The world's first large scale commercial Gas-to-Liquids
(GTL) fuel production plant using low temperature Fischer-Tropsch
(LTFT) technology, Oryx GTL, has been in operation in Qatar since
2007. The first on-specification diesel fuel produced by this plant
was subjected to a comprehensive fit-for-purpose validation
program, part of which comprised exhaust emission tests which were
conducted with two different passenger cars and two different
heavy-duty engines. Three neat GTL diesel fuels were included in
the study: commercial GTL diesel fuel, an equivalent full boiling
range GTL diesel fuel produced in a pilot plant, and a GTL diesel
fuel with a narrower distillation range. Commercial sulfur-free
(≺10 mg/kg) European EN590 diesel fuel was used as the reference
fuel. In addition, tests were performed with two different blending
ratios (20% and 50%) of GTL diesel in the EN590 diesel.
The neat GTL fuels showed reductions in PM, THC, and CO, while
NOx emissions were either neutral or reduced, depending on the
engine technology, when compared to the EN590 diesel. The blended
fuels generally showed reductions in emissions or a neutral
response, in some cases with a distinct non-linear characteristic
in relation to the blending ratio. The narrower cut of pilot plant
GTL diesel fuel also showed a varied response relative to the full
boiling range GTL diesel fuel, depending on the engine technology.
The results of the tests demonstrated that the commercial GTL
diesel fuel shows the same favorable exhaust emissions performance
that has come to be expected from extensive testing conducted
previously with GTL fuel produced in pilot plants. Interactions
with engine technology, specifically in terms of fuel injection
equipment, were also highlighted.
