D2 is a refinery abbreviation
for Gasoil. It is the second distillate from the
crude oil, and can be used without reformers and
additives. So, the first engines used D2 as
fuel — before petrol cars as we know them today
was invented. That is because the engine
invented by a German called Diesel, requires no
spark plugs. The diesel engine will ignite and
combust when the pressure increases so that the
heated “plug” makes it explode. Here we get the
name “Diesel” — since the same principles are
used in diesel engines today. However,
automotive diesel that you fill has additives
that the refinery will add to make the engine
more efficient and also easier to start in the
winter. Diesel changes “flash point” in the
winter. It also has additives to absorb water
that condense. If you use summer diesel in the
winter, you will get better mileage, but your
fuel pipes may freeze and can also burst, and
the wax makes the diesel flow thicker.
The principal difference between GASOIL and D2
is the content of sulphur. Just 10 years ago,
the US EPA introduced a limit of 4% sulphur in
the GASOIL, whereas Europe and the rest of the
world followed later. As in most other cases,
when you first have to remove the sulphur, it
was soon discovered ways of doing this more
efficient. Then it was discovered that the
sulphur, as sulphuric acid, could be traded with
a good profit — which now is the motivator for
extracting as much as possible.
So “Low sulphur Gasoil” is no longer 4
percent — but below 0.2 percent. Then we have a
new, “Ultra Low Sulphur” at 0.02% at the most,
and the limit here is (a) that mass spectographs
requires extensive calibration to measure below
1000ppm, and (b) sulphur has a way to form
clogs — the molecules binds to free hydrogen
molecules and form a cluster of molecules that
will break if “cracked” by the refinery, but as
explained above, D2 is a distillate and has not
been “cracked”.
ISO has a standard for D2 that most of oil
companies use as their reference.
In the U.S. it is ANSI that has defined the US
national standard for D2, according to proposals
from the ASTM, API and EPA.
In Europe there are similar national variants,
e.g. in Germany set by DIN, and in Russia by
GOST.
The GOST variant for D2/Gasoil is GOST 305–82
and specifies now a sulphur content of 0.02 MAX
which is according to the ISO standard. However,
the ANSI standard will call this “Ultra Low
Sulphur”, and retain 0.2% (2000ppm) as the “Low
sulphur”. The reduction of sulphur in the Gasoil
used for heating has contributed to less
pollution in many cities.
Automotive diesel has national variants — but
the usual variants traded are EN590 and EN560
which are specified by ISO in Paris. These
qualities may be sold in the U.S., and be
compliant with EPA regulations in the U.S.
Automotive diesel is now tested in planes with
great success, where you get greater mileage per
weight unit of fuel — as much as 40% increase.
In these days, when no stone remains unturned to
reduce emissions, one outcome may be that planes
will fly on Gasoil and not kerosene. The problem
is condensate / ice particles and wax that may
cause the jet engine (which is a turbine) to be
completely destroyed. A preliminary solution is
to heat the gasoil before injection, and pass it
through an electrostatic filter.