Post-treatment of SCR exhaust gas for commercial vehicles- -- Composition of SCR exhaust gas after-treatment system

The SCR system can be divided into three parts: the urea (AdBlue) injection system for urea injection (AdBlue), the SCR catalyst box assembly that serves as a catalyst for noise reduction, and components such as sensors. It mainly includes the urea (AdBlue) supply unit (urea (AdBlue) pump), urea (AdBlue) injection unit (urea (AdBlue) nozzle), urea (AdBlue) tank, urea (AdBlue) pipeline and injection control unit (DCU).

Urea (AdBlue) pump

The urea (AdBlue) pump is responsible for pressurizing the urea (AdBlue) solution in the urea (AdBlue) tank and sending it to the urea (AdBlue) nozzle. At the same time, it pumps the excess urea (AdBlue) solution back to the urea (AdBlue) tank, maintaining the system pressure at around 9bar. After the engine stops, the urea (AdBlue) pump will pump the urea (AdBlue) solution in the system back to the urea (AdBlue) tank to prevent the residual urea (AdBlue) solution from causing system failure. There is a replaceable filter inside the urea (AdBlue) pump to prevent fine dust particles (with a diameter >30 um) in the urea (AdBlue) solution from entering the injection valve. The filter element and its affiliated balancing elements need to be replaced regularly.

Urea (AdBlue) nozzle

The function of the urea (AdBlue) nozzle is to spray the urea (AdBlue) solution at a certain pressure provided by the urea (AdBlue) pump into the exhaust gas of the exhaust pipe. The urea (AdBlue) nozzle has one urea (AdBlue) pipe joint and two cooling water joints. The two cooling water joints are the water inlet and return ports for the engine coolant to cool the urea (AdBlue) nozzle, preventing the nozzle from failing due to high temperature.