JPH095233A - Spectroscopic analysis apparatus for gas - Google Patents

Abstract

PURPOSE: To provide a versatile and practical gas spectroscopic analysis apparatus which can analyze many kinds of gases and efficiently reduce a background thereby to achieve highly accurate analyses. CONSTITUTION: In the apparatus, a light from a light source 35 is passed through a gas to be measured, and a wavelength and the amount of light absorbed by a gas component to be measured of the gas are measured by a photodetector 40. A first and a second chambers 32, 33 respectively partitioned airtightly are provided at both sides of a measuring cell 31 via a window 34 formed of a light permeable material. The light source 35 is arranged in the first chamber 32 and the photodetector 40 is arranged in the second chamber 33. Other optical parts are also accommodated in the first or second chamber 32, 33. The apparatus is provided with a means 44 for vacuumizing the first and second chambers 32, 33 and a means 45 for filling the gas into the first and second chambers 32, 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for spectroscopically analyzing a gas component to be measured in a gas to be measured by utilizing the light absorption characteristics of the gas component to be measured, and particularly to efficiently reduce the background. The present invention relates to a device that can be performed.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring impurities in a gas, an infrared absorption spectroscopy method in which light in the infrared region is transmitted through a gas to be measured to measure an absorption spectrum and the amount of absorption of infrared rays by the impurities is measured. Are known. The applicant uses a semiconductor laser that oscillates at room temperature as a light source,
An apparatus shown in FIG. 4 has already been proposed as an analyzer for measuring a trace amount of water in gas (Japanese Patent Laid-Open No. 5-99845).

This moisture analyzer is roughly composed of a measuring section (I), an optical system section (II) and a control calculating section (III).
The measuring section (I) comprises a measuring cell 1 for introducing a sample gas,
As the measuring cell 1, a multi-optical path cell having a reflecting surface for increasing the optical path length is preferably used in the cell.
The optical system (II) is a semiconductor laser 4 (L
D), the photodetectors P, R, and M, and various optical components such as the lens 7 and the half mirrors 9 and 12, and the like. The optical system part including these is housed in the chamber 18, and the inside of the chamber 18 is purged with nitrogen. As the semiconductor laser 4, 1.3-
A device that oscillates a laser beam in the 1.55 μm wavelength band is used. The control calculation unit (III) is configured to control the semiconductor laser 4 (LD) and process the signals from the photodetectors P, R and M.

An example of a method of measuring the water content in the measurement gas using this apparatus will be briefly described. First, a measuring gas is introduced into the measuring cell 1 to oscillate the semiconductor laser 4. The oscillated laser light (indicated by a broken line in the figure) is the half mirror 1.
A measurement line 16 branched at 2, 12 and guided to the measurement cell 1 and then sent to the measurement photodetector M, and a reference photodetector R after being guided to the reference cell 15.
Is distributed to the reference line 14 sent to the power monitor line 13 and the power monitor line 13 sent to the power monitor photodetector P. Then, by controlling the injection current to the semiconductor laser 4 and the temperature of the Peltier element 5, the oscillation wavelength of the laser light is swept and the absorption spectrum is measured. After that, for example, the absorption peak of H ₂ O in the 1.38 μm band can be selected, and the water content in the gas can be measured by the absorption intensity and a calibration curve prepared in advance.

The Applicant has conducted further studies, and a spectroscopic analysis method for a gaseous substance using a semiconductor laser oscillating at room temperature as a light source is obtained by appropriately selecting the oscillation wavelength.
In addition to water as the gas component to be analyzed, for example, carbon dioxide, carbon monoxide, hydrogen fluoride, hydrogen chloride, hydrogen bromide,
It was found that the present invention can also be applied to hydrogen iodide, monosilane, methane, compounds having an —OH group, and the like. Therefore, further research was conducted to develop a general-purpose practical spectroscopic analyzer using various gases as analysis target gases.

[0006]

In a gas spectroscopic analyzer, reduction of background is a problem in order to perform highly accurate analysis. Therefore, conventionally, as described above, the optical system part (II) is housed in one chamber 18 and nitrogen is purged in the chamber 18, thereby reducing the background. However, in such a method, since it was necessary to purge the entire interior of the chamber 18 with nitrogen, a large amount of time and an excessive amount of purge gas were required, which was inefficient. Further, when adjusting or repairing the optical components in the chamber 18, the entire chamber 18 must be opened to the atmosphere, and it takes a lot of time to newly purge the chamber 18 after the adjustment or the repair. There was also the inconvenience of requiring it.

Furthermore, in the conventional device, the measuring cell 1
Since the multi-path cell used as is an internal reflection that has a reflective surface for increasing the optical path length in the cell, the gas component to be measured is corrosive such as a halide gas such as hydrogen fluoride. In the case of a strong gas, there is a disadvantage that the reflection surface is corroded and the reflectance is lowered.

The present invention has been made in view of the above circumstances, and is a versatile and practical spectroscopic analyzer capable of analyzing various gases, which can efficiently reduce the background and perform highly accurate analysis. An object of the present invention is to provide a spectroscopic analyzer for gas.

[0009]

A gas spectroscopic analyzer according to the present invention transmits light from a light source to a gas to be measured, and measures the absorption amount of light absorbed by a gas component to be measured in the gas to be measured. A spectroscopic analyzer for gas to be measured by a photodetector, in which both ends of a measuring cell into which a gas to be measured is introduced are airtightly divided through partition walls at least a part of which is made of a light transmissive material. The first chamber and the second chamber are connected in series, the light source is housed in either the first chamber or the second chamber, and the photodetector is in the first chamber or the second chamber. One of a vacuum evacuation unit that is housed in one side and that evacuates at least one of the first chamber and the second chamber, and a gas purge unit that purges gas into at least one of the first chamber and the second chamber, or To have both It is an butterfly. At least one of the first chamber and the second chamber can be preferably provided with a light reflecting member that re-enters the light transmitted through the measurement cell into the measurement cell. The gas purging means is for purging gas into both the first chamber and the second chamber, and preferably comprises means for separately controlling the gas purging rate in the first chamber and the second chamber. It is preferable that the evacuation means evacuates both the first chamber and the second chamber, and that the evacuation means is provided with means for separately controlling the evacuation speeds in the first chamber and the second chamber.

[0010]

According to the gas spectroscopic analyzer of the present invention, since the airtight first chamber and the second chamber are connected to both ends of the measuring cell, the light absorption characteristics of the gas to be measured including the light source are measured. The optical components necessary for measuring the above can be appropriately accommodated and arranged in the first chamber and the second chamber. Then, the first chamber and / or the second chamber in which the optical components are housed are evacuated and / or appropriately purged to separate them from the inner wall of each chamber and the optical components housed in each chamber. Since water and other gas components can be released to the outside of the room, the background can be reduced,
Highly accurate analysis can be performed. Moreover, since the optical components are housed in the chambers provided at both ends of the measurement cell, the portion of the optical path from the light source through the cell to the photodetector that passes outside the cell (that is, indoors) is shortened. And a lower background can be achieved.

Further, as compared with the conventional chamber in which the measuring cell and the entire optical system section are collectively housed,
Since the volumes of the first chamber and the second chamber are small, the entire device becomes compact. Also, when performing vacuum exhaust or gas purging, the amount of exhaust gas or purge gas can be small,
The background can be efficiently reduced.
In addition, when adjusting or repairing optical components,
Only the chamber containing the target part for adjustment or repair needs to be opened to the atmosphere. Compared to the conventional configuration in which the entire optical system is housed in one chamber, vacuum exhaust or gas purging after adjustment or repair is not required. It requires only a short time and is economically advantageous.

At least one of the first chamber and the second chamber is provided with a light reflecting member for making the light transmitted through the measuring cell incident on the measuring cell again, whereby the optical path length can be lengthened. With such a configuration, even if a gas having strong corrosiveness is introduced into the measurement cell, the light reflecting member is not likely to be corroded, and various gases including a halide gas can be used for measurement.

If the gas purging means is one for purging gas into both the first chamber and the second chamber, and is provided with means for separately controlling the gas purging rates in the first chamber and the second chamber, 2 A simple structure using one gas purging means for one chamber can be adopted. If both chambers are simultaneously purged with gas, the purging time can be greatly shortened and efficiency is improved. Furthermore, it is possible to efficiently adjust the gas purge amount according to the size, surface area, volume, etc. of each chamber, or according to the gas concentration required to obtain the desired background, and to save the purge gas amount. You can also

If the evacuation means is to evacuate both the first chamber and the second chamber, and is provided with a means for separately controlling the evacuation speed in the first chamber and the second chamber, 2 A simple structure using one evacuation means for one chamber can be adopted. Further, if both chambers are evacuated at the same time, the evacuation time can be greatly shortened, which is efficient. Further, it is possible to efficiently adjust the exhaust amount according to the size, surface area, volume, etc. of each chamber, or according to the degree of vacuum required to obtain a desired background.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the first embodiment shown in FIGS. FIG. 1 shows an embodiment of a gas spectral analyzer of the present invention. This apparatus is roughly composed of an optical system section A and a control calculation section B. In FIG. 1, a solid line shows an electric signal and a broken line shows a laser beam. FIG. 2 is an enlarged view showing one end of the measuring cell 31 and the second chamber connected to the one end. Optical system part A
Is a measurement cell 31 for introducing a measurement gas, a measurement cell 3
First chamber 32 and second chamber 3 that are connected to both ends of
3, an exhaust line 44 for evacuating the first chamber 32 and the second chamber 33, and a gas purge line 45 for purging gas into the first chamber 32 and the second chamber 33. In the present invention, "purging gas" means
Aeration of gas in a room to fill the room with the gas components.

The measuring cell 31 is preferably cylindrical, and both ends thereof are inserted into the first chamber 32 and the second chamber 33, and both end faces are hermetically sealed. The measurement cell 31 is preferably made of a material such as electrolytically-polished stainless steel that has a small amount of water adsorption on its surface. For example, SUS3
16 is preferably used. In addition, the measurement cell 31 and the measurement cell 3 serving as a partition wall of the first chamber 32 and the second chamber 33
On both end faces of the window 1, windows 34 are provided for entering and emitting laser light. The window 34 is made of a light transmissive material, and general visible range optical glass is preferably used. For example, quartz or sapphire can be preferably used. Further, the measurement cell 31 is appropriately provided with an inlet and an outlet (not shown) for introducing and discharging the gas to be measured.

As the first chamber 32 and the second chamber 33, for example, those made of iron and surface-treated, or those made of aluminum and treated with alumite sulfate are preferably used. The shapes of the first chamber 32 and the second chamber 33 are not particularly limited, as long as necessary optical components can be stored therein, and the volumes are preferably small. Further, as shown in FIG. 2, at the connecting portion between each of the first chamber 32 and the second chamber 33 and the measuring cell 31, a flange 43 provided with a sealing member such as a seal packing 52 on one surface side is attached by a screw 53. , Are firmly attached to the end faces of the first chamber 32 and the second chamber 33. Thereby, the gas in the first chamber 32 and the second chamber 33 is prevented from leaking from this connecting portion, and the outside air is prevented from entering the room, and the gas is discharged into the first chamber 32 and the second chamber 33. The state of being purged and being evacuated is maintained.

A gas exhaust port 46 is provided in each of the first chamber 32 and the second chamber 33, and a pipe connected to the gas exhaust port 46 is connected to a vacuum exhaust device 48 via a valve 49, and an exhaust line 44 is provided. Are configured. A gas supply port 47 is provided in each of the first chamber 32 and the second chamber 33, and a pipe body connected to the gas supply port 47 is connected to a gas supply unit 50 via a valve 51 to form a gas purge line 45. are doing. The connecting portion between the exhaust port 46 and the gas supply port 47 and the pipes forming the exhaust line 44 and the gas purge line 45 is hermetically configured by using a sealing member such as caulking 41 as shown in FIG. Has been done. Exhaust line 4
Reference numeral 4 is for evacuating the first chamber 32 and the second chamber 33, respectively.
It is possible to control the exhaust speed in each of them separately. The gas purge line 45 purges gas into the first chamber 32 and the second chamber 33, respectively, and the gas purge rate in the first chamber 32 and the gas purge rate in the second chamber 33 can be controlled separately. .

Here, in the apparatus of the present invention, each of the first chamber 32 and the second chamber 33 may be provided with at least one of vacuum evacuation means and gas purging means. That is, it is sufficient that both the first chamber 32 and the second chamber 33 are configured to be evacuated and / or purged with gas, and the configurations of the vacuum evacuation means and the gas purging means are not limited to those of this embodiment, and various types are applicable. Can be configured. In the present embodiment, both the first chamber 32 and the second chamber 33 are provided with both vacuum evacuation means and gas purging means. The background can be reduced by evacuating the interior of each chamber and then purging a purge gas such as nitrogen gas into the chambers 32 and 33 through the gas purge line 45. As described above, when purging gas after evacuation, the flow rate of the purge gas can be small, which is effective when it is desired to save the purge gas. Further, since the exhaust speed and the gas purge speed can be controlled separately for the first chamber 32 and the second chamber 33,
The exhaust amount and the gas purge amount can be efficiently adjusted according to the size, surface area, and volume of each chamber, or according to the degree of vacuum or the gas concentration required to obtain a desired background. In addition, the amount of purge gas can be suppressed to the required minimum amount according to each chamber to save the amount.

In this embodiment, a semiconductor laser 35 having a Peltier element 36, a lens 37, and a mirror 38 are arranged in the first chamber 32, and a mirror 39 and a photodetector 40 are accommodated in the second chamber 33. Has been done. That is, the laser light oscillated from the semiconductor laser 35 provided in the first chamber 32 enters the measuring cell 31 through the lens 37, passes through the measuring cell 31, and then enters the second chamber 33. The light is reflected by the mirror 39 provided at and is incident on the measuring cell 31 again. Then, after passing through the measuring cell 31, it is reflected by the mirror 38 provided in the first chamber 32, and further passes through the measuring cell 31. In this way, the laser light makes one round trip in the measuring cell 31 and then is guided to the photodetector 40 provided in the second chamber 33.

In this embodiment, the semiconductor laser 35 is used as the light source, but the light source is not limited to this. Although the light source is arranged in the first chamber 32 in this embodiment, the light source may be arranged in either the first chamber 32 or the second chamber 33. Further, the optical path length can be adjusted by the number of times the laser light is reflected by the mirror and reciprocated and the cell length. Therefore, the number of the mirrors and the cell length are appropriately set according to the desired optical path length. It is also possible to adopt a configuration in which a mirror is not provided, but for that reason, the measurement sensitivity deteriorates if the optical path length becomes short, and if the cell length is made long in order to increase the optical path length, the device becomes huge. Therefore, it is preferable to provide a mirror to secure an optical path length with which good sensitivity is obtained. Further, the optical components used in the optical system section A are not limited to those of the present embodiment, and various configurations can be adopted.

The control operation unit B amplifies the electric signal from the photodetector 40 with the lock-in amplifier 19, and the amplified signal and the signal from the wavelength meter are supplied to the computer system 2.
The Peltier temperature adjuster 22 is controlled by performing a calculation process at 0 and controlling this by sending a wavelength setting signal to the LD current adjuster 21. Also,
A display 23 and a keyboard 24 are connected to the computer system 20.

When the gas component to be measured in the gas to be measured is spectroscopically analyzed using this gas analyzer, the first chamber 32 and the second chamber 33 are evacuated in advance, and then the nitrogen gas is purged. I'll do it. First, the gas to be measured is supplied to the measurement cell 31.
Laser light is emitted from the semiconductor laser 35. Then, the photodetector 40 measures the absorption intensity of light transmitted through the gas to be measured. Further, by sweeping the wavelength of the light transmitted through the gas to be measured in an appropriate range to obtain an absorption spectrum, the gas component to be measured in the gas to be measured can be identified and quantified. Although nitrogen gas is used as the gas for purging the first chamber 32 and the second chamber 33 in the present embodiment, the present invention is not limited to this and may be any gas that does not have the same absorption wavelength as the gas to be measured. Nitrogen gas (N ₂ ) and argon gas (Ar) are preferably used.

FIG. 3 shows a second embodiment of the gas analyzer of the present invention, and is a schematic diagram of the optical system section A.
This embodiment is different from the first embodiment in that the first chamber 32
In addition, the semiconductor laser 35, the detector 40, the lens 37, and the mirror 38 are housed, the two mirrors 39 are arranged in the second chamber 33, and the exhaust line 44 is not provided, but only the gas purge line 45 is provided. That is the point.

In this embodiment, the laser light emitted from the semiconductor laser 35 provided in the first chamber 32 is
The light is incident on the measuring cell 31 through the lens 37, passes through the measuring cell 31, and then is provided in the second chamber 33.
The measuring cell 31 is reflected by the three mirrors 39, 39 and the mirror 38 provided in the first chamber 32.
After reciprocating two times, the photodetector 4 provided in the first chamber 32
It is designed to be guided to zero. Even with the configuration of the apparatus of this embodiment, the background can be effectively reduced, and high-accuracy measurement can be performed as in the case of the first embodiment. Further, according to the present embodiment, since the laser light is reflected by the mirror and reciprocated twice, the optical path length can be made longer than the cell length. Therefore, the length of the measuring cell 31 can be set short to make the entire apparatus compact.

Example 1 A gas spectroscopic analyzer having the structure shown in FIG. 1 was manufactured. An InGaAsP-based wavelength tunable semiconductor laser is used as a light source (semiconductor laser 35 provided with a Peltier element 36) and has a size of 200 × 20.
It was placed in the first chamber 32 of 0 × 200 (mm). On the other hand, a Ge photodiode is used as the photodetector 40, and the Ge photodiode is used as the second chamber 33 having a size of 200 × 200 × 200 (mm).
I placed it inside. A lens 37 and a mirror 39 are arranged in the first chamber 32, and a mirror 39 is arranged in the second chamber 33. The total volume of the first chamber 32 and the second chamber 33 in this example was 1/17 of the volume of the chamber 18 used in the conventional moisture analyzer shown in FIG. Using the apparatus of the present embodiment, hydrogen chloride containing water as an impurity is used as the gas to be measured, and the oscillation wavelength of the light source light is 1.35.
When the light absorption intensity was measured by sweeping in the range of 1.42 μm, the absorption spectrum could be obtained with high accuracy. Further, there was no corrosion of the measuring cell or the like due to hydrogen chloride.

In Example 1, the measurement was carried out for hydrogen chloride containing water as an impurity.
The present invention is not limited to this example, and can be applied to the measurement of various impurities in various measured gases as long as the measured gas and the impurities contained therein do not have the same absorption spectra. For example, it is possible to measure water in hydrogen fluoride, water in halide, water in various other gas components, hydrogen fluoride in hydrogen chloride gas, and other gas components in halide. It is a thing.

[0028]

As described above, the gas spectroscopic analyzer of the present invention allows the light from the light source to pass through the gas to be measured, and the absorption amount of the light absorbed by the gas component to be measured in the gas to be measured. Is a gas spectroscopic analyzer for measuring with a photodetector, at both ends of a measuring cell into which a gas to be measured is introduced,
At least a part of the partition wall made of a light-transmissive material, the first chamber and the second chamber, which are airtightly divided, are continuously provided, and the light source is provided in either the first chamber or the second chamber. A vacuum evacuation means for accommodating and accommodating the photodetector in either the first chamber or the second chamber, and evacuating at least one of the first chamber and the second chamber; One or both of a gas purging means for purging gas into at least one of the first chamber and the second chamber is provided.

Therefore, the optical components can be housed and arranged in the first chamber and the second chamber. Then, by performing vacuum evacuation and / or gas purging to the first chamber and the second chamber, the background can be efficiently reduced, and highly accurate analysis can be performed. Also, the entire device can be made compact,
A highly practical device can be obtained. Moreover, since each optical component can be housed in the chambers provided at both ends of the measuring cell, it is possible to shorten the portion of the optical path from the light source through the cell to the photodetector that passes outside the cell (that is, indoors), A lower background can be achieved. In addition, when adjusting or repairing optical parts, only the chamber that contains the target part for adjustment or repair needs to be open to the atmosphere. Compared with the configuration described above, vacuum evacuation or gas purging after adjustment or repair is required in a short time, which is economically advantageous.

At least one of the first chamber and the second chamber is provided with a light reflecting member for making the light transmitted through the measuring cell incident on the measuring cell again, whereby the optical path length can be lengthened. With such a configuration, even if a gas having strong corrosiveness is introduced into the measuring cell, the light reflecting member is not likely to be corroded, and therefore various gases including a halide gas can be measured. It is possible to obtain a versatile device.

If the gas purging means is one for purging gas into both the first chamber and the second chamber, and is provided with means for separately controlling the gas purging rate in the first chamber and the second chamber, 2 A simple structure using one gas purging means for one chamber can be adopted. If both chambers are simultaneously purged with gas, the purging time can be greatly shortened and efficiency is improved. Furthermore, it is possible to efficiently adjust the gas purge amount according to the size, surface area, volume, etc. of each chamber, or according to the gas concentration required to obtain the desired background, and to save the purge gas amount. You can also

If the vacuum evacuation means is configured to evacuate both the first chamber and the second chamber, and is provided with means for separately controlling the evacuation speed in the first chamber and the second chamber, 2 A simple structure using one evacuation means for one chamber can be adopted. Further, if both chambers are evacuated at the same time, the evacuation time can be significantly shortened and efficiency is improved. Further, it is possible to efficiently adjust the exhaust amount according to the size, surface area, volume, etc. of each chamber, or according to the degree of vacuum required to obtain a desired background.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a gas spectral analyzer of the present invention.

FIG. 2 is an explanatory view showing an enlarged second chamber in FIG.

FIG. 3 is a schematic configuration diagram showing an optical system section in another embodiment of the gas spectral analyzer of the present invention.

FIG. 4 is a schematic configuration diagram showing an example of a conventional moisture analyzer.

[Explanation of symbols]

31 ... Measuring cell, 32 ... First chamber, 33 ... Second chamber, 34
... window (partition wall), 35 ... semiconductor laser (light source), 4
0 ... Photodetector, 44 ... Vacuum exhaust line, 45 ... Gas purge line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Morishita 10 Okubo, Tsukuba City, Ibaraki, Japan Oxygen Stock Company Tsukuba Research Institute (72) Inventor Yoshio Ishihara 10 Okubo, Tsukuba City, Ibaraki Tsukuba Research Center, Japan Oxygen Stock Company

Claims (4)

[Claims] 1. The light from the light source is transmitted through the gas to be measured,
A gas spectroscopic analyzer for measuring an absorption amount of light absorbed by a gas component to be measured in the gas to be measured with a photodetector, wherein at least both ends of a measuring cell into which the gas to be measured is introduced, A first chamber and a second chamber, which are airtightly divided, are connected to each other through a partition wall partially made of a light-transmitting material, and the light source is housed in either the first chamber or the second chamber. And the photodetector is housed in either one of the first chamber or the second chamber, and a vacuum exhaust means for vacuum exhausting at least one of the first chamber and the second chamber; A gas spectroscopic analysis apparatus comprising one or both of a gas purging means for purging gas into at least one of the chamber and the second chamber. 2. The light reflecting member for causing the light transmitted through the measuring cell to enter the measuring cell again in at least one of the first chamber and the second chamber. Gas spectroscopic analyzer. 3. The gas purging means is for purging gas into both the first chamber and the second chamber, and comprises means for separately controlling the gas purging rate in the first chamber and the second chamber. The gas spectroscopic analyzer according to claim 1. 4. The vacuum evacuation means evacuates both the first chamber and the second chamber, and comprises means for separately controlling the evacuation speed in the first chamber and the second chamber. The gas spectroscopic analyzer according to claim 1.