Fused salt heat storage-based deep peak shaving system and method for combined cycle unit

Abstract

The invention provides a combined cycle unit deep peak shaving system and method based on fused salt heat storage, and the system comprises a gas turbine which is used for driving a generator to generate power; the steam turbine is used for driving the generator to generate power; the waste heat boiler is used for recycling heat in flue gas of the gas turbine to form high-temperature steam required by the steam turbine; the heat storage unit comprises a low-temperature molten salt tank and a high-temperature molten salt tank, and molten salt runs between the low-temperature molten salt tank and the high-temperature molten salt tank; the flue gas heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and is used for recycling heat in flue gas of the gas turbine to heat molten salt; and the electric heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank, is connected with the flue gas heater in parallel and is used for consuming electric energy to heat the molten salt. According to the scheme, the problems that a single flue gas heating system is large in system inertia and limited by the minimum safe operation working condition can be solved, the frequency modulation capacity and flexibility of a unit can be improved, and efficient operation and stable power supply of an electric power system are ensured.

Description

Technical Field

[0001] The present application relates to the technical field of power generation, and in particular, to a deep peak shaving system and method for a combined cycle unit based on molten salt thermal energy storage. Background Art

[0002] The gas-steam combined cycle method has become the fastest-growing power generation form in the world due to its advantages such as high power generation efficiency, short construction period, and convenient operation. This also has great guiding significance for the current power structure adjustment in China. However, when the combined cycle unit participates in power grid peak shaving, with the fluctuations of the electricity load and new energy power, the operating load fluctuates frequently, resulting in a significant reduction in the efficiency of the combined cycle unit. For example, when the unit operates at low load compared to full load, when the unit load rate is 60%, the heat consumption increases by 8%, and when the unit load rate is 40%, the heat consumption will increase by 20%. Therefore, it is crucial to integrate an energy storage device in the combined cycle system to ensure that the unit can still operate at a relatively high load when participating in power peak shaving, improving the efficiency and flexibility of the overall system.

[0003] Currently, molten salt energy storage technology is mainly used to improve the power peak shaving ability of combined cycle units, that is, the heat in the flue gas of the gas turbine is used to heat molten salt for thermal energy storage to improve the peak shaving ability of the unit. However, when using single flue gas heating, due to the large system inertia, there is a certain lag in its power change, and rapid and precise power change cannot be achieved. When using single flue gas to heat molten salt, due to the limitation of the minimum safe operating condition of the steam turbine, the power output of the unit cannot be further reduced. Summary of the Invention

[0004] The embodiments of the present application at least provide a deep peak shaving system and method for a combined cycle unit based on molten salt thermal energy storage, which can improve the problems of large system inertia and limitation by the minimum safe operating condition existing in the single flue gas heating system, is beneficial to improving the frequency modulation ability and flexibility of the unit, and ensures the efficient operation and stable power supply of the power system.

[0005] In a first aspect, an embodiment of the present application provides a deep peak shaving system for a combined cycle unit based on molten salt thermal energy storage, including: a gas turbine, a steam turbine, a generator, a waste heat boiler, a thermal energy storage unit, a flue gas heater, an electric heater, and a heat exchanger;

[0006] The gas turbine is connected to the generator and is used to drive the generator to generate electricity;

[0007] The steam turbine is connected to the generator and is used to drive the generator to generate electricity;

[0008] The waste heat boiler is connected to the gas turbine and the steam turbine and is used to recover the heat in the flue gas of the gas turbine to form the high-temperature steam required by the steam turbine;

[0009] The heat storage unit includes a low-temperature molten salt tank and a high-temperature molten salt tank, and molten salt circulates between the low-temperature molten salt tank and the high-temperature molten salt tank;

[0010] The flue gas heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and is connected to the gas turbine, and is used to recover the heat in the flue gas of the gas turbine to heat the molten salt;

[0011] The electric heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and is connected in parallel with the flue gas heater, and is used to consume the electric energy at the outlet of the high-voltage auxiliary transformer generator to heat the molten salt;

[0012] The heat exchanger is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and is connected to the steam turbine, and is used to release the heat of the molten salt to form the steam required by the steam turbine.

[0013] In an optional embodiment, a first valve is arranged between the flue gas heater and the gas turbine, and the first valve is used to adjust the flue gas flow rate passing through the flue gas heater;

[0014] A second valve is arranged between the flue gas heater and the low-temperature molten salt tank, and the second valve is used to adjust the molten salt flow rate passing through the flue gas heater.

[0015] In an optional embodiment, the first valve and the second valve are respectively connected to a flue gas heating controller, and the flue gas heating controller is used to control the first valve and the second valve to adjust the flue gas flow rate and the molten salt flow rate passing through the flue gas heater, so that the molten salt can be heated to a set temperature.

[0016] In an optional embodiment, a third valve is arranged between the electric heater and the low-temperature molten salt tank, and the third valve is used to adjust the molten salt flow rate passing through the electric heater.

[0017] In an optional embodiment, the third valve and the electric heater are respectively connected to an electric heating controller, and the electric heating controller is used to control the third valve and the electric heater to adjust the molten salt flow rate passing through the electric heater and the heating power of the electric heater, so that the molten salt is heated to a set temperature.

[0018] In an optional embodiment, a fourth valve is arranged between the heat exchanger and the high-temperature molten salt tank, and the fourth valve is used to adjust the molten salt flow rate passing through the heat exchanger;

[0019] A fifth valve is arranged between the heat exchanger and the steam turbine, and the fifth valve is used to adjust the steam flow rate entering the steam turbine.

[0020] In an alternative embodiment, a first molten salt pump is provided at the salt outlet of the low-temperature molten salt tank, and a second molten salt pump is provided at the salt outlet of the high-temperature molten salt pump.

[0021] Second, the embodiment of the present application further provides a deep peak shaving method for a combined cycle unit based on molten salt thermal energy storage, which is applicable to the deep peak shaving system for a combined cycle unit based on molten salt thermal energy storage according to any one of the first aspects, and includes:

[0022] If the unit needs to reduce the external output power, a part of the flue gas of the gas turbine flue gas is exchanged heat in the waste heat boiler to form the steam required by the steam turbine, and the remaining flue gas will heat the molten salt in the flue gas heater to a set temperature for heat storage;

[0023] If the unit needs to further reduce the external output power, the electric heater will heat the molten salt passing through the electric heater to a set temperature for heat storage;

[0024] When the unit needs to increase the external output power, the heat exchanger is used to release the heat of the molten salt to form the steam required by the steam turbine.

[0025] In an alternative embodiment, the remaining flue gas heating the molten salt in the flue gas heater to a set temperature specifically includes:

[0026] Controlling the third valve and the electric heater to adjust the flow rate of the molten salt passing through the electric heater and the heating power of the electric heater;

[0027] The molten salt enters the flue gas heat exchanger through the second valve, and the remaining flue gas enters the flue gas heat exchanger through the first valve to heat the molten salt to a set temperature.

[0028] In an alternative embodiment, the electric heater heating the molten salt passing through the electric heater to a preset temperature specifically includes:

[0029] Controlling the third valve and the electric heater to adjust the flow rate of the molten salt passing through the electric heater and the heating power of the electric heater;

[0030] The molten salt enters the electric heater through the third valve, and the electric heater heats the molten salt to a set temperature.

[0031] The above technical solutions of the present application have the following beneficial technical effects:

[0032] The deep peak shaving system of the combined cycle unit based on molten salt thermal energy storage in the embodiments of the present application uses two heat sources, namely flue gas heating and electric heating, to form an adjustable heat source. Compared with the single flue gas heating method, the electric heater can be used as a controllable load for adjustment. Its power change speed is fast and the response time is short, which can be used to improve the frequency modulation ability of the unit. Moreover, this system can break through the limitation of the minimum safe operating condition of the steam turbine, so as to further reduce the external output power of the unit, and even achieve zero-power grid connection, effectively improving the deep peak shaving ability of the unit.

[0033] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. The drawings here are incorporated into the specification and constitute a part of this specification. These drawings show embodiments that conform to the present application and, together with the specification, are used to illustrate the technical solutions of the present application. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0035] Figure 1 Shows a schematic diagram of a deep peak shaving system of a combined cycle unit based on molten salt thermal energy storage provided by an embodiment of the present application;

[0036] Reference Signs:

[0037] 1, compressor chamber; 2, combustion chamber; 3, gas turbine; 4, generator; 5, steam turbine; 6, waste heat boiler; 7, low-temperature molten salt tank; 8, high-temperature molten salt tank; 9, flue gas heater; 10, heat exchanger; 11, first molten salt pump; 12, second molten salt pump; 13, electric heater; 14, first valve; 15, second valve; 16, flue gas heating controller; 17, third valve; 18, electric heating controller; 19, fourth valve; 20, fifth valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Now, various exemplary embodiments of the present application will be described in detail with reference to the drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present application.

[0039] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary only for explaining the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts fall within the scope of protection of the present application.

[0040] The terms "first" and "second" in the description and claims of the present application may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, "a plurality of" means two or more. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / " generally means an "or" relationship between the associated objects before and after.

[0041] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.

[0042] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0043] A deep peak shaving system for a combined cycle unit based on molten salt thermal energy storage provided by an embodiment of the present application uses two heat sources, namely flue gas heating and electric heating, to form an adjustable heat source. Compared with the single flue gas heating method, the electric heater can be used as a controllable load for adjustment, with a fast power change speed and a short response time, and can be used to improve the frequency modulation ability of the unit. Moreover, this system can break through the limitation of the minimum safe operating condition of the steam turbine, so as to further reduce the external output power of the unit, and even achieve zero-power grid connection, effectively improving the deep peak shaving ability of the unit.

[0044] Reference Figure 1 , a deep peak shaving system for a combined cycle unit based on molten salt thermal energy storage, comprising: a gas turbine, a steam turbine 5, a generator 4 and a waste heat boiler 6. The gas turbine is connected to the generator 4 and is used to drive the generator 4 to generate electricity. The steam turbine 5 is connected to the generator 4 and is used to drive the generator 4 to generate electricity. The waste heat boiler 6 is connected to the gas turbine and the steam turbine 5 and is used to recover the heat in the flue gas of the gas turbine to form the high-temperature steam required by the steam turbine 5. Specifically, the gas turbine comprises a compressor chamber 1, a combustion chamber 2 and a gas turbine 3. The outlet of the compressor chamber 1 is connected to the inlet of the combustion chamber 2, the outlet of the combustion chamber 2 is connected to the inlet of the gas turbine 3, the outlet of the gas turbine 3 is connected to the inlet of the waste heat boiler 6, and the outlet of the waste heat boiler 6 is connected to the inlet of the steam turbine 5. During use, air enters the combustion chamber 2 after being compressed, and high-temperature flue gas generated after combustion with gas in the combustion chamber 2. The high-temperature flue gas enters the gas turbine 3 to do work to drive the generator 4 to generate electricity. Subsequently, the high-temperature flue gas after doing work enters the waste heat boiler 6 for heat exchange to form high-temperature and high-pressure steam, and the high-temperature and high-pressure steam enters the steam turbine 5 to do work to drive the generator 4 to generate electricity. In the above process, by utilizing the waste heat of the high-temperature flue gas, the peak shaving capacity of the unit can be improved.

[0045] In some embodiments, the system further includes: a heat storage unit, a flue gas heater 9, and a heat exchanger 10. The heat storage unit includes a low-temperature molten salt tank 7 and a high-temperature molten salt tank 8, and molten salt circulates between the low-temperature molten salt tank 7 and the high-temperature molten salt tank 8. The flue gas heater 9 is disposed between the low-temperature molten salt tank 7 and the high-temperature molten salt tank 8 and is connected to the gas turbine. That is, the salt inlet of the flue gas heater 9 is connected to the salt outlet of the low-temperature molten salt tank 7, the salt outlet of the flue gas heater 9 is connected to the salt inlet of the high-temperature molten salt tank 8, and the gas inlet of the flue gas heater 9 is connected to the gas outlet of the gas turbine 3. The heat exchanger 10 is disposed between the low-temperature molten salt tank 7 and the high-temperature molten salt tank 8 and is connected to the steam turbine 5. That is, the salt inlet of the heat exchanger 10 is connected to the salt outlet of the high-temperature molten salt tank 8, the salt outlet of the heat exchanger 10 is connected to the salt inlet of the low-temperature molten salt tank 7, and the gas outlet of the heat exchanger 10 is connected to the gas inlet of the steam turbine 5. During operation, the high-temperature flue gas after work can be divided into two paths. One path enters the waste heat boiler 6 for heat exchange, and the other path enters the flue gas heater 9 for heat exchange, enabling the flue gas heater 9 to recover the heat in the flue gas of the gas turbine. This heat can be used to heat the molten salt passing through the flue gas heater 9 for heat storage. In this way, the amount of flue gas entering the waste heat boiler 6 can be reduced to decrease the amount of steam entering the steam turbine 5, thereby reducing the power generation of the steam turbine 5 and the external output power of the unit. Additionally, when it is necessary to increase the external output power of the unit, the high-temperature molten salt tank 8 can output high-temperature molten salt so that the high-temperature molten salt releases heat when passing through the heat exchanger 10 to form high-temperature and high-pressure steam. In this way, the amount of steam entering the steam turbine 5 can be increased, thereby increasing the power generation of the steam turbine 5 and the external output power of the unit.

[0046] To enable the circulation of molten salt, the heat storage unit further includes: a first molten salt pump 11 and a second molten salt pump 12. The first molten salt pump 11 is disposed at the salt outlet of the low-temperature molten salt tank 7. That is, the first molten salt pump 11 is located between the salt outlet of the low-temperature molten salt tank 7 and the salt inlet of the flue gas heater 9, and the first molten salt pump 11 is used to output the low-temperature molten salt in the low-temperature molten salt pump to the flue gas heater 9 and the electric heater 13. The second molten salt pump 12 is disposed at the salt outlet of the high-temperature molten salt pump. That is, the second molten salt pump 12 is located between the salt outlet of the high-temperature molten salt pump and the salt inlet of the heat exchanger 10, and the second molten salt pump 12 is used to output the high-temperature molten salt in the high-temperature molten salt pump to the heat exchanger 10.

[0047] It should be understood that in addition to using molten salt for heat storage, the system can also adopt other heat storage methods, such as hot water heat storage and electrode steam boiler heat storage, etc.

[0048] In some embodiments, the system further includes: an electric heater 13. The electric heater 13 is disposed between the low-temperature molten salt tank 7 and the high-temperature molten salt tank 8. That is, the salt inlet of the electric heater 13 is connected to the salt outlet of the low-temperature molten salt tank 7, and the salt outlet of the electric heater 13 is connected to the salt inlet of the high-temperature molten salt tank 8. Moreover, the electric heater 13 is arranged in parallel with the flue gas heater 9. During specific use, the electric heater 13 can consume the electric energy at the outlet of the high-voltage auxiliary transformer generator 4 to heat the molten salt passing through the electric heater 13 for heat storage. That is to say, by supplementing heat energy in the way of electric heating, the high-temperature state of the molten salt can be maintained continuously under low load, ensuring that the steam flow rate and pressure entering the steam turbine 5 are kept within the safe range. This enables the unit not to be restricted by the minimum safe operating condition of the steam turbine 5, thereby further reducing the external output power of the unit.

[0049] In some embodiments, the system further includes: a first valve 14 and a second valve 15. The first valve 14 is disposed between the flue gas heater 9 and the gas turbine. That is, the gas outlet of the first valve 14 is connected to the gas inlet of the flue gas heater 9, and the gas inlet of the first valve 14 is connected to the gas outlet of the gas turbine 3. The first valve 14 is used to adjust the flue gas flow rate passing through the flue gas heater 9. The second valve 15 is disposed between the flue gas heater 9 and the low-temperature molten salt tank 7. That is, the salt outlet of the second valve 15 is connected to the salt inlet of the flue gas heater 9, and the salt inlet of the second valve 15 is connected to the salt outlet of the low-temperature molten salt tank 7. The second valve 15 is used to adjust the molten salt flow rate passing through the flue gas heater 9. During the use process, by controlling the first valve 14 and the second valve 15, the flue gas flow rate and the molten salt flow rate entering the flue gas heater 9 can be controlled, so as to control the heating temperature of the molten salt. For example, when it is necessary to reduce the external output power of the unit, first, under the condition of ensuring the minimum safe operating condition of the steam turbine 5, the output power of the gas turbine should be reduced. That is, the amount of flue gas generated by the gas turbine decreases, and the flue gas flow rate allocated to the flue gas heater 9 also decreases. In order to ensure that the molten salt can be heated to the set temperature, the molten salt flow rate entering the flue gas heater 9 should be reduced accordingly.

[0050] For the convenience of control, the system further includes: a flue gas heating controller 16. The flue gas heating controller 16 is respectively connected to the first valve 14 and the second valve 15. The heating controller is used to control the first valve 14 and the second valve 15 to adjust the flue gas flow rate and the molten salt flow rate passing through the flue gas heater 9, so that the molten salt can be heated to the set temperature.

[0051] In some embodiments, the system further includes: a third valve 17. The third valve 17 is disposed between the electric heater 13 and the low-temperature molten salt tank 7. That is, the salt outlet of the third valve 17 is connected to the salt inlet of the electric heater 13, and the salt inlet of the third valve 17 is connected to the salt outlet of the low-temperature molten salt tank 7. The third valve 17 is used to adjust the molten salt flow rate through the electric heater 13. During use, the molten salt flow rate into the electric heater 13 can be controlled by controlling the third valve 17, so as to control the heating temperature of the molten salt. For example, when the flue gas flow rate allocated to the flue gas heater 9 by the gas turbine decreases, in order to continue to maintain the high-temperature state of the molten salt, the heating power of the electric heater 13 can be increased and the molten salt flow rate into the electric heater 13 can be increased. In this way, the reduced flue gas heat storage can be compensated, so as to ensure that the system has sufficient heat storage to maintain the normal operation of the steam turbine 5.

[0052] For the convenience of control, the system further includes: an electric heating controller 18. The electric heating controller 18 is respectively connected to the third valve 17 and the electric heater 13. The electric heating controller 18 is used to control the third valve 17 and the electric heater 13 to adjust the molten salt flow rate through the electric heater 13 and the heating power of the electric heater 13, so that the molten salt is heated to a set temperature.

[0053] In some embodiments, the system further includes: a fourth valve 19. The fourth valve 19 is disposed between the heat exchanger 10 and the high-temperature molten salt tank 8. That is, the salt outlet of the fourth valve 19 is connected to the salt inlet of the heat exchanger 10, and the salt inlet of the fourth valve 19 is connected to the salt outlet of the high-temperature molten salt tank 8. The fourth valve 19 is used to adjust the molten salt flow rate through the heat exchanger 10. During use, the molten salt flow rate into the heat exchanger 10 can be controlled by controlling the fourth valve 19, so as to control the steam flow rate into the steam turbine 5. For example, when the unit needs to operate at peak load, on the one hand, the waste heat boiler 6 outputs steam to the steam turbine 5, and on the other hand, the fourth valve 19 can be opened so that the high-temperature molten salt returns to the low-temperature molten salt tank 7 after heat exchange through the heat exchanger 10. During this process, the water passing through the heat exchanger 10 exchanges heat with the high-temperature molten salt to form steam and send it into the steam turbine 5. In this way, the steam flow rate into the steam turbine 5 can be increased, thereby increasing the output power of the steam turbine 5. When the unit needs to reduce the external output power, while reducing the water inlet flow rate of the heat exchanger 10, the fourth valve 19 can be controlled to reduce the molten salt flow rate into the heat exchanger 10. In this way, the steam generation amount of the heat exchanger 10 can be reduced while ensuring that the steam temperature and pressure remain unchanged, so as to reduce the steam flow rate into the steam turbine 5, so that the unit can reduce the external output power.

[0054] In some embodiments, the system further includes: a fifth valve 20. The fifth valve 20 is disposed at the outlet of the heat exchanger 10, and the fifth valve 20 is used to output steam from the heat exchanger 10. During use, when it is necessary to release heat from the molten salt to increase the steam flow rate entering the steam turbine 5, the fifth valve 20 can be controlled to open; otherwise, the fifth valve 20 is in a closed state. Of course, when the fifth valve 20 is in a closed state, it can also prevent the steam output by the waste heat boiler 6 from flowing out through the heat exchanger 10, thereby causing heat loss.

[0055] The embodiment of the present application also provides a method for a deep peak shaving system of a combined cycle unit based on molten salt thermal energy storage, including: if the unit needs to reduce the externally output power, part of the flue gas of the gas turbine flue gas exchanges heat in the waste heat boiler 6 to form steam required by the steam turbine 5, and the remaining flue gas will heat the molten salt passing through the flue gas heater 9 to a set temperature for thermal energy storage; if the unit needs to further reduce the externally output power, the electric heater 13 will heat the molten salt passing through the electric heater 13 to a set temperature for thermal energy storage; if the unit needs to increase the externally output power, the heat exchanger 10 is used to release the heat of the molten salt to form steam required by the steam turbine 5.

[0056] The remaining flue gas will heat the molten salt passing through the flue gas heater 9 to a set temperature, specifically including: controlling the third valve 17 and the electric heater 13 to adjust the flow rate of the molten salt passing through the electric heater 13 and the heating power of the electric heater 13; the molten salt enters the flue gas heat exchanger 10 through the second valve 15, and the remaining flue gas enters the flue gas heat exchanger 10 through the first valve 14 to heat the molten salt to a set temperature.

[0057] The electric heater 13 heats the molten salt passing through the electric heater 13 to a preset temperature, specifically including: controlling the third valve 17 and the electric heater 13 to adjust the flow rate of the molten salt passing through the electric heater 13 and the heating power of the electric heater 13; the molten salt enters the electric heater 13 through the third valve 17, and the electric heater 13 heats the molten salt to a set temperature.

[0058] According to the above solution, the deep peak shaving system of the combined cycle unit based on molten salt thermal energy storage in the embodiment of the present application uses two heat sources, namely flue gas heating and electric heating, to form an adjustable heat source. Compared with the single flue gas heating method, the electric heater 13 can be used as a controllable load for adjustment, with a fast power change speed and a short response time, which can be used to improve the frequency modulation ability of the unit. Moreover, this system can break through the limitation of the minimum safe operating condition of the steam turbine, so as to further reduce the externally output power of the unit, and even achieve zero-power grid connection, effectively improving the deep peak shaving ability of the unit.

[0059] One or more embodiments of this specification are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification shall be included within the protection scope of this application.

[0060] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

1. A combined cycle unit deep peak regulation system based on molten salt heat storage, characterized in that: include: Gas turbines, steam turbines, generators, waste heat boilers, heat storage units, flue gas heaters, electric heaters and heat exchangers; The gas turbine is connected to the generator and is used to drive the generator to generate electricity; The steam turbine is connected to the generator and is used to drive the generator to generate electricity; The waste heat boiler is connected to the gas turbine and the steam turbine, and is used to recover the heat in the flue gas of the gas turbine to form high-temperature steam required by the steam turbine; The heat storage unit comprises a low-temperature molten salt tank and a high-temperature molten salt tank, and molten salt is circulated between the low-temperature molten salt tank and the high-temperature molten salt tank; The flue gas heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and connected to the gas turbine, and is used to recover heat in the flue gas of the gas turbine to heat the molten salt; The electric heater is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and connected in parallel with the flue gas heater, and is used to consume the electric energy at the outlet of the high-temperature transformer generator to heat the molten salt; The heat exchanger is arranged between the low-temperature molten salt tank and the high-temperature molten salt tank and connected to the steam turbine, and is used for releasing the heat of the molten salt to form steam required by the steam turbine.

2. The deep peak regulation system of combined cycle units based on molten salt heat storage according to claim 1 is characterized in that: A first valve is provided between the flue gas heater and the gas turbine, and the first valve is used to adjust the flue gas flow passing through the flue gas heater; A second valve is provided between the flue gas heater and the low-temperature molten salt tank, and the second valve is used to adjust the flow rate of the molten salt passing through the flue gas heater.

3. The deep peak regulation system of combined cycle unit based on molten salt heat storage according to claim 2 is characterized in that: The first valve and the second valve are respectively connected to a flue gas heating controller, and the flue gas heating controller is used to control the first valve and the second valve to adjust the flue gas flow and the molten salt flow passing through the flue gas heater so that the molten salt can be heated to a set temperature.

4. The deep peak regulation system of combined cycle units based on molten salt heat storage according to claim 1 is characterized in that: A third valve is provided between the electric heater and the low-temperature molten salt tank, and the third valve is used to adjust the flow rate of the molten salt passing through the electric heater.

5. The deep peak regulation system of combined cycle unit based on molten salt heat storage according to claim 4 is characterized in that: The third valve and the electric heater are respectively connected to an electric heating controller, and the electric heating controller is used to control the third valve and the electric heater to adjust the molten salt flow through the electric heater and the heating power of the electric heater so that the molten salt is heated to a set temperature.

6. The deep peak regulation system of combined cycle unit based on molten salt heat storage according to claim 1 is characterized in that: A fourth valve is provided between the heat exchanger and the high-temperature molten salt tank, and the fourth valve is used to adjust the flow rate of molten salt passing through the heat exchanger; A fifth valve is provided between the heat exchanger and the steam turbine, and the fifth valve is used to adjust the steam flow entering the steam turbine.

7. The deep peak regulation system of combined cycle unit based on molten salt heat storage according to claim 1 is characterized in that: The salt outlet of the low-temperature molten salt tank is provided with a first molten salt pump, and the salt outlet of the high-temperature molten salt pump is provided with a second molten salt pump.

8. A deep peak-shaving method for a combined cycle unit based on molten salt heat storage, applicable to the deep peak-shaving system for a combined cycle unit based on molten salt heat storage according to any one of claims 1 to 7, characterized in that: include: If the unit needs to reduce the external output power, part of the flue gas of the gas turbine is heat-exchanged in the waste heat boiler to form the steam required by the steam turbine, and the remaining flue gas is heated to the set temperature by the molten salt of the flue gas heater for heat storage; If the unit needs to further reduce the external output power, the electric heater heats the molten salt passing through the electric heater to a set temperature for heat storage; If the unit needs to increase external output power, the heat exchanger is used to release the heat of the molten salt to form steam required by the steam turbine.

9. The deep peak regulation method for combined cycle units based on molten salt heat storage according to claim 8 is characterized in that: The remaining flue gas is heated to a set temperature by the molten salt of the flue gas heater, specifically comprising: controlling the third valve and the electric heater to adjust the flow of molten salt passing through the electric heater and the heating power of the electric heater; The molten salt enters the flue gas heat exchanger through the second valve, and the remaining flue gas enters the flue gas heat exchanger through the first valve to heat the molten salt to a set temperature.

10. The deep peak regulation method for combined cycle units based on molten salt heat storage according to claim 8, characterized in that: The electric heater heats the molten salt passing through the electric heater to a preset temperature, specifically comprising: controlling the third valve and the electric heater to adjust the flow of molten salt passing through the electric heater and the heating power of the electric heater; The molten salt passes through the third valve and enters the electric heater, which heats the molten salt to a set temperature.

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