JP2018185194A - Gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas analyzer of non-dispersed infrared type which has high detection sensitivity and is compact.SOLUTION: The present invention is a gas analyzer of non-dispersed infrared type for analyzing gas components in a sample gas. The gas analyzer comprises a gas cell 10 for containing a sample gas, a light source 21 for irradiating the gas cell with infrared light, a thermostat bath 3, an optical detector 23 for detecting light having passed through the gas cell and arranged in the thermostat bath, a vacuum pump 5, and a suction flow channel including a first suction flow channel 11, a second suction flow channel 12 and a third suction flow channel 13. The vacuum pump is connected to the first suction flow channel. The first suction flow channel is connected to the thermostat bath via the second suction flow channel and connected to the gas cell via the third suction flow channel. The suction flow channel has a flow channel switching device 4 capable of controlling the opening/closing of each of the second suction flow channel and the third suction flow channel at the least.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas analyzer.

  For example, when an abnormality occurs inside the oil-filled transformer, the insulating oil or paper is decomposed and flammable gas is generated. In order to detect signs of internal abnormalities, it is necessary to measure the concentration of low-concentration combustible gas dissolved in oil.

  As one of gas analyzers, NDIR (Non Dispersive InfraRed) type gas analyzers are known. When the analysis target gas is irradiated with infrared light of a specific wavelength band, the energy of the infrared light is converted into the vibration and rotation of gas molecules, and the energy of the infrared light reaching the detector is reduced accordingly. In the NDIR type gas analyzer, the concentration of gas can be obtained by measuring the amount of decrease in the energy of the infrared light.

  As described above, since the NDIR gas analyzer uses infrared light for detection, if there is a temperature change in the detector, heat becomes noise and it is difficult to detect a low-concentration gas component. there were.

  As a countermeasure, in the apparatus described in Patent Document 1 (International Publication No. 2015/186407), in order to keep the detector at a constant temperature, a container containing the detector is wrapped with a heat insulating material such as urethane foam. ing.

  Moreover, in the apparatus described in Patent Document 2 (Japanese Patent Laid-Open No. 2006-30032), a vacuum pump is connected to an airtight container that houses a detection unit, and the inside of the container is maintained in a vacuum state to improve heat insulation. This suppresses the temperature change in the container (detection unit).

  Also in the apparatus described in Patent Document 3 (Japanese Patent Laid-Open No. 2008-16456), an optical chamber containing a detector and a light source is maintained in a vacuum state by a vacuum pump.

  In Patent Document 4 (Japanese Patent Laid-Open No. 2001-41877), the air in the system is discharged by evacuating a sealed container containing devices such as a light source, a cell, and a detector. A method for reducing is disclosed. However, the gas cell and the detector are not independent, and analysis is performed by introducing purge gas into the container. For this reason, the purge gas is filled in the container at the time of gas analysis, and the periphery of the detector is not maintained in a vacuum state. Therefore, the detector cannot be kept at a constant temperature.

International Publication No. 2015/186407 JP 2006-30032 A JP 2008-16456 A JP 2001-41877 A

  However, the apparatus of Patent Document 1 has a problem that the container becomes large because the periphery of the container is covered with a heat insulating material.

  Further, the apparatus of Patent Document 2 has a problem that the apparatus becomes large because a gas cylinder or the like for introducing the sample gas into the gas cell is required in addition to the vacuum pump that maintains the container in a vacuum state. Moreover, since the internal capacity of the gas cylinder decreases due to use, it is necessary to replace the gas cylinder periodically.

  Also in the apparatus of Patent Document 3, since the optical chamber and the sample cell are configured in separate lines, an air pump for introducing gas into the sample cell separately from the vacuum pump that evacuates the optical chamber, A vacuum pump, gas cylinder, etc. are required. For this reason, there existed a problem that an apparatus enlarged. Moreover, since the internal capacity of the gas cylinder decreases due to use, it is necessary to replace the gas cylinder periodically.

  Accordingly, an object of the present invention is to provide a non-dispersive infrared gas analyzer having high detection sensitivity and a small size.

  The gas analyzer of the present invention is a non-dispersive infrared type gas analyzer for analyzing gas components in a sample gas.

  The gas analyzer includes a gas cell that contains a sample gas, a light source that irradiates the gas cell with infrared light, a thermostat, an optical detector that is disposed in the thermostat and detects light transmitted through the gas cell, and a vacuum pump And a suction channel including a first suction channel, a second suction channel, and a third suction channel.

  The vacuum pump is connected to the first suction channel. The first suction channel is connected to the thermostatic bath via the second suction channel and is connected to the gas cell via the third suction channel. The suction channel has a channel switching device capable of opening and closing each of at least the second suction channel and the third suction channel.

  According to the present invention, it is possible to provide a non-dispersive infrared gas analyzer having high detection sensitivity and a small size.

1 is a schematic configuration diagram of a gas analyzer according to Embodiment 1. FIG. 6 is a schematic configuration diagram of a gas analyzer according to a modification of the first embodiment. FIG. FIG. 3 is a schematic configuration diagram of a gas analyzer according to a second embodiment. FIG. 6 is a schematic configuration diagram of a gas analyzer according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals represent the same or corresponding parts.

Embodiment 1 FIG.
The gas analyzer of the present embodiment is a non-dispersive infrared (NDIR) type gas analyzer for analyzing gas components in a sample gas.

  Although it does not specifically limit as sample gas, For example, the dissolved gas of the insulating oil in oil-filled electrical apparatuses, such as a transformer, is mentioned. As a method for extracting the sample gas from the insulating oil, for example, the insulating oil is contained in a sealed container, the upper part of the sealed container is made into a vacuum space, and the sample gas is extracted into the vacuum space. On the other hand, there are a method of extracting the sample gas by bubbling and a method of extracting the sample gas by stirring with a rotor disposed in the insulating oil.

Although it does not specifically limit as a gas component, When sample gas is dissolved gas in insulating oil, the hydrocarbon produced by decomposition | disassembly of insulating oil is mentioned, for example. Examples of such hydrocarbons include CH ₄ , C ₂ H ₂ , C ₂ H ₆ , C ₂ H _{4 and the} like. In addition, these gas components can become an index for monitoring the state (presence of internal abnormality) of oil-filled electrical equipment such as a transformer, for example.

  Referring to FIG. 1, a gas analyzer is disposed in a gas cell 10 that contains a sample gas, a light source 21 that irradiates the gas cell 10 with infrared light, a thermostat 3, and a thermostat 3. An optical detector 23 that detects transmitted light, a vacuum pump 5, and a suction channel including a first suction channel 11, a second suction channel 12, and a third suction channel 13 are provided.

  As described above, the gas analyzer of the present embodiment is an NDIR optical measuring machine. Therefore, the light source 21 is a light source that emits infrared light, the optical detector 23 is sensitive to infrared light, and the gas cell 10 has infrared transmission windows 22a at both ends through which infrared light passes. , 22b.

  The infrared light emitted from the light source 21 is preferably mid-infrared light (wavelength: about 3 to 5 μm). Further, for example, when the gas to be analyzed has a low concentration as in the case of analyzing gas (in-oil gas) contained in the insulating oil of the oil-filled electrical device, the light source 21 is used to increase the detection sensitivity. It is preferable that the infrared light radiated | emitted from contains the maximum absorption wavelength of each gas component.

  The vacuum pump 5 is connected to the first suction channel 11. The first suction channel 11 is branched on the upstream side, is connected to the thermostatic chamber 3 through the second suction channel 12, and is connected to the downstream side of the gas cell 10 through the third suction channel 13. The In the flow direction of the sample gas and the carrier gas, the supply channel 15 is connected to the upstream side of the gas cell 10, and the third suction channel 13 is connected to the downstream side of the gas cell 10.

  The suction flow path includes a flow path switching device 4 that can control opening and closing each of at least the second suction flow path 12 and the third suction flow path 13. In the gas analyzer shown in FIG. 1, the flow path switching device 4 includes a valve 4 a provided in the second suction flow path 12 and a valve 4 b provided in the third suction flow path 13. From the viewpoint of enabling the flow path switching device 4 to be automatically controlled, the valves 4a and 4b are preferably electromagnetic valves.

  From the viewpoint of preventing the sample gas and the carrier gas from being mixed into the thermostat, the flow path switching device preferably does not open the second suction flow path and the third suction flow path at the same time. Therefore, when the valves 4a and 4b are electromagnetic valves, the flow path switching device may have a control mechanism that controls opening / closing of the valves 4a and 4b (sequence control) so that both the valves 4a and 4b are not opened simultaneously. preferable.

  The thermostatic chamber 3 is a hermetically sealed container except for the connection portion with the second suction channel 12. The inside of the thermostatic chamber 3 is maintained in a vacuum state by the vacuum pump 5 at least during the analysis.

  Specifically, for example, before the gas analysis is performed, the thermostatic chamber 3 is operated via the first suction channel 11 and the second suction channel 12 by operating the vacuum pump 5 and opening the valve 4a. And the vacuum pump 5 are communicated with each other, whereby the air in the thermostat 3 is exhausted, and the thermostat 3 is evacuated. Since the inside of the thermostatic chamber 3 is in a vacuum state, the surroundings of the optical detector are thermally insulated from the vacuum, and heat from the outside is blocked, so that the temperature change of the optical detector 23 is suppressed.

  As in the past (see, for example, Patent Document 1), in the case where an optical detector is placed in a thermostat and the temperature change of the detector is suppressed by covering the periphery with a heat insulating material, the thermostat becomes large and the device There has been a problem of increasing the size.

  On the other hand, in the gas analyzer of the present embodiment, since the temperature change of the optical detector is suppressed by making the inside of the thermostatic chamber into a vacuum state using a vacuum pump, no heat insulating material is required, and the thermostatic bath is large. Therefore, the gas analyzer can be downsized.

  Moreover, in the gas analyzer of the present embodiment, the vacuum pump 5 for making the inside of the thermostatic chamber 3 into a vacuum state also serves as a suction pump for introducing the carrier gas and the sample gas into the gas cell 10. There is no need to increase the number of pumps, and the apparatus can be simplified and miniaturized.

  Hereinafter, an example of the operation of the gas analyzer will be described with reference to FIG. Basically, when gas (sample gas, carrier gas, etc.) is not introduced into the gas cell 10, the valve 4b (third suction flow path 13) is closed. Further, the valve 4 a of the second suction channel 12 that connects between the thermostatic chamber 3 and the vacuum pump 5 is opened, and the inside of the thermostatic chamber 3 is maintained in a vacuum state by the vacuum pump 5.

  Next, in the flow channel switching device 4 with the vacuum pump 5 activated, the valve 4a (second suction flow channel 12) is closed and the valve 4b (third suction flow channel 13) is opened. A sample gas is introduced into the gas cell 10 from the supply channel 15 into the gas cell 10 together with a predetermined carrier gas.

  After the gas is introduced into the gas cell 10, the carrier gas and the sample gas can be retained in the gas cell 10 by closing the valve 4 b. When the valve 4b is closed, when the operation of the vacuum pump 5 is continued, the valve 4a may be opened or may be kept closed. However, when stopping the operation of the vacuum pump 5, it is preferable to keep the valve 4b closed before the stop.

  Then, as shown in FIG. 1, the light source 21 irradiates the gas cell 10 (sample gas) with infrared light, and the optical detector 23 detects the infrared light that has passed through the gas cell 10 and the infrared transmission windows 22a and 22b. By doing so, it is possible to analyze the gas component contained in the sample gas based on the detected light intensity and the like. Specifically, for example, since the infrared light irradiated from the light source 21 is absorbed by the sample gas in the gas cell 10, the amount of infrared light input to the optical detector 23 (the gas component to be measured) The intensity of light in a specific wavelength range according to the absorption wavelength, etc.) decreases. For this reason, it is possible to analyze the gas component in the sample gas (detection of the gas component, concentration measurement, etc.) by obtaining the decrease amount of the light amount detected by the optical detector 23, the change amount of the light transmittance, and the like. . Examples of the method of irradiating light in a specific wavelength range corresponding to the absorption wavelength of the gas component to be measured include a method of passing through a bandpass filter that passes only light in a specific wavelength range, and a specific wavelength range. The method of using LED which irradiates only this light is mentioned.

  After the gas analysis is completed, the valve 4b is opened while the vacuum pump 5 is operated in order to eliminate the influence on the next analysis, and the carrier gas and the sample gas in the gas cell 10 are exhausted. At this time, the valve 4a is preferably closed in order to prevent the carrier gas and the sample gas from being mixed into the thermostat 3. After the exhaust is completed, the valve 4b is closed and the valve 4a is opened, so that the thermostatic chamber 3 is brought into a vacuum state and the state is maintained until the next measurement.

  In addition, when air | atmosphere can be used as carrier gas, the upstream of the supply pipe connected to the upstream of the gas cell may be open | released by air | atmosphere. Thus, by using the atmosphere as the carrier gas, a gas cylinder or the like becomes unnecessary, and the gas analyzer can be more easily downsized and simplified.

  A valve may be provided in the first suction channel 11. For example, the valve provided in the first suction channel 11 may normally remain open, and may be closed when the vacuum pump is removed from the gas analyzer.

  The longer the optical path length of the gas cell 10, the higher the sensitivity of the NDIR gas analyzer. When the sample gas is a very small amount (for example, about several tens of cc) of gas such as gas extracted from insulating oil, it is preferable to use a cell having a small inner diameter (for example, a hollow fiber) as the gas cell 10. Thereby, the optical path length of the gas cell 10 containing a small amount of sample gas can be increased, and the sensitivity of the gas analyzer is increased.

  The hollow fiber can introduce gas into the inside, and can pass infrared light in the length direction even in a bent state. For example, the hollow fiber can be bent with a bending radius of about several tens of centimeters. Therefore, there is an advantage that the gas analyzer can be downsized as compared with the case where the gas cell 10 is linear.

  FIG. 2 is a schematic configuration diagram of a gas analyzer according to a modification of the first embodiment. As shown in FIG. 2, in the present modification, the third suction channel 13 is connected to the gas cell 10 without passing through the inside of the thermostatic chamber 3. In the case of FIG. 1, processing or the like for maintaining the hermeticity of the thermostatic chamber 3 with respect to the third suction flow path 13 and the gas cell 10 is necessary, whereas in the case of the modification shown in FIG. Since only the gas cell 10 needs to be sealed, there is an advantage that the device is simplified and the device is easily manufactured.

  Note that the gas analyzer of the present embodiment further includes another analyzer for analyzing gas components (for example, a photoionization detector, a hydrogen sensor for measuring hydrogen, etc.) on the upstream side of the gas cell 10 or the like. You may have.

Embodiment 2. FIG.
Referring to FIG. 3, the gas analyzer of the present embodiment further includes a light source thermostat 31 connected to the thermostat 3 via the fourth suction flow path 14, and the light source 21 is a light source thermostat. 31 is different from the first embodiment in that it is disposed within the area 31. The other points are basically the same as in the first embodiment.

  Since the light source 21 is disposed in the light source thermostat 31 and the light source thermostat 31 is connected to the thermostat 3 for the optical detector 23 by the fourth suction flow path 14, the surroundings of the light source 21 are also vacuumed. It becomes a state. Thereby, the light source 21 is also thermally insulated by vacuum, and the temperature change of the light source 21 is suppressed. Therefore, the infrared light emitted from the light source 21 is also constant, the thermal noise of the optical detector 23 is reduced as compared with the first embodiment, and the sensitivity of the gas analyzer can be improved.

Embodiment 3 FIG.
Referring to FIG. 4, the gas analyzer according to the present embodiment is implemented in that optical detector 23 is connected to cooler 6 (the temperature is controlled to be kept constant by cooler 6). This is different from the first form. The other points are basically the same as in the first embodiment.

  The photoconductive element or the like used for the optical detector 23 has a characteristic that the sensitivity increases as the temperature decreases. For this reason, for example, by connecting the cooler 6 such as Peltier to the optical detector 23 with a metal bar having high thermal conductivity, the optical detector 23 is cooled to further increase the sensitivity of the gas analyzer. Thus, the temperature change of the optical detector 23 can be further suppressed. In addition, since the inside of the thermostat 3 is made into the vacuum state by the vacuum pump 5, the problem that dew condensation arises by the water | moisture content inside the thermostat 3 by cooling of the optical detector 23 does not arise.

  Although it does not specifically limit as a cooler, For example, the cooler using a Peltier device etc. are mentioned. The cooler preferably has a temperature control mechanism (such as a thermostat) for keeping the temperature of the optical detector 23 constant.

  Note that the above-described embodiment is an exemplification, and it is needless to say that partial replacement or combination of the configurations shown in different embodiments is possible. For example, the cooler of the third embodiment may be adopted as the second embodiment.

  The embodiment disclosed this time should 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 Optical measuring device, 10 Gas cell, 11 1st suction flow path, 12 2nd suction flow path, 13 3rd suction flow path, 14 4th suction flow path, 15 Supply flow path, 21 Infrared light source, 22a, 22b Red External transmission window, 23 optical detector, 3 thermostatic chamber, 31 thermostatic bath for light source, 4 flow path switching device, 4a, 4b valve, 5 vacuum pump, 6 cooler.

Claims (3)

A non-dispersive infrared gas analyzer for analyzing gas components in a sample gas,
A gas cell containing the sample gas;
A light source for irradiating the gas cell with infrared light;
A thermostat,
An optical detector that is disposed in the thermostat and detects light transmitted through the gas cell;
A vacuum pump,
A suction channel including a first suction channel, a second suction channel, and a third suction channel;
The vacuum pump is connected to the first suction flow path;
The first suction channel is connected to the thermostatic chamber via the second suction channel, and is connected to the gas cell via the third suction channel,
The gas analysis apparatus, wherein the suction flow path includes a flow path switching device capable of opening and closing at least each of the second suction flow path and the third suction flow path. Furthermore, a thermostat for light source connected to the thermostat via a fourth suction channel,
The gas analyzer according to claim 1, wherein the light source is disposed in the constant temperature bath for the light source.   The gas analyzer according to claim 1, wherein the optical detector is connected to a cooler.

Images