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PM
and sulfur
The chart below
compares PM emissions for buses running on regular diesel vs. the
low-sulfur MossGas¨. There is a strong correlation between fuel
sulfur content and particulate emissions.
As shown in
this figure, reducing the amount of sulfur in the fuel can eliminate
a significant portion of PM emissions. It is evident that the reduction
or elimination of sulfur in diesel fuel has significant benefits
with regard to the reduction of particulate emissions, as well as
increasing the performance potential of aftertreatment, emission
control devices.
The remaining
exhaust particulate is comprised mostly of unburned carbon, organic
compounds and other inert contaminants. The noticeable difference
in particulate emissions on the synthetic fuel between the conventional
NovaBUS diesel and the Orion-LMCS hybrid is achieved partially by
engine management in the hybrid and partially by the use of a regenerative
particulate trap on the hybrid-electric buses to burn off and complete
the combustion of unburned carbon.
While there
is very little PM mass remaining, there may still be a significant
particle count. These smaller and numerous nanoparticles may pose
a greater inhalation risk and the need to determine the exact composition
of this material warrants further in depth testing.
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