By Steve Sturgess, Executive Editor
Diesel exhaust fluid is almost certainly in your future – and not just because you run heavy- or medium-duty trucks that may need it to meet federal emissions regulations for 2010. If you drive a diesel vehicle in your personal life, DEF may be in your car today. DEF is the enabler that makes virtually zero NOx (nitrogen oxide) emissions from a diesel engine’s tailpipe, whether it’s in a car or a truck.
How DEF works
Nearly every truck manufacturer around the world will use exhaust aftertreatment to reduce diesel exhaust emissions – specifically NOx. The exception in North American is Navistar International, which will pursue its NOx reduction within the cylinder to meet the requirements of EPA 2010 – albeit with emissions credits. The only others are Scania and MAN, European truck markers which, like Navistar, are using exhaust gas recirculation to meet Euro 5 emissions regulations on some models.
Everyone else around the world is using selective catalytic reduction of the exhaust stream, treating it with a chemical reagent in the exhaust system – hence the term aftertreatment.
A reagent is a chemical compound involved in a reaction. In this case, it’s called diesel exhaust fluid, or DEF. It’s a 32.5 percent solution of ultra-pure urea, a chemical used as a fertilizer on farms across America and the world.
Urea is a nitrogen, oxygen and hydrogen compound made in vast quantities from natural gas. It gives up ammonia (NH3), in the aftertreatment equipment, which combines with NOx to form nitrogen and water vapor, both substances that make up much of the air we breathe.
It is an elegant way of disposing of pollutants, turning harmful emissions into those that are entirely benign.
But only very small amounts of the chemical are required to clean up the diesel’s exhaust. The actual amounts vary depending on the demands on the engine and the amount of NOx it is producing, but experience in Europe and Japan and throughout SCR development here shows that dosing will be about 2 percent of the diesel consumption. So where trucks may carry 240 gallons of diesel or more in the saddle tanks, the amount of DEF to complement this would only be around 5 gallons.
DEF tanks on trucks actually will be larger than that, so they don’t have to be filled at every fuel fill. Most likely, the exhaust fluid will need attention only every second or third diesel-fuel fill.
But there’s still no getting around the fact that drivers will have to understand their responsibilities in attending to the requirements of DEF replenishment.
(If you have a diesel car manufactured in 2009, the chances are that it has a DEF tank. But it is most likely out of sight and replenished at the same time the car has a lube service.)
Hot and cold
Many questions have surfaced about storage of the fluid, both on and off the truck, in temperature extremes. Because two-thirds of DEF is water, there could be issues with freezing.
As Dave Siler, marketing director of Detroit Diesel points out, DEF will “freeze” at 12 degrees, a temperature many fleets see in winter. Siler points out that the proponents of SCR well understood that in the development of aftertreatment systems. All have completed at least two winters of testing with no difficulty.
The DEF tanks have warmers in them and an instantaneous heater to get the DEF flowing to the engine on start-up. All have a pump system that draws fluid back into the DEF tank on key-off so there is no fluid to freeze in the lines.
In fact, said Siler, it takes an enormous effort to actually freeze the tank beyond the slushy stage. In testing, Detroit Diesel actually removed the DEF tank and cold-soaked it in a freezer. The truck still started up and DEF flowed freely and well within the time allowed by EPA.
Much has been made of SCR engines running during this warm-up period before the fluid flows. “Would you want your kids standing beside a school bus that was running out of compliance?” was one that was thrown at me. But a cold-soaked engine just started – and that wouldn’t be a bus just picking up the kids – has loads of very cold iron to quench the flame in the combustion chamber, and an engine at start-up is almost certainly making no NOx.
At the launch of its DEF delivery pump, Gilbarco Veeder-Root showed how the fuel-island pump is heated, both to keep the DEF above freezing in the tank and also how the hose and nozzle are stored in a heated cabinet attached to the pump.
At the other end of the temperature scale, it is possible that some degradation of the DEF could occur in areas where average ambient temperatures exceed 80 degrees. Even at that point DEF has a shelf life of one to two years. Jay Spooner from Colonial Chemical suggested during an Oil Price Information Service webinar on DEF that even Death Valley, Calif., does not see averages that high.
Is it toxic?
Another concern is about spills of the fluid. John Beumler from DEF supplier TerraCair, during the Gilbarco launch of its dispenser, quipped that the worst that could happen is the grass would grow quicker and greener, referring to the fertilizing effect of the urea.
However, the urea solution is mildly corrosive, so any spills on to a truck’s aluminum should be hosed off. Beyond that, DEF is less dangerous than diesel fuel or even windshield washer fluid.
Because of that corrosiveness, however, DEF cannot be stored in conventional tanks nor pumped by conventional fuel pumps. The Petroleum Equipment Institute recently published a recommended practice listing the materials that should and shouldn’t be used, but generally stainless steel and high-density polyethylene are good around DEF. That is what you see in the equipment on the vehicle as well as in the distribution chain.
It’s not just a matter of the corrosive properties damaging the containers, but also a matter of keeping the DEF pure. Non-ferrous metals and alloys can leach impurities into the fluid.
“It’s not what urea does to the equipment, it’s what the equipment does to urea,” said Steve Childers, general manager of the dispensing company Spatco DEF.
There are currently 12 suppliers licensed by the American Petroleum Institute as accredited suppliers of DEF. They are listed at the web site www.apidef.org under the DEF Locator tab. The suppliers will be audited regularly to ensure the DEF they sell and distribute meets the ISO22241 standard (also known as AUS32), and the list updated..
The ISO standard covers the DEF through specification and transportation right down to the end user to guarantee purity of the solution. Purity is important. The urea needs to be of the highest quality and the blended water de-ionized, and the concentration is precise at 32.5 percent urea. Anything else is not DEF and cannot have the API seal.
Some questions, especially in the off-highway arena where urea is freely available, have been asked about home brewing of the exhaust fluid. Not a good idea.
Chad Dombroski of DEF supplier Air1, speaking at the OPIS fleet fueling conference, cautioned carriers and distributors not to take the production process lightly. DEF cannot be made from plain old urea, he said. It requires a higher grade of urea than is used for fertilizer or emissions control in smokestacks.
The water is important, too. There was an occasion during SCR development when a “rogue” batch of DEF got into the hands of several engine manufacturers and caused issues with the DEF injectors in the aftertreatment system. The problem was caused by the water, not the urea.
On the road
Especially in the initial stages, most truckers will be getting DEF on the road at truckstops or from distributors such as the Cummins Filtration network. Big fleets that want to have DEF stations at their terminals can come to arrangements with companies such as Brenntag, the largest distributor of automotive DEF in the United States. Brenntag has 120 locations throughout the U.S. and Canada, so bulk and package supplies are easily available.
The roll-out of DEF supply has been the subject of much controversy, but the most recent meeting of the Diesel Exhaust Fluid Forum in Las Vegas in October underscored that concerns are pretty much groundless.
Shortly before this conference, Pilot announced the availability of bulk DEF at the fuel islands at two locations. One in Brooks, Ore., and another in Charlotte, N.C., are part of a rollout that will see 100 Pilot Travel Centers providing DEF from large, above-ground storage tanks and regular-looking dispensing pumps. TravelCenters of America (TA and Petro) will also have fuel island dispensers.
You already can go in to one of these truckstops and buy a 2.5-gallon jug of DEF. In bulk, the price of DEF is around $2.60. The jugs are $9 to $12.
During the OPIS DEF webinar, Cummins Filtration’s Holly Duarte spoke of the availability of DEF and on fleet planning to guarantee supplies. She said fleets need to understand the DEF market and the suppliers, but more importantly, their need for the fluid. Obviously, there is not going to be a huge demand on Jan. 1, as there are maybe a couple of hundred evaluation trucks using SCR currently operating on the highways. Depending on how fast the economy picks up and how keen fleets will be to purchase new trucks next year, the rate of growth of the DEF infrastructure and the way DEF is supplied will vary.
It will take another five years at least before most trucks are using DEF, said John Lounsbury, director of marketing for Terra Environmental Technologies, one of the world’s largest manufacturers of DEF, during the OPIS fleet fueling conference this fall.
That relatively slow rate of growth will dictate the basic economic decisions of the business: the cost per gallon of DEF, the method of distribution and details of purchasing and dispensing.
Major fleets may well look to install above-ground, heated tanks and dispensing pumps.
More likely, however, will be the 330- or 275-gallon IBCs (intermediate bulk containers) otherwise known as totes, that can be kept in the shop. These containers can be equipped with dispensing pumps and shipped back and forth for refills. They represent a minimum-investment strategy. Of course, additional handling will mean the DEF will be marginally more expensive than it would be in 2,000-gallon bulk deliveries.
There are also available 55-gallon drums that also can be equipped with dispensing pumps for convenience.
At the DEF Forum in Las Vegas, Bryan Gran, vice president for Micro Matic, a well-known chemicals dispenser company famous for its beer handling, said that in the quest for purity, it is best to obtain the storage medium and contents complete with dispensing equipment so the container remains closed at all times to avoid contamination.
Blue1USA, which uses the Micro Matic dispensing system, also touts the advantages of a closed liquid dispensing system. This ensures product integrity, it says, and the returnable containers are more cost-effective than single-use storage options. Blue1USA, a partnership of EZ Fuel & Tank Solutions and Blue1 International of Belgium, makes and distributes DEF storage and dispensing systems.
Given the sensitivity of the aftertreatment system – the injector and the catalyst chamber – to anything but pure DEF, contamination of the fluid must be avoided. One of the fears is cross-contamination on the truck: putting diesel fuel in the DEF or DEF in the diesel fuel. Obviously, some training should be given to drivers to explain which fluid goes where.
There has been no established standard, but a de facto installation of the DEF tank on the left, driver-side of the truck has evolved among truck makers.
Tanks are relatively small, usually packaged just ahead of the main fuel tank on that side. Again, the de facto standard is for a blue filler cap to identify the DEF tank.
The filler neck by agreement is sized smaller than the filler nozzle of a diesel fuel dispenser to discourage contamination by diesel. At the same time, it is becoming the norm to have a magnetic interlock at the neck of the DEF tank. With this and a suitable dispensing nozzle, the pump can be configured not to turn on unless the DEF nozzle is in a DEF tank. This prevents contamination of diesel fuel by DEF, in some ways a more likely scenario until drivers learn that DEF has its own tank.
What about the driver who puts straight water in to the DEF tank instead of the 32.5 percent solution of urea?
The controls that determine the amount of DEF injected into the exhaust stream will detect higher levels of NOx and try to compensate by upping the dosage rate. If the solution has been diluted too far, the diagnostics will assume the truck is out of DEF and it will go into a derate situation while logging a fault code. If DEF is added and the solution brought back in balance, the on-board diagnostics will recognize the problem has healed itself and the malfunction indicator light on the dash will go out.
Much has been made of the problems of diesel exhaust fluid. In reality, the industry has identified them, looked at their consequences and addressed them. True, SCR and its attendant DEF do require some additional involvement on the part of a driver in finding and pumping the DEF into the right tank.
It will add some to the cost of operation, but it’s believed that a gain in fuel economy with SCR engines will more than make up for the cost of the DEF. Because the diesel engine is allowed to make a little more NOx, the diesel particulate filter needs very little active regeneration (using less fuel). The parasitic losses in the cooling system are also lower with less EGR. The resulting offset will net a 2010 truck owner a 3 percent economy gain, or maybe a little more.
At today’s fuel prices, that’s about $1,300 to $1,500 per year. That’s not enough to pay for the upcharge for the aftertreatment system unless you keep the truck beyond the typical on-highway trade cycle, but it does offer some offset.
The availability of DEF seems assured, whether it is obtained in bulk, in totes, in 55-gallon drums or out on the highway at truckstops and parts counters.
By this time next year it’ll be like the scare over ultra-low-sulfur diesel fluid. We’ll look back and wonder what the fuss was all about.
DEF in the cab
From the driver’s perspective, the most obvious feature of a 2010 engine using selective catalytic reduction will be new gauges on the dash. In Volvo’s case, for instance, there will be separate gauges for diesel fuel and for diesel exhaust fluid.
In the Freightliner/Western Star dash, there will be a single gauge with an LED display across the bottom. This will represent the amount of DEF in the tank, with green LEDs down to 10 percent remaining. At that point the LED turns yellow. At 5 percent it turns red and other things start happening to encourage the driver to get with the program and find some DEF. These include a mild engine derate and a maximum 55-mph speed.
If the driver ignores the gauge till the tank is empty, the derate becomes a limp mode to allow the truck out of traffic lanes. But with the range from just a few gallons of DEF, pouring in a 2.5-gallon jug of DEF should allow a driver to get to the next fueling point.
Because the DEF tank is sized to be at the minimum two times the range of the fuel tanks, this occurrence would only be likely for a driver who was either extremely forgetful or deliberately trying to sabotage the truck.
Any problems with the aftertreatment system will be recognized by the on-board diagnostics. For that reason, there is also another dashboard light, the malfunction indicator lamp, or MIL. This corresponds to the “check engine” light on a car dashboard that is also tied in to that vehicle’s OBD. It functions in much the same way, except there are situations – such as running out of fluid followed by the DEF tank being refilled – where the heavy-duty system will realize it has self-healed. In this case the MIL light will go out again.
Washington Editor Oliver Patton contributed to this article.
From the December 2009 issue of Heavy Duty Trucking.