Gas measurement device, and method for determining concentration of component of interest

Abstract

The concentration of each of a plurality of gas components is expressed as a corrected concentration obtained by subtracting, from a pre-correction concentration corresponding to a detected value for said gas component, a measurement error to which the measurement of said gas component is subject due to one or more interfering components affecting said gas component. The measurement error to which the measurement of the gas component is subject is expressed by a linear sum of corrected concentrations of the interfering components affecting said gas component and influence coefficients indicating the degree to which said interfering components influence the measurement of said gas component. According to the relationship between the corrected concentration and the pre-correction concentration for each of the plurality of gas components, the concentration of a component of interest is determined on the basis of the multiple influence coefficients and the respective detected values for said plurality of gas components.

Description

Gas measuring device and method for determining the concentration of a target component

[0001] The present disclosure relates to a gas measurement device that measures a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap each other, and a method for determining the concentration of a target component among the multiple gas components.

[0002] Infrared gas analyzers that use non-dispersive infrared absorption (NDIR) are known as devices for determining the concentrations of target components in sample gases such as gases emitted from chemical plants and steel mills, combustion gases from boilers and combustion furnaces, the atmosphere, and automobile exhaust gases.

[0003] In gas measurement devices such as infrared gas analyzers that utilize the optical absorption characteristics of target components, errors occur in the measurement of the target component due to the influence of components other than the target component in the sample gas. Specifically, if an interfering component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of the target component is present in the sample gas, errors occur in the measurement of the target component due to the influence of the interfering component.

[0004] Patent Document 1 discloses a measurement method for measuring the concentration of nitrous oxide by measuring nitrous oxide and carbon dioxide, an interfering component with nitrous oxide, by infrared absorption analysis, and correcting the measurement result of nitrous oxide using the measurement result of carbon dioxide.

[0005] Patent Document 2 discloses an analyzer in which an optical filter is placed between a light source and a detector to cut off the absorption wavelength range of interference components.

[0006] Patent Document 3 discloses that an interference component detector and a measurement component detector are optically arranged in series in this order from the other end of the cell, and the measurement component is corrected using the detection signal obtained from the detector.

[0007] Japanese Patent No. 2952855 Japanese Utility Model Application Laid-Open No. 5-75654 Japanese Patent Laid-Open No. 2012-68164

[0008] As disclosed in Patent Documents 1 to 3, in gas measurement devices that utilize the infrared absorption characteristics of target components, it is required to determine the concentration of the target component while taking into account the influence of interfering components.

[0009] Patent Documents 1 to 3 disclose methods for determining the concentration of a target component, taking into consideration that the measurement of the target component is affected by interfering components, but do not take into consideration that the measurement of the interfering components is affected by other components.

[0010] An object of the present disclosure is to more accurately determine the concentration of a target component contained in a sample gas, taking into account that measurement of an interfering component is affected by other components.

[0011] A gas measurement device according to the present disclosure measures a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap with each other. The gas measurement device includes a detection unit that detects the amount of light in the absorption wavelength range of each of the multiple gas components by detecting light passing through the sample gas, and a calculation unit that calculates the concentration of a target component among the multiple gas components based on the detection values ​​of each of the multiple gas components detected by the detection unit. A gas component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of one of the multiple gas components is an interference component with respect to the one gas component. The concentration of each of the multiple gas components is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interference components with respect to the gas component from the uncorrected concentration corresponding to the detection value of the gas component. The measurement error caused by the interference component with respect to the gas component is expressed as a linear sum of the corrected concentration of the interference component with respect to the gas component and an influence coefficient indicating the degree of influence of the interference component on the measurement of the gas component. The calculation unit calculates the corrected concentration of the target component as the concentration of the target component based on the multiple influence coefficients and the detection values ​​of each of the multiple gas components, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the multiple gas components.

[0012] The disclosed method is a method for determining the concentration of a target component in a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap with each other. The method includes the steps of: detecting light passing through the sample gas to detect the amount of light in the absorption wavelength range of each of the multiple gas components, thereby acquiring detection values ​​for each of the multiple gas components; and determining the concentration of the target component from the multiple gas components based on the acquired detection values ​​for each of the multiple gas components. A gas component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of one of the multiple gas components is an interfering component with respect to the one gas component. The concentration of each of the multiple gas components is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interfering components with respect to the gas component from the uncorrected concentration corresponding to the detected value of the gas component. The measurement error caused by the interfering component with respect to the gas component is expressed as a linear sum of the corrected concentration of the interfering component with respect to the gas component and an influence coefficient indicating the degree of influence of the interfering component on the measurement of the gas component. In the step of determining the concentration of the target component, the corrected concentration of the target component is determined as the concentration of the target component based on a plurality of influence coefficients and the detection values ​​of each of the plurality of gas components, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components.

[0013] According to the present disclosure, the corrected concentration of a target component is expressed using a corrected concentration obtained by subtracting the measurement error of an interfering component from the pre-correction concentration of the interfering component. Furthermore, the concentration of the target component is determined according to the relationship between the corrected concentration of the target component and the corrected concentration of the interfering component. Therefore, the concentration of the target component can be determined more accurately by taking into account the influence of other components on the measurement of the interfering component.

[0014] 1 is a schematic diagram showing a method for determining the concentration of a target component in a gas measurement device; FIG. 2 is a schematic diagram showing a method for determining an influence coefficient in a gas measurement device; FIG. 3 is a diagram showing the configuration of a gas measurement device; FIG. 4 is a functional block diagram of a control unit; FIG. 5 is a flowchart showing the processing of the control unit when measuring a sample gas; FIG. 6 is a flowchart showing the processing of the control unit when calculating an influence coefficient; FIG. 7 is an infrared absorption spectrum of nitrous oxide and carbon dioxide; FIG. 8 is an infrared absorption spectrum of nitrous oxide, methane, and sulfur dioxide.

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0016] §1 Application Example An example of a situation in which the present invention is applied will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram showing a method for determining the concentration of a target component in a gas measurement device. Figure 2 is a schematic diagram showing a method for determining an influence coefficient in a gas measurement device.

[0017] <Method for Determining Concentration of Target Component> A method for determining the concentration of a target component will be described with reference to Figure 1. The gas measurement device 1a includes a detection unit 100a and a calculation unit 200a. The detection unit 100a detects the amount of light in the absorption wavelength range of each of multiple gas components contained in the sample gas by detecting transmitted light that has passed through the sample gas. The detection unit 100a sends the detection results to the calculation unit 200a. The calculation unit 200a is a calculation device that determines the concentration of the component in the sample gas based on the detection results.

[0018] Each of the multiple gas components has its own unique absorption wavelength range. The transmitted light is attenuated by being partially absorbed by each of the multiple gas components contained in the sample gas. The absorbance, which is the degree to which light is absorbed, is proportional to the concentration of the gas component. Therefore, the concentration of the gas component can be determined from the absorbance.

[0019] In the following, the gas component to be measured may be referred to as the "target component." Also, a gas component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of a given gas component may be referred to as an "interfering component with respect to the given gas component" or simply as an "interfering component." Also, the detection result obtained by detecting the amount of light in the absorption wavelength range of a given gas component may be referred to as the "detected value of the given gas component" or simply as the "detected value."

[0020] Consider a case where a sample gas contains both a target component and an interfering component. The detected value of the target component obtained by measuring the sample gas reflects not only the effect of light absorption by the target component but also the effect of light absorption by the interfering component. Therefore, even if the absorbance in the absorption wavelength range of the target component is detected, an error will occur in the measurement of the concentration of the target component due to the effect of the interfering component.

[0021] The gas measurement device 1a according to this embodiment detects the target component and the interfering components with respect to the target component, and calculates the concentration of the target component by correcting the detection value of the target component using the detection value of the interfering components.

[0022] In the example shown in Figure 1, the target component is component M, and the interfering components with component M are components C1 and C2. The detection unit 100a includes a first detector 10a that detects the amount of light in the absorption wavelength range of component M, a second detector 10b that detects the amount of light in the absorption wavelength range of component C1, and a third detector 10c that detects the amount of light in the absorption wavelength range of component C2. The method for detecting the amount of light is not particularly limited. For example, the amount of light may be detected directly using a photoconductive element or the like, or the amount of light may be detected indirectly by detecting the change in internal pressure when transmitted light passes through a cell containing the gas to be detected.

[0023] The calculation unit 200a calculates the concentration of component M based on the detection values ​​of each gas component sent from the detection unit 100a. The calculation unit 200a corrects the detection value of component M sent from the first detector 10a using the detection values ​​of components C1 and C2 sent from the second detector 10b and the third detector 10c, respectively, to calculate the concentration [M] of component M. Note that, hereinafter, for a certain component A, the uncorrected concentration corresponding to the detection value is represented as A, and the corrected concentration is represented as [A]. [M] is calculated according to equation (1). [C1] is calculated according to equation (2). [C2] is calculated according to equation (3). Note that the uncorrected concentration corresponding to the detection value obtained from one detector is a concentration calculated based on the detection value obtained from that detector without using detection values ​​obtained from other detectors.

[0024]

[0025]

[0026]

[0027] a and b are influence coefficients indicating the degree of influence that components C1 and C2 have on the measurement of component M. c and d are influence coefficients indicating the degree of influence that components M and C2 have on the measurement of component C1. e and f are influence coefficients indicating the degree of influence that components M and C1 have on the measurement of component C2.

[0028] As shown in equations (1) to (3), the concentration of each of multiple gas components in a sample gas is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interfering components for that gas component from the uncorrected concentration corresponding to the detected value of that gas component. The measurement error caused in the measurement of a gas component is expressed as a linear sum of the corrected concentration of the interfering component for that gas component and an influence coefficient indicating the degree of influence that the interfering component has on the measurement of that gas component.

[0029] The calculation unit 200a calculates the corrected concentration of component M as the concentration [M] of component M based on the detected values ​​of each of the multiple gas components and the multiple influence coefficients a to f, in accordance with the relationship between the corrected concentration and the uncorrected concentration shown in the above equations (1) to (3).

[0030] Specifically, the calculation unit 200a calculates the concentration [M] as follows: By solving the simultaneous equations of formulas (1) to (3), [M] can be expressed by the uncorrected concentrations (M, C1, and C2) corresponding to the detected values ​​and intermediate coefficients, as shown in formula (4) below. m １ , m3, m4, m5, m6, m7, m8, m9, m10, m11, m12, m13, m14, m15, m16, m17, m18, m19, m20, m21, m22, m23, m24, m25, m26, m27, m28, m29, m30, m31, m32, m33, m34, m35, m36, m37, m38, m39, m40, m41, m42, m43, m44, m45, m46, m47, m48, m49, m49, m49, m50, m51, m52, m53, m54, m55, m56, m57, m58, m59, m60, m61, m62, m63, m64, m65,

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] In addition, in the formula, a' is a-bf, b' is b-ad, c' is c-de, d' is d-bc, e' is e-cf, and f' is f-ae.

[0037] [M] is the uncorrected concentration M, C1, and C2 corresponding to the detected value, and the intermediate coefficient m １ ∼m3, the calculation unit 200a stores, for example, an intermediate coefficient and calculates the concentration [M] of the component M based on the detection value sent from the detection unit 100a and the intermediate coefficient.

[0038] As with component M, the concentrations [C1] and [C2] of components C1 and C2 can be expressed by M, C1, and C2, which correspond to the detection values, and an intermediate coefficient. Therefore, the calculation unit 200a can determine the concentrations [C1] and [C2] based on the detection values ​​and intermediate coefficients sent from the detection unit 100a, in the same way as with the concentration [M].

[0039] The method for calculating the concentration according to a plurality of relational expressions is not limited to the above-described method. For example, the calculation unit 200a may perform calculations using influence coefficients instead of intermediate coefficients.

[0040] As described above, the corrected concentration of the target component is expressed using the corrected concentration obtained by subtracting the measurement error that affects the measurement of the interfering component from the uncorrected concentration of the interfering component. Furthermore, the concentration of the target component is determined according to the relationship between the corrected concentration of the target component and the corrected concentration of the interfering component. Therefore, the concentration of the target component can be determined more accurately by taking into account the influence of other components on the measurement of the interfering component.

[0041] Although an example in which there are two types of interfering components has been shown, there may be one type of interfering component, or three or more types of interfering components. In this case as well, gas measurement device 1a can determine the concentration of the target component based on multiple detection values ​​obtained by detecting the light intensity in the absorption wavelength range of each of multiple gas components and multiple influence coefficients, in accordance with the relationship between the corrected concentration and the uncorrected concentration.

[0042] <Method of Calculating Influence Coefficients> A method of calculating influence coefficients will be described with reference to FIG. 2 . Consider the influence coefficient indicating the degree of influence a first component has on the measurement of a second component. The detection unit 100a detects the amount of light in the absorption wavelength range of the second component by detecting light that has passed through a standard gas composed of the first component and whose concentration is known. The calculation unit 200a calculates an influence coefficient indicating the degree of influence that the first component has on the measurement of the second component based on the detected value of the second component and the known concentration of the first component, in accordance with the relationship between the corrected and uncorrected concentrations of the second component. Specifically, the influence coefficients a to f are calculated as follows:

[0043] The standard gas consisting of the first component need not contain any components that interfere with the first component (e.g., the second component), and may contain, for example, a gas such as nitrogen that does not affect the measurement of the first component.

[0044] The detection unit 100a detects a first standard gas containing component M at a concentration x but not containing components C1 and C2 using the second detector 10b and the third detector 10c, respectively, to obtain detected values ​​of component C1 and component C2. The calculation unit 200a calculates an influence coefficient c from the concentration x and the uncorrected concentration of component C1 corresponding to the detected value of component C1 detected by the second detector 10b, according to equation (2). Similarly, the calculation unit 200a calculates an influence coefficient e from the concentration x and the uncorrected concentration of component C2 corresponding to the detected value of component C2 detected by the third detector 10c, according to equation (3).

[0045] The detection unit 100a detects a second standard gas containing component C1 at a concentration y but not containing components M and C2 using each of the first detector 10a and the third detector 10c to obtain a detected value of component M and a detected value of component C2. The calculation unit 200a calculates an influence coefficient a from the concentration y and the uncorrected concentration of component M corresponding to the detected value of component M detected by the first detector 10a, in accordance with equation (1). Similarly, the calculation unit 200a calculates an influence coefficient f from the concentration y and the uncorrected concentration of component C2 corresponding to the detected value of component C2 detected by the third detector 10c, in accordance with equation (3).

[0046] The detection unit 100a detects a third standard gas containing component C2 at a concentration z but not containing component M or component C1 using each of the first detector 10a and the second detector 10b to obtain a detected value of component M and a detected value of component C1. The calculation unit 200a calculates an influence coefficient b from the concentration z and the uncorrected concentration of component M corresponding to the detected value of component M detected by the first detector 10a in accordance with equation (1). Similarly, the calculation unit 200a calculates an influence coefficient d from the concentration z and the uncorrected concentration of component C1 corresponding to the detected value of component C1 detected by the second detector 10b in accordance with equation (2).

[0047] The calculation unit 200a stores the influence coefficients a to f calculated as described above and refers to them when measuring the sample gas to calculate the concentration of the target component. Note that the calculation unit 200a may calculate and store intermediate coefficients in addition to, or instead of, the influence coefficients a to f.

[0048] As described above, the influence coefficients a to f are calculated based on actual measurement values, and therefore it is possible to obtain influence coefficients that take into account individual differences between gas measurement devices, etc. Note that the influence coefficients a to f may be determined by a manufacturer or the like before shipping gas measurement device 1a to a user, or may be determined by a user after shipping gas measurement device 1a.

[0049] §2 Specific Example Hereinafter, an example of a specific gas measurement device for implementing the method shown in FIGS. 1 and 2 will be described with reference to FIGS.

[0050] <Configuration of Gas Measurement Apparatus> Fig. 3 is a diagram showing the configuration of a gas measurement apparatus. The gas measurement apparatus 1 measures exhaust gas as a sample gas and nitrous oxide (N ２ The gas measurement device 1 also measures the concentration of sulfur dioxide (SO O) as an interfering component of nitrous oxide. ２ ), methane (CH ４ ), and carbon dioxide (CO ２ ) and detects the amount of light in the absorption wavelength range of each of the following: (1) The gas measuring device 1 calculates the concentration of nitrous oxide by correcting the detected value of nitrous oxide using the detected values ​​of sulfur dioxide, methane, and carbon dioxide. Specific examples of exhaust gas include gases emitted from chemical plants and steel mills, combustion gases from boilers and combustion furnaces, and automobile exhaust gases. Furthermore, the sample gas is not limited to exhaust gas, and may be, for example, the atmosphere.

[0051] 3 , gas measurement device 1 includes detection unit 100, control unit 200, input unit 300, and display unit 400. Detection unit 100 detects the amount of light in the absorption wavelength range of each of multiple gas components in the sample gas. More specifically, detection unit 100 detects the amount of light in the absorption wavelength range of each of nitrous oxide, sulfur dioxide, methane, and carbon dioxide.

[0052] The control unit 200 controls the detection unit 100. The control unit 200 also functions as a calculation device that calculates the concentration of nitrous oxide based on the detection values ​​of each of the multiple gas components detected by the detection unit 100. The control unit 200 includes a processor 220, a memory 240, and an input / output interface (not shown) for inputting and outputting various signals.

[0053] The memory 240 includes, for example, a read-only memory (ROM) and a random access memory (RAM). The processor 220 loads a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program that describes the processing procedures of the control unit 200. The ROM stores various coefficients and relational expressions used to calculate the concentration of nitrous oxide. The control unit 200 executes various processes to calculate the concentration of nitrous oxide in accordance with these programs, coefficients, and relational expressions. The processes are not limited to those performed by software, but can also be performed by dedicated hardware (electronic circuits).

[0054] The input unit 300 is a device that accepts user operations such as a mouse or a keyboard. For example, the input unit 300 accepts input of the concentration of a gas component in a standard gas and sends it to the control unit 200. The display unit 400 is a display device such as a liquid crystal panel, and displays, for example, the concentration of nitrous oxide determined by the control unit 200.

[0055] <Configuration of Detection Unit> Referring to FIG. 3, the detection unit 100 includes a measurement gas line SL, a reference gas line RL, two switching valves 112 and 114, a first detection unit 120, a second detection unit 140, a motor 160, and a sector 180.

[0056] A measurement gas SG is introduced into the measurement gas line SL. The measurement gas SG is a gas to be measured in the detection unit 100, and includes a sample gas and a standard gas used in preparation for measuring the sample gas.

[0057] A reference gas RG is introduced into the reference gas line RL. The reference gas RG is a so-called zero gas, which is an inert gas such as nitrogen that does not absorb infrared light. The reference gas RG may be any gas that does not interfere with any of the gas components measured by the detection unit 100, and may also be a gas that absorbs infrared light.

[0058] The switching valve 112 is connected to the measurement gas line SL, the first line L1, and the third line L3, while the switching valve 114 is connected to the reference gas line RL, the second line L2, and the fourth line L4.

[0059] The first line L1 is connected to the first detection unit 120. The second line L2 is connected to the second detection unit 140. The third line L3 is connected to the second line L2. The fourth line L4 is connected to the first line L1.

[0060] That is, the switching valve 112 is connected to the measurement gas line SL, a flow path connected to the first sample cell 122, and a flow path connected to the second sample cell 142. The switching valve 114 is connected to the reference gas line RL, a flow path connected to the first sample cell 122, and a flow path connected to the second sample cell 142.

[0061] The control unit 200 controls the switching valve 112 at a predetermined cycle to switch the flow path connected to the measurement gas line SL to the flow path connected to the first detection unit 120 or the flow path connected to the second detection unit 140. The control unit 200 controls the switching valves 112, 114 to connect the reference gas line RL to the second sample cell 142 while the measurement gas line SL is connected to the first detection unit 120. The control unit 200 also controls the switching valves 112, 114 to connect the reference gas line RL to the first sample cell 122 while the measurement gas line SL is connected to the second sample cell 142.

[0062] As a result, the reference gas and the sample gas are alternately filled into each of the first detection unit 120 and the second detection unit 140. More specifically, while the first detection unit 120 is being filled with the reference gas, the second detection unit 140 is being filled with the sample gas, and while the first detection unit 120 is being filled with the sample gas, the second detection unit 140 is being filled with the reference gas.

[0063] Motor 160 rotates sector 180 in accordance with commands from control unit 200. Sector 180 is provided between first sample cell 122 and first light source 124, which will be described later, and between second sample cell 142 and second light source 144. Sector 180 has a light-shielding portion and a light-transmitting portion, and irradiates and blocks light from first light source 124 onto first sample cell 122. Sector 180 also irradiates and blocks light from second light source 144 onto second sample cell 142.

[0064] First detection unit 120 detects the amount of light in the absorption wavelength range of a target component that is the primary target when measuring gas components using gas measurement device 1. First detection unit 120 includes first sample cell 122, first light source 124, first detector 10A that detects the amount of light in the absorption wavelength range of nitrous oxide, optical filter 20, and first gas filter 30. First sample cell 122, first gas filter 30, optical filter 20, and first detector 10A are arranged on first optical path IR1 of first light source 124, in that order.

[0065] Second detection unit 140 detects the amount of light in the absorption wavelength range of an interfering component relative to the target component of primary interest when measuring gas components using gas measurement device 1. Second detection unit 140 includes second light source 144, second sample cell 142, second gas filter 40, second detector 10B that detects the amount of light in the absorption wavelength range of sulfur dioxide, third detector 10C that detects the amount of light in the absorption wavelength range of methane, and fourth detector 10D that detects the amount of light in the absorption wavelength range of carbon dioxide. Second sample cell 142, second gas filter 40, second detector 10B, third detector 10C, and fourth detector 10D are arranged on second optical path IR2 of second light source 144, in that order.

[0066] As described above, first detector 10A that detects nitrous oxide is disposed on first optical path IR1, separate from second optical path IR2 on which the detector that detects the interference components of nitrous oxide is disposed. This reduces light attenuation and prevents a decrease in the detection sensitivity of nitrous oxide. Furthermore, because the multiple detectors that detect the interference components of nitrous oxide (second detector 10B, third detector 10C, and fourth detector 10D) are disposed in series on second optical path IR2, the overall size of gas measurement device 1 can be prevented from increasing.

[0067] <Configuration of First Detection Unit> First detection unit 120 detects the amount of light in the absorption wavelength range of the target component that is the main target when measuring gas components using gas measurement device 1. In the present embodiment, first detection unit 120 detects the amount of light in the absorption wavelength range of nitrous oxide. First detection unit 120 includes first sample cell 122, first light source 124, first detector 10A, optical filter 20, and first gas filter 30.

[0068] The first light source 124 emits light that includes at least the absorption wavelength range of the target component. The first light source 124 is not particularly limited, and may be, for example, a light source that uses a nichrome wire.

[0069] First sample cell 122, first gas filter 30, optical filter 20, and first detector 10A are arranged in this order on first optical path IR1 of first light source 124. Although not shown, windows that transmit light from first light source 124 are formed on both ends of each of first sample cell 122, first gas filter 30, and optical filter 20 on first optical path IR1. As a result, light from first light source 124 passes through first sample cell 122, first gas filter 30, optical filter 20, and first detector 10A in this order.

[0070] The first sample cell 122 is hollow and includes a gas inlet 122 a and a gas outlet 122 b. The measurement gas SG or the reference gas RG is supplied from the first line L1 through the gas inlet 122 a into the first sample cell 122 and is discharged from the gas outlet 122 b.

[0071] First detector 10A detects the amount of light in the absorption wavelength range of nitrous oxide. First detector 10A includes first housing 12A filled with nitrous oxide as a gas component and first detection unit 14A that detects the pressure within first housing 12A. In this embodiment, first detector 10A indirectly detects the amount of light in the absorption wavelength range specific to nitrous oxide by detecting pressure changes within first housing 12A. First detector 10A detects light from first light source 124 that has been transmitted through first sample cell 122, first gas filter 30, and optical filter 20, in that order.

[0072] The optical filter 20 transmits light in a specific absorption wavelength range while blocking light in a specific absorption wavelength range. As will be described later with reference to FIGS. 7 and 8 , nitrous oxide has a first absorption wavelength range (an absorption wavelength range around 7.8 μm) and a second absorption wavelength range (an absorption wavelength range around 4.5 μm). Of the two absorption wavelength ranges, at least a portion of the second absorption wavelength range overlaps with the absorption wavelength range of carbon dioxide. The optical filter 20 blocks light in the second absorption wavelength range of nitrous oxide that overlaps with the absorption wavelength range of carbon dioxide, while transmitting light in the first absorption wavelength range. For example, the optical filter 20 blocks light with wavelengths of 5.5 μm to 6.5 μm or shorter, while transmitting light with wavelengths longer than 5.5 μm to 6.5 μm.

[0073] The first gas filter 30 is filled with an interference component gas having an absorption wavelength range that at least partially overlaps with the first absorption wavelength range of nitrous oxide. In this embodiment, the first gas filter 30 is filled with methane as the gas component.

[0074] The order of arrangement of optical filter 20 and first gas filter 30 may be reversed. Specifically, first sample cell 122, optical filter 20, first gas filter 30, and first detector 10A may be arranged on first optical path IR1 in this order.

[0075] <Second Detection Unit> Second detection unit 140 detects the amount of light in the absorption wavelength range of an interfering component relative to a target component of primary interest when measuring gas components using gas measurement device 1. In the present embodiment, second detection unit 140 includes second light source 144, second sample cell 142, second gas filter 40, second detector 10B, third detector 10C, and fourth detector 10D.

[0076] The second light source 144 and the second sample cell 142 are respectively common to the first light source 124 and the first sample cell 122 of the first detection unit 120. Specifically, the measurement gas SG or the reference gas RG is supplied from the second line L2 through a gas inlet 142a of the second sample cell 142 into the second sample cell 142 and is discharged from a gas outlet 142b.

[0077] Second sample cell 142, second gas filter 40, second detector 10B, third detector 10C, and fourth detector 10D are arranged in this order on second optical path IR2 of second light source 144. Although not shown, windows that transmit light from second light source 144 are formed on both ends of each of second sample cell 142, second gas filter 40, second detector 10B, and third detector 10C on second optical path IR2. Light from second light source 144 passes through second sample cell 142, second gas filter 40, second detector 10B, third detector 10C, and fourth detector 10D in this order.

[0078] The second detector 10B detects the amount of light in the absorption wavelength range of sulfur dioxide. The second detector 10B includes a second housing 12B filled with sulfur dioxide as a gas component and a second detection unit 14B that detects the pressure inside the second housing 12B. The second detector 10B indirectly detects the amount of light in the absorption wavelength range specific to sulfur dioxide by detecting pressure changes inside the second housing 12B. The second detector 10B detects light from the second light source 144 that has been transmitted through the second sample cell 142 and the second gas filter 40 in that order.

[0079] The third detector 10C detects the amount of light in the absorption wavelength range of methane. The third detector 10C includes a third housing 12C filled with methane as a gas component and a third detection unit 14C that detects the pressure inside the third housing 12C. The third detector 10C indirectly detects the amount of light in the absorption wavelength range specific to methane by detecting pressure changes inside the third housing 12C. The third detector 10C detects light from the second light source 144 that has been transmitted through the second sample cell 142, the second gas filter 40, and the second detector 10B in this order.

[0080] The fourth detector 10D detects the amount of light in the carbon dioxide absorption wavelength range. The fourth detector 10D includes a fourth housing 12D filled with carbon dioxide as a gas component and a fourth detection unit 14D that detects the pressure inside the fourth housing 12D. The fourth detector 10D indirectly detects the amount of light in the carbon dioxide absorption wavelength range by detecting pressure changes inside the fourth housing 12D. The fourth detector 10D detects light from the second light source 144 that has been transmitted through the second sample cell 142, the second gas filter 40, the second detector 10B, and the third detector 10C in this order.

[0081] Carbon dioxide is filled in the second gas filter 40. The second gas filter 40 reduces the amount of light in the absorption wavelength range of carbon dioxide out of the absorption wavelength ranges of sulfur dioxide and methane, thereby reducing the effect of carbon dioxide on the measurements of sulfur dioxide and methane.

[0082] <Software Configuration of Control Unit> Fig. 4 is a functional block diagram of the control unit. The control unit 200 includes a pre-correction density calculation unit 222, a correction value calculation unit 224, a coefficient calculation unit 226, and a storage unit 228. The functions shown in Fig. 4 are realized by the processor 220 executing a program. The storage unit 228 corresponds to the memory 240.

[0083] The uncorrected concentration calculation unit 222 calculates the concentration of the gas component in the sample gas by applying a predetermined arithmetic formula to the detection signal (reference signal) when the reference gas is sent to the detection unit 100 and the detection signal (measurement signal) when the sample gas is sent to the detection unit 100. In other words, the reference signal and the measurement signal correspond to the "detection value."

[0084] The uncorrected concentration calculation unit 222 calculates the uncorrected concentration of nitrous oxide based on the reference signal and measurement signal detected by the first detector 10 A. Similarly, the uncorrected concentration calculation unit 222 calculates the uncorrected concentration of sulfur dioxide based on the reference signal and measurement signal detected by the second detector 10 B, the uncorrected concentration of methane based on the reference signal and measurement signal detected by the third detector 10 C, and the uncorrected concentration of carbon dioxide based on the reference signal and measurement signal detected by the fourth detector 10 D.

[0085] In the present embodiment, pre-correction concentration calculation unit 222 uses a reference gas, but the concentration may be calculated based on the measurement signal without using a reference gas. Furthermore, gas measurement device 1 may obtain a reference signal by using a reference cell in which a cell is filled with a reference gas and sealed, rather than by circulating a reference gas.

[0086] The correction value calculation unit 224 corrects the nitrous oxide detection value obtained by the detection unit 100 using the detection values ​​of carbon dioxide, methane, and sulfur dioxide, which interfere with the nitrous oxide measurement, to determine the nitrous oxide concentration. The concentration of each gas component is calculated according to the following equations (9) to (12). Note that for a given component A, the pre-correction concentration corresponding to the detection value is represented as A, and the post-correction concentration is represented as [A].

[0087]

[0088]

[0089]

[0090]

[0091] In equation (9), a, b, and g are influence coefficients that indicate the degree of influence that nitrous oxide, sulfur dioxide, and carbon dioxide have on methane measurement. In equation (10), c, d, and h are influence coefficients that indicate the degree of influence that methane, sulfur dioxide, and carbon dioxide have on nitrous oxide measurement. In equation (11), e, f, and i are influence coefficients that indicate the degree of influence that methane, nitrous oxide, and carbon dioxide have on sulfur dioxide measurement.

[0092] As shown in equations (9) to (11), the concentration of each of the multiple gas components in the sample gas is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interfering components for that gas component from the uncorrected concentration corresponding to the detected value of that gas component. The measurement error caused in the measurement of the gas component is expressed as a linear sum of the corrected concentration of the interfering component for that gas component and an influence coefficient indicating the degree of influence that the interfering component has on the measurement of that gas component.

[0093] In this embodiment, the sample gas is exhaust gas. The carbon dioxide concentration in the exhaust gas is 100 times higher than the concentrations of the other components (nitrous oxide, sulfur dioxide, and methane). In this embodiment, since the carbon dioxide concentration is extremely high compared to the other components (nitrous oxide, sulfur dioxide, and methane), it is assumed that the other components have no effect on the measurement of carbon dioxide, as shown in equation (12).

[0094] The correction value calculation unit 224 calculates the concentration of nitrous oxide based on the influence coefficients and the uncorrected concentrations of the gas components corresponding to each detection value in accordance with the relationships of Equations (9) to (12). Specifically, by solving the simultaneous equations of Equations (9) to (12), the concentration of nitrous oxide is calculated as the uncorrected concentration (N ２ O, CH ４ , SO ２ , CO ２ ) and an intermediate coefficient expressed using a plurality of influence coefficients. Therefore, the correction value calculation unit 224 can calculate the concentration of nitrous oxide based on the influence coefficient or the intermediate coefficient and the pre-correction concentration of the gas component corresponding to each detection value. Note that the method for calculating the concentration according to the relationships of equations (9) to (12) is not limited to this method. For example, the correction value calculation unit 224 may perform calculations using the influence coefficients without using the intermediate coefficients.

[0095] The coefficient calculation unit 226 calculates the influence coefficients based on the detection value obtained by detecting a standard gas whose concentration is known and the concentration of the standard gas input from the input unit 300. Specifically, the influence coefficients a to i in the formulas (9) to (11) are calculated as follows:

[0096] The detection unit 100 detects a standard gas consisting of nitrous oxide, the concentration of which is known, using each of the second detector 10B and the third detector 10C. Based on the multiple detection values ​​thus obtained and the known concentration, the influence coefficients a and f in equations (9) and (11) are calculated.

[0097] Specifically, the control unit 200 calculates the influence coefficient a by dividing the uncorrected methane concentration corresponding to the detection value of the third detector 10C by the input dinitrogen monoxide concentration in accordance with the relationship in equation (9). The control unit 200 calculates the influence coefficient f by dividing the uncorrected sulfur dioxide concentration corresponding to the detection value of the second detector 10B by the input dinitrogen monoxide concentration in accordance with the relationship in equation (11).

[0098] The detection unit 100 detects a standard gas made of sulfur dioxide with a known concentration using each of the first detector 10A and the third detector 10C. Based on the multiple detection values ​​obtained in this way and the known concentration, the influence coefficients b and d in equations (9) and (10) are calculated.

[0099] Specifically, the control unit 200 calculates the influence coefficient b by dividing the uncorrected methane concentration corresponding to the detection value of the third detector 10C by the input sulfur dioxide concentration in accordance with the relationship in equation (9). The control unit 200 calculates the influence coefficient d by dividing the uncorrected nitrous oxide concentration corresponding to the detection value of the first detector 10A by the input sulfur dioxide concentration in accordance with the relationship in equation (10).

[0100] The detection unit 100 detects a standard gas consisting of methane with a known concentration using each of the first detector 10A and the second detector 10B. Based on the multiple detection values ​​obtained in this way and the known concentration, the influence coefficients c and e in equations (10) and (11) are calculated.

[0101] Specifically, the control unit 200 calculates the influence coefficient c by dividing the uncorrected concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input concentration of methane in accordance with the relationship in equation (10). The control unit 200 calculates the influence coefficient e by dividing the uncorrected concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input concentration of methane in accordance with the relationship in equation (11).

[0102] The detection unit 100 detects a standard gas made of carbon dioxide with a known concentration using the first detector 10A, the second detector 10B, and the third detector 10C. Based on the multiple detection values ​​obtained in this way and the known concentration, the influence coefficients g, h, and i in equations (9) to (11) are calculated.

[0103] Specifically, the control unit 200 calculates the influence coefficient g by dividing the uncorrected methane concentration corresponding to the detection value of the third detector 10C by the input carbon dioxide concentration according to the relationship in equation (9). The control unit 200 calculates the influence coefficient h by dividing the uncorrected nitrous oxide concentration corresponding to the detection value of the first detector 10A by the input carbon dioxide concentration according to the relationship in equation (10). The control unit 200 calculates the influence coefficient i by dividing the uncorrected sulfur dioxide concentration corresponding to the detection value of the second detector 10B by the input carbon dioxide concentration according to the relationship in equation (11).

[0104] The coefficient calculation unit 226 stores the determined influence coefficients a to i in the storage unit 228. The coefficient calculation unit 226 may determine an intermediate coefficient from the determined influence coefficients a to i, and store at least one of the influence coefficients and the intermediate coefficient in the storage unit 228. The coefficient calculation unit 226 may determine only the intermediate coefficient without determining the influence coefficient, and store the determined intermediate coefficient in the storage unit 228.

[0105] <Procedure for Determining the Concentration of a Target Component> A method for determining the concentration of a target component will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the processing of the control unit when measuring a sample gas. Note that, hereinafter, step will be abbreviated as "S".

[0106] In S12, the control unit 200 acquires detection values ​​for each of the plurality of gas components from the detection unit 100, which are obtained by detecting the amount of light in the absorption wavelength range of each of the plurality of gas components by detecting light that has passed through the sample gas. Specifically, the detection unit 100 detects the amount of light in the absorption wavelength range of each of nitrous oxide, sulfur dioxide, methane, and carbon dioxide. The detection unit 100 sends each of the detected detection values ​​to the control unit 200.

[0107] In S14, the control unit 200 calculates the concentration of nitrous oxide based on the detected values ​​of each of the plurality of gas components. More specifically, the control unit 200 calculates the concentration of nitrous oxide based on the plurality of influence coefficients a to f and the uncorrected concentrations of the gas components corresponding to each detected value, in accordance with the relationships of the above-mentioned equations (9) to (12).

[0108] In S16, the control unit 200 displays the determined concentration of nitrous oxide on the display unit 400.

[0109] As described above, the control unit 200 determines the concentration of nitrous oxide in the sample gas.

[0110] <Method of Calculating Influence Coefficient> A method of calculating the influence coefficient will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the processing of the control unit when calculating the influence coefficient.

[0111] In S22, the control unit 200 acquires the detection values ​​obtained by detecting a standard gas made of nitrous oxide, the concentration of which is known, using the second detector 10B and the third detector 10C. In S24, the control unit 200 receives an input of the concentration of nitrous oxide from the input unit 300.

[0112] In S26, the control unit 200 calculates an influence coefficient a in equation (9) that indicates the degree of influence that nitrous oxide has on the measurement of methane, and an influence coefficient f in equation (11) that indicates the degree of influence that nitrous oxide has on the measurement of sulfur dioxide.

[0113] In S28, the control unit 200 acquires the detection values ​​obtained by detecting a standard gas made of sulfur dioxide, the concentration of which is known, using the first detector 10A and the third detector 10C. In S30, the control unit 200 receives an input of the concentration of sulfur dioxide from the input unit 300.

[0114] In S32, the control unit 200 calculates an influence coefficient b in equation (9) that indicates the degree of influence that sulfur dioxide has on the measurement of methane, and an influence coefficient d in equation (10) that indicates the degree of influence that sulfur dioxide has on the measurement of nitrous oxide.

[0115] In S34, the control unit 200 acquires the detection values ​​obtained by detecting a standard gas made of methane, the concentration of which is known, using each of the first detector 10A and the second detector 10B. In S36, the control unit 200 receives an input of the concentration of methane from the input unit 300.

[0116] In S38, the control unit 200 calculates an influence coefficient c in equation (10) that indicates the degree of influence that methane has on the measurement of nitrous oxide, and an influence coefficient e in equation (11) that indicates the degree of influence that methane has on the measurement of sulfur dioxide.

[0117] In S40, the control unit 200 acquires the detected values ​​obtained by detecting a standard gas made of carbon dioxide, the concentration of which is known, using each of the first detector 10A, the second detector 10B, and the third detector 10C. In S42, the control unit 200 receives an input of the carbon dioxide concentration from the input unit 300.

[0118] In S44, the control unit 200 calculates an influence coefficient g indicating the degree of influence of carbon dioxide on the measurement of methane in equation (9), an influence coefficient h indicating the degree of influence of carbon dioxide on the measurement of nitrous oxide in equation (10), and an influence coefficient i indicating the degree of influence of carbon dioxide on the measurement of sulfur dioxide in equation (11).

[0119] As described above, gas measurement apparatus 1 obtains an influence coefficient that indicates the degree to which an interfering component for a given gas component influences the measurement of that given gas component.

[0120] <Examples and Comparative Examples> Table 1 shows the results of an example in which the uncorrected concentration obtained when measuring a sample gas using the gas measurement device 1 shown in FIG. 3 was corrected by the method according to the present embodiment, and a comparative example in which the concentration was corrected by a conventional method.

[0121]

[0122] In the examples, the pre-correction densities were corrected according to the above formulas (9) to (12). In the comparative examples, the pre-correction densities were corrected according to the following formulas (13) to (15) and the above formula (12). Note that the influence coefficients a to i are common coefficients in the examples and the comparative examples.

[0123]

[0124]

[0125]

[0126] As shown in equations (13) to (15), in the comparative example, the pre-correction concentration corresponding to the detected value is corrected using the pre-correction concentration of the interfering component, without taking into account that the measurement of the interfering component is affected by other components. As shown in Table 1, there is a difference in the post-correction concentration between the comparative example and the example. This difference is due to taking into account that the measurement of the interfering component is affected by other components. By taking into account that the measurement of the interfering component is affected by other components, the concentration of the target component can be determined more accurately.

[0127] <Infrared Absorption Spectrum of Each Gas Component> The infrared absorption spectrum of each gas component will be described with reference to Figures 7 and 8. Figure 7 shows the infrared absorption spectra of nitrous oxide and carbon dioxide. Figure 8 shows the infrared absorption spectra of nitrous oxide, methane, and sulfur dioxide. In Figures 7 and 8, the spectrum shown by the solid line is the infrared absorption spectrum of nitrous oxide. In Figure 7, the spectrum shown by the dashed-dotted line is the infrared absorption spectrum of carbon dioxide. In Figure 8, the spectrum shown by the dashed-dotted line is the infrared absorption spectrum of sulfur dioxide. In Figures 7 and 8, the horizontal axis represents wavelength, and the vertical axis represents absorbance.

[0128] As shown in Figures 7 and 8, nitrous oxide has absorption wavelength ranges around 4.5 μm and 7.8 μm. As shown in Figure 7, carbon dioxide has an absorption wavelength range around 4.25 μm, which at least partially overlaps with the absorption wavelength range around 4.5 μm of nitrous oxide.

[0129] In this embodiment, the first detection unit 120 includes an optical filter 20 that transmits light in the first absorption wavelength range while blocking light in the second absorption wavelength range that overlaps with the absorption wavelength range of carbon dioxide. As shown in Fig. 3, the first detector 10A detects light that has passed through the optical filter 20, and therefore detects the amount of light in the absorption wavelength range around 7.8 µm, rather than the absorption wavelength range around 4.5 µm that overlaps with that of carbon dioxide.

[0130] 7 and 8, when comparing the absorption wavelength range of nitrous oxide around 7.8 μm with the absorption wavelength range around 4.5 μm, the absorption around 7.8 μm detected by first detector 10A is weaker than the absorption around 4.5 μm. However, in this embodiment, exhaust gas is assumed as the sample gas, and the concentration of carbon dioxide in the exhaust gas is on the order of %, while the concentration of nitrous oxide is on the order of ppm. Because the concentration of carbon dioxide is higher than that of nitrous oxide, the impact of carbon dioxide on the measurement of nitrous oxide is extremely large.

[0131] Therefore, the first detection unit 120 according to this embodiment detects the amount of light in the absorption wavelength range around 7.8 μm, where absorption is weaker but does not overlap with the absorption wavelength range of carbon dioxide. This reduces the effect of carbon dioxide present in high concentrations in the sample gas on the measurement of nitrous oxide, enabling nitrous oxide to be measured with higher accuracy.

[0132] Carbon monoxide (CO) may be contained in exhaust gas. Although not shown, the absorption wavelength range of carbon monoxide is around 4.7 μm, which overlaps with the absorption wavelength range of carbon monoxide around 4.5 μm. Therefore, by providing optical filter 20, the effect of carbon monoxide on the measurement of nitrous oxide can be reduced, allowing nitrous oxide to be measured with higher accuracy.

[0133] The first detector 10A detects the amount of light in the absorption wavelength range around 7.8 μm within the absorption wavelength range of nitrous oxide. As shown in Figure 8, methane has an absorption wavelength range around 7.8 μm, and sulfur dioxide has an absorption wavelength range around 7.4 μm, and each gas component at least partially overlaps with the absorption wavelength range around 7.8 μm of nitrous oxide. Therefore, the detection value of the first detector 10A reflects the influence of light absorption by sulfur dioxide and methane in addition to the influence of light absorption by nitrous oxide.

[0134] In this embodiment, the first detection unit 120 includes a first gas filter 30 filled with a gas component having an absorption wavelength range that at least partially overlaps with a first absorption wavelength range of nitrous oxide, the first absorption wavelength range being different from a second absorption wavelength range that overlaps with the absorption wavelength range of carbon dioxide. This reduces the amount of light in the absorption wavelength range of the gas component that at least partially overlaps with the first absorption wavelength range. As a result, the influence of the gas component that at least partially overlaps with the first absorption wavelength range on the measurement of nitrous oxide can be reduced, allowing for more accurate measurement of nitrous oxide.

[0135] In this embodiment, the first gas filter 30 is filled with methane gas. The absorption wavelength range of methane overlaps more with the absorption wavelength range of nitrous oxide than with sulfur dioxide. Therefore, the influence of methane on nitrous oxide measurement is greater than that of sulfur dioxide. In this embodiment, the amount of light in the absorption wavelength range of methane, which has a large influence on nitrous oxide measurement, can be reduced, allowing nitrous oxide to be measured with higher accuracy.

[0136] In addition to the first gas filter 30 filled with methane, a gas filter filled with sulfur dioxide may be provided on the first optical path IR1 between the first sample cell 122 and the first detector 10A. The gas component filled in the first gas filter 30 may be sulfur dioxide instead of methane.

[0137] The effect of the first gas filter 30 can be adjusted by changing the partial pressure of the fill gas or the distance that light from the first light source 124 passes through the first gas filter 30. For example, the effect of the first gas filter 30 can be increased by increasing the partial pressure of the fill gas or increasing the distance that light from the first light source 124 passes through the first gas filter 30. However, increasing the effect of the first gas filter 30 also reduces the amount of light in the absorption wavelength range of nitrous oxide detected by the first detector 10A, thereby reducing the detection sensitivity of nitrous oxide. Therefore, the partial pressure of the fill gas and the distance that light from the first light source 124 passes through the first gas filter 30 are adjusted within a range that ensures detection sensitivity for nitrous oxide.

[0138] In this embodiment, the first detection unit 120 uses the optical filter 20 to block light in the absorption wavelength range of carbon dioxide. However, carbon dioxide also absorbs light in the absorption wavelength range around 7.8 μm, albeit to a small amount. As described above, the concentration of carbon dioxide in exhaust gas is higher than that of nitrous oxide. As a result, even a small amount of light absorption by carbon dioxide affects the measurement of nitrous oxide. Therefore, in this embodiment, the control unit 200 calculates the concentration of nitrous oxide, assuming that carbon dioxide affects the measurement of nitrous oxide, as shown in equation (10).

[0139] Similarly, carbon dioxide also absorbs light in the absorption wavelength ranges of sulfur dioxide and methane, albeit to a small amount. The concentration of carbon dioxide in exhaust gas is on the order of percent, while the concentrations of sulfur dioxide and methane are on the order of ppm. Therefore, control unit 200 calculates the concentration of nitrous oxide, assuming that carbon dioxide affects the measurements of sulfur dioxide and methane, as shown in equations (9) and (11).

[0140] The second detection unit 140 according to this embodiment also includes a second gas filter 40 filled with carbon dioxide. As described above, even slight absorption by carbon dioxide affects the measurement of sulfur dioxide and methane. Therefore, by including the second gas filter 40, the second detection unit 140 reduces the amount of light in the carbon dioxide absorption wavelength range among the absorption wavelength ranges of sulfur dioxide and methane. As a result, the impact of carbon dioxide on the measurements of sulfur dioxide and methane can be reduced, enabling sulfur dioxide and methane to be measured with higher accuracy. Note that increasing the effectiveness of the second gas filter 40 reduces the detection sensitivity of the fourth detector 10D. Therefore, the partial pressure of the gas filled in the second gas filter 40 and the distance that light from the second light source 144 travels through the second gas filter 40 are adjusted within a range that ensures carbon dioxide detection sensitivity.

[0141] As shown in FIG. 8 , the absorption wavelength ranges of sulfur dioxide and methane partially overlap, so sulfur dioxide affects methane measurement. In the second detection unit 140, a second detector 10B including a second housing 12B filled with sulfur dioxide is disposed between a third detector 10C that detects the amount of light in the methane absorption wavelength range and a second sample cell 142. Therefore, the third detector 10C detects light that passes through the second sample cell 142 and the second housing 12B in that order. This allows the second housing 12B to function as a gas filter, reducing the amount of light in the sulfur dioxide absorption wavelength range within the methane absorption wavelength range. As a result, methane measurement errors caused by sulfur dioxide can be reduced, enabling methane to be measured with higher accuracy.

[0142] Alternatively, the third detector 10C may be disposed on the second optical path IR2 between the second sample cell 142 and the second detector 10B. By disposing the detector in this manner, the third housing 12C of the third detector 10C, which is filled with methane, functions as a gas filter, reducing the amount of light in the methane absorption wavelength range within the sulfur dioxide absorption wavelength range. As a result, sulfur dioxide measurement errors caused by methane can be reduced, enabling sulfur dioxide to be measured with higher accuracy. The order of the second detector 10B and the third detector 10C is determined depending on whether higher accuracy is desired for the measurement of methane or sulfur dioxide.

[0143] In the present embodiment, gas measurement device 1 uses infrared light, but may use ultraviolet light depending on the absorption wavelength range of the target component.

[0144] In this embodiment, the amount of light is indirectly detected by detecting the change in internal pressure when transmitted light passes through a cell containing the gas to be detected. Alternatively, the amount of light may be directly detected using a photoconductive element or the like. Furthermore, the multiple detectors (first detector 10A to fourth detector 10D) included in the detection unit 100 share a common method for detecting the amount of light. Alternatively, the multiple detectors may each have a different method for detecting the amount of light. For example, the first detector 10A and the fourth detector 10D, which are located farthest from the light source, may be detectors equipped with pyroelectric sensors, while the remaining detectors, the second detector 10B and the third detector 10C, may be detectors equipped with the configurations of the above-described embodiments.

[0145] Although the gas measurement device 1 is designed to measure exhaust gas, it can also measure other gases. The detection target of each detector can be changed depending on the measurement target. The optical filter 20, the first gas filter 30, and the second gas filter 40 can also be adjusted depending on the measurement target.

[0146] In order to measure the concentration of nitrous oxide, gas measurement device 1 is equipped with detectors for three types of interference components, namely, sulfur dioxide, methane, and carbon dioxide. Gas measurement device 1 is only required to be equipped with a detector for at least one of the interference components of sulfur dioxide, methane, and carbon dioxide, and may also be equipped with detectors for other interference components in addition to the detectors for the three types of interference components.

[0147] The control unit 200 calculates the concentration of nitrous oxide as shown in equation (12), assuming that other components have no effect on the measurement of carbon dioxide.

[0148] Note that, for one or more interfering components for a single gas component, if the measurement error caused by the interfering component in the measurement of the single gas component is sufficiently smaller than the concentration of the single gas component, the control unit 200 may determine the concentration of the target component by setting the influence of the interfering component on the measurement of the single gas component to zero. Note that the measurement error caused by the interfering component in the measurement of the single gas component can be obtained by multiplying the corrected concentration of the interfering component by an influence coefficient indicating the degree of influence of the interfering component on the measurement of the single gas component.

[0149] For example, if the measurement error caused by an interfering component in the measurement of a gas component is 1 / 1000 or less of the concentration of the gas component, the effect of the interfering component on the measurement of the gas component may be set to zero. Alternatively, if the measurement error caused by an interfering component in the measurement of a gas component is 1 / 100 or less of the concentration of the gas component, the effect of the interfering component on the measurement of the gas component may be set to zero. The criteria for setting the effect to zero may be set according to the accuracy required of gas measurement device 1 and the expected maximum concentration of the interfering component in the sample gas.

[0150] For example, the measurement error (d[SO ２ ]) is the concentration of nitrous oxide ([N ２ O]), the control unit 200 may determine the concentration of nitrous oxide by setting the influence coefficient d in the formula (10) to zero.

[0151] In the above embodiment, gas measurement device 1 determines the concentration of nitrous oxide using exhaust gas as the sample gas and nitrous oxide as the target component. The sample gas and target component may be other gases and components. For example, gas measurement device 1 may be configured to measure a sample gas that contains, in addition to the target component, two or more interfering components with the target component. Even in this case, by arranging the detector for the target component and the detector for the interfering component on separate optical paths and arranging the detectors for each of the multiple interfering components in series on the same optical path, it is possible to prevent a decrease in detection sensitivity for the target component and an increase in the size of the gas measurement device.

[0152] In the above embodiment, control unit 200 controls both detection unit 100 and calculates the concentration. However, gas measurement device 1 may separately include a control unit that controls detection unit 100 and a calculation unit that calculates the concentration. In this case, each of the control unit and the calculation unit includes a processor, a memory, and an input / output interface.

[0153] [Aspects] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0154] (Item 1) A gas measurement device according to one aspect measures a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap with each other. The gas measurement device includes a detection unit that detects the amount of light in the absorption wavelength range of each of the multiple gas components by detecting light passing through the sample gas, and a calculation unit that calculates the concentration of a target component among the multiple gas components based on the detection values ​​of each of the multiple gas components detected by the detection unit. A gas component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of one of the multiple gas components is an interfering component with respect to the one gas component. The concentration of each of the multiple gas components is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interfering components with respect to the gas component from the pre-correction concentration corresponding to the detected value of the gas component. The measurement error caused by the interfering component with respect to the gas component is expressed as a linear sum of the corrected concentration of the interfering component with respect to the gas component and an influence coefficient indicating the degree of influence of the interfering component on the measurement of the gas component. The calculation unit calculates the corrected concentration of the target component as the concentration of the target component based on the multiple influence coefficients and the detection values ​​of each of the multiple gas components, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the multiple gas components.

[0155] According to the gas measurement device described in paragraph 1, the corrected concentration of a target component is expressed using a corrected concentration obtained by subtracting the measurement error that affects the measurement of an interfering component from the uncorrected concentration of the interfering component. Furthermore, the concentration of the target component is determined according to the relationship between the corrected concentration of the target component and the corrected concentration of the interfering component. Therefore, the concentration of the target component can be determined more accurately by taking into account the influence of other components on the measurement of the interfering component.

[0156] (2) In the gas measurement device described in (1), the detection unit detects the amount of light in the absorption wavelength range of a second component of the plurality of gas components by detecting light that has passed through a standard gas composed of a first component of the plurality of gas components and whose concentration is known. The calculation unit calculates an influence coefficient that indicates the degree of influence that the first component has on the measurement of the second component based on the detected value of the second component and the known concentration of the first component, in accordance with the relationship between the corrected and uncorrected concentrations of the second component.

[0157] According to the gas measurement device described in paragraph 2, the influence coefficient can be calculated based on the actual measurement value, and the influence coefficient can be obtained taking into account the individual difference between detectors and the like.

[0158] (3) In the gas measurement device described in paragraph 1 or 2, the corrected concentration of the target component is expressed by a linear sum of an intermediate coefficient represented by a plurality of influence coefficients and the pre-correction concentration corresponding to each of the detected values ​​of the plurality of gas components, based on a plurality of relational expressions indicating the relationship between the corrected concentration and the pre-correction concentration for each of the plurality of gas components. The calculation unit determines the corrected concentration of the target component as the concentration of the target component based on the intermediate coefficient and the detected values ​​of each of the plurality of gas components.

[0159] According to the gas measurement device described in paragraph 3, the calculation for determining the concentration of the target component can be easily performed, and the load on the calculation unit can be reduced.

[0160] (4) In the gas measurement device described in any one of paragraphs 1 to 3, the plurality of gas components include at least one component of carbon dioxide, methane, and sulfur dioxide, and nitrous oxide.

[0161] According to the gas measurement device described in paragraph 4, nitrous oxide, a greenhouse gas, can be measured with high accuracy using exhaust gas as the sample gas.

[0162] (5) In the gas measurement device described in any one of paragraphs 1 to 4, the calculation unit sets the influence of one or more interfering components on a single gas component, when the measurement error caused by the interfering component on the measurement of the single gas component is 1 / 100 or less of the concentration of the single gas component, to zero.

[0163] According to the gas measurement device described in paragraph 5, the calculation for determining the concentration of the target component can be easily performed, and the load on the calculation unit can be reduced.

[0164] (Item 6) In the gas measurement device according to any one of Items 1 to 4, the gas component different from the target component among the plurality of gas components includes carbon dioxide. The calculation unit determines the concentration of the target component assuming that the other gas components do not affect the measurement of carbon dioxide.

[0165] According to the gas measurement device described in paragraph 6, when measuring sample gas containing a high concentration of carbon dioxide, such as exhaust gas, the calculation for determining the concentration of the target component can be simplified, and the load on the calculation unit can be reduced.

[0166] (Item 7) A method according to one aspect is a method for determining the concentration of a target component in a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap each other. The method includes the steps of: detecting light passing through the sample gas to detect the amount of light in the absorption wavelength range of each of the multiple gas components, thereby acquiring detection values ​​for each of the multiple gas components; and determining the concentration of the target component from the multiple gas components based on the acquired detection values ​​for each of the multiple gas components. A gas component having an absorption wavelength range that at least partially overlaps with the absorption wavelength range of one of the multiple gas components is an interfering component with respect to the one gas component. The concentration of each of the multiple gas components is expressed as a corrected concentration obtained by subtracting the measurement error caused by one or more interfering components with respect to the gas component from the uncorrected concentration corresponding to the detected value of the gas component. The measurement error caused by the interfering component with respect to the gas component is expressed as a linear sum of the corrected concentration of the interfering component with respect to the gas component and an influence coefficient indicating the degree of influence of the interfering component on the measurement of the gas component. In the step of determining the concentration of the target component, the corrected concentration of the target component is determined as the concentration of the target component based on a plurality of influence coefficients and the detection values ​​of each of the plurality of gas components, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components.

[0167] According to the method described in Section 7, the corrected concentration of the target component is expressed using a corrected concentration obtained by subtracting the measurement error of the interfering component from the uncorrected concentration of the interfering component. Furthermore, the concentration of the target component is determined according to the relationship between the corrected concentration of the target component and the corrected concentration of the interfering component. Therefore, the concentration of the target component can be determined more accurately by taking into account the influence of other components on the measurement of the interfering component.

[0168] (Item 8) The method according to item 7 further includes a step of calculating an influence coefficient indicating the degree of influence of an interfering component with respect to one gas component on measurement of the one gas component. The step of calculating the influence coefficient includes a step of detecting the amount of light in the absorption wavelength range of a second component of the plurality of gas components by detecting light that has passed through a standard gas composed of a first component of the plurality of gas components and whose concentration is known, thereby obtaining a detection value obtained, and a step of calculating an influence coefficient indicating the degree of influence of the first component on measurement of the second component based on the detection value of the second component and the known concentration of the first component in accordance with the relationship between the corrected and uncorrected concentrations of the second component.

[0169] According to the method described in Section 8, the influence coefficient can be calculated based on the actual measurement value, and the influence coefficient can be obtained taking into account the individual difference between detectors and the like.

[0170] (Item 9) A gas measurement device according to one aspect measures a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap with each other. The gas measurement device includes a first detection unit for detecting a first component in the sample gas, a second detection unit for detecting a second component and a third component in the sample gas, each of which has an absorption wavelength range that at least partially overlaps with the absorption wavelength range of the first component, and a calculation unit for calculating the concentration of the first component by correcting the detection value of the first component detected by the first detection unit using the multiple detection values ​​detected by the second detection unit. The first detection unit includes a first light source, a first sample cell filled with the sample gas, and a first detector that detects light passing through the first sample cell to detect the amount of light in the absorption wavelength range of the first component. The first sample cell and the first detector are arranged in series on a first optical path of light irradiated from the first light source. The second detection unit includes a second light source, a second sample cell filled with a sample gas, a second detector that detects light passing through the second sample cell to detect the amount of light in the absorption wavelength range of the second component, and a third detector that detects light passing through the second sample cell to detect the amount of light in the absorption wavelength range of the third component. The second sample cell, the second detector, and the third detector are arranged in series on a second optical path of the light irradiated from the second light source.

[0171] According to the gas measurement device described in paragraph 9, by arranging a detector for detecting the first component on a first optical path that is separate from a second optical path in which a detector for a component that interferes with the detection of the first component is arranged, it is possible to suppress attenuation of light and thereby suppress a decrease in detection sensitivity for the first component. Furthermore, because the second and third detectors are arranged in series on the second optical path, it is possible to suppress an increase in the size of the entire gas measurement device.

[0172] (Item 10) In the gas measurement device according to item 9, the sample gas is exhaust gas, and the first component is nitrous oxide.

[0173] According to the gas measurement device described in paragraph 10, nitrous oxide, a greenhouse gas, can be measured using exhaust gas as a sample gas.

[0174] (Item 11) According to the gas measurement device described in Item 10, the first detector includes a first housing filled with a first component and a first detection unit that detects the pressure within the first housing. The first detection unit further includes an optical filter that blocks light in the second absorption wavelength range, which overlaps with the absorption wavelength range of carbon dioxide, of the first and second absorption wavelength ranges of nitrous oxide, but transmits light in the first absorption wavelength range, and a first gas filter filled with a gas component having an absorption wavelength range that at least partially overlaps with the first absorption wavelength range. The optical filter and the first gas filter are arranged on a first optical path between the first sample cell and the first detector.

[0175] According to the gas measurement device described in paragraph 11, the influence of carbon dioxide present in high concentrations in exhaust gas on the measurement of nitrous oxide can be reduced, and the influence of gas components having absorption wavelength ranges that at least partially overlap with the first absorption wavelength range on the measurement of nitrous oxide can be reduced.

[0176] (Item 12) According to the gas measurement device described in Item 11, the gas component filled in the first gas filter is methane.

[0177] According to the gas measurement device described in paragraph 12, the influence of methane present in the exhaust gas on the measurement of nitrous oxide can be reduced.

[0178] (Item 13) In the gas measurement device described in items 10 to 12, the second detection unit further includes a second gas filter filled with carbon dioxide, which is disposed on the second optical path between the second sample cell and the second detector.

[0179] According to the gas measurement device described in paragraph 13, the influence of carbon dioxide present in high concentrations in exhaust gas on the measurements of the second and third components can be reduced.

[0180] (Item 14) In the gas measurement device described in Items 10 to 13, the second component is sulfur dioxide. The third component is methane. The second detector includes a second housing filled with the second component and a second detection unit that detects the pressure inside the second housing. The third detector detects light that has passed through the second sample cell and the second housing in that order.

[0181] According to the gas measurement device described in paragraph 14, the second detector functions as a gas filter, and can reduce the influence of sulfur dioxide on the measurement of methane.

[0182] (Item 15) In the gas measurement device described in Items 10 to 13, the second detection unit further includes a fourth detector that detects light that has passed through the second sample cell and detects the amount of light in an absorption wavelength range of a fourth component in the sample gas that at least partially overlaps with the absorption wavelength range of the first component. The second component is sulfur dioxide. The third component is methane. The fourth component is carbon dioxide. The second sample cell, the second detector, the third detector, and the fourth detector are arranged in series on the second optical path in that order.

[0183] According to the gas measurement device described in paragraph 15, it is possible to obtain detected values ​​of a plurality of interfering components that affect the measurement of nitrous oxide, and to measure the concentration of nitrous oxide more accurately.

[0184] The embodiments disclosed herein are intended to be combined as appropriate within the scope of any technical inconsistency. The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0185] REFERENCE SIGNS LIST 1, 1a Gas measurement device, 10A, 10a First detector, 10B, 10b Second detector, 10C, 10c Third detector, 10D Fourth detector, 12A to 12D First housing to fourth housing, 14A to 14D First detection section to fourth detection section, 20 Optical filter, 30 First gas filter, 40 Second gas filter, 100, 100a Detection unit, 112, 114 Switching valve, 120 First detection unit, 122 First sample cell, 122a, 142a Gas inlet, 122b, 142b Gas outlet, 124 First light source, 140 Second detection unit, 142 Second sample cell, 144 Second light source, 160 Motor, 180 Sector, 200 Control unit, 200a Arithmetic unit, 220 Processor, 222 Pre-correction concentration calculation section, 224 Correction value calculation unit, 226 coefficient calculation unit, 228 storage unit, 240 memory, 300 input unit, 400 display unit, IR1 first optical path, IR2 second optical path, L1 to L4 first line to fourth line, RG reference gas, RL reference gas line, SG measurement gas, SL measurement gas line.

Claims

1. A gas measurement device for measuring a sample gas containing a plurality of gas components whose absorption wavelength ranges at least partially overlap each other, comprising: a detection unit that detects the amount of light in an absorption wavelength range of each of the plurality of gas components by detecting light that has passed through the sample gas; a calculation unit that calculates a concentration of a target component among the plurality of gas components based on detection values ​​of each of the plurality of gas components detected by the detection unit, a gas component having an absorption wavelength range that at least partially overlaps with an absorption wavelength range of one of the plurality of gas components is an interference component with the one gas component, the concentration of each of the plurality of gas components is represented by a corrected concentration obtained by subtracting a measurement error caused in the measurement of the gas component by one or more interference components for the gas component from a pre-correction concentration corresponding to the detection value of the gas component; a measurement error given to the measurement of the gas component is represented by a linear sum of a corrected concentration of an interfering component with respect to the gas component and an influence coefficient indicating a degree of influence of the interfering component on the measurement of the gas component, The gas component different from the target component among the plurality of gas components includes carbon dioxide, The calculation unit determines the corrected concentration of the target component as the concentration of the target component based on a plurality of influence coefficients and the detection values ​​of each of the plurality of gas components in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components, assuming that other gas components have no effect on the measurement of carbon dioxide.

2. the detection unit detects the amount of light in an absorption wavelength range of a second component of the plurality of gas components by detecting light that has passed through a standard gas having a known concentration and that is composed of a first component of the plurality of gas components; 2. The gas measurement device according to claim 1, wherein the calculation unit calculates an influence coefficient indicating a degree of influence of the first component on the measurement of the second component based on the detection value of the second component and the known concentration of the first component, in accordance with a relationship between the corrected concentration and the uncorrected concentration of the second component.

3. based on a plurality of relational expressions indicating a relationship between the corrected concentration and the pre-corrected concentration for each of the plurality of gas components, the corrected concentration of the target component is expressed by a linear sum of an intermediate coefficient represented by a plurality of influence coefficients and a pre-corrected concentration corresponding to each of the detection values ​​of the plurality of gas components; 3. The gas measurement device according to claim 1, wherein the calculation unit determines a corrected concentration of the target component as the concentration of the target component based on the intermediate coefficient and the detection values ​​of each of the plurality of gas components.

4. 3. The gas measurement device according to claim 1, wherein the plurality of gas components include at least one of methane and sulfur dioxide, and nitrous oxide.

5. 3. The gas measurement device according to claim 1, wherein the calculation unit sets the influence of one or more interference components on a single gas component, among which an interference component causes a measurement error in the measurement of the single gas component that is 1 / 100 or less of the concentration of the single gas component, to zero.

6. A gas measuring device as described in claim 1 or claim 2, wherein the calculation unit, when the concentration of carbon dioxide in the sample gas is 100 times or more higher than the concentrations of other gas components, determines the corrected concentration of the target component as the concentration of the target component based on a plurality of influence coefficients and the detection values ​​of each of the plurality of gas components, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components, assuming that other gas components have no effect on the measurement of carbon dioxide, in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components.

7. A method for determining a concentration of a target component in a sample gas containing a plurality of gas components whose absorption wavelength ranges at least partially overlap each other, comprising: a step of detecting light that has passed through the sample gas, thereby detecting an amount of light in an absorption wavelength range of each of the plurality of gas components, thereby obtaining a detection value of each of the plurality of gas components; determining a concentration of a target component among the plurality of gas components based on the acquired detection values ​​of each of the plurality of gas components; a gas component having an absorption wavelength range that at least partially overlaps with an absorption wavelength range of one of the plurality of gas components is an interference component with the one gas component, the concentration of each of the plurality of gas components is represented by a corrected concentration obtained by subtracting a measurement error caused in the measurement of the gas component by one or more interference components for the gas component from a pre-correction concentration corresponding to the detection value of the gas component; a measurement error given to the measurement of the gas component is represented by a linear sum of a corrected concentration of an interfering component with respect to the gas component and an influence coefficient indicating a degree of influence of the interfering component on the measurement of the gas component, The gas component different from the target component among the plurality of gas components includes carbon dioxide, a step of determining the concentration of the target component, the corrected concentration of the target component is determined as the concentration of the target component based on a plurality of influence coefficients and the detection values ​​of each of the plurality of gas components in accordance with the relationship between the corrected concentration and the uncorrected concentration for each of the plurality of gas components, assuming that other gas components have no effect on the measurement of carbon dioxide.

8. The method further includes a step of calculating an influence coefficient indicating an influence degree of an interference component with respect to a certain gas component on the measurement of the certain gas component, The step of determining the influence coefficient includes: a step of detecting light that has passed through a standard gas having a known concentration and composed of a first component among the plurality of gas components, thereby detecting an amount of light in an absorption wavelength range of a second component among the plurality of gas components, and acquiring a detection value obtained by the detection; and determining an influence coefficient indicating a degree of influence of the first component on the measurement of the second component based on the detected value of the second component and the known concentration of the first component in accordance with a relationship between the corrected concentration and the uncorrected concentration of the second component.