Single-tank fused salt heat storage system and method

Abstract

The invention relates to the technical field of energy storage, in particular to a single-tank fused salt heat storage system and method.The single-tank fused salt heat storage system comprises a fused salt storage tank, the interior of the fused salt storage tank is divided into a first area, a second area and a third area through partition layers, conveying pipes are arranged in the first area, the second area and the third area respectively, and fused salt pumps are arranged at the upper ends of the conveying pipes respectively; the fused salt pumps are connected with fused salt heaters through pipelines respectively, outlets of the fused salt heaters are connected with the bottoms of the first area, the second area and the third area through backflow pipes respectively, and the fused salt heaters are connected with a fused salt heat exchanger in parallel. A single fused salt storage tank system is adopted, the occupied area of the fused salt storage tank and the manufacturing cost of the storage tank are greatly saved, and the occupied area of the storage tank system is reduced by 50% or above; molten salt dead zones are reduced, the molten salt utilization rate is increased, the molten salt storage amount is reduced by more than 20%, the molten salt consumption is obviously reduced, and the system cost is reduced; the system has the advantages of being simple, low in manufacturing cost, small in occupied area and the like, and the advantages of a fused salt heat storage system can be brought into full play.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a single-tank molten salt heat storage system and method. Background Art

[0002] Molten salt heat storage is a sensible heat storage technology with the advantages of low price, high operating temperature, environmental friendliness and non-flammability. It is widely used in solar thermal power plants. There are many successful commercial application cases in the world, and most of them use molten salt heat storage technology. At present, it has been promoted and applied to the fields of flexibility transformation of thermal power plants and clean heating.

[0003] At present, the field of molten salt heat storage mainly adopts a double-tank molten salt heat storage system, which has two molten salt storage tanks, a low-temperature tank and a high-temperature tank. When storing energy, the molten salt in the low-temperature tank is pumped out using a molten salt pump to absorb heat (it can absorb the energy of sunlight on the absorber, or it can be the heat energy provided by electric heating). The temperature of the molten salt rises and flows into the high-temperature tank, and the heat energy is stored; when releasing energy, the molten salt in the high-temperature tank is pumped out using a molten salt pump, exchanges heat with water, generates steam for external use, and the temperature of the molten salt drops and flows back to the low-temperature tank, completing a cycle.

[0004] When the molten salt storage system is in operation, the molten salt circulates continuously between the low-temperature storage tank and the high-temperature storage tank. Both the low-temperature storage tank and the high-temperature storage tank need to meet all molten salt storage requirements, resulting in a large amount of storage space waste. At the same time, due to the minimum liquid level dead zone of the molten salt pump, there is a large amount of useless molten salt in the two storage tanks, which increases the system cost. Summary of the invention

[0005] The object of the present invention is to provide a single-tank molten salt heat storage system and method, which can solve the above-mentioned technical problems.

[0006] The present invention provides a single-tank molten salt heat storage system, comprising a molten salt storage tank, wherein the interior of the molten salt storage tank is divided into region one, region two and region three by a partition layer, wherein each of the region one, region two and region three is provided with a delivery pipe, wherein the upper ends of the delivery pipes are respectively provided with molten salt pumps, wherein the molten salt pumps are respectively connected to molten salt heaters through pipelines, wherein the outlets of the molten salt heaters are respectively connected to the bottoms of the region one, region two and region three through reflux pipes, wherein the molten salt heaters are connected in parallel with a molten salt heat exchanger. The molten salt storage tank is a cylindrical structure, wherein the internal partition layer is an annular partition layer, and regions two and three are similar to concentric circles.

[0007] Preferably, a first valve, a second valve and a third valve corresponding to each molten salt pump are respectively provided on the pipeline between the molten salt pump and the molten salt heater.

[0008] Preferably, a molten salt heater valve is provided on the pipeline corresponding to the molten salt heater.

[0009] Preferably, a molten salt heat exchanger valve is provided on the pipeline corresponding to the molten salt heat exchanger.

[0010] Preferably, the reflux pipe is provided with a first molten salt valve, a second molten salt valve and a third molten salt valve corresponding to area one, area two and area three, respectively.

[0011] Preferably, the outer wall of the molten salt storage tank is covered with a thermal insulation layer, and the bottom of the molten salt storage tank is provided with a molten salt tank foundation.

[0012] Preferably, the separation layer is made of insulating refractory bricks or sandwich steel plates containing an insulating layer.

[0013] Preferably, the end of the reflux pipe is connected to a molten salt distributor.

[0014] Preferably, a molten salt siphon is integrated inside the molten salt storage tank.

[0015] Preferably, the molten salt heat exchanger is connected to a cooling medium inlet and a cooling medium outlet through pipelines, and a cooling medium booster pump is provided on the pipeline corresponding to the cooling medium inlet.

[0016] The present invention also provides a heat storage method based on the above-mentioned single-tank molten salt heat storage system, comprising the following steps:

[0017] When storing energy:

[0018] Areas 1 and 2 are filled with molten salt, and area 3 is empty. The molten salt pump extracts the molten salt in area 1, heats it through the molten salt heater, and then discharges it into area 3, until all the molten salt in area 1 is heated and discharged into area 3; then the molten salt in area 2 is extracted, heated by the molten salt heater, and then all discharged into area 1, completing the energy storage process;

[0019] When releasing energy:

[0020] The molten salt pump extracts the high-temperature molten salt in area one, and turns it into low-temperature molten salt after heat exchange through the molten salt heat exchanger, which is then discharged into area two. The cooling medium is heated in the molten salt heat exchanger to supply heat to the outside until all the molten salt in area one is discharged into area two after heat exchange. Then the molten salt in area three is extracted, and after passing through the molten salt heat exchanger, it is all discharged into area one, completing the energy release process.

[0021] Beneficial effects:

[0022] The present invention separates a plurality of areas by arranging a partition layer in a single molten salt storage tank. Compared with the traditional molten salt cold and hot dual tank energy storage system, the present invention adopts a single molten salt storage tank system, which greatly saves the floor space and tank cost of the molten salt storage tank, and the floor space of the tank system is reduced by more than 50%; the molten salt dead zone is reduced to improve the utilization rate of the molten salt, the molten salt storage volume is reduced by more than 20%, the molten salt consumption is significantly reduced, and the system cost is reduced; the present invention has the advantages of simple system, low cost, small floor space, etc., and can give full play to the advantages of the molten salt heat storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a schematic diagram of the overall structure of Example 1 of the present invention.

[0025] Explanation of the accompanying drawings: 1-molten salt storage tank, 101-area one, 102-area two, 103-area three, 2-partition layer, 3-delivery pipe, 301-first valve, 302-second valve, 303-third valve, 401-first molten salt pump, 402-second molten salt pump, 403-third molten salt pump, 5-molten salt heater, 501-molten salt heater valve, 6-reflux pipe, 601-first molten salt valve, 602-second molten salt valve, 603-third molten salt valve, 7-molten salt heat exchanger, 701-molten salt heat exchanger valve, 702-cooling medium inlet, 703-cooling medium outlet, 7021-cooling medium booster pump, 8-insulation layer, 9-molten salt tank foundation, 10-molten salt distributor, 11-molten salt siphon. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Example 1

[0030] A single tank molten salt heat storage system, such as Figure 1 As shown, it includes a molten salt storage tank 1, and the interior of the molten salt storage tank 1 is divided by a partition layer 2 to form area one 101, area two 102 and area three 103. The molten salt storage tank 1 is a cylindrical structure, and the internal partition layer 2 is an annular partition layer. Areas two and three are similar to concentric circles. The material of the partition layer 2 is made of insulating refractory bricks, sandwich steel plates containing insulating layers, and other materials.

[0031] Each of the area 101, the area 2 102 and the area 3 103 is provided with a delivery pipe 3, and a molten salt pump (respectively a first molten salt pump 401, a second molten salt pump 402 and a third molten salt pump 403) is respectively provided at the upper end of the delivery pipe 3, and the molten salt pumps are respectively connected to the molten salt heater 5 through a pipeline, and a molten salt heater valve 501 is provided on the pipeline corresponding to the molten salt heater 5; a first valve 301, a second valve 302 and a third valve 303 corresponding to each molten salt pump are respectively provided on the pipeline between the molten salt pump and the molten salt heater 5; the outlet of the molten salt heater 5 is respectively connected to the area 101 through a reflux pipe 6. The bottoms of area one 101, area two 102 and area three 103 are connected, and the first molten salt valve 601, the second molten salt valve 602 and the third molten salt valve 603 corresponding to area one 101, area two 102 and area three 103 are respectively provided on the return pipe 6; the molten salt heater 5 is connected in parallel with the molten salt heat exchanger 7, and a molten salt heat exchanger valve 701 is provided on the pipeline corresponding to the molten salt heat exchanger 7, and a cooling medium inlet 701 and a cooling medium outlet 702 are respectively connected to the molten salt heat exchanger 7 through pipelines, and a cooling medium booster pump 7021 is provided on the pipeline corresponding to the cooling medium inlet 702.

[0032] The outer wall of the molten salt storage tank 1 is coated with an insulation layer 8, and a molten salt tank foundation 9 is provided at the bottom of the molten salt storage tank 1. The molten salt tank foundation 9 plays a bearing role, bearing the weight of the molten salt storage tank and the molten salt inside, ensuring that the storage tank is stably placed on the ground; it also plays a heat-insulating role. The molten salt tank foundation will use heat-insulating materials or designs to reduce the heat transfer between the molten salt and the ground, prevent the ground from being damaged by high temperature, and also help to keep the temperature of the molten salt stable. The end of the return pipe 6 is connected to a molten salt distributor 10 to ensure that the molten salt can flow and distribute evenly in the system to avoid local overheating or overcooling, which helps to improve the heat transfer efficiency and stability of the entire system, so that heat can be more evenly transferred to the equipment or area that needs to be heated or cooled. A molten salt siphon 11 is integrated inside the molten salt storage tank 1, which can ensure that the molten salt in a certain area is discharged when the molten salt pump in that area is damaged; at the same time, the molten salt siphon can also mix the molten salt in two different areas through the siphon effect, adjust the temperature and drain the liquid, so as to realize the molten salt temperature adjustment and salt mixing process in different areas inside the storage tank, without the need to set up a special molten salt temperature control pump and corresponding pipelines.

[0033] A single-tank molten salt heat storage method comprises the following steps:

[0034] During energy storage: two of the regions 101, 102, and 103 formed by the partition layer 2 inside the molten salt storage tank 1 are filled with molten salt (e.g., regions 1 and 2), and the other region is empty (e.g., region 3). The first molten salt pump 401 at the top of the molten salt storage tank extracts the molten salt in region 101, and after heating it through the molten salt heater 5, it is switched through the molten salt valve (only the third molten salt valve 603 is opened), and discharged into region 3 103 through the molten salt distributor 10 of region 3 103, until all the molten salt in region 101 is heated and discharged into region 3 103; then, the molten salt in region 2 102 is also extracted, and after being heated by the molten salt heater 5, it is all discharged into region 1, thereby completing the energy storage process.

[0035] When releasing energy:

[0036] The molten salt storage tank 1 is divided by the partition layer 2 into two areas, namely, area 1 101, area 2 102, and area 3 103, which are filled with high-temperature molten salt (e.g., area 1 and area 3), and the other area is empty (e.g., area 2). The first molten salt pump 401 at the top of the molten salt storage tank 1 extracts the high-temperature molten salt in area 1, and converts it into low-temperature molten salt after heat exchange through the molten salt heat exchanger 7. After the molten salt valve is switched (only the second molten salt valve 602 is opened), it is discharged into area 2 102 through the molten salt distributor 10 of area 2 102. The cooling medium is heated in the molten salt heat exchanger 7 to supply heat to the outside until all the molten salt in area 1 101 is discharged into area 2 102 after heat exchange; then, the molten salt in area 3 103 is also extracted, and after passing through the molten salt heat exchanger 7, it is all discharged into area 1 101, thereby completing the energy release process.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single tank molten salt heat storage system, characterized in that It includes a molten salt storage tank, the interior of the molten salt storage tank is divided into area one, area two and area three by a partition layer, and delivery pipes are provided in the areas one, two and three. Molten salt pumps are provided at the upper ends of the delivery pipes, and the molten salt pumps are connected to molten salt heaters through pipelines. The outlets of the molten salt heaters are connected to the bottoms of the areas one, two and three through reflux pipes, and the molten salt heaters are connected in parallel with molten salt heat exchangers.

2. The single-tank molten salt heat storage system according to claim 1, characterized in that: A first valve, a second valve and a third valve corresponding to each molten salt pump are respectively arranged on the pipeline between the molten salt pump and the molten salt heater.

3. The single-tank molten salt heat storage system according to claim 1, characterized in that: A molten salt heater valve is provided on the pipeline corresponding to the molten salt heater.

4. The single-tank molten salt heat storage system according to claim 1, characterized in that: A molten salt heat exchanger valve is provided on the pipeline corresponding to the molten salt heat exchanger.

5. The single-tank molten salt heat storage system according to claim 1, characterized in that: The reflux pipe is provided with a first molten salt valve, a second molten salt valve and a third molten salt valve corresponding to area one, area two and area three, respectively.

6. The single-tank molten salt heat storage system according to claim 1, characterized in that: The outer wall of the molten salt storage tank is covered with a thermal insulation layer, and the bottom of the molten salt storage tank is provided with a molten salt tank foundation.

7. The single-tank molten salt heat storage system according to claim 1, characterized in that: The material of the separation layer is thermal insulation refractory bricks or sandwich steel plates containing thermal insulation layers.

8. The single-tank molten salt heat storage system according to claim 1, characterized in that: The end of the reflux pipe is connected with a molten salt distributor.

9. The single-tank molten salt heat storage system according to claim 1, characterized in that: A molten salt siphon is integrated inside the molten salt storage tank.

10. A heat storage method based on the single-tank molten salt heat storage system according to any one of claims 1 to 9, characterized in that: The following steps are involved: When storing energy: Areas 1 and 2 are filled with molten salt, and area 3 is empty. The molten salt pump extracts the molten salt in area 1, heats it through the molten salt heater, and then discharges it into area 3, until all the molten salt in area 1 is heated and discharged into area 3; then the molten salt in area 2 is extracted, heated by the molten salt heater, and then all discharged into area 1, completing the energy storage process; When releasing energy: The molten salt pump extracts the high-temperature molten salt in area one, and turns it into low-temperature molten salt after heat exchange through the molten salt heat exchanger, which is then discharged into area two. The cooling medium is heated in the molten salt heat exchanger to supply heat to the outside until all the molten salt in area one is discharged into area two after heat exchange. Then the molten salt in area three is extracted, and after passing through the molten salt heat exchanger, it is all discharged into area one, completing the energy release process.

Images