Gas Measuring Device

Abstract

A gas measurement device (1) includes: a first detection unit (120) for detecting a first component in a sample gas; and a second detection unit (140) for detecting a second component and a third component, respectively, which are components interfering with the first component. The first detection unit includes a first sample cell (122) and a first detector (10A) which are arranged in series on a first optical path (IR1) of light emitted from a first light source (124). The second detection unit (140) includes a second sample cell (142), a second detector (10B) and a third detector (10C), which are arranged in series on a second optical path (IR2) of light emitted from a second light source (144).

Description

[Technical Field]

[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. [Background technology]

[0002] Infrared gas analyzers that use the non-dispersive infrared absorption method (NDIR) are known as devices for determining the concentration 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 with 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. For this reason, it is necessary to measure multiple gas components in the sample gas.

[0004] Patent Document 1 discloses a non-dispersive infrared gas analyzer in which a second radiation receiver is arranged behind a first radiation receiver.

[0005] Patent Documents 2 and 3 disclose analyzers in which a light source, a sample cell, and an NDIR-type detector are provided for each measurement target. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 3-170848 [Patent Document 2] Japanese Patent Application Publication No. 9-318534 [Patent Document 3] Japanese Utility Model Application Publication No. 61-199657 Summary of the Invention [Problem to be solved by the invention]

[0007] As disclosed in Patent Document 1, when measuring multiple components, arranging multiple detectors corresponding to each component in series results in a longer optical path, and when a gas-filled detector is used, the light is absorbed by the gas and attenuated, resulting in a decrease in detection sensitivity.

[0008] Furthermore, in the cases disclosed in Patent Documents 2 and 3, if multiple detection units each including a light source, a sample cell, and a detector are provided corresponding to each of the multiple components, the entire gas measurement device becomes large.

[0009] An object of the present disclosure is to suppress a decrease in detection sensitivity while suppressing an increase in the size of the entire gas measurement device. [Means for solving the problem]

[0010] 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 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 the amount of light in the absorption wavelength range of the first component by detecting light that has passed through the first sample cell. The first sample cell and the first detector are arranged in series on a first optical path of light emitted 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. [Effects of the Invention]

[0011] According to the present disclosure, by arranging a detector for detecting the first component on a first optical path separate from a second optical path on 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. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a gas measurement device. [Figure 2] FIG. 2 is a functional block diagram of a control unit. [Figure 3] 10 is a flowchart showing the processing of the control unit when measuring a sample gas. [Figure 4]10 is a flowchart showing the processing of the control unit when calculating an influence coefficient. [Figure 5] Infrared absorption spectra of nitrous oxide and carbon dioxide. [Figure 6] Infrared absorption spectra of nitrous oxide, methane, and sulfur dioxide. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] <Configuration of gas measurement device> 1 is a diagram showing the configuration of a gas measurement apparatus 1. The gas measurement apparatus 1 measures a sample gas containing a plurality of gas components.

[0015] 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.

[0016] 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."

[0017] 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.

[0018] Gas measurement apparatus 1 according to the present embodiment measures exhaust gas as a sample gas and determines the concentration of nitrous oxide (NO) as a target component. Gas measurement apparatus 1 also detects the light intensity in the absorption wavelength ranges of sulfur dioxide (SO), methane (CH), and carbon dioxide (CO) as interfering components of nitrous oxide. Gas measurement apparatus 1 determines the concentration of nitrous oxide by correcting the detected value of nitrous oxide using the detected values ​​of sulfur dioxide, methane, and carbon dioxide. Specifically, exhaust gas includes 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.

[0019] 1, 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 a 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.

[0020] 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.

[0021] The memory 240 includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). 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 in which the processing procedures of the control unit 200 are written. The ROM stores various coefficients and various 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, various coefficients, and various relational expressions. The processes are not limited to those performed by software, but can also be performed by dedicated hardware (electronic circuits).

[0022] The input unit 300 is a device that accepts user operations such as a mouse or 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.

[0023] <Detection unit configuration> Referring to FIG. 1, 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 and 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 and 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.

[0030] 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.

[0031] 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 is responsible for irradiating and blocking light from first light source 124 onto first sample cell 122. Sector 180 is also responsible for irradiating and blocking light from second light source 144 onto second sample cell 142.

[0032] 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. 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.

[0033] Second detection unit 140 detects the amount of light in the absorption wavelength range of components interfering with the primary target component 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.

[0034] As described above, first detector 10A that detects nitrous oxide is arranged on first optical path IR1, separate from second optical path IR2 on which the detector that detects the interference components of nitrous oxide is arranged. 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 arranged in series on second optical path IR2, the overall size of gas measurement apparatus 1 can be prevented from increasing.

[0035] <Configuration of the 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.

[0036] 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.

[0037] 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.

[0038] The first sample cell 122 is hollow and includes a gas inlet 122a and a gas outlet 122b. The measurement gas SG or the reference gas RG is supplied from the first line L1 through the gas inlet 122a into the first sample cell 122 and is discharged from the gas outlet 122b.

[0039] 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 inside 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 inside 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.

[0040] 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. 5 and 6, 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.

[0041] The first gas filter 30 is filled with a gas of an interference component 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.

[0042] 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.

[0043] <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 that is the main target 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.

[0044] 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 the gas inlet 142a of the second sample cell 142 into the second sample cell 142 and is discharged from the gas outlet 142b.

[0045] 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.

[0046] 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.

[0047] 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 that order.

[0048] 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 that order.

[0049] The second gas filter 40 is filled with carbon dioxide. The second gas filter 40 reduces the amount of light in the absorption wavelength range of carbon dioxide among the absorption wavelength ranges of sulfur dioxide and methane, thereby reducing the effect of carbon dioxide on the measurements of sulfur dioxide and methane.

[0050] <Control unit software configuration> 2 is a functional block diagram of the control unit 200. 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. 2 are realized by the processor 220 executing a program. The storage unit 228 corresponds to the memory 240.

[0051] 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."

[0052] The uncorrected concentration calculation unit 222 determines 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 determines 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.

[0053] 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.

[0054] 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 measurement of nitrous oxide, to determine the concentration of nitrous oxide. The concentration of each gas component is determined according to the following equations (1) to (4). 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].

[0055]

number

[0056]

number

[0057]

number

[0058]

number

[0059] In equation (1), a, b, and g are influence coefficients that indicate the degree to which nitrous oxide, sulfur dioxide, and carbon dioxide affect methane measurement. In equation (2), c, d, and h are influence coefficients that indicate the degree to which methane, sulfur dioxide, and carbon dioxide affect nitrous oxide measurement. In equation (3), e, f, and i are influence coefficients that indicate the degree to which methane, nitrous oxide, and carbon dioxide affect sulfur dioxide measurement.

[0060] As shown in equations (1) to (3), 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 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.

[0061] 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 concentration of carbon dioxide 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 (4).

[0062] The correction value calculation unit 224 calculates the concentration of nitrous oxide based on the influence coefficients and the pre-correction concentrations of the gas components corresponding to each detection value in accordance with the relationships of Equations (1) to (4). Specifically, by solving the simultaneous equations of Equations (1) to (4), the concentration of nitrous oxide is expressed as a linear sum of the pre-correction concentrations (N2O, CH4, SO2, CO2) corresponding to the detection value and an intermediate coefficient expressed using multiple influence coefficients. Therefore, the correction value calculation unit 224 can calculate the concentration of nitrous oxide based on the influence coefficients or intermediate coefficients and the pre-correction concentrations of the gas components corresponding to each detection value. Note that the method for calculating the concentration in accordance with the relationships of Equations (1) to (4) 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.

[0063] 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 (1) to (3) are calculated as follows.

[0064] 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 ​​obtained in this way and the known concentration, the influence coefficients a and f in equations (1) and (3) are calculated.

[0065] Specifically, the control unit 200 obtains the influence coefficient a by dividing the uncorrected concentration of methane corresponding to the detection value of the third detector 10C by the input dinitrogen monoxide concentration according to the relationship in formula (1). The control unit 200 obtains the influence coefficient f by dividing the uncorrected concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input dinitrogen monoxide concentration according to the relationship in formula (3).

[0066] The detection unit 100 detects a standard gas consisting 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 (1) and (2) are calculated.

[0067] Specifically, the control unit 200 calculates the influence coefficient b by dividing the uncorrected concentration of methane corresponding to the detection value of the third detector 10C by the input concentration of sulfur dioxide in accordance with the relationship in formula (1). The control unit 200 calculates the influence coefficient d by dividing the uncorrected concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input concentration of sulfur dioxide in accordance with the relationship in formula (2).

[0068] 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 (2) and (3) are calculated.

[0069] Specifically, the control unit 200 obtains 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 according to the relationship in formula (2). The control unit 200 obtains 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 according to the relationship in formula (3).

[0070] The detection unit 100 detects 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. Based on the multiple detection values ​​obtained in this way and the known concentration, the influence coefficients g, h, and i in equations (1) to (3) are calculated.

[0071] Specifically, the control unit 200 obtains the influence coefficient g by dividing the uncorrected concentration of methane corresponding to the detection value of the third detector 10C by the input carbon dioxide concentration according to the relationship in formula (1). The control unit 200 obtains the influence coefficient h by dividing the uncorrected concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input carbon dioxide concentration according to the relationship in formula (2). The control unit 200 obtains the influence coefficient i by dividing the uncorrected concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input carbon dioxide concentration according to the relationship in formula (3).

[0072] 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.

[0073] <Procedure for determining the concentration of target components> A method for determining the concentration of a target component will be described with reference to Figure 3. Figure 3 is a flowchart showing the processing of the control unit when measuring sample gas. Note that, hereinafter, step will be abbreviated as "S".

[0074] 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.

[0075] 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 (1) to (4).

[0076] In S16, the control unit 200 displays the determined concentration of nitrous oxide on the display section 400.

[0077] As described above, the control unit 200 determines the concentration of nitrous oxide in the sample gas.

[0078] <Method for calculating the influence coefficient> A method for determining the influence coefficient will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the processing of the control unit when calculating the influence coefficient.

[0079] In S22, the control unit 200 acquires the detection values ​​obtained by detecting 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. In S24, the control unit 200 receives an input of the concentration of nitrous oxide from the input unit 300.

[0080] In S26, the control unit 200 calculates an influence coefficient a indicating the degree of influence of nitrous oxide in equation (1) on the measurement of methane, and an influence coefficient f indicating the degree of influence of nitrous oxide in equation (3) on the measurement of sulfur dioxide.

[0081] 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 each of 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.

[0082] In S32, the control unit 200 calculates an influence coefficient b in equation (1) that indicates the degree of influence that sulfur dioxide has on the measurement of methane, and an influence coefficient d in equation (2) that indicates the degree of influence that sulfur dioxide has on the measurement of nitrous oxide.

[0083] In S34, the control unit 200 acquires the detection values ​​obtained by detecting a standard gas consisting 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.

[0084] In S38, the control unit 200 calculates an influence coefficient c in equation (2) that indicates the degree of influence that methane has on the measurement of nitrous oxide, and an influence coefficient e in equation (3) that indicates the degree of influence that methane has on the measurement of sulfur dioxide.

[0085] In S40, the control unit 200 acquires the detection 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 concentration of carbon dioxide from the input unit 300.

[0086] 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 (1), an influence coefficient h indicating the degree of influence of carbon dioxide on the measurement of nitrous oxide in equation (2), and an influence coefficient i indicating the degree of influence of carbon dioxide on the measurement of sulfur dioxide in equation (3).

[0087] As described above, gas measurement apparatus 1 obtains an influence coefficient that indicates the degree to which an interfering component with respect to a given gas component influences the measurement of that given gas component.

[0088] <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 Figure 1 was corrected using the method of this embodiment, and a comparative example in which the concentration was corrected using a conventional method.

[0089] [Table 1]

[0090] In the examples, the pre-correction densities were corrected according to the above formulas (1) to (4). In the comparative examples, the pre-correction densities were corrected according to the following formulas (5) to (7) and the above formula (4). In the examples and comparative examples, the influence coefficients a to i are common coefficients.

[0091]

number

[0092]

number

[0093]

number

[0094] As shown in equations (5) to (7), 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 consideration 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 working example. This difference is due to taking into consideration that the measurement of the interfering component is affected by other components. By taking into consideration that the measurement of the interfering component is affected by other components, the concentration of the target component can be determined more accurately.

[0095] <Infrared absorption spectrum of each gas component> The infrared absorption spectra of each gas component will be described with reference to Figures 5 and 6. Figure 5 shows the infrared absorption spectra of nitrous oxide and carbon dioxide. Figure 6 shows the infrared absorption spectra of nitrous oxide, methane, and sulfur dioxide. In Figures 5 and 6, the spectrum shown by the solid line is the infrared absorption spectrum of nitrous oxide. In Figure 5, the spectrum shown by the dashed-dotted line is the infrared absorption spectrum of carbon dioxide. In Figure 6, the spectrum shown by the dashed-dotted line is the infrared absorption spectrum of sulfur dioxide. In Figures 5 and 6, the horizontal axis represents wavelength, and the vertical axis represents absorbance.

[0096] As shown in Figures 5 and 6, nitrous oxide has absorption wavelength ranges around 4.5 μm and 7.8 μm. As shown in Figure 5, 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.

[0097] 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. 1, 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.

[0098] 5 and 6, 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 percent, 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.

[0099] 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, which is present in high concentrations in the sample gas, on the measurement of nitrous oxide, allowing for more accurate measurement of nitrous oxide.

[0100] Carbon monoxide (CO) may be contained in exhaust gas. Although not shown, the absorption wavelength range of carbon monoxide is around 4.7 μm. Nitrous oxide Therefore, by providing optical filter 20, the influence of carbon monoxide on the measurement of nitrous oxide can be reduced, and nitrous oxide can be measured with higher accuracy.

[0101] First detector 10A detects the amount of light in the absorption wavelength range of nitrous oxide around 7.8 μm. As shown in Figure 6, methane has an absorption wavelength range around 7.8 μm, and sulfur dioxide has an absorption wavelength range around 7.4 μm. Each gas component at least partially overlaps with the absorption wavelength range of nitrous oxide around 7.8 μm. Therefore, the detection value of 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.

[0102] 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.

[0103] 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 the measurement of nitrous oxide 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 the measurement of nitrous oxide, can be reduced, allowing nitrous oxide to be measured with higher accuracy.

[0104] 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.

[0105] 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 the detection sensitivity of nitrous oxide.

[0106] In this embodiment, the first detection unit 120 uses the optical filter 20 to cut 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 (2).

[0107] Similarly, carbon dioxide also absorbs light in the absorption wavelength ranges of sulfur dioxide and methane, albeit in small amounts. 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, the control unit 200 calculates the concentration of nitrous oxide by assuming that carbon dioxide affects the measurements of sulfur dioxide and methane, as shown in equations (1) and (3).

[0108] 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 measurements 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 effect 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.

[0109] As shown in FIG. 6, 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, which includes 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.

[0110] 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 methane or sulfur dioxide measurement.

[0111] In the present embodiment, gas measurement apparatus 1 uses infrared light, but may use ultraviolet light depending on the absorption wavelength range of the target component.

[0112] In this embodiment, the amount of light is indirectly detected by detecting a change in the internal pressure when transmitted light passes through a cell containing the gas to be detected. The amount of light may also be directly detected by a photoconductive element or the like. 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. The multiple detectors may also have different methods 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.

[0113] 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.

[0114] In order to measure the concentration of nitrous oxide, gas measurement device 1 is equipped with detectors for three types of interference components: 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.

[0115] The control unit 200 calculates the concentration of nitrous oxide as shown in equation (4), assuming that other components have no effect on the measurement of carbon dioxide.

[0116] Note that, for one or more interfering components for a given gas component, if the measurement error that the interfering component causes in the measurement of that gas component is sufficiently smaller than the concentration of that gas component, the control unit 200 may calculate the concentration of the target component by considering the influence of the interfering component on the measurement of that gas component to be zero. Note that the measurement error that the interfering component causes in the measurement of that gas component can be obtained by multiplying the corrected concentration of the interfering component by an influence coefficient that indicates the degree of influence the interfering component has on the measurement of that gas component.

[0117] 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 that gas component, the effect of that interfering component on the measurement of that gas component may be considered to be zero.Also, 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 that gas component, the effect of that interfering component on the measurement of that gas component may be considered to be zero.The criteria for determining the effect to be zero may be set depending on the accuracy required of gas measurement device 1 and the expected maximum concentration of interfering components in the sample gas.

[0118] For example, if the measurement error (d[SO2]) that sulfur dioxide causes in the measurement of nitrous oxide is 1 / 100 or less of the concentration of nitrous oxide ([N2O]), the control unit 200 may determine the concentration of nitrous oxide by setting the influence coefficient d in equation (2) to zero.

[0119] 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.

[0120] 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.

[0121] [Aspect] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0122] (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 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.

[0123] According to the gas measurement device described in paragraph 1, by arranging a detector for detecting the first component on a first optical path separate from a second optical path on 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 prevent 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 prevent the entire gas measurement device from becoming large.

[0124] (Item 2) In the gas measurement device described in item 1, the sample gas is an exhaust gas, and the first component is nitrous oxide.

[0125] According to the gas measurement device described in paragraph 2, nitrous oxide, a greenhouse gas, can be measured using exhaust gas as a sample gas.

[0126] (Item 3) According to the gas measurement device described in Item 2, the first detector includes a first housing filled with a first component and a first detection unit that detects the pressure inside 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.

[0127] According to the gas measurement device described in paragraph 3, it is possible to reduce the influence of carbon dioxide present in high concentrations in exhaust gas on the measurement of nitrous oxide, and it is also possible to reduce 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.

[0128] (Item 4) According to the gas measurement device described in item 3, the gas component filled in the first gas filter is methane.

[0129] According to the gas measurement device described in paragraph 4, the influence on the measurement of nitrous oxide caused by methane present in exhaust gas can be reduced.

[0130] (Item 5) In the gas measurement device described in items 2 to 4, 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.

[0131] According to the gas measurement device described in paragraph 5, the influence of carbon dioxide present in high concentrations in exhaust gas on the measurements of the second and third components can be reduced.

[0132] (Item 6) In the gas measurement device described in items 2 to 5, 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.

[0133] According to the gas measurement device described in paragraph 6, the second detector functions as a gas filter, and can reduce the influence of sulfur dioxide on the measurement of methane.

[0134] (Item 7) In the gas measurement device described in items 2 to 5, 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.

[0135] According to the gas measurement device described in paragraph 7, it is possible to obtain detection values ​​of a plurality of interfering components that affect the measurement of nitrous oxide, and to measure the concentration of nitrous oxide more accurately.

[0136] (Item 8) A gas measurement device according to one aspect measures a sample gas containing multiple gas components whose absorption wavelength ranges at least partially overlap 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 that has passed 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.

[0137] According to the gas measuring device described in paragraph 8, the target component The concentration The degree of interference is expressed using a corrected concentration obtained by subtracting the measurement error that affects the measurement of the interfering component from the uncorrected concentration of the interfering component for the target component. 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.

[0138] (Item 9) In the gas measurement device described in Item 8, 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.

[0139] According to the gas measurement device described in paragraph 9, the influence coefficient can be calculated based on the actual measurement value, and an influence coefficient that takes into account individual differences between detectors and the like can be obtained.

[0140] (Item 10) In the gas measurement device described in Items 8 or 9, 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 detection values ​​of the plurality of gas components, based on a plurality of relational equations 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 detection values ​​of each of the plurality of gas components.

[0141] According to the gas measurement device described in paragraph 10, the calculation for determining the concentration of the target component can be facilitated, and the load on the calculation unit can be reduced.

[0142] (Item 11) In the gas measurement device according to any one of items 8 to 10, the plurality of gas components include at least one component of carbon dioxide, methane, and sulfur dioxide, and nitrous oxide.

[0143] According to the gas measurement device described in paragraph 11, nitrous oxide, a greenhouse gas, can be measured with high accuracy using exhaust gas as a sample gas.

[0144] (Item 12) In the gas measurement device described in any one of items 8 to 11, 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.

[0145] According to the gas measurement device described in paragraph 12, the calculation for determining the concentration of the target component can be facilitated, and the load on the calculation unit can be reduced.

[0146] (Item 13) In the gas measurement device according to any one of items 8 to 11, 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.

[0147] According to the gas measurement device described in paragraph 13, 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 made easier, and the load on the calculation unit can be reduced.

[0148] (Item 14) 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 a detection value 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.

[0149] According to the method of paragraph 14, the target component The concentration The degree of interference is expressed using a corrected concentration obtained by subtracting the measurement error that affects the measurement of the interfering component from the uncorrected concentration of the interfering component for the target component. 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.

[0150] (Item 15) The method according to item 14 further includes a step of calculating an influence coefficient indicating the degree of influence that an interfering component with respect to one gas component has on the measurement of the one gas component. The step of calculating the influence coefficient includes the steps of: 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 detecting the amount of light in the absorption wavelength range of a second component of the plurality of gas components, and obtaining a detection value obtained by detecting the amount of light; and calculating an influence coefficient indicating the degree of influence that the first component has 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 the relationship between the corrected and uncorrected concentrations of the second component.

[0151] According to the method described in paragraph 15, 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, etc.

[0152] 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. [Explanation of symbols]

[0153] 1 gas measurement device, 10A first detector, 10B second detector, 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 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, 220 processor, 222 pre-correction concentration calculation section, 224 correction value calculation section, 226 coefficient calculation section, 228 memory section, 240 Memory, 300 input section, 400 display section, 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 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; a calculation unit that calculates the concentration of the first component by correcting the detection value of the first component detected by the first detection unit using a plurality of detection values ​​detected by the second detection unit, The first detection unit A first light source; a first sample cell filled with the sample gas; a first detector that detects light that has passed through the first sample cell and detects 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 emitted from the first light source; The second detection unit A second light source; a second sample cell filled with the sample gas; a second detector that detects the light that has passed through the second sample cell and detects the amount of light in the absorption wavelength range of the second component; a third detector that detects the light that has passed through the second sample cell and detects the amount of light in the absorption wavelength range of the third component, The gas measurement device, wherein the second sample cell, the second detector, and the third detector are arranged in series on a second optical path of light emitted from the second light source.

2. the sample gas is exhaust gas, 2. The gas measurement device of claim 1, wherein the first component is nitrous oxide.

3. The first detector is a first housing filled with the first component; a first detection unit that detects a pressure inside the first housing, The first detection unit an optical filter that does not transmit light in the second absorption wavelength range that overlaps with the absorption wavelength range of carbon dioxide, but transmits light in the first absorption wavelength range, out of a first absorption wavelength range and a second absorption wavelength range that dinitrogen monoxide has; 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 gas measurement device of claim 2 , wherein the optical filter and the first gas filter are disposed on the first optical path between the first sample cell and the first detector.

4. 4. The gas measurement device according to claim 3, wherein the gas component filled in the first gas filter is methane.

5. 3. The gas measurement device of claim 2, wherein the second detection unit further comprises a second gas filter filled with carbon dioxide and disposed on the second optical path between the second sample cell and the second detector.

6. the second component is sulfur dioxide; the third component is methane; The second detector is a second housing filled with the second component; a second detection unit that detects a pressure inside the second housing, The gas measurement device according to claim 2 , wherein the third detector detects light that has passed through the second sample cell and the second housing in this order.

7. 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 gas measurement device of claim 2 , wherein 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.

Images