Process for optimizing a removal of nitrogen oxides from the gases in an engine exhaust line according to a selective catalytic reduction

A process for optimizing a depollution of nitrogen oxides from the gases in an internal combustion engine exhaust line of a motor vehicle, the depollution of nitrogen oxides being carried out according to a selective catalytic reduction by injection of a quantity of reducing agent into the line making it possible to monitor a setpoint of an amount of nitrogen oxides per second at an outlet of the exhaust line, the process comprising:

• readjusting the setpoint of the amount of nitrogen oxides per second at the outlet of the exhaust line is made at each completion of successive running distance intervals, each distance interval being determined by integration of a speed of the vehicle over a time interval that ends as soon as a predetermined target cumulative amount of carbon dioxide released in the exhaust line is reached,
• calculating an amount of nitrogen oxides at the outlet of the exhaust line per kilometer traveled for each interval from a cumulative amount of nitrogen oxides measured at the outlet of the exhaust line and compared with a target amount of nitrogen oxides per kilometer for the calculation of a first deviation that is used for the readjustment of the setpoint of the amount of nitrogen oxides per second at the outlet of the exhaust line.