Transcript Biodiesel Cold Flow Basics

Biodiesel Cold Flow Basics
Information for Petroleum Distributors,
Blenders, and End-Users on Issues
Affecting Biodiesel in the Winter Months
Prepared by the National Biodiesel Board
2014
Diesel Fuel & Cold Weather Operability
Operability is defined as the
lowest temperature a vehicle
will operate without loss of
power due to waxing of the
fuel delivery system.
Diesel Fuel Background Information
Relevant to Biodiesel
Diesel fuels composition and cold flow properties vary
greatly across the United States. Cold flow characteristics of
diesel fuels are influenced by the source of the crude oil
they are made from, how they are refined and if they are
blended to improve performance during cold weather.
The cold temperature properties of diesel fuel vary across
the country depending on the time of year the fuel is
produced and the climate. Generally, diesel fuels used in
cold climates have better cold flow characteristics than
diesel fuels used in warmer regions.
Both of these statements have a direct impact on the
operability of biodiesel blends in cold weather
Three Important Cold Weather Parameters that
Define Operability for Diesel Fuels & Biodiesel

Cloud Point
Temperature where wax crystals first
appear

Cold Filter Plugging Point
The lowest operating temperature in
which a vehicle will operate

Pour Point
Lowest temperature where fuel is
observed to flow
Understanding the Cold Flow Mechanism
in Diesel Fuel and Biodiesel
NUCLEI
CRYSTALS GROW AND
BEGIN TO ADHERE TO
ONE ANOTHER
More wax
precipitates as
the temperature
decreases
VISIBLE CRYSTALS
Cloud Point
LARGE CRYSTALS
ADHERE, TRAPPING LIQUID.
POCKETS ARE FORMED SIMILAR
TO A HONEY COMB. FUEL GELLED.
Pour Point
Typical Treatment of Diesel for Cold
Weather Operation
Additives
 Commercial cold flow additives can help winter
operability by modifying the wax crystal structure
during crystal formation when cooling occurs.
 Dosage level (expressed in parts per million (ppm)) of
individual commercial additives varies depending on
wax content and temperature.
 Key Point: Additive must be added to fuel before it
reaches cloud point temperature to be effective.
 Screening your fuels with appropriate additives and
biodiesel blends is recommended.
Typical Treatment of Diesel for Cold
Weather Operation
Kerosene (#1-D)
 #1-D has excellent cold flow
properties and is generally blended
with #2-D in the winter months
across the United States to meet
customer cold flow specifications,
improving / insuring operability.
Cloud and pour points, and CFPPs
of some #1-D can be well below
-30º F.
Biodiesel and Cold Weather Operability
Basic Facts about Biodiesel & Cold Weather
 B100 freezes faster than most US petrodiesel.
 Untreated B20 freezes about 2-10° F faster than
#2 petrodiesel, depending on:
• the cold flow properties of the biodiesel
• the cold flow properties of the petrodiesel
• at blend levels of 20% and less (< B20),
the cold weather parameters of the diesel
fuel will dominate
Biodiesel Feedstock Composition and
Cold Weather Operability
 The cold flow properties of biodiesel fuels are dependant on the
feedstock (specific type of oil, fat or grease) from which they are made
and are a strong function of the level of saturated fat.
 Animal fats, palm and coconut oils are more highly saturated—
traditionaly higher Cetane Number, higher cloud point.
INCREASING CETANE NUMBER (CN) AND STABILITY
100%
90%
80%
70%
BETTER COLD FLOW PROPERTIES
60%
50%
40%
30%
20%
10%
Saturated
Monounsaturated
Polyunsaturated
Coconut
Palm
Beef
Tallow
Lard
Yellow
grease
Cottonseed
Peanut
Soybean
Olive
Corn
Sunflower
Safflower
Canola
0%
Cold Soak Filtration Test…

Under conditions prescribed
by ASTM D7501, a 300mL
test sample is chilled, warmed
and filtered.

The time required to pass
through a specific filter is
measured.

The entire sample volume
must pass through the filter
within 360 seconds.

If vehicle performance is
expected at or below -12o C /
10.4o F then a max of 200
seconds must not be
exceeded.
Blending Biodiesel
In The Cold
Common Cloud Points
for B100

Cold Weather Considerations:

When blending, the temperature
of the biodiesel should be a
minimum of 60oF or…




15oF above the cloud point.
In-line blending ensures the best
mixing
If in-line blending for loading
trucks is not available in cold
weather, first add half the diesel
(warm if possible). Followed by
warm biodiesel at high pressure
and volume to enhance thorough
mixing followed by the other half
of the diesel.
Avoid introducing biodiesel
directly into a cold and empty
tank.
CP Feed Stock Dependent
Plant Oils
Water Freezes
Recycled Grease
(UCO, WVO)
Animal Fat
Safe blend temp 60oF
Resource: “A Biodiesel Blend Handling Guide”. Minnesota Department of Agriculture.
“Room” Temperature
ASTM D6751-12
Cold Weather Performance with Biodiesel
 Establish a benchmark for cold flow protection
based on the ASTM D975 “Tenth Percentile
Minimum Ambient Air Temperature.”
the lowest ambient air temperature which will not go
lower on average more that 10% of the time
 Make sure the petroleum
distributor is aware of this
and incorporates it into
blending operations
Biodiesel Blending and Cold Weather Operability
 The impact of blending
biodiesel with diesel fuel
is dependent on the
characteristics of the
base diesel fuel and the
methyl ester.
Biodiesel Blending and Cold Weather Operability
 Generally, the better the cold flow
characteristics of the base diesel fuel, the
greater the effect of blending biodiesel on
its cold flow properties. Blending biodiesel
with #1-D and premium diesel fuels tends
to affect cold flow properties more than
blending biodiesel with #2-D.
Biodiesel Blending and Cold Weather Operability
 Concerns arise when the fuel
temperature falls below the
cloud point of either fuel,
independently, or as a
finished blend fuel.
B100 Cold Weather Storage and
Delivery Precautions
 B100 stored in cold temperatures
must be heated to at least 15 degrees higher than
the biodiesel feedstock being used prior to
distribution or blending into middle distillates of
any grade.
 If pumping biodiesel in cold weather through a
conventional fuel pump, keep the hose and supply
line to the pump equally protected with heat. An
option to heating the systems is to blend B100
with 50% kerosene to dilute the cold weather
properties of the biodiesel.
Cold Weather Blending Options and Precautions
 With any type of blending (splash, in-tank or
bottom loading), putting B100 into a cold
empty truck can cause the fuel to gel,
prohibiting proper mixing.
 Always maintain biodiesel
at 15º F above its cloud
point prior to blending
with diesel fuel.
Low Blends of Biodiesel and Cold
Weather Operability
 Blends of 2% and 5% biodiesel with
diesel fuel have little impact on cold
flow properties. Only small
increases in cloud and
pour point are observed
Low Blends of Biodiesel and Cold
Weather Operability
 As long as the B2 or B5 blend is
made using an appropriate “winter
grade” diesel fuel, no special
provisions are required for storing,
transferring or using the fuel.
Biodiesel and Cold Flow Additives
 Most cold flow additives essentially work only on
the diesel portion of the biodiesel blend as U.S.
oils and fats contain too high a level of saturated
compounds for most additives to be effective.
 The cold flow additive effectiveness can also
change dramatically depending on the exact type
of biodiesel and the processing it has undergone;
much like the situation found with diesel fuel.
Conclusions
 Cold flow properties of petrodiesel fuel vary widely.
 One MUST be aware of the cold flow properties of
both the biodiesel AND the petrodiesel.
• With blends of 20% and below, petrodiesel is
dominant
 Prepared properly, blends of B5 or less do not appear
to be appreciably different from the base petrodiesel.
Conclusions
 Blending biodiesel with #2 petrodiesel in blends of
20% (B20) does have an impact on the cold flow
properties.
• Saturated oils and fats have more of an effect on
cold flow properties.
 Blending biodiesel with #1 petrodiesel in blends of
20% (B20) results in more of an impact on cold flow
properties than with #2 petrodiesel.
• But the resulting #1 blend still has better cold flow
values than #2.
Cool Customers
How others use biodiesel in cold climates
Cranmore Mountain Resort
When snow falls at a rate of
several inches per hour and
all signs point to perfect
weekend ski conditions, this
ski resort has a lot riding on
successful operation of its
snow grooming equipment.
Cool Customers
How others use biodiesel in cold climates
City of Brooklyn Park, MN
The city has used biodiesel
blends since 1999 in its fleet
of over 100 vehicles—
including fire trucks, utility
and police vehicles.
Cool Customers
How others use biodiesel in cold climates
Yellowstone National Park
Biodiesel powers about 300
vehicles, boilers and other
diesel equipment at the
crown jewel of America’s
National Park System.