abstract |
FIELD OF THE INVENTION The present invention relates to an exhaust gas purification system (method and apparatus) for the treatment of diesel exhaust gas comprising nitrogen oxides and hydrocarbons, the system comprising a mixture of ammonia or compounds that can be decomposed to provide ammonia to the exhaust gas stream. In addition, subsequent conversion of the exhaust gas stream by the two SCR catalysts, wherein the two SCR catalysts are arranged one after the other, have various properties and compositions. Both SCR catalysts are free of vanadium compounds, and only the SCR catalyst installed downstream has zeolite compounds. The exhaust gas purification system according to the present invention is remarkable for its good starting behavior at low temperatures and at the same time high converting power within a wide temperature range. |