A stirred metal hydride hydrogen storage device and method of operation thereof

Abstract

This invention discloses a stirred metal hydride hydrogen storage device and its operation method. The device includes a cylindrical reaction vessel and an outer shell. The reaction vessel is disposed inside the outer shell, and a closed heat exchange fluid cavity is formed between the reaction vessel and the outer shell. A stirrer is provided on the inner axis of the reaction vessel. The stirrer consists of a rotating shaft and blades. The rotating shaft has a hollow structure inside, which forms a flow channel for the heat exchange fluid. The bottom end of the rotating shaft is connected to the cavity. The interior of the reaction vessel is filled with metal hydride. The hydrogen storage device provided by this invention realizes the circulation and mixing of metal hydride in the reaction vessel through the stirrer, continuously transporting the high-temperature, low-reaction-rate metal hydride to the vicinity of the heat exchange surface, effectively improving the rate of hydrogen absorption and desorption reactions, and improving the hydrogen absorption / desorption performance of the hydrogen storage tank.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage technology, specifically to a stirred metal hydride hydrogen storage device and its operation method. Background Technology

[0002] Currently, there are three main hydrogen storage schemes: high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, and solid-state hydrogen storage. Among them, high-pressure gaseous hydrogen storage has low hydrogen storage density and high storage pressure, and in order to improve economic efficiency, the storage pressure will continue to increase, posing significant safety risks. Cryogenic liquid hydrogen storage, although having a high hydrogen storage density, requires a large amount of energy to maintain the low temperature, resulting in poor economic efficiency, and also requires high insulation of the container. Solid-state hydrogen storage, especially solid-state hydrogen storage based on metal hydrides, has advantages such as low storage pressure, high hydrogen storage density, good hydrogen storage safety, and high hydrogen purity, and is an important direction for the future development of hydrogen storage technology.

[0003] Existing solid-state hydrogen storage systems primarily utilize heat exchange arrangements such as embedding heat exchange tube bundles in the bed material, using finned heat exchange tubes, designing heat exchange channels, and adding heat exchange jackets outside the hydrogen storage tank to quickly remove the heat released during hydrogen absorption and the heat required for hydrogen release. Existing embedded finned heat exchangers can exchange heat well with adjacent metal hydrides; however, due to the low thermal conductivity of metal hydrides, reactants far from the heat exchange surface have poor heat exchange conditions and are minimally affected by the heat exchanger, still resulting in slow reactions and prolonged hydrogen absorption / release times.

[0004] When using metal hydrides as the hydrogen storage medium, after multiple hydrogen storage and degassing cycles, the metal hydrides tend to pulverize and become finer particles. These finer metal hydrides deposit at the bottom of the storage tank under gravity, causing a decrease in the effective thermal conductivity of the metal hydrides and a deterioration in the heat exchange capacity of the storage tank. Furthermore, the fine metal hydride particles deposited at the bottom of the storage tank expand during hydrogen storage and degassing cycles, exerting greater pressure on the inner wall of the reaction vessel, and may even cause deformation and cracking of the wall surface. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a stirred metal hydride hydrogen storage device and its operation method. By installing a stirrer in the hydrogen storage device, the impact of metal hydride pulverization can be reduced, the hydrogen storage / discharge performance of the hydrogen storage reactor can be significantly increased, and the reaction time can be shortened.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the invention, a stirred metal hydride hydrogen storage device is provided, comprising a cylindrical reaction vessel and an outer shell, wherein the reaction vessel is disposed inside the outer shell, and a closed heat exchange fluid cavity is formed between the reaction vessel and the outer shell; a stirrer is provided on the inner axis of the reaction vessel, the stirrer consisting of a rotating shaft and blades, the rotating shaft having a hollow structure inside, the hollow structure forming a flow channel for the heat exchange fluid, and the bottom end of the rotating shaft communicating with the cavity; the interior of the reaction vessel is filled with metal hydride.

[0008] In some embodiments of the present invention, the rotating shaft extends outside the reaction vessel, and a shaft seal is provided at the position where the rotating shaft contacts the reaction vessel.

[0009] In some embodiments of the present invention, the top end of the rotating shaft is a heat exchange fluid inlet and the bottom end is a heat exchange fluid outlet, and the heat exchange fluid outlet of the rotating shaft also serves as the heat exchange fluid inlet of the heat exchange fluid cavity.

[0010] In some embodiments of the present invention, the upper part of the heat exchange fluid cavity is provided with two heat exchange fluid outlets, which are symmetrically arranged.

[0011] In some embodiments of the present invention, the top of the reaction vessel is further provided with a hydrogen inlet and outlet.

[0012] In some embodiments of the present invention, an upper helical blade and a lower helical blade are provided on the rotating shaft, and the angle between the upper helical blade and the axis of the rotating shaft is smaller than the angle between the lower helical blade and the axis of the rotating shaft.

[0013] In some embodiments of the present invention, the rotating shaft is connected to a low-speed motor via a transmission device, wherein the transmission device is a bevel gear.

[0014] In some embodiments of the present invention, the amount of metal hydride filled is 60%-80% of the volume of the reaction vessel.

[0015] In some embodiments of the present invention, the outer casing includes the outer wall surface of the heat exchange fluid cavity and a heat insulation material.

[0016] In a second aspect of the present invention, a method for operating a stirred metal hydride hydrogen storage device is provided, comprising the following steps:

[0017] (1) During the temperature rise stage of the hydrogen absorption reaction and the temperature drop stage of the hydrogen release reaction, the stirrer is continuously rotated.

[0018] (2) When absorbing / releasing hydrogen, stop running the stirrer after the temperature reaches the highest / lowest point;

[0019] (3) When the temperature of the metal hydride near the heat exchange surface decreases / increases and the reaction rate increases, rotate the stirrer again;

[0020] (4) Rotation stops when metal hydrides of different temperatures and reaction rates have completed circulation or mixing in the reaction vessel, and the above cycle of rotation and stopping continues until the reaction is complete.

[0021] One or more technical solutions of the present invention have the following beneficial effects:

[0022] (1) The hydrogen storage device provided by the present invention realizes the circulation and mixing of metal hydrides in the reaction vessel through a stirrer, which breaks through the limitation of low thermal conductivity and slow heat transfer rate of metal hydrides in traditional hydrogen storage reactors due to the stationary nature of metal hydrides. It continuously transports metal hydrides with high temperature and low reaction rate to the vicinity of the heat exchange surface, effectively improving the rate of hydrogen absorption and desorption reactions, and improving the hydrogen absorption / desorption performance of the hydrogen storage tank.

[0023] (2) The hydrogen storage device provided by the present invention has a hollow structure for the rotating shaft of the stirrer, which is filled with heat exchange fluid. It can simultaneously function as a finned tube heat exchanger to enhance heat exchange, accelerate the removal of heat during the hydrogen absorption process and the supply of heat during the hydrogen release process, effectively improve the reaction rate and improve the performance of the hydrogen storage tank.

[0024] (3) The hydrogen storage tank provided by the present invention realizes the periodic circulation and mixing of metal hydrides through stirring, which can ensure that the metal hydride powder is mixed evenly during the hydrogen absorption / desorption process, effectively reducing the deterioration of local heat transfer performance caused by the powdering of hydrogen storage alloy after multiple hydrogen absorption and desorption, and improving the performance of the hydrogen storage tank.

[0025] (4) The hydrogen storage tank provided by the present invention is in motion under the action of the stirrer during the hydrogen absorption and expansion process of the metal hydride, which prevents the local accumulation of the metal hydride, effectively reduces the pressure on the inner wall of the reactor caused by the expansion, avoids the reactor from deforming and being damaged due to local stress, and ensures the safety and life of the hydrogen storage tank.

[0026] (5) The operating method provided by the present invention can reduce the energy consumed by the rotation of the stirrer while achieving the purpose of transporting and mixing metal hydrides and improving the hydrogen absorption / desorption efficiency by cyclically starting and stopping the stirrer. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the stirred metal hydride hydrogen storage device of the present invention.

[0028] Figure 2 This is a schematic diagram of the hydrogen storage tank structure of the stirred metal hydride hydrogen storage device of the present invention;

[0029] Figure 3 This is a schematic diagram of the internal structure of the stirred metal hydride hydrogen storage device of the present invention.

[0030] Figure 4 This is a schematic diagram of the stirrer in the stirred metal hydride hydrogen storage device of the present invention.

[0031] In the diagram: 1. Low-speed motor; 2. Transmission device; 3. Outer shell; 4. Hydrogen inlet and outlet; 5. Filter; 6. Hydrogen valve; 7. First heat exchange fluid outlet; 8. Heat exchange fluid chamber; 9. Reaction vessel; 10. Upper shaft seal; 11. Metal hydride; 12. Second heat exchange fluid outlet; 13. Lower shaft seal; 14. Heat exchange fluid valve; 15. Stirrer. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, 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.

[0033] Example 1

[0034] In a typical embodiment of the present invention, such as Figure 1-3 As shown, a stirred metal hydride hydrogen storage device is proposed, comprising a cylindrical reaction vessel 9 and an outer shell 3. The reaction vessel 9 is disposed inside the outer shell 3 and is vertically positioned. The interior of the reaction vessel 9 is filled with metal hydride for hydrogen absorption and desorption reactions. A closed heat exchange fluid cavity is formed between the reaction vessel 9 and the outer shell 3, which is filled with heat exchange fluid. The heat exchange fluid is a coolant or a hot liquid, which exchanges heat with the metal hydride in the vessel to cool or heat the metal hydride.

[0035] A stirrer 15 is mounted on the inner axis of the reaction vessel 9. The stirrer 15 consists of a rotating shaft and blades. The rotating shaft has a hollow structure, which forms a flow channel for fluid exchange. The bottom end of the rotating shaft is connected to the cavity. Figure 4 As shown, the rotating shaft is equipped with upper and lower helical blades, and the shaft wall thickness is relatively large in the section where the blades are installed. The angle between the upper helical blade and the shaft axis is smaller than that between the lower helical blade and the shaft axis, reducing the circumferential pressure of the lower blades, improving stirring efficiency, and minimizing energy consumption. The rotating shaft is connected to a low-speed motor 1 via a transmission device 2. The low-speed motor 1 is a low-speed gear reducer motor, and the transmission device 2 is a bevel gear. The rotating shaft rotates under the drive of the low-speed motor, and the blades drive the metal hydride to move and mix in the reaction vessel 9, thus achieving stirring.

[0036] The rotating shaft extends outside the reaction vessel 9, and a shaft seal is provided at the position where the rotating shaft contacts the reaction vessel 9. The shaft seal includes an upper shaft seal 10 and a lower shaft seal 13. The shaft seal can prevent external air from flowing into the reaction vessel or hydrogen from flowing out of the reaction vessel; prevent heat exchange fluid from flowing into the reaction vessel; and prevent metal hydride powder from leaking into the heat exchange fluid cavity. Furthermore, the shaft seal can be a packing seal.

[0037] The top of the rotating shaft is the heat exchange fluid inlet, and a heat exchange fluid valve 14 is installed at the heat exchange fluid inlet to control the injection of heat exchange fluid. The bottom is the heat exchange fluid outlet. The heat exchange fluid outlet of the rotating shaft also serves as the heat exchange fluid inlet of the heat exchange fluid cavity. That is, the heat exchange fluid flows in from the top of the rotating shaft, flows out from the bottom of the rotating shaft through the flow channel, and enters the heat exchange fluid cavity. Furthermore, the upper part of the heat exchange fluid cavity is provided with two heat exchange fluid outlets, including a first heat exchange fluid outlet 7 and a second heat exchange fluid outlet 12. The two heat exchange fluid outlets are symmetrically arranged, and the heat exchange fluid in the heat exchange fluid cavity flows out from the two heat exchange fluid outlets, ensuring the uniformity of the heat exchange fluid flow.

[0038] The top of the reaction vessel 9 is also equipped with a hydrogen inlet and outlet 4. The pipes where the hydrogen inlet and outlet are located are equipped with filter plates 5 to filter and prevent metal hydrides from flowing out of the hydrogen storage tank with the hydrogen during the hydrogen absorption / desorption process. Valves are installed on the pipes where the hydrogen inlet and outlet 4 are located to control the inflow and outflow of hydrogen.

[0039] In this embodiment, the agitator's shaft and blades are made of metals with high thermal conductivity to improve the heat exchange performance of the shaft when used as a finned tube heat exchanger. The inner reaction vessel wall is made of metals with high thermal conductivity, such as aluminum, copper, aluminum alloy, or copper alloy, to improve the heat exchange between the heat exchange fluid and the metal hydride in the heat exchange fluid cavity. Furthermore, the outer shell of the hydrogen storage tank includes the outer wall of the heat exchange fluid cavity and insulation material, i.e., it is heat-insulating and heat-preserving to reduce the heat exchange between the heat exchange fluid and the external environment through the outer shell and reduce the heat loss of the heat exchange fluid during hydrogen release.

[0040] In this embodiment, the stirrer plays four main roles: (1) By stirring, the metal hydride is circulated in the internal reaction vessel, ensuring that the metal hydride with the low reaction rate is always in contact with the heat exchange surface, thereby increasing the reaction rate and improving the hydrogen absorption / desorption performance. (2) The stirrer consists of blades and a rotating shaft. The blades can be used as fins, and the rotating shaft is a straight pipe through which the heat exchange fluid flows. The stirrer can be used as a finned tube heat exchanger to cool / heat the metal hydride and improve the hydrogen absorption / desorption performance of the hydrogen storage tank. (3) By stirring, the metal hydride can be kept in motion, avoiding excessive local stress on the inner wall of the reaction vessel and the heat exchanger caused by the expansion of the metal hydride during the reaction process, which could cause deformation or even damage to the hydrogen storage tank, thereby extending the life of the hydrogen storage tank. (4) Due to repeated hydrogen absorption-desorption cycles, the metal hydride will gradually become smaller and powdery. By stirring, the metal hydride can be mixed evenly, preventing local heat transfer deterioration in the reaction vessel, thereby maintaining the performance of the hydrogen storage tank and extending the service life of the metal hydride.

[0041] Because the metal hydride expands during the hydrogen absorption reaction, and stirring the metal hydride requires additional space, the filling amount of the metal hydride is set to 60%-80% of the reaction vessel volume, preferably 65%. The internal space of the container is divided into a metal hydride zone and a reserved zone. The metal hydride zone is a porous medium that allows hydrogen gas to flow through it. Hydrogen gas flows in from the hydrogen inlet at the top of the hydrogen storage tank, passes through the reserved zone, and flows into the metal hydride zone, where it is adsorbed. The heat released during adsorption is absorbed and carried away by the heat exchange fluid through the internal container walls and the stirrer blades and tube walls.

[0042] In some embodiments of this example, the metal hydride material includes, but is not limited to, one or a combination of several of LaNi5, Mg, Mg2Ni, FeTi, etc.

[0043] In some embodiments of this example, the blade section on the agitator extends to the top of the reserved area, that is, the length of the blade section on the agitator should be greater than the thickness of the bed after the metal hydride expands, so as to ensure that the blades of the agitator can fully agitate the metal hydride.

[0044] The working principle of the stirred metal hydride hydrogen storage device provided in this embodiment is as follows:

[0045] During hydrogen absorption, once the hydrogen pressure inside the reaction vessel reaches the supply pressure, the hydrogen absorption reaction proceeds rapidly and with a high reaction rate in the area near the heat exchange surface due to the lower temperature. In the area farther from the heat exchange surface, the temperature approaches the equilibrium temperature under the supply pressure, resulting in a slow hydrogen absorption reaction and a low reaction rate. The rotating stirrer transports the high-reactivity metal hydrides to the top of the metal hydride zone, where they fall from the outside of the stirrer. Simultaneously, the low-reactivity metal hydrides move to the vicinity of the stirrer, contact the heat exchange surface, and rapidly undergo hydrogen absorption. This process is continuously repeated to ensure that the metal hydrides with lower reaction rates and higher temperatures are always cooled most efficiently, removing the heat released by the reaction most effectively and significantly increasing the hydrogen storage capacity of the hydrogen storage tank.

[0046] Similarly, during hydrogen release, the reaction absorbs heat, requiring a higher temperature to maintain the reaction and increase the reaction rate. In the initial stage, the temperature inside the reaction vessel drops rapidly to a lower value, necessitating the heat exchange fluid to provide the heat required for the hydrogen release reaction. The rotating stirrer, through the aforementioned metal hydride circulation, ensures that the metal hydride with the lowest hydrogen release rate and temperature is always heated with maximum efficiency. This ensures that the heat supplied by the heat exchange fluid is transferred to the metal hydride with the most efficient efficiency, effectively increasing the hydrogen release performance of the hydrogen storage tank.

[0047] In one specific implementation of this embodiment:

[0048] The stirred metal hydride hydrogen storage device includes an outer shell 3 and an inner reaction vessel 9. The outer shell 3 is made of seamless stainless steel tubing, wrapped with heat insulation cotton, with an outer diameter of 80-90 mm, preferably 84 mm, and a wall thickness of 4-6 mm, preferably 5 mm. The total height of the hydrogen storage tank is 105-120 mm, preferably 111 mm. The inner reaction vessel 9 is made of high thermal conductivity metals such as aluminum alloy and copper alloy, with an inner diameter of 48-52 mm, preferably 50 mm, a circumferential wall thickness of 2-3 mm, preferably 2 mm, an internal height of 80 mm, and upper and lower wall thicknesses of 6-8 mm, preferably 8 mm.

[0049] Furthermore, the stirrer 15 is made of a metal with high thermal conductivity such as aluminum alloy or copper alloy, and is set on the axis of the internal reaction vessel. The inner diameter of the rotating shaft is 3-6 mm, preferably 5 mm. The outer diameter of the section without blades is 7-9 mm, preferably 8 mm. The outer diameter of the section with blades is 9-11 mm, preferably 10 mm. The total length of the stirrer is 130-150 mm, preferably 144 mm.

[0050] Furthermore, the agitator blades are helical blades with a thickness of 1.5-3mm, preferably 2mm, and an outer diameter of 26-40mm, preferably 34mm. The blade mounting section includes upper and lower sections. The lower section is located 13mm-33mm above the shaft outlet, with 0.5 helical coils and a pitch of 40mm. The upper section is located 43mm-78mm above the shaft outlet, with 0.25 helical coils and a pitch of 140mm.

[0051] Furthermore, metal hydride powder 11 is filled between the internal reaction vessel 9 and the stirrer 15, preferably LaNi5, and the metal hydride 11 occupies 60%-80% of the volume of the internal space of the reaction vessel, preferably 65%.

[0052] Furthermore, the filter thickness is 0.7-1.1 mm, preferably 0.9 mm, and the filtration accuracy is 0.3-0.6 μm, preferably 0.5 μm.

[0053] Furthermore, the transmission device 2 is selected as a bevel gear, and the upper shaft seal 10 and the lower shaft seal 13 are selected as packing seals.

[0054] Furthermore, the heat exchange fluid is preferably water. Water flows in from the top of the agitator 15 shaft through the heat exchange fluid valve 14, passes through the shaft and the heat exchange fluid cavity 8, and flows out from the first heat exchange fluid outlet 7 and the second heat exchange fluid outlet 12 on the outer shell 3. When absorbing hydrogen, the water temperature is the ambient temperature, preferably 293K; when releasing hydrogen, the water temperature is 353K-373K, preferably 363K.

[0055] Example 2

[0056] In a typical embodiment of the present invention, a method for operating a stirred metal hydride hydrogen storage device is provided, comprising the following steps:

[0057] (1) During the temperature rise stage of the hydrogen absorption reaction and the temperature drop stage of the hydrogen release reaction, the stirrer is continuously rotated.

[0058] (2) When absorbing / releasing hydrogen, stop running the stirrer after the temperature reaches the highest / lowest point;

[0059] (3) When the temperature of the metal hydride near the heat exchange surface decreases / increases and the reaction rate increases, rotate the stirrer again;

[0060] (4) Rotation stops when metal hydrides of different temperatures and reaction rates have completed circulation or mixing in the reaction vessel, and the above cycle of rotation and stopping continues until the reaction is complete.

[0061] Specifically, the first 100 seconds of hydrogen absorption / desorption are set as the pressure change period from the equilibrium pressure before the reaction to the hydrogen supply pressure or the hydrogen release back pressure. The stirrer runs continuously during this period. At the 100th second, the temperature inside the reaction vessel reaches its highest / lowest point, and the stirrer stops running. It then runs every 30 seconds to circulate and mix the metal hydride.

[0062] The operating method provided in this embodiment, through the cyclic start and stop of the stirrer, can achieve the purpose of transporting and mixing metal hydrides, improve the hydrogen absorption / desorption efficiency, and reduce the energy consumed by the rotation of the stirrer.

[0063] The embodiments described above provide a detailed explanation of the technical solution of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for operating a stirred metal hydride hydrogen storage device, characterized in that, The device includes a cylindrical reaction vessel and an outer shell. The reaction vessel is disposed inside the outer shell, and a closed heat exchange fluid cavity is formed between the reaction vessel and the outer shell. A stirrer is provided on the axis inside the reaction vessel. The stirrer consists of a rotating shaft and blades. The rotating shaft has a hollow structure inside, which forms a flow channel for the heat exchange fluid. The bottom end of the rotating shaft is connected to the heat exchange fluid cavity. The interior of the reaction vessel is filled with a metal hydride. The rotating shaft extends outside the reaction vessel, and a shaft seal is provided at the position where the rotating shaft contacts the reaction vessel; the top end of the rotating shaft is the heat exchange fluid inlet, and the bottom end is the heat exchange fluid outlet. The heat exchange fluid outlet of the rotating shaft also serves as the heat exchange fluid inlet of the heat exchange fluid cavity; the rotating shaft is provided with an upper helical blade and a lower helical blade, and the angle between the upper helical blade and the axis of the rotating shaft is smaller than the angle between the lower helical blade and the axis of the rotating shaft. The stirrer's shaft and blades are made of a metal with high thermal conductivity; the reaction vessel walls are also made of a metal with high thermal conductivity. Includes the following steps: During the temperature rise phase of the hydrogen absorption reaction, the stirrer is continuously rotated; when the temperature reaches its maximum during hydrogen absorption, the stirrer is stopped; when the temperature of the metal hydride near the heat exchange surface decreases and the reaction rate increases, the stirrer is rotated again; until the metal hydrides at different temperatures and reaction rates have completed circulation or mixing in the reaction vessel, the rotation is stopped, and the above cycle of rotation and stopping is repeated until the reaction is complete. During the cooling phase of the hydrogen release reaction, the stirrer is continuously rotated. When hydrogen is released and the temperature reaches its lowest point, the stirrer is stopped. When the temperature of the metal hydride near the heat exchange surface rises and the reaction rate increases, the stirrer is rotated again. The rotation stops when the metal hydrides at different temperatures and reaction rates have completed circulation or mixing in the reaction vessel. The above cycle of rotation and stopping is repeated until the reaction is complete.

2. The operating method of the stirred metal hydride hydrogen storage device as described in claim 1, characterized in that, The upper part of the heat exchange fluid cavity is provided with two heat exchange fluid outlets, which are symmetrically arranged.

3. The operating method of the stirred metal hydride hydrogen storage device as described in claim 1, characterized in that, The top of the reaction vessel is also equipped with a hydrogen inlet and outlet.

4. The operation method of the stirred metal hydride hydrogen storage device as described in claim 1, characterized in that, The rotating shaft is connected to a low-speed motor via a transmission device, which uses bevel gears.

5. The operating method of the stirred metal hydride hydrogen storage device as described in claim 1, characterized in that, The amount of metal hydride filled is 60%-80% of the volume of the reaction vessel.

6. The operating method of the stirred metal hydride hydrogen storage device as described in claim 1, characterized in that, The outer casing includes the outer wall of the heat exchange fluid cavity and heat insulation material.

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