JPH08109402A - Hydrogen storage body and method for producing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a hydrogen storage material having a structure capable of increasing the filling rate of the hydrogen storage alloy as compared with the conventional one. [Structure] The hydrogen storage material 1 is made of a powder of a hydrogen storage alloy, and
A binder 3 made of a fluorinated resin such as FE is kneaded and pressed to bond the hydrogen storage alloy particles 2 to each other and shape them into an arbitrary shape.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the reversible absorption of hydrogen,
The present invention relates to a hydrogen storage body formed by molding a hydrogen storage alloy to be released into a predetermined shape, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, various hydrogen storage alloy application systems, such as heat pumps, hydrogen storage systems, and fuel cell systems, which utilize the hydrogen storage function and heat energy conversion function of hydrogen storage alloys, have been developed. . In such a system, the hydrogen storage alloy is filled in a powder state in a container having a predetermined shape. In this case, the hydrogen storage alloy may repeatedly expand and contract with absorption and release of hydrogen, and the stress at that time may act on the wall surface of the container to deform the container.

Particularly, when the particles of the hydrogen storage alloy are further pulverized and scattered in the process of repeatedly expanding and contracting, the fine powder is collected at the bottom of the container, and as a result, there is almost no gap between the alloy particles at the bottom of the container. There is a problem of so-called swelling in which the expansion of the alloy is directly transmitted to the container wall, which causes the container to be deformed and in some cases leads to destruction.

Therefore, conventionally, the above problem has been dealt with by pelletizing the powder of the hydrogen storage alloy as follows. The first method of pelletizing is to mix a polymer material with a powder of a hydrogen storage alloy and heat it to pelletize it into a predetermined shape (Japanese Patent Publication No. 56-56-
18521, JP 59-83901, JP 59-147032, JP 1-11
9501, JP-A 1-246101). In the second method, alloy powder is mixed with ceramics and pelletized by sintering or the like (JP-A-55-158101 and JP-A-61-2).
09901, JP-A-59-73401, JP-A-57-38302). Further, the third method is to add a metal such as aluminum to the alloy powder and pelletize it by sintering or the like.

[0005]

However, since the above first to third methods all require heat treatment,
There is a problem that the manufacturing process becomes complicated. In addition, the proportion of hydrogen storage alloy in the pellet (filling rate) is greatly reduced by mixing the binder such as a polymer material, and the standard filling rate of 5 in the container filled with only conventional hydrogen storage alloy powder.
There is a problem below 0%.

An object of the present invention is to provide a hydrogen storage body having a structure capable of increasing the filling rate of the hydrogen storage alloy as compared with the conventional case. Another object of the present invention is to provide a method for producing a hydrogen storage body, which does not require heat treatment when pelletizing the powder of the hydrogen storage alloy.

[0007]

A hydrogen storage material according to the present invention is obtained by mixing a powder of a hydrogen storage alloy with a binder made of a fluororesin and press-molding the mixture into a predetermined shape.

In a specific structure, the fluororesin is polytetrafluoroethylene (tetrafluoroethylene, PTFE). The mixing ratio of the binder is 5 to 30% by weight.
Furthermore, the hydrogen storage body is provided with one or a plurality of through holes in the central portion.

In the method for producing a hydrogen storage material according to the present invention, the powder of the hydrogen storage alloy and the binder made of the fluororesin are mixed and filled in the inside of the molding die, and this is pressure-molded. .

Specifically, the molding pressure is 40 Kg / cm ^2.
The above is set.

[0011]

In the above hydrogen storage material of the present invention, the powder of the hydrogen storage alloy is firmly integrated by the excellent binding force of the fluororesin, and at the same time, the shape of the fluororesin has an arbitrary predetermined shape. And the shape is maintained. In the hydrogen storage body, since the hydrogen storage alloy particles are strongly connected by the binding force of the fluororesin, when the hydrogen storage alloy absorbs and releases hydrogen, when expansion and contraction occur, Even if the hydrogen storage alloy is further pulverized, the swelling problem does not occur because the pulverized particles are prevented from scattering.

Further, when the powder of the hydrogen storage alloy is pressure-molded, the flexibility of the fluororesin causes the individual hydrogen storage alloy particles to enter the gaps between the hydrogen storage alloy particles, thereby filling the hydrogen storage alloy. The rate is increased.

When PTFE is used as the fluororesin, it becomes possible to mold it into a complicated shape due to the excellent moldability of PTFE. Moreover, if the mixing ratio of the binder (fluorinated resin) is set within the range of 5 to 30% by weight,
It is possible to increase the filling rate of the hydrogen storage alloy more than the conventional 50% while keeping the binding force of the fluororesin to a sufficient level.

Furthermore, by producing a pellet having one or a plurality of through holes formed in the hydrogen storage body, even if a large number of the pellets are filled in the container without any gap, the passage of hydrogen can be provided by the through hole of the pellet. Since it is formed, it is possible to take out hydrogen from the container and supply hydrogen to the container without any trouble.

In the method for producing a hydrogen storage material of the present invention, the powder of the hydrogen storage alloy and the binder made of the fluororesin are mixed and filled in the molding die, and compression force is applied to the mixture. The fluororesin exerts a binding force to strongly connect the alloy particles. As a result, the internal shape of the molding die is transferred, and a desired shape is obtained.

Here, if the molding pressure is set to 40 Kg / cm ² or more, the filling rate of the hydrogen storage alloy can be increased to near its limit value.

[0017]

EFFECTS OF THE INVENTION According to the hydrogen storage material of the present invention, the filling rate of the hydrogen storage alloy can be increased as compared with the conventional one, and thereby the performance of the hydrogen storage alloy application system can be improved. Further, according to the method for producing a hydrogen storage material of the present invention, no heat treatment is required when pelletizing the powder of the hydrogen storage alloy, which simplifies the manufacturing process.

[0018]

EXAMPLE As shown in FIG. 1, the hydrogen storage material of the present invention (1)
Is obtained by binding hydrogen-absorbing alloy particles (2) made of LaNi _4.55 Al _0.45 , for example, with PTFE (polytetrafluoroethylene), which is a kind of fluororesin, and having a predetermined pellet shape, for example, a diameter of 2 cm and a height of 1 to 1. It is pressure-molded into a 2 cm columnar shape.

Fluororesin is used for all chemicals at room temperature.
It has resistance to (acid, alkali, etc.) and also has excellent heat resistance. In particular, since PTFE is excellent in moldability among the fluororesins, it is possible to mold the hydrogen storage material (1) having an arbitrary shape.

FIG. 6 shows that the mixing ratio of PTFE is about 12% by weight.
Shows the relationship between the pressure at the time of pressure molding and the hydrogen storage alloy filling rate, and the filling rate rises above 0.5 with the increase of the molding pressure. 0.
It is saturated at 65. Therefore, the molding pressure is set to 40 Kg / cm ² or more, at which the filling rate is almost equal to that in the saturated state, and 100 Kg / cm ² in this embodiment.

FIG. 7 is a ratio of the original shape of the hydrogen storage material maintained in the process in which the hydrogen storage material repeats the hydrogen absorption and desorption cycle to gradually pulverize the alloy particles.
Change of (alloy retention rate) is 5% of PTFE addition, 10
% And 15% are measured. As shown in the figure, when the amount of PTFE added is 10% or more, the alloy retention rate hardly decreases. However, when the amount of PTFE added is less than 5%, the alloy retention rate significantly decreases when the number of cycles is 100 or more. ing. Therefore, the standard for the number of cycles is 1
If the number of times is 00, it can be said that the addition amount of PTFE needs to be set to 5% or more. This allows swelling,
The problem of micronization can be avoided.

FIG. 8 is a graph obtained by experimentally examining the relationship between the amount of PTFE added (binder mixing ratio) and the filling ratio of the hydrogen storage alloy. As shown, PTFE
A linear relationship is established between the addition amount and the filling rate, and in order to increase the filling rate from the conventional 50%, it is necessary to suppress the PTFE addition amount to about 30% or less.

From the results shown in FIGS. 7 and 8, therefore, in this embodiment, the mixing ratio of the binder is set in the range of 5% by weight to 30% by weight.

When molding the hydrogen storage body (1) shown in FIG. 1, a hydrogen absorbing alloy particle (2) and PTFE are kneaded and filled in a molding die (not shown) in predetermined amounts, respectively, and 100
A pressing force P of Kg / cm ² is applied. At this time, heating is unnecessary. As a result, the hydrogen-absorbing alloy particles (2) are bound to each other by PTFE, and the hydrogen-absorbing body (1) having a predetermined shape obtained by transferring the internal shape of the molding die is obtained.

FIG. 2 shows an example in which the present invention is applied to a hydrogen storage tank, and the hydrogen storage alloy of the present invention comprising hydrogen storage alloy particles (2) and a binder (3) in a tank container (4). And a cylindrical sintered filter (5) is installed in the center of the container (4) to form a passage for taking out and supplying hydrogen.

In the hydrogen storage tank, the expansion and contraction of the hydrogen storage alloy particles (2) are absorbed and relaxed by the PTFE binder (3) in the process of the hydrogen storage alloy particles (2) repeatedly absorbing and releasing hydrogen. Therefore, no excessive force is applied to the container (4). Therefore, the wall thickness of the container (4) can be formed thinner than before, and it is not necessary to give a special shape for increasing the strength.

Further, in the conventional hydrogen storage tank, a plurality of filters (5) are arranged to reduce the pressure loss due to the movement of hydrogen, but in the hydrogen storage body (1) of the present invention, Since the binder (3) itself has porosity and a sufficient passage for hydrogen is secured, the pressure loss is small and the filter
It is possible to reduce the number of (5) as compared with the conventional one.

The container (4) shown in FIG. 2 can be filled with a large number of small pellets as shown in FIG. 1, or a large hydrogen storage material corresponding to the shape of the container (4). It is also possible to mold and store this in the container (4).

FIG. 3 shows an example in which the hydrogen storage material of the present invention is applied to the actuator (8). In the container (41),
A hydrogen storage body composed of hydrogen storage alloy particles (2) and a binder (3) is press-molded into a predetermined shape and accommodated therein, and the lifting platform (81) is moved up and down as hydrogen is absorbed and released. is there.

Since PTFE of the binder (3) used in the hydrogen storage material of the present invention has excellent moldability, it is possible to mold a hydrogen storage material of any shape, for example, as shown in the figure. As described above, it is also possible to form an L-shape that avoids interference with other devices (9). by this,
It is possible to avoid the occurrence of dead space when arranging a plurality of devices, and it is possible to make the entire device compact.

Further, the hydrogen storage body (1) can be formed into a cylindrical shape having a through hole (7) in the center as shown in FIG. For example, if a hydrogen storage tank is configured by filling a large number of such hydrogen storage bodies (1) in the container (4) of FIG. 2, the hydrogen storage tank (1) can be filled with hydrogen through the through holes (7). Since the passage is formed, the filter (5) can be omitted.

When a heat utilization system is constructed using the hydrogen storage material of the present invention, metal powder such as aluminum or copper is added to the hydrogen storage material in order to improve the heat transfer performance of the hydrogen storage material of the system. In this case, it is necessary to avoid excessive reduction of the binding force of the binder (3) due to the addition of the metal powder.

FIG. 9 shows that when copper powder is added, P
The relationship between the amount of TFE added and an appropriate value of the amount of copper added is shown. When adding 5% by weight of PTFE, 38% by weight of copper is suitable, and the amount of addition of copper is reduced to 0 as the amount of addition of PTFE increases to 30% by weight.

FIG. 10 shows the relationship between the amount of PTFE added and the appropriate amount of aluminum added when aluminum powder is added. 5% by weight of PTFE
When it is added, the amount of aluminum added is appropriately 16% by weight, and the amount of aluminum added is decreased to 0 as the amount of PTFE added increases to 30% by weight.

As described above, the amount of addition of the metal powder is adjusted, the hydrogen storage body (1) is pressure-molded, and the hydrogen storage body is filled in a container such as a heat exchanger. The metal (6) scattered in the container directly contacts the heat exchange fins in the container, and the thermal conductivity increases. Also, since the binder (3) prevents swelling, the initial thermal conductivity can be maintained for a long time. Here, if the hydrogen storage body (1) is molded into a perforated shape as shown in FIG. 4, not only can the performance of the heat exchanger be improved, but also the structure can be simplified by omitting the filter.

According to the hydrogen storage material of the present invention, not only can the filling rate of the hydrogen storage alloy be increased as described above, but there is an advantage that handling is easy in transportation by a truck or the like. Further, in the conventional transportation by the powder of the hydrogen storage alloy, there is a problem that the alloy powder is scattered, but the hydrogen storage body of the present invention realizes the transportation without alloy loss.

The above description of the embodiments is for explaining the present invention and should not be construed to limit the invention described in the claims or to limit the scope thereof. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a perspective view of a hydrogen storage body according to the present invention.

FIG. 2 is a partially cutaway front view of a hydrogen storage tank.

FIG. 3 is a partially cutaway perspective view of an actuator.

FIG. 4 is a perspective view of a hydrogen storage body having a through hole.

FIG. 5 is a diagram showing a structure of a hydrogen storage material to which a metal is added.

FIG. 6 is a graph showing the relationship between molding pressure and filling rate.

FIG. 7 is a graph showing the relationship between the number of cycles and the alloy retention rate.

FIG. 8 is a graph showing the relationship between the amount of PTFE added and the filling rate.

FIG. 9 is a graph showing an appropriate amount of copper added with respect to the amount of PTFE added.

FIG. 10 is a graph showing an appropriate aluminum addition amount with respect to the PTFE addition amount.

[Explanation of symbols]

 (1) Hydrogen storage material (2) Hydrogen storage alloy particles (3) Binder (4) Container (5) Filter (6) Metal (7) Through hole (8) Actuator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ikuro Yonezu 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Yumiko Nakamura 2-5, Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd.

Claims (6)

[Claims] 1. A hydrogen storage body obtained by mixing a powder of a hydrogen storage alloy with a binder made of a fluororesin and press-molding the mixture into a predetermined shape. 2. The hydrogen storage material according to claim 1, wherein the fluororesin is polytetrafluoroethylene. 3. The hydrogen storage material according to claim 1, wherein the mixing ratio of the binder is 5 to 30% by weight. 4. The hydrogen storage body according to claim 1, wherein one or a plurality of through holes are formed in the central portion. 5. A method for producing a hydrogen storage body, which comprises mixing and filling a hydrogen storage alloy powder and a binder made of a fluororesin into a molding die, and press-molding the mixture. 6. The method for producing a hydrogen storage material according to claim 5, wherein the molding pressure is 40 kg / cm ² or more.