Hydrogen storage alloy tank

Abstract

To provide a hydrogen storage alloy tank which has a simple structure, can be easily and quickly filled with hydrogen storage alloy powder, has no fine agglomeration of the hydrogen storage alloy powder, and can be installed vertically.SOLUTION: Within a tank enclosure 1 composed of a cylindrical tube, there is provided a spiral fin 2 having an outer diameter being 0.8 times or more of an inner diameter of the tank enclosure 1, formed consecutively in a longitudinal direction, and composed of a heat conductive material. An hydrogen storage alloy 4 is filled between the spiral fins 2. The pitch of the spiral fin 2 is two times or less of an outer diameter of the tank enclosure 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cylindrical tank filled with a hydrogen storage alloy, which can be used in a vertical position. [Background technology]

[0002] In recent years, hydrogen storage alloy tanks have come to be used in stationary hydrogen storage facilities that gradually absorb hydrogen produced using surplus renewable energy and gradually release the hydrogen stored in large quantities.More recently, there is expected to be a demand for delivery and distribution systems using cylinders or tanks similar to those currently in widespread use, such as LPG tanks.

[0003] When considering the delivery and distribution method for this hydrogen storage alloy tank, it is desirable to make it as light as a conventional LPG cylinder. Furthermore, like conventional LPG cylinders, it is desirable to use a cylindrical tank in a vertical position, since this reduces the installation area during transportation and operation and increases the portability.

[0004] However, when using a normal cylindrical hydrogen storage alloy tank, the repeated expansion and contraction of the alloy powder due to the absorption and release of hydrogen causes the powder to become finely agglomerated, and in this state, the expansion due to hydrogen absorption causes localized stress increase in the tank casing near the powder agglomerations, so as a general rule, it is not recommended to use it upright.

[0005] In particular, with conventional alloys, the powder itself becomes finer as it absorbs and releases hydrogen, and as the powder aggregates, new surfaces are created, and the powder eventually solidifies into a porous shape. This creates a stronger expansion force, which can lead to the destruction of the tank casing.

[0006] On the other hand, if the alloy itself does not become fine, the fine agglomeration will reach a certain limit, and the expansion force will no longer increase. Therefore, whether the tank casing can withstand the external force caused by the expansion of the alloy when it has become fully agglomerated to a certain extent determines whether it can maintain long-term durability.

[0007] If the tank material exceeds its yield point before it is completely agglomerated, the residual strain increases with each repetition, and the permanent strain continues to increase. Even if the yield point is not reached, if the stress is not kept within the fatigue limit, the tank will not be able to withstand repeated hydrogen absorption and release indefinitely. Therefore, even if the alloy powder is not finely divided, it is necessary to increase the material strength of the tank housing in order to achieve long-term use as a vertical tank, which results in the use of expensive metals and an increase in plate thickness, resulting in a heavy tank and reduced delivery workability.

[0008] The force in the direction of the tank's internal pressure caused by the alloy expansion becomes larger as the aspect ratio increases. With a large aspect ratio, the weight per unit cross-sectional area increases, so the entire alloy packed layer cannot be pushed up in response to the expansion, and instead acts as an external force that increases the tank's internal pressure. In some cases, the alloy may locally aggregate finely in the middle of the tank's length, which may result in an increase in local stress.

[0009] In particular, in the case of alloys in which the hydrogen absorption and release causes the particles to become finer and new surfaces to be generated, the increase in the self-weight load per unit area due to the high aspect ratio promotes the solidification of the alloy powder into a porous shape. Therefore, it is necessary to consider an internal structure that prevents the alloy powder from agglomerating in the weight direction in response to the hydrogen absorption and release (expansion and contraction) of the alloy.

[0010] This hydrogen storage alloy tank requires a mechanism for removing the reaction heat generated when the alloy absorbs and releases hydrogen. The heat removal methods are roughly divided into water-cooled and air-cooled. In the water-cooled type, a heat transfer medium path is provided on the outer periphery or inside of the tank, and the alloy reaction heat is removed by heat exchange with the heat transfer medium. In the air-cooled type, the alloy reaction heat is removed mainly by heat exchange between the tank and the atmosphere. In both types, a heat transfer material is generally provided in the alloy-filled part inside the tank to remove the heat efficiently. As shown in Figures 14 and 15, the inside of the tank 20 is divided by radiating fins 21, and hydrogen storage alloy powder 22 is filled in the tank, which has been commercialized as a horizontal stationary type.

[0011] Several countermeasures have already been developed to prevent stress increases due to alloy agglomeration in such hydrogen storage alloy tanks. The one disclosed in Patent Document 1 is a capsule container and hydrogen storage tank in which a hydrogen storage alloy is filled into multiple capsule containers housed with gaps between them within a hydrogen storage tank, and these capsule containers are elastically deformable in response to the expansion of the storage alloy when it absorbs hydrogen and the contraction of the storage alloy when it releases hydrogen.

[0012] Patent Document 2 discloses a hydrogen storage tank in which a small chamber separated by radial fins inside the tank casing has a partially contractible space that contracts when the alloy expands, thereby suppressing the internal pressure on the tank casing. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2005-9549 A [Patent Document 2] JP 2009-222200 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0014] The device in Patent Document 1 requires providing multiple capsule containers in a tank with gaps between them, and filling each of these capsule containers with a hydrogen storage alloy, resulting in a complex structure and time-consuming process for filling them with the hydrogen storage alloy.In addition, the device in Patent Document 2 has a complex structure in which the inside of the tank container is divided into many small chambers by radial fins, and furthermore, a contractible space is provided in part of each small chamber, resulting in a complex structure and time-consuming process for manufacturing.

[0015] The present invention focuses on the above points and aims to provide a hydrogen storage alloy tank that has a simple structure, can be filled with hydrogen storage alloy powder easily and quickly, does not cause the hydrogen storage alloy powder to agglomerate, and can be placed vertically. [Means for solving the problem]

[0016] The invention of claim 1 is a hydrogen storage alloy tank having a cylindrical tank casing with spiral-shaped fins formed continuously in the longitudinal direction and having an outer diameter that is at least 80% of the inner diameter of the tank casing, and a hydrogen storage alloy filled between the spiral-shaped fins.

[0017] The invention of claim 2 provides the hydrogen storage alloy tank of claim 1, wherein the pitch of the spiral fin is set to be equal to or less than twice the outer diameter of the tank casing.

[0018] The invention of claim 3 is directed to the hydrogen storage alloy tank of claim 1 or 2, wherein the length of the spiral fin is 2 / 3 or more of the length of the tank.

[0019] The invention of claim 4 provides the hydrogen storage alloy tank of claim 1, wherein the spiral fin is made of a heat conductive material. Effect of the Invention

[0020] According to the invention of claim 1, the shape of the heat transfer fins that have been conventionally used is made into a continuous spiral shape, and the spaces between the spiral fins are filled with hydrogen storage alloy. Therefore, even when the hydrogen storage alloy tank is placed vertically, there are multiple partitions in the direction of gravity, which prevents the hydrogen storage alloy from expanding and contracting when it absorbs and releases hydrogen, and also prevents the formation of fine agglomerations at the bottom of the tank due to its own weight.

[0021] When a tank with conventional radiating fins is placed vertically, the aspect ratio of the small chambers formed by the partitions of the radiating fins is large, and in some cases exceeds 20. However, in this invention, by using spiral fins and filling the spaces between the spiral fins with hydrogen storage alloy, the alloy-filled section is formed into a tube shape with a low cross-sectional aspect ratio that spirals vertically from the bottom. This filling shape significantly reduces the force in the direction of gravity per unit cross-sectional area of ​​the alloy-filled layer. Therefore, even when the tank of this invention is placed vertically, although it is a cylindrical tank, the alloy-filled layer can be formed in the shape of a tube placed horizontally.

[0022] In addition, when the tank of the present invention is placed vertically, the continuous partition structure using the spiral-shaped fins causes the expansion force of the alloy to act as opposite component forces on the upper and lower surfaces of the partition, generating a shear force between the upper and lower layers of the alloy between the spiral pitches, separating the layers of the alloy and preventing excessive aggregation.

[0023] Even if the expansion force increases due to partial refinement of the alloy layer in the fin pitch, the spring deformation of the spiral-shaped fin allows the expansion force to be released vertically, preventing excessive alloy expansion force from acting in the direction of the tank's internal pressure.

[0024] As described above, the invention of claim 1 has a much simpler structure than the conventionally developed products that take measures to prevent the formation of fine agglomerations at the bottom of the tank due to the relationship between expansion, contraction, and the tank's own weight during hydrogen absorption and release, and can accommodate a variety of aspect ratios as long as the tank is cylindrical. Furthermore, since no completely independent small chambers are provided in the vertical direction, it is possible to fill the alloy from the top after inserting the spiral fins, making the tank highly mass-producible. Also, as described above, since the alloy expansion force can be significantly reduced, there is no need to consider excessive stress on the tank housing, which contributes to reducing the weight of the tank housing. Therefore, it can also be applied to the tank delivery system.

[0025] In addition, according to the invention of claim 2, the pitch of the spiral-shaped fin is set to a length less than twice the outer diameter of the tank casing, thereby ensuring that the length of the tube-shaped alloy layer is at a certain level or more, and the force in the gravitational direction per unit cross-sectional area of ​​the alloy filling layer is greatly reduced, ensuring the effect.

[0026] In addition, according to the invention of claim 3, the length of the spiral-shaped fin is made to be at least 2 / 3 of the length of the tank, thereby ensuring that the length of the tube-shaped alloy layer is at least a certain length, and the force in the gravitational direction per unit cross-sectional area of ​​the alloy packed bed is greatly reduced, ensuring the effect.

[0027] According to the invention of claim 4, the spiral fin is made of a thermally conductive material, so that the reaction heat of the hydrogen storage alloy can be transferred from the spiral fin to the outer wall of the tank, improving heat exchange with the atmosphere. [Brief description of the drawings]

[0028] [Figure 1] 1 is a longitudinal sectional view of a hydrogen storage alloy tank according to a first embodiment of the present invention placed upright. [Diagram 2] 1 is a front view of a hydrogen storage alloy tank according to a first embodiment of the present invention placed vertically with an upper cap removed. [Diagram 3] 1 is an enlarged cross-sectional view of a hydrogen storage alloy tank according to a first embodiment of the present invention placed vertically. [Figure 4] 1 is an enlarged partial vertical sectional view of a hydrogen storage alloy tank according to a first embodiment of the present invention placed vertically. [Diagram 5] FIG. 2 is an image diagram showing how a tube-shaped alloy layer is formed by a spiral fin in the hydrogen storage alloy tank according to the first embodiment of the present invention. [Figure 6] 4 is an image diagram of the force acting on the alloy layer by the spiral fin of the hydrogen storage alloy tank in the first embodiment of the present invention. FIG. [Figure 7] 4 is an enlarged cross-sectional view showing another example of the hydrogen storage alloy tank according to the first embodiment of the present invention in a vertically placed state. FIG. [Figure 8] 4 is an enlarged partial vertical sectional view showing another example of the hydrogen storage alloy tank according to the first embodiment of the present invention in a vertically placed state. FIG. [Figure 9] 4 is an enlarged cross-sectional view showing still another example of the hydrogen storage alloy tank according to the first embodiment of the present invention in a vertically placed state. FIG. [Figure 10] 4 is an enlarged partial vertical sectional view showing still another example of the hydrogen storage alloy tank according to the first embodiment of the present invention in a vertically placed state. FIG. [Figure 11] FIG. 1 is a graph showing the results of repeated hydrogen absorption / release tests on a conventional hydrogen storage alloy tank; (a) shows the stress versus hydrogen amount after the first absorption, and (b) shows the stress versus hydrogen amount after the tenth absorption. [Figure 12] FIG. 1 is a graph showing the results of repeated hydrogen absorption / release tests of a hydrogen storage alloy tank according to embodiment 1 of the present invention, in which (a) shows the stress versus hydrogen amount for the first absorption and (b) shows the stress versus hydrogen amount for the tenth absorption. [Figure 13] FIG. 11 is a vertical sectional view of a hydrogen storage alloy tank according to a second embodiment of the present invention, placed upright. [Figure 14] FIG. 1 is a longitudinal sectional view of a conventional hydrogen storage alloy tank placed vertically. [Figure 15] FIG. 1 is an enlarged cross-sectional view of a conventional hydrogen storage alloy tank placed vertically. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] (Embodiment Example 1) A hydrogen storage alloy tank A according to a first embodiment of the present invention will be described with reference to FIGS.

[0030] First, as shown in Fig. 1, the hydrogen storage alloy tank A is provided with a spiral fin 2 formed continuously in the longitudinal direction inside a cylindrical tank casing 1 and having an outer diameter that is 80% or more of the inner diameter of the tank casing 1. As shown in Fig. 3, the spiral fin 2 has a circular hole formed in the center when viewed from above, which defines a central cavity 3 from the upper end to the lower end of the spiral fin 2. Powder of hydrogen storage alloy 4 filled inside the tank casing 1 fills the gap partitioned by the spiral fin 2 and the central cavity 3 (see Fig. 4). A valve knob 5 for storing and releasing hydrogen is provided at the upper end of the tank casing 1.

[0031] The spiral fins 2 are made of a heat conductive material such as steel. The pitch of the spiral fins 2 is preferably equal to or smaller than the outer diameter of the tank casing 1, but in order to ensure that the length of the tube-shaped alloy layer is at least a certain length, the pitch may be equal to or smaller than twice the outer diameter of the tank casing 1. The length of the spiral fins 2 is set to 2 / 3 or more of the length of the tank body 1, thereby ensuring that the length of the tube-shaped alloy layer is at least a certain length.

[0032] When the hydrogen storage alloy tank A is placed vertically, the hydrogen storage alloy 4 is filled between the spiral fins 2, so that the alloy-filled section forms a tube shape with a low cross-sectional aspect ratio that spirals vertically from the bottom, as shown in Figure 5. In addition, due to the continuous partition structure of the spiral fins 2, the expansion force of the alloy 4 acts as opposite force components at the upper partition 2a and the lower partition 2b, as shown in Figure 6, so that a shear force is generated between the upper and lower layers of the alloy layer between the spiral pitches, and by separating the layers of the alloy 4, excessive aggregation can be prevented.

[0033] Furthermore, when the hydrogen storage alloy tank A is placed upright, the provision of the spiral-shaped fins 2 causes the alloy powder filled in the tank casing 1 to be in a state in which multiple partitions are provided in the direction of gravity, significantly reducing the force in the direction of gravity per unit cross-sectional area of ​​the alloy layer, and preventing fine agglomeration at the bottom of the tank casing 1 that would occur due to the alloy's expansion and contraction when absorbing and releasing hydrogen, as well as its own weight.

[0034] Although the spiral fin 2 can maintain its shape as is, in order to more firmly maintain the shape of the spiral fin 2, small diameter pillars 7 are provided at multiple locations on the inner periphery 6 within the central hollow portion 3 of the spiral fin 2, as shown in Figures 7 and 8, and each small diameter pillar 7 extends from the top to the bottom of the spiral fin 2, and the inner periphery 6 of the spiral fin 2 is abutted against each small diameter pillar 7 to support it.

[0035] In order to more firmly maintain the shape of the spiral fin 2, as shown in Figs. 9 and 10, a tube 8 is fitted into the central hollow portion 3 of the spiral fin 2, and the tube 8 extends from the top to the bottom of the spiral fin 2, and the inner peripheral edge 6 of the spiral fin 2 is abutted against the tube 8 to support it. Furthermore, the central hollow portion 3 of the spiral fin 2 may be omitted if possible in manufacturing. As a method of more firmly maintaining the shape of the spiral fin 2, a structure in which a solid cylinder is fitted into the central hollow portion 3 may be used. The alloy powder can be filled along the spiral fin 2 from the top of the tank housing 1 with any of the above fin structures.

[0036] Figures 11 and 12 show the results of repeated hydrogen absorption / release tests conducted on hydrogen storage alloy tank A of this invention and a conventional product placed vertically. In the tests, hydrogen was filled into the hydrogen storage alloy tank at a pressure of 1 MPa, and after it was fully filled, all of the hydrogen was released, repeatedly. The test results were obtained by measuring the stress at regular intervals along the length of the tank. The conventional product was a delivery tank with radial fins, with the same external dimensions as the hydrogen storage alloy tank (for delivery) of this invention, 1210 mm in length and 139.8 mm in diameter, and a tank weight of 65 kg (of which 45 kg was alloy filler).

[0037] With the conventional radial fin structure, the stress amplitude acting on the tank increases with each repetition, and as shown in Figure 11(b), it was confirmed that after 10 repetitions, the stress amplitude exceeded the yield point at 230 MPa. On the other hand, with the hydrogen storage alloy tank A of the present invention, as shown in Figure 12(b), the stress amplitude remained constant at about 20 MPa even after 10 repetitions, the same as the initial stress amplitude (Figure 12(a)). It was also confirmed that while the conventional product had a large stress variation (over 100 MPa) along the longitudinal direction of the tank, the present invention had an extremely small stress variation of only 5 MPa.

[0038] In addition, since the stress amplitude value of 20 MPa is close to the stress value when an internal pressure of 1 MPa acts on the tank, this indicates that in this invention, the alloy expansion force is not acting on the tank internal pressure side, and the effect of mitigating the alloy expansion force by the spiral fin structure was confirmed.

[0039] (Embodiment Example 2) Next, a hydrogen storage alloy tank B according to a second embodiment of the present invention will be described with reference to FIG.

[0040] 13, this hydrogen storage alloy tank B has mesh plates 9 spaced apart in the longitudinal direction within a tank casing 1 to divide the tank casing 1 into multiple stages, the spiral fins 2 are provided within each partition 10, and the hydrogen storage alloy 4 is filled between the spiral fins 2 within each partition 10, with each mesh plate 9 allowing hydrogen gas to pass through but not allowing the hydrogen storage alloy 4 to pass through. The other configuration is the same as that of the first embodiment.

[0041] As described above, the hydrogen storage alloy tanks A and B of the present invention can be used in a vertical position, but they can also be used in a horizontal position. These tanks can be either air-cooled or water-cooled. The hydrogen storage alloy powder to be filled can be either an alloy that becomes fine by repeated hydrogen absorption and release, or an alloy that does not become fine. The spiral fin 2 in the figure is a schematic drawing. [Explanation of symbols]

[0042] A Hydrogen storage alloy tank B Hydrogen storage alloy tank 1 Tank housing 2 Spiral fin 2a Top partition 2b Bottom partition 3 Central cavity 4 Hydrogen storage alloy 5 Valve knob 6 Inner edge 7 Small pole 8 Body 9 Mesh plate 10 Partition

Claims

1. A hydrogen storage alloy tank, characterized in that a spiral-shaped fin is provided inside a cylindrical tank casing, the spiral fin having an outer diameter that is 80% or more of the inner diameter of the tank casing and formed continuously in the longitudinal direction, and a hydrogen storage alloy is filled between the spiral fins.

2. 2. The hydrogen storage alloy tank according to claim 1, wherein the pitch of said spiral fin is equal to or less than twice the outer diameter of said tank casing.

3. 3. The hydrogen storage alloy tank according to claim 1, wherein the length of said spiral fin is at least 2 / 3 of the length of said tank.

4. 2. The hydrogen storage alloy tank according to claim 1, wherein the spiral fin is made of a heat conductive material.

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