Salt-water coupled cascade thermal storage system

Abstract

The utility model relates to a kind of molten salt-water coupling cascade heat storage system, it is related to heat storage technical field, it includes steam heat accumulator, molten salt single tank, molten salt electric heater, superheater, buffer tank.Couple water heat storage technology with molten salt single tank heat storage technology, saturated steam is superheated using molten salt, the problem that water heat storage technology can only supply saturated steam outside can be solved, the demand of all-weather overheat steam supply is realized.The utility model stores the energy required in water phase-change vaporization process using water heat storage technology, can greatly reduce steam supply cost, solve the problems of large amount of heat storage material, high cost, large floor area and complex control system of traditional molten salt double-tank heat storage system, while using molten salt single tank low arrangement, molten salt electric heater, superheater high arrangement design, facilitate quick salt in the process of start and stop, simplify system, suitable for the characteristics of industrial and commercial field steam supply system frequent start and stop.

Description

Technical Field

[0001] This utility model relates to the field of water thermal energy storage technology, specifically to a cascade thermal energy storage system coupled with molten salt and water. Background Technology

[0002] Industrial steam is a crucial raw material for industrial production, with significant market demand. Currently, thermal energy storage and steam supply technologies mainly include solid thermal energy storage, phase change thermal energy storage, molten salt thermal energy storage, and water thermal energy storage. Molten salt thermal energy storage is limited by the solidification issue of molten salt, resulting in complex systems and relatively high investment costs. Water thermal energy storage, on the other hand, uses water as the storage medium and can supply saturated steam externally through pressure reduction and flash evaporation, offering a simple system, high thermal efficiency, and low cost. However, given the diverse needs of users, supplying only saturated steam cannot meet the demand for superheated steam, which is a significant factor limiting the commercial application of water thermal energy storage technology. Therefore, there is an urgent need to design a molten salt-water coupled cascade thermal energy storage system that couples water and molten salt thermal energy storage technologies. This system utilizes the saturated steam generated by the water thermal energy storage system, which is then superheated by the molten salt thermal energy storage system to meet the demand for low-cost superheated steam, thus promoting the large-scale application of thermal energy storage technologies. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a molten salt-water coupled cascade thermal storage system, which utilizes the technical advantages of molten salt thermal storage technology and water thermal storage technology to make up for the deficiency of water thermal storage technology that can only supply saturated steam externally, and realize the demand for low-cost, all-weather external supply of superheated steam.

[0004] To achieve the above objectives, the present invention provides a cascaded thermal storage system coupled with molten salt and water, comprising a steam accumulator, a molten salt tank, a molten salt electric heater, a superheater, and a buffer tank; the inlet of the steam accumulator is connected to an external steam pipeline, and the outlet is connected to the inlet of the buffer tank; the outlet of the buffer tank is connected to the steam inlet of the superheater; the inlet of the molten salt tank is connected to the molten salt outlet of the superheater, and the outlet is connected to the inlet of the molten salt electric heater; the system can operate in thermal storage mode, thermal release mode, and simultaneous storage and release mode.

[0005] Preferably, the specific operating process of this utility model is as follows: a) Under the heat storage condition, the superheater is not working, and external steam enters the steam accumulator to heat the internal low-pressure saturated water. The steam cools down and condenses into water, which is stored in the steam accumulator. The molten salt in the molten salt tank flows to the molten salt electric heater. After the temperature rises, it flows through the superheater and then into the molten salt tank, realizing the molten salt heat storage and heating cycle.

[0006] b. Under heat release conditions, the molten salt electric heater is not working, and the steam accumulator releases heat to generate saturated steam. The saturated steam flows through the buffer tank and enters the superheater, where it is heated by the hot molten salt into superheated steam for external supply. The molten salt in the molten salt tank flows through the molten salt electric heater and then into the superheater. After releasing heat and cooling down, it flows back into the molten salt tank, thus realizing a molten salt heat release and cooling cycle. c. Under the simultaneous storage and release condition, external steam enters the steam accumulator to heat the internal low-pressure saturated water, while the steam accumulator releases heat to generate saturated steam. The saturated steam flows through the buffer tank and enters the superheater, where it is heated by molten salt into superheated steam for external supply. Molten salt in the molten salt tank flows into the molten salt electric heater, and after its temperature rises, it flows into the superheater, releases heat, cools down, and then flows back into the molten salt tank. In one cycle, the molten salt is first heated and then cooled down.

[0007] Preferably, the external steam originates from unit extraction steam, electrode boiler, or back pressure turbine exhaust steam.

[0008] Preferably, the outlet of the steam accumulator is equipped with a pressure reducing valve and a flow regulating valve to control the pressure and flow rate of the saturated steam at the outlet of the accumulator.

[0009] Preferably, the steam accumulator is provided with a water inlet at the bottom for adjusting the water level in the accumulator; and a steam-water separator is provided at the top of the steam accumulator to ensure the dryness of the saturated steam.

[0010] Preferably, the positions of the molten salt electric heater and the superheater can be interchanged according to the actual situation.

[0011] Preferably, the superheater is a hairpin heat exchanger, with steam flowing through the shell side and molten salt flowing through the tube side.

[0012] Preferably, the molten salt tank is a horizontal storage tank located at a low position, while the molten salt electric heater and the superheater are located at a high position, adopting a high-low position arrangement.

[0013] Preferably, the heat storage medium in the molten salt tank is a single molten salt or a multi-component mixed molten salt.

[0014] Preferably, the power source for the molten salt electric heater is off-peak electricity from the power grid or renewable energy.

[0015] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) This utility model couples water thermal storage technology with molten salt single-tank thermal storage technology, and uses molten salt to superheat saturated steam, which can solve the problem that water thermal storage technology can only supply saturated steam externally, and realize the demand for all-weather external supply of superheated steam.

[0016] (2) This utility model utilizes water thermal storage technology to store the energy required during the phase change vaporization of water, which can significantly reduce the cost of steam supply and solve the problems of large amount of thermal storage materials, high cost, large footprint and complex control system of traditional molten salt double tank thermal storage system.

[0017] (3) The present invention adopts a design with a low-position arrangement of a single molten salt tank and a high-position arrangement of a molten salt electric heater and a superheater, which facilitates rapid salt removal during start-up and shutdown, simplifies the system, and is suitable for the frequent start-up and shutdown characteristics of steam supply systems in the industrial and commercial fields. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a cascaded thermal storage system coupled with molten salt and water.

[0019] Reference numerals: 1. Steam accumulator; 2. Molten salt tank; 3. Molten salt electric heater; 4. Superheater; 5. Buffer tank. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] This utility model relates to a molten salt-water coupled cascade thermal storage system, such as... Figure 1 As shown, the system includes a steam accumulator 1, a molten salt tank 2, a molten salt electric heater 3, a superheater 4, and a buffer tank 5. The inlet of the steam accumulator 1 is connected to an external steam pipeline, and its outlet is connected to the inlet of the buffer tank 5. The outlet of the buffer tank 5 is connected to the steam inlet of the superheater 4. The inlet of the molten salt tank 2 is connected to the molten salt outlet of the superheater 4, and its outlet is connected to the inlet of the molten salt electric heater 3. A pressure reducing valve and a flow regulating valve are installed at the outlet of the steam accumulator 1 to control the pressure and flow rate of the saturated steam at the accumulator outlet. A water inlet is located at the bottom of the steam accumulator 1 to regulate the water level in the steam accumulator 1. A steam-water separator is located at the top of the steam accumulator 1 to ensure the dryness of the saturated steam. The superheater 4 is a haircarf type heat exchanger, with steam flowing through the shell side and molten salt flowing through the tube side. The molten salt tank 2 is a horizontal storage tank and can be arranged at a lower position, while the molten salt electric heater 3 and the superheater 4 are arranged at a higher position, employing a high-low arrangement.

[0022] As an optional embodiment, the external steam can be sourced from unit extraction steam, electrode boiler, or back pressure turbine exhaust steam; the positions of molten salt electric heater 3 and superheater 4 can be interchanged according to actual conditions; the heat storage medium in the molten salt tank 2 is a single molten salt or a multi-element mixed molten salt; the power source for the molten salt electric heater 3 is off-peak electricity from the power grid or new energy electricity.

[0023] In this embodiment, the molten salt used is Hitec ternary salt (53% KNO3 + 40% NaNO2 + 7% NaNO3), with an operating temperature range of 230-360℃. The external steam source is 3.8 MPa, 400℃ extracted steam from the unit, and the power supply is off-peak electricity from the power grid, capable of supplying 0.8 MPa, 220℃ industrial steam. The system based on water-based thermal storage and external superheated steam supply can flexibly switch between thermal storage, thermal release, and simultaneous storage and release modes according to different grid load conditions, achieving efficient energy management and supply. The following is the specific operation flow of the system: Thermal storage mode: Superheater 4 is inactive. Steam extracted from the 3.8 MPa, 400℃ unit flows into steam accumulator 1 to heat the internal low-pressure saturated water. The steam cools down and condenses into water, which is stored in steam accumulator 1. Molten salt electric heater 3 is started. Molten salt in molten salt tank 2 is pumped out by the molten salt pump and flows to molten salt electric heater 3. After the temperature rises, it flows through superheater 4 and then into molten salt tank 2. The molten salt is continuously circulated and heated until it reaches 360℃, at which point the thermal storage mode ends. Heat release operation: Molten salt electric heater 3 is inactive. Steam accumulator 1 releases heat to generate 0.8 MPa saturated steam. After flowing through buffer tank 5, the saturated steam is heated to 0.8 MPa and 220°C by hot molten salt in superheater 4 and directly supplied externally. Molten salt in molten salt tank 2 is pumped out by molten salt pump, flows through molten salt electric heater 3, and then flows to superheater 4. After the temperature decreases, it flows back into molten salt tank 2. The molten salt is continuously circulated and cooled. After the temperature drops to 230°C, the heat release operation ends. This invention provides a molten salt-water coupled cascade thermal storage system, which is simple to operate and highly safe. It couples water thermal storage technology with molten salt single-tank thermal storage technology, using molten salt to superheat saturated steam. This solves the problem that water thermal storage technology can only supply saturated steam externally, enabling all-weather external supply of superheated steam. This invention utilizes water thermal storage technology to store the energy required for water phase change vaporization, significantly reducing steam supply costs and solving the problems of large material consumption, high cost, large footprint, and complex control systems in traditional molten salt dual-tank thermal storage systems. This invention adopts a low-position arrangement of the molten salt single tank and a high-position arrangement of the molten salt electric heater and superheater, facilitating rapid salt removal during start-up and shutdown, simplifying the system, and making it suitable for the frequent start-up and shutdown characteristics of steam supply systems in industrial and commercial fields.

[0024] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A cascaded thermal storage system coupled with molten salt and water, characterized in that, The system includes a steam accumulator (1), a molten salt tank (2), a molten salt electric heater (3), a superheater (4), and a buffer tank (5). The inlet of the steam accumulator (1) is connected to an external steam pipeline, and the outlet is connected to the inlet of the buffer tank (5). The outlet of the buffer tank (5) is connected to the steam inlet of the superheater (4). The inlet of the molten salt tank (2) is connected to the molten salt outlet of the superheater (4), and the outlet is connected to the inlet of the molten salt electric heater (3). The system can operate in heat storage mode, heat release mode, and simultaneous heat storage and release mode.

2. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that, a. Under the aforementioned thermal storage conditions, the superheater (4) does not operate; b. Under the heat release condition, the molten salt electric heater (3) does not work; c. Under the simultaneous storage and release condition, the steam accumulator (1), superheater (4), and molten salt electric heater (3) are all working, and the molten salt first heats up and then cools down in one cycle.

3. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that... The external steam originates from the unit's extraction steam, electrode boiler, or back pressure turbine exhaust steam.

4. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that... The outlet of the steam accumulator (1) is equipped with a pressure reducing valve and a flow regulating valve to control the pressure and flow rate of the saturated steam at the outlet of the accumulator.

5. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that... The steam accumulator (1) is provided with a water inlet at the bottom to adjust the water level in the accumulator; the steam accumulator (1) is provided with a steam-water separator at the top to ensure the dryness of the saturated steam.

6. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that... The positions of the molten salt electric heater (3) and the superheater (4) can be interchanged according to the actual situation.

7. The molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that... The superheater (4) is a hairpin heat exchanger, with steam flowing through the shell side and molten salt flowing through the tube side.

8. A molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that, The molten salt tank (2) is a horizontal storage tank, located at a low position, while the molten salt electric heater (3) and superheater (4) are located at a high position, adopting a high-low position arrangement.

9. A molten salt-water coupled cascade thermal storage system according to claim 1, characterized in that, The heat storage medium in the molten salt tank (2) is a single molten salt or a multi-component mixed molten salt.

10. A molten salt-water coupled cascade thermal storage system according to any one of claims 1, 6, or 8, characterized in that, The molten salt electric heater (3) is powered by off-peak electricity from the power grid or by new energy sources.

Images