JP2012242311A - Gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas analyzer capable of achieving high detection sensitivity.SOLUTION: A gas analyzer comprises: a hollow fiber 4 into which an analyzing object gas is introduced; a light projection unit 12 which is disposed on one end side of the hollow fiber 4 and emits light into the inside of the hollow fiber 4; a detection unit 13 which is disposed on the other end side of the hollow fiber 4 and detects light having passed through the hollow fiber 4; and a lighting control/signal detection unit 21 and a system control unit 22 which analyze the analyzing object gas based on the light detected by the detection unit 13. The light projection unit 12 includes a plurality of infrared LEDs 2a to 2c having different emission wavelengths.

Description

  The present invention relates to a gas analyzer.

  As a method for monitoring the state of insulating oil inside oil-filled electrical equipment such as a transformer and a reactor, a method using a device for analyzing gas in the oil has been proposed. For example, Japanese Patent Application Laid-Open No. 11-142832 (Patent Document 1) discloses a specific example of such a method.

  In the gas analysis method disclosed in the above literature, the insulating oil is collected from the oil-filled electrical device main body, and then the gas dissolved in the insulating oil is extracted. The extracted gas is mixed with a carrier gas, and the mixed gas is passed through a separation column. The separation column is loaded with column packing materials having different separation times depending on the type of gas. The gas concentration for each separation time is detected by a gas sensor using an oxide semiconductor. The component and amount of the gas are detected based on the separation time and the gas concentration.

  Japanese Unexamined Patent Application Publication No. 2009-92511 (Patent Document 2) discloses a hollow fiber that allows a gas to be detected to pass through, a light emitting unit that irradiates light inside the hollow fiber, and light that is irradiated inside the hollow fiber. A gas detection device is disclosed that includes a detection unit that detects the return light and an analysis unit that analyzes the gas based on the return light.

JP 11-142832 A JP 2009-92511 A

  In the conventional gas analyzer described in Japanese Patent Application Laid-Open No. 11-142832, a plurality of gas components extracted from insulating oil are measured by one sensor. For some reason, for example, the amount of water is large, the separation of the gas components in the separation column may be insufficient. In such a case, the gas component cannot be detected properly. In addition, the gas extracted from the insulating oil may contain a specific substance that easily causes deterioration of the gas sensor, such as sulfur or silicon. Such a specific substance may cause a problem that the life of the gas sensor is shortened.

  On the other hand, according to the configuration described in Patent Document 2, the optical fiber that guides the light from the light source and the optical fiber that guides the return light from the hollow fiber to the light receiving unit are connected to one end of the hollow fiber via the fiber branching unit. Connected to. However, according to this configuration, there is a possibility that the amount of return light incident on the optical fiber on the light receiving unit side is small. Since the return light travels while reflecting inside the hollow fiber, there is a possibility that the return light cannot enter the optical fiber on the light receiving unit side unless the incident angle of the return light is within an appropriate range. Alternatively, it is conceivable that the return light may enter the optical fiber on the light source side. It can happen that the sensitivity of the analyzer is reduced due to a decrease in the intensity of the return light.

  An object of the present invention is to provide a gas analyzer capable of obtaining high detection sensitivity.

  A gas analyzer according to an aspect of the present invention includes a hollow fiber into which a gas to be analyzed is introduced, and a light projecting unit that is disposed on one end side of the hollow fiber and irradiates light inside the hollow fiber. And a detection unit that is disposed on the other end side of the hollow fiber and detects light that has passed through the hollow fiber, and an analysis unit that analyzes the gas to be analyzed based on the light detected by the detection unit. Prepare.

  According to the present invention, the detection sensitivity of the gas analyzer can be increased.

It is a figure explaining the principle of the gas analysis method by NDIR method. 1 is a configuration diagram of a gas analyzer according to Embodiment 1. FIG. It is the figure explaining the example of the spectral width of infrared LED, and the absorption region of gas (carbon monoxide and acetylene). It is the figure which showed the structure of the gas analyzer using chopper control. FIG. 4 is a configuration diagram of a gas analyzer according to a second embodiment. It is the figure which showed the structure of the part regarding the light source part of the gas analyzer which concerns on Embodiment 3, a detection part, and a hollow fiber. FIG. 6 is a configuration diagram of a gas analyzer according to a fourth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  In the embodiment of the present invention, a gas analyzer using analysis by NDIR (non-dispersive infrared absorption spectroscopy) method is presented. FIG. 1 is a diagram illustrating the principle of a gas analysis method based on the NDIR method. Referring to FIG. 1, a permeation cell 1 is provided with a gas inlet 1a and a gas outlet 1b. The gas to be analyzed is introduced into the permeation cell 1 from the gas inlet 1a along the direction a, and discharged from the gas outlet 1b to the outside of the permeation cell 1 along the direction b.

  The light source 2 irradiates the inside of the transmission cell 1 with infrared light. The detector 3 receives the infrared light transmitted through the transmission cell 1. Based on the light reception signal output from the detector 3, an absorption spectrum of infrared light is obtained. From this absorption spectrum, the type and amount of gas are determined.

  However, since the optical path length of the transmission cell 1 is short, the amount of infrared light absorbed by the gas is small in the configuration shown in FIG. For this reason, with the configuration shown in FIG. 1, it is difficult to measure with high accuracy. Furthermore, when the absorption spectrum of the target gas is close to the absorption spectrum of another gas, the spectrum of the light source 2 interferes. This can make measurement difficult.

  In the embodiment of the present invention, the gas to be measured and infrared light are passed through the hollow fiber. It is possible to lengthen the optical path length of infrared light by lengthening the hollow fiber. Increasing the optical path length of infrared light increases the amount of absorption of infrared light. Therefore, according to the embodiment of the present invention, the detection sensitivity of the gas analyzer can be increased.

  Hereinafter, each embodiment will be described in detail. The gas analyzer according to each embodiment is used for the purpose of analyzing gas dissolved in insulating oil in oil-filled electrical equipment. However, the present invention is not limited to such applications, and the present invention can also be used for general gas analysis applications.

[Embodiment 1]
FIG. 2 is a configuration diagram of the gas analyzer according to the first embodiment. Referring to FIG. 2, the gas analyzer according to Embodiment 1 includes a light source unit 12, a hollow fiber 4, a detection unit 13, a lighting control / signal detection unit 21, and a system control unit 22.

  The oil-filled electrical device 11 is, for example, an oil-filled transformer or an oil-filled reactor, and the inside thereof is filled with insulating oil. The gas extraction mechanism 16 is connected to the oil-filled electrical device 11 through the pipes 14a and 14b. An extraction container 15 for extracting gas dissolved in the insulating oil is provided in the gas extraction mechanism 16.

  The gas extraction mechanism 16 is provided with a pump (not shown) for decompressing the inside of the extraction container 15. By decompressing the inside of the extraction container 15, gas is extracted from the insulating oil inside the extraction container 15. The extracted gas is sent to the detection unit 13 through the pipe 18. A filter 17 for removing mist (water, oil, etc.) and sulfur components contained in the gas is provided in the middle of the pipe 18.

  The light source unit 12 includes a plurality of infrared LEDs (Light Emitting Diodes) 2a to 2c and a lens 5 for condensing light emitted from each LED. Although three LEDs are shown in FIG. 2, the number of LEDs is not limited. Further, the emission wavelengths of the plurality of LEDs are different from each other. In this specification, “emission wavelength” means the center wavelength of the emission spectrum. The detection unit 13 includes a detector 3 that detects infrared light.

  The light source unit 12 and the detection unit 13 are connected by a hollow fiber 4. Therefore, the light source unit 12 is disposed at one end of the hollow fiber 4 and the detection unit 13 is disposed at the other end of the hollow fiber 4. The hollow fiber 4 can be formed by various methods such as plating the cylindrical base material with Ni, Al, Au, etc., and then etching the cylindrical base material, and therefore the detailed description will not be repeated here.

  The lighting control / signal detection unit 21 controls the lighting of the infrared LEDs 2 a to 2 c and receives a light reception signal from the detector 3. The system control unit 22 controls the lighting control / signal detection unit 21 and the gas extraction mechanism 16 (for example, a pump motor). Further, the system control unit 22 receives the light reception signal from the lighting control / signal detection unit 21 and executes multivariate analysis based on the light reception signal.

  The lighting control / signal detection unit 21 and the system control unit 22 realize an analysis unit that analyzes the gas to be analyzed based on the infrared light detected by the detection unit 13. The lighting control / signal detection unit 21 and the system control unit 22 may be integrally formed. Further, an external port for transferring data to a personal computer or the like may be provided in the system control unit 22 as necessary.

  Next, the operation of the gas analyzer according to Embodiment 1 will be described. First, insulating oil is extracted from the oil-filled electrical device 11 via the pipe 14a. The collected insulating oil is sent to the extraction container 15. In order to extract the gas dissolved in the insulating oil, the extraction container 15 is decompressed. Thereby, gas is extracted from insulating oil. The extracted gas is sent out from the inside of the extraction container 15 to the pipe 18. Mist and sulfur components contained in the gas are removed by the filter 17 provided in the middle of the pipe 18. The gas that has passed through the filter 17 is sent to the detection unit 13.

  First, gas is sent to the detection unit 13 to fill the detection unit 13 with gas. Next, the pump 20 provided on the light source unit 12 side is operated. Thereby, the gas inside the detection unit 13 flows from the detection unit 13 to the light source unit 12 through the inside of the hollow fiber 4, and is further discharged from the light source unit 12 to the outside through the pipe 19. As a result, the gas to be analyzed is introduced into the hollow fiber 4.

  In a state where gas flows through the hollow fiber 4, the lighting control / signal detection unit 21 lights the infrared LEDs 2a to 2c. Infrared light emitted from each of the infrared LEDs 2 a to 2 c is collected by the lens 5 and guided to one end of the hollow fiber 4. The infrared light guided to one end of the hollow fiber 4 is transmitted through the inside of the hollow fiber 4 and emitted from the other end of the hollow fiber 4. At this time, infrared light is absorbed inside the hollow fiber 4 by the gas flowing from the detection unit 13 to the light source unit 12. Infrared light emitted from the other end of the hollow fiber 4 is received by the detector 3 on the detection unit 13 side. The detector 3 outputs an electrical signal having an intensity corresponding to the received light intensity.

  The lighting control / signal detection unit 21 switches lighting of the infrared LEDs 2a, 2b, and 2c in terms of time. An output signal from the detector 3 is sent to the lighting control / signal detection unit 21. The lighting control / signal detection unit 21 acquires the received light intensity data of the detection unit 13 for each light source (infrared LED) and sends the data to the system control unit 22. The system control unit 22 performs multivariate analysis using data from the lighting control / signal detection unit 21. As a result, a measured value of the amount (or concentration) of the target gas is obtained.

  FIG. 3 is a diagram illustrating an example of the spectral width of an infrared LED and an absorption region of gas (carbon monoxide and acetylene). Referring to FIG. 3, generally, infrared light emitted from an infrared LED is not monochromatic light but has a certain spectral width. As an example, the spectrum width when the center wavelength is 1500 nm is 200 nm (= ± 100 nm).

  The gas for measurement is acetylene. The absorption range of acetylene is in the vicinity of a wavelength of 1531 nm. On the other hand, carbon monoxide is considered as a gas other than the measurement purpose. The absorption region of carbon monoxide is in the vicinity of a wavelength of 1565 nm. That is, the infrared absorption wavelength of the measurement target gas is close to the infrared absorption wavelength of a different gas.

  For example, it is assumed that only the infrared LED indicated as “LED1” in FIG. The center wavelength of infrared light emitted from this light source is 1550 nm. In this case, infrared light absorption of both acetylene and carbon monoxide will be detected.

  In the first embodiment, a plurality of light sources (infrared LEDs) having different emission wavelengths are provided in the light source unit 12. When acetylene and carbon monoxide are included in the gas extracted from the insulating oil, for example, three infrared LEDs having emission wavelengths of 1550 nm, 1650 nm, and 1700 nm, respectively (in FIG. 3, indicated as LED1, LED2, and LED3) Is selected. In the configuration shown in FIG. 2, the emission wavelengths of the infrared LEDs 2a to 2c may be 1550 nm, 1650 nm, and 1700 nm, respectively.

  The lighting control / signal detection unit 21 switches light emission of the plurality of infrared LEDs in time, and acquires data of received light intensity at the detection unit 13. Since the emission wavelength of each LED is known in advance, data in which the emission wavelength and the received light intensity are associated is obtained. The system control unit 22 performs multivariate analysis based on the data to obtain the concentration of the target gas. In addition, each infrared absorption spectrum of acetylene and carbon monoxide is calculated | required previously, and the system control part 22 memorize | stores the infrared absorption spectrum previously. This infrared absorption spectrum data can be used for measurement of the target gas.

  In the first embodiment, a light source that emits infrared light is realized by an infrared LED. Accordingly, the chopper control of the light source can be executed by the lighting control / signal detection unit 21. FIG. 4 is a diagram showing a configuration of a gas analyzer using chopper control.

  Referring to FIG. 4, lighting control / signal detection unit 21 provides control signals for chopper-controlling infrared LEDs 2 a to 2 c to infrared LEDs 2 a to 2 c and also to lock-in amplifier 23. The lock-in amplifier 23 uses the control signal from the lighting control / signal detection unit 21 as a reference signal, and removes a noise component included in the output signal from the detector 3, so that the S of the output signal from the detector 3 is removed. / N ratio is improved. Therefore, according to the configuration shown in FIG. 4, detection with higher sensitivity becomes possible.

  Thus, according to the first embodiment, both infrared light and gas are present inside the hollow fiber. Thereby, the absorption amount of infrared light can be increased as compared with the case where a transmission cell is used. As a result, the detection sensitivity can be increased.

  Further, when performing analysis using a gas sensor, the gas sensor is deteriorated by the gas to be analyzed, and therefore the life of the analyzer depends on the life of the gas sensor. According to the first embodiment, a gas sensor is not necessary. Therefore, the life of the analyzer can be extended.

  Further, in the embodiment, infrared light is incident on one end of the hollow fiber 4 and infrared light is extracted from the other end of the hollow fiber 4. In the configuration in which infrared light is incident and emitted at one end of the hollow fiber 4, it is difficult to separate the infrared light emitted from the hollow fiber 4 from the infrared light incident on the hollow fiber 4. When the infrared light emitted from the hollow fiber 4 and the infrared light incident on the hollow fiber 4 are mixed, the intensity of the light detected by the detector becomes larger (or smaller) than the true intensity. )there is a possibility. In such a case, the detection accuracy can be reduced. In this embodiment, since infrared light travels along one direction, it is possible to prevent mixing of light emitted from the hollow fiber 4 and light incident on the hollow fiber 4. Therefore, according to the first embodiment, the detection sensitivity can be increased.

  Furthermore, in this embodiment, a plurality of light sources that emit infrared light having different wavelengths are used, and lighting of the plurality of light sources is switched over time. And multivariate analysis is performed based on the output signal in the detection part when each light source is turned on. Thereby, detection sensitivity can be increased. Furthermore, by using a lock-in amplifier, noise components can be removed from the output signal from the detection unit, so that the detection sensitivity can be further increased.

[Embodiment 2]
FIG. 5 is a configuration diagram of the gas analyzer according to the second embodiment. Referring to FIGS. 2 and 5, the gas analyzer according to the second embodiment is different from the gas analyzer according to the first embodiment in the configuration of light source unit 12. Specifically, in the second embodiment, the light source unit 12 includes a halogen lamp 2d, a plurality of infrared bandpass filters 6a to 6c, and an optical chopper 6d.

  The infrared bandpass filters 6a to 6c have their passbands so that only infrared light having an absorption wavelength of a specific gas component (for example, acetylene, carbon monoxide, etc.) contained in the gas to be analyzed passes. Therefore, the pass bands of the infrared bandpass filters 6a to 6c are different from each other.

  The spectrum of the infrared light emitted from the halogen lamp 2d includes the passbands of the infrared bandpass filters 6a to 6c. In other words, the spectrum of infrared light emitted from the halogen lamp 2d can cover the absorption wavelength of the target gas. However, the light source is not limited to the halogen lamp as long as it can cover the absorption wavelength of the target gas, and can be applied to the gas analyzer according to the second embodiment.

  A known configuration can be applied to the optical chopper 6d. The optical chopper 6d includes, for example, a light shielding plate formed of a thin plate of stainless steel or aluminum, a motor that rotates the light shielding plate, and the like. The optical chopper 6 d is driven by a control signal from the lighting control / signal detection unit 21. Thereby, it is possible to switch whether or not the light that has passed through each of the infrared bandpass filters 6 a to 6 c is introduced into one end of the hollow fiber 4. That is, the chopper control of the light source can be performed as in the first embodiment. Since the structure of the other part of the gas analyzer according to Embodiment 2 is the same as the structure of the corresponding part of the gas analyzer according to Embodiment 1, the following description will not be repeated.

  According to the second embodiment, a plurality of LEDs can be dispensed with. Furthermore, according to the second embodiment, it is possible to dispense with a lens.

[Embodiment 3]
FIG. 6 is a diagram illustrating a configuration of a light source unit, a detection unit, and a part related to the hollow fiber of the gas analyzer according to the third embodiment. Referring to FIGS. 2 and 6, in the gas analyzer according to Embodiment 3, in addition to hollow fiber 4, hollow fiber 4 a is used. The hollow fiber 4a is filled with a gas inert to infrared rays (a gas that absorbs less infrared rays). That is, both ends of the hollow fiber 4a are closed. Note that air may be sealed in the hollow fiber 4a.

  The light source unit 12 is provided with a reflection plate 7. Infrared light emitted from the infrared LED 2a is reflected by the reflecting plate 7, propagates through the hollow fibers 4 and 4a, and reaches the detector 3. Similar to the first and second embodiments, the gas to be measured passes through the hollow fiber 4.

  The intensity of infrared light that has passed through the gas sealed in the hollow fiber 4 a is detected by the detector 3. The detected intensity is used as a reference when measuring the intensity of infrared light that has passed through the hollow fiber 4. Since the inert gas is enclosed in the hollow fiber 4a, it can be kept stable.

Although only one light source is shown in FIG. 6, a plurality of light sources may be used. In this case, it is preferable to chopper-control a plurality of infrared LEDs as in the first embodiment.
Since the configuration of the gas analyzer other than the portion shown in FIG. 6 is the same as the configuration shown in FIG. 2, the following description will not be repeated.

  In addition, the detector 3 is provided in common for the two hollow fibers, but two detectors may be provided corresponding to the two hollow fibers.

  According to Embodiment 3, the light branched from one light source is incident on the hollow fiber 4 in which the target gas exists and the hollow fiber 4a in which the inert gas is sealed. The intensity of the infrared light that has passed through the gas sealed in the hollow fiber 4 a is detected by the detector 3 and used as a reference when measuring the intensity of the infrared light that has passed through the hollow fiber 4. Thereby, not only the sensitivity can be stabilized, but also the detection sensitivity can be improved as compared with the first and second embodiments.

[Embodiment 4]
FIG. 7 is a configuration diagram of a gas analyzer according to the fourth embodiment. 2 and 7, the gas analyzer according to the sixth embodiment is the gas analyzer according to the first embodiment in that a filter 24 is provided at a position immediately before the target gas flows into the hollow fiber 4. Is different. In FIG. 7, the filter 24 is provided at the outlet of the pipe 18, but the position of the filter 24 is not limited as long as the infrared light emitted from the hollow fiber 4 is not blocked.

  The filter 24 is a filter for removing moisture and dirt components from the gas. For example, moisture contained in the gas is removed by an air dryer. The removal of the dirt component is performed by removing components other than the target gas using a porous filter.

  Since the structure of the other part of the gas analyzer according to the fourth embodiment is the same as the structure of the corresponding part of the gas analyzer according to the first embodiment, the following description will not be repeated. Further, the gas analyzer according to each of the second and third embodiments may include the filter 24 shown in FIG.

  According to the fourth embodiment, since the filter 24 is provided at a position immediately before the target gas flows into the hollow fiber 4, the state of the hollow fiber can be kept good. Therefore, the detection sensitivity can be kept good.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Transmission cell, 1a Gas inflow port, 1b Gas exhaust port, 2 Light source, 2a-2c Infrared light LED, 2d Halogen lamp, 3 Detector, 4,4a Hollow fiber, 5 Lens, 6a-6c Infrared band pass filter, 6d optical chopper, 7 reflector, 11 oil-filled electrical equipment, 12 light source, 13 detector, 14a, 14b, 18, 19 piping, 15 extraction vessel, 16 gas extraction mechanism, 17, 24 filter, 20 pump, 21 lighting Control / signal detection unit, 22 system control unit, 23 lock-in amplifier, a and b directions.

Claims (6)

A first hollow fiber into which the gas to be analyzed is introduced;
A light projecting unit disposed on one end side of the first hollow fiber and irradiating light inside the first hollow fiber;
A detector that is disposed on the other end side of the first hollow fiber and detects light that has passed through the inside of the first hollow fiber;
A gas analysis apparatus comprising: an analysis unit that analyzes the gas to be analyzed based on the light detected by the detection unit. The light projecting unit irradiates light having different wavelengths by switching over time.
The said analysis part analyzes the gas of the said analysis object by the multivariate analysis based on the relationship between the intensity | strength of the light detected by the said detection part, and the wavelength of the said detected light. Gas analyzer. The light projecting unit includes a plurality of infrared light emitting diodes having different emission wavelengths.
The analysis unit generates a control signal for chopper-controlling the plurality of infrared light emitting diodes,
The gas analyzer is
The gas analyzer according to claim 2, further comprising a lock-in amplifier that increases an S / N ratio of an output signal from the detection unit and supplies the signal to the analysis unit by using the control signal as a reference signal. The light projecting unit is
A broadband light source that generates infrared light;
A plurality of band-pass filters respectively provided corresponding to a plurality of components contained in the gas to be analyzed;
An optical chopper that switches whether or not light that has passed through each of the plurality of bandpass filters is introduced into the one end of the first hollow fiber;
Each passband of the plurality of bandpass filters includes an absorption wavelength of a corresponding component of the plurality of components,
The gas analyzer according to claim 2, wherein an emission spectrum of the broadband light source includes a pass band of each of the plurality of bandpass filters. A second hollow fiber in which gas is sealed and light from the light projecting unit is passed;
The detection unit detects light that has passed through each of the first and second hollow fibers,
The analysis unit uses, as a reference of the intensity of light that has passed through the inside of the first hollow fiber, the intensity of light that has passed through the inside of the second hollow fiber and has been detected by the detection unit. Item 4. The gas analyzer according to Item 1. An extraction device for extracting the gas to be analyzed from the insulating oil collected from the oil-filled electrical device;
An introducing device for introducing the extracted gas from the other end of the first hollow fiber into the first hollow fiber;
The gas analyzer according to any one of claims 1 to 5, further comprising a filter that allows the extracted gas to pass before the extracted gas is introduced into the other end of the first hollow fiber.

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