JP2010151693A - Gas analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas analyzer hard to cause noise in a light signal in a light path, for precisely measuring the concentration and temperature of gas and for achieving simple constitution without being accompanied with complication and an increase in size even in the measurement of a plurality of kinds of gases. <P>SOLUTION: In the gas analyzer for analyzing the absorption spectrum of the laser beam allowed to irradiate a measuring target gas to measure the concentration and temperature of the gas, a pair of collimators 3a and 3b, which have both functions of an irradiation part for irradiating the measuring target gas with the laser beam emitted from a laser beam emitting part and a light detection part for detecting the laser beam passed through the measuring target gas, are installed toward the measuring target gas 2, optical fibers 7a and 7b are connected to the collimators to install light circulators 9a and 9b in the route of the optical fibers, so that both of an irradiation signal and a light detection signal are fed to the single laser beam route between both light circulators. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, there is a high possibility that gas generated in a closed container such as a boiler, a waste incinerator, a combustion chamber of a combustion engine or the like, or exhaust gas discharged to the outside from the closed container, or discharged gas is retained. The present invention relates to a gas analyzer in a place.

  Conventionally, a technology that uses laser light has been developed as a method for measuring the concentration of gas generated in closed containers such as boilers, garbage incinerators, and combustion chambers of combustion engines, and exhaust gas concentrations discharged from the combustion chambers to the outside. Has been. This gas concentration measurement technology using laser light utilizes the property of absorbing a specific wavelength for each gas type, and irradiates laser light of a specific wavelength in the gas atmosphere, and the laser light that has passed through the gas atmosphere. By analyzing the spectrum, the concentration and gas temperature of a specific gas type are grasped.

As an example of measuring the exhaust gas concentration and gas temperature from an engine using laser light, devices as shown in FIGS. 6A and 6B are known.
In FIG. 6A, the laser light from the laser diode LD is set to a predetermined absorption wavelength according to the gas component to be measured in the measurement target gas 01, and the irradiation unit 03 provided in the measurement cell 02. Irradiate from the collimator 05. Laser light that has passed through the measurement target gas 01 is received by the photodiode 09 of the light receiving unit 07. Note that windows 08 and 010 for laser light irradiation and light reception are provided.
A differential signal between the measurement light reception signal that has passed through the measurement target gas and the reference light reception signal that does not pass through the measurement target gas is amplified by the differential amplifier 011, and based on the amplified signal, the gas component in the measurement target gas The absorbed absorption spectrum is grasped, and the concentration and temperature of the gas component to be detected in the measurement object are measured by analyzing the absorption spectrum.

  FIG. 6B shows an irradiation unit provided in the measurement cell 02 in which the laser light from the laser diode LD is set to a predetermined absorption wavelength that matches the gas component to be measured in the measurement target gas 01. The laser beam irradiated from the collimator 05 of 03 and passed through the measurement target gas 01 is received by the photodiode 09 of the light receiving unit 07, and the signal received by the photodiode 09 is received by a PD amplifier (photodiode amplifier). ) Input to 013, amplify, detect a signal synchronized with the predetermined wavelength from the amplified signal (lock-in detection), grasp the absorption spectrum absorbed by the gas component in the gas to be measured, and absorb this absorption By analyzing the spectrum, the concentration and temperature of the gas component to be detected in the measurement object are measured.

6 (a) and 6 (b), since the measurement cell 02 is an interference part between the measurement target gas 01 and the laser, it is often used by being inserted in series in an engine pipe or the like. The surface temperature may exceed 200 ° C. depending on the exhaust gas temperature from the engine. The photodiode 09 and the PD amplifier 013 cannot be directly installed in the measurement cell 02, and a heat insulating jig is inserted between the measurement cell 02 and the surface temperature.
For this reason, the structure of the measurement cell has become complicated, and excessive care has been required in transportation, installation, and use.
Further, since the photodiode 09 and the PD amplifier 013 are installed in the vicinity of the measurement cell 02, there is a problem that it is easy to pick up noise from the exhaust pipe of the engine.

On the other hand, as a configuration in which the photodiode 09 and the PD amplifier 013 as shown in FIGS. 6A and 6B are not directly installed in the measurement cell 02, a technique such as Patent Document 1 (Japanese Patent Laid-Open No. 10-90170) is also available. Are known.
In Patent Document 1, as shown in FIG. 7, pulsed light locked to an absorption wavelength is emitted from a light source 020 through an optical fiber 022 to optical means 024, and from the optical means 024 through an optical fiber 026 to a gas tube 027. It is emitted to the gas detection sensor 028 inside. In the gas detection sensor 028, the passing light is lost and emitted according to the gas concentration existing in the vicinity. A part of the emitted light from the gas detection sensor 028 is reflected by the mirror of the reflection means 029 and enters the gas detection sensor 028 again, and the lost light passes through the optical means 024 and the photoelectric changer of the detection unit 030. It is converted into an electric signal by 032 and signal processing is performed by the signal processing unit 034 to calculate the gas concentration.

JP-A-10-90170

However, in the measurement apparatus shown in Patent Document 1, detection is performed via optical fibers 026 and 036 without directly installing a photodiode or photodiode amplifier in a measurement cell as shown in FIGS. 6 (a) and 6 (b). Since it is connected to the photoelectric changer 032 of the unit 030 and is converted into an electric signal, there is no problem that it is easy to insert a heat insulating jig or pick up noise of the engine piping, but the mirror of the reflecting means in the optical path Therefore, there is a problem that noise is likely to ride on the optical signal.
In addition, in the case of Patent Document 1, in order to detect a plurality of gas concentrations, a plurality of gas detection sensors 028 must be installed in accordance with the gas type, and there is a problem associated with an increase in the size of the apparatus.

  Therefore, the present invention has been made in view of such a background, makes it difficult for noise to be applied to an optical signal in an optical path, enables accurate gas concentration and gas temperature measurement, and further provides a plurality of types of gases. It is an object of the present invention to provide a gas analyzer that can be achieved with a simple configuration without increasing the complexity and size of the apparatus even in measurement.

  In order to solve the above-mentioned problems, the present invention relates to a laser beam emitted from a laser beam emitter in a gas analyzer that analyzes the absorption spectrum of a laser beam irradiated into a measurement target gas and measures the gas concentration and temperature. A plurality of transmitter / receiver units having both functions of an irradiation unit that irradiates the measurement target gas and a light receiving unit that receives laser light that has passed through the measurement target gas are installed toward the measurement target gas. An optical fiber is connected to the light receiving unit, an optical circulator is installed in the path of the optical fiber, and both irradiation and light reception signals are conveyed in a single laser light path between one and the other optical circulators. It is characterized by comprising.

According to this invention, since a measurement signal can be flowed bidirectionally through a single laser beam path, it interferes with the measurement target gas in the same path, so that a highly accurate gas concentration can be measured.
Further, since the circulator does not need to be installed in the vicinity of the measurement target gas, a heat insulating structure, a vibration preventing structure, or the like is not necessary, and the apparatus can be simplified.
In addition, both directions of irradiation and light reception signals are transported in a single laser beam path between both optical circulators, but there is no factor in the measurement path that causes optical noise to be generated in the transport path. Therefore, it is possible to measure the gas concentration with high accuracy with little noise generation.

  In the present invention, preferably, the light transmitting / receiving unit is formed of a collimator (optical lens), a pair of the collimators is installed in one measurement cell, and the optical circulators are installed in optical fibers connected to both collimators, It is good to comprise so that the laser beam of the absorption wavelength with respect to different gas types may be irradiated and light-received from each said light transmission / reception part via both optical circulators.

  According to such a configuration, concentration measurement can be performed on two different gas types by a pair of light transmitting / receiving units installed in one measurement cell, and thus the measurement apparatus can be downsized. That is, by setting the laser beam irradiated through one optical circulator and the laser beam irradiated through the other optical circulator to the absorption wavelengths of the gas species to be measured, two gas concentrations can be simultaneously measured. Can be performed with high accuracy and a simple device.

  In the present invention, it is preferable that the light transmission / reception unit includes a collimator, a pair of the collimators are installed in one measurement cell, the optical circulators are installed in optical fibers to both collimators, and both optical circulators are used. In this case, it is preferable to irradiate and receive laser beams having different absorption wavelengths for the same kind of gas from the respective light transmitting / receiving units.

  According to such a configuration, laser light having different absorption wavelengths for the same kind of gas is irradiated and received via both optical circulators, so that the concentration measurement accuracy for the same kind of gas is improved and the wavelength is the same even at the same gas concentration. The gas temperature can be measured together with the gas concentration measurement based on the fact that the amount of absorption with respect to the gas changes depending on the gas temperature (atmosphere temperature).

  In the present invention, it is preferable that the light transmission / reception unit includes a collimator, a pair of the collimators are installed in one measurement cell, the optical circulators are installed in optical fibers to both collimators, and one optical circulator is installed. It is preferable that the light flow direction is limited to one direction by short-circuiting, and the measurement signal is transmitted and received by the other optical circulator that is not short-circuited.

  According to this configuration, since the interference path length between the laser beam and the measurement target gas in the measurement cell can be doubled, the signal noise ratio (S / N ratio) can be increased, and the measurement accuracy can be improved. Since there is no large reflection point on the top, the generation factor of fringe (optical noise) is extremely small, so that the measurement accuracy can be improved.

  Furthermore, when an optical circulator that is short-circuited is installed in the vicinity of the measurement cell, the number of optical fibers for connection with other optical circulators that are not short-circuited becomes one, and the measurement apparatus can be further simplified.

  In the present invention, it is preferable that the light transmitting / receiving unit includes a collimator, and a plurality of collimators are installed in one measurement cell, and each pair of collimators is arranged to be able to irradiate the measurement target gas in different directions. Then, the laser beam paths are preferably connected in series.

  According to such a configuration, a plurality of pairs of laser light paths in different directions with respect to the measurement target gas are formed and connected in series, so that the measurement target gas can be measured without deviation and the interference path length with the measurement target gas is long. Therefore, the signal noise ratio (S / N ratio) is increased, and the measurement accuracy of the gas concentration is further improved.

  According to the present invention, it is difficult for noise to be applied to an optical signal in an optical path, and accurate gas concentration and gas temperature measurement can be performed. Further, even in measurement of a plurality of types of gases, the apparatus is not complicated or enlarged. It is possible to provide a gas analyzer that can be achieved with a simple configuration.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Only.

(First embodiment)
FIG. 1 is an overall configuration diagram of a gas analyzer according to a first embodiment of the present invention. The measurement target gas can be applied to a gas generated in a closed container such as a boiler, a waste incinerator, a combustion chamber of a combustion engine, or a gas discharged to the outside from the combustion chamber. The installation in the passage will be described.

  A collimator (optical lens) (transmission / reception unit) that irradiates and receives measurement laser light in a direction perpendicular to the exhaust gas flow of the measurement target gas 2 is placed in series in the middle of the exhaust passage. ) A pair of 3a and 3b are installed. Further, the light is irradiated and received from the windows 5a and 5b into the exhaust passage. An optical fiber 7a is connected to the collimator 3a, and the collimator 3a is connected to the second port of one optical circulator 9a via the optical fiber 7a.

  In this optical circulator, as shown in FIG. 5, the signal input to the first port 1 is output only to the next second port, the signal input to the second port is output only to the third port, and the last The signal input to the 3rd port is an electronic component having the characteristic of being output to the first 1st port, and an output 3 port (terminal) type is used.

  Laser light from the laser light emitting means 13 of the first analyzing means 11 is input to the first port of the first optical circulator 9a through the optical fiber 15, and is output from the third port by the first photodiode 17a. It is converted into an electrical signal. Thereafter, the signal is amplified by the first PD amplifier (photodiode amplifier) 19a, and the amplified signal is input to the analysis means 23 of the second analysis means 21 to grasp the absorption spectrum absorbed by the gas component in the measurement target gas. The absorption spectrum is analyzed to measure the concentration and temperature of the gas component in the measurement target.

  On the other hand, an optical fiber 7b is connected to the collimator 3b, and the collimator 3b is connected to the second port of the second optical circulator 9b via the optical fiber 7b. The first optical circulator 9b is input to the first port from the laser light emitting means 25 of the second analyzing means 21 through the optical fiber 27, and is output from the third port and is output by the second photodiode 17b. Is converted to Thereafter, the signal is amplified by the second PD amplifier (photodiode amplifier) 19b, and the amplified signal is input to the analysis unit 12 of the first analysis unit 11, and the absorption spectrum absorbed by the gas component in the measurement target gas is grasped. The absorption spectrum is analyzed to measure the concentration and temperature of the gas component in the measurement target.

In the gas analyzer configured as described above, the laser light set to the absorption wavelength for the first gas species to be analyzed is sent from the laser light emitting means 13 of the first analyzing means 11 to the first light by the optical fiber 15. The light is guided to the first port of the circulator 9a, outputted from the second port, inputted to the collimator 3a by the optical fiber 7a, and irradiated into the measurement target gas 2.
Thereafter, the transmitted light is received by the collimator 3b, guided to the second port of the second optical circulator 9b by the optical fiber 7b, output from the third port, and input to the second photodiode 17b by the optical fiber 31. Thereafter, as described above, the absorption spectrum that is input to the analysis unit 12 of the first analysis unit 11 and is absorbed by the gas component in the gas to be measured is analyzed.

Similarly, the laser light set to the absorption wavelength for the second gas species to be analyzed is sent from the laser light emitting means 25 of the second analyzing means 21 to the first port of the second optical circulator 9b by the optical fiber 27. It is guided, output from the second port, input to the collimator 3b by the optical fiber 7b, and irradiated into the measurement target gas 2.
Thereafter, the transmitted light is received by the collimator 3a, guided to the second port of the first optical circulator 9a by the optical fiber 7a, output from the third port, and input to the first photodiode 17a by the optical fiber 33. Thereafter, as already described, the absorption spectrum that is input to the analysis means 23 of the second analysis means 21 and is absorbed by the gas component in the gas to be measured is analyzed.

  Therefore, according to the first embodiment, a measurement signal can flow in both directions in a single laser beam path formed between the first optical circulator 9a and the second optical circulator 9b. Since it interferes with the measurement target gas in the same path, it is possible to measure and compare different gas concentrations at the same position and to measure the gas concentration with high accuracy.

Further, since the first optical circulator 9a and the second optical circulator 9b do not need to be installed in the vicinity of the measurement cell 1, a heat insulating structure, a vibration preventing structure, and the like are not necessary, and thus the apparatus can be simplified.
In addition, a single laser beam path formed between the first optical circulator 9a and the second optical circulator 9b carries both directions of irradiation and light reception signals. Since there is no cause for generating fringe (optical noise) to such a measurement signal, it is possible to measure the gas concentration with high accuracy and less noise.

  In addition, since the concentration measurement can be performed by conveying the laser beam bidirectionally with only a pair of collimators 3a and 3b installed in one measurement cell 1 for two different gas types, Can be downsized.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. FIG. 2A is an explanatory diagram of the overall configuration, and FIG. 2B is an explanatory diagram of gas temperature measurement, showing an example of the magnitude of an absorption spectrum at different absorption wavelengths (λ1, λ2) of the same gas type.
In the first embodiment, different gas types are measured, but the second embodiment is a case where different spectra of the same gas type are irradiated. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

Laser light emission means 13 of the first analysis means 11 emits laser light set to the first absorption wavelength for the gas species to be analyzed. Further, the laser light emitting means 25 of the second analyzing means 21 emits the laser light set to the second absorption wavelength for the gas species to be analyzed.
The irradiation of each laser beam to the measurement target gas 2 and the conveyance of the received light are the same as those described in the first embodiment.

  According to the second embodiment, since the same gas species are irradiated with laser beams having different absorption wavelengths, the measured concentrations are the same, but there is a difference in the intensity of the absorption spectrum. As shown in FIG. 2B, the spectrum sizes are different. This is because the spectra with different absorption wavelengths (λ1, λ2) have different temperature dependence, so the gas temperature can be measured by measuring the ratio (B / A) or difference of the absorption wavelength spectra. The gas temperature can be measured simultaneously with the gas concentration.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. FIG. 3 is an overall configuration diagram, and the first optical port of the second optical circulator 9b is short-circuited with the third port with respect to the first embodiment of FIG. is there.

  That is, the laser light set to the absorption wavelength for the gas species to be analyzed is guided from the laser light emitting means 13 of the first analyzing means 11 to the first port of the first optical circulator 9a through the optical fiber 15, and the second It is output from the port, input to the collimator 3a by the optical fiber 7a, and irradiated into the measurement target gas 2.

  Thereafter, the transmitted light is received by the collimator 3b, guided to the second port of the second optical circulator 9b by the optical fiber 7b, output from the third port, and the output from the third port is input to the first port. . As a result, the signal input to the first port is output again from the second port, guided to the collimator 3b by the optical fiber 7b, and irradiated from the collimator 3b. The transmitted light is received by the collimator 3a, guided to the second port of the first optical circulator 9a by the optical fiber 7a, output from the third port, and input to the first photodiode 17a by the optical fiber 33.

After that, as already described in the first embodiment, the signal is amplified by the first PD amplifier (photodiode amplifier) 19a, and the amplified signal is input to the analysis unit 12 of the first analysis unit 11, and the gas to be measured An absorption spectrum absorbed by the gas component in the inside is grasped, and the concentration and temperature of the gas component in the measurement object are measured by analyzing the absorption spectrum.
That is, the first and third ports of the second optical circulator 9b are short-circuited to limit the light flow direction to one direction, and the measurement signal is transmitted and received by the first optical circulator 9a that is not short-circuited. To do.

According to the third embodiment, since the interference path length between the laser beam and the measurement target gas 2 in the measurement cell 1 can be doubled, the signal noise ratio (S / N ratio) can be increased and the measurement accuracy can be improved. In addition, since there are no large reflection points on the optical path, the cause of fringe (optical noise) is extremely small, and the measurement accuracy can be improved.
Further, when the second optical circulator 9b that is short-circuited is installed in the vicinity of the measurement cell 1, it becomes one optical fiber 7a for connection to the first optical circulator 9a that is not short-circuited, thereby further simplifying the measuring device. Can be configured.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG. FIG. 4 shows an overall configuration diagram. In addition to the installation of a pair of collimators 3a and 3b, another pair of collimators 3c and 3d is installed in one measurement cell 50 as compared to the first embodiment of FIG. Each pair of collimators is arranged in a different direction with respect to the measurement target gas, as a specific example, in a direction orthogonal. Further, these two collimator pairs are connected in series. In addition, about the same component as 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The measuring cell 50 installed in series in the middle of the exhaust passage has collimators (optical lenses) (light transmitting / receiving units) 3a and 3b that irradiate and receive laser light for measurement in a direction perpendicular to the exhaust gas flow. A pair of collimators 3c and 3d are installed so as to be orthogonal to the collimators 3a and 3b.

  The laser light set to the absorption wavelength for the gas species to be analyzed is guided from the laser light emitting means 13 of the first analyzing means 11 to the first port of the first optical circulator 9a through the optical fiber 15, and from the second port. It is output and input to the collimator 3a by the optical fiber 7a, and irradiated into the measurement target gas 2.

Thereafter, the transmitted light is received by the collimator 3b, guided to the next collimator 3c by the optical fiber 52, irradiated again into the measurement target gas 2 from the collimator 3c, and the transmitted light is received by the collimator 3d.
The light is received by the collimator 3d, guided to the second port of the second optical circulator 9b by the optical fiber 54, output from the third port, and input to the second photodiode 17b by the optical fiber 31. Thereafter, as described above, the absorption spectrum that is input to the analysis unit 12 of the first analysis unit 11 and is absorbed by the gas component in the gas to be measured is analyzed.

  The laser light set to the absorption wavelength for the gas species to be analyzed from the laser light emitting means 25 of the second analyzing means 21 is also transported in the same manner as in the first embodiment. The laser light guided and irradiated to the collimator 3d by the light 54 is received by the collimator 3c, guided to the collimator 3b by the optical fiber 52, and again irradiated into the measurement target gas by the collimator 3b. Light is received by the collimator 3a.

According to the fourth embodiment, a plurality of pairs of laser light paths in different directions are formed with respect to the measurement target gas, and these are connected in series. Therefore, the measurement target gas can be measured without deviation and an interference path with the measurement target gas. Since the length can be increased, the signal-to-noise ratio (S / N ratio) is increased, and the measurement accuracy of the gas concentration is further improved.
In the fourth embodiment, the collimators 3c and 3d are suitable for measuring the measurement target gas without any deviation in the direction orthogonal to the collimators 3a and 3b. You may incline and install in different arbitrary directions. The length of the interference path with the measurement target gas can be increased, and installation can be performed in accordance with the purpose of measurement.

  According to the present invention, it is difficult for noise to be applied to an optical signal in an optical path, and accurate gas concentration and gas temperature measurement can be performed. Further, even in measurement of a plurality of types of gases, the apparatus is not complicated or enlarged. This can be achieved with a simple configuration, which is advantageous when applied to a gas analyzer.

1 is an overall configuration diagram of a gas analyzer according to a first embodiment of the present invention. (A) shows the whole block diagram of the gas analyzer which concerns on 2nd Embodiment, (b) shows an example of the magnitude | size of the absorption spectrum in absorption wavelength ((lambda) 1, (lambda) 2), and is explanatory drawing of gas temperature measurement. . It is a whole block diagram of the gas analyzer which concerns on 3rd Embodiment. It is a whole block diagram of the gas analyzer which concerns on 4th Embodiment. It is explanatory drawing of a circulator. (A), (b) is explanatory drawing which shows a prior art. It is explanatory drawing of a prior art.

Explanation of symbols

1, 50 Measurement cell 2 Measurement target gas 3a, 3b, 3c, 3d Collimator (transmission / reception unit)
7a, 7b, 15, 27, 31, 33 Optical fiber 9a First optical circulator 9b Second optical circulator 11 First analyzing means 12, 23 Analyzing means 13, 25 Laser light emitting means 17a First photodiode 17b Second photodiode 21 2nd analysis means 13 and 25 Laser light emission means

Claims (5)

In a gas analyzer that measures the gas concentration and temperature by analyzing the absorption spectrum of the laser light irradiated into the measurement target gas,
Measuring / transmitting / receiving unit having both functions of irradiation unit for irradiating laser beam emitted from laser beam emitting unit into measurement target gas and receiving unit for receiving laser beam that has passed through measurement target gas. A plurality of lasers are installed toward the gas, an optical fiber is connected to the light transmitting / receiving unit, an optical circulator is installed in the path of the optical fiber, and a single laser beam path between one and the other optical circulator is irradiated and A gas analyzer characterized in that it is configured to carry bidirectional light reception signals.   The light transmission / reception unit includes a collimator (optical lens), a pair of the collimators is installed in one measurement cell, the optical circulators are installed in optical fibers connected to both collimators, and the optical circulators are connected to the respective optical circulators. 2. The gas analyzer according to claim 1, wherein the gas analyzer is configured to irradiate and receive laser light having an absorption wavelength for different gas types from the light transmitting / receiving unit.   The transmitter / receiver unit is composed of a collimator, a pair of the collimators are installed in one measurement cell, the optical circulators are installed in the optical fibers to both collimators, and the same type is transmitted from the respective transmitter / receiver units via both optical circulators. The gas analyzer according to claim 1, wherein the gas analyzer is configured to irradiate and receive laser beams having different absorption wavelengths with respect to the gas.   The light transmitting / receiving unit is composed of a collimator. A pair of the collimators are installed in one measurement cell, the optical circulators are installed in the optical fibers to both collimators, one optical circulator is short-circuited, and the light flow direction is set to 1. 2. The gas analyzer according to claim 1, wherein the measurement signal is transmitted and received by the other optical circulator that is not short-circuited.   The light transmitting / receiving unit includes a collimator, and a plurality of collimators are installed in one measurement cell, and the laser beam paths are arranged in series by arranging each pair of collimators so as to be able to irradiate the measurement target gas in different directions. The gas analyzer according to claim 1, wherein the gas analyzer is connected.

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