JP3487990B2 - Self-calibration type oxygen analysis method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a self-calibration-type oxygen analysis method and device, and more particularly to self-correction (calibration) of an electromotive force measured by an oxygen concentration battery system so that the output of the device changes from an initial value. The present invention relates to a self-calibration type oxygen analysis method and an apparatus therefor capable of accurately obtaining the oxygen concentration (partial pressure) in a measured gas even under a deteriorated condition.

[0002]

BACKGROUND ART Oxygen analyzers have been widely used for combustion control and atmosphere control of boilers and industrial furnaces, and the principle of an oxygen concentration battery has been used as one of such oxygen analyzers. The one used is known. Specifically, for example, an electrochemically constituted solid electrolyte having oxygen ion conductivity such as zirconia porcelain and at least one pair of electrodes such as a porous platinum electrode provided in contact with the solid electrolyte. As is well known from the electromotive force induced by exposing a pair of electrodes to an atmosphere having different oxygen partial pressures, using the Nernst equation, oxygen in the target atmosphere It is used for combustion control and atmosphere control in search of partial pressure.

However, in such an oxygen analyzer, the measured value of the electromotive force obtained varies with time due to deterioration of the electrode exposed to the gas to be measured with time, adhesion of soot to the electrode surface, and the like. There is an inherent problem of changing to
After installation of the oxygen analyzer, calibration with standard gas or atmospheric air is performed manually or automatically at regular intervals, for example, once a month.Instruction calibration of the analyzer in the oxygen analyzer Are doing.

However, in such a calibration operation with a standard gas once a month, it is necessary to suspend combustion control and atmosphere control for the calibration.
This reduces the operation rate of the furnace, and even if such control is performed manually, there is a problem in that a complicated control system puts a heavy burden on the operator, and the calibration gas Since it is used once a month, there is an inherent problem that the amount of such calibration gas used is large.

[0005]

The present invention has been made in view of the above circumstances, and a problem to be solved by the present invention is that it is based on an oxygen partial pressure difference between a measured gas and a reference gas. The electromotive force generated by the oxygen concentration battery system is
It is an object of the present invention to provide a self-calibration type oxygen analysis method and device that can be output in a constantly calibrated state and substantially eliminate the need for periodic calibration operation.

[0006]

In order to solve such a problem, in the present invention, a first reference gas having a constant oxygen partial pressure and a gas to be measured existing in a first reference chamber provided in a sensor element are provided. While measuring the first electromotive force by the oxygen concentration cell between the, the oxygen of the first reference gas, which exists in the second reference chamber provided in the sensor element separately from the first reference chamber Measuring the second electromotive force by the oxygen concentration battery between the second reference gas of a constant oxygen partial pressure different from the partial pressure and the measured gas,
Furthermore, the third electromotive force by the oxygen concentration battery between the first reference gas and the second reference gas is measured, and based on the three electromotive force values obtained, the first or the first A gist of the self-calibration oxygen analysis method is characterized in that the second electromotive force value is calibrated, and the oxygen partial pressure in the measured gas is obtained from the calibrated electromotive force value.

As described above, according to the present invention, the first reference chamber and the second reference chamber, which are separately provided in the sensor element, have the first reference chambers having different constant oxygen partial pressures. Gas and a second reference gas are allowed to exist, and two electromotive forces of the oxygen concentration cell based on the oxygen partial pressure difference between the two reference gases and the gas to be measured are measured. Even if the electromotive force value, that is, the electromotive force due to the oxygen concentration battery between the first reference gas and the measured gas and between the second reference gas and the measured gas fluctuates due to deterioration over time, etc. The electromotive force due to the oxygen concentration battery between the first reference gas and the second reference gas, which is not affected by such phenomena as deterioration over time, is always a constant value. The correction calculation is performed using the power value, and the first or second It is possible to calibrate the electromotive force value due to the oxygen concentration cell between the quasi gas and the measured gas, and use the calibrated electromotive force value based on the well-known Nernst equation. Thus, the oxygen partial pressure in the measured gas can be calculated.

According to the desirable mode of the self-calibration type oxygen analysis method according to the present invention, the oxygen partial pressure of the first reference gas and the oxygen concentration are set so that the third electromotive force is always constant. The oxygen partial pressure of the second reference gas will be controlled relative to each other by the oxygen pumping action on the first and second reference chambers.

Further, the present invention is a device capable of advantageously implementing the above-mentioned method, wherein (a) a first reference gas having a constant oxygen partial pressure, which is provided in the sensor element, is present. A second reference gas having a constant oxygen partial pressure different from the oxygen partial pressure of the first reference gas, which is provided in the sensor element separately from the reference chamber and (b) the first reference chamber; A second reference chamber that is allowed to exist, (c) a first oxygen ion conductive solid electrolyte that constitutes a part of the wall of the first reference chamber, and a first oxygen ion conductive solid electrolyte A first reference electrode provided in contact with the exposed surface of the first reference chamber,
A first measurement electrode provided in contact with the measured gas exposed surface of the first oxygen ion conductive solid electrolyte,
A first electrochemical sensor cell that outputs a first electromotive force based on the oxygen partial pressure difference between the first reference gas and the measurement gas; and (d) one of the walls of the second reference chamber. A second oxygen ion conductive solid electrolyte constituting a part, a second reference electrode provided in contact with the second reference chamber exposed surface of the second oxygen ion conductive solid electrolyte, and the second A second measuring electrode provided in contact with the exposed surface of the measured gas of the oxygen ion conductive solid electrolyte, and a second based on the oxygen partial pressure difference between the second reference gas and the measured gas. A second electrochemical sensor cell that outputs an electromotive force of: (e) a third oxygen-ion conductive solid electrolyte that constitutes a part of the walls of the first and second reference chambers; and Third oxygen ion conductive solid electrolyte, the third provided in contact with the exposed surface of the first reference chamber A reference electrode and a third measurement electrode provided in contact with the exposed surface of the second reference chamber of the third oxygen-ion conductive solid electrolyte, the first reference gas and the second reference A third electrochemical sensor cell that outputs a third electromotive force based on the oxygen partial pressure difference between the gas,
(F) Based on the first, second, and third electromotive forces output from the first, second, and third electrochemical sensor cells, the first or second electromotive force value is calibrated. A self-calibration-type oxygen analyzer is provided which is characterized in that it has a calculation means for calculating the oxygen partial pressure in the gas to be measured from the calibrated electromotive force value.

In a preferred embodiment of the self-calibrating oxygen analyzer according to the present invention, at least two of the first, second and third oxygen ion conductive solid electrolytes are the same. ing.

In an advantageous aspect of the self-calibrating oxygen analyzer according to the present invention, the first reference electrode and the third reference electrode, the second reference electrode and the third measurement electrode, and Of the combination of the first measurement electrode and the second measurement electrode, at least one combination of electrodes is the same, and at least two of the electrochemical sensor cells including the same electrodes. However, the oxygen ion conductive solid electrolytes are the same.

Furthermore, in another preferred aspect of the self-calibrating oxygen analyzer of the present invention, a fourth oxygen-ion conductive solid electrolyte which constitutes a part of the walls of the first and second reference chambers, respectively. And an electrochemical pump cell comprising a pair of pump electrodes provided in contact with the exposed surface of the first reference chamber and the exposed surface of the second reference chamber of the fourth oxygen ion conductive solid electrolyte, respectively. A first oxygen pumping means including is provided, the first reference chamber and the second reference chamber are connected by a diffusion passage having a diffusion resistance, and the first oxygen pumping means is operated by a pump. While oxygen is pumped into the first reference chamber from the second reference chamber, oxygen in the first reference chamber can flow into the second reference chamber through the diffusion passage, and further, Third electrochemical sensor By controlling the pump operation of the first oxygen pump means based on the third electromotive force output from the first electromotive force so that the oxygen partial pressures of the reference gases in the first and second reference chambers become constant. Will be configured.

Furthermore, in another preferred embodiment of the self-calibrating oxygen analyzer according to the present invention, second oxygen pump means for pumping in or pumping out oxygen from the first reference chamber, It will be further provided.

And, such a second oxygen pump means advantageously comprises a fifth oxygen ion conductive solid electrolyte forming a part of the wall of the first reference chamber, and the fifth oxygen ion conductive solid electrolyte. An inner pump electrode provided in contact with the exposed surface of the first reference chamber of the oxygen ion conductive solid electrolyte, and an outer pump provided in contact with the measured gas exposed surface of the fifth oxygen ion conductive solid electrolyte. It includes an electrochemical pump cell composed of electrodes.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The self-calibration type oxygen analysis method and apparatus according to the present invention will be described in more detail below with reference to the drawings.

First, FIG. 1 shows a principle structure of a self-calibration type oxygen analysis method and device according to the present invention, in which 2 is a known oxygen ion conductive solid such as zirconia porcelain. The sensor element is an integral structure made of an electrolyte material. Then, in the sensor element 2, a first reference chamber 4 and a second reference chamber 6 are separately provided in a form partitioned from the outside, and inside the reference chambers 4 and 6, respectively. With constant oxygen partial pressures P ₁ and P ₂ ,
A first reference gas and a second reference gas with different oxygen partial pressures (P ₁ ≠ P ₂ ) are respectively present. The oxygen partial pressures P ₁ and P in the first and second reference gases are
₂ does not change with time and is maintained so that it is always constant.

A first reference electrode 8 is provided so as to come into contact with the exposed surface of the oxygen ion conductive solid electrolyte constituting the sensor element 2 in the first reference chamber 4, and further, such a solid electrolyte is provided. In contact with the exposed surface in the second reference chamber 6,
While the second reference electrode 10 is provided, the measurement electrode 12 is provided on the outer surface of the sensor element 2. Accordingly, the first reference gas having a constant oxygen partial pressure P ₁ is brought into contact with the first reference electrode 8, and the second reference electrode 10
Is contacted with a second reference gas having a constant oxygen partial pressure P ₂ different from P ₁ , while the measurement electrode 12 is contacted with a gas to be measured (oxygen partial pressure: P _s ). It has become. The reference electrodes 8,
Each of 10 and the measurement electrode 12 has a known electrode structure, and is composed of, for example, a porous platinum electrode or the like.

Then, the solid electrolyte of the sensor element 2, the first reference electrode 8 and the measuring electrode 12 constitute a first electrochemical sensor cell which is a first oxygen concentration battery, and a first reference gas. The first electromotive force V ₁ based on the oxygen partial pressure difference between the measurement target gas and the measured gas is detected by the first voltmeter 14, and the solid electrolyte of the sensor element 2 and the second A second electrochemical sensor cell, which is a second oxygen concentration battery, is composed of the reference electrode 10 and the measurement electrode 12, and a second electrochemical sensor cell based on the oxygen partial pressure difference between the second reference gas and the measurement gas is formed. The electromotive force V ₂ is detected by the second voltmeter 16, and at the same time from the solid electrolyte of the sensor element 2, the first reference electrode 8 and the second reference electrode 10, A third electrochemical sensor cell, which is an oxygen concentration battery, is constructed and The third electromotive force V ₃ based on the oxygen partial pressure difference between the reference gas and the second reference gas is detected by the third voltmeter 18.

Then, each electrochemical sensor cell (oxygen concentration cell) generates the corresponding voltmeter 14,
The first, second, and third electromotive force values V ₁ , V ₂ , and V ₃ detected at 16 and 18 are input to the arithmetic device 20, and based on these three electromotive force values, The first electromotive force value V ₁ or the second electromotive force value V ₂ that changes with time is calibrated (corrected), and from the calibrated electromotive force value HV ₁ or HV ₂ , the well-known Nernst The oxygen partial pressure P _sn in the gas to be measured is calculated according to the above equation.

By the way, in the oxygen analyzer having the above construction, the oxygen partial pressure P ₁ of the first reference gas in the first reference chamber 4 and the oxygen partial pressure of the second reference gas in the second reference chamber 6 Since P ₂ is constant in all cases, P ₁ / P ₂ always has a constant value, and the oxygen partial pressure of the measured gas is understood to change with time. . The oxygen partial pressure P ₁ of the first reference gas is usually made higher than the oxygen partial pressure P ₂ of the second reference gas,
The oxygen partial pressure of the gas to be measured is set so as to be located between the two oxygen partial pressures P ₁ and P ₂ . In Figure 2,
The three oxygen partial pressure states are shown. The oxygen partial pressure P ₁ of the first reference gas is generally ₁ at
m is adopted, and as the oxygen partial pressure P ₂ of the second reference gas, a state of substantially 0, for example, about 5 × 10 ⁻⁸ atm is adopted.

Under such a circumstance, when the above-mentioned oxygen analyzer is normally operated in the initial measurement stage at the time of installation, as shown in FIG.
As shown in (a), the sum of the electromotive force V ₁ of the _first oxygen concentration battery and the electromotive force V ₂ of the second oxygen concentration battery for the gas to be measured is constant oxygen. Partial pressure P
_Although it is equal to the constant generated electromotive force V ₃ of the third oxygen concentration battery based on the constant oxygen partial pressure difference between the two reference gases ₁ and P ₂ , when the oxygen analyzer is deteriorated with time. As shown in FIG. 3 (b), the sum of the electromotive force V ₁ generated by the first oxygen concentration battery and the electromotive force V ₂ generated by the second oxygen concentration battery is It is no longer equal to the electric power V ₃ and therefore such an electromotive force V 3
_When the oxygen partial pressure P _sn in the measured gas is calculated from ₁ or V ₂ , a large difference occurs from the actual oxygen partial pressure P _s ,
It becomes impossible to measure the oxygen partial pressure accurately. Therefore, it is necessary to correct the electromotive force V ₁ or V ₂ generated by the first or second oxygen concentration battery to the electromotive force value in the initial normal operation state of the oxygen analyzer, and the gain thereof. Corrected generated electromotive force value HV
_An accurate oxygen partial pressure value can be obtained by calculating the oxygen partial pressure in the gas to be measured from the normal Nernst equation based on ₁ or HV ₂ .

By the way, when correcting the electromotive forces V ₁ and V ₂ generated by the first or second oxygen concentration cell, the fluctuation of the oxygen partial pressure of the gas to be measured is utilized to measure the device (receiver). It suffices to constantly monitor the gain and correct it according to the amount of deviation. Specifically, using the electromotive force V ₁ generated by the first oxygen concentration battery, the electromotive force V ₂ generated by the second oxygen concentration battery, and the generated electromotive force V ₃ by the stabilized third oxygen concentration battery, , The ratio of the amount of change in the electromotive force generated by the first and second oxygen concentration batteries: | dV ₁ / dV ₂ | From the electromotive forces V ₁ and V ₂ generated by the first and second oxygen concentration batteries, The generated electromotive force components of one and the other are converted to the generated electromotive force level of the one and added, and the generated electromotive force V _{3 of} the third oxygen concentration battery is calculated.
By determining the gain of the receiver so as to match the barrel reference electrode and correcting the gain, it is possible to obtain the target corrected electromotive force value HV ₁ or HV ₂ .
It can be represented by the following equations (1) and (2), and FIG. 4 shows an example of such a form of gain correction. HV ₁ = (V ₃ · V ₁ ) / [V ₁ + | dV ₁ / dV ₂ | · V ₂ ] ... (1) HV ₂ = (V ₃ · V ₂ ) / [V ₂ + | dV ₁ / DV ₂ | · V ₁ ] (2)

As described above, according to the present invention, the first reference chamber 4 and the second reference chamber 6 provided in the sensor element 2 are allowed to have the reference gas having a constant oxygen partial pressure, respectively. And, on the premise of a constant generated electromotive force based on the oxygen partial pressure difference between the reference gases, the generated electromotive force V ₁ , V ₂ of the first or second oxygen concentration battery is corrected,
Thus, the oxygen partial pressure in the measured gas is calculated from the correction values HV ₁ and HV ₂ , and the oxygen partial pressure in the atmosphere in the first and second reference chambers 4 and 6 is Sensor element 2
It is apt to be changed due to the leakage from the laminated structure of the electrode and the arrangement of the lead portion connected to each electrode, and further due to the movement of oxygen by the oxygen concentration battery itself. Therefore, in practice, the first standard Appropriate oxygen pumping means is provided for the chamber 4 and the second reference chamber 6, and oxygen is pumped by the oxygen pumping means in the first reference chamber 4 and the second reference chamber 6. It is desirable that the oxygen partial pressure in the atmosphere (reference gas) be maintained at a predetermined constant value, and a desirable example thereof is shown in FIG.

That is, in the specific example shown in FIG. 5, the sensor element 2 is shown as a laminated structure of two oxygen ion conductive solid electrolytes 2a and 2b. By stacking
A first reference chamber 4 and a second reference chamber 6 are formed inside, and a diffusion passage 22 is provided so as to connect the two reference chambers 4 and 6 to each other. The first reference gas having a high oxygen partial pressure is introduced into the second reference chamber 6 having a low oxygen partial pressure under a predetermined diffusion resistance. In addition, here, the permeability coefficient of oxygen returning from the first reference chamber 4 to the second reference chamber 6 is shown by K _b . Further, since the oxygen partial pressure of the first reference gas in the first reference chamber 4 is made higher than the oxygen partial pressure of the measured gas outside, the leak passage 24 is discharged from the first reference chamber 4.
Through, the first reference gas is decided to leak to the outside, the transmission coefficient of oxygen by such leak, here, there is a K _o. Further, an external measured gas having an oxygen partial pressure higher than that of the second reference gas is supposed to enter and leak into the second reference chamber 6 through the intrusion passage 26, and such an intrusion leak. The permeability coefficient of oxygen due to is defined as K _i .

In the sensor element 2 having such a structure, the first pump electrode 28 is provided so as to come into contact with the oxygen ion conductive solid electrolyte 2b portion exposed in the first reference chamber 4. A second pump electrode 30 is provided in the oxygen ion conductive solid electrolyte 2b portion exposed in the second reference chamber 6, and by the two pump electrodes 28, 30 and the solid electrolyte 2b, An electrochemical cell is provided that provides the first oxygen pump.
The first oxygen pump has a third electromotive force V ₃ based on the oxygen partial pressure difference between the first reference chamber 4 and the second reference chamber 6 detected by the third voltmeter 18. The pump is operated so as to be equal to the set voltage E of the one oxygen pump, and oxygen is pumped from the second reference chamber 6 side to the first reference chamber 4 side. The pump operation of the first oxygen pump is controlled by the well-known PID control.

Further, the oxygen ion conductive solid electrolyte 2b portion exposed in the first reference chamber 4 is provided with an inner pump electrode 32 so as to be in contact with it, and
An outer pump electrode 34 is provided on the outer surface of the solid electrolyte 2b, and the two pump electrodes 32, 34 and the oxygen ion-conducting solid electrolyte 2b are used to provide an electrochemical pump that provides a second oxygen pump. The cell is configured.
By the pump operation of the second oxygen pump, oxygen is pumped into the first reference chamber 4 from the measured gas outside,
In the first reference chamber 4, the first reference gas having a predetermined reference oxygen partial pressure is formed. In addition, the second oxygen pump determines the oxygen content of the measurement gas from the oxygen content necessary for creating the oxygen partial pressure in the first reference gas, and the oxygen content flowing out from the first reference chamber to the measurement gas. The second oxygen pump current proportional to the oxygen amount obtained by subtracting the sum of the oxygen amount pushed into the second reference chamber from the oxygen partial pressure of the pressure and the oxygen partial pressure of the measurement gas, the first and second It is pumped by prior control using the oxygen partial pressure in the measurement gas measured with the corrected electromotive force of the oxygen concentration cell.

The four pump electrodes 28, 30, provided on the solid electrolyte 2b portion of the sensor element 2 as described above,
32 and 34 are the same as the reference electrodes 8 and 10 and the measurement electrode 12 described above, and are generally composed of porous platinum electrodes. Further, on the outer surface of the sensor element 2, the measurement electrode 12 and the outer pump electrode 3 provided therein are provided.
In order to protect 4, the porous protective layers 36a and 36b made of alumina or the like are integrally laminated. Known heaters 38a and 38b are provided integrally or separately on the porous protective layers 36a and 36b, respectively.
At 38b, the sensor element 2 can be heated to the desired operating temperature. In addition, those heaters 3
Even if 8a and 38b are integrally laminated on the porous protective layers 36a and 36b, the measured gas outside enters from the exposed portion of the measured gas of the porous protective layers 36a and 36b, and the measurement electrode 12 And reaches the outer pump electrode 34.

In the oxygen analyzer using the sensor element having such a configuration, the oxygen concentration of the third oxygen concentration battery based on the oxygen partial pressure difference between the first reference chamber 4 and the second reference chamber 6 is used. The generated electromotive force is controlled to a constant voltage (practically about 300 to 500 mV) by the first oxygen pump that pumps oxygen from the second reference chamber 6 to the first reference chamber 4. Become.

On the other hand, the gas to be measured flows into the second reference chamber 6 through the inflow passage 26, and the first oxygen pump (2
b, 28, 30) of the amount of oxygen pumped up and flowing into the first reference chamber 4 and the amount of oxygen flowing out of the first reference chamber 4 to the outside measured gas side through the leak passage 24, The oxygen amount for extraction, which corresponds to the sum of the oxygen amounts pushed back by the oxygen partial pressure (P _s ) of the measured gas, is specified by the oxygen partial pressure measured by the first oxygen concentration battery, and the first reference gas Oxygen is injected from the gas to be measured into the first reference chamber 4 using an oxygen pump current proportional to the amount of oxygen obtained by subtracting the amount of oxygen extracted from the amount of oxygen required to create the partial pressure of oxygen in The oxygen partial pressure (P ₁ ) in the first reference gas is changed by the second oxygen pump (2b, 32, 34)
It is controlled constantly. Then, the pump current (I ₁ ) of the _first oxygen pump, the pump current (I ₂ ) of the second oxygen pump, and the oxygen permeation coefficient (K) of the inflow passage (26).
_i ), the oxygen permeation coefficient (K _o ) of the outflow passage (24), and the oxygen permeation coefficient (K _b ) of the return passage (22), the oxygen partial pressure (P ₁ ) of the known first reference gas and the The oxygen partial pressure (P ₂ ) in the second reference gas is specified. For example, the oxygen partial pressure of the first reference gas in the first reference chamber 4 is calculated by the following equation (3). P ₁ = [(K _o + K _i ) · I ₁ + K _i · I ₂ ] / [(K _o + K _i ) · K _b + K _o · K _i ] ... (3)

On the other hand, the electromotive force V generated by the first oxygen concentration battery
_{Using the} electromotive force V ₂ generated by the _first and second oxygen concentration cells and the generated electromotive force V ₃ (= E) generated by the third oxygen concentration cell, the first and second oxygen concentration cells From the change ratio of the generated electromotive force: dV ₁ / dV ₂ , the generated electromotive force V ₁ of the first oxygen concentration battery and the generated electromotive force V of the second oxygen concentration battery
₂ is converted to the electromotive force level generated by the first oxygen concentration battery and added, and the gain of the receiver (apparatus) is determined so as to match the electromotive force V ₃ generated by the third oxygen concentration battery. For this reason, the electromotive forces V ₁ and V ₂ generated in the first and second oxygen concentration batteries are constantly monitored, and the ratio of their amounts of change is calculated to calculate the gain. There is. Then, from the obtained gain, the above (1)
The generated electromotive force V ₁ or V ₂ of the first or second oxygen concentration battery is corrected based on the equation or (2) to obtain H
V ₁ or HV ₂ is obtained, and based on the correction value,
Oxygen partial pressure P ₁ or P ₂ in each reference gas,
The ratio with the oxygen partial pressure P _s of the measured gas is obtained.

Then, from the ratio of the reference oxygen partial pressure thus obtained to the oxygen partial pressure of the measurement gas and the calculated value of the oxygen partial pressure in the reference chamber, the oxygen partial pressure of the measurement gas is calculated. The calculation is performed, and the target oxygen partial pressure value (calculation value) P _sn is obtained as the output of the analyzer.

FIG. 6 shows an example of an algorithm block diagram for measuring the oxygen partial pressure of the gas to be measured using the oxygen analyzer having such a configuration. There, the oxygen partial pressure of the gas to be measured uses the electromotive force V ₁ generated by the first oxygen concentration battery, and from the gain correction value HV ₁ , the oxygen partial pressure P ₁ in the first reference gas and the measured oxygen partial pressure P ₁ are measured. Gas oxygen partial pressure P
_While the ratio with _s : P ₁ / P _s is calculated, the oxygen partial pressure P ₁ in the first reference chamber 4 is calculated from the pump currents I ₁ and I _{2 of} the first and second oxygen pumps. And those P
The oxygen partial pressure in the target gas to be measured is calculated from the ₁ / P _s value and the P ₁ value.

Thus, according to the present invention, two reference gases having a constant oxygen partial pressure are used, and the electromotive forces V ₁ and V ₂ generated between the reference gases and the gas to be measured, and further between the reference gases. By making the oxygen partial pressure of the reference gas known from the measured value of the generated electromotive force V ₃ , it becomes possible to effectively correct the oxygen partial pressure in the target measured gas by self-correction by calculation. Therefore, the frequent calibration operation of once a month as in the conventional method is completely unnecessary. However, since the signal processing is performed while the calibration and correction operations are constantly performed inside the apparatus in this manner, the present invention provides
Basically, it is possible to measure the oxygen partial pressure of the measured gas without calibration operation, but for peace of mind, for example, at the time of regular inspection once every six months of the furnace, It is also possible to perform traceability with the calibration gas.

The present invention should not be construed as being limited to the specific examples described above, and various modifications may be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Modifications, improvements and the like can be carried out in the embodiment, and as long as such an embodiment does not depart from the gist of the present invention,
It should be understood that it is within the scope of the present invention.

For example, the sensor element 2 is generally constituted by an integral laminated structure of a plurality of ceramic layers including an oxygen ion conductive solid electrolyte layer, and in the present invention as well, the same is applied. It goes without saying that such a laminated structure can be adopted, and therefore the first, second and third oxygen ion conducting solid electrolytes in the first, second and third electrochemical sensor cells are In addition to the case of being composed of one oxygen ion conductive solid electrolyte, at least two of the first, second and third oxygen ion conductive solid electrolytes may be the same solid electrolyte. I can.

In the illustrated embodiment, the first reference electrode in the first electrochemical sensor cell and the reference electrode in the third electrochemical sensor cell, and the reference electrode in the second electrochemical sensor cell and the third reference electrode in the third electrochemical sensor cell. Both the measurement electrode in the electrochemical sensor cell of, and the combination of the measurement electrode in the first electrochemical sensor cell and the measurement electrode in the second electrochemical sensor cell are formed of the same electrode, Any of the combined electrodes can be configured as separate electrodes. Further, in the case where the electrodes of at least one of the combinations are the same, the oxygen ion conductive solid electrolytes of at least two of the electrochemical sensor cells including the same electrodes are the same. Will be done.

Furthermore, in the specific example shown in FIG.
A solid electrolyte forming the first oxygen pump and a solid electrolyte forming the second oxygen pump are simultaneously supplied by one of the oxygen ion conductive solid electrolytes 2b, but they form the oxygen pumps. It goes without saying that the solid electrolytes can be separate from each other.

[0038]

As is apparent from the above description, according to the self-calibration type oxygen analysis method and device according to the present invention, the oxygen concentration of the gas to be measured and the oxygen concentration of the reference chamber provided in the sensor element are constant. Since the electromotive force generated by the oxygen concentration battery obtained from the partial pressure is always output in a calibrated state, it is always guaranteed to be within the specified measurement accuracy, and the oxygen partial pressure of the measured gas is accurate. Since it is possible to measure, and the calibration interval can be made extremely long, and frequent calibration operations can be eliminated, which effectively eliminates problems such as reduced operation rate due to calibration operations. In addition to the improvement, the amount of calibration gas used can be significantly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a basic example of a self-calibrating oxygen analyzer according to the present invention.

FIG. 2 is a graph showing an example of a temporal state of an oxygen partial pressure of a first reference gas, an oxygen partial pressure of a second reference gas, and an oxygen partial pressure of a measured gas in the present invention.

FIG. 3 is a graph showing the mutual relationship of the electromotive forces generated by the first, second, and third oxygen concentration cells, in which (a) shows the relationship in the normal operation state at the initial stage of device installation,
Further, (b) shows the relationship of the electromotive force generated after the deterioration of the device.

FIG. 4 shows a state where the electromotive force generated by the first and second oxygen concentration batteries obtained after deterioration with time of the device is set to a gain in accordance with a reference voltage and the voltage generation coefficient level of the first oxygen concentration battery is set. It is a graph shown.

FIG. 5 is an explanatory view schematically showing a specific example of the self-calibrating oxygen analyzer according to the present invention.

FIG. 6 is an algorithm block diagram according to an example of obtaining the oxygen partial pressure of the gas to be measured in the specific example shown in FIG.

[Explanation of symbols]

2 sensor elements 4 First standard room 6 Second standard room 8 First reference electrode 10 Second reference electrode 12 Measuring electrode 14 First Voltmeter 16 Second Voltmeter 18 Third Voltmeter 20 arithmetic unit 22 diffusion passage 24 leak passages 26 Invasion passage 28 First pump electrode 30 Second pump electrode 32 inner pump electrode 34 Outer pump electrode 36a, 36b Porous protective layer 38a, 38b heater

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI G01N 27/46 327P

Claims (8)

(57) [Claims] 1. A first electromotive force generated by an oxygen concentration cell between a first reference gas having a constant oxygen partial pressure and a gas to be measured, which is present in a first reference chamber provided in a sensor element. ,
A second reference gas having a constant oxygen partial pressure different from the oxygen partial pressure of the first reference gas, which exists in a second reference chamber provided in the sensor element separately from the first reference chamber; The second electromotive force by the oxygen concentration battery between the measured gas and the third electromotive force by the oxygen concentration battery between the first reference gas and the second reference gas is measured. And calibrate the first or second electromotive force value based on the obtained three electromotive force values, and obtain the oxygen partial pressure in the measured gas from the calibrated electromotive force value. Self-calibration type oxygen analysis method characterized by the following. 2. The oxygen partial pressure of the first reference gas and the oxygen partial pressure of the second reference gas are adjusted so that the third electromotive force is always constant. The self-calibrating oxygen analysis method according to claim 1, wherein the oxygen is pumped by oxygen to the chamber and controlled in a mutually related manner. 3. A first reference chamber provided in the sensor element, in which a first reference gas having a constant oxygen partial pressure is present, and a first reference chamber provided separately in the sensor element. Was
A second reference chamber in which a second reference gas having a constant oxygen partial pressure different from the oxygen partial pressure of the first reference gas is allowed to exist, and constitutes a part of a wall portion of the first reference chamber. A first oxygen ion conductive solid electrolyte, a first reference electrode provided in contact with the exposed surface of the first reference chamber of the first oxygen ion conductive solid electrolyte, and the first oxygen ion conductive Composed of a first measurement electrode provided in contact with the measured gas exposed surface of a polar solid electrolyte, the first electromotive force based on the oxygen partial pressure difference between the first reference gas and the measured gas. A first electrochemical sensor cell for outputting, a second oxygen ion conductive solid electrolyte forming a part of the wall portion of the second reference chamber, and the second oxygen ion conductive solid electrolyte of the second A second reference electrode provided in contact with the exposed surface of the second reference chamber, and the second oxygen ion A second measurement electrode provided in contact with the exposed surface of the measured gas of the conductive solid electrolyte, and a second electromotive force based on the oxygen partial pressure difference between the second reference gas and the measured gas. A second electrochemical sensor cell for outputting, a third oxygen ion conductive solid electrolyte constituting a part of the walls of the first and second reference chambers, and the third oxygen ion conductivity A third reference electrode provided in contact with the exposed surface of the first reference chamber of the solid electrolyte, and a third reference electrode provided in contact with the exposed surface of the second reference chamber of the third oxygen ion conductive solid electrolyte. A third electrochemical sensor cell comprising three measuring electrodes and outputting a third electromotive force based on the oxygen partial pressure difference between the first reference gas and the second reference gas; , A first output from each of the second and third electrochemical sensor cells, Based on the second and third electromotive force, the first or second electromotive force value is calibrated, and a calculating means for calculating the oxygen partial pressure in the measured gas from the calibrated electromotive force value. And a self-calibrating oxygen analyzer. 4. The self-calibrating oxygen analyzer according to claim 3, wherein at least two of the first, second and third oxygen ion conductive solid electrolytes are the same. 5. A combination of the first reference electrode and the third reference electrode, the second reference electrode and the third measurement electrode, and the combination of the first measurement electrode and the second measurement electrode. Among them, at least one combination of electrodes is the same, and at least two of the electrochemical sensor cells including the same electrodes have the same oxygen ion conductive solid electrolyte. The self-calibrating oxygen analyzer according to claim 4. 6. A fourth oxygen-ion conductive solid electrolyte that constitutes a part of the walls of the first and second reference chambers, and the first oxygen-ion conductive solid electrolyte of the fourth oxygen-ion conductive solid electrolyte. A first oxygen pump means including an electrochemical pump cell including a reference chamber exposed surface and a pair of pump electrodes provided in contact with the second reference chamber exposed surface, and diffusion having diffusion resistance. The first reference chamber and the second reference chamber are connected by a passage, and oxygen is pumped from the second reference chamber to the first reference chamber by the pump operation of the first oxygen pump means. Meanwhile, the oxygen in the first reference chamber is configured to be able to flow into the second reference chamber through the diffusion passage, and the third electromotive force output from the third electrochemical sensor cell is further added. Based on the first oxygen pump means 6. The self control according to claim 3, wherein the pump partial pressure is controlled so that the oxygen partial pressures of the reference gases in the first and second reference chambers are constant. Calibration type oxygen analyzer. 7. The self-calibration type oxygen analyzer according to claim 6, further comprising second oxygen pump means for pumping oxygen into or pumping out oxygen from the first reference chamber. 8. A fifth oxygen ion conductive solid electrolyte, wherein the second oxygen pump means constitutes a part of a wall portion of the first reference chamber, and the fifth oxygen ion conductive solid electrolyte. And an inner pump electrode provided in contact with the exposed surface of the first reference chamber, and an outer pump electrode provided in contact with the exposed surface of the gas to be measured of the fifth oxygen ion conductive solid electrolyte. 8. An electrochemical pump cell is included.
The self-calibrating oxygen analyzer described.