Exhaust apparatus for low NOx emission internal combustion engines and process for reducing NOx emitted in the exhaust gas

摘要

The new system suppresses the emission of nitrogen oxides, the presence of which is significant in exhausts from lean burn petrol and diesel engines. The process for reducing the content of nitrogen oxides uses a catalytic system comprising a primary oxidation section (2) upstream from a second catalytic reduction section (3) for the reduction of nitrogen oxides with or without entrapment of NOx. The system also comprises :- a post-injection of hydrocarbons at a site upstream from the oxidation section ; and -conveyance of the injected hydrocarbons beyond the oxidation section to a position upstream from the second section. The post-injection is effected in one of the cylinders of the engine or downstream of the cylinder. The injected hydrocarbons and exhaust gases are both directed to the reduction section. The injector is mechanical or by a ramp.