NH3 SLIPPAGE PREVENTION SYSTEM AND METHOD FOR NH3

摘要

The present invention relates to an apparatus for reducing nitrogen oxides by selectively reducing nitrogen oxides contained in exhaust gas of a vehicle through reaction with a catalyst by injecting urea water as a reducing agent and converting the nitrogen oxides into nitrogen. In the present invention, in order to prevent the NH ₃ slip phenomenon, it is intended to provide a technique of calculating the NH ₃ slip condition in the catalyst of the SCR and controlling the LP-EGR to prevent the NH ₃ from slipping. According to an embodiment of the present invention, there is provided a supercharger comprising: a supercharger including a turbine and a compressor; An SCR reactor including an SCR catalyst for purification of exhaust gas; And is connected to the compressor front end from the turbine downstream of the supercharger, the amount of opening of the EGR valve LP-EGR unit that is configured to be variable; as the SCR of the NH ₃ slip preventing system comprising a, calculates the NH ₃ slip condition, NH ₃ slip A slip model prepared for predicting whether or not there is a slip; An LP-EGR opening degree model for determining a correction value of the LP-EGR opening amount according to the NH ₃ slip amount when NH ₃ slip is predicted; And control means for applying the correction value of the LP-EGR opening amount to the NH ₃ slip prevention system of the SCR.