JP3241418U - Hydrogen gas detector - Google Patents

Abstract

A hydrogen gas detection device capable of detecting leaked hydrogen before it is combusted is provided. A hydrogen gas detection device (1a) comprises a substrate (2a) and a metal thin film (5) formed on the surface of the substrate and made of a metal belonging to the platinum group and containing hydrogen. By providing a gas chromic metal thin film that reversibly changes color upon contact with gas, a hydrogen detection function is provided with a very simple configuration without requiring a special metal catalyst or the like. [Selection drawing] Fig. 2

Description

The present invention relates to a hydrogen gas detection device for detecting hydrogen gas.

In recent years, hydrogen has attracted attention as a raw material for next-generation clean energy. For example, technological developments are actively being carried out for use in fuel cells using hydrogen as fuel, fuel cell vehicles, and the like. On the other hand, hydrogen gas may be generated in the manufacturing process of industrial products such as glass, steel, chemicals, fuel cells or semiconductors.

Tomi No. 3192457

On the other hand, hydrogen has the danger of exploding in an oxygen atmosphere and must be handled with care. Furthermore, hydrogen itself is tasteless and odorless, and since the flame when hydrogen burns is invisible, it is difficult to monitor when hydrogen leaks, even if it is burning, it cannot be visually confirmed. .

Therefore, in order to handle hydrogen, a technology that can monitor and detect leaked hydrogen before it is combusted is required.

In addition, in order to monitor leakage of tasteless and odorless hydrogen without leaking, it is necessary to install a large number of detection means. Therefore, it is desirable that the detection means have a structure as simple as possible.

Therefore, as a means for solving the above problems, the hydrogen detection device according to the present invention comprises a substrate, and a metal thin film formed on the surface of the substrate and made of a metal belonging to the platinum group and containing hydrogen, The metal thin film is characterized by being a gaschromic metal thin film whose light transmittance reversibly changes upon contact with hydrogen gas.

A high-frequency sputtering method, a DC sputtering method, a molecular beam epitaxy method, or a vacuum vapor deposition method can be used to form (deposit) the metal thin film on the substrate surface. The metal thin film formed on the substrate surface is preferably formed as a thin film having a thickness of, for example, 30 nm to 100 nm.

Moreover, it is preferable that the inside of the metal thin film is in contact with a gas containing oxygen. Furthermore, it is preferable that the gas containing oxygen is air.

The platinum group metal is preferably platinum, ruthenium, rhodium, osmium, iridium, or palladium, which has a hydrogen storage function. Palladium is particularly preferred. Alternatively, it may be an alloy of a metal belonging to the platinum group and magnesium or nickel.

Preferably, the substrate is transparent. Since the substrate is transparent, it is possible to construct a hydrogen detection system having a structure in which detection light for detecting hydrogen is transmitted from the back side of the substrate to a metal film belonging to the platinum group formed on the front surface of the substrate. be. As a result, the hydrogen gas detection device according to the present invention can be arranged between the light source member for the detection light and the optical input member for acquiring the detection light, so that the structure of the hydrogen detection system can be simplified. . In this case, the substrate is preferably transparent glass. For example, amorphous quartz glass (SiO ₂ ) can be used as the transparent substrate. This is because, by using glass as the substrate, it is possible not only to obtain the raw material for the substrate at a low cost, but also to provide a hydrogen gas detection device having a substrate that is stable against the surrounding environment.

Furthermore, it is preferable that the hydrogen detection system is provided with a hydrogen gas detection device. The hydrogen detection system is preferably an optical hydrogen detection system or an electrical hydrogen detection system.

The optical hydrogen detection system includes the hydrogen gas detection device, a light source member for irradiating detection light to the metal film, and detection light transmitted or reflected by the metal film to detect changes in light characteristics. It is preferable to have a detection means.

The electrical hydrogen detection system includes the hydrogen gas detection device, a power source for applying a voltage through the metal film that constitutes the hydrogen gas detection device, and hydrogen generated in the metal film by the hydrogen gas detection device sensing hydrogen. It is preferable to have voltage detection means for detecting a voltage change. In particular, the electrical hydrogen detection system is a bridge circuit comprising two hydrogen gas detection devices having the same configuration, one of the hydrogen gas detection devices being isolated from the surrounding environment and output from the bridge circuit. It is preferable to have a voltage measuring member capable of measuring voltage. At this time, it is preferable that the one hydrogen gas detection device, which is isolated from the ambient environment, is housed in an isolation container that blocks hydrogen sufficiently.

Furthermore, it is preferable that the present invention is a hydrogen detection method characterized by detecting hydrogen using the hydrogen gas detection device. The hydrogen detection method can include a method of detecting hydrogen using the hydrogen detection system.

ADVANTAGE OF THE INVENTION According to this invention, the hydrogen detection apparatus provided with a hydrogen detection function by a very simple structure without requiring a special metal catalyst etc., and the hydrogen detection method using the same can be provided.

1 is a schematic diagram showing a laminated structure of the hydrogen gas detection device 1. FIG. 1 is a schematic block diagram of an optical hydrogen detection system X1; FIG. It is a figure which shows the electrical characteristic of the hydrogen gas detection apparatus 1a. 1 is a schematic block diagram of an optical hydrogen detection system X2; FIG. FIG. 2 is a block diagram showing an outline of an electrical hydrogen detection system X3; FIG. It is a schematic diagram showing a laminated structure of hydrogen gas detectors 1ca and 1cb.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

FIG. 1 shows a schematic diagram of a cross-sectional structure of a hydrogen gas detection device 1 according to the present invention.

As shown in FIG. 1A, the substrate 2 can be made of amorphous quartz glass (SiO ₂ ), metal such as aluminum (Al) or iron (Fe), or ceramic. Hereinafter, the substrate 2 using transparent quartz glass will be referred to as a glass substrate 2a, and the substrate using aluminum will be referred to as an aluminum substrate 2b.

The palladium thin film 3 is formed on the surface of the substrate 2 by sputtering (for example, high-frequency magnetron sputtering) using palladium metal as a target.

Next, as shown in FIG. 1(b), the substrate 2 on which the palladium thin film 3 is formed is exposed to a mixed gas atmosphere having a hydrogen concentration of 2% with respect to nitrogen gas, so that hydrogen 4 is introduced into the palladium thin film 3. Absorb. As a result, a gaschromic metal thin film 5 containing hydrogen 4 is formed as shown in FIG. 1(c). The substrate 2 on which the gaschromic metal thin film 5 containing hydrogen 4 is formed is taken out and exposed to the atmosphere A, and the hydrogen gas detector 1 is obtained. In this embodiment, the atmosphere A is synonymous with the atmosphere. The hydrogen 4 contained in the gaschromic metal thin film 5 includes hydrogen atoms dissociated in the gaschromic metal thin film 5 .

Through intensive research, the inventor has found that when hydrogen gas is brought into contact with the hydrogen gas detector 1 and hydrogen is contained in the palladium thin film 3, which is a metal belonging to the platinum group, the light transmission of the gaschromic metal thin film 5 is improved. We found that the rate changed reversibly. Based on this characteristic, the hydrogen gas detection device 1 uses the optical hydrogen detection systems X1 and X2 to be described below. Hydrogen gas leakage can be detected by detecting a change in the light intensity of .

[First embodiment]
Next, a configuration example of an optical hydrogen detection system X1 using the hydrogen gas detection device 1a will be described as a first embodiment. FIG. 2 shows a schematic block diagram of the optical hydrogen detection system X1. The optical hydrogen detection system X1 includes a device housing 6 which is a box-like body having an internal space K, a hydrogen gas detection device 1a, a light detection means 7, a hydrogen determination means 8, and an alarm section 9. Part of the light detection means 7 and the hydrogen determination means 8 are housed in a determination device housing 60 .

In the optical hydrogen detection system X1, the hydrogen gas detection device 1a has a gaschromic metal thin film 5 formed on the surface of a glass substrate 2a made of transparent quartz glass. The hydrogen gas detection device 1a is arranged in the internal space K of the device housing 6, as shown in FIG.

The light detection means 7 detects detection light input through the inside of the gaschromic metal thin film 5 of the hydrogen gas detection device 1a, converts the intensity of the detected light into an input electric signal f1, and outputs the input electric signal f1.
As shown in FIG. 2, the light detection means 7 is composed of a light sensor and includes a light emitting unit 10 and a light receiving unit 11. As shown in FIG.

The light emitting unit 10 is composed of a light projecting lens 12 , a light emitting element 13 and a light emitting side optical fiber element 14 .

The light projection lens 12 irradiates the light emitted from the light emitting element 13 onto the gaschromic metal thin film 5 from the back side of the substrate 2 . The projection lens 12 is arranged in the internal space K of the apparatus housing 6, as shown in FIG.

The light emitting element 13 is, for example, a light emitting diode (LED) that emits white light (hereinafter referred to as "light emitting diode 13"). The light emitting diode 13 is electrically connected to the LED drive circuit 15 . The LED drive circuit 15 is electrically connected to the LED power supply 16 .

The light emitting side optical fiber element 14 is glass fiber or poly fiber, and is used as an optical fiber cable, for example.
The light-emitting side optical fiber element 14 optically connects the light-emitting diode 13 and the projection lens 12 and transmits light emitted from the light-emitting diode 13 to the projection lens 12 .

The light receiving unit 11 is composed of a light receiving lens 17 , a light receiving element 18 and a light receiving side optical fiber element 19 .

The light-receiving lens 17 collects the detection light transmitted through the gaschromic metal thin film 5 and introduces it into the light-receiving element 18 . The light-receiving lens 17 is arranged in the internal space K of the apparatus housing 6, as shown in FIG. The light-receiving lens 17 is arranged in the internal space K at a position separated from the front surface of the gaschromic metal thin film 5 .

The light receiving element 18 is composed of, for example, a phototransistor (hereinafter referred to as "phototransistor 18"). The phototransistor 18 receives detection light in the wavelength range of visible light (380 nm to 780 nm), converts the light intensity into an input electrical signal f1 (photocurrent in the first and second embodiments), and outputs the signal. The phototransistor 18 is electrically connected to the hydrogen determining means 8 through the signal amplifying section 20 . The signal amplifier 20 amplifies the input electric signal f1 and outputs it to the hydrogen discrimination means 8 .
Thereby, the phototransistor 18 converts the light intensity of the detected light into an input electrical signal f1.

The light-receiving side optical fiber element 19 is made of glass fiber or polyfiber, and is used as an optical fiber cable, for example. The light-receiving side optical fiber element 19 optically connects the photodiode 39 and the light-receiving lens 17 and transmits the light condensed by the light-receiving lens 17 to the photodiode 39 .

The hydrogen discriminating means 8 receives the input electric signal f1 and discriminates hydrogen leakage based on the change in the input electric signal f1. The hydrogen discrimination means 8 includes a control section 21, a signal storage section 22, a signal calculation section 23, and a hydrogen gas discrimination section 24, as shown in FIG.

The controller 21 is electrically connected to the phototransistor 18 through the signal amplifier 20 . The control unit 21 is electrically connected to the signal storage unit 22 and the signal calculation unit 23 .
The controller 21 is also electrically connected to the LED drive circuit 15 and outputs a photoelectric signal fd to the LED drive circuit 15 .

The signal storage unit 22 stores the reference electric signal f2 as data. The reference electric signal f2 is the intensity of the electric signal output from the light receiving element 18 via the inside of the gaschromic metal thin film 5 in an air atmosphere (no leakage of hydrogen gas).

The signal calculator 23 subtracts the input electric signal f1 from the reference electric signal f2 to calculate the absolute value (f3=|f2-f1|) of the difference electric signal f3. The signal calculator 23 is electrically connected to the hydrogen gas discriminator 24 and outputs the differential electric signal f3 to the hydrogen gas discriminator 24 .

The hydrogen gas discrimination unit 24 compares the difference electric signal f3 and the discrimination electric signal fh, and judges that hydrogen gas is detected when the difference electric signal f3 is equal to or greater than the discrimination electric signal fn. In order to avoid erroneously determining that hydrogen gas has been detected due to changes in the noise level of the electrical signal, the discrimination electric signal fh is set to a certain intensity, and the hydrogen gas is detected for signal strengths below the discrimination electric signal fh. This is the signal strength value for not judging that it has been detected.

The hydrogen gas determination unit 24 is electrically connected to the alarm unit 9 and outputs an alarm electric signal fk to the alarm unit 9 when it determines that hydrogen gas has been detected. As shown in FIG. 2, the alarm unit 9 (alarm device) receives the alarm electric signal fk from the hydrogen gas discrimination unit 24 and issues an alarm. The alarm unit 9 is composed of an alarm whistle, a bell, an indicator lamp, or the like, and is electrically connected to the hydrogen gas discrimination unit 24 .

[Characteristics of hydrogen gas detector 1]
Next, characteristics of the hydrogen gas detection device 1 will be described. As an example, hydrogen gas is detected based on changes in voltage characteristics measured based on an optical hydrogen detection system X1 using a hydrogen gas detection device 1a formed by forming a gaschromic metal thin film 5 on a glass substrate 2a. Explain how to do it.

According to FIG. 3, immediately after forming the palladium thin film 3 on the glass substrate 2a, the voltage was about 4 V in the atmosphere. Adsorption of hydrogen 4 to the saturate state, decreased to about 2.5 V, and showed a constant voltage. After forming the palladium thin film 3 on the glass substrate 2a, even if the palladium thin film 3 was simply kept exposed to the atmosphere, the voltage did not change with time.

Next, when the hydrogen gas detector 1a was exposed to the air from a 2% concentration hydrogen mixed gas at 10 minutes, the voltage further decreased to about 1.9 V and became constant. In FIG. 3, this voltage of approximately 1.9 V is referred to as a reference voltage Vf2 (reference electric signal f2).

Here, when the 2% concentration hydrogen mixed gas was blown again to the hydrogen gas detection device 1a at the time of 13 minutes, the voltage increased by about 0.6V. The presence of hydrogen gas could be detected by this change in voltage.

Further, when the blowing of the 2% concentration hydrogen mixed gas was stopped at 15 minutes, the voltage dropped to the reference voltage Vf2. Furthermore, when a 2% concentration hydrogen mixed gas was sprayed at 18 minutes, a similar increase in voltage was observed, and it was found that the voltage increase was about the same with hydrogen gas having the same concentration.

Further, when the 0.4% concentration hydrogen mixed gas was blown to the hydrogen gas detection device 1a at the reference voltage Vf2 at the time point of 23 minutes, the voltage increased by about 0.3V from the reference electric signal f2. As a result, it was found that the presence of hydrogen gas can be detected even if the concentration of hydrogen gas is different.

In addition, when the spraying of the 0.4% concentration hydrogen mixed gas is stopped at 25 minutes, the voltage returns to the reference voltage Vf2. An increase in voltage was observed, and it was found that even with the 0.4% concentration hydrogen mixed gas, the increase in voltage was about the same for hydrogen gas with the same concentration.

In addition, since the amount of voltage that rises when 2% concentration hydrogen mixed gas is sprayed and when 0.4% concentration hydrogen mixed gas is sprayed, it is possible to determine how much concentration hydrogen gas leaked from the voltage. can also be measured.

Furthermore, as shown in FIG. 3, after the reference voltage Vf2 is determined, the hydrogen gas detection device 1a does not stop spraying the hydrogen mixed gas even if exposure to the atmosphere by spraying and stopping the hydrogen mixed gas is repeated several times. After stopping, the reference voltage Vf2, which is a constant value, is indicated. Moreover, even if the hydrogen concentration in the hydrogen mixed gas to be sprayed changes, the voltage is recovered to the reference voltage Vf2. Therefore, the hydrogen gas detection device 1a can stably detect hydrogen gas even after repeated use. Such tendency is the same even if the substrate 2 is other than the glass substrate 2a.

[Second embodiment]
Next, a configuration example of an optical hydrogen detection system X2 using the hydrogen gas detection device 1b will be described as a second embodiment. FIG. 4 shows a schematic block diagram of the optical hydrogen detection system X2. Components common to those of the optical hydrogen detection system X1 are denoted by the same reference numerals, thereby omitting redundant description.

In the optical hydrogen detection system X2, the hydrogen gas detection device 1b has a gaschromic metal thin film 5 formed on the surface of an aluminum substrate 2b. The hydrogen gas detection device 1b is arranged in the internal space K of the device housing 6, as shown in FIG.

The projection lens 12 irradiates the light emitted from the light emitting element 13 onto the gaschromic metal thin film 5 from the surface side of the substrate 2 . The projection lens 12 is arranged in the internal space K of the apparatus housing 6, as shown in FIG.

The light-receiving lens 17 converges the detection light reflected by the aluminum substrate 2 b through the inside of the gaschromic metal thin film 5 and introduces it into the light-receiving element 18 . The light receiving lens 17 is arranged in the internal space K of the apparatus housing 6, as shown in FIG. The light-receiving lens 17 is arranged in front of the gaschromic metal thin film 5 in the internal space K at a position where it can receive the detection light reflected by the hydrogen gas detector 1b.

The hydrogen gas discriminator 24 discriminates the difference electric signal f3 in the same manner as in the case of the optical hydrogen detection system X1. Further, the hydrogen gas determination unit 24 is electrically connected to the alarm unit 9, and outputs an alarm electric signal fk to the alarm unit 9 when it determines that hydrogen gas is detected. As shown in FIG. 4, the alarm unit 9 (alarm device) receives the alarm electric signal fk from the hydrogen gas discrimination unit 24 and issues an alarm. The alarm unit 9 is composed of an alarm whistle, a bell, an indicator lamp, or the like, and is electrically connected to the hydrogen gas discrimination unit 24 .

[Third embodiment]
Next, a configuration example of an electrical hydrogen detection system X3 using the hydrogen gas detection device 1c will be described as a third embodiment. FIG. 5 shows a schematic block diagram of the electrical hydrogen detection system X3. Components common to those of the optical hydrogen detection system X1 are denoted by the same reference numerals, thereby omitting redundant description.

The optical hydrogen detection system X3 includes a bridge circuit 25 and a power supply 26 that applies a voltage to the bridge circuit 25, and obtains a voltage Vg from a current galvanometer 27 in the bridge circuit 25 to determine hydrogen gas detection. It has means 8 and an alarm unit 9 .

In the bridge circuit 25, a hydrogen gas detector 1ca is connected between diagonals A and B, a hydrogen gas detector 1cb is connected in series between diagonals B and C, and a resistor is connected between diagonals A and D. A resistor R2 is connected between R1 and diagonals D and C. Here, as shown in FIG. 6, the hydrogen gas detectors 1ca and 1cb are formed by stacking electrode films 28 and 28 on both sides of a gaschromic metal thin film 5 formed on a glass substrate 2a, and conducting wires 29 and 29. become connected. The hydrogen gas detection device 1ca is housed in an isolation container 30 that prevents hydrogen gas from entering from the outside and blocks hydrogen as much as necessary.

The voltage Vg between the diagonal B and the diagonal D of the bridge circuit 25 is adjusted to 0 in a state where no hydrogen leaks. Here, when the hydrogen gas reaches the surroundings of the hydrogen gas detection devices 1ca and 1cb, the hydrogen gas contacts only the gaschromic metal thin film 5 of the hydrogen gas detection device 1cb, which is not protected by the isolation container 30, and its resistance value changes. change.

At that time, the voltage Vg is detected by the current detector 27 and the input electrical signal f1 is output to the hydrogen discriminating means 8 . The hydrogen discriminating means 8 to which the input electric signal f1 is input discriminates the difference electric signal f3 in the same manner as the optical hydrogen detection system X1. Further, the hydrogen gas determination unit 24 is electrically connected to the alarm unit 9, and outputs an alarm electric signal fk to the alarm unit 9 when it determines that hydrogen gas is detected. As shown in FIG. 5, the alarm unit 9 (alarm device) receives the alarm electric signal fk from the hydrogen gas discrimination unit 24 and issues an alarm. The alarm unit 9 is composed of an alarm whistle, a bell, an indicator lamp, or the like, and is electrically connected to the hydrogen gas discrimination unit 24 .

REFERENCE SIGNS LIST 1 hydrogen gas detection device 2 substrate 5 gaschromic metal thin film 8 hydrogen discrimination means 9 alarm unit 13 light emitting element 18 light receiving element 20 signal amplification unit 24 hydrogen gas discrimination unit 25 bridge circuit

Claims (7)

a substrate;
A metal thin film formed on the substrate surface and made of a metal belonging to the platinum group and containing hydrogen in a saturated adsorption state,
The metal thin film is in contact with a gas containing oxygen,
A hydrogen gas detector, wherein the metal thin film is a gaschromic metal thin film whose light transmittance reversibly changes upon contact with hydrogen gas. 2. The hydrogen gas detection device according to claim 1, wherein the gas containing oxygen is air. 3. The hydrogen gas detector according to claim 1, wherein the metal belonging to the platinum group is palladium. 4. The hydrogen gas detector according to claim 1, wherein said substrate is transparent. 5. The hydrogen gas detector according to claim 1, wherein said substrate is a transparent glass substrate. A hydrogen detection system comprising the hydrogen gas detection device according to any one of claims 1 to 5. The hydrogen gas detection device according to any one of claims 1 to 5 is a bridge circuit connected in parallel to the output,
one of the hydrogen gas detection devices is isolated from the surrounding environment;
A hydrogen detection system comprising a voltage measuring member capable of measuring a voltage output from the bridge circuit.

Images