EXHAUST GAS PURIFICATION METHOD AND EXHAUST GAS PURIFICATION SYSTEM

摘要

In an exhaust gas purification system (1) comprising an exhaust gas purification device (12) having an oxidation catalyst device (12a) carrying an oxidation catalyst and a DPF (12b) arranged in order from an upstream side or a DPF carrying an oxidation catalyst in an exhaust passage (11) of an internal combustion engine (10), in which at regeneration of the DPF (12b), when a catalyst temperature index temperature (Tg2) indicating a temperature of the oxidation catalyst becomes equal to a predetermined determining temperature (Tc1) or above, control of raising a temperature of the DPF (12b) is conducted by supplying an unburned fuel to the upstream side of the oxidation catalyst to thereby oxidize the unburned fuel by the oxidation catalyst, wherein the predetermined determining temperature (Tc1) is changed according to an engine speed Ne of the internal combustion engine (10). By this arrangement, at the regeneration of the DPF (12b), in the regeneration control of raising the temperature of the DPF (12b) by oxidizing the unburned fuel supplied into an exhaust gas by the oxidation catalyst (12a), the unburned fuel supplied into the exhaust gas is surely oxidized and outflow of white smoke is prevented regardless of an operation state of the internal combustion engine (10).