JP5397296B2 - Gas analyzer - Google Patents

Description

  The present invention relates to a gas analyzer that measures trace components in a gas by a light absorption analysis method.

  When measuring gas concentration by optical absorption analysis, the sensitivity is proportional to the optical path length according to Lambert-Beer's law. Therefore, in analyzers that require high sensitivity, the optical path length is increased by multiple reflection of light inside the cell. Structure is adopted. For example, the example shown in Patent Document 1 has a configuration in which two plane mirrors are arranged in parallel and the light is folded back and forth between them.

In FIG. 3, the structural example of the conventional general multiple reflection cell similar to patent document 1 is shown.
In the figure, both ends of a cylindrical cell body 10 are sealed by two facing end plates 11 and 12 to form a cell. The inside of the cell is filled with the analysis target gas flowing from the gas inlet 13 to the gas outlet 14. The opposing surfaces (mirror surfaces) of the end plates 11 and 12 are arranged in parallel and are subjected to mirror finishing. The mirror plate 12 is provided with light transmission windows 15 and 16 at two locations, and a structure in which a long optical path length is obtained by a plurality of diffractions of light entering and exiting the cell through the two mirror surfaces.

JP-A-2005-147862

Since the mirror surface may be contaminated or corroded depending on the type of gas introduced into the cell, the mirror surface is cleaned as necessary as a maintenance operation. Cleaning takes time and does not always recover completely even after cleaning, so eventually it is necessary to replace the end plate. However, the end plate is an expensive precision processed member. The problem was the high cost of
The present invention has been made in view of the above circumstances, and it is an object of the present invention to reduce the maintenance cost by omitting the work of maintaining a mirror surface in a gas analyzer equipped with multiple reflection cells.

  In order to solve the above problems, the present invention attaches a detachable reflector made of a thin plate having a mirror surface to the inner wall surface of a gas cell. Thin reflectors can be manufactured at low cost, so this configuration allows them to be disposable. When the mirror surface is contaminated or corroded, the reflector can be replaced with a new one, saving maintenance and reducing maintenance costs. . In addition, if mirror surfaces are provided on both sides of a thin reflector, it can be turned over and used again, so that further cost reduction and quick first aid on site are possible.

  Since the present invention is configured as described above, the reflector can be disposable, and not only maintenance work can be saved, but also maintenance costs can be reduced.

It is a figure which shows one Example of this invention. It is a figure which shows the other Example of this invention. It is a figure which shows the example of a conventional structure.

FIG. 1 shows an embodiment of the present invention.
In the same figure, both ends of a cylindrical cell body 10 are sealed with facing end plates 11 and 12 to form a cell, and a light transmission window 15 is formed in a cell interior space filled with an analysis target gas flowing from a gas inlet 13 to a gas outlet 14. , 16 that the light entering and exiting through the light 16 diffracts a plurality of times is the same as in the conventional configuration described above. The light transmission windows 15 and 16 and other members are sealed with an O-ring (not shown) or the like, and the inside of the cell is airtight except for the gas inlet 13 and the gas outlet 14.

The difference from the prior art is that the opposed inner wall surfaces of the mirror plates 11 and 12 do not have a mirror surface, and instead the thin reflector plates 17 and 18 that are mirror-finished on both surfaces are opposed to the inner wall surfaces of the mirror plates 11 and 12, respectively. It is that it is worn and covered. With this configuration, light coming from a light source (not shown) is introduced through one light transmission window 15, and after multiple reflection between the mirror surfaces of the two reflection plates 17 and 18, passes through the other light transmission window 16. Then, the light is guided to a photodetector (not shown), where measurement is performed by detecting light absorption according to the gas type and concentration in the cell.
In addition, since the hole (not shown) is opened in the reflecting plate 18 in the position corresponding to the light transmission windows 15 and 16, the entrance and exit of light is not hindered.

The reflecting plates 17 and 18 are fastened to the end portions of the cell body 10 by screws 19 so as to overlap the end plates 11 and 12, respectively, and can be easily removed by loosening the screws 19.
Further, since the reflecting plates 17 and 18 are made of thin plates and can be manufactured at a low cost, when the mirror surface is contaminated or corroded, it can be replaced with a new one without washing. As a result, it is possible to save the trouble of cleaning and the like and to reduce the maintenance cost.

  Further, in this embodiment, the reflecting plates 17 and 18 are mirror-finished on both sides, so that when the mirror surface on one side is contaminated or corroded, it can be turned over and used again. Since the reflectors 17 and 18 can be used twice before being thrown away, there is an effect that the maintenance cost is greatly reduced, and that an on-site repair can be quickly dealt with. In this case, since the concave portions 11a and 12a are provided by recessing part of the surfaces of the mirror plates 11 and 12 that are covered with the reflecting plates 17 and 18, the mirror surfaces of the reflecting plates 17 and 18 that are not in use hit and are scratched or soiled. Can be prevented.

  The reflectors 17 and 18 can be manufactured by processing a mirror surface by electrolytic composite polishing or the like using a metal plate such as stainless steel having a thickness of about 1 mm.

The above is an example in which the reflecting plates 17 and 18 having mirror surfaces on both sides are used. However, even if a mirror surface is provided on only one side, the maintenance cost reduction effect is somewhat inferior, but it is useful. Further, even when the mirrors have a mirror surface only on one side of the reflectors 17 and 18, providing the recesses 11a and 12a is effective in that unnecessary force is not applied to the mirror surface.
Furthermore, the present invention can be applied not only to the case where light is reflected a plurality of times in the cell (multiple reflection) but also to the case where it is reflected only once. In that case, the reflector 18 in FIG. 1 is unnecessary, and the light from the light source enters the cell from the light transmission window 15, is reflected only once by the reflection plate 17, and reaches the photodetector from the light transmission window 16. It becomes composition.

FIG. 2 shows another embodiment of the present invention in which the present invention is applied to a pass-through cell in which a light source and a photodetector are arranged on opposite sides of the cell.
In the same figure, the light transmission windows 15 and 16 are different from the structure of FIG. In addition, the member which attached | subjected the same code | symbol as FIG. 1 has the same function as FIG. In this configuration, light from a light source (not shown) enters through the light transmission window 15 from the right side of the drawing, is folded between the reflecting plates 17 and 18, and exits from the light transmission window 16 to the left side. (Not shown).
Even in this configuration, it is obvious that the effects of the present invention are not impaired as compared with the case of FIG.

  INDUSTRIAL APPLICABILITY The present invention can be used for a gas analyzer that measures a trace component in a gas by a light absorption analysis method.

DESCRIPTION OF SYMBOLS 10 Cell body 11 End plate 11a Recess 12 End plate 12a Recess 13 Gas inlet 14 Gas outlet 15 Light transmission window 16 Light transmission window 17 Reflection plate 18 Reflection plate 19 Screw

Claims (3)

A light absorption analysis method comprising a cell into which a sample gas is introduced, a light source that makes light incident on the cell, and a light detector that detects the intensity of light reflected from a mirror surface in the cell and emitted from the cell. The gas analyzer according to claim 1, wherein the mirror surfaces are formed on both surfaces of a reflection plate that is detachably mounted in contact with the inner wall surface of the cell. Gas analyzer according to claim 1, characterized in that a recess on the inner wall surface covered by said reflector is mounted. The cell includes a hollow cylindrical cell body having an open end and a removable end plate that seals the open end of the cell body, and the reflector is between the open end of the cell body and the end plate. The gas analyzer according to claim 1 or 2 , wherein the gas analyzer is sandwiched.

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