ENGINE EXHAUST PURIFICATION DEVICE AND ENGINE EXAUST PURIFICATION METHOD

摘要

An engine exhaust purification device that improves the NOx purification rate and minimizes ammonia slip in urea SCR. The engine exhaust purification device comprises: a selective reduction type NOx catalyst; a reducing agent adding device that adds ammonia or a precursor thereof to engine exhaust; and a control device that controls the reducing agent adding device. A catalytic reaction model that converts the chemical reaction involved in the reduction of NOx, which makes the ammonia adsorbed by the catalytic layer of the NOx catalyst an effective reducing agent, into a numerical expression, is designed, and the amount of ammonia adsorbed is calculated according to the catalytic reaction model for each of a plurality of cells that partitions the inside of the NOx catalyst so as to extend in the axial direction thereof. From the amount of ammonia adsorbed by each cell, the amount of ammonia to be supplied is calculated on the basis of the amount of ammonia adsorbed by prescribed cells according to the engine operating state.