Urea-SCR System Development in the Mitigation of NOx Emissions from Diesel Engines – A Review Study

Introduction: Due to energy demand concerns, diesel engines have gained much attraction recently compared to petrol engines because of their higher thermal efficiencies. However, they emit a larger amount of NOx emissions into the atmosphere. Objective: Nitrogen oxides are known as important ambient air pollutants that are responsible for health problems, forest damage, and buildings corrosion. Therefore, using emissions control strategies for diesel engines is required in order to have a cleaner environment. Urea-SCR (selective catalytic reduction of NOx by urea) after-treatment system is considered as one of the most efficient techniques available to reduce engine-out NOx emissions sufficiently. Conclusion: This review article discusses all the methods suggested to diminish nitrogen oxides emissions and then presents a comprehensive survey on developing urea-SCR unit -whether from catalyst development aspect or from injection system modification point of view- in diesel engines to meet strict emissions regulations.