JP3563399B2 - Gas analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to NO_XGas analysis for measuring gas components that have bound oxygen, such asIn totalRelated.
[0002]
[Prior art]
Conventionally, various measuring methods and devices have been proposed in order to know the concentration of a desired gas component in a gas to be measured. For example, NO._XIs measured by measuring the NO of Rh._XA method is known in which a Pt electrode and a Rh electrode are formed on an oxygen ion conductive solid electrolyte such as zirconia using a reducing property, and an electromotive force between the two electrodes is measured. ing. However, such a sensor not only changes the electromotive force greatly due to a change in the oxygen concentration contained in the combustion gas that is the gas to be measured, but also produces a NO._XThe change in the electromotive force is small with respect to the change in the density of, so that it is easily affected by noise.
Also, NO_XSince a reducing gas such as CO is indispensable to bring out the reducing property of NO, generally a large amount of NO_XUnder the combustion condition of insufficient fuel in which CO is generated, the amount of generated CO is NO._XIs less than the amount generated, so that there is a disadvantage that measurement cannot be performed with a combustion gas formed under such combustion conditions.
[0003]
Further, a pair of electrochemical pump cells and sensor cells composed of a Pt electrode and an oxygen ion-conductive solid electrolyte, and another pair of electrochemical pump cells and sensor cells composed of a Rh electrode and an oxygen ion-conductive solid electrolyte, Due to the difference between the pump current values, NO_XA method for measuring the temperature is disclosed (see Patent Documents 1 and 2).
Further, two sets of a pair of electrochemical pump cells and sensor cells are prepared._XIs measured under a partial pressure of oxygen that is not reduced, and NO is measured by a sensor composed of a pair of pump cells and a sensor cell._XThe limiting pump current is measured under the oxygen partial pressure at which the gas is reduced, and the difference between the limiting pump currents is determined. The oxygen partial pressure in the gas to be measured is determined as NO by using a sensor including a pair of pump cells and sensor cells._XThere has been proposed a method of switching between an oxygen partial pressure at which oxygen can be reduced and an oxygen partial pressure at which oxygen cannot be reduced, and measuring the difference in the limiting current (see Patent Documents 3 and 4).
[0004]
However, the aforementioned NO_XIn the measurement method, usually, the value of the limiting current is mostly a current due to a large amount of contained oxygen, and the target NO_XIs extremely small, the difference between the two large current values indicates that NO_XWill be obtained. For this reason, when performing measurement by switching a set of sensors, there arise problems that continuous measurement cannot be performed, and responsiveness and accuracy are poor. In addition, when two sets of sensors are used, if the oxygen concentration in the gas to be measured greatly changes, an error easily occurs in the measured value, and the sensor cannot be used if the oxygen concentration in the gas to be measured greatly changes. This is because the dependence of the pump current of one sensor on the oxygen concentration is different from the dependence of the pump current on the other sensor in the oxygen concentration.
[0005]
Furthermore, if there is a difference in the change over time of the characteristics of the two sets of sensors, the difference becomes an error as it is, and there is a drawback that it cannot withstand long-term use.
Thus, the oxygen present in the gas to be measured is NO_XThis causes problems such as a decrease in measurement accuracy when measuring other gas components to be measured.
[0006]
For this reason, the present inventors attempted to solve the above-mentioned problem by using NO in the gas to be measured._XUsing the first and second electrochemical pump cells having gas components to be measured having bonded oxygen such as in series, without being affected by the oxygen concentration in the gas to be measured or a change thereof. Proposed a new measurement method that enables continuous measurement with good responsiveness and accurate measurement for a long time (see Patent Document 5).
[0007]
This new measuring method is a method in which a gas to be measured containing a gas component to be measured having bound oxygen to be measured is subjected to first and second treatments under a predetermined diffusion resistance from an external space where the gas to be measured exists. In the first processing zone, first, oxygen in the atmosphere is reduced to a low oxygen partial pressure value that does not substantially affect the measurement of the gas component amount to be measured in the first electrochemical pump cell. On the other hand, in the second processing zone, the gas component to be measured in the atmosphere led from the first processing zone is reduced or decomposed, and oxygen generated at that time is supplied to a second electrochemical pump cell. By pumping by the pumping action of oxygen, the pump current flowing through the second electrochemical pump cell is detected, and from the detected value, the component amount of the gas to be measured in the gas to be measured is calculated. One in which the.
[0008]
[Patent Document 1]
JP-A-63-38154
[Patent Document 2]
JP-A-64-39545
[Patent Document 3]
JP-A 1-277751
[Patent Document 4]
JP-A-2-1543
[Patent Document 5]
Japanese Patent No. 2885336
[0009]
[Problems to be solved by the invention]
The present invention relates to a further improvement of the above-described measurement method, and the object thereof is that even if the oxygen concentration in the gas to be measured is increased, the response is continuously affected without being affected by the oxygen concentration. Gas analysis that enables good and accurate measurement for a long time, high S / N ratio, and large signal change even when measuring low-concentration gas components to be measured.TotalTo provide.
[0010]
[Means for Solving the Problems]
That is, according to the present invention, the measurement gas containing the measurement target gas component having the bound oxygen to be measured is guided from the external measurement gas existence space to the first processing zone under a predetermined diffusion resistance. In the first processing zone, after the oxygen partial pressure of the atmosphere in the first processing zone is controlled to a predetermined oxygen partial pressure by a pumping action of oxygen by a first electrochemical pump cell, The second partial treatment zone is introduced into the second treatment zone under the diffusion resistance of the above, and oxygen is further pumped out by the second electrochemical pump cell in the second treatment zone, whereby the oxygen partial pressure of the atmosphere is measured. The oxygen content was controlled to a low oxygen partial pressure value that did not substantially affect the measurement of the gas component amount, and was further led to a third processing zone, and then the third processing zone was led from the second processing zone. In the atmosphere A gas sensor for detecting a pumping current flowing through the third electrochemical pump cell by reducing or decomposing the measured gas component and pumping out oxygen generated at that time by a third electrochemical pump cell; A driving unit for oxygen pumping the first to third processing zones in the gas sensor, and a pumping current flowing through the third electrochemical pump cell is calculated into a measured gas value, and the first processing is performed. A calculation unit for guiding the pumping current in the zone and calculating the amount of oxygen in the measured atmosphere, or the amount of oxygen deficiency, or the equivalent, and displaying the value calculated by the calculation unit, or to the outside as an electrical output A gas analyzer comprising: a display output unit to be taken out; and a heater driving unit for heating the gas sensor to a predetermined temperature.
[0011]
Further, according to the present invention, the measurement gas containing the measurement target gas component having the bound oxygen to be measured is guided from the external measurement gas existence space to the first processing zone under a predetermined diffusion resistance. In the first processing zone, after the oxygen partial pressure of the atmosphere in the first processing zone is controlled to a predetermined oxygen partial pressure by a pumping action of oxygen by a first electrochemical pump cell, The second partial treatment zone is introduced into the second treatment zone under the diffusion resistance of the above, and oxygen is further pumped out by the second electrochemical pump cell in the second treatment zone, whereby the oxygen partial pressure of the atmosphere is measured. The oxygen content was controlled to a low oxygen partial pressure value that did not substantially affect the measurement of the gas component amount, and was further led to a third processing zone, and then the third processing zone was led from the second processing zone. Said in the atmosphere A gas sensor that detects a pumping current flowing through the third electrochemical pump cell by reducing or decomposing the measurement gas component and pumping out oxygen generated at that time by a third electrochemical pump cell; A driving unit for oxygen pumping the first to third processing zones in the gas sensor, and a pump current flowing through the third electrochemical pump cell is calculated to a measured gas value, and the first processing zone is A pumping current, a pumping current in the second processing zone and a pumping current in the third processing zone, and a calculating unit for calculating the amount of oxygen in the measured atmosphere, or the amount of oxygen deficiency, or the equivalent, A display output unit for displaying the value calculated by the calculation unit or taking it out as an electrical output; Gas analyzer is provided which is characterized by comprising a heater drive section for heating the.
[0012]
PerformanceCalculated powerOf the atmosphere to be measuredMeasured by the value of oxygen content or oxygen deficiency, or equivalent valueGas component to be measuredIs preferably corrected.The gas component to be measured is NO _X It is preferable that
In addition, it is preferable that at least the driving unit is integrally formed with the gas sensor.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the gas analyzer of the present invention will be described in detail and specifically.
First, a gas sensor which is a constituent element of the gas analyzer of the present invention will be described in detail.
FIG. 3 is a view showing the constituent elements of the gas analyzer of the present invention._XIt is a block diagram which shows an example of a sensor, FIG.3 (a) is a plane explanatory drawing, FIG.3 (b) is a principal part enlarged explanatory drawing in the AA sectional drawing of FIG.3 (a).
As shown in FIG. 3, reference numeral 2 denotes a sensor element having a slender and long plate-like shape. As is clear from FIG. 3B, the sensor element 2 includes a plurality of dense and airtight oxygen ions. It is a plate-like body having an integral structure that is laminated including the conductive solid electrolyte layers 4a, 4b, 4c, 4d, 4e, and 4f. Each of the solid electrolyte layers 4a to 4f is formed using a known oxygen ion conductive solid electrolyte material such as zirconia porcelain. Then, the sensor element 2 having the integrated structure is manufactured by integrally firing the unfired solid electrolyte laminate, as in the conventional case.
[0017]
A first internal space 6, a second internal space 7, and a third internal space 8, each of which has a rectangular planar shape, are provided in the sensor element 2 having such an integral structure. The first internal space 6 is located at the base end side of the element, and the third internal space 8 is located at the base end side of the device. The first processing zone, the second processing zone, and the third processing zone are configured, and the first, second, and third internal cavities 6, 7, and 8 are independent from each other and vertically. In the form of overlapping, a reference air introduction passage 10 as a reference gas existence space is provided so as to extend in the longitudinal direction of the sensor element 2, and the reference air introduction passage 10 is provided at an end on the base side of the sensor element 2. It is open so that it can communicate with the atmosphere . Here, the first, second and third internal cavities 6, 7 and 8 are covered with the corresponding solid cavities formed in the solid electrolyte layer 4b by the upper and lower solid electrolyte layers 4a and 4c. Thus, the reference air inlet 10 is formed in a state where it is located on substantially the same plane, and the corresponding space formed in the solid electrolyte layer 4d is covered with the solid electrolyte layers 4c and 4e from above and below. It is formed by doing.
[0018]
Further, a first diffusion-controlling passage 12 as first diffusion-controlling means for connecting the first internal space 6 to an external measurement gas existing space is formed by cutting out the solid electrolyte layer 4b and forming a tip of the sensor element 2. It is provided so as to open to the portion, and through the first diffusion-controlling passage 12, NO under a predetermined diffusion resistance as a gas component to be measured._XIs introduced into the first internal space 6. Further, a portion of the solid electrolyte layer 4b located between the first internal void 6 and the second internal void 7 and a location between the second internal void 7 and the third internal void 8 The solid electrolyte layer 4b is also provided with a groove-shaped notch, respectively, to form second and third diffusion-controlling passages 13 and 14 constituting second and third diffusion-controlling means, respectively. ing. The second and third diffusion-controlling passages 13 and 14 are filled and arranged with a porous body made of alumina or the like, and the diffusion resistance of the passages is controlled by the diffusion resistance of the first diffusion-controlling resistance 12. Has been larger than. Then, the atmosphere in the first internal space 6 is introduced into the second internal space 7 under a predetermined diffusion resistance through the second diffusion-controlled passage 13. The atmosphere in the second internal space 7 is guided into the third internal space 8 under a predetermined diffusion resistance.
[0019]
A portion of the solid electrolyte layer 4a exposed in the first internal space 6 is provided with a first inner pump electrode 16 made of a rectangular porous cermet electrode in contact with the portion, and further provided with the first inner pump electrode. A first outer pump electrode 18 made of a porous cermet electrode having a similar rectangular shape is provided on the outer surface portion of the solid electrolyte layer 4a corresponding to the electrode 16 so as to be in contact therewith. The first electrochemical pump cell is constituted by the layer 4a. Then, a desired voltage is applied between the two electrodes 16, 18 of the first electrochemical pump cell by an external variable power supply 20, and a direction from the first outer pump electrode 18 to the first inner pump electrode 16 is applied. By passing a current through the first internal space 6, oxygen in the atmosphere in the first internal space 6 can be pumped out to the external gas-existing space where the gas is to be measured. It can be pumped. The porous cermet electrode is made of a metal such as Pt and ZrO.₂The first inner pump electrode 16 disposed in the first internal space 6 that contacts the gas to be measured is made of NO._XIt is necessary to use a metal having reduced or non-reducible components, for example, a Pt-Au alloy and ZrO₂The cermet is preferably composed of
[0020]
Further, a measurement electrode 22 made of a porous cermet electrode similar to the first inner pump electrode 16 is provided in contact with a portion of the solid electrolyte layer 4c exposed in the first internal space 6; A reference electrode 24 made of a porous cermet electrode similar to the first outer pump electrode 18 is provided in contact with a portion of the solid electrolyte layer 4 c exposed in the reference air introduction passage 10. The reference cell 24, the reference electrode 24, and the solid electrolyte layer 4c constitute an electrochemical cell as an oxygen partial pressure detecting means, that is, an electrochemical sensor cell. The electromotive force generated between the measurement electrode 22 and the reference electrode 24 is measured by the potentiometer 26 based on the oxygen concentration difference between the reference air (atmosphere) in the reference air introduction passage 10 and No. Partial pressure of oxygen in the atmosphere in the internal space 6 is adapted to be detected in. The voltage of the variable power supply 20 is controlled based on the value of the oxygen partial pressure of the atmosphere in the first internal space 6 detected by the potentiometer 26, and thus the voltage in the first internal space 6 is controlled. The pump operation of the first electrochemical pump cell is controlled so that the oxygen partial pressure of the atmosphere of the above (2) has a predetermined value low enough to control the oxygen partial pressure in the next second internal space 7. It is supposed to be.
[0021]
On the other hand, on the solid electrolyte layer 4c, a second inner pump electrode 28 made of a porous cermet electrode similar to the first inner pump electrode 16 is provided on the solid electrolyte layer 4c so as to be located in the second inner space 7. A portion of the solid electrolyte layer 4c corresponding to the inner pump electrode 28 and exposed in the reference air introduction passage 10 is provided with a second cermet electrode similar to the first outer pump electrode 18. An outer pump electrode 30 is provided, and the inner pump electrode 28, the outer pump electrode 30, and the solid electrolyte layer 4c constitute a second electrochemical pump cell. Then, a desired voltage is applied between the two electrodes 28 and 30 of the second electrochemical pump cell by the external DC power supply 32, and the voltage is applied from the second outer pump electrode 30 side to the second inner pump electrode 28 side. By passing the electric current, the oxygen partial pressure of the atmosphere in the second internal space 7 substantially increases the gas component to be measured (NO_X) Cannot be reduced or decomposed, the oxygen partial pressure is controlled to a low oxygen partial pressure value that does not substantially affect the measurement of the gas component amount to be measured.
[0022]
Further, in the third internal space 8, a portion of the solid electrolyte layer 4c exposed therethrough is provided with a rectangular third inner pump electrode 36 in contact therewith. The third inner pump electrode 36 is connected to NO, which is a gas component to be measured._XWhich is a metal capable of reducing manganese and ZrO as ceramics₂Is formed of a porous cermet consisting of: NO 2 present in the atmosphere in the third internal space 8._XNO that can reduce_XWhile a constant voltage is applied by the DC power source 34 between the third pump electrode 38 disposed in the reference air introduction passage 10 corresponding to the inner pump electrode 36 while functioning as a reduction catalyst, Oxygen in the atmosphere in the third internal space 8 is pumped into the reference air introduction passage 10. Therefore, here, the third inner pump electrode 36, the third outer pump electrode 38, and the solid electrolyte layer 4c constitute a third electrochemical pump cell. The pump current flowing by the pump operation of the electrochemical pump cell is detected by the ammeter 40. The constant voltage (DC) power supply 34 is controlled by the third diffusion-controlling passage 14 to restrict NO._XUnder inflow, NO in the third electrochemical pump cell_XWith respect to the pumping of oxygen generated during decomposition, a voltage that gives a limit current can be applied.
[0023]
In the sensor element 2, a heater 42, which is heated by external power supply, is buried between the solid electrolyte layers 4 e and 4 f from above and below. Although not shown, a ceramic layer of alumina or the like is formed on the upper and lower surfaces of the heater 42 in order to obtain electrical insulation from the solid electrolyte layers 4e and 4f. As shown in FIG. 3 (b), the heater 42 is provided from the first internal space 6 to the entire third internal space 8, whereby the internal space is reduced. 6, 7, and 8 are heated to predetermined temperatures, respectively, so that the first, second, and third electrochemical pump cells as well as the electrochemical sensor cells are each heated and held at predetermined temperatures. It is supposed to be.
[0024]
Therefore, in the sensor element 2 having such a configuration, the tip end side is disposed in the measured gas existing space, whereby the measured gas is provided to the first sensor element 2 provided in the sensor element 2. Through the diffusion-controlling passage 12 and into the first internal space 6 under a predetermined diffusion resistance. Then, the gas to be measured introduced into the first internal space 6 is oxygen generated by applying a predetermined voltage between the two electrodes 16 and 18 constituting the first electrochemical pump cell. Is controlled so that the oxygen partial pressure becomes a predetermined value.
[0025]
In order to set the oxygen partial pressure of the atmosphere in the first internal space 6 to a predetermined value, the measurement electrode 22 and the reference electrode 24 in the electrochemical sensor cell are determined based on the well-known Nernst equation. Is measured by a potentiometer 26 to control the voltage (variable voltage 20) applied between the two electrodes 16 and 18 of the first electrochemical pump cell.
That is, the voltage of the first electrochemical pump cell may be controlled so that the electromotive force corresponds to the difference between the predetermined oxygen concentration in the first internal space 6 and the oxygen concentration of the reference air. Here, the first diffusion-controlling passage 12 determines the amount of oxygen in the measured gas that diffuses and flows into the measurement space (the first internal space 6) when a voltage is applied to the first electrochemical pump cell. It serves to narrow down and suppress the current flowing through the first electrochemical pump cell.
If the oxygen concentration in the gas to be measured is higher than a predetermined value, oxygen is pumped out by the oxygen pumping action of the first electrochemical pump cell, while the oxygen concentration in the gas to be measured is lower than a predetermined value, or In the case of zero, pumping oxygen from the external space by the oxygen pumping action of the first electrochemical pump cell to control the oxygen partial pressure of the atmosphere in the first processing zone to a predetermined oxygen partial pressure. become.
[0026]
Further, in the first internal space 6, even under the environment of heating by the external gas to be measured and the heating environment of the heater 42, the NO 2 in the atmosphere is_XUnder reduced oxygen partial pressure, for example, NO → 1 / 2N₂+ 1 / 2O₂A situation has been formed under oxygen partial pressure where the reaction does not occur. In the first internal space 6, NO in the gas to be measured (atmosphere)_XIs reduced, the NO in the third internal space 8 later becomes_XIn this sense, NO in the first internal space 6 cannot be measured._X(Here, metal components of the inner pump electrode 16 and the measurement electrode 22) involved in the reduction of NO_XThere is a need to create a situation in which can not be reduced.
[0027]
For this reason, the second electrochemical pump cell (4c, 28c) is set so that the oxygen partial pressure of the atmosphere inside the second internal space 7 can always be kept at a constant low oxygen partial pressure value. , 30), the operation of the pump allows the second internal cavity to be opened even if the oxygen partial pressure of the atmosphere introduced from the first internal cavity 6 changes according to the oxygen concentration of the gas to be measured. 7, the oxygen partial pressure of the atmosphere in the atmosphere 7 can always be kept at a constant low value._XCan be controlled to a low oxygen partial pressure value that does not substantially affect the measurement of the pressure.
[0028]
In the second internal space 7, similarly to the first internal space 6, under the heating environment by the external gas to be measured and the heating environment by the heater 42, the second inner pump electrode 28 is used. NO in the atmosphere_XIs formed under a partial pressure of oxygen in which is not reduced. For this reason, even in the case of the second inner pump electrode 28, similarly to the first inner pump electrode 16 and the measurement electrode 22, an electrode material having no reducing property or a weak reducing property with respect to the gas to be measured is used. Become.
[0029]
As described above, the gas to be measured whose oxygen partial pressure is controlled in the second internal space 7 passes through the third diffusion-controlling passage 14 and passes through the third internal space under a predetermined diffusion resistance. It is led into the empty space 8. The gas to be measured introduced into the third internal space 8 is supplied with oxygen between the third inner pump electrode 36 and the third outer pump electrode 38 constituting the third electrochemical pump cell. Is pumped from the third internal space 8 by applying a predetermined voltage in a direction to be pumped from the third internal space 8 to the reference air introduction passage 10 side. In particular, the oxygen concentration is further reduced at the three-phase interface of the third inner pump electrode 36, and NO_XAround the inner pump electrode 36, which also functions as a reduction catalyst, NO_XIs controlled to be reduced. At this time, the current flowing through the third electrochemical pump cell depends on the oxygen concentration in the atmosphere led to the third internal space 8, that is, the oxygen concentration in the atmosphere in the second internal space 7 and the third concentration. NO at inner pump electrode 36_XIs reduced in proportion to the sum of the concentration of oxygen generated by the reduction, and the concentration of oxygen in the atmosphere in the second internal space 7 is controlled to be constant by the second electrochemical pump cell. Therefore, the current flowing through the third electrochemical pump cell is NO_XWill be proportional to the concentration of And that NO_XIs limited by the third diffusion-controlling passage 14_XAnd thus the amount of NO_XThe concentration can be measured.
[0030]
FIG. 4 is a diagram showing NO of constituent elements constituting the gas analyzer of the present invention._XIt is sectional explanatory drawing which shows the modification of a sensor.
In the modification shown in FIG. 4, unlike the example of FIG. 3, the second internal space 7 and the third internal space 8 are integrated to form a united internal space formed of one narrow flat space. Where the second inner pump electrode 28 and the third inner pump electrode 36 are disposed, and the reference electrode 24 of the electrochemical sensor cell disposed in the reference air introduction passage 10; It is characterized in that the second outer pump electrode 30 in the second electrochemical pump cell and the third outer pump electrode 38 in the third electrochemical pump cell are constituted by one common electrode 44.
[0031]
In this modification, the combined internal space 9 is configured to include a second processing zone and a third processing zone, and is guided from the first internal space 6 through the second diffusion-controlled passage 13. The gas to be measured is a second inner pump electrode 28, a second outer pump electrode 30, and a second solid electrolyte layer 4a, 4b, 4c which are arranged at the inlet side of the united internal space 9. Oxygen is pumped by the electrochemical pump cell to control the oxygen partial pressure to a low and constant oxygen partial pressure, while maintaining a predetermined diffusion resistance defined by the narrow flat space of the united internal space 9. To the third electrochemical pump cell arranged at the back of the united internal space 9, where the gas component to be measured is NO._XIs reduced at the third inner pump electrode 36, and the pumping of oxygen from the third inner pump electrode 36 to the third outer pump electrode 38 is performed, so that the pump current of the third electrochemical pump cell is reduced. Is detected by the ammeter 40.
[0032]
Next, a gas analyzer according to the present invention incorporating the above-described gas sensor will be described.
FIG. 1 is a block diagram illustrating an example of a configuration of a gas analyzer according to the present invention. The gas analyzer according to the present invention includes a gas sensor 100, a driving unit 101 that pumps the gas sensor 100 with oxygen, and a gas sensor 100. A calculation unit 102 for calculating a pumping current flowing through the electrochemical pump cell into a measured gas value, a display output unit 103 for displaying the value calculated by the calculation unit 102 or extracting the value as an electrical output, and a gas sensor It basically comprises a heater driving unit 104 for heating 100 to a predetermined temperature.
[0033]
Here, the calculation unit 102 has a function of calculating the pumping current flowing through the third electrochemical pump cell into the measured gas value. However, the calculation unit 102 further includes a pumping current ( Ip1) or a pumping current in the first processing zone (Ip1), a pumping current in the second processing zone (Ip2) and a pumping current in the third processing zone (Ip3) Then, the calculation unit 102 calculates and outputs the amount of oxygen in the measured gas, the amount of insufficient oxygen, or the equivalent. Here, specific examples of the equivalent of the gas to be measured include an oxygen excess ratio (lambda value) and an air-fuel ratio (A / F value).
This can be determined based on the fact that (A * Ip1 + B * Ip2 + C * Ip3) is proportional to the total oxygen amount in the gas to be measured. Here, A, B and C are constants, respectively, and Ip3 is a pumping current flowing through the third electrochemical pump cell, that is, a pumping current in the third processing zone.
[0034]
In the present invention, the value of the amount of oxygen or the amount of oxygen deficient in the gas to be measured or the equivalent value is used to determine the amount of NO_XIt is preferable to correct the density. In this case, NO_XIt is preferable to use a value calculated based on (Ip1 + Ip2 + Ip3) as an oxygen amount, a deficient oxygen amount, or an equivalent amount (oxygen excess rate, air-fuel ratio, etc.) for correcting the concentration. A value calculated based on (Ip1 + Ip2) may be used.
For example, the pumping current (Ip3) in the third processing zone depends on the oxygen concentration in the gas to be measured. As shown in FIG. 6, the NO concentration in the measured gas depends on the oxygen concentration in the measured gas._XIf the concentration is high, it fluctuates somewhat. Therefore, the dependence between the pumping current (Ip3) and the oxygen concentration in the gas to be measured is measured in advance, and this measurement data is taken into the arithmetic unit 102, and the NO in the gas to be measured is measured._XIt is preferable to correct the density.
In FIG. 6, the correction for the oxygen dependency is described as an example. However, as another example, if the horizontal axis is equivalent (oxygen excess rate, air-fuel ratio, etc.), reducing gas, neutral gas, oxidizing gas NO in_XIt is also possible to correct for the dependence of the concentration measurements.
[0035]
FIG. 2 is a block diagram showing another example of the configuration of the gas analyzer according to the present invention. The gas analyzer shown in FIG. 2 shows a configuration in which a gas sensor and a receiver unit such as an arithmetic unit are separated from each other. The gas sensor 100, a driving unit 101 that pumps the gas sensor 100 with oxygen, and a driving unit 101 An amplifier 105 for amplifying the obtained pumping current is integrally disposed to constitute a sensor probe 110. At a position distant from the sensor probe 110, an arithmetic unit 102, a display output unit 103, and a heater driving unit 104 Is provided.
[0036]
FIG. 5 is a gas analyzer embodying the gas analyzer shown as a block diagram in FIG.
In FIG. 5, the gas analyzer 50 includes a measured gas introduction unit 60 and a NO._XAnd a detection unit 70. In the measured gas introducing section 60, a gas inlet 63 and a gas outlet 64 are formed on the side of the distal end of the cylindrical probe 62. Grids 65 and 66 are provided at predetermined intervals in the gas inlet 63 and the gas outlet 64, respectively. In the probe 62, an inner tube 67 having a flange 67a is provided concentrically with the probe 62. Then, as indicated by the arrow in the figure, the gas to be measured taken in from the gas inlet 63 enters through the inside of the inner tube 67, returns between the inner tube 67 and the probe 62 at the end of the inner tube 67, The gas is discharged from the gas outlet 64 to the outside of the probe 62.
[0037]
NO_XThe detection unit 70 has NO in the detection unit main body 72._XThe sensor unit 73 is housed therein. NO_XThe sensor unit 73 is a plate-shaped NO_XA sensor 74 is provided so as to be exposed at one end, and NO is provided at the other end._XA terminal block 75 used to establish an electrical connection with the outside of the sensor 74 is provided integrally by means such as screwing. The measured gas introduction unit 60 and the NO_XA flange 77 for connecting to the detection unit 70 is provided.
The calibration gas is set to NO_XA calibration gas inlet 78 for supplying the sensor 74 is provided. In addition, the NO_XAt the end opposite to the end where the sensor 74 is provided, a flange 79 and a lid 80 for accommodating the terminal block 75 are provided. Further, on the side surface of the flange 79, a wiring port 81 for leading out an electrode or the like (wiring of a driving unit or the like to be described later) from the terminal block 75 is provided. Also, NO_XThe sensor unit 73 is provided with a gas seal portion using an O-ring 82 so that the measurement gas does not leak to the terminal block 75. Note that the terminal block 75 has the same_XNO for sensor unit 73_XA terminal screw 86 for fixing to the detection unit 70 is attached.
[0038]
The terminal block 75 is provided with a drive unit 85 including an amplifier. The drive unit 85 is electrically connected to a receiver 90 including an arithmetic unit, a display output unit, and the like._XPumping of the sensor 74 and predetermined calculation and display / output are performed.
As described above, by integrally configuring the drive unit near the gas sensor, the pumping current in the drive unit is amplified by the amplifier and guided to the calculation unit, so that electrical noise can be reduced.
[0039]
In the gas analyzer of the present invention, it is preferable to measure the pumping current (Ip3) for a plurality of known measured gas component amounts, create a calibration curve, and calibrate the gas analyzer. That is, the pumping current (Ip3) data for a plurality of known measured gas component amounts is accumulated in the arithmetic unit of the gas analyzer, and the pumping current (Ip3) of the target measured gas component is calculated based on this data. Conversion to the measured gas component amount and calibration are performed.
For example, as shown in FIG. 7, measurement is performed using calibration gases (standard gases) having respective concentrations of a, b, and c, and pumping currents (Ia, Ib, Ic) at that time are obtained, and a calibration curve is created. Can be performed. The calibration curve is a primary straight line, a quadratic curve, or the like, and the calculation unit can automatically create the calibration curve.
Further, it is more preferable that the above-mentioned dependence on oxygen or dependence on equivalence is measured to correct the calibration curve.
[0040]
The gas analyzer of the present invention is preferably calibrated using the calibration curve as described above, but the known gas component to be measured (calibration gas) used at that time is, in addition to the known gas component to be measured, , At least H₂O, CO₂It is preferable to use a gas containing any one of the above gas components.
That is, as shown in FIG.₂O or CO₂When a calibration gas containing no is used, the generated electromotive force of the solid electrolyte becomes low, the pumping current (Ip3) increases, sometimes becomes unstable, and the reliability of the numerical value of the gas concentration to be measured decreases. Occurs. On the other hand, at least H₂O, CO₂When a calibration gas containing any one of the above gas components is used, the pumping current (Ip3) is stabilized. The reason for this is unknown, but is presumed to be due to a change or stabilization of the surface state of the solid electrolyte electrode.
H₂O, CO₂Is preferably 0.1 vol% or more, and more preferably 1 vol% or more.
[0041]
In the gas analyzer according to the present invention, CO, OH or a toxic substance is excessively adsorbed on an electrode of a solid electrolyte constituting an electrochemical pump cell before or at a predetermined time after use, and gas analysis is performed. The analysis accuracy of the meter may be reduced.
Therefore, in the gas analyzer, it is preferable to remove a poisoning substance or the like from the solid electrolyte electrode and measure the electrode in a normal state before measuring the calibration curve.
The desorption method can be roughly classified into high temperature and forced energization of the sensor.
That is, a method in which a sensor provided with an electrochemical pump cell is raised to 50 ° C. or more from its operating temperature for a certain period of time, and then returned to the operating temperature and a calibration curve is created with a calibration gas is preferably used (sensor High temperature method). Here, about 10 minutes is sufficient for keeping the sensor at a high temperature.
In addition, as a method of forcibly energizing the sensor, the sensor is separated from the driving unit, an alternating power supply is connected between each pair of electrodes in the first to third processing zones, and an alternating current of, for example, 1 Hz or more is passed for a predetermined time. Alternatively, a method of returning the sensor to a driving state and creating a calibration curve using a calibration gas is also preferably used. Here, the time for flowing the alternating current is about 10 minutes is sufficient.
[0042]
As described above, the present invention has been specifically described. However, it is needless to say that the present invention can be implemented in an embodiment in which various changes, modifications, improvements, etc. are added based on the knowledge of those skilled in the art. It is to be understood that such embodiments are within the scope of the present invention without departing from the spirit thereof.
[0043]
【The invention's effect】
As described above, the gas analysis of the present inventionIn totalAccording to the target NO_XThus, a stable pumping current or electromotive force corresponding to the concentration of the gas to be measured can be obtained, and the concentration of the gas component to be measured can be accurately measured. In addition, even if the oxygen concentration of the gas to be measured is high, it is not affected by the oxygen concentration, continuously has a good response, and can perform accurate measurement for a long time. High S / N ratio can be obtained, and a large signal change can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a configuration of a gas analyzer according to the present invention.
FIG. 2 is a block diagram showing another example of the configuration of the gas analyzer according to the present invention.
FIG. 3 is a diagram showing the NO components constituting the gas analyzer of the present invention._XFIG. 2A is a configuration diagram illustrating an example of a sensor, in which FIG. 2A is an explanatory plan view, and FIG.
FIG. 4 is a diagram showing the NO components constituting the gas analyzer of the present invention._XIt is sectional explanatory drawing which shows the modification of a sensor.
FIG. 5 is a gas analyzer embodying the gas analyzer shown as a block diagram in FIG.
FIG. 6 is a graph showing a relationship between an oxygen concentration in a gas to be measured and a pumping current (Ip3).
FIG. 7 is a graph showing a calibration curve.
FIG. 8: H in calibration gas₂O, CO₂Is a graph showing the relationship between the content of P and the pumping current (Ip3).
[Explanation of symbols]
2 ... Sensor element, 4a, 4b, 4c, 4d, 4e, 4f ... Solid electrolyte layer, 6 ... First internal space, 7 ... Second internal space, 8 ... Third internal space, 9 ... Combined internal space, 10: reference air introduction passage, 12: first diffusion-controlled passage, 13: second diffusion-controlled passage, 14: third diffusion-controlled passage, 16: first inner pump electrode, 18: first Outer pump electrode, 20: variable power supply, 22: measuring electrode, 24: reference electrode, 26: potentiometer, 28: second inner pump electrode, 30: second outer pump electrode, 36: third inner pump electrode, 38 ... third outer pump electrode, 42 ... heater, 44 ... common electrode, 50 ... gas analyzer, 60 ... measured gas introduction part, 70 ... NO_XDetector, 62: Probe, 63: Gas inlet, 64: Gas outlet, 67a: Flange, 67: Inner tube, 72: Detector body, 73: NO_XSensor unit, 74 ... NO_XSensor, 75 terminal block, 77 flange, 78 calibration gas inlet, 79 flange, 80 lid, 81 wiring port, 82 O-ring, 85 drive unit, 86 terminal screw, 90 receiver , 100: gas sensor, 101: drive unit, 102: arithmetic unit, 103: display output unit, 104: heater drive unit, 105: amplifier, 110: sensor probe, 120: receiver unit.

Claims (5)

From the external measured gas existing space, a measured gas containing a measured gas component having bound oxygen to be measured is guided to a first processing zone under a predetermined diffusion resistance, and in the first processing zone, After the oxygen partial pressure of the atmosphere in the first processing zone is controlled to a predetermined oxygen partial pressure by the oxygen pumping action of the first electrochemical pump cell, In the second processing zone, oxygen is further pumped out by a second electrochemical pump cell, whereby the oxygen partial pressure of the atmosphere is substantially measured for measuring the amount of the gas component to be measured. The oxygen content is controlled to a low oxygen partial pressure value which does not affect the gas content, and thereafter, the gas component to be measured in the atmosphere guided from the second processing zone is guided to the third processing zone. Reduce Allowed decomposition, a gas sensor by pumping out oxygen generated at that time in the third electrochemical pumping cell, for detecting a pumping current flowing through said third electrochemical pumping cell,
A driving unit for oxygen pumping the first to third processing zones in the gas sensor,
While calculating the pumping current flowing through the third electrochemical pump cell to the measured gas value, deriving the pumping current in the first processing zone, the amount of oxygen in the measured atmosphere, or the amount of oxygen deficiency, or the equivalent A calculation unit for calculating,
A display output unit that displays the value calculated by the calculation unit, or takes out the output as an electrical output,
A heater driving unit for heating the gas sensor to a predetermined temperature;
A gas analyzer comprising: From the external measured gas existing space, a measured gas containing a measured gas component having bound oxygen to be measured is guided to a first processing zone under a predetermined diffusion resistance, and in the first processing zone, After the oxygen partial pressure of the atmosphere in the first processing zone is controlled to a predetermined oxygen partial pressure by the oxygen pumping action of the first electrochemical pump cell, In the second processing zone, oxygen is further pumped out by a second electrochemical pump cell, whereby the oxygen partial pressure of the atmosphere is substantially measured for measuring the amount of the gas component to be measured. The oxygen content is controlled to a low oxygen partial pressure value which does not affect the gas content, and thereafter, the gas component to be measured in the atmosphere guided from the second processing zone is guided to the third processing zone. Reduce Allowed decomposition, a gas sensor by pumping out oxygen generated at that time in the third electrochemical pumping cell, for detecting a pumping current flowing through said third electrochemical pumping cell,
A driving unit for oxygen pumping the first to third processing zones in the gas sensor,
A pump current flowing in the third electrochemical pump cell is calculated into a measured gas value, and a pump current in the first processing zone, a pump current in the second processing zone, and the third processing zone. A computing unit that derives the pumping current at and calculates the amount of oxygen in the atmosphere to be measured, or the amount of oxygen deficiency, or the equivalent.
A display output unit that displays the value calculated by the calculation unit, or takes out the output as an electrical output,
A heater driving unit for heating the gas sensor to a predetermined temperature;
A gas analyzer comprising: The value of the oxygen amount or deficient amount of oxygen in the measured atmosphere, or by equivalent value, gas analyzer according to claim 1 or 2 for correcting the measured the measurement gas component. The gas analyzer according to any one of claims 1 to 3 the measurement gas component is NO _X. The gas analyzer according to any one of claims 1 to 4, wherein at least the driving unit is integrally formed with the gas sensor.

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