Patent ID: 8209956

Claim:
An emissions control system, comprising: an SCR device that receives a flow of exhaust and is configured to reduce NOx in the exhaust by a plurality of SCR reactions including a reaction of NH 3 , NO, and NO 2 to produce N 2 and H 2 O, a reaction of NH 3 , NO, and O 2 to produce N 2 and H 2 O, and a reaction of NH 3 and NO 2 to produce N 2 and H 2 O; an injector that introduces a reduction agent into the flow of exhaust at or upstream of a catalyst within the SCR device; and a controller in communication with the injector, the controller configured to: calculate a first amount of the reduction agent by using an approximation that the reaction of NH 3 , NO, and NO 2 to produce N 2 and H 2 O must be completed before the reaction of NH 3 , NO, and O 2 to produce N 2 and H 2 O or the reaction of NH 3 and NO 2 to produce N 2 and H 2 O commences; and adjust the injector according to at least the first amount.