JP2003270113A - Hydrogen storage device, and method of detecting residual amount of hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately grasp a hydrogen residual amount in a storage tank over the whole range of 0-100%. <P>SOLUTION: This device is provided with the storage tank 3 packed with hydrogen storage alloy MH to store hydrogen supplied from a hydrogen cylinder 2, a quartz oscillator 20 provided in the storage tank 3 and formed with a hydrogen adsorption film 25 by surface treatment, a detecting circuit 13 for measuring a characteristic frequency of the quartz oscillator 20 varied in response to a hydrogen gas amount adsorbed to the hydrogen adsorption film 25, and a computing circuit 14 for computing the residual amount of the hydrogen in the storage tank 3, based on the characteristic frequency of the quartz oscillator 20 measured by the detecting circuit 13. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrogen storage device for storing hydrogen gas in a storage tank filled with a hydrogen storage alloy,
For example, the present invention relates to a stationary hydrogen storage device or a mobile hydrogen storage device mounted on a transportation device such as an automobile for energy storage.
The present invention relates to a hydrogen storage device and a hydrogen remaining amount detection method that can be accurately grasped over the entire range of 100%.

[0002]

2. Description of the Related Art In the hydrogen storage device described above, the hydrogen storage alloy filled in the storage tank has a PCT shown in FIG.
As shown in the curve (hydrogen pressure-composition isotherm), there is a region called the plateau region where the hydrogen storage amount changes greatly with a small pressure change, but in this plateau region there is a difference between hydrogen adsorption and hydrogen desorption. Since there is a hysteresis in which the amount of stored hydrogen differs depending on the pressure, it is difficult to accurately predict the amount of stored hydrogen, that is, to detect the amount of hydrogen remaining in the tank, even if the pressure is measured in this region. Is.

Conventionally, as a method of detecting the amount of hydrogen remaining in the tank of the above hydrogen storage device, for example, a method of detecting the temperature in the hydrogen tank (Japanese Patent Laid-Open No. 63-
No. 246459) or a level sensor in which the volume (bulk) of the hydrogen storage alloy is installed in the tank by utilizing the property that the crystal lattice expands and the volume increases as the hydrogen storage alloy stores hydrogen. A method for detecting and estimating the residual hydrogen amount (Japanese Patent Laid-Open No. 5-223012) or a homogenizing heat treatment for ensuring a plateau property, followed by a further reheat treatment to obtain a P-C-T curve A method of making it possible to detect the remaining amount by pressure by providing an inclination (Japanese Patent Laid-Open No. 10-245).
663).

[0004]

However, in the above-described method for detecting the temperature in the hydrogen tank, it is practically impossible to detect the remaining amount under conditions where the temperature of the tank is low such as during cold start. This is possible, and in addition, the temperature is low while the remaining amount is high, and the temperature rises rapidly when the remaining amount decreases, so there is a problem that the situation cannot be recognized until just before the hydrogen runs out.

Further, in the method of estimating the hydrogen remaining amount by detecting the volume (bulk) of the hydrogen absorbing alloy with the level sensor installed in the tank, the hydrogen remaining amount is measured at the initial stage when the hydrogen absorbing alloy is not deteriorated. Although it can be detected relatively accurately, if the hydrogen storage alloy is pulverized and the volume changes due to repeated adsorption and desorption, or if it is affected by vibration such as when it is used as energy storage for transportation equipment. However, unlike the liquid fuel, it is difficult to measure the volume of the hydrogen storage alloy accurately.

Further, the method capable of detecting the remaining amount by the pressure increases the cost because two heat treatment steps are required, and it is difficult to delicately control the slope of the PCT curve by the heat treatment. In addition, inclining the P-C-T curve may lead to a decrease in the hydrogen storage amount per unit weight of the alloy. Furthermore, when the hydrogen absorption / desorption is reversed in the plateau region in which the above-mentioned hysteresis exists (when hydrogen filling is started while hydrogen is being consumed), the change in the hydrogen storage amount with respect to the pressure causes an extremely complicated behavior. Therefore, there is a problem that it becomes more difficult to predict the remaining amount of hydrogen, and it has been a conventional problem to solve these problems.

[0007]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above-mentioned conventional problems. The hydrogen storage alloy has a hydrogen storage capacity of 0 to 100 without lowering the storage capacity per unit weight of the storage alloy. It is an object of the present invention to provide a hydrogen storage device and a hydrogen remaining amount detection method capable of accurately grasping the entire range of%.

[0008]

According to a first aspect of the present invention, there is provided a hydrogen storage device, comprising: a storage tank filled with a hydrogen storage alloy for storing hydrogen gas supplied from a hydrogen supply source; A quartz oscillator provided with a hydrogen gas adsorption film formed by surface treatment, and a measuring means for measuring the natural frequency of the quartz oscillator that changes according to the amount of hydrogen gas adsorbed to the hydrogen gas adsorption film, The hydrogen storage device is characterized in that it has an arithmetic means for calculating the remaining amount of hydrogen in the storage tank based on the natural frequency of the crystal unit measured by the measuring means. This is a means for solving the conventional problems.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the hydrogen storage device and the remaining hydrogen detection method according to the present invention, when a hydrogen gas adsorption film formed by surface treatment on a quartz oscillator adsorbs hydrogen gas, only the adsorbed hydrogen gas is absorbed. The weight of the crystal unit changes. Along with this, the natural frequency of the crystal unit changes, so by monitoring the amount of change in the natural frequency, the hydrogen gas adsorption amount can be calculated.

That is, the natural frequency of the crystal resonator when the hydrogen gas adsorption film formed by the surface treatment does not adsorb hydrogen gas is F0, and the natural frequency of the crystal resonator when hydrogen gas is adsorbed. Is Fa, and the change in the natural frequency of the crystal unit due to the change in the adsorption amount of hydrogen gas is Δ
When the amount of adsorbed hydrogen gas per unit area of Fa and the adsorbed hydrogen gas film is A, the relation of Expression 1 is established.

[0011]

[Formula 1] ΔFa = Fa−F0 = −K · A

In the above relational expression, K is a constant, and the relationship between the hydrogen gas adsorption film and hydrogen gas can be experimentally obtained in advance. If this constant is calculated in advance, the crystal oscillator The amount of adsorbed hydrogen A can be obtained by calculating the amount of change ΔFa in the natural frequency and performing back calculation.
Therefore, if the relationship between the hydrogen storage amount and the remaining amount is clarified in advance, the hydrogen remaining amount in the tank of the hydrogen storage device using the hydrogen storage alloy can be detected.

Further, in the hydrogen storage device and the hydrogen remaining amount detecting method according to the present invention, as a specification of the crystal unit for measuring the change of the resonance frequency, the shear vibration mode is set as described in claims 3 and 12. A Y-plate crystal oscillator for detection is suitable, but a device in which the cutting angle is slightly shifted from the Y-plate is also included in consideration of temperature characteristics and the like.

This quartz oscillator has a structure in which metal electrodes are provided on both sides of a quartz plate, and a hydrogen gas adsorption film by surface treatment is formed on at least one side (both sides are acceptable) of the metal electrode. It At this time, it is desirable that the hydrogen gas adsorption film is formed to have a thickness of 0.01 to 10 μm capable of suppressing resonance resistance.

Further, in the hydrogen storage device and the hydrogen remaining amount detecting method according to the present invention, there are various kinds of materials as described above as materials that can be used for the hydrogen gas adsorption film, but the degree of freedom in design is high. Moreover, it is most preferable to employ a carbon-based material capable of controlling the adsorption capacity for hydrogen. If a carbon-based material is used for the hydrogen gas adsorption film,
When a hydrogen storage alloy is used, problems such as pulverization that occur during repeated use are unlikely to occur, and handling becomes easy.

When amorphous carbon is used as the carbonaceous material, carbon nanotubes and fullerenes having a large hydrogen storage capacity per unit weight (activated carbon, graphite, graphite intercalation compounds, carbon nanofibers can also be used)
The detection sensitivity and accuracy are improved by mixing such substances.

Furthermore, in the hydrogen storage device and the hydrogen remaining amount detecting method according to the present invention, when a carbon-based material is used for the hydrogen gas adsorption film, the hydrogen-gas adsorption film made of the carbon-based material is formed on the quartz oscillator. As a surface treatment method for achieving this, as described in claims 7 and 16, a method of forming by firing a carbon-based material in an inert gas is typical. Further, as described in claims 8 and 17, a surface treatment method is adopted in which a solution containing a carbon-based material and a binder resin is formed on a quartz oscillator through a drying step for removing a solvent. Is also possible.

Furthermore, in the hydrogen storage device and the hydrogen remaining amount detecting method according to the present invention, the hydrogen storage alloy filled in the storage tank and the material used for the hydrogen gas adsorption film formed on the quartz resonator by the surface treatment are used. The combination is
Although not particularly limited, as described in claims 9 and 18, if the same material and material having the same property are used in common for both, a similar P-C-T curve is exhibited. So desirable. When a material different from the hydrogen storage alloy to be filled in the storage tank is used for the hydrogen gas adsorption film, it can be adopted if the relationship of the P-C-T curve for each material is clarified in advance.

[0019]

EFFECTS OF THE INVENTION According to the present invention, because of the above-mentioned configuration, the plateau region of the hydrogen storage alloy, in which it is difficult to detect the remaining amount by simply monitoring the internal pressure of the tank and performing arithmetic processing, Over the entire range of 0-100%,
This has an extremely excellent effect that the remaining amount of hydrogen in the storage tank can be easily and accurately detected in real time in any amount.

In particular, in the inventions set forth in claims 2, 3 and 11, 12, because of the above-mentioned structure, it is possible to detect the remaining amount of hydrogen in the storage tank more accurately. Excellent effect is brought about.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the hydrogen storage device according to the present invention.

As shown in FIG. 1, this hydrogen storage device 1
Is equipped with a storage tank 3 for storing hydrogen supplied from a hydrogen cylinder (hydrogen supply source) 2 filled with a hydrogen storage alloy MH, and a hydrogen supply path 4 connected to the hydrogen cylinder 2 is
A hydrogen cylinder regulator 5, a stop valve 6 and a quick connector 7 are provided.

The storage tank 3 communicates with a power source through a storage-side hydrogen take-out passage 8, and a hydrogen take-out regulator 9 and a hydrogen flow rate controller 10 are provided in the flow passage 8, respectively. The hydrogen gas in the storage tank 3 is supplied to the power source through the storage-side hydrogen extraction passage 8.

Further, the storage tank 3 is provided with a crystal oscillator 20 for monitoring the internal condition, a pressure gauge 11 as pressure detection means, and a thermometer 12 as temperature detection means.

In this embodiment, the crystal unit 20 is
As shown in FIGS. 2A and 2B, a crystal plate having a diameter of 25 mm and a thickness of 0.35 mm (AT cut, fundamental frequency: 6 M)
Hz) 21 and a front surface side electrode 22 and a back surface side electrode 23 are formed on the front surface and the back surface, respectively,
A lead wire 24 is connected to each of the electrodes 22 and 23.

The center of the surface of the crystal plate 21 is shown in FIG.
As shown in (c) and (d), a hydrogen gas adsorption film 25 is formed. The hydrogen gas adsorption film 25 is formed by arranging a solution in which a carbon-based material is dissolved or dispersed in an appropriate solvent on the surface of the quartz plate 21 and then firing it in an inert gas. At this time, in order to form the hydrogen gas adsorption film 25 only on the central portion of the electrode 22 on the surface side of the crystal plate 21, a masking process was performed on the surface of the crystal plate 21 in advance. The carbonaceous material to be dissolved or dispersed may be a polymer compound that produces non-graphitizable carbon after firing in an inert gas.

The crystal oscillator 20 having the hydrogen gas adsorption film 25 is connected to the arithmetic circuit (arithmetic means) 14 via the detection circuit (measuring means) 13, and in the arithmetic circuit 14,
In the storage tank 3, based on the natural frequency of the crystal unit 20 measured in the detection circuit 13, that is, the natural frequency of the crystal unit 20 that changes according to the amount of hydrogen gas adsorbed on the hydrogen gas adsorption film 25. The remaining hydrogen amount is calculated and the calculation result is displayed on the remaining hydrogen meter 15.

The pressure gauge 11 and the thermometer 12 are also the detection circuit 1
3 are connected to the arithmetic circuit 14 respectively, and each data from the pressure gauge 11 and the thermometer 12 is connected to the arithmetic circuit 14
It is used as a correction for the calculation of the remaining hydrogen amount in.

Further, a circulating medium line 16 is arranged in the storage tank 3, and a large number of fins are provided in the circulating medium line 16 so as to have a function of a heat exchanger, so that hydrogen adsorption / desorption can be performed efficiently. In addition, when the storage tank 3 is filled with hydrogen, the circulating medium line 16 functions as a cooler to remove the heat of adsorption generated, while the storage tank 3 is filled with hydrogen.
When hydrogen is taken out from the tank, the circulating medium line 16 is made to function as a heater to promote desorption of hydrogen.

A backflow prevention valve can be installed in the hydrogen supply passage 4 and the storage-side hydrogen extraction passage 8 if necessary.

Therefore, in an environment of 25 ° C., the storage tank 3 of the hydrogen storage device 1 is filled with hydrogen gas.
When the behavior of the hydrogen gas filling amount and the frequency when the extraction was repeated was examined, the results shown in FIG. 3 were obtained.

Basic frequency of the crystal plate 21 adopted for the crystal unit 20 (frequency before forming the hydrogen gas adsorption film 25)
Was 6 MHz, but the fundamental frequency (frequency when the hydrogen storage amount was 0 wt%) after the treatment for forming the hydrogen gas adsorption film 25 was in the range of 5.926370 to 5.926380 MHz. As shown in Fig. 3, the frequency decreases as the hydrogen storage amount increases, and at 2 wt% it is approximately 5.925000 MHz, 4 wt%
Was about 5.923500 MHz, and 6 wt% was about 5.922000 MHz.

That is, when the filling of the storage tank 3 with hydrogen gas is started, the hydrogen gas is also stored in the hydrogen gas adsorption film 25 of the crystal plate 21 adopted in the crystal resonator 20, and the mass increases, so that the resonance frequency is increased. Will fall. On the contrary, when the hydrogen gas is taken out from the storage tank 3, the hydrogen gas is also released from the hydrogen gas adsorption film 25 on the crystal plate 21 adopted for the crystal resonator 20 and the mass is reduced, so that the resonance frequency is increased again. Return to the frequency before filling with hydrogen gas.

Although there is a hysteresis with respect to the pressure at the time of filling / extracting, the amount of hydrogen gas adsorbed is directly measured in the measurement by the crystal unit 20 in this embodiment, and therefore the hysteresis with respect to the pressure is measured. It has nothing to do with hysteresis. Further, the relationship between the hydrogen gas adsorption amount and the frequency change plotted in FIG. 3 is almost linear in the measurement region. Therefore, it has been proved that the remaining amount of hydrogen gas in the storage tank 3 can be predicted more accurately than the conventional method.

In the above-described embodiment, when the hydrogen gas adsorption film 25 is formed on the crystal plate 21 of the crystal unit 20, a solution in which a carbonaceous material is dissolved or dispersed in an appropriate solvent is applied to the surface of the crystal plate 21. After being placed on top, it is formed by firing in an inert gas,
The method is not limited to this, and as another method of forming the hydrogen gas adsorption film 25 on the quartz plate 21, a binder resin for binding the carbon-based material to be surface-treated and the carbon-based material that is fine powder is used as a solvent. It is also possible to adopt a method in which a solution containing a carbon material and a binder resin is melted, and a solution containing a carbon material and a binder resin is placed on the crystal plate 21, followed by a drying step for removing the solvent.

At this time, if necessary, carbon nanotubes or fullerenes having a large hydrogen storage capacity (activated carbon, graphite, graphite intercalation compounds, carbon nanofibers may be used) or the like may be mixed to improve the detection accuracy. It is possible.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a hydrogen storage device according to the present invention.

2A and 2B are front side perspective explanatory views (a), back side perspective explanatory views (b), and a hydrogen gas adsorption film are formed before forming a hydrogen gas adsorption film showing the crystal oscillator of the hydrogen storage device in FIG. It is a front side perspective explanatory view (c) and a sectional explanatory view (d) after forming a hydrogen gas adsorption film.

3 is a graph showing the behavior of the hydrogen gas filling amount and the frequency when the hydrogen gas is repeatedly filled and taken out from the storage tank of the hydrogen storage device in FIG.

FIG. 4 P-C-T of hydrogen storage alloy filled in storage tank
It is a graph which shows a curve.

[Explanation of symbols]

1 Hydrogen storage device 2 Hydrogen cylinder (hydrogen supply source) 3 storage tanks 11 Pressure gauge (pressure measuring means) 12 Thermometer (temperature detection means) 13 Detection circuit (measuring means) 14 Arithmetic circuit (arithmetic means) 20 crystal unit 25 Hydrogen gas adsorption film MH hydrogen storage alloy

Claims (18)

[Claims] 1. A storage tank for storing hydrogen gas supplied from a hydrogen supply source filled with a hydrogen storage alloy, and a quartz resonator provided in the storage tank and having a hydrogen gas adsorption film formed by surface treatment. A measuring means for measuring the natural frequency of the crystal unit, which changes according to the amount of hydrogen gas adsorbed on the hydrogen gas adsorption film, and the storage based on the natural frequency of the crystal unit measured by the measuring unit. A hydrogen storage device comprising a calculation means for calculating the remaining amount of hydrogen in the tank. 2. The hydrogen storage device according to claim 1, wherein the storage tank is provided with a pressure detecting means for detecting a pressure inside the tank and a temperature detecting means for detecting a temperature inside the tank. 3. The hydrogen storage device according to claim 1, wherein the Y-plate crystal oscillator capable of detecting the shear vibration mode is a crystal oscillator. 4. The hydrogen gas adsorbing film contains hydrogen chemically or physically such as a hydrogen storage alloy, a carbonaceous material, zeolite, alumina, silica, titania, a mixture of any combination thereof, or a substitute of a different element. The hydrogen storage device according to any one of claims 1 to 3, which is made of an adsorbable material. 5. The hydrogen storage device according to claim 4, wherein the carbon-based material used as the hydrogen gas adsorption film is any one of amorphous carbon, carbon nanotube, fullerene, and a mixture of any combination thereof. 6. Amorphous carbon is activated carbon, graphite,
The hydrogen storage device according to claim 5, wherein the hydrogen storage device is made of any one of a graphite intercalation compound, carbon nanofibers, and a mixture of any combination thereof. 7. The hydrogen storage device according to claim 5, wherein the hydrogen gas adsorption film is formed by firing a carbon-based material in an inert gas. 8. The hydrogen gas adsorption film according to claim 5, wherein the hydrogen gas adsorption film is formed through a drying step for removing a solvent, which is performed in a state in which a solution containing a carbon-based material and a binder resin is placed on a quartz oscillator. The hydrogen storage device described. 9. The hydrogen storage device according to claim 1, wherein the hydrogen gas adsorption film is formed of a hydrogen storage alloy exhibiting the same P-C-T curve as the hydrogen storage alloy in the storage tank. 10. A crystal resonator having a hydrogen gas adsorption film formed by surface treatment is used as a storage tank when detecting the remaining amount of hydrogen in the storage tank of a hydrogen storage device having a storage tank filled with a hydrogen storage alloy. In addition to measuring the natural frequency of the crystal unit, which changes according to the amount of hydrogen gas adsorbed on the hydrogen gas adsorption film, and performing an operation based on the measured natural frequency of the crystal unit, A method for detecting the remaining amount of hydrogen, which comprises estimating the remaining amount of hydrogen. 11. The method for detecting the remaining amount of hydrogen according to claim 10, wherein the method is used to calculate the remaining amount of hydrogen by detecting the pressure and temperature in the storage tank. 12. The crystal oscillator used is a Y-plate crystal oscillator capable of detecting a shear vibration mode.
1. The method for detecting the remaining amount of hydrogen according to 1. 13. A hydrogen gas adsorbing film comprising hydrogen or a hydrogen absorbing alloy, a carbonaceous material, zeolite, alumina, silica, titania, and a mixture of any combination thereof, or a substitute of a different element, such as hydrogen chemically or physically. 13. The method for detecting the remaining amount of hydrogen according to claim 10, wherein an adsorbable material is used. 14. The method for detecting the remaining amount of hydrogen according to claim 13, wherein any one of amorphous carbon, carbon nanotube, fullerene and a mixture of any combination thereof is used as the carbon-based material. 15. The method for detecting the remaining amount of hydrogen according to claim 14, wherein any material of activated carbon, graphite, a graphite intercalation compound, carbon nanofibers, and a mixture of any combination thereof is used as the amorphous carbon. 16. The method for detecting the remaining amount of hydrogen according to claim 14, wherein a hydrogen gas adsorption film formed by firing a carbon-based material in an inert gas is used. 17. The hydrogen gas adsorption film according to claim 14 or 15, wherein the hydrogen gas adsorption film is formed through a drying process for removing a solvent, which is performed while a solution containing a carbonaceous material and a binder resin is placed on a quartz oscillator. The method for detecting the remaining amount of hydrogen described. 18. The method for detecting the remaining amount of hydrogen according to claim 10, wherein a hydrogen storage alloy that exhibits the same P-C-T curve as the hydrogen storage alloy in the storage tank is used as the hydrogen gas adsorption film. .