Single-tank molten salt heat storage and heat exchange device

Abstract

The application relates to a single-tank molten salt heat storage and heat exchange device, which comprises a heat storage tank containing molten salt, a heating mechanism and a heat exchange mechanism; the heating mechanism comprises at least one electric heater arranged in the heat storage tank to heat the molten salt; the heat exchange mechanism comprises at least one first header and a second header, the first header and the second header are connected through at least one heat exchange pipeline to form a heat exchange space for circulating heat exchange medium, the first header is arranged in the heat storage tank to absorb the heat of the molten salt and transfer the heat to the second header through the heat exchange medium, and the second header is arranged outside the heat storage tank. The single-tank molten salt heat storage and heat exchange device is constructed, heat storage and heat exchange of the molten salt can be realized by only one tank, the device has small floor area and low cost, and the heat exchange medium can be kept in a high-temperature state higher than the solidification temperature of the molten salt, so that the molten salt cannot be frozen and blocked.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molten salt heat exchange, in particular to a single-tank molten salt heat storage and exchange device. BACKGROUND

[0002] Solar energy has the advantages of inexhaustibility, safety and reliability. Solar thermal power generation is not affected by energy crisis and fuel market instability, does not use fuel, has very low operating cost, and is not easy to produce pollution waste during power generation, so it is an ideal clean energy. According to the increase and decrease of load, mirror field can be added or reduced arbitrarily to avoid waste. In the solar thermal power station heat storage and exchange system, molten salt storage tank, molten salt heat exchanger and related salt melting and preheating system are key equipment.

[0003] Molten salt heat storage technology has been widely used in the solar photovoltaic industry. It can convert solar energy into heat energy and store it, and then convert it into steam to drive a steam turbine to generate electricity, which can realize continuous, stable and controllable power supply. Molten salt heat storage technology can produce steam of different grades, which has very good application scenarios in coal-fired unit heating and steam supply. However, there are few reports on the actual engineering application of molten salt heat storage coupled with coal-fired unit peak shaving and heat supply. On the one hand, the power grid needs thermal power units to peak shave, and on the other hand, the thermal power unit needs to ensure heat supply or steam supply. When the two needs conflict, part of the electricity generated by the coal-fired unit can be used to heat the molten salt in the form of electric heating, converting electrical energy into heat energy for storage, improving the unit's peak shaving capacity, and obtaining rewards for peak shaving auxiliary services. At the same time, the heat energy stored in the molten salt can be released as steam or hot water at any time to improve the unit's heat supply or steam supply capacity, realizing the thermal and electrical decoupling of the unit.

[0004] The traditional electric heating molten salt heat storage and exchange technology mainly adopts the cold-hot double-tank heat storage mode. During heat storage, the molten salt in the cold tank is heated by electric heating, and the heated molten salt is introduced into the hot tank. During heat release, the molten salt in the hot tank is discharged for heat exchange, and the exchanged molten salt returns to the cold tank. The double-tank molten salt heat storage technology is mature, but it has the disadvantages of large investment and large land occupation. Therefore, more scholars have shifted their research to single-tank molten salt heat storage technology. However, the single-tank molten salt technology has the disadvantages of complex system, high risk of freezing and uneven temperature distribution in the tank. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a single-tank molten salt heat storage and exchange device.

[0006] The present application adopts the following technical solutions:

[0007] A single-tank molten salt heat storage and exchange device is constructed, comprising:

[0008] a heat storage tank containing molten salt inside,

[0009] a heating mechanism, the heating mechanism comprising at least one electric heater arranged in the heat storage tank to heat the molten salt; and

[0010] a heat exchange mechanism, the heat exchange mechanism comprising at least one first header and a second header, the first header and the second header being connected by at least one heat exchange pipe to form a heat exchange space for a heat exchange medium to circulate, the first header being arranged in the heat storage tank to absorb heat from the molten salt and transfer to the second header through the heat exchange medium, the second header being arranged outside the heat storage tank.

[0011] In some embodiments, the second header has a higher horizontal level than the first header.

[0012] In some embodiments, the heat exchange medium is water, and the pressure in the heat exchange space is such that the vaporization temperature of the high-pressure water is higher than the solidification temperature of the molten salt.

[0013] In some embodiments, the number of electric heaters is several, and the several electric heaters are uniformly spaced in the heat storage tank or uniformly spaced in the circumferential direction of the first header.

[0014] In some embodiments, the first header is cylindrical, and the axis of the first header coincides with the axis of the heat storage tank.

[0015] Alternatively, the first header is arranged on the axis of the heat storage tank.

[0016] In some embodiments, the number of first headers is several, and the several first headers are uniformly spaced in the heat storage tank along a direction perpendicular or parallel to the axis of the heat storage tank.

[0017] The number of electric heaters is several, and at least one electric heater is arranged between two adjacent first headers.

[0018] In some embodiments, the heat storage tank comprises a tank body and at least one stirring assembly for stirring the molten salt in the tank body, and the stirring assembly is arranged in the tank body.

[0019] In some embodiments, the stirring assembly comprises a stirring rod arranged at one end on the tank body and at least one stirring blade rotatably arranged on the stirring rod.

[0020] In some embodiments, the number of stirring assemblies is several, and the several stirring assemblies are uniformly spaced in the circumferential direction in the heat storage tank.

[0021] Alternatively, the stirring assembly is arranged on the axis of the tank body.

[0022] In some embodiments, the number of heat exchange pipes is several, and two ends of each of the heat exchange pipes are connected to the first header and the second header respectively;

[0023] The second header is provided with a heat supply pipe, and the heat supply pipe is provided with a heat supply medium for heat exchange with the heat exchange medium;

[0024] The heat exchange medium is water, wherein the heat exchange medium absorbs the heat of the molten salt in the first header to form high-temperature and high-pressure steam, and reaches the second header through the heat exchange pipe, exchanges heat with the heat supply medium in the heat supply pipe to cool down, and returns to the first header.

[0025] The present application has the following advantages:

[0026] The present application realizes heat storage and heat exchange of molten salt by a single tank, has small occupied area and low cost.

[0027] In addition, the present application is provided with a heat exchange mechanism containing a heat exchange medium, so as to change the circulation state of the heat exchange medium by pressure increase, so that the heat exchange medium is always in a high-temperature state higher than the solidification temperature of the molten salt, and the risk of freezing of the molten salt is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the present application, the present application will be further described below in combination with the drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0029] Figure 1 is a structural schematic diagram of a single-tank molten salt heat storage and heat exchange device in the first embodiment of the present application;

[0030] Figure 2 is Figure 1 is a top view structural schematic diagram of the single-tank molten salt heat storage and heat exchange device shown in the figure;

[0031] Figure 3 is a top view structural schematic diagram of a single-tank molten salt heat storage and heat exchange device in the second embodiment of the present application;

[0032] Figure 4 is a top view structural schematic diagram of a single-tank molten salt heat storage and heat exchange device in the third embodiment of the present application;

[0033] Figure 5 is a structural schematic diagram of a single-tank molten salt heat storage and heat exchange device in the fourth embodiment of the present application;

[0034] Figure 6 Figure 5 is a structural schematic diagram of a single-tank molten salt heat storage and heat exchange device in the fifth embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "back", "upper", "lower", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", etc. are based on the directions or positional relationships shown in some of the drawings, the specific directions of construction and operation, and are only for the convenience of describing the technical solutions, and do not indicate that the devices or elements indicated must have the specific directions, and therefore cannot be understood as a limitation on the present application.

[0036] It should also be noted that unless specifically defined and limited, the terms "mount", "connect", "connect", "fix", "set", etc. should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. When an element is referred to as "on" or "under" another element, the element can be "directly" or "indirectly" located on the other element, or there can be one or more intervening elements. The terms "first", "second", etc. are only for the convenience of describing the technical solutions, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features with "first", "second", etc. can explicitly or implicitly include one or more of the features. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] In the following description, specific details such as specific system structures, techniques, etc. are presented for the purpose of explanation, not for the purpose of limitation, so as to thoroughly understand the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted to avoid unnecessary details that hinder the description of the present application.

[0038] Figure 1 and Figure 2This invention illustrates a single-tank molten salt thermal storage and heat exchange device 1 according to a first embodiment. The device stores and exchanges heat energy through molten salt within the tank. The single-tank molten salt thermal storage and heat exchange device 1 includes a storage tank 10, a heating mechanism 20, and a heat exchange mechanism 30. The storage tank 10 contains molten salt. The heating mechanism 20 is disposed within the storage tank 10 and is used to heat the molten salt within the storage tank 10. The heat exchange mechanism 30 circulates a heat exchange medium to transfer the heat stored in the molten salt to the heat-using equipment.

[0039] Specifically, the thermal storage tank 10 includes a tank body 11 and a stirring assembly 12. The tank body 11 is used to contain molten salt. The stirring assembly 12 is disposed inside the tank body 11 and is used to stir the molten salt inside the tank body 11 to ensure the uniformity of the temperature of the molten salt inside the tank body 11 and reduce the risk of freezing blockage of the molten salt.

[0040] In this embodiment, the tank 11 is a closed cylinder, including an inlet and an outlet (not shown in the figure) for replacing molten salt. The inlet is located at the upper end of the tank 11, and the outlet is located at the lower end of the tank 11. Both are sealed by a sealing element to keep the tank 11 sealed.

[0041] In some other alternative embodiments, the tank 11 may also be in other shapes such as rectangular columnar or polygonal columnar.

[0042] The number of stirring components 12 is several, and the several stirring components 12 are evenly spaced along the circumferential direction inside the tank 11 in a direction parallel to the axis of the tank 11. Figure 1 (Only one is shown in the image). This is to ensure the uniformity of the molten salt temperature within the tank 11. The stirring assembly 12 includes a stirring rod 121 and stirring blades 122. The upper end of the stirring rod 121 is located at the upper end of the tank 11, thus fixing the stirring rod 121 within the tank 11. Several stirring blades 122 are rotatably mounted on the stirring rod 121, and are evenly spaced on the stirring rod 121. Rotation of these blades stirs the molten salt, thereby achieving uniform molten salt temperature.

[0043] In this embodiment, the upper end of the stirring rod 121 is fixed to the upper end of the tank 11. In some other optional embodiments, the upper end of the stirring rod 121 can also pass through the upper end of the tank 11 and be sealed by a sealing element. While being fixed, the stirring rod 121 can also move up and down along its length. In some other optional embodiments, the upper end of the stirring rod 121 can also be fixed to the tank 11, and the lower end can be rotatably disposed inside the tank 11, so that the stirring rod 121 itself also has a certain stirring function, and at the same time drives several stirring blades 122 to move while rotating itself, thereby increasing the stirring range of the stirring assembly 12.

[0044] The heating mechanism 20 comprises at least one electric heater 21 which receives wind light abandoned electricity, valley electricity and other electric energy to heat the molten salt. In the embodiment, the number of the electric heater 21 is several (only one is shown in the figure), and the several electric heaters 21 are uniformly spaced on the circumference of the tank body 11 and arranged on the outer periphery of the stirring assembly 12 to ensure the uniformity of the heating of the molten salt. Figure 1

[0045] The heat exchange mechanism 30 comprises at least one first header 31, a second header 32 and at least one heat exchange pipeline 33. The first header 31 and the second header 32 are connected by the heat exchange pipeline 33 to form a heat exchange space for the circulation of the heat exchange medium between the first header 31 and the second header 32, and the heat exchange of the molten salt is realized by the flow of the heat exchange medium. Specifically, the first header 31 is arranged in the tank body 11, the second header 32 is arranged outside the tank body 11, and the second header 32 is further provided with a heat supply pipeline (not shown in the figure) in which a heat supply medium is arranged to exchange heat with the heat exchange medium in the second header 32, and then the heat is transferred to the heat using equipment.

[0046] It should be understood that the heat storage temperature of the molten salt is higher than its melting point, but in the heat exchange process, if the temperature of the heat exchange medium is lower than the melting point of the molten salt, the molten salt will easily freeze and block. In order to avoid the freezing and blocking of the molten salt medium in the heat exchange process, the temperature in the tank body 11 needs to be maintained above the melting point of the molten salt to ensure that the molten salt will not freeze. At the same time, in order to avoid the freezing of the molten salt due to the too low temperature of the heat exchange medium circulating in the tank body 11, a high temperature medium is generally used, which can realize heat exchange, so that the heat supply medium can obtain heat from the heat exchange medium, and after the heat exchange medium transfers heat to the heat supply medium, the temperature of the heat exchange medium is still above the melting point of the molten salt, so that the molten salt will not freeze in the process of returning to the first header 31. Specifically, the heat exchange medium is water, and the pressure in the heat exchange space makes the gasification temperature of the water higher than the freezing temperature of the molten salt, so as to ensure that after the high-pressure gaseous water outputs heat in the second header 32 and is converted into high-pressure liquid water, the temperature of the water is still higher than the freezing temperature of the molten salt.

[0047] In some embodiments, the horizontal height of the first header 31 is lower than the horizontal height of the second header 32 to facilitate the automatic flow of the water medium between the first header 31 and the second header 32.

[0048] ​In the embodiment, the first header 31 and the second header 32 are both one, the first header 31 is arranged on the axis of the tank 11, and a plurality of heat exchange pipes 33 are arranged between the first header 31 and the second header 32. Both ends of each heat exchange pipe 33 are connected to the first header 31 and the second header 32 respectively, so that the high-pressure liquid water heated by the molten salt is converted into gaseous water, flows to the second header 32 through the heat exchange pipe 33, and exchanges heat with the heat supply medium. The high-pressure gaseous water after heat exchange is converted into high-pressure liquid water, flows back to the first header 31 through the heat exchange pipe 33, and exchanges heat with the molten salt or the higher-temperature gaseous water rising, to form a stable state.

[0049] In the embodiment, the first header 31, the electric heater 21 and the stirring assembly 12 are arranged so that the stirring assembly 12 and the electric heater 21 are both arranged on the circumference of the first header 31, and the stirring assembly 12 is arranged between the electric heater 21 and the first header 31 (i.e. the electric heater 21 is arranged on the outer circumference of the stirring assembly 12). This has a plurality of beneficial effects, including but not limited to: first, it can ensure that the molten salt around the first header 31 is converted in time, and the high-temperature molten salt around the electric heater 21 can be immediately moved to the first header 31 by the stirring assembly 12. Second, it can ensure the uniformity of the temperature of the molten salt, and avoid the situation that the temperature of the molten salt around the first header 31 is too low, resulting in low heat exchange efficiency.

[0050] In other optional embodiments, the first header 31, the second header 32 and the heat exchange pipe 33 can also be integrally formed, and can be fixed to each other by welding, sealing connection or the like, to jointly define a closed heat exchange space.

[0051] In other optional embodiments, the first header 31 and the second header 32 can also be plate heat exchangers or spiral plate tube heat exchangers or spiral heat exchangers, and the heat exchange medium in the heat exchange space can also be other media such as hydraulic oil and high-pressure high-temperature gas, and a loop is formed by arranging two heat exchange pipes 33 between the first header 31 and the second header 32, and a one-way valve and a power pump are arranged on the loop to realize the circulation of the heat exchange medium.

[0052] In other optional embodiments, the number of the first header 31 can also be a plurality, and the plurality of first headers 31 are connected to the second header 32 through the heat exchange pipes 33, to improve the heat exchange efficiency. The number of the first header 31 and the second header 32 can both be a plurality, and each first header 31 is connected to one second header 32 through the heat exchange pipe 33.

[0053] Figure 3A single-tank molten salt heat storage and heat exchange device 1b in a second embodiment of the present application is shown, and the main difference between the single-tank molten salt heat storage and heat exchange device 1b and the first embodiment includes that:

[0054] In the present embodiment, the first header 31b is cylindrically arranged, and the arrangement position of the first header 31b in the tank body 11b is such that the axis of the first header 31b coincides with the axis of the tank body 11b. The number of the stirring assemblies 12b is one, and the stirring assembly 12b is arranged on the axis of the tank body 11b. The number of the electric heaters 21b is several, and the several electric heaters 21b are uniformly and spacedly arranged on the circumference of the first header 31b, which is arranged between the stirring assembly 12b and the electric heaters 21b.

[0055] Figure 4 A single-tank molten salt heat storage and heat exchange device 1c in a third embodiment of the present application is shown, and the main difference between the single-tank molten salt heat storage and heat exchange device 1c and the first embodiment includes that:

[0056] In the present embodiment, the first header 31c is cylindrically arranged, and the arrangement position of the first header 31c in the tank body 11c is such that the axis of the first header 31c coincides with the axis of the tank body 11c. The number of the stirring assemblies 12c is one, and one stirring assembly 12c is arranged on the axis of the tank body 11c. The number of the electric heaters 21c is several, and the several electric heaters 21c are divided into two groups and arranged on the two sides of the first header 31c. The number of the two groups of electric heaters 21c can be the same, and the two groups of electric heaters 21c are arranged on the two sides of the first header 31c in one-to-one correspondence.

[0057] In other optional embodiments, the two groups of electric heaters 21c can also be arranged in a staggered manner on the two sides of the first header 31c to ensure a larger heating area of the molten salt around the first header 31c.

[0058] In other optional embodiments, the number of the two groups of electric heaters 21c can also be different.

[0059] In other optional embodiments, the stirring assembly 12c can also not be arranged.

[0060] Figure 5 A single-tank molten salt heat storage and heat exchange device 1d in a fourth embodiment of the present application is shown, and the main difference between the single-tank molten salt heat storage and heat exchange device 1d and the first embodiment includes that:

[0061] In the embodiment, the stirring assembly is not provided. The first header box 31d is in a plate shape, and the number of the first header boxes 31d is several. The several first header boxes 31d are horizontally arranged and uniformly spaced along the axial direction of the tank body 11d in the tank body 11d. The number of the electric heaters 21d is several. At least one electric heater 21d (only one is shown in the figure) is arranged between any two adjacent first header boxes 31d to ensure the uniformity of heating. At least one electric heater 21d is also arranged below the first header box 31d at the bottom of the tank body 11d and above the first header box 31d at the top of the tank body 11d. Figure 5

[0062] It should be understood that, in the embodiment, the several first header boxes 31d are connected to the same second header box 32d through the heat exchange pipes 33d. In some other optional embodiments, the several first header boxes 31d can be connected to different second header boxes through different heat exchange pipes 33d. The specific arrangement needs to be flexibly arranged according to the selection of the internal heat exchange medium and the type of the heat exchanger.

[0063] Figure 6 The single-tank molten salt heat storage and heat exchange device 1e in the fifth embodiment of the application is shown. The main difference between the single-tank molten salt heat storage and heat exchange device 1e and the first embodiment includes:

[0064] In the embodiment, the stirring assembly is not provided. The first header box 31e is in a plate shape, and the number of the first header boxes 31e is several. The several first header boxes 31e are vertically arranged and uniformly spaced along the axial direction perpendicular to the tank body 11e in the tank body 11e. The number of the electric heaters 21e is several. At least one electric heater 21e (only one is shown in the figure) is arranged between any two adjacent first header boxes 31e to ensure the uniformity of heating. At least one electric heater 21e is also arranged between the two first header boxes 31e at the two sides and the tank body 11e. Figure 6

[0065] It should be understood that, in the embodiment, the several first header boxes 31e are connected to the same second header box 32e through the heat exchange pipes 33e. In some other optional embodiments, the several first header boxes 31e can be connected to different second header boxes through different heat exchange pipes 33e. The specific arrangement needs to be flexibly arranged according to the selection of the internal heat exchange medium and the type of the heat exchanger.

[0066] ​​It can be understood that the above embodiments only express the preferred embodiments of the present application, which are described more specifically and in detail, but cannot be understood as a limitation to the patent scope of the present application; it should be pointed out that the above technical features can be freely combined without departing from the concept of the present application for those skilled in the art, and several modifications and improvements can be made, which all belong to the protection scope of the present application; therefore, any equivalent transformation and modification made to the patent claim scope of the present application shall belong to the coverage of the patent claim of the present application.

Claims

1. A single tank molten salt heat storage and heat exchange device, characterized by, The application relates to a molten salt heat storage device, which comprises: a heat storage tank (10) containing molten salt, a heating mechanism (20) comprising at least one electric heater (21) arranged in the heat storage tank (10) to heat the molten salt; and a heat exchange mechanism (30) comprising at least one first header (31) and a second header (32), the first header (31) and the second header (32) being connected through at least one heat exchange pipeline (33) to form a heat exchange space for a heat exchange medium to circulate in a closed high-pressure mode, the first header (31) being arranged in the heat storage tank (10) to absorb heat of the molten salt and transfer the heat to the second header (32) through the heat exchange medium, and the second header (32) being arranged outside the heat storage tank (10); the second header (32) is arranged at a higher level than the first header (31); the heat exchange medium is water, and the pressure in the heat exchange space is such that the vaporization temperature of the water is higher than the solidification temperature of the molten salt.

2. The single tank molten salt heat storage and heat exchange device according to claim 1, characterized in that, The number of the electric heaters (21) is several, and the several electric heaters (21) are uniformly arranged in the heat storage tank (10) or uniformly arranged on the circumference of the first header (31).

3. The single tank molten salt heat storage and heat exchange device of claim 1, wherein, The first header (31) is in a cylindrical shape, and the axis of the first header (31) coincides with the axis of the heat storage tank (10). Alternatively, the first header (31) is arranged on the axis of the heat storage tank (10).

4. The single tank molten salt heat storage and heat exchange device of claim 1, wherein, The number of the first headers (31) is several, and the several first headers (31) are uniformly arranged in the heat storage tank (10) along a direction vertical or parallel to the axis of the heat storage tank (10). The number of the electric heaters (21) is several, and at least one electric heater (21) is arranged between two adjacent first headers (31).

5. The single tank molten salt heat storage and heat exchange device of claim 1, wherein, The heat storage tank (10) comprises a tank body (11) and at least one stirring assembly (12) for stirring the molten salt in the tank body (11), and the stirring assembly (12) is arranged in the tank body (11).

6. The single tank molten salt heat storage and heat exchange device according to claim 5, characterized in that, The stirring assembly (12) comprises a stirring rod (121) and at least one stirring blade (122), one end of the stirring rod (121) is arranged on the tank body (11), and the at least one stirring blade (122) is rotatably arranged on the stirring rod (121).

7. The single tank molten salt heat storage and heat exchange device of claim 5, wherein, The number of the stirring assemblies (12) is several, and the several stirring assemblies (12) are uniformly arranged in the heat storage tank (10) along a circumferential direction. Alternatively, the stirring assembly (12) is arranged on the axis of the tank body (11).

8. The single tank molten salt heat storage and heat exchange device of claim 1, wherein, The number of the heat exchange pipelines (33) is several, and two ends of each heat exchange pipeline (33) are connected with the first header (31) and the second header (32) respectively. The second header (32) is provided with a heat supply pipeline, and the heat supply pipeline is provided with a heat supply medium for heat exchange with the heat exchange medium. The heat exchange medium is water, wherein the heat exchange medium absorbs the molten salt heat in the first header (31) to form high-temperature and high-pressure steam, and reaches the second header (32) through the heat exchange pipeline (33), exchanges heat with the heat supply medium in the heat supply pipeline to be cooled, and returns to the first header (31).

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