SYSTEM INTENDED TO REDUCE THE AMOUNT OF NOX IN THE EXHAUST GASES OF A MOTOR VEHICLE

摘要

The invention relates to a system intended to reduce the amount of NOx in the exhaust gases of a motor vehicle. The system comprises a storage space (1) containing a reducing agent; an SCR (selective catalytic reduction) catalytic converter (5) for treating the exhaust gases laden with reducing agent, and an injection module (6c) designed to inject the reducing agent from the storage space (1) into the exhaust gases of the motor vehicle upstream of the SCR catalytic converter (5). The system further comprises: at least one heat exchanger (2) connected to the storage space (1) and containing a porous matrix intended to absorb the reducing agent originating from the storage space (1); a valve or an injector (11) downstream of the storage space (1) and upstream of the exchanger (2) and designed to control the addition of reducing agent to the exchanger (2), and a valve (12) positioned between the storage space (1) and the exchanger (2). This is designed to transfer thermal energy to the exhaust gases of the motor vehicle upstream of the SCR catalytic converter (5) during a first period known as the starting period following the starting of said vehicle. The valve or the injector (11) is designed to control the rate of flow of reducing agent into the exchanger (2) during said starting period so that the absorption of the reducing agent by the porous matrix of the exchanger (2) raises the temperature thereof. The valve or the injector (11) is also designed then to be closed during a period known as the period at operating temperature when the motor vehicle is running as soon as the exhaust gases have reached a certain temperature. The valve (12) is designed firstly to regulate the pressure inside the exchanger (2) during said period at operating temperature and secondly to convey the reducing agent contained in the exchanger (2) to the storage space (1) when the pressure inside the exchanger (2) is higher than the pressure inside the storage space (1).