Molten salt energy storage system incorporating chemical heat storage, and working method thereof

Abstract

The present invention belongs to the technical field of energy storage. Disclosed are a molten salt energy storage system incorporating chemical heat storage, and a working method thereof. Chemical energy storage and molten salt energy storage are combined; chemical heat storage has the advantages of high heat storage density, low cost, capability of seasonal and long-time heat storage, etc., thus being suitable for storage of medium- and high-temperature heat energy; a chemical heat storage carrier is used for storing new energy waste electricity or peak shaving and frequency regulation electricity of power plants; generated steam heats a molten salt, such that the high-temperature molten salt can provide heat for high-temperature heat users, and condensed saturated water generated after the steam releases heat can further provide heat for low-temperature heat users, thereby achieving gradient utilization of heat. In the whole heat storage process, sensible heat of a heater, heat storage of the chemical heat storage carrier and molten salt heat storage are fully utilized, so that the system can continuously generate heat at higher temperature, thereby satisfying the requirements of heat users at different grades. In addition, due to a modular unit structure, the present invention can be widely applied to new construction of power plants and retrofitting of existing power plants, thus having good application prospects.

Description

A molten salt energy storage system combined with chemical heat storage and its working method Technical Field

[0001] The present invention belongs to the field of energy storage technology, and in particular relates to a molten salt energy storage system combined with chemical heat storage and a working method thereof. Background Art

[0002] Molten salt has the advantages of low viscosity, low vapor pressure, high stability, and high heat storage density. It is an ideal heat storage medium. Molten salt heat storage is characterized by large scale, long time, safety and stability, and is not restricted by site selection. It can be applied to solar thermal power generation, peak and frequency regulation of thermal power units and other fields.

[0003] However, existing molten salt energy storage systems all have the problem of high costs to varying degrees. There is a pinch point temperature in the molten salt-steam heat exchange process, and the steam saturation section consumes a large amount of high-grade heat.

[0004] Summary of the Invention

[0005] In order to solve the above-mentioned existing problems, the purpose of the present invention is to provide a molten salt energy storage system combined with chemical heat storage and its working method, which combines the advantages of large heat storage capacity of chemical heat storage and low cost of molten salt heat storage, fully utilizes the abandoned electricity of power plants, stores it in the form of heat, and meets the needs of heat users at all levels.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention discloses a molten salt energy storage system combined with chemical heat storage, comprising a molten salt storage tank, a first heat exchanger, a second heat exchanger, a low-temperature heat exchanger and a plurality of outer sleeves; the plurality of outer sleeves are arranged in the molten salt storage tank, a heater is provided in the outer sleeve, the heater is connected to a power supply terminal, and the power supply terminal is connected to a power supply of a power plant; a chemical heat storage carrier is sealed and filled between the heater and the outer sleeve; a high-temperature mixed gas outlet, a water inlet and a gas inlet are respectively provided on the outer sleeve; a low-temperature molten salt outlet, a high-temperature molten salt inlet, a high-temperature molten salt outlet and a low-temperature molten salt inlet are respectively provided on the molten salt storage tank; the low-temperature molten salt outlet and the high-temperature molten salt inlet are connected to the low-temperature side of the first heat exchanger; the high-temperature mixed gas outlet and the gas inlet are connected to the high-temperature side of the first heat exchanger; a water outlet is provided on the high-temperature side of the first heat exchanger, and the water outlet and the water inlet are connected to the high-temperature side of the low-temperature heat exchanger; the high-temperature molten salt outlet and the low-temperature molten salt inlet are respectively connected to the high-temperature side of the second heat exchanger; the low-temperature side of the second heat exchanger is connected to a high-temperature heat user; and the low-temperature side of the low-temperature heat exchanger is connected to a low-temperature heat user.

[0008] Preferably, the low-temperature molten salt outlet and the high-temperature molten salt inlet are arranged on one side of the molten salt storage tank, and the high-temperature molten salt outlet and the low-temperature molten salt inlet are arranged on the other side of the molten salt storage tank; the low-temperature molten salt outlet and the low-temperature molten salt inlet are located at the bottom of the molten salt storage tank, and the high-temperature molten salt outlet and the high-temperature molten salt inlet are located at the upper part of the molten salt storage tank; the high-temperature mixed gas outlet is arranged at the top of the outer casing, and the water inlet and the gas inlet are both located at the bottom of the outer casing.

[0009] Preferably, the chemical heat storage carrier is a chemical heat storage material mainly based on magnesium, calcium or iron.

[0010] Preferably, the heater is a graphite electrode heater, a resistive electric heater or a sleeve electric heater.

[0011] Preferably, a thermal insulation layer is provided on the outside of the molten salt storage tank.

[0012] Preferably, the outer wall of the outer sleeve is provided with ribs.

[0013] Preferably, a fan is provided on the pipeline between the high-temperature mixed gas outlet and the low-temperature side of the first heat exchanger; a first molten salt pump is provided on the pipeline between the low-temperature side of the first heat exchanger and the high-temperature molten salt inlet; and a second molten salt pump is provided on the pipeline between the high-temperature molten salt outlet and the high-temperature side of the second heat exchanger.

[0014] Preferably, a buffer molten salt tank is provided on the pipeline between the low-temperature side of the first heat exchanger and the high-temperature molten salt inlet.

[0015] Preferably, a buffer water tank is provided on the pipeline between the water outlet and the high-temperature side of the low-temperature heat exchanger.

[0016] The working method of the molten salt energy storage system combined with chemical heat storage disclosed in the present invention includes:

[0017] When the power plant generates abandoned electricity, the heater is connected through the power supply terminal, and the heater heats the chemical heat storage carrier. The chemical heat storage carrier is decomposed by heat, and the generated high-temperature mixed gas enters the high-temperature side of the first heat exchanger through the high-temperature mixed gas outlet to release heat and generate gas and condensed saturated water. The gas returns to the outer casing through the gas inlet, and the condensed saturated water enters the high-temperature side of the low-temperature heat exchanger through the water outlet to release heat to the low-temperature heat user, and then returns to the outer casing through the water inlet, reacts chemically with the decomposition product and turns into the chemical heat storage carrier again; the heat generated in the process is transferred to the molten salt in the molten salt storage tank through the wall of the outer casing, achieving preliminary preheating and salt melting;

[0018] The low-temperature molten salt in the molten salt storage tank enters the low-temperature side of the first heat exchanger from the low-temperature molten salt outlet to absorb heat and then turns into high-temperature molten salt and returns to the molten salt storage tank from the high-temperature molten salt inlet;

[0019] The high-temperature molten salt enters the high-temperature side of the second heat exchanger from the high-temperature molten salt outlet, releases heat to the high-temperature heat user, and turns into low-temperature molten salt and returns to the molten salt storage tank.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The present invention discloses a molten salt energy storage system combined with chemical heat storage, which combines chemical energy storage with molten salt energy storage. Chemical heat storage has the advantages of high heat storage density, low cost, and long-term heat storage across seasons, and is suitable for the storage of medium and high temperature thermal energy. Chemical heat storage carriers are used to store abandoned electricity from new energy sources or peak-shaving and frequency-modulating electricity from power plants. The generated water vapor heats the molten salt, and the high-temperature molten salt can provide heat for high-temperature heat users; the condensed saturated water generated after the water vapor releases heat can also provide heat for low-temperature users, realizing the cascade utilization of heat. The entire heat storage process fully utilizes the sensible heat of the heater, the heat storage of the chemical heat storage carrier, and the heat storage of the molten salt. The system can continuously generate heat at a relatively high temperature (about 400°C) to meet the needs of heat users at all levels. Combining chemical heat storage can give full play to its low-cost advantage, and the chemical heat storage reaction temperature is stable, which is conducive to matching the steam heat exchange curve. At the same time, the modular unit structure can be widely applied to new power plants and the transformation of existing power plants.

[0022] Furthermore, the low-temperature molten salt outlet and the high-temperature molten salt inlet are located on one side of the molten salt storage tank, while the high-temperature molten salt outlet and the low-temperature molten salt inlet are located on the other side of the molten salt storage tank; the low-temperature molten salt outlet and the low-temperature molten salt inlet are located at the bottom of the molten salt storage tank, while the high-temperature molten salt outlet and the high-temperature molten salt inlet are located at the top of the molten salt storage tank. Due to buoyancy, the molten high-temperature molten salt moves upwards to the molten salt storage tank, which is conducive to the circulation of the molten salt. The high-temperature mixed gas outlet is located at the top of the outer casing, which is conducive to the discharge of the high-temperature mixed gas; the water inlet and the gas inlet are both located at the bottom of the outer casing, so that the water and dry air return to the outer casing and mix with the decomposed chemical heat storage carrier inside, making the internal chemical reaction more complete.

[0023] Furthermore, the chemical heat storage carrier adopts a magnesium-based, calcium-based or iron-based chemical heat storage material, which has high heat storage density, safety, environmental protection and low cost.

[0024] Furthermore, an insulation layer is provided on the outside of the molten salt storage tank to reduce heat loss.

[0025] Furthermore, the outer wall of the outer sleeve is provided with fins, which can enhance heat exchange and improve the operating efficiency of the system.

[0026] Furthermore, a buffer molten salt tank is provided on the pipeline between the low temperature side of the first heat exchanger and the high temperature molten salt inlet, which can buffer the high temperature molten salt and return it to the molten salt storage tank, thereby improving the safety and stability of the system operation.

[0027] Furthermore, a buffer water tank is provided on the pipeline between the water outlet and the high-temperature side of the low-temperature heat exchanger, which can release the pressure fluctuation caused by the mixing of liquid and gas and improve the stability of the system.

[0028] The working method of the molten salt energy storage system combined with chemical heat storage disclosed in the present invention has high heat utilization, low operating cost, simple layout, and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic diagram of the overall structure of the system of the present invention.

[0030] In the figure: 1 is a molten salt storage tank, 2 is an insulation layer, 3 is a power supply terminal, 4 is a heater, 5 is an outer casing, 6 is a chemical heat storage carrier, 7 is a fan, 8 is a first heat exchanger, 9 is a buffer water tank, 10 is a buffer molten salt tank, 11 is a second heat exchanger, and 12 is a low-temperature heat exchanger. DETAILED DESCRIPTION

[0031] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it:

[0032] As shown in Figure 1, a molten salt energy storage system combined with chemical heat storage of the present invention includes a molten salt storage tank 1, a first heat exchanger 8, a second heat exchanger 11, a low-temperature heat exchanger 12 and a plurality of outer sleeves 5; the plurality of outer sleeves 5 are arranged in the molten salt storage tank 1, a heater 4 is provided in the outer sleeve 5, the heater 4 is connected to a power supply terminal 3, and the power supply terminal 3 is connected to the power supply of the power plant; a chemical heat storage carrier 6 is sealed and filled between the heater 4 and the outer sleeve 5; a high-temperature mixed gas outlet, a water inlet and a gas inlet are respectively opened on the outer sleeve 5; a low-temperature molten salt outlet, a high-temperature molten salt inlet, A high-temperature molten salt outlet and a low-temperature molten salt inlet; the low-temperature molten salt outlet and the high-temperature molten salt inlet are connected to the low-temperature side of the first heat exchanger 8; the high-temperature mixed gas outlet and the gas inlet are connected to the high-temperature side of the first heat exchanger 8; a water outlet is provided on the high-temperature side of the first heat exchanger 8, and the water outlet and the water inlet are connected to the high-temperature side of the low-temperature heat exchanger 12; the high-temperature molten salt outlet and the low-temperature molten salt inlet are respectively connected to the high-temperature side of the second heat exchanger 11; the low-temperature side of the second heat exchanger 11 is connected to a high-temperature heat user; the low-temperature side of the low-temperature heat exchanger 12 is connected to a low-temperature heat user.

[0033] In a preferred embodiment of the present invention, the low-temperature molten salt outlet and the high-temperature molten salt inlet are arranged on one side of the molten salt storage tank 1, and the high-temperature molten salt outlet and the low-temperature molten salt inlet are arranged on the other side of the molten salt storage tank 1; the low-temperature molten salt outlet and the low-temperature molten salt inlet are located at the bottom of the molten salt storage tank 1, and the high-temperature molten salt outlet and the high-temperature molten salt inlet are located at the upper part of the molten salt storage tank 1; the high-temperature mixed gas outlet is arranged at the top of the outer casing 5, and the water inlet and the gas inlet are both located at the bottom of the outer casing 5.

[0034] In a preferred embodiment of the present invention, the chemical heat storage carrier 6 is a chemical heat storage material mainly composed of magnesium, calcium or iron.

[0035] In a preferred embodiment of the present invention, the heater 4 is a graphite electrode heater, a resistance electric heater or a sleeve electric heater.

[0036] In a preferred embodiment of the present invention, a thermal insulation layer is provided on the outside of the molten salt storage tank 1 .

[0037] In a preferred embodiment of the present invention, the outer wall of the outer sleeve 5 is provided with ribs.

[0038] In a preferred embodiment of the present invention, a fan 7 is provided on the pipeline between the high-temperature mixed gas outlet and the low-temperature side of the first heat exchanger 8; a first molten salt pump 13 is provided on the pipeline between the low-temperature side of the first heat exchanger 8 and the high-temperature molten salt inlet; and a second molten salt pump 14 is provided on the pipeline between the high-temperature molten salt outlet and the high-temperature side of the second heat exchanger 11.

[0039] In a preferred embodiment of the present invention, a buffer molten salt tank 10 is provided on the pipeline between the low-temperature side of the first heat exchanger 8 and the high-temperature molten salt inlet.

[0040] In a preferred embodiment of the present invention, a buffer water tank 9 is provided on the pipeline between the water outlet and the high-temperature side of the low-temperature heat exchanger 12 .

[0041] The working method of the molten salt energy storage system combined with chemical heat storage includes:

[0042] When the power plant generates abandoned electricity, the heater 4 is connected through the power terminal 3, and the heater 4 heats the chemical heat storage carrier 6. The chemical heat storage carrier 6 is decomposed by heat. When the chemical heat storage carrier 6 uses calcium hydroxide, the decomposition products are calcium oxide, water vapor, and hot air. The generated high-temperature mixed gas mainly includes water vapor and hot air, and the temperature can reach 600°C. The high-temperature mixed gas enters the high-temperature side of the first heat exchanger 8 through the fan 7 from the high-temperature mixed gas outlet to release heat and generate gas and condensed saturated water. The gas returns to the outer casing 5 through the gas inlet, and the condensed saturated water enters the buffer water tank 9 through the water outlet to release pressure, and then enters the high-temperature side of the low-temperature heat exchanger 12 to release heat to the low-temperature heat user, and then returns to the outer casing 5 through the water inlet, and reacts with calcium oxide to generate calcium hydroxide and release heat; the heat generated in the process is transferred to the molten salt in the molten salt storage tank 1 through the outer casing 5 to achieve preliminary salting;

[0043] The low-temperature molten salt in the molten salt storage tank 1 enters the low-temperature side of the first heat exchanger 8 from the low-temperature molten salt outlet to absorb heat and then turns into high-temperature molten salt. It enters the buffer molten salt tank 10 through the first molten salt pump 13 for buffering and then returns to the molten salt storage tank 1 from the high-temperature molten salt inlet.

[0044] The high-temperature molten salt enters the high-temperature side of the second heat exchanger 11 through the high-temperature molten salt outlet through the second molten salt pump 14 to release heat to the high-temperature heat user to become low-temperature molten salt and then returns to the molten salt storage tank 1.

[0045] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention, or equivalent structures or equivalent process transformations made using the contents of the present invention's description and drawings, or direct or indirect applications in other related technical fields, should all be covered by the scope of protection of the present invention.

Claims

1. A molten salt energy storage system combined with chemical heat storage, characterized in that: The invention comprises a molten salt storage tank (1), a first heat exchanger (8), a second heat exchanger (11), a low-temperature heat exchanger (12) and a plurality of outer sleeves (5); the plurality of outer sleeves (5) are arranged in the molten salt storage tank (1); a heater (4) is arranged in the outer sleeve (5); the heater (4) is connected to a power supply terminal (3); the power supply terminal (3) is connected to a power supply of a power plant; a chemical heat storage carrier (6) is sealed and filled between the heater (4) and the outer sleeve (5); a high-temperature mixed gas outlet, a water inlet and a gas inlet are respectively provided on the outer sleeve (5); a low-temperature molten salt outlet, a high-temperature molten salt inlet and a high-temperature molten salt inlet are respectively provided on the molten salt storage tank (1); A molten salt outlet and a low-temperature molten salt inlet; the low-temperature molten salt outlet and the high-temperature molten salt inlet are connected to the low-temperature side of the first heat exchanger (8); the high-temperature mixed gas outlet and the gas inlet are connected to the high-temperature side of the first heat exchanger (8); a water outlet is provided on the high-temperature side of the first heat exchanger (8), and the water outlet and the water inlet are connected to the high-temperature side of the low-temperature heat exchanger (12); the high-temperature molten salt outlet and the low-temperature molten salt inlet are respectively connected to the high-temperature side of the second heat exchanger (11); the low-temperature side of the second heat exchanger (11) is connected to a high-temperature heat user; and the low-temperature side of the low-temperature heat exchanger (12) is connected to a low-temperature heat user.

2. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: The low-temperature molten salt outlet and the high-temperature molten salt inlet are arranged on one side of the molten salt storage tank (1), and the high-temperature molten salt outlet and the low-temperature molten salt inlet are arranged on the other side of the molten salt storage tank (1); the low-temperature molten salt outlet and the low-temperature molten salt inlet are located at the bottom of the molten salt storage tank (1), and the high-temperature molten salt outlet and the high-temperature molten salt inlet are located at the upper part of the molten salt storage tank (1); the high-temperature mixed gas outlet is arranged at the top of the outer casing (5), and the water inlet and the gas inlet are both located at the bottom of the outer casing (5).

3. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: The chemical heat storage carrier (6) is a chemical heat storage material mainly composed of magnesium, calcium or iron.

4. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: The heater (4) is a graphite electrode type heater, a resistance type electric heater or a sleeve type electric heater.

5. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: A thermal insulation layer is provided on the outside of the molten salt storage tank (1).

6. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: The outer wall of the outer sleeve (5) is provided with ribs.

7. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: A fan (7) is provided on the pipeline between the high-temperature mixed gas outlet and the low-temperature side of the first heat exchanger (8); a first molten salt pump (13) is provided on the pipeline between the low-temperature side of the first heat exchanger (8) and the high-temperature molten salt inlet; and a second molten salt pump (14) is provided on the pipeline between the high-temperature molten salt outlet and the high-temperature side of the second heat exchanger (11).

8. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: A buffer molten salt tank (10) is provided on the pipeline between the low-temperature side of the first heat exchanger (8) and the high-temperature molten salt inlet.

9. The molten salt energy storage system combined with chemical heat storage according to claim 1, characterized in that: A buffer water tank (9) is provided on the pipeline between the water outlet and the high-temperature side of the low-temperature heat exchanger (12).

10. The operating method of the molten salt energy storage system combined with chemical heat storage according to claims 1 to 9, characterized in that: include: When the power plant generates abandoned electricity, the heater (4) is connected through the power supply terminal (3), and the heater (4) heats the chemical heat storage carrier (6). The chemical heat storage carrier (6) is decomposed by heat, and the generated high-temperature mixed gas enters the first heat exchanger (8) through the high-temperature mixed gas outlet, releases heat on the high-temperature side, and generates gas and condensed saturated water. The gas returns to the outer casing (5) through the gas inlet, and the condensed saturated water enters the low-temperature heat exchanger (12) through the water outlet, releases heat to the low-temperature heat user on the high-temperature side, and returns to the outer casing (5) through the water inlet, and reacts chemically with the decomposition product to become the chemical heat storage carrier (6) again. The heat generated in the process is transferred to the molten salt in the molten salt storage tank (1) through the wall of the outer casing (5), thereby achieving preliminary preheating and salting. The low-temperature molten salt in the molten salt storage tank (1) enters the first heat exchanger (8) from the low-temperature molten salt outlet, absorbs heat on the low-temperature side, and becomes high-temperature molten salt, which then returns to the molten salt storage tank (1) from the high-temperature molten salt inlet; The high-temperature molten salt enters the second heat exchanger (11) from the high-temperature molten salt outlet, releases heat to the high-temperature heat user on the high-temperature side, and turns into low-temperature molten salt and returns to the molten salt storage tank (1).

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