Method for controlling an exhaust gas treatment system
Provided is a method for controlling an exhaust gas treatment system, wherein the system includes an exhaust gas stream supplied by an exhaust gas source to a selective catalytic reduction (SCR) device and a particulate filter device. The method comprises detecting a threshold level of reductant deposits proximate the SCR device, and initiating a selective catalytic reduction device service in response thereto. A threshold level of reductant deposits is detected using a reductant deposit model comprising determining an actual SCR NO x conversion using measured process variables; and comparing the actual SCR NO x conversion to a calibrated NO x conversion value. The calibrated NO x conversion value is determined using exhaust gas flow and system temperature values which substantially correspond to the process variables under which the actual SCR NO x conversion was determined. The device service can include increasing the exhaust gas temperature or initiating an active regeneration of the particulate filter device.
1. A method for controlling an exhaust gas treatment system including an exhaust gas stream supplied by an exhaust gas source to a selective catalytic reduction (SCR) device and a particulate filter device, the method comprising:
detecting a threshold level of reductant deposits proximate the SCR device, wherein the threshold level of reductant deposits is represented as a NO x conversion discrepancy, and is detected using a reductant deposit model comprising:
determining an actual SCR NO x conversion using measured process variables including exhaust gas flow and system temperature values, and
comparing the actual SCR NO x conversion to a calibrated NO x conversion value to determine a NO x conversion discrepancy; and
initiating a SCR device service in response thereto.
2. The method of claim 1 , wherein the SCR device comprises a selective catalytic reduction filter device.
3. The method of claim 1 , wherein the SCR device service comprises an active regeneration of the particulate filter device.
4. The method of claim 3 , wherein active regeneration comprises increasing the exhaust gas temperature.
5. The method of claim 3 , wherein active regeneration comprises one or more of utilizing an electrically heated catalyst and utilizing an oxidizing catalyst device.
6. The method of claim 1 , wherein comparing the actual SCR NO x conversion to the calibrated NO x conversion value comprises comparing several corresponding actual SCR NO x conversion values and calibrated NO x conversion values over a period of time.
7. The method of claim 1 , wherein the SCR device and a particulate filter device comprise a single selective catalytic reduction filter device.
8. The method of claim 1 , wherein the particulate filter device is oriented upstream of the SCR device.
9. The method of claim 1 , further comprising satisfying a secondary condition prior to initiating a SCR device service.
10. The method of claim 9 , wherein the secondary condition comprises a reductant deposit threshold.
11. The method of claim 9 , wherein the secondary condition comprises a mileage threshold for a vehicle powered by the exhaust gas source.
12. The method of claim 9 , wherein the secondary condition comprises a sulfur storage threshold.
13. The method of claim 9 , wherein the secondary condition comprises a SCR device age threshold.
14. The method of claim 9 , wherein the secondary condition comprises an NH3 slip threshold.
15. The method of claim 9 , wherein the secondary condition comprises a duration since the most recent SCR device service.
16. The method of claim 9 , wherein the secondary condition comprises a reductant dosing adaptation.
17. The method of claim 1 , wherein the exhaust gas stream comprises one or more NOx species.
18. A method for determining the presence of reductant deposits in a selective catalytic reduction (SCR) device, the method comprising:
determining an actual SCR NO x conversion using measured process variables including exhaust gas flow and system temperature values; and
comparing the actual SCR NO x conversion to a calibrated NO x conversion value to determine a NO x conversion discrepancy, wherein the NOx conversion discrepancy represents a threshold level of reductant deposits.
19. The method of claim 18 , wherein comparing the actual SCR NO x conversion to the calibrated NO x conversion value comprises comparing several corresponding actual SCR NO x conversion values and calibrated NO x conversion values over a period of time.