Infrared gas analyzer, infrared gas analysis method, and infrared gas analysis program

Abstract

To more accurately calculate a concentration of a measured component when the sensitivity of a main detector or the sensitivity of a compensation detector varies after an influence of an interference component is corrected.SOLUTION: An infrared gas analyzer includes: a measuring cell into which sample gas is introduced; a light source which irradiates the measuring cell with infrared rays; a measured component detector which detects intensity of an absorption wavelength range of a measured component in the infrared rays transmitted through the measuring cell; a first interference component detector which detects intensity of an absorption wavelength range of a component interfering with the measured component in the infrared rays transmitted through the measuring cell; a second interference component detector which detects an interference component contained in the sample gas; and an arithmetic unit which calculates a concentration of the measured component and / or the interference component on the basis of outputs of those detectors. The arithmetic unit has: a first corrected concentration calculation section which corrects difference between the outputs of the measured component detector and the first interference component detector using an output of the second interference component detector to correct an influence of the interference component; and a second corrected concentration calculation section which corrects an influence of the interference component on the basis of a first corrected concentration and the output of second interference component detector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an infrared gas analyzer, an infrared gas analysis method, and an infrared gas analysis program. [Background technology]

[0002] In recent years, nitrous oxide (N2O) has been attracting attention as a greenhouse gas that causes global warming. Reduction of N2O emissions is being sought in various industrial sectors, including sewage treatment plants, incineration plants, industrial waste disposal sites, and chemical plants.

[0003] On the other hand, as an apparatus for measuring the concentration of a measurement component in exhaust gas emitted in the above-mentioned industrial fields, as shown in Patent Document 1, an infrared gas analyzer of a non-dispersive infrared absorption type is used.

[0004] This type of infrared gas analyzer is equipped with an infrared detector having a main detector for measuring the concentration of the measured component, nitrous oxide (N2O), and a compensation detector for measuring the concentration of carbon dioxide (CO2), an interfering component that interferes with the measured component, and a CO2 measurement unit for measuring the concentration of CO2 in the exhaust gas.The infrared gas analyzer calculates the concentration of the measured component (N2O) with the interference effect of the interfering component (CO2) corrected by correcting the difference between the output of the main detector and the output of the compensation detector using the output of the CO2 measurement unit.

[0005] However, after the interference effect of the above-mentioned interfering component (CO2) is corrected, the sensitivity of the main detector or the compensation detector may fluctuate over time. In this case, it is desirable to calculate the concentration of the measured component (N2O) more accurately in accordance with the fluctuations in the sensitivity of the main detector or the compensation detector. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2023-218983 publication Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and its main objective is to calculate the concentration of the measured component more accurately when the sensitivity of the main detector or the sensitivity of the compensation detector fluctuates after the interference effects of the interfering components have been corrected. [Means for solving the problem]

[0008] That is, the infrared gas analyzer according to the present invention includes a measurement cell into which a sample gas is introduced, an infrared light source that irradiates the measurement cell with infrared rays, a measurement component detector that detects the infrared intensity of the infrared rays that have passed through the measurement cell in a wavelength range corresponding to the infrared absorption spectrum of the measurement component, a first interference component detector that detects the infrared intensity of the infrared rays that have passed through the measurement cell in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, a second interference component detector that is provided separately from the first interference component detector and detects the interference component contained in the sample gas, and an output of the measurement component detector, an output of the first interference component detector, and / or and a calculation device that calculates the concentration of the measurement component and / or the interfering component based on the output of the second interference component detector, wherein the calculation device has a first corrected concentration calculation unit that calculates a first corrected concentration, which is the concentration of the measurement component in which the interference effect of the interfering component has been corrected, by correcting the difference between the output of the measurement component detector and the output of the first interference component detector using the output of the second interference component detector, and a second corrected concentration calculation unit that calculates a second corrected concentration, which is the concentration of the measurement component in which the interference effect of the interfering component has been further corrected, based on the first corrected concentration and the output of the second interference component detector.

[0009] According to such an infrared gas analyzer, after calculating the first corrected concentration, the second corrected concentration calculation unit calculates the second corrected concentration based on the first corrected concentration and the output of the second interference component detector. Therefore, even if the sensitivity of the measurement component detector or the first interference component detector fluctuates after calculating the first corrected concentration, the concentration of the measurement component can be calculated more accurately.

[0010] It is desirable that the second corrected concentration calculation unit calculates the second corrected concentration based on an interference correction coefficient determined based on the output of the measurement component detector and / or the first interference component detector and the first corrected concentration.

[0011] In this case, the second-corrected concentration is calculated based on the interference correction coefficient determined based on the output of the measurement component detector and / or the first interference component detector, so that fluctuations in the sensitivity of the measurement component detector or the first interference component detector can be reflected in the second-corrected concentration. As a result, even if the sensitivity of the measurement component detector or the first interference component detector fluctuates, the second-corrected concentration calculation unit calculates the second-corrected concentration using the interference correction coefficient, making it possible to calculate the concentration of the measurement component more accurately.

[0012] It is desirable that the interference correction coefficient be obtained based on the first corrected concentration obtained by measuring an interference component gas in which the concentration of the interference component is known and the concentration of the interference component.

[0013] In this case, the interference correction coefficient is obtained based on the first-corrected concentration obtained by measuring an interference component gas whose concentration is known and the concentration of the interference component, so that measurement errors due to fluctuations in the sensitivity of each detector after calculating the first-corrected concentration can be reliably reduced when calculating the second-corrected concentration.

[0014] It is desirable that the interference correction coefficient be adjusted based on the first corrected concentration obtained during span calibration, which calibrates the sensitivity of the measurement component detector and / or the first interference component detector by introducing the interference component gas into the measurement cell.

[0015] In this case, the interference correction coefficient is adjusted based on the first corrected concentration obtained during span calibration, so the interference correction coefficient can be automatically changed at the same time as span calibration, eliminating the need for the user to change the interference correction coefficient during span calibration.

[0016] As a specific embodiment, the measurement component detector and the first interference component detector are preferably pneumatic detectors.

[0017] A specific aspect of the first corrected concentration calculation unit is characterized in that it calculates the first corrected concentration by correcting the difference between the output of the measurement component detector and the output of the first interference component detector by a weighting coefficient obtained from the output of the second interference component detector.

[0018] Preferably, the component to be measured is nitrous oxide and the interfering component is carbon dioxide.

[0019] This allows nitrous oxide and carbon dioxide, whose infrared absorption regions overlap, to be analyzed using a single infrared gas analyzer. Furthermore, since nitrous oxide, which is a greenhouse gas that causes global warming, is included in the infrared absorption region, the infrared gas analyzer of the present invention can be suitably used in industrial fields where a reduction in environmental impact is required.

[0020] In order for one infrared gas analyzer to analyze four components contained in a sample gas, it is necessary to further include two infrared detectors each having the measurement component detector and the first interference component detector, and the measurement component and the interference component in one of the infrared detectors are nitric oxide and water, respectively, and the measurement component and the interference component in the other infrared detector are sulfur dioxide and methane or water, respectively.

[0021] Furthermore, the infrared gas analysis method of the present invention is an infrared gas analysis method that analyzes a measurement component in a sample gas by irradiating infrared rays onto a measurement cell into which a sample gas has been introduced, and detecting the infrared rays that have passed through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of the measurement component, and an interference component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, wherein the interference components contained in the sample gas are detected separately from the interference component detector, and the difference between the output of the measurement component detector and the output of the interference component detector is corrected using the output of the interference component detected separately from the interference component detector to calculate a first corrected concentration, which is the concentration of the measurement component corrected for the influence of the interference component, and then calculating a second corrected concentration, which is the concentration of the measurement component further corrected for the influence of the interference component, based on the first corrected concentration and the output of the interference component detected separately from the interference component detector. Alternatively, the infrared gas analysis method of the present invention is an infrared gas analysis method that analyzes a measurement component in a sample gas by irradiating infrared rays onto a measurement cell into which a sample gas has been introduced, and detecting the infrared rays that have passed through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of the measurement component, and an interference component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, wherein a first corrected concentration, which is the concentration of the measurement component corrected for the interference effect of the interference component, is calculated based on the difference between the output of the measurement component detector and the output of the interference component detector, and a second corrected concentration, which is the concentration of the measurement component, is calculated by correcting the sensitivity of the measurement component detector and / or the interference component detector, which varies over time, based on the first corrected concentration and the output of the interference component detected by a second interference component detector different from the first interference component detector. Furthermore, the present invention provides an infrared gas analysis program for analyzing a measurement component in a sample gas by irradiating a measurement cell containing a sample gas with infrared rays and detecting infrared rays transmitted through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of the measurement component and an interference component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component. The infrared gas analysis program is characterized in that the program causes a computer to function as a first corrected concentration calculation unit that calculates a first corrected concentration, which is the concentration of the measurement component in which the influence of interference by the interference component has been corrected, by correcting the difference between the output of the measurement component detector and the output of the interference component detector using the output of the interference component detected separately from the interference component detector, and a second corrected concentration calculation unit that calculates a second corrected concentration, which is the concentration of the measurement component in which the influence of interference by the interference component has been further corrected, based on the first corrected concentration and the output of the interference component detected separately from the interference component detector.

[0022] With this configuration, it is possible to obtain the same effects as those of the above-mentioned infrared gas analyzer. [Effects of the Invention]

[0023] According to the present invention configured in this manner, the concentration of the measured component can be calculated more accurately even if the sensitivity of the main detector or the sensitivity of the compensation detector fluctuates after the interference effects of the interfering components have been corrected. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing an infrared gas analyzer according to an embodiment of the present invention. [Figure 2] 3 is a flowchart showing an infrared gas analysis method according to the embodiment. [Figure 3] FIG. 10 is a schematic diagram showing an infrared gas analyzer according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of an infrared gas analyzer according to the present invention will be described below with reference to the drawings. Note that in all of the drawings shown below, some parts may be omitted or exaggerated for clarity. The same components are designated by the same reference numerals, and their description will be omitted where appropriate.

[0026] The infrared gas analyzer 100 according to this embodiment is configured to measure nitrous oxide (NO), nitrogen oxides (NO) and the like in a sample gas such as exhaust gas (flue gas) emitted from industrial facilities such as sewage treatment plants, incineration plants, industrial waste treatment plants, and chemical plants. X It measures the concentrations of components such as sulfur dioxide (SO2), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) using non-dispersive infrared absorption (NDIR).

[0027] Specifically, the infrared gas analyzer 100 measures the concentration of NO in a sample gas, and as shown in FIG. 1, it includes a measurement cell 2 into which the sample gas is introduced, an infrared light source 3 provided at one end of the measurement cell 2 and irradiating the measurement cell 2 with infrared rays, an infrared detector 4 provided at the other end of the measurement cell 2 and detecting the infrared rays that have passed through the measurement cell 2, a second interference component measurement unit 5 provided separately from the infrared detector 4, and a calculation device 6 that acquires outputs from the infrared detector 4 and calculates the concentration of the measurement component (NO).

[0028] The measurement cell 2 has, for example, a roughly cylindrical shape, and both ends thereof are sealed by cell window members 2a and 2b made of an infrared-transparent material. An inlet port P1 for introducing sample gas into the cell and an outlet port P2 for discharging the sample gas to the outside of the cell are provided on the side wall.

[0029] The infrared light source 3 is provided at one end side of the measurement cell 2 facing the cell window member 2a, and irradiates infrared light into the inside of the measurement cell 2. The infrared light source 3 in this embodiment is of a fluid modulation type that introduces a sample gas and a reference gas into the measurement cell 2 alternately at a constant period, but is not limited to this.

[0030] The infrared detector 4 is provided facing the cell window member 2b at the other end of the measurement cell 2, and has a measurement component detector 41 serving as a main detector for measuring the concentration of a measurement component (N2O) and a first interference component detector 42 serving as a compensation detector for measuring the concentration of an interference component (CO2 in this case). The measurement component detector 41 and the first interference component detector 42 are optically arranged in series in this order from the other end of the measurement cell 2. The detection signal obtained by the measurement component detector 41 and the detection signal obtained by the first interference component detector 42 are output to the calculation device 6.

[0031] The measurement component detector 41 is, for example, a pneumatic detector of the condenser microphone type. This measurement component detector 41 has a main body block made of corrosion-resistant metal, both ends of which are sealed with window members made of an infrared-transparent material, and a condenser microphone 41x is disposed inside. The measurement component detector 41 is filled with the measurement component (NO) or a measurement gas exhibiting equivalent infrared absorption characteristics, and detects the infrared intensity in a wavelength range that matches the infrared absorption spectrum of the measurement component. The measurement component detector 41 of this embodiment is sensitive to both the measurement component and interference components.

[0032] In this embodiment, the component to be measured is NO, and therefore a predetermined concentration of NO gas is sealed inside the component detector 41. This allows the component detector 41 to detect the intensity of infrared light in a wavelength range that matches the infrared absorption spectrum of NO. Note that the sensitivity of the component detector 41 fluctuates over time as the NO gas changes into nitric oxide (NO) or nitrogen dioxide (NO) and reaches an equilibrium state.

[0033] Like the analyte detector 41, the first interferent detector 42 is, for example, a pneumatic detector of the condenser microphone type. The first interferent detector 42 has a main body block made of corrosion-resistant metal, both ends of which are sealed with window members made of an infrared-transparent material, and a condenser microphone 42x is disposed inside the block. The first interferent detector 42 is filled with an interfering component (CO2) or an interfering gas exhibiting equivalent infrared absorption characteristics, and detects the infrared intensity in a wavelength range that matches the infrared absorption spectrum of the interfernt component. The first interferent detector 42 is located downstream of the analyte detector 41, and is sensitive to the interfernt component because most of the N2O is absorbed by the analyte detector 41.

[0034] In this embodiment, to correct for the interference effect of CO2 on N2O, the first interference component detector 42 is filled with N2O gas at a higher concentration than the N2O gas in the measurement component detector 41. This allows the first interference component detector 42 to detect infrared intensity in a wavelength range that matches the infrared absorption spectrum of CO2. Note that the sensitivity of the first interference component detector 42 fluctuates over time as N2O gas changes into nitric oxide (NO) or nitrogen dioxide (NO2) and reaches an equilibrium state.

[0035] The second interference component measuring unit 5 has a second measurement cell 51 into which the sample gas is introduced, an infrared irradiating unit 52 that irradiates the second measurement cell 51 with infrared rays, and a second interference component detector 53 that detects the infrared rays that have passed through the second measurement cell 51. In this embodiment, the sample gas that has passed through the second measurement cell 51 is configured to be introduced into the measurement cell 2, but the reverse may also be true.

[0036] The second measuring cell 51 has the same configuration as the measuring cell 2 described above, but its cell length is shorter than that of the measuring cell 2 in accordance with the CO2 concentration.

[0037] The second interference component detector 53 is provided separately from the first interference component detector 42 and detects interference components contained in the sample gas. Similar to the above-mentioned measurement component detector 41, the second interference component detector 53 is, for example, a condenser microphone type pneumatic detector.

[0038] Here, the infrared irradiating unit 52 is configured using the above-mentioned infrared light source 3 and a condensing member 7 provided between the infrared light source 3 and the measurement cell 2. The condensing member 7 has a first optical path 7a formed from a tapered inner wall surface that condenses infrared light. By passing through this first optical path 7a, the infrared light from the infrared light source 3 is condensed and irradiated onto the measurement cell 2. In addition, a second optical path 7b for irradiating the second measurement cell 51 with infrared light is connected to the inner wall surface forming the first optical path 7a. Infrared light reflected by the tapered inner wall surface passes through this second optical path 7b, and the infrared light that has passed through the second optical path 7b is irradiated onto the second measurement cell 51. In this embodiment, to reduce costs, the infrared light source 3 is shared by the infrared detector 4 and the second interference component measuring unit 5. However, the infrared light source 3 may be independent of the infrared detector 4 and the second interference component measuring unit 5. In this case, the infrared irradiating section 52 does not have to be configured using the light collecting member 7 having a tapered inner wall surface.

[0039] Furthermore, in this embodiment, in order to reduce the influence of interference from components such as SO2 and CH4 in the sample gas, an optical filter 8 is provided to narrow the wavelength of infrared light detected by the infrared detector 4. This optical filter 8 transmits infrared light in the absorption wavelength range of NO, specifically, the optical filter 8 transmits wavelengths in the range of 4 μm to 5 μm, for example. The optical filter 8 in this embodiment is provided between the measurement cell 2 and the infrared detector 4.

[0040] The arithmetic unit 6 constitutes a so-called computer equipped with a CPU, memory, A / D converter, D / A converter, and various input / output devices, and calculates the concentrations of the measured component and / or the interfering component based on the output of the measured component detector 41, the output of the first interfering component detector 42, and / or the output of the second interfering component detector. The arithmetic unit 6 can display the calculated measurement results, such as the NO concentration, on a display unit 60.

[0041] Specifically, the calculation device 6 is equipped with a measurement preamplifier 61 that amplifies and outputs the output signal of the measurement component detector 41, a first interference preamplifier 62 that amplifies and outputs the output signal of the first interference component detector 42, a second interference preamplifier 63 that amplifies and outputs the output signal of the second interference component detector 53, a first corrected concentration calculation unit 64 that calculates a first corrected concentration, which is the concentration of the measurement component corrected for the interference effect of the interference component, and a second corrected concentration calculation unit 65 that calculates a second corrected concentration, which is the concentration of the measurement component further corrected for the interference effect of the interference component.

[0042] The first corrected concentration calculation unit 64 calculates a first corrected concentration, which is the concentration of the measured component (N2O) corrected for the interference effect of the interfering component (CO2), by correcting the difference between the output of the measured component detector 41 and the output of the first interfering component detector 42 using the output of the second interfering component detector 53. Specifically, the first corrected concentration calculation unit 64 calculates the first corrected concentration by correcting the difference between the output of the measured component detector 41 and the output of the first interfering component detector 42 with a weighting coefficient k obtained from the output of the second interfering component detector 53.

[0043] Here, the predetermined weighting coefficient k is a coefficient representing the ratio (M2 / M1) of the output signal (M2) of the measurement component detector 41 to the output signal (M1) of the first interference component detector 42 when measuring the interference component (CO2). This weighting coefficient k is adjusted to be close to 1, that is, so that the output signal of the measurement component detector 41 and the output signal of the first interference component detector 42 are approximately the same. Specifically, it is possible to bring the weighting coefficient k closer to 1 by adjusting the resistance value built into the first interference preamplifier 62. Alternatively, it is possible to bring the weighting coefficient k closer to 1 by adjusting the concentration of the measurement filler gas or the interference filler gas.

[0044] Furthermore, since the weighting coefficient k changes depending on the concentration of the interfering component (CO2), there is a risk of measurement errors occurring if a constant weighting coefficient k is used. For this reason, the first corrected concentration calculation unit 64 changes or corrects the weighting coefficient k based on the output of the second interfering component detector 53.

[0045] Here, the weighting coefficient k is determined in advance using a plurality of interfering component gases whose concentrations of the interfering component (CO2) are known, and is stored in the calculation device 6. During measurement, the weighting coefficient k is changed or corrected according to the output of the second interfering component detector 53. Then, the first corrected concentration is calculated by multiplying the difference between the output of the measurement component detector 41 and the output of the first interfering component detector 42 by the changed or corrected weighting coefficient k.

[0046] The second-corrected concentration calculation unit 65 calculates a second-corrected concentration, which is the concentration of the measured component (N2O) after further correcting the influence of interference due to interference components, based on the first-corrected concentration and the output of the second interference component detector 53. Specifically, the second-corrected concentration calculation unit 65 calculates the second-corrected concentration based on an interference correction coefficient kc determined based on the output of the infrared detector 4 and the first-corrected concentration. In this embodiment, the second-corrected concentration calculation unit 65 uses the interference correction coefficient kc to calculate the second-corrected concentration based on the difference between the first-corrected concentration and the output of the second interference component detector 53 multiplied by the interference correction coefficient kc, but this is not limited to this. In other words, the second-corrected concentration is obtained by an electrical calculation of "first-corrected concentration" - "output of the second interference component detector 53 × kc," and the influence of interference due to the interference component (CO2) is corrected after the calculation of the first-corrected concentration.

[0047] Here, the interference correction coefficient kc is a coefficient for correcting the influence of interference from the interfering component (CO2) in accordance with the change in sensitivity when the sensitivity of the measurement component detector 41 and / or the first interfering component detector 42 changes after the first corrected concentration is calculated. Specifically, the interference correction coefficient kc is obtained by dividing the first corrected concentration obtained by measuring an interfering component gas whose concentration of the interfering component (CO2) is known by the concentration of the interfering component (CO2) in the interfering component gas, but is not limited to this.

[0048] Furthermore, the interference correction coefficient kc is changed based on the first corrected concentration obtained during span calibration, which calibrates the sensitivity of the second interferent detector 53 by introducing an interferent gas into the measurement cell 2. Specifically, if the sensitivity of at least one of the measurement component detector 41 or the first interferent detector 42 fluctuates, the first corrected concentration obtained during span calibration of the second interferent detector 53 will be a value other than 0. The interference correction coefficient kc is then changed to a value obtained by dividing the first corrected concentration obtained during span calibration of the second interferent detector 53 by the concentration of the interferent (CO2) in the interferent gas. In this case, the second corrected concentration is the value obtained by subtracting the output of the second interferent detector 53 multiplied by the interference correction coefficient kc from the first corrected concentration.

[0049] On the other hand, if the sensitivity of the measurement component detector 41 and the first interference component detector 42 does not fluctuate, the first corrected concentration obtained during span calibration of the second interference component detector 53 will be 0, and therefore the interference correction coefficient kc will be changed to 0. In this case, the second corrected concentration will have the same value as the first corrected concentration.

[0050] <Infrared gas analysis method> Next, an example of an infrared gas analysis method according to this embodiment will be described with reference to FIG.

[0051] First, a sample gas is introduced into the measurement cell 2 and the second measurement cell 51. Then, infrared light is irradiated from the infrared light source 3 onto the measurement cell 2 into which the sample gas has been introduced (S1).

[0052] Next, the infrared detector 4 detects the infrared light transmitted through the measurement cell 2 (S2). Specifically, the measurement component detector 41 detects the infrared intensity in a wavelength range that matches the infrared absorption spectrum of the measurement component. Also, the first interference component detector 42 detects the infrared intensity in a wavelength range that matches the infrared absorption spectrum of the interference component.

[0053] Next, the second interference component detector 53 detects the infrared light that has passed through the second measuring cell 51 (S3).

[0054] Next, the first corrected concentration calculation unit 64 calculates the difference between the output of the measurement component detector 41 and the output of the first interference component detector 42. Then, the first corrected concentration calculation unit 64 calculates the first corrected concentration by performing correction using the output of the second interference component detector 53 (S4).

[0055] Next, the second corrected concentration calculation unit 65 acquires the interference correction coefficient kc obtained during span calibration (S5). Here, it is sufficient for the second corrected concentration calculation unit 65 to acquire the interference correction coefficient kc at least before calculating the second corrected concentration. Note that the second corrected concentration calculation unit 65 may calculate the interference correction coefficient kc by dividing the first corrected concentration by the concentration of the interference component (CO2) in the interference component gas.

[0056] Then, the second-corrected concentration calculation unit 65 calculates the second-corrected concentration based on the interference correction coefficient kc and the first-corrected concentration (S6). Specifically, the second-corrected concentration calculation unit 65 calculates the second-corrected concentration based on the difference between the first-corrected concentration and the output of the second interference component detector 53 multiplied by the interference correction coefficient kc. Note that, although the second-corrected concentration is calculated after the first-corrected concentration in the above description, the order in which the first-corrected concentration and the second-corrected concentration are calculated is not limited to this. For example, the first-corrected concentration may be calculated after the second-corrected concentration is calculated, or the first-corrected concentration and the second-corrected concentration may be calculated simultaneously.

[0057] <Effects of this embodiment> According to the infrared gas analyzer 100 of this embodiment configured as described above, after calculating the first corrected concentration, the second corrected concentration calculation unit 65 calculates the second corrected concentration based on the first corrected concentration and the output of the second interference component detector. Therefore, even if the sensitivity of the measurement component detector 41 or the first interference component detector 42 fluctuates after calculating the first corrected concentration, the concentration of the measurement component can be calculated more accurately.

[0058] <Other embodiments>

[0059] In the above embodiment, the infrared gas analyzer 100 may further include a gas filter that reduces or removes the absorption spectrum of an interfering component that interferes with the absorption spectrum of the measurement component.

[0060] In the above embodiment, an optical filter 8 is used to narrow the wavelength of infrared light detected by the infrared detector 4 in order to reduce the interference effects of components such as SO2 and CH4, but the optical filter 8 does not have to be used.

[0061] The infrared gas analyzer of the above embodiment is of a fluid modulation type, but may be of an optical chopping type in which an optical chopper is used to periodically chop the infrared light from the infrared light source 3. In the optical chopping type, an optical chopper (not shown) is provided between the infrared light source 3 and the measurement cell 2, and may be configured to be rotated by, for example, a motor to periodically chop the infrared light generated by the infrared light source 3.

[0062] Furthermore, the infrared gas analyzer of the above embodiment measures the concentration of N2O, but it can also measure the concentration of NO X The concentration of other components such as SO2, CO, CO2, CH4, and H2O may be measured, or the concentration of two or more of these components may be measured.

[0063] An example of the configuration of an infrared gas analyzer 100 that measures the concentrations of four components is shown in Fig. 3. The infrared gas analyzer 100 shown in Fig. 3 measures the concentrations of four components, for example, N2O, SO2, CO2, and NO, and includes an SO2 measurement unit 10 and an NO measurement unit 11 in addition to the configuration of the above embodiment.

[0064] The SO2 measurement unit 10 has an SO2 detector 101 that detects infrared rays transmitted through the measurement cell 2. The NO measurement unit 11 has an NO detector 111 that detects infrared rays transmitted through the measurement cell 2. The SO2 detector 101 and the NO detector 111 are, for example, pneumatic detectors of a condenser microphone type, similar to the above-mentioned measurement component detector 41.

[0065] In addition, in this configuration example, the infrared rays that have passed through the measurement cell 2 are split into the infrared detector 4 (N2O detector), the SO2 detector 101, and the NO detector 111 using a beam splitter 12 that uses half mirrors M1, M2, etc.

[0066] Here, an optical filter 8 is also provided between the beam splitter 12 and the infrared detector 4 (NO detector). Optical filters 13 and 14 are also provided between the beam splitter 12 and the SO detector 101 and the NO detector 111. Furthermore, gas filters may be provided between the beam splitter 12 and the SO detector 101 and the NO detector 111 to remove the influence of interfering components on the components to be measured. Note that while FIG. 4 shows an example of a configuration for measuring the concentrations of four components, it is also possible to configure the system to measure the concentrations of three components or five or more components by changing the configuration of the beam splitter, for example.

[0067] In the above embodiment, exhaust gas emitted from an external combustion engine is analyzed, but exhaust gas emitted from an internal combustion engine of a vehicle, ship, or the like may also be analyzed.

[0068] In the above embodiment, the first corrected concentration calculation unit 64 calculates the first corrected concentration by correcting the difference between the output of the measurement component detector 41 and the output of the first interference component detector 42 using the output of the second interference component detector 53, but this is not limited to this. For example, the first corrected concentration calculation unit 64 may calculate the first corrected concentration based on the difference between the output of the measurement component detector 41 and the output of the first interference component detector 42. Even in this case, by calculating the second corrected concentration, it is possible to correct the sensitivity of the measurement component detector 41 and / or the first interference component detector 42, which varies over time.

[0069] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0070] 100···Infrared Gas Analyzer 2. Measuring cell 3. Infrared light source 4. Infrared detector 41 Measurement component detector 42 First interference component detector 5. Second interference component measuring section 53 Second interference component detector 6...Arithmetic unit 7. Light-collecting member 8 Optical Filter

Claims

1. a measurement cell into which a sample gas is introduced; an infrared light source that irradiates the measurement cell with infrared rays; a measurement component detector that detects the intensity of infrared light in a wavelength range corresponding to the infrared absorption spectrum of the measurement component among the infrared light transmitted through the measurement cell; a first interference component detector that detects the intensity of infrared light in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, among the infrared light transmitted through the measurement cell; a second interference component detector provided separately from the first interference component detector and configured to detect the interference components contained in the sample gas; a calculation device that calculates the concentration of the measurement component and / or the interference component based on the output of the measurement component detector, the output of the first interference component detector, and / or the output of the second interference component detector, The computing device a first corrected concentration calculation unit that calculates a first corrected concentration, which is the concentration of the measurement component in which the influence of interference by the interference component has been corrected, by correcting the difference between the output of the measurement component detector and the output of the first interference component detector using the output of the second interference component detector; and a second corrected concentration calculation unit that calculates a second corrected concentration, which is the concentration of the measured component in which the influence of interference by the interfering component has been further corrected, based on the first corrected concentration and an output of the second interfering component detector.

2. 2. The infrared gas analyzer according to claim 1, wherein the second corrected concentration calculation unit calculates the second corrected concentration based on an interference correction coefficient determined based on an output of the measurement component detector and / or the first interference component detector and the first corrected concentration.

3. 3. The infrared gas analyzer according to claim 2, wherein the interference correction coefficient is obtained based on the first corrected concentration obtained by measuring an interference component gas whose concentration of the interference component is known and the concentration of the interference component.

4. 4. The infrared gas analyzer according to claim 3, wherein the interference correction coefficient is changed based on the first corrected concentration obtained during span calibration, which calibrates the sensitivity of the measurement component detector and / or the first interference component detector by introducing the interference component gas into the measurement cell.

5. 5. The infrared gas analyzer according to claim 1, wherein the measurement component detector and the first interference component detector are pneumatic detectors.

6. 6. The infrared gas analyzer according to claim 1, wherein the first corrected concentration calculation unit calculates the first corrected concentration by correcting a difference between the output of the measurement component detector and the output of the first interference component detector by a weighting coefficient obtained from the output of the second interference component detector.

7. 7. The infrared gas analyzer according to claim 1, wherein the measurement component is nitrous oxide and the interference component is carbon dioxide.

8. two further infrared detectors each having the measurement component detector and the first interference component detector; the measured component and the interfering component in one of the infrared detectors are nitric oxide and water, respectively; 8. The infrared gas analyzer according to claim 7, wherein the measurement component and the interference component in the other infrared detector are sulfur dioxide and methane or water, respectively.

9. An infrared gas analysis method for analyzing a measurement component in a sample gas by irradiating a measurement cell containing a sample gas with infrared rays and detecting the infrared rays transmitted through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range that matches the infrared absorption spectrum of the measurement component, and an interference component detector that detects the infrared intensity in a wavelength range that corresponds to the infrared absorption spectrum of an interference component that interferes with the measurement component, comprising: Detecting the interference components contained in the sample gas separately from the interference component detector; a first corrected concentration, which is the concentration of the measurement component corrected for the influence of interference by the interference component, by correcting a difference between the output of the measurement component detector and the output of the interference component detector using the output of the interference component detected separately from the interference component detector; and calculating a second corrected concentration, which is the concentration of the measured component in which the influence of interference by the interfering component has been further corrected, based on the first corrected concentration and an output of the interfering component detected separately from the interfering component detector.

10. An infrared gas analysis method for analyzing a measurement component in a sample gas by irradiating a measurement cell containing a sample gas with infrared rays and detecting the infrared rays transmitted through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of the measurement component and an interference component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, comprising: calculating a first corrected concentration, which is the concentration of the measurement component corrected for the influence of the interference component, based on a difference between the output of the measurement component detector and the output of the interference component detector; an infrared gas analysis method for calculating a second corrected concentration, which is the concentration of the measured component, by correcting the sensitivity of the measured component detector and / or the interference component detector, which varies over time, based on the first corrected concentration and the output of the interference component detected by a second interference component detector different from the interference component detector.

11. An infrared gas analysis program for analyzing a measurement component in a sample gas by irradiating a measurement cell into which a sample gas has been introduced with infrared rays and detecting the infrared rays transmitted through the measurement cell with a measurement component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of the measurement component and an interference component detector that detects the infrared intensity in a wavelength range corresponding to the infrared absorption spectrum of an interference component that interferes with the measurement component, a function as a first corrected concentration calculation unit that calculates a first corrected concentration, which is the concentration of the measurement component in which the influence of interference by the interference component has been corrected, by correcting the difference between the output of the measurement component detector and the output of the interference component detector using the output of the interference component detected separately from the interference component detector; and a second corrected concentration calculation unit that calculates a second corrected concentration, which is the concentration of the measured component in which the influence of interference by the interfering component has been further corrected, based on the first corrected concentration and an output of the interfering component detected separately from the interfering component detector.

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