Retrofit Aftertreatment System for Treating Diesel Exhaust

An exhaust aftertreatment system for diesel engines includes a filtration station, a NOx reduction station, a temperature sensor, a pressure data generator, a NOx sensor, a reductant dispenser, and a controller. The filtration station filters particulate material from the exhaust. The NOx reduction station reduces NOx concentration in the exhaust. The temperature sensor generates first data that is representative of a temperature of the exhaust. The pressure data generator generates second data that is indicative of a pressure differential across a control volume that is located at the NOx reduction station. The control volume includes at least one catalyzed substrate. The NOx sensor generates third data that is representative of the NOx concentration in the exhaust. The reductant dispenser dispenses reductant into the exhaust. The controller controls a dosing rate of the reductant dispenser. The controller uses the first, second, and third data to determine the dosing rate.