A coal-fired power generation unit coupled with steam energy storage and its operation method

Abstract

The present invention relates to the technical field of coal-fired power generation, and particularly relates to a coal-fired power generation unit coupled with steam energy storage and an operation method thereof. The coal-fired power generation unit coupled with steam energy storage includes: a coal-fired system and a steam heat storage system; the coal-fired system includes a coal-fired boiler, high, medium, and low pressure cylinders, a condenser, a deaerator, a high-pressure heater, and a low-pressure heater, and the steam heat storage system includes a superheated steam high-temperature heat exchanger, a superheated steam low-temperature heat exchanger, a superheated steam thermal energy storage tank, a first cold storage tank, a first outlet pump, a high-temperature feed water heat exchanger, a reheated steam high-temperature heat exchanger, a reheated steam low-temperature heat exchanger, a saturated steam thermal energy storage tank, a second cold storage tank, a second outlet pump, a second feed water heat exchanger, and a condensate water tank. Through the coal-fired power generation unit coupled with steam energy storage provided by the present invention, the peak shaving capacity of the coal-fired power generation unit can be further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and particularly relates to a coal-fired power generation unit coupled with steam energy storage and an operation method thereof to achieve deep peak shaving. Background Art

[0002] At present, due to the slow growth rate of power consumption in the power grid, the rapid increase in the installed capacity of the power grid, and the rapid increase in the proportion of renewable energy power generation in the power grid, the peak-valley difference of the load in the daily operation of the power grid is constantly increasing. As the main power generation source, thermal power plants need to bear huge peak shaving pressures to maintain the stability of the power grid. During the daily load dispatching process, the frequency and time of peak shaving with a load lower than 50% of the rated load are constantly increasing, and the operating load even needs to be reduced to 30% of the rated load in some periods. However, if the normal peak shaving method is used to switch to the "wet state" load reduction method, it will increase the operation volume of the power plant and require fuel injection to stabilize combustion, with great risks and poor economy.

[0003] Therefore, regarding the flexibility of coal-fired units, some scholars have proposed an external energy storage system for steam pressure and heat storage. The two patents, "A Coal-Fired Power Generation System with Heat Storage and Pressure Storage and an Operation Method Thereof" (application patent number 202211068265.6) and "A Coal-Fired Power Generation System Coupled with Steam Energy Storage and an Operation Method Thereof" (application patent number 202210980571.0), both use steam as the heat storage method for thermal power units. However, a large number of storage devices that can withstand high-temperature and high-pressure steam need to be added to the systems of the above two technologies. However, due to the high requirements of high-temperature and high-pressure steam for storage devices, the safety is low, and a large floor area is required. Moreover, "A Thermal Power Plant Energy Storage and Heat Supply System and Method for Energy Cascade Utilization" (application patent number 202111267192.9) proposes to input the high-parameter extraction steam and low-parameter extraction steam of the steam turbine into the same energy storage device for energy storage, which is not conducive to achieving the hierarchical utilization of energy, and the energy utilization rate of its system is low. How to further improve the external energy storage system is a huge challenge for the energy industry in China. Summary of the Invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a coal-fired power generation unit coupled with steam energy storage and an operation method thereof, to achieve the hierarchical utilization of energy, improve the energy utilization rate of the system, and obtain a faster load increase rate, so that the unit can reach the target load faster.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A coal-fired power generation unit coupled with steam energy storage includes a coal-fired system and a steam heat storage system;

[0007] The coal-fired system includes a coal-fired boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a deaerator 6, a high-pressure heater 7, a high-temperature feed-water heat exchanger 8, a condenser 9, a low-pressure heater 10, a low-temperature feed-water heat exchanger 11, a superheated steam high-temperature heat exchanger 12, a reheated steam high-temperature heat exchanger 15, a first valve V1, a second valve V2, a third valve V3, a fourth valve V4, a twelfth valve V12, a thirteenth valve V13, and a fourteenth valve V14; the superheated steam outlet end of the coal-fired boiler 1 is connected to the hot-end inlet of the superheated steam high-temperature heat exchanger 12 through the third valve V3; the reheated steam outlet end of the coal-fired boiler 1 is connected to the hot-end inlet of the reheated steam high-temperature heat exchanger 15 through the fourth valve V4; the superheated steam outlet end of the coal-fired boiler 1 is connected to the high-pressure cylinder 2; the reheated steam outlet end of the coal-fired boiler 1 is connected to the intermediate-pressure cylinder 3; the outlet of the high-pressure cylinder 2 is respectively connected to the hot-end inlets of the coal-fired boiler 1 and the high-pressure heater 7; the outlet of the intermediate-pressure cylinder 3 is connected to the hot-end inlet of the high-pressure heater 7 through the thirteenth valve V13; the outlet of the intermediate-pressure cylinder 3 is connected to the deaerator 6 and the low-pressure cylinder 4; the outlet of the low-pressure cylinder 4 is connected to the hot-end inlet of the low-pressure heater 10 through the twelfth valve V12; the outlet of the low-pressure cylinder 4 is connected to the condenser 9; the outlet of the deaerator 6 is connected to the cold-end inlet of the high-pressure heater 7 through the first valve V1; the outlet of the deaerator 6 is connected to the cold-end inlet of the high-temperature feed-water heat exchanger 8 through the second valve V2; the cold-end outlets of the high-pressure heater 7 and the high-temperature feed-water heat exchanger 8 are connected to the coal-fired boiler 1; the condenser 9 is connected to the cold-end inlet of the low-pressure heater 10 through the fourteenth valve V14; the condenser 9 is connected to the cold-end inlet of the low-temperature feed-water heat exchanger 11 through the ninth valve V9; the cold-end outlets of the low-pressure heater 10 and the low-temperature feed-water heat exchanger 11 are connected to the inlet of the deaerator 6;

[0008] The steam heat storage system includes a first cold storage tank 13, a superheated steam heat storage tank 14, a reheated steam low-temperature heat exchanger 16, a superheated steam low-temperature heat exchanger 17, a second cold storage tank 18, a saturated steam heat storage tank 19, a condensate water tank 20, a first outlet pump P1, a second outlet pump P2, a fifth valve V5, a sixth valve V6, a seventh valve V7, an eighth valve V8, a tenth valve V10, an eleventh valve V11, and a condensate water pressure regulating valve V15; the cold-end outlet of the superheated steam high-temperature heat exchanger 12 is communicated with the superheated steam heat storage tank 14; the cold-end outlet of the reheated steam high-temperature heat exchanger 15 is communicated with the superheated steam heat storage tank 14; the cold-end inlet of the superheated steam high-temperature heat exchanger 12 is communicated with the first cold storage tank 13 through the fifth valve V5; the cold-end inlet of the reheated steam high-temperature heat exchanger 15 is communicated with the first cold storage tank 13 through the sixth valve V6; the superheated steam heat storage tank 14 is communicated with the hot-end inlet of the high-temperature feed water heat exchanger 8 through the tenth valve V10 and the first outlet pump P1; the hot-end outlet of the superheated steam high-temperature heat exchanger 12 is communicated with the hot-end inlet of the superheated steam low-temperature heat exchanger 17; the hot-end outlet of the reheated steam high-temperature heat exchanger 15 is communicated with the hot-end inlet of the reheated steam low-temperature heat exchanger 16; the cold-end outlet of the superheated steam low-temperature heat exchanger 17 is communicated with the inlet of the saturated steam heat storage tank 19; the cold-end outlet of the reheated steam high-temperature heat exchanger 16 is communicated with the inlet of the saturated steam heat storage tank 19; the cold-end inlet of the superheated steam low-temperature heat exchanger 17 is communicated with the second cold storage tank 18 through the seventh valve V7; the cold-end inlet of the reheated steam high-temperature heat exchanger 16 is communicated with the second cold storage tank 18 through the eighth valve V8; the outlet of the saturated steam heat storage tank 19 is communicated with the hot-end inlet of the low-temperature feed water heat exchanger 11 through the eleventh valve V11 and the second outlet pump P2; the hot-end outlets of the superheated steam low-temperature heat exchanger 17 and the reheated steam low-temperature heat exchanger 16 are communicated with the inlet of the condensate water tank 20; the outlet of the condensate water tank 20 is communicated with the deaerator 6 through the condensate water pressure regulating valve V15.

[0009] In the coal-fired system, a superheated steam diverter F5 is provided between the superheated steam outlet end of the coal-fired boiler 1 and the hot-end inlet of the superheated steam high-temperature heat exchanger 12 and the high-pressure cylinder 2; a reheated steam diverter F6 is provided between the reheated steam outlet end of the coal-fired boiler 1 and the hot-end inlet of the reheated steam high-temperature heat exchanger 15 and the intermediate-pressure cylinder 3; a first diverter F1 is provided between the deaerator 6 and the cold-end inlet of the high-pressure heater 7 and the cold-end inlet of the high-temperature feed water heat exchanger 8; a second diverter F2 is provided between the condenser 9 and the cold-end inlet of the low-pressure heater 10 and the cold-end inlet of the low-temperature feed water heat exchanger 11; a first feed water mixer M1 is provided between the coal-fired boiler 1 and the cold-end outlet of the high-pressure heater 7 and the cold-end outlet of the high-temperature feed water heat exchanger 8, and a second feed water mixer M2 is provided between the deaerator 6 and the cold-end outlet of the low-pressure heater 10 and the cold-end outlet of the low-temperature feed water heat exchanger 11.

[0010] In the steam energy storage system, a third diverter F3 is provided between the cold-end inlets of the first cold storage tank 13 and the superheated steam high-temperature heat exchanger 12 and the cold-end inlet of the reheated steam high-temperature heat exchanger 15; a fourth diverter F4 is provided between the cold-end inlets of the second cold storage tank 18 and the superheated steam low-temperature heat exchanger 17 and the cold-end inlet of the reheated steam low-temperature heat exchanger 16.

[0011] The steam temperature at the reheated steam outlet of the coal-fired boiler 1 is 580 - 650 °C, and the pressure is greater than 20 bar; the steam temperature at the steam outlet of the coal-fired boiler 1 is 580 - 650 °C, and the pressure is greater than 100 bar.

[0012] The coal-fired power generating unit integrated with steam energy storage can sequentially select to extract reheated steam and superheated steam from the coal-fired boiler 1 according to the load requirement of the coal-fired power generating unit to improve the peak shaving capacity of the unit.

[0013] In the coal-fired power generating unit integrated with steam energy storage, when the unit is increasing load and the condensate water tank 20 injects water into the deaerator 6, the condensate water pressure regulating valve V15 can be used to adjust the pressure of the condensate water to make it consistent with the pressure in the deaerator 6.

[0014] In the steam energy storage system, due to the high temperature in the superheated steam thermal energy storage tank 14, the heat transfer medium in the superheated steam thermal energy storage tank 14 is molten salt that can flow in the pipeline, and its allowable use temperature reaches 560 °C; while the temperature in the saturated steam thermal energy storage tank 19 is low, and the heat transfer medium in the saturated steam thermal energy storage tank 19 is Dowtherm, a high-temperature heat transfer oil of Dow Chemical that can flow in the pipeline, and the maximum working temperature of this heat transfer oil is 400 °C to save equipment costs.

[0015] Operation method of a coal-fired power generation unit coupled with steam energy storage. When the coal-fired power generation unit needs to start reducing load, first open the fourth valve V4, the sixth valve V6, and the eighth valve V8, and close the second valve V2, the ninth valve V9, the tenth valve V10, the eleventh valve V11, and the condensate pressure regulating valve V15. The reheated steam in the coal-fired boiler 1 exchanges heat with the molten salt flowing out of the first cold storage tank 13 through the reheated steam high-temperature heat exchanger 15. After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank 14. The reheated steam becomes saturated steam after releasing heat. Subsequently, the saturated steam continues to enter the reheated steam low-temperature heat exchanger 16 to exchange heat with the heat-conducting oil flowing out of the second cold storage tank 18. After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank 19, and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank 20. If the coal-fired power generation unit needs to continue reducing load, open the third valve V3, the fifth valve V5, and the seventh valve V7. The superheated steam in the coal-fired boiler 1 exchanges heat with the molten salt flowing out of the first cold storage tank 13 through the superheated steam high-temperature heat exchanger 12. After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank 14. The superheated steam becomes saturated steam after releasing heat. Subsequently, the saturated steam continues to enter the superheated steam low-temperature heat exchanger 17 to exchange heat with the heat-conducting oil flowing out of the second cold storage tank 18. After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank 19, and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank 20.

[0016] When the coal-fired power generation unit needs to start increasing load, open the tenth valve V10, the eleventh valve V11, the second valve V2, the ninth valve V9, and the fifteenth valve V15, and close the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6, the seventh valve V7, and the eighth valve V8. The molten salt flowing out of the superheated steam thermal energy storage tank 14 flows into the high-temperature feed water heat exchanger 8 through the first outlet pump P1 to heat the feed water flowing out of the deaerator 6. During the process of ensuring the stability of the feed water temperature, the extraction steam of the intermediate pressure cylinder 3 is reduced by adjusting the thirteenth valve V13. Subsequently, the heated feed water is mixed with the feed water heated by the high-pressure heater 7 at the first feed water mixer M1 and then enters the coal-fired boiler 1. The heat-conducting oil flowing out of the saturated steam thermal energy storage tank 19 flows into the low-temperature feed water heat exchanger 11 through the second outlet pump P2 to heat the feed water flowing out of the condenser 9. During the process of ensuring the stability of the feed water temperature, the extraction steam of the low-pressure cylinder 4 is reduced by adjusting the twelfth valve V12. Subsequently, the heated feed water is mixed with the feed water heated by the low-pressure heater 10 at the second feed water mixer M2 and then flows into the deaerator 6. The condensate water flowing out of the condensate water tank 20 is directly injected into the deaerator 6.

[0017] The advantages of the present invention are that the thermal power unit can respectively utilize molten salt and heat-conducting oil to store high-temperature heat energy and low-temperature heat energy during load reduction, and can utilize the high-temperature heat energy in the lava to reduce the extraction steam of the high-pressure cylinder and the low-temperature heat energy in the heat-conducting oil to reduce the extraction steam of the low-pressure cylinder during load increase, thereby realizing the cascade utilization of energy, improving the energy utilization rate of the system, and obtaining a faster load increase rate, enabling the unit to reach the target load faster. In addition, compared with directly storing high-temperature and high-pressure steam in the storage device, the high-temperature and high-pressure steam has high requirements for the storage device, low safety, and requires a large floor area. Utilizing lava and heat-conducting oil to respectively achieve heat storage in different temperature ranges can improve the safety and economy of the system. Brief Description of the Drawings

[0018] Figure 1 It is a structural schematic diagram of a coal-fired power generation unit with coupled steam energy storage according to the present invention.

[0019] In the figure, 1. Coal-fired boiler; 2. High-pressure cylinder; 3. Intermediate-pressure cylinder; 4. Low-pressure cylinder; 5. Generator; 6. Deaerator; 7. High-pressure heater; 8. High-temperature feed water heat exchanger; 9. Condenser; 10. Low-pressure heater; 11. Low-temperature feed water heat exchanger; 12. Superheated steam high-temperature heat exchanger; 13. First cold storage tank; 14. Superheated steam heat energy storage tank; 15. Reheat steam high-temperature heat exchanger; 16. Reheat steam low-temperature heat exchanger; 17. Superheated steam low-temperature heat exchanger; 18. Second cold storage tank; 19. Saturated steam heat energy storage tank; 20. Condensate water tank; V1-V14. Valves; V15. Condensate water pressure regulating valve; F1-F4. Dividers; F5. Superheated steam diverter; F6. Reheat steam diverter; M1. First feed water mixer; M2. Second feed water mixer; M3. Condensate water mixer; M4. Mixer; P1. First outlet pump; P2. Second outlet pump. Detailed Description of the Invention

[0020] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0021] The solutions in the embodiments are not intended to limit the protection scope of the present invention. Any equivalent implementation or modification without departing from the present invention is included in the protection scope of the present invention.

[0022] Such as Figure 1As shown in the figure, a coal-fired power generation unit coupled with steam energy storage according to the present invention includes: a coal combustion system and a steam heat storage system. Among them, the coal combustion system includes a coal-fired boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a deaerator 6, a high-pressure heater 7, a high-temperature feed water heat exchanger 8, a condenser 9, a low-pressure heater 10, a low-temperature feed water heat exchanger 11, a superheated steam high-temperature heat exchanger 12, a reheated steam high-temperature heat exchanger 15, a first diverter F1, a second diverter F2, a superheated steam diverter F5, a reheated steam diverter F6, a first valve V1, a second valve V2, a third valve V3, a fourth valve V4, a twelfth valve V12, a thirteenth valve V13, and a fourteenth valve V14; the superheated steam outlet end of the coal-fired boiler 1 is connected to the hot end inlet of the superheated steam high-temperature heat exchanger 12 through the third valve V3; the reheated steam outlet end of the coal-fired boiler 1 is connected to the hot end inlet of the reheated steam high-temperature heat exchanger 15 through the fourth valve V4; the superheated steam outlet end of the coal-fired boiler 1 is connected to the high-pressure cylinder 2; the reheated steam outlet end of the coal-fired boiler 1 is connected to the intermediate-pressure cylinder 3; the outlet of the high-pressure cylinder 2 is respectively connected to the hot end inlets of the coal-fired boiler 1 and the high-pressure heater 7; the outlet of the intermediate-pressure cylinder 3 is connected to the hot end inlet of the high-pressure heater 7 through the thirteenth valve V13; the outlet of the intermediate-pressure cylinder 3 is connected to the deaerator 6 through a combiner M4, and the outlet of the intermediate-pressure cylinder 3 is connected to the low-pressure cylinder 4; the outlet of the low-pressure cylinder 4 is connected to the hot end inlet of the low-pressure heater 10 through the twelfth valve V12; the outlet of the low-pressure cylinder 4 is connected to the condenser 9; the outlet of the deaerator 6 is connected to the cold end inlet of the high-pressure heater 7 through the first valve V1; the outlet of the deaerator 6 is connected to the cold end inlet of the high-temperature feed water heat exchanger 8 through the second valve V2; the cold end outlets of the high-pressure heater 7 and the high-temperature feed water heat exchanger 8 are connected to the coal-fired boiler 1; the condenser 9 is connected to the cold end inlet of the low-pressure heater 10 through the fourteenth valve V14; the condenser 9 is connected to the cold end inlet of the low-temperature feed water heat exchanger 11 through the ninth valve V9; the cold end outlets of the low-pressure heater 10 and the low-temperature feed water heat exchanger 11 are connected to the inlet of the deaerator 6; a superheated steam diverter F5 is provided between the superheated steam outlet end of the coal-fired boiler 1 and the hot end inlet of the superheated steam high-temperature heat exchanger 12 and the high-pressure cylinder 2; a reheated steam diverter F6 is provided between the reheated steam outlet end of the coal-fired boiler 1 and the hot end inlet of the reheated steam high-temperature heat exchanger 15 and the intermediate-pressure cylinder; a first diverter F1 is provided between the deaerator and the cold end inlets of the high-pressure heater 7 and the high-temperature feed water heat exchanger 8; a second diverter F2 is provided between the condenser 9 and the cold end inlets of the low-pressure heater 10 and the low-temperature feed water heat exchanger 11.

[0023] The steam heat storage system includes a first cold storage tank 13, a superheated steam heat storage tank 14, a reheated steam low-temperature heat exchanger 16, a superheated steam low-temperature heat exchanger 17, a second cold storage tank 18, a saturated steam heat storage tank 19, a condensate water tank 20, a first outlet pump P1, a second outlet pump P2, a fifth valve V5, a sixth valve V6, a seventh valve V7, an eighth valve V8, a tenth valve V10, an eleventh valve V11, a condensate water pressure regulating valve V15, a third diverter F3, and a fourth diverter F4; the cold-end outlet of the superheated steam high-temperature heat exchanger 12 is communicated with the superheated steam heat storage tank 14; the cold-end outlet of the reheated steam high-temperature heat exchanger 15 is communicated with the superheated steam heat storage tank 14; the cold-end inlet of the superheated steam high-temperature heat exchanger 12 is communicated with the first cold storage tank 13 through the fifth valve V5; the cold-end inlet of the reheated steam high-temperature heat exchanger 15 is communicated with the first cold storage tank 13 through the sixth valve V6; the superheated steam heat storage tank 14 is communicated with the hot-end inlet of the high-temperature feed water heat exchanger 8 through the tenth valve V10 and the first outlet pump P1; the hot-end outlet of the superheated steam high-temperature heat exchanger 12 is communicated with the hot-end inlet of the superheated steam low-temperature heat exchanger 17; the hot-end outlet of the superheated steam high-temperature heat exchanger 15 is communicated with the hot-end inlet of the reheated steam low-temperature heat exchanger 16; the cold-end outlet of the superheated steam low-temperature heat exchanger 17 is communicated with the inlet of the saturated steam heat storage tank 19 through the condensate water mixer M3; the cold-end outlet of the reheated steam high-temperature heat exchanger 16 is communicated with the inlet of the saturated steam heat storage tank 19 through the condensate water mixer M3; the cold-end inlet of the superheated steam low-temperature heat exchanger 17 is communicated with the second cold storage tank 18 through the seventh valve V7; the cold-end inlet of the reheated steam high-temperature heat exchanger 16 is communicated with the second cold storage tank 18 through the eighth valve V8; the outlet of the saturated steam heat storage tank 19 is communicated with the hot-end inlet of the low-temperature feed water heat exchanger 11 through the eleventh valve V11 and the second outlet pump P2; the hot-end outlets of the superheated steam low-temperature heat exchanger 17 and the reheated steam low-temperature heat exchanger 16 are communicated with the inlet of the condensate water tank 20; the outlet of the condensate water tank 20 is communicated with the deaerator 6 through the condensate water pressure regulating valve V15 and the mixer M4; a third diverter F3 is provided between the first cold storage tank 13 and the cold-end inlets of the superheated steam high-temperature heat exchanger 12 and the reheated steam high-temperature heat exchanger 15; a fourth diverter F4 is provided between the second cold storage tank 18 and the cold-end inlets of the superheated steam low-temperature heat exchanger 17 and the reheated steam low-temperature heat exchanger 16.

[0024] When the coal-fired power generation unit needs to start reducing the load, first open the fourth valve V4, the sixth valve V6, and the eighth valve V8, and close the second valve V2, the ninth valve V9, the tenth valve V10, the eleventh valve V11, and the condensate pressure regulating valve V15. The reheated steam in the coal-fired boiler 1 exchanges heat with the molten salt flowing out of the first cold storage tank 13 through the reheated steam high-temperature heat exchanger 15. After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank 14. The reheated steam becomes saturated steam after releasing heat, and then the saturated steam continues to enter the reheated steam low-temperature heat exchanger 16 to exchange heat with the heat-conducting oil flowing out of the second cold storage tank 18. After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank 19, and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank 20. If the coal-fired power generation unit needs to continue reducing the load, open the third valve V3, the fifth valve V5, and the seventh valve V7. The superheated steam in the coal-fired boiler 1 exchanges heat with the molten salt flowing out of the first cold storage tank 13 through the superheated steam high-temperature heat exchanger 12. After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank 14. The superheated steam becomes saturated steam after releasing heat, and then the saturated steam continues to enter the superheated steam low-temperature heat exchanger 17 to exchange heat with the heat-conducting oil flowing out of the second cold storage tank 18. After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank 19, and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank 20.

[0025] When the coal-fired power generation unit needs to start increasing the load, open the tenth valve V10, the eleventh valve V11, the second valve V2, the ninth valve V9, and the fifteenth valve V15, and close the third valve V3, the fourth valve V4, the fifth valve V5, the sixth valve V6, the seventh valve V7, and the eighth valve V8. The molten salt flowing out of the superheated steam thermal energy storage tank 14 flows into the high-temperature feed water heat exchanger 8 through the first outlet pump P1 to heat the feed water flowing out of the deaerator 6. Therefore, during the process of ensuring the stability of the feed water temperature, the extraction of the intermediate pressure cylinder 3 can be reduced by adjusting the thirteenth valve V13. Subsequently, the heated feed water is mixed with the feed water heated by the high-pressure heater 7 at the feed water mixer M1 and then enters the coal-fired boiler 1. The heat-conducting oil flowing out of the saturated steam thermal energy storage tank 19 flows into the low-temperature feed water heat exchanger 11 through the second outlet pump P2 to heat the feed water flowing out of the condenser 9. Therefore, during the process of ensuring the stability of the feed water temperature, the extraction of the low-pressure cylinder 4 can be reduced by adjusting the twelfth valve V12. Subsequently, the heated feed water is mixed with the feed water heated by the low-pressure heater 10 at the feed water mixer M2 and then flows into the deaerator 6. The condensate water flowing out of the condensate water tank 20 is directly injected into the deaerator 6.

[0026] Since the temperature in the superheated steam thermal energy storage tank 14 is relatively high, the heat transfer medium in the superheated steam thermal energy storage tank 14 is molten salt that can flow in the pipeline, and its allowable operating temperature can reach 560 °C; while the temperature in the saturated steam thermal energy storage tank 19 is relatively low, and the heat transfer medium in the saturated steam thermal energy storage tank 19 is Dowtherm, a high-temperature heat transfer oil of Dow Chemical that can flow in the pipeline. The maximum operating temperature of this heat transfer oil is 400 °C to save equipment costs.

[0027] The steam temperature at the reheat steam outlet of the coal-fired boiler is 580 - 650 °C, and the pressure is greater than 20 bar; the steam temperature at the steam outlet of the coal-fired boiler is 580 - 650 °C, and the pressure is greater than 100 bar.

[0028] A first diverter F1 and a second diverter F2 are respectively arranged at the outlets of the deaerator 6 and the condenser 9. A first feed water mixer M1 is arranged between the cold end outlet of the coal-fired boiler 1 and the high-pressure heater 7 and the cold end outlet of the high-temperature feed water heat exchanger 8. A second feed water mixer M2 is arranged between the cold end outlet of the deaerator 6 and the low-pressure heater 10 and the cold end outlet of the low-temperature feed water heat exchanger 11.

[0029] A superheated steam diverter F5 and a third valve V3 are arranged at the superheated steam outlet end of the coal-fired boiler. A reheat steam diverter F6 and a fourth valve V4 are arranged at the reheat steam outlet end of the coal-fired boiler 1.

[0030] According to the load requirements of the coal-fired unit, reheat steam and superheated steam can be sequentially extracted from the coal-fired boiler 1 to improve the peak shaving capacity of the unit. Moreover, when the unit is increasing load, when the condensate water tank 20 injects water into the deaerator 6, the condensate water pressure regulating valve V15 can be used to adjust the pressure of the condensate water to make it consistent with the pressure in the deaerator 6.

Claims

1. A coal-fired power generation unit coupled with steam energy storage, characterized in that, It includes a coal-fired system and a steam energy storage system; The coal-fired system includes a coal-fired boiler (1), a high-pressure cylinder (2), an intermediate-pressure cylinder (3), a low-pressure cylinder (4), a generator (5), a deaerator (6), a high-pressure heater (7), a high-temperature feed water heat exchanger (8), a condenser (9), a low-pressure heater (10), a low-temperature feed water heat exchanger (11), a superheated steam high-temperature heat exchanger (12), a reheated steam high-temperature heat exchanger (15), a first valve (V1), a second valve (V2), a third valve (V3), a fourth valve (V4), a twelfth valve (V12), a thirteenth valve (V13) and a fourteenth valve (V14); The superheated steam outlet end of the coal-fired boiler (1) is connected to the hot-end inlet of the superheated steam high-temperature heat exchanger (12) through the third valve (V3); The reheated steam outlet end of the coal-fired boiler (1) is connected to the hot-end inlet of the reheated steam high-temperature heat exchanger (15) through the fourth valve (V4); The superheated steam outlet end of the coal-fired boiler (1) is connected to the high-pressure cylinder (2); The reheated steam outlet end of the coal-fired boiler (1) is connected to the intermediate-pressure cylinder (3); The outlet of the high-pressure cylinder (2) is respectively connected to the hot-end inlets of the coal-fired boiler (1) and the high-pressure heater (7); The outlet of the intermediate-pressure cylinder (3) is connected to the hot-end inlet of the high-pressure heater (7) through the thirteenth valve (V13); The outlet of the intermediate-pressure cylinder (3) is connected to the deaerator (6) and the low-pressure cylinder (4); The outlet of the low-pressure cylinder (4) is connected to the hot-end inlet of the low-pressure heater (10) through the twelfth valve (V12); The outlet of the low-pressure cylinder (4) is connected to the condenser (9); The outlet of the deaerator (6) is connected to the cold-end inlet of the high-pressure heater (7) through the first valve (V1); The outlet of the deaerator (6) is connected to the cold-end inlet of the high-temperature feed water heat exchanger (8) through the second valve (V2); The cold-end outlet of the high-pressure heater (7) and the cold-end outlet of the high-temperature feed water heat exchanger (8) are connected to the coal-fired boiler (1); The condenser (9) is connected to the cold-end inlet of the low-pressure heater (10) through the fourteenth valve (V14); The condenser (9) is connected to the cold-end inlet of the low-temperature feed water heat exchanger (11) through the ninth valve (V9); The cold-end outlet of the low-pressure heater (10) and the cold-end outlet of the low-temperature feed water heat exchanger (11) are connected to the inlet of the deaerator (6); The steam heat storage system includes a first cold storage tank (13), a superheated steam heat storage tank (14), a reheated steam low-temperature heat exchanger (16), a superheated steam low-temperature heat exchanger (17), a second cold storage tank (18), a saturated steam heat storage tank (19), a condensate water tank (20), a first outlet pump (P1), a second outlet pump (P2), a fifth valve (V5), a sixth valve (V6), a seventh valve (V7), an eighth valve (V8), a tenth valve (V10), an eleventh valve (V11), and a condensate water pressure regulating valve (V15); the cold-end outlet of the superheated steam high-temperature heat exchanger (12) is communicated with the superheated steam heat storage tank (14); the cold-end outlet of the reheated steam high-temperature heat exchanger (15) is communicated with the superheated steam heat storage tank (14); the cold-end inlet of the superheated steam high-temperature heat exchanger (12) is connected to the first cold storage tank (13) through the fifth valve (V5); the cold-end inlet of the reheated steam high-temperature heat exchanger (15) is connected to the first cold storage tank (13) through the sixth valve (V6); the superheated steam heat storage tank (14) is connected to the hot-end inlet of the high-temperature feed water heat exchanger (8) through the tenth valve (V10) and the first outlet pump (P1); the hot-end outlet of the superheated steam high-temperature heat exchanger (12) is communicated with the hot-end inlet of the superheated steam low-temperature heat exchanger (17); the hot-end outlet of the reheated steam high-temperature heat exchanger (15) is communicated with the hot-end inlet of the reheated steam low-temperature heat exchanger (16); the cold-end outlet of the superheated steam low-temperature heat exchanger (17) is connected to the inlet of the saturated steam heat storage tank (19); the cold-end outlet of the reheated steam low-temperature heat exchanger (16) is connected to the inlet of the saturated steam heat storage tank (19); the cold-end inlet of the superheated steam low-temperature heat exchanger (17) is connected to the second cold storage tank (18) through the seventh valve (V7); the cold-end inlet of the reheated steam low-temperature heat exchanger (16) is connected to the second cold storage tank (18) through the eighth valve (V8); the outlet of the saturated steam heat storage tank (19) is connected to the hot-end inlet of the low-temperature feed water heat exchanger (11) through the eleventh valve (V11) and the second outlet pump (P2); the hot-end outlets of the superheated steam low-temperature heat exchanger (17) and the reheated steam low-temperature heat exchanger (16) are connected to the inlet of the condensate water tank (20); the outlet of the condensate water tank (20) is connected to the deaerator (6) through the condensate water pressure regulating valve (V15).

2. The coal-fired power generation unit with coupled steam energy storage according to claim 1, wherein In the coal-fired system, a superheated steam diverter (F5) is provided between the superheated steam outlet end of the coal-fired boiler (1), the hot-end inlet of the superheated steam high-temperature heat exchanger (12), and the high-pressure cylinder (2); a reheated steam diverter (F6) is provided between the reheated steam outlet end of the coal-fired boiler (1), the hot-end inlet of the reheated steam high-temperature heat exchanger (15), and the intermediate-pressure cylinder (3); a first diverter (F1) is provided between the deaerator (6), the cold-end inlet of the high-pressure heater (7), and the cold-end inlet of the high-temperature feed water heat exchanger (8); a second diverter (F2) is provided between the condenser (9), the cold-end inlet of the low-pressure heater (10), and the cold-end inlet of the low-temperature feed water heat exchanger (11); a first feed water mixer (M1) is provided between the coal-fired boiler (1) and the cold-end outlets of the high-pressure heater (7) and the high-temperature feed water heat exchanger (8), and a second feed water mixer (M2) is provided between the deaerator (6) and the cold-end outlets of the low-pressure heater (10) and the low-temperature feed water heat exchanger (11).

3. A coal-fired power generation unit with coupled steam energy storage according to claim 1, characterized in that, In the steam energy storage system, a third diverter (F3) is provided between the first cold storage tank (13), the cold-end inlet of the superheated steam high-temperature heat exchanger (12), and the cold-end inlet of the reheated steam high-temperature heat exchanger (15); a fourth diverter (F4) is provided between the second cold storage tank (18), the cold-end inlet of the superheated steam low-temperature heat exchanger (17), and the cold-end inlet of the reheated steam low-temperature heat exchanger (16).

4. A coal-fired power generation unit coupled with steam energy storage according to claim 1, characterized in that: The steam temperature at the reheated steam outlet of the coal-fired boiler (1) is 580 - 650 °C, and the pressure is greater than 20 bar; the steam temperature at the steam outlet of the coal-fired boiler (1) is 580 - 650 °C, and the pressure is greater than 100 bar.

5. A coal-fired power generation unit coupled with steam energy storage according to claim 1, characterized in that: It is possible to sequentially select to extract reheated steam and superheated steam from the coal-fired boiler (1) according to the load requirement of the coal-fired power generation unit to improve the peak shaving capacity of the unit.

6. A coal-fired power generation unit coupled with steam energy storage according to claim 1, characterized in that: When the unit is increasing load and the condensate water tank (20) injects water into the deaerator (6), the condensate water pressure regulating valve (V15) is used to adjust the pressure of the condensate water to make it consistent with the pressure in the deaerator (6).

7. A coal-fired power generation unit coupled with steam energy storage according to claim 1, characterized in that: In the steam energy storage system, since the temperature in the superheated steam thermal energy storage tank (14) is high, the heat transfer medium in the superheated steam thermal energy storage tank (14) is molten salt that can flow in the pipeline, and its allowable use temperature reaches 560 °C; while the temperature in the saturated steam thermal energy storage tank (19) is low, and the heat transfer medium in the saturated steam thermal energy storage tank (19) is Dowtherm, a high-temperature heat transfer oil of Dow Chemical that can flow in the pipeline, and the maximum working temperature of this heat transfer oil is 400 °C to save equipment costs.

8. The operating method of a coal-fired power generation unit coupled with steam energy storage according to any one of claims 1 to 7, characterized in that: When the coal-fired power generation unit needs to start reducing the load, first open the fourth valve (V4), the sixth valve (V6) and the eighth valve (V8), and close the second valve (V2), the ninth valve (V9), the tenth valve (V10), the eleventh valve (V11) and the condensate pressure regulating valve (V15). The reheated steam in the coal-fired boiler (1) exchanges heat with the molten salt flowing out of the first cold storage tank (13) through the reheated steam high-temperature heat exchanger (15). After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank (14). After releasing heat, the reheated steam becomes saturated steam. Subsequently, the saturated steam continues to enter the reheated steam low-temperature heat exchanger (16) to exchange heat with the heat-conducting oil flowing out of the second cold storage tank (18). After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank (19), and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank (20); if the coal-fired power generation unit needs to further reduce the load, open the third valve (V3), the fifth valve (V5) and the seventh valve (V7). The superheated steam in the coal-fired boiler (1) exchanges heat with the molten salt flowing out of the first cold storage tank (13) through the superheated steam high-temperature heat exchanger (12). After absorbing heat, the molten salt flows into the superheated steam thermal energy storage tank (14). After releasing heat, the superheated steam becomes saturated steam. Subsequently, the saturated steam continues to enter the superheated steam low-temperature heat exchanger (17) to exchange heat with the heat-conducting oil flowing out of the second cold storage tank (18). After absorbing heat, the heat-conducting oil flows into the saturated steam thermal energy storage tank (19), and the saturated steam becomes condensate after releasing heat and continues to flow into the condensate water tank (20). When the coal-fired power generation unit needs to start increasing the load, open the tenth valve (V10), the eleventh valve (V11), the second valve (V2), the ninth valve (V9) and the condensate pressure regulating valve (V15), and close the third valve (V3), the fourth valve (V4), the fifth valve (V5), the sixth valve (V6), the seventh valve (V7) and the eighth valve (V8). The molten salt flowing out of the superheated steam thermal energy storage tank (14) flows into the high-temperature feed water heat exchanger (8) through the first outlet pump (P1) to heat the feed water flowing out of the deaerator (6). During the process of ensuring the stability of the feed water temperature, the thirteenth valve (V13) is adjusted to reduce the extraction steam of the intermediate pressure cylinder (3). Subsequently, the heated feed water is mixed with the feed water heated by the high-pressure heater (7) at the first feed water mixer (M1), and then enters the coal-fired boiler (1); the heat-conducting oil flowing out of the saturated steam thermal energy storage tank (19) flows into the low-temperature feed water heat exchanger (11) through the second outlet pump (P2) to heat the feed water flowing out of the condenser (9). During the process of ensuring the stability of the feed water temperature, the twelfth valve (V12) is adjusted to reduce the extraction steam of the low-pressure cylinder (4). Subsequently, the heated feed water is mixed with the feed water heated by the low-pressure heater (10) at the second feed water mixer (M2), and then flows into the deaerator (6); the condensate water flowing out of the condensate water tank (20) is directly injected into the deaerator (6).

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