WO2024019029A1 - Gas analyzing device - Google Patents

Abstract

The present invention is provided with: a multi-reflection cell 30 into which sample gas comprising a plurality of components is introduced; a first analyzing mechanism 10 that causes first light to enter the multi-reflection cell 30, that detects the first light passed through the multi-reflection cell 30, and that analyzes the components of the sample gas according to a first principle; and a second analyzing mechanism 20 that causes second light to enter the multi-reflection cell 30, that detects the second light passed through the multi-reflection cell, and that analyzes the components of the sample gas according to a second principle, which is different from the first principle.

Description

gas analyzer

The present invention relates to a gas analyzer using a multiple reflection cell.

Conventionally, gas analyzers for analyzing components contained in sample gas include those using multiple reflection cells such as White cells and Herriot cells. Various types of multiple reflection cells are used depending on the principle used. For example, a white cell is used when analyzing multiple components in a sample gas by Fourier Transform Infrared Spectroscopy (FTIR) (see Patent Document 1). Further, when analyzing components in a sample gas by laser absorption spectroscopy (LAS), for example, a Herriot cell is used.

Incidentally, although FTIR allows broad spectrum measurement and simultaneous analysis of a very large number of components, it is inferior in performance, for example, in terms of sensitivity, when compared to laser absorption spectroscopy. On the other hand, laser absorption spectroscopy allows component analysis at high speed and high sensitivity, but because it uses laser light, component analysis is performed in a limited wavenumber range compared to FTIR, and the number of components that can be analyzed simultaneously is small. Become. In other words, each principle has different performance items that it is good at or bad at. Therefore, in order to compensate for the shortcomings in each principle, it is conceivable to use two gas analyzers, one for FTIR and one for laser absorption spectroscopy.

However, simply using two gas analyzers, each with a different principle, not only increases costs, but also causes problems with the analysis results of each gas analyzer. Specifically, if multiple analysis cells of each gas analyzer are installed in series (serial), there will be a time difference in each analysis result, whereas if multiple analysis cells of each analyzer are installed in parallel (parallel), it will be difficult to measure the same sample. do not become.

Japanese Patent Application Publication No. 2020-094990

The present invention has been made in view of the above-mentioned problems, and provides a gas analyzer that can minimize the time difference in analysis results using a plurality of different principles and also enables analysis of the same sample. The purpose is to

That is, the gas analyzer according to the present invention includes a multiple reflection cell into which a sample gas consisting of a plurality of components is introduced, and a first light incident on the multiple reflection cell to analyze the inside of the multiple reflection cell. a first analysis mechanism that detects the first light that has passed through and analyzes the components of the sample gas according to a first principle; The apparatus is characterized by comprising a second analysis mechanism that detects second light that has passed through the sample gas and analyzes the components of the sample gas based on a second principle different from the first principle.

In such a case, the first light and the second light are introduced into one multi-reflection cell, and the first light and the second light that pass through the multi-reflection cell are different from each other. Since components can be analyzed based on the principles, it is possible to almost eliminate the time difference between analyzes based on each principle, and it is also possible to analyze the same sample. In addition, since there is no need to prepare separate gas analyzers for the first principle and the second principle, it is easier to configure an integrated operation system as a system, and it is also possible to improve operability. . In addition, since the multiple reflection cell is shared by each principle, costs can be reduced compared to simply preparing two gas analyzers.

In order to be able to simultaneously measure a large number of components and also to measure specific components of interest at high speed and high sensitivity, the first principle is Fourier transform infrared spectroscopy, and the second principle is Fourier transform infrared spectroscopy. Any method (laser absorption spectroscopy) may be used. If this is the case, a large number of components can be analyzed using Fourier transform infrared spectroscopy (FTIR), and the components of particular interest can be analyzed using laser absorption spectroscopy (LAS), which is fast and highly sensitive. analysis becomes possible. In addition, since FTIR can analyze components other than those targeted by LAS, it is possible to correct the coexistence or interference effects of other components on the analysis results for a given component obtained by LAS to obtain more accurate analysis results. is also possible.

In order to be able to perform analysis by, for example, FTIR and LAS using one multiple reflection cell, the multiple reflection cell is provided in a cell body into which the sample gas is introduced into an internal space, and a cell body in which the sample gas is introduced into the internal space. the cell body includes a light introduction window through which the first light is introduced into the cell body; and the cell body includes a light introduction window through which the first light is introduced into the cell body; A light emitting window is formed through which the first light that has passed is guided out of the cell main body, and the multiple reflection mechanism includes a field mirror, which faces the field mirror, and is located on the light incident side of the multiple reflection mechanism. Any configuration may be used as long as it includes a first objective mirror provided therein, and a second objective mirror provided on the light exit side of the multiple reflection mechanism while facing the field mirror.

The first light and the second light are simultaneously introduced into the multiple reflection cell so that each component of the sample gas can be analyzed without creating a time difference between the first principle and the second principle. The first analysis mechanism includes a first light source that emits first light that is continuous light that includes light of a plurality of wave numbers, and a first light detection device that detects the first light that has passed through the multiple reflection cell. The second analysis mechanism includes a second light source that emits a second light that is a laser beam, and a second photodetector that detects the second light that has passed through the multiple reflection cell. It is fine as long as it is something.

In order to make the first light and the second light pass through the same point at the same time in the multi-reflection cell to minimize the time difference in analysis, the second analysis mechanism: The second light emitted from the second light source is introduced into the cell main body through the light introduction window, and the second photodetector detects the second light emitted from the light exit window. It is fine as long as it has been done.

Preventing the first light from entering the second photodetector so that the analysis results based on the second principle are not influenced by the first light, thereby improving the accuracy of the analysis based on the second principle. In the second analysis mechanism, the second light emitted from the second light source is introduced into the cell main body from the light guide window, and the second light emitted from the light guide window is introduced into the cell body. Any device configured to be detected by two photodetectors may be used.

As a specific optical path configuration for simultaneously introducing the first light and the second light into the multiple reflection cell, the first analysis mechanism includes an interferometer into which the light emitted from the first light source enters. an entrance mirror that reflects the first light that has passed through the interferometer and makes it enter the light introduction window; and an entrance mirror that reflects the first light that is emitted from the light exit window and makes it enter the first photodetector. An example of the light emitting device further includes an exit side mirror through which the second light enters, and the entrance side mirror and the exit side mirror are formed with a light passage hole for allowing the second light to pass therethrough.

In order to further reduce the cost of the gas analyzer by reducing the number of detectors required to perform the analysis based on the first principle and the second principle, the first analysis mechanism: The second analysis mechanism includes a first light source that emits first light that is continuous light that includes light of a plurality of wave numbers, and an interferometer that receives the light emitted from the first light source, and the second analysis mechanism includes: A second light source that emits a second light that is a laser beam is provided, and the first light or the second light that has passed through the multiple reflection cell is detected by one common photodetector. It is fine as long as it has been done.

In order to perform analysis based on each principle with high accuracy using only one photodetector, the method further includes a concentration calculation unit that calculates the concentration of the component in the sample gas based on the output of the common photodetector. , the concentration calculation unit calculates the concentration of one or more components in the sample gas by Fourier transform infrared spectroscopy (FTIR) while the movable mirror of the interferometer is moving; While the sample gas is stopped, the concentration of one or more components in the sample gas may be calculated by laser absorption spectroscopy (LAS).

If the device is further equipped with a pressure control mechanism that controls the pressure of the sample gas in the multi-reflection cell according to the principle used in the concentration calculation section, the analysis accuracy can be improved by adjusting the pressure suitable for each principle. can be improved.

In a preferred embodiment of the pressure control, the pressure control mechanism is configured to lower the pressure of the sample gas while the movable mirror is stopped than when the movable mirror is moving. can be mentioned.

In order to easily improve analysis accuracy by using the interferometer to calibrate the wavelength of the second light, which is a laser beam emitted from the second light source, a measurement optical path in which the second light from the second light source bypasses the interferometer and enters the multi-reflection cell; and an adjustment optical path in which the second light emitted from the second light source enters the interferometer. Any device may be used as long as it further includes an optical path switching mechanism that switches the optical path between the two.

In order to further improve the analysis accuracy based on each principle by individually setting optical path lengths suitable for the first principle and the second principle in the multiple reflection cell, the multiple reflection cell , further comprising a pair of reflection mirrors provided in the cell body separately from the multiple reflection mechanism, and after the second light emitted from the second light source is multiple-reflected by the pair of reflection mirrors, It may be of any type as long as it is configured to be emitted from the multiple reflection cell to the outside.

For example, in order to be able to perform analysis based on further principles such as NDIR, and to make it easier to correct coexistence effects or interference effects, it is possible to pass through the multiple reflection cell without being reflected within the multiple reflection cell. Any device may be used as long as it further includes a third light source that emits third light so as to do so, and a third photodetector that detects the third light that has passed through the multiple reflection cell. If this is the case, there may be interference effects that cause errors in the calculated concentration when the absorption wavelength bands of each target component overlap, or even if the absorption wavelength bands of each target component do not overlap. It is also possible to correct for coexistence effects that cause errors in calculated concentrations simply due to the presence of components.

In this way, with the gas analyzer according to the present invention, the first light and the second light are introduced into the multiple reflection cell, and each of the first light and the second light that has passed through the multiple reflection cell is Components can be analyzed using different principles. In other words, since there is no need to prepare separate multiple reflection cells for each principle, it is possible to substantially eliminate the time difference in analysis for each principle, and it is also possible to analyze the same sample. In addition, since only one multi-reflection cell is required, costs can be reduced compared to the case of preparing two gas analyzers for analysis based on each principle, and interfaces etc. can be integrated as an analysis system. becomes easier.

FIG. 1 is a schematic diagram showing a gas analyzer according to a first embodiment of the present invention. FIG. 1 is a schematic diagram showing the structure of a multiple reflection cell according to the first embodiment. FIG. 3 is a schematic diagram showing a method of modulating a laser oscillation wavelength in the same embodiment. The time series graph which shows an example of the oscillation wavelength, optical intensity I(t), logarithmic intensity L(t), characteristic signal F _i (t), and correlation value S _i in the same embodiment. FIG. 3 is a diagram showing a conceptual diagram of concentration or partial pressure calculation using an individual correlation value and a sample correlation value of the same embodiment. FIG. 3 is a schematic diagram showing a modification of the gas analyzer according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing a gas analyzer according to a second embodiment of the present invention. FIG. 7 is a timing chart showing that analysis based on each principle is performed alternately in the second embodiment. FIG. 5 is a timing chart showing aspects of batch measurement in a modified example of the second embodiment. FIG. 7 is a schematic diagram showing the configuration of a gas analyzer in another modification of the second embodiment. FIG. 7 is a schematic diagram showing a state in which the gas analyzer according to the third embodiment of the present invention is switched to the measurement optical path. FIG. 7 is a schematic diagram showing a state in which the gas analyzer according to the third embodiment is switched to an adjustment optical path. FIG. 4 is a schematic diagram showing a gas analyzer according to a fourth embodiment of the present invention. FIG. 7 is a schematic diagram showing a gas analyzer according to a fifth embodiment of the present invention. FIG. 7 is a schematic diagram showing a configuration around a multiple reflection cell according to a fifth embodiment of the present invention. FIG. 3 is a schematic diagram showing a configuration around a multiple reflection cell according to another embodiment of the present invention.

A gas analyzer 100 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The gas analyzer 100 of the first embodiment analyzes target components (here, for example, CO, CO ₂ , N ₂ O, NO, NO ₂ , H ₂ O) contained in a sample gas such as exhaust gas from an internal combustion engine. , SO ₂ , CH ₄ , NH ₃ , etc.). This gas analyzer 100 is configured to be able to measure the concentration of a component to be analyzed using two different principles by introducing two types of light into one multiple reflection cell 30 into which a sample gas is introduced. .

Here, "principle" refers to, for example, the qualitative analysis of an analyte component in a sample gas, the quantitative determination of an analyte component, the detection of the presence or absence of an analyte component, or the analysis to measure the temperature of an analyte component or a sample gas. I'm talking about principles.

Specifically, as shown in FIG. 1, the gas analyzer 100 includes a multiple reflection cell 30, a first analysis mechanism 10 for performing gas analysis by Fourier transform infrared spectroscopy (hereinafter also referred to as FTIR), a second analysis mechanism 20 for performing gas analysis by infrared laser absorption modulation method (hereinafter also referred to as IRLAM), which is a type of laser absorption spectroscopy (hereinafter also referred to as LAS); It includes an information processing device COM that controls each device. The first analysis mechanism 10 and the second analysis mechanism 20 respectively introduce the first light and the second light into the multiple reflection cell 30, and the first light and the second light that have passed through the multiple reflection cell 30. Each is configured to be detected individually. Furthermore, the first analysis mechanism 10 and the second analysis mechanism 20 share an optical path at least within the multiple reflection cell 30.

Here, in the second principle, infrared laser absorption modulation method (see Patent No. 6886507; IRLAM (Infrared Laser Absorption Modulation), the feature value is calculated from the light intensity signal obtained by irradiating the sample gas with laser light. is extracted, and the concentration of the target component in the sample gas is calculated by performing a least squares calculation using the feature amount.

As shown in FIG. 2, the multiple reflection cell 30 is a so-called white cell, and includes a cell body 31 into which a sample gas is introduced into an internal space, and a cell body 31 which is provided in the internal space and emits incident light to the outside after multiple reflections. A multiple reflection mechanism 32 is provided.

The cell body 31 has a generally hollow cylindrical shape, and one end face of the cell body 31 has a light introduction window 36 through which the first light is introduced into the cell body 31 and a light through which the first light passes through the multiple reflection mechanism 32. Light emitting windows 37 through which the first light is emitted to the outside of the cell main body 31 are formed side by side. Further, the cell body 31 is provided with a gas introduction hole and a gas outlet hole (neither of which are shown) for introducing and deriving a sample gas. Further, a pressure gauge (not shown) for measuring the pressure of the sample gas within the cell body 31 is provided in the cell body or on an inlet path or an outlet path communicating with the cell body.

The multiple reflection mechanism 32 is composed of three spherical mirrors, including a field mirror 33 disposed on the end face side where the light introduction window 36 and the light output window 37 are formed in the cell body 31; a first objective mirror 34 facing the field mirror 33 and provided on the light incidence side of the multiple reflection mechanism 32; and a second objective mirror 35 facing the field mirror 33 and provided on the light exit side of the multiple reflection mechanism 32. , is provided. Further, the first objective mirror 34 and the second objective mirror 35 are arranged within the cell body 31 on the opposite end surface side from the end surface where the light introduction window 36 and the light output window 37 are formed. By adjusting the angle of the first objective mirror 34 or the second objective mirror 35 with respect to the field mirror 33, the number of reflections of light between each mirror can be changed. In the first embodiment, the light entering from the light introduction window 36 first enters the first objective mirror 34 and is finally reflected by the second objective mirror 35 to reach the light exit window 37. Note that the configuration may be such that the light incident from the light introduction window 36 first enters the second objective mirror 35 and is finally reflected by the first objective mirror 34 and reaches the light exit window 37.

Here, the multiple reflection cell 30 has a configuration suitable for performing analysis by FTIR, for example, but it is also possible to perform analysis by IRLAM using laser light.

The first analysis mechanism 10 is equipped with a first light source 11, an interferometer IF, and a first photodetector 18, as shown in FIG.

The first light source 11 emits light with a broad spectrum (continuous light including light of many wave numbers) as the first light, and uses, for example, a tungsten-iodine lamp or a high-intensity ceramic light source. A light guide mirror 12 is provided between the first light source 11 and the interferometer IF to reflect the first light emitted from the first light source 11 and make it enter the interferometer IF. In the first embodiment, the light guiding mirror 12 is, for example, a parabolic mirror provided so as to bend the optical axis of the first light emitted from the first light source 11 by 90 degrees.

The interferometer IF utilizes a so-called Michelson interferometer, which is equipped with one half mirror 13 (beam splitter), a fixed mirror 14, and a movable mirror 15. The first light from the first light source 11 that enters the interferometer IF is split by the half mirror 13 into reflected light and passing light. One of the lights is reflected by the fixed mirror 14, and the other is reflected by the movable mirror 15, returns to the half mirror 13 again, is combined, and is emitted from the interferometer IF. An incident-side mirror 16 is provided between the exit of the interferometer IF and the multiple reflection cell 30 to guide the first light that has passed through the interferometer IF to the light introduction window 36 of the multiple reflection cell 30. The incident side mirror 16 is, for example, a parabolic mirror, and reflects the first light once so that the optical axis of the first light is obliquely incident on the light introduction window 36 at a predetermined angle.

The first photodetector 18 detects the first light output from the multiple reflection cell 30, and is configured such that the incident light intensity is linear with the output value within a predetermined range and nonlinear in other ranges. For example, it is a photodetector called an MCT photodetector. Based on the spectrum of the first light detected by the first photodetector 18, the concentrations of many components in the sample gas are calculated by FTIR.

Furthermore, an exit side mirror 17 is provided between the multiple reflection cell 30 and the first photodetector 18 to guide the first light that has passed through the multiple reflection cell 30 to the first photodetector 18. The exit side mirror 17 is a parabolic mirror configured to reflect the first light led out from the light guide window 37 twice so that its optical axis has a crank shape, and guide it to the first photodetector 18. be.

The second analysis mechanism 20 includes a second light source 21 that emits second light that is a laser beam, and a second photodetector 22 that detects the second light that has passed through the multiple reflection cell 30.

The second light source 21 is a quantum cascade laser (QCL) and oscillates a mid-infrared (4 μm to 10 μm) laser beam. This second light source 21 is capable of modulating (changing) the oscillation wavelength by applying a current (or voltage). Note that other types of lasers may be used as long as the oscillation wavelength is variable, and the temperature may be changed in order to change the oscillation wavelength.

The second light source 21 is provided so as to sandwich the above-mentioned incident side mirror 16 between it and the light introduction window 36 of the multiple reflection cell 30, and the second light emitted from the second light source 21 passes through the incident side mirror 36. The light is configured to enter the light introduction window 36 of the multiple reflection cell 30 through the light passage hole 2H formed in the light beam 16 .

The second photodetector 22 uses a relatively inexpensive thermal type such as a thermopile, but it also uses other types of photodetectors, such as quantum type photoelectric elements such as HgCdTe, InGaAs, InAsSb, and PbSe, which have good responsiveness. You may also use The second photodetector 22 is provided so as to sandwich the above-mentioned exit side mirror 17 between it and the light exit window 37 of the multiple reflection cell 30, and the second light emitted from the light exit window 37 is transmitted to the exit side mirror 17. The light passes through a light passage hole 2H formed in , and reaches the second detector.

By forming the respective optical paths of the first light and the second light in this way, the first light and the second light simultaneously travel through the multiple reflection cell 30, and each of the first light and the second light travels through the first photodetector. 18. Each intensity can be measured almost simultaneously with the second photodetector 22.

The information processing device COM is equipped with an analog electric circuit consisting of buffers, amplifiers, etc., a digital electric circuit consisting of a CPU, memory, etc., and an A/D converter, a D/A converter, etc. that mediate between these analog/digital electric circuits. By the cooperation of the CPU and its peripheral devices according to a predetermined program stored in a predetermined area of the memory, it functions as a concentration calculation section 40 and a light source control section 43 as shown in FIG. .

The concentration calculation unit 40 includes an FTIR unit 41 that calculates the concentration of each component of the sample gas by FTIR based on the absorbance of the first light, and an FTIR unit 41 that calculates the concentration of each component of the sample gas by IRLAM based on the absorbance of the second light. It includes at least an IRLAM unit 42 that calculates the concentration of the component.

The FTIR unit 41 calculates the spectrum of light that has passed through the sample gas from the output value indicated by the detection signal of the first photodetector 18, and analyzes the sample gas by determining the absorbance of light at each wave number from this optical spectrum. . The FTIR section 41 calculates the optical spectrum as follows.

When the movable mirror 15 is moved back and forth and the light intensity of the first light that has passed through the sample gas is observed with the position of the movable mirror 15 as the horizontal axis, in the case of single wave number light, the light intensity draws a sine curve due to interference. On the other hand, the first light that has passed through the sample gas has many wave numbers, and the sine curve is different for each wave number, so the actual light intensity is a superposition of the sine curves drawn by each wave number, and the interference pattern ( interferogram) is in the form of a wave packet.

The FTIR section 41 determines the position of the movable mirror 15 using a range finder (not shown) such as a HeNe laser, and detects the light intensity of the first light at each position of the movable mirror 15 as the output of the first photodetector 18. By performing a fast Fourier transform (FFT) on the interference pattern obtained from these, it is converted into an optical spectrum with each wavenumber component as the horizontal axis and the optical intensity signal as the vertical axis. Finally, the FTIR section 41 calculates the concentration of each component corresponding to each wave number based on the obtained optical spectrum.

Next, the IRLAM section 42 and the light source control section 43 will be explained.

The light source control unit 43 controls at least the current source (or voltage source) of the second light source 21 by outputting a current (or voltage) control signal. Specifically, the light source control unit 43 changes the drive current (or drive voltage) of the second light source 21 at a predetermined frequency, and changes the oscillation wavelength of the laser beam output from the second light source 21 at a predetermined frequency with respect to the center wavelength. (See Figure 3). As a result, the second light source 21 emits modulated light modulated at a predetermined modulation frequency.

In this embodiment, the light source control unit 43 changes the drive current in a triangular waveform and modulates the oscillation frequency in a triangular waveform (see "oscillation wavelength" in FIG. 4). In reality, the drive current is modulated using a different function so that the oscillation frequency becomes a triangular wave. Further, as shown in FIG. 3, the oscillation wavelength of the laser beam is modulated with the peak of the optical absorption spectrum of the component to be measured as the center wavelength. In addition, the light source control unit 43 may change the drive current in a sine wave shape, a sawtooth wave shape, or an arbitrary function shape, and modulate the oscillation frequency in a sine wave shape, a sawtooth wave shape, or an arbitrary function shape.

The IRLAM unit 42 includes a logarithm calculation unit 42a, a correlation value calculation unit 42b, a storage unit 42c, a density output unit 42d, and the like.

The logarithm calculation unit 42a performs a logarithm calculation on the light intensity signal, which is the detection signal of the photodetector 23. The function I(t) indicating the change over time of the light intensity signal obtained by the photodetector 23 becomes "light intensity I(t)" in FIG. Logarithmic intensity L(t).

The correlation value calculation unit 42b calculates a correlation value between an intensity-related signal related to the intensity of sample light obtained when measuring a sample gas and a plurality of predetermined characteristic signals. The feature signal is a signal for extracting waveform features of the intensity-related signal by correlating with the intensity-related signal. As the characteristic signal, various signals can be used, such as a sine wave signal or other signals that match the waveform characteristics to be extracted from other intensity-related signals. Here, the correlation value calculation unit 42b uses the logarithmically calculated light intensity signal (logarithmic intensity L(t)) as the intensity-related signal.

Further, the correlation value calculation unit 42b calculates a number of feature signals F _i (t) (i=1 , 2, _. It is something. Note that T in Equation 1 is the modulation period.

When calculating the sample correlation value, the correlation value calculation unit 42b calculates the reference light from the correlation value S _i between the intensity-related signal L(t) of the sample light and the plurality of characteristic signals F _i (t), as shown in Equation 1. It is desirable to calculate a sample correlation value S _i ′ that is corrected by subtracting a reference correlation value R _i that is a correlation value between the intensity-related signal L ₀ (t) and the plurality of feature signals F _i (t). As a result, the offset included in the sample correlation value is removed, and the correlation value becomes proportional to the concentration of the measurement target component and the interference component, thereby reducing measurement errors. Note that a configuration may be adopted in which the reference correlation value is not subtracted.

Here, the acquisition timing of the reference light is at the same time as the sample light, before or after the measurement, or at any timing. The intensity-related signal or reference correlation value of the reference light may be acquired in advance and stored in the storage unit 42c. Further, a method of simultaneously acquiring the reference light is, for example, by providing two second photodetectors 22, splitting the modulated light from the second light source 21 using a beam splitter, and using one for measuring the sample light. It is conceivable to use the other one for reference light measurement.

In this embodiment, the correlation value calculation unit 42b uses a function that is easier to capture the waveform feature of the logarithmic strength L(t) than a sine function as the plurality of feature signals F _i (t). In the case of a sample gas containing a component to be measured and one interference component, it is possible to use two or more characteristic signals F ₁ (t), F ₂ (t), and two characteristic signals F ₁ (t) , F ₂ (t), it is conceivable to use, for example, a function based on a Lorentz function that is close to the shape of the absorption spectrum, and a differential function of the function based on the Lorentz function. Furthermore, instead of a function based on a Lorentz function, a function based on a Voigt function, a function based on a Gaussian function, or the like may be used as the feature signal. By using such a function for the feature signal, a larger correlation value can be obtained than when a sine function is used, and measurement accuracy can be improved.

Here, it is desirable to remove the DC component of the characteristic signal, that is, adjust the offset so that it becomes zero when integrated over the modulation period. By doing so, it is possible to eliminate the influence of an offset added to the intensity-related signal due to fluctuations in light intensity. Note that instead of removing the DC component of the feature signal, the DC component of the intensity-related signal may be removed, or the DC component of both the feature signal and the intensity-related signal may be removed. In addition, sample values of absorption signals of measurement target components and/or interference components, or values imitating them may be used as the characteristic signals.

Note that by setting the two feature signals F ₁ (t) and F ₂ (t) to be orthogonal function sequences that are orthogonal to each other or a function sequence that is close to orthogonal function sequences, the feature of logarithmic strength L(t) can be more efficiently obtained. Therefore, the concentration obtained by simultaneous equations described later can be obtained with high accuracy.

The storage unit 42c stores unit concentrations of the measurement target component and each interference component obtained from the respective intensity-related signals and the plurality of characteristic signals F _i (t) when the measurement target component and each interference component exist alone. It stores the single correlation value that is the winning correlation value. The plurality of feature signals F _i (t) used to obtain this single correlation value are the same as the plurality of feature signals F _i (t) used in the correlation value calculation section 42b.

Here, when storing the independent correlation value, the storage unit 42c subtracts the reference correlation value from the correlation value when the measurement target component and each interference component exist alone, and then performs a correction to convert it per unit concentration. It is desirable to store the single correlation value. As a result, the offset included in the single correlation value is removed, and the correlation value becomes proportional to the concentration of the measurement target component and the interference component, thereby reducing measurement errors. Note that a configuration may be adopted in which the reference correlation value is not subtracted.

Note that the independent correlation value of the interference component stored in the storage unit 42c may be a value calculated based on the concentration of the interference component measured by FTIR by the first analysis mechanism 10, for example. By doing so, it becomes possible to further improve the accuracy of measurement of the concentration of the target component by the IRLAM performed by the second analysis mechanism 20 by using the measurement results of the concentration of the interference component by the first analysis mechanism 10.

The concentration output unit 42d calculates the concentration of the component to be measured using the plurality of sample correlation values obtained by the correlation value calculation unit 42b.

Specifically, the concentration output section 42d calculates the concentration of the component to be measured based on the plurality of sample correlation values obtained by the correlation value calculation section 42b and the plurality of single correlation values stored in the storage section 42c. It is something. More specifically, the concentration output unit 42d outputs a plurality of sample correlation values obtained by the correlation value calculation unit 42b, a plurality of individual correlation values stored in the storage unit 42c, and each of the measurement target component and each interference component. The concentration of the component to be measured is calculated by solving simultaneous equations consisting of the concentration and concentration. Note that FIG. 5 shows a conceptual diagram of concentration or partial pressure calculation using the single correlation value and sample correlation value in the concentration output section 42d.

When the sample gas contains one measurement target component and one interference component, the concentration output unit 42d outputs the sample correlation values S _{1 ′} , S ₂ ′ calculated by the correlation value calculation unit 42 b, and the storage unit The following two-dimensional simultaneous equations consisting of the independent correlation values s _1t , s _2t , s _1i , s _2i of 42c and the concentrations C _tar , C _int of the component to be measured and each interference component are solved. Note that s _1t is the single correlation value of the component to be measured in the first feature signal, s _2t is the single correlation value of the component to be measured in the second feature signal, and s _1i is the single correlation value of the interference component in the first feature signal. The value s _2i is the single correlation value of the interference component in the second feature signal.

As a result, the concentration C _tar of the component to be measured from which interference effects have been removed can be determined by simple and reliable calculation of solving the simultaneous equations of the above equation (Equation 2).

Note that even if it can be assumed that two or more interference components exist, the interference effect can be similarly eliminated by adding as many independent correlation values as the number of interference components and solving simultaneous equations with the same number of elements as the number of component types. The concentration of the removed component to be measured can be determined.

According to the gas analyzer 100 of the first embodiment configured in this way, the optical path of the first analysis mechanism 10 for performing FTIR analysis and the second analysis mechanism 20 for performing IRLAM analysis is Since one multiple reflection cell 30 is used in common, analysis of a sample gas by FTIR and analysis of the same sample gas by IRLAM can be performed simultaneously without any time difference.

Furthermore, while the concentration of many components in the sample gas can be measured by FTIR, the concentration of the component of interest can be measured at high speed and with high sensitivity by IRLAM. In other words, the performance items that FTIR and IRLAM are weak in can be compensated for, and multi-component concentration measurement and high-sensitivity measurement can be made compatible.

Furthermore, since analysis by FTIR and analysis by IRLAM can be performed with one multi-reflection cell 30, the entire gas analyzer 100 can be made compact and its introduction cost can be reduced. In addition, since the measurements of each principle can be realized with one CPU, it is easy to integrate the user interface, etc., and it is possible to improve the usability even though it is a multi-functional analysis.

Next, a modification of the first embodiment will be described with reference to FIG. 6.

In the first embodiment, the laser light, which is the second light emitted from the second light source 21, travels in the same direction as the first light, and enters the multiple reflection cell 30 from the light introduction window 36. Although the second light is configured to be emitted to the outside from the light emitting window 37, the second light may be configured to travel in the opposite direction to the first light, as shown in FIG. That is, the second light emitted from the second light source 21 enters the interior through the light guide window 37 of the multiple reflection cell 30, is multiple reflected at the multiple reflection mechanism 32, and is then output to the outside through the light introduction window 36. It may also be configured such that the second photodetector 22 detects the detected light.

With the gas analyzer 100 configured in this way, it becomes difficult for the first light to enter the second photodetector 22, and the output of the second photodetector 22 comes from only the second light. can. Therefore, since the influence of the first light can be largely eliminated, it is possible to further improve the accuracy of analysis by IRLAM.

Next, a gas analyzer 100 according to a second embodiment of the present invention will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7, in the gas analyzer 100 according to the second embodiment, the first analysis mechanism 10 and the second analysis mechanism 20 each have a photodetector. They differ in that they share one photodetector, rather than having one. Specifically, the first photodetector 18 in the first embodiment is used as a shared photodetector CD in the second embodiment, and in the second embodiment, only the incident side mirror 16 is provided with light from the second light source 21. A light passage hole 2H is formed through which a laser beam, which is the second light to be emitted, passes. Therefore, in the second embodiment, not only the first light but also the second light is reflected by the exit side mirror 17 and is detected by the shared photodetector CD.

Further, in the first embodiment, the FTIR section 41 and the IRLAM section 42 always output the concentration of the component at the same time, but in the second embodiment, the FTIR section 41 and the IRLAM section 42 are configured to output the concentration alternately. ing. That is, in the concentration calculating section 40 of the second embodiment, only either the FTIR section 41 or the IRLAM section 42 outputs the concentration according to the movement of the movable mirror 15, as shown in the timing chart of FIG. More specifically, the concentration calculation unit 40 stops the movable mirror 15 at the closest point or the farthest point from the half mirror 13 for a predetermined period of time, performs the IRLAM analysis, and after the IRLAM analysis is completed, the movable mirror 15 FTIR analysis is performed while moving at a constant speed. In other words, the concentration calculation unit 40 is configured to change the position of the movable mirror 15 with respect to time in a substantially trapezoidal manner, and to alternately perform analysis by FTIR and analysis by IRLAM.

According to the gas analyzer 100 of the second embodiment configured as described above, analysis by FTIR and analysis by IRLAM can be performed on the same sample using only one shared photodetector CD and one multiple reflection cell 30. This can be done at approximately the same time. Therefore, it is possible to realize substantially the same analysis as in the first embodiment while reducing the number of components of the gas analyzer 100 and reducing costs.

Next, a modification of the batch measurement of the second embodiment will be described with reference to FIG. 9. In this modification, FTIR analysis is performed while the movable mirror 15 is reciprocated multiple times, and after the FTIR analysis is completed, the movable mirror 15 is stopped for a predetermined time and IRLAM analysis is performed. In addition, this modification further includes a pressure control mechanism (not shown) that controls the pressure of the sample gas within the multiple reflection cell 30, and is configured to change the pressure in accordance with the analysis of each principle. The pressure control mechanism includes, for example, the above-mentioned pressure gauge, a control valve (not shown) provided in either or both of the sample gas introduction path and/or outlet path connected to the cell body, and the pressure gauge. It includes a pressure controller (not shown) that performs pressure feedback control of the opening degree of the control valve so that the measured pressure becomes the set pressure. Specifically, the pressure control mechanism controls the pressure of the sample gas so that the pressure of the sample gas during the IRLAM analysis is lower than the sample gas pressure during the FTIR analysis. Therefore, as shown in FIG. 9, the pressure of the sample gas is configured to repeatedly rise and fall periodically.

With such a device, the analysis can be performed with the pressure of the sample gas adjusted to the optimum value in the analysis of each principle, so that the accuracy of the analysis of each principle can be further improved.

Next, a modification of the optical system of the second embodiment will be described with reference to FIG. 10. In this modification, a small reflecting mirror 23 is arranged on the optical path of the first light without forming a light passing hole 2H in the incident side mirror 16 for passing the laser light which is the second light. The configuration is such that the second light emitted from the light source 21 is reflected by the incident side mirror 16 and enters the light introduction window 36.

Even with such a case, if the area where the small reflecting mirror 23 blocks the first light is made sufficiently small, it will be possible to perform IRLAM analysis while having almost no effect on FTIR analysis. .

Next, a gas analyzer 100 according to a third embodiment of the present invention will be described with reference to FIGS. 11 and 12. The gas analyzer 100 of the third embodiment is configured to be able to calibrate the second light emitted from the second light source 21 using the interferometer IF of the first analysis mechanism 10. That is, the gas analyzer 100 of the third embodiment has a measurement optical path L1 in which the second light emitted from the second light source 21 shown in FIG. 11 bypasses the interferometer IF and enters the multiple reflection cell 30. , an optical path switching mechanism 50 that switches the optical path to either the adjustment optical path L2 through which the second light emitted from the second light source 21 shown in FIG. 12 enters the interferometer IF. The optical path switching mechanism 50 includes a switching section 51 that includes a pair of mirrors 52 and 53 and is configured to be movable. When the mirrors 52 and 53 of the switching unit 51 are respectively arranged on the optical axis of the second light emitted from the second light source 21 and on the optical axis of the first light on the output side of the interferometer IF, The state is switched to the measurement optical path L1, and the second light bypasses the interferometer IF and directly enters the multiple reflection cell 30. On the other hand, when the switching unit 51 moves so that the mirrors 52 and 53 are not on the optical axis of each light, the light path is switched to the adjustment optical path L2, and the mirrors 52 and 53 are switched to the adjustment fixed mirror 54 fixed near the light guide mirror 12. The second light enters the interferometer IF through the light guide hole formed in the light guide mirror 12. By moving the movable mirror 15 in this state, the interference state of the laser beam can be confirmed on the shared photodetector CD, and the oscillation wavelength can be calibrated.

Next, a gas analyzer 100 according to a fourth embodiment of the present invention will be described with reference to FIG. 13.
In the gas analyzer 100 according to the fourth embodiment, the optical paths of the first light and the second light are not common in the multiple reflection cell 30, and optical path lengths suitable for each principle are realized. It is configured to That is, the multiple reflection cell 30 is provided with both a reflection mechanism as a white cell and a reflection mechanism as a Herriot cell in the cell body 31. Specifically, the multiple reflection cell 30 further includes a pair of reflection mirrors 38 provided within the cell body 31 separately from the multiple reflection mechanism 32, and the second light emitted from the second light source 21 is After being multiple reflected by the reflecting mirror 38, the light is emitted from the multiple reflection cell 30 to the outside. In the fourth embodiment, the direction in which the field mirror 33 faces the first objective mirror 34 and the second objective mirror 35 and the direction in which the pair of reflection mirrors 38 face each other are approximately perpendicular to each other. The second light source 21 emits second light from the side surface of the cell body 31, and the second light is introduced between a pair of reflective mirrors 38 through a port P formed in the center of the reflective mirror, and is multiplexed. After the reflection is completed, the second light is led out to the outside of the cell body 31 again. The second light that has passed through the multiple reflection cell 30 is then guided by the external mirror 24 to the shared photodetector CD.

According to the gas analyzer 100 according to the fourth embodiment, it is possible to individually realize optical path lengths in the multi-reflection cell 30 suitable for each of FTIR and IRLAM, and to optimize analysis accuracy for each principle. It becomes possible.

Next, a gas analyzer 100 according to a fifth embodiment of the present invention will be described with reference to FIG. 14. In the fifth embodiment, one multiple reflection cell 30 is configured so that not only FTIR analysis and IRLAM analysis but also NDIR analysis can be performed simultaneously. That is, this gas analyzer 100 includes a third light source section 61 that emits infrared rays of a predetermined wavelength as third light so as to pass through the multiple reflection cell 30 without being reflected within the multiple reflection cell 30; It further includes a third light detection section 62 that detects the third light that has passed through the reflection cell 30. The third light source section 61 and the third light detection section 62 are arranged to sandwich the side surfaces of the cell body 31, and measure the absorbance of the third light independently of the first analysis mechanism 10 and the second analysis mechanism 20. Measure.

In this embodiment, as shown in FIG. 15, on both sides of the cell body 31 where the reflecting mirrors 33, 34, and 35 are not formed, there is a second light source that introduces the third light emitted from the third light source. A light introducing window 613 and a second light emitting window 623 through which the third light passing through the cell body 31 is guided out of the cell body 31 are formed. This pair of second light introduction window 613 and second light guide window 623 are formed at positions facing each other. In this embodiment, the third light source section 61 and the third light detection section 62 are each configured to form a condensing optical system.

Specifically, the third light source section 61 includes a third light source 611 that emits infrared rays, such as a thermal light source, an infrared LED, or an infrared laser, and a second light source that is in front of the third light source 611 in the light emission direction. A parabolic mirror 612 is arranged at a position facing the light introduction window 612 of the mirror. The light emitted from the third light source 611 is reflected by the reflective surface of the parabolic mirror 612, condensed into substantially parallel light, and guided to the second light introduction window 612. On the other hand, the third photodetector 62 includes a parabolic mirror 622 disposed at a position facing the second light guide window 623 and a third photodetector 621 that detects infrared rays. The light led out from the second light guide window 623 is reflected by the reflective surface of the parabolic mirror 622 and focused onto the detection surface of the third photodetector 621. The third photodetector 621 is preferably a four-element pyrodetector, for example. In this way, it becomes possible to measure a maximum of three components with one third photodetector 621.

In another embodiment, as shown in FIG. 16, a plurality of pairs of third light source section 61 and third light detection section 62 may be provided. In this case, a plurality of pairs (here, two pairs) of second light introduction windows 613 and second light guide windows 623 are formed on both side surfaces of the cell body 31 where the reflecting mirrors 33, 34, and 35 are not formed. may have been done. In this way, if a four-element pyrodetector, for example, is used as the third photodetector 621, it becomes possible to measure six or more components at most in NDIR analysis.

With such a device, it is possible to measure the concentrations of multiple components, and for example, it is possible to perform interference correction or examine the validity of the measurement based on each measurement result.

Other embodiments will be described.

In the third to fifth embodiments, a shared photodetector is used, but similarly to the first embodiment, the first photodetector and the second photodetector are used to detect the first light and the second light individually. It may also be equipped with a photodetector.

The first principle and the second principle are not limited to FTIR and IRLAM, and may be other combinations. For example, the first principle may be NDIR and the second principle may be IRLAM. Further, the second principle is not limited to IRLAM, which is a type of LAS, and may be another LAS such as TDLAS (Tunable diode laser absorption spectroscopy). In short, each principle should be different. Note that the principles using continuous light including light of many wave numbers that can be applied to the first principle or the second principle in the present invention include ultraviolet/visible spectrophotometry, infrared spectrophotometry, and Fourier transform red light. Examples include external spectrophotometry (FTIR), non-dispersive infrared spectrophotometry (NDIR), near-infrared spectrophotometry (NIR), and the like. In addition to LAS, examples of principles using laser light that can be applied to the first principle or the second principle include cavity ring-down spectroscopy (CRDS), cavity enhanced absorption spectroscopy (CEAS), etc. . In addition, the first principle or the second principle is not limited to measuring the intensity of light that has passed through the cell; for example, in photoacoustic spectroscopy (PAS), the wavelength of the sample gas changes periodically. The sample gas may be analyzed by detecting an acoustic signal (pressure fluctuation of the sample gas) generated by irradiation with light using a detector. More specifically, each principle may be combined such that FTIR or LAS is used as the first principle and PAS is used as the second principle.

The multiple reflection cell is not limited to those described in each embodiment, and may have other aspects. For example, the multiple reflection cell may not only include a multiple reflection mechanism as a white cell, but may also include only a multiple reflection mechanism as a Herriot cell. Furthermore, the pressure control mechanism that controls the pressure of the sample gas within the cell body is not limited to the second embodiment, and may be provided in each embodiment other than the second embodiment. For example, when the sample gas is analyzed simultaneously using the first principle and the second principle, the pressure control mechanism is configured to control the pressure of the sample gas to a pressure suitable for simultaneous analysis using each principle. You may. For example, if there is an optimal first pressure and second pressure for each analysis based on the first principle and second principle, the pressure control mechanism controls the sample gas so that the weighted average pressure of the first pressure and the second pressure is obtained. The pressure may also be controlled. Note that the weighting coefficient may be appropriately set so that each analysis can be performed with a predetermined accuracy, or may be a simple average pressure of the first pressure and the second pressure.

Based on the concentration of each analyte component in the sample gas calculated by the concentration calculation section of the gas analyzer and the flow rate of the sample gas or analyte component, the information processing device calculates the instantaneous mass of each analyte component and the analyte component. It may be configured to calculate the total amount of each analysis target component discharged during the period.

In addition, various modifications of the embodiments and combinations of parts of each embodiment may be made as long as they do not go against the spirit of the present invention.

To provide a gas analyzer that can reduce time differences as much as possible in analysis results using a plurality of different principles, and also allows analysis of the same sample.

100 : Gas analyzer 10 : First analysis mechanism 11 : First light source IF : Interferometer 12 : Light guide mirror 13 : Half mirror 14 : Fixed mirror 15 : Movable mirror 16 : Incident side mirror 17 : Exit side mirror 18 : First 1 Photodetector 20: Second analysis mechanism 21: Second light source 22: Second photodetector 2H: Light passing hole 23: Small reflecting mirror 24: External mirror CD: Shared photodetector 30: Multiple reflection cell 31: Cell Main body 32: Multiple reflection mechanism 33: Field mirror 34: First objective mirror 35: Second objective mirror 36: Light introduction window 37: Light output window 38: Pair of reflection mirrors P: Port COM: Information processing device 40: Concentration calculation unit 41: FTIR section 42: IRLAM section 50: Optical path switching mechanism L1: Measurement optical path L2: Adjustment optical path 51: Switching sections 52, 53: Mirror 54: Adjustment fixed mirror 61: Third light source 62: Third photodetector

Claims (14)

a multiple reflection cell into which a sample gas consisting of multiple components is introduced;
a first analysis mechanism that causes a first light to enter the multiple reflection cell, detects the first light that has passed through the multiple reflection cell, and analyzes the components of the sample gas according to a first principle; ,
A second light is input into the multiple reflection cell, the second light passing through the multiple reflection cell is detected, and the sample gas is determined according to a second principle different from the first principle. A gas analyzer comprising: a second analysis mechanism for analyzing components. The gas analysis device according to claim 1, wherein the first principle is Fourier transform infrared spectroscopy, and the second principle is laser absorption spectroscopy. The multiple reflection cell includes a cell body into which the sample gas is introduced into an internal space, and a multiple reflection mechanism provided in the internal space that multiple-reflects incident light and then emits it to the outside,
The cell body is formed with a light introduction window through which first light is introduced into the cell body, and a light output window through which the first light that has passed through the multiple reflection mechanism is guided out of the cell body. Ori,
The multiple reflection mechanism is
field mirror,
a first objective mirror facing the field mirror and provided on the light incident side of the multiple reflection mechanism;
3. The gas analyzer according to claim 1, further comprising a second objective mirror facing the field mirror and provided on the light exit side of the multiple reflection mechanism. The first analysis mechanism is
a first light source that emits first light that is continuous light including light of a plurality of wave numbers;
comprising a first photodetector that detects the first light that has passed through the multiple reflection cell,
The second analysis mechanism is
a second light source that emits second light that is a laser beam;
The gas analyzer according to claim 3, further comprising a second photodetector that detects the second light that has passed through the multiple reflection cell. The second analysis mechanism causes second light emitted from the second light source to be introduced into the cell main body from the light introduction window, and detects the second light emitted from the light exit window. 5. The gas analyzer according to claim 4, wherein the gas analyzer is configured to detect. The second analysis mechanism causes second light emitted from the second light source to be introduced into the cell main body from the light guide window, and detects the second light emitted from the light guide window. 5. The gas analyzer according to claim 4, wherein the gas analyzer is configured to detect. The first analysis mechanism,
an interferometer into which the light emitted from the first light source is incident;
an entrance side mirror that reflects the first light that has passed through the interferometer and causes it to enter the light introduction window;
further comprising an exit side mirror that reflects the first light emitted from the light exit window and causes it to enter the first photodetector,
4. The gas analyzer according to claim 3, wherein the entrance side mirror and the exit side mirror are formed with a light passage hole for allowing the second light to pass therethrough. The first analysis mechanism is
a first light source that emits first light that is continuous light including light of a plurality of wave numbers;
an interferometer into which the light emitted from the first light source is incident;
The second analysis mechanism is
comprising a second light source that emits a second light that is a laser beam,
4. The gas analyzer according to claim 3, wherein the first light or the second light that has passed through the multiple reflection cell is detected by one common photodetector. further comprising a concentration calculation unit that calculates the concentration of the component in the sample gas based on the output of the common photodetector,
The concentration calculation unit calculates the concentration of one or more components in the sample gas by Fourier transform infrared spectroscopy while the movable mirror of the interferometer is moving;
9. The gas analyzer according to claim 8, wherein the concentration of one or more components in the sample gas is calculated by laser absorption spectroscopy while the movable mirror is stopped. The gas analyzer according to claim 9, further comprising a pressure control mechanism that controls the pressure of the sample gas in the multiple reflection cell according to the principle used in the concentration calculation section. The gas analyzer according to claim 10, wherein the pressure control mechanism is configured to lower the pressure of the sample gas while the movable mirror is stopped than when the movable mirror is moving. a measurement optical path in which second light emitted from the second light source bypasses the interferometer and enters the multiple reflection cell; and a measurement optical path in which the second light emitted from the second light source enters the interferometer. 9. The gas analyzer according to claim 7, further comprising an optical path switching mechanism for switching the optical path to either one of the adjustment optical paths. The multiple reflection cell is
further comprising a pair of reflection mirrors provided within the cell body separately from the multiple reflection mechanism,
13. The second light emitted from the second light source is multiple-reflected by the pair of reflection mirrors and then emitted from the multiple reflection cell to the outside, according to any one of claims 3 to 12. gas analyzer. a third light source that emits third light so as to pass through the multiple reflection cell without being reflected within the multiple reflection cell;
The gas analyzer according to any one of claims 3 to 13, further comprising a third photodetector that detects the third light that has passed through the multiple reflection cell.

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