Method and apparatus for reducing harmful emissions from a diesel engine by urea injection scr

摘要

Emission of NOx from diesel engines is reduced by hydrolyzing or otherwise gasifying urea on an as-needed basis. Preferably, an aqueous urea solution is introduced into a catalyzed chamber (60) maintained at least partially in contact with the exhaust system (12). The heat of the exhaust gases is utilized to gasify the urea. The gaseous breakdown products of the urea are then introduced into the exhaust gases upstream of an SCR catalyst. In one form of the invention, an oxidation catalyst (22) is provided down stream of the SCR catalyst (20) for the purpose of eliminating any ammonia which might otherwise pass through the system and provide an objectionable odor.