Gas measurement device

Abstract

A gas measurement device (1) is provided with: a first detection means (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, which are interference components with respect to the first component, respectively. The first detection unit includes a first sample cell (122) and a first detector (10A) arranged in series on a first optical path (IR1) of light irradiated 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) arranged in series on a second optical path (IR2) of the light emitted from the second light source (144).

Description

Technical Field

[0001] The present disclosure relates to a gas measuring device for measuring a sample gas containing a plurality of gas components, wherein at least a portion of the absorption wavelength regions of the plurality of gas components overlap with each other. Background Art

[0002] As a device for determining the concentration of a target component in sample gases such as gases discharged from chemical plants and steelworks, combustion gases from boilers and furnaces, the atmosphere, and automobile exhaust, an infrared gas analyzer using the non-dispersive infrared absorption method (NDIR) is known.

[0003] In a gas measuring device such as an infrared gas analyzer that utilizes the light absorption characteristics of the target component, the measurement of the target component is affected by components other than the target component in the sample gas, resulting in errors. Specifically, when there is an interfering component in the sample gas having an absorption wavelength region that at least partially overlaps with the absorption wavelength region of the target component, the measurement of the target component is affected by the interfering component, resulting in errors. For this reason, it is desired 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 disposed behind a first radiation receiver.

[0005] Patent Documents 2 and 3 disclose an analyzer provided with a light source, a sample cell, and an NDIR-type detector for each measurement object.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 3-170848

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 9-318534

[0010] Patent Document 3: Japanese Utility Model Publication No. 61-199657 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] As disclosed in Patent Document 1, when a plurality of detectors corresponding to respective components are arranged in series when measuring a plurality of components, the optical path becomes longer, or when a detector filled with gas is used, light is absorbed by the gas and attenuated, thereby reducing the detection sensitivity.

[0013] In addition, in the cases disclosed in Patent Documents 2 and 3, if a plurality of detection units including a light source, a sample cell, and a detector are provided corresponding to each of the plurality of components, the gas measurement device as a whole becomes larger.

[0014] One object of the present disclosure is to suppress a decrease in detection sensitivity and to suppress an increase in the size of the entire gas measurement device.

[0015] Solutions for solving problems

[0016] The gas measuring device disclosed in the present invention measures a sample gas containing multiple gas components, and at least a part of the absorption wavelength regions of the multiple gas components overlap with each other. The gas measuring device includes: a first detection unit, which is used to detect a first component in the sample gas; a second detection unit, which is used to detect a second component and a third component, respectively, and the second component and the third component each have an absorption wavelength region that at least a part overlaps with the absorption wavelength region of the first component in the sample gas; and a calculation unit, which 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 includes: a first light source; a first sample cell, which is filled with sample gas; and a first detector, which detects the light passing through the first sample cell to detect the light amount of the absorption wavelength region of the first component. The first sample cell and the first detector are arranged in series on the first optical path of the 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 the light that has passed through the second sample cell to detect the amount of light in the absorption wavelength region of the second component; and a third detector that detects the light that has passed through the second sample cell to detect the amount of light in the absorption wavelength region 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.

[0017] Effects of the Invention

[0018] According to the present disclosure, by arranging a detector for detecting the first component on a first optical path different from a second optical path on which a detector for a component interfering with the detection of the first component is arranged, it is possible to suppress the attenuation of light and thus suppress the reduction in the detection sensitivity of the first component. In addition, since the second detector and the third detector are arranged in series on the second optical path, it is possible to suppress the overall enlargement of the gas measuring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a diagram showing the structure of a gas measuring device.

[0020] Figure 2 It is a functional block diagram of the control unit.

[0021] Figure 3 This is a flowchart showing the processing of the control unit when measuring the sample gas.

[0022] Figure 4 : is a flowchart showing the processing of the control unit when calculating the influence coefficient.

[0023] Figure 5 It is the infrared absorption spectrum of nitrous oxide and carbon dioxide.

[0024] Figure 6 It is the infrared absorption spectrum of nitrous oxide, methane and sulfur dioxide. DETAILED DESCRIPTION

[0025] Next, refer to the attached Figure 1 In addition, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0026] <Structure of Gas Measuring Device>

[0027] Figure 1 1 is a diagram showing the configuration of a gas measuring device. The gas measuring device 1 measures a sample gas containing a plurality of gas components.

[0028] The various gas components each have a unique absorption wavelength region. Part of the transmitted light is absorbed and attenuated by the various gas components contained in the sample gas. The absorbance, which is the degree of light absorption, is proportional to the concentration of the gas component. Therefore, the concentration of the gas component is calculated based on the absorbance.

[0029] In addition, below, the gas component to be measured may be referred to as the "target component". In addition, a gas component having an absorption wavelength region that at least partially overlaps with the absorption wavelength region of a gas component may be referred to as an "interference component for a gas component" or simply an "interference component". In addition, the detection result obtained by detecting the light amount in the absorption wavelength region of a gas component may be referred to as a "detection value of a gas component" or simply a "detection value".

[0030] Here, consider the case where the sample gas contains the target component and the interfering component for the target component. In the detection value of the target component obtained by measuring the sample gas, in addition to the influence of light absorption by the target component, the influence of light absorption by the interfering component is also reflected. Therefore, even if the absorbance of the absorption wavelength region of the target component is detected, it is affected by the interfering component and an error occurs in the measurement of the concentration of the target component.

[0031] The gas measuring device 1 according to the present embodiment measures the exhaust gas as the sample gas to obtain the concentration of nitrous oxide (N2O) as the target component. In addition, the gas measuring device 1 detects the light amount of the absorption wavelength region of sulfur dioxide (SO2), methane (CH4) and carbon dioxide (CO2) as the interference components of nitrous oxide. The gas measuring device 1 corrects the detection value of nitrous oxide by using the detection values ​​of sulfur dioxide, methane and carbon dioxide to obtain the concentration of nitrous oxide. In addition, specifically, the exhaust gas includes the gas discharged from the chemical plant, the iron and steel plant, the combustion gas of the boiler, the combustion furnace and the automobile exhaust gas. In addition, the sample gas is not limited to the exhaust gas, for example, it can also be the atmosphere.

[0032] Reference Figure 1 The gas measuring device 1 includes a detection unit 100, a control unit 200, an input unit 300, and a display unit 400. The detection unit 100 detects the light amount in the absorption wavelength region of each gas component among the plurality of gas components in the sample gas. More specifically, the detection unit 100 detects the light amount in the absorption wavelength region of each of nitrous oxide, sulfur dioxide, methane, and carbon dioxide.

[0033] The control unit 200 controls the detection unit 100. In addition, the control unit 200 functions as a computing device that calculates the concentration of nitrous oxide based on the detection values ​​of each gas component among the plurality of 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.

[0034] The memory 240 includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The processor 220 expands the program stored in the ROM into the RAM and executes it. The program stored in the ROM is a program that describes the processing procedures of the control unit 200. Various coefficients and various relationship equations for calculating the concentration of nitrous oxide are stored in the ROM. The control unit 200 performs various processes for calculating the concentration of nitrous oxide according to these programs, various coefficients and various relationship equations. The processing is not limited to being based on software, and can also be performed by dedicated hardware (electronic circuit).

[0035] The input unit 300 is a device such as a mouse or a keyboard that accepts user operations. For example, the input unit 300 accepts input of the concentration of gas components in the standard gas and sends the input 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 obtained by the control unit 200.

[0036] <Structure of detection unit>

[0037] Reference Figure 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 .

[0038] The 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 prepared in advance for measuring the sample gas.

[0039] Reference gas RG is introduced into reference gas line RL. Reference gas RG is a so-called zero gas, and is an inert gas such as nitrogen that does not absorb infrared rays. In addition, reference gas RG can be any gas that does not interfere with any gas component measured in detection unit 100, and can also be a gas that absorbs infrared rays.

[0040] The switching valve 112 is connected to the measurement gas line SL, the first line L1, and the third line L3. The switching valve 114 is connected to the reference gas line RL, the second line L2, and the fourth line L4.

[0041] 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.

[0042] Specifically, the switching valve 112 is connected to the measurement gas line SL, the flow path connected to the first sample cell 122, and the flow path connected to the second sample cell 142. The switching valve 114 is connected to the reference gas line RL, the flow path connected to the first sample cell 122, and the flow path connected to the second sample cell 142.

[0043] The control unit 200 controls the switching valve 112 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 at a predetermined period. The control unit 200 controls the switching valves 112 and 114 so that the reference gas line RL is connected to the second sample cell 142 while the measurement gas line SL is connected to the first detection unit 120. In addition, the control unit 200 controls the switching valves 112 and 114 so that the reference gas line RL is connected to the first sample cell 122 while the measurement gas line SL is connected to the second sample cell 142.

[0044] As a result, the reference gas and the sample gas are alternately filled into the first detection cell 120 and the second detection cell 140. More specifically, while the reference gas is being filled into the first detection cell 120, the sample gas is being filled into the second detection cell 140, and while the sample gas is being filled into the first detection cell 120, the reference gas is being filled into the second detection cell 140.

[0045] The motor 160 rotates the fan-shaped member 180 according to the command from the control unit 200. The fan-shaped member 180 is provided between the first sample cell 122 and the first light source 124 and between the second sample cell 142 and the second light source 144, which will be described later. The fan-shaped member 180 has a light shielding portion and a light transmitting portion, and performs irradiation and blocking of light from the first light source 124 to the first sample cell 122. In addition, the fan-shaped member 180 performs irradiation and blocking of light from the second light source 144 to the second sample cell 142.

[0046] In the measurement of gas components using the gas measurement device 1, the first detection unit 120 detects the amount of light in the absorption wavelength region of the target component as the main target. The first detection unit 120 includes a first sample cell 122, a first light source 124, a first detector 10A, an optical filter 20, and a first gas filter 30. The first detector 10A detects the amount of light in the absorption wavelength region of nitrous oxide. The first sample cell 122, the first gas filter 30, the optical filter 20, and the first detector 10A are respectively arranged in this order on the first optical path IR1 of the first light source 124.

[0047] In the measurement of gas components using the gas measurement device 1, the second detection unit 140 detects the light amount in the absorption wavelength region of the interfering component with respect to the target component as the main target. The second detection unit 140 includes a second light source 144, a second sample cell 142, a second gas filter 40, a second detector 10B, which detects the light amount in the absorption wavelength region of sulfur dioxide, a third detector 10C, which detects the light amount in the absorption wavelength region of methane, and a fourth detector 10D, which detects the light amount in the absorption wavelength region of carbon dioxide. The second sample cell 142, the second gas filter 40, the second detector 10B, the third detector 10C, and the fourth detector 10D are respectively arranged in this order on the second optical path IR2 of the second light source 144.

[0048] As described above, the first detector 10A for detecting nitrous oxide is arranged on the first optical path IR1 which is different from the second optical path IR2 on which the detector for detecting the interfering component of nitrous oxide is arranged. Therefore, the attenuation of light can be suppressed to suppress the reduction of the detection sensitivity of nitrous oxide. In addition, a plurality of detectors (the second detector 10B, the third detector 10C, and the fourth detector 10D) for detecting the interfering component of nitrous oxide are arranged in series on the second optical path IR2, so that the overall large-scale of the gas measuring device 1 can be suppressed.

[0049] <Structure of the First Detection Unit>

[0050] In the measurement of gas components using the gas measurement device 1, the first detection unit 120 detects the light amount in the absorption wavelength region of the target component as the main target. In the present embodiment, the first detection unit 120 detects the light amount in the absorption wavelength region of nitrous oxide. The first detection unit 120 includes a first sample cell 122, a first light source 124, a first detector 10A, an optical filter 20, and a first gas filter 30.

[0051] The first light source 124 emits light including at least the absorption wavelength region of the target component. The first light source 124 is not particularly limited, and is, for example, a light source using a nichrome wire.

[0052] The first sample cell 122, the first gas filter 30, the optical filter 20, and the first detector 10A are arranged in this order on the first optical path IR1 of the first light source 124. Although not shown in the figure, windows for transmitting the light from the first light source 124 are formed on the first optical path IR1 and at both ends of each of the first sample cell 122, the first gas filter 30, and the optical filter 20. As a result, the light from the first light source 124 is transmitted in the order of the first sample cell 122, the first gas filter 30, the optical filter 20, and the first detector 10A.

[0053] The first sample cell 122 is hollow inside and has 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 into the first sample cell 122 through the gas inlet 122a and is discharged from the gas outlet 122b.

[0054] The first detector 10A detects the light amount of the absorption wavelength region of nitrous oxide. The first detector 10A is provided with a first housing 12A filled with nitrous oxide as a gas component, and a first detection unit 14A that detects the pressure in the first housing 12A. In the present embodiment, the first detector 10A indirectly detects the light amount of the absorption wavelength region peculiar to nitrous oxide by detecting the pressure change in the first housing 12A. In addition, the first detector 10A detects the light from the first light source 124 and transmitted in the order of the first sample cell 122, the first gas filter 30 and the optical filter 20.

[0055] The optical filter 20 transmits light in a specific absorption wavelength range, and on the other hand, does not transmit light in a specific absorption wavelength range. Figure 5 and Figure 6 As described later, nitrous oxide has a first absorption wavelength region (absorption wavelength region near 7.8 μm) and a second absorption wavelength region (absorption wavelength region near 4.5 μm). At least a portion of the second absorption wavelength region of the two absorption wavelength regions overlaps with the absorption wavelength region of carbon dioxide. The optical filter 20 does not transmit light in the second absorption wavelength region of the absorption wavelength region of nitrous oxide that overlaps with the absorption wavelength region of carbon dioxide, and on the other hand, transmits light in the first absorption wavelength region of the absorption wavelength region of nitrous oxide. For example, the optical filter 20 does not transmit light with a wavelength below 5.5 μm to 6.5 μm, and on the other hand, transmits light with a wavelength longer than 5.5 μm to 6.5 μm.

[0056] The first gas filter 30 is filled with a gas having an interfering component having an absorption wavelength region at least partially overlapping with the first absorption wavelength region among the absorption wavelength regions of nitrous oxide. In the present embodiment, the first gas filter 30 is filled with methane as a gas component.

[0057] Furthermore, the order of arranging the optical filter 20 and the first gas filter 30 may be reversed. Specifically, the first sample cell 122, the optical filter 20, the first gas filter 30, and the first detector 10A may be arranged in the first optical path IR1 in this order.

[0058] <Second Detection Unit>

[0059] In the measurement of gas components using the gas measurement device 1, the second detection unit 140 detects the amount of light in the absorption wavelength region of the interfering component with respect to the main target component. In the present embodiment, the second detection unit 140 includes a second light source 144, a second sample cell 142, a second gas filter 40, a second detector 10B, a third detector 10C, and a fourth detector 10D.

[0060] 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 into the second sample cell 142 through the gas inlet 142a of the second sample cell 142, and is discharged from the gas outlet 142b.

[0061] The second sample cell 142, the second gas filter 40, the second detector 10B, the third detector 10C, and the fourth detector 10D are arranged in this order on the second optical path IR2 of the second light source 144. Although not shown in the figure, windows for transmitting the light from the second light source 144 are formed on the second optical path IR2 and at both ends of the second sample cell 142, the second gas filter 40, the second detector 10B, and the third detector 10C. The light from the second light source 144 is transmitted in the order of the second sample cell 142, the second gas filter 40, the second detector 10B, the third detector 10C, and the fourth detector 10D.

[0062] The second detector 10B detects the amount of light in the absorption wavelength region 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 in the second housing 12B. The second detector 10B indirectly detects the amount of light in the absorption wavelength region unique to sulfur dioxide by detecting the pressure change in the second housing 12B. In addition, the second detector 10B detects light from the second light source 144 that has passed through the second sample cell 142 and the second gas filter 40 in this order.

[0063] The third detector 10C detects the amount of light in the absorption wavelength region 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 in the third housing 12C. The third detector 10C indirectly detects the amount of light in the absorption wavelength region specific to methane by detecting the pressure change in the third housing 12C. In addition, the third detector 10C detects light from the second light source 144 that has passed through the second sample cell 142, the second gas filter 40, and the second detector 10B in this order.

[0064] The fourth detector 10D detects the amount of light in the absorption wavelength region of carbon dioxide. 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 in the fourth housing 12D. The fourth detector 10D indirectly detects the amount of light in the absorption wavelength region specific to carbon dioxide by detecting the pressure change in the fourth housing 12D. In addition, the fourth detector 10D detects light that is transmitted from the second light source 144 and passes through the second sample cell 142, the second gas filter 40, the second detector 10B, and the third detector 10C in this order.

[0065] Carbon dioxide is filled in the second gas filter 40. The second gas filter 40 reduces the influence of carbon dioxide on the measurement of sulfur dioxide and methane by reducing the amount of light in the absorption wavelength region of carbon dioxide in the absorption wavelength regions of sulfur dioxide and methane.

[0066] <Software structure of control unit>

[0067] Figure 2 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. Figure 2 Each of the functions shown is realized by executing the program by the processor 220. The storage unit 228 corresponds to the memory 240.

[0068] The pre-correction concentration calculation unit 222 obtains the concentration of the gas component in the sample gas by applying the detection signal (reference signal) when the reference gas is delivered to the detection unit 100 and the detection signal (measurement signal) when the sample gas is delivered to the detection unit 100 to a predetermined calculation formula. That is, the reference signal and the measurement signal are equivalent to the "detection value".

[0069] The pre-correction concentration calculation unit 222 calculates the pre-correction concentration of nitrous oxide based on the reference signal and the measurement signal detected by the first detector 10A. Similarly, the pre-correction concentration calculation unit 222 calculates the pre-correction concentration of sulfur dioxide based on the reference signal and the measurement signal detected by the second detector 10B, calculates the pre-correction concentration of methane based on the reference signal and the measurement signal detected by the third detector 10C, and calculates the pre-correction concentration of carbon dioxide based on the reference signal and the measurement signal detected by the fourth detector 10D.

[0070] In addition, in this embodiment, the 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. In addition, the gas measurement device 1 may obtain a reference signal by using a reference cell filled with a reference gas and sealed without circulating the reference gas.

[0071] The correction value calculation unit 224 uses the detection values ​​of carbon dioxide, methane, and sulfur dioxide that interfere with the determination of nitrous oxide to correct the detection value of nitrous oxide obtained by the detection unit 100 to obtain the concentration of nitrous oxide. The concentration of each gas component is obtained according to the following formula (1) to formula (4). In addition, for a certain component A, the concentration before correction corresponding to the detection value is expressed as A, and the concentration after correction is expressed as [A].

[0072] [Number 1]

[0073] [CH4]=CH4-(a[N2O]+b[SO2]+g[CO2])…(1)

[0074] [Number 2]

[0075] [N2O]=N2O-(c[CH4]+d[SO2]+h[CO2])…(2)

[0076] [Number 3]

[0077] [SO2]=SO2-(e[CH4]+f[N2O]+i[CO2])…(3)[Number 4]

[0078] [CO2] = CO2…(4)

[0079] A, b, and g in formula (1) are influence coefficients representing the degree of influence of nitrous oxide, sulfur dioxide, and carbon dioxide on the determination of methane. C, d, and h in formula (2) are influence coefficients representing the degree of influence of methane, sulfur dioxide, and carbon dioxide on the determination of nitrous oxide. E, f, and i in formula (3) are influence coefficients representing the degree of influence of methane, nitrous oxide, and carbon dioxide on the determination of sulfur dioxide.

[0080] As shown in equations (1) to (3), the concentration of each gas component among the plurality of gas components in the sample gas is represented by a corrected concentration obtained by subtracting the measurement error given to the measurement of the gas component by one or more interfering components for the gas component from the pre-corrected concentration corresponding to the detection value of the gas component. Furthermore, the measurement error given to the measurement of the gas component is represented by the linear sum of the corrected concentration of the interfering component for the gas component and the influence coefficient indicating the degree of influence of the interfering component on the measurement of the gas component.

[0081] In addition, in the present embodiment, the sample gas is exhaust gas. The concentration of carbon dioxide in the exhaust gas is 100 times higher than the concentration of other components (nitrous oxide, sulfur dioxide and methane). In the present embodiment, the concentration of carbon dioxide is extremely high compared to other components (nitrous oxide, sulfur dioxide and methane), so as shown in formula (4), it is assumed that other components have no influence on the measurement of carbon dioxide.

[0082] The correction value calculation unit 224 calculates the concentration of nitrous oxide based on the influence coefficient and the pre-correction concentration of the gas component corresponding to each detection value according to the relationship between formula (1) to formula (4). Specifically, by solving the simultaneous equations of formula (1) to formula (4), the concentration of nitrous oxide is represented by the linear sum of the pre-correction concentration (N2O, CH4, SO2, CO2) corresponding to the detection value and the intermediate coefficient represented by multiple 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. In addition, the method of calculating the concentration according to the relationship between formula (1) to formula (4) is not limited to this method. For example, the correction value calculation unit 224 can also use the influence coefficient instead of the intermediate coefficient for calculation.

[0083] The coefficient calculation unit 226 obtains the influence coefficient based on the detection value obtained by detecting the standard gas with a known concentration and the concentration of the standard gas input from the input unit 300. Specifically, each influence coefficient a to i in equations (1) to (3) is obtained as follows.

[0084] The detection unit 100 detects standard gas composed of nitrous oxide with known concentration using the second detector 10B and the third detector 10C, respectively. Based on the multiple detection values ​​obtained and the known concentration, the influence coefficients a and f in equations (1) and (3) are obtained.

[0085] Specifically, the control unit 200 divides the pre-correction concentration of methane corresponding to the detection value of the third detector 10C by the input concentration of nitrous oxide according to the relationship of formula (1), thereby obtaining the influence coefficient a. The control unit 200 divides the pre-correction concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input concentration of nitrous oxide according to the relationship of formula (3), thereby obtaining the influence coefficient f.

[0086] The detection unit 100 detects standard gas composed of sulfur dioxide with known concentration using the first detector 10A and the third detector 10C, respectively. Based on the multiple detection values ​​obtained and the known concentration, the influence coefficients b and d in equations (1) and (2) are obtained.

[0087] Specifically, the control unit 200 divides the pre-correction concentration of methane corresponding to the detection value of the third detector 10C by the input concentration of sulfur dioxide according to the relationship of formula (1), thereby obtaining the influence coefficient b. The control unit 200 divides the pre-correction concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input concentration of sulfur dioxide according to the relationship of formula (2), thereby obtaining the influence coefficient d.

[0088] The detection unit 100 detects a standard gas composed of methane of known concentration using the first detector 10A and the second detector 10B, respectively. Based on the plurality of detection values ​​obtained and the known concentration, the influence coefficients c and e in equations (2) and (3) are obtained.

[0089] Specifically, the control unit 200 divides the pre-correction concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input concentration of methane according to the relationship of formula (2), thereby obtaining the influence coefficient c. The control unit 200 divides the pre-correction concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input concentration of methane according to the relationship of formula (3), thereby obtaining the influence coefficient e.

[0090] The detection unit 100 detects a standard gas composed of carbon dioxide with a known concentration using the first detector 10A, the second detector 10B, and the third detector. Based on the multiple detection values ​​obtained and the known concentration, the influence coefficients g, h, and i in equations (1) to (3) are obtained.

[0091] Specifically, the control unit 200 divides the pre-corrected concentration of methane corresponding to the detection value of the third detector 10C by the input carbon dioxide concentration according to the relationship of formula (1), thereby obtaining the influence coefficient g. The control unit 200 divides the pre-corrected concentration of nitrous oxide corresponding to the detection value of the first detector 10A by the input carbon dioxide concentration according to the relationship of formula (2), thereby obtaining the influence coefficient h. The control unit 200 divides the pre-corrected concentration of sulfur dioxide corresponding to the detection value of the second detector 10B by the input carbon dioxide concentration according to the relationship of formula (3), thereby obtaining the influence coefficient i.

[0092] The coefficient calculation unit 226 stores the obtained influence coefficients a to i in the storage unit 228. In addition, the coefficient calculation unit 226 may obtain an intermediate coefficient based on the obtained influence coefficients a to i, and store at least one of the influence coefficient and the intermediate coefficient in the storage unit 228. In addition, the coefficient calculation unit 226 may obtain only the intermediate coefficient instead of the influence coefficient, and store the obtained intermediate coefficient in the storage unit 228.

[0093] <Process of Determining the Concentration of the Target Component>

[0094] Reference Figure 3 A method for obtaining the concentration of a target component will be described below. Figure 3 1 is a flowchart showing the processing of the control unit when measuring the sample gas. In addition, the step is abbreviated as "S" below.

[0095] In S12, the control unit 200 obtains the detection value of each gas component among the plurality of gas components obtained by detecting the light amount of the absorption wavelength region of each gas component among the plurality of gas components by detecting the light passing through the sample gas from the detection unit 100. Specifically, the detection unit 100 detects the light amount of the absorption wavelength region of each of nitrous oxide, sulfur dioxide, methane, and carbon dioxide. The detection unit 100 sends each detected detection value to the control unit 200.

[0096] In S14, the control unit 200 obtains the concentration of nitrous oxide based on the detection values ​​of various gas components among the plurality of gas components. More specifically, the control unit 200 obtains the concentration of nitrous oxide based on the relationship of the above-mentioned formulas (1) to (4) and based on the plurality of influence coefficients a to f and the pre-correction concentration of the gas component corresponding to each detection value.

[0097] In S16 , control unit 200 displays the obtained concentration of nitrous oxide on display unit 400 .

[0098] As described above, the control unit 200 obtains the concentration of nitrous oxide in the sample gas.

[0099] <Method for calculating influence coefficient>

[0100] Reference Figure 4 The method of calculating the influence coefficient is explained below. Figure 4 : is a flowchart showing the processing of the control unit when calculating the influence coefficient.

[0101] In S22, the control unit 200 acquires the detection values ​​obtained by the second detector 10B and the third detector 10C respectively detecting the standard gas composed of nitrous oxide with a known concentration. In S24, the control unit 200 receives the input of the concentration of nitrous oxide from the input unit 300.

[0102] In S26, control unit 200 obtains influence coefficient a in equation (1) indicating the degree of influence of nitrous oxide on the measurement of methane and influence coefficient f in equation (3) indicating the degree of influence of nitrous oxide on the measurement of sulfur dioxide.

[0103] In S28, the control unit 200 acquires detection values ​​obtained by detecting the standard gas composed of sulfur dioxide having a known concentration by the first detector 10A and the third detector 10C, respectively. In S30, the control unit 200 receives input of the concentration of sulfur dioxide from the input unit 300.

[0104] In S32, the control unit 200 obtains the influence coefficient b in equation (1) indicating the degree of influence of sulfur dioxide on the measurement of methane and the influence coefficient d in equation (2) indicating the degree of influence of sulfur dioxide on the measurement of nitrous oxide.

[0105] In S34 , the control unit 200 acquires detection values ​​obtained by detecting the standard gas composed of methane with a known concentration by the first detector 10A and the second detector 10B, respectively. In S36 , the control unit 200 receives input of the concentration of methane from the input unit 300 .

[0106] In S38, the control unit 200 obtains the influence coefficient c in equation (2) indicating the degree of influence of methane on the measurement of nitrous oxide and the influence coefficient e in equation (3) indicating the degree of influence of methane on the measurement of sulfur dioxide.

[0107] In S40 , the control unit 200 acquires detection values ​​obtained by detecting the standard gas composed of carbon dioxide having a known concentration by the first detector 10A, the second detector 10B, and the third detector 10C. In S42 , the control unit 200 receives input of the concentration of carbon dioxide from the input unit 300 .

[0108] In S44, the control unit 200 calculates the influence coefficient g in formula (1) indicating the degree of influence of carbon dioxide on the measurement of methane, the influence coefficient h in formula (2) indicating the degree of influence of carbon dioxide on the measurement of nitrous oxide, and the influence coefficient i in formula (3) indicating the degree of influence of carbon dioxide on the measurement of sulfur dioxide.

[0109] As described above, the gas measurement device 1 obtains the influence coefficient indicating the degree of influence of the interfering component with respect to one gas component on the measurement of the one gas component.

[0110] <Examples and Comparative Examples>

[0111] Table 1 shows the method used in this embodiment. Figure 1 The results of the pre-correction concentration obtained when the gas measuring device 1 measures the sample gas are shown in the example in which the correction is performed and in the comparative example in which the correction is performed by the conventional method.

[0112] [Table 1]

[0113]

[0114] Here, in the embodiment, the pre-correction concentration is corrected according to the above formula (1) to formula (4). In the comparative example, the pre-correction concentration is corrected according to the following formula (5) to formula (7) and the above formula (4). In addition, in the embodiment and the comparative example, the influence coefficients a to i are universal coefficients.

[0115] [Number 5]

[0116] [CH4]=CH4-(aN2O+bSO2+gCO2)…(5)

[0117] [Number 6]

[0118] [N2O]=N2O-(cCH4+dSO2+hCO2)…(6)

[0119] [Number 7]

[0120] [SO2]=SO2-(eCH4+fN2O+iCO2)…(7)

[0121] As shown in formulas (5) to (7), in the comparative example, the situation where the determination of the interfering component is affected by other components is not considered, and the pre-correction concentration corresponding to the detection value is corrected using the pre-correction concentration of the interfering component. As shown in Table 1, there is a difference in the corrected concentration between the comparative example and the embodiment. This difference is caused by referring to the situation where the determination of the interfering component is affected by other components. By referring to the situation where the determination of the interfering component is affected by other components, the concentration of the target component can be more accurately calculated.

[0122] <Infrared absorption spectrum of each gas component>

[0123] Reference Figure 5 and Figure 6 To illustrate the infrared absorption spectrum of each gas component. Figure 5 It is the infrared absorption spectrum of nitrous oxide and carbon dioxide. Figure 6 It is the infrared absorption spectrum of nitrous oxide, methane and sulfur dioxide. Figure 5 and Figure 6 In the figure, the spectrum shown by the solid line is the infrared absorption spectrum of nitrous oxide. Figure 5 In the figure, the spectrum indicated by the dashed line is the infrared absorption spectrum of carbon dioxide. Figure 6 In the figure, the spectrum indicated by the double-dashed line is the infrared absorption spectrum of sulfur dioxide. Figure 6 In the figure, the spectrum shown by the dotted line is the infrared absorption spectrum of methane. Figure 5 and Figure 6 In the figure, the horizontal axis is wavelength and the vertical axis is absorbance.

[0124] like Figure 5 and Figure 6 As shown in FIG. 1 , nitrous oxide has absorption wavelength regions near 4.5 μm and 7.8 μm. Figure 5 As shown, carbon dioxide has an absorption wavelength region near 4.25 μm, at least a portion of which overlaps with the absorption wavelength region near 4.5 μm of nitrous oxide.

[0125] In this embodiment, the first detection unit 120 includes an optical filter 20 that does not transmit light in the second absorption wavelength region that overlaps with the absorption wavelength region of carbon dioxide, but transmits light in the first absorption wavelength region. Figure 1 As shown, the first detector 10A detects the light that has passed through the optical filter 20, and therefore detects the amount of light in the absorption wavelength region near 7.8 μm, rather than detecting the amount of light near 4.5 μm whose absorption wavelength region overlaps with carbon dioxide.

[0126] like Figure 5 and Figure 6 As shown, when the absorption wavelength region near 7.8 μm of nitrous oxide is compared with the absorption wavelength region near 4.5 μm, the absorption near 7.8 μm detected by the first detector 10A is weaker than the absorption near 4.5 μm. However, in the present embodiment, exhaust gas is assumed as the sample gas, and the concentration of carbon dioxide in the exhaust gas is at the % level, while the concentration of nitrous oxide is at the ppm level. The concentration of carbon dioxide is high compared with the concentration of nitrous oxide, so the influence of carbon dioxide on the determination of nitrous oxide is great.

[0127] Therefore, the first detection unit 120 involved in this embodiment detects the light amount in the absorption wavelength region near 7.8 μm, which does not overlap with the absorption wavelength region of carbon dioxide but has weak absorption. Thus, the influence of carbon dioxide existing in high concentration in the sample gas on the measurement of nitrous oxide can be reduced, and nitrous oxide can be measured with higher accuracy.

[0128] Sometimes, carbon monoxide (CO) is contained in the exhaust gas. Although not shown in the figure, the absorption wavelength region of carbon monoxide is around 4.7 μm, and overlaps with the absorption wavelength region of carbon monoxide around 4.5 μm. Therefore, by providing the 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.

[0129] The first detector 10A detects the amount of light in the absorption wavelength region near 7.8 μm in the absorption wavelength region of nitrous oxide. Figure 6As shown, methane has an absorption wavelength region near 7.8 μm, sulfur dioxide has an absorption wavelength region near 7.4 μm, and at least a portion of each gas component overlaps with the absorption wavelength region near 7.8 μm of nitrous oxide. Therefore, in addition to reflecting the influence of light absorption by nitrous oxide, the detection value of the first detector 10A also reflects the influence of light absorption by sulfur dioxide and methane.

[0130] In the present embodiment, the first detection unit 120 is provided with a first gas filter 30, and the first gas filter 30 is filled with a gas component having an absorption wavelength region that at least partially overlaps with a first absorption wavelength region in the absorption wavelength region of nitrous oxide, and the first absorption wavelength region is different from a second absorption wavelength region in the absorption wavelength region of nitrous oxide that overlaps with an absorption wavelength region of carbon dioxide. Thus, the amount of light in the absorption wavelength region of the gas component that at least partially overlaps with the first absorption wavelength region is reduced. As a result, the influence of the gas component that at least partially overlaps with the first absorption wavelength region on the measurement of nitrous oxide can be reduced, and nitrous oxide can be measured with higher accuracy.

[0131] In the present embodiment, methane gas is filled in the first gas filter 30. The overlap between the absorption wavelength region of methane and the absorption wavelength region of nitrous oxide is greater than the overlap between the absorption wavelength region of sulfur dioxide and nitrous oxide. Therefore, the influence of methane on the measurement of nitrous oxide is greater than the influence of sulfur dioxide on the measurement of nitrous oxide. In the present embodiment, the light amount of the absorption wavelength region of methane that has a greater influence on the measurement of nitrous oxide can be reduced, and nitrous oxide can be measured with higher accuracy.

[0132] 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. In addition, the gas component filled in the first gas filter 30 may be sulfur dioxide instead of methane.

[0133] In addition, the effect of the first gas filter 30 can be adjusted by changing the partial pressure of the filling gas or changing the distance that the light from the first light source 124 passes through the first gas filter 30. For example, by increasing the partial pressure of the filling gas or extending the distance that the light from the first light source 124 passes through the first gas filter 30, the effect of the first gas filter 30 becomes greater. However, if the effect of the first gas filter 30 is increased, the amount of light in the absorption wavelength region of nitrous oxide detected by the first detector 10A is also reduced, and the detection sensitivity of nitrous oxide is reduced. Therefore, the partial pressure of the filling gas and the distance that the light from the first light source 124 passes through the first gas filter 30 are adjusted within the range of ensuring the detection sensitivity of nitrous oxide.

[0134] In the present embodiment, the first detection unit 120 utilizes the optical filter 20 to cut off the light of the absorption wavelength region of carbon dioxide. However, although it is slight, carbon dioxide also absorbs the light of the absorption wavelength region near 7.8 μm. In addition, as mentioned above, the concentration of carbon dioxide in the exhaust gas is a high concentration relative to nitrous oxide. As a result, even if carbon dioxide slightly absorbs light, it also affects the measurement of nitrous oxide. Therefore, in the present embodiment, the control unit 200 obtains the concentration of nitrous oxide when it is set as carbon dioxide to affect the measurement of nitrous oxide as shown in formula (2).

[0135] Similarly, although it is slight, carbon dioxide also absorbs light in the absorption wavelength regions of sulfur dioxide and methane. The concentration of carbon dioxide in the exhaust gas is in the % level, while the concentrations of sulfur dioxide and methane are in the ppm level. Therefore, the control unit 200 calculates the concentration of nitrous oxide under the assumption that carbon dioxide affects the measurements of sulfur dioxide and methane as shown in equations (1) and (3).

[0136] In addition, the second detection unit 140 involved in the present embodiment is provided with a second gas filter 40 filled with carbon dioxide. As described above, even if carbon dioxide is slightly absorbed, it will affect the measurement of sulfur dioxide and methane. Therefore, the second detection unit 140 is provided with a second gas filter 40, so that the amount of light in the absorption wavelength region of sulfur dioxide and methane and the absorption wavelength region of carbon dioxide is reduced. As a result, the influence of carbon dioxide on each measurement of sulfur dioxide and methane can be reduced, and sulfur dioxide and methane can be measured with higher accuracy. In addition, if the effect of the second gas filter 40 is increased, the detection sensitivity of the fourth detector 10D is reduced. Therefore, the partial pressure of the filling gas of the second gas filter 40 and the distance of the light from the second light source 144 through the second gas filter 40 are adjusted within the range of ensuring the detection sensitivity of carbon dioxide.

[0137] like Figure 6As shown, the absorption wavelength regions of sulfur dioxide and methane partially overlap each other, so sulfur dioxide affects the measurement of methane. In the second detection unit 140, a second detector 10B having a second housing 12B filled with sulfur dioxide is arranged between the third detector 10C that detects the amount of light in the absorption wavelength region of methane and the second sample cell 142. Therefore, the third detector 10C detects the light that passes through the second sample cell 142 and the second housing 12B in this order. As a result, the second housing 12B functions as a gas filter to reduce the amount of light in the absorption wavelength region of sulfur dioxide in the absorption wavelength region of methane. As a result, the measurement error of methane caused by sulfur dioxide can be reduced, and methane can be measured with higher accuracy.

[0138] In addition, the third detector 10C may be arranged on the second optical path IR2 between the second sample cell 142 and the second detector 10B. By arranging in this way, the third housing 12C filled with methane of the third detector 10C functions as a gas filter, and reduces the amount of light in the absorption wavelength region of sulfur dioxide and the absorption wavelength region of methane. As a result, the measurement error of sulfur dioxide generated by methane can be reduced, and sulfur dioxide can be measured with higher accuracy. The order of the second detector 10B and the third detector 10C is determined according to which of methane and sulfur dioxide the measurement accuracy of which is to be improved.

[0139] Furthermore, in the present embodiment, the gas measuring device 1 uses infrared light, but ultraviolet light may be used depending on the absorption wavelength region of the target component.

[0140] Furthermore, in the present embodiment, the amount of light is indirectly detected based on the change in internal pressure when the transmitted light passes through a cell sealed with a gas to be detected. Alternatively, the amount of light may be directly detected by a photoconductive element or the like. Furthermore, the method of detecting the amount of light is common to the plurality of detectors (the first detector 10A to the fourth detector 10D) included in the detection unit 100. Alternatively, the methods of detecting the amount of light of the plurality of detectors may be different from each other. For example, the first detector 10A and the fourth detector 10D, which are arranged at the position farthest from the light source, may be detectors having a pyroelectric sensor, and the second detector 10B and the third detector 10C, which are other than the first detector 10A and the fourth detector 10D, may be detectors having the structure of the above-mentioned embodiment.

[0141] In addition, although the gas measuring device 1 measures exhaust gas, it is also possible to measure other gases. In addition, the detection object of each detector can be changed according to the measurement object. In addition, the optical filter 20, the first gas filter 30 and the second gas filter 40 can also be adjusted according to the measurement object.

[0142] In addition, it is assumed that the gas measuring device 1 has detectors for three interfering components, namely, sulfur dioxide, methane, and carbon dioxide, in order to measure the concentration of nitrous oxide. In addition, the gas measuring device 1 only needs to have a detector for at least one interfering component among sulfur dioxide, methane, and carbon dioxide. In addition, in addition to the detectors for the three interfering components, it may also have detectors for other interfering components.

[0143] Regarding the control unit 200, the control unit 200 obtains the concentration of nitrous oxide under the assumption that other components do not affect the measurement of carbon dioxide as shown in the formula (4).

[0144] In addition, for an interfering component among one or more interfering components for a gas component, for which the measurement error given by the interfering component for the gas component to the measurement of the gas component is sufficiently smaller than the concentration of the gas component, the control unit 200 may also set the influence of the interfering component on the measurement of the gas component to zero to obtain the concentration of the target component. In addition, the measurement error given by the interfering component to the measurement of the gas component is 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 gas component.

[0145] For example, when the measurement error imparted by the interfering component to the measurement of a gas component is less than 1 / 1000 of the concentration of the gas component, the influence of the interfering component on the measurement of the gas component may be set to zero. In addition, when the measurement error imparted by the interfering component to the measurement of a gas component is less than 1 / 100 of the concentration of the gas component, the influence of the interfering component on the measurement of the gas component may be set to zero. The standard for setting the influence to zero can be set according to the accuracy required by the gas measuring device 1 and the maximum concentration of the interfering component in the sample gas.

[0146] For example, when the measurement error (d[SO2]) imparted by sulfur dioxide to the measurement of nitrous oxide is less than 1 / 100 of the concentration of nitrous oxide ([N2O]), the control unit 200 may also set the influence coefficient d in formula (2) to zero to calculate the concentration of nitrous oxide.

[0147] In the above-mentioned embodiment, the gas measuring device 1 is set to use the sample gas as exhaust gas and nitrous oxide as the target component to obtain the concentration of nitrous oxide. In addition, the sample gas and the target component may also be other gases and components. For example, the gas measuring device 1 may also be configured to measure a sample gas containing two or more interfering components for the target component in addition to measuring the target component. Even in this case, by arranging the detector of the target component and the detector of the interfering component on different optical paths and arranging the detectors of various interfering components in series on the same optical path, it is possible to suppress the reduction of the detection sensitivity of the target component and the enlargement of the gas measuring device.

[0148] In the above embodiment, the control unit 200 performs both control of the detection unit 100 and concentration calculation. In addition, the gas measurement device 1 may also include a control unit that controls the detection unit 100 and a calculation unit that calculates the concentration. In this case, the control unit and the calculation unit each include a processor, a memory, and an input / output interface.

[0149] [Way]

[0150] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0151] (Item 1) A gas measuring device according to one embodiment measures a sample gas containing a plurality of gas components, wherein at least a portion of the absorption wavelength regions of the plurality of gas components overlap with each other. The gas measuring 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, respectively, wherein the second component and the third component each have an absorption wavelength region that at least a portion overlaps with the absorption wavelength region of the first component in the sample gas; 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 a plurality of 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 for detecting the light amount in the absorption wavelength region of the first component by detecting the 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 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 the light that has passed through the second sample cell to detect the amount of light in the absorption wavelength region of the second component; and a third detector that detects the light that has passed through the second sample cell to detect the amount of light in the absorption wavelength region 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.

[0152] According to the gas measuring device described in the first item, by arranging the detector for detecting the first component on the first optical path different from the second optical path on which the detector for the component interfering with the detection of the first component is arranged, it is possible to suppress the attenuation of light and thus suppress the reduction in the detection sensitivity of the first component. In addition, since the second detector and the third detector are arranged in series on the second optical path, it is possible to suppress the overall size of the gas measuring device.

[0153] (Item 2) In the gas measuring device described in Item 1, the sample gas is exhaust gas and the first component is nitrous oxide.

[0154] According to the gas measuring device described in the second aspect, nitrous oxide, which is a greenhouse gas, can be measured using exhaust gas as a sample gas.

[0155] (Item 3) According to the gas measuring 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 in the first housing. The first detection unit further includes: an optical filter that does not transmit light in the second absorption wavelength region of the first absorption wavelength region and the second absorption wavelength region of nitrous oxide that overlaps with the absorption wavelength region of carbon dioxide, and transmits light in the first absorption wavelength region; and a first gas filter that is filled with a gas component having an absorption wavelength region that at least partially overlaps with the first absorption wavelength region. The optical filter and the first gas filter are arranged on a first optical path between the first sample cell and the first detector.

[0156] According to the gas measuring device described in the third item, the influence of carbon dioxide present in high concentration in the exhaust gas on the measurement of nitrous oxide can be reduced, and the influence of gas components having an absorption wavelength region that at least partially overlaps with the first absorption wavelength region on the measurement of nitrous oxide can be reduced.

[0157] (Item 4) According to the gas measuring device described in Item 3, the gas component filled in the first gas filter is methane.

[0158] According to the gas measuring device described in the fourth aspect, the influence of methane present in the exhaust gas on the measurement of nitrous oxide can be reduced.

[0159] (Item 5) In the gas measuring device described in Items 2 to 4, the second detection unit further includes a second gas filter, the second gas filter is arranged in the second optical path between the second sample cell and the second detector, and the second gas filter is filled with carbon dioxide.

[0160] According to the gas measuring device described in the fifth aspect, it is possible to reduce the influence of carbon dioxide present at a high concentration in the exhaust gas on the measurement of the second component and the third component.

[0161] (Item 6) In the gas measuring 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 in the second housing. The third detector detects light that has passed through the second sample cell and the second housing in this order.

[0162] According to the gas measuring device described in Item 6, the second detector functions as a gas filter, and can reduce the influence of sulfur dioxide on the measurement of methane.

[0163] (Item 7) In the gas measuring device described in Items 2 to 5, the second detection unit further includes a fourth detector, which detects light passing through the second sample cell to detect the amount of light in the absorption wavelength region of the fourth component that at least partially overlaps with the absorption wavelength region of the first component in the sample gas. 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 this order.

[0164] According to the gas measuring device described in the seventh item, it is possible to obtain detection values ​​of a plurality of interfering components that affect the measurement of nitrous oxide, and it is possible to more accurately measure the concentration of nitrous oxide.

[0165] (Item 8) A gas measuring device according to one embodiment measures a sample gas containing a plurality of gas components, wherein at least a portion of the absorption wavelength regions of the plurality of gas components overlap with each other. The gas measuring device includes: a detection unit that detects the amount of light in the absorption wavelength region of each gas component among the plurality of gas components by detecting light passing through the sample gas; and a calculation unit that calculates the concentration of a target component among the plurality of gas components based on the detection value of each gas component among the plurality of gas components detected by the detection unit. A gas component having an absorption wavelength region that at least a portion overlaps with the absorption wavelength region of one gas component among the plurality of gas components is an interference component for the one gas component. The concentration of each gas component among the plurality of gas components is represented by a corrected concentration obtained by subtracting a measurement error given to the measurement of the gas component by one or more interference components for the gas component from a pre-corrected concentration corresponding to the detection value of the gas component. The measurement error given to the measurement of the gas component is represented by a linear sum of the corrected concentration of the interference component for the gas component and an influence coefficient representing the degree of influence of the interference component on the measurement of the gas component. The calculation unit obtains 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 gas component among the plurality of gas components according to the relationship between the corrected concentration and the uncorrected concentration of each gas component among the plurality of gas components.

[0166] According to the gas measuring device described in the eighth item, the corrected concentration of the target component is expressed by subtracting the measurement error given to the measurement of the interfering component from the pre-corrected concentration of the interfering component for the target component. In addition, the concentration of the target component is obtained 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 obtained more accurately by referring to the situation in which the measurement of the interfering component is affected by other components.

[0167] (Item 9) In the gas measuring device described in Item 8, the detection unit detects light that has passed through a standard gas composed of a first component among the plurality of gas components and having a known concentration, thereby detecting the amount of light in the absorption wavelength region of a second component among the plurality of gas components. The calculation unit calculates an influence coefficient indicating the 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 according to the relationship between the concentration after correction and the concentration before correction of the second component.

[0168] According to the gas measuring device described in Item 9, the influence coefficient can be obtained based on the actual measurement value, thereby obtaining the influence coefficient taking into account the individual differences of the detectors and the like.

[0169] (Item 10) In the gas measuring device described in Item 8 or Item 9, the corrected concentration of the target component is represented by a linear sum of an intermediate coefficient and a pre-corrected concentration corresponding to a detection value of each gas component among the plurality of gas components, based on a plurality of relational expressions representing the relationship between the corrected concentration and the pre-corrected concentration of each gas component among the plurality of gas components, wherein the intermediate coefficient is represented by a plurality of influence coefficients. The calculation unit obtains the corrected concentration of the target component as the concentration of the target component based on the intermediate coefficient and the detection value of each gas component among the plurality of gas components.

[0170] According to the gas measuring device described in the tenth item, the calculation for obtaining the concentration of the target component can be easily performed, and the load applied to the calculation unit can be reduced.

[0171] (Item 11) In the gas measuring device described in any one of Items 8 to 10, the plurality of gas components include at least one of carbon dioxide, methane, and sulfur dioxide, and nitrous oxide.

[0172] According to the gas measuring device described in the eleventh item, it is possible to measure nitrous oxide, which is a greenhouse gas, with high accuracy using exhaust gas as the sample gas.

[0173] (Item 12) In the gas measuring device described in any one of Items 8 to 11, with respect to one or more interfering components for a gas component, for which the interfering component imparts a measurement error of less than 1 / 100 of the concentration of the gas component to the measurement of the gas component, the operation unit sets the influence of the interfering component on the measurement of the gas component to zero.

[0174] According to the gas measuring device described in the twelfth item, the calculation for obtaining the concentration of the target component can be easily performed, and the load applied to the calculation unit can be reduced.

[0175] (Item 13) In the gas measuring device described in 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 obtains the concentration of the target component assuming that the other gas components do not affect the measurement of carbon dioxide.

[0176] According to the gas measuring device described in the thirteenth item, when measuring a sample gas such as exhaust gas containing carbon dioxide at a high concentration, calculation for obtaining the concentration of the target component can be easily performed, and the load imposed on the calculation unit can be reduced.

[0177] (Item 14) A method according to one embodiment is a method for obtaining the concentration of a target component in a sample gas containing a plurality of gas components, wherein at least a portion of the absorption wavelength regions of the plurality of gas components overlap with each other. The method comprises the following steps: obtaining detection values ​​of each gas component among the plurality of gas components, obtained by detecting the amount of light of the absorption wavelength region of each gas component among the plurality of gas components by detecting light passing through the sample gas; and obtaining the concentration of the target component among the plurality of gas components based on the obtained detection values ​​of each gas component among the plurality of gas components. A gas component having an absorption wavelength region that at least a portion overlaps with the absorption wavelength region of one gas component among the plurality of gas components is an interference component for the one gas component. The concentration of each gas component among the plurality of gas components is represented by a corrected concentration obtained by subtracting a measurement error given to the measurement of the gas component by one or more interference components for the gas component from a pre-corrected concentration corresponding to the detection value of the gas component. The measurement error given to the measurement of the gas component is represented by a linear sum of the corrected concentration of the interference component for the gas component and an influence coefficient representing the degree of influence of the interference component on the measurement of the gas component. In the step of calculating the concentration of the object component, the corrected concentration of the object component is calculated as the concentration of the object component based on multiple influence coefficients and detection values ​​of each gas component among the multiple gas components according to the relationship between the corrected concentration and the pre-corrected concentration of each gas component among the multiple gas components.

[0178] According to the method described in the fourteenth item, the corrected concentration of the target component is expressed by subtracting the measurement error given to the measurement of the interfering component from the pre-corrected concentration of the interfering component for the target component. In addition, the concentration of the target component is obtained 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 obtained more accurately by referring to the situation in which the measurement of the interfering component is affected by other components.

[0179] (Item 15) The method described in Item 14 also includes the step of obtaining an influence coefficient, wherein the influence coefficient indicates the degree of influence of an interfering component of a gas component on the measurement of the gas component. The step of obtaining the influence coefficient includes the following steps: obtaining a detection value obtained by detecting the amount of light in the absorption wavelength region of a second component among the multiple gas components by detecting light that has passed through a standard gas composed of a first component among the multiple gas components and whose concentration is known; and obtaining an influence coefficient indicating the 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 according to the relationship between the corrected concentration and the uncorrected concentration of the second component.

[0180] According to the method described in the fifteenth item, the influence coefficient can be obtained based on the actual measurement value, thereby obtaining the influence coefficient taking into account the individual differences of the detectors and the like.

[0181] The embodiments disclosed this time are also intended to be implemented in appropriate combinations within the scope of technical non-contradiction. Moreover, the embodiments disclosed this time should be considered to be illustrative and non-restrictive in all aspects. The scope of the present invention is not represented by the description of the above-mentioned embodiments, but by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0182] Description of Reference Numerals

[0183] 1: gas measuring 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 unit to fourth detection unit; 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 detection unit; 125: second detection unit; 126: first detection unit; 127: first sample cell; 128: first detection unit; 129: first detection unit; 130: first detection unit; 131: first detection unit; 132: first detection unit; 133: first detection unit; 134: first detection unit; 135: first detection unit; 136: first detection unit; 137: first detection unit; 138: first detection unit; 139: first detection unit; 140: first detection unit; 141: first detection unit; 142: first detection unit; 143: first detection unit; 144: first detection unit; 145: first detection unit; 146: first detection unit; 147: first detection unit; 148: first detection unit; 149: first detection unit; 150: first detection unit; 151: first detection unit; 152: first detection unit; 153: first detection unit; 154: first detection unit; 155: first detection unit; 156: first detection unit; 157: first detection unit; 158: first detection unit; 159: first detection unit; 160: first detection unit; 161: first detection unit; 16 A light source; 140: a second detection unit; 142: a second sample cell; 144: a second light source; 160: a motor; 180: a fan-shaped part; 200: a control unit; 220: a processor; 222: a pre-correction concentration calculation unit; 224: a correction value calculation unit; 226: a coefficient calculation unit; 228: a storage unit; 240: a memory; 300: an input unit; 400: a display unit; IR1: a first optical path; IR2: a second optical path; L1~L4: a first line~a fourth line; RG: a reference gas; RL: a reference gas line; SG: a measurement gas; SL: a measurement gas line.

Claims

1. A gas measuring device for measuring a sample gas containing a plurality of gas components, wherein at least a portion of the absorption wavelength regions of the plurality of gas components overlap with each other, the gas measuring device comprising: A first detection unit, which is used to detect a first component in the sample gas; a second detection unit for detecting a second component and a third component, respectively, the second component and the third component respectively having an absorption wavelength region at least partially overlapping with the absorption wavelength region of the first component in the sample gas; as well as 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 the plurality of detection values ​​detected by the second detection unit, Wherein, the first detection unit comprises: The first light source; a first sample cell filled with the sample gas; and a first detector for detecting the light having passed through the first sample cell to detect the amount of light in the absorption wavelength region 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 comprises: 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 to detect the amount of light in an absorption wavelength region of the second component; and a third detector for detecting the light having passed through the second sample cell to detect the amount of light in the absorption wavelength region 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 light irradiated from the second light source.

2. The gas measuring device according to claim 1, wherein: The sample gas is exhaust gas, The first component is nitrous oxide.

3. The gas measuring device according to claim 2, wherein: The first detector has: a first shell filled with the first component; and a first detection unit for detecting the pressure in the first housing; The first detection unit also has: an optical filter that does not transmit light in a first absorption wavelength region and a second absorption wavelength region of nitrous oxide that overlaps with an absorption wavelength region of carbon dioxide, and transmits light in the first absorption wavelength region; and a first gas filter filled with a gas component having an absorption wavelength region at least partly overlapping with the first absorption wavelength region, Wherein, the optical filter and the first gas filter are arranged on the first optical path between the first sample cell and the first detector.

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

5. The gas measuring device according to any one of claims 2 to 4, wherein: The second detection unit further includes a second gas filter disposed on the second optical path between the second sample cell and the second detector, and the second gas filter is filled with carbon dioxide.

6. The gas measuring device according to any one of claims 2 to 4, wherein: The second component is sulfur dioxide, The third component is methane, The second detector has: a second shell filled with the second component; and a second detection unit for detecting the pressure in the second housing, The third detector detects light that passes through the second sample cell and the second housing in this order.

7. The gas measuring device according to any one of claims 2 to 4, wherein: The second detection unit further includes a fourth detector, the fourth detector detecting the light passing through the second sample cell to detect the amount of light in an absorption wavelength region of a fourth component at least partially overlapping with the absorption wavelength region of the first component in the sample gas. 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 in this order on the second optical path.

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