| 摘要 |
PURPOSE: A system for purifying exhaust gas and a method for controlling the same are provided to naturally regenerate soot in a soot filter to a predetermined level regardless of an LNT(Lean NOx Trap) catalyst deterioration level by changing the supplying amount of NOx which is discharged from an engine. CONSTITUTION: A system for purifying exhaust gas and a method for controlling the same comprises an LNT catalyst, a soot filter, and a control unit. The LNT catalyst occludes which is contained in an exhaust gas; desorbs nitrogen oxides; and leaks the desorbed nitrogen oxides according to the concentration of nitrogen oxides. The soot filter collects a particulate material which is contained in the exhaust gas and regenerates the particulate material by using the leaked nitrogen oxides from the LNT catalyst. The control unit controls the leaked amount of NOx by controlling the discharging amount of NOx from the engine according to an LNT catalyst deterioration level. [Reference numerals] (AA) Start; (BB) Return; (S100) Operating an engine; (S110) Accumulated distance >= First set value ?; (S120,S180) Supplying a predetermined amount of R_aw NO_X; (S130) Desorbing NO_2 in a rich atmosphere; (S140) Slipping a predetermined amount of the desorbed NO_2; (S150) Regenerating a DPF using the slept NO_2; (S160) Accumulated distance >= Second set value ?; (S170) Supplying R_aw NO_X differently according to accumulated distances |
