Urea injection for GM diesels

[Colonel Cadillac]

GM leans toward urea injection to clean up diesel emissions
RICHARD TRUETT | Automotive News
Posted Date: 8/31/05
DETROIT -- General Motors is leaning toward a controversial emissions system, urea injection, that enables diesel engines to meet tough pollution standards in place for 2009.

The technology, also known as selective catalytic reduction, is used on freight-hauling trucks in Europe.

But the EPA questions the use of selective catalytic reduction because the driver must keep the vehicle from running out of urea.

If the urea tank runs dry, the driver will notice no difference in performance. But the vehicle won't meet emissions standards for smog-producing oxides of nitrogen, or NOx.

The stakes are huge for GM. Thanks mostly to the quiet, powerful and smooth-running Duramax diesel V-8 developed with Isuzu, GM says its share of the U.S. heavy-duty diesel truck market has ballooned from about 2 percent in 1999 to more than 25 percent today.

The diesel-powered Chevrolet Silverado and GMC Sierra pickups are among the few GM vehicles that sell without profit-eating incentives.

The automaker expects to sell about 200,000 diesel-powered trucks in 2006.

Decision within a year

GM officials say they will decide in the next 12 months whether to install the urea injection system on heavy-duty diesel trucks in North America.

The alternative, a filter in the exhaust system called a lean NOx trap, also is being evaluated by GM.

But David Brown, a General Motors staff engineer in Milford, Mich., who works on advanced propulsion systems controls, says the lean NOx trap uses expensive precious metals and has not been proven to meet EPA requirements of 10 years and 150,000 miles.

Asked about the chances of GM using selective catalytic reduction, Brown said: "I think they are better than 50-50."

Selective catalytic reduction is cost-effective and meets durability requirements, he said.

Acid into the exhaust pipes

The urea injection system works by shooting an ammonia-like acid into the exhaust pipes, radically reducing NOx.

Because engineers need two to three years to design, develop, integrate, test and validate an emissions system, GM soon must decide which technology it will install.

Starting in 2009, emission standards require diesel engines on heavy-duty trucks to run as cleanly as gasoline engines.

If GM doesn't have a new emission system ready when the tougher rules go into effect, it could cost the company billions of dollars in lost sales on the Silverado and Sierra.

Ford Motor Co. also is considering selective catalytic reduction and NOx traps.

DaimlerChrysler AG recently confirmed that it will use selective catalytic reduction on its new generation of diesel models for the United States, which include sedans and SUVs.

DaimlerChrysler also is considering diesel versions of the Jeep Grand Cherokee and Chrysler 300 sedan. Those, too, would be equipped with selective catalytic reduction.

[Colonel Cadillac]

I say that the Urea should be apart of the service plan to check, just like oil. Simple sollution.  

[280Z Turbo]

If the urea tank runs dry, the driver will notice no difference in performance. But the vehicle won't meet emissions standards for smog-producing oxides of nitrogen, or NOx.

There would be a lot of empty urea tanks here in Michigan.

[Secret Chimp]

Why are they planning on INJECTING this cow-piss-derivative instead of just creating a urea-based converter/filter like everyone else is? Weird idea.

[giant_mtb]

If the urea tank runs dry, the driver will notice no difference in performance. But the vehicle won't meet emissions standards for smog-producing oxides of nitrogen, or NOx.

There would be a lot of empty urea tanks here in Michigan.

Deffinitely!

In case you guys didn't know...we don't have to do smog tests and stuff to see if our vehicles meet EPA standards...

[Nebtek2002]

As someone involved in the production of commercial and agricultural grades of urea for 24 years (until my co-workers and I were NAFTA-shafta'd in 1999 by a Canadian company that bought 7 plants though they only wanted 5 of them), I can't see how liquid urea injection is going to work.

Urea at a given concentration solidifies at roughly the same Centigrade temperature as it's % concentration. The three temperatures this old brain recalls are that 100%urea is solid at 115C,70% @72C, 50%@ 54C.

Even at 10% concentration, the urea is going to "salt out" at temperatures well above freezing.

You'll need an heated tank that will have to be super-insulated when the car is not in use and thus not producing either electricity or exhaust heat to keep the contents from becoming a rock.

And then, there are the injection nozzles ,which will have to purged every time you shut down.

At the plant, our loading nozzles were purged with steam. Are we going to carry on-board steam generators to clear urea injection systems and require every driver to take a stationary engineer's test before operating the car?

If thousands of urea injection-equipped vehicles come together in a stadium or arena parking lot, won't thousands of simultaneous urea purges create their own environmental problem?

Urea in solid form, either urea-impregnated catalysts or a chamber filled with urea prills (beads or granules) separate from the the convetional catalyst makes far more sense.

BTW, urea is alkaline, not acidic, as was mis-stated in the source article of this thread.
And, yes urea occurs naturally in urine, but commercial production does not derive it from piss.
It is formed at by combining CO2 and ammonia at 3000 or 5000 psi, depending upon which process you use.

[S204STi]

Would a urea-prill chamber or urea-impregnated catalyst be able to last 10yrs/150kmiles?

[Galaxy]

It should not be to hard to build a system that will not allow the car to restart if the refill period has been missed by say 500km. Problem solved. Sure some people will find a way to disable the system, proberly the same ones that take out the catalytic converter not realising that the NOx, when it comes into contact with the humidity in the lungs turns into sulfuric acid  but those are fortunately in the extream minority.

[93JC]

... take out the catalytic converter not realising that the NOx, when it comes into contact with the humidity in the lungs turns into sulfuric acid

I don't want to rain on your parade, but, uh... you can't get sulfuric acid from nitrogen oxides...

[S204STi]

It should not be to hard to build a system that will not allow the car to restart if the refill period has been missed by say 500km. Problem solved. Sure some people will find a way to disable the system, proberly the same ones that take out the catalytic converter not realising that the NOx, when it comes into contact with the humidity in the lungs turns into sulfuric acid  but those are fortunately in the extream minority.

I had a similar thought.  Either that or have the PCM programmed so that if the Urea tank becomes empty the engine goes into some sort of of "limp" mode, so that the driver is made painfully aware of his/her neglect.

[gasoline]

I say that the Urea should be apart of the service plan to check, just like oil. Simple sollution. 

Why are emissions standards going up?

What criteria is used to raise emissions standards?

Do they go up and up every year until they arrive at zero?

All of this is simply arbitrary.

How does the EPA know what's scientifically attainable and what's not?

Or are they trying to legislate technological advancement?

If so, how does that make any sense at all?

[gasoline]

I don't want to rain on your parade, but, uh... you can't get sulfuric acid from nitrogen oxides...

Lemme tell you...
Carbon Dioxide has been increasingly affecting the ozone layer lately!


(I tell you...I doesn't matter anymore just keep flinging it till something sticks!...hehehe...)

[Raza]

Urea?  That stuff is in my cigarettes!

[Colonel Cadillac]

So is rat poison!

[SVT_Power]

So is rat poison!

[Submariner]

The closest to production ready is the System Merc is developing.  How it works, (the Urea part) is beyond me.

[Autobahn]

Mercedes calls it "BlueTec" and the Urea is produced chemically.

It works fine in big trucks and will be on the market I guess next year in the GL and E 320 Bluetec

[Galaxy]

I don't want to rain on your parade, but, uh... you can't get sulfuric acid from nitrogen oxides...

That was dumb of me. I meant aqua fortis. Nitric acid.

Thanks for the heads up.

[Submariner]

Mercedes calls it "BlueTec" and the Urea is produced chemically.

It works fine in big trucks and will be on the market I guess next year in the GL and E 320 Bluetec

We only have the 45 state BluTec...the Urea injection wont be ready until 2008 (?)

[J86]

So can I just piss in the gas tank?

[93JC]

"Pull over dude, I need to fill the urea tank."



(No you goof, of course not)

[J86]

"Pull over dude, I need to fill the urea tank."



(No you goof, of course not)

damn

[93JC]

It's urea injection, not urine injection.

[J86]

close doesn't cut it, huh?

[93JC]

Nope.

[Galaxy]

We only have the 45 state BluTec...the Urea injection wont be ready until 2008 (?)

Why did they even bother changing the name then? I thought that BluTec meant urea injection is on board?

[Nebtek2002]

This system will be nothing more than feel-good. It will be of limited value as an actual pollutant reducer.

The first time the temperature of the cooled injection nozzle drops below the "salt-out" temperature of the urea, the nozzle will plug, no urea will flow, the motorist will sing the praises of an antipollution "miracle" that seems to "use no chemical at all. The needle on the urea guage seems never to move." But emissions won't be affected in the least.

[Autobahn]

Why did they even bother changing the name then? I thought that BluTec meant urea injection is on board?

Zach is correct.

The E 320 BlueTec will not use Urea (or AdBlue in DCX terminology  ), while the BlueTec engines in the Actros trucks use it.

The E 320 BlueTec uses the standard particle filter and oxi-kat along with a scr- catalytic converter and a NOx - catalytic converter.

So obviously BlueTec is just a marketing name to denote "clean" Diesels. (and to not have the "Diesel"/CDI name in the model designation)