APPARATUS, SYSTEM, AND METHOD FOR ESTIMATING AN NOx CONVERSION EFFICIENCY OF A SELECTIVE CATALYTIC REDUCTION CATALYST

• US 20100242440A1
• Filed: 12/07/2009
• Published: 09/30/2010
• Est. Priority Date: 12/05/2008
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Osburn, Andy, Chi, John N., Wills, Joan M., Garimella, Phanindra
• Granted Patent: US 8,225,595 B2
• Time in Patent Office: Days
• US Class Current: 60/276
• CPC Class Codes: B01D 2255/20723 Vanadium
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 53/9409 Nitrogen oxides
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2560/021 for measuring or detecting ammonia NH3
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2900/1616 NH3-slip from catalyst
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

According to one exemplary embodiment, an apparatus is disclosed for estimating an NO_x conversion efficiency of an SCR catalyst. The apparatus includes a catalyst degradation module for determining an SCR catalyst degradation factor and a NO_x concentration module for determining an SCR catalyst inlet NO_x concentration based on an interpretation of at least one NO_x detector signal. Additionally, the apparatus includes an NH₃ concentration module for determining an SCR catalyst inlet NH₃ concentration, a temperature module for determining an SCR catalyst bed temperature of the at least one SCR catalyst, and a space velocity (SV) module for determining an exhaust gas SV for the SCR catalyst. A NO_x conversion efficiency module calculates a NO_x conversion efficiency value based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NO_x concentration, the SCR catalyst inlet NH₃ concentration, the exhaust gas SV, and the SCR catalyst bed temperature.

Claims

1. An apparatus for estimating an NO_x conversion efficiency of at least one selective catalytic reduction (SCR) catalyst, the apparatus comprising:

a catalyst degradation module configured to determine an SCR catalyst degradation factor associated with the at least one SCR catalyst;

an NO_x concentration module configured to determine an SCR catalyst inlet NO_x concentration;

an NH₃ concentration module configured to determine an SCR catalyst inlet NH₃ concentration;

a space velocity (SV) module configured to determine an exhaust gas SV for the SCR catalyst based at least partially on a set of operating parameters;

a temperature module configured to determine an SCR catalyst bed temperature; and

a NO_x conversion efficiency module configured to calculate a NO_x conversion efficiency value for the at least one SCR catalyst based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NO_x concentration, the SCR catalyst inlet NH₃ concentration, the exhaust gas SV, and the SCR catalyst bed temperature.

2. The apparatus of claim 1, wherein the NO_x concentration module is configured to determine an SCR catalyst inlet NO₂/NO_x concentration based at least partially on the interpretation of at least one NO_x detector signal, and wherein the calculation of the NO_x conversion efficiency value is based at least partially on the SCR catalyst inlet NO₂/NO_x concentration.

3. The apparatus of claim 1, wherein the NH₃ concentration module is configured to determine an amount of NH₃ slip at an SCR catalyst outlet based at least partially on an interpretation of an NH₃ detector signal, wherein the NO_x conversion efficiency value for the at least one SCR catalyst is based at least partially on the NH₃ slip at the SCR catalyst outlet.

4. The apparatus of claim 1, wherein the set of operating parameters comprises an exhaust gas mass flow rate, an exhaust gas density, and a volume of the at least one SCR catalyst.

5. The apparatus of claim 1, wherein the calculation of the NO_x conversion efficiency value is based at least partially on an NH₃ slip target.

6. The apparatus of claim 1, wherein the determination of the SCR inlet NO_x concentration is based at least partially on at least one chemical kinetics reaction formula.

7. The apparatus of claim 1, wherein the at least one NO_x detector comprises at least one of a NO_x sensor, an NO₂ sensor, and a combination NO₂/NO_x sensor, the at least one NO_x detector being positioned in at least one location selected from the group consisting of proximal to the SCR catalyst inlet, upstream of the SCR catalyst inlet, disposed within the SCR catalyst.

8. The apparatus of claim 1, wherein the at least one SCR catalyst comprises a first catalyst in series with a second catalyst, and wherein the at least one NO_x detector is positioned between the first and second SCR catalysts.

9. The apparatus of claim 1, wherein the SCR catalyst bed temperature is determined by combining a weighted SCR catalyst inlet exhaust temperature signal from a first temperature detector and a weighted SCR catalyst outlet exhaust temperature signal from a second temperature detector.

10. The apparatus of claim 1, wherein the NH₃ signal is generated by at least one NH₃ detector comprising at least one of a dedicated NH₃ sensor and a combination NO_x/NH₃ sensor.

11. A method for estimating a maximum NO_x conversion efficiency of a selective catalytic reduction (SCR) catalyst, the method comprising:

determining an SCR catalyst degradation factor;

determining a space velocity of exhaust entering the SCR catalyst;

determining an SCR catalyst inlet NO_x concentration;

determining an SCR catalyst inlet NH₃ concentration;

determining an SCR catalyst bed temperature; and

calculating a maximum NO_x conversion efficiency value for the SCR catalyst based at least partially on the SCR catalyst degradation factor, the space velocity of exhaust entering the SCR catalyst, the SCR catalyst inlet NO_x concentration, the SCR catalyst inlet NH₃ concentration, and the SCR catalyst bed temperature.

12. The method of claim 11, further comprising determining an SCR catalyst inlet NO₂/NO_x concentration, wherein the maximum NO_x conversion efficiency value for the SCR catalyst is calculated based at least partially on the NO₂/NO_x concentration.

13. The method of claim 11, further comprising determining a conversion capability of an AMOX catalyst downstream of the SCR catalyst, wherein the maximum NO_x conversion efficiency value for the SCR catalyst is calculated based at least partially on the conversion capability of the AMOX catalyst.

14. The method of claim 11, further comprising communicating the maximum NO_x conversion efficiency value to an aftertreatment system controller.

15. The method of claim 11, wherein the maximum NO_x conversion efficiency value for the SCR catalyst is calculated based at least partially on a predetermined SCR catalyst outlet NH₃ slip target.

16. The method of claim 11, further comprising determining an amount of NH₃ slip at an SCR catalyst outlet, wherein the maximum NO_x conversion efficiency value for the SCR catalyst is calculated based at least partially on the NH₃ slip at the SCR catalyst outlet

17. A system for estimating a maximum NO_x conversion efficiency of a selective catalytic reduction (SCR) catalyst, the system comprising:

an internal combustion engine producing an exhaust gas stream;

an exhaust aftertreatment system in exhaust receiving communication with the internal combustion engine, the exhaust aftertreatment system comprising at least one SCR catalyst; and

a controller comprising;

a catalyst degradation module configured to determine an SCR catalyst degradation factor;

an NO_x concentration module configured to determine an SCR catalyst inlet NO_x concentration;

an NH₃ concentration module configured to determine an SCR catalyst inlet NO₃ concentration;

a temperature module configured to determine an SCR catalyst bed temperature;

a space velocity (SV) module configured to determine an exhaust gas SV for the SCR catalyst; and

a maximum NO_x conversion efficiency module configured to calculate a maximum NO_x conversion efficiency value for the at least one SCR catalyst based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NO_x concentration, the SCR catalyst inlet NH₃ concentration, the SCR catalyst bed temperature, and the exhaust gas SV.

18. The system of claim 17, wherein the at least one SCR catalyst comprises a first SCR catalyst upstream of a second SCR catalyst, the first SCR catalyst having a different NO_x conversion efficiency than the second SCR catalyst.

19. The system of claim 18, further comprising first and second NO_x sensors, the first NO_x sensor being position between the first and second SCR catalyst and the second NO_x sensor being position downstream of the second SCR catalyst.

20. The system of claim 18, wherein the first SCR catalyst comprises one of a copper zeolite SCR catalyst, an iron zeolite SCR catalyst, and a vanadium SCR catalyst and the second SCR catalyst comprises another of the copper zeolite SCR catalyst, iron zeolite SCR catalyst, and vanadium SCR catalyst.

21. The system of claim 17, wherein the exhaust aftertreatment system comprises an ammonia oxidation (AMOX) catalyst downstream of the at least one SCR catalyst, wherein the controller comprises an AMOX NH₃ conversion module configured to determine an AMOX NH₃ conversion capability, wherein the NH₃ concentration module is configured to determine an SCR outlet NH₃ concentration, and wherein the maximum NO_x conversion efficiency value is based at least partially on the AMOX NH₃ conversion capability, the SCR outlet NH₃ concentration, and an NH₃ slip target.

22. A computer program product for estimating a maximum NO_x conversion efficiency of a selective catalytic reduction (SCR) catalyst, wherein the computer readable program when executed on a computer causes the computer to:

determine a SCR catalyst degradation factor and an NH₃ slip target;

determine an SCR catalyst inlet NO_x concentration and an SCR catalyst inlet NO₂/NO_x concentration;

determine an SCR catalyst inlet NH₃ concentration;

determine an exhaust gas space velocity for the SCR catalyst;

determine an SCR catalyst bed temperature determine an AMOX conversion capability;

determine an amount of NH₃ slip at an SCR catalyst outlet; and

calculate a maximum NO_x conversion efficiency value for the SCR catalyst based at least partially on the SCR catalyst degradation factor, the SCR catalyst inlet NO_x concentration, the SCR catalyst inlet NO₂/NO_x concentration, the exhaust gas SV, the SCR catalyst bed temperature, the NH₃ slip at the SCR catalyst outlet, the AMOX conversion capability, and the NH₃ slip target.