JP2023155645A - Hydrogen gas concentration meter - Google Patents

Abstract

To provide a hydrogen gas concentration meter capable of accurately detecting hydrogen gas concentration in a measurement gas even when the measurement gas contains a combustion gas other than hydrogen.SOLUTION: A hydrogen gas concentration meter includes: a combustion part to which an ordinary temperature catalyst for catalytically combusting hydrogen at ordinary temperatures is attached so as to catalytically combust a measurement gas at ordinary temperatures; a temperature sensor for detecting heat generation by the combustion at the combustion part; a measurement part for measuring the measurement gas to be predetermined volume so as to supply it to the combustion part; and a derivation part for deriving hydrogen concentration of the measurement gas by a temperature rise due to the heat generation detected by the temperature sensor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hydrogen gas concentration meter that measures hydrogen gas concentration in a measurement gas.

As an attempt to detect hydrogen gas contained in a measurement gas, techniques described in Patent Documents 1 to 4 listed below have been disclosed. Patent Document 1 below describes a gas detection device that uses two catalytic combustion sensors with different temperatures, with the low-temperature sensor detecting carbon monoxide, and the high-temperature sensor detecting hydrocarbons such as hydrogen and methane. 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 Document 3 and Patent Document 4 listed below disclose a gas sensor in which two different sensors are connected in series and gas flows or does not flow to the subsequent sensor depending on the output information of the preceding sensor.

Japanese Patent Application Publication No. 1990-145956 Japanese Patent Application Publication No. 2001-137708 JP2012-251951A Japanese Patent Application Publication No. 2016-85131

If the measurement gas contains a flammable gas other than hydrogen gas, for example a hydrocarbon such as methane, when the measurement gas comes into contact with the catalyst that makes up the sensor, the combustible gas will burn along with the hydrogen. Therefore, it is not possible to purely detect hydrogen.

Embodiments of the present disclosure make it possible to detect only hydrogen in the measurement gas and accurately measure the hydrogen concentration in the measurement gas even when the measurement gas contains combustible gas other than hydrogen gas. Our goal is to provide a hydrogen gas concentration meter.

(1) First aspect The hydrogen gas concentration meter according to the first aspect includes a combustion section that is equipped with a room temperature catalyst that catalytically burns hydrogen gas at room temperature and catalytically burns the measurement gas at room temperature, and a combustion section that catalytically burns the measurement gas at room temperature. a temperature sensor that detects the heat generated by the heat generation, a measuring unit that measures the measured gas into a predetermined volume and supplies the measured gas to the combustion section, and a derivation unit that derives the hydrogen gas concentration of the measured gas based on the temperature rise caused by the generated heat detected by the temperature sensor. It is equipped with a section and a section.

That is, the hydrogen gas concentration meter according to the first aspect includes a combustion section, a temperature sensor, a measuring section, and a deriving section. A room temperature catalyst is installed in the combustion section. A room-temperature catalyst is a catalyst that causes combustion of hydrogen gas when it comes into contact with hydrogen gas at room temperature. Examples of such room-temperature catalysts include catalysts containing 0.2% by mass or more of platinum. Furthermore, the term "normal temperature" as used herein refers to a temperature at which no special 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 section is not heated with a heater or the like when the catalyst is brought into contact with the measurement gas. The temperature sensor detects a temperature rise due to heat generated by combustion in the combustion section. For example, a thermocouple can be used as the temperature sensor.

The measuring section measures the measurement gas to a predetermined volume. This metering can be performed, for example, by temporarily holding the measurement gas in a metering tube having a predetermined volume. The metered volume of measurement gas is supplied to the combustion section by being forced out with a carrier gas, such as air, for example. Thereby, the heat generated by the catalytic combustion in the combustion section 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 including a central processing unit (CPU) and a storage device such as a Read-Only Memory (ROM) and a Random Access Memory (RAM). Then, the temperature rise (ΔT) caused by the catalytic combustion of the predetermined volume is measured in advance for a measurement gas having a known hydrogen gas concentration, and calibration curve data is derived from the correlation between the hydrogen gas concentration and ΔT. This is stored in, for example, a storage device of the deriving unit.

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

(2) Second aspect The hydrogen gas concentration meter according to the second aspect has, in addition to the configuration of the first aspect, a preparatory device for mixing the measured gas and air between the measuring section and the combustion section. Equipped with a mixing section. In the premixing section, the measurement gas measured in the metering section is sufficiently mixed with air before being supplied to the combustion section, making it possible for the hydrogen gas contained in the measurement gas to be sufficiently combusted. .

(3) Third aspect In addition to the configuration of the first aspect or the second aspect, the hydrogen gas concentration meter according to the third aspect is provided downstream of the combustion section, after being subjected to catalytic combustion at room temperature in the combustion section. The engine further includes a second combustion section to which exhaust gas is supplied and catalytic combustion accompanied by 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, thereby reducing the environmental load caused by exhaust gas.

Since the embodiment of the present disclosure is configured as described above, even if the measurement gas contains a combustible gas other than hydrogen gas, only the hydrogen in the measurement gas is detected, and the hydrogen in the measurement gas is detected. It becomes possible to provide a hydrogen gas concentration meter that can accurately measure 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. 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 an enlarged cross-sectional view of a 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. FIG. FIG. 2 is a block diagram showing the configuration of an information processing section included in the hydrogen gas concentration meter of FIG. 1. FIG. 2 is a graph showing the relationship between rising temperature and hydrogen concentration, which are input in advance to a derivation unit included in the hydrogen gas concentration meter of FIG. 1. FIG. 2 is a graph showing the relationship between temperature detected by a temperature sensor included in the hydrogen gas concentration meter of FIG. 1 and time. FIG. 2 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. The schematic structure of the combustion part in an Example is shown. It 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 schematically expressed, and do not necessarily reflect the actual size of each part and the ratio between each part. Note that the reference numerals commonly assigned in each figure indicate the same object even if there is no particular explanation. Moreover, among the arrows attached to the sides of the flow paths in each figure, the white arrows indicate the flow of gas or the carrier gas containing gas, and the solid arrows indicate the flow of only the 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.

(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 a measurement section 50 that catalytically burns the hydrogen gas in the measurement gas. It includes a premixing section 60 that premixes with air, a derivation section 80 that derives the hydrogen gas concentration in the measurement gas, and an information processing section 70 (see FIGS. 2 and 11) that includes a control section 90 that controls each section. 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 material 211, a temperature sensor 212, a normal temperature catalyst 214, a stopper member 215, and a protective container 29 that accommodates these. The tube material 211 is a tube material that has heat resistance against the temperature during combustion of the measurement gas and low heat conductivity that suppresses heat radiation of the measurement gas to the outside of the tube material 211 during combustion. The tube material 211 of this embodiment is a cylindrical ceramic tube with an inner diameter of 4 mm. Note that the inner diameter of the tube material 211 is preferably 2 mm or more and 10 mm or less. Further, the tube material 211 may be a stainless steel tube. Temperature sensor 212 is connected to derivation section 80 which is part of information processing section 70 .

The tube material 211 is arranged vertically, and a mixed gas supply path 68 through which a mixed gas is supplied from a premixing section 60, which will be described later, is connected to the upper end of the tube material 211. An exhaust hole 211A is formed near the lower end of the tube material 211. Exhaust gas exhausted from the exhaust hole 211A is released to the outside world from an exhaust path 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 contact P at one end (upper end). The sheath 212B is a hard and thin tube 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 inside of the sheath 212B is filled with an insulator. The temperature sensor 212 of this embodiment is of a non-grounded type. Note that the temperature sensor 212 may be changed to a grounded type or an exposed type.

The sleeve 212C is a hard and thin tube that maintains a highly linear shape, and covers the other end of the thermocouple wire 212A. One end of this 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 tube attachment portion 212Z and a nut-shaped projecting portion 212Y. The tube attachment portion 212Z and the overhang portion 212Y are integrally formed and coaxially arranged. The overhanging portion 212Y is a portion that overhangs radially outward from the outer surface of the tube attachment portion 212Z. A sleeve 212C is inserted through the tube attachment portion 212Z and the overhang portion 212Y. The tube attachment portion 212Z is inserted into the tube 211 from the lower end of the tube 211. The projecting portion 212Y and the sleeve 212C are joined by welding or the like. Further, the overhanging portion 212Y and the lower end of the tube member 211 are joined by adhesive or the like. Note that the projecting portion 212Y does not have to be nut-shaped. Furthermore, it is not essential to join the adapter 212D and the lower end of the tube 211 by joining the protruding portion 212Y and the lower end of the tube 211 with adhesive or the like. For example, the adapter 212D and the lower end of the tube 211 may be joined by threading the tube attachment portion 212Z and the lower end of the tube 211 together.

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

The cable 212E is a flexible compensation conducting wire, and one end of the 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. 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 an alumina supported platinum catalyst (Pt-Al ₂ O ₃ ) can be used. . Here, when 1000 ppm of hydrogen is combusted using a catalyst (0.2% Pt-Al ₂ O ₃ catalyst) in which 0.2% by mass of platinum is supported on an alumina carrier, the combustion start temperature is room temperature ( (Hiroki Sadamori, “Special Combustion Technology Special Feature: Current Status of Catalytic Combustion Technology, Focusing on Catalytic Combustion Barter”, Fuel Association Journal, Vol. 58, No. 626, June 1979, (pp. 422-423).

The mass and filling height of the room-temperature catalyst 214 filled in the combustion chamber 211B of the combustion section 20 may be appropriately set so that the temperature measuring contact point P is exposed from the room-temperature catalyst 214. For example, when the inner diameter of the tube material 211 is 4 mm, In some cases, the weight is 0.075g, approximately 3mm, etc. A catalyst layer 212S is formed on the surface of one end side (upper end side in the figure) of the temperature sensor 212 so as to cover the temperature measuring contact point P (see FIG. 3). Note that it is not essential that the temperature measuring contact P be exposed from the room temperature catalyst 214, and the combustion chamber 211B of the combustion section 20 may be filled with the room temperature catalyst 214 so as to cover the temperature measuring contact P.

The stopper member 215 is arranged below the combustion chamber 211B. This stopper member 215 is a plate made of metal such as stainless steel and fitted onto the inner circumferential surface of the tube material 211. The stopper member 215 of this embodiment is a disk. Further, the thickness of the stopper member 215 of this embodiment is approximately 1 mm. Note that the stopper member 215 may be made of glass wool.

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

The ventilation holes 215A are densely formed in the entire area of the stopper member 215 except for the center. On the other hand, a hole 215B having a larger diameter than the ventilation hole 215A is formed in the center of the stopper member 215. A sheath 212B is inserted through this hole 215B. Here, the center portion of the stopper member 215 and the sheath 212B are bonded together 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 contact 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 film made of a catalyst that burns hydrogen at room temperature, such as an alumina-supported platinum catalyst. An example of a method for forming the catalyst layer 212S is to apply a liquid catalyst, which is a mixture of a powdered catalyst and distilled water, to the sheath 212B and dry it. The temperature measuring contact point P is preferably located in the radial center of the combustion chamber 211B. Further, the distance from the lower end of the combustion chamber 211B (the upper surface of the stopper member 215) to the temperature measuring contact point P is, for example, about 4 mm.

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

The top plate 29A of the protective container 29 has an opening through which the tube 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 passage 69 is provided near the lower end of the side plate 29C of the protective container 29. The bottom plate 29B of the protective container 29 supports the projecting portion 212Y of the temperature sensor 212.

An exhaust passage 69 is formed near the lower end of the side plate 29C of the protective container 29. As a result, exhaust gas generated in the combustion chamber 211B due to combustion of the measurement gas is discharged from the inside of the tube 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.

[Measuring section 50]
As shown in FIG. 1, the metering section 50 includes a flow path switching valve 51 constituted by a hexagonal valve, a gas supply path 53 that supplies measurement gas to the flow path switching valve 51, and a gas supply path 53 that supplies gas from the flow path switching valve 51. The measuring tube 52 includes a gas exhaust path 56 for discharging gas and a measuring tube 52 having a predetermined volume for measuring the measuring gas. Furthermore, the measuring section 50 includes a carrier gas supply path 57 that supplies air as a carrier gas to the flow path switching valve 51.

-Flow path switching valve 51-
The flow path switching valve 51 has six ports 51a to 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. Connections between these ports 51a to 51f are controlled by a control section 90 (see FIG. 11).

Specifically, the flow path switching valve 51 connects the port 51a and the port 51b, the port 51c and the port 51d, and the first connection state (FIG. and FIG. 6), and a second connected state in which ports 51a and 51d are connected, ports 51c and 51e are connected, and ports 51b and 51f are connected (see FIGS. 7 to 10). The connection mode can be switched to any one of the following.

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

Further, the port 51e is connected to a carrier gas supply path 57, and the port 51f is connected to a metering gas supply path 63 that supplies a predetermined volume of gas metered by the metering tube 52 to the premixing section 60.

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

-Gas exhaust path 56-
The gas exhaust path 56 is connected to the port 51d. Note that a valve that opens and closes this gas exhaust path 56 may be provided.

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

-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 that supplies air as a carrier gas. Further, the carrier gas supply path 57 includes a mass flow controller 57b provided between the port 51e and the pump 57a. Note that any known device may be used instead of the mass flow controller 57b as long as it can control the flow rate of the fluid.

[Premixing section 60]
As shown in FIG. 1, the premixing section 60 supplies a premixing channel valve 61 configured with a hexagonal valve and a predetermined volume of measurement gas measured by the measuring section 50 to the premixing channel valve 61. A metering gas supply path 63, a gas discharge path 66 for discharging the measurement gas from the premixing flow path valve 61, and a premixing chamber 62 with a predetermined volume larger than the volume of the metering tube 52, in which a predetermined volume of gas is premixed with air. It is equipped with Further, the premixing section 60 includes a carrier gas supply path 67 that supplies air as a carrier gas to the premixing flow path valve 61.

-Premix flow path valve 61-
Premixing channel valve 61 has six ports 61a to 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. The connections between these ports 61a to 61f are controlled by a control section 90 (see FIG. 11).

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

The port 61a is connected to the metering gas supply path 63, the port 61b 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 61d is connected to the gas exhaust path 66.

Further, 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.

-Measuring gas supply path 63-
The metering gas supply path 63 includes a metering gas supply valve 63a that connects the port 61a and the port 51f of the flow path switching valve 51 of the metering section 50 and opens and closes the flow path. In this configuration, the metering gas supply valve 63a is controlled by the control unit 90 to open and close the flow path of the metering gas supply path 63.

-Gas exhaust path 66-
The gas exhaust path 66 is connected to the port 61d. A gas exhaust valve 66a is provided in the middle of the gas exhaust path 66 to open and close 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 to the port 61b via a connecting path 64. The other end of the premixing chamber 62 is connected to the port 61c via a connecting path 65. 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 path 67 is connected to the port 61e, and the other end is provided with a pump 67a that supplies air as a carrier gas. Further, the carrier gas supply path 67 includes a mass flow controller 67b provided between the port 61e and the pump 67a. Note that any known device may be used instead of the mass flow controller 67b as long as it can control the flow rate of the fluid.

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

-Control unit 90-
The control section 90 operates the hydrogen gas concentration meter 10 by controlling each section. Specifically, switching between the first connected state and the second connected state between the ports 51a to 51f is controlled. It also controls switching between the first connection mode and the second connection mode between the ports 61a to 61f. It also controls 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 and 67a.

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

Specifically, in the derivation unit 80, the relationship between the hydrogen gas concentration in the measurement gas and the increased temperature ΔT caused by catalytic combustion of hydrogen gas is recorded in advance 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 rising temperature ΔT, and the vertical axis is the hydrogen gas concentration in the measurement gas. In this way, the hydrogen gas concentration in the measurement gas increases in proportion to the increased temperature ΔT. This relationship is input to the derivation unit 80.

Furthermore, the derivation unit 80 calculates the temperature increase ΔT 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 increased temperature ΔT that has increased due to catalytic combustion of hydrogen gas in the measurement gas.

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

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

[Flowing process]
In the flow process, the measurement gas is flowed through a metering tube 52 of a predetermined volume included in the metering 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, so that the gas supply path 53 and the connecting path 54 communicate with each other, and the connecting path 55 and the gas exhaust path 56 communicate with each other. are in communication, and the carrier gas supply path 57 and metering gas supply path 63 are in communication. Further, by opening the gas supply valve 53a of the gas supply path 53 by the control unit 90, the flow path of the flow path switching valve 51 is switched to the flowing state. That is, the measurement gas fills the metering tube 52 through the gas supply path 53 and the connecting path 54, and is further discharged from the gas exhaust path 56 through the connecting path 55.

On the other hand, by driving the pump 57a, the carrier gas flows from the carrier gas supply path 57 to the metering gas supply path 63, and flows into the premixing section 60. At this time, in the premixing section 60, the ports 61a to 61f are switched to the first connection state by the control section 90, so that the metering gas supply path 63 and the connection path 64 communicate with each other, and the connection path 65 and the gas discharge path 66 The carrier gas supply path 67 and the mixed gas supply path 68 communicate with each other. In this state, air as a carrier gas that has flowed in from the metering gas supply path 63 passes through the connection path 64 to fill the premixing chamber 62, and further passes through the connection path 65 and is discharged from the gas discharge path 66. Further, by driving the pump 67a, the carrier gas is supplied from the carrier gas supply path 67 to the combustion section 20 via the mixed gas supply path 68 via ports 61e and 61f.

[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 ports 51a to 51f of the flow path switching valve 51 remain in the first connected state, and the gas supply valve 53a of the gas supply path 53 is closed by the control unit 90, so that the flow path is closed. 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 blocked, and the predetermined volume of measurement gas G1 filling the metering tube 52 is retained within the metering tube 52 as it is. Note that the flow of the carrier gas in the premixing section 60 is maintained in the same state as in the flowing process.

[Extrusion process]
In the extrusion step, a predetermined volume of the measurement gas G1 held in the metering tube 52 in the holding step is pushed out from the metering section 50 to the premixing section 60. That is, as shown in FIG. 7, while the gas supply valve 53a of the gas supply path 53 remains closed, the ports 51a to 51f are switched to the second connected state by the control unit 90, thereby connecting the gas supply path 53 and the gas discharge. The channel 56 is in communication, the carrier gas supply channel 57 is in communication with the connecting channel 55, and the connecting channel 54 is in communication with the metering gas supply channel 63, so that the channel of the channel switching valve 51 is in the extrusion state. can be switched to In this extrusion 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 path 57 via the connecting path 55, and from the connecting path 54 to the port. 51b and 51f, it flows into the metering gas supply path 63 and heads to the premixing section 60. In this embodiment, the flow rate of the carrier gas that pushes out the predetermined volume of the measurement gas G1 held in the metering tube 52 is, for example, 120 [ml/min]. Note that the flow of the carrier gas in the premixing section 60 is maintained in the same state as in the holding step.

[Premixing process]
In the premixing step, a predetermined volume of the measurement gas G1 pushed out in the extrusion step and air are mixed in advance 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 premix flow path valve 61, passes through the connection path 64, and reaches the premix chamber 62. At the timing, as shown in FIG. 8, the control unit 90 closes the metering gas supply valve 63a and the gas discharge valve 66a. In this state, the flow rate of the predetermined volume of the measurement gas G1 becomes almost zero, and while it remains in the premixing chamber 62, it diffuses and is mixed with air as a carrier gas, as shown in FIG. It becomes gas G2. Note that the flow of the carrier gas from the carrier gas supply path 67 to the combustion section 20 via the mixed gas supply path 68 in the premixing section 60 is the same 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. That is, as shown in FIG. 10, the ports 61a to 61f of the premix flow path valve 61 are switched to the second connected state by the control unit 90 while the metering gas supply valve 63a and the gas discharge valve 66a are kept closed. The metering gas supply path 63 and the gas discharge path 66 communicate with each other, the carrier gas supply path 67 and the connection path 65 communicate with each other, and the connection path 64 and the mixed gas supply path 68 communicate with each other. In this state, the mixed gas G2 held in the premixing chamber 62 is pushed out by the carrier gas flowing into the premixing chamber 62 from the carrier gas supply path 67 via the connecting path 65, and is premixed from the connecting path 64. The mixed gas passes through ports 61b and 61f of the flow path valve 61, flows into the mixed gas supply path 68, and is then 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 to the combustion section 20 from the mixed gas supply path 68 is subjected to catalytic combustion by the room temperature catalyst 214 while remaining 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 combusted more efficiently and more completely. It becomes.

[Derivation process]
In the derivation step, the hydrogen gas concentration corresponding to the predetermined volume of the measurement gas G1 is derived based on the temperature increased by the combustion step. That is, the temperature of the room temperature catalyst 214 rises due to catalytic combustion that occurs when the hydrogen gas contained in the mixed gas G2 contacts the room temperature catalyst 214, and the temperature sensor 212 detects the temperature rise.

The derivation unit 80 shown in FIG. 11 monitors the temperature detected by the temperature sensor 212 and derives the increased temperature 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 increase ΔT and the relationship between the hydrogen gas concentration and the temperature rise ΔT that has been input in advance.

Here, the temperature rise ΔT caused in the combustion process is directly caused by the combustion of the mixed gas G2, but this mixed gas G2 is caused by the predetermined volume of the measurement gas G1. Furthermore, the catalytic combustion by the room temperature catalyst is caused by the hydrogen gas contained in the measurement gas G1. Even if the measurement gas G1 contains flammable gas other than hydrogen gas, such as methane gas, such combustible gas does not cause catalytic combustion at room temperature. Therefore, the temperature increase caused by 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 metering section 50 and the premixing section 60 periodically supply the measurement gas in a sufficiently mixed state with air to the combustion section 20; The resulting mixed gas G2 is catalytically combusted at room temperature. Furthermore, the derivation unit 80 periodically derives the hydrogen gas concentration corresponding to the predetermined volume of the measurement gas G1 based on the increased temperature ΔT that is increased due to catalytic combustion at room temperature. In other words, the pouring step, holding step, extrusion step, combustion step, and derivation step are performed periodically in this order.

Note that if the measurement gas metered in the metering section 50 contains a sufficient amount of air for hydrogen gas to burn, the metered gas can be measured without providing the premixing section 60. The gas may be supplied directly to the combustion section 20 from the gas supply path 63.

<Second embodiment>
The 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. 14 is provided downstream of the combustion section 20.

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 tube material 311, a temperature sensor 312, a heater 313, a granular catalyst 314, and a stopper member 315. The tube material 311 is the same as the tube material 211 of the first embodiment. 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, and an adapter 312D (including a projecting portion 312Y and a tube attachment portion 312Z). ) and the cable 312E, the structure of the temperature sensor 212 of the first embodiment is the thermocouple wire 212A, the sheath 212B, the sleeve 212C, the adapter 212D (including the projecting part 212Y and the tube attachment part 212Z), and the cable 212E. Each is similar.

The tube 311 is arranged vertically, and the exhaust path 69 from the combustion section 20 is connected to the upper end of the tube 311 . An exhaust hole 311A is formed near the lower end of the tube material 311.

Here, the lower end of the tube material 311 is closed by the bottom plate 39B of the protective container 39. On the other hand, the exhaust hole 311A formed in the tube material 311 is arranged closer to the upper side than the bottom plate 39B. As a result, the exhaust gas that flows downward inside the tube 311 and has been subjected to catalytic combustion within the tube 311 flows out of the tube 311 through the exhaust hole 311A.

The heater 313 is a coil type heater into which the tube material 311 is inserted. The coil portion 313A of the heater 313 is wound around at least an area of the tube member 311 that includes the combustion chamber 311B. The coil portion 313A is connected to the constant voltage power source 32 via the lead portion 313B, and generates heat when voltage is applied from the constant voltage power source 32. Note that a temperature sensor (not shown) is provided inside the pipe 311,

The shape of the granular catalyst 314 and the manner 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, one supported by a metal or metal oxide such as palladium (Pd) or platinum (Pt). Note that the same catalyst as the room temperature catalyst 214 may be used as the granular catalyst 314.

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 gas other than hydrogen gas remaining in the exhaust gas. During this heating, the temperature of the granular catalyst 314 is constantly monitored by the temperature sensor 312, and the temperature information is input from the derivation section 80 to the control section 90, and the control section 90 appropriately controls the output of the constant pressure power source 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 houses the entire tube member 311 except for the upper end side.

The top plate 39A of the protective container 39 has an opening through which the tube 311 is inserted. A groove is formed in the side plate 39C of the protective container 39, into 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 projecting portion 312Y of the temperature sensor 312.

An opening 39F is formed in the back plate 39D of the protective container 39, and a wire mesh 39G, which is a metal mesh member, is provided in the opening 39F. That is, the back plate 39D has a large number of openings partitioned into a mesh pattern. As a result, the final exhaust gas generated when the exhaust gas from the combustion section 20 is subjected to combustion in the combustion chamber 211B is discharged from the inside of the pipe 311 to the protective container 39 through the exhaust hole 311A, and through the numerous openings in the back plate 39D to the protective container. 39 is ejected outside.

Here, the exhaust gas from the combustion section 20 contains hydrocarbons such as methane that have not been catalytically burned by the room temperature catalyst 214. Such exhaust gas is subjected to catalytic combustion by the granular catalyst 314 accompanied by heating in the second combustion section 30, and carbon dioxide, which has a much lower environmental impact than methane, is finally produced. It is discharged to the outside world as final exhaust gas.

Using the experimental apparatus schematically shown in FIG. 15, it was verified whether the hydrogen gas concentration could be detected correctly in the combustion section 20. First, a test gas, which will be described later, is introduced into the combustion section 20 equipped with the room-temperature catalyst 214 (see FIG. 2) from the introduction path 100, which corresponds to the mixed gas supply path 68 (see FIG. 1), and is provided for catalytic combustion. did. The exhaust gas that has undergone catalytic combustion in the combustion section 20 is discharged from an exhaust path 110 corresponding to the exhaust path 69 (see FIG. 2) of the protective container 29. As the room temperature catalyst 214, a catalyst containing 6.6% by mass of platinum (6.6%Pt-15%Pd/Al ₂ O ₃ ) was used. This normal temperature catalyst 214 was filled into the combustion chamber 211B as shown in FIG. However, the catalyst layer 212S as shown in FIG. 2 was not provided on the front end surface of the temperature sensor 212, and the combustion chamber 211B of the combustion section 20 was filled with room temperature catalyst 214 so as to cover the temperature measuring contact point P.

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 introduced into an environment of 25° C. and normal pressure using air as a carrier gas at a flow rate of 85 ml/min. The fuel was then sent to the combustion section 20 and subjected to catalytic combustion at the room 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 listed in Table 1 below.

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

As a result of the above, it was found that in the combustion section 20 at room temperature, only hydrogen gas among the test gases was catalytically combusted, and methane gas and butane gas were not catalytically combusted. In other words, it was found that methane gas passes through the combustion section 20 without catalytic combustion in the room temperature catalyst 214 in a room temperature environment.

Further, from the results of Table 1 above, a graph plotting the relationship between hydrogen gas concentration and temperature rise ΔT is shown in FIG.

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

y=0.7374x...Formula (1)

The coefficient of determination (R ² ) of the above formula (1) is 0.9997, which indicates that there is a correlation of approximately 100%.

10 Hydrogen gas concentration meter 20 Combustion section 214 Room temperature catalyst 30 Second combustion section 50 Measuring section 60 Premixing section 80 Derivation section

Claims (3)

a combustion section equipped with a room temperature catalyst that catalytically burns hydrogen gas at room temperature and catalytically burns the measurement gas at room temperature;
a temperature sensor that detects heat generated by combustion in the combustion section;
a measuring section that measures the measurement gas to a predetermined volume and supplies it to the combustion section;
a derivation unit that derives the hydrogen gas concentration of the measurement gas based on a temperature rise due to heat generation detected by the temperature sensor;
Hydrogen gas concentration meter equipped with The hydrogen gas concentration meter according to claim 1, further comprising a premixing section that mixes the measured gas and air between the measuring section and the combustion section. 1 or 2 , further comprising a second combustion section downstream of the combustion section, to which exhaust gas after being subjected to catalytic combustion at room temperature in the combustion section is supplied, and where catalytic combustion accompanied by heating is performed. The hydrogen gas concentration meter according to item 2.