METHOD AND SYSTEM FOR THE REMOVAL OF NOXIOUS COMPOUNDS FROM ENGINE EXHAUST GAS

摘要

Method and system for the removal of noxious compounds from lean burning engines, the method comprising in series the steps of contacting the exhaust gas with a catalyst being active in oxidation of volatile organic compounds and carbon monoxide, passing the treated exhaust gas through a particulate filter catalysed with a first SCR catalyst, and passing the exhaust gas leaving the particulate filter through a second SCR catalyst, wherein ammonia is injected into the exhaust upstream of the catalysed particulate filter at a temperature below or at about 220° C. and wherein urea is injected into the exhaust gas between the first and the second SCR catalyst when the exhaust gas has reached a temperature of about 200° C.

主权项

1. A method for the removal of noxious compounds from exhaust gas of a lean burning internal compression ignition engine comprising in series the steps of
contacting the exhaust gas with a catalyst being active in oxidation of volatile organic compounds and carbon monoxide to carbon dioxide and water and nitrogen oxide to nitrogen dioxide; passing the thus treated exhaust gas through a particulate filter being catalysed with a first SCR catalyst for selective reduction of nitrogen oxides; and passing the exhaust gas leaving the filter through a second SCR catalyst for the selective reduction of nitrogen oxides, wherein ammonia reducing agent is injected into the exhaust gas upstream the catalysed particulate filter during a cold start phase of the engine when the gas has a temperature of below or at about 220° C., and wherein injection of ammonia is discontinued and urea as precursor for the ammonia reducing agent is injected into the gas between the first and second SCR catalyst when the gas has reached a temperature of about 200° C.