Catalytic denitrification of engine exhaust gas with reducing agent - in amt. controlled according to nitrogen oxide concn. before and/or after redn. and pref. residual reducing agent content

摘要

In catalytic redn. of NOx in engine exhaust gas by adding a reducing agent (I), the amt. of (I) added is calculated and controlled according to the amt. of NOx before and/or after redn. The amt. of (I) added is reduced if residual (I) is present after redn. ADVANTAGE - Redn. of NOx is maximised without residual (I) after redn. In an example, a control unit (2) sent signals to an i.c. engine (1) and (I) dosing unit (4), which injected (I) through a pipe (10) into the front exhaust pipe (5) leading to the catalyst (3) and back exhaust pipe (9). There was a NOx sensor (6) in the front exhaust pipe and a NOx sensor (7) and (I) sensor (8) in the back exhaust pipe, all sensors being connected to input terminals of the control unit. This system allowed simple, accurate and fast regulation to maximise the NOx conversion rate and minimise (I) residues in the exhaust gas.