Gas analysis system

Abstract

To accurately analyze carbon isotopes while suppressing the maintenance frequency of a reduction part in a gas analysis system equipped with a gas treatment apparatus in which the reduction part is arranged in the preceding stage of a gas separation part.SOLUTION: The gas analysis system (1) includes a combustion device (10), a gas treatment device (20), and a CRDS gas analysis device (30). The gas treatment device (20) includes a first gas separation section (22) for separating the sample gas generated in the combustion device (10) into a first mixed gas containing carbon dioxide and nitrous oxide and a gas other than the first mixed gas and allowing the first mixed gas to pass therethrough, a reduction section (23) for reducing nitrous oxide in the first mixed gas to nitrogen and allowing a second mixed gas containing carbon dioxide and nitrogen to pass therethrough, and a second gas separation section (24) for separating the second mixed gas into carbon dioxide gas and a gas other than carbon dioxide gas and supplying the carbon dioxide gas to the CRDS gas analyzer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a gas analysis system that combusts and gasifies an organic sample and analyzes the gasified sample using cavity ring-down absorption spectroscopy (CRDS). [Background technology]

[0002] One method for clarifying the elemental composition of solid or liquid organic samples is to combust the sample to gasify it, and then analyze the gasified sample. When performing analysis using this method, the sample is analyzed by flowing through a combustion device, a gas treatment device, and a gas detection device in that order.

[0003] The combustion device is supplied with the sample and oxygen gas (O2 gas) as a combustion supporting gas that promotes the combustion of the sample, and the sample is completely combusted and gasified. In the gas treatment device, the gas generated in the combustion device is converted into a state that can be measured by the gas detection device. For example, when an organic sample containing carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) is burned, the combustion device produces carbon dioxide (CO2), water (H2O), and nitrogen oxides (NO X ), sulfur oxides (SO X The sample gas contains nitrogen oxides (NO X ) includes nitrous oxide (NO), nitric oxide (NO), nitrogen dioxide (NO), and sulfur oxides (SO X ) includes sulfur dioxide (SO2) and sulfur trioxide (SO3). When O2 gas supplied to the combustion device plays the role of not only a combustion support gas but also a carrier gas, the gas treatment device can also contain CO2, H2O, NO X , SO X In addition, excess O2 gas that was not used for combustion in the combustion device is introduced.

[0004] The gas detection device can be a device that analyzes the elemental composition of a gas using cavity ring-down spectroscopy (CRDS) (hereinafter referred to as a "CRDS gas analyzer"). CRDS is a spectroscopic technique that uses an optical resonator (cavity) containing a high-reflectivity mirror to increase the effective optical path length for light absorption by the gas, thereby quantifying the target component contained in the gas with high sensitivity.

[0005] When a CRDS gas analyzer is used as a gas detection device, isotopes of carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) can be analyzed. For example, International Publication No. 2018 / 135619 (Patent Document 1) describes a method for analyzing carbon isotopes ( 12 C. 13 C. 14 In order to accurately analyze CO2 (carbon dioxide) using a CRDS gas analyzer, the sample gas generated in the combustion device is passed through a gas processing device to increase the partial pressure of CO2 (carbon dioxide), which is the target of measurement, and gas with a high partial pressure of CO2 is supplied to the CRDS gas analyzer.

[0006] Furthermore, for example, International Publication No. 2020 / 105715 (Patent Document 2) or Japanese Patent Publication No. 61-33468 (Patent Document 3) describe that in an apparatus for analyzing organic elements, oxides contained in sample gas generated in a combustion apparatus are reduced in a reduction section filled with reduced copper. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 135619 [Patent Document 2] International Publication No. 2020 / 105715 [Patent Document 3] Special Publication No. 61-33468 Summary of the Invention [Problem to be solved by the invention]

[0008] As a configuration for increasing the partial pressure ratio of CO2, which is the object of measurement, in the gas treatment device, it is possible for the gas treatment device to be equipped with a gas separation section that temporarily captures CO2 gas contained in the gas generated in the combustion device and exhausts the other gases to the outside, thereby separating CO2 gas from the other gases.

[0009] However, in reality, it is difficult to separate CO2 gas and N2O (nitrous oxide) gas using only one gas separation unit. In other words, it has been difficult to realize a gas separation unit that captures CO2 without capturing N2O. In reality, it is expected that not only CO2 but also N2O will be captured in the gas separation unit, and as a result, not only CO2 but also N2O will be introduced into the CRDS gas analyzer. If CO2 and N2O are introduced into the CRDS gas analyzer, 14 The absorption lines of N2O exist near the absorption lines of CO2, so interference of the spectral peaks 14 This can lead to a problem of reduced accuracy in CO2 quantification.

[0010] To address this issue, it is envisaged to provide a reduction section before the gas separation section. The reduction section is constructed by maintaining a reduction tube filled with reduced copper at a high temperature (for example, about 600 to 850°C), and NO containing NO is removed. X It plays three roles: reducing nitrogen to N2, reducing SO3 to SO2, and removing excess O2.

[0011] However, simply providing the reduction unit upstream of the gas separation unit can pose a new problem: the reduction unit requires extremely frequent maintenance. As described above, the reduction unit fulfills three functions (reducing nitrogen oxides, reducing sulfur oxides, and removing excess O). However, these chemical reactions oxidize the reduced copper in the reduction unit, converting it to copper oxide. This necessitates periodic replacement or regeneration of the reduced copper. In particular, when the O gas supplied to the combustion device serves as both a combustion support gas and a carrier gas, a large amount of excess O gas is introduced into the reduction unit. Therefore, for example, if 100 g of reduced copper is filled in the reduction tube and 900 mL of O gas is introduced into the reduction tube per analysis, the reduced copper must be replaced or regenerated approximately once every two analyses, resulting in extremely frequent maintenance of the reduction unit.

[0012] The present disclosure has been made to solve these problems, and its purpose is to enable accurate analysis of carbon isotopes while reducing the frequency of maintenance of the reduction unit in a gas analysis system equipped with a gas processing device in which a reduction unit is located upstream of a gas separation unit. [Means for solving the problem]

[0013] A gas analysis system according to the present disclosure includes a combustion device that introduces oxygen and combusts a sample to generate a sample gas, a gas treatment device that increases the partial pressure of carbon dioxide gas in the sample gas, and a CRDS gas analyzer that analyzes the carbon dioxide gas that has passed through the gas treatment device using cavity ring-down spectroscopy. The gas treatment device has a first gas separation unit that separates the sample gas into a first mixed gas of carbon dioxide gas and nitrous oxide gas and gases other than the first mixed gas and passes the first mixed gas, and a reduction unit that is disposed downstream of the first gas separation unit and reduces the nitrous oxide gas in the first mixed gas to nitrogen gas and passes a second mixed gas containing carbon dioxide gas and nitrogen gas. [Effects of the Invention]

[0014] According to the present disclosure, in a gas analysis system equipped with a gas processing device in which a reduction unit is arranged upstream of a gas separation unit, it is possible to reduce the frequency of maintenance of the reduction unit while enabling accurate analysis of carbon isotopes. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram (part 1) schematically illustrating an example of the overall configuration of a gas analysis system. [Figure 2] FIG. 2 is a diagram showing the gas flow in the first step of gas treatment by the gas treatment device. [Figure 3] FIG. 10 is a diagram showing the gas flow in the second step of gas treatment by the gas treatment device. [Figure 4] FIG. 10 is a diagram showing the gas flow in the third step of the gas treatment by the gas treatment device. [Figure 5] FIG. 1 is a diagram showing a schematic example of the configuration of a general organic elemental analyzer using a GC column. [Figure 6] FIG. 2 is a diagram (part 2) schematically illustrating an example of the overall configuration of a gas analysis system. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present embodiment will now be described in detail with reference to the drawings, in which the same or corresponding parts in the drawings are designated by the same reference characters and description thereof will not be repeated.

[0017] <Overall configuration of gas analysis system 1> 1 is a diagram schematically illustrating an example of the overall configuration of a gas analysis system 1 according to this embodiment. The gas analysis system 1 combusts and gasifies an organic sample, and can analyze the composition ratio of carbon isotopes in the sample from CO2 contained in the gasified sample.

[0018] The gas analysis system 1 includes a combustion device 10 , a gas processing device 20 , and a CRDS gas analyzer 30 .

[0019] An organic sample and O2 gas are supplied to the combustion device 10 from the outside. The O2 gas supplied to the combustion device 10 serves as a combustion supporting gas that promotes the combustion of the sample, and as a carrier gas that transports the sample gas after combustion to a subsequent stage. The combustion device 10 completely combusts the organic sample to generate a sample gas. The sample gas generated by the combustion device 10 contains carbon dioxide (CO2), water (H2O), nitrogen oxides (NO X ), sulfur oxides (SO X ), and excess oxygen gas (O2) that was not used in combustion.

[0020] The gas processing device 20 converts the sample gas generated in the combustion device 10 into a state in which CO2 can be analyzed by the CRDS gas analyzer 30, and supplies the converted gas to the CRDS gas analyzer 30. The configuration of the gas processing device 20 will be described in detail later.

[0021] The CRDS gas analyzer 30 uses CRDS to quantify carbon isotopes in a sample of gas supplied from the gas processing device 20. As described above, CRDS is a spectroscopic technique that uses an optical resonator (cavity) including a high-reflectivity mirror to increase the effective optical path length for light absorption by the gas, thereby quantifying target components contained in the gas with high sensitivity.

[0022] In addition, radioactive carbon isotopes, which are one type of carbon isotope, 14 C is the only long-lived radionuclide among elemental isotopes and is used as an environmental tracer. 14 By measuring the abundance ratio of C, it is possible to determine whether the organic resource is biomass derived from plants or fossil fuels. 14 C is also used as a biological tracer. In pharmaceutical development, some of the carbon in a compound is 14 C-labeled compounds are administered to living organisms and accumulated in the blood, urine, feces, and organs. 14 By measuring the concentration of C, it is possible to analyze the in vivo kinetics of the administered compound. 14 The C isotope ratio is very low, 14To measure C, other carbon isotopes 12 C, 13 Distinguish it from C, 14 It is necessary to detect C with high sensitivity. In CRDS, an optical resonator is used to increase the effective optical path length for light absorption by gas, thereby improving sensitivity. 14 C can be detected with high sensitivity.

[0023] <Configuration of gas treatment device 20> The gas treatment device 20 has a gas drying section 21, a first gas separation section 22, a reduction section 23, and a second gas separation section 24. The gas drying section 21, the first gas separation section 22, the reduction section 23, and the second gas separation section 24 are arranged in this order between the combustion device 10 and the CRDS gas analyzer 30.

[0024] The gas drying unit 21 is disposed between the combustion device 10 and the first gas separation unit 22 and removes HO (water component) from the sample gas generated in the combustion device 10. If HO were introduced into the CRDS gas analyzer 30, the HO would adhere to the high-reflectivity mirror in the CRDS gas analyzer 30, reducing the reflectivity of the mirror and the accuracy of the CRDS measurement. However, in the gas treatment device 20 according to this embodiment, the HO in the sample gas generated in the combustion device 10 is removed by the gas drying unit 21. This prevents HO from adhering to the high-reflectivity mirror in the CRDS gas analyzer 30 and reducing the accuracy of the CRDS measurement. Note that because HO does not change even after passing through the reduction unit 23, the gas drying unit 21 is not limited to being disposed before the reduction unit 23 and may be disposed after the reduction unit 23 (for example, between the reduction unit 23 and the second gas separation unit 24).

[0025] The first gas separation section 22 is disposed before the reduction section 23 (specifically, between the gas drying section 21 and the reduction section 23), and separates the sample gas that has passed through the gas drying section 21 into a first mixed gas of CO2 and N2O and gases other than the first mixed gas, and passes the first mixed gas. The gases other than the first mixed gas are exhausted to the outside. The gases other than the first mixed gas include NO other than N2O. X , SOX , O2. That is, the first gas separation section 22 has a function of removing excess oxygen gas (O2) that has not been used for combustion in the combustion device 10.

[0026] The first gas separation unit 22 according to this embodiment is configured to temporarily capture (trap) the first mixed gas, discharge gases other than the first mixed gas to the outside while the first mixed gas is temporarily captured, and supply the first mixed gas to the reduction unit 23 after discharging gases other than the first mixed gas to the outside.

[0027] For example, the first gas separation section 22 can be configured as an adsorption column filled with an adsorbent that adsorbs CO2 and N2O. Zeolite 13X, zeolite 5A, zeolite 4A, or other types of adsorption columns can be used as the adsorption column that configures the first gas separation section 22. Regardless of the type of adsorption column used, it is practically difficult to capture only CO2 without capturing N2O in the first gas separation section 22, and in reality, both CO2 and N2O are captured in the first gas separation section 22.

[0028] The first gas separation unit 22 is not necessarily limited to being configured as an adsorption column. For example, the first gas separation unit 22 may be configured to temporarily capture CO2 by locally cooling a portion of the gas flow path using liquid nitrogen or the like to temporarily solidify and solidify CO2. However, even in this case, since the freezing points of CO2 and N2O are close, it is practically difficult to capture only CO2 in the first gas separation unit 22 without capturing N2O, as with an adsorption column. In reality, both CO2 and N2O are captured in the first gas separation unit 22.

[0029] A carrier gas having a composition different from O2 (for example, helium He or argon Ar) is supplied from the outside to the first gas separation unit 22. As a result, even if the O2 gas that also functions as a carrier gas is removed in the first gas separation unit 22, the first mixed gas can be transported to the reduction unit 23 by the carrier gas having a composition different from O2 gas.

[0030] The reduction unit 23 reduces N2O in the first mixed gas that has passed through the first gas separation unit 22 to N2, and passes the second mixed gas containing CO2 and N2.

[0031] The reduction section 23 is constructed by maintaining a reduction tube filled with reduced copper at a high temperature (for example, about 600 to 850°C), and generates NO containing NO. X In addition, when the first mixed gas contains trace amounts of SO3 and O2 that could not be completely removed by the first gas separation unit 22, the reduction unit 23 also serves to reduce SO3 to SO2 and to remove O2.

[0032] The second gas separation unit 24 separates the second mixed gas that has passed through the reduction unit 23 into CO2 gas and gases other than CO2, and supplies the CO2 gas to the CRDS gas analyzer 30. The gases other than CO2 are exhausted to the outside. The gases other than CO2 include carrier gas and N2.

[0033] The second gas separation unit 24 according to this embodiment may have a configuration similar to that of the first gas separation unit 22. That is, for example, the second gas separation unit 24 may be configured as an adsorption column filled with an adsorbent that adsorbs CO2. As with the first gas separation unit 22, the adsorption column of the second gas separation unit 24 may be a column made of zeolite 13X, zeolite 5A, zeolite 4A, or the like. However, regardless of the type of adsorption column used, as described above, it is difficult to configure the second gas separation unit 24 to capture only CO2 without capturing N2O. In practice, not only CO2 but also N2O will be captured in the second gas separation unit 24.

[0034] However, in the gas processing device 20 according to the present embodiment, a reduction unit 23 that reduces N2O to N2 is disposed upstream of the second gas separation unit 24. This prevents N2O from being present in the second mixed gas supplied to the second gas separation unit 24. As a result, only CO2 is captured in the second gas separation unit 24, and the gas that passes through the second gas separation unit 24 and is introduced into the CRDS gas analyzer 30 contains only CO2, not N2O. As a result, interference between the spectral peaks of CO2 and N2O can be avoided in the CRDS gas analyzer 30, enabling accurate quantification of carbon isotopes.

[0035] Furthermore, in the gas treatment device 20 according to this embodiment, the first gas separation section 22 is disposed in the upstream stage of the reduction section 23. This makes it possible to reduce the frequency of maintenance of the reduction section 23.

[0036] That is, if the first gas separation unit 22 is not arranged in front of the reduction unit 23, the reduction unit 23 will separate NO containing N2O. X The first gas separation unit 22 performs three functions: reducing SO₃ to N₂, reducing SO₃ to SO₂, and removing excess O₂. These chemical reactions oxidize the reduced copper in the reduction unit 23, converting it to copper oxide. Therefore, the reduced copper in the reduction unit 23 must be periodically replaced or regenerated. In particular, in this embodiment, the O₂ supplied to the combustion device 10 serves as a carrier gas. Therefore, without the first gas separation unit 22 upstream of the reduction unit 23, a large amount of excess O₂ is introduced into the reduction unit 23, resulting in a problem of requiring frequent maintenance of the reduction unit 23. For example, if the reduction unit 23 is filled with 100 g of copper and 900 mL of O₂ gas is introduced into the reduction unit 23 in one analysis, the reduction unit 23 must be replaced or regenerated once every two analyses, which is an unrealistic maintenance frequency.

[0037] However, in the gas treatment device 20 according to the present embodiment, the excess O2 is removed by the first gas separation unit 22 disposed upstream of the reduction unit 23. This prevents a large amount of excess O2 from being supplied to the reduction unit 23. As a result, the maintenance frequency of the reduction unit 23 can be kept low.

[0038] <Switching of gas flow paths in the gas processing device 20> In the gas processing by the gas processing device 20 according to this embodiment, the gas flow path is switched by operating valves (not shown) in the order of the first step, second step, and third step.

[0039] 2 is a diagram showing the gas flow in the first step of gas treatment by the gas treatment device 20. In the first step, with the first gas separation unit 22 in a state where it is kept at a low temperature (a state where the first mixed gas is captured), the sample gas flows through the gas drying unit 21 and the first gas separation unit 22 and is exhausted to the outside from the first gas separation unit 22. As a result, the first mixed gas (CO2, N2O) is captured in the first gas separation unit 22, and gases other than the first mixed gas (NO2, N2O other than N2O) are captured. X , SO X , O2) is exhausted to the outside.

[0040] 3 is a diagram showing the gas flow in the second step of gas treatment by the gas treatment device 20. In the second step, the first gas separation unit 22 is heated to a high temperature (a state in which the first mixed gas is released) and the second gas separation unit 24 is cooled to a low temperature (a state in which the second mixed gas is captured). A carrier gas other than O is supplied to the first gas separation unit 22, whereby the first mixed gas (CO, N) captured in the first gas separation unit 22 is released, flows through the reduction unit 23 and the second gas separation unit 24, and is discharged from the second gas separation unit 24 to the outside. As a result, the first mixed gas (CO, N) is converted into a second mixed gas (CO, N) in the reduction unit 23 and supplied to the second gas separation unit 24. The CO in the second mixed gas is captured in the second gas separation unit 24, and gases other than CO are discharged to the outside.

[0041] 4 is a diagram showing the gas flow in the third step of gas treatment by the gas treatment device 20. As shown in Fig. 4, in the third step, the second gas separation unit 24 is heated to a high temperature, whereby CO2 captured in the second gas separation unit 24 is released and supplied to the CRDS gas analyzer 30. By performing such gas treatment by the gas treatment device 20, gas with a high partial pressure of CO2 can be supplied to the CRDS gas analyzer 30.

[0042] As described above, in the gas analysis system 1 according to this embodiment, the sample gas generated by burning an organic sample in the combustion device 10 passes through the first gas separation section 22, the reduction section 23, and the second gas separation section 24 in this order, and is supplied to the CRDS gas analysis device 30.

[0043] In the first gas separation unit 22, gases other than the first mixed gas (CO2, N2O) are removed, and the first mixed gas is supplied to the reduction unit 23. That is, in the first gas separation unit 22 arranged in the upstream stage of the reduction unit 23, NO 3 other than N2O is removed. X , SO X As a result, the amount of oxygen reduced by the reduced copper in the reduction unit 23 is reduced, and the frequency of maintenance of the reduction unit 23 can be kept low.

[0044] In the reduction unit 23, N2O contained in the first mixed gas is reduced to N2, and the second mixed gas containing CO2 and N2 is supplied to the second gas separation unit 24. In this way, the second mixed gas not containing N2O can be supplied to the second gas separation unit 24.

[0045] In the second gas separation unit 24, gases other than CO2 are removed from the second mixed gas, and the CO2 is supplied to the CRDS gas analyzer 30. As described above, the second mixed gas introduced into the second gas separation unit 24 does not contain N2O due to the reduction action of the reduction unit 23. Therefore, even if the second gas separation unit 24 is configured not to separate CO2 and N2O, CO2 is introduced into the CRDS gas analyzer 30 without introducing N2O. As a result, interference between the spectral peaks of CO2 and N2O can be avoided in the CRDS gas analyzer 30, allowing carbon isotopes to be quantified with high accuracy.

[0046] As a result of the above, the gas analysis system 1 according to the present disclosure can analyze carbon isotopes with high accuracy while reducing the frequency of maintenance of the reduction unit 23.

[0047] <Variation 1> By using a solid combustion device for TOC (Total Organic Carbon) measurement as the combustion device 10 in the above-described embodiment, the solid combustion device for TOC measurement may be combined with the gas processing device 20 and the CRDS gas analyzer 30 in the above-described embodiment.

[0048] When a sample containing carbon, hydrogen, nitrogen, and sulfur is combusted in the solid combustion device of a TOC analyzer, CO2, NO X , SO X Therefore, a solid combustion device for a TOC meter may be used as the combustion device 10 in the above-described embodiment.

[0049] <Variation 2> As the combustion device 10 in the above-described embodiment, a combustion section of a general organic elemental analyzer using a gas chromatography (GC) column may be used, so that the general organic elemental analyzer using a GC column may be combined with the gas processing device 20 and the CRDS gas analyzer 30 in the above-described embodiment.

[0050] Figure 5 is a schematic diagram showing an example of the configuration of a typical organic elemental analyzer using a GC column. A typical organic elemental analyzer using a GC column introduces a sample of the combustion gas generated in the combustion tube into a reduction tube, a GC column, and a gas detector for organic elemental analysis. Although the capacity of a typical GC column is very small (e.g., a few μL), the maximum sample volume combusted in an organic elemental analyzer is significantly larger than the capacity of the GC column (e.g., about 2 g for solids and about 5 mL for liquids). Therefore, the amount of gas generated in the combustion tube significantly exceeds the capacity of the GC column. Therefore, only a small amount (e.g., 1%) of the gas generated in the combustion tube is used for measurement, while the majority (e.g., 99%) is exhausted to the outside.

[0051] In the CRDS gas analyzer 30, if the pressure inside the cavity is low, the spectral intensity will be low and the signal-to-noise (SN) ratio will deteriorate, so the pressure inside the cavity must be kept above a certain level. Therefore, when an organic element analyzer such as that shown in Fig. 5 is used as the combustion device 10, it is more advantageous in terms of increasing the pressure to introduce a large amount of the mixed gas that will be exhausted into the CRDS gas analyzer 30 than to measure a small amount of the combustion gas sampled for measurement.

[0052] 6 is a diagram schematically illustrating an example of the overall configuration of a gas analysis system 1A that combines an organic elemental analyzer using a GC column with the gas processing device 20 and CRDS gas analyzer 30 according to the above-described embodiment. In the gas analysis system 1A, as shown in FIG. 6, a large amount of mixed gas exhausted from the combustion tube of the organic elemental analyzer using a GC column is introduced into the gas processing device 20. This allows the mixed gas that is exhausted without being used for measurement by the organic elemental analyzer using a GC column to be effectively used as sample gas for CRDS.

[0053] [Aspect] It will be understood by those skilled in the art that the above-described embodiments and their modifications are specific examples of the following aspects.

[0054] (Item 1) A gas analysis system according to the present disclosure includes a combustion device that introduces oxygen and combusts a sample to generate a sample gas, a gas treatment device that increases the partial pressure of carbon dioxide in the sample gas, and a CRDS gas analyzer that analyzes the carbon dioxide gas that has passed through the gas treatment device using cavity ring-down spectroscopy. The gas treatment device has a first gas separation unit that separates the sample gas into a first mixed gas of carbon dioxide and nitrous oxide and gases other than the first mixed gas and passes the first mixed gas through, and a reduction unit that is located downstream of the first gas separation unit and reduces the nitrous oxide in the first mixed gas to nitrogen and passes a second mixed gas containing carbon dioxide and nitrogen through.

[0055] In the gas analysis system described in paragraph 1, the sample gas generated by burning an organic sample in a combustion device passes through the first gas separation section and the reduction section in that order, and is supplied to the CRDS gas analyzer.

[0056] In the first gas separation unit, gases other than the first mixed gas (carbon dioxide and nitrous oxide) are removed, and the first mixed gas is supplied to the reduction unit. That is, oxygen gas (gases other than the first mixed gas) is removed in the first gas separation unit, which is disposed upstream of the reduction unit. This reduces the amount of oxygen reduced in the reduction unit, thereby reducing the maintenance frequency of the reduction unit.

[0057] In the reduction section, the nitrous oxide contained in the first mixed gas is reduced to nitrogen, and the second mixed gas containing carbon dioxide and nitrogen is supplied to the CRDS gas analyzer. This allows the second mixed gas without nitrous oxide to be supplied to the CRDS gas analyzer.

[0058] Therefore, carbon dioxide, not nitrous oxide, is introduced into the CRDS gas analyzer, which prevents interference between the spectral peaks of carbon dioxide and nitrous oxide, enabling accurate analysis of carbon isotopes.

[0059] As a result, the gas analysis system according to the present disclosure can accurately analyze carbon isotopes while reducing the frequency of maintenance of the reduction unit.

[0060] (Item 2) In the gas analysis system described in item 1, the first gas separation unit temporarily captures the first mixed gas, exhausts gases other than the first mixed gas to the outside while the first mixed gas is temporarily captured, and supplies the first mixed gas to the reduction unit after exhausting gases other than the first mixed gas to the outside.

[0061] In the gas analysis system described in paragraph 2, the first gas separation unit temporarily captures carbon dioxide and nitrous oxide contained in the sample gas, thereby making it possible to remove oxygen from the sample gas.

[0062] (Item 3) In the gas analysis system described in Item 2, the first gas separation section includes a column packed with an adsorbent that adsorbs carbon dioxide and nitrous oxide.

[0063] In the gas analysis system described in paragraph 3, the first gas separation unit can remove oxygen from the sample gas by temporarily adsorbing the carbon dioxide and nitrous oxide contained in the sample gas with an adsorbent in the column.

[0064] (4) In the gas analysis system described in paragraph 2, the combustion device is supplied with a sample and oxygen gas that functions as a combustion supporting gas and a carrier gas from the outside. The gas discharged to the outside by the first gas separation unit includes nitrogen oxides other than nitrous oxide, sulfur oxides, and excess oxygen gas that was not used in combustion in the combustion device.

[0065] In the gas analysis system described in paragraph 4, oxygen gas, which functions not only as a combustion supporting gas but also as a carrier gas, is supplied to the combustion device, resulting in a large amount of oxygen gas being introduced from the combustion device to the gas treatment device. However, the oxygen gas is removed by the first gas separation unit located upstream of the reduction unit. This prevents a large amount of oxygen gas from being introduced into the reduction unit. This reduces the frequency of maintenance of the reduction unit.

[0066] (Item 5) In the gas analysis system according to item 4, a carrier gas different from oxygen gas is supplied to the first gas separation unit from the outside.

[0067] In the gas analysis system described in paragraph 5, even if oxygen gas, which also functions as a carrier gas, is removed in the first gas separation section, the first mixed gas can be transported to the reduction section by a carrier gas other than oxygen gas.

[0068] (Item 6) In the gas analysis system described in item 1, the gas processing device further has a gas drying section that is arranged between the combustion device and the CRDS gas analysis device and removes water components from the sample gas generated in the combustion device.

[0069] In the gas analysis system described in paragraph 6, the water component in the sample gas generated in the combustion device is removed by the gas drying unit. This prevents the water component from being introduced into the CRDS gas analyzer. This prevents the water component from adhering to the high-reflectivity mirror in the CRDS gas analyzer, which would reduce the accuracy of the CRDS measurement.

[0070] (Item 7) In the gas analysis system according to item 1, a combustion tube of an organic elemental analyzer using a gas chromatography column is used as the combustion device.

[0071] In the gas analysis system described in paragraph 7, the mixed gas that is not used for measurement in an organic elemental analyzer using a gas chromatography column and is discharged can be effectively used as sample gas for CRDS.

[0072] (Item 8) In the gas analysis system described in any one of Items 1 to 7, the gas processing device further has a second gas separation unit that is arranged downstream of the reduction unit, separates the second mixed gas into carbon dioxide gas and a gas other than carbon dioxide gas, and supplies the carbon dioxide gas to the CRDS gas analysis device.

[0073] In the gas analysis system described in paragraph 8, the sample gas generated by burning an organic sample in a combustion device passes through the first gas separation section, reduction section, and second gas separation section in that order, and is supplied to the CRDS gas analysis device.

[0074] In the second gas separation unit, gases other than carbon dioxide are removed from the second mixed gas introduced from the reduction unit, and the carbon dioxide gas is supplied to the CRDS gas analyzer. The second mixed gas introduced into the second gas separation unit is free of nitrous oxide due to the reduction action of the reduction unit. Therefore, even if the second gas separation unit is configured not to separate carbon dioxide and nitrous oxide, carbon dioxide is introduced into the CRDS gas analyzer without nitrous oxide. As a result, interference between the spectral peaks of carbon dioxide and nitrous oxide can be avoided in the CRDS gas analyzer, allowing for accurate carbon isotope analysis.

[0075] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0076] 1, 1A gas analysis system, 10 combustion device, 20 gas treatment device, 21 gas drying section, 22 first gas separation section, 23 reduction section, 24 second gas separation section, 30 CRDS gas analyzer.

Claims

1. a combustion device that introduces oxygen and burns the sample to generate sample gas; a gas treatment device for increasing the partial pressure of carbon dioxide in the sample gas; a CRDS gas analyzer that analyzes the carbon dioxide gas that has passed through the gas treatment device using cavity ring-down spectroscopy; The gas treatment device comprises: a first gas separation unit that separates the sample gas into a first mixed gas of carbon dioxide and nitrous oxide and a gas other than the first mixed gas and passes the first mixed gas; a reduction unit disposed downstream of the first gas separation unit, which reduces nitrous oxide in the first mixed gas to nitrogen gas and allows a second mixed gas containing carbon dioxide and nitrogen to pass through.

2. The first gas separation unit is temporarily trapping the first gas mixture; While the first mixed gas is temporarily trapped, gases other than the first mixed gas are discharged to the outside; 2. The gas analysis system according to claim 1, wherein the first mixed gas is supplied to the reduction unit after gases other than the first mixed gas are exhausted to the outside.

3. 3. The gas analysis system according to claim 2, wherein the first gas separation section includes a column packed with an adsorbent that adsorbs carbon dioxide and nitrous oxide.

4. The sample and oxygen gas functioning as a combustion supporting gas and a carrier gas are supplied to the combustion device from the outside, 3. The gas analysis system according to claim 2, wherein the gas discharged from the first gas separation unit to the outside includes nitrogen oxides other than nitrous oxide, sulfur oxides, and excess oxygen gas not used in combustion in the combustion device.

5. The gas analysis system according to claim 4 , wherein a carrier gas different from the oxygen gas is supplied to the first gas separation unit from an external source.

6. 2. The gas analysis system according to claim 1, wherein the gas processing device further comprises a gas drying section disposed between the combustion device and the CRDS gas analyzer, for removing water components from the sample gas generated in the combustion device.

7. 2. The gas analysis system according to claim 1, wherein the combustion device is a combustion tube of an organic elemental analyzer using a gas chromatography column.

8. The gas analysis system according to any one of claims 1 to 7, wherein the gas processing device further comprises a second gas separation unit disposed downstream of the reduction unit, which separates the second mixed gas into carbon dioxide gas and a gas other than carbon dioxide gas, and supplies the carbon dioxide gas to the CRDS gas analyzer.

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