UREA-SCR ON{sub}x removal efficiency for a diesel engine in the suggested European ETC-TEST cycle

摘要

Urea-SCR is one of the candidate techniques suitable for meeting the Euro 4 NO{sub}x emission standards taking force year 2005. This study demonstrates the potential of an SCR system applied on a medium duty 6.7 litre diesel engine. The amount ofcatalyst used in the test was 2.4 litre per litre of cylinder. Above 84% NO{sub}x removal was demonstrated in the proposed European transient test cycle (ETC) with urea as reducing agent and with the urea injection controlled by a newly developedinjection algorithm. Hydrolysis and thermal decomposition of urea into NH{sub}3, which is the active Specie, is completed in the catalyst at temperatures down to 200°C at space velocities up to 50 000 h-1. Up to 5% fuel saving and compliance even with the EU 5 NO{sub}x limit could be obtained by Optimising the engine disregarding the formation of NO{sub}x, provided that NO{sub}x is removed in a downstream SCR reactor as demonstrated.