| 摘要 |
The present invention relates to an apparatus and a method to purify exhaust gas capable of improving an efficiency of nitrogen oxide purification under all driving conditions. According to an embodiment of the present invention, the apparatus to purify the exhaust gas comprises: an engine having an injector to spray fuel thereinto to generate a driving force by combusting a mixed gas composed of air and fuel, and emitting exhaust gas resulting from a combustion process to the outside through an exhaust pipe; a lean NOx trap (LNT) mounted on the exhaust pipe to absorb nitrogen oxide (NOx) included in the exhaust gas in a lean atmosphere, desorb absorbed nitrogen oxide in a rich atmosphere, and deoxidize the nitrogen oxide included in the exhaust gas or desorbed nitrogen oxide; a spray module mounted on the exhaust pipe to spray a deoxidizing agent into the exhaust gas; a selective catalytic reduction on a diesel particulate filter (SDPF) mounted on a lower portion of the spray module on the exhaust pipe to collect particulate materials included in the exhaust gas, and deoxidizing the nitrogen oxide included in the exhaust gas using the deoxidizing agent sprayed from the spray module; and a control device to perform denitrification (DeNOx) using the LNT if an exhaust gas temperature is lower than a transition temperature, and perform denitrification using the SDPF if the exhaust gas temperature is higher than or equal to a transition temperature. |
