JP2014105991A - Gas cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas cell which achieves easy maintenance.SOLUTION: A gas cell 40 includes: a cylindrical body 10 into which a sample gas is introduced; a first plane mirror 2 arranged in a manner to close one end of the cylindrical body 10; an entrance window 21 letting the light which heads for a reflecting surface of the first plane mirror 2 inside the cylindrical body 10 enter, and an exit window 22 letting the light exit from the inside of the cylindrical body 10. A first optically-transparent aperture plate 31 can be arranged in front of the reflecting surface of the first plane mirror 2.

Description

  The present invention relates to a gas cell for measuring the concentration of trace components in various gases.

The exhaust gas that causes environmental pollution and air pollution contains sulfur compounds such as H ₂ S and SO _x , nitrogen compounds such as NO _x and NH ₃ , various hydrocarbons, etc. The influence of these substances on the health status of residents has been pointed out, and the measurement of the concentration of these substances in the air is regarded as important. In addition, as a greenhouse gas, measurement of the concentration of substances such as carbon dioxide and methane in the air is being performed more and more widely.

  In measuring the concentration of trace components in air, the sample gas is filled into the gas cell, light is transmitted through the sample gas, the light absorption by the target component is measured, and the following equation (1) using Lambert-Beer's law is used. The concentration of the target component is calculated.

Here, I ₀ (ν) is the light intensity when the target component is not absorbed at the frequency ν, I (ν) is the transmitted light intensity at the frequency ν, c (mol / cm ³ ) is the number density of the target component, L (cm) is the length of the optical path passing through the sample gas, and S (T) (cm ⁻¹ / (mol / cm ⁻² )) is a function of the gas temperature T at a predetermined absorption line intensity.

  At this time, in order to perform measurement with as high sensitivity as possible using a relatively small amount of sample gas, a multiple reflection gas cell that expands the optical path length L is used (for example, see Patent Document 1).

FIG. 5 is a schematic configuration diagram showing an example of a conventional multiple reflection gas cell. One direction horizontal to the ground is defined as an X direction, a direction horizontal to the ground and perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the X direction and the Y direction is defined as a Z direction.
The gas analyzer 101 includes an analysis box 50 having a laser light source 51 and a detector 52, and a multiple reflection gas cell 140 attached in a flow path through which a sample gas flows.

  The multi-reflection gas cell 140 includes a cylindrical body 110, a first plane mirror holder 3 disposed at the left end of the cylindrical body 110, a second plane mirror holder 4 disposed at the right end of the cylindrical body 110, A first plane mirror 2 held by one plane mirror holder 3 and a second plane mirror 6 held by a second plane mirror holder 4 are provided.

Tubular member 110, which cavity block in a cylindrical shape with a diameter r ₁ of a rectangular parallelepiped shape is formed, the central axis of the cavity of the cylindrical shape is disposed such that the horizontal direction (X direction), the upper ( A cylindrical gas introduction hole 111 for introducing the sample gas into the cylindrical body 110 in the -Z direction, and a cylindrical gas for discharging the sample gas from the cylindrical body 110 downward (in the Z direction). A discharge hole 112 is provided. Thereby, a circulation channel through which the sample gas flows in the Z direction is formed inside the cylindrical body 110.

  The first plane mirror holder 3 is a rectangular plate-like body, and is attached with a bolt 9 so as to close the left end portion of the tubular body 110. And the back surface of the disk-shaped 1st plane mirror 2 is hold | maintained on the right end surface of the 1st plane mirror holder 3 by adhesion | attachment etc. The second plane mirror holder 4 is a rectangular plate-like body, and is attached with a bolt (not shown) so as to close the right end portion of the cylindrical body 110. The back surface of the disk-shaped second plane mirror 6 is held on the left end surface of the second plane mirror holder 4 by bonding or the like. Thereby, the reflective surface of the 1st plane mirror 2 and the reflective surface of the 2nd plane mirror 6 are arrange | positioned facing.

In addition, the second plane mirror holder 4 and the second plane mirror 6 are provided with an incident window hole 21 through which laser light enters the cylindrical body 110 and an emission window through which laser light exits from the cylindrical body 110. The light transmitting window plate 7 is airtightly held in the incident window hole 21 and the emission window hole 22 by a window plate holder and a gasket (not shown), respectively.
In addition, in order to ensure the airtightness inside the cylindrical body 110, the contact part of the 1st plane mirror holder 3 and the cylindrical body 110, the contact part of the 2nd plane mirror holder 4 and the cylindrical body 110, or the 2nd plane mirror holder 4 A gasket 3 a is sandwiched between the contact portions of the window plate 7 and the window plate 7.

According to such a gas analyzer 101, first, the sample gas is introduced through the gas introduction hole 111 by means (not shown) such as a pump or a valve to fill the inside of the cylindrical body 110. Then, in a state in which the cylindrical body 110 is filled with the sample gas, laser light having a predetermined wavelength ν from the laser light source 51 enters the cylindrical body 110 in the substantially X direction through the window plate 7 from the incident window hole 21. The incident laser light is repeatedly reflected a certain number of times between the reflecting surface of the first plane mirror 2 and the reflecting surface of the second plane mirror 6, and then substantially -X from the exit window hole 22 to the outside of the cylindrical body 110 through the window plate 7. Exit in the direction. Intensities I (ν) and I ₀ (ν) of the emitted laser light are detected by the detector 52.

JP 2006-58009 A

  By the way, in the gas analyzer 101 as described above, since the sample gas is introduced into the cylindrical body 110, the reflection surfaces of the first plane mirror 2 and the second plane mirror 6 may become dirty. When the reflecting surfaces of the first plane mirror 2 and the second plane mirror 6 are soiled, the bolts 9 are removed, the first plane mirror holder 3 and the second plane mirror holder 4 are removed, and then the new first plane mirror holder 3 and second Maintenance for attaching the plane mirror holder 4 with the bolts 9 is performed. FIG. 6 is a view for explaining maintenance of the multiple reflection gas cell 140.

However, only when the optical axis of the first plane mirror 2 and the optical axis of the second plane mirror 6 facing each other exactly coincide with each other, the laser light incident from the incident window hole 21 is reflected on the reflection surface of the first plane mirror 2. And the reflecting surface of the second plane mirror 6 are reflected a predetermined number of times and then accurately taken out from the exit window hole 22. Therefore, it is necessary to position the first plane mirror holder 3 and the second plane mirror holder 4 with extremely high accuracy. is there. As is clear from FIG. 6, it is necessary to remove a number of peripheral members in order to remove the light source side mirror. Therefore, the work of attaching the first plane mirror holder 3 and the second plane mirror holder 4 is very laborious.
Accordingly, an object of the present invention is to provide a gas cell that can be easily maintained.

  The gas cell of the present invention made to solve the above problems includes a cylindrical body into which sample gas is introduced, and a first mirror that is arranged so as to close one end of the cylindrical body, A gas cell in which an incident window for entering light toward the reflecting surface of the first mirror inside the cylindrical body and an exit window for emitting light from the inside of the cylindrical body are formed. The first light transmissive window plate can be disposed in front of the reflecting surface of the first mirror.

  According to the gas cell of the present invention, when measuring the sample gas, the first light transmissive window plate is arranged in front of the reflecting surface of the first mirror. Thereby, since a 1st light transmissive window board touches sample gas previously rather than the reflective surface of a 1st surface mirror, contamination of the reflective surface of a 1st surface mirror can be reduced as much as possible. Then, the sample gas is introduced to fill the inside of the cylindrical body. And the light of the predetermined wavelength from a light source injects into a cylindrical body inside from an incident window in the state which filled the sample gas inside the cylindrical body. The incident light passes through the first light transmissive window plate and is reflected by the reflection surface of the first mirror, and then exits from the exit window to the outside of the cylindrical body.

  Thereafter, when the first light transmissive window plate is soiled, after the soiled first light transmissive window plate is removed, maintenance is performed to attach a cleaned or new first light transmissive window plate. At this time, since the first mirror is a direct optical reflecting surface, if there is an arrangement position error or surface accuracy error of the first mirror, the influence on the performance is inevitable, but the first light transmissive window plate is transmissive. Since the arrangement position and surface accuracy error of the first light transmissive window plate do not affect the performance, the maintenance for attaching the first light transmissive window plate can be performed very easily. In addition, it is difficult to reuse the first mirror, but the first light-transmitting window plate is made to transmit, so the first light-transmitting window plate is reused by cleaning or surface polishing. be able to.

  As described above, according to the gas cell of the present invention, maintenance can be easily performed. Furthermore, since it is not necessary to replace the first mirror for a long time, the running cost can be suppressed.

(Means and effects for solving other problems)
Moreover, in said invention, it has the 2nd surface mirror arrange | positioned so that the other end part of the said cylindrical body may be obstruct | occluded, and the 2nd light transmissive window board is ahead of the reflective surface of the said 2nd surface mirror. It may be possible to arrange them.

  According to the gas cell of the present invention, when measuring the sample gas, the second light transmissive window plate is arranged in front of the reflecting surface of the second mirror. Accordingly, since the second light transmitting window plate comes into contact with the sample gas before the reflecting surface of the second mirror, the contamination of the reflecting surface of the second mirror can be minimized. Then, the sample gas is introduced to fill the inside of the cylindrical body. And the light of the predetermined wavelength from a light source injects into a cylindrical body inside from an incident window in the state which filled the sample gas inside the cylindrical body. The incident light passes through the second light transmissive window plate, is reflected by the reflecting surface of the second mirror, and then exits from the exit window to the outside of the cylindrical body.

  Thereafter, when the second light-transmitting window plate is soiled, the dirty second light-transmitting window plate is removed, and maintenance is performed to attach a cleaned or new second light-transmitting window plate. At this time, since the second mirror is a direct optical reflecting surface, if there is an arrangement position error or surface accuracy error of the second mirror, the influence on the performance is unavoidable, but the second light transmissive window plate is transmissive. Since the arrangement position and surface accuracy error of the second light transmissive window plate do not affect the performance, the maintenance for attaching the second light transmissive window plate can be performed very easily. In addition, it is difficult to reuse the second mirror, but the second light transmissive window plate transmits light, so the second light transmissive window plate is reused by cleaning or polishing the surface. be able to.

  As described above, according to the gas cell of the present invention, maintenance can be easily performed. Furthermore, since it is not necessary to replace the second mirror for a long time, the running cost can be reduced.

  Furthermore, in the above invention, the entrance window and the exit window are formed in the second surface mirror, and the first light transmissive window plate and the second light transmissive window plate are the cylindrical body. It may be possible to insert and remove from a direction perpendicular to the central axis.

The schematic block diagram which shows an example of the gas analyzer which is one Embodiment of this invention. Sectional drawing of the AA line shown in FIG. The sectional view of the horizontal direction of a gas analyzer. Explanatory drawing which concerns on the maintenance of the multiple reflection type gas cell of this invention. The schematic block diagram which shows an example of the conventional multiple reflection type gas cell. Explanatory drawing which concerns on the maintenance of the conventional multiple reflection type gas cell.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and includes various modes without departing from the spirit of the present invention.

FIG. 1 is a schematic configuration diagram illustrating an example of a gas analyzer according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA shown in FIG. 1, and FIG. 3 is a horizontal cross-sectional view of the gas analyzer. One direction horizontal to the ground is defined as an X direction, a direction horizontal to the ground and perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the X direction and the Y direction is defined as a Z direction. The same reference numerals are assigned to the same components as those of the conventional gas analyzer 101 described above.
The gas analyzer 1 includes an analysis box 50 having a laser light source 51 and a detector 52, and a multiple reflection gas cell 40 attached in a flow path through which a sample gas flows.

  The multi-reflection gas cell 40 includes a cylindrical body 10, a first plane mirror holder 3 disposed at the left end of the cylindrical body 10, a second plane mirror holder 4 disposed at the right end of the cylindrical body 10, The first plane mirror 2 held by the one plane mirror holder 3, the second plane mirror 6 held by the second plane mirror holder 4, and the first light transmissive window disposed in front of the first plane mirror 2 (−X direction). The board 31 and the 2nd light transmissive window board 32 arrange | positioned ahead (X direction) of the 2nd plane mirror 6 are provided.

The first light transmissive window plate 31 is a disk-shaped body having a diameter r ₂ (> r ₁ ), and is formed of a material that transmits laser light. Examples of the material that transmits laser light include, for example, fluororesin, polyethylene, polypropylene, and polyimide from the viewpoint of light transmittance and weather resistance, and the surface of the first light transmissive window plate 31 has a target wavelength. It is preferable that an antireflective coating for light is applied. Further, the thickness of the first light transmissive window plate 31 is preferably thin (about 2 mm or less) to the extent that it has a strength that can be self-supported and is not broken by normal handling, and may be a film instead of a plate-like body.
The second light transmissive window plate 32 also has the same structure as the first light transmissive window plate 31.

Cylindrical body 10, which cavity block in a cylindrical shape with a diameter r ₁ of a rectangular parallelepiped shape is formed, the central axis of the cavity of the cylindrical shape is disposed such that the horizontal direction (X direction), the upper ( A cylindrical gas introduction hole 11 for introducing the sample gas into the cylindrical body 10 in the -Z direction, and a cylindrical gas for discharging the sample gas from the cylindrical body 10 downward (in the Z direction). The discharge hole 12 and a rectangular opening 13 for inserting the first light transmissive window plate 31 and the second light transmissive window plate 32 into the cylindrical body 10 are provided in the front (Y direction). ing. A rectangular plate-like lid 14 is attached to the opening 13 with a bolt 14b. In addition, in order to ensure the airtightness inside the cylindrical body 10, a rectangular annular O-ring 14 a is sandwiched between the contact portions of the lid 14 and the cylindrical body 10.

  Further, a first groove (slot) 16 having a predetermined depth for attaching the first light transmitting window plate 31 is provided on the inner peripheral surface having a predetermined distance from the left end portion toward the central portion of the cylindrical body 10. Is formed, and a second groove having a predetermined depth for attaching the second light transmissive window plate 32 is formed on the inner peripheral surface having a predetermined distance from the right end portion toward the central portion of the cylindrical body 10. (Slot) 17 is formed. The predetermined distance is preferably a distance close to the mirror but not in contact, for example, 1 mm or more and 2 mm or less. At this time, the contact portion between the first light transmissive window plate 31 and the tubular body 10 and the contact portion between the second light transmissive window plate 32 and the tubular body 10 are not required to be airtight and maintain isobaric properties. A gap 16a through which air passes is formed. In addition, since resistance becomes large in the clearance gap 16a, sample gas is between the 1st light transmissive window plate 31 and the 1st plane mirror 2, and between the 2nd light transmissive window plate 32 and the 2nd plane mirror 2. FIG. The amount of entry is negligible.

  According to such a multiple reflection type gas cell 40, after removing the bolt 14b and removing the lid 14 from the opening 13, the first light transmitting window plate 31 is inserted into the first groove 16 in the -Y direction. The first light transmissive window plate 31 can be pulled out from the first groove 16 in the Y direction. Further, the second light transmissive window plate 32 can be inserted into the second groove 17 in the −Y direction, and the second light transmissive window plate 32 can be pulled out from the second groove 17 in the Y direction. ing. FIG. 4 is a view for explaining maintenance of the multiple reflection gas cell 40.

As a method often used when measuring the sample gas using such a gas analyzer 1, one of the gas inlets of the cell is closed and a vacuum pump is connected to the other gas inlet of the cell. Then, the inside of the cell is pulled. Thereafter, the valve (not shown) is closed to keep the inside of the cell at a vacuum, and when the gas inlet is opened with the gas inlet exposed to the sample gas, the sample gas is filled into the cylindrical body 10. At this time, the first light transmissive window plate 31 touches the sample gas before the reflecting surface of the first plane mirror 2, and the second light transmissive window plate 32 contacts the sample gas before the reflecting surface of the second plane mirror 6. Since it touches, contamination with the reflective surface of the 1st plane mirror 2 and the reflective surface of the 2nd plane mirror 6 can be decreased as much as possible. Then, with the sample gas filled in the cylindrical body 10, laser light having a predetermined wavelength ν from the laser light source 51 enters the cylindrical body 10 from the incident window hole 21 through the window plate 7 in the approximately X direction. The incident laser light passes through the first light transmissive window plate 31 and the second light transmissive window plate 32 and passes between the reflection surface of the first plane mirror 2 and the reflection surface of the second plane mirror 6 a certain number of times. After repeated reflection, the light is emitted from the emission window hole 22 through the window plate 7 to the outside of the cylindrical body 10 in a substantially −X direction. Intensities I (ν) and I ₀ (ν) of the emitted laser light are detected by the detector 52. In addition, even when the inside of the cell is pulled by a vacuum pump, the pressure on both surfaces of the light transmission window is the same, and therefore the light transmission window does not need to have a material and thickness that can withstand atmospheric pressure.

  Thereafter, when the first light transmissive window plate 31 or the second light transmissive window plate 32 is soiled, the bolt 14b is removed, the lid 14 is removed from the opening 13, and the soiled first light transmissive property. The window plate 31 and the second light transmissive window plate 32 are pulled out. And the maintenance which inserts the cleaned 1st light permeable window board 31 and the 2nd light transmissive window board 32 is performed. At this time, the reflecting surface of the first plane mirror 2 and the reflecting surface of the second plane mirror 6 are directly optical reflecting surfaces. Therefore, if there is an arrangement position error or a surface accuracy error of the first plane mirror 2 or the second plane mirror 6, performance is improved. Although the influence is inevitable, the first light transmissive window plate 31 and the second light transmissive window plate 32 are transmissive, and the first light transmissive window plate 31 and the second light transmissive window plate 32 are arranged. Since the position and surface accuracy errors do not affect the performance, the maintenance for attaching the first light transmissive window plate 31 and the second light transmissive window plate 32 can be performed very easily. In addition, it is difficult to reuse the first plane mirror 2 and the second plane mirror 6, but the first light transmission window plate 31 and the second light transmission window plate 32 transmit the first light transmission window. The window plate 31 and the second light transmissive window plate 32 can be reused by washing or surface polishing.

  As described above, according to the gas analyzer 1, maintenance can be easily performed. Furthermore, since it is not necessary to replace the first plane mirror 2 and the second plane mirror 6 for a long period of time, the running cost can be suppressed.

<Other embodiments>
(1) In the gas analyzer 1 described above, the first plane mirror 2 and the second plane mirror 6 are used. However, the first concave mirror and the second concave mirror may be used.
(2) In the gas analyzer 1 described above, the first light transmissive window plate 31 having a flat surface and the second light transmissive window plate 32 having a flat surface are used. However, the first light transmissive window having a curved surface is used. It is good also as a structure which uses the 2nd light transmissive window plate which has a board and a curved surface.

  The present invention can be used for a gas cell or the like for measuring the concentration of a trace component in various gases.

DESCRIPTION OF SYMBOLS 1 Gas analyzer 2 First plane mirror 10 Cylindrical body 21 Entrance window hole 22 Outgoing window hole 31 1st light transmittance window board 40 Multiple reflection type gas cell

Claims (3)

A cylindrical body into which the sample gas is introduced;
A first mirror arranged to close one end of the cylindrical body,
A gas cell in which an incident window for entering light toward the reflecting surface of the first mirror inside the cylindrical body and an exit window for emitting light from the inside of the cylindrical body are formed. ,
A gas cell characterized in that a first light-transmissive window plate can be disposed in front of the reflecting surface of the first mirror. A second mirror arranged to close the other end of the cylindrical body;
The gas cell according to claim 1, wherein a second light transmissive window plate can be disposed in front of the reflecting surface of the second mirror. The entrance window and the exit window are formed on the second mirror.
The gas cell according to claim 2, wherein the first light transmissive window plate and the second light transmissive window plate can be taken in and out from a direction perpendicular to a central axis of the cylindrical body. .

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