Method for operating an exhaust gas purification system

摘要

The invention concerns a method for operating an exhaust gas purification system, said system comprising a controllable internal combustion engine adapted to predominantly operate under lean conditions, and a NO x -adsorbing unit capable of storing NO x during lean conditions and converting NO x into N 2 during rich or stoichiometric conditions, said system having a capability of oxidizing HC and CO and reducing NO x under stoichiometric conditions. The invention is characterized in that the method comprises the steps of determining a representation of a mass flow of NO x in the exhaust gas and a current storage capacity of the NO x -adsorbing unit, and switching engine operation mode between lean conditions and stoichiometric conditions depending on the representation of the NO x mass flow in the exhaust gas and the current storage capacity of the NO x -adsorbing unit.