Patent ID: 8230677

Claim:
An exhaust aftertreatment control system for exhaust gases, comprising: a selective catalytic reduction (SCR) catalyst in fluid communication with an exhaust stream from an engine, a urea solution injector, upstream of the SCR catalyst, in fluid communication with the exhaust stream; a gas sensor, downstream of the SCR catalyst, in fluid communication with the exhaust stream; a diagnostic unit, operatively connected to the engine; and a dosing control unit, operatively connected to the gas sensor, the urea solution injector, and the diagnostic unit, wherein the dosing control unit receives a signal indicative of NO, NO 2 or NH 3 concentrations from the gas sensor, receives a signal indicative of engine operating parameters from the diagnostic unit, converts the engine operating parameters to a NO concentration and a NO 2 concentration, estimates a NO concentration downstream from the SCR catalyst, estimates a NO 2 concentration downstream from the SCR catalyst, estimates the fractional surface coverage of NH 3 in the SCR catalyst, calculates a quantity of urea solution needed to minimize NO x emissions, and signals the urea solution injector to inject the quantity of the urea solution into the exhaust stream.