Patent ID: 7797928

Claim:
A method of purifying an exhaust gases from a combustion engine in a purification unit in which the purification unit contains a fuel burner and combining counter-current heat exchange and catalytic conversion of noxious compounds, the method comprising the steps of: a) allowing the incoming exhaust gas ( 2 ) to enter the unit via an inlet region ( 3 ) from where the incoming exhaust gas ( 2 ) is axially distributed to a plurality of parallel inflow passages ( 6 ), after flowing through the passages the incoming exhaust gas ( 2 ) is deflected in a diversion region ( 9 ), located opposite to the inlet region ( 3 ), into a plurality of parallel outflow passages ( 7 ), each of which is situated between two inflow passages ( 6 ), flowing therein an opposite direction and providing heat exchange with the incoming exhaust gas ( 2 ) and exiting the plurality of parallel outflow passages ( 7 ) through an outlet region ( 4 ) located adjacent the inlet region ( 3 ), and the inlet region ( 3 ) and the outlet region ( 4 ) are sealed with respect to one another; b) the plurality of inflow passages ( 6 ) being partially coated with an oxidation catalyst ( 15 ) for the conversion of oxidizable compounds including NO to NO 2 , and the plurality of parallel outflow passages ( 7 ) being partially coated with a NOx conversion catalyst ( 33 ), and all catalysts being located adjacent the diversion region ( 9 ) thereby leaving the inlet region ( 3 ), located adjacent the engine exhaust inlet, substantially catalyst-free; c) a catalytic fuel burner ( 19 ), containing at least one oxidation catalyst ( 33 , 34 ), being operatable in one of a lean burn mode or a rich burn mode with air or with portion of the lean engine exhaust gas as an oxidizing agent, the burner exhaust being fed into the diversion region ( 9 ), and in the rich burn mode, the burner exhaust is further oxidized at the oxidation catalyst ( 34 ) to at least one of create additional heat and enhance NOx reduction at the NOx conversion catalyst ( 33 ).