Binary fused salt heat storage application system

Abstract

The utility model relates to a binary fused salt heat storage application system which comprises a steam generator, a low-temperature fused salt tank, a fused salt heater, a high-temperature fused salt tank, a fused salt-material heat exchanger and a fused salt-conduction oil heat exchanger, a feeding port of the fused salt heater is communicated with the low-temperature fused salt tank, and a discharging port of the fused salt heater is communicated with the high-temperature fused salt tank; a thermal medium inlet of the fused salt-material heat exchanger is communicated with the high-temperature fused salt tank, and a thermal medium outlet of the fused salt-material heat exchanger is communicated with a thermal medium inlet of the fused salt-conduction oil heat exchanger; a thermal medium outlet of the fused salt-heat conduction oil heat exchanger is communicated with the low-temperature fused salt tank, and a material channel of the fused salt-heat conduction oil heat exchanger and a thermal medium channel of the steam generator form a circulation channel. According to the utility model, heat of a low-temperature section of fused salt heat storage can be fully utilized, the temperature range of generated steam is enlarged, and the application range of fused salt heat storage is widened; and off-peak electricity can be fully utilized for heat storage, and the energy cost is reduced.

Description

Technical Field

[0001] This utility model relates to the field of energy storage and comprehensive energy utilization technology, and in particular to a binary molten salt thermal energy storage application system. Background Technology

[0002] With the development of new energy technologies and the transformation of energy structure in my country, energy storage technology has gradually become an important way of energy consumption. At present, the main energy storage methods include electrochemical energy storage, gravity energy storage, compressed air energy storage, molten salt energy storage, flywheel energy storage, and supercapacitor energy storage.

[0003] Among various energy storage methods, molten salt energy storage is an emerging clean energy storage method. Molten salt energy storage has more advantages in renewable energy consumption and clean energy heating. As one of the important support points for the development of renewable energy, molten salt energy storage can be applied on a large scale in concentrated areas such as solar thermal power generation, utilization of waste electricity from new energy sources, and grid peak shaving, or it can be distributed in areas such as smart energy, centralized clean energy heating, and combined heat and power (CHP) systems for clean energy.

[0004] However, most current molten salt energy storage systems are single-function energy storage systems, which limits the application scope of molten salt energy storage and is not conducive to improving the overall energy utilization rate. Utility Model Content

[0005] This invention addresses the shortcomings of existing technologies by providing a binary molten salt thermal energy storage system, forming a composite energy storage system with binary molten salt energy storage as the main component. This enriches the application scenarios of molten salt energy storage and improves the comprehensive utilization rate of energy.

[0006] This utility model is achieved through the following technical solution, providing a binary molten salt thermal storage application system, including a steam generator, a water supply system connected to the inlet of the steam generator, and a low-temperature molten salt tank, a molten salt heater, a high-temperature molten salt tank, a molten salt-material heat exchanger, and a molten salt-thermal oil heat exchanger arranged in sequence. The inlet of the molten salt heater is connected to the low-temperature molten salt tank through a first feed pipe, and the outlet of the molten salt heater is connected to the high-temperature molten salt tank through a second feed pipe. A low-temperature molten salt pump is installed on the first feed pipe.

[0007] The heat medium inlet of the molten salt-material heat exchanger is connected to the high-temperature molten salt tank through the discharge pipe, and a high-temperature molten salt pump is installed on the discharge pipe. The heat medium outlet of the molten salt-material heat exchanger is connected to the heat medium inlet of the molten salt-thermal oil heat exchanger through a pipeline. The heat medium outlet of the molten salt-thermal oil heat exchanger is connected to the low-temperature molten salt tank. The material channel of the molten salt-thermal oil heat exchanger and the heat medium channel of the steam generator form a circulation channel, and a thermal oil circulation pump is installed on the circulation channel.

[0008] During off-peak electricity pricing periods, this solution activates the molten salt heater and cryogenic molten salt pump, heating the binary salt in the cryogenic molten salt tank before it enters the high-temperature molten salt tank for thermal energy storage. During peak electricity pricing periods, the high-temperature molten salt pump activates, causing the binary salt in the high-temperature molten salt tank to pass sequentially through the heat medium channels of the molten salt-material heat exchanger and the molten salt-thermal oil heat exchanger, respectively heating the material in the molten salt-material heat exchanger and the thermal oil in the molten salt-thermal oil heat exchanger. The heated material in the molten salt-material heat exchanger is discharged through its material outlet, while the heated thermal oil in the molten salt-thermal oil heat exchanger heats the water injected into the steam generator inlet to form steam. Due to the low melting point and wide operating temperature range of the thermal oil, the temperature range of the steam produced by the steam generator is increased.

[0009] As an optimization, the water supply system includes a main water supply pipe connected to the inlet of the steam generator, and an electric heater, a subcritical water storage tank, and a feed pump sequentially arranged along the water supply pipe. This optimized water supply system can use the electric heater to heat the water in the subcritical water storage tank during off-peak electricity hours, forming a preheating stage for molten salt thermal storage applications. This maximizes the utilization of off-peak electricity for thermal storage, and the feed pump provides pressure to the steam generator's inlet water.

[0010] As an optimization, a makeup water pump located upstream of the electric heater is also installed on the main water supply pipe. This optimized solution provides power for the demineralized water to enter the subcritical storage tank after being heated by the makeup water pump.

[0011] As an optimization, a heat transfer oil buffer tank is also installed on the circulation channel, and the heat transfer oil buffer tank is located between the heat transfer oil circulation pump and the heat medium outlet of the steam generator. This optimization scheme improves the stability of the heat transfer oil system by setting up a heat transfer oil buffer tank as a temporary storage for the heat exchange heat transfer oil.

[0012] As an optimization, an electric heating device is installed inside the heat transfer oil buffer tank. This optimization scheme, by installing an electric heating device inside the heat transfer oil buffer tank, allows for heating of the heat transfer oil during off-peak electricity pricing periods, further improving the utilization rate of off-peak electricity.

[0013] The beneficial effects of this utility model are as follows: by setting up a molten salt-thermal oil heat exchanger, the low-temperature heat of molten salt heat storage can be fully utilized, increasing the temperature range for generating steam and improving the application range of molten salt heat storage; it can make full use of off-peak electricity for heat storage, reducing energy costs; and by setting up a molten salt-thermal oil heat exchanger, the low-temperature water of molten salt does not directly exchange heat, thus making the system safer and more efficient. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the process structure of this utility model;

[0015] As shown in the figure:

[0016] 1. High-temperature molten salt tank; 2. Low-temperature molten salt tank; 3. Molten salt-material heat exchanger; 4. Molten salt-thermal oil heat exchanger; 5. Molten salt heater; 6. High-temperature molten salt pump; 7. Low-temperature molten salt pump; 8. Steam generator; 9. Thermal oil buffer tank; 10. Thermal oil circulating pump; 11. Subcritical water storage tank; 12. Electric heater; 13. Feed water pump; 14. Make-up water pump; 15. Nitrogen blanketing system. Detailed Implementation

[0017] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to describe the solution.

[0018] like Figure 1 The diagram illustrates a binary molten salt thermal energy storage system, comprising a steam generator 8, a water supply system connected to the inlet of the steam generator, and sequentially arranged components including a low-temperature molten salt tank 2, a molten salt heater 5, a high-temperature molten salt tank 1, a molten salt-material heat exchanger 3, and a molten salt-thermal oil heat exchanger 4. The high-temperature molten salt tank 1 is constructed of 347H stainless steel, with a maximum operating temperature of 570℃, meeting the thermal storage temperature requirements of binary molten salt. The low-temperature molten salt tank 2 is constructed of Q345R steel, with a maximum operating temperature of 400℃, also meeting the thermal storage temperature requirements of binary molten salt. The molten salt heater 5 is an electrode-type molten salt heater, which can be directly connected to a 10KV power supply.

[0019] Steam generator 8 is used to heat water to produce saturated steam. Its structure can utilize existing technology. In this embodiment, heat transfer oil is used as the heating medium for the steam generator. The water entering the steam generator is heated by the heat transfer oil, and the generated steam enters the steam supply pipeline for use. The steam generator in this embodiment is a heat transfer oil-water heat exchange device. The heat transfer oil inlet temperature is 350~360℃, the outlet temperature is 250~260℃, and the saturated steam temperature is 150~220℃.

[0020] Molten salt-material heat exchanger 3 is used for heat exchange between high-temperature molten salt and materials. The heat exchanger contains a heat medium channel and a material channel. High-temperature molten salt serves as the heating medium, heating the material entering the material channel. After heat exchange, the molten salt exits through the heat medium outlet, and the heated material exits through the material channel outlet. Molten salt-material heat exchanger 3 is used in the high-temperature section of molten salt, with an inlet temperature of 550~570℃ and an outlet temperature of 400~500℃. The inlet and outlet temperatures and flow rates of the molten salt are controlled according to the material's flow and temperature requirements.

[0021] The molten salt-thermal oil heat exchanger is used for heat exchange between molten salt and thermal oil. The molten salt-thermal oil heat exchanger is equipped with a heat medium channel and a thermal oil channel. Molten salt is used as the heating medium of the molten salt-thermal oil heat exchanger to heat the thermal oil. After heat exchange, the molten salt is output through the heat medium outlet, and the heated thermal oil is output through the outlet of the thermal oil channel.

[0022] Specifically, the inlet of the molten salt heater is connected to the cryogenic molten salt tank via a first feed pipe, and the feed end of the first feed pipe extends into the molten salt in the cryogenic molten salt tank. The outlet of the molten salt heater is connected to the high-temperature molten salt tank via a second feed pipe. A cryogenic molten salt pump 7 is installed on the first feed pipe, which delivers the molten salt in the cryogenic molten salt tank to the molten salt heater and the high-temperature molten salt tank. The cryogenic molten salt pump 7 is a molten salt submersible pump, resistant to high temperatures up to 400℃, and equipped with a cooling water system.

[0023] The heat medium inlet of the molten salt-material heat exchanger is connected to the high-temperature molten salt tank via a discharge pipe. A high-temperature molten salt pump 6 is installed on the discharge pipe, which powers the molten salt to flow through the molten salt-material heat exchanger and the molten salt-thermal oil heat exchanger into the low-temperature molten salt tank. The high-temperature molten salt pump 6 is a submerged pump for molten salt, resistant to temperatures up to 600℃, and equipped with a cooling water system. The heat medium outlet of the molten salt-material heat exchanger is connected to the heat medium inlet of the molten salt-thermal oil heat exchanger via a pipeline. The material channel inlet of the molten salt-material heat exchanger is connected to the material input pipe, and the material channel outlet of the molten salt-material heat exchanger is connected to the material output pipe.

[0024] The heat medium outlet of the molten salt-thermal oil heat exchanger is connected to a cryogenic molten salt tank via a pipeline, allowing the molten salt after heat exchange to enter the cryogenic molten salt tank. The material channel of the molten salt-thermal oil heat exchanger and the heat medium channel of the steam generator form a circulation channel. A thermal oil circulation pump 10 is installed on the circulation channel to provide circulation power for the heat exchange thermal oil. To improve system stability, a thermal oil buffer tank 9 is also installed on the circulation channel, located between the thermal oil circulation pump and the heat medium outlet of the steam generator. The thermal oil buffer tank 9 serves as a temporary storage container for the heat exchange thermal oil, with a volume of 3 m³. An electric heating device is installed inside the thermal oil buffer tank 9 to heat the thermal oil in the buffer tank during off-peak electricity hours, reducing costs and heating the thermal oil to 250~260℃. Molten salt-heat transfer oil heat exchanger 4 is an intermediate heat exchange system that transfers the heat stored in the molten salt to the heat transfer oil. The heat transfer oil itself does not participate in large-scale heat storage, but only in the heat exchange cycle. The inlet temperature of the molten salt is 400~500℃ and the outlet temperature is 290℃. The inlet temperature of the heat transfer oil is 250~260℃ and the outlet temperature is 350~360℃. The temperature and flow rate of both the molten salt and the heat transfer oil can be adjusted by the control system.

[0025] In this embodiment, the material channel outlet of the molten salt-thermal oil heat exchanger is connected to the heat medium inlet of the steam generator via a first oil pipe, and the material channel inlet of the molten salt-thermal oil heat exchanger is connected to the heat medium outlet of the steam generator via a second oil pipe. The thermal oil buffer tank 9 and the thermal oil circulation pump are both installed on the second oil pipe. The thermal oil heated by the molten salt serves as the heating medium for the steam generator, heating the water supplied to the steam generator from the water supply system to produce usable steam.

[0026] The water supply system includes a main water supply pipe connected to the inlet of the steam generator, and an electric heater 12, a subcritical water storage tank 11, and a feed pump 13 arranged sequentially along the water supply pipe. A makeup water pump 14 is also installed on the main water supply pipe upstream of the electric heater 12. The subcritical water storage tank 11 can store hot water at 100~180℃, serving as a preheating stage for molten salt thermal storage applications, maximizing the utilization of off-peak electricity for thermal storage. The hot water electric heater 12 heats the demineralized water at 20℃ to 100~180℃ and stores it in the subcritical water storage tank 11. The feed pump 13 provides pressure for the water intake of the steam generator 8, and the makeup water pump 14 provides power for the heated demineralized water to enter the subcritical water storage tank 11.

[0027] In this embodiment of the binary molten salt thermal energy storage system, during off-peak electricity pricing, the molten salt heater 5 and the electric heater 12 are activated to heat the molten salt in the low-temperature molten salt tank 2 to 550~570℃, and then pump it to the high-temperature molten salt tank 1. The high-temperature molten salt is then stored in the high-temperature molten salt tank 1, and this process is pressurized by the low-temperature molten salt pump 7. The demineralized water is then heated to 100~180℃ by the electric heater and stored in the subcritical water storage tank 11, and this process is pressurized by the water replenishment pump 14.

[0028] During peak electricity prices, the energy release process is activated. The high-temperature molten salt in high-temperature molten salt tank 1 is pressurized by a high-temperature molten salt pump and enters the molten salt-material heat exchanger for heat exchange, providing heat to the reactants and heating them. The temperature of the molten salt drops to 400~500℃. After exchanging heat with the reactants, the molten salt then enters the molten salt-thermal oil heat exchanger for heat exchange, heating the thermal oil and lowering its temperature to 290℃ before returning to the low-temperature molten salt tank.

[0029] The thermal oil heat exchange system formed by the molten salt-thermal oil heat exchanger, thermal oil buffer tank, and thermal oil circulation pump mainly serves as a transition. Since the melting point of the binary salt is 220℃, temperatures below this are not conducive to the normal operation of the system. Therefore, the thermal oil, as an intermediate heat exchange system, can make full use of the low-temperature heat stored in the molten salt. Because the melting point of the thermal oil is relatively low, the heat exchange between water and thermal oil at even lower temperatures has little impact on the system. By adding the thermal oil buffer tank 9 and the thermal oil circulation pump 10 as intermediate media for the heat exchange between salt and water, the system is safe and effective, and the operating temperature range of the thermal oil is 250~360℃.

[0030] The heat from the heat transfer oil is transferred to the steam via the steam generator 8, producing steam with a wide temperature range, which can enrich the application of energy storage. The steam generator is pressurized and supplied with water by the feed water pump 13.

[0031] In order to stabilize the pressure and prevent oxidation of the high-temperature molten salt tank and the low-temperature molten salt tank, this embodiment provides a nitrogen sealing system 15 on the top of the tank body of the high-temperature molten salt tank and the low-temperature molten salt tank. The structure of the nitrogen sealing system can be based on existing technology and will not be described in detail.

[0032] The binary molten salt thermal energy storage system in this embodiment is a composite energy storage system. It can meet the needs of molten salt in the high-temperature range and ensure the thermal energy application of molten salt in the low-temperature range through the design of the intermediate heat exchange system. Its application range is wide; the system can be used not only for heating applications at 570℃ but also for applications at 150℃, which is wider than the thermal storage temperature range (290-570℃) of the binary salt itself, thus enriching the application scenarios of molten salt energy storage. It also facilitates the reduction of energy costs, as molten salt energy storage makes full use of off-peak electricity for heat storage, resulting in low energy costs. By setting up an intermediate heat exchange system, the molten salt does not directly exchange heat with low-temperature water, making the system safer and more efficient.

[0033] Of course, the above description is not limited to the examples above. Technical features of this utility model not described can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solution of this utility model and are not intended to limit this utility model. This utility model has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this utility model do not depart from the spirit of this utility model and should also fall within the protection scope of the claims of this utility model.

Claims

1. A binary molten salt thermal energy storage system, characterized in that: It includes a steam generator (8), a water supply system connected to the inlet of the steam generator, and a low-temperature molten salt tank (2), a molten salt heater (5), a high-temperature molten salt tank (1), a molten salt-material heat exchanger (3), and a molten salt-heat transfer oil heat exchanger (4) arranged in sequence. The inlet of the molten salt heater is connected to the low-temperature molten salt tank through a first feed pipe, and the outlet of the molten salt heater is connected to the high-temperature molten salt tank through a second feed pipe. A low-temperature molten salt pump (7) is installed on the first feed pipe. The heat medium inlet of the molten salt-material heat exchanger is connected to the high-temperature molten salt tank through the discharge pipe. A high-temperature molten salt pump (6) is installed on the discharge pipe. The heat medium outlet of the molten salt-material heat exchanger is connected to the heat medium inlet of the molten salt-heat transfer oil heat exchanger through the pipeline. The heat medium outlet of the molten salt-thermal oil heat exchanger is connected to the low-temperature molten salt tank. The material channel of the molten salt-thermal oil heat exchanger and the heat medium channel of the steam generator form a circulation channel. A thermal oil circulation pump (10) is installed on the circulation channel.

2. The binary molten salt thermal energy storage system according to claim 1, characterized in that: The water supply system includes a water supply main pipe connected to the water inlet of the steam generator, and an electric heater (12), a subcritical water storage tank (11), and a water pump (13) arranged sequentially on the water supply main pipe along the water supply direction.

3. The binary molten salt thermal energy storage system according to claim 2, characterized in that: The main water supply pipe is also equipped with a water replenishment pump (14) located upstream of the electric heater (12).

4. The binary molten salt thermal energy storage system according to claim 1, characterized in that: A heat transfer oil buffer tank (9) is also installed on the circulation channel, and the heat transfer oil buffer tank is located between the heat transfer oil circulation pump and the heat medium outlet of the steam generator.

5. The binary molten salt thermal energy storage system according to claim 4, characterized in that: An electric heating device is installed inside the heat transfer oil buffer tank (9).

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