| 摘要 |
Lean mix engines require an exhaust gas system having nitrogen oxide storage catalysts for the removal of nitrogen oxides from the exhaust gases. If the lean mix engine is operated using exhaust gas comprising sulfur, the storage catalysts must be desulfurized from time to time. The desulfurization process has an inherent risk of high emissions of harmful substances. These emissions can be prevented if the cylinders of the lean mix engine are combined in two groups, which emit their exhaust gas in two associated exhaust gas lines, in which at least one nitrogen oxide storage catalyst is disposed. The two exhaust gas lines are combined to a common exhaust gas line behind the storage catalysts, the line comprising a catalyst, which has a three-way function under stoichiometric conditions. The two nitrogen oxide storage catalysts are desulfurized time-shifted from each other. While rich exhaust gas having a high temperature flows through the one storage catalyst for the desulfurization process, lean exhaust gas flows through the second storage catalyst such that the combined exhaust gas has a stoichiometric composition during the entire desulfurization duration. Under the stoichiometric conditions, the catalyst having a three-way function is capable of converting hydrocarbons, carbon monoxide, and nitrogen oxides into harmless components.
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