EP3155412A1 - Procédé et capteur de gaz pour détecter des oxydes d'azote dans un mélange gazeux - Google Patents

Procédé et capteur de gaz pour détecter des oxydes d'azote dans un mélange gazeux

Info

Publication number
EP3155412A1
EP3155412A1 EP15744512.3A EP15744512A EP3155412A1 EP 3155412 A1 EP3155412 A1 EP 3155412A1 EP 15744512 A EP15744512 A EP 15744512A EP 3155412 A1 EP3155412 A1 EP 3155412A1
Authority
EP
European Patent Office
Prior art keywords
electrodes
polarization
voltage
period
current
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP15744512.3A
Other languages
German (de)
English (en)
Inventor
Sabine Fischer
Jürgen Janek
Erhard Magori
Ralf Moos
Roland Pohle
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP3155412A1 publication Critical patent/EP3155412A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0037—NOx
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/4073—Composition or fabrication of the solid electrolyte
    • G01N27/4074—Composition or fabrication of the solid electrolyte for detection of gases other than oxygen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

  • the invention relates to a gas sensor and a method for detecting nitrogen oxides in a gas mixture, wherein the gas sensor comprises an oxygen ion conductor and two electrodes.
  • Nitrogen oxides can occur in addition to the occurrence of combustion gases as process gases and chemical plants. Again, the detection of nitrogen oxides may be of interest.
  • Known sensors for the measurement of NOx are optical or chemoluminescence-based systems. In addition to the high price, these systems have the disadvantage that an extractive measurement is necessary, that is, a gas extraction is necessary. For many applications this is associated with great expense.
  • Known sensors that overcome these disadvantages are based on yttrium-stabilized zirconia (YSZ) and are similar in construction to the conventional lambda probe; Electro ⁇ the same material are used, for example from Pla ⁇ tin.
  • the principle of operation is based on a two-chamber system with simultaneous measurement of oxygen and NOx.
  • the disadvantage here is still a complex one
  • a central principle of the lambda probe is, for example, that one of the electrodes must face the gas mixture to be measured, while the other electrode must face a gas with a defined oxygen partial pressure.
  • mixed potential sensors which include electrodes made of different materials and as a sensor signal between the potential difference between these evaluate.
  • US 2005/0284772 A1 discloses a measuring method in which zirconia-based lambda probes or mixed-potential sensors be used to build a NOx sensor.
  • the measurement principle here is a dynamic method in which defi ned ⁇ voltage pulses applied to the sensor and the jewei ⁇ celled gas-dependent depolarization is measured is used.
  • the discharge curves recorded in this way have a strong dependence on the surrounding gas atmosphere. Nitrogen oxides can be easily differentiated from other gases because with this type of sensor other gases have very little influence on the measurement signal. However, the sensor is therefore unable to detect any other gases in isolation.
  • Another disadvantage of the sensor is a change in the response of the sensor to the voltage pulses after a long period of operation or, in other words, a lack of long-term stability.
  • the object of the present invention is to specify a method and a gas sensor for measuring nitrogen oxides, which have improved long-term stability.
  • the solution consists in a gas sensor with the features of claim 7.
  • a gas sensor which comprises an oxygen ion conductor and at least two electrodes arranged thereon and the gas sensor is connected to the gas mixture in such a way that both electrodes come into contact with the gas mixture. Furthermore, a polarization voltage or a polarization current is applied to the electrodes during a polarization period and the current or the voltage at the electrodes is measured during a depolarization period following the polarization period. Finally, the nitrogen oxide content in the gas mixture is determined from the measured voltage or the measured current. It is particularly important that the polarization period is ended as soon as a definable charge quantity has flowed since the beginning of the polarization period.
  • the gas sensor according to the invention for the detection of nitrogen oxides in a gas mixture is configured for performing the method and has an oxygen ion conductor and Wenig ⁇ least two arranged on the oxygen ion conductor electrodes. Further, the gas sensor includes a Steuereinrich- tung, which is designed for applying a bias voltage or a bias current to the electrodes during a of polarization ⁇ tion period, and a measuring device for measuring the current or the voltage at the electrodes during the polarization period following depolarized sationszeitraums. Finally, the gas sensor includes an off ⁇ worth means for determining the nitrogen oxide content of the measured voltage and the measured current. In this case, the gas sensor is designed so that the polarization period is terminated as soon as a definable charge amount has flowed since the beginning of the polarization period.
  • Electrodes is introduced. Advantageously, it is ⁇ enough that even after prolonged periods of operation, the accuracy of the detection of nitrogen oxides is not changed too much.
  • advantageous embodiments and developments of the invention are set forth. These relate to both the gas sensor and the method.
  • the fixed amount of charge can be introduced into the electrodes in two ways:
  • the polarization time can become longer or shorter with increasing age of the gas sensor, depending on how the resistance of the elements of the gas sensor changes with the operating time. In any case, however, the transferred charge amount remains the same during each polarization period.
  • a fixed polarization current for a period of time can be impressed on the electrodes.
  • there is the transferred charge from the product of Po ⁇ larisa tion current and polarization time, ie the polarization- ⁇ onszeit can be determined from the outset here. It should be noted that the resulting polarization voltage varies depending on the resistance R of the sensor and thus is dependent on the temperature and the aging of the sensor.
  • the depolarization period can be terminated when a termination criterion is reached, in particular after a definable period of time has elapsed or when a definable voltage has been reached between the electrodes.
  • the depolarization time varies depending on the gas composition. This termination criterion has the advantage over the discharge for a defined time interval that the final voltage at the electrodes is independent of the
  • Gas composition is identical and thus the associated oxygen activity at the end of the depolarization is the same.
  • the electrodes can be made of platinum or gold. Particularly preferably, the electrodes are made of the same material.
  • the gas sensor may have a heating device configured to heat the oxygen ion conductor and the electrodes to a temperature at which an oxygen ion line is present. The gas sensor is thus expediently operated at a temperature at which oxygen ion is present.
  • the oxygen ion conductor and the electrodes are maintained at a temperature of at least 350 ° C. It has been experimentally found that the best from this Be ⁇ operating temperature, in particular between 400 ° C and 450 ° C, the measurement of nitrogen oxides works.
  • the heater may be oriented ⁇ staltet for example as an electric heater in form of a flat layer of, for example, platinum. It is suitably electrically separated from ion-conducting material and of course the gas sensor electrodes by an insulator layer, for example by the carrier.
  • the gas sensor may comprise three or more electrodes, wherein all electrodes are made of the same material and are arranged such that at least two of the electrodes in an operation of the gas sensor with the gas mixture in con ⁇ tact occur.
  • two of the electrodes may be arranged on one side of the ion-conducting material, while the other electrodes are arranged on the other side of the ion-conducting material.
  • the impressing of a voltage during a respective pulse period for the different pairs of electrodes can be made with a time offset, that is, in other words phase-shifted. This generates a measuring point more frequently and thus improves the temporal resolution.
  • ⁇ pairs of electrodes can be connected in series and thus an improvement in signal range can be achieved.
  • the electrodes can be geometrically designed to achieve an improvement in signal quality.
  • the electrodes can be designed as finger electrodes (interdigital electrodes).
  • the ionically conductive material can be a porous material out ⁇ leads.
  • the gradients in the partial pressure of the various gases result in diffusion of the gases through the ion conducting material, resulting in deterioration of the gas Sensor signal leads.
  • the ion-conducting material is no longer adjacent to the ambient air, but is suitably surrounded on all sides by the gas to be measured, no such diffusion happens more and a porous, in particular of ⁇ fenporiges material can be used.
  • a porous ion-conducting material is easier to produce, more stable against the stresses of changing temperatures and has a higher specific surface, which brings advantages for the interaction with gases and thus for the sensor signal.
  • the gas sensor includes electrical connections to the electrodes and means, propose this with a voltage to beauf ⁇ and polarization means for measuring voltage or current to the electrodes during the subsequent dismantling.
  • the ion-conducting material may, for example
  • YSZ yttrium stabilized zirconia
  • the ion-conducting material it is also possible for the ion-conducting material to be applied as a layer on a support, for example of aluminum oxide. The electrodes are then suitably applied again on the layer of the ion-conducting material.
  • the polarization voltage can be between 10mV and 2.5V.
  • the maximum voltage is expedient ⁇ SSIG less than the decomposition voltage of the ion conductor, ie for YSZ about 2.5 V.
  • the pulse time span is preferably between 10 ms and 10 s, in particular between 100 ms and 500 ms.
  • the catalytically active layer can be the corresponding
  • FIG. 1 shows a gas sensor according to the invention with two electrodes
  • Figure 2 is a diagram of the measuring method for operating the gas sensor.
  • FIG. 1 shows a highly schematic diagram of a first gas sensor 10 according to the invention.
  • This comprises a block 11 of YSZ material.
  • a first platinum electrode 12 and a second platinum electrode 13 are arranged, while on a second side, which is opposite to the first side, a heater structure 14 is arranged.
  • the platinum electrodes 12, 13 are electrically connected to means 16 for generating and measuring voltage.
  • mixed filled space can be introduced, for example, a flange for screwing into a correspondingly shaped opening.
  • FIG. 2 shows a diagram for the voltage curve 21.
  • a fixed polarization voltage referred to as Uo
  • Uo a fixed polarization voltage
  • the duration of the first pulse period 31 is not fixed, but results from the charge that has flowed through.
  • the charge is determined by the device 16 from a measured current and past time. If a charge threshold is exceeded or reached, the polarization is aborted.
  • the voltage decreases (in terms of absolute value), the course being influenced by the presence of nitrogen oxides in the gas mixture.
  • the course after the first polarization period 31 corresponds to the state that no NOx is present.
  • the fixed voltage Uo is applied with negative polarity and subsequently followed in a second depolarization period 34, the course of the voltage. It is useful here not the entire voltage curve measured. Rather, the voltage is tracked and the elapsed time is used as a measurement signal upon reaching a threshold value Ui for the depolarization.
  • the second polarization ⁇ period 33 is slightly shorter than the first polarization time ⁇ margin 31. This corresponds to a reduced resistance and increased current flow, which in turn amount of manure in a shorter time flows in the fixed laser.
  • the second depolarization period 34 is followed by a third polarization period 35. This is again approximately as long as the first polarization period 31. This is only an example because typically the polarization periods 31, 33, 35 are only very slow Are subject to change.
  • the third polarization period 35 in turn fixed voltage Uo is applied with positi ⁇ ver polarity.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • Immunology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Medicinal Chemistry (AREA)
  • Food Science & Technology (AREA)
  • Molecular Biology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

Procédé pour détecter des oxydes d'azote dans un mélange gazeux, selon lequel on utilise un capteur de gaz comportant un conducteur d'ions oxygène et au moins deux électrodes agencées sur le conducteur d'ions oxygène. Le capteur de gaz est amené en contact avec le mélange gazeux de telle sorte que les deux électrodes entrent en contact avec le mélange gazeux. Une tension ou un courant de polarisation est appliqué(e) sur les électrodes pendant une période de polarisation, la tension ou le courant étant mesuré(e) aux électrodes pendant une période de dépolarisation qui suit la période de polarisation. La teneur du mélange gazeux en oxydes d'azote est déterminée à partir de la tension ou du courant mesuré(e). La période de polarisation se termine dès qu'une quantité de charge qui peut être déterminée a circulé depuis le début de ladite période.
EP15744512.3A 2014-07-23 2015-07-20 Procédé et capteur de gaz pour détecter des oxydes d'azote dans un mélange gazeux Withdrawn EP3155412A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102014214400.0A DE102014214400A1 (de) 2014-07-23 2014-07-23 Verfahren und Gassensor zur Detektion von Stickoxiden in einem Gasgemisch
PCT/EP2015/066563 WO2016012407A1 (fr) 2014-07-23 2015-07-20 Procédé et capteur de gaz pour détecter des oxydes d'azote dans un mélange gazeux

Publications (1)

Publication Number Publication Date
EP3155412A1 true EP3155412A1 (fr) 2017-04-19

Family

ID=53762149

Family Applications (1)

Application Number Title Priority Date Filing Date
EP15744512.3A Withdrawn EP3155412A1 (fr) 2014-07-23 2015-07-20 Procédé et capteur de gaz pour détecter des oxydes d'azote dans un mélange gazeux

Country Status (3)

Country Link
EP (1) EP3155412A1 (fr)
DE (1) DE102014214400A1 (fr)
WO (1) WO2016012407A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3223007A1 (fr) * 2016-03-22 2017-09-27 Zircoa Inc. Procédé de conditionnement de capteur pour améliorer la stabilité de la sortie de signal pour des mesures de gaz mélangé

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE513477C2 (sv) * 1993-11-08 2000-09-18 Volvo Ab Sensor för detektering av kväveoxidföreningar
US8029656B2 (en) * 2003-01-30 2011-10-04 Emisense Technologies Llc System, apparatus, and method for measuring an ion concentration of a measured fluid
US7585402B2 (en) 2004-06-18 2009-09-08 Bjr Sensors, Llc Method of sensor conditioning for improving signal output stability for mixed gas measurements
AU2009219207A1 (en) * 2008-02-28 2009-09-03 Nextech Materials, Ltd. Amperometric electrochemical cells and sensors
WO2013134738A1 (fr) * 2012-03-08 2013-09-12 Nextech Materials, Ltd. Capteur ampérométrique de gaz à électrolyte solide et procédé de détection, l'électrode de détection comprenant au moins un composé de molybdate ou de tungstate

Also Published As

Publication number Publication date
DE102014214400A1 (de) 2016-01-28
WO2016012407A1 (fr) 2016-01-28

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