Biodiesel Cold Flow Basics

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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
• Winter 2007/2008

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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.

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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
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Three Important Cold Weather Parameters that
Define Operability for Diesel Fuels Biodiesel

• Cloud Point
• Temperature where 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

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Understanding the Cold Flow Mechanism in Diesel
Fuel and Biodiesel
VISIBLE CRYSTALS Cloud Point
NUCLEI
LARGE CRYSTALS ADHERE, TRAPPING LIQUID. POCKETS
ARE FORMED SIMILAR TO A HONEY COMB. FUEL GELLED.
Pour Point
CRYSTALS GROW AND BEGIN TO ADHERE TO ONE ANOTHER
More wax precipitates as the temperature decreases
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Typical Treatment of Diesel for Cold Weather
Operation

• Additives
• All commercial cold flow additives work 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.

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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.

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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 (lt B20), the cold
  weather parameters of the diesel fuel will
  dominate

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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 saturatedhigher CN, higher cloud point.

INCREASING CETANE NUMBER (CN) AND STABILITY
BETTER COLD FLOW PROPERTIES
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Cloud Point (CP) Variation in 3 Different Diesel
Biodiesel BlendsSoy Methyl Ester (SME)
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Variation in Pour Point (PP) of 3 Different
Biodiesel Base Feedstocks
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Biodiesel Blends Cold Flow Characteristics
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ASTM D 6751-07a

• Property Test Method Limits Units
• Calcium Magnesium EN 14538 5 max ppm (ug/g)
• Alcohol Control
• either Flash Point D 93 130 min Degrees C
• or GC Methanol EN 14110 0.2 Volume
• Flash Point D 93 93 min Degrees C
• Kin. Viscosity, 40C D 445 1.9 - 6.0 mm²/sec.
• Sulfated Ash D 874 0.02 max mass
• Sulfur S500 D 5453 0.05 max (500) mass (ppm)
• S15 D 5453 0.0015 max (15) mass (ppm)
• Copper Corrosion D 130 No. 3 max
• Cetane Number D 613 47 min
• Cloud Point D2500 Report degrees C
• Carbon Residue D 4530 0.05 max mass
• Acid Number D 664 0.50 max mg KOH/g
• Free Glycerin D 6854 0.020 mass
• Total Glycerin D 6854 0.240 mass
• Phosphorous Content D 4951 0.001 max mass

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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

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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.

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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.

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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.

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B100 Cold Weather Storage and Delivery Precautions

• B100 stored in cold temperatures (less than 40º
  F) must be heated to at least 60ºF 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.

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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 1015º F above its
  cloud point prior to blending with diesel fuel.

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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, while the CFPP often decreases
  slightly when using B2.

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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.

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Biodiesel and Cold Flow Additives

• 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.

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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.

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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.

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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.
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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.
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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 Americas National Park
System.