Optimization Of Urea-SCR System And Development Of Catalyst

SCR(selective catalytic reduction) is currently considered one of the most effective diesel after treatment technologies.With the aid of catalyst,reducing agent and NOx reacted into nitrogen and water.An after treatment system based on the SCR process can reduce the NOx emissions of heavy-duty diesel engines to values below the forthcoming Chinaâ…£,â…¤emission standards.The research is mainly about SCR system characteristic.It is composed of dosing valve,catalyst and control unit.With the aid of CFD,a 3 dimension model has been made to set up the flow of diesel SCR systems,mixed-mathematical model and simulate urea spray,evaporation and the distribution of mixed gas field.According to results,dosing valve installation position and exhaust pipe layout have been optimized. It will not only be to improve SCR conversion ratio but also avoid crystallization phenomena.In this paper,6-cylinder engine vehicles have been targeted to match the study of catalytic converters.A appropriate catalyst is need,mainly taking into account coat, carrier,encapsulation.According to lots of information and simulated results,a barrel catalyst with TiO₂-V₂O₅ 400/7 is choosed.The catalyst can keep high conversion ratio at the main temperature range of engine exhaust,and can cause smaller backpressure.It is cost-effective and easy to installation.Urea dosing strategy is a key problem.By the experiment research,a dosing strategy has been set down under the different speed and torque.The engine with SCR can reduce NOx emission by 65%and reduce NH3 slip in ETC and ESC...