JP2009014465A - Infrared gas analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily-handleable infrared gas analyzer capable of coping with various applications. <P>SOLUTION: This analyzer is equipped with a sample cell 1 constituting a circulation passage of sample gas; an infrared light source 2 for radiating infrared light to the inside of the sample cell 1; and gas cell detectors 3, 3 for receiving the infrared light radiated from the infrared light source 2 and propagating in the sample cell 1, while being reflected inside the sample cell 1. The gas cell detectors 3, 3 are mounted on a position away from the optical axis of the infrared light source 2. The sample cell 1 is constituted by combining mutually-detachable base material 1A and cover material 1B, and the inside of the sample cell 1 can be opened by separating both materials, to thereby enable maintenance or cleaning of the inside of the sample cell 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an infrared gas for analyzing the gas concentration of a sample gas in a sample cell by detecting the amount of absorption of infrared light irradiated into the sample cell from an infrared light source by a detector that receives the infrared light. Related to analyzers.

  A non-dispersive infrared gas analyzer (NDIR) is known as an apparatus for quantitatively analyzing the gas concentration of a predetermined component in a sample gas. Non-dispersive infrared gas analyzers include a single beam analyzer and a double beam analyzer. In the former, the sample gas is circulated in a cylindrical sample cell and one end of the sample cell is provided. And an infrared light source and a gas cell detector at the other end. By detecting the amount of infrared absorption received when the infrared light emitted from the infrared light source passes through the sample cell with a gas cell detector having two chambers stacked along the optical axis of the infrared light, The gas concentration of the gas can be analyzed. The two chambers of the detector are filled with the detection target gas, and the flow of gas in the flow path communicating between the two chambers is detected by a thermal flow sensor, so that infrared is detected via the difference in the amount of infrared absorption in the two chambers. It is possible to grasp the amount of infrared absorption received when light passes through the sample cell.

In the latter double-beam type non-dispersive infrared gas analyzer, a reference cell having the same structure as the cylindrical sample cell is further provided, and the reference cell has an inert gas such as nitrogen that does not exhibit infrared absorption. Fill. Further, infrared light from the infrared light source is distributed and irradiated from one end side of each of the sample cell and the reference cell. Furthermore, the detector is composed of a sample chamber and a reference chamber, the sample chamber is arranged on the other end side of the sample cell, the reference chamber is arranged on the other end side of the reference cell, and the gas in the flow passage connecting the two chambers is arranged. By detecting the going and going by the thermal flow sensor, it is possible to grasp the infrared absorption amount received when the infrared light passes through the sample cell through the difference between the infrared absorption amounts in the two chambers as a comparison result with the reference cell.
JP 2001-255269 A

  In the conventional infrared gas analyzer, the optical axes of the infrared light source and the detector are designed to coincide with each other, and when assembling the optical system, it is necessary to strictly match the optical axes of the components. Due to the slight deviation of the optical axis, the intensity of the emitted infrared light, the propagation efficiency, the intensity of the infrared light incident on the detector, and the like are affected, and the accuracy of quantitative analysis decreases. For this reason, a method is generally used in which an optical component is attached on the basis of a strong and stable optical bench as a base. The optical bench is designed so that the mechanical positional relationship does not fluctuate due to vibration and disturbance. However, assembling an optical system using an optical bench is a work burden, and increases the size and weight of the entire apparatus.

  The inner diameter of the cylinder of the sample cell or reference cell correlates with the absorption length, the diameter of the reflector of the infrared light source or the reflector mounted on the light source, or the light receiving diameter of each chamber of the gas cell detector. ing. Therefore, the inner diameter of the cylinder of the sample cell or the reference cell is optimally designed so that the propagation loss of light is minimized and the absorption of the sample gas can be efficiently captured. For this reason, once the inner diameter is determined, the change is not easy, and it is not practical because the dimensions of a series of related parts such as a light source and a detector need to be changed. For this reason, changing the sample cell length is performed as a means for changing according to the purpose of analysis. Since the infrared absorption of the detection target gas is different, the sample cell length is shortened for gas that is strongly absorbed depending on the gas type, and the sample cell length is lengthened for gas that is weakly absorbed It is common to make a choice. However, stocking various types of sample cells corresponding to various types of applications and selecting them appropriately is a factor in complicating work and increasing costs.

  Furthermore, as a trend in recent years, the application field of infrared gas analyzers has expanded, and there has been a demand for easy-to-handle analyzers that are reduced in size and cost. Along with this, the parts used are also downsized, and in particular, there are increasing examples in which MEMS (Micro Electro Mechanical System) parts are used. For example, small and planar light sources and detectors formed from semiconductor wafers have been developed. Since conventional infrared gas analyzers do not assume the use of these optical components, it is difficult to achieve structural consistency such as a difference in size and an attachment method.

  An object of the present invention is to provide an infrared gas analyzer that is easy to handle and can be used for various applications.

The infrared gas analyzer of the present invention detects the amount of absorption of the infrared light irradiated into the sample cell from the infrared light source by a detector that receives the infrared light, so that the sample gas in the sample cell is detected. In the infrared gas analyzer for analyzing the gas concentration, the detector is arranged at a position off the optical axis of the infrared light source.
According to this infrared gas analyzer, since the detector is disposed at a position off the optical axis of the infrared light source, it is easy to handle and can be used for various applications.

  Reflecting means for reflecting the infrared light in the sample cell to make the effective optical path length of the infrared light in the sample cell longer than a linear distance from the infrared light source to the detector. Good.

  An adjusting means for adjusting the effective optical path length obtained by the reflecting means may be provided.

  The inner wall surface of the sample cell may be used as the reflecting means.

  A plurality of detectors having different detection target gases may be provided as the detector.

  The sample cell may be provided with a mounting portion for mounting the infrared light source or the detector.

  The inside of the sample cell may be openable.

  The infrared light source or the detector may be configured as a MEMS component.

  According to the infrared gas analyzer of the present invention, since the detector is arranged at a position off the optical axis of the infrared light source, it is easy to handle and can be used for various applications.

  Hereinafter, an embodiment of an infrared gas analyzer according to the present invention will be described with reference to FIGS.

  FIG. 1A is a perspective view showing a configuration of an embodiment of an infrared gas analyzer according to the present invention, and FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. The infrared gas analyzer of the present embodiment constitutes a single beam type non-dispersive infrared gas analyzer.

  As shown in FIGS. 1 (a) and 1 (b), the infrared gas analyzer of the present embodiment emits infrared light into the sample cell 1 constituting the flow path of the sample gas and the inside of the sample cell 1. Irradiating infrared light source 2 and gas cell detectors 3 and 3 ′ receiving infrared light irradiated from infrared light source 2 and propagating through sample cell 1 are provided. As shown in FIGS. 1A and 1B, the gas cell detectors 3 and 3 ′ are attached at positions off the optical axis of the infrared light source 2.

  As shown in FIGS. 1 (a) and 1 (b), the sample cell 1 is configured by combining a base material 1A and a cover material 1B which are detachable from each other. The sample cell 1 can be opened for maintenance and cleaning.

  On the flat substrate 1A, an attachment portion 11 for attaching the infrared light source 2 and an attachment portion 12 and an attachment portion 13 for attaching the detectors 3 and 3 'are formed. A calcium fluoride plate or the like for obtaining airtightness and infrared transmittance may be disposed on the attachment portions 11, 12, and 13. Or when the structure which ensures airtightness and infrared transmittance is taken in the infrared light source 2 or the detectors 3 and 3 'side, the opening corresponding to the attachment parts 11, 12, and 13 is made in the base material 1A. It may be formed.

  The cover material 1B is provided with a sample gas inflow path 4 and a sample gas discharge path 5, and the sample gas is allowed to flow through the inflow path 4 and the exhaust path 5 in a state where the base material 1A and the cover material 1B are hermetically coupled. Through the sample cell 1.

  As shown in FIG. 1B, the infrared light source 2 is formed with a chamber 21 for storing a light emitter that emits infrared light and a chamber 22 for storing an interference gas, both of which are infrared transmissive plates 23. Separated by By controlling the interference gas in the chamber 22, the wavelength component that interferes with the measurement among the wavelength components emitted from the chamber 21 into the sample cell 1 can be removed in advance.

  As shown in FIG. 1B, the detector 3 is formed with a chamber 31 arranged on the sample cell 1 side and a chamber 32 placed at a position farther from the sample cell 1. The chamber 31 and the chamber 32 are filled with the same component gas as the detection target gas, and both are separated by an infrared transmitting plate member 23. The chamber 31 and the chamber 32 are connected to each other by a flow passage 34, and a thermal flow sensor 35 that detects the flow of gas in the flow passage 34 is attached to the flow passage 34.

  In the detector 3, the infrared light incident on the chamber 32 is light that has received infrared absorption in the chamber 31, and thus the degree of thermal expansion in the chamber 31 is higher than that in the chamber 32. The difference in the degree of thermal expansion is proportional to the energy of the infrared absorption spectrum corresponding to the detection target gas in the infrared light incident on the detector 3, and therefore the absorption in the infrared absorption spectrum in the sample cell 1. There is a correlation with the quantity. The thermal flow sensor 35 converts the difference in the degree of thermal expansion, that is, the difference in the amount of infrared absorption between the chamber 31 and the chamber 32 into a gas concentration signal, thereby analyzing the concentration of the detection target gas in the sample gas. Since the function of the detector 3 is well known, detailed description thereof is omitted.

  Next, the operation of the infrared gas analyzer of this embodiment will be described.

  As shown in FIG. 1B, in the infrared gas analyzer of the present embodiment, the detector 3 is not disposed on the optical axis of the infrared light source 2, and the infrared light 6 emitted from the infrared light source 2. Reaches the detector 3 while repeatedly reflecting on the inner wall surface of the sample cell 1. In the process of propagating through the sample cell 1 with multiple reflections, the infrared light receives infrared absorption by the sample gas introduced into the sample cell 1.

  The infrared light that has received infrared absorption by the sample gas is incident on the detector 3 attached to the sample cell 1, and the amount of infrared absorption caused by the detection target gas of the detector 3 is detected. Thereby, the gas concentration of the detection target gas in the sample gas can be analyzed. In the infrared gas analyzer of the present embodiment, gas concentrations can be analyzed for two different detection target gases by filling the two detectors 3 and 3 ′ with different gases.

  As described above, in the infrared gas analyzer of the present embodiment, the effective optical path length of the infrared light propagating in the sample cell 1 is set to the infrared by the multiple reflection of the infrared light using the inner wall surface of the sample cell 1 as the reflecting means. The linear distance from the light source 2 to the detector 3 can be made longer. For this reason, it is possible to secure a sufficient amount of infrared absorption while reducing the size of the apparatus. Therefore, high detection sensitivity can be obtained while downsizing the apparatus.

  In addition, since the infrared gas analyzer of the present embodiment employs a configuration in which the infrared light source 2 or the detector 3 is attached to the flat substrate 1A, the infrared light source 2 or the detector 3 is a MEMS (Micro Electro Mechanical System). When a component is used, a structure suitable for mounting these small and planar components can be obtained. Furthermore, since the sample cell 1 can be miniaturized, the size of the entire apparatus can be made suitable for the MEMS component.

  Further, in the infrared gas analyzer of the present embodiment, the detector 3 is not disposed on the optical axis of the infrared light source 2, and the infrared light irradiated from the infrared light source 2 is directly applied to the detector 3. It does not enter but enters the detector 3 after being diffused in the sample cell 1. For this reason, the mechanical positional relationship between the infrared light source 2 and the detector 3 hardly affects the detection sensitivity. Therefore, it is possible to suppress fluctuations in the detected value with respect to vibrations and disturbances, while eliminating the need for attaching optical components based on a solid optical bench as in the prior art. Furthermore, since there is no restriction that the detector 3 is arranged on the optical axis of the infrared light source 2, it is possible to attach a plurality of detectors directly to the sample cell 1 and to independently determine a plurality of types of gases without affecting each other. It becomes possible to analyze the concentration. Unlike the conventional single-beam type gas analyzer, it is not necessary to stack detectors for each type of gas to be detected in multiple stages, so the latter detector is affected by the infrared absorption by the former detector. There is no inconvenience.

  Conventionally, the dimensions of large parts such as a cylindrical sample cell have been optimally designed in advance, and it has been difficult to secure multiple types of sample cells according to the application. In this infrared gas analyzer, the design can be easily changed, and it is easy to reduce the cost by reducing the size of the sample cell, and it is possible to prepare many types of sample cells. For this reason, it can respond to various applications flexibly.

  Next, FIG. 2 is a sectional view showing the configuration of another embodiment of the infrared gas analyzer according to the present invention. The same components as those in FIGS. 1A and 1B are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 2, in the infrared gas analyzer of the present embodiment, a reflector 7 is provided inside a sample cell 10 constituted by a base material 1A and a cover material 1C that are detachable from each other. Infrared light emitted from the infrared light source 2 reaches the detectors 3 and 3 ′ while being repeatedly reflected on the surface of the reflecting plate 7 as the reflecting means and the inner wall surface of the sample cell 1 as the reflecting means.

  As shown in FIG. 2, the reflecting plate 7 is movable in the vertical direction inside the sample cell 1 while maintaining the airtightness of the sample cell 1 by an actuator 8 as an adjusting means. In the example of FIG. 2, the effective optical path length can be adjusted by changing the light propagation path of infrared light by changing the distance from the inner wall surface of the sample cell 1 by the movement of the reflecting plate 7. For this reason, the optimal effective optical path length corresponding to the infrared light quantity of the infrared light source 2, the sensitivity of the detectors 3 and 3 ', or the absorption coefficient of the sample gas can be obtained.

  Thus, according to the infrared gas analyzer of the present embodiment, the effective optical path length can be adjusted, so that an appropriate effective optical path length can always be obtained, and a single sample cell 1 can cope with a wide range of applications. Become.

  FIG. 3 is a plan view showing an example of a specific arrangement method of optical components in the infrared gas analyzer according to the present invention.

In FIG. 3, for example, a base material on a flat plate constituting the sample cell 100 is provided with a light source unit mounting portion and four mounting portions for a detector, and each mounting portion includes a light source unit. 20, a detector 3A for CO ₂ detection, a detector 3B for CO detection, a detector 3C for NO detection, and a detector 3D for SO ₂ detection are respectively attached. The detection target gas of each detector can be selected as appropriate, and a shielding lid for maintaining airtightness can be attached to an attachment portion that is not used.

  In the example of FIG. 3, the infrared light amount is increased by using two infrared light sources 20 a for the light source unit 20.

As described above, by increasing the number of mounting portions of the detector, it is possible to simultaneously analyze the gas concentration of any kind of multicomponent. Further, by increasing the number of infrared light sources, the amount of infrared light can be increased as necessary, and the detection sensitivity can be improved.

  In each of the above embodiments, a single beam type infrared gas analyzer is shown, but the present invention can also be applied to a double beam type infrared gas analyzer. In the double beam type infrared gas analyzer, a reference cell having the same structure as the sample cell shown in each of the above embodiments is provided, and infrared light is distributed to both cells, and a sample chamber attached to the sample cell and a reference cell What is necessary is just to detect the flow of the gas of the flow path provided between the reference | standard chambers attached to the cell with the thermal flow sensor. In this case, the sample chamber and the reference chamber function as a part of the “detector that receives infrared light”.

  The form and shape of the sample cell are not limited to those of the above embodiment. The configurations of the infrared light source and the detector can be arbitrarily selected. A specular reflection surface may be used as the reflection means, or a diffuse reflection surface may be used. The shape of the reflecting means is not limited, and a flat or arbitrary curved reflecting surface can be adopted. The configuration of the adjusting means can be arbitrarily selected. For example, the effective optical path length of infrared light can be adjusted by changing the shape of the sample cell or its inner surface.

  As described above, according to the infrared gas analyzer of the present invention, since the detector is disposed at a position off the optical axis of the infrared light source, it can be handled easily and can be used for various applications.

  The scope of application of the present invention is not limited to the above embodiment. The present invention relates to an infrared gas for analyzing the gas concentration of a sample gas in a sample cell by detecting the amount of absorption of infrared light irradiated into the sample cell from an infrared light source by a detector that receives the infrared light. It can be widely applied to analyzers.

It is a figure which shows the structure of one Embodiment of the infrared gas analyzer by this invention, (a) is a perspective view, (b) is the Ib-Ib sectional view taken on the line in (a). Sectional drawing which shows the structure of another embodiment of the infrared gas analyzer by this invention. The top view which shows the example of the specific arrangement | positioning method of the optical component in the infrared gas analyzer by this invention.

Explanation of symbols

1 Sample cell (reflection means)
2 Infrared light source 3, 3 'detector 7 Reflector (reflecting means)
8 Actuator (Adjustment means)

Claims (8)

An infrared gas analyzer that analyzes the gas concentration of the sample gas in the sample cell by detecting the amount of absorption of infrared light irradiated into the sample cell from an infrared light source with a detector that receives the infrared light In
An infrared gas analyzer, wherein the detector is disposed at a position off the optical axis of the infrared light source. Reflecting means for reflecting the infrared light in the sample cell to make the effective optical path length of the infrared light in the sample cell longer than a linear distance from the infrared light source to the detector. The infrared gas analyzer according to claim 1, wherein The infrared gas analyzer according to claim 2, further comprising an adjusting unit that adjusts the effective optical path length obtained by the reflecting unit. The infrared gas analyzer according to claim 2 or 3, wherein an inner wall surface of the sample cell is used as the reflecting means. The infrared gas analyzer according to claim 1, wherein a plurality of detectors having different detection target gases are provided as the detector. The infrared gas analyzer according to any one of claims 1 to 5, wherein the sample cell is provided with a mounting portion for mounting the infrared light source or the detector. The infrared gas analyzer according to claim 1, wherein the inside of the sample cell is openable. The infrared gas analyzer according to claim 1, wherein the infrared light source or the detector is configured as a MEMS component.

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