Electrochemical sensor for reactive gas mixtures

• US 3,981,785 A
• Filed: 07/18/1969
• Issued: 09/21/1976
• Est. Priority Date: 07/18/1969
• Status: Expired due to Term

• Current Assignee: Rosemount Analytical, Inc. (Emerson Electric Company)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Sandler, Yehuda L.
• Primary Examiner(s): Tung, T.
• Application Number:
  US04/843,038
• Time in Patent Office: 2,622 Days
• Field of Search: 136/86 F, 204/1 T, 204/195
• US Class Current: 204/410
• CPC Class Codes: G01N 27/4074 for detection of gases other than oxygen
• CPC Class Codes: G01N 27/4075 Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
• CPC Class Codes: G01N 27/417 using cells , i.e. more than one cell and probes with solid electrolytes

Abstract

An electrochemical device is designed to respond to a constituent such as oxygen in a reactive mixture which may include a fuel such as methane. The device includes an electrochemical cell employing an electrolye such as a stabilized zirconia associated with two electrodes and designed for operation at an elevated temperature such as 200°C to 1000°C. An electrode for such a cell is designed to have no catalytic action on the mixture.

The system may be arrnaged to assure a full reaction of the mixture before the cell responds to the desired constituent. Thus the mixture may also be subjected to the action of a catalyst before it reaches the electrode area. If the mixture is applied to another non-catalytic cell before it is subjected to the catalyst further information is obtained concerning the desired constitent. The amount of a constituent such as oxygen present before and after the mixture is catalyzed may be compared to provide an indication of the amount of another constituent of the mixture such as methane.

Claims

1. An electrochemical device for monitoring constituents of an oxygen-fuel mixture comprising, a solid electrolyte electrochemical cell having a first and second electrode disposed on opposite surfaces thereof, said first electrode has a composition exhibiting negligible catalytic action on said mixture, means for supplying a first portion of said mixture to said first electrode and a second portion of said mixture to said second electrode, said first portion of said mixture forming an oxygen reference media and said first electrode serving as an oxygen reference electrode, and catalytic means for equilibrating said second portion of said mixture, said electrochemical device generating an EMF indicative of the difference between the oxygen content of said first portion of said mixture and the equilibrated second portion of said mixture.

2. An electrochemical device as claimed in claim 1 wherein said second electrode has a composition producing substantial catalytic action among the constituents of said mixture, said second electrode serving as said catalytic means.

3. An electrochemical device as claimed in claim 1 wherein said second electrode has a composition exhibiting negligible catalytic action on said mixture, and said catalytic means equilibrating said second portion of said mixture in advance of contact with said second electrode.

4. An electrochemical device as claimed in claim 3 wherein said first and second electrodes are silver compositions.

5. An electrochemical device as claimed in claim 2 wherein said first electrode is a silver composition and said second electrode is a platinum composition.

6. An electrochemical device for monitoring constituents of an oxygen-fuel mixture comprising a first solid electrolyte electrochemical cell having a first and second electrode disposed on opposite surfaces thereof, a second solid electrolyte electrochemical cell having a first and second electrode disposed on opposite surfaces thereof, means for supplying an oxygen reference media in contact with said second electrodes of said first and second solid electrolyte electrochemical devices, said second electrodes functioning as oxygen reference electrodes, means for supplying said mixture in a consecutive manner to the first electrode of said first solid electrolyte electrochemical cell device and subsequently to the first electrode of said second solid electrolyte electrochemical device, said first electrode of said first solid electrolyte electrochemical device has a composition exhibiting negligible catalytic action on said mixture, catalystic means for equilibrating said mixture following passage of said mixture in contact with said first electrode of said first solid electrolyte electrochemical device to provide an equilibrated mixture in contact with said first electrode of said second solid electrolyte electrochemical device, said first solid electrolyte electrochemical device developing an EMF between said first and second electrodes which is indicative of the actual partial pressure of oxygen in said mixture, said second solid electrolyte electrochemical device developing an EMF between said first and second electrodes which is indicative of the oxygen partial pressure of the mixture following equilibration of said mixture.

7. An electrochemical device as claimed in claim 6 wherein said first electrodes are silver compositions.

8. An electrochemical device as claimed in claim 6 wherein said first electrode of said first solid electrolyte electrochemical device is a silver composition, and said first electrode of said second solid electrolyte electrochemical device is a composition producing substantial catalytic action among the constituents of said mixture, said first electrode of said second solid electrolyte electrochemical device serving as said catalytic means.