JP2002286543A - Flame detector, and method of detecting flame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect a burning condition in a combustor even when a temperature of a furnace is relatively high (1000 deg.C-1400 deg.C), in the furnace provided with the combustor where combustion is carried out to form blue flame. SOLUTION: This flame detector for detecting light generated in combustion flame by a semiconductor type optical sensor via an ultraviolet transmission fliter to detect the combustion flame formed in the furnace by the combustor is provided with an ultraviolet color glass filter as the ultraviolet transmission fliter, and a semiconductor type ultraviolet sensor having no sensitivity in an area having a wavelength of 650 nm or more as the semiconductor type optical sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame detection technique for detecting a combustion state (ignited or not ignited) of a combustor disposed in a furnace in a relatively high temperature state.

[0002]

2. Description of the Related Art Conventionally, a photoelectric tube type or semiconductor type optical sensor has been used at a practical level for detecting the combustion state of a combustor provided in a furnace.

[0003] Although the phototube-type optical sensor has high detection sensitivity, it has a problem that it requires a high-voltage power supply and is expensive.

As a technology using a semiconductor type optical sensor, a technology using a CdS or CdSe-based semiconductor in the sensitive part is at a practical level.

This type of semiconductor optical sensor detects infrared rays emitted from a combustion flame, and is used, for example, to detect the combustion state of an oil burner whose fuel is oil. However, when detecting the combustion flame of a gas burner in which the fuel is city gas containing methane as a main component, sufficient sensitivity cannot be secured because this type of burner forms a blue fire. Further, when an attempt is made to detect a combustion flame in a so-called furnace having a relatively high temperature, radiation from the furnace wall becomes noise.

[0006] Under such circumstances, the inventors of the present invention, in Japanese Patent Application No. 10-273232, mainly detect ultraviolet light from a combustion flame while avoiding radiation light to detect the combustion state of a combustor. Propose that.

[0007]

However, for example, when the furnace temperature is relatively high, ie, 1000 ° C. to 1400 ° C.
It has been found that in some furnaces, the combustion flame cannot be sufficiently detected even though the above detection method is employed.

This situation will be described in more detail. In the case where a Si-based photodiode is used as the semiconductor optical sensor and U-340 (manufactured by Hoya Glass Co., Ltd.) is used as the ultraviolet transmission filter, the following problems occur. It was found to happen.

FIG. 4 shows the temperature in the furnace on the horizontal axis and the output of the semiconductor type optical sensor on the vertical axis. The circles indicate the optical sensor output when a Si-based photodiode is used. ing. In the figure, the black circles indicate the case where the combustor is in the ignition state, and the white circles indicate the case where the fire extinguisher.

[0010] As can be seen from the figure, in this structure, even when the combustor is in a fire extinguishing state, the temperature is 1000 ° C to
When the temperature is in the temperature range of 00 ° C., a strong optical signal is detected. Here, the difference between the optical signal intensity in the ignited state and the optical signal intensity in the extinguished state is the signal (S) of the combustion flame, and the optical signal intensity in the extinguished state is smaller than the signal intensity. Noise (N), which is very large. That is, since the S / N ratio rapidly decreases as the temperature rises, it is substantially difficult to detect the combustion flame effectively in such a relatively high temperature range.

An object of the present invention is to provide a so-called blue fire in a furnace provided with a combustor for forming and burning, even when the temperature in the furnace is relatively high (1000 ° C. to 1400 ° C.). An object of the present invention is to provide a technique capable of reliably detecting a combustion state.

[0012]

According to the present invention, the light generated from a combustion flame is detected by a semiconductor type optical sensor via an ultraviolet transmission filter and formed in a furnace by a combustor. The flame detector for detecting the combustion flame is provided with an ultraviolet color glass filter as the ultraviolet transmission filter as described in claim 1, and 650n as the semiconductor type optical sensor.
A semiconductor type ultraviolet sensor having no sensitivity in a wavelength region of m or more is provided.

[0013] In the detection method planned by this flame detector,
Attempts to check the combustion state of the combustor by detecting light in the ultraviolet region. That is, by using an ultraviolet color glass filter to guide only light in the ultraviolet region to the semiconductor type ultraviolet sensor, it is planned to detect the combustion flame (blue fire) well.

However, when the inventors obtained the spectrum of the light reaching the semiconductor ultraviolet sensor, the situation as shown in FIG. 5 was obtained in a state where U-340 was used as an ultraviolet color glass filter. It has been found. FIG. 5 shows the wavelength on the horizontal axis and the spectrum intensity on the vertical axis, with the furnace temperature as a parameter.

As can be seen from the figure, the optical signal reaching the optical sensor has a spectrum region on the low wavelength side in a region near the wavelength of 250 to 450 nm and a wavelength region of 650 to 850 nm.
A region near the nm has a spectral region on the long wavelength side. That is, when a commercially available ultraviolet color glass filter is used at present, in addition to the light in the ultraviolet region that is originally required, a transmission region exists around 650 to 850 nm on the longer wavelength side than this region. It was found that when the temperature was extremely high, the transmitted light on the long wavelength side was large and became noise for the optical sensor. This situation was the same for other ultraviolet color glass filters. This phenomenon is
This is particularly noticeable in a high temperature state where the temperature inside the furnace is high. That is, when the relationship between the signal intensity on the low wavelength side (which becomes the signal S) and the signal intensity on the long wavelength side (which becomes the noise N) is viewed at about 700 ° C. in relation to the furnace temperature, If the signal S is relatively strong, but exceeds 1000 ° C., the intensity on the noise N side is superior even when an ultraviolet color glass filter is mounted.

Therefore, in the present application, a semiconductor ultraviolet light sensor having no sensitivity at 650 nm or more is used as the semiconductor ultraviolet light sensor. In this case, even if the inside of the furnace is maintained at a high temperature and the radiation inside the furnace is strong, the signal caused by the combustion flame of the present application is not affected by the above-mentioned optical signal on the long wavelength side. , Can be selectively detected,
The presence or absence of a combustion flame can be determined well.

Further, when the spectrum of the light from the furnace (the combustor is in an ignited state) is taken over the entire wavelength range of 250 nm to 850 nm, the spectrum becomes as shown in FIG. Changes as shown. The horizontal axis in FIG. 6 shows the wavelength, and the vertical axis shows the spectrum.
This figure also shows that the light intensity on the long wavelength side has a stronger tendency to increase with temperature than on the short wavelength side.

The ultraviolet transmission filter includes a color glass type filter and an interference film type filter. However, the filter of the interference film type is expensive, and there is no filter that transmits only ultraviolet rays in a wide wavelength range from ultraviolet rays to infrared rays. On the other hand, a color glass type ultraviolet transmission filter is inexpensive, has a stable product quality, and has a low transmittance in the visible light region. Therefore, a colored glass type ultraviolet transmission filter is suitable for this application where the use environment is relatively high temperature and the combustion flame is to be detected.

In the above structure, the semiconductor type optical sensor may be GaAsP.
Alternatively, a GaP-based optical sensor is preferable. These optical sensors have an upper limit of the detection wavelength near 600 nm, and the above-mentioned object can be satisfactorily achieved. Further, as described later, the upper limit of some of them is 400 nm.

Therefore, as described in claim 3, the combustion state of the combustor in the temperature range of 1000 to 1400 ° C. using the flame detector according to claim 1 or 2 is described. Is preferably detected. By doing so, it is possible to avoid the influence of radiation in the furnace and reliably detect a so-called blue fire when burning in a so-called complete combustion state.
In other words, when such a combustor occurs in a state in which it blows out in the furnace, it can be detected well. Here, the reason why the temperature is particularly preferable at 1000 ° C. or higher is that the transmitted light intensity on the long wavelength side is weak and does not cause much problem below this temperature, and the upper limit of 1400 ° C. is as the furnace temperature rises. This is because an excessive increase in the intensity of the transmitted light on the long wavelength side is observed, and an increase in the light intensity in a region close to the ultraviolet region due to radiation is also observed, which easily causes noise.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. The flame detector 1 of the present application is provided with an ultraviolet color glass filter 3 at a light incident portion of a semiconductor type optical sensor 2, and as shown in FIG. 1 (a), a city gas burner 4 for heating the furnace. Is used as the detection area. Further, the flame detector 1 includes a condenser lens 5 for condensing light on the front side of the ultraviolet color glass filter 3. As for the configuration of the ultraviolet color glass filter 3 and the condenser lens 5, as shown in FIG. 1B, both may be integrated.

Hereinafter, a specific description will be given. As the semiconductor type optical sensor 2, a GaAsP photodiode (model G5645, G5842, G626) manufactured by Hamamatsu Photonics, Inc.
For 2), U-340 of sea squirt glass was employed as the ultraviolet color glass filter 3.

FIGS. 2A and 2B show the light receiving sensitivity of the GaAsP photodiode. Of these, G564
5, G6262 has no sensitivity in the wavelength region of 650 nm or more, and G5842 has no sensitivity in the wavelength region of 450 nm or more.

FIG. 3 shows the light transmission characteristics of U-340.

In the above configuration, the semiconductor optical sensor 2
Is amplified by an amplifier circuit (not shown) to obtain an output. At the same time, a device using a Si photodiode as a semiconductor optical sensor was also manufactured for comparison.

The detection result of the flame detector thus prepared is shown in FIG. 4 described above. GaAs according to the present application
Those using sP photodiodes are indicated by square marks. The description of the ignition and extinguishing states is the same as that of the Si photodiode. As can be seen from the figure, in the flame detector using the Si photodiode, the furnace temperature 10
Noise from the furnace wall increases in the area above 00 ° C,
The S / N ratio has dropped significantly. On the other hand, in the flame detector according to the present application using a GaAsP photodiode,
The S / N ratio was ensured even in the region where the furnace temperature was 1000 ° C. or higher, and the combustion flame could be detected without being affected by noise.

That is, with this flame detector, it is possible to determine with a simple structure that if the signal intensity is larger than a predetermined judgment value, it is determined that the flame is present in an ignited state, and if the signal intensity is smaller, the fire is extinguished. It became.

[Alternative Embodiment] In the above embodiment, the case where U-340 manufactured by Hoya Glass Co., Ltd. is used as the ultraviolet color glass filter has been described.
60, 350, an ultraviolet color glass filter manufactured by Shot Glass, an ultraviolet color glass filter manufactured by Toshiba Glass, or the like can also be used. In the above embodiment, an example in which an ultraviolet GaAsP photodiode is used as a semiconductor ultraviolet sensor has been described. However, a GaP photodiode can be used for the purpose of the present application. As a GaP-based photodiode, in the case of Hamamatsu Photonx, model G1
961, 1962, and 1963.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a flame detector of the present application.

FIG. 2 is a diagram showing sensitivity characteristics of a semiconductor ultraviolet sensor used in the present application.

FIG. 3 is a diagram showing transmission characteristics of an ultraviolet transmission filter used in the present application.

FIG. 4 is a diagram showing output characteristics of a flame detector of the present application and a conventional structure.

FIG. 5 is a diagram showing a spectrum corresponding to the furnace temperature of the furnace light transmitted through U-340.

FIG. 6 is a diagram showing a spectrum of light in the furnace corresponding to the temperature in the furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flame detector 2 Semiconductor type optical sensor 3 Ultraviolet color glass filter 4 Burner 5 Condensing lens A Combustion flame formation area

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 27/14 D (72) Inventor Takatoshi Saeki 4-1-2, Hiranocho, Chuo-ku, Osaka-shi, Osaka Osaka F-term in Gas Co., Ltd. (reference) 2G065 AB05 BA02 BB26 CA08 DA06 3K005 QA03 QC03 SA07 SA13 4M118 AA05 AB10 CB01 GA10 GC11 GC20

Claims (3)

[Claims] 1. A flame detector for detecting light generated from a combustion flame by a semiconductor optical sensor via an ultraviolet transmission filter to detect the combustion flame formed in a furnace by a combustor, An ultraviolet color glass filter is provided as the ultraviolet transmission filter, and 650 is provided as the semiconductor type optical sensor.
A flame detector equipped with a semiconductor type ultraviolet sensor having no sensitivity in a wavelength region of nm or more. 2. The flame detector according to claim 1, wherein the semiconductor optical sensor is a GaAsP or GaP-based optical sensor. 3. The method according to claim 1, wherein the temperature in the furnace is in a temperature range of 1000 to 1400 ° C. using the flame detector according to claim 1 or 2.
A flame detection method for detecting a combustion state of the combustor.