JP2017194391A - Gas detection device and gas detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device that more correctly detects detection object gas such as hydrogen gas mixed in air containing water vapor and dry air.SOLUTION: A gas detection device according to the present invention is a gas detection device 1 that detects detection object gas in measurement object gas in which the detection object gas is contained in air containing water vapor and dry air. The device comprises: a signal intensity detection unit 2 that detects signal intensity relevant to thermal conductivity of the measurement object gas; and a detection object gas detection unit 3 that detects the detection object gas on the basis of the signal intensity. The detection object gas detection unit 3 is configured to detect the detection object gas from a correlation function indicative of a correspondence between the signal intensity and concentration of the detection object gas, and signal intensity obtained by the signal intensity detection unit. The correlation function is obtained from a thermal conductivity function of the measurement object gas to be obtained by an interaction function considering an interaction between the air and the detection object gas, and a thermal conductivity function of the measurement object gas to be obtained by thermal conductivity of the air and thermal conductivity of the detection object gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas detection device and a gas detection method. More specifically, the present invention relates to a gas detection device and a gas detection method for detecting a detection target gas mixed in air containing water vapor and dry air.

  Various devices for detecting a detection target gas in the air are known. For example, a gas heat conduction type gas detection device disclosed in Patent Document 1 is known as a device for detecting gas contained in air. Such a detection device detects a detection target gas in the air using the thermal conductivity of the gas. More specifically, when the detection target gas is hydrogen gas, the thermal conductivity of the hydrogen gas is significantly larger than a substance that can exist as a gas in the standard state. Compared to air that does not contain hydrogen gas, the amount of heat released from the heat source is increased. In the gas heat conduction type gas detection device, it is possible to detect a detection target gas such as hydrogen gas contained in the air using such a principle.

JP 2001-242114 A

  However, in this type of gas heat conduction type gas detector, when the detection target gas is hydrogen gas, for example, the thermal conductivity of air containing hydrogen gas is not only the concentration of hydrogen gas but also water vapor in the air. Therefore, it is difficult to accurately detect hydrogen gas as a measurement target in an environment where the humidity varies. In other words, even if a difference in thermal conductivity between “air containing hydrogen gas” and “dry air” used for the standard gas is detected, the difference in thermal conductivity is determined to be “including hydrogen gas” as described later. Since it is not simply proportional to changes in the concentration of hydrogen gas and water vapor between “air” and “dry air”, even if the concentration of water vapor in “air containing hydrogen gas” is known, “air containing hydrogen gas” It is difficult to accurately detect the hydrogen gas. Such a problem is not limited to hydrogen gas contained in the air, and the same can be said for other detection target gases contained in the air. In this way, when other gases such as hydrogen gas are generated in the air, accurate measurement is possible even if the difference in thermal conductivity between the air containing the detection target gas and the standard gas is simply used. It was difficult.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an apparatus and a method for more accurately detecting a detection target gas mixed in air including water vapor and dry air.

  The gas detection device of the present invention is a gas detection device for detecting the detection target gas in the measurement target gas in which the detection target gas is contained in air containing water vapor and dry air, and the thermal conductivity of the measurement target gas A signal intensity detection unit that detects a signal intensity related to the detection signal, and a detection target gas detection unit that detects the detection target gas based on the signal intensity, and the detection target gas detection unit includes the signal intensity and the detection It is configured to detect the detection target gas from a correlation function indicating a correspondence between the concentration of the target gas and the signal intensity obtained by the signal intensity detection unit, and the correlation function includes i) the water vapor And the interaction between the air and the detection target gas based on the viscosity and molecular weight of the air with the dry air as one component and the viscosity and molecular weight of the detection target gas. And ii) the concentration of the detection target gas in the measurement target gas determined by the thermal conductivity of the air and the thermal conductivity of the detection target gas as variables. It is obtained from a thermal conductivity function.

λ_m：混合ガスの気体熱伝導率
λ_i：成分ｉの気体熱伝導率
ｘ_i、ｘ_j：成分ｉおよび成分ｊのモル分率
Ａ_ij：相互作用を考慮した相互作用関数（Ａ_ii＝１） Further, in the gas detection device of the present invention, the thermal conductivity function of the measurement target gas uses the interaction function, the thermal conductivity of the air, and the thermal conductivity of the detection target gas. It is preferable to be obtained from Equation 1].

λ _m : gas thermal conductivity of mixed gas λ _i : gas thermal conductivity of component i x _i , x _j : mole fraction of component i and component j A _ij : interaction function considering interaction (A _ii = 1)

Ｍ_i、Ｍ_j：成分ｉおよび成分ｊの分子量
λ_tri、λ_trj：成分ｉおよび成分ｊの気体熱伝導率
γ：相互作用パラメータ

η_i、η_j：成分ｉおよび成分ｊの粘度 Further, in the gas detection device of the present invention, the interaction function uses the viscosity and molecular weight of the air containing the water vapor and the dry air and the viscosity and molecular weight of the detection target gas, and the following [Formula 2 It is preferable that it is calculated | required from this.

M _i , M _j : molecular weight of component i and component j λ _tri , λ _trj : gas thermal conductivity of component i and component j γ: interaction parameter

η _i , η _j : viscosity of component i and component j

  Further, in the gas detector of the present invention, the viscosity of the air is such that the molecular weight of the water vapor, the dipole moment, the critical pressure, the critical temperature, the concentration in the air, the molecular weight of the dry air, the dipole moment, the critical pressure. Preferably, it is determined using the critical temperature and the concentration in the air.

η_m：混合ガスの粘度
Ｍ_i、Ｍ_j、Ｍ_k：成分ｉ、成分ｊおよび成分ｋの分子量
ｘ_i、ｘ_k：成分ｉおよび成分ｋのモル分率
η_i：成分ｉの粘度
Ｔ_rij：対臨界温度（reduced temperature）

Ｔ_ci、Ｔ_cj：成分ｉ、成分ｊの臨界温度

μ：双極子モーメント
Ｐ_c：臨界圧力
Ｔ_c：臨界温度 Further, in the gas detector of the present invention, the viscosity of the air is such that the molecular weight of the water vapor, the dipole moment, the critical pressure, the critical temperature, the concentration in the air, the molecular weight of the dry air, the dipole moment, the critical pressure. It is preferable to obtain from the following [Equation 3] using the critical temperature and the concentration in the air.

η _m : viscosity of mixed gas M _i , M _j , M _k : molecular weight of component i, component j and component k _xi , x _k : molar fraction of component i and component k η _i : viscosity of component i T _rij : Reduced temperature

T _ci and T _cj : critical temperatures of component i and component j

μ: Dipole moment P _c : Critical pressure T _c : Critical temperature

  Further, in the gas detection device of the present invention, the correlation function includes a plurality of signal intensities obtained from measurement target gases in a plurality of states in which the concentration of the water vapor in the air and the concentration of the detection target gas are different, and It is preferably obtained by fitting a thermal conductivity function of the measurement object gas.

  The gas detection method of the present invention is a gas detection method for detecting the detection target gas in a measurement target gas in which the detection target gas is contained in air containing water vapor and dry air, and relates to the thermal conductivity of the measurement target gas. A signal intensity detection step for detecting the detected signal intensity and a detection target gas detection step for detecting the detection target gas based on the signal intensity, wherein the detection target gas detection step includes the signal intensity and the detection target. The detection target gas is detected from a correlation function indicating a correspondence between the gas concentration and the signal intensity obtained in the signal intensity detection step, and the correlation function includes i) the water vapor and the dry air. Considering the interaction between the air and the detection target gas based on the viscosity and molecular weight of the air as one component and the viscosity and molecular weight of the detection target gas Interaction function, and ii) the thermal conductivity of the measurement target gas obtained from the thermal conductivity of the air and the thermal conductivity of the detection target gas, with the concentration of the detection target gas in the measurement target gas as a variable It is obtained from a function.

  ADVANTAGE OF THE INVENTION According to this invention, the apparatus and method of detecting more correctly detection object gas, such as hydrogen gas mixed in the air containing water vapor | steam and dry air, can be provided.

It is the schematic of the gas detection apparatus which concerns on one Embodiment of this invention. (A) is a schematic perspective view which shows the detection element of the gas detection apparatus of FIG. 1, (b) is a schematic perspective view which shows the compensation element of the gas detection apparatus of FIG. Cd of a detection circuit for a change in relative humidity in the air when the ambient temperature of the measurement environment is 80 ° C., the concentration of hydrogen gas in the measurement target gas is 0 vol%, and the first variable resistor has different temperature conditions It is a graph which shows the change of the electrical potential difference (measured value) between. Measurement target gas and standard gas for changes in relative humidity in air when the ambient temperature of the measurement environment is 80 ° C., the concentration of hydrogen gas in the measurement target gas is 0 vol%, and the first variable resistor has different temperature conditions It is a graph which shows the change of the difference (calculated value) of thermal conductivity of. C- of the detection circuit for a change in relative humidity in the air when the ambient temperature of the measurement environment is 80 ° C., the temperature of the first variable resistor is 200 ° C., and the hydrogen gas concentration in the measurement target gas is different. It is a graph which shows the change of the electric potential difference (measured value) between d. Measurement target gas and standard for changes in relative humidity in air when the ambient temperature of the measurement environment is 80 ° C., the temperature of the first variable resistor is 200 ° C., and the concentration of hydrogen gas in the measurement target gas is different It is a graph which shows the change of the difference (calculated value) of the thermal conductivity of gas. 6 is a graph showing the relationship between the difference in thermal conductivity (calculated value) shown in FIG. 6 and the potential difference (actually measured value) shown in FIG. 5, where (a) shows the relative air in the measurement target gas. Humidity is a condition of 20%, (b) is a condition in which the relative humidity of the air in the measurement target gas is 40%, and (c) is a condition in which the relative humidity of the air in the measurement target gas is 60%. (D) is a condition where the relative humidity of the air in the measurement target gas is 80%. 6 is a graph showing the result of superimposing the value obtained by converting the difference in thermal conductivity shown in FIG. 6 into a value corresponding to the potential difference between cd of the detection circuit on FIG. 5 (dotted lines are calculated values). The plot shows actual measurement values). Measurement target gas and standard for changes in relative humidity in air when the ambient temperature of the measurement environment is 80 ° C., the temperature of the first variable resistor is 200 ° C., and the concentration of hydrogen gas in the measurement target gas is different It is a graph which shows the change of the difference (calculated value) of the thermal conductivity of gas. 9 is a graph showing the relationship between the difference in thermal conductivity (calculated value) shown in FIG. 9 and the potential difference (actually measured value) shown in FIG. 5, where (a) shows the relative air in the measurement target gas. Humidity is a condition of 20%, (b) is a condition in which the relative humidity of the air in the measurement target gas is 40%, and (c) is a condition in which the relative humidity of the air in the measurement target gas is 60%. (D) is a condition where the relative humidity of the air in the measurement target gas is 80%. 9 is a graph showing the result of superimposing the value obtained by converting the difference in thermal conductivity shown in FIG. 9 into a value corresponding to the potential difference between cd of the detection circuit on FIG. 5 (dotted lines are calculated values). The plot shows actual measurement values).

  Hereinafter, a gas detection device and a gas detection method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  The gas detection device and the gas detection method of this embodiment are an apparatus and a method for detecting a detection target gas in a measurement target gas in which the detection target gas is contained in air containing water vapor and dry air, respectively. The gas detection device and the gas detection method are used, for example, for the purpose of detecting hydrogen gas in the air inside the reactor containment vessel or the reactor building, or for the purpose of detecting hydrogen gas leaking into the air from the fuel cell. Although it can be used, its application range is not limited to these, and it can be applied to detection of gases other than hydrogen gas that requires gas detection.

  The detection target gas to be detected by the gas detection device and the gas detection method of the present embodiment is not particularly limited as long as it is a gas different from the water vapor and dry air contained in the measurement target gas. One kind of single gas or two or more kinds of mixed gas may be used. However, it is preferable that the detection target gas is a gas having a difference value of thermal conductivity between water vapor and dry air that is larger than the difference value between heat conductivity of water vapor and dry air. The detection apparatus and the gas detection method can be more suitably applied, and the detection target gas in the measurement target gas can be detected more accurately as described in detail below. Gases to be detected include hydrogen gas, helium gas, argon gas, krypton gas, carbon monoxide gas, carbon dioxide gas, nitrogen monoxide gas, nitrogen dioxide gas, sulfur dioxide gas, nitrous oxide gas, ethane gas, methane gas, Propane gas, propene gas, butane gas, 1-butene gas, 2-butene gas, pentane gas, 1-pentene gas, trans-2-pentene gas, cis-2-pentene gas, hexane gas, 1-hexene gas, trans-2-hexene gas, cis- 2-hexene gas, heptane gas, octane gas, nonane gas, cyclohexane gas, cyclohexanone gas, isobutane gas, sulfur hexafluoride gas, nitrogen trifluoride gas, benzene gas, toluene gas, xylene gas, trimethylbenzene gas, iodobenzene gas, chloroform Selected from Zen gas, fluorobenzene gas, dimethyl ether gas, diethyl ether gas, fluorocarbon gas, chlorofluorocarbon gas, hydrochlorofluorocarbon gas, hydrofluorocarbon gas, trifluoroiodomethane gas, hydrofluoroether gas and hydrofluoroolefin gas One kind of single gas or two or more kinds of mixed gases can be exemplified.

  The water vapor contained in the measurement target gas is a gas composed of water molecules, and the dry air contained in the measurement target gas is the remaining gas obtained by removing water vapor from the air.

<Gas detection device>
The gas detection device detects the signal intensity related to the thermal conductivity of the measurement target gas including water vapor, dry air, and the detection target gas, and detects the detection target gas included in the measurement target gas from the signal intensity. Details of the gas detection device will be described below. In the following description, a gas heat conduction type gas detection device is cited as an example of the gas detection device, and the gas heat conduction type gas detection device is a detection target gas such as hydrogen gas. This will be described using an example applied to detection of hydrogen gas in the measurement target gas. However, the gas detection device is not limited to the gas heat conduction type gas detection device exemplified below, and is a device to which the measurement principle of another known heat conductivity measurement method such as the unsteady hot wire method is applied. There may be. Further, the detection target gas is not limited to hydrogen gas, and may be another gas as described above.

<Gas heat conduction type gas detector>
In this embodiment, the gas heat conduction type gas detection device detects hydrogen gas in a three-component measurement target gas in which hydrogen gas is contained in air containing water vapor and dry air. As shown in FIG. 1, the gas heat conduction type gas detection device 1 includes a signal intensity detection unit 2 that detects a signal intensity related to the thermal conductivity of the measurement target gas, and hydrogen gas (detection based on the signal intensity. And a detection target gas detection unit 3 that detects a target gas).

<Signal intensity detector>
In this embodiment, the signal intensity detection unit 2 detects the difference in thermal conductivity between the measurement target gas and the standard gas by detecting the signal intensity due to the difference in thermal conductivity between the measurement target gas and the standard gas. . As shown in FIG. 1, the signal intensity detection unit 2 applies a DC voltage to the detection circuit 4 that generates a potential difference as a signal intensity resulting from a difference in thermal conductivity between the measurement target gas and the standard gas. And a potentiometer 6 for detecting a potential difference generated in the detection circuit 4.

  The detection circuit 4 is configured as a Wheatstone bridge circuit, resulting in a difference in resistance value in the circuit due to a difference in thermal conductivity between the measurement target gas and the standard gas, and a difference in thermal conductivity between the measurement target gas and the standard gas. A potential difference caused by the is generated. As shown in FIG. 1, the detection circuit 4 includes a detection piece in which a detection element 41 and a compensation element 42 are connected in series, and a bridge circuit in which a first fixed resistor 43 and a second fixed resistor 44 are connected in series. The opposite side resistance piece with respect to the detection piece in is provided in parallel. Both ends (points a and b) of the detection piece and the opposite resistance piece are connected to the two positive and negative terminals of the DC voltage source 5, respectively, between the detection element 41 and the compensation element 42 (point c), Between the 1st fixed resistance 43 and the 2nd fixed resistance 44 (d point), it connects to each of two terminals of the positive electrode of the potentiometer 6, and a negative electrode.

  The detection element 41 is a member whose resistance value changes due to a heat balance with the measurement target gas through which the measurement target gas flows (natural diffusion). As shown in FIG. 2A, the sensing element 41 contains a first variable resistor 41a whose resistance value changes due to a heat balance with the measurement target gas, and a first variable resistor 41a. Is provided with a detection container 41b. Since the heat balance with the measurement target gas is affected by the thermal conductivity of the measurement target gas, the resistance value of the first variable resistor 41a changes according to the thermal conductivity of the measurement target gas. The first variable resistor 41a is not particularly limited as long as the resistance value is configured to change in accordance with the change in the thermal conductivity of the measurement target gas. For example, a known platinum thin film resistor is used. be able to. In the present embodiment, as shown in FIG. 2A, the detection container 41b is provided with a through hole through which the measurement target gas can flow, so that the measurement target gas can flow therethrough. However, the detection container 41b is not limited to the illustrated structure as long as the measurement target gas can flow so that the first variable resistor 41a is exposed to the measurement target gas. Other structures, such as being provided on the side of the container 41b, may be used.

  The compensation element 42 is a member that is filled with a standard gas serving as a reference for the measurement target gas, and whose resistance value changes due to a heat balance with the standard gas. As shown in FIG. 2B, the compensation element 42 contains a second variable resistor 42a that is thermally equivalent to the first variable resistor 41a and a second variable resistor 42a, and is filled with a standard gas. Compensation container 42b. Since the heat balance with the standard gas is affected by the thermal conductivity of the standard gas, the resistance value of the second variable resistor 42a changes according to the thermal conductivity of the standard gas. In addition, during the measurement, when the state is kept constant so that the thermal conductivity of the standard gas does not change, the resistance value of the second variable resistor 42a does not change. The second variable resistor 42a is not particularly limited as long as it is thermally equivalent to the first variable resistor 41a. For example, the second variable resistor 42a having the same configuration as the first variable resistor 41a can be used. The compensation container 42b is configured to be filled with standard gas and prevent other gases from flowing in. The compensation container 42b may have any structure as long as the filled standard gas is maintained in a predetermined state and the second variable resistor 42a is exposed to the standard gas. Also good. The standard gas is not particularly limited as long as it is a reference gas with respect to the measurement target gas. For example, dry air, helium gas, nitrogen gas, or the like can be used.

  The first fixed resistor 43 and the second fixed resistor 44 are members having fixed predetermined resistance values. In the present embodiment, the first fixed resistor 43 and the second fixed resistor 44 each have a potential difference between the points cd of the detection circuit 4 when the thermal conductivity of the measurement target gas is the same as that of the standard gas. The resistance value is set so as not to occur. However, the detection circuit 4 is generated between points cd of the detection circuit 4 when the measurement target gas and the standard gas have the same thermal conductivity and when the measurement target gas and the standard gas have different thermal conductivities. It is sufficient that a significant difference occurs in the potential difference. Therefore, the first fixed resistor 43 and the second fixed resistor 44 are not limited to the above-described resistance values, respectively, and the case where the measurement target gas and the standard gas have the same thermal conductivity and the measurement target gas and the standard gas The resistance value may be set so that a significant difference occurs in the potential difference generated between the points cd of the detection circuit 4 when the thermal conductivity is different.

  In the signal intensity detection unit 2 of the present embodiment, if the thermal conductivity of the measurement target gas is the same as the thermal conductivity of the standard gas, the resistance values of the first variable resistor 41a and the second variable resistor 42a are the same. Therefore, no potential difference is generated between the points cd of the detection circuit 4. On the other hand, when the thermal conductivity of the measurement target gas is different from the thermal conductivity of the standard gas, the heat of each of the first variable resistor 41a and the second variable resistor 42a and each of the measurement target gas and the standard gas. Since the balance is different, a difference occurs in the resistance values of the first variable resistor 41a and the second variable resistor 42a, thereby generating a potential difference between the cd points of the detection circuit 4. The signal intensity detection unit 2 measures the potential difference generated between the points c and d of the detection circuit 4 with the potentiometer 6, so that the potential difference caused by the difference in thermal conductivity between the measurement target gas and the standard gas is used as the signal intensity. Can be detected. However, the signal intensity detection unit 2 is not limited to the above-described configuration as long as it is configured to detect the signal intensity due to the difference in thermal conductivity between the measurement target gas and the standard gas. Instead of the meter, an ammeter may be used to detect the current as the signal intensity.

  In this embodiment, the signal intensity detection unit 2 is configured to detect the signal intensity due to the difference in thermal conductivity between the measurement target gas and the standard gas, as described above. However, the signal intensity detection unit is not limited to the present embodiment as long as the signal intensity detection unit is configured to detect the signal intensity related to the thermal conductivity of the measurement target gas. For example, another measurement principle is applied. The gas detector may be configured to detect a signal resulting from a change in the thermal conductivity of the measurement target gas.

<Detection target gas detection unit>
The detection target gas detection unit 3 is configured to detect hydrogen gas from the correlation function indicating the correspondence between the signal intensity and the hydrogen gas concentration and the signal intensity obtained by the signal intensity detection unit 2. Yes. That is, the detection target gas detection unit 3 detects the signal intensity using a correlation function (V = F (x) or V≈F (x)) indicating the correspondence between the signal intensity V and the hydrogen gas concentration x. The signal intensity V obtained by the unit 2 is converted into a value corresponding to the hydrogen gas concentration x (x = F ⁻¹ (V) or x≈F ⁻¹ (V)). It is configured to detect the presence and / or concentration of hydrogen gas. Here, the correlation function is a function indicating a correspondence between the signal intensity and the concentration of hydrogen gas, and a function (V = F (x)) indicating the relationship between the signal intensity and the concentration of hydrogen gas in a complete form. In addition, for example, a function (V≈F (x)) configured such that the signal intensity corresponds to the hydrogen gas concentration, for example, the signal intensity increases or decreases according to the increase or decrease of the hydrogen gas concentration. Including. The value corresponding to the concentration of hydrogen gas includes not only the concentration of hydrogen gas but also an indirect value that increases or decreases in accordance with the increase or decrease of the concentration of hydrogen gas.

  The detection target gas detection unit 3 is shown in FIG. 1 as an information processing apparatus that is communicably connected to the DC voltage source 5 and the potentiometer 6 of the signal intensity detection unit 2. In the present embodiment, the detection target gas detection unit 3 receives a potential difference from the potentiometer 6 and calculates a value corresponding to the concentration of hydrogen gas in the measurement target gas using the received potential difference and the correlation function. The detection target gas detection unit 3 includes an arithmetic processing device such as a CPU, a storage device such as a hard disk, a communication device such as a network interface, an input device such as a keyboard / mouse, a display device such as a liquid crystal display, etc. inside or outside. A known computing device such as a personal computer can be used. However, the detection target gas detection unit 3 is configured to detect hydrogen gas from the correlation function indicating the correspondence between the signal intensity and the hydrogen gas concentration and the signal intensity obtained by the signal intensity detection unit 2. If it is, the present invention is not limited to the above-described embodiment, and various modifications such as being provided integrally with the signal intensity detection unit 2 instead of the outside of the signal intensity detection unit 2 are allowed.

The correlation function (V = F (x) or V≈F (x)) indicating the correspondence between the signal intensity V and the hydrogen gas concentration x is a measurement using the hydrogen gas concentration x in the measurement target gas as a variable. It is obtained from the thermal conductivity function (λ _samp (x)) of the target gas (V = F (λ _samp (x)) or _V≈F (λ _samp (x))). More specifically, in the present embodiment, the correlation function includes a thermal conductivity function (λ _samp (x)) of the measurement target gas with the concentration x of the hydrogen gas in the measurement target gas as a variable, and a standard that is a constant. (V = F (Δλ (x)) or V≈F (Δλ () including a difference (λ _samp (x) −λ _ref = Δλ (x)) from the thermal conductivity (λ _ref ) of the gas. x))). However, the correlation function only needs to be obtained from the thermal conductivity function of the measurement target gas with the concentration of hydrogen gas in the measurement target gas as a variable, and the specific configuration thereof is the gas heat conduction type gas used. It can be appropriately determined according to the detection principle and / or actual measurement value of the detection device, and when a gas detection device other than the gas heat conduction type gas detection device is used, the detection principle and / or actual measurement of the gas detection device. It can be determined appropriately according to the value.

  Here, the thermal conductivity function of the measurement target gas cannot be obtained by simply multiplying the respective thermal conductivities of the gas components contained in the measurement target gas and multiplying the respective ratios. This is because the gas components interact with each other and this interaction cannot be ignored. Therefore, the thermal conductivity function of the gas to be measured is calculated by, for example, using the Wassiljewa's equation (the following Equation 1) while considering the interaction between the gas components contained in the gas to be measured. It is obtained by multiplying the ratio by the ratio of each gas component to obtain the sum. When the method using Formula 1 is adopted for the measurement target gas containing the three components of dry air, water vapor, and hydrogen gas, each interaction of dry air, water vapor, and hydrogen gas is considered. However, the thermal conductivity of dry air, water vapor, and hydrogen gas is multiplied by the respective ratios and added up. However, the present inventors have examined the method using Equation 1 in detail. In this method, as will be described in detail later, the heat conduction corresponding to the signal intensity obtained by the signal intensity detector 2 is performed. It was found that the rate function could not be obtained, and therefore an accurate correlation function could not be obtained. This is because the gas to be measured contains water vapor (water molecule) with a large dipole moment, and the water vapor (water molecule) has the ability to form hydrogen bonds as a unique intermolecular interaction. Alternatively, it is likely that the same type of molecules tend to interact with each other, easily collide with different types of molecules or the same type of molecules, and have a specific influence on the thermal conductivity of the measurement target gas. Therefore, in order to more accurately determine the thermal conductivity function of the measurement target gas and more accurately determine the correlation function, it is necessary to consider the dipole moment of water vapor (water molecule).

λ_m：混合ガスの気体熱伝導率
λ_i：成分ｉの気体熱伝導率
ｘ_i、ｘ_j：成分ｉおよび成分ｊのモル分率
Ａ_ij：相互作用を考慮した相互作用関数（Ａ_ii＝１）

λ _m : gas thermal conductivity of mixed gas λ _i : gas thermal conductivity of component i x _i , x _j : mole fraction of component i and component j A _ij : interaction function considering interaction (A _ii = 1)

  For the reasons described above, in this embodiment, the thermal conductivity function of the measurement target gas is not the three components of dry air, water vapor, and hydrogen gas, but the mutual relationship between air containing dry air and water vapor and hydrogen gas. It is obtained by an interaction function considering the action, and the thermal conductivity of air and the thermal conductivity of hydrogen gas. More specifically, the thermal conductivity function of the measurement target gas includes an interaction function that takes into account the interaction of two components between air and hydrogen gas, and the thermal conductivity of air and the thermal conductivity of hydrogen gas. Is obtained from Equation 1 described above. The interaction function considering the interaction of the two components between air and hydrogen gas is obtained based on the viscosity and molecular weight of air with water vapor and dry air as one component, and the viscosity and molecular weight of hydrogen gas. It is done. In obtaining the thermal conductivity function of the gas to be measured, the water vapor and the dry air are set to 1 by considering the interaction of the two components between the air and the hydrogen gas, not the three components of the dry air, the water vapor and the hydrogen gas. Since the influence of the dipole moment of water vapor (water molecule) can be reflected on the viscosity of air as a component, a more accurate thermal conductivity function can be obtained. Furthermore, as a relative comparison, hydrogen gas and water vapor having a large difference in thermal conductivity between each other are not treated as one component, but water vapor and dry air having a small difference in each other's thermal conductivity are treated as one component. Thus, a more accurate thermal conductivity function can be obtained. Therefore, the correlation function can be obtained more accurately, and the hydrogen gas in the measurement target gas can be detected more accurately. From the same point of view, if the gas to be measured includes a gas other than hydrogen gas such as helium gas or argon gas, which has a large difference in thermal conductivity with water vapor, the dipole moment of water vapor is considered, Steam and dry air are handled as one component, and the thermal conductivity function of the measurement target gas is obtained.

  Here, the interaction function is a function that considers the interaction between the two component gases, and is an empirical parameter (interaction parameter) related to the molecular weight, viscosity, and intermolecular interaction of each of the interacting two component gases. Is represented by In the present embodiment, the interaction function considering the interaction of two components between air and hydrogen gas has the viscosity and molecular weight of air with water vapor and dry air as one component, and the viscosity and molecular weight of hydrogen gas. And obtained from the following Mason and Saxena equations (Equation 2).

Ｍ_i、Ｍ_j：成分ｉおよび成分ｊの分子量
λ_tri、λ_trj：成分ｉおよび成分ｊの気体熱伝導率
γ：相互作用パラメータ

η_i、η_j：成分ｉおよび成分ｊの粘度

M _i , M _j : molecular weight of component i and component j λ _tri , λ _trj : gas thermal conductivity of component i and component j γ: interaction parameter

η _i , η _j : viscosity of component i and component j

  The viscosity of air can also be measured by, for example, a known viscosity sensor. In this embodiment, the molecular weight of water vapor, the dipole moment, the critical pressure, the critical temperature, the concentration in air, and the molecular weight of dry air. , Dipole moment, critical pressure, critical temperature and concentration in air. More specifically, the viscosity of air is the molecular weight of water vapor, dipole moment, critical pressure, critical temperature and concentration in air and the molecular weight of dry air, dipole moment, critical pressure, critical temperature and concentration in air. And the following Reichenberg equation (Equation 3).

η_m：混合ガスの粘度
Ｍ_i、Ｍ_j、Ｍ_k：成分ｉ、成分ｊおよび成分ｋの分子量
ｘ_i、ｘ_k：成分ｉおよび成分ｋのモル分率
η_i：成分ｉの粘度
Ｔ_rij：対臨界温度（reduced temperature）

Ｔ_ci、Ｔ_cj：成分ｉ、成分ｊの臨界温度

μ：双極子モーメント
Ｐ_c：臨界圧力
Ｔ_c：臨界温度

η _m : viscosity of mixed gas M _i , M _j , M _k : molecular weight of component i, component j and component k _xi , x _k : molar fraction of component i and component k η _i : viscosity of component i T _rij : Reduced temperature

T _ci and T _cj : critical temperatures of component i and component j

μ: Dipole moment P _c : Critical pressure T _c : Critical temperature

In addition, when detection object gas is a mixed gas containing 2 or more types of gas like city gas (13A), the air containing water vapor | steam and dry air, and 2 or more types of gas contained in detection target gas In consideration of the interaction of the combination of three or more gas components, the thermal conductivity function of the gas to be measured may be obtained, or two or more gases are handled as one gas to be detected, The thermal conductivity function of the measurement target gas may be obtained in consideration of the interaction between air and the detection target gas. At this time, as the thermal conductivity of each of the two or more gases included in the detection target gas, an experimentally obtained value may be used, or a value obtained by an empirical formula or a semi-empirical formula. Or may be calculated using a hard sphere approximation described below. When two or more kinds of gases are handled as one detection target gas, the thermal conductivity of the detection target gas can be obtained by a different method depending on the magnitude of the interaction between the two or more kinds of gases. it can. For example, when the interaction between two or more gases is relatively strong, the thermal conductivity of the detection target gas takes into account the interaction between the two or more gases, and the above-described Equations 1, 2 and It may be calculated using Equation 3, or the above-described Equation 1 and Equation 2 and the Roy-Thodos method for _obtaining the thermal conductivity ratio (λ _tri / λ _trj ) in Equation 2 (Formula 7 below) You may calculate using. Also, when the interaction between two or more gases can be ignored, the ratio of the two or more gases is multiplied by the respective thermal conductivity and simply added to obtain the thermal conductivity of the third component gas. May be calculated.

  Here, the water vapor concentration in the air can be measured using a known humidity sensor or the like. For example, when the humidity in the air that does not contain hydrogen gas is measured by a humidity sensor, the humidity measured by the humidity sensor can be converted to the water vapor concentration in the air, and the measurement object that contains hydrogen gas When the humidity in the gas is measured by a humidity sensor, the water vapor concentration in the air is expressed as a function of the hydrogen gas concentration x. For this purpose, the gas heat conduction type gas detector 1 is a water vapor concentration measuring device using a known humidity sensor or the like for measuring the water vapor concentration in the air and / or the water vapor concentration in the measurement target gas. You may have.

  In addition, the gas heat conduction type gas detection device 1 may include a known temperature sensor for directly or indirectly measuring the temperature of the measurement target gas and / or the standard gas. For example, when the temperature of the measurement target gas and / or the standard gas varies, the thermal conductivity of the measurement target gas and / or the standard gas changes, so that the temperature sensor is used to compensate for the influence of the temperature change. be able to.

Correlation function indicating the correspondence _{(V = F (λ samp (} x)) or _{V ≒ F (λ samp (x} ))) , the thermal conductivity of the gas to be measured between the concentration x of the signal strength V and hydrogen gas From the function (λ _samp (x)), for example, it can be theoretically determined according to the detection principle of the gas heat conduction type gas detection device used, or the concentration of water vapor in the air and the concentration of hydrogen gas are different. It can also be obtained by fitting a plurality of signal intensities obtained from the measurement target gas in the above state and the thermal conductivity function of the measurement target gas. In the latter case, in this embodiment, a function (Δλ (x)) of the difference between the thermal conductivity function (λ _samp (x)) of the measurement target gas and the thermal conductivity (λ _ref ) of the standard gas, and the water vapor A correlation function can be obtained in accordance with the concentration of water vapor in the air by fitting the relationship of the change in signal intensity with the change in the concentration of hydrogen gas obtained under different conditions.

  Next, the gas detection method of this embodiment will be described.

<Gas detection method>
The gas detection method includes a signal intensity detection step for detecting a signal intensity related to the thermal conductivity of a measurement target gas including water vapor, dry air, and a detection target gas, and detection for detecting the detection target gas based on the signal intensity. And a target gas detection process. In addition, the gas detection method may optionally include a water vapor concentration measurement step of measuring the concentration of water vapor in the air including water vapor and dry air and / or the concentration of water vapor in the measurement target gas. In addition, the gas detection method may optionally include a gas temperature measurement step for directly or indirectly measuring the temperature of the measurement target gas and / or the standard gas.

  Further details of the gas detection method will be described below. In the following description, the detection target gas detects hydrogen gas in the measurement target gas, which is hydrogen gas, using the gas heat conduction type gas detection device 1 described above. An example will be described. However, the gas detection method of the present invention is not limited to the following example, and a device other than the gas heat conduction type gas detection device 1 may be used, or a gas other than hydrogen gas may be used as the detection target gas. Good. Note that the thermal conductivity function of the measurement target gas, the interaction function considering the interaction of the two components between the air and hydrogen gas, and the viscosity of the air are obtained by the same method as described above. Detailed description thereof is omitted.

  In the signal intensity detection step, in the embodiment using the gas heat conduction type gas detection device 1 described above, the signal intensity is obtained by using the gas heat conduction type gas detection device 1 and the heat conductivity of the measurement target gas and the standard gas. Detected due to differences. More specifically, as a pre-stage of signal intensity detection, the compensation container 42b of the signal intensity detection unit 2 of the gas heat conduction type gas detection device 1 is filled with dry air as a standard gas, and the detection container 41b The measurement target gas around the gas heat conduction type gas detector 1 is naturally diffused. A current is supplied between points a and b of the detection circuit 4 by the DC voltage source 5. At this time, the first variable resistor 41a of the detection element 41 and the second variable resistor 42a of the compensation element 42 are heated by the current supplied to the detection circuit 4, respectively, while being measured in the detection container 41b. The heat is dissipated into the gas and the standard gas in the compensation vessel 42b. When hydrogen gas is not generated, the thermal conductivity of the measurement target gas is the same as that of the standard gas, but when hydrogen gas is generated, the thermal conductivity of the measurement target gas is the same. Since the thermal conductivity of the standard gas is different from that of the standard gas, the first variable resistor 41a and the second variable resistor 42a have a difference in heat dissipation efficiency and a difference in temperature and resistance value. As a result, a potential difference is generated between cd of the detection circuit 4, and this potential difference is detected as a signal intensity by the potentiometer 6. By detecting this potential difference, a difference in thermal conductivity between the measurement target gas and the standard gas is detected. However, in the signal intensity detection step, the apparatus used for detection is not particularly limited as long as the signal intensity related to the thermal conductivity of the measurement target gas can be detected, and the gas heat conduction type gas detection according to the present embodiment. It may be carried out using another known gas heat conduction type gas detection device that is not the device 1, or it is not a gas heat conduction type gas detection device, and the signal intensity related to the thermal conductivity of the measurement target gas is detected. It may be implemented using other possible devices.

In the detection target gas detection step, in the embodiment using the gas heat conduction type gas detection device 1 described above, a correlation function indicating a correspondence between the signal intensity obtained by the signal intensity detection step and the concentration of hydrogen gas, and Hydrogen gas is detected from the signal intensity obtained in the signal intensity detection step. More specifically, the signal intensity detecting step using a correlation function (V = F (x) or V≈F (x)) indicating the correspondence between the potential difference V, which is the signal intensity, and the hydrogen gas concentration x. Is converted into a value corresponding to the hydrogen gas concentration x (x = F ⁻¹ (V) or x≈F ⁻¹ (V)), so that the hydrogen gas in the measurement target gas Detect presence and / or concentration.

At this time, the correlation function (V = F (x) or V≈F (x)) indicating the correspondence between the signal intensity and the hydrogen gas concentration uses the hydrogen gas concentration x in the measurement target gas as a variable. It is obtained from the thermal conductivity function (λ _samp (x)) of the gas to be measured (V = F (λ _samp (x)) or _V≈F (λ _samp (x))). In addition, the thermal conductivity function (λ _samp (x)) of the measurement target gas is not the three components of dry air, water vapor, and hydrogen gas, but the two components between air containing dry air and water vapor and hydrogen gas. It is obtained by an interaction function considering the action, and the thermal conductivity of air and the thermal conductivity of hydrogen gas. The interaction function considering the interaction of the two components between air and hydrogen gas is obtained based on the viscosity and molecular weight of air with water vapor and dry air as one component, and the viscosity and molecular weight of hydrogen gas. It is done. As already mentioned above, in determining the thermal conductivity function of the gas to be measured, by considering the interaction of the two components between air and hydrogen gas instead of the three components of dry air, water vapor and hydrogen gas, Since the influence of the dipole moment of water vapor (water molecule) can be reflected on the viscosity of air containing water vapor and dry air as one component, a more accurate thermal conductivity function can be obtained. Furthermore, as a relative comparison, hydrogen gas and water vapor having a large difference in thermal conductivity between each other are not treated as one component, but water vapor and dry air having a small difference in each other's thermal conductivity are treated as one component. Thus, a more accurate thermal conductivity function can be obtained. Therefore, the correlation function can be obtained more accurately, and the hydrogen gas in the measurement target gas can be detected more accurately. In particular, when a gas with a risk of explosion, such as hydrogen gas, is contained in the air, it is necessary to monitor the mixture ratio (concentration) below the lower explosion limit with high accuracy in order to avoid the risk of explosion. is there. In the case of hydrogen gas, it has a very low explosion limit of 4.1% as a mixture ratio with air, and higher detection accuracy is required within a very narrow mixture ratio range of 0 to 4.1%. Is done. The gas detection device and gas detection method of the present embodiment can detect hydrogen gas more accurately even within a very narrow mixing ratio range of 0 to 4.1%. It has sufficient monitoring function to avoid it.

  The detection target gas detection step can be performed by, for example, the detection target gas detection unit 3 of the gas heat conduction type gas detection device 1 of the present embodiment, but the signal intensity and hydrogen gas concentration obtained by the signal intensity detection step are As long as the detection target gas (hydrogen gas) can be detected from the correlation function indicating the correspondence between the two and the signal intensity obtained in the signal intensity detection step, other detection target gas detection unit 3 is different. You may implement using an apparatus.

  Hereinafter, although the outstanding effect of the gas detection apparatus and gas detection method of this invention is demonstrated based on an Example, this invention is not limited to a following example.

<Example>
As the gas heat conduction type gas detection device, the device shown in FIG. 1 and FIG. 2 is prepared, and a three-component measurement target gas containing water vapor, dry air and hydrogen gas, and a standard gas which is dry air, The potential difference between the points cd in the detection circuit 4 was measured. Regarding the measurement object gas, the standard gas, the first variable resistor 41a of the detection element 41, and the second variable resistor 42a of the compensation element 42, the following conditions were used. As for the first fixed resistor 43 and the second fixed resistor 44, when the thermal conductivity of the measurement target gas is the same as that of the standard gas, no potential difference is generated between the points cd of the detection circuit 4. The resistance value was set.
(1) Gas gas type to be measured: water vapor, dry air, and hydrogen gas concentration (vol%) in the gas to be measured (vol%) = hydrogen gas / (water vapor + dry air + hydrogen gas) × 100 (vol%): 0, 1 2, 3, 4
Relative humidity (% RH) when the hydrogen gas concentration is 0 vol%: 4.5, 36.5, 55.9, 75.8, 90.2
Relative humidity (% RH) when the hydrogen gas concentration is 1 to 4 vol%: 20, 40, 60, 80
Temperature (° C): 80
(2) Standard gas type: Dry air temperature (° C): 80
(3) First variable resistor manufacturing method: platinum is formed in a meandering shape by sputtering on an alumina substrate, and silica is coated on the upper layer, and manufacturing temperature (° C.): 100, 200, 300, 400, 500, 600
(4) Second variable resistor manufacturing method: same temperature (° C.) as the first variable resistor: 80

Next, the difference between the thermal conductivity of the measurement target gas and the thermal conductivity of the standard gas was obtained by calculation, and the calculation result was compared with the measurement result described above. The thermal conductivity of the measurement target gas and the standard gas were calculated by the following methods. In the following examples, the thermal conductivity and the like of each gas are obtained by calculation using Equations 4 to 6, but may be obtained using other equations, and experimentally obtained values and experiences. A value obtained by a manual or semi-empirical formula may be adopted.
(1) Thermal conductivity of measurement object gas The thermal conductivity of measurement object gas was calculated | required in the following procedures. First, the viscosity of air with water vapor and dry air as one component was determined by the above-described formula 3, and the viscosity of hydrogen gas was determined by a hard sphere approximation (the following formula 4). When determining the viscosity of the air, it was assumed that the temperature of the measurement target gas had risen to the same temperature as that of the first variable resistor 41a, and was the same as the temperature of the first variable resistor 41a. Next, using the viscosity and molecular weight of air and the viscosity and molecular weight of hydrogen gas, an interaction function (interaction coefficient) that takes into account the interaction of the two components between air and hydrogen gas according to the above-described formula 2. ) In this case, the empirical parameter (interaction parameter) γ is a value recommended by Tandon and Saxena (PK Tandon and SC Saxena, Appl.) In consideration of the interaction between polar molecules (air) and nonpolar molecules (hydrogen gas). Sci. Res., 19, 163 (1965)). Finally, using the obtained interaction function (interaction coefficient), the thermal conductivity of air, and the thermal conductivity of hydrogen gas, the thermal conductivity of the measurement target gas was obtained by Equation 3 described above. In addition, the thermal conductivity of air was calculated | required by the empirical formula (following Numerical formula 5) represented by a polynomial, and the thermal conductivity of hydrogen gas was calculated | required by the hard sphere approximation (following Numerical formula 6).

η：粘度
ｍ：分子の質量
ｋ：ボルツマン定数
Ｔ：気体の温度
ε：ポテンシャルパラメータ
ａ₀：０．３５４１２５
ａ₁：−０．４２７５８１
ａ₂：０．１４９２５１
ａ₃：−０．０３７１７４
ａ₄：０．００３１７６
σ＝０．２９６８ｎｍ（水素の分子直径）
（参考文献）M. J. Assael and S. Mixafendi, J. Phys. Chem. Ref. Data, 15, 4(1986)

η: viscosity m: mass of the molecule k: Boltzmann constant T: gas temperature ε: potential parameter a ₀ : 0.354125
a ₁ : -0.427581
a ₂ : 0.149251
a _3: -0.037174
a _4: 0.003176
σ = 0.2968 nm (molecular diameter of hydrogen)
(Reference) MJ Assael and S. Mixafendi, J. Phys. Chem. Ref. Data, 15, 4 (1986)

[Formula 5]
λ _A = A _A + B _A · T + C _A · T ² + D _A · T ³
λ _A : thermal conductivity of gas T: gas temperature A _A , B _A , C _A , D _A : constants according to gas type (reference) A. Melling, et al., J. Phys. Chem. Ref Data, 26, 4 (1997)

λ（Ｈ₂）：水素ガスの熱伝導率
Ｔ：水素ガスの温度
Ｍ：水素ガスの分子量

ｋ：ボルツマン定数
Ｔ：気体の温度
ε：ポテンシャルパラメータ
σ＝０．２９６８ｎｍ（水素の分子直径）
Ａ：１．１６１４５
Ｂ：０．１４８７４
Ｃ：０．５２４８７
Ｄ：０．７７３２０
Ｅ：２．１６１７８
Ｆ：２．４３７８７
（参考文献）P. D. Neufeld, A. R. Janzen, and R. A. Aziz, J. Chem. Phys., 57, 1100 (1972)
（２）標準ガスの熱伝導率
標準ガスの熱伝導率は、多項式で表わされる経験的な式（上記数式５）により求めた。

λ (H ₂ ): thermal conductivity of hydrogen gas T: temperature of hydrogen gas M: molecular weight of hydrogen gas

k: Boltzmann constant T: gas temperature ε: potential parameter σ = 0.2968 nm (molecular diameter of hydrogen)
A: 1.16145
B: 0.14874
C: 0.52487
D: 0.77320
E: 2.16178
F: 2.437787
(Reference) PD Neufeld, AR Janzen, and RA Aziz, J. Chem. Phys., 57, 1100 (1972)
(2) Thermal conductivity of standard gas The thermal conductivity of the standard gas was determined by an empirical formula (the above formula 5) represented by a polynomial.

  FIG. 3 shows the measurement results when the ambient temperature of the measurement environment is 80 ° C., the hydrogen gas concentration is 0 vol%, and the first variable resistor 41a is under different temperature conditions, and a detection circuit for a change in relative humidity in the air. 4 shows a change in potential difference between cd of 4; From FIG. 3, when the temperature of the first variable resistor 41a is 200 ° C. or lower, the potential difference increases until the relative humidity increases to 50%, but the potential difference decreases when the relative humidity increases beyond 50%. You can see that It can also be seen that when the temperature of the first variable resistor 41a is 300 ° C. or higher, the potential difference increases as the relative humidity increases, but the increase rate gradually decreases.

  FIG. 4 is a calculation result corresponding to the measurement result of FIG. 3, in which the ambient temperature of the measurement environment is 80 ° C., the hydrogen gas concentration is 0 vol%, and the first variable resistor 41 a has different temperature conditions (the measurement target gas is The change of the difference of the heat conductivity of measurement object gas and standard gas with respect to the change of the relative humidity in the air in different temperature conditions) is shown. From FIG. 4, when the temperature of the first variable resistor 41 a is 200 ° C. or less (when the measurement target gas is 200 ° C. or less), the difference in thermal conductivity increases until the relative humidity increases to 50%. It can be seen that the difference in thermal conductivity decreases as the relative humidity increases beyond 50%. Further, when the temperature of the first variable resistor 41a is 300 ° C. or higher (the temperature of the measurement target gas is 300 ° C. or higher), the difference in thermal conductivity increases as the relative humidity increases, but the increase rate gradually decreases. You can see that The change in the difference in thermal conductivity with respect to the change in relative humidity shown in FIG. 4 is very well matched with the change in potential difference with respect to the change in relative humidity shown in FIG.

  FIG. 5 shows the measurement results when the ambient temperature of the measurement environment is 80 ° C., the temperature of the first variable resistor 41a is 200 ° C., and the hydrogen gas concentration in the measurement target gas is different. The change of the potential difference between cd of the detection circuit 4 with respect to the change of humidity is shown. FIG. 4 shows that the potential difference decreases with increasing relative humidity in the air at any hydrogen gas concentration of 1 to 4 vol%, but the decrease rate gradually decreases.

  FIG. 6 is a calculation result corresponding to the measurement result of FIG. 5, and is measured when the ambient temperature of the measurement environment is 80 ° C., the temperature of the first variable resistor 41 a is 200 ° C. (the temperature of the measurement target gas is 200 ° C.). The change of the difference of the heat conductivity of measurement object gas and standard gas with respect to the change of the relative humidity in air in the case where the density | concentration of hydrogen gas in object gas differs is shown. FIG. 6 shows that the difference in thermal conductivity decreases with increasing relative humidity in the air at any hydrogen gas concentration of 1 to 4 vol%, but the rate of decrease gradually decreases. . The change in the difference in thermal conductivity with respect to the change in relative humidity shown in FIG. 6 is very well matched with the change in potential difference with respect to the change in relative humidity shown in FIG.

  7A to 7D show the relationship between the difference in thermal conductivity shown in FIG. 6 and the potential difference shown in FIG. In any case where the relative humidity in the air is 20 to 80%, the calculated difference in thermal conductivity and the measured potential difference have a very good linear relationship and almost the same slope. (The slope is in the range of about 2.6 to 2.7). FIG. 8 shows the result of superimposing the values obtained by converting the difference in thermal conductivity shown in FIG. 6 on FIG. 4 using this linear relationship (average value of four inclinations). FIG. 8 shows that the measured potential difference agrees very well with the value converted from the calculated difference in thermal conductivity. As can be seen from this result, according to the method of the present embodiment, even when the concentration of hydrogen gas is below the lower explosion limit (4.1%) as described above, hydrogen gas can be detected with high accuracy. .

<Comparative example>
The difference between the thermal conductivity of the gas to be measured and the thermal conductivity of the standard gas was obtained by calculation using a method different from the above-described example, and the calculation result was compared with the above-described measurement result. The thermal conductivity of the measurement object gas was calculated by the following method. The conditions not described here were the same as in the above example.

First, using the respective molecular weight, critical temperature, and critical pressure of water vapor, dry air, and hydrogen gas, the value of λ _tri / λ _trj in Equation 2 described above by the Roy-Thodos method (Formula 7 below) Asked. Using the obtained values of λ _tri / λ _trj , the interaction between the two components of all combinations of the three components of water vapor, dry air, and hydrogen gas is considered according to Equation 2 described above. A function (interaction coefficient) was obtained. At this time, the empirical parameter (interaction parameter) γ is a combination of nonpolar gas (dry air) and nonpolar gas (hydrogen gas) in consideration of the interaction between nonpolar molecules and nonpolar molecules, The recommended values by Mason and Saxena (EA Mason and SC Saxena, Phys. Fluids, 1, 361 (1958)) are used. For combinations of polar gas (water vapor) and nonpolar gas (dry air or hydrogen gas), Considering the interaction between polar and nonpolar molecules, the recommended values by Tandon and Saxena (PK Tandon and SC Saxena, Appl. Sci. Res., 19, 163 (1965)) were adopted. Then, using the obtained interaction function (interaction coefficient), the thermal conductivity of water vapor, the thermal conductivity of dry air, and the thermal conductivity of hydrogen gas, the heat of the measurement target gas is calculated according to the above-described Equation 1. The conductivity was determined. In addition, the heat conductivity of water vapor and the heat conductivity of dry air were calculated | required by Numerical formula 5 mentioned above, and the heat conductivity of hydrogen gas was calculated | required by the hard sphere approximation (Formula 6).

λ_tri、λ_trj：成分ｉおよび成分ｊの気体熱伝導率
Ｔ_c：臨界温度
Ｐ_c：臨界圧力
Ｍ：分子量

λ _tri , λ _trj : gas thermal conductivity of component i and component j T _c : critical temperature P _c : critical pressure M: molecular weight

  FIG. 9 is a calculation result corresponding to the measurement result of FIG. 5, and is measured when the ambient temperature of the measurement environment is 80 ° C. and the temperature of the first variable resistor 41 a is 200 ° C. (the temperature of the measurement target gas is 200 ° C.). The change of the difference of the heat conductivity of measurement object gas and standard gas with respect to the change of the relative humidity in air in the case where the density | concentration of hydrogen gas in object gas differs is shown. From FIG. 9, it can be seen that the difference in thermal conductivity decreases linearly as the relative humidity in the air increases at any hydrogen gas concentration of 1 to 4 vol%. This indicates that the change in potential difference with respect to the change in relative humidity shown in FIG. 5 and the change in difference in thermal conductivity with respect to the change in relative humidity shown in FIG. 9 do not match.

  10A to 10D show the relationship between the difference in thermal conductivity shown in FIG. 9 and the potential difference shown in FIG. In any case where the relative humidity in the air is 20 to 80%, although the calculated difference in thermal conductivity and the measured potential difference have a linear relationship, FIGS. Unlike the example shown, it can be seen that the slopes of each are greatly different (the slope is in the range of about 3.2 to 4.3). FIG. 11 shows the result of superimposing the values obtained by converting the difference in thermal conductivity shown in FIG. 9 on FIG. 5 using this linear relationship (average value of four inclinations). It can be seen from FIG. 8 that the measured potential difference and the value converted from the calculated difference in thermal conductivity do not match at all.

  As can be seen from the above-described Examples and Comparative Examples, even if the interaction function is obtained as the three components of water vapor, dry air, and hydrogen gas and the thermal conductivity of the measurement target gas is calculated, the difference in the calculated thermal conductivity is calculated. Is not obtained, but when calculating the thermal conductivity of the gas to be measured by calculating the interaction function as two components of water and hydrogen gas including water vapor and dry air A good correlation is obtained between the calculated difference in thermal conductivity and the measured potential difference. In particular, according to the conventional method (calculated with three components), the relationship (slope) between the calculated difference in thermal conductivity and the measured potential difference is accompanied by a change in the concentration of water vapor in the measurement target gas. Although it changes, according to the method of this embodiment (calculated with two components), the difference between the calculated thermal conductivity and the measured potential difference are not affected by the change in the concentration of water vapor in the measurement target gas. A good correlation (slopes are almost the same) can be obtained. Therefore, if the three components of water vapor, dry air, and hydrogen gas are handled as two components of air and hydrogen gas, and the thermal conductivity function of the gas to be measured with the concentration of hydrogen gas as a variable is obtained, the thermal conductivity function is obtained. Thus, a more accurate correlation function showing the correspondence between the potential difference (signal intensity) and the concentration of hydrogen gas can be obtained. And by using the correlation function, the hydrogen gas in the measurement target gas can be detected with high accuracy. In particular, when water vapor is present in a high concentration in the air, the thermal conductivity of the gas to be measured is more affected by water vapor having a dipole moment, and thus the detection error becomes larger in the conventional method. . For example, in the accident at the Fukushima Daiichi Nuclear Power Station during the Great East Japan Earthquake, cooling water evaporated in the reactor containment vessel and a large amount of water vapor was generated. However, according to the gas detection device and the gas detection method of the present embodiment, it is possible to accurately detect hydrogen gas without being affected by a change in the concentration of water vapor in the measurement target gas.

DESCRIPTION OF SYMBOLS 1 Gas heat conduction type gas detection apparatus 2 Signal intensity detection part 3 Detection target gas detection part 4 Detection circuit 41 Detection element 41a 1st fluctuation resistor 41b Detection container 42 Compensation element 42a 2nd fluctuation resistor 42b Compensation container 43 1st 1 fixed resistor 44 2nd fixed resistor 5 DC voltage source 6 potentiometer

Claims (7)

A gas detection device for detecting the detection target gas in a measurement target gas in which the detection target gas is contained in air containing water vapor and dry air,
A signal intensity detector for detecting a signal intensity related to the thermal conductivity of the measurement object gas;
A detection target gas detection unit that detects the detection target gas based on the signal intensity,
The detection target gas detection unit,
A correlation function indicating a correspondence between the signal intensity and the concentration of the detection target gas, and a signal intensity obtained by the signal intensity detection unit are configured to detect the detection target gas,
The correlation function is
i) Considering the interaction between the air and the gas to be detected based on the viscosity and molecular weight of the air with the water vapor and the dry air as one component and the viscosity and molecular weight of the gas to be detected Interaction function, and ii) the thermal conductivity of the measurement target gas obtained from the thermal conductivity of the air and the thermal conductivity of the detection target gas, with the concentration of the detection target gas in the measurement target gas as a variable A gas detection device obtained from a function. The thermal conductivity function of the measurement target gas is obtained from the following [Equation 1] using the interaction function, the thermal conductivity of the air, and the thermal conductivity of the detection target gas. The gas detection device according to claim 1.

λ _m : gas thermal conductivity of mixed gas λ _i : gas thermal conductivity of component i x _i , x _j : mole fraction of component i and component j A _ij : interaction function considering interaction (A _ii = 1) The interaction function is obtained from the following [Equation 2] using the viscosity and molecular weight of the air including the water vapor and the dry air and the viscosity and molecular weight of the detection target gas. Item 3. The gas detection device according to Item 1 or 2.

M _i , M _j : molecular weight of component i and component j λ _tri , λ _trj : gas thermal conductivity of component i and component j γ: interaction parameter

η _i , η _j : viscosity of component i and component j The viscosity of the air includes the molecular weight, dipole moment, critical pressure, critical temperature and concentration in the air of the water vapor, and the molecular weight, dipole moment, critical pressure, critical temperature and concentration in the air of the dry air. The gas detection device according to claim 1, wherein the gas detection device is obtained by using a gas detector. The viscosity of the air includes the molecular weight, dipole moment, critical pressure, critical temperature and concentration in the air of the water vapor, and the molecular weight, dipole moment, critical pressure, critical temperature and concentration in the air of the dry air. The gas detection device according to claim 1, wherein the gas detection device is obtained from the following [Equation 3].

η _m : viscosity of mixed gas M _i , M _j , M _k : molecular weight of component i, component j and component k _xi , x _k : molar fraction of component i and component k η _i : viscosity of component i T _rij : Reduced temperature

T _ci and T _cj : critical temperatures of component i and component j

μ: Dipole moment P _c : Critical pressure T _c : Critical temperature The correlation function includes a plurality of signal intensities obtained from measurement target gases in a plurality of states in which the concentration of the water vapor in the air and the concentration of the detection target gas are different, and a thermal conductivity function of the measurement target gas. The gas detection device according to claim 1, wherein the gas detection device is obtained by fitting. A gas detection method for detecting the detection target gas in a measurement target gas in which the detection target gas is contained in air containing water vapor and dry air,
A signal intensity detection step of detecting a signal intensity related to the thermal conductivity of the measurement target gas;
A detection target gas detection step of detecting the detection target gas based on the signal intensity,
The detection target gas detection step includes
From the correlation function indicating the correspondence between the signal intensity and the concentration of the detection target gas, and the signal intensity obtained in the signal intensity detection step, the detection target gas is detected,
The correlation function is
i) Considering the interaction between the air and the gas to be detected based on the viscosity and molecular weight of the air with the water vapor and the dry air as one component and the viscosity and molecular weight of the gas to be detected Interaction function, and ii) the thermal conductivity of the measurement target gas obtained from the thermal conductivity of the air and the thermal conductivity of the detection target gas, with the concentration of the detection target gas in the measurement target gas as a variable A gas detection method obtained from a function.

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