Retrofit aftertreatment system for treating diesel exhaust

An exhaust aftertreatment system for treating exhaust generated by a diesel engine, the system comprising:

• a filtration station for filtering particulate material from the exhaust;
• a NOx reduction station located downstream from the filtration station for reducing a concentration of NOx in the exhaust;
• a temperature sensor for generating first data representative of a temperature of the exhaust;
• a pressure data generator for generating second data indicative of a pressure differential across a control volume located at the NOx reduction station, the control volume including at least one catalyzed substrate;
• a NOx sensor for generating third data representative of the concentration of the NOx in the exhaust;
• a reductant dispenser for dispensing reductant into the exhaust at a location between the filtration station and the NOx reduction station;
• and
• a controller that controls a dosing rate at which the reductant dispenser dispenses the reductant into the exhaust, wherein the controller uses the first data, the second data and the third data to determine the dosing rate at which the reductant dispenser dispenses the reductant into the exhaust, and wherein the controller determines an exhaust flow rate based on a correlation of the second data from the pressure data generator with the control volume.