Patent ID: 7805929

Claim:
A method of controlling ammonia and nitric oxides production for selective catalytic reduction systems, comprising: producing an ammonia-containing gas stream having an ammonia concentration; operating an engine to continuously produce a NOx-containing gas stream having a NOx concentration; supplying the ammonia-containing gas stream to an exhaust system upstream of a selective catalytic reduction catalyst and evaluating the ammonia concentration at a first location at a first time; supplying the NOx-containing gas stream to the exhaust system upstream of the selective catalytic reduction catalyst; evaluating the NOx concentration at a second location at a second time, the second time being later than the first time by a time interval, the time interval being based on the difference between a time required for the ammonia-containing gas stream to travel from the first location to the selective catalytic reduction catalyst and a time required for the NOx-containing gas stream to travel from the second location to the selective catalytic reduction catalyst; and adjusting the NOx concentration based at least on the ammonia concentration at the first time and the NOx concentration at the second time.