Patent ID: 8646259

Claim:
An exhaust gas treatment system for an internal combustion engine, comprising: an exhaust gas conduit in fluid communication with, and configured to receive an exhaust gas from the internal combustion engine; a passive selective catalyst reduction (SCR) device in fluid communication with the exhaust gas conduit and configured to receive the exhaust gas, wherein the overall temperature of the passive SCR device is represented by a passive SCR temperature profile; a heated SCR device in fluid communication with the exhaust gas conduit and configured to receive the exhaust gas, the heated SCR device located upstream of the passive SCR, and wherein the heated SCR is selectively activated to produce heat; a control module in communication with the heated SCR and the internal combustion engine, comprising: a control logic for determining the passive SCR temperature profile; a control logic for determining if the passive SCR temperature profile is below a threshold value; and a control logic for activating the heated SCR, wherein the heated SCR is activated if the passive SCR temperature is below the threshold value; a first temperature sensor situated between the passive SCR and the heated SCR; and a second temperature sensor situated downstream of both the passive SCR and the heated SCR.