JP6797598B2 - Hydrogen flame detector - Google Patents

Description

The present invention relates to a hydrogen flame detection device that is obliged to be installed, for example, in a hydrogen supply station. More specifically, for example, there is a factory nearby, and hydrogen flames can be reliably generated without causing false reports due to ambient light such as ultraviolet rays generated by welding or grinders in the factory or ultraviolet rays generated from pantographs such as trains. The present invention relates to an inexpensive hydrogen flame detector capable of detecting.

Today, hydrogen gas is also used in automobiles, and continuous monitoring of hydrogen gas utilization facilities such as hydrogen supply stations and fuel cells is becoming important. Even if hydrogen gas burns, it looks almost transparent to the naked eye under the sun's rays, and according to the example standards of the General High Pressure Gas Safety Act revised in 2010, it is a device for detecting a fire at a specific compressed hydrogen stand. It is stipulated to use a method of detecting ultraviolet rays emitted by a hydrogen flame. The ultraviolet rays generated from this hydrogen flame have a particularly short wavelength of UV-C (280 to 100 nm), which is a wavelength band that adversely affects the human body.

As such an ultraviolet ray detection sensor, for example, a flame sensor manufactured by Hamamatsu Photonics Co., Ltd. and UV TRON (registered trademark) (model number R2868) are known. This ultraviolet detection sensor has a relative sensitivity capable of detecting a wavelength as shown in FIG. 4A, for example, and can detect light having a wavelength of 185 to 260 nm while blocking sunlight. In FIG. 4, A shows the relative sensitivity to the wavelength band of ultraviolet rays that can be detected, B is the spectrum of sunlight on the ground surface, C is the spectrum of an example of hydrogen flame, and D is the spectrum of a tungsten light bulb. Shown. That is, it is utilized that the ultraviolet rays of this short wavelength of sunlight are blocked by the ozone layer and do not reach the surface of the earth. However, when this flame sensor is installed outdoors such as a hydrogen supply station, there is a problem that ultraviolet rays are detected, that is, false alarms are likely to occur even though a hydrogen flame is not generated.

On the other hand, an apparatus for visualizing a hydrogen flame by detecting near-infrared rays and thermal images in the range of 930 to 950 nm is also disclosed (see, for example, Patent Document 1). Even in this case, it is also disclosed that an ultraviolet ray detecting means having an ultraviolet ray receiving element having a specific wavelength caused by a hydrogen flame is used. Even when an ultraviolet detector is used, it is thought that false alarms due to ambient light can be prevented by notifying the occurrence of a flame when both are detected in combination with an infrared light receiving element in this way. However, even so, false alarms have not been completely prevented.

Japanese Unexamined Patent Publication No. 2013-36974

By using the above-mentioned ultraviolet detection sensor, it is possible to block the light of sunlight and effectively detect the ultraviolet rays emitted from the hydrogen flame. However, when it is installed outdoors such as a hydrogen supply station, there is a problem that an alarm is often issued even though a hydrogen flame is not actually generated.

Further, in addition to the above-mentioned ultraviolet detection sensor, an infrared detection sensor or the like is installed, and when both are detected, it is determined that a hydrogen flame has actually occurred. There is a problem that it is necessary and the cost increases.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an inexpensive hydrogen flame detection device in which false alarms are unlikely to occur while using a commercially available ultraviolet detection sensor.

The present inventors have conducted extensive studies in order to detect hydrogen flames without false alarms even if a conventional commercially available compact, high-sensitivity, high-field UV on / off sensor is used. As a result, it was found that the cause of the false alarm is the incident of ambient light generated on the ground, although the sunlight does not contain ultraviolet rays whose wavelength band overlaps with the hydrogen flame. That is, ultraviolet rays emitted from sparks generated during welding such as arc welding or polishing with a grinder in factories, etc., and sparks generated by lightning or pantographs of trains are detected as ultraviolet rays directly or as reflected light by buildings. It was found that the light was incident on the sensor and caused false reports.

As a result of further intensive studies by the present inventors, the above-mentioned commercially available ultraviolet on / off sensor has been pursued with high sensitivity and high field of view due to the characteristics of the sensor. For example, a hydrogen supply station We have found that it is better to reduce the sensitivity of a hydrogen flame detector used for hydrogen flame monitoring at a location relatively close to such a sensor. Then, a bandpass filter that transmits a part of a narrow band in the range of 185 to 280 nm, preferably 200 to 260 nm is inserted, a polarizing filter that easily cuts reflected light is inserted, and the transmission of the sensor is performed. By narrowing the viewing angle by making the window smaller or increasing the distance between the transmitting window and the ultraviolet detection element, the intrusion of ambient light can be prevented and a hydrogen flame detection device with almost no false alarms can be obtained. The present inventors have found.

The hydrogen flame detection device of the present invention has an ultraviolet detection element for detecting ultraviolet rays of a hydrogen flame, a transmission window provided in front of the ultraviolet detection element to take in external light, and the transmission window as a part thereof. It has a housing that covers an ultraviolet ray detecting element to block the incident light from other than the transmission window, and an ambient light attenuating means that attenuates ambient light other than the hydrogen flame.

Here, the ambient light means ultraviolet rays other than ultraviolet rays caused by a hydrogen flame. Further, the disturbance light attenuating means means that ultraviolet rays from other than the hydrogen flame are attenuated to the extent that they are hardly detected. Therefore, even if the ambient light is not completely cut, it is sufficient if it is attenuated to the extent that it is not detected by the ultraviolet detection element, and even if the ultraviolet rays caused by the hydrogen flame are attenuated, the ultraviolet rays caused by the hydrogen flame are attenuated. If it can be detected, a little attenuation is not a problem.

According to the present invention, it is possible to almost eliminate false alarms of the hydrogen flame detection device by simply providing a simple disturbance light attenuation means while using a commercially available ultraviolet detection element. This disturbance light attenuation means limits the incident light to the ultraviolet detection element to a narrow range within the band of ultraviolet rays derived from hydrogen flame detected by a bandpass filter provided in front of the ultraviolet detection element, or a polarizing filter. By being provided in front of the ultraviolet detection element, it is formed by cutting polarized reflected light, limiting the incident of ambient light by reducing the viewing angle, and the like. As a result, false alarms can be reliably eliminated while being able to be configured at a very low cost.

It is a figure which shows the structure of one Embodiment of the hydrogen flame detection apparatus of this invention. It is a figure which shows the structure of the other embodiment of the hydrogen flame detection apparatus of this invention. It is a figure explaining still another embodiment of the hydrogen flame detection apparatus of this invention. It is a figure which shows the spectral sensitivity characteristic of a certain ultraviolet ray detection sensor.

Next, the hydrogen detection device of the present invention will be described with reference to FIGS. 1 to 3 showing specific configuration examples. The hydrogen flame detection device of the present invention is provided with an ultraviolet detection element 1 for detecting ultraviolet rays of a hydrogen flame and an ultraviolet detection element 1 in front of the ultraviolet detection element 1, as shown in FIG. 1 for a schematic structural diagram of the embodiment. A housing 4 that has a transmitting window 3 that takes in light and a transmitting window 3 as a part, and that covers the ultraviolet detection element 1 to block the incident of light from other than the transmitting window 3, and attenuates ambient light other than hydrogen flame. It has disturbance light attenuation means 2 (21, 22) for causing disturbance.

As the ultraviolet detection element 1, an element that detects ultraviolet rays emitted from a hydrogen flame is used. The hydrogen flame spectrum has peaks at 285 nm, 306 nm, and 309 nm, and emits light over 185 nm to 320 nm. That is, as shown in FIG. 4C, the spectrum of the hydrogen flame, there is a band having a slight radiant intensity even if it is not the peak wavelength. In this case, since the ultraviolet rays of sunlight reach the ground surface in the vicinity of 300 nm or more, the light of 185 to 280 nm becomes weak, but it is suitable for detection. For example, the above-mentioned flame sensor UV TRON (registered trademark) manufactured by Hamamatsu Photonics Co., Ltd. can be used, but the present invention is not limited thereto. Further, although this flame sensor is a discharge tube, it may be an ultraviolet detection element composed of a semiconductor element instead of the discharge tube. The flame sensor described above has a sensitivity wavelength in the range of 185 to 260 nm and is suitable for detecting a hydrogen flame. However, even an ultraviolet detection element that does not have this spectral sensitivity characteristic can have a desired wavelength band by providing a bandpass filter 21 that transmits a band within the wavelength band of 185 to 280 nm, preferably 200 to 260 nm. It is possible to receive only the ultraviolet rays of the above and to eliminate unwanted disturbance light. That is, the ultraviolet detection element 1 may exceed the range as long as it can detect the range of 185 to 280 nm, and the wavelength band to be detected is not limited. In the present embodiment, the bandpass filter 21 is provided for the purpose of attenuating ambient light other than the hydrogen flame. Therefore, if light in a certain wavelength band within 185 to 280 nm, preferably 200 to 260 nm, which is transmitted by the bandpass filter 21, is detected, the sensitivity characteristics of the ultraviolet detection element 1 are not limited.

As described above, the disturbance light attenuating means 2 blocks the disturbance light by various methods such as a bandpass filter 21 (see FIG. 1), a polarizing filter 22 (see FIG. 2), and a viewing angle control means (see FIG. 3). It is something that can be done. Two or more of these means can be used in combination. In the example shown in FIG. 1, a bandpass filter 21 is used as the ambient light attenuation means 2. The bandpass filter 21 in the ultraviolet region not only has the characteristic of passing only a desired wavelength band and blocking other wavelength bands, but also causes attenuation of about 20 to 40% in the pass band. The present inventors have found that a decrease in transmittance in this pass band is preferable for eliminating ambient light. That is, as described above, in the hydrogen flame detection device installed in the hydrogen supply station, it is installed in a place relatively close to the place where the hydrogen flame is expected to occur. Therefore, the ultraviolet rays emitted from the hydrogen flame to be detected are much larger than the ultraviolet rays of the ambient light, and even if the ultraviolet rays to be detected are slightly attenuated, there is no problem in the detectability of the hydrogen flame to be detected. On the other hand, ambient light such as ultraviolet rays generated by welding in a factory is weakened because it passes through many paths, and is further attenuated so that it cannot be detected by the ultraviolet detecting element 1.

Further, the spectrum of the hydrogen flame is similar to C in FIG. 4 described above, and constantly weak light is generated in the non-peak range of 185 to 280 nm, preferably 200 to 260 nm. Therefore, it is possible to know the occurrence of hydrogen flame even if the ultraviolet rays are not detected in the entire range or only in a part of the band, and the disturbance is disturbed by narrowing the pass band with the bandpass filter. We have found that light can be eliminated. That is, by inserting the bandpass filter 21 that transmits the pass band of the bandpass filter 21 in the above-mentioned range of 185 to 280 nm, preferably 200 to 260 nm, for example, in the band of 10 to 20 nm, the ambient light is greatly increased. We have found that it can be reduced to. In short, by narrowing the pass band of the bandpass filter 21, it becomes easy to prevent the intrusion of ambient light. If the wavelength of ultraviolet rays that is particularly likely to be generated is known, a bandpass filter outside the wavelength band can be used. As such a bandpass filter 21, for example, Asahi Spectroscopy Co., Ltd.'s trade name HQBP248-UV and model number LX0248 can be used. The bandpass filter 21 has a transmission band (60% or more) of 240 to 250 nm and a blocking band (transmission rate of 0.1% or less) of 280 to 570 nm. Therefore, if the above-mentioned ultraviolet detection element 1 is used, it is possible to exclude ultraviolet rays other than a very narrow band while detecting the hydrogen flame. When the ultraviolet detection element 1 has an ability to detect light having a wavelength shorter than 200 nm, a high-pass filter that blocks the short wavelength side may be used in combination.

In such a filter, a filter that blocks only light in a predetermined wavelength band is formed by laminating a dielectric film on quartz glass or mixing a substance that absorbs light. Therefore, without being limited to the bandpass filter described above, a filter that transmits a desired wavelength band and blocks other wavelength bands can be used. The bandpass filter 21 is a single filter, and even if it is not a filter that transmits only a certain band, it has a wavelength of 185 to 280 nm, preferably 200 to 260 nm in combination with the detection band of the ultraviolet detection element 1. The purpose is to be able to detect the band. Further, a bandpass filter may be formed by combining a highpass filter and a lowpass filter. In short, the structure may be such that only the desired wavelength band is detected by the ultraviolet detection element 1.

As the disturbance light attenuation means 2, as described later, a polarizing filter that selectively cuts the reflected light may be provided. Further, the viewing angle may be narrowed so as to prevent the incident light from being incident as much as possible. In this way, even if the ultraviolet rays generated from the hydrogen flame that should be detected are attenuated, the ambient light can be cut. Therefore, it does not mean that the disturbance light is attenuated in absolute value, but it is sufficient that the disturbance light is cut relative to the sensitivity of the ultraviolet detection element 1.

The transmission window 3 is a part of the housing 4 and is provided on the front side of the ultraviolet detection element 1. Any glass that transmits ultraviolet rays may be used, but it is preferable to use quartz glass because ordinary glass attenuates ultraviolet rays and is easily discolored by ultraviolet rays. If it is not necessary to make the inside airtight, a through hole may be used. However, from the viewpoint of protecting the ultraviolet detection element 1, it is preferable that the housing 4 is sealed with quartz glass or the like.

The housing 4 is provided to protect the ultraviolet detection element 1 and prevent light from entering from the outside. It may be formed of a metal plate or a plastic. It is not necessary to transmit light. In FIG. 1, reference numeral 5 denotes a drive / detection alarm circuit including an alarm circuit that drives the hydrogen flame detection device and notifies when a hydrogen flame is detected, and a conventional one can be used.

FIG. 2 shows an example in which the polarizing filter 22 is provided on the front side of the ultraviolet detection element 1 as the ambient light attenuation means 2. Except for the polarizing filter 22, the configuration is the same as that shown in FIG. 1, and the same parts are designated by the same reference numerals and the description thereof will be omitted. As the polarizing filter 22, for example, an ultra-wideband wire grid polarizing filter manufactured by Edmund Optics Japan Co., Ltd. can be used. This polarizing filter has a structure in which, for example, a thin layer of aluminum microwires is sandwiched between two synthetic quartz glass plates from both sides. With this structure, it is polarized by the birefringence action on the surface of the wire grid that constitutes the aluminum wire network, and when the incident light enters the wire grid surface, the light of the p component enters the dielectric part and is transmitted, and the s component The light hits the mirror surface and is reflected. On the other hand, it is known that light that is reflected and becomes ambient light is polarized into vibration in one direction by being reflected by a reflecting surface. Therefore, only the reflected light can be cut. Since the ambient light is generally reflected, the reflected ambient light can be shot and cut. Due to the action of the polarizing filter, half of the ultraviolet rays generated from the hydrogen flame cannot be transmitted, and the intensity of the ultraviolet rays is dimmed by half. However, as mentioned above, the intensity of the hydrogen flame to be detected is strong, which is a particular problem. There is no.

FIG. 3 is an explanatory diagram of an example in which the viewing angle is narrowed as the ambient light attenuation means 2. That is, the viewing angle is θ1 when the transmission window 3 and the ultraviolet detection element 1 are provided so as to cover the monitored area 6. Now, the monitored area 6 does not have to be the entire hydrogen supply station, and the place where the hydrogen flame is generated is limited, and it is sufficient that a specific place such as a joint or a discharge port of a hydrogen pipe is covered. Therefore, for example, the diameter of the transmission window 3 may be reduced from d1 to d2 to set the viewing angle to θ2, or the distance between the transmission window 3 and the ultraviolet detection element 1 may be increased from h1 to h2 while the transmission window 3 remains unchanged. As a result, the viewing angle can be set to θ3, and each can be made smaller than the initial viewing angle θ1. By narrowing the viewing angle in this way, for example, as shown in FIG. 3, the disturbance light P and its reflected light, when the viewing angle is θ1, the disturbance light P incident on the ultraviolet detection element 1 becomes a field of view. When the angle becomes narrower to θ2, it cannot be reflected and transmitted around the transmission window 3 and does not reach the ultraviolet detection element 1. As a result, the ambient light P can be removed.

As a method of narrowing the viewing angle, the viewing angle can be narrowed not by reducing the diameter of the transmission window 3 but also by increasing the distance between the transmission window 3 and the ultraviolet detection element 1 from h1 to h2. .. That is, in FIG. 3, the transmission window 3 has the same diameter d1 as the conventional one, and when the distance between the ultraviolet detection element 1 and the transmission window 3 is widened to h2, the ambient light P is reflected and passes through the transmission window 3. , The light does not enter the ultraviolet detection element 1. Therefore, the ambient light P is not detected.

This viewing angle varies depending on the range and structure of the monitored area 6, but is generally 10 ° or more and 60 ° or less is sufficient. If it changes depending on the installation location, for example, if a diaphragm mechanism is laid in the transmission window 3 and the opening can be changed, the optimum viewing angle can be set each time according to the installation location. ..

Example 1
In the structure shown in FIG. 1, the above-mentioned flame sensor of Hamamatsu Photonics Co., Ltd. and UV TRON (registered trademark) are used as the ultraviolet detection element 1, and a commercially available bandpass filter is used to measure the size of the hydrogen flame. The distance that can be detected was investigated by changing. According to this example, the amount of ultraviolet rays transmitted was reduced to about 1/6. The results are shown in Table 1 in comparison with a comparative example in which the bandpass filter 21 is not provided. As for the false alarm, as a result of repeating the operation 5 times a day, the false alarm was 0 in the example shown in FIG. 1, but in the comparative example, there was a false alarm 2 to 3 times / day.

As is clear from Table 1, according to this embodiment, the sensitivity is reduced to about 1/6, so that the detection distance is also significantly reduced as compared with the comparative example. However, since the false alarm becomes 0, it can be seen that the reliability is greatly improved.

Example 2
With the structure shown in FIG. 2, the detection distance of the hydrogen flame was similarly investigated. As a result, the amount of ultraviolet rays transmitted was halved and the viewing angle was halved, but when the height of the hydrogen flame was 15 cm, the hydrogen flame could be detected at a distance of 3.5 m. .. The number of false alarms was also 0. The number of false alarms when the polarizing filter 22 is not provided is based on the above example.

1 Ultraviolet ray detection element 2 Disturbed light attenuation means 21 Bandpass filter 22 Polarizing filter 3 Transmission window 4 Housing 5 Drive / detection / alarm circuit A Spectral sensitivity of flame sensor B Sunlight spectrum C Example of hydrogen flame spectrum D Tungsten bulb Spectrum P disturbance light

Claims (5)

An ultraviolet detection element that detects the ultraviolet rays of a hydrogen flame, and
A transmission window provided in front of the ultraviolet detection element to take in outside light,
A housing having the transmissive window as a part and covering the ultraviolet detection element to block light incident from other than the transmissive window.
Disturbant light attenuation means for attenuating ambient light other than the hydrogen flame, and
Have a, the ambient light attenuating means, a band-pass filter provided in front of the ultraviolet detector elements, or 185 nm, in the range below 280 nm, 10 nm or more, a band-pass filter that passes below the band 20nm der Ru hydrogen flame detection device. The bandpass filter 10nm passes above, the following band 20nm is, 200 nm or more on a hydrogen flame detector of claim 1, wherein in the range below 260 nm. In the hydrogen flame detector according to claim 1 or 2, further polarizing filter is a hydrogen flame detector is provided in front of the ultraviolet detector element. In the hydrogen flame detection device according to any one of claims 1 to 3 , the viewing angle is 60 by adjusting the distance between the ultraviolet detection element and the transmission window and / or adjusting the size of the transmission window. ° hereinafter, controlled and are hydrogen flame detector to be 10 ° or more. The hydrogen flame detection device according to any one of claims 1 to 4, wherein the hydrogen flame detection device is installed toward a hydrogen pipe in a hydrogen supply station.

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