into two paths: one connected to the heat source inlet of high-temperature heat exchanger 50, and the other connected to the inlet of diverter valve 45. The heat source inlet of the high-temperature heat exchanger 51 is connected to the heat source inlet of the diverter valve 46; the diverter valve 46 divides the extracted steam into two paths, one connected to the heat source inlet of the high-temperature heat exchanger 52 and the other connected to the heat source inlet of the high-temperature heat exchanger 53; the heat source outlets of the high-temperature heat exchanger 50 and the low-temperature heat exchanger 51 are connected to the inlet of the mixing valve 47; the outlet of the mixing valve 47 and the heat source outlet of the low-temperature heat exchanger 52 are connected to the inlet of the mixing valve 48; the outlet of the mixing valve 48 and the heat source outlet of the low-temperature heat exchanger 53 are connected to the inlet of the mixing valve 49; the outlet of the mixing valve 49 is connected to the inlet of the mixing valve 22; the expanders 63, 64, 65 and 66 are connected by a rotating shaft and jointly drive the generator 62 to output electrical power.

[0014] Furthermore, the power source for the compressor 34 is the electricity that the coal-fired power generation system cannot connect to the grid during deep peak shaving.

[0015] Furthermore, the gas storage tank 24 is filled with high-pressure air at a pressure of 10.248 MPa.

[0016] Furthermore, the cascade heating structure uses steam extracted from the fifth stage turbine of the coal-fired unit (steam entering the low-temperature heater 13) as low-temperature steam to preliminarily heat the high-pressure air; and uses steam extracted from the third stage turbine of the coal-fired unit (steam entering the high-temperature heater 19) as high-temperature steam to further heat the high-pressure air.

[0017] Furthermore, the high-pressure air is heated to 145°C after the first stage of heating, and then enters the expander at 220°C after the second stage of heating.

[0018] Furthermore, the waste heat recovery structure uses the outlet air of the expander 63 as a heat source and employs a waste heat recovery heat exchanger 61 to heat the high-pressure air after it has been throttled by the throttle valve 43.

[0019] Furthermore, the outlet air temperature of the expander 63 is 105°C.

[0020] Furthermore, the exhaust temperature of the waste heat recovery heat exchanger 61 is 29°C.

[0021] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0022] First, this invention proposes a highly efficient thermodynamic coupling scheme between a compressed air energy storage system and a coal-fired power generation unit, significantly improving the peak-shaving capacity and operational flexibility of the coal-fired unit. In the energy storage phase, the system utilizes the surplus power generation capacity or off-peak electricity of the coal-fired unit to drive a compressor, compressing air to a high-pressure state. The heat of compression is absorbed through the unit's condensate system, achieving heat recovery and reuse, thus improving the overall energy efficiency of the system. In the energy release phase, the system uses multi-stage steam extraction to heat the high-pressure air in stages, driving an expander to generate electricity once the temperature reaches a suitable level, thereby achieving efficient energy release and power output regulation. This scheme realizes deep collaborative operation between the energy storage system and the coal-fired power generation unit, effectively overcoming problems such as low operating efficiency and difficulty in regulation under low-load conditions. It provides a feasible and practical system integration path for the flexible transformation of traditional coal-fired power plants, filling the technological gap in the multi-load collaborative operation of compressed air energy storage technology and coal-fired power generation units.

[0023] Secondly, this invention introduces the concept of energy cascade utilization to optimize the system structure. By rationally designing the compressed air heating path and heat recovery mechanism, a highly efficient coupled system for deep recycling of thermal energy is constructed. During the energy release process, high-pressure air is heated by extracting steam from a multi-stage steam turbine, and a waste heat recovery heat exchanger is installed during the expansion stage to fully recover the low-grade heat energy in the exhaust gas after expansion, which is then used for the preheating process of compressed air, significantly improving the thermodynamic efficiency of the entire system. Simultaneously, addressing the significant differences in the operating characteristics of coal-fired units under different load conditions, a set of optimal matching structures and operating parameters is obtained through thermodynamic simulation calculations, further enhancing the system's thermal matching capability and load regulation performance under dynamic operating conditions.

[0024] Third, this invention addresses the technical bottlenecks of traditional coal-fired heating and power generation systems, such as insufficient load regulation capacity and limited peak-shaving depth, by overcoming the limitation of the minimum stable combustion load of the boiler. Through the introduction and coordinated control of a compressed air energy storage system, flexible load regulation is achieved without altering the boiler's thermal load, effectively reducing the load factor of the coupled power generation system. The minimum stable operating load can be reduced from 30% THA to 20% THA, giving the unit a wider operating regulation range and effectively mitigating the response lag problem caused by boiler thermal inertia. Furthermore, the compressed air energy storage system can significantly improve the unit's load increase and decrease rates, enhance the system's rapid response capability to fluctuations in renewable energy output, and significantly strengthen the peak-shaving support role of coal-fired power generation systems in the new power system. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the collaborative power generation system of the present invention, which uses compressed air energy storage and efficient thermal coupling with a coal-fired unit to improve peak-shaving capability.

[0026] Figure 2 The simulation results are presented for different coupling schemes between compressed air energy storage systems and coal-fired power units under different load conditions of the coal-fired power units during the energy storage process.

[0027] Figure 3 The simulation results of different coupling schemes between the compressed air energy storage system and the coal-fired unit during the energy release process are presented under different load conditions of the coal-fired unit.

[0028] Figure 4 Due to the variations in peak-shaving capacity and depth of the coupled system under different loads, the parameters of coal-fired units under variable loads change significantly.

[0029] Figure 5 This represents the change in power generation of the coupled system under different loads.

[0030] In the diagram: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Diverter valve; 4. Intermediate-pressure cylinder of steam turbine; 5. Low-pressure cylinder of steam turbine; 6. Generator; 7. Condenser; 8. Condensate pump; 9. Diverter valve; 10-13. Low-pressure heater; 14. Diverter valve; 15. Deaerator; 16. Mixing valve; 17. Feedwater pump; 18. Diverter valve; 19-21. High-pressure heater; 22. Mixing valve; 23-26. Mixing valve; 27-29. 30-33, Flow divider valve; 34, Heat exchanger; 35-38, Electric motor; 39, Compressor; 40-42, Flow divider valve; 43, Throttling valve; 44-46, Flow divider valve; 47, Mixing valve; 48, Mixing valve; 49, Mixing valve; 50-53, High-temperature heat exchanger; 54-56, Mixing valve; 57-60, Low-temperature heat exchanger; 61, Waste heat recovery heat exchanger; 62, Generator; 63-66, Expander. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] like Figure 1 As shown, the present invention provides a synergistic power generation system for improving peak-shaving capacity through efficient thermal coupling of compressed air energy storage and coal-fired power units, comprising a coal-fired power generation system and a compressed air energy storage system coupled thereto;

[0033] The coal-fired power generation system includes a boiler 1, a high-pressure cylinder of a steam turbine 2, a diversion valve 3, an intermediate-pressure cylinder of a steam turbine 4, a low-pressure cylinder of a steam turbine 5, a generator 6, a condenser 7, a condensate pump 8, a diversion valve 9, low-pressure heaters 10, 11, 12, and 13, a diversion valve 14, a deaerator 15, a mixing valve 16, a feedwater pump 17, a diversion valve 18, high-pressure heaters 19, 20, and 21, a mixing valve 22, and a mixing valve 23.

[0034] The main steam outlet of boiler 1 is connected to the steam inlet of the high-pressure cylinder 2 of the steam turbine; the extraction steam outlet of the high-pressure cylinder 2 is connected to the extraction steam inlet of the high-pressure heater 21, and the steam outlet of the high-pressure cylinder 2 is connected to the inlet of the diversion valve 3; the diversion valve 3 divides the steam into two paths, one connected to the reheat steam inlet of boiler 1 and the other connected to the extraction steam inlet of the high-pressure heater 20; the reheat steam outlet of boiler 1 is connected to the steam inlet of the intermediate-pressure cylinder 4 of the steam turbine; the extraction steam outlet of the intermediate-pressure cylinder 4 is connected to the inlet of the deaerator 15 and the inlet of the diversion valve 18; the diversion valve 18 divides the steam into two paths, one connected to the compressed air storage... The inlet of the diversion valve 44 in the energy release process of the energy storage system is connected, and one path is connected to the inlet of the high-pressure heater 19; the steam outlet of the intermediate-pressure cylinder 4 of the turbine is connected to the steam inlet of the low-pressure cylinder 5 of the turbine; the extraction steam from the low-pressure cylinder 5 of the turbine is connected to the inlets of the low-pressure heaters 10, 11, and 12 and the inlet of the diversion valve 14; the diversion valve 14 divides the steam into two paths, one path is connected to the inlet of the diversion valve 40 in the energy release process of the compressed air energy storage system, and the other path is connected to the inlet of the low-pressure heater 13; the steam outlet of the low-pressure cylinder 5 of the turbine is connected to the steam inlet of the condenser 7; the condensate outlet of the condenser 7 is connected to the condensate pump 8. The inlet is connected; the outlet of condensate pump 8 is connected to the inlet of diverter valve 9; diverter valve 9 divides the condensate into two paths, one connected to the inlet of diverter valve 29 in the compressed air energy storage system, and the other connected to the water inlet of low-pressure heater 10; the condensate outlet of low-pressure heater 10 is connected to the condensate inlet of condenser 7; the condensate outlet of low-pressure heater 13 is connected to the inlet of mixing valve 23, the other inlet of mixing valve 23 is connected to mixing valve 56 in the compressed air energy storage system's energy release process, and the outlet of mixing valve 23 is connected to the condensate inlet of low-pressure heater 12; the water inlet of low-pressure heater 13... The outlet is connected to the water inlet of deaerator 15; the water outlet of deaerator 15 enters the inlet of mixing valve 16; the outlet of mixing valve 16 is connected to the inlet of feedwater pump 17; the outlet of feedwater pump 17 is connected to the water inlet of high-pressure heater 19; the condensate outlet of high-pressure heater 19 is connected to the inlet of mixing valve 22, and the outlet of mixing valve 22 is connected to the condensate inlet of deaerator 15; the water outlet of high-temperature heater 21 is connected to the feedwater inlet of boiler 1; the high-pressure cylinder 2, intermediate-pressure cylinder 4, and low-pressure cylinder 5 of the turbine are connected by a rotating shaft and jointly drive generator 6 to output electrical power.

[0035] The energy storage circuit of the compressed air energy storage system includes mixing valves 24, 25, and 26, flow divider valves 27, 28, and 29, heat exchangers 30, 31, 32, and 33, electric motor 34, compressors 35, 36, 37, and 38, and air storage tank 39.

[0036] Air enters compressor 35, and the outlet of compressor 35 is connected to the heat source inlet of heat exchanger 30; the heat source outlet of heat exchanger 30 is connected to the inlet of compressor 36; the outlet of compressor 36 is connected to the heat source inlet of heat exchanger 31; the heat source outlet of heat exchanger 31 is connected to the inlet of compressor 37; the outlet of compressor 37 is connected to the heat source inlet of heat exchanger 32; the heat source outlet of heat exchanger 32 is connected to the inlet of compressor 38; the outlet of compressor 38 is connected to the heat source inlet of heat exchanger 33; the heat source outlet of heat exchanger 33 is connected to the inlet of air receiver 39; compressors 35, 36, 37, and 38 are connected via a rotating shaft and driven by motor 34; the outlet of flow divider valve 9 is connected to flow divider valve 2. 9 are connected; the diverter valve 29 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 33 and the other connected to the inlet of diverter valve 28; the diverter valve 28 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 32 and the other connected to the inlet of diverter valve 27; the diverter valve 27 divides the condensate into two paths, one connected to the cold source inlet of heat exchanger 31 and the other connected to the cold source inlet of heat exchanger 30; the cold source outlets of heat exchangers 30 and 31 are connected to the inlet of mixing valve 24; the cold source outlets of heat exchangers 32 and 33 are connected to the inlet of mixing valve 26; the outlets of mixing valves 24 and 26 are connected to the inlet of mixing valve 25, and the outlet of mixing valve 25 is connected to the inlet of mixing valve 16.

[0037] The energy release circuit of the compressed air energy storage system includes flow divider valves 40, 41, and 42; throttle valve 43; flow divider valves 44, 45, and 46; mixing valves 47, 48, and 49; high-temperature heat exchangers 50, 51, 52, and 53; mixing valves 54, 55, and 56; low-temperature heat exchangers 57, 58, 59, and 60; waste heat recovery heat exchanger 61; generator 62; and expanders 63, 64, 65, and 66.

[0038] The outlet of the gas storage tank 39 is connected to the inlet of the throttle valve 43, and the outlet of the throttle valve 43 is connected to the cold source inlet of the waste heat recovery heat exchanger 61; the cold source outlet of the waste heat recovery heat exchanger 61 is connected to the cold source outlet of the low-temperature heat exchanger 60; the cold source outlet of the low-temperature heat exchanger 60 is connected to the cold source inlet of the high-temperature heat exchanger 53; the cold source outlet of the high-temperature heat exchanger 53 is connected to the inlet of the expander 66; the outlet of the expander 66 is connected to the cold source inlet of the low-temperature heat exchanger 59, the cold source outlet of the low-temperature heat exchanger 59 is connected to the cold source inlet of the high-temperature heat exchanger 52, the cold source outlet of the high-temperature heat exchanger 52 is connected to the inlet of the expander 65; the outlet of the expander 65 is connected to the cold source inlet of the low-temperature heat exchanger 58, and the cold source outlet of the low-temperature heat exchanger 58 is connected to the cold source inlet of the high-temperature heat exchanger 51. The cold source inlet of the high-temperature heat exchanger 51 is connected to the cold source outlet of the expander 64; the outlet of the expander 64 is connected to the cold source inlet of the low-temperature heat exchanger 57, the cold source outlet of the low-temperature heat exchanger 57 is connected to the cold source inlet of the high-temperature heat exchanger 50, and the cold source outlet of the high-temperature heat exchanger 50 is connected to the inlet of the expander 63; the outlet of the expander 63 is connected to the heat source inlet of the waste heat recovery heat exchanger 61; the outlet of the diversion valve 14 is connected to the inlet of the diversion valve 40; the diversion valve 40 divides the extracted steam into two paths, one connected to the heat source inlet of the low-temperature heat exchanger 57 and the other connected to the inlet of the diversion valve 41; the diversion valve 41 divides the extracted steam into two paths, one connected to the heat source inlet of the low-temperature heat exchanger 58 and the other connected to the inlet of the diversion valve 42; the diversion valve 42 The extracted steam is divided into two paths: one connected to the heat source inlet of low-temperature heat exchanger 59, and the other connected to the heat source inlet of low-temperature heat exchanger 60; the heat source outlets of low-temperature heat exchangers 57 and 58 are connected to the inlet of mixing valve 54; the outlet of mixing valve 54 and the heat source outlet of low-temperature heat exchanger 59 are connected to the inlet of mixing valve 55; the outlet of mixing valve 55 and the heat source outlet of low-temperature heat exchanger 60 are connected to the inlet of mixing valve 56; the outlet of mixing valve 56 is connected to the inlet of mixing valve 23; the outlet of diverter valve 18 is connected to the inlet of diverter valve 44; diverter valve 44 divides the extracted steam into two paths: one connected to the heat source inlet of high-temperature heat exchanger 50, and the other connected to the inlet of diverter valve 45; diverter valve 45 divides the extracted steam into two paths: one connected to the heat source inlet of high-temperature heat exchanger 50, and the other connected to the inlet of diverter valve 45. The heat source inlet of the high-temperature heat exchanger 51 is connected to the heat source inlet of the diverter valve 46; the diverter valve 46 divides the extracted steam into two paths, one connected to the heat source inlet of the high-temperature heat exchanger 52 and the other connected to the heat source inlet of the high-temperature heat exchanger 53; the heat source outlets of the high-temperature heat exchanger 50 and the low-temperature heat exchanger 51 are connected to the inlet of the mixing valve 47; the outlet of the mixing valve 47 and the heat source outlet of the low-temperature heat exchanger 52 are connected to the inlet of the mixing valve 48; the outlet of the mixing valve 48 and the heat source outlet of the low-temperature heat exchanger 53 are connected to the inlet of the mixing valve 49; the outlet of the mixing valve 49 is connected to the inlet of the mixing valve 22; the expanders 63, 64, 65 and 66 are connected by a rotating shaft and jointly drive the generator 62 to output electrical power.

[0039] In a preferred embodiment of the present invention, the power source of the compressor 34 is the power that the coal-fired power generation system cannot connect to the grid during deep peak shaving.

[0040] In a preferred embodiment of the present invention, the gas storage tank 24 is filled with high-pressure air at a pressure of 10.248 MPa.

[0041] As a preferred embodiment of the present invention, the stepped heating structure uses the steam extracted from the fifth stage turbine of the coal-fired unit (the steam entering the low-temperature heater (13)) as low-temperature steam to preliminarily heat the high-pressure air; and uses the steam extracted from the third stage turbine of the coal-fired unit (the steam entering the high-temperature heater (19)) as high-temperature steam to further heat the high-pressure air.

[0042] In a preferred embodiment of the present invention, the high-pressure air is heated to 145°C after the first stage of heating, and then enters the expander at 220°C after the second stage of heating.

[0043] In a preferred embodiment of the present invention, the waste heat recovery structure uses the outlet air of the expander (63) as a heat source and employs a waste heat recovery heat exchanger (61) to heat the high-pressure air after it has been throttled by the throttle valve (43).

[0044] In a preferred embodiment of the present invention, the outlet air temperature of the expander (63) is 105°C.

[0045] In a preferred embodiment of the present invention, the exhaust temperature of the waste heat recovery heat exchanger (61) is 29°C.

[0046] Evidence related to the technical effects obtained by the embodiments of the present invention.

[0047] To more intuitively illustrate the innovation and technical value of the present invention, this invention takes a 700MW subcritical coal-fired power unit in Shandong Province as the research object. This unit is allowed to operate continuously at 30%~100% load. Under rated load, the unit's power generation is 700MW, the heat consumption is 7777kJ / kWh, the main steam temperature is 538℃, the pressure is 16.67MPa, the flow rate is 2084.7t / h, the reheat steam temperature is 538℃, the pressure is 3.448MPa, the flow rate is 1772.5t / h, the exhaust temperature is 49.1℃, and the exhaust pressure is 0.01MPa. Since the parameters of the coal-fired power unit vary significantly under different loads, this paper provides a comparison chart of the efficiency of different coupling schemes under different loads (see...). Figure 2 and Figure 3 ) and the peak-shaving performance diagram of the coupled system under variable load (see Figure 4 and Figure 5 ).

[0048] Figure 2 The simulation results of different coupling schemes between the compressed air energy storage system and the coal-fired unit under different load conditions of the coal-fired unit are shown in the figure. It can be seen from the figure that different return water positions have a significant impact on the energy efficiency of the coupling system. The scheme of returning water to the outlet of the deaerator (15) shows the best energy efficiency of the coupling system under all operating loads, and reaches a maximum value of 54.3% under 40% load conditions, which is 4.7% to 11.3% higher than other schemes. Therefore, the present invention finally adopts the scheme of returning condensate to the deaerator during the energy storage process to maximize the system energy efficiency.

[0049] Figure 3 Simulation results of different coupling schemes between the compressed air energy storage system and the coal-fired power unit during the energy release process under different load conditions of the coal-fired power unit are presented. These include four different cascade heating schemes and a single-stage extraction steam heating scheme with the highest efficiency obtained through research. As shown in the figure, the energy efficiency of the coupled system with the cascade heating structure is significantly improved compared to the single-stage extraction steam scheme. The cascade extraction steam scheme with stages 3 and 5 exhibits the highest energy efficiency, reaching 62.9% at 100% THA, an improvement of 5.1% compared to the single-stage extraction steam structure. This is because the cascade heating structure has the smallest heat exchange temperature difference and the lowest heat loss. Therefore, this invention ultimately adopts a scheme using stage 3 and 5 cascade extraction steam to heat the high-pressure air during the energy release process to maximize the system's energy efficiency.

[0050] Figure 4 To account for the variations in peak-shaving capacity and depth of the coupled system under different loads, the parameters of coal-fired units change significantly under varying loads. While the compressed air energy storage system maintains the same power output during storage and release, its impact on unit power differs, thus altering the peak-shaving capacity. The maximum upward and downward peak-shaving capacities are observed at 30% THA, at 47.7MW and 70MW, respectively. The trend in peak-shaving depth mirrors that of peak-shaving capacity, with the maximum upward and downward peak-shaving depths at 30% THA, at 22.7% and 33.9%, respectively.

[0051] Figure 5 The figure shows the changes in power generation of the coupled system under different loads. Under 30% THA load of the coal-fired unit, the minimum load of the system decreases from 210MW to 140MW, of which the power generation of the coal-fired unit is 221MW and the energy storage capacity of the compressed air system is 81MW. Under 100% THA load of the coal-fired unit, the maximum power generation of the system increases from 700MW to 742MW, of which the power generation of the coal-fired unit is 682MW and the energy storage capacity of the compressed air system is 60MW.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A compressed air energy storage and coal-fired power generation system, characterized in that, This includes coal-fired power generation systems and their coupled compressed air energy storage systems; The coal-fired power generation system includes: Boiler (1), high-pressure cylinder of steam turbine (2), diversion valve (3), intermediate-pressure cylinder of steam turbine (4), low-pressure cylinder of steam turbine (5), generator (6), condenser (7), condensate pump (8), feed water pump (17), and matching heaters and valves; The compressed air energy storage system includes: Heat exchangers (30, 31, 32, 33), electric motor (34), compressor (35, 36, 37, 38), air tank (39), high-temperature heat exchangers (50, 51, 52, 53), low-temperature heat exchangers (57, 58, 59, 60), waste heat recovery heat exchangers (61), generator (62), expander (63, 64, 65, 66), and matching valves; During the energy storage process, the condensate from the coal-fired power generation system enters the compressed air energy storage system through the diversion valve (9) to absorb the heat of compression and then returns to the unit through the mixing valve (17). During the energy release process, the steam extracted from the fifth-stage turbine enters the compressed air energy storage system through the diversion valve (14) to preheat the high-pressure air and then returns to the unit through the mixing valve (26). The steam extracted from the third-stage turbine enters the compressed air energy storage system through the diversion valve (18) to further heat the high-pressure air and then returns to the unit through the mixing valve (22). At the same time, the waste heat recovery heat exchanger (61) is used to recover the exhaust gas from the expander (63) and preheat the high-pressure air.

2. The system according to claim 1, characterized in that, The compressor (34) is powered by electricity generated by the coal-fired power generation system during deep peak shaving that cannot be connected to the grid.

3. The system according to claim 1, characterized in that, The steam turbine extraction is carried out in stages according to the principle of energy cascade utilization, including the fifth stage extraction of steam from the low-pressure cylinder and the third stage extraction of steam from the intermediate-pressure cylinder, which are used for preliminary heating and secondary heating of compressed air, respectively.

4. The system according to claim 1, characterized in that, The waste heat recovery heat exchanger (61) is used to recover the residual heat in the expander exhaust and use the heat to heat the high-pressure air after throttling and depressurization, so as to preheat the compressed air and improve the system thermal efficiency.

5. The system according to claim 1, characterized in that, The compressors (35, 36, 37, 38) in the compressed air energy storage system are arranged in a multi-stage series, with intermediate cooling heat exchangers (30, 31, 32, 33) between each stage to reduce the air temperature in stages and reduce compression power consumption.

6. The system according to claim 1, characterized in that, During the energy storage phase, the condensate enters the intermediate heat exchanger in the compressed air energy storage system via the diversion valve (9), absorbs the heat of compression, and then flows back to the coal-fired power generation system via the mixing valve (17), thereby improving the heat recovery and utilization rate.

7. The system according to claim 1, characterized in that, The expanders (63, 64, 65, 66) in the energy release stage adopt a multi-stage series structure to adapt to compressed air of different pressure levels, realize efficient segmented expansion and drive the generator (62) to output electricity.

8. The system according to claim 1, characterized in that, The energy storage and release process is flexibly switched by setting up multiple sets of valves and diversion pipelines. It can adjust the air compression and expansion path according to the actual load of the coal-fired unit and the grid demand, thereby realizing the dynamic conversion of the system operation status and efficient peak shaving.

9. The system according to claim 1, characterized in that, The high-temperature heat exchangers (50, 51, 52, 53) and low-temperature heat exchangers (57, 58, 59, 60) are configured according to the temperature rise requirements of compressed air. The air is heated in multiple stages by the exhaust heat from the steam turbine and the waste heat from the expander, thereby improving the heat-to-work conversion efficiency.

10. The system according to claim 1, characterized in that, During peak-shaving operation, the minimum heat load of the boiler can be kept stable. The output power is adjusted by storing and releasing energy through the compressed air energy storage system, thereby breaking through the minimum operating load limit of the boiler and enhancing the peak-shaving depth and flexibility of the system.

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