Integrated Power Generation and Energy Storage System of a Coupled Coal-Fired Unit and RSOC and Its Operation Method

Abstract

The invention discloses a power generation and energy storage integrated system and an operation method coupling a coal-fired unit and an RSOC. By coupling the high-temperature environment required for RSOC operation with the high-temperature heat flow of the coal-fired unit boiler through a molten salt heat exchanger, a power generation and energy storage integrated system with RSOC as the core component is constructed. The system includes a coal-fired unit power generation unit, an RSOC power generation and energy storage unit, and high- and low-temperature zone molten salt heat exchange and heat storage units. During the low electricity consumption valley of the power grid, the RSOC starts the energy storage mode, uses the high-temperature heat flow in the boiler and the electric energy generated by the coal-fired unit to electrolyze water to prepare hydrogen and oxygen; during the high electricity consumption peak of the power grid, the RSOC starts the power generation mode, and the generated electricity is converged with the electricity generated by the coal-fired unit and transmitted into the power grid. At the same time, the heat released by the RSOC is transported into the boiler through molten salt to heat the steam-water working medium. The invention improves the energy utilization efficiency, expands the stable operation load range of the coal-fired unit, increases the rapid load change rate of the unit, and improves the flexibility of the coal-fired unit.

Description

Technical Field

[0001] The present invention belongs to the energy fields such as the operation of RSOC power generation and energy storage systems and the thermal energy utilization of coal-fired power plants, and particularly relates to a technology for coupling and integrating an RSOC power generation and energy storage system with a coal-fired unit, which can be used for reference by coal-fired generating units operating in deep, rapid and flexible peak shaving for a long time. Background Art

[0002] China is building a new power system with new energy as the main body. However, new energy powers such as wind energy and solar energy have characteristics such as intermittency and periodicity, which bring great challenges to the safe and stable operation of the power grid. The power grid urgently needs highly flexible power sources to enhance its peak shaving ability. Coal-fired power generation is the main body of peak shaving power sources in China, and coal-fired power generation will face increasingly arduous power grid peak shaving tasks in the next few years. Limited by the requirement of stable combustion inside the boiler furnace, the minimum operating load of a general supercritical unit is 30% of the rated load; when the unit operating load is further reduced, oil needs to be injected to assist combustion inside the furnace to ensure the stability of combustion in the boiler. The thermal power system of coal-fired power generation is complex and huge. During the transient process of load change of the unit, affected by its thermal inertia, the maximum load change rate is limited. It can be seen that improving operation flexibility is the most urgent technical requirement faced by coal-fired generating units. A solid oxide fuel cell / electrolyzer (RSOC) is an energy conversion device that can operate in power generation and electrolysis modes respectively. When it operates in the power generation mode, it can directly convert the chemical energy of fuel into electrical energy; when it operates in the electrolysis mode, it can convert electrical energy into chemical energy for storage. Taking RSOC as the core component and making full use of its characteristics of both power generation and energy storage, coupling it with the power generation system of a coal-fired power plant to construct an integrated power generation and energy storage system can greatly improve the operation flexibility of the power generation system and reduce the power grid peak shaving pressure.

[0003] Since RSOC needs to operate in a high-temperature environment of 600 - 1000°C, and at the same time, the boiler combustion of a coal-fired unit can generate a large amount of thermal energy, RSOC can be coupled with the coal-fired unit to utilize the heat generated by combustion to maintain the stable operation of the RSOC system. By reasonably configuring the coupling system, an efficient, flexible and stable integrated power generation and energy storage system can be constructed. Summary of the Invention

[0004] The object of the present invention is to provide an integrated power generation and energy storage system coupling a coal-fired unit and an RSOC, and an operation method thereof. The heat required for the operation of the RSOC is coupled with the high-temperature environment of the boiler of the coal-fired power plant through molten salt, and an integrated power generation and energy storage system with the RSOC as the core component is constructed. When the power grid is in a low-load period, the RSOC stack enters the energy storage mode, and the heat in the high-temperature zone of the boiler and the electric energy generated by the coal-fired unit are used to decompose water vapor into hydrogen and oxygen. When the power grid is in a peak-load period, the RSOC stack enters the power generation mode, and the heat released by the stack is transported into the boiler of the coal-fired unit by molten salt for utilization, and the generated oxygen is transported into the boiler furnace for combustion support. The DC power generated by the stack is combined with the power generated by the coal-fired unit after passing through an AC inverter and then transmitted to the power grid. The present invention can lay a theoretical foundation for the construction and operation of an integrated power generation and energy storage system of a future coal-fired power plant and an RSOC.

[0005] To achieve the above object, the technical solution adopted by the present invention to solve its technical problems is:

[0006] An integrated power generation and energy storage system coupling a coal-fired unit and an RSOC, comprising a coal-fired unit power generation unit, an RSOC power generation and energy storage unit, a high-temperature zone molten salt heat exchange and heat storage unit, and a low-temperature zone molten salt heat exchange and heat storage unit;

[0007] The coal-fired unit power generation unit includes a boiler 1, a steam turbine, a generator 5, a first condenser 6, a deaerator 7, a condensate pump 8, a low-pressure heater 9, a feed water pump 10, and a high-pressure heater 11; the steam turbine includes a high-pressure cylinder 2 of the steam turbine, an intermediate-pressure cylinder 3 of the steam turbine, and a low-pressure cylinder 4 of the steam turbine. The main steam of the boiler 1 enters the inlet of the high-pressure cylinder 2 of the steam turbine, and the steam at the outlet of the high-pressure cylinder 2 of the steam turbine returns to the boiler 1 for reheating. The reheated steam enters the intermediate-pressure cylinder 3 of the steam turbine and then enters the low-pressure cylinder 4 of the steam turbine from the outlet of the intermediate-pressure cylinder 3 of the steam turbine. The high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4 of the steam turbine are coaxially arranged and connected to the generator 5; the exhaust steam of the low-pressure cylinder 4 of the steam turbine enters the first condenser 6, and the condensate water in the first condenser 6 is pressurized by the condensate pump 8 and enters the regenerative system of the steam turbine, i.e., the low-pressure heater 9 and the high-pressure heater 11, and enters the deaerator 7 after flowing through the low-pressure heater 9; the water at the outlet of the deaerator 7 is pressurized by the feed water pump 10 and then enters the high-pressure heater 11, and the feed water at the outlet of the high-pressure heater 11 enters the economizer in the tail flue of the boiler 1; the heat sources for heating the condensate water and the feed water in the regenerative system of the steam turbine are the extraction steam of each stage of the steam turbine, and the drain water of the low-pressure heater 9 and the high-pressure heater 11 is of a step-by-step self-flow type;

[0008] The RSOC power generation and energy storage unit includes an RSOC stack 12, an AC-to-DC inverter 13, a DC-to-AC inverter 14, a first switch 61, a second switch 62, a first regenerator 15, a second regenerator 16, a third regenerator 17, a fourth regenerator 20, a three-way mixing valve 19, a first fan 18, a second fan 26, a water pump 21, a first hydrogen storage tank 23, a second hydrogen storage tank 27, a first water storage tank 22, a second water storage tank 28, a second condenser 29, a steam-water separator 25, and a dryer 24. Among them, the first water storage tank 22, the water pump 21, and the fuel side of the fourth regenerator 20 are sequentially connected by pipelines and connected to the pipeline formed by connecting the first hydrogen storage tank 23, the first fan 18, the fuel side of the third regenerator 17, and the fuel side of the second regenerator 16 at the three-way mixing valve 19, and then enter the fuel inlet end of the RSOC stack 12 after passing through the fuel side of the first molten salt-gas heat exchanger 33. The fuel outlet end of the RSOC stack 12 sequentially passes through the tail gas side of the second regenerator 16, the fuel tail gas side of the second molten salt-gas heat exchanger 40, the second condenser 29, the steam-water separator 25, the dryer 24, and then is connected to the second hydrogen storage tank 27 to form a fuel closed pipeline. The water separated by the steam-water separator 25 enters the second water storage tank 28 for storage. The outside air passes through the second fan 26, the oxygen side of the first regenerator 15, and the oxygen side of the molten salt-gas heat exchanger 33 and enters the oxygen inlet end of the RSOC stack 12. The oxygen outlet end of the RSOC stack 12 passes through the tail gas side of the first regenerator 15, the tail gas side of the third regenerator 17, the tail gas side of the fourth regenerator 20, and the oxygen tail gas side of the second molten salt-gas heat exchanger 40, and then enters the boiler through the first switching valve 50 or is discharged to the outside environment through the second switching valve 51. The RSOC stack 12 is connected to the AC-to-DC inverter 13 and the DC-to-AC inverter 14 by cables. The AC-to-DC inverter 13 is connected to the power grid through the first switch 61, and the DC-to-AC inverter 14 is connected to the power grid through the second switch 62.

[0009] The high-temperature molten salt heat exchange and energy storage unit includes a boiler high-temperature collector 30, a first molten salt expansion tank 32, a first molten salt-gas heat exchanger 33, a first molten salt pump 31, a second molten salt pump 35, a first control valve 36, a second control valve 37, and a first low-temperature molten salt storage tank 34. The high-temperature collector 30, the first molten salt pump 31, the first molten salt expansion tank 32, and the molten salt side of the heat exchanger 33 are connected by pipelines to form a high-temperature cycle loop. The first control valve 36, the first low-temperature molten salt storage tank 34, the second molten salt pump 35, and the second control valve 37 are connected by pipelines to form a high-temperature molten salt bypass. The high-temperature molten salt bypass is connected to the high-temperature cycle loop through the first molten salt three-way valve 38 and the second molten salt three-way valve 39.

[0010] The low-temperature zone molten salt heat exchange and energy storage unit includes a boiler low-temperature zone feed water preheater 43, a second molten salt expansion tank 42, a second molten salt-gas heat exchanger 40, a third molten salt pump 41, a fourth molten salt pump 45, a third control valve 46, a fourth control valve 47, and a second low-temperature molten salt storage tank 44. The molten salt sides of the second molten salt expansion tank 42, the third molten salt pump 41, the heat exchanger 40, and the low-temperature zone feed water preheater 43 are connected by pipelines to form a low-temperature zone circulation loop; the fourth control valve 47, the fourth molten salt pump 45, the second low-temperature molten salt storage tank 44, and the third control valve 46 are connected by pipelines to form a low-temperature zone molten salt bypass, and the low-temperature zone molten salt bypass is connected to the low-temperature zone circulation loop through a third molten salt three-way valve 48 and a fourth molten salt three-way valve 49.

[0011] The operation method of a power generation and energy storage integrated system coupling a coal-fired unit and an RSOC is as follows:

[0012] 1) When there is an excess of electric energy in the power grid, the coal-fired unit power generation unit operates at an ultra-low load, and the RSOC stack 12 operates in the electrolysis mode. The electric energy comes from the power grid. The first switch 61 is closed and the second switch 62 is cut off. After being converted into direct current by the AC-DC inverter 13, it is connected to the RSOC stack 12; when the RSOC stack 12 operates in the electrolysis mode, the current direction is controlled by the AC-DC inverter 13 and the DC-AC inverter 14 to consume the electric energy of the coal-fired unit power generation unit. The second fan 26 is turned on to allow air to flow through the RSOC stack 12. The oxygen-rich air at the outlet of the air electrode of the RSOC stack 12 preheats the reaction gas through the first heater 15, the third heater 17 and the fourth heater 20. The oxygen-rich air after waste heat recovery is beneficial to the stable combustion of the boiler 1. At this time, the first switching valve 50 is in the open state and the second switching valve 51 is in the closed state. The heat-exchanged oxygen-rich air is transported into the boiler furnace through the pipeline; the first fan 18 is turned on to draw a small amount of hydrogen from the first hydrogen storage tank 23. At the same time, the water pump 21 is turned on. By adjusting the speed of the water pump, water is taken from the first water storage tank 22 and introduced into the fourth heater 20, where it is mixed with hydrogen at the three-way mixing valve 19. Finally, the mixed gas flows into the RSOC stack 12 for electrolysis to consume external electric energy; the hydrogen generated by the chemical reaction and the hydrogen input at the front end of the RSOC stack are used to regenerate the unreacted gas through the high-temperature second heater 16. Finally, it flows through the second condenser 29, the steam-water separator 25 and the dryer 24 and into the second hydrogen storage tank 27 for fuel storage; when the RSOC stack 12 operates in the electrolysis mode, a large amount of heat will be generated. The first control valve 36 in the high-temperature molten salt heat exchange and heat storage unit is opened, the second control valve 37 is closed, and the second molten salt pump 35 is closed. The molten salt in the circulation pipeline is stored in the first molten salt storage tank 34, gradually reducing the amount of circulating molten salt in the high-temperature area and reducing the heat consumption in the boiler; the third control valve 46 in the low-temperature molten salt heat exchange and heat storage unit is closed, the fourth control valve 47 is opened, and the fourth molten salt pump 45 is opened to increase the amount of circulating molten salt in the low-temperature area and improve the heat recovery utilization rate of the air-side tail gas;

[0013] 2) When the power grid needs electric energy, the RSOC stack 12 operates in the power generation mode. After converting the generated electric energy into alternating current through the DC-AC inverter 14, the first switch 61 is cut off and the second switch 62 is closed, and then it is combined with the electricity generated by the coal-fired unit power generation unit to supply power to the power grid; in the power generation mode of the RSOC stack 12, the current direction is controlled through the AC-DC inverter 13 and the DC-AC inverter 14 to complete the external power supply. The second blower 26 is turned on to allow air to flow through the RSOC stack 12. The oxygen-depleted air at the outlet of the oxygen electrode of the RSOC stack 12 preheats the reaction gas through the first heater 15, the third heater 17 and the fourth heater 20. The oxygen-depleted air after waste heat recovery continues to flow along the pipeline. At this time, the first switching valve 50 is in the closed state and the second switching valve 51 is in the open state. Finally, the oxygen-depleted air flows directly into the atmosphere after passing through the second switching valve 51; the first blower 18 is turned on to draw out the hydrogen from the first hydrogen storage tank 23. At the same time, the water pump 21 is turned on. By controlling the rotation speed of the water pump, the water in the first water storage tank 22 is introduced into the fourth heater 20 and then mixed with the hydrogen in the three-way mixing valve 19. Finally, the mixed gas flows into the RSOC stack 12 to undergo an electrochemical reaction with oxygen to supply power externally; the fuel gas that has not fully participated in the chemical reaction uses its own high temperature to regenerate the gas that has not participated in the reaction through the second heater 16. Finally, it flows through the second condenser 29, the steam-water separator 25 and the dryer 24 and into the second hydrogen storage tank 27 to recover the hydrogen; in the power generation mode of the RSOC stack 12, heat will be consumed. In the high-temperature molten salt heat exchange and heat storage unit, the first control valve 36 is closed, the second control valve 37 is opened, and the second molten salt pump 35 is opened to gradually increase the amount of circulating molten salt in the high-temperature area to ensure the heat supply of the RSOC stack; in the low-temperature molten salt heat exchange and heat storage unit, the third control valve 46 is opened, the fourth control valve 47 is closed, and the fourth molten salt pump 45 is closed to reduce the amount of circulating molten salt in the low-temperature area;

[0014] 3) When the power grid requires the coal-fired unit power generation unit to quickly change the load operation, the working mode and current density of the RSOC stack 12 are set according to the load change rate set by the power grid; the opening conditions of each valve are adjusted following the working mode of the RSOC stack.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1) The present invention can realize the complete recycling of the working medium inside the system, including oxygen, water and fuel, under working conditions such as the power generation mode, energy storage mode and mode switching of the power generation and energy storage integrated system.

[0017] 2) During the operation mode switching process of the power generation and energy storage integrated system of the present invention, there is no need to stop the machine, and only the current direction needs to be controlled through the AC-DC inverter.

[0018] 3) The boiler of the coal-fired power generation unit can provide heat for the RSOC power generation and energy storage unit to ensure the safe and stable operation of the RSOC stack; the high-temperature exhaust gas of the RSOC power generation and energy storage unit can be used to preheat the steam of the coal-fired power generation unit, which can improve the energy utilization efficiency of the overall system.

[0019] 4) When the coal-fired power generation unit receives the load dispatching instruction from the power grid, the RSOC stack can operate in the power generation or electrolysis mode according to the dispatching of the power grid and the requirements of the unit, and can adjust the input or output power of the stack by adjusting the externally applied current density of the stack. Therefore, by coupling the coal-fired unit with the solid oxide fuel cell / electrolyzer device, the operation flexibility of the power generation system can be comprehensively improved. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of an integrated power generation and energy storage system coupling a coal-fired unit and RSOC. Detailed Embodiments

[0021] In order to make the objectives, technical solutions and other contents of the present invention more clear and understandable, the present invention will be further described below with reference to the drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] As Figure 1 shown, the integrated power generation and energy storage system coupling a coal-fired unit and RSOC includes a coal-fired power generation unit, an RSOC power generation and energy storage unit, a high-temperature molten salt heat exchange and energy storage unit, and a low-temperature molten salt heat exchange and energy storage unit.

[0023] The coal-fired power generation unit includes a boiler 1, a steam turbine, a generator 5, a first condenser 6, a deaerator 7, a condensate pump 8, a low-pressure heater 9, a feed water pump 10, and a high-pressure heater 11. The steam turbine includes a high-pressure cylinder 2 of the steam turbine, an intermediate-pressure cylinder 3 of the steam turbine, and a low-pressure cylinder 4 of the steam turbine. The main steam of the boiler 1 enters the inlet of the high-pressure cylinder 2 of the steam turbine. The steam at the outlet of the high-pressure cylinder 2 of the steam turbine returns to the boiler 1 for reheating. The reheated steam enters the intermediate-pressure cylinder 3 of the steam turbine and then enters the low-pressure cylinder 4 of the steam turbine from the outlet of the intermediate-pressure cylinder 3 of the steam turbine. The high-pressure cylinder 2 of the steam turbine, the intermediate-pressure cylinder 3 of the steam turbine, and the low-pressure cylinder 4 of the steam turbine are coaxial and connected to the generator 5. The exhaust steam of the low-pressure cylinder 4 of the steam turbine enters the first condenser 6. The condensate water in the first condenser 6 is pressurized by the condensate pump 8 and enters the regenerative system of the steam turbine, flows through the low-pressure heater 9 and then enters the deaerator 7. The water at the outlet of the deaerator 7 is pressurized by the feed water pump 10 and enters the high-pressure heater 11. The feed water at the outlet of the high-pressure heater 11 enters the economizer in the tail flue of the boiler 1. The heat source for heating the condensate water and feed water in the regenerative system of the steam turbine is the extraction steam of each stage of the steam turbine, and the drain water of the low-pressure heater 9 and the high-pressure heater 11 is of a step-by-step self-flow type.

[0024] The RSOC power generation and energy storage unit includes an RSOC stack 12, an AC-DC inverter 13, a DC-AC inverter 14, a first regenerator 15, a second regenerator 16, a third regenerator 17, a fourth regenerator 20, a three-way mixing valve 19, a first fan 18, a second fan 26, a water pump 21, a first hydrogen storage tank 23, a second hydrogen storage tank 27, a first water storage tank 22, a second water storage tank 28, a second condenser 29, a steam-water separator 25, a dryer 24, pipelines connecting various devices, and lines connecting the AC-DC and DC-AC inverters to the RSOC stack. Among them, the fuel sides of the first water storage tank 22, the water pump 21, and the fourth regenerator 20 are sequentially connected by pipelines and connected to the pipeline connected by the first hydrogen storage tank 23, the first fan 18, the fuel side of the third regenerator 17, and the fuel side of the second regenerator 16 at the three-way mixing valve 19, enter the fuel inlet end of the RSOC stack 12 after passing through the fuel side of the molten salt-gas heat exchanger 33, and the fuel outlet end of the RSOC stack 12 passes through the tail gas side of the second regenerator 16, the fuel tail gas side of the second molten salt-gas heat exchanger 40, the second condenser 29, the steam-water separator 25, and the dryer 24 and is finally connected to the second hydrogen storage tank 27 to form a fuel closed pipeline. The water separated by the steam-water separator 25 enters the second water storage tank 28 for storage; the outside air passes through the second fan 26, the oxygen side of the first regenerator 15, and the oxygen side of the molten salt-gas heat exchanger 33 and enters the oxygen inlet end of the RSOC stack 12. The oxygen outlet end of the RSOC stack 12 passes through the tail gas side of the first regenerator 15, the tail gas side of the third regenerator 17, the tail gas side of the fourth regenerator 20, and the oxygen tail gas side of the second molten salt-gas heat exchanger 40 and finally enters the boiler through the first switch valve 50 or is discharged to the outside environment through the second switch valve 51; the RSOC stack 12 is connected to the AC-DC inverter 13 and the DC-AC inverter 14 by cables. The AC-DC inverter 13 is connected to the power grid through the first switch 61, and the DC-AC inverter 14 is connected to the power grid through the second switch 62.

[0025] The high-temperature molten salt heat exchange and energy storage unit includes a boiler high-temperature collector 30, a first molten salt expansion tank 32, a first molten salt-gas heat exchanger 33, a first molten salt pump 31, a second molten salt pump 35, a first control valve 36, a second control valve 37, and a first low-temperature molten salt storage tank 34. The first molten salt three-way valve 38 and the second molten salt three-way valve 39. The molten salt sides of the high-temperature collector 30, the first molten salt pump 31, the first molten salt expansion tank 32, and the heat exchanger 33 are connected by pipelines to form a high-temperature cycle loop; the first control valve 36, the first low-temperature molten salt storage tank 34, the second molten salt pump 35, and the second control valve 37 are connected by pipelines to form a high-temperature molten salt bypass, and the high-temperature molten salt bypass and the cycle loop are connected by the first molten salt three-way valve 38 and the second molten salt three-way valve 39.

[0026] The low-temperature zone molten salt heat exchange and energy storage unit includes the boiler low-temperature zone feed water preheater 43, the second molten salt expansion tank 42, the second molten salt-gas heat exchanger 40, the third molten salt pump 41, the fourth molten salt pump 45, the third control valve 46, the fourth control valve 47, the second low-temperature molten salt storage tank 44, the third molten salt three-way valve 48, and the fourth molten salt three-way valve 49. The molten salt sides of the second molten salt expansion tank 42, the third molten salt pump 41, the heat exchanger 40, and the low-temperature zone feed water preheater 43 are connected by pipelines to form a low-temperature zone circulation loop; the fourth control valve 47, the fourth molten salt pump 45, the second low-temperature molten salt storage tank 44, and the third control valve 46 are connected by pipelines to form a low-temperature zone molten salt bypass, and the low-temperature zone molten salt bypass is connected to the low-temperature zone circulation loop through the third molten salt three-way valve 48 and the fourth molten salt three-way valve 49.

[0027] The working method of the integrated power generation and energy storage system is as follows:

[0028] When there is an excess of electric energy in the power grid, the coal-fired generating unit operates at an ultra-low load. The RSOC stack 12 operates in the electrolysis mode, and the electric energy is sourced from the power grid. The first switch 61 is closed and the second switch 62 is cut off. After being converted into direct current by the AC-DC converter 13, it is connected to the RSOC stack 12. When the RSOC stack 12 operates in the electrolysis mode, the direction of the current is controlled by the AC-DC inverter 13 and the DC-AC inverter 14 to consume the external electric energy. The second blower 26 is turned on to allow a small amount of air to flow through the RSOC stack 12. The oxygen-rich air at the outlet of the air electrode of the RSOC stack 12 preheats the reaction gas through the first heater 15, the third heater 17, and the fourth heater 20. The oxygen-rich air after waste heat recovery is beneficial to the stable combustion of the boiler. At this time, the first switching valve 50 is in the open state and the second switching valve 51 is in the closed state. The heat-exchanged oxygen-rich air is finally transported into the boiler furnace through the pipeline; the first blower 18 is turned on to draw a small amount of hydrogen from the first hydrogen storage tank 23. At the same time, the water pump 21 is turned on. By adjusting the speed of the water pump, an appropriate amount of water is taken from the first water storage tank 22 and introduced into the fourth heater 20, where it is mixed with hydrogen at the three-way mixing valve 19. Finally, the mixed gas flows into the RSOC stack 12 for electrolysis to consume the external electric energy; the hydrogen generated by the chemical reaction and the hydrogen input at the front end of the RSOC stack are used to regenerate the unreacted gas through the high-temperature second heater 16. Finally, it flows into the second hydrogen storage tank 27 through the second condenser 29, the steam-water separator 25, and the dryer 24 for fuel storage. When the RSOC stack 12 operates in the electrolysis mode, a large amount of heat is generated. The first control valve 36 in the high-temperature molten salt heat exchange and energy storage unit is opened, the second control valve 37 is closed, and the second molten salt pump 35 is closed. The molten salt in the circulation pipeline is stored in the first molten salt storage tank 34, gradually reducing the amount of circulating molten salt in the high-temperature area and reducing the heat consumption in the boiler. The third control valve 46 in the low-temperature molten salt heat exchange and energy storage unit is closed, the fourth control valve 47 is opened, and the fourth molten salt pump 45 is opened to increase the amount of circulating molten salt in the low-temperature area and improve the heat recovery utilization rate of the air-side tail gas.

[0029] When the power grid needs electric energy, the RSOC stack 12 operates in the power generation mode. After converting the generated electric energy into alternating current through the DC-AC inverter 14, it supplies power to the power grid together with the electricity generated by the coal-fired unit power generation unit. In the power generation mode of the RSOC stack 12, the current direction is controlled by the AC-DC inverter 13 and the DC-AC inverter 14 to complete the external power supply. The second blower 26 is turned on to allow air to flow through the RSOC stack 12. The oxygen-depleted air at the outlet of the oxygen electrode of the RSOC stack 12 preheats the reaction gas through the first heater 15, the third heater 17, and the fourth heater 20. The oxygen-depleted air after waste heat recovery continues to flow along the pipeline. At this time, the first switching valve 50 is in the closed state and the second switching valve 51 is in the open state. Finally, the oxygen-depleted air directly enters the atmosphere after flowing through the second switching valve 51. The first blower 18 is turned on to draw out the hydrogen gas from the first hydrogen storage tank 23. At the same time, the water pump 21 is turned on. By controlling the rotation speed of the water pump, a small amount of water from the first water storage tank 22 is introduced after the fourth heater 20 and mixed with the hydrogen gas at the three-way mixing valve 19. Finally, the mixed gas flows into the RSOC stack 12 to undergo an electrochemical reaction with oxygen to supply power externally. The fuel gas that has not fully participated in the chemical reaction uses its own high temperature to regenerate heat for the gas that has not participated in the reaction through the second heater 16. Finally, it flows through the second condenser 29, the steam-water separator 25, and the dryer 24 and into the second hydrogen storage tank 27 to recover the hydrogen gas. In the power generation mode of the RSOC stack 12, heat is consumed. In the high-temperature molten salt heat exchange and heat storage unit, the first control valve 36 is closed, the second control valve 37 is open, and the second molten salt pump 35 is open. The amount of circulating molten salt in the high-temperature area is gradually increased to ensure the heat supply of the RSOC stack. In the low-temperature molten salt heat exchange and heat storage unit, the third control valve 46 is open, the fourth control valve 47 is closed, and the fourth molten salt pump 45 is closed to reduce the amount of circulating molten salt in the low-temperature area.

[0030] When the power grid requires the coal-fired unit power generation unit to operate with a rapid load change, the working mode and current density of the RSOC stack 12 are set according to the load change rate set by the power grid; the opening conditions of each valve are consistent with the working mode of the RSOC stack.

Claims

1. An integrated power generation and energy storage system coupling a coal-fired power unit and an RSOC, characterized in that: It includes a coal-fired unit power generation unit, an RSOC power generation and energy storage unit, a molten salt heat exchange and heat storage unit in the high-temperature area, and a molten salt heat exchange and heat storage unit in the low-temperature area; The coal-fired unit power generation unit includes a boiler (1), a steam turbine, a generator (5), a first condenser (6), a deaerator (7), a condensate pump (8), a low-pressure heater (9), a feed water pump (10), and a high-pressure heater (11); the steam turbine includes a high-pressure cylinder (2) of the steam turbine, a medium-pressure cylinder (3) of the steam turbine, and a low-pressure cylinder (4) of the steam turbine. The main steam of the boiler (1) enters the inlet of the high-pressure cylinder (2) of the steam turbine. The steam at the outlet of the high-pressure cylinder (2) of the steam turbine returns to the boiler (1) again for reheating. The reheated steam enters the medium-pressure cylinder (3) of the steam turbine and then enters the low-pressure cylinder (4) of the steam turbine from the outlet of the medium-pressure cylinder (3) of the steam turbine. The high-pressure cylinder (2), the medium-pressure cylinder (3), and the low-pressure cylinder (4) of the steam turbine are coaxial and connected to the generator (5); the exhaust steam of the low-pressure cylinder (4) of the steam turbine enters the first condenser (6). The condensate water in the first condenser (6) is pressurized by the condensate pump (8) and enters the regenerative system of the steam turbine, that is, the low-pressure heater (9) and the high-pressure heater (11), and then enters the deaerator (7) after flowing through the low-pressure heater (9); the water at the outlet of the deaerator (7) is pressurized by the feed water pump (10) and then enters the high-pressure heater (11). The feed water at the outlet of the high-pressure heater (11) enters the economizer in the tail flue of the boiler (1); the heat source for heating the condensate water and the feed water in the regenerative system of the steam turbine is the extraction steam of each stage of the steam turbine. The drain water of the low-pressure heater (9) and the high-pressure heater (11) is of a step-by-step self-flow type; The RSOC power generation and energy storage unit includes an RSOC stack (12), an AC-to-DC inverter (13), a DC-to-AC inverter (14), a first switch (61), a second switch (62), a first regenerator (15), a second regenerator (16), a third regenerator (17), a fourth regenerator (20), a three-way mixing valve (19), a first fan (18), a second fan (26), a water pump (21), a first hydrogen storage tank (23), a second hydrogen storage tank (27), a first water storage tank (22), a second water storage tank (28), a second condenser (29), a steam-water separator (25), and a dryer (24); wherein, the first water storage tank (22), the water pump (21), and the fuel side of the fourth regenerator (20) are sequentially connected by pipelines and connected to the pipeline formed by connecting the first hydrogen storage tank (23), the first fan (18), the fuel side of the third regenerator (17), and the fuel side of the second regenerator (16) at the three-way mixing valve (19), and then enter the fuel inlet end of the RSOC stack (12) after passing through the fuel side of the first molten salt-gas heat exchanger (33). The fuel outlet end of the RSOC stack (12) is sequentially connected to the second regenerator (16) exhaust side, the second molten salt-gas heat exchanger (40) fuel exhaust side, the second condenser (29), the steam-water separator (25), the dryer (24), and then connected to the second hydrogen storage tank (27) to form a fuel closed pipeline. The water separated by the steam-water separator (25) enters the second water storage tank (28) for storage; the outside air passes through the second fan (26), the oxygen side of the first regenerator (15), the oxygen side of the first molten salt-gas heat exchanger (33), and enters the oxygen inlet end of the RSOC stack (12). The oxygen outlet end of the RSOC stack (12) passes through the exhaust side of the first regenerator (15), the exhaust side of the third regenerator (17), the exhaust side of the fourth regenerator (20), and the oxygen exhaust side of the second molten salt-gas heat exchanger (40), and then enters the boiler through the first switching valve (50) or is discharged to the outside environment through the second switching valve (51); the RSOC stack (12) is connected to the AC-to-DC inverter (13) and the DC-to-AC inverter (14) by cables. The AC-to-DC inverter (13) is connected to the power grid through the first switch (61), and the DC-to-AC inverter (14) is connected to the power grid through the second switch (62); The molten salt heat exchange and energy storage unit in the high-temperature zone includes a high-temperature collector (30) of the boiler, a first molten salt expansion tank (32), a first molten salt-gas heat exchanger (33), a first molten salt pump (31), a second molten salt pump (35), a first control valve (36), a second control valve (37), and a first low-temperature molten salt storage tank (34). The molten salt sides of the high-temperature collector (30), the first molten salt pump (31), the first molten salt expansion tank (32), and the first molten salt-gas heat exchanger (33) are connected by pipelines to form a high-temperature zone circulation loop; the first control valve (36), the first low-temperature molten salt storage tank (34), the second molten salt pump (35), and the second control valve (37) are connected by pipelines to form a molten salt bypass in the high-temperature zone. The molten salt bypass in the high-temperature zone is connected to the high-temperature zone circulation loop through a first molten salt three-way valve (38) and a second molten salt three-way valve (39). The molten salt heat exchange and energy storage unit in the low-temperature zone includes a feed water preheater (43) in the low-temperature zone of the boiler, a second molten salt expansion tank (42), a second molten salt-gas heat exchanger (40), a third molten salt pump (41), a fourth molten salt pump (45), a third control valve (46), a fourth control valve (47), and a second low-temperature molten salt storage tank (44). The molten salt sides of the second molten salt expansion tank (42), the third molten salt pump (41), the second molten salt-gas heat exchanger (40), and the feed water preheater (43) in the low-temperature zone are connected by pipelines to form a low-temperature zone circulation loop; the fourth control valve (47), the fourth molten salt pump (45), the second low-temperature molten salt storage tank (44), and the third control valve (46) are connected by pipelines to form a molten salt bypass in the low-temperature zone. The molten salt bypass in the low-temperature zone is connected to the low-temperature zone circulation loop through a third molten salt three-way valve (48) and a fourth molten salt three-way valve (49).

2. The operating method of an integrated power generation and energy storage system of a coupled coal-fired unit and RSOC according to claim 1, characterized in that: Specifically as follows: 1) When there is an excess of electrical energy in the power grid, the coal-fired unit power generation unit operates at an ultra-low load, and the RSOC stack (12) operates in the electrolysis mode. The electrical energy is sourced from the power grid. The first switch (61) is closed and the second switch (62) is cut off. After being converted into direct current by the AC-DC inverter (13), it is connected to the RSOC stack (12). When the RSOC stack (12) operates in the electrolysis mode, the current direction is controlled by the AC-DC inverter (13) and the DC-AC inverter (14) to consume the electrical energy of the coal-fired unit power generation unit. The second blower (26) is turned on to let air flow through the RSOC stack (12). The oxygen-rich air at the air electrode outlet of the RSOC stack (12) preheats the reaction gas through the first recuperator (15), the third recuperator (17), and the fourth recuperator (20). The oxygen-rich air after waste heat recovery is beneficial to the stable combustion of the boiler (1). At this time, the first switching valve (50) is in the open state and the second switching valve (51) is in the closed state. The heat-exchanged oxygen-rich air is transported through the pipeline into the boiler furnace. The first blower (18) is turned on to draw a small amount of hydrogen from the first hydrogen storage tank (23). At the same time, the water pump (21) is turned on. By adjusting the rotational speed of the water pump, water is taken from the first water storage tank (22) and introduced into the fourth recuperator (20), where it is mixed with hydrogen at the three-way mixing valve (19). Finally, the mixed gas flows into the RSOC stack (12) for electrolysis to consume external electrical energy. The hydrogen generated by the chemical reaction and the hydrogen input at the front end of the RSOC stack are used to regenerate the unreacted gas through the high-temperature second recuperator (16). Finally, it flows into the second hydrogen storage tank (27) through the second condenser (29), the steam-water separator (25), and the dryer (24) for fuel storage. When the RSOC stack (12) operates in the electrolysis mode, a large amount of heat is generated. In the high-temperature molten salt heat exchange and thermal energy storage unit, the first control valve (36) is opened, the second control valve (37) is closed, and the second molten salt pump (35) is closed. The molten salt in the circulation pipeline is stored in the first low-temperature molten salt storage tank (34), gradually reducing the amount of circulating molten salt in the high-temperature area and reducing the heat consumption in the boiler. In the low-temperature molten salt heat exchange and thermal energy storage unit, the third control valve (46) is closed, the fourth control valve (47) is opened, and the fourth molten salt pump (45) is opened, increasing the amount of circulating molten salt in the low-temperature area and improving the heat recovery utilization rate of the air-side tail gas; 2) When the power grid needs electric energy, the RSOC stack (12) operates in the power generation mode. After converting the generated electric energy into alternating current through the DC-AC inverter (14), the first switch (61) is cut off and the second switch (62) is closed. Then, the generated electric energy is combined with that of the coal-fired unit power generation unit and supplied to the power grid. In the power generation mode of the RSOC stack (12), the current direction is controlled by the AC-DC inverter (13) and the DC-AC inverter (14) to complete the external power supply. The second blower (26) is turned on to let air flow through the RSOC stack (12). The oxygen-depleted air at the outlet of the oxygen electrode of the RSOC stack (12) preheats the reaction gas through the first recuperator (15), the third recuperator (17), and the fourth recuperator (20). The oxygen-depleted air after waste heat recovery continues to flow along the pipeline. At this time, the first switching valve (50) is in the closed state and the second switching valve (51) is in the open state. Finally, the oxygen-depleted air directly enters the atmosphere after flowing through the second switching valve (51). The first blower (18) is turned on to draw hydrogen from the first hydrogen storage tank (23). At the same time, the water pump (21) is turned on. By controlling the rotation speed of the water pump, the water in the first water storage tank (22) is introduced into the fourth recuperator (20) and mixed with hydrogen at the three-way mixing valve (19). Finally, the mixed gas flows into the RSOC stack (12) to undergo an electrochemical reaction with oxygen to supply power externally. The fuel gas that has not fully participated in the chemical reaction uses its own high temperature to regenerate the gas that has not participated in the reaction through the second recuperator (16). Finally, it flows into the second hydrogen storage tank (27) through the second condenser (29), the steam-water separator (25), and the dryer (24) to recover hydrogen. In the power generation mode of the RSOC stack (12), heat is consumed. In the high-temperature molten salt heat exchange and energy storage unit, the first control valve (36) is closed, the second control valve (37) is opened, and the second molten salt pump (35) is opened to gradually increase the amount of circulating molten salt in the high-temperature area to ensure the heat supply of the RSOC stack. In the low-temperature molten salt heat exchange and energy storage unit, the third control valve (46) is opened, the fourth control valve (47) is closed, and the fourth molten salt pump (45) is closed to reduce the amount of circulating molten salt in the low-temperature area; 3) When the power grid requires the coal-fired unit power generation unit to quickly change the load operation, the working mode and current density of the RSOC stack (12) are set according to the load change rate set by the power grid. The opening conditions of each valve follow the adjustment of the RSOC stack working mode.

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