New technology adds another twist to emissions solutions for next EPA mandate.
by Deborah Whistler, Editor
August 1, 2008
4 min to read
Come 2010 you may be faced with yet another technology path and a difficult decision to comply with the stringent EPA emissions standard that hits at that time. In addition to the all-exhaust gas recirculation (EGR) and the urea selective catalytic reduction (SCR) alternatives comes another technology just announced jointly by Argonne National Labs and Integrated Fuels Technologies, a relatively new start up that is commercializing a catalyst process that uses good old diesel fuel as the NOx reducing reagent.
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The beauty of the new technology is that it could make the need to add an SCR tank - and require the driver to top it off with a different fluid - redundant.
But, as Robert Firebaugh, IFT chairman and chief technology officer, admits, the technology and the commercial application come to the scene "late in the game."
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This could present an added problem for equipment managers who have to decide on a technology path come 2010: While this diesel SCR appears to offer the best of all worlds and to make urea SCR redundant, it is unlikely to be in the marketplace soon enough to meet 2010.
To this point, the Washington-state based IFT has been talking with Paccar about developing the technology under license. The truck manufacturer (Peterbilt and Kenworth) has indicated it may well pursue a parallel development of urea SCR and diesel SCR so that it has the necessary production volume to meet 2010 with SCR, be it diesel, urea or both.
The diesel NOx reducer has a catalytic chamber with a ceramic monolith not unlike a diesel particulate filter. This is coated with the new catalyst developed by Argonne's Chris Marshall who is one of the patent holders. He is group leader of Heterogeneous Catalysis at the laboratory and says that the process can reduce the NOx down to the required 0.2g per hp hr. To date, the technology has moved from the lab to a single demonstration vehicle. According to Firebaugh, the researchers have already demonstrated up to 80 percent reduction in levels of NOx out of an admittedly dirty engine. They are at the point of reaching an 85 percent reduction, the point at which IFT gets to move into a co-development with Paccar.
The process is continuous with a very specific diesel fuel injector that can achieve very fine atomization of diesel fuel in a continuous injection. This is mounted in the exhaust stream between the DPF and the new NOx catalytic chamber. The dosage levels are very low. Argonne's Marshall talked of 1-2 percent but IFT's Firebaugh said it was less than 1 percent. At these levels, even with today's diesel costing maybe twice as much as the urea diesel emissions fluid (though pricing is not yet available for DEF) the DEF may need to be injected at levels as high as 3-5 percent. This would make the Argonne/IFT system cheaper to run as well as a lot more convenient, since it uses diesel from the vehicle tank.
Given that SCR technologies allow for optimization of the diesel combustion, with the NOx cleanup in the exhaust rather than the combustion chamber, the fuel economy gains of 5-8 percent from optimizing the engine are only mildly eroded by the exhaust aftertreatment.
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The big question has to be: What does this mean for urea-based SCR in the longer term? Firebaugh says that diesel SCR will obsolete urea and that the urea technology will eventually run up against a dead-end.
If Firebraugh is right, it's not good news for equipment buyers in 2010. A fleet manager who chooses the urea SCR technology because it will deliver better economy may be faced with a change down the road. It also throws into question the option of the all-EGR solution. Since this technology means optimizing the NOx production in the combustion chamber it comes at a fuel penalty compared with SCR - of whichever type.
So does a fleet manager opt for the likely cheaper EGR as installed in the vehicle and hope that the lifetime cost will not overtake either of the SCR technologies? Or does he go for one of the SCRs and hope that it will continue to be available? Or does he sit on the sidelines and see what will develop?
With this new solution clouding the picture, savvy specifiers will likely study the situation had before making purchasing decisions. That could mean a gloomy truck sales year in 2010.
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