Page 25 - Fuels & Lubes International 2014 - Q2

25
FUELS & LUBES INTERNATIONAL Volume 20 Issue 2
The impact of such
diffe­rences on performance, emis-
sions, reliability and other aspects
of engines could be significant.
Thus, original equipment makers
(OEMs) and some end users are
apprehensive that ASTM D975,
which defines diesel fuel based
on the fuel’s performance during
certain tests, may no longer pro-
vide the protection it once did.
“There has been concern that
D975 fuels in the past have been
primarily petroleum-based, and
equipment designed for a D975
petroleum-based fuel may not be
compatible with fuels of different
origins,” said Allan Morrison, a
senior environmental scientist who
works in the fuels and lubricant
laboratory at the California De-
partment of Food and Agriculture.
California’s goal of promoting
renewable fuels led Morrison to ask
for clarification of what constitutes
a D975-compliant fuel. He’s not
alone. Fuel suppliers, OEMs,
consultants and others are engaged
in a tug-of-war over the standard
with some pushing for and others
against a broadening of the spec
or the adoption of new diesel
fuel-related standards.
One change that may soon
pass involves nailing down just
what constitutes “hydrocarbon oil”.
These two words have been in the
section of ASTM D975 that covers
what defines diesel fuel for at least
a couple of decades and possibly
longer, according to Donna Hoel,
who retired from ExxonMobil
and is now a consultant.
But, the phrase is no longer
quite as clear as it once was,
because diesel fuel is no longer
what it once was. “Over the
intervening 20 years or more,
diesel fuel has changed a lot,”
Hoel said. “It has become much
more important, and, of course,
the interest in conserving energy
resources and reducing greenhouse
gases, a variety of things, leads to
an interest in alternative fuels.”
An ester isn’t a hydrocarbon
oil, in part because it contains
oxygen. Yet esters are in biodiesel
with oxygen content above 10%.
Given that D975 is used by
regulators, OEMs and operators to
determine what is and isn’t diesel,
Hoel felt that the definition in
the standard needed clarification.
Hoel is in charge of the current
ballot to re-define hydrocarbon oil.
In the current standard,
a hydrocarbon oil is a mixture
or solution composed of the ele-
ments hydrogen and carbon. This
solution can contain sulfur, oxygen
or nitrogen from residual impuri-
ties and contaminants. Specifically
excluded from the definition are
added oxygenates, such as alcohols,
esters, ethers and triglycerides.
One of the issues under debate
is whether or not to add an explicit
statement that the definition of the
mixture is independent of its source.
A clarification of the definition
is one of the current ballot items.
A second item is that hydrocar-
bon oil is not restricted to any one
source. Passage of either of these
items is independent of the other.
“Depending on what happens
on the D2 ballot now open, there
may be another set of subcommittee
ballots on the subject,” said Hoel.
“Hydrocarbon oil” also is in
ASTM D396, which covers fuel oils,
and in D2880, which covers gas
turbine oil. These other hydrocar-
bon oil-based products sometimes
share tank space with diesel fuel
and may be blended with the fuel.
Hence, there is a physical link
among the three products.
Changing an ASTM standard
isn’t easy. It goes through several
stages of balloting. At the subcom-
mittee level, a ballot has to get
two-thirds’ vote to proceed to com-
mittee balloting. If there are any
negative votes, the subcommittee
has to declare these non-persuasive.
At the committee level, a ballot
must receive at least 90% affirma-
tive votes to pass. Any negative vote
also must be ruled non-persuasive.
This consensus process can
take some time. Thus, revising
an ASTM standard has been
described as moving at a slow,
or even glacial, pace.
Hoel has been working on the
hydrocarbon oil ballot for the past
Oneof the reasonswhy the
biodiesel industry is backing the
proposed changes to the
standard is that some suppliers have
used rawvegetableoil as blend
stock, according toHowell.
five years or so. Last December,
the subcommittee voted all the
negatives as non-persuasive and a
few negatives were also withdrawn.
Balloting at the committee level is
taking place.
As for accommodating biodie-
sel, that is being handled through
a special section in the standard.
Steve Howell, chairman of the
ASTM Biodiesel Task Force, said
that the industry he represents
acknowledges that what it sells is
not a hydrocarbon. At the same
time, what’s in an ASTM standard
has, until recently, been based on
processing petroleum, he added.
Howell noted that this means
that some specifications that are
important for operating a diesel
engine with alternative sourced
fuels are not found in D975.
Two examples are energy, or BTU,
content and oxidation stability.
Neither are specified for diesel fuel
produced from petroleum, but
both parameters are important if a
fuel is to be used in an unmodified
engine. The need for additional
specs is magnified given that biod-
iesel could be blended into diesel
fuel at a 20:1 ratio. Because of this,
such parameters are difficult to
test for and evaluate in the finished
fuel. Consequently, pure biodiesel
has to be tested before it is blended
with petroleum diesel fuel.
“There’s been a lot of work
with the engine companies and
the ASTM group. When you have
a fuel that can be used in basically