Patent ID: 6415602
Filing Date: 2002-07-09
Classification: B01D,F01N,Y02A,Y02T

Abstract:
A method for reducing NOx emissions produced in mobile internal combustion engine applications by an external reductant supplied to an SCR system having a reducing catalyst comprising the steps of:a) sensing one or more engine operating parameters to predict a concentration of NOx emissions indicative of the actual quantity of NOx emissions produced by the engine; b) when the actual concentration of NOx emissions changes and the temperature of said reducing catalyst is within a set range, varying the actual concentration of NOx emissions by a time constant to produce a calculated concentration of NOx emissions different than the actual concentration of NOx emissions; said time constant determined as a function of the relative time it takes for any given fresh reducing catalyst to store said reductant at any given temperature within said set range and ineffective to change the actual concentration of emissions when the catalyst temperature is above said set range; and, c) metering the external reductant to the reducing catalyst in said SCR system at a rate sufficient to cause the reducing catalyst to reduce said calculated concentration of NOx emissions whereby metering of the reductant accounts for the effects on said SCR system attributed to transient NOx emissions.