OXIDES OF NITROGEN GAS SENSORS AND METHODS

• US 20070051641A1
• Filed: 09/02/2005
• Published: 03/08/2007
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: Garrett Transportation I Inc. (Garrett Motion, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Rhodes, Michael, Kroot, Peter
• Granted Patent: US 7,820,028 B2
• Time in Patent Office: Days
• US Class Current: 205/785.500
• CPC Class Codes: G01N 27/417 using cells , i.e. more than one cell and probes with solid electrolytes
• CPC Class Codes: G01N 33/0024 a chemical reaction taking place or a gas being eliminated in one or more channels
• CPC Class Codes: G01N 33/0037 NOx
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

Apparatus and methods for measuring NO_x concentrations are disclosed. One method includes the steps of providing a gas stream having a NO concentration and a NO₂ concentration, wherein a sum of the NO concentration and the NO₂ concentration is a total NO_x concentration; contacting the gas stream with a first zirconium oxide based oxygen sensor at a first temperature to achieve a first NO:NO₂ equilibrium at the first temperature; contacting the gas stream with a second zirconium oxide based oxygen sensor at a second temperature to achieve a second NO:NO₂ equilibrium at the second temperature; and determining the total NO_x concentration by measuring a response of the first zirconium oxide based oxygen sensor to achieve the first NO:NO₂ equilibrium and a response of the second zirconium oxide based oxygen sensor to achieve the second NO:NO₂ equilibrium. The second temperature is different than the first temperature.

Claims

1. A method comprising steps of:

providing a gas stream having a NO concentration and a NO₂ concentration, wherein a sum of the NO concentration and the NO₂ concentration is a total NO_x concentration;

contacting the gas stream with a first zirconium oxide based oxygen sensor at a first temperature to achieve a first NO;

NO₂ equilibrium at the first temperature;

contacting the gas stream with a second zirconium oxide based oxygen sensor at a second temperature to achieve a second NO;

NO₂ equilibrium at the second temperature, the second temperature being different than the first temperature; and

determining the total NO_x concentration by measuring a response of the first zirconium oxide based oxygen sensor to achieve the first NO;

NO₂ equilibrium and a response of the second zirconium oxide based oxygen sensor to achieve the second NO;

NO₂ equilibrium.

2. A method according to claim 1 wherein the providing a gas stream step comprises providing a gas stream further comprising an oxygen concentration.

3. A method according to claim 1 wherein the contacting the gas stream with a first zirconium oxide based sensor step comprises contacting the gas stream with a first zirconium oxide based sensor comprising a catalyst that assists in providing the gas stream having the first NO:

NO₂ equilibrium at the first temperature.

4. A method according to claim 1 wherein the contacting the gas stream with a second zirconium oxide based sensor step comprises contacting the gas stream with a second zirconium oxide based sensor comprising a catalyst that assists in providing the gas stream having the second NO:

NO₂ equilibrium at the second temperature.

5. A method according to claim 1 wherein the contacting the gas stream with a first zirconium oxide based sensor step comprises contacting the gas stream with a first zirconium oxide based sensor comprising a catalyst that assists in providing the gas stream having the first NO:

NO₂ equilibrium at the first temperature and the contacting the gas stream with a second zirconium oxide based sensor step comprises contacting the gas stream with a second zirconium oxide based sensor comprising a catalyst that assists in providing the gas stream having the second NO;

NO₂ equilibrium at the second temperature.

6. A method according to claim 1 wherein the determining step comprises determining the total NO_x concentration by measuring a difference of the response of the first zirconium oxide based oxygen sensor to achieve the first NO:

NO₂ equilibrium and the response of the second zirconium oxide based oxygen sensor to achieve the second NO;

NO₂ equilibrium.

10. A method according to claim 1 wherein the contacting step comprises contacting the gas stream with a zirconium oxide based oxygen sensor comprising a catalyst that assists in providing the gas stream having a NO concentration and a NO₂ concentration at the second NO:

NO₂ equilibrium at the second temperature.

7. A method comprising steps of:

providing a gas stream having a NO concentration and a NO₂ concentration at a first NO;

NO₂ equilibrium at a first temperature, wherein the total of the NO concentration and the NO₂ concentration is a total NO_x concentration;

contacting the gas stream with a zirconium oxide based oxygen sensor at a second temperature to achieve a second NO;

NO₂ equilibrium at the second temperature, the second temperature is different than the first temperature; and

determining the total NO_x concentration by measuring a response of the zirconium oxide based oxygen sensor to achieve the second NO;

NO₂ equilibrium.

8. A method according to claim 7 further comprising flowing the gas stream through a porous media comprising a catalyst that assists in providing the gas stream having a NO concentration and a NO₂ concentration at the first NO:

NO₂ equilibrium at the first temperature, wherein the porous media is at the first temperature.

9. A method according to claim 7 wherein the providing a gas stream step comprises providing a gas stream further comprising an oxygen concentration.

11. An NO_x sensor apparatus comprising:

a first zirconium oxide based oxygen sensor in fluid connection with a NO_x gas source and in electrical connection with a sensor controller, the first zirconium oxide based oxygen sensor comprises a first platinum sense electrode;

a heating element in thermal communication with the first zirconium oxide based oxygen sensor; and

a second zirconium oxide based oxygen sensor in fluid connection with the NO_x gas source and in electrical connection with the sensor controller, the first zirconium oxide based oxygen sensor comprise a second platinum sense electrode.

12. An apparatus according to claim 11 further comprising a second heating element in thermal communication with the second zirconium oxide based oxygen sensor.

13. An apparatus according to claim 11 wherein the first and second platinum sense electrodes comprises a catalyst that assists in NO+½

O₂⇄

NO₂ equilibrium.

14. An apparatus according to claim 11 wherein the first and second platinum sense electrode comprises a catalyst selected from the group consisting of gold, nickel or rhodium.

15. An apparatus according to claim 11 further comprising a housing disposed about the first zirconium oxide based oxygen sensor and the second zirconium oxide based oxygen sensor.

16. An apparatus according to claim 11 further comprising a porous media comprising a catalyst that assists in NO+½

O₂⇄

NO₂ equilibrium and in fluid communication with a NO_x gas source and disposed between the gas source and the first zirconium oxide based oxygen sensor or the second zirconium oxide based oxygen sensor.

17. An NO_x sensor apparatus comprising:

a porous media comprising a catalyst that assists in NO+½

O₂⇄

NO₂ equilibrium and in fluid communication with a NO_x gas source;

a zirconium oxide based oxygen sensor in fluid communication with the porous media and in electrical connection with a sensor controller, the zirconium oxide based oxygen sensor comprising a platinum sense electrode; and

a heating element in thermal communication with the first zirconium oxide based oxygen sensor.

18. An apparatus according to claim 17 further comprising a second heating element in thermal communication with the porous media.

19. An apparatus according to claim 17 wherein the platinum sense electrode comprises a catalyst that assists in NO+½

O₂⇄

NO₂ equilibrium.

20. An apparatus according to claim 17 wherein the platinum sense electrode comprises a catalyst selected from the group consisting of gold, nickel or rhodium.