| abstract |
An exhaust gas purification system for lowering the content of impurities in a lean exhaust gas of an internal combustion engine comprising, a feeding device that feeds ammonia or a compound decomposable to ammonia into an exhaust gas stream containing nitrogen oxides; a selective catalytic reduction catalyst comprising vanadium (V-SCR catalyst) which catalyses the nitrogen oxides with ammonia in a temperature range of about 150°C to about 400°C and at an NO2/NOx ratio of about 0.3 to about 0.9; and a downstream system comprising a diesel oxidation catalyst (DOC). The system may also comprise a turbocharger and a secondary fuel injector. The downstream system may further comprise one or more of an additional DOC, ammonia slip catalyst (ASC), filter, NOx storage catalyst, three-way catalyst or a selective catalytic reduction catalyst (SCR). The downstream system may be a catalysed soot filter. A second aspect relates to an exhaust gas system comprising a feeding device, V-SCR, a turbocharger, secondary fuel injector and downstream DOC and a third aspect relates to a method of treatment of diesel engine exhaust gas. Further aspects relate to a system comprising a first reductant feeding device, a V-SCR catalyst and a cold start catalyst. |