EXHAUST GAS PURIFICATION SYSTEM AND EXHAUST GAS PURIFICATION METHOD

An exhaust gas purification system which feeds hydrocarbon (HC) by means of a post-injection under preset conditions to the upstream side of an exhaust gas purification device which is positioned on the exhaust path of an internal combustion engine, restoring the purifying capacity of the exhaust gas purification device or purifying the exhaust gas of the exhaust gas purification device, wherein under hydrocarbon feed conditions, if the combination of the exhaust gas temperature and exhaust gas flowrate or intake flowrate during control is deemed to be in a misfire region in which hydrocarbon (L) which is fed to the exhaust path no longer combusts in the exhaust gas purification unit, the feed of hydrocarbon (L) is stopped. As a result, it is possible to prevent the deposit of hydrocarbon on catalysts or other exhaust gas purification units of an exhaust gas purification device, making it possible to constantly maintain the temperature of the exhaust gas purification unit in a controllable state.