Patent ID: 8578705

Claim:
An apparatus comprising a controller configured to control the rate of an introduction component for providing a NO x reducing precursor to a catalyst component, the controller: obtaining an amount of NO x entering the catalyst component from a NO x sensor, modeling an amount of NO x reducing substance or precursor in the catalytic component to react with the NO x obtained by the NO x sensor, and controlling the rate of the introduction component to produce NO x reducing substance or precursor to reduce NO x , wherein an optimum NO x reducing precursor introduction rate, Mu_inj_rate_opt, satisfies the relation: Mu_inj_rate_opt=(ku·Mnox_rate−Mu_stored/Tau_rel)/ X wherein ku is the amount of NO x reducing substance required to reduce one mole of NO x ; Mu_stored is the mass of NO x reducing precursor stored in the catalyst; Tau_rel is a time constant for the rate of NO x reducing precursor release from the catalyst; and Mnox_rate is the mass flow rate of NO x emission entering the catalyst component, and X is the fraction of introduced NO x reducing precursor that immediately decomposes into NH 3 .