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Latest Information of Ultra-Low Sulfur Diesel
December 2007
The Ultra-Low Sulfur Diesel (ULSD or S-15) fuel story
continues to unfold and there is not much good news to be told.
ULSD is causing more and more problems in the field,
with little explanation and no help from the major refiners.
Burying our heads in the sand will not solve any of
these problems. They will not go away on their own, and unless forced by
customers or legislation the major refiners are very unlikely to make any
changes.
Some ULSD basics:
ULSD is hygroscopic, it actually holds more dissolved or
suspended water (up to 2X as much) than Low Sulfur Diesel (Non-Road, Locomotive,
Marine (NRLM), LSD, or S-500) or High Sulfur Diesel (HSD or S-5000).
This dissolved water causes several problems.
It causes higher levels of gum formation, varnish
formation, and carbon deposit formation.
This water will corrode (rust) fuel tanks, pumps,
injectors, and any other metal it touches. We have seen dozens of examples of
engines stored for a few weeks to few months that have significant corrosion in
the injectors and other fuel system components even though they are immersed in
fuel.
Dissolved water encourages and increases oxidation,
speeding the breakdown (destabilization) of the fuel. We are seeing fuel
destabilize due to oxidative and thermal breakdown much quicker than ever
before. This destabilization takes many forms including darkening of the fuel
and formation of asphaltene droplets which blacken and plug filter in a few
hundred to a few thousand miles.
Dissolved water is affected by the temperature of the
fuel. ULSD at 30?F can only hold approximately 35% of the water it can at 75?F.
As fuel cools it loses its ability to hold dissolved water. The water is
actually pushed out of the fuel into tiny droplets. These droplets explain why
you can look at fuel in a tank and see no water and yet a fuel separator or
filter can constantly be accumulating water. Furthermore at temperatures below
32?F those water droplets turn to ice crystals. These ice crystals will quickly
plug a fuel filter with a white ice that looks remarkably like wax to the
uninformed. We regularly hear from people who believe their fuel is gelling at
temperatures of 32?F or just below it. This icing was a major problem last
winter and is already causing problems this season. To add to the problems
caused by this high water content, bacteria and fungi can and do actually grow
in fuels with little or no visible free water in the tank.
The size and shape of the paraffin wax seed crystals
have changed dramatically in ULSD as compared to previous fuels. In ULSD these
crystals are larger and regularly shaped than in the LSD and HSD fuels. These
larger crystals cause a series of problems for users of ULSD.
First ULSD will ?gel? several degrees sooner (warmer)
than the previous fuels. The larger crystals are harder to ?treat? to prevent
gelling.
Next, there is a new cold weather operability problem
that was previously unknown and until recently undefined. This is ?Wax Dropout?,
an occurrence that happens when ULSD is subjected to a ?Cold Soak? period of
approximately 48 to 72 hours. When the fuel is continuously at or below a given
temperature for an extended period of time (Cold Soak); the larger heavier wax
crystals agglomerate and drop to the bottom of the storage container. This
paraffin wax has the further problem that it is not readily reabsorbed by the
fuel as the temperature rises.
On Monday February 5th of 2007 in the
Northeast we had had a weekend where the temperature dropped to approximately
8?F and stayed there all weekend. On that Monday morning after approximately 72
hours of 8?F or colder we saw a massive region-wide problem with WDO. We have
now tested for and seen this problem happen at temperatures between 12?F and
0?F.
The temperature where this WDO phenomenon occurs does
not appear to directly correlate to any of the commonly used cold weather
operability measures such as Cloud Point (CP), Cold Filter Plug Point (CFPP),
Low Temperature Flow Test (LTFT), and Pour Point (PP) traditionally used to
discuss and rate diesel fuels.
The traditional method for improving cold weather
operability for diesel and heating fuels was to blend with Kerosene (#1 Fuel) or
Jet A. Depending on ambient temperature, cost, and availability, blends of 10%,
20%, 30%, 40%, 50%, and even higher have been used to lower the CP, CFPP, PP of
fuels.
Due to a combination of factors including EPA
regulations, Catalytic Cracking, and Severe Hydrotreating ULSD has a lower
aromatic content and less solvency. The EPA regulations requiring the fuel to be
delivered to the vehicle with a Sulfur content of 15 ppm or less have eliminated
High Sulfur Kerosene and Jet A as blending agents.
This situation has theoretically forced refiners to
create an ULSD #1 (Ultra-Low Sulfur Kerosene) for blending purposes. There are
however a number of significant problems with using ULSD #1 for winter blending.
For one thing, the major refiners don?t want to produce this product. There are
several reasons including but not limited to; limited demand, the need for
segregated storage, the inability to use ULSD #1 for other uses, and high cost
of production.
In short, the biggest problems are nobody wants to make
ULSD #1, nobody has any place to store it, it is much more expensive than
regular Kerosene, and last but not least, it doesn?t work anywhere near as well
as the old high sulfur Kerosene.
The old industry ?Rule of Thumb? for winter blending HSD
and LSD was that for every 10% Kerosene or Jet A that you blended in you would
improve (lower) the CP, CFPP, and PP by 5?F.
An example would be if you had LSD with CFPP of 10?F and
you blended in 50% Kerosene you could expect to lower the CFPP to approximately
-15?F. This standard has been used since before World War II.
Today using ULSD and ULSD #1 for blending the new ?Rule
of Thumb? is that for every 10% ULSD #1 you blend into ULSD you only improve
CFPP by 2?F or less.
An example today would be starting with ULSD with CFPP
of 10?F and you blended in 50% ULSD #1 you might lower the CFPP to
approximately 0?F. We say might because we have seen a high number of instances
where 10% ULSD #1 provides a 1?F or less improvement.
In order to successfully operate using ULSD an Anti-Gel
product formulated to work with ULSD must be used. Many if not most of the
old-line anti-gel products that have been on the market for 10, 20, even 30
years do not work effectively on Catalytically Cracked fuels including ULSD.
To successfully treat ULSD requires new formulations
that include an Anti-Gel additive with ?Seed Crystal Wax Modifiers?, Cold Flow
Improvers, Wax Anti-Settling Agents, and Anti-Icing agents that have been
modified to work with this new fuel.
Enertech Labs offers a wide range of products including
Complete Fuel Treatment?, Polar Flow?, and the Matrix? products with chemistry
formulated address these and the many other problems found in today?s fuels.
They are designed to remove (Disperse) water, including dissolved water;
stabilize fuels, and provide extreme cold weather operability (Anti-Gel)
improvement for ULSD, LSD, NRLM, HSD, IFO, and MFO.
? Copyright Enertech Labs ?
William Richards 12/2007
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sales@enertechlabs.com with
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Enertech Labs, Inc.
Last modified:
01/12/09
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