JP4124536B2 - Hydrogen sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen sensor that measures a hydrogen concentration in a gas phase, a liquid phase, or a solid phase, and particularly relates to a hydrogen sensor that can operate normally even in a harsh environment in a temperature range of about 200 ° C. to 500 ° C. is there.
[0002]
[Prior art]
Measurement of the concentration of trace amounts of hydrogen molecules or hydrogen atoms contained in water, atmospheric gas, organic solvent, and metal is important in measuring the degree of material deterioration and managing the manufacturing process.
[0003]
For example, (1) In boiling water type light water reactors, hydrogen is injected into the system for the purpose of preventing intergranular stress corrosion cracking and irradiation-induced stress corrosion cracking of austenitic stainless steel used in the reactor internal structure. However, if the hydrogen concentration is too high, active dissolution of the metal material occurs, causing various problems due to this, and it is necessary to strictly control the hydrogen concentration. Also, even in pressurized water reactors, there is a problem that the accumulation of hydrogen generated by neutron irradiation causes the zircaloy that constitutes the fuel rod to be corroded by hydrogen and the fuel rod is easily destroyed, so it is necessary to control the hydrogen concentration. is there. (2) Also, in the power generation system of thermal power plants, the temperature and pressure of hydrogen boilers are increased with the aim of further improving the efficiency of the power generation system. There is a need for a hydrogen sensor that can operate in such a harsh environment. (3) In addition, hydrogen contained in a solution alloy containing an active metal having a strong affinity for hydrogen is known to cause defects during solidification and low-temperature brittleness. Process monitoring to measure hydrogen concentration is needed. (4) In a synthesis process such as methane or ammonia, it is also necessary to monitor the process by measuring the hydrogen gas concentration in a reaction vessel without being affected by other component gases.
[0004]
As a conventional hydrogen sensor, for example, as disclosed in Japanese Patent No. 2813578, a metal alloy film made of amorphous NiZr is formed on a non-conductive substrate, and a palladium thin film is formed on the metal alloy film. However, this type of hydrogen sensor operates only in the measurement temperature range of room temperature to about 150 ° C. Also, SnO of metal oxide semiconductor sensor material₂There are also known hydrogen sensors that are poisoned with silicone vapor to eliminate the sensitivity to gases other than hydrogen and obtain hydrogen selectivity, but the measurement temperature range is about room temperature to about 200 ° C.
[0005]
In addition, solid electrolyte hydrogen sensors that have been put to practical use at high temperatures are also known. However, such solid electrolyte hydrogen sensors can be used for solid electrolyte hydrogen ions in harsh environments with high temperature changes and high pressures. The transport number of (proton) decreases and the solid electrolyte does not show a Nernst type response, making it impossible to measure the concentration based on the Nernst equation, and a large amount of other component gases other than hydrogen, such as hydrocarbon compound gas Under the atmosphere, the solid electrolyte reacts with other component gases to cause decomposition and the like, and it becomes difficult to maintain a chemical equilibrium state, and the measurement accuracy of the hydrogen concentration is significantly lowered.
[0006]
[Problems to be solved by the invention]
Thus, even if the conventional hydrogen sensor operates only in a low temperature range of room temperature to about 200 ° C., or operates in a high temperature range such as a solid electrolyte sensor, the above-described (1), ( In a harsh environment as shown in 2), or in an atmosphere where a large amount of other components other than hydrogen as shown in (3) and (4) above is present, the transport number of hydrogen ions decreases. However, the hydrogen concentration cannot be accurately measured due to the influence of other components.
[0007]
The present invention has been made in view of such problems, and an object of the present invention is to provide a hydrogen sensor that can operate normally even in a severe environment of high temperature and high pressure in a medium temperature range of about 200 ° C. to 500 ° C. .
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, the present inventors have conducted intensive research focusing on metal palladium that selectively permeates hydrogen well, and as a result, have reached the following invention. In other words, the concentration cell type hydrogen sensor according to the first aspect of the invention comprises a main body mainly composed of metallic palladium and provided with a measuring electrode for selectively permeating hydrogen in a substance to be measured, and a predetermined portion disposed in the main body. A concentration electrode comprising a reference electrode that defines a reference potential corresponding to a hydrogen concentration; and an ion conductor that includes hydrogen ions that are interposed between and in contact with the measurement electrode and the reference electrode; And a measuring device for measuring the electromotive force between the reference electrode and the hydrogen concentration in the substance to be measured corresponding to the electromotive force based on the Nernst equationThe ionic conductor comprises a hydroxide ion conductive molten salt electrolyte.It is characterized by that.
[0010]
Moreover, it is preferable to form a concentration cell using the reference electrode that is in contact with a sample material having a predetermined hydrogen concentration and selectively permeates hydrogen in the sample material. As such a reference electrode, the same metal palladium as the measurement electrode may be used. Further, a hydrogen-containing gas having a predetermined hydrogen concentration can be used as the sample material.
[0011]
  Next, the limiting current type hydrogen sensor of the second invention is, for example, a main body part mainly composed of metallic palladium and provided with a measuring electrode (anode) for selectively transmitting hydrogen in a substance to be measured at the tip, A reference electrode (cathode) that is disposed and takes in hydrogen, an ion conductor that includes hydrogen ions that are interposed between and in contact with the reference electrode (cathode) and the measurement electrode (anode), and the measurement electrode (anode) And an external power source for applying a voltage between the measurement electrode (anode) and the reference electrode (cathode), and a limit between both electrodes. A measuring device for measuring a current value and calculating a hydrogen concentration in a substance to be measured corresponding to the limit current valueThe ionic conductor comprises a hydroxide ion conductive molten salt electrolyte.It is characterized by that.
[0013]
When it is desired to control the hydrogen diffusion rate, it is preferable to form a diaphragm or a coating layer having a single or a plurality of diffusion holes around the measurement electrode (anode).
[0014]
Further, in order to remove the hydrogen transported by the polarization of the measurement electrode (anode) and the reference electrode (cathode) from the surface of the reference electrode, a hydrogen selective permeable material such as metal palladium is used as the reference electrode (cathode), It is desirable to use an active metal or hydrogen storage metal having an affinity for hydrogen.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, various embodiments of a hydrogen sensor according to the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a schematic sectional view showing an embodiment of a concentration cell type hydrogen sensor according to the present invention. The hydrogen sensor 1 of the present embodiment seals a protective tube (main body portion) 2 made of a stainless material having sufficient strength and stability even under high temperature and high pressure, and one end of the protective tube (main body portion) 2. A measuring electrode 3 of a hydrogen permselective membrane mainly composed of metallic palladium, a gas flow tube 4 coaxially disposed inside the protective tube 2, and metal palladium for sealing one end of the gas flow tube 4 A hydrogen selective permeable membrane reference electrode 5 as a main body, and a hydroxide ion conductive molten salt electrolyte 6 interposed between the measurement electrode 3 and the reference electrode 5 and in contact with both electrodes 3, 5. Configured. The thickness of the measuring electrode 3 is set to be sufficiently thin so as to respond quickly to changes in the hydrogen concentration of the substance to be measured, and is preferably 1 mm or less.
[0017]
In addition, the gas distribution tube 4 is provided with a gas introduction tube 7 for introducing a reference gas having a predetermined hydrogen concentration and bringing it into contact with the reference electrode 5, and a gas exhaust hole 8 for distributing the introduced reference gas. It has been. The other end of the gas distribution tube 4 is sealed with a sealing member 9 so that the outside air does not come into contact with the reference gas, and the other end of the protective tube 2 is also in contact with the outside air by the molten salt electrolyte 6. In order to prevent it from reacting with carbon dioxide gas to become solid carbonate, etc., it is sealed with a sealing member 10. Lead wires 11 and 12 are led out from the protective tube 2 and the gas flow tube 4, respectively, and are electrically connected to the measurement electrode 3 and the reference electrode 5. An insulating spacer 13 is interposed between the gas flow tube 4 and the protective tube 2 so as to avoid electrical contact therebetween. In this embodiment, the measurement electrode 3 and the reference electrode 5 are pressed in a gas-tight state on the protective tube 2 and the gas flow tube 4 using compression-type jigs 15 and 16, respectively. It may be joined. Further, such a hydrogen sensor 1 is fixed using a flange or the like so that the surface of the measurement electrode 3 is exposed to the substance to be measured.
[0018]
As the hydroxide ion conductive electrolyte 6, a NaOH-KOH mixed molten salt is used. It is known that this molten salt system has a eutectic temperature of about 170 ° C., and becomes a molten salt electrolyte above this temperature and exhibits high ionic conductivity. Therefore, it is possible to obtain a hydrogen sensor that operates in a low temperature range of about 200 ° C. or higher, which is difficult with a conventional solid electrolyte hydrogen sensor. Instead of using the molten salt electrolyte, the In doped CaZrO_ThreeBaCeO doped with Gd_ThreeSolid electrolytes such as antimonic acid, uranic acid, and hydronium type β-alumina may be used. Such a molten salt electrolyte 6 and a solid electrolyte are protected by the measuring electrode 3 and the protective tube 2 from reacting with the substance to be measured so as not to be altered, so that the solid electrolyte of the conventional solid electrolyte type hydrogen sensor is altered. It is possible to obtain a highly reliable hydrogen sensor that can accurately measure the hydrogen concentration even in a harsh environment.
[0019]
The lead wires 11 and 12 are connected to a voltmeter 14. As will be described later, when the surface of the measuring electrode 3 is exposed to the substance to be measured, an electromotive force generated between both electrodes is measured by the voltmeter 14, and hydrogen in the substance to be measured is measured based on the electromotive force. The concentration is calculated.
[0020]
The concentration cell formula of such a hydrogen sensor 1 is represented by a reference gas (Ar-1 vol% H₂) | Reference electrode (Pd film) | molten salt electrolyte (KOH-NaOH) | measuring electrode (Pd film) | substance to be measured. As a reference gas, a mixed gas containing 1% by volume of hydrogen gas in Ar gas was used. Further, since the hydrogen selective permeable membrane made of metallic palladium is used for the measurement electrode 3, it is possible to cause partial equilibrium only for hydrogen between the measurement electrode 3 and hydrogen in the substance to be measured. Therefore, other components other than hydrogen and other components generated by a secondary electrode reaction do not affect the partial equilibrium related to hydrogen. Since the hydrogen partial equilibrium is established in this way and the hydrogen potential at both ends of the molten electrolyte is determined, the theoretical electromotive force of this battery is E = −K ln (P₁/ P₂), K = RT / (2F). Where E: electromotive force, P₁: Hydrogen partial pressure in the measurement substance (gas), P₂: Hydrogen partial pressure in reference gas, R: gas constant, T: absolute temperature, F: Faraday constant.
[0021]
Where P₂Is constant, by measuring the absolute temperature (T) and the electromotive force (E), the hydrogen partial pressure (P₁) Can be calculated. When the substance to be measured is a gas as in this example, the hydrogen partial pressure (P₁), The hydrogen gas concentration can be calculated using a calibration curve prepared in advance.
[0022]
In addition to the above gases, liquids and solids can be applied to the substance to be measured. At this time, if hydrogen is dissolved in an atomic form, P.P.₁= KC_H ^1/2(K: constant, C_H: Hydrogen atom concentration) is substituted, and hydrogen is dissolved in molecular form, P₁= K'C_H2(K ': constant, C_H2: The concentration of hydrogen atoms dissolved in the substance to be measured can be measured by substituting the relational expression: hydrogen molecule concentration.
[0023]
In order to examine the measurement performance of the above concentration cell type hydrogen sensor 1, a test environment was set. FIG. 2 is a schematic explanatory diagram showing this test environment. The concentration cell type hydrogen sensor 1 was installed in a glass tube 21 disposed in an electric furnace 20. Further, in the glass tube 21, the gas to be measured (Ar and H₂Gas) was introduced from the inflow hole 21a and out of the discharge hole 21b. When the hydrogen gas concentration and temperature in the flow gas were changed, the electromotive force generated between the measurement electrode 3 and the reference electrode 5 was measured, and the response characteristics were examined. The measurement results are shown in FIGS.
[0024]
FIG. 3 is a graph showing changes in electromotive force over time when the hydrogen concentration of the circulating gas is changed in an environment of 400 ° C. The numbers attached to the curves in the figure indicate the hydrogen concentration (% by volume). As can be seen from this figure, the response speed of the electromotive force with respect to the change in the hydrogen concentration is fast, indicating the good response of the concentration cell type hydrogen sensor 1 of this embodiment.
[0025]
FIG. 4 shows the hydrogen partial pressure (P₁) And the electromotive force (E). As can be seen from this figure, the measurement points are distributed with high correlation in the vicinity of the straight line 30 created by the method of least squares in a wide hydrogen concentration range (0.01 to 100% by volume), and thus the Nernst equation is established. Confirmed to do. In actual hydrogen concentration measurement, a calibration curve indicating the relationship between such concentration and electromotive force is prepared in advance, whereby the hydrogen partial pressure and thus the hydrogen concentration is measured from the measurement voltage.
[0026]
FIG. 5 is a graph showing the correspondence between the hydrogen concentration and the electromotive force when the gas to be measured contains saturated water vapor in an environment at room temperature (about 30 ° C.). As shown in this figure, the measurement points of both the case where saturated water vapor (oxygen) is included and the case where saturated water vapor (oxygen) is not included are highly correlated in the vicinity of the straight line 31 created by the method of least squares within the error range. It was confirmed that a partial equilibrium for hydrogen was established without being affected by water vapor and oxygen as other components. It has been theoretically shown that the electromotive force when oxygen passes through the measuring electrode 3 and the electromotive force when only hydrogen permeates are different (for example, “Carl Wagner; Advances in Electrochemistry and Electrochemical Engineering”). , Vol. 4, (INTERSCIENCE, NY) 1966, p.1). Therefore, it was confirmed that the concentration cell type hydrogen sensor 1 of this example can measure the concentration of hydrogen alone with high accuracy even in an environment where other components other than hydrogen and hydrogen coexist. .
[0027]
Although one embodiment of the concentration cell type hydrogen sensor has been described above, various modifications can be made in the present invention depending on the use environment, temperature / pressure conditions, and the like. For example, in order to suppress the reaction between the protective tube 2 and the molten salt electrolyte 6 and extend the life of the sensor, the inner surface of the protective tube may be coated with Pd, Au or the like.
[0028]
In the above embodiment, a hydrogen selective permeable membrane made of metallic palladium is used for the reference electrode 5 and it is necessary to always supply a reference gas in contact with the hydrogen selective permeable membrane. Therefore, in order to eliminate the need for a reference gas, a solid or solid-liquid reference electrode that can keep the hydrogen potential at the reference electrode constant, that is, the equilibrium partial pressure of hydrogen, can be adopted. Such a reference electrode preferably reacts with the ionic conductor to generate a constant hydrogen potential but does not cause a secondary reaction. For example, when a NaOH-KOH molten salt is used as the molten salt electrolyte, Pd + PdO (+ H₂The reference electrode which consists of O) type solid is mentioned. This is Pd + H₂O (gas) = PdO + H₂It uses a chemical equilibrium of (gas), and allows a constant hydrogen potential at the reference electrode by keeping the water vapor partial pressure in the space between the protective tube and the reference electrode constant.
[0029]
As another example, when a solid-liquid coexisting electrolyte of (NaOH-KOH) (liquid) + KOH (solid) is used as the ionic conductor, Pd (solid) + PdO (solid) + M₂O_Three+ K₂M₂O_Four(Solid) (M: metal element). For example, when the metal element (M) is iron, the reference electrode is Pd (solid) + PdO (solid) + Fe₂O_Three+ K₂Fe₂O_Four(Solid). This is 2KOH (solid) + M₂O_Three(Solid) + Pd (solid) = PdO (solid) + K₂M₂O_Four(Solid) + H₂Using a chemical equilibrium called (gas), a constant hydrogen potential at the reference electrode is made possible.
[0030]
Next, another embodiment according to the present invention will be described. FIG. 6 is a schematic sectional view showing an embodiment of the limiting current type hydrogen sensor according to the present invention. In addition, the same code | symbol is attached | subjected to the component substantially the same as said concentration cell type hydrogen sensor 1, and the detailed description is abbreviate | omitted.
[0031]
The limiting current type hydrogen sensor 40 of this embodiment includes a protective tube 2, a measurement electrode (anode) 3 ′ of a hydrogen selective permeable membrane mainly composed of metallic palladium that seals one end of the protective tube 2, and the protective tube. 2, a gas flow tube 4 disposed coaxially, a hydrogen selective permeable membrane reference electrode (cathode) 5 ′ sealing one end of the gas flow tube 4, and the measurement electrode (anode) 3 ′. And a reference electrode (cathode) 5 ′ and a hydroxide ion conductive molten salt electrolyte 6 interposed between and in contact with both electrodes 3 ′ and 5 ′, and the measurement electrode (anode) 3 ′ and the reference electrode An external power source 41 connected to the lead wires 11 and 12 for applying an external voltage to the (cathode) 5 'and an ammeter 42 for measuring the amount of current between both electrodes are provided. . Instead of the molten salt electrolyte 6, the above-described solid electrolyte may be used.
[0032]
In addition, a gas introduction tube 7 is disposed inside the gas circulation tube 4, and the circulation gas introduced from the gas introduction hole 7a of the gas introduction tube 7 is Ar gas or a mixed gas containing Ar and oxygen. Etc. When a DC voltage is applied using an external power source 41 so that the anode (measurement electrode) 3 ′ is positive and the cathode (reference electrode) 5 ′ is negative, both electrodes are polarized, and the molten salt electrolyte 6 is anoded. Hydrogen is transported from the 3 ′ side to the cathode 5 ′ side, and the transported hydrogen passes through the cathode 5 ′ that is selectively permeable to hydrogen. The circulating gas serves to carry this permeated hydrogen out of the system. As an alternative to circulating gas, the cathode (reference electrode) has an active metal having strong affinity for hydrogen such as titanium, LaNi_FiveA hydrogen storage alloy such as can be used. In this case, it is preferable to coat the surface of the reference electrode with palladium having good hydrogen permeability in order to avoid a reaction between the active metal or the hydrogen storage alloy and the molten salt electrolyte 6 (or solid electrolyte).
[0033]
The configuration of the limiting current type hydrogen sensor 40 of the present embodiment is expressed as: flowing gas | cathode (Pd film) | molten salt electrolyte (KOH-NaOH) | anode (Pd film) | diffusion layer | substance to be measured. This diffusion layer diffuses the hydrogen in the substance to be measured and generates a limiting current, and is formed in the anode 3 ′ or in an adjacent region on the substance to be measured side. In order to obtain a good hydrogen diffusion rate-determining process, the thickness of the anode 3 ′ is adjusted as appropriate depending on the hydrogen permeability of the anode (measurement electrode). Was preferably about 1 mm to 10 mm. Then, a DC voltage is applied so that the anode 3 ′ is positive and the cathode 5 ′ is negative, so that hydrogen is transported from the anode 3 ′ side to the cathode 5 ′ side. At this time, hydrogen in the substance to be measured is diffusion-limited in the diffusion layer, and a limit current that does not depend on the applied voltage is generated. Further, this limit current value is proportional to the hydrogen concentration in the substance to be measured, and this hydrogen concentration is proportional to the 1/2 power of the hydrogen partial pressure according to the Siebels law. In accordance with the above principle, the dissolved hydrogen concentration in the substance to be measured can be calculated based on the measured limit current value using a calibration curve prepared in advance.
[0034]
Next, in order to investigate the measurement performance of the limiting current type hydrogen sensor 40 of the present embodiment, the same test environment as in FIG. 2 was set. When a DC voltage is applied between the anode (measuring electrode) 3 ′ and the cathode (reference electrode) 5 ′ to change the hydrogen concentration and temperature in the substance to be measured, the electrodes 3 ′ and 5 ′ The limit current flowing was measured and the response characteristics were investigated. The results are shown in FIGS.
[0035]
FIG. 7 is a graph showing the correspondence between the applied voltage and the current value when the hydrogen concentration in the substance to be measured is changed under an environment of 400 ° C. The number attached below each curve indicates the hydrogen concentration (% by volume). This figure shows that limit currents 43, 44, 45, and 46 corresponding to the hydrogen concentration are generated, and that the limit current type hydrogen sensor 40 of this embodiment is functioning.
[0036]
FIG. 8 is a graph showing the correspondence between the hydrogen partial pressure in the substance to be measured and the limit current in each environment at 400 ° C. and 300 ° C. The measurement point when each voltage of 800 mV, 1000 mV, and 1200 mV is applied between the electrodes 3 ′ and 5 ′ in an environment of 400 ° C. is approximately proportional to the 1/2 power of the hydrogen partial pressure. It is distributed with high correlation in the vicinity of the created straight line 47. The measurement point when a voltage of 1200 mV is applied between the electrodes 3 ′ and 5 ′ in an environment of 300 ° C. is also approximately proportional to the half power of the hydrogen partial pressure, and is a straight line created by the method of least squares. It is distributed with high correlation in the vicinity of 48. In actual hydrogen concentration measurement, by preparing such a calibration curve in advance, the hydrogen concentration is measured from the measured limit current value.
[0037]
FIG. 9 is a graph showing the change over time in the limit current value when a voltage of 1000 mV is applied between the electrodes 3 ′ and 5 ′ in an environment of 400 ° C. and the hydrogen concentration of the substance to be measured is changed. . The numbers attached to the curves in the figure indicate the hydrogen concentration (% by volume). From this figure, it can be seen that the limiting current changes rapidly in response to the change in the hydrogen concentration, indicating a sufficient response speed.
[0038]
By the way, if the concentration of dissolved hydrogen in the substance to be measured is too high, it may be difficult to control the diffusion rate of hydrogen in the diffusion layer. In such a case, it is preferable to use an alloy in which metal element such as nickel or silver that traps permeated hydrogen is added to metal palladium as the measurement electrode 3 ′. By selecting the additive element and adjusting the amount of addition, the amount of permeated hydrogen at the measurement electrode can be adjusted, so that the diffusion rate of permeated hydrogen can be easily controlled.
[0039]
The limiting current type hydrogen sensor 40 can be used as a monitor for hydrogen permeating from the lumen of the pipe. For example, stainless steel pipes are known to have a property of limiting the diffusion of hydrogen that permeates through the crystal grain boundaries. Utilizing this property, the hydrogen selectively permeable anode (measuring electrode) 3 ′ is brought into contact with the surface of the pipe, and the permeated hydrogen from the pipe is passed through the anode (measuring electrode) 3 ′ to measure the limiting current. The hydrogen concentration can be calculated. As a result, the state of the fluid flowing through the lumen of the pipe can be monitored and the degree of deterioration of the pipe can be estimated.
[0040]
As shown in FIG. 10, it is also effective to provide a diaphragm 50 having a diffusion hole 50a around the measurement electrode 3 'in order to stabilize the hydrogen diffusion rate-determining process. By appropriately adjusting the diameter and length of this diffusion hole, it becomes possible to control the diffusion rate of hydrogen and create an environment for generating a limiting current. Further, the same effect can be obtained by providing a coating layer made of a porous sintered body or the like on the surface of the anode (measurement electrode) 3 ′ instead of the diaphragm 50. Such a hydrogen sensor provided with a diaphragm 50 and a coating layer is suitably used for detecting the concentration of hydrogen molecules slightly dissolved in high-temperature hot water or hydrogen atoms slightly dissolved in a metal solution.
[0041]
【The invention's effect】
As described above, the concentration cell-type hydrogen sensor of the present invention has a main body provided with a measurement electrode at its tip, which is mainly composed of metallic palladium and selectively transmits hydrogen in a substance to be measured, and defines a reference potential provided in the main body. Since it comprises a reference electrode and an ion conductor containing hydrogen ions interposed between the measurement electrode and the reference electrode, (1) a conventional chemical battery type sensor by using a molten salt electrolyte in particular for the ion conductor (2) In addition, the ion conductor is protected from the substance to be measured by the presence of a hydrogen-selective measuring electrode provided at the tip of the main body. Therefore, alteration of the ionic conductor can be prevented, so that the sensor performance can be prevented from being deteriorated and the selection range of the ionic conductor can be expanded. (3) Furthermore, an electromotive force generated between the measurement electrode and the reference electrode Signal output From the can continuously measure, it is possible to measure the (4) a severe environment (high temperature and high pressure) even accurate hydrogen concentration, such as high-temperature hot water and petroleum reforming process.
[0042]
In addition, the limiting current type hydrogen sensor of the present invention includes a main body provided with a measuring electrode (anode) for selectively permeating hydrogen in a substance to be measured at the tip, and a reference electrode (cathode) arranged in the main body to take in hydrogen. ), An ionic conductor containing hydrogen ions interposed between the reference electrode (cathode) and the measurement electrode (anode), and hydrogen diffusion rate-limiting in the measurement electrode (anode) or in the adjacent region on the measured substance side In this case, the same effect as the above (1) and (2) is obtained, and (5) the measurement electrode (anode) and the reference electrode Since the signal output of the limiting current generated between the (cathodes) can be obtained and continuously measured, the hydrogen concentration can be measured with high accuracy even in a harsh environment (high temperature and high pressure) as in the case (4).
[0043]
In addition, by forming a diaphragm or coating layer having a single or a plurality of diffusion holes around the measurement electrode (anode), it becomes possible to control the diffusion rate of hydrogen and easily create a limit current generation environment. For example, it is possible to detect the concentration of hydrogen molecules slightly dissolved in high-temperature hot water or hydrogen atoms slightly dissolved in a metal solution with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an embodiment of a concentration cell type hydrogen sensor according to the present invention.
FIG. 2 is a schematic view showing a test environment of a concentration cell type hydrogen sensor according to the present invention.
FIG. 3 is a graph showing response characteristics of a concentration cell type hydrogen sensor according to the present invention.
FIG. 4 is a graph showing a correspondence relationship between electromotive force and hydrogen concentration.
FIG. 5 is a graph for explaining partial equilibrium related to hydrogen.
FIG. 6 is a schematic sectional view showing one embodiment of a limiting current type hydrogen sensor according to the present invention.
FIG. 7 is a graph showing limit current characteristics of a limit current type hydrogen sensor according to the present invention.
FIG. 8 is a graph showing a correspondence relationship between limit current and hydrogen partial pressure.
FIG. 9 is a graph showing response characteristics of a limiting current type hydrogen sensor according to the present invention.
FIG. 10 is a schematic sectional view showing a state in which a diaphragm having a diffusion hole is provided around a measurement electrode (anode) of a limiting current type hydrogen sensor according to the present invention.
[Explanation of symbols]
1 Concentration cell type hydrogen sensor 2 Protective tube (main part)
3 Measuring electrode 3 'Anode
4 Gas distribution tube 5 Reference electrode
5 'cathode 6 Molten salt electrolyte
7 Gas introduction tube 7a Gas introduction hole
8 Gas exhaust hole 9 Sealing member
10 Sealing member 11, 12 Lead wire
13 Spacer 14 Voltmeter
15,16 Compression jig 20 Electric furnace
21 Glass tube 21a Gas inflow hole
21b Gas exhaust hole 30 straight line
31 Straight line 40 Limit current type hydrogen sensor
41 External power supply 42 Ammeter
43, 44, 45, 46 Limit current 47 Linear
50 Diaphragm 50a Diffusion hole

Claims (8)

A main body part mainly composed of metallic palladium and provided with a measuring electrode that selectively transmits hydrogen in the substance to be measured at the tip, and a reference electrode that is disposed in the main body part and defines a reference potential corresponding to a predetermined hydrogen concentration, An ion conductor including hydrogen ions interposed between the measurement electrode and the reference electrode and in contact with both electrodes, and forming a concentration cell, measuring an electromotive force between the measurement electrode and the reference electrode, hydrogen sensor comprising a measuring device for calculating the hydrogen concentration of the analyte in corresponding to electromotive force based on the formula, the ion conductor is characterized Rukoto such a hydroxide ion conductivity of the molten salt electrolyte . Hydrogen sensor of the sample material and contact with claim 1 Symbol placement to constitute a concentration cell equipped with a reference electrode which selectively transmits hydrogen in said sample substance having a predetermined hydrogen concentration. The hydrogen sensor according to claim 2 , wherein a hydrogen-containing gas is used as the sample material. A main body provided with a measuring electrode (anode) for selectively permeating hydrogen in the substance to be measured, a reference electrode (cathode) arranged in the main body for taking in hydrogen, the reference electrode (cathode), and the measurement An ion conductor including hydrogen ions interposed between the electrodes (anode) and in contact with both electrodes, and a diffusion layer that causes a rate of diffusion of hydrogen in the measurement electrode (anode) or in an adjacent region on the measured substance side are provided. In addition, an external power source that applies a voltage between the measurement electrode (anode) and the reference electrode (cathode) and a limit current value between both electrodes are measured, and a hydrogen concentration in a measured substance corresponding to the limit current value is calculated. and a measuring device for the hydrogen sensor in which the ionic conductor is characterized Rukoto such a hydroxide ion conductivity of the molten salt electrolyte. The hydrogen sensor according to claim 4 , wherein a measurement electrode (anode) mainly composed of metallic palladium is used. The hydrogen sensor according to claim 4 or 5 , wherein a diaphragm or a coating layer having one or a plurality of diffusion holes is formed around the measurement electrode (anode). The hydrogen sensor according to any one of claims 4 to 6 , further comprising a reference electrode that selectively transmits hydrogen transported by polarization of the measurement electrode (anode) and the reference electrode (cathode). The hydrogen according to any one of claims 4 to 7 , wherein a reference electrode made of an active metal or a hydrogen storage metal having an affinity for hydrogen transported by polarization of the measurement electrode (anode) and the reference electrode (cathode) is used. Sensor.

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