Engine tail gas NOx purification system, control method thereof and engine

Abstract

The invention discloses an engine tail gas NOx purification system. The engine tail gas NOx purification system at least comprises a DOC, a first-stage SCR and a DPF which are sequentially arranged onan engine exhaust pipe in the tail gas flowing direction. A first-stage urea injection valve used for injecting urea to the first-stage SCR is arranged between the DOC and the first-stage SCR. The first-stage SCR is arranged between the DOC and the DPF, so that the problem that NOx in tail gas is too high in the cold start stage of an engine can be effectively solved, so that vehicle tail gas emission meets the requirement, and the purpose of protecting the environment is achieved. The invention further discloses the engine and a control method of the engine tail gas NOx purification system.

Description

technical field [0001] The invention relates to the technical field of engine exhaust treatment, in particular to an engine exhaust NO x A purification system and a control method thereof, and an engine. Background technique [0002] SCR (selective catalytic reduction) technology is to control engine NO x An important technical means of emission, this technology is to spray the standard vehicle urea solution (32.5% urea concentration) into the SCR mixer, meet the high-temperature exhaust gas and decompose ammonia (NH 3 ), using NH on the catalyst surface 3 with NO x Reaction occurs to realize NO x reduction, eventually making NO x The nitrogen atoms in form the environmentally friendly N 2 , so as to reduce NO in engine exhaust x content. [0003] At present, the exhaust gas treatment system of most diesel engines only includes one SCR system. According to the number of SCR systems, the traditional exhaust gas treatment system can be called a single-stage SCR system....

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Problems solved by technology

[0004] The SCR is far away from the exhaust manifold of the engine, so the temperature of the exhaust gas reaches the SCR position is reduced, although the SCR can effectively reduce the NOx during normal operation of the vehicle. x However, since the temperature of the engine itself is low when the vehicle is cold started, the exhaust gas cannot heat the SCR to the starting temperature when the exhaust gas reaches the SCR position, so the NO x The treatment effect is not ideal, which leads to NO in the engine exhaust when the vehicle is cold started. x The content is still high

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