Purification capacity recovery method of exhaust gas emission control system

摘要

When a fuel as a reducing agent is supplied to a NOx catalyst on which a NOx or a SOx is reduced, a flow rate of exhaust gas that flows through an exhaust passage is changed, and the fuel is supplied to the exhaust gas flowing through the exhaust passage at a plurality of timings (ΔT1,ΔT2) when the exhaust gas flows at different flow rates.