Oxides of nitrogen gas sensors and methods

• US 7,820,028 B2
• Filed: 09/02/2005
• Issued: 10/26/2010
• 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 L., Kroot, Peter J. M.
• Primary Examiner(s): Nguyen; Nam X
• Assistant Examiner(s): Dinh; Bach T
• Application Number:
  US11/162,251
• Publication Number:
  US 20070051641A1
• Time in Patent Office: 1,880 Days
• Field of Search: 204424-429, 2057835-785, 205/781, 73 2331- 2332, 73/232
• US Class Current: 205/781
• 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 for 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 of calculating a total NOx concentration, 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 NOx concentration;

contacting the gas stream with a first zirconium oxide based oxygen sensor at a first temperature to measure a first oxygen concentration and then using the first oxygen concentration to predict a first ratio of NO;

NO2 at equilibrium at the first temperature;

contacting the gas stream with a second zirconium oxide based oxygen sensor at a second temperature to measure a second oxygen concentration and then using the second oxygen concentration to predict a second ratio of NO;

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

calculating the total NOx concentration using the first ratio of NO;

NO2 at equilibrium and the second ratio of NO;

NO2 at equilibrium.

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

3. A method of calculating the total NOx concentration 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 ratio of NO:

NO2 at equilibrium at the first temperature.

4. A method of calculating the total NOx concentration 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 ratio of NO:

NO2 at equilibrium at the second temperature.

5. A method of calculating the total NOx concentration 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 ratio of NO:

NO2 at 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 ratio of NO;

NO2 at equilibrium at the second temperature.

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

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

NO2 at equilibrium.

7. 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 ratio of NO:

NO2 at equilibrium at the second temperature.