Importance

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Abstract

According to the method of the present invention, NO (nitrogen monoxide) in the exhaust gas of a diesel engine is first oxidized to NO.sub.2 (nitrogen dioxide) by an oxidizing catalyst. Further, carbon particles in the exhaust gas are trapped by a DPF (diesel particulate filter). The exhaust gas containing NO.sub.2 formed by oxidation of nitrogen monoxide is, then, fed to the DPF, and NO.sub.2 in the exhaust gas reacts with the carbon particles trapped in the DPF. When the NO.sub.2 reacts with carbon particles, carbon particles are oxidized (burned) by NO.sub.2 and removed from DPF, and, at the same time, NO.sub.2 is reduced to NO by the carbon particles. The exhaust gas containing NO formed by the reaction between the carbon particles and NO.sub.2 is fed to an NO.sub.X absorbent. In the NO.sub.X absorbent, NO is absorbed by the NO.sub.X absorbent and, thereby, removed from the exhaust gas. Therefore, according this method, the carbon particles collected by the DPF can be easily burned by NO.sub.2, thereby being removed from the DPF without increasing the amount of NO released to the atmosphere.

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First Claim