Fuelling compliance

While engine manufacturers develop systems to reduce NOx and PM, fuel is another area that can influence exhaust emissions. Project leader for the commercial diesel fuel programme at Shell Global Solutions, Keith Reading told CE, "The combustion in the engine dictates PM emissions, but we can influence this with the fuel."

Shell produces a gas to liquid (GTL) fuel that is 100% paraffinic, meaning it has well defined properties and performance, such as a high cetane number (short time period between the start of injection and start of combustion). Dr Reading explained, "GTL still produces PM, but in heavy-duty engines reductions of 20% in PM, compared to regular diesel fuel, are not untypical.

"There is a trade-off between NOx and PM, but through the use of GTL simultaneous reductions of both PM and NOx, in the region of 15%, are possible," he said.

Technology manager for diesel fuel at Shell Global Solutions, Nick Davenport said, "Achieving lower levels of NOx and PM emissions are possible simply through the use of GTL fuel, which could be particularly beneficial in mega-cities with strict emission controls."

Shell currently has a GTL facility in Malaysia and within 12 months the company will be opening a new facility in the Middle East. "At the moment our commercial scale GTL capacity is limited, but our investment in Qatar demonstrates that this is an area in which we're interested," said Dr Reading.