Technical advantages of urea SCR for light-duty and heavy-duty diesel vehicle applications

摘要

The 2007 emission standards for both light-duty and heavy-duty diesel vehicles remain a challenge. A level of about 90% NO{sub}x conversion is required to meet the standards. Technologies that have the most potential to achieve very high NO{sub}x conversion at low temperatures of diesel exhaust are lean NO{sub}x traps (LNTs) and Selective Catalytic Reduction (SCR) of NO{sub}x using aqueous urea, typically known as Urea SCR. The LNT has the advantage of requiring no new infrastructure, and does not pose any new customer compliance issues. However, Urea SCR has high and durable NO{sub}x conversion in a wider temperature window, a lower equivalent fuel penalty, and lower system cost. On a technical basis, Urea SCR has the best chance of meeting the 2007 NO{sub}x targets. This paper reviews the results of some demonstration programs for both light- and heavy-duty applications.