Interesting thing it seems like the new diesel tech closely matches the technology that powerplants been using for some time, specifically coal plants because of the waste they put out. They have used particulate filters of course, but also SCR (selective catalyst reduction) that uses ammonia injected into the flue gasses in the scrubbers. They make ammonia from urea since huge quantities of ammonia is dangerous to ship and handle. I wonder how similar these systems are. Sensors monitor NOx and and if levels get to high powerplants have to derate, same thing as SO3/4 (sulfer oxides) and sometimes its not a minor derate, we have to bring the powerplants offline if they cant get back within federal limits. This has even efected them economically, as any derate effects prices as well as having to make up the power with more costly units. Also for SCR's to work they have to maintain a higher output, if its the middle of the night and power demand is low the units with SCRs on cannot go to minimum as the SCRs require certain temperatures, so that costs us more money. Just a little tidbit from the power co.
The SCR that will be used for on-highway diesel emissions has a catalyst that converts the urea to ammonia, the ammonia then reacts with the Nitrogen Oxides to form pure Nitrogen and water. NOx levels will be monitored as well. Mainly to adjust the amount of urea being injected, but also to verify the proper concentration of urea. OBDII will be used to monitor emissions related
conditions and act appropriately based on severity.
Chris, read post #30--ammonia is very dangerous to ship and handle, particularly in the concentrations it would need to be for this kind of application. Urea is much safer.
Found this blurb on the internet, note it is alledgedly a question posed to Navistar truck/bus spokespeople and their response, from www.schoolbusfleet.com ;
A previous question was posed in regard to the EPA emission regulations for the 2010 and 2015 time frame. What work and / or research is being doen to move away from use of urea in SCR systems - given the relative scarcity of the raw material (urea) due to the huge purchases by China to monopolize the urea supply worldwide? Is the use of urea in the exhaust stream a viable application for emissions control given this limited availability and supply?
The school bus industry appears to be split 50/50 on the use of SCR vs. the use of other technologies to meet 2010 standards. IC Bus will use advanced EGR to be compliant to 2010 emissions standards. While the use of SCR as a 2010 emissions solution is viable, SCR as a solution offers a number of problems for fleet operators: supply may be limited, SCR solutions require significant additional hardware, and urea is temperature dependent, beginning to degrade at 105 degrees F and will freeze at 10 degrees F. Additionally, engines may derate if the urea tanks run empty, requiring the vehicle to limp to the next urea filling station. On the other hand, while still requiring some additional hardware, advanced EGR is a proven technology which school bus operators and maintainers are familiar with servicing.
__________________
2004 E-450 6.0 139,000 miles
7,500 mile, 15 quart oil changes, 5W-40 Rotella.
UOAs consist of checking for metal on drain plug magnet. All stock, no mods. Dyed fuel with no additives. Never been reflashed.
Total parts replaced;
one EGR valve.
Found this blurb on the internet, note it is alledgedly a question posed to Navistar truck/bus spokespeople and their response, from www.schoolbusfleet.com ;
A previous question was posed in regard to the EPA emission regulations for the 2010 and 2015 time frame. What work and / or research is being doen to move away from use of urea in SCR systems - given the relative scarcity of the raw material (urea) due to the huge purchases by China to monopolize the urea supply worldwide? Is the use of urea in the exhaust stream a viable application for emissions control given this limited availability and supply?
The school bus industry appears to be split 50/50 on the use of SCR vs. the use of other technologies to meet 2010 standards. IC Bus will use advanced EGR to be compliant to 2010 emissions standards. While the use of SCR as a 2010 emissions solution is viable, SCR as a solution offers a number of problems for fleet operators: supply may be limited, SCR solutions require significant additional hardware, and urea is temperature dependent, beginning to degrade at 105 degrees F and will freeze at 10 degrees F. Additionally, engines may derate if the urea tanks run empty, requiring the vehicle to limp to the next urea filling station. On the other hand, while still requiring some additional hardware, advanced EGR is a proven technology which school bus operators and maintainers are familiar with servicing.
In all of the articles I've read from Navistar, nothing is ever mentioned about the fuel economy impact their concept will impose. When questioned, they always refer to the EPA Smartway program with respect to truck specification and also aerodynamics. Truth is, they don't want to admit their engines will burn more fuel then than now. Freightliner, Volvo, Mack and now Paccar are all touting the significant fuel economy savings SCR systems offer. By 2010, urea supply will not be an issue. If a urea tank runs empty, it's simple enough to fill it up. If an egr system has problems, you have to take it to the dealer. I know which system I'd rather have.
International has told us there will be a fuel mileage reduction with more EGR, they say however the costs will be offset because you won't have to also buy urea.
It will be interesting to see how it all shakes out. I can't say that I want more EGR but I am also leary of the whole urea situation.
We have bought two 2008 model year buses with left over 2006 built engines so we don't even have a 2007 engine with a DPF yet. I imagine we will also avoid buying the 2010 engines as long as possible and let others be the test pilots.
__________________
2004 E-450 6.0 139,000 miles
7,500 mile, 15 quart oil changes, 5W-40 Rotella.
UOAs consist of checking for metal on drain plug magnet. All stock, no mods. Dyed fuel with no additives. Never been reflashed.
Total parts replaced;
one EGR valve.
International has told us there will be a fuel mileage reduction with more EGR, they say however the costs will be offset because you won't have to also buy urea.
It will be interesting to see how it all shakes out. I can't say that I want more EGR but I am also leary of the whole urea situation.
We have bought two 2008 model year buses with left over 2006 built engines so we don't even have a 2007 engine with a DPF yet. I imagine we will also avoid buying the 2010 engines as long as possible and let others be the test pilots.
Here are some numbers for comparisson.
Assuming an average 6 mpg for a 2007 engine. At $4.80/gal for fuel, your cost per mile = $0.80.
Assuming a fuel economy increase of 3% for a SCR engine, that equals 6.18 mpg or $0.776/mile. Urea is consumed at a rate of 2% of fuel. That's .02 gallons of urea per gallon of fuel. If the cost per gallon is $2, your cost per mile for urea is $0.007 for a total cost per mile of $0.783.
Assuming a fuel economy penalty of 2% for massive egr engines, that equals 5.88 mpg or $0.816/mile.
As you can see, the SCR engine is saving you $0.03/mile. The average OTR truck will turn 150,000 miles/year. That's $4,500 in fuel savings/year.
These numbers are all hypotheticall since we don't know what fuel will cost come January 1, 2010 and we don't know what urea will cost either. One thing is for certain, the higher the price of fuel goes, the more attractive SCR engines become.
My concerns with urea use would be in a fleet of school buses averaging more like 10,000 to 15,000 per year. These buses also are parked out side in temperatures as low as -20F, many of which we have no way to plug in block or tank heaters.
It will be interesting, Freightliner owns Thomas bus and will use either Cummins or MB engines, Bluebird bus will be left with Cummins since Caterpillar is exiting from the scene and Internationals own IC brand bus.
__________________
2004 E-450 6.0 139,000 miles
7,500 mile, 15 quart oil changes, 5W-40 Rotella.
UOAs consist of checking for metal on drain plug magnet. All stock, no mods. Dyed fuel with no additives. Never been reflashed.
Total parts replaced;
one EGR valve.
My concerns with urea use would be in a fleet of school buses averaging more like 10,000 to 15,000 per year. These buses also are parked out side in temperatures as low as -20F, many of which we have no way to plug in block or tank heaters.
It will be interesting, Freightliner owns Thomas bus and will use either Cummins or MB engines, Bluebird bus will be left with Cummins since Caterpillar is exiting from the scene and Internationals own IC brand bus.
Not to worry. In our testing, it takes over 30 hours at -25C (-13F) to freeze 9 gallons of urea completely solid. The EPA is giving the OEMs 30 minutes from engine start up to thaw and start injecting. With coolant heated tanks and electrically heated lines, we've found this time to be more than adequate.
We've done winter testing in Winnipeg, MB at -40F with no problems. We've been testing this system on this continent since 2000. I think with that much experience and time, we should have all the bugs worked out.
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A previous question was posed in regard to the EPA emission regulations for the 2010 and 2015 time frame. What work and / or research is being doen to move away from use of urea in SCR systems - given the relative scarcity of the raw material (urea) due to the huge purchases by China to monopolize the urea supply worldwide? Is the use of urea in the exhaust stream a viable application for emissions control given this limited availability and supply?
The school bus industry appears to be split 50/50 on the use of SCR vs. the use of other technologies to meet 2010 standards. IC Bus will use advanced EGR to be compliant to 2010 emissions standards. While the use of SCR as a 2010 emissions solution is viable, SCR as a solution offers a number of problems for fleet operators: supply may be limited, SCR solutions require significant additional hardware, and urea is temperature dependent, beginning to degrade at 105 degrees F and will freeze at 10 degrees F. Additionally, engines may derate if the urea tanks run empty, requiring the vehicle to limp to the next urea filling station. On the other hand, while still requiring some additional hardware, advanced EGR is a proven technology which school bus operators and maintainers are familiar with servicing.
What it is
