The big engine that could

With the stringent EPA 2015 regulations on large diesel engines for locomotive, marine, and stationary generator applications, the need for NOx reduction via urea SCR catalyst arises given the proven performance of urea SCR.

Because of its early adoption in on- and off-highway applications, urea selective catalytic reduction (SCR) has a first-comer advantage across multiple regions and markets. The advantages of urea SCR are satisfactory NOx-reduction efficiencies, durable performance, a wide performance window, reasonable cost, and available infrastructure.

The primary disadvantage, though, is system complexity given the multitude of components and stringent performance targets under various operating conditions. Large system size and constrained packaging space necessitates optimization of the overall system, flow layouts, and pipe geometries.