Gas analysis device, gas analysis method, and program for gas analysis device

Abstract

This gas analysis device is for analyzing a target gas containing hydrogen gas that is a main component and at least one impurity gas that is a sub-component. The gas analysis device comprises: a comparison chamber where a first resistance element that has a constant current flowing therethrough and that generates heat is disposed, and where hydrogen gas is introduced into; a measurement chamber where a second resistance element that has a constant current flowing therethrough and that generates heat is disposed, and where the target gas is introduced into; a bridge circuit that is formed by comprising the first resistance element and the second resistance element in a closed circuit and that detects the resistivity of the second resistance element or a related value thereof; a calibration curve data storage unit that is for storing calibration curve data that indicates, using the hydrogen gas as a base gas and a predetermined single component gas other than the hydrogen gas as a span gas, the relationship between the resistivity of the second resistance element detected by the bridge circuit or a related value thereof and the concentration of the span gas; and a concentration calculation unit for estimating the total concentration of the impurity gas in the target gas in terms of a gas component in which the thermal conductivity is greater than or equal to that of oxygen, on the basis of the calibration curve data and the resistivity of the second resistance element detected by the bridge circuit or the related value thereof.

Description

Gas analyzer, gas analysis method, and program for gas analyzer

[0001] The present invention relates to a thermal conduction type gas analyzer, a gas analysis method, and a program for a gas analyzer that measures the concentration of a predetermined gas component by utilizing the difference in thermal conductivity between two components.

[0002] Fuel cells utilize the principle of water electrolysis to generate electricity through a chemical reaction between hydrogen and oxygen. The hydrogen gas that is supplied to these fuel cells must be highly pure, for example, at least 99.98 vol% (i.e., the total concentration of impurity gases must be 200 ppm or less).

[0003] Therefore, in the conventional hydrogen gas production process, in order to ensure a certain level of purity of hydrogen gas, a portion of the produced hydrogen gas is measured by gas chromatography to confirm its purity. However, this method only allows batch measurement, in which the measurement target is collected in a container and measured, and it is not possible to continuously measure the purity of the produced hydrogen gas. It is also possible to measure the purity of hydrogen gas by measuring the concentration of impurity gases contained in the hydrogen gas, but this method is difficult to achieve using a methane meter or CO ２ However, there is a problem in that it is necessary to prepare a measuring device for each type of impurity gas, such as a gas analyzer, which is costly.

[0004] JP 2016-042054 A

[0005] The present invention has been made to solve the above-mentioned problems, and its main objective is to continuously monitor the concentration of the hydrogen gas produced using an inexpensive configuration and to ensure its purity.

[0006] To solve the above problems, the inventors focused on a thermal conduction gas analyzer that measures the concentration of a specific gas component by utilizing the difference in thermal conductivity between two components. As shown in Patent Document 1, for example, a thermal conduction gas analyzer can continuously measure the concentration of, for example, hydrogen gas contained in a target gas by utilizing the difference in thermal conductivity between a reference gas sealed in a reference chamber and a target gas introduced into a measurement chamber. Specifically, in this gas analyzer, a platinum wire (electrical resistance element) that generates heat when a constant current is passed through it is placed in each of the reference chamber and the measurement chamber. Each platinum wire is combined with two external fixed resistors to form a bridge circuit. A change in the concentration of the target component in the target gas changes the thermal conductivity in the measurement chamber, which in turn changes the temperature of the platinum wire. This temperature change is detected as a change in electrical resistance value by the bridge circuit and converted into the concentration of the target component.

[0007] However, this thermal conduction gas analyzer has the drawback of being susceptible to interference in environments where many coexisting components are present, resulting in measurement errors.The hydrogen gas production process produces not only hydrogen gas but also many impurity components such as methane gas and propane gas, so thermal conduction gas analyzers were thought to be unsuitable for monitoring hydrogen gas concentrations.

[0008] After extensive research, the inventors of the present invention have come up with the idea of ​​using this thermal conduction gas analyzer to measure the total concentration of multiple impurity gases contained in a gas to be analyzed, rather than directly measuring the concentration of hydrogen gas, and then using this measured total concentration of impurity gases to calculate the concentration of hydrogen gas. Although it is not possible to accurately measure the concentration of each impurity gas in an environment where many coexisting components exist, as described above, by treating the coexisting multiple impurity gases as a single gas component, and by treating the single gas component as having a thermal conductivity equal to or higher than that of oxygen gas, which has a relatively high thermal conductivity among the impurity gases generated in the hydrogen production process, and calculating its concentration, it is possible to estimate the total concentration of the multiple impurity gases present, although it is not possible to accurately derive it, and therefore it is possible to estimate it higher than the actual concentration. As a result, the derived hydrogen gas concentration can also be estimated lower than the actual concentration, and it has been found that it is possible to monitor the decrease in hydrogen gas purity on the safe side, which led to the present invention.

[0009] That is, the gas analyzer of the present invention is for analyzing a target gas containing hydrogen gas as a major component and one or more impurity gases as minor components, and is characterized by comprising: a comparison chamber into which hydrogen gas is introduced and in which a first resistor element through which a constant current flows and which generates heat is disposed; a measurement chamber into which the target gas is introduced and in which a second resistor element through which a constant current flows and which generates heat is disposed; a bridge circuit formed by including the first resistor element and the second resistor element in a closed circuit and detecting the resistivity or a related value of the second resistor element; a calibration curve data storage unit that stores calibration curve data showing the relationship between the resistivity or related value of the second resistor element detected by the bridge circuit and the concentration of a predetermined single-component gas other than hydrogen gas, using hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas; and a concentration calculation unit that estimates the total concentration of the impurity gases in the target gas in terms of gas components having thermal conductivity equal to or greater than oxygen, based on the resistivity or related value of the second resistor element detected by the bridge circuit and the calibration curve data.

[0010] With this configuration, one or more impurity gases contained in the target gas are treated as a single gas component with a thermal conductivity equal to or greater than that of oxygen, and their concentrations are calculated accordingly. This allows the total concentration of impurity gases contained in the target gas to be estimated higher than the actual concentration. Using the estimated impurity gas concentrations allows the hydrogen gas concentration to be calculated lower than the actual concentration, enabling the reduction in hydrogen gas purity to be monitored on the safe side. Furthermore, since there is no need to install an analyzer for each type of impurity gas, and the concentration of the target gas can be measured while it is being introduced into the measurement chamber, the concentration of the generated hydrogen gas can be continuously monitored with an inexpensive configuration. In this specification, the term "major component" refers to a gas component that occupies "85 vol% or more of the target gas."

[0011] The gas analyzer exhibits a remarkable effect when the target gas contains a plurality of impurity gases.

[0012] In the gas analyzer, the concentration calculation unit preferably estimates the total concentration of the impurity gases in the target gas in terms of the gas component with the highest thermal conductivity among the impurity gases contained in the target gas. In this way, the concentration of one or more impurity gases contained in the target gas is calculated by treating the gas component with the highest thermal conductivity (i.e., the gas component with a small difference in thermal conductivity from hydrogen gas and a low sensitivity) as the single gas component. This allows the total concentration of the impurity gases contained in the target gas to be reliably estimated higher than the actual concentration. Using the estimated impurity gas concentration, the hydrogen gas concentration can also be reliably estimated lower than the actual concentration, allowing for reliable monitoring of the decrease in hydrogen gas purity on the safe side. Note that the impurity gas contained in the target gas refers to gases (e.g., air) that are inevitably generated as a by-product or are mixed in during the production process of the main component, hydrogen gas, and does not include gases artificially mixed in that are not related to the hydrogen generation reaction. The same applies hereinafter.

[0013] In addition, in the gas analyzer, it is preferable that the predetermined single-component gas is the gas with the highest thermal conductivity among the impurity gases contained in the target gas, so that the total concentration of the impurity gases in the target gas can be calculated directly (i.e., without intermediate calculation) in terms of the gas component with the highest thermal conductivity among the impurity gases contained in the target gas.

[0014] Specific examples of the predetermined single-component gas include one selected from methane gas, carbon monoxide gas, carbon dioxide gas, nitrogen gas, and oxygen gas.

[0015] In the gas analyzer, the predetermined single-component gas is preferably methane gas. In the hydrogen gas production process, components such as methane, propane, water vapor, carbon monoxide, carbon dioxide, nitrogen, and oxygen may be generated as impurity gases. However, if a calibration curve is created using methane, which has the highest thermal conductivity among these, as the span gas, it becomes possible to more reliably detect a decrease in the purity of hydrogen gas.

[0016] In a specific embodiment of the gas analyzer, the concentration calculation unit calculates the concentration of the hydrogen gas in the target gas using the estimated total concentration of the impurity gases.

[0017] A specific embodiment of the gas analyzer includes a closed circuit in which the bridge circuit combines the first resistance element and the second resistance element, which have the same specifications, with a third resistance element and a fourth resistance element, which are arranged outside the measurement chamber and the comparison chamber and have the same specifications; a voltage input circuit that inputs a bridge voltage to the closed circuit; and an output voltage measurement circuit that measures an output voltage from the closed circuit.

[0018] A gas analysis method according to the present invention is a method for analyzing a target gas containing hydrogen gas as a primary component and one or more impurity gases as secondary components, the method comprising the steps of: introducing hydrogen gas into a comparison chamber containing a first resistor element through which a constant current flows and generates heat; introducing the target gas into a measurement chamber containing a second resistor element through which a constant current flows and generates heat; detecting the resistivity or a related value of the second resistor element using a bridge circuit formed by including the first resistor element and the second resistor element in a closed circuit; storing calibration curve data showing the relationship between the resistivity or related value of the second resistor element detected by the bridge circuit and the concentration of a predetermined single-component gas other than hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas; and estimating the total concentration of the impurity gases in the target gas in terms of gas components having thermal conductivities equal to or greater than oxygen based on the resistivity or related value of the second resistor element detected by the bridge circuit and the calibration curve data. Such a gas analysis method can achieve the same effects as those of the gas analyzer according to the present invention.

[0019] The present invention also provides a gas analyzer program for analyzing a target gas containing hydrogen gas as a main component and one or more impurity gases as secondary components, the program comprising: a comparison chamber into which hydrogen gas is introduced and in which a first resistor element through which a constant current flows and which generates heat is disposed; a measurement chamber into which the target gas is introduced and in which a second resistor element through which a constant current flows and which generates heat is disposed; and a bridge circuit formed by providing the first resistor element and the second resistor element in a closed circuit and detecting the resistivity or a value related thereto of the second resistor element, the program comprising: a calibration curve data storage unit that stores calibration curve data showing the relationship between the resistivity or a value related thereto of the second resistor element detected by the bridge circuit and the concentration of a predetermined single-component gas other than hydrogen gas, using hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas; and a concentration calculation unit that causes a computer to function as a concentration calculation unit that estimates the total concentration of the impurity gases in the target gas in terms of gas components having thermal conductivity equal to or greater than oxygen, based on the resistivity or the value related thereto of the second resistor element detected by the bridge circuit and the calibration curve data. Such a program for a gas analyzer can achieve the same effects as the gas analyzer of the present invention described above.

[0020] According to the present invention as described above, it is possible to continuously monitor the concentration of the hydrogen gas produced with an inexpensive configuration and ensure its purity.

[0021] 1A and 1B are diagrams showing a configuration of a gas analyzer according to an embodiment of the present invention, a diagram showing a configuration of a bridge circuit according to the embodiment, and a functional block diagram of the gas analyzer according to the embodiment.

[0022] A gas analyzer 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0023] The gas analyzer 100 of this embodiment continuously monitors the purity of hydrogen gas generated, for example, in a hydrogen gas generation process for fuel cells. This gas analyzer 100 is a so-called thermal conduction type that measures the concentration of a predetermined gas species by utilizing the difference in thermal conductivity between two different gas components. It is configured to analyze a mixed gas (hereinafter referred to as target gas) generated in the hydrogen generation process, which contains hydrogen gas as a main component and multiple impurity gases as secondary components, and measure the concentration (purity) of hydrogen gas in the target gas. Note that the hydrogen gas, which is the main component constituting the target gas, is derived from natural gas and contains at least one of methane gas and propane gas as an impurity gas.

[0024] Specifically, as shown in FIG. 1 , the gas analyzer 100 includes a comparison chamber 1 into which a reference gas is introduced, a measurement chamber 2 into which a target gas is introduced, a bridge circuit 3 that detects changes in the thermal conductivity of the target gas introduced into the measurement chamber 2, and a calculation device 4.

[0025] A reference gas, which is a single-component gas with a constant concentration, is introduced into the comparison chamber 1. This comparison chamber 1 is formed by a comparison cell 10 made of, for example, a metal material, and the reference gas is sealed inside the comparison chamber 1. The metal cell that forms the comparison chamber 1 is regulated to a constant temperature by a temperature control mechanism (not shown).

[0026] The measurement chamber 2 is formed by a measurement cell 20 made of, for example, a metal material. The measurement chamber 2 is provided with a gas inlet 2a through which a target gas supplied from the outside is introduced, and a gas outlet 2b through which the target gas is discharged to the outside. The target gas is continuously introduced into the measurement chamber 2 through the gas inlet 2a, and at the same time, is continuously discharged from the measurement chamber 2 to the outside through the gas outlet 2b. The metal cell forming the measurement chamber 2 is regulated to a constant temperature by a temperature control mechanism (not shown).

[0027] 2, the bridge circuit 3 includes a closed circuit 31 formed by combining four electrical resistance elements, a voltage input circuit 32 that inputs a voltage (bridge voltage) to the closed circuit 31, and an output voltage measurement circuit that measures the output voltage from the closed circuit 31. The voltage input circuit 32 includes a constant current power supply 32a that inputs a constant current to the bridge circuit 3. Note that the term "constant current" includes not only a current whose value remains constant without fluctuation, but also a current whose value fluctuates within a range of ±10 mA or less.

[0028] The closed circuit 31 is configured by combining a first resistor element 3a and a second resistor element 3b having the same specifications with a third resistor element 3c and a fourth resistor element 3d having the same specifications. In this bridge circuit 3, the first resistor element 3a and the third resistor element 3c are connected diagonally to each other, and the second resistor element 3b and the fourth resistor element 3d are connected diagonally to each other.

[0029] The first resistor element 3a is made of a metal wire such as a platinum wire, and is installed in the comparison chamber 1 in a state insulated from the metallic reference cell 10. This first resistor element 3a generates heat within the comparison chamber 1 when a constant current output from the constant current power supply 32a flows through it. As described above, the reference gas, which is a single-component gas with an invariable concentration, is sealed within the comparison chamber 1, so the thermal conductivity within the comparison chamber 1 is constant. Therefore, the temperature and electrical resistivity of the first resistor element 3a are maintained at approximately constant values.

[0030] The second resistor element 3b is also made of a metal wire such as a platinum wire, and is installed in the measurement chamber 2 in a state insulated from the metal measurement cell 20. This second resistor element 3b generates heat in the measurement chamber 2 when a constant current output from the constant current power supply 32a flows through it. As described above, the target gas is continuously introduced into the measurement chamber 2, and when the concentration of the components contained in the target gas changes, the thermal conductivity in the measurement chamber 2 changes, and the temperature of the second resistor element 3b changes, and the electrical resistivity of the second resistor element 3b also changes.

[0031] In this embodiment, the third resistive element 3c and the fourth resistive element 3d are both fixed manganese resistors, and are arranged outside the measurement chamber 2 and the comparison chamber 1, and their temperature and electrical resistivity are kept approximately constant.

[0032] The bridge circuit 3 is configured to measure the electrical resistivity of the second resistor element 3b, which changes when the target gas flows into the measurement chamber 2, and output the measured value. Specifically, when the electrical resistivity of the second resistor element 3b changes when the target gas flows into the measurement chamber 2, the output voltage measured by the output voltage measurement circuit 33 changes. The output voltage measurement circuit 33 converts the measured change in output voltage into the electrical resistivity of the second resistor element 3b using a predetermined algorithm, and outputs the converted value.

[0033] The calculation device 4 is a computer having a CPU, memory, an A / D converter, a D / A converter, various input / output devices, etc., and performs at least the functions of a calibration curve data storage unit 41 and a concentration calculation unit 42, as shown in FIG. 3, by the CPU and peripheral devices working together based on a predetermined program stored in the memory.

[0034] The calibration curve data storage unit 41 is set in a predetermined area of ​​the memory and stores calibration curve data that is prepared in advance using hydrogen gas as the base gas and a predetermined single-component gas other than hydrogen gas as the span gas, and that shows the relationship between the electrical resistivity of the second resistance element 3b detected by the bridge circuit 3 and the concentration of the span gas.

[0035] In this embodiment, the calibration curve data is created using a single-component gas having a thermal conductivity equal to or greater than that of oxygen as the span gas. More specifically, in this embodiment, the calibration curve data is created using one gas having the highest thermal conductivity among multiple impurity gases contained in the target gas as the span gas, and even more specifically, the calibration curve data is created using methane gas as the span gas.

[0036] The concentration calculation unit 42 includes an impurity gas concentration estimation unit 42a that estimates and calculates the total concentration of impurity gas in the target gas, and a hydrogen gas concentration calculation unit 42b that calculates the hydrogen gas concentration in the target gas based on the estimated impurity gas concentration (estimated impurity gas concentration).

[0037] The impurity gas concentration estimation unit 42a estimates and calculates the total concentration of impurity gases in the target gas, assuming that the impurity gases contained in the target gas have a thermal conductivity equal to or greater than that of oxygen. In this embodiment, the impurity gas concentration estimation unit 42a estimates and calculates the total concentration of impurity gases in the target gas, assuming that the target gas contains only one gas with the highest thermal conductivity among multiple impurity gases contained in the target gas, more specifically, methane gas. Specifically, the impurity gas concentration estimation unit 42a estimates and calculates the total concentration of impurity gases in the target gas based on the electrical resistivity of the second resistor element 3b detected by the bridge circuit 3 and the calibration curve data stored in the calibration curve data storage unit 41. As described above, the change in the electrical resistivity of the second resistor element 3b detected by the bridge circuit 3 is due to the change in thermal conductivity caused by the change in the concentrations of multiple impurity gases contained in the target gas. On the other hand, the calibration curve data was created using methane gas, a single-component gas, as the span gas. That is, the impurity gas concentration estimation unit 42a calculates the total concentration of impurity gases in the target gas by assuming that the target gas contains only two components, hydrogen gas and methane gas, in other words, that the target gas contains only one type of impurity gas, methane gas. It can also be said that the impurity gas concentration estimation unit 42a of this embodiment calculates the total concentration of impurity gases in the target gas in methane gas equivalent terms.

[0038] The hydrogen gas concentration calculation unit 42b regards the remainder of the calculated impurity gas concentration as the hydrogen gas concentration, calculates the hydrogen gas concentration, and outputs it to a display or the like.

[0039] According to the gas analyzer 100 of this embodiment configured as described above, the concentration of one or more impurity gases contained in the target gas is calculated by treating the single gas component with the highest thermal conductivity (i.e., the gas component with the smallest difference in thermal conductivity from hydrogen gas and therefore low sensitivity). This allows the total concentration of impurity gases contained in the target gas to be estimated higher than the actual concentration. Using the estimated impurity gas concentrations allows the hydrogen gas concentration to be calculated lower than the actual concentration, enabling reliable monitoring of the decrease in hydrogen gas purity on the safe side. Furthermore, since there is no need to install an analyzer for each type of impurity gas, and the concentration of the target gas can be measured while it is being introduced into the measurement chamber 2, the concentration of the generated hydrogen gas can be continuously monitored with an inexpensive configuration.

[0040] The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the target gas contains multiple impurity gases, but the present invention is not limited to this. In other embodiments, the target gas may contain hydrogen gas as a main component and only one impurity gas as a secondary component.

[0041] In the gas analyzer 100 of the above embodiment, the impurity gas concentration estimator 42a calculates the total concentration of impurity gases in the target gas using calibration curve data created using a gas with the highest thermal conductivity among the multiple impurity gases contained in the target gas as the span gas. However, this is not limited to this. In other embodiments of the gas analyzer 100, the impurity gas concentration estimator 42a may calculate the total concentration of impurity gases in the target gas using calibration curve data created using a gas other than the "one gas with the highest thermal conductivity among the multiple impurity gases contained in the target gas" (e.g., oxygen gas, nitrogen gas, etc., or a gas not contained in the target gas). In this case, the impurity gas concentration estimator 42a may calculate the total concentration of impurity gases in the target gas in terms of the gas with the highest thermal conductivity by multiplying the span gas concentration calculated based on the calibration curve data and the electrical resistivity of the second resistor element 3b detected by the bridge circuit 3 by a predetermined coefficient stored in advance.

[0042] Furthermore, although the gas analyzer 100 of the above embodiment includes the hydrogen gas concentration calculation unit 42b and outputs the calculated hydrogen gas concentration, this is not limiting. The gas analyzer 100 of other embodiments may not include the hydrogen gas concentration calculation unit 42b, and may instead display only the estimated impurity gas concentration on a display or the like.

[0043] Furthermore, in the above embodiment, the concentration calculation unit 42 calculates the total concentration of impurity gases and the hydrogen gas concentration using calibration curve data created using hydrogen gas as the base gas and methane gas as the span gas. However, this is not limited to this. The span gas used to create the calibration curve data may be changed as appropriate depending on the origin of the hydrogen gas constituting the target gas. For example, if the hydrogen gas constituting the target gas is derived from the electrolysis of water, the target gas will contain at least one of water vapor, oxygen gas, and nitrogen gas as impurity gases. In this case, the total concentration of impurity gases in the target gas may be calculated using calibration curve data created using hydrogen gas as the base gas and nitrogen gas, which has the highest thermal conductivity, as the span gas.

[0044] In the above embodiment, the calibration curve data indicates the relationship between the electrical resistivity of the second resistor element 3b detected by the bridge circuit 3 and the concentration of the span gas, but this is not limiting. In other embodiments, the calibration curve data may indicate the relationship between a value related to the electrical resistivity of the second resistor element 3b detected by the bridge circuit 3 (for example, the output voltage or output current detected by the output voltage measuring circuit 33 of the bridge circuit 3) and the concentration of the span gas.

[0045] The gas analyzer 100 of another embodiment may be configured to output the calculated impurity gas concentration to a display or the like instead of or together with the calculated hydrogen gas concentration.

[0046] In the gas analyzer 100 of the above embodiment, the impurity gas concentration estimating unit 42a calculates the total concentration of impurity gases in the target gas in methane gas equivalents, but this is not limited thereto. In other embodiments, the impurity gas concentration estimating unit 42a may be configured to estimate the total concentration of impurity gases in the target gas in terms of a gas component having a thermal conductivity equal to or greater than oxygen (for example, oxygen gas equivalent, carbon monoxide gas equivalent, nitrogen gas equivalent, air gas equivalent, or ammonia gas equivalent).

[0047] In another embodiment, the target gas analyzed by the gas analyzer 100 may be a mixed gas that does not contain hydrogen gas as a main component.

[0048] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention.

[0049] According to the present invention described above, it is possible to continuously monitor the concentration of the hydrogen gas produced with an inexpensive configuration and ensure its purity.

[0050] REFERENCE SIGNS LIST 100: Gas analyzer 1: Comparison chamber 2: Measurement chamber 3: Bridge circuit 3a: First resistor element 3b: Second resistor element 41: Calibration curve data storage section 42: Concentration calculation section

Claims

1. An apparatus for analyzing a target gas containing hydrogen gas as a main component and one or more impurity gases as sub-components, comprising: a comparison chamber in which a first resistance element through which a constant current flows and generates heat is disposed and into which hydrogen gas is introduced; a measurement chamber in which a second resistance element through which a constant current flows and generates heat is disposed and into which the target gas is introduced; a bridge circuit formed by providing the first resistance element and the second resistance element in a closed circuit and detecting the resistivity or a related value thereof of the second resistance element; a calibration curve data storage unit storing calibration curve data indicating the relationship between the resistivity or a related value thereof of the second resistance element detected by the bridge circuit and the concentration of the span gas, with hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas; and a concentration calculation unit estimating the total concentration of the impurity gases in the target gas in terms of a gas component having a thermal conductivity equal to or higher than that of oxygen based on the resistivity or a related value thereof of the second resistance element detected by the bridge circuit and the calibration curve data.

2. The gas analysis apparatus according to claim 1, wherein the target gas contains a plurality of impurity gases.

3. The gas analysis apparatus according to claim 1 or 2, wherein the concentration calculation unit estimates the total concentration of the impurity gases in the target gas in terms of the gas component having the highest thermal conductivity among the impurity gases contained in the target gas.

4. The gas analysis apparatus according to any one of claims 1 to 3, wherein the predetermined single-component gas is the gas having the highest thermal conductivity among the impurity gases contained in the target gas.

5. The gas analysis apparatus according to any one of claims 1 to 4, wherein the predetermined single-component gas is one selected from methane gas, carbon monoxide gas, carbon dioxide gas, nitrogen gas, and oxygen gas.

6. The gas analysis apparatus according to claim 5, wherein the predetermined single-component gas is methane gas.

7. The gas analysis apparatus according to any one of claims 1 to 6, wherein the concentration calculation unit calculates the concentration of the hydrogen gas in the target gas using the estimated total concentration of the impurity gases.

8. The gas analyzer according to any one of claims 1 to 7, comprising: the bridge circuit including the first resistor element and the second resistor element having the same specifications as each other, and the third resistor element and the fourth resistor element having the same specifications as each other and arranged outside the measurement chamber and the comparison chamber, which are combined to form a closed circuit; a voltage input circuit for inputting a bridge voltage to the closed circuit; and an output voltage measurement circuit for measuring an output voltage from the closed circuit.

9. A method for analyzing a target gas containing hydrogen gas as a main component and one or more impurity gases as sub-components, comprising: introducing hydrogen gas into a comparison chamber in which a first resistor element through which a constant current flows and generates heat is arranged; introducing the target gas into a measurement chamber in which a second resistor element through which a constant current flows and generates heat is arranged; detecting a resistivity or a related value thereof of the second resistor element by a bridge circuit formed by providing the first resistor element and the second resistor element in a closed circuit; storing calibration curve data indicating a relationship between the resistivity or a related value thereof of the second resistor element detected by the bridge circuit and the concentration of the span gas, with hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas; and estimating a total concentration of the impurity gases in the target gas in terms of a gas component having a thermal conductivity equal to or higher than that of oxygen, based on the resistivity or a related value thereof of the second resistor element detected by the bridge circuit and the calibration curve data.

10. A program for a gas analyzer that analyzes a target gas containing hydrogen gas as a main component and one or more impurity gases as sub-components, in which a first resistance element through which a constant current flows and generates heat is arranged, a comparison chamber into which hydrogen gas is introduced, a second resistance element through which a constant current flows and generates heat is arranged, a measurement chamber into which the target gas is introduced, and a bridge circuit that is formed by including the first resistance element and the second resistance element in a closed circuit and detects the resistivity of the second resistance element or a related value thereof. The program causes a computer to function as a calibration curve data storage unit that stores calibration curve data indicating the relationship between the resistivity of the second resistance element or a related value thereof detected by the bridge circuit and the concentration of the span gas, with hydrogen gas as a base gas and a predetermined single-component gas other than hydrogen gas as a span gas, and a concentration calculation unit that estimates the total concentration of the impurity gases in the target gas in terms of a gas component having a thermal conductivity equal to or higher than that of oxygen based on the resistivity of the second resistance element or a related value thereof detected by the bridge circuit and the calibration curve data.

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