Hydrogen storage alloy container

Abstract

To provide a hydrogen storage alloy container which can carry out activation treatment at low cost and can stably supply a large amount of high-purity hydrogen gas even when a hydrogen storage alloy has a large effective hydrogen storage amount.SOLUTION: A hydrogen storage alloy container according to an embodiment, which stores and releases hydrogen, includes a filling layer in which hydrogen storage alloy powder and Ni fine powder are mixed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydrogen storage alloy container.

Background Art

[0002] In recent years, considering the environment, it has been considered to use hydrogen as a fuel for power generation, automobiles, etc., and the demand for hydrogen is increasing. For example, when hydrogen is used as a fuel for mobility such as fuel cell vehicles, it is necessary to store hydrogen gas in a container within the mobility. Also, a system for temporarily storing hydrogen is required at hydrogen stations that supply hydrogen.

[0003] As a method for storing hydrogen gas, there is the hydrogen storage alloy method which can store at a low temperature of 100°C or lower and a low pressure of 10 atm or lower, and is easy to miniaturize the device (see, for example, Japanese Patent Application Laid-Open No. 2014-125385). This method is a method of obtaining high-purity hydrogen by selectively storing only hydrogen in the hydrogen-containing gas in the hydrogen storage alloy to separate it from the impurity gas and releasing only hydrogen from the hydrogen storage alloy. In this hydrogen storage alloy method, since the hydrogen storage alloy can selectively store hydrogen, an improvement in hydrogen recovery rate can be expected. Also, the hydrogen storage alloy method has a higher hydrogen recovery rate than the hydrogen PSA method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Before being used for hydrogen storage applications, a hydrogen storage alloy requires an activation treatment. This activation treatment removes gas components and oxides adhering to the surface of the hydrogen storage alloy, making the surface of the hydrogen storage alloy suitable for hydrogen absorption and dehydrogenation reactions. The general procedure for the activation treatment consists of a step of removing the gas adhering to the surface by heating and evacuation, and a step of causing the hydrogen storage alloy to absorb hydrogen by supplying hydrogen at a pressure higher than the hydrogen equilibrium pressure, and activation is performed by repeating these steps.

[0006] On the other hand, since the container for storing hydrogen gas has a usable design pressure and temperature range, if the activation treatment is carried out at a pressure and temperature higher than the operating conditions such as during normal hydrogen gas supply, it becomes necessary to design the container itself according to the conditions of the activation treatment, which results in a significant cost increase factor. Therefore, it is necessary to perform the activation treatment within the normal operating conditions.

[0007] By the way, the higher the hydrogen equilibrium pressure of the hydrogen storage alloy and the larger the effective hydrogen storage amount of the hydrogen storage alloy, the more difficult it is for the activation treatment to proceed. When the pressure and temperature of the activation treatment are lowered, the number of repetitions of the above-mentioned steps increases, leading to a cost increase in terms of both the process time of the activation treatment and the hydrogen consumption.

[0008] The present disclosure has been made based on the circumstances as described above, and an object thereof is to provide a hydrogen storage alloy container that can be activated at low cost even for a hydrogen storage alloy having a large effective hydrogen storage amount, and can stably supply a large amount of high-purity hydrogen gas.

Means for Solving the Problems

[0009] A hydrogen storage alloy container according to one aspect of the present disclosure is a hydrogen storage alloy container that stores and releases hydrogen, and includes a packed bed in which hydrogen storage alloy powder and Ni fine powder are mixed.

Effects of the Invention

[0010] The hydrogen storage alloy container of the present disclosure can be activated at low cost even with a hydrogen storage alloy having a large effective hydrogen storage amount, and can stably supply a large amount of high-purity hydrogen gas.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0012] [Description of Embodiments of the Present Disclosure] (1) A hydrogen storage alloy container according to one aspect of the present disclosure is a hydrogen storage alloy container that stores and releases hydrogen, and includes a packed layer in which hydrogen storage alloy powder and Ni fine powder are mixed.

[0013] By providing the hydrogen storage alloy container with a packed layer in which hydrogen storage alloy powder and Ni fine powder are mixed, the Ni fine powder promotes the dissociation of hydrogen molecules into hydrogen atoms in the hydrogen storage alloy powder, and the activation treatment in the gas phase can proceed rapidly. Therefore, in this hydrogen storage alloy container, the time for the activation treatment can be reduced, and the activation treatment at low cost can be enabled.

[0014] (2) In the hydrogen storage alloy container described in (1) above, the mass ratio of the Ni fine powder to the hydrogen storage alloy powder is preferably 0.0004 or more and 0.002 or less. By setting the mass ratio of the Ni fine powder within the above range, the number of activation treatments can be further reduced.

[0015] (3) The hydrogen storage alloy container according to the above (1) or (2), wherein the mass of the hydrogen storage alloy powder is preferably 10 kg or more. The hydrogen storage alloy container exhibits particular effects under conditions where the effective hydrogen storage amount is large.

[0016] (4) In the hydrogen storage alloy container according to any one of the above (1) to (3), it is preferable that the average particle diameter of the Ni fine powder is smaller than the average particle diameter of the hydrogen storage alloy powder. In this hydrogen storage alloy container, it is considered that the Ni fine powder is adsorbed on the surface of the hydrogen storage alloy powder, promoting the dissociation of hydrogen molecules into hydrogen atoms. Therefore, by making the average particle diameter of the Ni fine powder smaller than the average particle diameter of the hydrogen storage alloy powder, the Ni fine powder can be easily adsorbed on the surface of the hydrogen storage alloy powder, and thus the number of activation treatments can be further reduced.

[0017] ((5) In the hydrogen storage alloy container according to the above (4), the ratio of the average particle diameter of the Ni fine powder to the average particle diameter of the hydrogen storage alloy powder is preferably 0.01 or more and 0.2 or less. By setting the average particle diameter of the Ni fine powder within the above range, the number of activation treatments can be further reduced.

[0018] Here, the "average particle diameter" means the particle size (D50) of the 50% volume integration value from the small particle size side calculated based on the measurement result of the particle size distribution of the particles by a general particle size distribution meter.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, a hydrogen storage alloy container according to an embodiment of the present disclosure will be described.

[0020] The hydrogen storage and release device 100 shown in FIG. 1 includes a hydrogen storage alloy container 1 according to an embodiment of the present disclosure and a heat medium flow-through portion 2 attached to the hydrogen storage alloy container 1.

[0021] <Hydrogen Storage Alloy Container> The hydrogen storage alloy container 1 is a hydrogen storage alloy container that stores and releases hydrogen, and includes a container body 11 and a filling layer 12. The filling layer 12 is mixed with hydrogen storage alloy powder 12a and Ni fine powder 12b.

[0022] (Container body) The container body 11 is provided with a hydrogen-containing gas supply port 11a for supplying a hydrogen-containing gas, an off-gas discharge port 11b for discharging off-gas after the hydrogen storage alloy powder 12a absorbs hydrogen from the hydrogen-containing gas, and a hydrogen discharge port 11c for discharging hydrogen released by the hydrogen storage alloy powder 12a.

[0023] The hydrogen-containing gas supply port 11a is connected to a supply source (not shown) of the hydrogen-containing gas by a hydrogen-containing gas supply pipe 13, and a gas first on-off valve 13a is provided in the middle of the hydrogen-containing gas supply pipe 13. The presence or absence of the supply of the hydrogen-containing gas is controlled by this gas first on-off valve 13a.

[0024] The off-gas discharge port 11b is connected to a discharge destination of the off-gas by an off-gas discharge pipe 14, and a gas second on-off valve 14a and a pressure control valve 14b are provided in the middle of the off-gas discharge pipe 14 in order from the container body 11 side. With this configuration, the presence or absence of off-gas discharge can be controlled together with its flow rate.

[0025] The hydrogen discharge port 11c is connected to a supply destination (for example, a fuel cell, etc.) of hydrogen gas by a hydrogen discharge pipe 15, and a gas third on-off valve 15a and a mass flow controller 15b for adjusting the mass flow rate of the hydrogen gas are provided in the middle of the hydrogen discharge pipe 15 in order from the container body 11 side. With this configuration, the presence or absence of hydrogen discharge can be controlled together with its flow rate.

[0026] (Filling layer) As the hydrogen storage alloy powder 12a contained in the filling layer 12, a LaNi-based hydrogen storage alloy is preferable from the viewpoint of hydrogen storage amount.

[0027] As the upper limit of the flattening index in the plateau region during hydrogen release of the hydrogen storage alloy powder 12a, 0.5 is preferable, and 0.4 is more preferable. When the above flattening index is large, the release pressure may vary greatly, and the amount of hydrogen that can be effectively utilized may be limited. The "flattening index of the plateau region" is an amount calculated by [log(a) - log(b)] / 1.20, where a is the release pressure when the occlusion amount is 1.45% by mass and b is the release pressure when the occlusion amount is 0.25% by mass.

[0028] Examples of the hydrogen storage alloy powder 12a with a large flattening index include hydrogen storage alloys produced by the strip casting method. The hydrogen storage alloy powder 12a obtained by the strip casting method has a significantly reduced precipitation of impurity phases, resulting in a uniform alloy structure and a structure with less element segregation, and a flat plateau region, that is, a large effective hydrogen storage amount can be achieved.

[0029] As the lower limit of the mass of the hydrogen storage alloy powder 12a, 10 kg is preferable, and 30 kg is more preferable. On the other hand, as the upper limit of the mass of the hydrogen storage alloy powder 12a, 500 kg is preferable, and 100 kg is more preferable. When the mass of the hydrogen storage alloy powder 12a is within the above range, activation treatment within the design pressure and temperature range, which are the operating conditions, is particularly required. The hydrogen storage alloy container 1 exhibits particular effects under such conditions where the effective hydrogen storage amount is large.

[0030] As the lower limit of the average particle size of the hydrogen storage alloy powder 12a, 10 μm is preferable, and 50 μm is more preferable from the viewpoint of easily ensuring contact with the Ni fine powder 12b. On the other hand, as the upper limit of the average particle size of the hydrogen storage alloy powder 12a, 1000 μm is preferable, 300 μm is more preferable, and 100 μm is even more preferable from the viewpoint of ensuring the surface area for hydrogen occlusion.

[0031] The lower limit of the hydrogen equilibrium pressure of the hydrogen storage alloy powder 12a at 25°C is preferably 0.05 MPaA, more preferably 0.1 MPaA. The upper limit of the hydrogen equilibrium pressure is preferably 10 MPaA, more preferably 5 MPaA. By setting the hydrogen equilibrium pressure at or above the lower limit, the heating temperature for releasing hydrogen can be reduced. By setting the hydrogen equilibrium pressure at or below the upper limit, the supply pressure of the hydrogen-containing gas for absorbing hydrogen can be reduced. Therefore, equipment costs can be reduced. The hydrogen equilibrium pressure is the pressure at which the hydrogen concentration (H / M) is 0.5 on the PCT line of the hydrogen storage alloy obtained by the vacuum origin method based on the method for measuring pressure-composition isotherms (PCT lines) of hydrogen storage alloys (JIS H7201). In this specification, "MPaA" represents absolute pressure, and "MPaG" represents gauge pressure.

[0032] Generally, hydrogen storage alloy powder 12a with a large effective hydrogen storage capacity tends to be difficult to activate. The inventors speculate that hydrogen storage alloy powder 12a with a large effective hydrogen storage capacity has a uniform alloy structure and a structure with little element segregation, making it difficult for hydrogenation, which creates metal hydrides, to occur on the surface of the hydrogen storage alloy powder 12a. In contrast, hydrogen storage alloy powder 12a with a low plateau region flatness may undergo hydrogenation starting from element segregation, for example. If a portion of the hydrogen storage alloy powder 12a is hydrogenated, the hydrogenation process progresses in a chain reaction, and therefore activation is believed to proceed easily. Therefore, the inventors conceived the idea that even with hydrogen storage alloy powder 12a with a large effective hydrogen storage capacity, activation can be easily performed if hydrogenation can be initiated. They then discovered that adding Ni fine powder 12b is effective and completed the hydrogen storage alloy container 1 of the present disclosure. Therefore, the packed layer 12 of the hydrogen storage alloy container 1 contains Ni fine powder 12b.

[0033] As described above, it is sufficient for the Ni fine powder 12b to have an amount sufficient to cause hydrogenation starting from the surface of the hydrogen storage alloy powder 12a. Also, from the viewpoint of efficiently recovering / supplying hydrogen gas, it is desirable that the proportion of the hydrogen storage alloy powder 12a is high, that is, the proportion of the Ni fine powder 12b is low. From the above viewpoints, as the lower limit of the mass ratio of the Ni fine powder 12b to the hydrogen storage alloy powder 12a, 0.0004 is preferable, and 0.0005 is more preferable. On the other hand, as the upper limit of the above mass ratio, 0.002 is preferable, and 0.001 is more preferable.

[0034] As the lower limit of the average particle size of the Ni fine powder 12b, from the viewpoint of ensuring the surface area serving as the starting point of hydrogenation, 1 μm is preferable, and 2 μm is more preferable. On the other hand, as the upper limit of the average particle size of the Ni fine powder 12b, from the viewpoint of easily ensuring contact with the hydrogen storage alloy powder 12a, 10 μm is preferable, and 5 μm is more preferable.

[0035] The average particle size of the Ni fine powder 12b is preferably smaller than the average particle size of the hydrogen storage alloy powder 12a. In the hydrogen storage alloy container 1, it is considered that the Ni fine powder 12b is adsorbed on the surface of the hydrogen storage alloy powder 12a and promotes the dissociation of hydrogen molecules into hydrogen atoms. Therefore, by making the average particle size of the Ni fine powder 12b smaller than the average particle size of the hydrogen storage alloy powder 12a, the Ni fine powder 12b can be easily adsorbed on the surface of the hydrogen storage alloy powder 12a, so that the number of activation treatments can be further reduced.

[0036] As the lower limit of the ratio of the average particle size of the Ni fine powder 12b to the average particle size of the hydrogen storage alloy powder 12a, from the viewpoint of ensuring the surface area serving as the starting point of hydrogenation, 0.01 is preferable, and 0.02 is more preferable. On the other hand, as the upper limit of the above average particle size ratio, from the viewpoint of easily ensuring contact with the hydrogen storage alloy powder 12a, 0.2 is preferable, and 0.1 is more preferable.

[0037] <Heat medium flow-through part> The heat medium flow-through part 2 is attached to the hydrogen storage alloy container 1 and has a heat medium inlet 2a at the lower part and a heat medium outlet 2b at the upper part.

[0038] In the hydrogen storage alloy method, the hydrogenation reaction that occurs during hydrogen storage is an exothermic reaction. In order to efficiently store and purify hydrogen, it is necessary to remove the heat of reaction from the packed bed 12. On the other hand, hydrogen release is a dehydrogenation reaction, which is an endothermic reaction, so it is necessary to supply heat corresponding to the heat of reaction to the packed bed 12.

[0039] To control the temperature of this packed bed 12, the heat medium flow passage 2 circulates a heat medium such as water or oil. For example, when heating is required, hot water is circulated through the heat medium flow passage 2 for heating, and when removal of the heat of reaction is required, cold water is circulated through the heat medium flow passage 2 for cooling.

[0040] <Advantages> The hydrogen storage alloy container 1 includes a packed bed 12 in which hydrogen storage alloy powder 12a and Ni fine powder 12b are mixed. Thus, the Ni fine powder 12b promotes the dissociation of hydrogen molecules into hydrogen atoms in the hydrogen storage alloy powder 12a, and the activation treatment in the gas phase can proceed rapidly. Therefore, in the hydrogen storage alloy container 1, the number of activation treatments can be reduced, enabling low-cost activation treatment.

[0041] [Other Embodiments] The above embodiments do not limit the configuration of the present invention. Therefore, based on the description in this specification and common general knowledge in the art, omission, substitution, or addition of the constituent elements of each part of the above embodiments is possible, and all of them should be construed as belonging to the scope of the present invention.

[0042] In the above embodiment, the case where the hydrogen storage alloy container is used in a hydrogen storage alloy device that performs heating and cooling through a heat medium flow passage has been described. However, the heating and cooling method of the hydrogen storage alloy container is not limited to being performed by the heat medium flow passage.

Examples

[0043] Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples.

[0044] [No.1] 100 g of LaNi-based hydrogen storage alloy powder (manufactured by Santoku Co., Ltd.) adjusted so that the hydrogen equilibrium pressure at 25°C becomes 0.1 MPaA and 0.05 g of Ni fine powder (average particle size 2 to 3 μm, manufactured by High Purity Chemical Research Institute) (mass ratio to hydrogen storage alloy powder 0.0005) were each weighed and mixed. This mixture was filled into a double-tube jacketed container body (inner diameter 22.4 mm, maximum filling height 120 mm) to prepare a hydrogen storage alloy container equipped with a packed bed.

[0045] The above hydrogen storage alloy container was activated in the following steps. (1) Warm water at 80°C was supplied to the jacket part (heat medium circulation part) for heating, and evacuation was carried out for 2 hours while maintaining the heated zone. (2) After flowing 1 NLM of hydrogen through the container body, heating at 80°C was maintained, and the reduced pressure state by the vacuum pump (the state 2 hours after (1)) was maintained for 2 hours. (3) Cold water at 10°C was supplied to the jacket part to cool the inside of the packed bed, and pure hydrogen at a pressure of 0.9 MPaG was supplied.

[0046] After performing the above operations, a cycle test in which the following (4) and (5) were repeated was carried out 7 cycles. (4) Heat to 80°C and perform hydrogen release for 30 minutes. (5) Cool to 10°C and perform hydrogen supply for 30 minutes.

[0047] Each time each cycle was completed, the hydrogen storage amount was determined. The results are shown in Figure 2. In the process of (5), when the hydrogen storage alloy powder absorbs hydrogen, the pressure of the above hydrogen storage alloy container decreases, but when the hydrogen storage alloy powder stops absorbing hydrogen, the pressure of the above hydrogen storage alloy container increases to the supply pressure (0.9 MPaG). The hydrogen storage amount was calculated from this pressure change. The maximum absorption amount assumed computationally for 100 g of the hydrogen storage alloy powder used is 14 NL.

[0048] From the results in Figure 2, it shows the hydrogen storage amount near 14 NL, which is the maximum storage amount since the first cycle, and it can be said that the activation process is completed in one cycle.

[0049] [No.2] The activation treatment was carried out in the same manner as in No.1, except that the packed bed was made of only 100 g of LaNi-based hydrogen storage alloy powder (manufactured by Santoku Corporation) adjusted so that the hydrogen equilibrium pressure at 25°C was 0.1 MPaA.

[0050] The results of obtaining the hydrogen storage amount every time each cycle was completed are shown in Figure 3. It can be seen that even after performing the activation treatment for 7 cycles, the hydrogen storage amount is 8 NL, and it is necessary to repeat the treatments (4) and (5) further to reach 14 NL.

[0051] The activation treatment was carried out in the same manner as in No.1, except that the amount of Ni fine powder was 0.01 g (mass ratio to the hydrogen storage alloy powder of 0.0001).

[0052] The results of obtaining the hydrogen storage amount every time each cycle was completed are shown in Figure 4. Although the hydrogen storage amount after 7 cycles does not reach 14 NL, it exceeds 8 NL from the first cycle, and it can be seen that the progress of the activation treatment is faster compared to No.2.

Industrial Applicability

[0053] The hydrogen storage alloy container of the present disclosure can be activated at low cost even for a hydrogen storage alloy with a large effective hydrogen storage amount, and can stably supply a large amount of high-purity hydrogen gas.

Explanation of Signs

[0054] 100 Hydrogen storage and release device 1 Hydrogen storage alloy container 11 Container body 11a Hydrogen-containing gas supply port 11b Off-gas discharge port 11c Hydrogen discharge port 12 Packed bed 12a Hydrogen storage alloy powder 12b Ni fine powder 13 Hydrogen-containing gas supply pipe 13a Gas first on-off valve 14 Off-gas discharge pipe 14a Gas second on-off valve 14b Pressure control valve 15 Hydrogen discharge pipe 15a Gas third on-off valve 15b Mass flow controller 2 Heat medium flow-through part 2a Heat medium inlet 2b Heat medium outlet

Claims

Claim 1 A hydrogen storage alloy container that stores and releases hydrogen, The hydrogen storage alloy container is provided with a packed bed in which hydrogen storage alloy powder and Ni fine powder are mixed. Claim 2 The hydrogen storage alloy container according to claim 1, wherein the mass ratio of the Ni fine powder to the hydrogen storage alloy powder is 0.0004 or more and 0.002 or less. Claim 3 The hydrogen storage alloy container according to claim 1 or 2, wherein the mass of the hydrogen storage alloy powder is 10 kg or more. Claim 4 The hydrogen storage alloy container according to claim 1 or 2, wherein the average particle size of the Ni fine powder is smaller than the average particle size of the hydrogen storage alloy powder. Claim 5 The hydrogen storage alloy container according to claim 4, wherein the ratio of the average particle size of the Ni fine powder to the average particle size of the hydrogen storage alloy powder is 0.01 or more and 0.2 or less.

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