JP7129580B1 - Hydrogen gas concentration meter - Google Patents

Abstract

A hydrogen gas concentration meter capable of accurately detecting the hydrogen gas concentration in a measurement gas even when the measurement gas contains a combustible gas other than hydrogen is provided. A combustion unit equipped with a normal temperature catalyst for catalytically burning hydrogen at normal temperature and catalytically burning a measurement gas at normal temperature; a temperature sensor for detecting heat generated by combustion in the combustion unit; and a derivation unit for deriving the hydrogen concentration of the measurement gas according to the temperature rise due to heat generation detected by the temperature sensor. [Selection drawing] Fig. 1

Description

The present invention relates to a hydrogen gas concentration meter for measuring hydrogen gas concentration in measurement gas.

Techniques described in Patent Documents 1 to 4 below are disclosed as attempts to detect hydrogen gas contained in the measurement gas. Patent Literature 1 below discloses a gas detection device that uses two catalytic combustion sensors with different temperatures to detect carbon monoxide with the sensor on the low temperature side and detect hydrocarbons such as hydrogen and methane with the sensor on the high temperature side. is disclosed. Patent Document 2 listed below discloses a catalyst that selectively oxidizes carbon monoxide in a mixed gas of carbon monoxide and hydrogen, and a catalyst that selectively oxidizes hydrogen. Patent Literature 3 and Patent Literature 4 below disclose a gas sensor in which two different sensors are connected in series and gas flows or does not flow to the latter sensor depending on the output information of the former sensor.

JP-A-1990-145956 Japanese Patent Application Laid-Open No. 2001-137708 JP 2012-251951 A JP 2016-85131 A

If the measurement gas contains a combustible gas other than hydrogen gas, such as a hydrocarbon such as methane, the combustible gas will burn together with the hydrogen when the measurement gas contacts the catalyst that constitutes the sensor. Therefore, pure hydrogen alone cannot be detected.

Embodiments of the present disclosure are capable of detecting only hydrogen in the measurement gas and accurately measuring the hydrogen concentration in the measurement gas even when the measurement gas contains combustible gases other than hydrogen gas. The object is to provide a hydrogen gas concentration meter.

(1) First aspect A hydrogen gas concentration meter according to the first aspect comprises a combustion unit equipped with a normal temperature catalyst for catalytically burning hydrogen gas at normal temperature and catalytically burning a measurement gas at normal temperature; and combustion in the combustion unit. a temperature sensor that detects the heat generated by the gas, a measuring unit that measures the measurement gas to a predetermined volume and supplies it to the combustion unit, and a derivation that derives the hydrogen gas concentration of the measurement gas from the temperature rise due to the heat generation detected by the temperature sensor and

That is, the hydrogen gas concentration meter according to the first aspect includes a combustion section, a temperature sensor, a measuring section, and a lead-out section. A normal temperature catalyst is attached to the combustion portion. A room temperature catalyst is a catalyst that causes combustion of hydrogen gas when it contacts with hydrogen gas at room temperature. Such normal temperature catalysts include, for example, catalysts containing 0.2% by mass or more of platinum. Further, normal temperature as used herein refers to a temperature at which no particular heating or cooling is performed, and specifically refers to a temperature in the range of approximately 15 to 30°C. "Catalytic combustion at room temperature" means that the combustion portion is not heated by a heater or the like when the measurement gas is brought into contact with the catalyst. The temperature sensor detects temperature rise due to heat generated by combustion in the combustion section. Thermocouples, for example, can be used as temperature sensors.

The measuring unit measures the measurement gas to a predetermined volume. This measurement can be performed, for example, by temporarily holding the measuring gas in a measuring tube having a predetermined volume. A metered predetermined volume of measurement gas is supplied to the combustion section by being forced out by a carrier gas such as air. As a result, the heat generated by the catalytic combustion by the combustor is caused by the hydrogen gas contained in the predetermined volume of the measurement gas. A temperature sensor detects the temperature rise due to this heat generation.

The derivation unit can be configured, for example, as a computer with a central processing unit (CPU) and storage devices such as Read-Only Memory (ROM) and Random Access Memory (RAM). Then, for a measurement gas having a known hydrogen gas concentration in advance, the temperature rise (ΔT) caused by catalytic combustion of the predetermined volume is measured, and calibration curve data is derived from the correlation between the hydrogen gas concentration and ΔT, This is stored in the derivation unit, for example in a storage device.

Then, for a measurement gas with an unknown hydrogen gas concentration, the derivation unit refers to calibration curve data for ΔT detected by the temperature sensor in catalytic combustion in the combustion unit, and derives the hydrogen gas concentration of the measurement gas. At this time, since the combustor is at room temperature, even if the measurement gas contains combustible gas other than hydrogen gas, such as methane, combustion does not occur at room temperature. Therefore, ΔT detected by the temperature sensor is caused only by the hydrogen gas, and this makes it possible to specify the hydrogen gas concentration in the measurement gas.

(2) Second Aspect A hydrogen gas concentration meter according to a second aspect, in addition to the configuration of the first aspect, has a pre-mixing of the measured measurement gas and air between the measuring portion and the combustion portion. A mixing section is provided. In the premixing section, the measurement gas weighed by the measuring section is sufficiently mixed with air before being supplied to the combustion section, so that the hydrogen gas contained in the measurement gas can be sufficiently combusted. .

(3) Third aspect A hydrogen gas concentration meter according to the third aspect, in addition to the configuration of the first aspect or the second aspect, is provided downstream of the combustion unit after being subjected to catalytic combustion at room temperature in the combustion unit. of the exhaust gas is supplied, and catalytic combustion with heating is performed. If the measurement gas contains, for example, methane as a combustible gas other than hydrogen gas, methane remains in the exhaust gas after the hydrogen gas is burned in the combustion section. By subjecting this to catalytic combustion by heating in the second combustion section, carbon dioxide can be discharged instead of methane, so that the environmental load caused by the exhaust gas can be reduced.

Since the embodiments of the present disclosure are configured as described above, even when the measurement gas contains combustible gas other than hydrogen gas, only hydrogen in the measurement gas is detected, and hydrogen in the measurement gas is detected. It is possible to provide a hydrogen gas concentration meter capable of accurately measuring gas concentration.

1 is a schematic diagram showing the configuration of a hydrogen gas concentration meter according to a first embodiment of the present disclosure; FIG. FIG. 2 is a cross-sectional view schematically showing the configuration of a combustion section in the hydrogen gas concentration meter shown in FIG. 1; FIG. 3 is a cross-sectional view showing an enlarged part of the combustion section shown in FIG. 2; FIG. 4 is a plan view showing a stopper member of the combustion section shown in FIG. 3; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; FIG. 2 is a schematic diagram illustrating a process of measuring concentration in the hydrogen gas concentration meter of FIG. 1; 2 is a block diagram showing the configuration of an information processing section provided in the hydrogen gas concentration meter of FIG. 1; FIG. FIG. 2 is a graph showing the relationship between the hydrogen concentration and the temperature rise input in advance to a lead-out portion provided in the hydrogen gas concentration meter of FIG. 1. FIG. 2 is a graph showing the relationship between temperature detected by a temperature sensor provided in the hydrogen gas concentration meter of FIG. 1 and time. FIG. 5 is a cross-sectional view schematically showing the configuration of a second combustion section in a hydrogen gas concentration meter according to a second embodiment of the present disclosure; 1 shows a schematic configuration of a combustion section in an embodiment; 4 is a graph showing the relationship between temperature rise and hydrogen gas concentration in the combustion section.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The size of each part and the ratio between each part in each drawing referred to below are represented schematically, and do not necessarily reflect the actual size of each part and the ratio between each part. It should be noted that, even if there is no particular description, the reference numerals commonly assigned in each drawing indicate the same object. Of the arrows attached to the sides of the flow paths in each figure, the hollow arrows indicate the flow of gas or gas-containing carrier gas, and the solid arrows indicate the flow of only carrier gas that does not contain gas.

<First embodiment>
A hydrogen gas concentration meter and a hydrogen gas concentration measuring method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 13. FIG.

(Configuration of hydrogen gas concentration meter 10)
FIG. 1 shows the configuration of a hydrogen gas concentration meter 10 of this embodiment. The hydrogen gas concentration meter 10 includes a combustion section 20 that catalytically burns the hydrogen gas in the measurement gas at room temperature, a measurement section 50 that measures the measurement gas and pushes it out to the premixing section, and the measured measurement gas before catalytic combustion. Equipped with a premixing unit 60 for premixing with air, an information processing unit 70 (see FIGS. 2 and 11) including a derivation unit 80 for deriving the concentration of hydrogen gas in the measurement gas, and a control unit 90 for controlling each unit. ing.

[Combustion section 20]
FIG. 2 is a cross-sectional view schematically showing the configuration of the combustion section 20 shown in FIG. 1. As shown in FIG. As shown in this figure, the combustion section 20 includes a tube member 211, a temperature sensor 212, a normal temperature catalyst 214, a stopper member 215, and a protective container 29 that accommodates them. The tube member 211 is a tube member having heat resistance to the temperature of the combustion of the measurement gas and low heat conductivity that suppresses heat radiation of the measurement gas to the outside of the tube member 211 during combustion. The tube member 211 of this embodiment is a cylindrical ceramic tube with an inner diameter of 4 mm. In addition, the inner diameter of the pipe material 211 is preferably 2 mm or more and 10 mm or less. Also, the tube member 211 may be a stainless tube. Temperature sensor 212 is connected to derivation section 80 which is part of information processing section 70 .

The pipe member 211 is arranged vertically, and the upper end of the pipe member 211 is connected to a mixed gas supply passage 68 through which the mixed gas is supplied from the premixer 60 described later. 211 A of exhaust holes are formed in the vicinity of the lower end of the pipe material 211. As shown in FIG. Exhaust gas discharged from the exhaust hole 211A is released to the outside through an exhaust passage 69 provided near the lower end of the protective container 29 .

The temperature sensor 212 is configured as a thermocouple and includes a thermocouple wire 212A, a sheath 212B, a sleeve 212C, an adapter 212D and a cable 212E, and measures temperature using the Seebeck effect. The thermocouple wire 212A is provided with a temperature measuring junction P at one end (upper end). The sheath 212B is a hard and thin tubular material that maintains a highly linear shape, and covers the thermocouple wire 212A. The sheath 212B of this embodiment is a metal tube with an outer diameter of 0.5 mm. The sheath 212B is filled with an insulator. The temperature sensor 212 of this embodiment is non-grounded. Note that the temperature sensor 212 may be changed to a grounded type or an exposed type.

The sleeve 212C is a rigid and thin tubular material that maintains a highly linear shape, and covers the other end side of the thermocouple wire 212A. One end of the sleeve 212C and the other end of the sheath 212B are joined by silver brazing or the like. The sleeve 212C of this embodiment has an outer diameter of 6 mm and is made of metal.

The adapter 212D includes a cylindrical tubular member attachment portion 212Z and a nut-shaped projecting portion 212Y. The tube attachment portion 212Z and the projecting portion 212Y are integrally formed and arranged coaxially. The protruding portion 212Y is a portion that protrudes radially outward from the outer surface of the pipe material attachment portion 212Z. A sleeve 212C is inserted through the tube attachment portion 212Z and the projecting portion 212Y. The pipe material attachment portion 212Z is inserted into the pipe material 211 from the lower end of the pipe material 211 . The projecting portion 212Y and the sleeve 212C are joined by welding or the like. Also, the protruding portion 212Y and the lower end of the pipe member 211 are joined by adhesion or the like. Note that the projecting portion 212Y does not have to be nut-shaped. Also, it is not essential to join the adapter 212D and the lower end of the pipe member 211 by joining the protruding portion 212Y and the lower end of the pipe member 211 with an adhesive or the like. For example, the adapter 212D and the lower end of the tubular member 211 may be joined by screwing the tubular member attachment portion 212Z and the lower end of the tubular member 211 together.

Here, the lower end of the tube member 211 is closed by an adapter 212D. On the other hand, the exhaust hole 211A formed in the pipe member 211 is arranged above the upper end of the pipe member mounting portion 212Z. As a result, the measurement gas that has flowed downward inside the tube member 211 flows out of the tube member 211 through the exhaust hole 211A, and is released to the outside through the exhaust path 69. FIG.

The cable 212E is a flexible compensating wire, and one end of this cable 212E is connected to the other end (lower end) of the thermocouple wire 212A. The other end of this cable 212E is connected to the lead-out portion 80. As shown in FIG. A portion of cable 212E is inserted into sleeve 212C.

The normal temperature catalyst 214 is capable of burning hydrogen at normal temperature (room temperature), and for example, a metal oxide supported platinum catalyst such as alumina supported platinum catalyst (Pt—Al ₂ O ₃ ) can be used. . Here, when 1000 ppm of hydrogen is burned using a catalyst in which 0.2% by mass of platinum is supported on an alumina carrier (0.2% Pt—Al ₂ O ₃ catalyst), the combustion start temperature is room temperature ( (Hiroki Sadamori, "Special Issue on Special Combustion Technology, Current State of Catalytic Combustion Technology, Focusing on Catalytic Combustion Barter", Fuel Association Journal, Vol. 58, No. 626, June 1979, 422-423).

The mass and filling height of the normal temperature catalyst 214 filled in the combustion chamber 211B of the combustion unit 20 may be appropriately set so that the temperature measuring junction P is exposed from the normal temperature catalyst 214. 0.075 g, about 3 mm, etc. in some cases. A catalyst layer 212S is formed on the surface of one end side (upper end side in the drawing) of the temperature sensor 212 so as to cover the temperature measuring junction P (see FIG. 3). It is not essential that the temperature measuring junction P is exposed from the normal temperature catalyst 214, and the combustion chamber 211B of the combustion section 20 may be filled with the normal temperature catalyst 214 so as to cover the temperature measuring junction P.

The stopper member 215 is arranged below the combustion chamber 211B. The stopper member 215 is a metal plate such as stainless steel fitted to the inner peripheral surface of the pipe member 211 . The stopper member 215 of this embodiment is a disc. Moreover, the thickness of the stopper member 215 of this embodiment is about 1 mm. Note that the stopper member 215 may be made of glass wool.

4 is a plan view showing the stopper member 215 of the combustion section 20 shown in FIG. 3. FIG. As shown in FIGS. 3 and 4, the stopper member 215 is formed with a plurality of vent holes 215A. The diameter of the vent hole 215A is smaller than the particle size (average value) of the normal temperature catalyst 214. As shown in FIG. As a result, the measurement gas passes through the ventilation hole 215A, but the room-temperature catalyst 214 is deposited on the stopper member 215 without passing through the ventilation hole 215A. The diameter of the vent hole 215A in this embodiment is 0.3 mm.

The vent holes 215A are densely formed over the entire area of the stopper member 215 except for the central portion. On the other hand, a hole 215B having a diameter larger than that of the air hole 215A is formed in the central portion of the stopper member 215. As shown in FIG. A sheath 212B is inserted through the hole 215B. Here, the central portion of the stopper member 215 and the sheath 212B are adhered with an adhesive such as a ceramic adhesive. This adhesive fills the gap between the hole 215B and the sheath 212B.

Here, the surface of the temperature measuring junction P at the tip of the temperature sensor 212 is covered with the catalyst layer 212S as described above. This catalyst layer 212S is a coating made of a catalyst such as an alumina-supported platinum catalyst that burns hydrogen at room temperature. As a method of forming the catalyst layer 212S, a method of applying a liquid catalyst obtained by mixing a powdery catalyst and distilled water or the like to the sheath 212B and drying it can be exemplified. It is preferable that the position of the temperature-measuring junction P is the central portion in the radial direction of the combustion chamber 211B. Further, the distance from the lower end of combustion chamber 211B (upper surface of stopper member 215) to temperature measuring junction P is approximately 4 mm, for example.

As shown in FIG. 2, the protective container 29 is a heat-insulating casing whose vertical dimension is larger than its horizontal dimension, and accommodates the entire tube member 211 except for the upper end side.

The top plate 29A of the protective container 29 is formed with an opening through which the tube member 211 is inserted. On the other hand, the bottom plate 29B of the protective container 29 is formed with an opening through which the sleeve 212C is inserted. An exhaust path 69 is provided in the vicinity of the lower end of the side plate 29C of the protective container 29 . The bottom plate 29B of the protective container 29 supports the overhanging portion 212Y of the temperature sensor 212. As shown in FIG.

An exhaust path 69 is formed near the lower end of the side plate 29C of the protective container 29 . As a result, the exhaust gas generated in the combustion chamber 211B by the combustion of the measurement gas is discharged from the inside of the pipe member 211 to the protective container 29 through the exhaust hole 211A, and is discharged to the outside of the protective container 29 through the exhaust path 69.

[Weighing unit 50]
As shown in FIG. 1, the metering unit 50 includes a flow path switching valve 51 configured by a hexagonal valve, a gas supply path 53 for supplying the measurement gas to the flow path switching valve 51, and a gas flow from the flow path switching valve 51. and a metering tube 52 with a predetermined volume for metering the measurement gas. Furthermore, the measuring unit 50 includes a carrier gas supply path 57 that supplies air, which is a carrier gas, to the flow path switching valve 51 .

-Flow switching valve 51-
The channel switching valve 51 has six ports 51a-51f. These ports 51a to 51f are circumferentially arranged in the order of port 51e, port 51f, port 51b, port 51c and port 51d clockwise in the drawing from port 51a connected to gas supply path 53. As shown in FIG. Connections between these ports 51a to 51f are controlled by a control section 90 (see FIG. 11).

Specifically, the channel switching valve 51 connects the ports 51a and 51b, connects the ports 51c and 51d, and connects the ports 51e and 51f in a first connection state (FIG. 5). and FIG. 6), and a second connection state in which the ports 51a and 51d are connected, the ports 51c and 51e are connected, and the ports 51b and 51f are connected (see FIGS. 7 to 10). can be switched to any connection mode with.

The port 51 a is connected to the gas supply path 53 , the port 51 b is connected to one end of the metering tube 52 , and the port 51 c is connected to the other end of the metering tube 52 . The port 51 d is connected with the gas discharge path 56 .

The port 51 e is connected to a carrier gas supply path 57 , and the port 51 f is connected to a metered gas supply path 63 for supplying a predetermined volume of gas metered by the metering tube 52 to the premixer 60 .

-Gas supply path 53-
The gas supply path 53 connects the port 51a and a gas supply source (not shown), and includes a gas supply valve 53a that opens and closes the path. In this configuration, the gas supply valve 53 a is controlled by the controller 90 to open and close the gas supply path 53 .

-Gas discharge path 56-
The gas discharge path 56 is connected to the port 51d. A valve for opening and closing the gas discharge path 56 may be provided.

-Measuring tube 41-
The metering tube 52 has a cylindrical shape with a predetermined volume extending in one direction. One longitudinal end of the metering tube 52 is connected to the port 51b via a connecting passage 54. As shown in FIG. The other longitudinal end of the metering tube 52 is connected to the port 51c via a connecting passage 55. As shown in FIG. In this embodiment, the volume of the measuring tube 52 is 1.5 [ml] as an example.

-Carrier gas supply path 57-
One end of the carrier gas supply path 57 is connected to the port 51e, and the other end is provided with a pump 57a for supplying air as a carrier gas. Further, the carrier gas supply line 57 has a mass flow controller 57b provided between the port 51e and the pump 57a. Any known device that can control the flow rate of the fluid may be used instead of the mass flow controller 57b.

[Premixer 60]
As shown in FIG. 1, the premixing section 60 supplies a premixing flow path valve 61 configured by a six-way valve and a predetermined volume of measurement gas measured by the measuring section 50 to the premixing flow path valve 61. A metering gas supply passage 63, a gas discharge passage 66 for discharging the measurement gas from the premixing passage valve 61, and a premixing chamber 62 having a predetermined volume larger than the volume of the metering tube 52 for premixing a predetermined volume of gas with air. and Furthermore, the premixing section 60 includes a carrier gas supply path 67 that supplies air, which is a carrier gas, to the premixing flow path valve 61 .

- Premixing flow path valve 61 -
The premix channel valve 61 has six ports 61a-61f. These ports 61a to 61f are circumferentially arranged in the order of port 61e, port 61f, port 61b, port 61c and port 61d clockwise in the drawing from port 61a connected to metering gas supply path 63. As shown in FIG. Connections between these ports 61a to 61f are controlled by a control section 90 (see FIG. 11).

Specifically, the premixing flow path valve 61 connects the ports 61a and 61b, connects the ports 61c and 61d, and connects the ports 61e and 61f in a first connection state (Fig. 5 to 9) and a second connected state (see FIG. 10) in which the ports 61a and 61d are connected, the ports 61c and 61e are connected, and the ports 61b and 61f are connected. Either connection mode can be switched.

The port 61 a is connected to the metering gas supply passage 63 , the port 61 b is connected to one end of the premixing chamber 62 , and the port 61c is connected to the other end of the premixing chamber 62 . The port 61 d is connected with the gas discharge path 66 .

The port 61e is connected to a carrier gas supply path 67, and the port 61f is connected to a mixed gas supply path 68 that supplies a predetermined volume of measurement gas mixed with air in the premixing chamber 62 to the combustion section 20. there is

- metering gas supply path 63 -
The metered gas supply passage 63 connects the port 61a and the port 51f of the passage switching valve 51 of the metering section 50, and includes a metered gas supply valve 63a for opening and closing the passage. In this configuration, the metering gas supply valve 63 a is controlled by the control section 90 to open and close the flow path of the metering gas supply path 63 .

-Gas discharge path 66-
The gas discharge path 66 is connected to the port 61d. A gas discharge valve 66a is provided in the middle of the gas discharge path 66 for opening and closing the flow path.

- Premixing chamber 62 -
The premixing chamber 62 has a cylindrical shape extending in one direction and having a predetermined volume. One end of the premixing chamber 62 is connected via a connecting passage 64 to the port 61b. The other end of the premixing chamber 62 is connected via a connecting passage 65 to the port 61c. In this embodiment, the volume of the premixing chamber 62 is, for example, 5.0 [ml].

-Carrier gas supply path 67-
One end of the carrier gas supply line 67 is connected to the port 61e, and the other end is provided with a pump 67a for supplying air as a carrier gas. Further, the carrier gas supply line 67 has a mass flow controller 67b provided between the port 61e and the pump 67a. Any known device that can control the flow rate of the fluid may be used instead of the mass flow controller 67b.

[Information processing section 70]
As shown in FIG. 11, the information processing section 70 includes a derivation section 80 that derives the calorie of the gas, and a control section 90 that controls each section.

-Control unit 90-
The control unit 90 operates the hydrogen gas concentration meter 10 by controlling each unit. Specifically, it controls switching between the first connection state and the second connection state between the ports 51a to 51f. It also controls switching between the first connection mode and the second connection mode between the ports 61a to 61f. It also controls the opening and closing of each of the gas supply valve 53a, metering gas supply valve 63a and gas discharge valve 66a. It also controls the operation of each of the pumps 57a, 67a.

- Derivation unit 80 -
The derivation unit 80 derives the calorie of the gas based on the temperature detected by the temperature sensor 212 .

Specifically, the relationship between the concentration of hydrogen gas in the measurement gas and the temperature rise ΔT caused by the catalytic combustion of the hydrogen gas is recorded in advance in the lead-out unit 80 as a relationship represented by the graph shown in FIG. 12, for example. ing. Here, the horizontal axis of the graph shown in FIG. 12 is the temperature rise ΔT, and the vertical axis is the hydrogen gas concentration in the measurement gas. Thus, the hydrogen gas concentration in the measurement gas increases in proportion to the temperature rise ΔT. This relationship is input to the derivation unit 80 .

Also, the temperature rise ΔT is calculated by the derivation unit 80 based on the temperature detected by the temperature sensor 212 . The horizontal axis of the graph shown in FIG. 13 is the elapsed time, and the vertical axis is the temperature detected by the temperature sensor 212 . As shown in this graph, the derivation unit 80 monitors the temperature detected by the temperature sensor 212 and calculates the temperature rise ΔT that has increased due to the catalytic combustion of the hydrogen gas in the measurement gas.

In this configuration, the derivation unit 80 derives the hydrogen gas concentration in the measurement gas from the temperature rise ΔT (peak value) calculated by monitoring the temperature detected by the temperature sensor 212 .

(Hydrogen gas concentration measurement method)
A hydrogen gas concentration measuring method using the hydrogen gas concentration meter 10 of FIG. 1 will be described below.

[Flushing process]
In the flow step, the measurement gas is flowed through a measuring tube 52 having a predetermined volume provided in the measuring section 50 . That is, as shown in FIG. 5, the ports 51a to 51f are switched to the first connected state by the control unit 90, whereby the gas supply path 53 and the connection path 54 are connected, and the connection path 55 and the gas discharge path 56 are connected. are in communication, and the carrier gas supply line 57 and the metering gas supply line 63 are in communication. Further, the gas supply valve 53a of the gas supply path 53 is opened by the controller 90, so that the flow path of the flow path switching valve 51 is switched to the flowing state. That is, the measurement gas passes through the gas supply channel 53 and the connecting channel 54 to fill the metering tube 52 , passes through the connecting channel 55 and is discharged from the gas discharge channel 56 .

On the other hand, when the pump 57 a is driven, the carrier gas flows from the carrier gas supply passage 57 to the metering gas supply passage 63 and into the premixing section 60 . At this time, in the premixing section 60, the control section 90 switches the ports 61a to 61f to the first connection state, thereby connecting the measurement gas supply path 63 and the connection path 64, and connecting the connection path 65 and the gas discharge path 66. are in communication with each other, and the carrier gas supply path 67 and the mixed gas supply path 68 are in communication. In this state, the air as carrier gas flowing from the metering gas supply path 63 passes through the connecting path 64 and fills the premixing chamber 62 , and then passes through the connecting path 65 and is discharged from the gas discharge path 66 . Further, the carrier gas is supplied from the carrier gas supply path 67 to the combustor 20 through the mixed gas supply path 68 via the ports 61e and 61f by driving the pump 67a.

[Holding process]
In the holding step, a predetermined volume of gas G1 filling the metering tube 52 is held. That is, as shown in FIG. 6, the gas supply valve 53a of the gas supply path 53 is closed by the control unit 90 while the ports 51a to 51f of the flow path switching valve 51 remain in the first connection state, whereby the flow path The flow path of the switching valve 51 is switched to the holding state. In this holding state, the flow of gas to the metering tube 52 is cut off, and the predetermined volume of measurement gas G1 filling the metering tube 52 is retained in the metering tube 52 as it is. In addition, the flow of the carrier gas in the premixing section 60 maintains the same state as in the flow process.

[Extrusion process]
In the extrusion process, a predetermined volume of the measurement gas G1 held in the measuring tube 52 in the holding process is pushed out from the measuring section 50 to the premixing section 60 . That is, as shown in FIG. 7, the ports 51a to 51f are switched to the second connected state by the control unit 90 while the gas supply valve 53a of the gas supply path 53 is kept closed, whereby the gas supply path 53 and the gas are discharged. The channel 56 communicates, the carrier gas supply channel 57 communicates with the connecting channel 55, and the connecting channel 54 communicates with the metering gas supply channel 63, whereby the channel of the channel switching valve 51 is pushed out. can be switched to In this extruded state, the predetermined volume of gas G1 held in the metering tube 52 is pushed out by the carrier gas flowing into the metering tube 52 from the carrier gas supply passage 57 through the connecting passage 55, and is pushed out from the connecting passage 54 to the port. 51 b and 51 f, it flows into the metering gas supply passage 63 and goes to the premixing section 60 . In this embodiment, the flow velocity of the carrier gas for pushing out the predetermined volume of the measurement gas G1 held in the measuring tube 52 is, for example, 120 [ml/min]. The flow of the carrier gas in the premixing section 60 maintains the same state as in the holding step.

[Premixing process]
In the premixing step, a predetermined volume of the measurement gas G1 extruded in the extrusion step and air are premixed before catalytic combustion in the combustion section 20 . That is, a predetermined volume of gas G1 (see FIG. 7) pushed out to the metering gas supply path 63 passes through the ports 61a and 61b of the premixing flow path valve 61, passes through the connecting path 64, and reaches the premixing chamber 62. At the timing, as shown in FIG. 8, the controller 90 closes the metering gas supply valve 63a and the gas discharge valve 66a. In this state, the predetermined volume of measurement gas G1 has a flow velocity of approximately zero, diffuses while staying in the premixing chamber 62, and as shown in FIG. It becomes gas G2. In the premixing section 60, the carrier gas flows from the carrier gas supply path 67 to the combustion section 20 via the mixed gas supply path 68 in the same manner as in the extrusion process.

[Combustion process]
In the combustion process, the mixed gas G2, which is the measurement gas mixed with air in the premixing process, is subjected to catalytic combustion in the combustion section 20. FIG. That is, as shown in FIG. 10, the control unit 90 switches the ports 61a to 61f of the premixing flow path valve 61 to the second connected state while the metering gas supply valve 63a and the gas discharge valve 66a remain closed. , the metering gas supply path 63 and the gas discharge path 66 communicate, the carrier gas supply path 67 communicates with the connection path 65, and the connection path 64 communicates with the mixed gas supply path 68. In this state, the mixed gas G2 held in the premixing chamber 62 is pushed out by the carrier gas that has flowed into the premixing chamber 62 from the carrier gas supply passage 67 through the connecting passage 65, and is premixed from the connecting passage 64. Through the ports 61 b and 61 f of the flow path valve 61 , the mixed gas flows into the mixed gas supply path 68 and is supplied to the combustion section 20 . In this embodiment, the flow rate of the carrier gas that pushes out the mixed gas G2 held in the premixing chamber 62 is, for example, 120 [ml/min].

The mixed gas G2 supplied from the mixed gas supply passage 68 to the combustion section 20 is subjected to catalytic combustion by the normal temperature catalyst 214 at room temperature. Here, since the mixed gas G2 contains sufficient air necessary for combustion of the measurement gas, the hydrogen gas contained in the measurement gas contained in the mixed gas G2 can be burned more efficiently and more completely. It has become.

[Extraction process]
In the derivation step, the hydrogen gas concentration corresponding to the predetermined volume of the measurement gas G1 is derived from the temperature raised by the combustion step. That is, the temperature of the room-temperature catalyst 214 rises due to catalytic combustion caused by contact of the hydrogen gas contained in the mixed gas G2 with the room-temperature catalyst 214, and the temperature sensor 212 detects the temperature rise.

A derivation unit 80 shown in FIG. 11 monitors the temperature detected by the temperature sensor 212 and derives the temperature rise ΔT (see FIG. 10) caused by catalytic combustion of hydrogen gas. Further, the derivation unit 80 derives the hydrogen gas concentration from the derived temperature rise ΔT and the previously input relationship between the hydrogen gas concentration and the temperature rise ΔT.

Here, the temperature rise ΔT generated in the combustion process is directly caused by the combustion of the mixed gas G2, which is caused by the predetermined volume of the measurement gas G1. Furthermore, the catalytic combustion by the normal temperature catalyst is caused by the hydrogen gas contained in the measurement gas G1. Even if the measurement gas G1 contains combustible gas other than hydrogen gas, such as methane gas, such combustible gas does not cause catalytic combustion at room temperature. Therefore, the temperature rise generated in this combustion process is caused only by the hydrogen gas contained in the predetermined volume of the measurement gas G1.

By repeating such steps, the measuring unit 50 and the premixing unit 60 periodically supply the measurement gas sufficiently mixed with air to the combustion unit 20, and the combustion unit 20 periodically supplies The resulting mixed gas G2 is catalytically combusted at room temperature. Furthermore, the lead-out part 80 periodically leads out the hydrogen gas concentration corresponding to the predetermined volume of the measurement gas G1 by the temperature rise ΔT which is raised by catalytic combustion at room temperature. In other words, the pouring, holding, extruding, burning, and extracting steps are cyclically performed in this order.

If the gas to be measured in the measuring unit 50 contains a sufficient amount of air to burn the hydrogen gas, the measured gas to be measured can be measured without providing the premixing unit 60. Alternatively, the gas may be supplied directly from the gas supply path 63 to the combustion section 20 .

<Second embodiment>
A hydrogen gas concentration meter according to the second embodiment of the present invention differs from the first embodiment in that a second combustion section 30 shown in FIG.

FIG. 14 is a cross-sectional view schematically showing the configuration of the second combustion section 30. As shown in FIG. As shown in this figure, the second combustion section 30 includes a pipe member 311 , a temperature sensor 312 , a heater 313 , a granular catalyst 314 and a stopper member 315 . The pipe material 311 is the same as the pipe material 211 of the first embodiment. Further, the temperature sensor 312 is the same as the temperature sensor 212 of the first embodiment, and its structure includes a thermocouple wire 312A, a sheath 312B, a sleeve 312C, an adapter 312D (including an overhang portion 312Y and a tube mounting portion 312Z). ) and the cable 312E also include the thermocouple wire 212A, the sheath 212B, the sleeve 212C, the adapter 212D (including the projecting portion 212Y and the tube mounting portion 212Z) and the cable 212E, which are the structures of the temperature sensor 212 of the first embodiment. They are the same.

The pipe member 311 is arranged vertically, and the upper end of the pipe member 311 is connected to the exhaust passage 69 from the combustion section 20 . 311 A of exhaust holes are formed in the vicinity of the lower end of the pipe material 311. As shown in FIG.

Here, the lower end of the tube member 311 is closed by the bottom plate 39B of the protective container 39. As shown in FIG. On the other hand, the exhaust holes 311A formed in the pipe member 311 are arranged above the bottom plate 39B. As a result, the exhaust gas that flows downward in the pipe member 311 and is subjected to catalytic combustion in the pipe member 311 flows out of the pipe member 311 through the exhaust hole 311A.

The heater 313 is a coil-type heater through which the tube member 311 is inserted. A coil portion 313A of the heater 313 is wound around a range including at least the combustion chamber 311B of the tubular member 311 . The coil portion 313A is connected to the constant-voltage power source 32 via the lead portion 313B, and generates heat when a voltage is applied from the constant-voltage power source 32 . A temperature sensor (not shown) is provided in the pipe member 311,

The shape of the granular catalyst 314 and the mode of filling in the combustion chamber 211B are the same as the normal temperature catalyst 214 in the first embodiment. The granular catalyst 314 is, for example, supported by a metal such as palladium (Pd) or platinum (Pt), or a metal oxide. As the granular catalyst 314, the same catalyst as the normal temperature catalyst 214 may be used.

The stopper member 315 is the same as the stopper member 215 of the first embodiment.

When the coil portion 313A generates heat by applying a voltage from the constant-voltage power source 32, the granular catalyst 314 is heated to a predetermined temperature. This heating causes catalytic combustion of combustible gases other than hydrogen gas remaining in the exhaust gas. During this heating, the temperature sensor 312 constantly monitors the temperature of the granular catalyst 314 , and the temperature information is input from the derivation unit 80 to the control unit 90 , and the control unit 90 appropriately controls the output of the constant-voltage power supply 32 .

As shown in FIG. 14, the protective container 39 is a heat-insulating casing whose vertical dimension is larger than its horizontal dimension, and accommodates the entire tube member 311 except for the upper end side.

A top plate 39A of the protective container 39 is formed with an opening through which the pipe member 311 is inserted. A side plate 39C of the protective container 39 is formed with a groove through which the lead portion 313B is inserted. On the other hand, the bottom plate 39B of the protective container 39 is formed with an opening through which the sleeve 312C is inserted. The bottom plate 29B of the protective container 39 supports the overhanging portion 312Y of the temperature sensor 312. As shown in FIG.

An opening 39F is formed in the back plate 39D of the protective container 39, and the opening 39F is provided with a wire mesh 39G, which is a metallic mesh member. That is, the back plate 39D is formed with a large number of mesh-like openings. As a result, the exhaust gas from the combustion unit 20 is burned in the combustion chamber 211B, and the final exhaust gas generated is discharged from the inside of the pipe member 311 to the protective container 39 through the exhaust hole 311A, and through the many openings of the back plate 39D. 39 is discharged outside.

Here, the exhaust gas from the combustion unit 20 contains hydrocarbons such as methane that are not catalytically combusted by the normal temperature catalyst 214 . Such exhaust gas undergoes catalytic combustion by the granular catalyst 314 accompanied by heating in the second combustion unit 30, and finally carbon dioxide, which has a much lower environmental load than methane, is generated. It is discharged to the outside as the final exhaust gas.

Whether or not the hydrogen gas concentration can be correctly detected in the combustion section 20 was verified using an experimental apparatus schematically shown in FIG. 15 . First, a test gas, which will be described later, is introduced into the combustion section 20 to which the room-temperature catalyst 214 (see FIG. 2) is mounted through an introduction passage 100 corresponding to the mixed gas supply passage 68 (see FIG. 1), and is supplied for catalytic combustion. did. Exhaust gas that has undergone catalytic combustion in the combustion unit 20 is discharged from an exhaust passage 110 corresponding to the exhaust passage 69 (see FIG. 2) of the protective container 29 . A catalyst containing 6.6% by mass of platinum (6.6% Pt-15% Pd/Al ₂ O ₃ ) was used as the normal temperature catalyst 214 . The normal temperature catalyst 214 was filled in the combustion chamber 211B as shown in FIG. However, the tip surface of the temperature sensor 212 was not provided with the catalyst layer 212S as shown in FIG.

From the introduction path 100, 0.36 ml of each test gas, which is a mixture of hydrogen gas, methane gas, and butane gas with the composition shown in Table 1 below, is supplied with air as a carrier gas at a flow rate of 85 ml/min in an environment of 25° C. and normal pressure. It was sent to the combustion section 20 below and subjected to catalytic combustion in the normal temperature catalyst 214 . The temperature of the combustion section 20 was approximately 25°C. The temperature rise ΔT measured in the combustion section 20 is also shown in Table 1 below.

That is, in the test gas 1 containing 0% by volume of hydrogen gas and 100% by volume of methane gas, the temperature rise ΔT in the combustion section 20 was 0°C. Further, in the test gas 2 containing 20.1% by volume of hydrogen gas and 79.9% by volume of methane gas, the temperature rise ΔT in the combustion section 20 was 13.85°C. Further, in the test gas 3 containing 50% by volume of hydrogen gas and 50% by volume of methane gas, the temperature rise ΔT in the combustion section 20 was 37°C. Further, in the test gas 4 containing 50.6% by volume of hydrogen gas, 41.3% by volume of methane gas, and 8.1% by volume of butane gas, the temperature rise ΔT in the combustion section 20 was 37.55°C. . Furthermore, in test gas 5 containing 100% by volume of hydrogen gas and 0% by volume of methane gas, the temperature rise ΔT in the combustion section 20 was 73.75°C.

As a result, it was found that only hydrogen gas among the test gases was catalytically combusted, and methane gas and butane gas were not catalytically combusted in the normal temperature combustion unit 20 . In other words, it has been found that methane gas does not undergo catalytic combustion in the normal temperature catalyst 214 and passes through the combustion section 20 under a normal temperature environment.

FIG. 16 shows a graph plotting the relationship between the hydrogen gas concentration and the temperature rise ΔT from the results of Table 1 above.

First, from FIG. 16, it was found that the relationship between the hydrogen gas concentration (x) and the temperature rise ΔT(y) can be approximated by the linear regression line of the following formula (1).

y=0.7374x Expression (1)

The coefficient of determination (R ² ) of formula (1) above was 0.9997, and it was estimated that there was a correlation of almost 100%.

10 Hydrogen gas concentration meter 20 Combustion unit 214 Normal temperature catalyst 30 Second combustion unit 50 Weighing unit 60 Premixing unit 80 Derivation unit

Claims (3)

a combustion unit equipped with a normal temperature catalyst for catalytically burning hydrogen gas at normal temperature and catalytically burning a measurement gas at normal temperature;
a temperature sensor that detects heat generated by combustion in the combustion unit;
a measuring unit that measures a measurement gas to a predetermined volume and supplies it to the combustion unit;
a derivation unit for deriving the hydrogen gas concentration of the measurement gas by a temperature rise due to heat generation detected by the temperature sensor;
A hydrogen gas concentration meter. 2. The hydrogen gas concentration meter according to claim 1, further comprising a premixing section for mixing the measured measurement gas and air between the measuring section and the combustion section. 2. Further comprising a second combustion section downstream of said combustion section, in which exhaust gas after being subjected to catalytic combustion at room temperature in said combustion section is supplied, and catalytic combustion accompanied by heating is performed. Item 3. The hydrogen gas concentration meter according to item 2.

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