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SCR: The European experience

BRUSSELS, Belgium - Selective Catalytic Reduction (SCR) is coming to North America, but trucking companies here can rest assured they won't be the guinea pigs when the technology is rolled out to meet...

BRUSSELS, Belgium – Selective Catalytic Reduction (SCR) is coming to North America, but trucking companies here can rest assured they won’t be the guinea pigs when the technology is rolled out to meet EPA 2010 emissions requirements.

That distinction went to truck fleets in Europe, which are already using SCR as a means to meeting Euro 4 emissions standards introduced in 2006.

On a recent trade press expedition to Brussels, Truck West had the opportunity to visit Volvo Truck Corporation’s Belgium headquarters to get a first-hand look at the technology.

SCR is no longer new in Europe. Volvo alone has sold about 60,000 SCR-equipped trucks there (about 100,000 if you take Renault sales into account).

Other truck manufacturers in Western Europe have also adopted the technology to meet Euro 4 standards.

Eric Mulkienls, area sales manager with Volvo Trucks Belgium, said the company’s SCR system is paired with a normal Volvo engine, which burns about 100 C hotter than previous generation engines to burn off particulate matter.

The higher combustion temperature has resulted in improved performance, he pointed out, leading to a more responsive throttle.

In Europe, a key component to SCR is a solution comprised of urea, ammonia and water which is marketed as AdBlue.

The AdBlue solution is housed in a separate tank ranging between 40 and 125 litres.

A metering unit injects AdBlue into the exhaust stream, which then travels through the SCR catalytic converter.

All that is emitted from the stack is a harmless combination of nitrogen and water.

The muffler is larger and about 55 kg heavier than today’s version, since it houses a catalyst which helps facilitate the chemical reactions needed to eliminate NOx.

The entire system, including the AdBlue storage tank, pumps, fluid, muffler and piping, weighs about 150 kg, Mulkienls said.

The catalytic muffler reaches extremely hot temperatures, so three heat shields are in place to protect the driver from burning himself should he get too close.

A gauge on the dash alerts drivers when their AdBlue tank is getting low.

If they ignore the warning, the truck will receive a 40% power loss following its next stop, thanks to new legislation in Europe requiring on-board diagnostics that continuously measure exhaust emissions.

AdBlue costs about 0.75 Euro ($1.06 CAD) per litre but it can be had for as little as 0.35 Euro ($0.50 CAD) per litre when purchased in bulk, Mulkienls explained.

About one litre of AdBlue is burned for every 20 litres of diesel fuel. AdBlue does have its flaws.

It freezes at -11 C, so on-board heaters are required to keep the liquid thawed.

If it does happen to freeze, it will still be effective when it returns to liquid form, as it’s not perishable, Mulkienls said.

In construction applications, Mulkienls said that ground clearance has not been an issue.

The truck’s batteries have been moved to the back of the chassis to free up some room for the SCR components closer to the front of the cab.

Of course in Europe, the cabover still reigns supreme. Also of note, the vertical muffler is history on European trucks.

Mulkienls said drivers have adapted quite well to the SCR system.

Drivability is good, he said, and drivers appreciate the improved throttle response resulting from the improved combustion process. Most importantly, SCR trucks have proven to deliver the same fuel mileage as previous generation Volvo trucks, he added.

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