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US EPA verifies Johnson Matthey retrofit SCRT system

14 August 2010 | updated 19 August 2010

The US Environmental Protection Agency (EPA) has verified the Johnson Matthey SCRT system for onroad, heavy-duty diesel engines. The SCRT system combines a passive diesel particulate filter (DPF) with urea-based selective catalytic reduction (SCR) system.

The SCRT system has been verified for retrofitting model year 1994-2002 onroad, non-EGR engines rated between 250 and 500 hp. The verified emission reductions are: 70% for NOx; 90% for PM; 90% for CO; and 95% for HC.

Engine exhaust temperature must be greater than 240°C for 40% of operation and greater than 200°C for 65% of operation. The engines must produce a NOx/PM ratio of at least 8, with optimum approaching 20. The system must not be sold or operated in geographic areas where urea solutions may freeze (-11°C). The SCRT system includes a monitoring system that displays warning lights to the operator for low urea tank level and other system abnormalities. To ensure that appropriate urea is purchased, the customers are required to maintain urea purchase receipts and refill records and make them available to Johnson Matthey upon request.

Schematic of JM SCRT system

It is the first EPA verification for an onroad SCR system. Johnson Matthey expects an EPA verification for the SCRT system for 2002-2006 model year EGR and non-EGR engines later this year, followed by a California ARB verification.

The verified SCRT system will support retrofit programs in states where mobile NOx emissions need to be reduced, including Texas, California and other ozone non-attainment areas.

Source: US EPA, Johnson Matthey