NOx gas sensor method and device
First Claim
1. An apparatus for determining NOx concentration of an exhaust gas, the apparatus comprising;
- an input assembly capable of receiving the exhaust gas and producing a conditioned output gas, the input assembly including at least three of the following four stages;
a first stage including a first catalyst structure for converting NH3 in the exhaust gas to N2 and H2O;
a second stage including second catalyst structure having an absorbent material for absorbing SO2 or H2S from the exhaust gas;
a third stage including a third catalyst structure for oxidizing unburned hydrocarbons and gases to higher oxidation states; and
, a fourth stage including a fourth catalyst structure for establishing a steady state equilibrium concentration ratio between NO and NO2; and
, a NOx sensor operably connected to the input assembly and receiving the conditioned output gas of the input assembly wherein the concentration of the total NOx present can be determined.
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Accused Products
Abstract
The present invention is a method and apparatus for measuring the total NOx concentration in a gas stream utilizing the principles of a NOx sensor, i.e., mixed potential sensor. The exhaust gas is first conditioned by a catalyst assembly that converts the various species of nitrogen oxide gases present to a fixed steady state concentration ratio of NO2/NO, where NO2 is approximately 0-10% of the total NOx concentration present in the gas exhaust, thereby enabling the NOx sensor to generate a meaningful and reproducible determination of the concentration of total NOx present in the gas being measured. The catalyst assembly also functions to oxidize any unburned combustibles such as CH4, CO, etc., and remove potential contaminants such as SO2.
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Citations
60 Claims
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1. An apparatus for determining NOx concentration of an exhaust gas, the apparatus comprising;
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an input assembly capable of receiving the exhaust gas and producing a conditioned output gas, the input assembly including at least three of the following four stages;
a first stage including a first catalyst structure for converting NH3 in the exhaust gas to N2 and H2O;
a second stage including second catalyst structure having an absorbent material for absorbing SO2 or H2S from the exhaust gas;
a third stage including a third catalyst structure for oxidizing unburned hydrocarbons and gases to higher oxidation states; and
,a fourth stage including a fourth catalyst structure for establishing a steady state equilibrium concentration ratio between NO and NO2; and
,a NOx sensor operably connected to the input assembly and receiving the conditioned output gas of the input assembly wherein the concentration of the total NOx present can be determined. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 25, 27, 30, 32, 33, 36, 39, 47, 50, 53, 55)
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22. The apparatus of claim 22 wherein the second stage of the input assembly resides within an environment having a temperature range of approximately 600-800°
- C.
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24. The apparatus of claim 24 wherein third stage of the input assembly resides within an environment having a temperature range of approximately 600-800°
- C.
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26. The apparatus of claim 26 wherein the fourth stage of the input assembly resides within an environment having a temperature range of approximately 600-800°
- C.
- 28. The apparatus of claim 28, wherein the known gas concentration being atmospheric air.
- 31. The apparatus of claim 31 wherein the mixed potential sensor and the oxygen sensor being constructed of an electrolyte material.
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35. The apparatus of claim 35 wherein the temperature range is approximately 600-800°
- C.
- 37. The apparatus of claim 37 wherein the electrolyte of the mixed potential sensor is tubular.
- 40. The apparatus of claim 40 wherein the sensing electrode of the mixed potential senor is a semi-conductive oxide material.
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41. The apparatus of claim 41 wherein the semi-conductive oxide material includes at least one of the following:
- WO3, Cr2O3, Mn2O3, Fe2O3, TiO2, Co3O4.
- 43. The apparatus of claim 43 wherein the multi-component oxide material is a spinel or perovskite.
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46. The apparatus of claim 46 wherein the metallic material includes at least one of the following:
- Pt, Ag, Au, Rh.
- 48. The apparatus of claim 48 wherein the electrolyte material having a range of approximately 15-25 vol. % with the oxide.
- 51. The apparatus of claim 51 wherein the electrolyte material is approximately 15-25 vol. % with the metal.
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54. The apparatus of claim 54 wherein the physical property is resistance, capacitance, or RF frequency.
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56. For an apparatus capable of determining NOx concentration of an exhaust gas, the apparatus including a NOx sensor for receiving a conditioned output gas wherein the concentration of the total NOx present can be determined, an input assembly providing the conditioned output gas and comprising at least three of the following stages:
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a first stage including a first catalyst structure for converting NH3 in the exhaust gas to N2 and H2O;
a second stage including a second catalyst structure having an absorbent material for absorbing SO2 or H2S from the exhaust gas;
a third stage including a third catalyst structure for oxidizing unburned hydrocarbons and gases to higher oxidation states; and
,a fourth stage including a fourth catalyst structure for establishing a steady state equilibrium concentration ratio between NO and NO2, wherein the input assembly being operably connected to the NOx sensor.
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57. A method for determining total NOx concentration in a gas composition, the method comprising the steps of:
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receiving an exhaust gas stream;
conditioning the exhaust gas stream through an input catalyst assembly, the input assembly comprising at least three of the following stages;
a first stage for converting NH3 compounds to N2 and H2O;
a second stage for absorbing SO2 from the exhaust stream to improve the lifetime performance of the sensor by minimizing any long term poisoning effects associated with SO;
a third stage for oxidizing unburned hydrocarbons and oxidizes gases to higher oxidation states; and
,a fourth stage for establishing a steady state equilibrium concentration ratio between NO and NO2; and
,generating a voltage signal that is a function of the concentration of the total NOx present in the exhaust gas stream.
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58. The method of claim 58 further comprising:
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providing an oxygen sensor; and
,providing a first heating zone and a second heating zone, the first heating zone being positioned proximate the mixed potential sensor and the second heating zone being proximate the oxygen sensor.
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59. The method of claim 59 further comprising:
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heating the first heating zone; and
,heating the second heating zone, wherein the first and second heating zones include different temperatures.
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60. The method of claim 60 wherein the temperature of the first heating zone is at least 300°
- C. and the temperature of the second heating zone is at least 500°
C.
- C. and the temperature of the second heating zone is at least 500°
Specification