JPH0253362B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method of operating a hydrogen storage/release device, and more specifically, the present invention relates to a method of operating a hydrogen storage/release device, and in particular, a partition wall between a hydrogen storage metal (a general term for metals and metal hydrides; the same shall apply hereinafter) and a heat medium is separated as much as possible. The present invention relates to a method of operating a hydrogen storage/release device that can be made thinner, thereby improving heat exchange efficiency and increasing the storage/release rate of hydrogen gas.

A hydrogen storage/release device constructed by partitioning the hydrogen storage metal storage part and the passage path of the heat medium with a heat exchange wall is shown in Figures 1 and 2 (-line cross-sectional arrow in Figure 1). There are an external heat medium flow path type shown in FIG. 3 and FIG. 4 (a cross-sectional view taken along the line - in FIG. 3). In Figures 1 to 4, 1 is Ciel,
Reference numeral 6 indicates a metal storage container for storing hydrogen, 6a indicates a heat exchange wall, 7 indicates a hydrogen gas pipe, 7a indicates a header for hydrogen gas distribution and collection, and 13 indicates a filter. Hydrogen gas is introduced into the container 6 through the filter 13. It is structured to supply and discharge. And the first,
In FIG. 2, hydrogen gas is stored or released while exchanging heat by flowing a heat medium L around the container 6 containing the hydrogen storage metal M, and in FIGS. A heat medium passage is formed inside the chamber, and by flowing a heat medium L through the passage as shown by arrows A and B, hydrogen gas is stored or released while exchanging heat. By the way, in this type of hydrogen storage/release device, hydrogen storage metal M
The heat exchange wall 6a between the heat exchanger and the heat medium L had to be considerably thick. That is, the following reaction formula: Metal + H ₂ The equilibrium dissociation pressure in a metal hydride varies depending on the type of hydrogen storage metal and operating temperature, but for example, if the hydrogen storage metal is LaNi ₅ and the operating temperature is 80°C, it is approximately 21
It is known that it can reach up to Kg/ ^cm2 . On the other hand, the pressure on the heat medium side is generally low, although it depends on the discharge power of the heat medium supply pump, and is usually less than 4 kg/cm ² , so the pressure difference across the heat exchange wall 6a is 17 kg/cm ² or more. Become. Therefore, it was necessary for the heat exchange wall 6a to have a pressure-resistant design that fully takes such a large pressure difference into consideration. As a result, the thickness of the heat exchange wall 6a had to be increased, and the following disadvantages had to be complied with.

(1) The reaction rates of hydrogen gas storage and desorption in hydrogen storage metals are generally controlled by the heat transfer rate, but because the heat exchange wall is thick, the heat transfer rate decreases and the hydrogen gas storage and release rate decreases.・Release rate decreases.

(2) When the cycle of hydrogen absorption and desorption is repeated, the temperature of the storage container also rises and falls repeatedly, and if the heat exchange wall is thick, the heat capacity of the storage container increases. Therefore, sensible heat loss increases and hydrogen storage and
The thermal efficiency of the emitting device is reduced.

(3) Hydrogen storage metals are usually filled in the form of fine powder, but by storing hydrogen gas, the metal lattice expands and the metal powder becomes even more finely divided, reducing its bulk density. The volume of the entire metal powder expands. On the other hand, pressure vessels cannot be made of flexible materials or processed to give them flexibility, and in order to be designed to withstand pressure, the wall thickness of the vessel must be increased. There is almost no elastic deformation ability, and the expansion of the metal powder layer appears as an increased compaction force between the fine powder particles and a pressing force against the heat exchange wall surface. These pressures are surprisingly large; for example, in experiments on LaNi ₅ ,
It can reach up to 450Kg/ ^cm2 . If the pressing force applied to the heat exchange wall surface becomes excessive, the container will undergo plastic deformation, leading to destruction in extreme cases.

(4) When the compressive force applied to the fine powder exceeds a certain value, the metal powder begins to sinter and solidify, increasing the resistance to passage of hydrogen gas. As a result, a pressure distribution is formed in the flow direction of the hydrogen gas inside the storage heat container.
By the way, the hydrogen absorption/release reaction rate depends on the ease of heat absorption and heat generation, and of course, the hydrogen gas pressure,
To be precise, it is also affected by the pressure difference between the hydrogen gas pressure and the equilibrium dissociation pressure. Therefore, if there is a distribution of hydrogen gas pressure within the storage container, a uniform reaction will be difficult to occur and the operating efficiency of the hydrogen storage/release device will be reduced. In order to prevent deformation or destruction of the storage container or sintering and solidification of the metal powder layer, it is possible to take measures such as lowering the filling rate of the hydrogen storage metal in the storage container or reducing the hydrogen pressure itself. Naturally, all of these measures sacrifice the hydrogen gas storage/release ability, resulting in the loss of practical value as a hydrogen storage/release device.

As described above, the conventional apparatus has various drawbacks due to the large thickness of the heat exchange wall, and it has been desired to reduce the thickness of the heat exchange wall as much as possible.

The present invention has been made with attention to these circumstances, and is a method for storing and desorbing hydrogen without causing wear and tear on the device, and in which excellent thermal efficiency and hydrogen storage and desorption speed can be obtained. This paper attempts to provide a method for operating a hydrogen storage/release device.

Therefore, the operating method of the present invention is a method of operating a hydrogen storage/release device in which a heat medium is passed through in contact with a housing portion of a hydrogen storage metal, and the method includes equalizing the pressure difference between the inside and outside of the storage portion. The key point is to operate with as little energy as possible.

The configuration and effects of the present invention will be explained below with reference to the drawings.

Figure 5 shows hydrogen storage and storage for carrying out the method of the present invention.
1 is a flowchart showing an example of a discharge device, 1 is a shell, 2 is a heat medium feeding pump, 4 is a pressure equalization device, and 9 is a heat medium heating/cooling device (hereinafter referred to as a heating/cooling device). The illustrated hydrogen storage/release device 5 is of the above-mentioned external heat medium flow path type, and a plurality of containers 6 storing hydrogen storage metals M are disposed in the shell 1, and one end of the storage container 6 is disposed in the shell 1. A hydrogen gas pipe 7 is connected to the side via a header 7a. An on-off valve 3 is interposed in the hydrogen gas pipe 7.

Further, a heat medium introduction pipe 8 and a heat medium discharge pipe 8a are attached to the shell 1, and the shell 1, the heating/cooling device 9, and the heat medium supply pump 2 are connected to the heat medium introduction pipe 8.
A heat medium circulation system is formed by connecting them through a discharge pipe 8a and the like.

On the other hand, the pressure equalizing device 4 in the illustrated example is divided into two chambers by a piston 11 that can slide inside the device, and a branch pipe 8b from the heat medium introduction pipe 8 is in one chamber, and a hydrogen gas Branch pipes 7b from the pipe 7 are connected to the other chamber, respectively.

When performing a hydrogen gas storage operation using the device shown in this figure, hydrogen is introduced from the hydrogen gas pipe 7 into the storage container 6 while flowing the heat medium L cooled by the heating/cooling device 9 into the shell 1. Inject gas under pressure. On the other hand, when performing a hydrogen gas release operation, the heat medium L heated by the heating/cooling device 9 is transferred to the shell 1.
Hydrogen storage metal M inside the storage container 6
Hydrogen gas is dissociated from the hydrogen gas, collected in the hydrogen gas pipe 7, and taken out of the system.

By the way, as mentioned above, the hydrogen gas pressure and the heat medium pressure are transmitted to the pressure equalizing device 4 via the branch pipes 7b and 8b, respectively, so that all conditions including during each step of the hydrogen storage operation and hydrogen release operation described above In this case, when the hydrogen gas pressure is high, the piston 11 in the pressure equalizing device 4 is pushed and slid toward the heat medium side, and the pressure of the heat medium L is increased. Moreover, when the hydrogen gas pressure is lower, contrary to the above, the piston 11 slides toward the hydrogen gas side, thereby lowering the pressure of the heat medium L.
In other words, the pressure of the hydrogen gas that presses the heat exchange wall 6a from the inside and the pressure of the heat medium that presses the heat exchange wall 6a from the outside always try to be equal due to the function of the pressure equalization device, so that The pressure difference has become extremely small, so it is no longer necessary to increase the thickness of the heat exchange wall 6a as in the past. In other words, there is no longer any risk of deformation or breakage even if the structure is made relatively thin. As a result, heat transfer through the heat exchange wall 6a is rapid, the heat capacity of the storage container 6 itself is small, and sensible heat loss is greatly reduced, resulting in extremely high heat exchange efficiency.

Although the basic structure of the present invention is as described above, the specific means and apparatus for performing the pressure equalization operation may also be based on the embodiments shown below. FIG. 6 shows an example in which a bellows 18 is provided inside the cylinder S. The inside of the bellows 18 is communicated with a hydrogen gas branch pipe 7b, and the space between the cylinder S and the bellows 18 is communicated with a heat medium branch pipe 8b. Note that a diaphragm may be used instead of the bellows 18. Fig. 7 shows an example in which the pressure equalization device is composed of two cylinder chambers S ₁ and S ₂ .
Pistons 11a and 11b disposed in S ₁ and S ₂ are connected by a rod 22. One cylinder _S1 is connected to the hydrogen gas branch pipe 7b, and the other cylinder chamber _S2 is connected to the heat medium branch pipe 8b. In addition, if the heat medium is a liquid, the vapor pressure at the above operating temperature is low, and there is no problem even if a small amount of vapor mixes into the hydrogen gas, the piston 11 is omitted in the pressure equalizing device shown in FIG. It may be something that has been done.

In each of the above embodiments, a pressure equalization device was used, but the point is that the pressure difference between the internal pressure and the external pressure should be as small as possible by sandwiching the heat exchange wall of the hydrogen storage metal storage container. As an alternative method, for example, in Fig. 5, the installation of the pressure equalizing device is omitted, and pressure detection devices are attached to the hydrogen gas pipe 7 and the heating medium introduction pipe 8, respectively, so that the pressure of the hydrogen gas and the pressure of the heating medium are equalized. For example, a method may be used to adjust the pressure to push the heat medium into the storage shell.

As described above, by making the hydrogen gas pressure and the pressure of the heat medium substantially equal, there is no need to design the heat exchange wall to withstand pressure as in the past, and many constraints are eliminated, improving the thermal efficiency of the equipment. It became possible to improve efficiency.

Since the method of the present invention has the above-described configuration, it is possible to form a thin heat exchange wall, and it is possible to design and manufacture a device with a structure that has not been previously used in this field. is possible. As a typical example, devices as shown in FIGS. 8 to 19 are exemplified.

8 and 9 (a cross-sectional view taken along the line - in FIG. 8) show a hydrogen storage metal storage container 6 which is equipped with a filter tube 13 with heat transfer fins, and the container 6 is a flexible metal storage container 6. It is formed by joining a side plate 10 to a corrugated plate 12 made of a thin plate, and has a hydrogen storage metal M filling port 14 at one end, and a hydrogen gas pipe 7 communicating with a filter pipe 13 at the other end. . Note that the filling port 14 is closed after the hydrogen storage metal M is stored in the container 12. The reason why the container is formed in the shape of a corrugated plate is that when the hydrogen storage metal M stores hydrogen and expands in volume, the troughs of the corrugated plate 12 swell to absorb the expansion. On the other hand, the heat transfer fin 15 includes a horizontal plate 16 whose end edge is fixed to the filter tube 13 and a vertical plate 17 attached in a direction perpendicular to the horizontal plate 16 at a position corresponding to the bulge of the container 12. It is housed in the container 6 so as to be buried in the hydrogen storage metal M. The heat transfer fins 15 have the function of quickly transferring the heat that has entered through the heat exchange wall and homogenizing the heat distribution inside the storage container 6, thereby further improving the heat transfer effect and quickly transferring the heat. This enables a hydrogen gas storage/release cycle.

FIG. 10 shows the storage container 6 shown in FIGS. 8 and 9.
This is a partially cutaway side view showing a hydrogen absorbing/releasing body 5a combined via a plurality of rod-shaped spacers 18. The heat medium L enters the shell 1 from the inlet 8c and passes between the spacer 18 and the container 12. The liquid then passes through and is further discharged from the discharge port 8d. In addition, when combining the hydrogen storage/release body 5a, it is also possible to fix it with a frame. The combined hydrogen storage/release body 5a is fixed to the inner wall of the shell 1 using a fixture 23 or the like.

FIG. 11 is a partially cutaway perspective view showing another application example, in which a corrugated metal plate 17 acting as a heat transfer member is disposed inside a box-shaped storage container 6b made of a thin metal plate, and a corrugated A filter 13 is installed at one longitudinal end of the metal plate 17 (the opening on the left front side in the drawing).
A hydrogen gas collection passage 19 is formed through the hydrogen gas collection passage 19, and the hydrogen gas collection passage 19 communicates with the hydrogen gas pipe 7 through a header pipe. The other longitudinal end of the corrugated metal plate 17 (the opening on the right side in the figure) communicates with the hydrogen storage metal filling port 14, and the filling port 14 is closed after the metal is filled. When a plurality of such storage containers 6 are combined, the corrugated spacers 20 having the same shape as the corrugated metal plates 17 are alternately combined so as to be perpendicular to each other to form the hydrogen storage/release body 5a. The heat medium L is flowing in the direction of arrow C along the waves of the spacer 20. By incorporating such a hydrogen storage/release body 5a into the shell 1 as shown in FIG. 12, an external heat medium flow path type hydrogen storage/release device 5 can be manufactured. Further, FIG. 13 is a schematic side view showing the internal heat medium flow path type hydrogen storage/release device 5, in which the hydrogen storage/release body 5a shown in FIG.
The hydrogen storage/release body 5b corresponds to the form in which the hydrogen gas collection passage 19 is omitted (however, the filter 1
3a and the spacer 20 are attached as they are), a cover plate 21 is attached to the openings at both ends of the spacer 20 in the longitudinal direction so as to seal some space, and the cover plate 21 is penetrated through the cover plate 21 to A heat medium inlet pipe 8e and a heat medium discharge pipe 8f communicating with the containment space are attached and housed in the shell 1. Although the hydrogen gas pipe 7 is attached to the shell 1, it is not necessary to attach a header pipe to each container 6b.

14 and 15 (cross-sectional view taken along the line - in FIG. 14) show a hydrogen storage/release body 5c formed by combining a plurality of cylindrical containers 6 with different diameters in a layered manner with spacers 20 interposed therebetween. For example, the heat medium L flows from the inlet pipe 8a through the shell 1 to the outlet pipe 8b.

16 and 17 (cross-sectional view taken along the line - in FIG. 16) are application examples in which a flat storage container is spirally curved, and the filter tube 13 is installed inside along the terminal edge of the outermost layer. ing.

18 and 19 (a cross-sectional view taken along the line - in FIG. 18) show an example of a spiral storage container similar to the above, but the filter tube 13 is also curved in a spiral shape and has a spiral edge on one side. It is decorated along.

The application examples shown in FIGS. 14 to 19 above are all structures that can be adopted because the heat exchange walls are thin, and the storage containers can be arranged densely in a small-volume shell, so the unit volume A large heat transfer area can be obtained, and excellent heat transfer efficiency can be obtained.

The present invention is configured as described above, and has been able to obtain the effects summarized below.

(1) Since the pressure of the hydrogen gas inside the storage container and the pressure of the heat medium are almost equal, the wall thickness of the storage container can be made thinner, and the efficiency of heat transfer through the heat exchange wall is extremely improved. . For example, when using LaNi ₅ as a hydrogen storage alloy, the outer diameter
When hydrogen is filled in a 21.7mm stainless steel pipe and heat exchanged with a heat medium at 110℃, the dissociation pressure of hydrogen is 48℃.
Kg/cm ² G, so the conventional method required the wall thickness of the stainless steel pipe to be 3 mm or more, but with the method of the present invention, the pressure difference between the heat medium and hydrogen is 4 Kg/cm ² G.
This means that the wall thickness of the pipe can be kept within 1 mm. Therefore, the heat transfer rate was improved by about 5%.

(2) Since the heat exchange wall thickness of the storage container could be made thinner, the heat capacity of the storage container was reduced, and sensible heat loss during the hydrogen storage/release cycle was minimized, improving thermal efficiency. In the above example, when the stainless steel tube is filled with 40% by volume of alloy, the heat capacity per 1 kg of alloy is
The heat capacity was 0.37 cal/g, whereas in the present invention, the wall thickness of the tube can be made thinner, so the heat capacity is lower.
0.09cal/g, resulting in sensible heat loss of 34%
Decrease.

(3) Since the heat exchange wall could be made thinner, the processability of the container improved, and it became possible to freely form flexible types or types with complex shapes.

[Brief explanation of drawings]

Fig. 1 is an explanatory side view showing an external heat medium flow type storage container, Fig. 2 is a cross-sectional view taken along the line - in Fig. 1, and Fig. 3 is a side view showing an internal heat medium flow type storage container. 4 is a cross-sectional view taken along the - line in FIG. 3, and FIG. 5 is a hydrogen storage system using the method of the present invention.
FIGS. 6 and 7 are flow diagrams of the discharge device, FIGS. 6 and 7 are examples of the pressure equalization device, and FIGS. 8 to 19 are explanatory diagrams of the storage container to which the method of the present invention is applied. 1... Shell, 4... Pressure equalization device, 5... Hydrogen storage/release device, 6... Storage container, 7... Hydrogen gas pipe, 8... Heat medium introduction pipe, 8a... Discharge pipe, 1
3...Filter, 20...Spacer.

Claims (1)

[Claims] 1. A method of operating a hydrogen storage/release device in which a heat medium is passed through in contact with a metal housing for hydrogen storage, the method comprising reducing the pressure difference between the inside and outside of the housing as much as possible by pressure equalization operation. A method of operating a hydrogen storage/release device characterized by: