EXHAUST GAS PURIFICATION SYSTEM FOR THE TREATMENT OF ENGINE EXHAUST GASES BY MEANS OF A SCR CATALYST

摘要

The present invention relates to an exhaust gas purification system (method and apparatus) for the treatment of diesel exhaust gases comprising nitrogen oxides and hydrocarbons, said system comprising an addition of compounds which can be decomposed to provide ammonia to the ammonia or exhaust gas stream And subsequent conversion of the exhaust gas stream by two SCR catalysts, two SCR catalysts being one behind the other and having various characteristics and compositions. Both SCR catalysts do not have vanadium compounds and only SCR catalysts installed on the downstream side contain zeolite compounds. The exhaust gas purifying system according to the present invention is notable for a good starting behavior at a low temperature and at the same time, a high converting power within a wide temperature range.