JP5119212B2 - Ammonia concentration detection method - Google Patents

Description

  The present invention relates to a method for detecting the concentration of ammonia in a gas.

In recent years, development of a urea-added SCR system for purifying NOx (nitrogen oxide) in exhaust gas has been promoted in internal combustion engines such as automobiles (particularly diesel engines).
The urea addition SCR system adds urea as a reducing agent upstream of a selective reduction type NOx purification catalyst (SCR catalyst) provided in an exhaust pipe. In the NOx purification catalyst, the exhaust gas is purified by selectively reducing NOx with ammonia generated by decomposition of the added urea.

In the urea-added SCR system, the ammonia concentration in the exhaust gas is measured using a gas sensor or the like. And the addition amount of urea is adjusted according to the measured ammonia concentration. In order to efficiently purify the exhaust gas, it is necessary to accurately measure the ammonia concentration in the exhaust gas and accurately adjust the amount of urea added.
Here, as a method for detecting the ammonia concentration in the gas to be measured (for example, exhaust gas), various methods have been conventionally proposed.

For example, in Patent Document 1, after oxygen concentration is controlled to be constant using an oxygen ion conductor, ammonia is oxidized by a catalyst, and the remaining oxygen concentration is obtained from a limit current, and consumed when ammonia is oxidized. A method for detecting the ammonia concentration from the amount of oxygen is disclosed.
Patent Document 2 discloses a method of detecting ammonia concentration by a mixed potential method in which a potential generated between a reference electrode serving as a reference and a measurement electrode is measured using a proton conductor.

JP 2000-121604 A Special Table 2003-518619

  However, in the method of Patent Document 1, the ammonia concentration is indirectly measured by changing the oxygen concentration using an oxygen ion conductor. That is, the ammonia concentration cannot be measured directly. Therefore, the measurement accuracy is lower than that in the case of direct measurement. In addition, it is difficult to measure only the ammonia concentration in a gas containing a hydrogen-containing gas component (for example, hydrocarbon or the like) other than ammonia or hydrogen.

  In the method of Patent Document 2, the ammonia concentration is measured using a mixed potential method. However, in this method, the relationship between the gas concentration and the generated potential is not linear. Therefore, there is a problem that the measurement accuracy is lowered particularly at a low gas concentration. In addition, when hydrogen-containing gas components other than ammonia (such as hydrocarbons) or hydrogen are present in the gas, the proton conductor is sensitive to these, and it is difficult to selectively detect the ammonia concentration. It is.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an ammonia concentration detection method that can selectively and directly detect the ammonia concentration in a gas with high accuracy.

The present invention relates to a proton conductive solid electrolyte body, a measured gas side electrode and a reference gas side electrode provided on one surface and the other surface of the proton conductive solid electrolyte body, and the measured gas side Using a gas sensor element comprising a gas chamber to be measured for introducing a gas to be measured facing the electrode and a gas chamber for introducing the reference gas facing the reference gas side electrode, A method for detecting ammonia concentration,
In the measured gas chamber held at a temperature higher than the ignition point of the hydrogen-containing gas component other than ammonia and the ignition point of hydrogen in the measured gas and lower than the ignition point of ammonia, the measured gas A gas combustion step of burning hydrogen-containing gas components other than ammonia and hydrogen in the gas to be measured,
A voltage is applied between the measured gas side electrode and the reference gas side electrode, and based on the magnitude of the current flowing between both electrodes via the proton conductive solid electrolyte body, A method for detecting ammonia concentration, comprising: a concentration detecting step for detecting ammonia concentration.

  In the present invention, in the gas combustion step, the temperature in the measured gas chamber is higher than the ignition point of a hydrogen-containing gas component other than ammonia and the ignition point of hydrogen (about 500 ° C.) in the measured gas, and It is kept at a temperature lower than the ignition point of ammonia (about 651 ° C.). By introducing the measured gas into the measured gas chamber whose temperature has been adjusted in this way, the hydrogen-containing gas component other than ammonia and hydrogen in the measured gas are combusted. At this time, ammonia remains in the measured gas without burning.

  Next, in the concentration detection step, the gas to be measured after combustion is introduced onto the gas to be measured side electrode, and a voltage is applied between the electrodes so that the gas to be measured does not burn. Protons are released from ammonia, which is the remaining hydrogen-containing gas component, and a current (limit current) corresponding to the amount of the protons flows between the electrodes via the proton solid electrolyte body. At this time, the magnitude of the current flowing between the electrodes depends on the ammonia concentration in the gas to be measured. Therefore, by measuring the magnitude of this current, the ammonia concentration in the measured gas can be detected.

  That is, in the present invention, the current (limit current) flowing through the proton solid electrolyte body between the electrodes is measured by ammonia, which is a hydrogen-containing gas component remaining without being burned in the gas to be measured. Therefore, ammonia in the measurement gas can be selectively and directly detected. Therefore, the ammonia concentration in the measurement gas can be detected with high accuracy.

  As described above, according to the present invention, it is possible to provide an ammonia concentration detection method capable of selectively and directly detecting the ammonia concentration in the gas with high accuracy.

FIG. 3 is a cross-sectional view of the gas sensor element in the longitudinal direction in the first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 9 is an explanatory diagram showing the relationship between the oxygen concentration and the limit current for each gas type in Example 2. Explanatory drawing which shows the relationship between the gas kind in Example 2, its density | concentration, and a limiting current. Explanatory drawing which shows the relationship between the gas kind in Example 2, its density | concentration, and a limiting current. Explanatory drawing which shows the relationship between ammonia concentration in Example 2, and a limiting current.

In the present invention, in the gas combustion step, it is preferable to burn at least hydrocarbons and hydrogen which are hydrogen-containing gas components.
In this case, the effect of the present invention that the ammonia concentration in the gas to be measured can be selectively and directly detected accurately can be further exhibited.

As the aforementioned hydrocarbon, ethylene (C ₂ H _4, ignition point: about 450 ° C.), ethane (C ₂ H _6, ignition point: about 530 ° C.), propane (C ₃ H _8, ignition point: about 432 C), butane (C ₄ H ₁₀ , ignition point: about 430 ° C.), formaldehyde (HCHO, ignition point: about 424 ° C.), acetaldehyde (CH ₃ CHO, ignition point: about 185 ° C.) and the like.

Needless to say, in the gas combustion step, it is preferable that substantially all the hydrogen-containing gas components other than ammonia and hydrogen in the gas to be measured are burned.
In this case, the effect of the present invention that the ammonia concentration in the gas to be measured can be selectively and directly detected accurately can be further exhibited.

Further, in the gas combustion step, the gas to be measured is sufficiently and reliably burned between the time when the gas to be measured is introduced into the gas chamber to be measured and the time when the gas reaches the electrode to be measured. It is preferable to ensure a sufficient distance from the measurement gas chamber where the measurement gas is introduced to the measurement gas side electrode.
In this case, hydrogen-containing gas components other than ammonia and hydrogen in the measurement gas can be sufficiently and reliably burned, and the ammonia concentration in the measurement gas can be detected with higher accuracy.

In the gas combustion step, it is preferable that the amount of the measurement gas introduced into the measurement gas chamber is kept constant. For example, this can be realized by providing a diffusion resistance layer that allows the gas to be measured to pass under a predetermined diffusion resistance between the outside of the gas sensor element and the gas chamber to be measured.
In this case, the ammonia concentration in the measurement gas can be detected with higher accuracy.

Moreover, it is preferable that the temperature in the measured gas chamber is maintained at 600 ° C. or higher.
In this case, in the gas combustion step, hydrogen-containing gas components other than ammonia and hydrogen in the gas to be measured can be sufficiently and reliably burned. Thereby, the detection accuracy of the ammonia concentration in the measurement gas can be further enhanced.

The temperature in the gas chamber to be measured is preferably adjusted by a heating element that generates heat by energization provided in the gas sensor element.
In this case, the temperature in the measurement gas chamber can be adjusted quickly and easily by the heating element. Thereby, the measurement gas in the gas combustion process can be burned well.

The proton conductive solid electrolyte is preferably made of a material having a basic structure of at least one of SrZrO ₃ , SrCeO _3, SrTiO _3, and CaZrO ₃ (claim 4).
In this case, the proton conductive solid electrolyte body has excellent heat resistance. Therefore, it is particularly effective in the ammonia concentration detection method of the present invention in which the gas chamber to be measured has a high temperature.

In addition, as the proton conductor solid electrolyte body, specifically, the above-described SrZrO ₃ , SrCeO _3, SrTiO ₃ , CaZrO _3, etc. have a basic structure, and a part of Zr, Ce, Ti, etc. in the basic structure is used. A material substituted with Yb, In, or the like can be used.

The gas to be measured is preferably exhaust gas from a diesel engine.
That is, oxygen is sufficiently present in the exhaust gas of the diesel engine. For this reason, the gas under measurement in the gas combustion step can be favorably burned.

  Moreover, if the ammonia concentration detection method of this invention is used, the ammonia concentration in the said to-be-measured gas can be detected accurately. Therefore, the ammonia concentration detection method of the present invention is applied to a urea-added SCR system that purifies NOx (nitrogen oxides) in exhaust gas from a diesel engine and requires accurate measurement of ammonia concentration in exhaust gas. It is particularly effective to apply.

Example 1
An ammonia concentration detection method according to an embodiment of the present invention will be described with reference to the drawings.
The ammonia concentration detection method of this example is performed using the gas sensor element 1 shown in FIGS. The gas sensor element 1 includes a proton conductive solid electrolyte body 13, a measured gas side electrode 14 and a reference gas side electrode 15 provided on one surface and the other surface of the proton conductive solid electrolyte body 13, respectively, A measurement gas chamber 140 that introduces a measurement gas G facing the gas side electrode 14 and a reference gas chamber 150 that faces the reference gas side electrode 15 and introduces a reference gas are provided.
Hereinafter, the gas sensor element 1 will be described in detail.

  The gas sensor element 1 of this example is attached to an exhaust pipe of a diesel engine, and is built in a gas sensor that detects an ammonia concentration in exhaust gas. The gas sensor is applied to a urea-added SCR system that purifies NOx (nitrogen oxide) in exhaust gas. The urea addition SCR system adjusts the amount of urea added to the exhaust gas according to the ammonia concentration in the exhaust gas detected by the gas sensor.

As shown in FIGS. 1 and 2, in the gas sensor element 1, a measured gas side electrode 14 made of platinum (Pt) is provided on one surface of a proton conductive solid electrolyte body 13 made of SrZr _0.9 Yb _0.1 O _3. It has been. A reference gas side electrode 15 made of platinum (Pt) is provided on the other surface of the proton conductive solid electrolyte body 13.

  Further, on the reference gas side electrode 15 side of the proton conductive solid electrolyte body 13, a reference gas chamber forming layer 16 made of alumina ceramics that is electrically insulating and dense and does not transmit gas is laminated. The reference gas chamber forming layer 16 is provided with a groove 160 that forms the reference gas chamber 150. The reference gas chamber 150 is configured to be able to introduce a reference gas. In this example, the reference gas is the atmosphere.

  A heater substrate 17 is laminated on the surface of the reference gas chamber forming layer 16 opposite to the proton conductive solid electrolyte body 13. A heater (heating element) 18 made of platinum (Pt) is provided on the heater substrate 17 so as to face the reference gas chamber forming layer 16. The heater 18 can generate heat when energized, heats the gas sensor element 1 to an activation temperature, and adjusts the temperature of the gas chamber 140 to be described later to a predetermined temperature.

Further, a measured gas chamber forming layer 12 having an opening 120 is laminated on the measured gas side electrode 14 side of the proton conductive solid electrolyte body 13. At one end in the longitudinal direction of the gas chamber forming layer 12 to be measured, a diffusion resistance layer 121 made of gas permeable alumina ceramics having a high porosity is provided.
In addition, a shielding layer 11 made of alumina ceramic that is electrically insulating and dense and does not transmit gas is laminated on the surface of the measured gas chamber forming layer 12 opposite to the proton conductive solid electrolyte body 13. Has been.

  A gas chamber 140 to be measured is formed at a location covered by the shielding layer 11, the opening 120 of the gas chamber forming layer 12 and the proton conductive solid electrolyte body 13. The measured gas chamber 140 is configured to be able to introduce the measured gas G that has passed through the diffusion resistance layer 121 under a predetermined diffusion resistance. The gas to be measured G in this example is exhaust gas from a diesel engine.

Next, an ammonia concentration detection method using the gas sensor element 1 having the above-described configuration and its function and effect will be described.
The ammonia concentration detection method of this example includes the following gas combustion step and concentration detection step.
In the gas combustion process, the measurement gas chamber 140 is held at a temperature higher than the ignition point of the hydrogen-containing gas component other than ammonia and the ignition point of hydrogen in the measurement gas G and lower than the ignition point of ammonia. By introducing the measurement gas G, hydrogen-containing gas components other than ammonia and hydrogen in the measurement gas G are combusted.
In the concentration detection step, a voltage is applied between the measured gas side electrode 14 and the reference gas side electrode 15 and based on the magnitude of the current flowing between the electrodes 14 and 15 via the proton conductive solid electrolyte body 13. Then, the ammonia concentration in the measurement gas G is detected.
This will be described in detail below.

  First, in the gas combustion process, the heater 18 is heated by energization, and the temperature in the measured gas chamber 140 is kept at a predetermined temperature. Specifically, the ignition point (about 530 ° C. or less) of hydrogen-containing gas components other than ammonia (for example, hydrocarbons such as ethylene, ethane, propane, butane, formaldehyde, and acetaldehyde) and hydrogen ignition in the gas G to be measured The temperature is kept higher than the point (about 500 ° C.) and lower than the ignition point of ammonia (about 651 ° C.). In this example, the temperature in the measured gas chamber 140 was maintained at 600 ° C.

  Then, the measurement gas G is introduced into the measurement gas chamber 140 held at a predetermined temperature from the outside of the gas sensor element 1 through the diffusion resistance layer 121 having a predetermined diffusion resistance. As a result, the hydrogen-containing gas component other than ammonia and hydrogen whose ignition point is lower than the temperature in the measured gas chamber 140 are combusted. At this time, ammonia remains in the measurement gas G without burning.

Next, in the concentration detection step, the measured gas G after combustion is introduced onto the measured gas side electrode 14, and a voltage is applied between the electrodes 14 and 15. As a result, protons are released from ammonia, which is a hydrogen-containing gas component remaining in the measurement gas G without being burned, and a current (limit current) corresponding to the amount of the protons is generated between the electrodes 14 and 15. It flows through the conductive solid electrolyte body 13.
At this time, the magnitude of the current flowing between the electrodes 14 and 15 depends on the ammonia concentration in the measurement gas G. Therefore, the magnitude of this current is measured, and the ammonia concentration in the measured gas G is detected.

  As described above, in the ammonia concentration detection method of this example, hydrogen-containing gas components other than ammonia and hydrogen in the gas G to be measured are burned. Then, a proton conductive solid electrolyte is used to measure the current (limit current) flowing between the electrodes 14 and 15 depending on ammonia, which is a hydrogen-containing gas component that remains without being burned in the gas G to be measured. To do. Thereby, the ammonia concentration in the measurement gas G can be selectively and directly detected. Therefore, the ammonia concentration in the measurement gas G can be detected with high accuracy.

  In this example, in the gas combustion process, the amount of the measurement gas G introduced into the measurement gas chamber 140 is adjusted to be constant. That is, the diffusion resistance layer 121 that allows the gas G to be measured to pass through under a predetermined diffusion resistance is provided between the outside of the gas sensor element 1 and the gas chamber 140 to be measured. Therefore, the ammonia concentration in the measurement gas G can be detected with higher accuracy.

  Further, the temperature in the measured gas chamber 140 is kept at 600 ° C. or higher. Therefore, in the gas combustion process, the hydrogen-containing gas component other than ammonia and hydrogen in the measurement gas G can be combusted sufficiently and reliably. Thereby, the ammonia concentration in the gas G to be measured can be detected more selectively and with high accuracy.

  Further, the temperature in the measured gas chamber 140 is adjusted by a heater (heating element) 18 that generates heat by energization provided in the gas sensor element 1. Therefore, the temperature adjustment in the measured gas chamber 140 can be performed quickly and easily by the heater 18. Thereby, combustion of the measurement gas G in the gas combustion process can be performed satisfactorily.

The proton conductive solid electrolyte body 13 is composed of SrZr _0.9 Yb _0.1 O ₃ having SrZrO ₃ as a basic structure and a part of Zr in the basic structure substituted with Yb. Therefore, the proton conductive solid electrolyte body 13 has excellent heat resistance and proton conductivity at the same time. This is particularly effective in the ammonia concentration detection method of this example in which the temperature in the measured gas chamber 140 is high.

The gas to be measured G is exhaust gas from a diesel engine. Here, oxygen is sufficiently present in the exhaust gas of the diesel engine. Therefore, combustion of the measurement gas G in the gas combustion process can be performed satisfactorily.
Moreover, the ammonia concentration detection method of this example can accurately detect the ammonia concentration in the exhaust gas that is the gas G to be measured. Therefore, it is particularly effective to apply this ammonia concentration detection method to a urea-added SCR system that purifies NOx (nitrogen oxide) in exhaust gas from a diesel engine.

  Thus, according to this example, it is possible to provide an ammonia concentration detection method that can selectively and directly accurately detect the ammonia concentration in the gas.

(Example 2)
In this example, a test for confirming the effectiveness of the ammonia concentration detection method of the present invention was conducted.
In this example, first, as shown in FIG. 3, for the gas to be measured including one kind of the target gas, the combustion state of each gas is determined from the relationship between the oxygen concentration in the gas to be measured and the limit current value. confirmed.
The target gas is ammonia (NH ₃ , ignition point: about 651 ° C.), hydrogen (H ₂ , ignition point: about 500 ° C.), ethylene (C ₂₎ of hydrocarbons that are hydrogen-containing gas components other than ammonia. H ₄ , ignition point: about 450 ° C.).

Specifically, platinum (Pt) electrodes are respectively formed on both sides of a pellet made of the proton conductive solid electrolyte body SrZr _0.9 Yb _0.1 O ₃ , and a small hole is formed in the center so as to cover the platinum electrode on one side. A test sample provided with the provided diffusion resistor was used. A test sample was placed in a tubular furnace, a temperature G was set to 600 ° C., a measurement gas G was introduced, and a predetermined voltage was applied between the pair of platinum electrodes, thereby measuring a limit current value. And the combustion state (concentration change) of each gas was confirmed from the change of the limit current value with respect to the oxygen concentration in the measurement gas.
The concentration of each gas (ammonia (NH ₃ ), hydrogen (H ₂ ), ethylene (C ₂ H ₄ )) contained in the measurement gas G is as shown in FIG.

The measurement results are shown in FIG. In the figure, the vertical axis represents the limit current (mA) and the horizontal axis represents the oxygen concentration (ppm).
As shown in the figure, the limit current value of hydrogen (H ₂ ) and ethylene (C ₂ H ₄ ) decreases as the oxygen concentration increases, that is, the concentration decreases. This indicates that hydrogen (H ₂ ) and ethylene (C ₂ H ₄ ) are burning.

On the other hand, ammonia (NH ₃ ) has an almost constant limit current value even when the oxygen concentration changes in the region where the oxygen concentration is 750 ppm or more, that is, there is almost no change in the concentration. This indicates that ammonia (NH ₃ ) remains without burning.
Note that the limit current value when the oxygen concentration is 0 ppm is slightly higher than the limit current value in the region where the oxygen concentration is 750 ppm or more. This is due to the catalytic action of platinum (Pt) used as the electrode. It is thought to have influenced. In other words, in an atmosphere where oxygen is present, ammonia whose ignition point (about 651 ° C.) is higher than the measurement temperature (600 ° C.) present near the electrode is oxidized by the catalytic action of the electrode, and the ammonia concentration decreases. In an atmosphere with an oxygen concentration of 0 ppm, this is not the case, and it is considered that the above phenomenon occurs.

Next, as shown in FIGS. 4 and 5, the gas sensor element 1 of Example 1 was used to measure and compare the limit current values of various measured gases G (samples A1 to A3 and samples B1 to B3). .
Specifically, various measured gases G were introduced into a measured gas chamber 140 held at a predetermined temperature (600 ° C.), and the limit current value was measured. And the detection accuracy of ammonia concentration was confirmed by comparing the measured limiting current value.
In addition, the gas kind contained in various measurement gas G (sample A1-A3, sample B1-B3) and its density | concentration are as showing in FIG. 4, FIG.

The measurement results are shown in FIGS. In the figure, the vertical axis represents limit current (mA), and the horizontal axis represents various gases to be measured G (samples A1 to A3, samples B1 to B3).
As shown in FIG. 4, when the sample A1 and the sample A2 are compared, the limit current value of the sample A2 is lower than that of the sample A1. This indicates that hydrogen (H ₂ ) in the measurement gas G is combusted by oxygen (O ₂ ) contained in the sample A2.
When the sample A2 and the sample A3 are compared, the limit current values are almost the same value. Here, the sample A3 is obtained by measuring the concentration of ammonia (NH ₃ ) in the measurement gas G that does not contain hydrogen (H ₂ ). Therefore, in the sample A2, hydrogen (H ₂ ) in the measurement gas G is almost entirely combusted, and the concentration of ammonia (NH ₃ ) remaining unburned from the measurement gas G after combustion is accurate. It shows that it is well detected.

Further, as shown in FIG. 5, when the sample B1 and the sample B2 are compared, the limit current value of the sample B2 is lower than that of the sample B1. This indicates that ethylene (C ₂ H ₄ ) in the measurement gas G is combusted by oxygen (O ₂ ) contained in the sample B2.
When the sample B2 and the sample B3 are compared, the limit current values are almost the same value. Here, the sample B3 is obtained by measuring the concentration of ammonia (NH ₃ ) in the measurement gas G that does not contain ethylene (C ₂ H ₄ ), which is a hydrogen-containing gas component. Therefore, in the sample B2, ethylene (C ₂ H ₄ ) in the measurement gas G is almost entirely burned, and the concentration of ammonia (NH ₃ ) remaining without burning from the measurement gas G after the combustion. Is detected with high accuracy.

Next, as shown in FIG. 6, for various gases to be measured G (samples C <b> 1 to C <b> ₃ ), the concentration of ammonia (NH ₃ ) was changed and the limit current values were measured and compared.
Specifically, various measured gases G were introduced into a measured gas chamber 140 held at a predetermined temperature (600 ° C.), and the limit current value was measured. And the detection accuracy of ammonia concentration was confirmed by comparing the measured limiting current value.
In addition, the gas kind contained in various measurement gas G (samples C1-C3) and its density | concentration are as showing in FIG. The concentration of ammonia (NH ₃ ) was 300 ppm, 500 ppm, 700 ppm, and 1000 ppm.

The measurement results are shown in FIG. In the figure, the vertical axis represents the limit current (mA), and the horizontal axis represents the NH ₃ concentration (ppm).
As shown in the figure, when the samples C1 to C3 are compared, even if the concentration of ammonia (NH ₃ ) in the gas G to be measured changes, the measured current values are almost the same. Here, the sample C1 is obtained by measuring the concentration of ammonia (NH ₃ ) in the gas G to be measured that does not contain ethylene (C ₂ H ₄ ) and hydrogen (H ₂ ), which are hydrogen-containing gas components. . Therefore, almost all of the hydrogen (H ₂ ) or ethylene (C ₂ H ₄ ) in the gas G to be measured is burned by the oxygen (O ₂ ) contained in each of the samples C 2 and C 3. This shows that the concentration of ammonia (NH ₃ ) remaining without burning from the later measured gas G is detected with high accuracy.
Further, the relationship between the limit current value and the ammonia (NH ₃ ) concentration is linear (proportional). Therefore, the concentration of ammonia (NH ₃ ) can be accurately detected by measuring the limit current value.

From the above results, when the ammonia concentration detection method of the present invention is used, even if hydrogen (H ₂ ) or hydrocarbon (for example, C ₂ H ₄ ) is contained in the gas to be measured G, ammonia (NH ₃ ) Was selectively detected with high accuracy.
In addition, the concentration of ammonia (NH ₃ ) in the gas G to be measured is determined by measuring the magnitude of the current (limit current value) that flows depending on ammonia (NH ₃ ) using a proton conductive solid electrolyte. It was found that it can be detected directly and accurately.

DESCRIPTION OF SYMBOLS 1 Gas sensor element 13 Proton conductive solid electrolyte body 14 Measured gas side electrode 140 Measured gas chamber 15 Reference gas side electrode 150 Reference gas chamber G Measured gas

Claims (5)

A proton conductive solid electrolyte body, a gas side electrode to be measured and a reference gas side electrode provided on one side and the other side of the proton conductive solid electrolyte body, respectively, and the gas side electrode to be measured The ammonia concentration in the measured gas is detected using a gas sensor element having a measured gas chamber for introducing the measured gas and a reference gas chamber for introducing the reference gas facing the reference gas side electrode. A way to
In the measured gas chamber held at a temperature higher than the ignition point of the hydrogen-containing gas component other than ammonia and the ignition point of hydrogen in the measured gas and lower than the ignition point of ammonia, the measured gas A gas combustion step of burning hydrogen-containing gas components other than ammonia and hydrogen in the gas to be measured,
A voltage is applied between the measured gas side electrode and the reference gas side electrode, and based on the magnitude of the current flowing between both electrodes via the proton conductive solid electrolyte body, And a concentration detecting step for detecting the ammonia concentration.   2. The ammonia concentration detection method according to claim 1, wherein the temperature in the gas chamber to be measured is maintained at 600 ° C. or higher.   3. The ammonia concentration detection method according to claim 1, wherein the temperature in the gas chamber to be measured is adjusted by a heating element that generates heat by energization provided in the gas sensor element. 4. The proton conductive solid electrolyte body according to claim 1, wherein the proton conductive solid electrolyte body is made of a material having a basic structure of any one or more of SrZrO ₃ , SrCeO ₃ , SrTiO ₃ and CaZrO _3. Ammonia concentration detection method.   5. The ammonia concentration detection method according to claim 1, wherein the gas to be measured is exhaust gas of a diesel engine.

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