Selective Catalytic Reduction System

Abstract

A selective catalytic reduction system comprises a reducing agent tank, a metering and spraying module, a reducing agent supply line, a compressed air source, an auxiliary air line and a reducing agent cleaning line, wherein the metering and spraying module comprises a reducing agent metering valve and a reducing agent spraying channel; the reducing agent supply line is connected between the reducing agent tank and the metering valve; the auxiliary air line operates together with the reducing agent supply line; the upstream end of the auxiliary air line is connected with the compressed air source, and the downstream end of the auxiliary air line leads to an outlet of the reducing agent spraying channel, so that compressed air from the compressed air source is sprayed towards reducing agent flow; the upstream end of the reducing agent cleaning line is connected with the compressed air source, the downstream end of the reducing agent cleaning line leads to the reducing agent spraying channel, the reducing agent cleaning line is controlled to operate after operation of the reducing agent supply line and operation of the auxiliary air line are finished so that compressed air from the compressed air source can be sprayed towards the metering valve, and residual reducing agents in the metering valve are forced to return towards the reducing agent tank. The selective catalytic reduction system can reduce the cost and shorten the cleaning time of the residual reducing agents.

Description

technical field [0001] The present application relates to a selective catalytic reduction (SCR) system for aftertreatment of engine exhaust with a reductant cleaning module that returns the reductant after operation. Background technique [0002] In order to reduce harmful components in vehicles, current vehicles are usually equipped with appropriate exhaust aftertreatment systems to reduce the amount of harmful gases emitted by the engine. For example, a selective catalytic reduction system is an effective engine exhaust aftertreatment system that reduces NOx in exhaust gas by more than 50% by injecting a solution of urea as a reducing agent into the vehicle exhaust pipe. [0003] After the engine runs out, the exhaust system temperature drops, and the urea solution can crystallize or freeze at low temperatures, which can cause problems. For example, a 32.5% urea aqueous solution used as a standard reductant freezes at ambient temperatures below -11°C. After the vehicle i...

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