JP2023157201A - gas sensor - Google Patents

Abstract

To provide a COe gas sensor with high COe gas sensitivity without depending on the concentration of sulfur dioxide gas.SOLUTION: A COe gas sensor includes a first sensor part including a first sensing electrode and a counter electrode connected through a solid electrolyte substrate to be ionically conductive, and a second sensor part including a second sensing electrode and a counter electrode connected through the solid electrolyte substrate to be ionically conductive, in which a) the film thickness of the first sensing electrode is smaller than the film thickness of the second sensing electrode, or b) a mechanism that can keep the temperature of the first sensing electrode lower than the temperature of the second sensing electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas sensor. In particular, the present invention relates to a COe gas sensor that eliminates false detection due to sulfur dioxide and has excellent COe sensitivity.

Conventionally, various gas sensors have been used to detect gas components or determine gas concentrations in gas mixtures to be measured, such as sensors constructed based on solid electrolytes and operated on the mixed potential principle, and catalytic combustion type gas sensors. It has been known.

These gas sensors are required to accurately detect the gas to be detected without being affected by the miscellaneous gas even if the gas to be detected is mixed with the gas to be detected. For example, a catalytic combustion type gas sensor is equipped with two sensor sections, and separately detects the concentration of a mixture of target gas and miscellaneous gas, and the concentration of miscellaneous gas alone, and subtracts the miscellaneous gas concentration from the mixed gas concentration. , a technique for determining the concentration of a target gas is known (for example, see Patent Document 1).

International Publication No. 2018/135100

The composition of miscellaneous gases that may be included in the gas to be measured varies greatly depending on the environment in which the gas sensor is placed, and there are also various miscellaneous gases that cause false detection. For example, when the detection target gas is COe (CO equivalent) gas, sulfur dioxide (SO ₂ ) gas may cause false detection as a miscellaneous gas. In particular, when the gas to be measured is exhaust gas that is used as a fuel such as coal, the exhaust gas may contain as much as 2000 ppm of SO ₂ gas. In such a case, the influence of SO ₂ gas as a miscellaneous gas on COe gas detection is large, and accurate measurement may be difficult.

When detecting COe gas using a mixed potential type gas sensor, it is required to eliminate the influence of SO ₂ gas, eliminate false detections, and accurately obtain the COe gas concentration.

As a result of extensive studies, the present inventors have noticed that the film thickness dependence or temperature dependence characteristics of COe gas sensitivity and SO ₂ gas sensitivity are different. By using at least two sensors with different sensing electrode film thicknesses or temperatures, it is possible to calculate both COe concentration and SO ₂ concentration, and it is possible to reduce false detection of COe gas due to SO ₂ gas. They discovered this and completed the present invention.

According to one embodiment, the present invention includes a first sensor section including a first sensing electrode and a counter electrode that are ionically conductively connected via a solid electrolyte substrate; A COe gas sensor comprising a second sensing electrode and a counter electrode, the COe gas sensor comprising:
a) the thickness of the first sensing electrode is smaller than the thickness of the second sensing electrode, or
b) The present invention relates to a COe gas sensor including a mechanism capable of keeping the temperature of the first sensing electrode lower than the temperature of the second sensing electrode.

In the COe gas sensor, the first sensing electrode and the second sensing electrode are sintered bodies containing alloy particles containing platinum and solid electrolyte particles, and the counter electrode is a sintered body containing metal particles containing platinum and solid electrolyte particles. It is preferable that it is a sintered body containing.

In the COe gas sensor, it is preferable that the thickness of the first sensing electrode be 10 μm or more thinner than the thickness of the second sensing electrode.

In the COe gas sensor, it is preferable that the first sensing electrode has a film thickness of 15 μm to 90 μm.

In the COe gas sensor, it is preferable that the mechanism is a heating unit that can independently control the temperatures of the first sensing electrode and the second sensing electrode.

According to another embodiment of the present invention, there is provided a gas detection meter in which the above-described COe gas sensor is built in a tubular casing having an open end, the first sensing electrode and the The present invention relates to a gas detection meter in which a second sensing electrode and the counter electrode are configured to be able to contact the gas to be measured flowing in from the open end.

The gas detection meter further includes an oxygen gas sensor in the tubular casing having the open end, the oxygen gas sensor comprising a solid electrolyte substrate and at least a pair of electrodes connected to each other in an ion conductive manner via the solid electrolyte substrate. an oxygen sensing electrode made of a sintered body containing metal particles containing platinum and solid electrolyte particles; and an oxygen detection electrode made of a sintered body containing metal particles containing platinum and solid electrolyte particles. a counter electrode for detection, the oxygen detection electrode is configured to be able to come into contact with the gas to be measured flowing in from the open end, and the counter electrode for oxygen detection is shielded from the atmosphere of the gas to be measured. It is preferable.

According to another embodiment of the present invention, there is provided a method for detecting COe gas using the aforementioned gas sensor, which includes a step of obtaining an electromotive force Em ₁ of the first sensor section and an electromotive force Em ₂ of the second sensor section. , parameters a ₁₁ , a ₂₁ , b 11 , b 21 determined in advance for the first sensor section, parameters a ₁₂ , a ₂₂ , b ₁₂ , _{b 22 determined} in advance for _the second sensor section, and Em ₁ , and a step of calculating the COe gas concentration Xcoe and the _SO2 gas concentration _XSO2 based on the correlation with _Em2 , where _a11 and _a12 are constants indicating the concentration dependence of the COe gas electromotive force, b ₁₁ and b ₁₂ are constants indicating the sensitivity limit concentration of COe gas, a ₂₁ and a ₂₂ are constants indicating the concentration dependence of SO ₂ gas electromotive force, and b ₂₁ and b ₂₂ are constants indicating the sensitivity limit concentration of COe _gas ; This invention relates to a detection method in which the sensitivity limit concentration of a gas is a constant.

In the detection method, the constant is a constant determined by setting the first sensing electrode at a first temperature and setting the second sensing electrode at a second temperature, and in the step of obtaining the electromotive force, the first sensing electrode is set at a second temperature. and the second sensing electrode is set at a second temperature, the first temperature is 580 to 650°C, and the second temperature is 30 to 100°C higher than the first temperature. preferable.

According to the present invention, it is possible to provide a mixed potential type COe gas sensor that can selectively detect COe gas with high sensitivity without being affected by SO ₂ gas.

FIG. 1 is a conceptual diagram showing a cross-sectional structure of a COe gas sensor according to a first embodiment of the present invention. FIG. 2 is a conceptual logarithmic graph for explaining characteristic measurement of the first sensor section in the COe gas detection method using the COe gas sensor according to the first embodiment of the present invention. FIG. 3 is a conceptual logarithmic graph for explaining characteristic measurement of the second sensor section in the COe gas detection method using the COe gas sensor according to the first embodiment of the present invention. FIG. 4 is a conceptual diagram showing an example of a gas detector according to the second embodiment of the present invention. FIG. 5 is a conceptual cross-sectional view of a COe gas sensor located inside the casing of the gas detector shown in FIG. FIG. 6 is a conceptual diagram showing another example of the gas detector according to the second embodiment of the present invention. FIG. 7 is a conceptual cross-sectional view of a COe gas sensor located inside the casing of the gas detector shown in FIG. FIG. 8 is a cross-sectional view taken along line AA in FIG. 6. FIG. 9 is a conceptual diagram showing yet another example of the gas detector according to the second embodiment of the present invention. FIG. 10 is a conceptual diagram showing still another example of the gas detector according to the second embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

[First embodiment: COe gas sensor]
According to a first embodiment, the present invention relates to a COe gas sensor. The COe gas sensor according to the present embodiment includes a first sensor section including a first sensing electrode and a counter electrode that are ionically conductively connected via a solid electrolyte substrate, and a first sensor section that is ionically conductively connected via the solid electrolyte substrate. A COe gas sensor including a second sensor section including two sensing electrodes and a counter electrode,
a) the thickness of the first sensing electrode is smaller than the thickness of the second sensing electrode, or
b) A COe gas sensor including a mechanism capable of keeping the temperature of the first sensing electrode lower than the temperature of the second sensing electrode.

The COe gas sensor according to the present embodiment includes a COe gas as a detection target gas, and also includes a non-detection target gas as a measurement target gas. Here, COe gas is a gas generated during incomplete combustion of fuel, and is a gas containing carbon monoxide (CO) and hydrogen (H ₂ ). Therefore, in this specification, the COe gas concentration refers to the total concentration of CO gas and H ₂ gas. The COe gas sensor according to the present invention is a gas sensor that can detect the concentration of COe gas and also detect the concentration of sulfur dioxide (SO ₂ ) gas, distinguishing it from COe gas.

In the COe gas sensor according to the present embodiment, the COe gas concentration and the SO ₂ gas concentration are obtained based on the difference in electromotive force obtained from two or more sensor parts having different film thicknesses of the sensing electrode (aspect a), and There may be an embodiment (aspect b) in which the COe gas concentration and SO ₂ gas concentration are obtained based on the electromotive force difference obtained from two or more sensor sections having different temperatures. Each aspect will be explained below.

[Aspect a: Sensor using difference in film thickness of sensing electrode]
FIG. 1 is a schematic cross-sectional view of a COe gas sensor according to aspect a of the first embodiment. The COe gas sensor 1 according to aspect a includes a first sensor section 13 and a second sensor section 17. The first sensor section 13 includes a solid electrolyte substrate 10 , a first sensing electrode 11 , and a counter electrode 12 . The second sensor section 17 includes a solid electrolyte substrate 14 , a second sensing electrode 15 , and a counter electrode 16 .

The first sensor section 13 will be explained. The solid electrolyte substrate 10 is a member that forms a three-phase interface between the first sensing electrode 11 or the counter electrode 12 and a gas phase containing the gas to be detected, and enables ion conduction. The shape of the solid electrolyte substrate 10 is not particularly limited, as long as it can connect the first sensing electrode 11 and the counter electrode 12 such that ion conduction is possible. Therefore, for example, in addition to the flat solid electrolyte substrate 10 shown in FIG. 1, a cylindrical substrate or a cylindrical substrate with one end closed may be used.

The solid electrolyte substrate 10 is preferably made of stabilized zirconia, and examples thereof include, but are not limited to, zirconia stabilized with rare earth metal oxides such as yttria and ceria, calcia-stabilized zirconia, and magnesia-stabilized zirconia. From the viewpoint of ionic conductivity, it is particularly preferable to use yttria-stabilized zirconia.

The first sensing electrode 11 functions as a working electrode and is configured to be able to measure the difference in electromotive force between it and the counter electrode 12. In FIG. 1, the first sensing electrode 11 and the counter electrode 12 are each formed in contact with the solid electrolyte substrate 10, and the first sensing electrode 11 and the counter electrode 12 are provided apart from each other. However, it is sufficient that the first sensing electrode 11 and the counter electrode 12 are connected to each other in an ion-conductive manner via the solid electrolyte substrate 10. It may also be through other sexual members. Further, in FIG. 1, the first sensing electrode 11 and the counter electrode 12 are provided on one surface of the flat solid electrolyte substrate 10 at a distance from each other. It is also possible to arrange a sensing electrode on one surface and a counter electrode on the other surface. However, it is necessary to configure the first sensing electrode 11 and the counter electrode 12 so that they are in contact with the same gaseous atmosphere, and the atmosphere between the first sensing electrode 11 and the counter electrode 12 is not blocked by the solid electrolyte substrate. , the first sensing electrode 11 and the counter electrode 12 are arranged.

The first sensing electrode 11 may be a sintered body containing solid electrolyte particles and metal particles made of a metal containing platinum (Pt) or a metal alloy containing platinum (Pt). The metal alloy containing Pt may include an alloy of Pt and rhodium (Rh), an alloy of Pt and gold (Au), and the like. The mass ratio of Pt to other metals in the alloy containing Pt may be, for example, about 98:2 to 85:15, but is not particularly limited. The average particle diameter of the metal particles may be about 0.5 to 2.5 μm, but is not particularly limited. The solid electrolyte particles may be stabilized zirconia particles, and may be one or more types selected from any stabilized zirconia listed as the material for the solid electrolyte substrate 10. Further, the stabilized zirconia may have the same composition as the stabilized zirconia that is the main component of the solid electrolyte substrate 10, or may have a different composition. The solid electrolyte particles are particularly preferably yttria-stabilized zirconia particles. The average particle diameter of the solid electrolyte particles may be about 0.1 to 1 μm, but is not particularly limited.

Such a sintered body is made by dispersing a paste obtained by dispersing a mixture containing metal particles made of Pt or a Pt alloy and solid electrolyte particles in an appropriate solvent such as an organic solvent dissolved in a binder. It can be obtained by coating and forming, for example, a thin layer onto the solid electrolyte substrate 10 and firing it at 1200 to 1400° C. in the atmosphere.

The material of the counter electrode 12 may be a sintered body containing metal particles containing platinum (Pt) or metal particles made of platinum (Pt), and solid electrolyte particles. The particle size and preferred composition range of the metal particles and solid electrolyte particles may be the same as those of the first sensing electrode 11, and the method of manufacturing the sintered body may also be the same as the method of manufacturing the first sensing electrode 11. good.

The first sensor section includes a detection section (not shown) connected to the first detection electrode 11 and the counter electrode 12, respectively. The detection section includes a detection circuit and wiring. The wiring includes a wiring whose one end is connected to the first sensing electrode 11 and the other end is connected to the detection circuit, and a wiring whose one end is connected to the counter electrode 12 and the other end is connected to the detection circuit. The detection circuit may be a device capable of measuring the electromotive force (potential difference) between the first detection electrode 11 and the counter electrode 12, and may be a general electrometer. Further, the wiring may be made of a conductive material, and may be a Pt wire or a wiring made of a sintered body having the same composition as the electrode material to which the wiring is connected.

The second sensor section 17 will be explained. The configuration of the second sensor section 17 may be substantially the same as that of the first sensor section 13. Therefore, the material and shape of the solid electrolyte substrate 14, the material and shape of the second sensing electrode 15 and the counter electrode 16, and the positional relationship thereof may also be substantially the same as those of the first sensor section 13. The configuration of the detection section (not shown) may also be the same, and may include a detection circuit composed of a device capable of measuring the electromotive force between the second detection electrode 15 and the counter electrode 16 wiring, and wiring connecting these. Bye.

In aspect a, the thickness t ₁ of the first sensing electrode 11 is configured to be smaller than the thickness t ₂ of the second sensing electrode 15 . The difference between the thickness t ₁ of the first sensing electrode 11 and the thickness t ₂ of the second sensing electrode is preferably 10 μm or more, more preferably 30 μm or more. Further, it is preferable that the film thickness t ₁ of the first sensing electrode is 15 μm to 90 μm. This is because, in this film thickness range, there is a clear difference between the electromotive force characteristics of COe and the electromotive force characteristics of SO ₂ .

The relationship between the thickness t1 of the first sensing electrode ₁₁ and the thickness of the counter electrode 12 is not particularly limited. Furthermore, the relationship between the thickness _t2 of the second sensing electrode 15 and the thickness of the counter electrode 16 is not particularly limited. Although the relationship between the film thicknesses of the two counter electrodes 12 and 16 is not limited, it is preferable that the film thicknesses are the same, and can be, for example, about 20 to 50 μm.

In the illustrated embodiment, the first sensor section 13 and the second sensor section 17 each independently include a separate solid electrolyte substrate and a counter electrode. Two sensor sections 17 can share the solid electrolyte substrate. In that case, the counter electrodes can optionally be shared. That is, on one continuous solid electrolyte substrate, a first sensing electrode, a second sensing electrode, and a counter electrode combined with each sensing electrode may be provided, and the first sensing electrode, the second sensing electrode, It may have a single counter electrode.

The COe gas sensor according to this embodiment may include a heater (not shown) as a further optional element. The heater may be a device that can raise the temperature of the solid electrolyte substrate 10 to a predetermined temperature as necessary, and may be a thin layer type heater made of a tungsten (W) thin film or a platinum (Pt) thin film. It may be a ceramic heater or any other heater. When the first sensor section 13 shown in FIG. 1 further includes a heater, the heater is, for example, located on one surface of the solid electrolyte substrate 10 opposite to the surface on which the first sensing electrode 11 and the counter electrode 12 are provided. An insulating film may be provided on the side surface, and the first sensing electrode 11, the counter electrode 12, and the heater may be formed in a positional relationship facing each other with the solid electrolyte substrate 10 and the insulating film interposed therebetween. Alternatively, the heater may be provided in the vicinity of the solid electrolyte substrate, for example around the solid electrolyte substrate, without contacting the solid electrolyte substrate, but the heater is not limited to a particular embodiment. The second sensor section 17 can also be provided with a heater in a similar configuration. The first sensor section 13 and the second sensor section 17 may be provided with separate heaters, or may be provided with a single heater that heats both sensor sections.

Next, a method for manufacturing a gas sensor having such a configuration will be described. The method for manufacturing a gas sensor according to this embodiment includes a step of forming sensing electrodes 11 and 15 and counter electrodes 12 and 16 on solid electrolyte substrates 10 and 14 for both the first sensor section 13 and the second sensor section 17.

In the electrode forming step of the first sensor section 13, the first sensing electrode 11 and the counter electrode 12 are formed on the solid electrolyte substrate 10. The method for forming each electrode is as described above. Both a paste made of the material of the first sensing electrode 11 and a paste made of the material of the counter electrode 12 are formed on the solid electrolyte substrate 10, and each of the first sensing electrode 11 and the counter electrode 12 is connected to the detection circuit. It is preferable to sinter the wirings after disposing them on the solid electrolyte substrate 10. The solid electrolyte substrate 10 can be a commercially available product, or can be manufactured by molding a solid electrolyte material into a desired shape prior to the electrode forming step. In addition, in a gas sensor that includes a heater, which is an optional component, on a solid electrolyte substrate, an electrically insulating layer such as alumina is formed in advance, and then a heater electrode pattern made of Pt paste or the like is formed by a printing method or the like. By firing the solid electrolyte substrate 10, a heater can be formed on the solid electrolyte substrate 10. Through the electrode forming step, a gas sensor including the solid electrolyte substrate 10, the first sensing electrode 11, the counter electrode 12, and wiring can be obtained. The same applies to the second sensor section 17. When forming a first sensing electrode, a second sensing electrode, and a counter electrode on a single solid electrolyte substrate, these can be formed into films at the same time and fired.

Note that although FIG. 1 illustrates a COe gas sensor 1 that includes a first sensor section and a second sensor section, the COe gas sensor may include an additional sensor section. The additional sensor section may include an additional sensing electrode, and the thickness of the additional sensing electrode is within the preferred thickness range of the first sensing electrode or the second sensing electrode, and the thickness of the additional sensing electrode is within the preferable thickness range of the first sensing electrode or the second sensing electrode. The above predetermined preferable film thickness difference can be provided depending on the relationship between the two sensing electrodes. The number of additional sensor units is not particularly limited in principle. Providing an additional sensor unit may have the advantage of obtaining more accurate calculation results.

Next, a COe gas detection method using the COe gas sensor according to aspect a will be described. The COe gas detection method can also be called a COe gas sensor operating method. The COe gas detection method using the COe gas sensor according to aspect a includes the following steps.
(1) Step of obtaining the electromotive force Em ₁ of the first sensor section and the electromotive force Em ₂ of the second sensor section (2) Parameters a ₁₁ , a ₂₁ , b ₁₁ , b ₂₁ determined in advance for the first sensor section, Calculating COe gas concentration Xcoe and _SO2 gas concentration _XSO2 based on the correlation between parameters a ₁₂ , a ₂₂ , b ₁₂ , b ₂₂ determined in advance for the second sensor section and Em ₁ and Em ₂

The gas to be measured may generally be a gas that may include COe gas. Typically, the gas may be gas generated in equipment such as a garbage incinerator or a boiler, but is not limited thereto. The temperature of the gas generated in the equipment is not particularly limited, but may be, for example, -10°C to 600°C. When these gases contact the first sensor section and the second sensor section, the temperature can be controlled to be a predetermined temperature of 600° C. or higher. In detecting gas, the sensor according to aspect a of the first embodiment can be installed in a flue or the like through which such a gas to be measured flows. In this case, the gas sensor is operated in such a manner that both the first sensing electrode 11 and the counter electrode 12 of the first sensor section 13 and the second sensing electrode 15 and the counter electrode 16 of the second sensor section 17 are in contact with the gas to be measured. Install.

Preliminary Step: Determination of Sensor Characteristics In the method according to this embodiment, a step of determining sensor characteristics is performed before operation of the COe gas sensor. Taking into account the individual differences among COe gas sensors, this process needs to be performed individually for all COe gas sensors before operation. A COe gas sensor typically only needs to be characterized once before it is put into use. Optionally, it is also possible to carry out periodic characterization and calibrate the sensor characteristics. Determination of sensor characteristics can be carried out by the following steps.
1) Regarding the first sensor section, the dependence of the electromotive force difference between the first sensing electrode and the counter electrode (hereinafter referred to as sensitivity; the unit is -Ewc/mV) on the COe gas concentration (ppm), and the dependence of the sensitivity on the SO ₂ gas concentration ( 2) For the second sensor section, the COe gas concentration (ppm) dependence of the sensitivity (-Ewc/mV) and the SO ₂ gas concentration (ppm) dependence of the sensitivity (-Ewc/mV) Step of obtaining the dependence by experiment 3) Plot the experimental results on a graph in which the X axis is the gas concentration, the Y axis is the sensitivity, and the X axis is semilogarithmic, and an approximate straight line on the high concentration side is obtained, Process of obtaining the slope and X-axis intercept of the approximate straight line

In 1), sensitivity is measured by bringing an experimental gas containing a known concentration of COe and containing no miscellaneous gas into contact with the first sensor section. The measurement can be performed at about 4 to 10 points within the expected COe concentration range during measurement when the gas sensor is in operation, and preferably within the range of 10 ppm to 3000 ppm, for example. COe here can be, for example, an equimolar mixture of CO and H ₂ . Similarly, sensitivity is measured by bringing an experimental gas containing a known concentration of SO ₂ gas and containing no miscellaneous gas into contact with the first sensor section. The concentration range of SO ₂ gas to be measured may also be the same as that of COe gas, and may be, for example, 10 ppm to 3000 ppm. Further, the sensor temperature conditions and the flow rate conditions of the experimental gas in this step are preferably the conditions assumed for the sensor temperature and the flow rate of the gas to be measured when the gas sensor is in operation. When using the sensor according to aspect a, the sensor temperature can generally be about 600 to 700°C, but is not limited to this condition. Furthermore, the flow rate of the gas to be measured refers to the flow rate of the gas to be measured when it comes into contact with the sensor.

In 2), the second sensor section is measured in the same manner as in 1). Measurements 1) and 2) can be performed simultaneously.

In 3), plots are created for each of the first sensor section and the second sensor section. FIG. 2 is an example of a plot created for the first sensor section. In the three-phase interface type gas sensor according to the first embodiment, when the dependence of sensitivity on gas concentration is plotted on an X-axis semilogarithmic graph as shown in FIG. 2, the slope is generally constant on the high concentration side. Shows a linear relationship. The high concentration here varies depending on the characteristics of the sensor and is not limited to a specific numerical range. Those skilled in the art can extract a high-concentration side region exhibiting a linear relationship with a constant slope based on the plotting results. In FIG. 2, the concentration dependence of COe gas is shown in black, and the concentration dependence of SO ₂ gas is shown in white circles. Further, the straight line extrapolated to the plot on the high concentration side is represented by a broken line, and the X-axis intercept of the extrapolated straight line is also represented by a black or white circle. Here, the parameter representing the slope is a _ij , and the parameter representing the X-axis intercept at which the sensitivity is 0 is b _ij . i=1 is a parameter related to COe, i=2 is a parameter related to _SO2 , and i=m is a parameter related to mixed gas. j=1 is a parameter related to the first sensor section, and j=2 is a parameter related to the second sensor section.

From FIG. 2, the slope a ₁₁ and the intercept b ₁₁ of the COe graph, and the slope a ₂₁ and the intercept b ₂₁ of the SO ₂ graph are obtained. Both are values specific to the first sensor section and are constants. Similarly, from FIG. 3, the slope a ₁₂ and intercept b ₁₂ of the COe graph, and the slope a ₂₂ and intercept b ₂₂ of the SO ₂ graph are obtained. Both values are unique to the second sensor section and are constants. By configuring the first sensor part and the second sensor part so that the film thickness of the sensing electrode is different, the X-axis which represents the gas concentration dependence characteristic of sensitivity for both COe gas and SO ₂ gas. It was found that the intercept and the slope of the graph were different. Then, using the eight parameters a ₁₁ , b ₁₁ , a ₂₁ , b _{21 ,} a ₁₂ , b ₁₂ , a ₂₂ , and b ₂₂ , the relationship between COe gas concentration, SO ₂ gas concentration, and the electromotive force of each sensor section is calculated. We came up with the idea of deriving a relational expression. An example of a method for deriving a relational expression will be explained.

From FIGS. 2 and 3, if the COe gas concentration is the variable X _COe , the SO ₂ gas concentration is the variable X _SO2 , and the sensitivity variable E _ij , in the region where a linear relationship holds, the relationship between the gas concentration and the sensitivity is It can be expressed using the following formula.

When the sensitivity (electromotive force E _m ) in the case of a mixed gas is calculated assuming a parallel circuit of internal resistance R and electromotive force E, gas sensitivities E ₁₁ , E ₂₁ of the first sensor section, internal resistance R ₁ , second In the case of gas sensitivities E ₁₂ and E ₂₂ and internal resistance R ₂ of the sensor section, E _m1 and E _m2 can be expressed by the following equations.
E _m1 = 1/(1+A) E ₁₁ + 1/(1+A ^-1 )E ₂₁
E _m2 = 1/(1+A) E ₁₂ + 1/(1+A ^-1 )E ₂₂

Here, A is the internal resistance ratio of the electrodes A = R ₁ /R ₂ , but since it is the gas sensitivity with the same electrode, assuming A = 1, the mixture of the first sensor part and the second sensor part is The sensitivity (electromotive force) to gas can be expressed by the following formula.
2E _m1 =E ₁₁ +E ₂₁
2E _m2 =E ₁₂ +E ₂₂

2E _m1 = E ₁₁ + E ₂₁ = a ₁₁ (log(X _COe )-log(b ₁₁ ))+a ₂₁ (log(X _SO2 )-log(b ₂₁ ))
2E _m2 = E ₁₂ + E ₂₂ = a ₁₂ (log(X _COe )-log(b ₁₂ ))+a ₂₂ (log(X _SO2 )-log(b ₂₂ ))

の逆行列を両辺の左側からかけ、対数を外すとＸ_ＣＯｅ、Ｘ_ＳＯ２は以下の式（１）、（２）で表すことができる。

Summarized as log(X _COe ) and log(X _SO2 ),

By multiplying the inverse matrix of from the left side of both sides and removing the logarithm, X _COe and X _SO2 can be expressed by the following equations (1) and (2).

A method for detecting COe gas is implemented using the main equation obtained in the preliminary step. Note that the calculation method for deriving the formula is not limited to the method described in this specification. If the COe gas concentration and SO ₂ gas concentration can be derived from the relational expressions shown in FIGS. 2 and 3, it is also possible to use a calculation method using artificial intelligence.

First step: Step of obtaining electromotive force Em ₁ and Em ₂ In the first step, electromotive force Em ₁ of the first sensor section and electromotive force Em ₂ of the second sensor section are obtained. When obtaining the electromotive force, the COe gas sensor according to aspect a is used, and the temperature of the gas in contact with the first sensing electrode 11 and the second sensing electrode 15 and the gas flow rate are the same as those in the characterization experiment in the preliminary step.

Second step: gas concentration calculation step In the second step, the COe gas concentration and SO ₂ gas concentration are calculated from the equation derived in the preliminary step and the electromotive forces Em ₁ and Em ₂ obtained in the first step. Through this calculation step, the COe gas concentration and the SO ₂ gas concentration can be obtained separately without erroneously detecting SO ₂ gas as COe gas, making it possible to accurately measure COe gas.

Note that when an additional sensor section is provided, and if the additional sensor section is an n-th sensor section, further parameters a _1n , b _{1n ,} a _2n , and b _2n are determined for the n-th sensor in a preliminary step. . Then, by sequentially deriving the relational expression between gas concentration and sensitivity and the relational expression between the sensitivity (electromotive force) of the nth sensor to the mixed gas, X _COe and X _SO2 are calculated as in equations (1) and (2). A relational expression can be obtained using the electromotive force and parameters of each sensor.

[Aspect b: Sensor that utilizes temperature difference between sensing electrodes]
The COe gas sensor according to aspect b also includes a first sensor section and a second sensor section, and each sensor section includes a solid electrolyte substrate, a sensing electrode, and a counter electrode. The materials and manufacturing methods of the solid electrolyte substrate, the sensing electrode, and the counter electrode are also common, and the solid electrolyte substrate and the counter electrode may be one in number.

Aspect B differs from Aspect A in that the first sensing electrode and the second sensing electrode may have the same film thickness and do not need to have different thicknesses. Aspect b is different in that it includes a mechanism (hereinafter referred to as a temperature holding mechanism) that can maintain the first sensing electrode and the second sensing electrode at different temperatures. The temperature holding mechanism is not particularly limited, and may be a device that can hold the first sensing electrode at the first temperature and the second sensing electrode at the second temperature when performing detection, or a device that can hold the gas to be measured. It may be a relative positional relationship. Here, the temperature of the first sensing electrode is the temperature at the intersection of diagonals when the electrode pattern of the first sensing electrode excluding the lead part is rectangular, and is the temperature at the intersection of the diagonals, using an electrically insulated thermocouple or Temperature measured by a temperature resistor type sensor. The first temperature may be 580-650°C, preferably 600-620°C. Further, it is preferable that the second temperature is 30 to 100° C. higher than the first temperature.

An example of the temperature holding mechanism is a heater that can separately control the temperature of the first sensing electrode and the second sensing electrode. It may be a mechanism that includes the heater illustrated in aspect a, a temperature sensor, and a device that enables temperature control.

An example of the temperature maintenance mechanism is the positional relationship between the first sensing electrode and the second sensing electrode on the solid electrolyte substrate. The COe gas sensor according to this embodiment is usually used by being placed in a pipe or the like through which a gas to be measured flows through plant equipment or the like. At this time, the gas sensor can be configured such that the second sensing electrode is located closer to the gas to be measured than the first sensing electrode on the solid electrolyte substrate. In this case, a temperature sensor may be provided to detect the temperature of each sensing electrode.

According to a typical embodiment, in aspect b, the first sensing electrode and the second sensing electrode may have the same film thickness, surface area, material, and structure. However, one or more of these characteristics may be different.

Similarly to aspect a, the COe gas detection method using the COe gas sensor according to aspect b includes a preliminary step of determining sensor characteristics, a first step of obtaining the electromotive forces Em ₁ and Em ₂ , and a second step of calculating the gas concentration. process.

In the preliminary process, the dependence of the sensitivity (-Ewc/mV) on the COe gas concentration (ppm) and the dependence of the sensitivity (-Ewc/mV) on the SO ₂ gas concentration (ppm) are determined for each of the first sensor section and the second sensor section. ) Dependency is obtained by experiment. In aspect b, the first sensor section maintains the temperature of the first sensing electrode at a first temperature to obtain the gas concentration dependence of sensitivity, and the second sensor section maintains the temperature of the second sensing electrode at a second temperature. to obtain the gas concentration dependence of sensitivity. By operating the first sensor section and the _second sensor section under conditions in which the temperature of the sensing electrode is different, the inventor has determined that the , we found that the slopes of the graphs were different. Therefore, also in aspect b, the plot shown in FIG. 2 can be obtained from the first sensor section, and the plot shown in FIG. 3 can be obtained from the second sensor section. As in aspect a, the parameter representing the slope is a _ij , the parameter representing the X-axis intercept at which the sensitivity is 0 is b _ij , and both i and j are defined in the same manner as in aspect a. As a result, regarding the operation of each sensor section at the first temperature and the second temperature, using eight parameters a ₁₁ , b ₁₁ , a ₂₁ , b 21 , a _{12 ,} b ₁₂ , _{a 22 ,} and b ₂₂ , It is possible to derive a relational expression between the COe gas concentration, the SO ₂ gas concentration, and the electromotive force of each sensor section. The specific relational expressions are the same as the expressions (1) and (2) of aspect a.

In aspect b, the parameters derived in the preliminary step are unique to the sensor in view of individual differences in COe gas sensors, and are unique to the first temperature and the second temperature. Therefore, even when using a COe gas sensor, when changing the first temperature and second temperature, which are the measurement conditions during gas sensor operation, a preliminary process is performed to change the first temperature and second temperature to specific values. It is necessary to determine the values of eight unique parameters and derive the relational expressions (1) and (2). Further, in the preliminary step, by determining parameter values at a larger number of temperatures, detection can be performed using the temperature difference between two temperatures selected from them.

The first step using the COe gas sensor of aspect b is the same as aspect a except that the first sensing electrode is maintained at the first temperature and the second sensing electrode is maintained at the second temperature to obtain the electromotive forces Em ₁ and Em ₂ . It can be carried out in the same manner, and the second step can be carried out in the same manner as in aspect a.

Regarding aspect b, an additional sensor section can also be provided, parameters can be obtained under additional temperature conditions, a relational expression can be derived, and X _COe and X _SO2 can be calculated.

It is also possible to combine the sensors of embodiments a and b to form a single COe gas sensor.

According to the COe gas sensor according to the first embodiment of the present invention, by including at least two sensor sections in both aspects a and b, it is possible to accurately obtain the COe gas concentration without being affected by SO ₂ gas. can. Aspect a is particularly advantageous in that it is easy to maintain the same sensor temperature by making the positional relationship between the heater and the electrode similar. Embodiment b is particularly advantageous in that the conditions for film thickness can be made the same when applying and forming a thin layer during electrode formation, and the manufacturing conditions are simplified.

[Second embodiment: gas detection meter]
According to a second embodiment, the present invention relates to a gas detection meter. The gas detection meter according to the present embodiment is a gas detection meter in which the COe gas sensor of the first embodiment is built in a tubular casing having an open end, the first sensing electrode, the second sensing electrode, and the second sensing electrode. The counter electrode is a gas detector configured to be able to come into contact with the gas to be measured flowing in from the open end.

The gas detection meter includes a COe gas sensor and may optionally include an oxygen gas sensor. The gas detection meter can have a plurality of embodiments in which the structure of the solid electrolyte substrate and the arrangement of the plurality of electrodes are different. Each aspect will be described below with reference to illustrative drawings.

[Aspect 1]
4 and 5 are conceptual diagrams showing an example of a gas detector according to the second embodiment, FIG. 4 is a side view of a test tube-shaped solid electrolyte substrate, and FIG. 5 is a diagram showing the central axis of the solid electrolyte substrate. FIG. The gas detection meter 2 according to aspect 1 is a direct insertion type gas detection meter incorporating a structure in which the COe gas sensor according to aspect a of the first embodiment and the oxygen gas sensor are integrated. Referring to FIGS. 4 and 5, the casing 28 includes a test tube-shaped solid electrolyte substrate 21, a first sensing electrode 22, a second sensing electrode 24, a counter electrode/oxygen sensing electrode 23, and an oxygen sensing counter electrode 25. Additionally, COe detection sections 26 and 29 are connected to the first detection electrode 22, the second detection electrode 24, and the counter electrode/oxygen detection electrode 23, and the oxygen detection section is connected to the counter electrode/oxygen detection electrode 23 and the oxygen detection counter electrode 25. Furthermore, it is equipped with.

The solid electrolyte substrate 21 is a tubular structure with one end closed. More specifically, the solid electrolyte substrate 21 is formed in an elongated cylindrical shape that extends for a predetermined length with a constant diameter, and is open at its base end in the longitudinal direction and closed at its distal end in the longitudinal direction. , has a test tube shape. The first sensing electrode 22 , the second sensing electrode 24 , and the counter electrode/oxygen sensing electrode 23 are provided on the outer wall of the solid electrolyte substrate 21 .

The first sensing electrode 22 and the second sensing electrode 24 are arranged at substantially the same distance from the tip of the solid electrolyte substrate 21 . Thereby, the first sensing electrode 22 and the second sensing electrode 24 can be maintained at substantially the same temperature regardless of the presence or absence of the temperature control device.

The counter electrode/oxygen sensing electrode 23 is provided on the outer wall of the solid electrolyte substrate 21 at the tip of the test tube shape, apart from the first sensing electrode 22 and the second sensing electrode 24 . The first sensing electrode 22, the second sensing electrode 24, and the counter electrode/oxygen sensing electrode 23 are ionically conductively connected via the solid electrolyte substrate 21. The counter electrode/oxygen detection electrode 23 functions as a counter electrode common to the first detection electrode 22 and the second detection electrode 24 for COe detection, and also functions as a working electrode that comes into contact with the gas to be measured for oxygen detection. do.

The detection circuit 26 measures the electromotive force E _m1 between the first detection electrode 22 and the counter electrode/oxygen detection electrode 23, and the detection circuit 29 measures the electromotive force E m1 between the second detection electrode 24 and the counter electrode/oxygen detection electrode 23. Measure the electromotive force E _m2 .

The materials and formation methods of the first sensing electrode 22, the second sensing electrode 24, and the counter electrode/oxygen sensing electrode 23 may be as described in the first embodiment. The gas detection meter according to aspect 1 has the first sensing electrode 22, the second sensing electrode 24, and the counter electrode/oxygen sensing electrode 23 arranged as shown in the figure, so that the film thickness of the first sensing electrode 22 and the second sensing electrode 24 can be reduced. The sensor properties due to the difference allow COe and SO ₂ concentrations to be measured separately and accurately.

Next, an oxygen gas sensor, which is an optional component of the gas detector according to this embodiment, will be explained. The oxygen gas sensor includes a detection section including a solid electrolyte substrate 21 , a counter electrode/oxygen detection electrode 23 , an oxygen detection counter electrode 25 , and a detection circuit 27 . The material and structure of the counter electrode/oxygen sensing electrode 23 may be the same as the counter electrode of the first embodiment. The material and structure of the oxygen sensing counter electrode 25 may also be the same as the counter electrode of the first embodiment. The detection circuit 27 measures the electromotive force between the counter electrode/oxygen sensing electrode 23 and the oxygen sensing counter electrode 25. The oxygen sensing counter electrode 25 is provided on the inner wall of the solid electrolyte substrate 21 corresponding to the tip of the test tube shape, and is in a positional relationship generally opposing the counter electrode/oxygen sensing electrode 23 . That is, the oxygen sensing counter electrode 25 is ionically conductively connected to the counter electrode/oxygen sensing electrode 23 via the solid electrolyte substrate 21, and functions as an electrode that comes into contact with the calibration gas for oxygen sensing. The oxygen sensing counter electrode 25 is configured to be isolated from the atmosphere with which the counter electrode/oxygen sensing electrode 23 is in contact, that is, the atmosphere of the gas to be measured, by the solid electrolyte substrate 21 . The oxygen detection unit can detect oxygen by measuring the electromotive force caused by the difference between the oxygen concentration of the atmosphere with which the counter electrode/oxygen detection electrode 23 is in contact and the oxygen concentration with which the oxygen detection counter electrode 25 is in contact. The oxygen gas sensor is within the same casing as the COe gas sensor and can function separately and independently. Therefore, the gas detection meter according to this embodiment may or may not include an oxygen gas sensor.

The inner wall of the casing 28 may optionally be provided with a heater (not shown). The heater can be provided around the solid electrolyte substrate 21 in a manner capable of heating the solid electrolyte substrate 21, and can be connected to an external power source.

A gas detection method using a gas detector according to this embodiment will be explained. The gas detection meter according to this embodiment can be directly inserted into a flue or the like through which a high-temperature measurement target gas flows to measure COe, SO _2, and optionally oxygen concentrations. In this case, generally, the tip end of the solid electrolyte substrate 21, that is, the position where the counter electrode/oxygen sensing electrode 23 is provided, has the highest temperature, and the closer it gets to the base end, the lower the temperature becomes. Depends on distance from. The gas to be measured is introduced to the outer periphery of the solid electrolyte substrate 21 within the casing 28, and a calibration gas, for example, air, is introduced to the inner periphery of the solid electrolyte substrate 21. These introduction paths are hermetically blocked so that the two atmospheres do not mix. Then, by heating the first sensing electrode 22 and the second sensing electrode 24 to a predetermined temperature with a heater, the distance between the first sensing electrode 22 and the second sensing electrode 24 and the counter electrode described in the first embodiment is increased. The electromotive force of can be measured, and the COe and SO ₂ concentrations in the gas to be measured can be obtained. Furthermore, an electromotive force is generated in the solid electrolyte substrate 21 due to the difference in oxygen partial pressure between the measurement target gas in contact with the counter electrode/oxygen detection electrode 23 and the calibration gas in contact with the oxygen detection counter electrode 25, and this electromotive force is measured. By doing so, the oxygen concentration in the gas to be measured can be obtained. According to the gas detection meter according to this embodiment, since the counter electrode for COe and SO ₂ detection can also be used as an oxygen detection electrode, there is an advantage that accurate and simple measurement can be performed with a small number of electrodes.

This aspect is an arrangement mainly used in a gas detection meter including the COe gas sensor according to aspect a of the first embodiment. However, by providing a heater that can individually control the temperatures of the first sensing electrode 22 and the second electrode 24, the present invention can also be applied to a gas detection meter including the COe gas sensor according to aspect b of the first embodiment.

[Aspect 2]
6 to 8 are conceptual diagrams showing other examples of the gas detector according to the second embodiment. 6 is a side view of a test tube-shaped solid electrolyte substrate, FIG. 7 is a cross-sectional view passing through the central axis of the solid electrolyte substrate, and FIG. 8 is a cross-sectional view taken along line AA in FIG. 6. . The gas detection meter 3 according to aspect 2 is also a direct insertion type gas detection meter incorporating the COe gas sensor according to aspect a of the first embodiment and an oxygen gas sensor. Referring to FIGS. 6 to 8, the casing 37 includes a test tube-shaped solid electrolyte substrate 31, a first sensing electrode 32, a counter electrode 38 of the first sensing electrode, a second sensing electrode 39, and a counter electrode 40 of the second sensing electrode. . Further, an oxygen sensing electrode 33 and an oxygen sensing counter electrode 34 are provided. Also, a COe detection circuit 35 connected to the first sensing electrode 32 and the counter electrode 38 of the first sensing electrode, a COe detection circuit (not shown) connected to the second sensing electrode 39 and the counter electrode 40 of the second sensing electrode, It further includes an oxygen detection circuit 36 connected to the oxygen detection electrode 33 and the oxygen detection counter electrode 34.

Aspect 2 differs from Aspect 1 in the following points. The counter electrode 38 of the first sensing electrode and the counter electrode 40 of the second sensing electrode are provided separately. Further, the first sensing electrode 32, the counter electrode 38 of the first sensing electrode, the second sensing electrode 39, and the counter electrode 40 of the second sensing electrode are all on the outer wall surface of the solid electrolyte substrate 31, and the tip of the solid electrolyte substrate 31 is located substantially equidistant from the section. Referring to FIG. 8, the four electrodes are also arranged equidistantly along the outer periphery of the solid electrolyte substrate 31 and adjacent to a pair of sensing electrodes and a counter electrode that are ionically conductively connected. The oxygen sensing electrode 33 and the oxygen sensing counter electrode 34, which are optional components, are provided separately from the electrode for COe sensing, so that the electrodes are not shared between different detection circuits.

In the second aspect as well, the gas detection method is substantially the same as in the first aspect, and the same effects can be obtained. Furthermore, as in the first aspect, the second aspect can also be applied to the gas detection meter including the COe gas sensor according to the aspect b of the first embodiment by providing a heater or the like.

Aspect 2 is particularly advantageous in that, when controlling the oxygen sensing electrode and the COe sensing electrode to different temperatures, it is possible to use a simple method of setting, for example, the distance from the heater.

[Aspect 3]
FIG. 9 is a conceptual diagram showing yet another example of the gas detector according to the second embodiment. The gas detector 4 is a direct insertion type gas detector in which a COe gas sensor 40 according to aspect a of the first embodiment and an oxygen gas sensor 46 are built into a tubular casing 49 having an open end as separate structures. be.

The COe gas sensor 40 has a flat solid electrolyte substrate 41 on which a first sensing electrode 42 , a counter electrode 43 of the first sensing electrode, a second sensing electrode 44 , and a counter electrode 45 of the second sensing electrode are arranged at the tip of the solid electrolyte substrate 41 . located substantially equidistant from the section. The tip of the flat solid electrolyte substrate 41 refers to the end near the open end of the casing 49. The oxygen gas sensor 47 has the same structure as Aspect 1 and Aspect 2, with an oxygen detection electrode 48 provided at the tip of the outer wall surface of a test tube-shaped solid electrolyte substrate 47, and an oxygen detection counter electrode (not shown) provided at the tip of the inner wall surface. It is. It also includes a detection circuit (not shown) that connects each electrode.

Aspect 3 differs from Aspect 2 in that solid electrolyte substrate 41 on which electrodes for COe detection are provided is configured in a flat plate shape and is provided as a separate structure from oxygen gas sensor 47. With this configuration, in particular, it is possible to manufacture the oxygen sensor and the COe sensor independently, and the sensor characteristics can also be evaluated independently. It is advantageous in that it can be kept high.

In the third aspect as well, the gas detection method is substantially the same as in the first aspect, and the same effects can be obtained. Further, as in the first aspect, the third aspect can also be applied to the gas detection meter including the COe gas sensor according to the aspect b of the first embodiment by providing a heater or the like.

[Aspect 4]
FIG. 10 is a conceptual diagram showing yet another example of the gas detector according to the second embodiment. The gas detection meter 5 includes a first sensor section 50, a second sensor section 54 of the COe gas sensor according to aspect b of the first embodiment, and an oxygen gas sensor 58 as separate structures in a tubular casing 61 having an open end. It is a built-in direct insertion type gas detection meter.

The COe gas sensor includes a first sensor section 50 in which a first sensing electrode 53 and a counter electrode 52 of the first sensing electrode are provided on a flat solid electrolyte substrate 51, and a first sensor section 50 in which a first sensing electrode 53 and a counter electrode 52 of the first sensing electrode are provided on a flat solid electrolyte substrate 51. The second sensing electrode 57 and the second sensor section 54 provided with the counter electrode 56 of the second sensing electrode are formed as separate structures. The first sensor section 50 and the second sensor section 54 are equipped with heaters (not shown) and are configured to be able to independently control their temperatures. The oxygen gas sensor 58 has the same structure as Embodiment 3, with an oxygen sensing electrode 60 provided at the tip of the outer wall surface of a test tube-shaped solid electrolyte substrate 59, and an oxygen sensing counter electrode (not shown) provided at the tip of the inner wall surface. It also includes a detection circuit (not shown) that connects each electrode.

Aspect 4 differs from Aspect 3 in that the first sensor section 50 and the second sensor section 54 are provided on different solid electrolyte substrates. By providing the first sensor section 50 and the second sensor section 54 on independent and separate solid electrolyte substrates, the first sensing electrode 53 can be accurately controlled at the first temperature, and the second sensing electrode 57 can be accurately controlled at the second temperature. , and it is possible to accurately detect COe using the temperature difference characteristics of the electrodes according to aspect b. In the fourth embodiment, the flow of the gas to be measured and the method of oxygen gas detection are substantially the same as those in the first embodiment, and the same effects can be obtained.

The gas detection meter according to the present embodiment can detect COe, SO ₂ , and optionally oxygen with high sensitivity with a single device, and can be advantageously used for industrial gas measurement. .

(Example 1)
A COe gas sensor according to aspect a of the first embodiment of the present invention was manufactured. An yttria-stabilized zirconia substrate was used as the solid electrolyte substrate, and a first sensing electrode, a second sensing electrode, and a counter electrode were formed on the substrate. The arrangement of the solid electrolyte substrate, first sensing electrode, second sensing electrode, and counter electrode was the same as in the embodiment shown in FIGS. 6 to 8. The first sensing electrode, the second sensing electrode, and the counter electrode all had the same composition, molded using a paste in which a mixture of Pt alloy particles and yttria-stabilized zirconia particles was dispersed in a solvent. Furthermore, Pt wires were used as wiring and fixed onto the electrodes using the respective electrode materials. Next, by firing these in the atmosphere at 1300° C., a COe gas sensor including a first sensor portion and a second sensor portion was manufactured. The film thickness of each electrode after firing was as shown in Table 1 below.

In the preliminary process, the manufactured COe gas sensor was placed in a furnace tube heated in a tube furnace, gas was passed through it, and sensor characteristics were measured. The gas to be measured was flowed at 300 ccm through a core tube with an inner diameter of 28 mm, and the flow rate was 8.1 mm/s. The COe gas used to measure the sensor characteristics was a mixture of hydrogen gas and CO gas at a molar ratio of 1:1. The ambient temperature was 650°C. As a result of creating plots according to FIGS. 2 and 3, eight parameters were determined as shown in Table 1 below, and relational expressions (1) and (2) were obtained.

Using the COe gas sensor of this example, the electromotive force E m1 of the first sensor section and the electromotive force E _m1 of the second sensor section were calculated under the same conditions as the measurement conditions of the sensor characteristics for the target gases of known concentrations of COe gas and SO ₂ gas. The electromotive force E _m2 was measured. Next, the gas concentration was calculated using the derived relational expression. As a result, the difference between the calculated concentration and the known concentration was within an acceptable range.

(Example 2)
A COe gas sensor according to aspect b of the first embodiment of the present invention was manufactured. The materials and manufacturing method of the electrodes were the same as in Example 1. The arrangement of the solid electrolyte substrate, the first sensing electrode, the second sensing electrode, and the counter electrode was the same as in the embodiment shown in FIG. 10, and the temperature maintenance mechanism was as follows. A COe gas sensor including a first sensor section and a second sensor section was manufactured by installing a heater that separately heats the first sensing electrode and the second sensing electrode. The film thickness of each electrode after firing was as shown in Table 2 below. In the preliminary step, gas was flowed under the same conditions as in Example 1, the first sensing electrode and the second sensing electrode were heated to a predetermined temperature listed in Table 2, and sensor characteristics were measured. As a result of creating plots according to FIGS. 2 and 3, eight parameters were determined as shown in Table 2 below, and relational expressions (1) and (2) were obtained.

Using the COe gas sensor of this example, the electromotive force E m1 of the first sensor section and the electromotive force E _m1 of the second sensor section were calculated under the same conditions as the measurement conditions of the sensor characteristics for the target gases of known concentrations of COe gas and SO ₂ gas. The electromotive force E _m2 was measured. Next, the gas concentration was calculated using the derived relational expression. As a result, as in Example 1, the difference between the calculated concentration and the known concentration was within the allowable range.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention as described in the claims. - Can be changed.

The COe gas sensor according to the present invention can be inserted into the flue of a boiler or the like to accurately monitor the COe concentration in combustion exhaust gas. It is particularly suitable for systems using raw materials with high sulfur content, such as coal fuel. Furthermore, by combining it with existing oxygen concentration sensors, it becomes possible to construct combustion control systems such as boilers, contributing to energy savings.

1 COe gas sensor 10 solid electrolyte substrate, 11 first sensing electrode, 12 counter electrode, 13 first sensor section 14 solid electrolyte substrate, 15 second sensing electrode, 16 counter electrode, 17 second sensor section

Claims (9)

a first sensor section including a first sensing electrode and a counter electrode that are ionically conductively connected via a solid electrolyte substrate;
A COe gas sensor including a second sensor section including a second sensing electrode and a counter electrode connected in an ionically conductive manner via a solid electrolyte substrate,
a) the thickness of the first sensing electrode is smaller than the thickness of the second sensing electrode, or
b) comprising a mechanism capable of keeping the temperature of the first sensing electrode lower than the temperature of the second sensing electrode;
COe gas sensor. The first sensing electrode and the second sensing electrode are sintered bodies containing alloy particles containing platinum and solid electrolyte particles, and the counter electrode is a sintered body containing metal particles containing platinum and solid electrolyte particles. The COe gas sensor according to claim 1. The COe gas sensor according to claim 1, wherein the thickness of the first sensing electrode is 10 μm or more thinner than the thickness of the second sensing electrode. The COe gas sensor according to claim 3, wherein the first sensing electrode has a film thickness of 15 μm to 90 μm. The COe gas sensor according to claim 1, wherein the mechanism is a heating unit that can independently control the temperatures of the first sensing electrode and the second sensing electrode. A gas detection meter incorporating the COe gas sensor according to claim 1 in a tubular casing having an open end, wherein the first sensing electrode, the second sensing electrode, and the counter electrode are connected from the open end. A gas detection meter configured to be able to come into contact with the inflowing gas to be measured. further comprising an oxygen gas sensor in the tubular casing having the open end;
The oxygen gas sensor includes a solid electrolyte substrate and at least a pair of electrodes connected in an ionically conductive manner via the solid electrolyte substrate,
The pair of electrodes is an oxygen sensing electrode made of a sintered body containing metal particles containing platinum and solid electrolyte particles, and an oxygen detection electrode made of a sintered body containing metal particles containing platinum and solid electrolyte particles. including the opposite pole,
The gas detection according to claim 6, wherein the oxygen detection electrode is configured to be able to contact the gas to be measured flowing in from the open end, and the counter electrode for oxygen detection is isolated from the atmosphere of the gas to be measured. Total. A method for detecting COe gas using the gas sensor according to claim 1,
obtaining an electromotive force Em ₁ of the first sensor section and an electromotive force Em ₂ of the second sensor section;
Parameters a ₁₁ , a ₂₁ , b ₁₁ , b ₂₁ determined in advance for the first sensor section, parameters a ₁₂ , a ₂₂ , b ₁₂ , b ₂₂ determined in advance for the second sensor section, Em ₁ , Em ₂ , calculating the COe gas concentration Xcoe and the _SO2 gas concentration _XSO2 ,
a ₁₁ and a ₁₂ are constants indicating the concentration dependence of COe gas electromotive force,
b ₁₁ and b ₁₂ are constants indicating the sensitivity limit concentration of COe gas,
a ₂₁ and a ₂₂ are constants indicating the concentration dependence of the SO ₂ gas electromotive force,
b ₂₁ and b ₂₂ are constants indicating the sensitivity limit concentration of SO ₂ gas,
Detection method. The constant is a constant determined by setting the first sensing electrode at a first temperature and setting the second sensing electrode at a second temperature,
The step of obtaining the electromotive force is carried out with the first sensing electrode at a first temperature and the second sensing electrode at a second temperature,
The method of claim 8, wherein the first temperature is 580-650°C and the second temperature is 30-100°C higher than the first temperature.

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