JP5022349B2 - Gas component measuring device - Google Patents

Description

  The present invention relates to a gas component measuring device by emission analysis using a laser.

  As a method for measuring the gas concentration in a gas pipe in a gas plant of an industrial facility, a method using a semiconductor laser absorption method has been established and JIS has been developed (JIS B 7993: Non-Patent Document 1).

An outline of a laser device by this semiconductor laser absorption method is shown in FIG.
As shown in FIG. 5, the sample pipe 101 branched from the gas pipe is irradiated with laser light L from the laser device 110 to analyze the gas component of the gas to be measured 102.
Here, reference numerals 101a and 101b denote quartz windows, 112 denotes a reflection mirror, 113 denotes a first detector, and 114 denotes a second detector.
The first detector 113 obtains the reference light (I ₀ ), and the second detector 114 obtains the light (I) transmitted through the sample pipe 101, and the transmittance T = (I / I _0). ) With this analysis technique, online analysis of various gas component concentrations has become possible.

JISB7993

  By the way, when analyzing the gas component, when measuring by the semiconductor laser absorption method using the sample pipe 101 branched from the pipe as shown in FIG. 5, there is no problem of light absorption, but FIG. When the length of the gas pipe 120 as shown is long, there is a problem in that the incident laser beam L is scattered, so that the second detector 114 cannot detect a sufficient light intensity. In FIG. 6, reference numerals 121a and 121b denote quartz windows.

  In addition, when the gas absorption amount is large, the incident laser beam is absorbed, and there is a problem that sufficient light intensity cannot be detected.

  Therefore, there is an urgent need for a method that can analyze gas components online without incident light being absorbed and scattered, even when the piping length of industrial plants is long or when the amount of gas absorption is large. Yes.

  In view of the above problems, the present invention provides a gas component measuring apparatus capable of analyzing gas components online even when the piping length at the site of an industrial equipment plant is long or when the gas absorption amount is large. Let it be an issue.

  In the first invention of the present invention for solving the above-described problem, when excited molecules excited to a high level by laser light irradiated to a gas to be measured are electronically relaxed to a low level, The gas component measuring apparatus is characterized in that the gas component in the gas to be measured 12 is measured from amplified spontaneous emission (ASE) generated when the level is lowered.

  According to a second invention, there is provided the gas component measuring device according to the first invention, wherein the laser beam is a laser beam having two kinds of wavelengths.

  According to a third aspect of the present invention, there is provided a first wavelength converter that converts the wavelength of the laser light oscillated from the laser device into the first laser light, and converts the wavelength of the oscillated laser light into a second laser light Two wavelength conversion units, a gas measurement unit for introducing the first and second laser beams, and a low level of excited molecules excited to a higher level by the irradiated first and second laser beams. And a photodetector for measuring spontaneous emission (ASE) generated when the level is lowered electronically. .

  According to a fourth invention, in the third invention, the gas measuring unit includes a light introduction line for introducing laser light and a light emission line for emitting generated spontaneous emission (ASE). The gas component measuring device is characterized in that:

  A fifth invention is the gas component measuring apparatus according to the third invention, wherein the light introduction line and the light emission line are formed of the same line.

According to the present invention, since the gas component can be measured by emission analysis in the infrared region of ASE, the gas component can be obtained even when the pipe length of the measurement target in the industrial facility is long or the gas absorption amount is large. The concentration analysis of can be analyzed online.
In addition, since ASE oscillates as directional light, the ASE light emission component is easily condensed and the measurement sensitivity is high.
Furthermore, since ASE is light in the infrared region, separation from incident laser light (visible light, ultraviolet light) is facilitated, and detection with a high signal-to-noise ratio is possible.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A gas component measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of a gas component measuring apparatus according to the first embodiment. As shown in FIG. 1, the gas component measuring apparatus 10 </ b> A according to the present embodiment has a low quasi-excited molecule excited to a high level by a laser beam 22 irradiated to the gas 11 to be measured in the flue 15. When the level is electronically relaxed, the gas component in the measured gas 11 is measured from amplified spontaneous emission (ASE) generated when the level drops.

As a specific apparatus configuration, as shown in FIG. 1, the gas component measuring apparatus 10A according to the present embodiment uses a laser beam (1064 nm) 22 oscillated from the laser apparatus 21 as a first laser beam (wavelength: 226 nm). ) The first wavelength conversion unit 23 that converts the wavelength to 22-1 and the second wavelength conversion unit 24 that converts the wavelength of the oscillated laser beam 22 into a second laser beam (wavelength: 600 nm) 22-2. And the gas measuring unit 25 for introducing the first and second laser beams, and the first laser beam 22-1 and the second laser beam 22-2 to be irradiated are excited to a higher level (E level). When the excited excited molecules are electronically relaxed to a low level (C level), light that measures a spontaneous emission light (Amplified Spontaneous Emission: hereinafter referred to as “ASE”) 14 generated when the level is lowered. And a detector 26.
In FIG. 1, 15a and 15b are quartz windows through which laser light is transmitted, 29 is a spectroscope, 31 is a condenser lens, 33 is an optical filter, and 34a to 34d are mirrors.

  The gas component measuring apparatus of the present invention uses the principle of ASE emission, and is different from conventional absorption analysis, so that the influence of gas absorption of the gas to be measured 11 is eliminated.

Next, the light emission principle of ASE will be described with reference to a schematic diagram of the energy level of NO shown in FIG.
When, for example, nitric oxide (NO) in the measurement gas is irradiated with laser light 22 and excited electronically, as shown in FIG. 2, the ground state (X) transitions to the excited state (X level). → A level → E level).

Specifically, it is excited from the X level to the A level at the excitation wavelength of the first laser beam (226 nm) 22-1 and then from the A level at the excitation wavelength of the second laser beam (600 nm) 22-2. Excited to E level.
At this time, when the number of molecules at the E level is larger than the number of molecules at the C level, an inversion distribution state occurs, and spontaneous emission from the E level to the C level occurs. Spontaneous radiation amplified light (ASE) of 1170 to 1184 nm, which is stimulated emission of the level, is generated.

As gas components to be measured in the gas to be measured, in addition to nitrogen monoxide (NO), for example, carbon monoxide (CO), water (H ₂ O), nitrogen dioxide (NO ₂ ), methane (CH ₄ ), Ammonia, benzene and the like can be exemplified.

FIG. 3 is a schematic diagram of energy levels of carbon monoxide (CO).
As shown in FIG. 3, carbon monoxide (CO) is excited from the X level to the A level at the excitation wavelength of 215 nm from the ground state, and then excited from the A level to the E level at the excitation wavelength of 215 nm. The

  At this time, when the number of molecules at the E level is larger than the number of molecules at the B level, an inversion distribution state occurs, and spontaneous emission from the E level to the B level occurs. A spontaneous emission amplified light (ASE) of 1.7 μm, which is stimulated emission of the C level, is generated.

  Moreover, since ASE has a wavelength in the infrared region (for example, 1170 to 1184 nm in the case of NO), unlike the visible region and the ultraviolet region, separation by the filter 33 is easy, and measurement accuracy is improved.

While luminescence analysis such as fluorescence and Raman is isotropic emission, light spreads in all directions and has no directivity, whereas ASE has directivity (ASE 14 emits light only in the incident direction and the outgoing direction of laser light 22). Separation with high sensitivity is possible.
Therefore, in this embodiment, a light introduction line through which laser light is introduced into the gas measurement unit 25 and a light emission line in the same direction as the traveling direction of the laser light that emits the generated ASE 14 are provided.

As a result, the concentration analysis of the gas component can be performed online even when the pipe length of the measurement target in the industrial facility is long or the gas absorption amount is large.
In addition, since ASE oscillates as directional light, the ASE light emission component is easily condensed and the measurement sensitivity is high.
Furthermore, since ASE is light in the infrared region, separation from incident laser light (visible light, ultraviolet light) is facilitated, and detection with a high signal-to-noise ratio is possible.

Next, in Example 2, another gas component measuring device of the present invention will be described with reference to the drawings.
FIG. 4 is a schematic diagram of a gas component measuring apparatus according to the second embodiment. As shown in FIG. 4, the gas component measuring apparatus 10 </ b> B according to the present embodiment includes a damper 41 that absorbs laser light in the flue 15, and light in which the ASE 14 is provided on the incident line side of the laser light 22. Measurement is performed by the detector 26.

  In the present embodiment, since the light introduction line and the light emission line are the same line, it is not necessary to provide two quartz windows in the flue as in the first embodiment, and the apparatus configuration is simplified. It becomes.

  In the present embodiment, since the laser light and the ASE have different wavelength ranges, they can be separated, and the filter 33 can be used to transmit only the infrared region, so that the measurement with the photodetector 26 is possible. .

  As described above, according to the gas component measuring apparatus according to the present invention, the gas component can be measured by emission analysis. Therefore, when the pipe length of the measurement target in the industrial facility is long or the gas absorption amount is large. In addition, it is possible to analyze the concentration of gas components.

1 is a schematic diagram of a gas component measurement device according to Embodiment 1. FIG. It is a schematic diagram of the energy level of NO. It is a schematic diagram of the energy level of CO. 6 is a schematic diagram of a gas component measurement device according to Embodiment 2. FIG. It is the schematic of the laser apparatus by the conventional semiconductor laser absorption method. It is a schematic diagram which measures a flue by the semiconductor laser absorption method.

Explanation of symbols

10A, 10B Gas component measuring device 11 Gas to be measured 14 ASE
DESCRIPTION OF SYMBOLS 21 Laser apparatus 22 Laser beam 22-1 1st laser beam 22-2 2nd laser beam 23 1st wavelength conversion part 24 2nd wavelength conversion part 25 Gas measurement part 26 Photodetector

Claims (5)

  Amplified Spontaneous Emission (Amplified Spontaneous Emission) generated when the excited molecule excited to a higher level by the laser beam irradiated to the gas to be measured is electronically relaxed to a lower level. A gas component measuring device that measures a gas component in a gas to be measured from ASE). In claim 1,
The gas component measuring device, wherein the laser beam is a laser beam having two types of wavelengths. A first wavelength converter that converts the wavelength of laser light oscillated from the laser device into first laser light;
A second wavelength converter that converts the wavelength of the oscillated laser light into a second laser light;
A gas measuring section for introducing the first and second laser beams;
When excited molecules excited to a high level by the first laser light and the second laser light to be irradiated are electronically relaxed to a low level, spontaneously amplified light generated when the level is lowered ( A gas component measuring apparatus comprising a photodetector that measures Amplified Spontaneous Emission (ASE). In claim 3,
The gas measuring section, a light introduction line for introducing laser light;
A gas component measuring apparatus comprising: a light emission line that emits generated spontaneous emission (ASE) light (Amplified Spontaneous Emission: ASE). In claim 3,
The gas component measuring apparatus, wherein the light introduction line and the light emission line are formed of the same line.

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