Method of regenerating selective catalytic reduction catalyst on diesel particulate filter and exhaust purification system

An exhaust purification system comprising:

• an engine including an injector for injecting a fuel thereinto, generating power by burning a mixture of air and the fuel, and exhausting exhaust gas generated during a combustion process to an exterior thereof through an exhaust pipe;
• a dosing module mounted on an exhaust pipe downstream of the engine and directly injecting a reducing agent into the exhaust gas;
• a selective catalytic reduction catalyst on a diesel particulate filter (SDPF) mounted on the exhaust pipe downstream of the dosing module and the selective catalytic reduction catalyst trapping a particulate matter (PM) contained in the exhaust gas and to reduce the nitrogen oxide contained in the exhaust gas using the reducing agent injected through the dosing module;
• and
• a controller configured to perform denitrification using the SDPF,
• wherein the controller predicts a reducing agent amount oxidized in the SDPF during regeneration of the SDPF if the regeneration of the SDPF is necessary, calculates a quantity of heat generated from the reducing agent amount oxidized in the SDPF, calculates a target temperature when regenerating the SDPF from the generated quantity of heat, and performs the regeneration according to the target temperature, and
• wherein the controller predicts the reducing agent amount oxidized in the SDPF during regeneration of the SDPF from a temperature of the SDPF, a mass flow of the exhaust gas, a mass flow of nitrogen oxide supplied to the SDPF, a reducing agent amount absorbed in the SDPF, and a mass of the reducing agent supplied to the SDPF.