Molten salt heat storage heating system and heating method

Abstract

The application discloses a molten salt heat storage heating system and a heating method, wherein the molten salt heat storage heating system comprises a heat storage module, the heat storage module comprises a molten salt storage tank, and the molten salt storage tank is used for storing heat energy; the molten salt heat storage heating system further comprises a heat exchange module and a third circulating loop, the heat exchange module comprises a first heat exchange unit and a second heat exchange unit, the first heat exchange unit is connected with the outside of the molten salt storage tank through a first pipeline and forms a first circulating loop; the second heat exchange unit is connected with the inside of the molten salt storage tank through a second pipeline and forms a second circulating loop; the first heat exchange unit and the second heat exchange unit are connected with a heat user through the third circulating loop to heat the heat user. The system integrates heat production, heat storage and heat supply, can continuously and stably heat the heat user, can adopt a single or multiple molten salt storage tanks according to the demand of the heat user, can store heat in the molten salt storage tank according to the electricity use time period, and has low heat use cost.

Description

Technical Field

[0001] This invention belongs to the field of thermal energy engineering, and in particular relates to a molten salt thermal storage heating system and heating method. Background Technology

[0002] Currently disclosed molten salt thermal storage systems suffer from problems such as high system cost, poor economic efficiency, freezing and blockage of molten salt pipelines, low heat storage density, localized overheating, and large temperature differences between the upper and lower parts of the molten salt tank. For example, patents CN201410093965.X discloses a "molten salt thermal storage electric heating centralized heating system," and CN208832573U discloses a "molten salt heating device and molten salt heating system." Both disclose a dual-tank molten salt thermal storage heating system, but the molten salt storage tank capacity is at most half of its volume, and expensive molten salt pumps are used to draw molten salt to an external heat exchanger for heat transfer. These systems suffer from high cost, low thermal efficiency, and the risk of pipeline freezing. Issues such as risk mitigation hinder product promotion. Publication numbers CN106369824A disclose "a molten salt electric heating furnace," CN112082194A discloses "a single-tank molten salt energy storage and heating system and its energy storage and heating method," CN108954459A discloses "a molten salt thermal storage single-tank heating system," and CN108954459A discloses a "molten salt heating device and molten salt heating system." All of these utilize single-tank molten salt systems. The principle of thermocline (the natural stratification of molten salt with high density at low temperatures and low density at high temperatures) is used for heat storage and release. A molten salt pump draws high-temperature molten salt into a heat exchanger for heat exchange, improving the utilization rate of the molten salt storage tank. However, the risk of freezing and blockage still exists during the heat storage / release process. Furthermore, the molten salt storage tank suffers from problems such as easy mixing of upper and lower layers, unstable outlet temperature, and insufficient heat charging / releasing of the molten salt material during heat storage / releasing. These issues lead to low system heat storage / releasing capacity, low heat storage density, insufficient molten salt heat charging / releasing, and high cost. CN107687687A discloses a "Hot Air Heating System for Molten Salt Off-Peak Electricity Thermal Storage". This system uses a fan to exchange heat in a molten salt tank to generate hot air output. This system solves the freezing and blockage problem of single-tank inclined temperature layer systems. However, the hot air pipeline occupies too much molten salt in the tank, and the temperature difference between the upper and lower parts of the molten salt tank is too large during the heat release process, resulting in incomplete charging / releasing of molten salt. The high-temperature hot air from the molten salt is directly delivered to the heat users, resulting in large heat loss in the pipeline and problems such as low system thermal efficiency and low energy storage density. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects in the prior art and provide a molten salt thermal storage heating system and heating method.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] A molten salt thermal energy storage and heating system includes: a thermal storage module, which includes a molten salt storage tank for storing thermal energy; the system also includes a heat exchange module and a third circulation loop.

[0006] The heat exchange module includes a first heat exchange unit and a second heat exchange unit. The first heat exchange unit is connected to the outside of the molten salt storage tank through a first pipeline and forms a first circulation loop. The second heat exchange unit is connected to the inside of the molten salt storage tank through a second pipeline and forms a second circulation loop.

[0007] Both the first heat exchange unit and the second heat exchange unit are connected to the heat user through a third circulation loop to provide heating to the heat user.

[0008] In this technical solution, the system integrates heat generation, heat storage, and heat supply to provide sustainable and stable heating for users. It supplies heat to users through two different circulation loops (first and second), resulting in a large number of heat exchange points. Therefore, one or more molten salt storage tanks can be used depending on the user's needs. Furthermore, the molten salt storage tanks can store heat according to the electricity consumption period, resulting in low heating costs. In addition, because two different circulation loops are set on the inner and outer sides of the molten salt storage tank, the two loops are integrated into a single molten salt storage tank, improving the volume utilization rate of the molten salt storage tank and further increasing thermal efficiency.

[0009] Preferably, the molten salt storage tank includes an inner shell, a first pipeline that extends from one side of the inner shell to the other side around the outer wall of the inner shell, and a second pipeline that extends from one side of the inner shell to the other side inside the inner shell.

[0010] In this technical solution, the structure avoids direct contact between the molten salt and the heat exchange medium in the circulation loop. On the other hand, it enables two different circulation loops to exchange heat with the molten salt tank. Furthermore, the surrounding and extending pipeline structure increases the contact area between the pipeline and the molten salt tank or the molten salt material inside, which is beneficial to improving the heat exchange efficiency.

[0011] Preferably, the flow direction of the heat exchange medium in the first circulation loop on the molten salt tank is opposite to the flow direction of the heat exchange medium in the second circulation loop on the molten salt tank.

[0012] In this technical solution, the flow direction of the heat exchange medium in the first circulation loop on the molten salt storage tank is opposite to the flow direction of the heat exchange medium in the second circulation loop on the molten salt storage tank. This causes the molten salt inside the heat exchange system to form convection and heat exchange waves inside the molten salt storage tank, avoiding the phenomenon of overheating at the top and undercooling at the bottom of the molten salt material inside the molten salt storage tank. This makes the charging and releasing of heat by the molten salt material more complete, and has the advantages of high energy storage density, low system cost, high thermal efficiency, no freezing blockage, and small footprint. It solves the problems of low heat storage / heat release and insufficient charging and releasing of heat in single-tank "climate layer" thermal storage systems.

[0013] Preferably, the first conduit is a spiral conduit; and / or, the second conduit is a spiral conduit.

[0014] In this technical solution, the spiral tube has the characteristics of compact structure, larger heat transfer area than straight tube, and low thermal stress, making it suitable for heating or cooling fluids with high viscosity. Furthermore, in this embodiment, it saves more energy (steam). Specifically, the unique internal reverse-winding, spirally rising coil structure exchanges heat in a counter-current manner, allowing the steam to fully condense in the heat exchange tube bundle without needing secondary heat exchange, thus saving a significant amount of steam.

[0015] Preferably, the spiral tube is a bare tube; or, the spiral tube is provided with at least one of square fins, spirals, circular fins, and hexagonal fins on its exterior.

[0016] In this technical solution, the spiral tube can be either a plain tube or a finned tube. Compared with a plain tube, the heat transfer area of ​​a finned tube can be increased by 2 to 10 times, and the heat transfer coefficient can be increased by 1 to 2 times. Furthermore, due to the large heat transfer area per unit volume, the heat transfer capacity of a finned tube is enhanced. Under the same heat load, compared with a plain tube, a finned tube heat exchanger has fewer tubes, thus making the structure compact and easy to arrange.

[0017] Preferably, the molten salt storage tank further includes an insulation component and an outer shell, the inner shell being housed within the outer shell, the first pipeline being located between the interior of the outer shell and the outer wall of the inner shell, and the insulation component being disposed between the first pipeline of the inner shell and the outer shell.

[0018] In this technical solution, some heat will always be lost during the heat exchange process. Therefore, the insulation component is placed between the first pipe of the inner shell and the outer shell to reduce the heat loss of the heating ring during the transportation process, save fuel, and ensure the quality of heating.

[0019] Preferably, the first heat exchange unit is a steam-water heat exchanger, the second heat exchange unit is a wind-water heat exchanger, the steam-water heat exchanger and the wind-water heat exchanger are connected in series with the heat user, and the steam-water heat exchanger and the wind-water heat exchanger are respectively connected in series with the molten salt storage tank for supplying heat to the heat user.

[0020] In this technical solution, during heat release, water and air flow into the outer wall and inside of the storage tank respectively to carry away the heat, or the high-temperature hot air generated by the heat storage device exchanges heat with the return water supplied by the secondary heat user. This integrates two heat exchange methods, which can solve problems such as low heat capacity or insufficient heat release in single-tank heat storage systems.

[0021] Preferably, the first circulation loop includes a water tank, a first water pump, and a first shut-off valve; wherein the steam-water heat exchanger, the water tank, the first water pump, and the first shut-off valve are connected in series with the molten salt storage tank via pipelines.

[0022] In this technical solution, the heat exchange mode between the steam-water heat exchanger and the molten salt storage tank can be effectively controlled through the cooperation of the water tank, water pump, shut-off valve and steam-water heat exchanger, ensuring the reliability of the heat exchange system during heat exchange and its sealing when not in use.

[0023] Preferably, the second circulation loop is further provided with a fan and a second shut-off valve; wherein the fan, the air-water heat exchanger and the second shut-off valve are connected in series with the molten salt storage tank via pipelines.

[0024] In this technical solution, the cooperation between the fan, the shut-off valve and the air-water heat exchanger can effectively ensure the reliability of the heat exchange system during heat exchange and improve the heat exchange efficiency.

[0025] Preferably, the third circulation loop includes a second water pump and a third shut-off valve; wherein the second water pump, the third shut-off valve, the steam-water heat exchanger, and the air-water heat exchanger are connected in series with the heat user.

[0026] In this technical solution, the steam-water heat exchanger and the air-water heat exchanger are connected in series with the heat user, and the heat exchange with the heating system is controlled by a water pump and a shut-off valve, which can continuously provide heating for the heat user and has sustainability.

[0027] Preferably, the molten salt storage tank further includes a header, an air inlet, and an air outlet. Cold air is blown in through the air inlet, flows into the header, exchanges heat through the second pipeline, and is discharged through the air outlet.

[0028] Preferably, the molten salt thermal storage and heating system further includes an electric heating module. The molten salt storage tank contains molten salt material, which is electrically connected to the electric heating module. The electric heating module is used to provide heat energy to the molten salt material.

[0029] In this technical solution, electric heating has high thermal efficiency and fast heating compared with other energy sources. It can generate a large amount of heat energy in a very small area, reach the predetermined temperature more quickly, and has strong controllability, making it easy to achieve automatic temperature control and remote temperature adjustment.

[0030] Preferably, the electric heating module includes an electrical control cabinet and at least one electric heating rod, the electric heating rod being electrically connected to the electrical control cabinet and immersed in the molten salt material to provide heat energy to the molten salt material.

[0031] In this technical solution, the electric heating rod provides uniform heating, has a long service life, and low power consumption.

[0032] Preferably, there are multiple electric heating rods, which are evenly distributed inside the molten salt storage tank.

[0033] In this technical solution, multiple electric heating rods are evenly distributed inside the molten salt storage tank, which ensures that the molten salt material is heated evenly and that there will be no local overcooling or overheating.

[0034] Preferably, the molten salt storage tank further includes an agitator for agitating the molten salt material inside the tank.

[0035] In this technical solution, the stirrer makes the temperature field of the molten salt material in the molten salt storage tank more uniform by stirring, thus avoiding local overcooling and overheating during the charging process.

[0036] The present invention also provides a molten salt thermal storage heating method, wherein the heating method uses the heating system described in any of the above claims, and the method includes:

[0037] The heating mode of the heating system is determined based on the time period of electricity consumption.

[0038] The heating mode includes a first mode;

[0039] If the heating system is in the first mode, the molten salt storage tank is heated and the first circulation loop is started, and then the second circulation loop is started, so that the first circulation loop and the second circulation loop respectively supply heat to the heat users.

[0040] In this technical solution, the heating method using the aforementioned heating system integrates heat generation, heat storage, and heat supply, providing sustainable and stable heating for users. Furthermore, it allows for the use of single or multiple molten salt storage tanks based on user needs, and the molten salt tanks can store heat according to electricity consumption periods, resulting in low heating costs. For example, the first mode is suitable for off-peak electricity or periods of wind / solar power curtailment, enabling simultaneous heat storage and heating.

[0041] Preferably, starting the first circulation loop operation includes: controlling the first heat exchange unit to first exchange heat with the molten salt storage tank, and then exchange heat with the heat user; and / or, starting the second circulation loop operation includes: controlling the second heat exchange unit to first exchange heat with the molten salt storage tank, and then exchange heat with the heat user.

[0042] Preferably, the heating mode further includes a second mode; the heating method further includes: if the heating system is in the second mode, closing the first circulation loop and the second circulation loop, heating the molten salt storage tank until the temperature inside the molten salt storage tank reaches the upper limit operating temperature, at which point the heat storage ends, or, according to the electricity consumption period, the heat storage ends.

[0043] In this technical solution, the mode is applicable during off-peak electricity or wind / solar power curtailment, and can store heat without supplying heat.

[0044] Preferably, the heating mode further includes a third mode, and the heating method further includes: if the heating system is in the third mode, stopping the heating of the molten salt storage tank, starting the first circulation loop, and then starting the second circulation loop, wherein the first circulation loop and the second circulation loop respectively provide heat to the heat users.

[0045] In this technical solution, the mode is applicable during peak electricity hours or when users need heating, without storing heat but only providing heating.

[0046] The significant advantages of this invention are as follows: This system integrates heat generation, heat storage, and heat supply, providing sustainable and stable heating to users. It supplies heat through two different circulation loops (first and second), resulting in a greater number of heat exchange points. Therefore, one or more molten salt storage tanks can be used depending on user needs. Furthermore, the molten salt storage tanks can store heat according to electricity usage periods, leading to low heating costs. In addition, the integration of two different circulation loops on the inner and outer sides of the molten salt storage tanks within a single tank improves volume utilization and further increases thermal efficiency. Attached Figure Description

[0047] Figure 1 This is a structural diagram of the heating and heat storage system in Embodiment 1 of the present invention;

[0048] Figure 2 This is a schematic diagram of the molten salt storage tank in Embodiment 1 of the present invention;

[0049] Figure 3 This is a schematic diagram of the internal structure of the molten salt storage tank in Embodiment 1 of the present invention;

[0050] Figures 4(a)-4(d) This is a cross-sectional schematic diagram of the spiral tube in Embodiment 1 of the present invention;

[0051] Figure 5 This is the molten salt thermal storage and heating method in Embodiment 2 of the present invention.

[0052] Explanation of reference numerals in the attached figures:

[0053] Steam-water heat exchanger 1

[0054] Air-water heat exchanger 2

[0055] Water tank 3

[0056] First water pump 4

[0057] First shut-off valve 5

[0058] Fan 6

[0059] Second shut-off valve 7

[0060] Second water pump 8

[0061] Third shut-off valve 9

[0062] Molten salt storage tank 10

[0063] Inner shell 11

[0064] Electric heating rod 12

[0065] Mixer 13

[0066] First pipeline 14

[0067] Second pipeline 15

[0068] Container 16

[0069] Air inlet 17

[0070] Air outlet 18

[0071] Hot User 19 Detailed Implementation

[0072] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0073] Example 1

[0074] like Figure 1 As shown in Figure 4, this embodiment provides a molten salt thermal energy storage and heating system. The system includes: a thermal energy storage module, which includes a molten salt storage tank 10 for storing thermal energy; the molten salt thermal energy storage and heating system also includes a heat exchange module and a third circulation loop. The heat exchange module includes a first heat exchange unit and a second heat exchange unit. The first heat exchange unit is connected to the outside of the molten salt storage tank 10 through a first pipe 14, forming a first circulation loop; the second heat exchange unit is connected to the inside of the molten salt storage tank 10 through a second pipe 15, forming a second circulation loop; both the first and second heat exchange units are connected to a heat user 19 through the third circulation loop to provide heating to the heat user 19.

[0075] In this embodiment, preferably, the thermal storage and heating system is applicable to a single molten salt storage tank 10, but in other alternative embodiments, the thermal storage and heating system is also applicable to two or more molten salt storage tanks 10.

[0076] This system integrates heat generation, storage, and supply to provide sustainable and stable heating for users. It utilizes two different circulation loops (first and second) to supply heat, resulting in numerous heat exchange points. Therefore, it can employ single or multiple molten salt storage tanks depending on user needs. Furthermore, the molten salt tanks can store heat according to electricity consumption periods, leading to low heating costs. In addition, the integration of two different circulation loops on the inner and outer sides of the molten salt tanks within a single tank improves volume utilization and further enhances thermal efficiency.

[0077] In this embodiment, the first heat exchange unit is a steam-water heat exchanger 1, and the second heat exchange unit is an air-water heat exchanger 2. Both the steam-water heat exchanger 1 and the air-water heat exchanger 2 are connected in series with the heat user 19, and are also connected in series with the molten salt storage tank 10 to supply hot water to the heat user 19. The steam-water heat exchanger 1 is a device that exchanges heat between the generated high-temperature steam (or steam-water mixture) and the return water of the secondary heat user 19. The air-water heat exchanger 2 exchanges heat between the high-temperature hot air generated by the heat storage device and the return water of the secondary heat user. The structures of these two heat exchangers can be plate type, shell-and-tube type, or tube-and-shell type heat exchangers.

[0078] During heat release, water and air flow into the outer wall and inside of the storage tank respectively to carry away the heat, or the high-temperature hot air generated by the heat storage device exchanges heat with the heating return water of the heat user 19. This single-tank heat storage heating system integrates two heat exchange methods, which can solve problems such as low heat or heat release of single-tank heat storage systems and insufficient heat release.

[0079] It should be noted that in other embodiments, the first heat exchange unit and the second heat exchange unit are not limited to the steam-water heat exchanger 1 and the air-water heat exchanger 2 described above. Other heat exchange media can also be used to exchange heat with the molten salt storage tank 10, as long as the effect of supplying heat to the heat user 19 can be achieved.

[0080] like Figure 2As shown, in this embodiment, the molten salt storage tank 10 includes an inner shell 11. A first pipe 14 surrounds the outer wall of the inner shell 11 from one side to the other, and a second pipe 15 extends from one side of the inner shell 11 into the interior of the inner shell 11. This structure avoids direct contact between the molten salt and the heat exchange medium in the circulation loop, and enables two different circulation loops to exchange heat with the molten salt storage tank. The surrounding and extending pipe structure increases the contact area between the pipe and the molten salt storage tank or the molten salt material inside, which is beneficial to improving heat exchange efficiency. In addition, in this embodiment, both the first pipe 14 and the second pipe 15 are spiral tubes. Spiral tubes have the characteristics of compact structure, larger heat transfer area than straight tubes, and low thermal stress, and are suitable for heating or cooling fluids with high viscosity. Furthermore, in this embodiment, it saves more energy (steam). Specifically, the unique internal reverse winding, spiral rising coil structure exchanges heat in a counter-current manner, allowing the steam to be fully condensed in the heat exchange tube bundle without secondary heat exchange, thus saving a large amount of steam.

[0081] It should be noted that in other embodiments, the first pipe on the outer wall of the inner shell and the second pipe inside can also be straight pipes, as long as they can serve as heat exchange channels with the steam-water heat exchanger 1 and the air-water heat exchanger 2. No specific limitation is made here.

[0082] In this embodiment, as shown in Figure 4(a), the spiral tube is a smooth tube. It should be noted that, as shown in Figures 4(b)-(d), in other embodiments, square fins, spiral fins, circular fins, or hexagonal fins can also be provided on the outside of the spiral tube; the specific shape of the fins is not specifically limited. Compared to a smooth tube, the heat transfer area of ​​a finned tube can be increased by 2 to 10 times, and the heat transfer coefficient can be increased by 1 to 2 times. Furthermore, due to the larger heat transfer area per unit volume, the heat transfer capacity of the finned tube is enhanced. Under the same heat load, compared to a smooth tube, the finned tube heat exchanger requires fewer tubes, resulting in a more compact structure and easier arrangement. The material of the spiral tube can be carbon steel, stainless steel, copper, etc., and is not specifically limited here.

[0083] The interaction between the steam-water heat exchanger and the first pipeline 14 is specifically manifested as follows: the first pipeline 14 is wrapped around the outer wall of the molten salt storage tank 10, and water flows inside the first pipeline 14. The water exchanges heat through the outer wall of the molten salt storage tank 10 and then exchanges heat with the molten salt material inside the molten salt storage tank 10. This structure avoids direct contact between the molten salt material inside the molten salt storage tank 10 and the water. However, as a large amount of heat from the molten salt material inside the tank is carried away and a large amount of the molten salt material solidifies into a solid, the heat carried away by the first pipeline 14 decreases, and the output heat gradually decreases. The form of heat output by the first pipeline 14 changes from high temperature to low temperature steam, then to a steam-water mixture, and then to hot water.

[0084] like Figure 3As shown, the molten salt storage tank 10 also includes a header 16, an air inlet 17, and an air outlet 18. Cold air is blown in through the air inlet 17, flows into the header 16, and exchanges heat through the second pipeline 15, and is discharged through the air outlet 18.

[0085] The interaction between the air-water heat exchanger and the second pipeline 15 is as follows: cold air is blown in from the air inlet 17 and flows into the header 16 for diversion. It then undergoes heat exchange through the second pipeline 15, carrying away the heat of the molten salt material. The air is then connected to the lower header 16 and carries away the heat. As the temperature of the molten salt material in the storage tank decreases, the air volume of the fan 6 gradually increases.

[0086] In this embodiment, the molten salt storage tank 10 also includes an outer shell and a container lid (not shown in the figure). The container lid is used to open the outer shell. The inner shell 11 is housed within the outer shell. The first pipeline 14 is located between the inside of the outer shell and the outer wall of the inner shell 11. Both the inner shell 11 and the outer shell are cylindrical structures. The container lid is a circular or arc-shaped structure that matches the shape of the outer shell. The materials of the inner shell 11, the outer shell, and the container lid can all be copper, steel, or iron with good thermal conductivity. As long as good thermal conductivity can be achieved, no specific limitation is made here.

[0087] The molten salt storage tank 10 also includes an insulation component, which is disposed between the first pipe 14 of the inner shell 11 and the outer shell. Since some heat is always lost during the heat exchange process, the insulation component disposed between the first pipe 14 of the inner shell 11 and the outer shell can reduce the heat loss of the heating ring during the transportation process, save fuel, and ensure the quality of heating.

[0088] The insulation material can be a low thermal conductivity material, such as one or more of vermiculite, foam glass, rock wool, aerogel felt or ceramic fiber. There are no specific restrictions, as long as it can achieve a good insulation effect.

[0089] In this embodiment, the flow direction of the heat exchange medium in the first circulation loop on the molten salt storage tank 10 is opposite to the flow direction of the heat exchange medium in the second circulation loop on the molten salt storage tank 10. This causes convection within the molten salt in the heat exchange system, creating heat exchange waves within the molten salt storage tank 10. This prevents overheating at the top and undercooling at the bottom of the molten salt material within the tank 10, resulting in more complete heat charging and discharging of the molten salt material. It offers advantages such as high energy storage density, low system cost, high thermal efficiency, no freezing or blockage, and small footprint, solving problems such as low heat storage / discharging capacity and insufficient heat charging / discharging in single-tank "climate layer" thermal storage systems.

[0090] Specifically, in this embodiment, during the heat release process, the molten salt storage tank 10 adopts an upward-inward and downward-outward heat exchange method inside, while the outer wall of the tank adopts a downward-inward and upward-outward heat exchange method. This structure can promote the natural flow of molten salt inside the molten salt, improve the system's heat exchange efficiency, and make the molten salt material release heat more fully.

[0091] It should be noted that in other embodiments, the interior of the molten salt storage tank 10 may adopt a heat exchange method of bottom inlet and top outlet or left inlet and right outlet, and the outer wall may adopt a heat exchange method of top inlet and bottom outlet or right inlet. As long as the flow direction of the heat exchange medium in the first circulation loop and the second circulation loop is opposite, no specific limitation is made here.

[0092] In this embodiment, the first circulation loop is provided with a water tank 3, a first water pump 4 and a first shut-off valve 5; wherein, the steam-water heat exchanger 1, the water tank 3, the first water pump 4 and the first shut-off valve 5 are connected in series with the molten salt storage tank 10 through pipelines.

[0093] The interaction between the water tank 3, the first water pump 4, the first shut-off valve 5 and the steam-water heat exchanger 1 can effectively control the heat exchange mode between the steam-water heat exchanger 1 and the molten salt storage tank 10, ensuring the reliability of the heat exchange system during heat exchange and its sealing performance when not in use.

[0094] In this embodiment, the water tank 3 is a softened water tank 3, which supplies water to the molten salt storage tank 10 on one hand, and the water that has finished exchanging heat with the steam-water heat exchanger 1 flows back to the water tank 3 for storage on the other hand. Using a softened water tank 3 can avoid scaling on the heat exchanger tube walls. The water pump is used to transport water for the heating system, and its two ends are connected to the outlet of the softened water tank 3 and the inlet of the molten salt storage tank 10, respectively.

[0095] The second circulation loop also includes a fan 6 and a second shut-off valve 7; wherein, the fan 6, the air-water heat exchanger, and the second shut-off valve 7 are connected in series with the molten salt storage tank 10 via pipelines. The cooperation between the fan 6, the second shut-off valve 7, and the air-water heat exchanger effectively ensures the reliability of the heat exchange system during heat exchange and improves the heat exchange efficiency. In this embodiment, the fan 6 is a high-temperature fan, and its material can be cast iron, cast steel, carbon steel, or stainless steel, etc.

[0096] The third circulation loop includes a second water pump 8 and a third shut-off valve 9. The second water pump 8, the third shut-off valve 9, the steam-water heat exchanger 1, and the air-water heat exchanger 2 are connected in series with the heat user 19. The second water pump 8 delivers the return water from the secondary heat user 19 to the steam-water heat exchanger 1 and the air-water heat exchanger 2 for heat exchange. The steam-water heat exchanger 1 and the air-water heat exchanger 2 are connected in series with the heat user 19, and the heat exchange with the heating system is controlled by the water pump and the shut-off valve, ensuring continuous heating for the heat user 19 and providing sustainability.

[0097] The heat release principle of the system is as follows: During heat release, water and air flow into the outer wall and inside of the molten salt storage tank 10 respectively to carry away heat; the molten salt storage tank 10 has two ports that can be adjusted by opening and closing the first shut-off valve 5 on the water supply pipeline to exchange heat with the steam-water heat exchanger 1 to carry away heat; the molten salt heat storage device also has two ports that can be adjusted by opening and closing the second shut-off valve 7 on the hot air pipeline to exchange heat with the air-water heat exchanger 2 to carry away heat.

[0098] The molten salt storage tank 10 also includes an agitator 13, which is used to stir the molten salt material inside the tank. The agitator 13 ensures a more uniform temperature field for the molten salt material within the tank, preventing localized overcooling and overheating during the heating process. Since the molten salt material has a high viscosity at low temperatures, a high-viscosity agitator 13 should be selected. This agitator can be a ribbon type or an anchor type. The specific structure of the agitator 13 is not specifically limited here, as long as it is suitable for stirring high-viscosity molten salt materials.

[0099] The molten salt thermal storage heating system also includes an electric heating module. Molten salt material is contained within the molten salt storage tank 10, and the molten salt material is electrically connected to the electric heating module, which provides heat energy to the molten salt material. Compared to other energy sources, electric heating offers higher thermal efficiency, faster temperature rise, and the ability to generate a large amount of heat energy within a very small area, reaching the predetermined temperature more quickly. Furthermore, it offers strong controllability, facilitating automatic temperature control and remote temperature adjustment.

[0100] It should be noted that in other embodiments, other heating methods can also be selected, such as gaseous fuel and liquid fuel, as long as they can be used to achieve the heating effect on the molten salt storage tank 10 so that the molten salt storage tank 10 can store thermal energy. No specific details are provided here.

[0101] Specifically, the electric heating module includes an electrical control cabinet and multiple electric heating rods. The electric heating rods are electrically connected to the control cabinet and are immersed in the molten salt material to provide heat energy to it. The multiple electric heating rods are evenly distributed inside the molten salt storage tank 10. The electric heating rods feature uniform heating, long service life, and low power loss. Furthermore, the even distribution of multiple electric heating rods inside the molten salt storage tank 10 ensures uniform heating of the molten salt material, preventing localized overheating or undercooling.

[0102] It should be noted that in other embodiments, the heating rod can be replaced with a heating wire, as long as it can heat the molten salt material; no specific limitation is made here. In this embodiment, the heating rod 12 can be made of high-temperature and corrosion-resistant materials such as carbon steel, alloy steel, and stainless steel. As a preferred embodiment, stainless steel is selected as the heating material, and the material can be 304, 316L, 347H, 310s, etc.

[0103] In this embodiment, the density of the molten salt material in the molten salt storage tank 10 decreases as the temperature rises during the heating process. Under natural convection, the molten salt material with higher temperature rises to the top of the molten salt storage tank 10, while the molten salt with lower temperature sinks to the bottom, forming a temperature stratification. Natural convection is slow, and after complete heating, the temperature difference of the molten salt in the molten salt storage tank 10 may reach more than 100°C. During the heating process, after the molten salt material rises to a certain temperature above the melting point, the stirrer 13 can be turned on to slowly stir, which can mix the upper and lower molten salts. The temperature of the molten salt in the storage tank is uniform, and there will be no temperature stratification.

[0104] The molten salt material can be a mixed molten salt composed of one or more of the following: NaNO3, KNO3, NaNO2, Ca(NO3)2, Mg(NO3)2, LiNO3, Na2CO3, K2CO3, CaCO3, etc., such as binary Solar salt, ternary HTS salt, or ternary HTS XL salt. Preferably, in order to further improve the energy storage density of the molten salt material, the molten salt material is a molten salt thermal storage material with a low melting point and a high upper limit of operating temperature, but no specific limitation is made here.

[0105] Example 2

[0106] like Figure 5 As shown, this embodiment provides a molten salt thermal storage heating method. The heating method uses the heating system of Embodiment 1 above, and the method includes:

[0107] S100. Determine the heating mode of the heating system based on the electricity consumption period.

[0108] Among them, the heating mode includes the first mode, which is a mode of simultaneous heat storage and heating;

[0109] S210. If the heating system is in the first mode, the molten salt storage tank 10 is heated and the first circulation loop is started, and then the second circulation loop is started, so that the first circulation loop and the second circulation loop respectively supply heat to the heat user 19.

[0110] The operation of starting the first circulation loop includes: controlling the first heat exchange unit to exchange heat with the molten salt storage tank 10 first, and then exchange heat with the heat user 19; the operation of starting the second circulation loop includes: controlling the second heat exchange unit to exchange heat with the molten salt storage tank 10 first, and then exchange heat with the heat user 19.

[0111] The specific operation is as follows: during off-peak electricity or wind / solar power curtailment, the second water pump 8 is turned on first, followed by the first water pump 4 and the fan 6. Then, the electric heating rod is turned on to store a portion of the heat in the molten salt material. Another portion of the heat is carried out by water from bottom to top through the first pipe of the molten salt storage tank 10. The heat carried out is exchanged with the steam-water heat exchanger 1 to form low-temperature water that flows back to the softened water tank 3. Another portion of the heat is carried out by the air from top to bottom through the air duct heat exchanger inside the storage tank and exchanged with the air-water heat exchanger 2 before flowing back to the fan 6. The return water temperature of the secondary heat user 19 is raised by the steam-water heat exchanger 1 and then by the air-water heat exchanger 2 before being supplied to the heat user 19.

[0112] The heating mode also includes a second mode, which is a mode that only stores heat and does not supply heat.

[0113] S220. If the heating system is in the second mode, close the first and second circulation loops and heat the molten salt storage tank 10 until the temperature inside the molten salt storage tank 10 reaches the upper limit of the operating temperature, at which point the heat storage ends, or the heat storage ends according to the electricity consumption period.

[0114] The specific operation is as follows: during off-peak electricity or wind / solar curtailment periods, close the first shut-off valve 5 and the second shut-off valve 7 of the external interface of the molten salt storage tank 10, turn on the electric heating rod, and store the heat in the molten salt thermal storage material 20 until the molten salt thermal storage material reaches the upper limit of the operating temperature, the thermal storage device is full of heat, and the thermal storage ends; or the thermal storage ends when the off-peak electricity or wind / solar curtailment period ends.

[0115] The heating system also includes a third mode, which is a non-heat storage heating mode.

[0116] S230. If the heating system is in the third mode, the heating of the molten salt storage tank 10 is stopped, and the first circulation loop is started. Then the second circulation loop is started. The first circulation loop and the second circulation loop respectively supply heat to the heat user 19.

[0117] The specific operation is as follows: during peak electricity demand or periods when heat is needed, the electric heating rod is turned off, the second water pump 8 is turned on first, and then the first water pump 4 and the fan 6 are turned on. A portion of the heat is stored in the molten salt material, and another portion of the heat is carried out from bottom to top by water through the first pipeline 14 of the molten salt storage tank 10. The heat carried out is exchanged with the steam-water heat exchanger 1 to form low-temperature water that flows back to the softened water tank 3. Another portion of the heat is carried out from top to bottom by the air through the air duct heat exchanger inside the storage tank and exchanged with the air-water heat exchanger 2 before flowing back to the fan 6. The return water temperature of the secondary heat user 19 is raised by the steam-water heat exchanger 1 and then by the air-water heat exchanger 2 before being supplied to the heat user 19.

[0118] In summary, the molten salt thermal energy storage heating system provided in Example 1 and the heating method using the system of Example 1 in Example 2 have the following advantages:

[0119] This system integrates heat generation, storage, and supply to provide sustainable and stable heating for users. It utilizes two different circulation loops (first and second) to supply heat, resulting in numerous heat exchange points. Therefore, it can employ single or multiple molten salt storage tanks depending on user needs. Furthermore, the molten salt tanks can store heat according to electricity consumption periods, leading to low heating costs. In addition, the integration of two different circulation loops on the inner and outer sides of the molten salt tanks within a single tank improves volume utilization and further enhances thermal efficiency.

[0120] Furthermore, a single-tank molten salt system is used for heat storage / release. The outer wall of the molten salt storage tank 10 adopts an external spiral tube structure to bring water in from the lower wall of the molten salt storage tank for heat exchange with the molten salt material. Inside the molten salt storage tank 10, a spiral tube heat exchange structure is used to bring hot air in from the top for heat exchange with the molten salt material. The molten salt inside the system forms convection, and the heat exchange wave inside the molten salt storage tank 10 avoids the phenomenon of overheating at the top and undercooling at the bottom of the molten salt material inside the molten salt storage tank 10. The charging and releasing of the molten salt material is more complete, which has the advantages of high energy storage density, low system cost, high thermal efficiency, no freezing blockage, and small footprint. It solves the problems of low volume utilization and high cost of dual-tank heat storage; at the same time, it solves the problems of low heat storage / release and insufficient charging and releasing of heat in single-tank "climate layer" heat storage systems.

[0121] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A molten salt thermal energy storage and heating system, the molten salt thermal energy storage and heating system comprising: A heat storage module, comprising a molten salt storage tank for storing thermal energy; characterized in that the molten salt heat storage heating system further comprises a heat exchange module and a third circulation loop, the heat exchange module comprising a first heat exchange unit and a second heat exchange unit, the first heat exchange unit being connected to the outside of the molten salt storage tank via a first pipeline to form a first circulation loop; the second heat exchange unit being connected to the inside of the molten salt storage tank via a second pipeline to form a second circulation loop; the hot water in the first pipeline flows from the bottom to the top of the molten salt storage tank, and the air medium in the second pipeline flows from the top to the bottom of the molten salt storage tank; Both the first heat exchange unit and the second heat exchange unit are connected to the heat user through a third circulation loop. The heat exchange medium in the third circulation loop exchanges heat with the first heat exchange unit and the second heat exchange unit in sequence to provide heating to the heat user. The molten salt storage tank includes an inner shell, a first pipeline that extends from one side of the inner shell to the other side around the outer wall of the inner shell, and a second pipeline that extends from one side of the inner shell to the other side inside the inner shell; The first heat exchange unit is a steam-water heat exchanger, the second heat exchange unit is a wind-water heat exchanger, and the molten salt storage tank also includes a header, an air inlet and an air outlet. Cold air is blown in through the air inlet, flows into the header and is then diverted, undergoes heat exchange through the second pipeline, and is connected to the lower header and discharged through the air outlet.

2. The molten salt thermal storage and heating system as described in claim 1, characterized in that, The first pipeline is a spiral pipe; And / or, the second conduit is a spiral conduit.

3. The molten salt thermal storage and heating system as described in claim 2, characterized in that, The spiral tube is a light tube; Alternatively, the spiral tube may be provided with at least one of square fins, spirals, circular fins, and hexagonal fins on its exterior.

4. The molten salt thermal storage and heating system as described in claim 1, characterized in that, The molten salt storage tank also includes an insulation component and an outer shell. The inner shell is housed within the outer shell. The first pipeline is located between the interior of the outer shell and the outer wall of the inner shell. The insulation component is disposed between the first pipeline of the inner shell and the outer shell.

5. The molten salt thermal storage and heating system as described in claim 1, characterized in that, The first heat exchange unit is a steam-water heat exchanger, and the second heat exchange unit is a wind-water heat exchanger. The steam-water heat exchanger and the wind-water heat exchanger are connected in series with the heat user, and the steam-water heat exchanger and the wind-water heat exchanger are connected in series with the molten salt storage tank respectively, for supplying heat to the heat user.

6. The molten salt thermal storage and heating system as described in claim 5, characterized in that, The first circulation loop is equipped with a water tank, a first water pump, and a first shut-off valve; The steam-water heat exchanger, the water tank, the first water pump, and the first shut-off valve are connected in series with the molten salt storage tank via pipelines.

7. The molten salt thermal storage and heating system as described in claim 5, characterized in that, The second circulation loop is equipped with a fan and a second shut-off valve; The fan, the air-water heat exchanger, and the second shut-off valve are connected in series with the molten salt storage tank via pipelines.

8. The molten salt thermal storage and heating system as described in claim 5, characterized in that, The third circulation loop is equipped with a second water pump and a third shut-off valve; The second water pump, the third shut-off valve, the steam-water heat exchanger, and the air-water heat exchanger are connected in series with the heat user to provide heat to the heat user.

9. The molten salt thermal storage and heating system as described in claim 1, characterized in that, The molten salt thermal storage and heating system also includes an electric heating module. Molten salt material is provided in the molten salt storage tank. The molten salt material is electrically connected to the electric heating module, which is used to provide heat energy to the molten salt material.

10. The molten salt thermal storage and heating system as described in claim 9, characterized in that, The electric heating module includes an electrical control cabinet and at least one electric heating rod. The electric heating rod is electrically connected to the electrical control cabinet and is immersed in the molten salt material to provide heat energy to the molten salt material.

11. The molten salt thermal storage and heating system as described in claim 10, characterized in that, The electric heating rods are multiple in number and are evenly distributed inside the molten salt storage tank.

12. The molten salt thermal storage and heating system as described in claim 1, characterized in that, The molten salt storage tank also includes an agitator, which is used to agitate the molten salt material inside the molten salt storage tank.

13. A method for molten salt thermal storage and heating, characterized in that, The heating method uses the heating system as described in any one of claims 1-12, the method comprising: The heating mode of the heating system is determined based on the electricity consumption period, wherein the heating mode includes a first mode; If the heating system is in the first mode, the molten salt storage tank is heated and the first circulation loop is started, and then the second circulation loop is started, so that the first circulation loop and the second circulation loop respectively supply heat to the heat users.

14. The molten salt thermal storage and heating method as described in claim 13, characterized in that, The operation of starting the first circulation loop includes: controlling the first heat exchange unit to first exchange heat with the molten salt storage tank, and then exchange heat with the heat user; And / or, starting the second circulation loop operation includes: controlling the second heat exchange unit to exchange heat first with the molten salt storage tank, and then with the heat user.

15. The molten salt thermal storage and heating method as described in claim 13, characterized in that, The heating mode further includes a second mode; the heating method further includes: If the heating system is in the second mode, the first circulation loop and the second circulation loop are closed, and the molten salt storage tank is heated until the temperature inside the molten salt storage tank reaches the upper limit of the operating temperature, at which point the heat storage ends; or, the heat storage ends according to the electricity consumption period.

16. The molten salt thermal storage and heating method as described in claim 15, characterized in that, The heating mode also includes a third mode, and the heating method further includes: If the heating system is in the third mode, heating of the molten salt storage tank is stopped, and the first circulation loop is started, followed by the second circulation loop. The first circulation loop and the second circulation loop respectively supply heat to the heat users.

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