Phase change fused salt and solid heat storage combined heat storage device and working method thereof

Abstract

The invention relates to the technical field of heat storage devices, and discloses a phase change fused salt and solid heat storage combined heat storage device and a working method thereof. Comprising a combined heat storage device shell, a heat preservation material, a heat exchange gas channel, a solid heat storage brick, a shaped graphite-based solid heat storage block, a phase change fused salt packaging channel, a heater, an electrical wiring terminal, a power source, a gas fan and a heat exchanger. A layer of thermal insulation material is arranged in the combined heat storage device shell, a layer of solid heat storage bricks is arranged in the thermal insulation material, and the solid heat storage bricks are filled with the shaped graphite-based solid heat storage blocks; the heat exchange gas channels and the phase change fused salt packaging channels are alternately arranged in the shaped graphite-based solid heat storage block, and the two channels are arranged in parallel. According to the invention, through combination of the solid heat storage brick and the shaped graphite-based heat storage block, rapid heat storage and long-acting heat release are realized; the phase change fused salt packaging channel prolongs the heat output and improves the energy density.

Description

Technical Field

[0001] This invention relates to the field of thermal storage device technology, specifically to a combined phase change molten salt and solid thermal storage device and its working method. Background Technology

[0002] Currently, the thermal storage materials used in high-temperature solid thermal storage technologies both domestically and internationally are mostly magnesia bricks or alumina bricks. These materials exhibit stable performance and strong insulation under high temperature and pressure, and can be used in high-temperature and high-pressure energy storage environments above 800℃, possessing high fire resistance and insulation properties. However, solid thermal storage is sensible heat storage with low energy density, thus requiring a large footprint and is not suitable for applications with limited construction sites.

[0003] Molten salt thermal energy storage technology utilizes the absorption of heat when the temperature of liquid salt rises and the release of heat when the temperature falls to achieve the storage and release of heat. It has technical advantages such as a wide liquid temperature range, large temperature difference, high thermal density, and long lifespan. Conventional molten salt energy storage technology uses binary salt (60% sodium nitrate + 40% potassium nitrate) or Hitec salt (53% potassium nitrate + 40% sodium nitrite + 7% sodium nitrate) as the thermal storage medium. It adopts a dual-tank liquid sensible heat storage scheme. During energy storage, the molten salt pump extracts the low-temperature molten salt from the low-temperature tank and enters the molten salt heater (electric heater, steam / flue gas-molten salt heat exchanger, solar concentrator, etc.) to be heated into high-temperature molten salt and enters the high-temperature tank to achieve heat storage. During energy release, the high-temperature molten salt pump extracts the high-temperature molten salt from the high-temperature tank and enters the molten salt heat exchanger to heat water and generate steam. It can directly supply steam to industry, or it can be equipped with a steam turbine to drive the steam turbine to generate electricity, or generate low-parameter steam for industrial heating / heating. It has a wide range of applications in solar thermal power generation, thermal power plant thermal storage and peak shaving, molten salt thermal storage for heating and steam supply, compressed air energy storage and compressed heat storage. It is a low-cost, large-capacity and long-life long-term energy storage technology.

[0004] However, conventional dual-tank molten salt energy storage technology suffers from several drawbacks. The molten salt storage medium circulates between the hot and cold tanks, and the system includes critical materials and equipment such as molten salt circulation pipes, valves, and pumps. Ultra-high temperature chloride salts can cause severe corrosion to the system equipment, and upgrading the materials significantly increases the cost of the molten salt system. Furthermore, because the molten salt medium circulates between the hot and cold tanks, the molten salt must remain molten throughout the entire operating range. Molten salts have high melting points (220°C for binary salts and approximately 160°C for Hitec salts). To prevent solidification, the cold end temperature of the heat exchange medium during energy release must exceed its melting point, limiting the widespread application of ultra-high temperature molten salts. In addition, molten salt pipes and valves require continuous heat tracing, further increasing the operating costs of the molten salt energy storage system. Summary of the Invention

[0005] To address existing problems, this invention provides a combined phase change molten salt and solid heat storage device. By combining solid heat storage bricks with shaped graphite-based heat storage blocks, it achieves rapid heat storage and long-term heat release. The phase change molten salt encapsulation channel extends heat output and increases energy density. An independent circulation loop avoids thermal contamination, and the gas fan precisely controls the speed to optimize heat conduction. The modular design supports multi-level series and parallel connections, flexibly adapting to different scales of thermal energy demand, reducing expansion costs, and featuring a simple, stable, and feasible structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] This invention provides a combined phase change molten salt and solid heat storage device, which can be arranged in multiple stages. It includes a combined heat storage device shell, insulation material, heat exchange gas channels, solid heat storage bricks, shaped graphite-based solid heat storage blocks, a phase change molten salt encapsulation channel, a heater, electrical terminals, a power supply, a gas fan, and a heat exchanger. The combined heat storage device shell contains a layer of insulation material, within which a layer of solid heat storage bricks is placed. The solid heat storage bricks are filled with the shaped graphite-based solid heat storage blocks. Alternating arrangements of [missing information - likely related to heat storage devices] are present within the shaped graphite-based solid heat storage blocks. The heat exchange gas channel and the phase change molten salt encapsulation channel are arranged in parallel. The heater is uniformly disposed inside the shaped graphite-based solid heat storage block. The electrical terminal on one side of the heater is connected to a power source located outside the housing of the combined heat storage device via a wire. The heat exchange gas channel is connected to the heat exchanger through an external gas pipeline to form a gas circulation loop. A gas fan is installed on the external gas pipeline. A pipeline for the heat exchange gas is provided on one side of the heat exchanger, and a pipeline for the heat exchange medium is provided on the other side.

[0008] As a further improvement of the present invention, it also includes a gas storage tank, a gas replenishment device, and a gas replenishment valve; one branch of the heat exchange gas channel is connected to the gas storage tank and the gas replenishment device, and the gas replenishment valve is provided on the branch.

[0009] As a further improvement of the present invention, the heat exchange gas channel contains an inert gas or a non-oxidizing gas; the inert gas is nitrogen, helium, neon, argon, krypton or xenon; the non-oxidizing gas is N2, SF6 or CF4.

[0010] As a further improvement of the present invention, the solid heat storage brick is made of magnesium oxide or aluminum oxide.

[0011] As a further improvement of the present invention, the shaped graphite-based solid heat storage block is in the shape of a cube or a cylinder.

[0012] As a further improvement of the present invention, the cross-sectional shapes of the heat exchange gas channel and the phase change molten salt encapsulation channel are respectively one of the following: circular, square, triangular and trapezoidal.

[0013] As a further improvement of the present invention, the phase change molten salt encapsulation channel is provided with an ultra-high temperature molten salt formulation based on a chloride system or a carbonate system.

[0014] As a further improvement of the present invention, the heat exchanger adopts a single-stage or multi-stage heat exchange structure, and the heat exchange medium is one of air, carbon dioxide, water and steam.

[0015] As a further improvement of the present invention, the voltage level of the power supply is 380V, 690V, 10kV, 35kV or 66kV.

[0016] The present invention also provides a method for operating a combined phase change molten salt and solid thermal storage device, comprising the following steps: The gas fan is started, and gas is introduced into the heat exchange gas channel through the external gas pipeline. If the heat exchange gas channel contains inert gas, inert gas is continuously supplied to the heat exchange gas channel through the preparation machine until the oxygen concentration in the channel is ≤0.5%. If the heat exchange gas channel contains non-oxidizing gas, non-oxidizing gas is supplied to the heat exchange gas channel through a high-pressure liquefied gas cylinder, and the gas pressure is adjusted to 0.2-0.5 MPa through the gas supply valve. When the heat storage mode is activated, the heater is controlled to operate with a single-stage or multi-stage heat exchange structure, so that the shaped graphite-based solid heat storage block is heated to 600-800℃, and at the same time, the ultra-high temperature molten salt in the phase change molten salt encapsulation channel undergoes phase change and heat absorption. When the heat release mode is activated, a heat exchange medium is introduced into the pipeline on the other side of the heat exchanger, so that the heat stored in the shaped graphite-based solid heat storage block and the molten salt in the phase change molten salt encapsulation channel is released to the heat exchange medium at the heat exchanger 13 through the heat exchange gas channel and the external gas pipeline 9.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This device achieves rapid heat storage and long-term heat release through a combination of solid heat storage bricks (high thermal conductivity magnesium oxide / alumina) and shaped graphite-based heat storage blocks (high specific heat capacity). The latent heat storage of the phase change molten salt encapsulation channel further extends the heat output time and improves the overall energy density. The heat exchange gas channel and the heat exchanger form an independent circulation loop, avoiding thermal pollution to the environment caused by gas leakage. At the same time, the flow rate is precisely controlled by the gas fan to optimize the heat transfer efficiency. The modular design supports multi-stage series or parallel connection to adapt to different scales of heat energy demand (such as industrial waste heat recovery and district heating) and reduce expansion costs.

[0018] Preferably, the gas storage tank and the replenishment valve monitor and adjust the pressure of the heat exchange gas channel (0.2-0.5MPa) in real time to prevent channel deformation or molten salt leakage due to pressure fluctuations and improve the stability of system operation; the automatic gas replenishment function reduces manual intervention, for example, when the pressure is lower than 0.1MPa, the replenishment device is automatically started to reduce the risk of shutdown, which is suitable for unattended scenarios (such as energy storage stations in remote areas).

[0019] Preferably, an inert gas or a non-oxidizing gas is used as the heat exchange medium to prevent the solid heat storage bricks or graphite blocks from being oxidized at high temperatures, thus extending the equipment's lifespan.

[0020] Preferably, magnesium oxide and aluminum oxide can withstand temperatures above 800°C, making them suitable for ultra-high temperature molten salts, such as chloride salt systems with melting points of 600-800°C, to meet phase transformation requirements. Magnesium oxide / alumina raw materials are readily available, and their cost is significantly lower than that of ceramic-based materials, making them suitable for large-scale industrial applications.

[0021] Preferably, the cubic or cylindrical structures can be closely arranged to reduce the porosity inside the heat storage device and increase the energy storage density per unit volume; the regular shape avoids local thermal stress concentration and reduces the risk of cracking of the graphite block, making it particularly suitable for scenarios with frequent charging and discharging, such as power grid peak shaving.

[0022] Preferably, circular channels reduce gas / molten salt flow resistance and lower gas fan energy consumption; square channels facilitate processing and modular assembly; triangular or trapezoidal channels enhance the heat exchange efficiency between gas and molten salt by increasing surface area, making them suitable for high power density applications.

[0023] Preferably, chloride salt systems (such as NaCl-KCl-ZnCl2) have a melting point of 600-800℃, and carbonate systems (such as Li2CO3-Na2CO3-K2CO3) have a melting point of 500-700℃, which can store high-temperature heat sources (>500℃) such as industrial waste heat and solar thermal power generation, breaking through the temperature limitations of traditional water / steam energy storage; the cost of chloride / carbonate raw materials is more than 50% lower than that of fluoride salts, and they are non-toxic and harmless, meeting the requirements of green energy storage.

[0024] Preferably, the single-stage heat exchange structure is suitable for low-temperature difference scenarios, such as building heating, while the multi-stage structure can realize the cascade utilization of heat energy with high-temperature difference (≥300℃), which greatly improves the comprehensive energy utilization rate. Air is low-cost, carbon dioxide is in a supercritical state and has high heat exchange efficiency, and water / steam is a mature industrial medium. It can be switched according to user needs without modifying the main structure of the device.

[0025] Preferably, low voltage (380V / 690V) is suitable for small and medium-sized devices (such as energy storage in commercial complexes), while high voltage (10kV-66kV) is directly connected to the power grid to reduce transformer losses and lower the cost of long-distance power transmission. The high voltage level supports the construction of MW-level large-scale energy storage stations to meet the large-scale energy storage needs of grid peak shaving and renewable energy consumption.

[0026] This working method achieves unattended and safe operation through oxygen concentration monitoring, pressure regulation, and segmented temperature control; the heat storage mode starts up quickly, and the heat release mode can adjust the flow rate of the heat exchange medium in real time according to demand, adapting to dynamic load scenarios such as power grid frequency regulation and industrial steam supply. Attached Figure Description

[0027] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and are not intended to specifically limit the shapes and proportions of the components. In the drawings: Figure 1 This is a schematic diagram of a combined phase change molten salt and solid heat storage device in the embodiment. Figure 2 This is a flowchart illustrating the working steps of a combined phase change molten salt and solid heat storage device in the embodiment.

[0028] The components include: 1. the outer shell of the combined thermal storage device; 2. the insulation material; 3. the heat exchange gas channel; 4. the solid thermal storage brick; 5. the shaped graphite-based solid thermal storage block; 6. the phase change molten salt encapsulation channel; 7. the electrical wiring terminal; 8. the power supply; 9. the external gas pipeline; 10. the gas fan; 11. the gas storage tank; 12. the gas replenishment device; 13. the heat exchanger; 14. the heat exchange medium; and 15. the gas replenishment valve. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0030] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Example 1 like Figure 1 As shown, this embodiment provides a combined phase change molten salt and solid heat storage device, which can be arranged in multiple stages. It includes a combined heat storage device shell 1, insulation material 2, heat exchange gas channel 3, solid heat storage brick 4, shaped graphite-based solid heat storage block 5, phase change molten salt encapsulation channel 6, heater, electrical wiring terminal 7, power supply 8, gas fan 10, heat exchanger 13, gas storage tank 11, gas replenishment device 12, and gas replenishment valve 15.

[0033] The combined heat storage device has an inner layer of insulation material 2 inside the outer shell 1, and a layer of solid heat storage brick 4 inside the insulation material 2. The solid heat storage brick 4 is filled with the shaped graphite-based solid heat storage block 5. The heat exchange gas channel 3 and the phase change molten salt encapsulation channel 6 are alternately arranged in the shaped graphite-based solid heat storage block 5, and the two channels are arranged in parallel.

[0034] The heater is uniformly arranged inside the shaped graphite-based solid heat storage block 5. The electrical terminal 7 on one side of the heater is connected to the power supply 8 located outside the housing 1 of the combined heat storage device via a wire. The heat exchange gas channel 3 is connected to the heat exchanger 13 via an external gas pipe 9 to form a gas circulation loop. The gas fan 10 is installed on the external gas pipe 9. A pipeline for the heat exchange gas is provided on one side of the heat exchanger 13, and a pipeline for the heat exchange medium 14 is provided on the other side.

[0035] One branch of the heat exchange gas channel 3 is connected to the gas storage tank 11 and the gas replenishment device 12, and the gas replenishment valve 15 is provided on the branch.

[0036] The heat exchange gas channel 3 contains an inert gas, which may be nitrogen, helium, neon, argon, krypton, or xenon; the gas replenishment device 12 is an inert gas generator.

[0037] The solid heat storage brick 4 is made of magnesium oxide or aluminum oxide.

[0038] The shaped graphite-based solid heat storage block 5 is a cube or a cylinder.

[0039] The heat exchange gas channel 3 and the phase change molten salt encapsulation channel 6 have cross-sectional shapes that are one of the following: circular, square, triangular, and trapezoidal.

[0040] The phase change molten salt encapsulation channel 6 is equipped with an ultra-high temperature molten salt formulation based on the chloride salt system NaCl-KCl-ZnCl2 or the carbonate system Li2CO3-Na2CO3-K2CO3.

[0041] The heat exchanger 13 adopts a single-stage or multi-stage heat exchange structure, and the heat exchange medium 14 is one of air, carbon dioxide, water and steam.

[0042] The voltage level of the power supply 8 is 380V, 690V, 10kV, 35kV or 66kV.

[0043] Example 2 The difference between this embodiment and Embodiment 1 is that: 1) The heat exchange gas channel 3 contains a non-oxidizing gas, including N2, SF6 or CF4, and the gas replenishment device 12 is a high-pressure liquefied gas cylinder.

[0044] Example 3 The difference between this embodiment and Embodiment 1 is that: like Figure 2 As shown, the present invention also provides a method for operating a combined phase change molten salt and solid thermal storage device, comprising the following steps: The gas blower 10 is started, and gas is introduced into the heat exchange gas channel 3 through the external gas pipeline 9. If the heat exchange gas channel 3 contains inert gas, inert gas is continuously supplied to the heat exchange gas channel 3 through the preparation machine until the oxygen concentration in the channel is ≤0.5%. If the heat exchange gas channel 3 contains non-oxidizing gas, non-oxidizing gas is supplied to the heat exchange gas channel 3 through a high-pressure liquefied gas cylinder, and the gas pressure is adjusted to 0.2-0.5 MPa through the gas supply valve 15. When the heat storage mode is activated, the heater is controlled to operate with a single-stage or multi-stage heat exchange structure, so that the shaped graphite-based solid heat storage block 5 is heated to 600-800℃, and at the same time, the ultra-high temperature molten salt in the phase change molten salt encapsulation channel 6 undergoes phase change and heat absorption. When the heat release mode is activated, the heat exchange medium 14 is introduced into the pipeline on the other side of the heat exchanger 13, so that the heat stored in the shaped graphite-based solid heat storage block 5 and the molten salt in the phase change molten salt encapsulation channel 6 is released to the heat exchange medium 14 at the heat exchanger 13 through the heat exchange gas channel 3 and the external gas pipeline 9.

[0045] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A phase change molten salt and solid heat storage combined heat storage device, characterized by, The application relates to a multi-stage combined heat storage device, which comprises a combined heat storage device shell (1), heat preservation material (2), heat exchange gas channels (3), solid heat storage bricks (4), shaped graphite-based solid heat storage blocks (5), phase change molten salt encapsulation channels (6), a heater, electrical connection terminals (7), a power supply (8), a gas blower (10) and a heat exchanger (13). The combined heat storage device shell (1) is provided with a layer of heat preservation material (2), the heat preservation material (2) is provided with a layer of solid heat storage bricks (4), and the solid heat storage bricks (4) are filled with the shaped graphite-based solid heat storage blocks (5). The shaped graphite-based solid heat storage blocks (5) are alternately provided with the heat exchange gas channels (3) and the phase change molten salt encapsulation channels (6), and the two kinds of channels are arranged in parallel. The heater is uniformly arranged in the shaped graphite-based solid heat storage blocks (5), the electrical connection terminals (7) arranged on one side of the heater are connected with the power supply (8) outside the combined heat storage device shell (1) through wires, the heat exchange gas channels (3) are connected with the heat exchanger (13) through external gas pipelines (9) to form a gas circulation loop, the gas blower (10) is arranged on the external gas pipelines (9), and one side of the heat exchanger (13) is provided with a pipeline through which heat exchange gas flows, and the other side of the heat exchanger (13) is provided with a pipeline through which a heat exchange medium (14) flows.

2. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The heat exchange gas channels (3) are provided with a gas storage tank (11), a gas supplementing device (12) and a gas supplementing valve (15).

3. The phase change molten salt and solid heat storage combined heat storage device according to claim 2, characterized in that, The heat exchange gas channels (3) are filled with inert gas or non-oxidizing gas; the inert gas is nitrogen, helium, neon, argon, krypton or xenon; and the non-oxidizing gas is N2, SF6 or CF4.

4. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The solid heat storage bricks (4) are made of magnesium oxide or aluminum oxide material.

5. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The shaped graphite-based solid heat storage blocks (5) are in the shape of a cube or a cylinder.

6. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The cross-sectional shape of the heat exchange gas channels (3) and the phase change molten salt encapsulation channels (6) is one of a circle, a square, a triangle and a trapezoid.

7. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The phase change molten salt encapsulation channels (6) are provided with an ultrahigh-temperature molten salt formula based on a chloride salt system or a carbonate salt system.

8. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The heat exchanger (13) adopts a single-stage or multi-stage heat exchange structure, and the heat exchange medium (14) is one of air, carbon dioxide, water and steam.

9. The phase change molten salt and solid heat storage combined heat storage device according to claim 1, characterized in that, The voltage level of the power supply (8) is 380V, 690V, 10kV, 35kV or 66kV.

10. The method of operating a phase change molten salt and solid thermal energy storage combined thermal energy storage device according to any one of claims 1 to 9, wherein, The application further relates to a method for operating the combined heat storage device. Start the gas blower (10) to fill gas into the heat exchange gas passage (3) through the external gas pipeline (9); if the heat exchange gas passage (3) is filled with inert gas, continuously supplement inert gas into the heat exchange gas passage (3) through the preparation machine until the oxygen concentration in the passage is less than or equal to 0.5%; if the heat exchange gas passage (3) is filled with non-oxidizing gas, supplement non-oxidizing gas into the heat exchange gas passage (3) through the high-pressure liquefied gas cylinder, and adjust the gas pressure to 0.2-0.5 MPa through the gas supplement valve (15); When the heat storage mode is started, the heater is controlled to operate in a single-stage or multi-stage heat exchange structure, so that the shaped graphite-based solid heat storage block (5) is heated to 600-800℃, and the ultrahigh-temperature molten salt in the phase-change molten salt encapsulation passage (6) is phase-changed to absorb heat; When the heat release mode is started, the heat exchange medium (14) is introduced into the pipeline on the other side of the heat exchanger (13), so that the heat storage of the shaped graphite-based solid heat storage block (5) and the molten salt in the phase-change molten salt encapsulation passage (6) is released to the heat exchange medium (14) at the heat exchanger (13) through the heat exchange gas passage (3) and the external gas pipeline (9).

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