METHOD OF REGENERATING LEAN NOx TRAP OF EXHAUST PURIFICATION SYSTEM PROVIDED WITH LEAN NOx TRAP AND SELECTIVE CATALYTIC REDUCTION CATALYST AND EXHAUST PURIFICATION SYSTEM

According to an embodiment of the present invention, an exhaust gas purification system comprises: a lean NOx trap (LNT); and a selective catalyst reduction (SCR) catalyst. The method to regenerate an LNT comprises: a step of determining if the necessary condition for regeneration of the LNT is satisfied; a step of determining if the requirement for regeneration of the LNT is satisfied; and a step of, if both the necessary condition and the requirement for regeneration of the LNT are satisfied, regenerating the LNT. Whether the necessary condition for regeneration of the LNT is satisfied can be determined based on the quantity of NOx, which is occluded by the LNT, the quantity of NH3, which is stored in the SCR catalyst, and the shear temperature of the SCR catalyst. The present invention aims to provide a method to regenerate an LNT in an exhaust gas purification system having an LNT and an SCR catalyst and the exhaust gas purification system, which are able to improve purification efficiency and fuel efficiency of nitrogen oxides and to prevent a discharge of ammonia. 본 발명의 실시예에 따른 린 녹스 트랩(Lean NOx Trap; LNT)과 선택적 환원(Selective Catalytic Reduction; SCR) 촉매를 구비한 배기 가스 정화 장치에서, LNT의 재생 방법은 상기 LNT의 재생 필요 조건을 만족하는지 판단하는 단계; 상기 LNT의 재생 요구 조건을 만족하는지 판단하는 단계; 그리고 LNT의 재생 필요 조건과 LNT의 재생 요구 조건을 모두 만족하면, LNT의 재생을 진행하는 단계;를 포함하며, 상기 LNT의 재생 필요 조건의 만족 여부는 LNT에 흡장된 NOx의 양, SCR 촉매에 저장된 NH3의 양 및 SCR 촉매의 전단 온도를 기초로 판단될 수 있다.