A combined cycle cascading molten salt thermal storage system, method of use, apparatus, and storage medium

Abstract

The application discloses a combined cycle cascade molten salt heat storage system, an application method, equipment and a storage medium. The system comprises a gas turbine, a waste heat boiler, a first-stage molten salt heat storage module and a second-stage molten salt heat storage module. The gas turbine is used for providing generated first flue gas to the first-stage molten salt heat storage module. The waste heat boiler is used for generating steam based on second flue gas generated by the gas turbine. The first-stage molten salt heater is used for heating first low-temperature molten salt by using the first flue gas, obtaining first high-temperature molten salt and storing the first high-temperature molten salt in a first-stage high-temperature molten salt tank. The second-stage molten salt heater is used for heating second low-temperature molten salt by using third flue gas, second high-temperature molten salt and storing the second high-temperature molten salt in a second-stage high-temperature molten salt tank. The third flue gas is flue gas exhausted after the first flue gas heats the first low-temperature molten salt. In this way, the minimum stable operation load of the combined cycle cascade molten salt heat storage system can be reduced, and the stringent demand of the power grid on deep peak shaving and rapid load regulation under the condition of high-proportion new energy grid connection can be met.

Description

Technical Field

[0001] This application relates to the field of power generation technology, and in particular to a combined cycle cascade molten salt thermal energy storage system, its application method, equipment, and storage medium. Background Technology

[0002] As the global energy structure shifts towards low-carbon and high-proportion renewable energy, the power system faces increasingly severe challenges in terms of flexibility and operational stability. Renewable energy sources such as wind power and photovoltaics are characterized by significant intermittency and volatility, and their large-scale grid connection exacerbates the pressure on grid supply and demand balance, urgently requiring regulating power sources with rapid response capabilities and wide load regulation ranges as support.

[0003] Gas turbine combined cycle units (GTCUs) have advantages such as fast start-up, strong regulation capability, and flexible operation, and have become an important power source for peak shaving in the current power system. However, the minimum stable operating load of existing GTCUs is usually about 30% of the rated load. Under conditions of high proportion of renewable energy integration, traditional GTCUs struggle to achieve stable operation at low loads. Summary of the Invention

[0004] This application provides a combined cycle cascade molten salt thermal energy storage system, its application method, equipment, and storage medium, which can reduce the minimum stable operating load of the combined cycle cascade molten salt thermal energy storage system.

[0005] In a first aspect, embodiments of this application provide a combined cycle cascade molten salt thermal energy storage system, the system including a gas turbine, a waste heat boiler, a first-stage molten salt thermal energy storage module and a second-stage molten salt thermal energy storage module, wherein the first-stage molten salt thermal energy storage module includes a first-stage molten salt heater and a first-stage high-temperature molten salt tank, and the second-stage molten salt thermal energy storage module includes a second-stage molten salt heater and a second-stage high-temperature molten salt tank;

[0006] The gas turbine is used to supply the first flue gas it generates to the first-stage molten salt thermal storage module;

[0007] The waste heat boiler is used to generate steam based on the second flue gas produced by the gas turbine.

[0008] The first-stage molten salt heater is used to heat the first low-temperature molten salt with the first flue gas to obtain the first high-temperature molten salt and store it in the first-stage high-temperature molten salt tank;

[0009] The second-stage molten salt heater is used to heat the second low-temperature molten salt with the third flue gas to obtain the second high-temperature molten salt and store it in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt in the first flue gas. The temperature of the first high-temperature molten salt is higher than the temperature of the second high-temperature molten salt.

[0010] In one feasible implementation, the waste heat boiler includes a high-pressure superheater, and the first-stage molten salt heat storage module further includes a first-stage superheater, a first-stage evaporator, a first-stage economizer, and a first-stage low-temperature molten salt tank.

[0011] The first high-temperature molten salt in the first-stage high-temperature molten salt tank is used to exchange heat sequentially through the first-stage superheater, the first-stage evaporator and the first-stage economizer to obtain the first low-temperature molten salt and store it in the first-stage low-temperature molten salt tank;

[0012] The steam outlet of the first-stage superheater is connected to the high-pressure superheater to introduce the first steam generated by the first-stage molten salt thermal storage module into the high-pressure superheater.

[0013] One feasible implementation includes a first-stage molten salt heater for heating a first low-temperature molten salt using the first flue gas to obtain a first high-temperature molten salt and storing it in a first-stage high-temperature molten salt tank, comprising:

[0014] The first-stage molten salt heater is used to heat the first low-temperature molten salt in the first-stage low-temperature molten salt tank to a first preset temperature using the first flue gas, thereby obtaining the first high-temperature molten salt and storing it in the first-stage high-temperature molten salt tank.

[0015] One possible implementation of the system further includes a steam turbine for generating electricity based on steam produced by the waste heat boiler.

[0016] In one feasible implementation, the steam turbine includes a low-pressure cylinder, and the second-stage molten salt thermal storage module further includes a second-stage superheater, a second-stage evaporator, a second-stage economizer, and a second-stage cryogenic molten salt tank.

[0017] The second high-temperature molten salt in the second-stage high-temperature molten salt tank is used to exchange heat sequentially through the second-stage superheater, the second-stage evaporator, and the second-stage economizer to obtain the second low-temperature molten salt, which is then stored in the second-stage low-temperature molten salt tank.

[0018] The steam outlet of the second-stage superheater is connected to the low-pressure cylinder of the turbine, and is used to introduce the second steam generated by the second-stage molten salt thermal storage module into the low-pressure cylinder of the turbine.

[0019] One feasible implementation includes a second-stage molten salt heater for heating a second low-temperature molten salt using a third flue gas to obtain a second high-temperature molten salt, which is then stored in a second-stage high-temperature molten salt tank, comprising:

[0020] The second-stage molten salt heater is used to heat the second low-temperature molten salt in the second-stage low-temperature molten salt tank to a second preset temperature using the third flue gas, thereby obtaining the second high-temperature molten salt and storing it in the second-stage high-temperature molten salt tank.

[0021] In one feasible implementation, the flue gas outlet of the first-stage molten salt heater in the first-stage molten salt thermal storage module is connected to the flue gas inlet of the second-stage molten salt heater in the second-stage molten salt thermal storage module, for introducing the third flue gas obtained after heat exchange by the first-stage molten salt heater into the second-stage molten salt heater.

[0022] Secondly, embodiments of this application provide an application method for a combined cycle cascade molten salt thermal energy storage system, applied to any of the combined cycle cascade molten salt thermal energy storage systems described in the first aspect, comprising:

[0023] The gas turbine in the combined cycle cascade molten salt thermal energy storage system provides the first flue gas generated to the first-stage molten salt thermal energy storage module.

[0024] Steam is generated from the waste heat boiler in the combined cycle cascade molten salt thermal energy storage system, based on the second flue gas produced by the gas turbine.

[0025] The first low-temperature molten salt is heated by the first flue gas through the first-stage molten salt heater in the combined cycle cascade molten salt thermal storage system to obtain the first high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank.

[0026] The second-stage molten salt heater in the combined cycle cascade molten salt thermal storage system uses the third flue gas to heat the second low-temperature molten salt, thereby obtaining the second high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt in the first flue gas. The temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt.

[0027] Thirdly, embodiments of this application provide an electronic device, the device including: a processor, a memory, and a system bus;

[0028] The processor and the memory are connected via the system bus;

[0029] The memory is used to store a program, which includes instructions that, when executed by the processor, cause the processor to perform any of the implementation steps of the application method of the combined cycle cascade molten salt thermal storage system described above.

[0030] Fourthly, embodiments of this application provide a computer-readable storage medium for storing a computer program, which, when executed by a terminal device, implements any of the implementation steps of the application method for the combined cycle cascade molten salt thermal storage system described above.

[0031] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0032] As can be seen from the above technical solution, the present invention provides a combined cycle cascade molten salt thermal energy storage system. The system includes a gas turbine, a waste heat boiler, a first-stage molten salt thermal energy storage module, and a second-stage molten salt thermal energy storage module. The first-stage molten salt thermal energy storage module includes a first-stage molten salt heater and a first-stage high-temperature molten salt tank. The second-stage molten salt thermal energy storage module includes a second-stage molten salt heater and a second-stage high-temperature molten salt tank. The gas turbine provides the first flue gas it generates to the first-stage molten salt thermal energy storage module. The waste heat boiler generates steam based on the second flue gas generated by the gas turbine. The first-stage molten salt heater heats a first low-temperature molten salt using the first flue gas to obtain a first high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater heats a second low-temperature molten salt using a third flue gas to obtain a second high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt from the first flue gas. The temperature of the first high-temperature molten salt is higher than the temperature of the second high-temperature molten salt.

[0033] As can be seen, this application achieves graded recovery of flue gas heat and high / low temperature heat storage by splitting the flue gas generated by the gas turbine into first flue gas and second flue gas, and combining them with a two-stage molten salt thermal storage module. Specifically, the first-stage molten salt heater uses the first flue gas to heat the first low-temperature molten salt to obtain the first high-temperature molten salt, which is stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater uses the third flue gas to heat the second low-temperature molten salt to obtain the second high-temperature molten salt, which is also stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt from the first flue gas, and this discharged flue gas is further used to heat the second molten salt to reduce the situation where flue gas heat is not utilized. The temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt, thus forming a high / low temperature gradient thermal storage structure. Due to the high heat capacity and low heat loss characteristics of the molten salt medium, the above-mentioned high / low temperature gradient thermal storage structure can absorb the flue gas heat generated by the gas turbine under low load conditions, thereby reducing the minimum stable operating load of the combined cycle cascade molten salt thermal storage system. Compared with existing technologies, this application effectively solves the problem that traditional gas turbine combined cycle units are unable to achieve stable operation at low loads under conditions of high proportion of renewable energy access. Attached Figure Description

[0034] Figure 1 A schematic diagram of a combined cycle cascade molten salt thermal energy storage system provided in this application embodiment;

[0035] Figure 2 A schematic diagram illustrating an application method of a combined cycle cascade molten salt thermal energy storage system provided in this application embodiment;

[0036] Figure 3 This is a schematic diagram of a combined cycle cascade molten salt thermal storage system provided in an embodiment of this application. Detailed Implementation

[0037] As mentioned earlier, with the global energy structure transitioning towards low-carbon and high-proportion renewable energy, the power system faces increasingly severe challenges in terms of flexibility and operational stability. Renewable energy sources such as wind power and photovoltaics have significant intermittency and volatility, and their large-scale grid connection exacerbates the pressure on grid supply and demand balance, urgently requiring regulating power sources with rapid response capabilities and wide load regulation ranges as support.

[0038] Gas turbine combined cycle (GTCB) units offer advantages such as rapid start-up, strong regulation capabilities, and flexible operation, making them a crucial power source for peak shaving in current power systems. However, the minimum stable operating load of existing GTCB units is typically around 30% of their rated load. Under conditions of high-proportion renewable energy integration, traditional GTCB units struggle to achieve stable operation at low loads. Furthermore, from an energy utilization perspective, gas turbine exhaust temperatures reach as high as 500-600℃, but existing thermal storage technologies (such as hydrothermal storage) are difficult to efficiently match with the high-temperature flue gas, resulting in low waste heat resource utilization.

[0039] To address the aforementioned problems, this application provides a combined cycle cascade molten salt thermal energy storage system. The system includes a gas turbine, a waste heat boiler, a first-stage molten salt thermal energy storage module, and a second-stage molten salt thermal energy storage module. The first-stage molten salt thermal energy storage module includes a first-stage molten salt heater and a first-stage high-temperature molten salt tank. The second-stage molten salt thermal energy storage module includes a second-stage molten salt heater and a second-stage high-temperature molten salt tank. The gas turbine supplies the first-stage molten salt thermal energy storage module with first-stage flue gas. The waste heat boiler generates steam based on the second-stage flue gas produced by the gas turbine. The first-stage molten salt heater heats a first-stage low-temperature molten salt using the first-stage flue gas to obtain a first-stage high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater heats a second-stage low-temperature molten salt using a third-stage flue gas to obtain a second-stage high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank. The third-stage flue gas is the flue gas discharged after heating the first-stage low-temperature molten salt from the first-stage flue gas. The temperature of the first-stage high-temperature molten salt is higher than that of the second-stage high-temperature molten salt.

[0040] As can be seen, this application achieves graded recovery of flue gas heat and high / low temperature heat storage by splitting the flue gas generated by the gas turbine into first flue gas and second flue gas, and combining them with a two-stage molten salt thermal storage module. Specifically, the first-stage molten salt heater uses the first flue gas to heat the first low-temperature molten salt to obtain the first high-temperature molten salt, which is stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater uses the third flue gas to heat the second low-temperature molten salt to obtain the second high-temperature molten salt, which is also stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt from the first flue gas, and this discharged flue gas is further used to heat the second molten salt to reduce the situation where flue gas heat is not utilized. The temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt, thus forming a high / low temperature gradient thermal storage structure. Due to the high heat capacity and low heat loss characteristics of the molten salt medium, the above-mentioned high / low temperature gradient thermal storage structure can absorb the flue gas heat generated by the gas turbine under low load conditions, thereby reducing the minimum stable operating load of the combined cycle cascade molten salt thermal storage system. Compared with existing technologies, this application effectively solves the problem that traditional gas turbine combined cycle units are unable to achieve stable operation at low loads under conditions of high proportion of renewable energy access.

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] Figure 1 This is a schematic diagram of a combined cycle cascade molten salt thermal energy storage system provided as an embodiment of this application. (Combined with...) Figure 1 As shown, the combined cycle cascade molten salt thermal energy storage system in this application embodiment includes a gas turbine, a waste heat boiler, a first-stage molten salt thermal energy storage module, and a second-stage molten salt thermal energy storage module.

[0043] In this embodiment, a gas turbine is used to supply the generated first flue gas to the first-stage molten salt thermal storage module. Specifically, the gas turbine includes a compressor, a combustion chamber, a turbine, and a generator, and the gas turbine outputs the first flue gas to the first-stage molten salt thermal storage module through the turbine outlet.

[0044] In addition, the combined cycle cascade molten salt thermal energy storage system also includes a steam turbine, deaerator, condenser, pumps, distributor, and mixer, etc. The steam turbine is used to generate electricity based on the steam produced by the waste heat boiler. Specifically, it includes a high-pressure cylinder and a low-pressure cylinder of the steam turbine.

[0045] Waste heat boilers are used to generate steam from the second flue gas produced by a gas turbine. Specifically, a waste heat boiler includes a high-pressure superheater, a high-pressure superheater, a high-pressure evaporator, a low-pressure superheater, a high-pressure economizer, a low-pressure evaporator, a low-pressure economizer, and a final economizer.

[0046] The first-stage molten salt thermal storage module includes a first-stage molten salt heater, a first-stage high-temperature molten salt tank, a first-stage superheater, a first-stage evaporator, a first-stage economizer, and a first-stage low-temperature molten salt tank. The second-stage molten salt thermal storage module includes a second-stage molten salt heater, a second-stage high-temperature molten salt tank, a second-stage superheater, a second-stage evaporator, a second-stage economizer, and a second-stage low-temperature molten salt tank.

[0047] During the heat storage stage, the first-stage molten salt heater uses first flue gas to heat the first low-temperature molten salt in the first-stage low-temperature molten salt tank to a first preset temperature, obtaining the first high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater uses third flue gas to heat the second low-temperature molten salt in the second-stage low-temperature molten salt tank to a second preset temperature, obtaining the second high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank.

[0048] It should be noted that the third flue gas is the flue gas discharged after heating the first low-temperature molten salt in the first flue gas. Specifically, by connecting the flue gas outlet of the first-stage molten salt heater in the first-stage molten salt heat storage module to the flue gas inlet of the second-stage molten salt heater in the second-stage molten salt heat storage module, the third flue gas obtained after heat exchange in the first-stage molten salt heater is introduced into the second-stage molten salt heater.

[0049] In this embodiment, the temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt to form a high-low temperature gradient thermal storage structure. Furthermore, in this embodiment, the first low-temperature molten salt can be solar salt (a binary nitrate molten salt with a chemical composition of 60% NaNO3 + 40% KNO3), and the second low-temperature molten salt in the second-stage low-temperature molten salt tank can be HITEC molten salt (a ternary nitrate molten salt with a chemical composition of 53% KNO3 + 7% NaNO3 + 40% NaNO2).

[0050] Furthermore, the first-stage molten salt thermal storage module in this embodiment also includes a first-stage electric heater, and the second-stage molten salt thermal storage module also includes a second-stage electric heater. When the gas turbine operates in the low-load region (i.e., below 35% of rated load), the heat of the flue gas at the turbine outlet may decrease, causing the first and second cryogenic molten salts to fail to reach their respective first and second preset temperatures after passing through the first and second stage molten salt heaters. To ensure that both the first and second cryogenic molten salts are heated to their preset temperatures after passing through the first stage molten salt, this embodiment supplements the heating of the first and second cryogenic molten salts using the first and second stage electric heaters, thereby ensuring that the first and second stage molten salt thermal storage modules can complete their predetermined thermal storage functions even under low-load conditions.

[0051] During the exothermic phase, the first high-temperature molten salt in the first-stage high-temperature molten salt tank undergoes heat exchange sequentially through the first-stage superheater, the first-stage evaporator, and the first-stage economizer to obtain the first low-temperature molten salt, which is then stored in the first-stage low-temperature molten salt tank, thus realizing the heat storage-heat release cycle of the first-stage molten salt heat storage module. Simultaneously, a portion of the feedwater at the deaerator outlet passes through the first-stage economizer, the first-stage evaporator, and the first-stage superheater, and is then pumped out by a pump to heat the first high-temperature molten salt, thereby generating the first steam. This first steam is introduced into the high-pressure superheater of the waste heat boiler through the steam outlet of the first-stage superheater. It should be noted that the first steam in this embodiment is high-temperature, high-pressure steam.

[0052] The second high-temperature molten salt in the second-stage high-temperature molten salt tank undergoes heat exchange sequentially through the second-stage superheater, the second-stage evaporator, and the second-stage economizer to obtain the second low-temperature molten salt, which is then stored in the second-stage low-temperature molten salt tank, thus realizing the heat storage-heat release cycle of the second-stage molten salt heat storage module. Simultaneously, a portion of the feedwater at the deaerator outlet passes through the second-stage economizer, the second-stage evaporator, and the second-stage superheater, and is then pumped out to heat the second high-temperature molten salt, thereby generating second steam. The generated second steam is introduced into the low-pressure cylinder of the steam turbine through the steam outlet of the second-stage superheater. It should be noted that, since the temperature of the first high-temperature molten salt in this embodiment is higher than the temperature of the second high-temperature molten salt, the temperature of the first steam is also higher than the temperature of the second steam.

[0053] In the energy storage phase of this application, the first-stage molten salt thermal storage module and the second-stage molten salt thermal storage module absorb the flue gas generated by the gas turbine in stages, forming a thermal storage structure with a high and low temperature gradient. This high and low temperature gradient thermal storage structure can absorb the heat from the flue gas generated by the gas turbine under low load conditions, thereby reducing the minimum stable operating load of the combined cycle cascade molten salt thermal storage system.

[0054] In the exothermic phase of this application, the first and second high-temperature molten salts stored in the first and second high-temperature molten salt tanks are sequentially passed through their corresponding superheaters, evaporators, and economizers. The resulting first and second steam are then introduced into the high-pressure superheater and low-pressure turbine, respectively, achieving cascaded utilization of thermal energy. Specifically, the first steam generated by the first high-temperature molten salt can be used for high-pressure power generation, and the second steam generated by the second high-temperature molten salt can be used for low-pressure power generation, thereby fully utilizing high and low temperature waste heat and improving the overall energy efficiency of the combined cycle cascade molten salt thermal energy storage system.

[0055] Through the above-mentioned heat storage-heat release cycle, the embodiments of this application form a deep peak-shaving mode that couples a high-low temperature gradient heat storage structure with a steam cascade utilization structure. This mode can maintain stable operation of the gas turbine at low load when a high proportion of renewable energy is connected, and can maximize the recovery of high-temperature flue gas waste heat, thereby improving the overall energy efficiency of the combined cycle cascade molten salt heat storage system.

[0056] Therefore, this application embodiment, by employing a combined cycle cascade molten salt thermal storage system, achieves tiered recovery and efficient utilization of high-temperature flue gas heat, significantly reducing irreversible heat loss in the system and thereby increasing the system's heat storage-release round-trip efficiency to over 90%. Furthermore, by introducing a two-stage molten salt thermal storage structure and coordinating it with an electric heater, the system's stable operating range under low-load conditions is effectively broadened, significantly reducing the minimum stable operating load of the combined cycle cascade molten salt thermal storage system from 30%-50% of traditional gas-steam combined cycle units to approximately 15%. Moreover, leveraging the active regulation capability of the two-stage molten salt thermal storage modules for the bottom cycle power, the combined cycle cascade molten salt thermal storage system achieves flexible and continuous response within a 15%-100% load range, thus meeting the stringent requirements of the power grid for deep peak shaving and rapid load adjustment under conditions of high-proportion renewable energy grid integration.

[0057] The above analysis shows that the combined cycle cascade molten salt thermal energy storage system provided by the present invention includes a gas turbine, a waste heat boiler, a first-stage molten salt thermal energy storage module, and a second-stage molten salt thermal energy storage module. The first-stage molten salt thermal energy storage module includes a first-stage molten salt heater and a first-stage high-temperature molten salt tank, and the second-stage molten salt thermal energy storage module includes a second-stage molten salt heater and a second-stage high-temperature molten salt tank. The gas turbine provides the first flue gas it generates to the first-stage molten salt thermal energy storage module; the waste heat boiler generates steam based on the second flue gas generated by the gas turbine. The first-stage molten salt heater uses the first flue gas to heat a first low-temperature molten salt to obtain a first high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater uses a third flue gas to heat a second low-temperature molten salt to obtain a second high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt from the first flue gas, and the temperature of the first high-temperature molten salt is higher than the temperature of the second high-temperature molten salt.

[0058] As can be seen, this application achieves graded recovery of flue gas heat and high / low temperature heat storage by splitting the flue gas generated by the gas turbine into first flue gas and second flue gas, and combining them with a two-stage molten salt thermal storage module. Specifically, the first-stage molten salt heater uses the first flue gas to heat the first low-temperature molten salt to obtain the first high-temperature molten salt, which is stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater uses the third flue gas to heat the second low-temperature molten salt to obtain the second high-temperature molten salt, which is also stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt from the first flue gas, and this discharged flue gas is further used to heat the second molten salt to reduce the situation where flue gas heat is not utilized. The temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt, thus forming a high / low temperature gradient thermal storage structure. Due to the high heat capacity and low heat loss characteristics of the molten salt medium, the above-mentioned high / low temperature gradient thermal storage structure can absorb the flue gas heat generated by the gas turbine under low load conditions, thereby reducing the minimum stable operating load of the combined cycle cascade molten salt thermal storage system. Compared with existing technologies, this application effectively solves the problem that traditional gas turbine combined cycle units are unable to achieve stable operation at low loads under conditions of high proportion of renewable energy access.

[0059] Furthermore, Figure 2 This is a schematic diagram illustrating an application method of a combined cycle cascade molten salt thermal energy storage system provided in an embodiment of this application. (Combined with...) Figure 2 As shown, it may include steps S201-S204.

[0060] S201: The first flue gas generated is supplied to the first-stage molten salt thermal storage module through the gas turbine in the combined cycle cascade molten salt thermal storage system.

[0061] In this embodiment of the application, the first flue gas generated by the gas turbine in the combined cycle cascade molten salt thermal storage system is supplied to the first-stage molten salt thermal storage module. Specifically, the gas turbine includes a compressor, a combustion chamber, a turbine, and a generator, and the gas turbine outputs the first flue gas to the first-stage molten salt thermal storage module through the turbine outlet.

[0062] S202: Steam is generated by a waste heat boiler in a combined cycle cascade molten salt thermal storage system, based on the second flue gas produced by the gas turbine.

[0063] In this embodiment, steam is generated from the second flue gas produced by the gas turbine through a waste heat boiler in a combined cycle cascade molten salt thermal energy storage system. Specifically, the waste heat boiler includes a high-pressure superheater, a high-pressure superheater, a high-pressure evaporator, a low-pressure superheater, a high-pressure economizer, a low-pressure evaporator, a low-pressure economizer, and a final economizer.

[0064] S203: The first low-temperature molten salt is heated by the first flue gas through the first stage molten salt heater in the combined cycle cascade molten salt thermal storage system to obtain the first high-temperature molten salt and store it in the first stage high-temperature molten salt tank.

[0065] In this embodiment, the first-stage molten salt thermal storage module in the combined cycle cascade molten salt thermal storage system further includes a first-stage superheater, a first-stage evaporator, a first-stage economizer, and a first-stage cryogenic molten salt tank. During the thermal storage stage, the first-stage molten salt heater uses first flue gas to heat the first cryogenic molten salt in the first-stage cryogenic molten salt tank to a first preset temperature, thereby obtaining a first high-temperature molten salt and storing it in the first-stage high-temperature molten salt tank.

[0066] During the exothermic phase, the first high-temperature molten salt in the first-stage high-temperature molten salt tank undergoes heat exchange sequentially through the first-stage superheater, the first-stage evaporator, and the first-stage economizer to obtain the first low-temperature molten salt, which is then stored in the first-stage low-temperature molten salt tank. Next, the steam outlet of the first-stage superheater is connected to the high-pressure superheater, thereby introducing the first steam generated by the first-stage molten salt thermal storage module into the high-pressure superheater.

[0067] S204: The second low-temperature molten salt is heated by the second-stage molten salt heater in the combined cycle cascade molten salt thermal storage system using the third flue gas to obtain the second high-temperature molten salt, which is then stored in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after heating the first low-temperature molten salt in the first flue gas. The temperature of the first high-temperature molten salt is higher than that of the second high-temperature molten salt.

[0068] In this embodiment, the second-stage molten salt thermal storage module in the combined cycle cascade molten salt thermal storage system further includes a second-stage superheater, a second-stage evaporator, a second-stage economizer, and a second-stage cryogenic molten salt tank. During the thermal storage stage, the second-stage molten salt heater uses third flue gas to heat the second cryogenic molten salt in the second-stage cryogenic molten salt tank to a second preset temperature, obtaining a second high-temperature molten salt which is then stored in the second-stage high-temperature molten salt tank.

[0069] It should be noted that the combined cycle cascade molten salt thermal energy storage system in this application embodiment also includes a steam turbine, which is used to generate electricity based on the steam generated by the waste heat boiler. The steam turbine includes a low-pressure cylinder.

[0070] During the exothermic phase, the second high-temperature molten salt in the second-stage high-temperature molten salt tank undergoes heat exchange sequentially through the second-stage superheater, the second-stage evaporator, and the second-stage economizer to obtain the second low-temperature molten salt, which is then stored in the second-stage low-temperature molten salt tank. Next, the steam outlet of the second-stage superheater is connected to the low-pressure cylinder of the turbine to introduce the second steam generated by the second-stage molten salt thermal storage module into the turbine's low-pressure cylinder, thereby increasing the turbine's power generation.

[0071] Furthermore, in this embodiment, the flue gas outlet of the first-stage molten salt heater in the first-stage molten salt thermal storage module is connected to the flue gas inlet of the second-stage molten salt heater in the second-stage molten salt thermal storage module, for introducing the third flue gas obtained after heat exchange by the first-stage molten salt heater into the second-stage molten salt heater.

[0072] Furthermore, as can be seen from the above embodiments, the combined cycle cascade molten salt thermal energy storage system includes a gas turbine, a waste heat boiler, a steam turbine, a first-stage molten salt thermal energy storage module, and a second-stage molten salt thermal energy storage module. Figure 3 This application provides a schematic diagram of a combined cycle cascade molten salt thermal energy storage system, combined with... Figure 3 It can be seen that the gas turbine includes a compressor 1, a combustion chamber 2, a turbine 3, and a generator 4; the waste heat boiler includes a high-pressure superheater 1 5, a high-pressure superheater 2 6, a high-pressure evaporator 7, a low-pressure superheater 8, a high-pressure economizer 9, a low-pressure evaporator 10, a low-pressure economizer 11, and a final economizer 12; the steam turbine includes a high-pressure cylinder 18 and a low-pressure cylinder 19; the first-stage molten salt thermal storage module includes a first-stage low-temperature molten salt tank 20, a first-stage molten salt heater 21, a first-stage electric heater 22, a first-stage high-temperature molten salt tank 23, a first-stage superheater 24, a first-stage evaporator 25, and a first-stage economizer 26; the second-stage molten salt thermal storage module includes a second-stage low-temperature molten salt tank 27, a second-stage molten salt heater 28, a second-stage electric heater 29, a second-stage high-temperature molten salt tank 30, a second-stage superheater 31, a second-stage evaporator 32, and a second-stage economizer 33.

[0073] In addition, combined Figure 3 As can be seen, the combined cycle cascade molten salt thermal energy storage system also includes a deaerator 16, a condenser 17, a mixer 13, a pump 14, and a distributor 15. Among them, multiple mixers 13, pumps 14, distributors 15, and generators 4 are arranged in the figure. Their structures and functions are basically the same, and they are all used to realize the mixing, transportation, distribution, and power generation of the working fluid.

[0074] Furthermore, embodiments of this application also provide an electronic device, including: a processor, a memory, and a system bus;

[0075] The processor and the memory are connected via the system bus;

[0076] The memory is used to store one or more programs, the one or more programs including instructions that, when executed by the processor, cause the processor to perform any of the implementation steps of the above-described method for applying the combined cycle cascade molten salt thermal storage system.

[0077] Furthermore, embodiments of this application also provide a computer-readable storage medium for storing a computer program, which, when executed by a terminal device, implements any of the implementation steps of the above-described application method for a combined cycle cascade molten salt thermal energy storage system.

[0078] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that all or part of the steps in the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, a server, or a network communication device such as a media gateway, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application. It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on describing the differences from other embodiments. The same or similar parts between the various embodiments can be referred to mutually.

[0079] The system disclosed in the embodiments is described in a relatively simple manner because it corresponds to the method disclosed in the embodiments. For relevant details, please refer to the method section.

[0080] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A combined cycle cascade molten salt thermal energy storage system, characterized in that, The system includes a gas turbine, a waste heat boiler, a first-stage molten salt thermal storage module, and a second-stage molten salt thermal storage module. The first-stage molten salt thermal storage module includes a first-stage molten salt heater and a first-stage high-temperature molten salt tank. The second-stage molten salt thermal storage module includes a second-stage molten salt heater and a second-stage high-temperature molten salt tank. The gas turbine is used to supply the first flue gas it generates to the first-stage molten salt thermal storage module; The waste heat boiler is used to generate steam based on the second flue gas produced by the gas turbine. The first-stage molten salt heater is used to heat the first low-temperature molten salt with the first flue gas to obtain the first high-temperature molten salt and store it in the first-stage high-temperature molten salt tank; The second-stage molten salt heater is used to heat the second low-temperature molten salt with the third flue gas to obtain the second high-temperature molten salt and store it in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after the first flue gas heats the first low-temperature molten salt. The temperature of the first high-temperature molten salt is higher than the temperature of the second high-temperature molten salt. The first low-temperature molten salt and the second low-temperature molten salt are two different types of molten salts. The first low-temperature molten salt is solar salt, and the second low-temperature molten salt is ternary nitrate. The waste heat boiler includes a high-pressure superheater, and the first-stage molten salt heat storage module also includes a first-stage superheater, a first-stage evaporator, a first-stage economizer, and a first-stage low-temperature molten salt tank. The first high-temperature molten salt in the first-stage high-temperature molten salt tank is used to exchange heat sequentially through the first-stage superheater, the first-stage evaporator and the first-stage economizer to obtain the first low-temperature molten salt and store it in the first-stage low-temperature molten salt tank; The steam outlet of the first-stage superheater is connected to the high-pressure superheater to introduce the first steam generated by the first-stage molten salt thermal storage module into the high-pressure superheater. The system also includes a steam turbine for generating electricity based on the steam produced by the waste heat boiler; The steam turbine includes a low-pressure cylinder, and the second-stage molten salt thermal storage module also includes a second-stage superheater, a second-stage evaporator, a second-stage economizer, and a second-stage cryogenic molten salt tank. The second high-temperature molten salt in the second-stage high-temperature molten salt tank is used to exchange heat sequentially through the second-stage superheater, the second-stage evaporator, and the second-stage economizer to obtain the second low-temperature molten salt, which is then stored in the second-stage low-temperature molten salt tank. The steam outlet of the second-stage superheater is connected to the low-pressure cylinder of the turbine, and is used to introduce the second steam generated by the second-stage molten salt thermal storage module into the low-pressure cylinder of the turbine.

2. The combined cycle cascade molten salt thermal energy storage system according to claim 1, characterized in that, The first-stage molten salt heater, used to heat the first low-temperature molten salt with the first flue gas to obtain the first high-temperature molten salt and store it in the first-stage high-temperature molten salt tank, includes: The first-stage molten salt heater is used to heat the first low-temperature molten salt in the first-stage low-temperature molten salt tank to a first preset temperature using the first flue gas, thereby obtaining the first high-temperature molten salt and storing it in the first-stage high-temperature molten salt tank.

3. The combined cycle cascade molten salt thermal energy storage system according to claim 1, characterized in that, The second-stage molten salt heater, used to heat the second low-temperature molten salt with the third flue gas to obtain the second high-temperature molten salt and store it in the second-stage high-temperature molten salt tank, includes: The second-stage molten salt heater is used to heat the second low-temperature molten salt in the second-stage low-temperature molten salt tank to a second preset temperature using the third flue gas, thereby obtaining the second high-temperature molten salt and storing it in the second-stage high-temperature molten salt tank.

4. The combined cycle cascade molten salt thermal storage system according to claim 1, characterized in that, The flue gas outlet of the first-stage molten salt heater in the first-stage molten salt thermal storage module is connected to the flue gas inlet of the second-stage molten salt heater in the second-stage molten salt thermal storage module, so as to introduce the third flue gas obtained after heat exchange by the first-stage molten salt heater into the second-stage molten salt heater.

5. An application method for a combined cycle cascade molten salt thermal energy storage system, characterized in that, The combined cycle cascade molten salt thermal energy storage system according to any one of claims 1 to 4 comprises: The gas turbine in the combined cycle cascade molten salt thermal energy storage system provides the first flue gas generated to the first-stage molten salt thermal energy storage module. Steam is generated from the waste heat boiler in the combined cycle cascade molten salt thermal energy storage system, based on the second flue gas produced by the gas turbine. The first low-temperature molten salt is heated by the first flue gas through the first-stage molten salt heater in the combined cycle cascade molten salt thermal storage system to obtain the first high-temperature molten salt, which is then stored in the first-stage high-temperature molten salt tank. The second-stage molten salt heater in the combined cycle cascade molten salt thermal storage system uses the third flue gas to heat the second low-temperature molten salt, thereby obtaining the second high-temperature molten salt and storing it in the second-stage high-temperature molten salt tank. The third flue gas is the flue gas discharged after the first flue gas heats the first low-temperature molten salt, and the temperature of the first high-temperature molten salt is higher than the temperature of the second high-temperature molten salt. The first low-temperature molten salt and the second low-temperature molten salt are two different types of molten salts. The first low-temperature molten salt is solar salt, and the second low-temperature molten salt is ternary nitrate. The waste heat boiler includes a high-pressure superheater, and the first-stage molten salt heat storage module also includes a first-stage superheater, a first-stage evaporator, a first-stage economizer, and a first-stage low-temperature molten salt tank. The first high-temperature molten salt in the first-stage high-temperature molten salt tank undergoes heat exchange sequentially through the first-stage superheater, the first-stage evaporator, and the first-stage economizer to obtain the first low-temperature molten salt, which is then stored in the first-stage low-temperature molten salt tank. The steam outlet of the first-stage superheater is connected to the high-pressure superheater, and the first steam generated by the first-stage molten salt thermal storage module is introduced into the high-pressure superheater. The system also includes a steam turbine for generating electricity based on the steam produced by the waste heat boiler; The steam turbine includes a low-pressure cylinder, and the second-stage molten salt thermal storage module also includes a second-stage superheater, a second-stage evaporator, a second-stage economizer, and a second-stage cryogenic molten salt tank. The second high-temperature molten salt in the second-stage high-temperature molten salt tank undergoes heat exchange sequentially through the second-stage superheater, the second-stage evaporator, and the second-stage economizer to obtain the second low-temperature molten salt, which is then stored in the second-stage low-temperature molten salt tank. The steam outlet of the second-stage superheater is connected to the low-pressure cylinder of the turbine, and is used to introduce the second steam generated by the second-stage molten salt thermal storage module into the low-pressure cylinder of the turbine.

6. An electronic device, characterized in that, The device includes: a processor, a memory, and a system bus; The processor and the memory are connected via the system bus; The memory is used to store a program, the program including instructions that, when executed by the processor, cause the processor to perform the steps of the application method of the combined cycle cascade molten salt thermal storage system as described in claim 5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store a computer program, which, when executed by a terminal device, implements the steps of the application method of the combined cycle cascade molten salt thermal energy storage system as described in claim 5.

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