Eaton Developing Non-Urea SCR System
On-board formation of ammonia to cut exhaust NOx for 2010 would eliminate urea tanks on trucks and at fueling stations.
Eaton Corp. is developing an aftertreatment system that would eliminate some of the equipment many diesel builders are contemplating, while cleansing exhaust of a key pollutant to meet 2010 emissions limits.
The Eaton system generates its own ammonia to lower oxides of nitrogen, or NOx – the chief target of the 2010 regulations – instead of "dosing" exhaust with ammonia-laden urea, which at least two builders have said they'll do with their engines in 2010.
The Eaton system is a form of Selective Catalytic Reduction (SCR), which heretofore has been synonymous with urea dosing. Now used on diesels in Europe, that system requires an on-board storage tank for a urea additive. The fluid is injected into the exhaust stream to treat NOx that has been produced in spite of exhaust-gas recirculation, which will be used at higher '07 levels on 2010-model diesels in North America.
Eaton's method is also a form of SCR, but it uses a series of on-board aftertreatment devices, and one – a lean NOx trap, or LNT – that chemically breaks down NOx into nitrogen and ammonia. Ammonia is sent downstream to an SCR catalyst, where it treats NOx that has slipped past the trap. This cuts NOx to legal levels.
"Essentially, Eaton has taken two NOx-reducing technologies, packaged them in a system that allows them to work together, and taken advantage of a naturally occurring chemical reaction to eliminate a major cost and logistics hurdle that exists for urea-based systems," said Vishal Singh, who is overseeing its development at Eaton's Innovation Center in Southfield, Mich.
The Eaton system also uses a fuel reformer catalyst with fuel doser and an SCR catalyst, he said. It focuses on NOx, which must be cut by 80 percent from levels emitted by 2007 diesels and 90 percent compared to current models. The system would continue to use a diesel particulate filter to trap soot – a process that will begin with '07-model diesels starting in January.
Eaton's system would eliminate the on-board urea tank and injector, cutting complexity and weight from a truck and reducing its operating costs, Singh said. Operators wouldn't have to keep an on-board urea tank filled or find urea at distant fuel stops, and the trucking industry wouldn't need to build a urea infrastructure.
Building an infrastructure to produce, distribute and store urea throughout the U.S. and Canada by early 2010 concerns engine and truck builders, fleet managers and government authorities. Most envision truckstops and fleet fuel islands adding storage tanks with pumps to dispense the fluid, and a fleet of tankers to carry it there from production facilities. Urea could also be sold in jugs, but is far more expensive than bulk dispensing, Eaton managers said.
Authorities also worry that some drivers will not keep their trucks' urea tanks filled and engines will emit excessive amounts of NOx. So the Environmental Protection Agency is uneasy about urea-based SCR. Some builders say electronic controls would sense the absence of urea and cut power or shut down engines, but this could cause other problems.
Eaton is talking with engine builders about its ammonia-generating system, and has begun presenting the technology at industry meetings in the U.S. and Europe. Singh said that the builders are interested, but he noted that those with European ties will be inclined to use urea-based SCR to help recoup costs of developing the systems for Europe.
Due to manufacturing lead times and the need for testing, builders will have to commit to a NOx-reduction method for 2010 in the next six to 12 months, and Eaton views this period as critical to the possible adoption of its system. Singh hopes that even those who have announced a urea-based SCR approach might be persuaded to switch to the Eaton method.
Detroit Diesel and Volvo Trucks North America, both with European connections, have announced that they'll use urea SCR on their 2010 diesels. None wanted to comment on the Eaton system.
Mack Trucks, Volvo's sister company, said it is aware of the system but has not discussed it with Eaton. Caterpillar and Cummins were mum. International Truck and Engine has previously said that it doesn't like urea-based SCR because of the infrastructure issues; it is considering several possible paths for 2010, but won't say if Eaton's non-urea system is one of them.
Meanwhile, engineers and technicians at Eaton's tech center continue testing and refining the system. They've fitted hardware to a road tractor to verify its performance outside the lab. Singh stressed that much remains to be done to prepare the system for production and general use.
—Tom Berg,Senior Equipment Editor
Emissions Authority continued...
