JPH0510874A - Absorption gas analyzer - Google Patents

Abstract

PURPOSE:To enable an error of an interference gas to be compensated by providing a first filter which absorbs a light only at a specified wavelength region, a second filter which does not absorb light at a measurement wavelength region, a detector of quantity of light, and an operation portion for calculating a difference of the detection signal and then measuring a concentration of the constituent gas. CONSTITUTION:A primary detection signal 20a of a detector 21 of quantity of light where a flux of light which is transmitted through a measurement cell 2 and a first light filter 23 enter becomes a signal which indicates a quantity of light which is obtained by subtracting an amount of light absorption within a specified wavelength band according to the light filter 23 and the amount of light absorption according to an interference gas within the cell 2 from the quantity of light in the measurement wavelength band out of a flux of light from a light source 1. A detection signal of the detector 21 where the flux of light which is transmitted through the cell 2 and a second light filter 24 enter becomes a signal which indicates an amount of light absorption which is obtained by subtracting the amount of light absorption according to the filter 24 and the amount of each light absorption according to a measurement constituent gas and an interference gas within the cell 2 from the quantity of light within the measurement wavelength band. An operation portion 22 calculates a difference between signals 20a and 20b, outputs the secondary detection signal 22a, and then measures a gas concentration by the signal 22a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption type gas analyzer for qualitatively and quantitatively analyzing a gas by utilizing its absorption characteristic such as infrared absorption characteristic, and in particular, a light amount detecting mechanism constituting this gas analyzer. The present invention relates to an analyzer which is easy to manufacture and has a small interference error as a measurement error due to an interference gas.

[0002]

2. Description of the Related Art FIG. 5 is a longitudinal sectional view of a main part of a conventional infrared gas analyzer. In the figure, 1 is a light source section for emitting a light beam 1a of infrared rays having a continuous spectrum, and 2 is a light beam 1a.
Is arranged in the middle of the optical path 3 through which the light beam 1a passes, and a gas inlet 2a and a gas outlet 2b are provided, and the analyzed gas 4 guided to the gas inlet 2a flows through and flows out from the gas outlet 2b. In this case, the measuring cell 2 is constructed in such a way that the light beam 1a passes through this cell 2 together with the gas 4 in the cell 2. Reference numeral 5 is a chopper which is rotated by a motor 6 so that the light beam 1a is periodically made incident on the cell 2, and 7, 8, 9 are all arranged in parallel so that the light beam 1a transmitted through the measuring cell 2 is made incident. And bandpass optical filters 10, 11 and 11, which respectively transmit light in bands Δλ1, Δλ2 and Δλ3 having different light wavelengths λ in the infrared region shown in FIG.
Reference numeral 12 is a light beam 1a that has passed through the filters 7, 8 and 9, respectively.
Primary detection signals 10a, 11a, 12a such as a voltage signal or an electrical resistance signal corresponding to the detection result by detecting each light amount of
Is a solid-state sensor such as a pyroelectric sensor or a semiconductor sensor, which receives the signals 10a to 12a and performs a calculation to be described later using these signals to detect a secondary detection signal 14a. Is a calculation unit that outputs Reference numeral 15 is an infrared gas analyzer equipped with the above-mentioned parts. In this case, the light transmission wavelength bands Δλ1 to Δλ3 of the filters 7 to 9 described above are the absorption characteristic lines A and B1 of the gas shown in FIG. , B2, C1, C2 among A, B2, C2
Are in the band Δλ1, B1 are in the band Δλ2, and C2 is in the band Δλ3, and the characteristic line A is the analysis target of the analyzer 15. Peaks of infrared absorption characteristics exhibited by the measurement component gas Gm as the analysis target component gas, B1 and B2 are peaks of infrared absorption characteristics exhibited by the interference gas Gi1, and C
1 and C2 have peaks in the infrared absorption characteristics exhibited by the interference gas Gi2.

Since each part of the gas analyzer 15 is configured as described above, the analyzed gas 4 exhibits infrared absorption in the wavelength band Δλ1 in addition to the above-mentioned measurement component gas Gm and the interference gases Gi1 and Gi2. If no gas can be present, the signal values of the primary detection signals 10a, 11a, 12a are S10, Sb1, Sc1 and the signal value S10.
The signal values based on each of the above-mentioned absorption characteristic lines A, B2, C2 in the above are Sa, Sb2, Sc2, and Kb, K
When c is a constant, the equations (1), (2), and (3) are established. Therefore, from equations (1) to (3), (4)
Since the equation is obtained and it is clear that both Kb and Kc are known constants in this case, signals 10a, 11a and 1
When 2a and 2a are used, the signal value Sa can be obtained by the equation (4). Then, this Sa is gas Gm
It is clear that the value corresponds to the concentration of
In the above, the calculation unit 14 is configured to perform the calculation of the equation (4) and output the signal 14a representing Sa. Therefore,
According to the analyzer 15, the concentration of the gas Gm can be measured by the signal 14a. S10 = Sa + Sb2 + Sc2 ──────────────────────── (1) Sb2 = (Kb) ・ (Sb1) ───────────────── ( 2) Sc2 = (Kc) · (Sc1) ────────────────── (3) Sa = S10− (Kb) · (Sb1) − (Kc) · (Sc1) ─── (4)

[0004]

According to the analyzer 15, the concentration Cm of the measurement component gas Gm can be accurately measured by the signal 14a even if the interference gases Gi1 and Gi2 are present. Then, as is clear from the above description, the interference compensation detector D including the bandpass optical filter 8 and the solid-state sensor 11 for each type of interference gas Gi.
Since one interference compensation detector Di such as i1 is required, the number of detectors Di increases as the number of types of the interference gas Gi increases. As a result, the light amount detection mechanism 16 including the filters 7 to 9 and the sensors 10 to 12 is used. There is a problem in that the structure of the corresponding light amount detection mechanism becomes complicated, and therefore, in such a case, the analyzer 15 is complicated to manufacture the light amount detection mechanism. Then, since the analyzer 15 is configured as described above, when the interference gas Gi other than the interference gases Gi1 and Gi2 appears in the analyzed gas 4, the light amount detection mechanism 16 and There is also a problem that each function of the calculation unit 14 is insufficient and an interference error occurs in the measurement result for the concentration Cm of the gas Gm. Then, further, in the analyzer 15, by narrowing the light wavelength band Δλ1, the detection mechanism 16
Although it is possible to simplify the configuration and prevent the occurrence of unexpected interference errors, in this case, since the band Δλ1 has to be narrowed, there is a problem that the manufacturing of the filter 7 becomes troublesome.

The object of the present invention is to facilitate the manufacture of the light amount detection mechanism by eliminating the need for the interference compensation detector Di for each type of the interference gas Gi, and to predict the presence in the gas to be analyzed 4. Even if an interference gas appears, interference compensation is performed immediately so that an interference error does not occur, and the wavelength band of the bandpass optical filter to be used does not have to be extremely narrowed, so that the filter can be easily manufactured. Is to be.

[0006]

In order to achieve the above object, according to the present invention, 1) a light source section for emitting a light beam, and an analyte gas which is arranged in the middle of an optical path through which the light beam passes. Measuring cell,
Detects the amount of light in a predetermined measurement wavelength band including a specific wavelength band that is a light wavelength band occupied by at least one specific peak in the absorption characteristic of the measurement component gas, and outputs a primary detection signal according to the detection result. Light quantity detectors, a first optical filter arranged so as to be in series with the measurement cell in the middle of the optical path and absorbing light only in the specific wavelength band in the measurement wavelength band, and in the middle of the optical path A second optical filter that is arranged so as to be in series with the measurement cell and that hardly absorbs the light in the measurement wavelength band or absorbs the light at substantially the same absorption coefficient over the entire measurement wavelength band, And a computing unit for computing a difference between the two primary detection signals and outputting a secondary detection signal according to the computation result. An absorption gas analyzer for measuring the concentration of the measurement component gas in a deposition gas, wherein the measurement cell is configured such that the light flux passes through the measurement cell together with the analyzed gas in the measurement cell, and In both of the light quantity detectors, one of the light quantity detectors receives the light flux that has passed through the measurement cell and the first optical filter, and the other light quantity detector transmits the measurement cells and the second light filter. The absorption type gas analyzer is arranged so that the light flux is incident, and 2) in the gas analyzer according to the above 1), a bandpass light that allows the light amount detector to transmit light in a measurement wavelength band. 3. An absorption gas analyzer is configured to include a filter and a solid-state sensor that detects the amount of the light that has passed through the bandpass optical filter and outputs a primary detection signal according to the detection result. ) Above 1 Or the above-mentioned 2), the first optical filter is a measurement component gas filter having a measurement component gas as a filtering element, and the second optical filter is a simple air layer and the filtering element. The absorption type gas analyzer is configured as either one of an inert gas filter that uses as an inert gas.

[0007]

With the above configuration, in any of the gas analyzers, the primary detection signal output by the light quantity detector on which the light flux transmitted through the measurement cell and the first optical filter is incident is the light flux emitted by the light source. A signal representing the amount of light obtained by subtracting the amount of light absorbed in the specific wavelength band by the first optical filter and the amount of light absorbed by the interference gas in the measurement cell from the amount of light in the measurement wavelength band, and the measurement cell and the second The primary detection signal output by the light amount detector, which receives the light beam that has passed through the optical filter, is calculated from the light amount in the measurement wavelength band of the light beams emitted by the light source as the light absorption amount in the measurement wavelength band by the second optical filter. It becomes a signal representing the amount of light that is obtained by subtracting the measurement component gas in the measurement cell and each light absorption by the interference gas, and as a result, the secondary detection signal is absorbed by the measurement component gas in the measurement cell within the specified wavelength band. It is possible to signal corresponding to eventually will be able to measure the concentration of the measurement gas components in the analyte gas by a secondary detection signal. Then, in this case, even if the kind of the interference gas as the gas other than the measurement component gas having the peak of the absorption characteristic in the measurement wavelength band changes, the above-described light amount detection mechanism 16 including two light amount detectors is used. It is clear that the density measurement can be normally performed without changing the configuration of the corresponding light amount detection mechanism. Therefore, according to the above-described configuration of the present invention, the light amount detection mechanism can be easily manufactured without causing an interference error. A gas analyzer is obtained. Then, further, when the gas analyzer is configured as described above, it is also clear that it is not necessary to extremely narrow the bandwidth of the measurement wavelength band corresponding to the above-mentioned light transmission wavelength band Δλ1, so that the present invention According to the characteristics of (1), it is possible to easily manufacture the bandpass optical filter that constitutes the light amount detector.

[0008]

1 is a longitudinal sectional view of an infrared gas analyzer 17 according to an embodiment of the present invention. The difference from FIG. 5 in this drawing is that the light quantity detection corresponding to the light quantity detection mechanism 16 in FIG. The mechanism 18 has a configuration in which two light quantity detectors 21 each including a bandpass optical filter 19 corresponding to the filter 7 in FIG. 5 and a solid-state sensor 20 corresponding to the sensor 10 in FIG. Calculation unit 1 in FIG.
4 corresponds to the primary detection signal 20a as a signal output from one sensor 20 and the other sensor 20
And a primary detection signal 20b as a signal output by the input signal is calculated, a difference between the two signals 20a and 20b is calculated, and a secondary detection signal 22a corresponding to the calculation result is output, and the measurement is performed. A measurement component gas filter 23 including a bottomed cylindrical container 23b whose both ends are sealed by infrared transmitting windows 23a and a measurement component gas Gm sealed in the container 23b between the cell 2 and the light amount detection mechanism 18. And a bottomed cylindrical container 24b whose both ends are closed by infrared transmitting windows 24a.
And the inert gas filter 24 composed of the inert gas Gx sealed in the container 24b, the cell 2 and the filter 2
3 is incident on the light amount detector 21 that outputs the signal 20a, and the light beam 1a that is sequentially transmitted through the cell 2 and the filter 24 outputs the signal 20b.
In this case, the light transmission wavelength band Δλm of the filter 19 is substantially equal to the wavelength band Δλ1 shown in FIG.
Then, it is clear from FIG. 6 that this band Δλm is a light wavelength band including the specific wavelength band Δλs which is the light wavelength band occupied by the peak A in the infrared absorption characteristics of the measurement component gas Gm shown in FIG. .

In FIG. 1, since each part is configured as described above, the spectrum of the spectral energy E of the light beam 1a incident on the gas filters 23 and 24 is absorbed by the analyzed gas 4 in the measuring cell 2 due to infrared absorption. For example in Figure 2
If the spectrum 25 shown in FIG. 3 is obtained, the gas filter 23 is configured so that almost all of the light of the specific wavelength band Δλs of the incident light is absorbed, so that the primary detection is performed. The energy spectrum of the light beam 1a incident on the light quantity detector 21 that outputs the signal 20a is as shown by reference numeral 26 in FIG. 2. As a result, the signal 20a is shown by the hatched portion 27 in FIG.
The signal represents the sum M1 of each area of 28. Then, again, since the gas filter 24 hardly absorbs the transmitted light by infrared rays, the detector 21 that outputs the signal 20b is detected.
As shown in FIG. 3, the energy spectrum of the light beam 1a incident on is an energy spectrum 29 which is almost unchanged from the spectrum 25.
0b becomes a signal representing the area M2 of the portion 30 shown by hatching in FIG. Then, in FIGS. 2 and 3, P
Reference characters a, Pb, and Pc are absorption peaks of the energy spectrum corresponding to the peaks A, B2, and C2 of the infrared absorption characteristics shown in FIG. 6, respectively. That is, in the analyzer 17, when the light beam 1a having the spectrum 25 is emitted from the measurement cell 2, the primary detection signals 20a and 20b become signals representing the areas M1 and M2, respectively, so that the secondary detection signal 22a is shown in FIG. A signal representing the area M3 of the portion 31 indicated by hatching is obtained, and in this case, the signal 22a influences the concentration Cm of the measurement component gas Gm in the gas to be analyzed 4 by the interference gases Gi1 and Gi2 existing in the gas 4. It is clear from the above that the correct representation is given without being subjected to.
Therefore, in this case, the concentration Cm can be accurately measured by the signal 22a without including an interference error.

Since the analyzer 17 performs the measurement for the concentration Cm as described above, the analyzer 17 has a peak of the absorption characteristic in the measurement wavelength band Δλm and is present in the gas to be analyzed 4. Even if the kind of the interference gas Gi as a gas other than the measurement component gas Gm to be increased or decreased, high-precision concentration measurement can be performed immediately without changing the configuration of the light amount detection mechanism 18 and without being affected by the gas Gi. Therefore, the analyzer 17 is an analyzer in which the light amount detection mechanism 18 is easy to manufacture and does not cause an interference error. Then, in the case of the analyzer 17, considering the unbalance of the dependence of the output signal value on the incident light wavelength of both solid-state sensors 20, the measurement wavelength band Δλ
There is a limit to widening m, but in this case Δλm
Since it is clear from the above description that the filter need not be extremely narrow, the analyzer 17 is an analyzer in which the filter 19 can be easily manufactured. Although the light beam 1a is infrared in the above description of the embodiment, the present invention can be applied to the case where the light beam 1a is light other than the infrared region.
Further, in the above description of the embodiment, the inert gas filter 24 that hardly absorbs infrared rays between the measuring cell 2 and the detector 21.
However, in the present invention, when the concentration measurement error based on the infrared absorption gas such as carbon dioxide gas in the air can be ignored, an air filter in which the air is enclosed in the container 24b is used instead of the filter 24. Maybe,
Further, a simple air layer may be used instead of this air filter. Further, in the present invention, instead of the gas filter 24, an optical filter that absorbs light with substantially the same absorptance over the entire measurement wavelength band Δλm may be used.

[0011]

As described above, in the present invention, 1) a light source section for emitting a light beam, a measurement cell arranged in the optical path through which the light beam passes and into which an analyte gas is introduced,
Detects the amount of light in a predetermined measurement wavelength band including a specific wavelength band that is a light wavelength band occupied by at least one specific peak in the absorption characteristic of the measurement component gas, and outputs a primary detection signal according to the detection result. Light quantity detectors, a first optical filter arranged in series with the measurement cell in the middle of the optical path and absorbing light only in a specific wavelength band in the measurement wavelength band, and a measurement cell in the middle of the optical path A second arrangement which is arranged so as to be in series with and which hardly absorbs light in the measurement wavelength band or absorbs light at substantially the same absorption rate over the entire measurement wavelength band.
An optical filter and an arithmetic unit that calculates a difference between both primary detection signals and outputs a secondary detection signal according to the calculation result,
An absorption gas analyzer for measuring the concentration of a measurement component gas in a gas to be analyzed by a secondary detection signal, wherein the light flux passes through the measurement cell together with the gas to be analyzed in the measurement cell. Both light quantity detectors are configured so that one light quantity detector receives the light flux that has passed through the measurement cell and the first optical filter, and the other light quantity detector receives the light flux that has passed through the measurement cell and the second optical filter. To form an absorption gas analyzer, and 2) in the gas analyzer according to 1) above, a bandpass optical filter that allows the light amount detector to transmit light in the measurement wavelength band and the bandpass light. The absorption type gas analyzer is configured to include a solid-state sensor that detects the amount of light transmitted through the filter and outputs a primary detection signal according to the detection result, and 3) above 1 or 2 above. ) Any of the The gas analyzer according to claim 1, wherein the first optical filter is a measuring component gas filter having a measuring component gas as a filtering element, and the second optical filter is a simple air layer and the filtering element is an inert gas filter. An absorption gas analyzer was configured as either one of the above.

Therefore, with the above configuration, the secondary detection signal can be converted into a signal corresponding to the amount of light absorption in the specific wavelength band by the measurement component gas in the measurement cell.
After all, the concentration of the measurement component gas in the analyzed gas can be measured by the secondary detection signal. Then, in this case, even if the kind of the interference gas as the gas other than the measurement component gas having the peak of the absorption characteristic in the measurement wavelength band changes, the above-described light amount detection mechanism 16 including two light amount detectors is used. It is clear that the density measurement can be normally performed without changing the configuration of the corresponding light amount detection mechanism. Therefore, according to the above-described configuration of the present invention, the light amount detection mechanism can be easily manufactured without causing an interference error. A gas analyzer is obtained. Then, further, when the gas analyzer is configured as described above, it is also clear that it is not necessary to extremely narrow the bandwidth of the measurement wavelength band corresponding to the above-mentioned light transmission wavelength band Δλ1, so that the present invention According to the constitution (1), the bandpass optical filter constituting the light quantity detector can be easily manufactured, and therefore, the present invention has an effect that the absorption type gas analyzer can be mass-produced economically and the gas concentration measurement can be performed. There is an effect that the accuracy of can be improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment shown in FIG.

3 is an operation explanatory view different from the operation explanatory view shown in FIG. 2 of the embodiment shown in FIG.

FIG. 4 is an operation explanatory diagram different from each of the operation explanatory diagrams shown in FIGS. 2 and 3 of the embodiment shown in FIG. 1;

FIG. 5 is a vertical cross-sectional view of a main part of a conventional infrared gas analyzer

FIG. 6 is an operation explanatory diagram of infrared gas analysis shown in FIG.

[Explanation of symbols]

1 light source 1a luminous flux 2 measuring cells 3 optical paths 4 gas to be analyzed 17 Infrared gas analyzer (absorption type gas analyzer) 19 Bandpass optical filter 20 Solid-state sensor 20a Primary detection signal 20b Primary detection signal 21 Light intensity detector 22 Operation part 22a Secondary detection signal 23 Measurement component gas filter (first optical filter) 24 Inert gas filter (second optical filter) Δλm Measurement wavelength band Δλs Specific wavelength band

Claims (3)

[Claims] 1. A light source section for emitting a light flux, a measurement cell arranged in the optical path through which the light flux passes and into which an analyte gas is introduced, and light occupied by at least one specific peak in the absorption characteristic of a measurement component gas. Two light amount detectors that detect the amount of light in a predetermined measurement wavelength band including a specific wavelength band that is a wavelength band and output a primary detection signal according to the detection result, and the measurement cell in the middle of the optical path. A first optical filter arranged so as to be in series with said measurement wavelength band and absorbing light only in said specific wavelength band, and arranged so as to be in series with said measurement cell in the middle of said optical path and said measurement A second optical filter that does not substantially absorb the light in the wavelength band or that absorbs the light with substantially the same absorptance over the entire measurement wavelength band; An absorption type gas for calculating the concentration of the measurement component gas in the gas to be analyzed by calculating a difference between the signals and outputting a secondary detection signal according to the calculation result. An analyzer, wherein the measurement cell is configured such that the light flux passes through the measurement cell together with the gas to be analyzed in the measurement cell, and the both light quantity detectors are provided in one of the light quantity detectors. And the first optical filter, the luminous flux is incident, and the light amount detector on the other side is arranged so that the luminous flux transmitted through the measurement cell and the second optical filter is incident. Gas analyzer. 2. The gas analyzer according to claim 1, wherein the light amount detector detects a bandpass optical filter for transmitting light in a measurement wavelength band, and detects the amount of the light transmitted through the bandpass optical filter. An absorption gas analyzer, comprising: a solid-state sensor that outputs a primary detection signal according to a detection result. 3. The gas analyzer according to claim 1 or 2, wherein the first optical filter is a measurement component gas filter having a measurement component gas as a filtering element, and the second optical filter is An absorptive gas analyzer characterized in that it is either one of a simple air layer and an inert gas filter using the filtering element as an inert gas.