DE102006014007B3 - Opto-pneumatic detector for non-dispersive infrared gas analyzer, has chamber with surface carrying coating of silicon oxide formed by plasma enhanced chemical vapor deposition, where coating is airtight against polar gas components - Google Patents

Opto-pneumatic detector for non-dispersive infrared gas analyzer, has chamber with surface carrying coating of silicon oxide formed by plasma enhanced chemical vapor deposition, where coating is airtight against polar gas components Download PDF

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DE102006014007B3
DE102006014007B3 DE200610014007 DE102006014007A DE102006014007B3 DE 102006014007 B3 DE102006014007 B3 DE 102006014007B3 DE 200610014007 DE200610014007 DE 200610014007 DE 102006014007 A DE102006014007 A DE 102006014007A DE 102006014007 B3 DE102006014007 B3 DE 102006014007B3
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coating
opto
pneumatic detector
chamber
vapor deposition
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Ludwig Kimmig
Martin Kionke
Jürgen Sandritter
Ingeborg Schroth
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/37—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using pneumatic detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/09—Cuvette constructions adapted to resist hostile environments or corrosive or abrasive materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/59—Transmissivity
    • G01N21/61—Non-dispersive gas analysers

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
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  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
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  • Spectroscopy & Molecular Physics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

Abstract

The detector has a detector chamber that comprises a metal such as aluminum, forming metal oxide at a surface in an interior of the chamber and contains a gas mixture with polar gas components. The surface carries a coating of silicon oxide formed through plasma enhanced chemical vapor deposition, where the coating is airtight against the polar gas components. The coating with a non-polar polymer surface is multi-layered, and the polar gas components are sulfur dioxide.

Description

Die Erfindung betrifft einen opto-pneumatischen Detektor für ein nichtdispersives Infrarot-Gasanalysengerät mit mindestens einer Detektorkammer aus einem ein Metalloxid an der Oberfläche bildenden Metall, die ein Gasgemisch mit einer polaren Gaskomponente enthält.The The invention relates to an opto-pneumatic detector for a non-dispersive Infrared gas analyzer with at least one detector chamber of a metal oxide the surface forming metal, which is a gas mixture with a polar gas component contains.

Derartige, beispielsweise aus der DE 35 29 482 A1 , DE 195 40 072 B4 oder DE 10 2004 031 643 A1 bekannte opto-pneumatische Detektoren sind Bestandteil eines nichtdispersiven Infrarot-(NDIR-)Gasanalysators, bei dem eine mittels einer Strahlungszerhackereinrichtung modulierte Infrarot-Strahlung durch eine Messküvette, die mit einem aus unterschiedlichen Gaskomponenten bestehenden, zu analysierenden Messgas gefüllt ist, in den Detektor geleitet wird. Dieser besteht aus einer strahlungsdurchlässigen Detektorkammer, die mit der zu bestimmenden Gaskomponente oder einem Ersatzgas gefüllt ist und über eine Leitung mit einem darin befindlichen druck- oder strömungsempfindlichen Sensor mit einem Gasvolumen verbunden ist. Das Gasvolumen kann aus einer weiteren Detektorkammer bestehen, die hinter einer mit Inertgas gefüllten und gegenüber der Messküvette gegenphasig durchstrahlten Vergleichsküvette angeordnet ist. Die in die Detektorkammern fallende modulierte Strahlung wird von dem darin enthaltenen Gas wellenlängenspezifisch teilweise absorbiert, wobei sich das Gas entsprechend der Modulation erwärmt bzw. abkühlt und dadurch Druckschwankungen erzeugt, die mittels des druck- oder strömungsempfindlichen Sensors erfasst werden. Die in der Messküvette enthaltene, zu bestimmende Gaskomponente mit gleicher wellenlängenspezifischer Charakteristik wie das Gas in dem Detektor verringert durch Vorabsorption die in diesem Wellenlängenbereich in die Detektorkammer hinter der Messküvette fallende Strahlung. Aus der Differenz zwischen den Druckschwankungen, die entweder bei nicht vorhandener Vergleichsküvette einmal bei mit Inertgas gefüllter Messküvette und ein anderes Mal bei mit dem Messgas gefüllten Messküvette erfasst werden können oder zwischen der Detektorkammer hinter der mit Messgas gefüllten Messküvette und der Detektorkammer hinter der mit dem Inertgas gefüllten Vergleichsküvette erfasst werden, kann die Konzentration der zu bestimmenden Gaskomponente ermittelt werden.Such, for example from the DE 35 29 482 A1 . DE 195 40 072 B4 or DE 10 2004 031 643 A1 Known opto-pneumatic detectors are part of a non-dispersive infrared (NDIR) gas analyzer, in which an infrared radiation modulated by means of a radiation chopper device is passed into the detector through a measuring cuvette filled with a sample gas to be analyzed comprising different gas components , This consists of a radiation-permeable detector chamber, which is filled with the gas component to be determined or a replacement gas and is connected via a line with a pressure or flow-sensitive sensor located therein with a gas volume. The gas volume can consist of a further detector chamber, which is arranged behind a comparison cuvette filled with inert gas and opposite the measuring cuvette. The modulated radiation falling into the detector chambers is partially absorbed by the gas contained therein in a wavelength-specific manner, whereby the gas is heated or cooled in accordance with the modulation and thereby generates pressure fluctuations which are detected by means of the pressure- or flow-sensitive sensor. The gas component to be determined, which is contained in the measuring cuvette and has the same wavelength-specific characteristic as the gas in the detector, reduces the radiation falling in the detector chamber behind the measuring cuvette by pre-absorption. The difference between the pressure fluctuations that can be detected either with the sample cell not filled with inert gas and another with the sample cell filled with the sample gas or between the detector chamber behind the sample cell filled with sample gas and the detector chamber behind with the inert gas filled comparison cuvette are detected, the concentration of the gas component to be determined can be determined.

Der Detektor kann auch in bekannter Weise als Zweischichtdetektor aufgebaut sein. Dabei wird in der oberen Detektorschicht bevorzugt die Absorptionsbandenmitte absorbiert, während die Bandenflanken in der unteren und oberen Schicht etwa in gleichem Maße absorbiert werden. Die obere und untere Detektorschicht sind pneumatisch über den druck- oder strömungsempfindlichen Sensor miteinander verbunden. Diese Gegenkopplung führt dazu, dass die spektrale Empfindlichkeit sehr schmalbandig wird.Of the Detector can also be constructed in a known manner as a two-layer detector be. In this case, the absorption band center is preferred in the upper detector layer absorbed while the band edges in the lower and upper layers are approximately the same Absorbed dimensions become. The upper and lower detector layers are pneumatically over the pressure or flow sensitive Sensor connected together. This negative feedback causes that the spectral sensitivity becomes very narrowband.

Um Schwefeldioxid (SO2) zu messen, können als Frästeile aus Aluminium ausgeführte opto-pneumatischen Mehrschicht-Detektoren verwendet werden. Das Aluminium bildet nach der Bearbeitung sehr schnell eine Aluminiumoxidschicht (Al2O3) an seiner Oberfläche, die sehr widerstandsfähig gegen aggressive Gase ist, so dass das SO2 die Oberfläche nicht angreifen kann.To measure sulfur dioxide (SO 2 ), opto-pneumatic multi-layer detectors made of aluminum may be used. The aluminum forms very quickly after processing an aluminum oxide layer (Al 2 O 3 ) on its surface, which is very resistant to aggressive gases, so that the SO 2 can not attack the surface.

Es wurde nun beobachtet, dass das Nullpunktsignal eines solchen Gasanalysengeräts für SO2 bei konstanter Temperatur von zum Beispiel 5°C über Tage und Wochen auf einen stabilen Wert hin driftet. Diese Drift ist jedoch nicht reproduzierbar und wirkt sich störend auf die Messgenauigkeit aus, besonders in empfindlichen Messbereichen. Wenn nun die Drift nach längerer Zeit bei 5°C abgeklungen ist und die Umgebungstemperatur beispielsweise auf 45° C verändert wird, so fängt das Nullpunktsignal erneut zu driften an und bewegt sich über Wochen auf einen anderen stabilen Wert zu. Die Detektoren verhalten sich also so, als ob in ihnen bei 5°C und 45°C die Konzentration von SO2 jeweils unterschiedlich sei und sich dieser Unterschied langsam über Wochen hin einstelle.It has now been observed that the zero point signal of such SO 2 gas analyzer drifts to a steady state at constant temperature of, for example, 5 ° C for days and weeks. However, this drift is not reproducible and has a disturbing effect on the measuring accuracy, especially in sensitive measuring ranges. Now, if the drift has subsided after a long time at 5 ° C and the ambient temperature is changed, for example, to 45 ° C, the zero point signal begins to drift again and moves to another stable value over weeks. The detectors behave as if the concentration of SO 2 is different at 5 ° C and 45 ° C, and this difference slowly settles for weeks.

Gemäß der Erfindung wird dieses Problem dadurch gelöst, dass bei dem opto-pneumatischen Detektor der eingangs angegebenen Art die Oberfläche im Inneren der Detektorkammer eine durch plasmainduzierte Materialabscheidung erzeugte Beschichtung trägt, die gegenüber der polaren Gaskomponente dicht ist.According to the invention this problem is solved by that in the opto-pneumatic detector of the above-specified Kind the surface in the interior of the detector chamber through a plasma-induced material deposition wearing coated coating, the opposite the polar gas component is dense.

Der Erfindung liegt die Erkenntnis zu Grunde, dass Ursache des Problems die feinporige polare Oberfläche des Aluminiumoxids ist. Es ist bekannt, dass Metalloxide in ihren Poren Wasser speichern können. SO2 ist nun von seiner Struktur ein ähnliches Molekül wie H2O und daher in vielen physikalischen Eigenschaften ähnlich, beispielsweise in der Polarität. Wie bei H2O kann man daher erwarten dass sich auch SO2 gut an die polare Oberfläche des Aluminiumoxids anlagert bzw. in seinen Poren gespeichert wird. Dies wird entsprechend der Erfindung durch die glatte und porenfreie Beschichtung der Oberfläche im Inneren der Detektorkammer vermieden.The invention is based on the finding that the cause of the problem is the fine-pored polar surface of the aluminum oxide. It is known that metal oxides can store water in their pores. SO 2 is now structurally similar to H 2 O and therefore similar in many physical properties, such as polarity. As with H 2 O, it can therefore be expected that SO 2 will also adhere well to the polar surface of the aluminum oxide or be stored in its pores. This is avoided according to the invention by the smooth and non-porous coating of the surface inside the detector chamber.

Die Beschichtung wird vorzugsweise durch Plasma-Enhanced Chemical Vapor Deposition (PECVD) oder Plasmapolymerisation, erzeugt. PECVD und Plasmapolymerisation sind beides plasmagestützte Dünnschichtprozesse, wobei anorganische oder organische Precurser im Plasma dissoziiert werden und die resultierenden Fragmente und Radikale eine dünne Schicht auf dem zu beschichteten Substrat bilden. Es ist zwar aus der DE 3942325 A1 bekannt, bei einem NDIR-Gasanalysator die reflektierende Innenseite der Analysenkammer (Messküvette) mit einer Beschichtung aus SiO2 und/oder SiC zu versehen, welche mittels PECVD erzeugt werden kann, jedoch dient diese Beschichtung zum Schutz der Analysenkammer gegen korrosive Gase. Wie oben bereits erwähnt, bildet aber bereits das Aluminium der Detektorkammer nach seiner Bearbeitung sehr schnell eine Al2O3-Oberflächenschicht aus, die sehr widerstandsfähig gegen aggressive Gase wie SO2 ist, so dass es daher in der Detektorkammer keiner Schutzbeschichtung wie im Falle der Analysenkammer bedarf.The coating is preferably produced by plasma-enhanced chemical vapor deposition (PECVD) or plasma polymerization. PECVD and plasma polymerization are both plasma enhanced thin-film processes, whereby inorganic or organic precursors are dissociated in the plasma and the resulting fragments and radicals form a thin layer on the substrate to be coated. It is indeed from the DE 3942325 A1 In the case of an NDIR gas analyzer, it is known to provide the reflective inside of the analysis chamber (measuring cuvette) with a coating of SiO 2 and / or SiC which can be produced by means of PECVD, but this coating serves to protect the analysis chamber against corrosive gases. As already mentioned above, however, the aluminum of the detector chamber after processing very quickly forms an Al 2 O 3 surface layer which is very resistant to aggressive gases such as SO 2 , so that it does not have a protective coating in the detector chamber as in the case of Analysis chamber required.

Bei dem erfindungsgemäßen opto-pneumatischen Detektor lässt sich glatte porenfreie Beschichtung beispielsweise in Form einer glasartigen Schicht aus SiOx realisieren. Da SiOx jedoch auch eine polare Oberfläche bildet, kann alternativ oder zusätzlich eine unpolare polymere, z. B. PTFE-ähnliche, Schicht aufgebracht werden. Darüber hinaus kommen für die Beschichtung alle durch plasmainduzierte Materialabscheidung erzeugbaren bekannten Abscheidungsprodukte in Frage, welche gegenüber der jeweiligen polaren Gaskomponente in der Detektorkammer dicht sind oder, beispielsweise als Haftvermittler, zum Aufbau einer solchen dichten Schicht dienen.In the opto-pneumatic detector according to the invention, smooth pore-free coating can be realized, for example, in the form of a vitreous layer of SiO x . However, since SiO x also forms a polar surface, alternatively or additionally, a nonpolar polymeric, z. As PTFE-like, layer are applied. In addition, all known deposition products which can be produced by plasma-induced material deposition are suitable for the coating, which are dense in the detector chamber relative to the respective polar gas component or serve, for example as adhesion promoters, to build up such a dense layer.

Da ähnliche Driftverhalten wie im Fall von SO2 auch bei anderen polaren Gasarten wie NO oder N2O, wenn auch nicht so deutlich, beobachtet wurden, kommt die erfindungsgemäße Beschichtung allgemein für opto-pneumatische Detektoren mit polaren Gaskomponenten in der Gasfüllung in Frage. Als Material für die Detektoren sind außer Aluminium ebenfalls andere Metalle wie z. B. Magnesium denkbar, die eine Metalloxid-Oberfläche bilden.Since similar drift behaviors as in the case of SO 2 have also been observed in other polar gas species such as NO or N 2 O, although not so clearly, the coating according to the invention is generally suitable for opto-pneumatic detectors with polar gas components in the gas filling. As a material for the detectors are also other metals such as aluminum, such as aluminum. As magnesium conceivable that form a metal oxide surface.

Claims (8)

Opto-pneumatischer Detektor für ein nichtdispersives Infrarot-Gasanalysengerät mit mindestens einer Detektorkammer aus einem ein Metalloxid an der Oberfläche bildenden Metall, die ein Gasgemisch mit einer polaren Gaskomponente enthält, dadurch gekennzeichnet, dass die Oberfläche im Inneren der Detektorkammer eine durch plasmainduzierte Materialabscheidung erzeugte Beschichtung trägt, die gegenüber der polaren Gaskomponente dicht ist.An opto-pneumatic detector for a non-dispersive infrared gas analyzer comprising at least one metal oxide surface-forming metal detector chamber containing a gas mixture with a polar gas component, characterized in that the surface inside the detector chamber carries a coating generated by plasma-induced material deposition which is dense to the polar gas component. Opto-pneumatischer Detektor nach Anspruch 1, dadurch gekennzeichnet, dass die Beschichtung eine durch Plasma-Enhanced Chemical Vapor Deposition (PECVD) erzeugte Beschichtung ist.Opto-pneumatic detector according to claim 1, characterized in that the coating is a plasma enhanced chemical Vapor Deposition (PECVD) is generated coating. Opto-pneumatischer Detektor nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Beschichtung eine durch Plasmapolymerisation erzeugte Beschichtung ist.Opto-pneumatic detector according to claim 1 or 2, characterized in that the coating is a by plasma polymerization produced coating is. Opto-pneumatischer Detektor nach einem der vorangehenden Ansprüche 1, dadurch gekennzeichnet, dass die Beschichtung aus SiOx besteht.Opto-pneumatic detector according to one of the preceding claims 1, characterized in that the coating consists of SiO x . Opto-pneumatischer Detektor nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Beschichtung aus einer unpolaren Polymeroberfläche besteht.Opto-pneumatic detector according to one of claims 1 to 4, characterized in that the coating of a nonpolar polymer surface consists. Opto-pneumatischer Detektor nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die Beschichtung mehrschichtig ist.Opto-pneumatic detector according to one of the preceding Claims, characterized in that the coating is multi-layered. Opto-pneumatischer Detektor nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die polare Gaskomponente Schwefeldioxid ist.Opto-pneumatic detector according to one of the preceding Claims, characterized in that the polar gas component is sulfur dioxide. Opto-pneumatischer Detektor nach einem der vorangehenden Ansprüche 1, dadurch gekennzeichnet, dass das Metall Aluminium ist.Opto-pneumatic detector according to one of the preceding claims 1, characterized in that the metal is aluminum.
DE200610014007 2006-03-27 2006-03-27 Opto-pneumatic detector for non-dispersive infrared gas analyzer, has chamber with surface carrying coating of silicon oxide formed by plasma enhanced chemical vapor deposition, where coating is airtight against polar gas components Expired - Fee Related DE102006014007B3 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016177720A1 (en) 2015-05-04 2016-11-10 Emerson Process Management Gmbh & Co. Ohg Radiation detector for a non-dispersive infrared gas analyzer

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2625448A1 (en) * 1976-06-05 1977-12-15 Bosch Gmbh Robert METHOD FOR PRODUCING A PROTECTIVE LAYER ON THE SURFACE OF OPTICAL REFLECTORS AND REFLECTORS PRODUCED BY THIS PROCESS
DE19540072B4 (en) * 1995-10-27 2004-12-30 Emerson Process Management Manufacturing Gmbh & Co. Ohg Optical-pneumatic radiation detector
DE102004031643A1 (en) * 2004-06-30 2006-02-02 Abb Patent Gmbh Non-dispersive infrared gas analyzer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2625448A1 (en) * 1976-06-05 1977-12-15 Bosch Gmbh Robert METHOD FOR PRODUCING A PROTECTIVE LAYER ON THE SURFACE OF OPTICAL REFLECTORS AND REFLECTORS PRODUCED BY THIS PROCESS
DE19540072B4 (en) * 1995-10-27 2004-12-30 Emerson Process Management Manufacturing Gmbh & Co. Ohg Optical-pneumatic radiation detector
DE102004031643A1 (en) * 2004-06-30 2006-02-02 Abb Patent Gmbh Non-dispersive infrared gas analyzer

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016177720A1 (en) 2015-05-04 2016-11-10 Emerson Process Management Gmbh & Co. Ohg Radiation detector for a non-dispersive infrared gas analyzer
DE102015106915A1 (en) 2015-05-04 2016-11-10 Emerson Process Management Gmbh & Co. Ohg Radiation detector for a non-dispersive infrared gas analyzer
US9952145B2 (en) 2015-05-04 2018-04-24 Emerson Process Management Gmbh & Co. Ohg Radiation detector for a non-dispersive infrared gas analyzer
DE102015106915B4 (en) * 2015-05-04 2020-01-30 Emerson Process Management Gmbh & Co. Ohg Radiation detector for a non-dispersive infrared gas analyzer

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