Continuous Washing of Biodiesel

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Continuous Washing of Biodiesel
Group Members Trevor Binney Rebecca Solano Gabe
Montero May 31, 2005
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Washing Biodiesel

• When Biodiesel is created, there are contaminants
  in the fuel.
• Washing Biodiesel means using water as a means of
  removing contaminants through liquid liquid
  extraction.
• Refining the fuel (by removing impurities)
• Test overall quality (does an emulsion form)

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Common BD washing techniques

• Bubble Washing
• Common and Inexpensive
• Mist Washing
• Low Agitation Method
• Bulk (Batch) Washing
• Primarily Homebrewers
• Podbielniak Washing
• Fast Continuous

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Comparison of Washing Methods

• Bubble Mist Bulk Pod
• Cost low mod lowest high
• H2O Use low mod high mod
• Elec Use low none
  high
• Speed mod mod slow fast
• Agitation mod low mod
  high
• Labor low low high
  mod

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Project Planning

• Initially we wanted to include three types of
  Liquid-Liquid Extraction designs
• Box Type Mixer Settler
• Packed Column
• Centrifugal
• Two of the three would have been too slow for
  continuous extraction due to an unusually long
  settling time unless we could find a way to
  enhance separation.

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Project Planning

• Ternary Phase Diagram
• Glycerol separates to the bottom
• During testing, we found that we could not
  dissolve any glycerin in the biodiesel
• Methanol separates to the top
• Accurate measurement problems

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Project Planning

• Problem with Emulsion

Biodiesel Layer is the least dense and rises to
the top Emulsion Layer remains below the
biodiesel but above the water with clear
separation Water Layer is the most dense and
settles to the bottom
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Safety Considerations
Oil and water spills All spills were small and
were easily and quickly cleaned up to prevent
slipping hazards for ourselves and
others Unwashed biodiesel will contain dissolved
caustic (NaOH) Any skin contact requires washing
with soap and copious amounts of
water Appropriate lab coats and safety glasses
are required during operation Podbielniak
operates at high rotational speeds Remain aware
of any unusual vibrations or sounds coming from
the unit especially when increasing the drive
speed Wear safety goggles while operating unit
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Safety Considerations
Moving machinery Use caution when working around
the pumps, they build up heat and could
potentially cause burns Drive belt is not fully
enclosed. DO NOT stick your hands or feet
anywhere near the drive belt
Variable Speed Motor
Drive Belt
Podbielniak
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Calibration

• Flow Meters
• One was calibrated for Biodiesel
• The other was calibrated for Water

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What causes an emulsion to form?

• Mono- and Diglycerides lead to creation of soaps
  which allow for a stable water-soap-biodiesel
  emulsion to form
• The emulsion forms upon agitation of the liquid
  mixture
• Smaller droplets are more stable

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Why Our Samples Emulsified
In the Biodiesel Phase
In the Water Phase
Water
Polar Group
Non-Polar Tail
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Emulsion Busting, time to bust it up!

• Several possible methods for breaking emulsions
  were found while researching
• Wait, (it may separate over time)
• Add heat (higher temp means more movemnt)
• Add acid (to help eliminate emulsion causing
  soaps)
• Add salt (salt ions preferred over soap???)
• Use less lye during production process

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Temperature Experiments

• Water Bath Heating To Increase Separation Speed

• Results
• Still takes 24 hours to separate at 40 deg C
• Room temperature samples can take as much as 5
  days to reach the same degree of separation

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Salting

• Tested salts of NaCl, KI, and CaCl2

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Salting

• Tested least expensive salts at equal
  concentrations
• Results Initially the NaCl
• separated out faster than CaCl2
• After letting the mix settle for two days,
• the NaCl solution had separated out
• further with little change in
• the CaCl2 wash

CaCl2 on the left NaCl on the right
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Salting

• Tested varying concentrations of NaCl
• Results More salt can cause emulsion in the
  biodiesel phase, but is better for separation of
  the emulsion.

1 Still has very small emulsion layer
cloudiness noted in water layer. 5 Largest
emulsion layer 10 Less emulsion than 5
solution, but more than 1 20 Barely
distinguishable emulsion water phase is very
clear.
1
20
5
10
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Why Salting Works
Na
Im out of here!
Its getting too crowded!
Biodiesel
Water
Cl-
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Why Salting Doesnt Work
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Salting with the Pod
Heavy Phase Without Salting Heavy Phase With
Salting
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Effect of Rotation Speed on Separation

• Decreasing Podbielniak rotation speed from left
  to right
• There is less water present in the biodiesel rich
  phase for lower rotation speeds
• The test was conducted twice, once starting at
  low speed and increasing, and once starting at
  high speed and decreasing
• The results are the same for both trials

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Drying Biodiesel

• After washing biodiesel, it may be somewhat hazy.
  This is caused by residual water in the fuel
• Over time, the water will evaporate, and the fuel
  will clear
• The samples washed early in the term have cleared
  considerably since the wash

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Measurement and Analysis

• GC analysis was performed using technique similar
  to the ASTM standard for measuring total and free
  glycerin in biodiesel
• Visible spectral analysis could not be obtained
  due to a burnt out bulb.

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GC Analysis

• Areas of every peak but the first one were added
  together
• Largest peak was assumed to be biodiesel
• Relative signal peaks were measured against the
  unwashed biodiesel
• Concentration of biodiesel in sample was compared
  to concentration of biodiesel in unwashed sample

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Statistical Analysis

• ASTM standard vs. unwashed
• Difference between averages 0.0460 biodiesel
• t 1.816
• tdf,a t3,0.1 1.638 lt 1.816, so null
  hypothesis is rejected. Purity of our unwashed
  biodiesel is greater than ASTM standard
  biodiesel.

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Statistical Analysis

• Continuous wash vs. unwashed
• Difference between averages .00824 biodiesel
• t 0.193
• tdf,a t4,0.1 1.533 gt 0.193, so null
  hypothesis cannot be rejected.

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Statistical Analysis

• Hypothesis test
• for continuously washed vs. unwashed
• For unwashed vs. ASTM standard
• Is there a difference in purity?
• If confidence level is less than 90, then the
  test is statistically inconclusive (null
  hypothesis cannot be rejected)
• If confidence level is greater than 90, then
  samples are statistically different (null
  hypothesis is rejected)

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Conclusions

• Adding NaCl (table salt) can break up an emulsion
  of biodiesel in water, but not an emulsion of
  water in biodiesel
• Heating an emulsion of biodiesel and water will
  decrease separation time
• Use lower rotational speeds until further testing
  can be done

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Recommendations

• Other extractors box-type mixer-settler and
  column extractor may work at extremely low feed
  rates or with the addition of heating the feeds
• If fatty acid soaps can be obtained and
  accurately measured, they could be used as the
  model contaminant
• Pumps have been calibrated for biodiesel and
  water, if any future groups are interested

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More Recommendations

• Perhaps spectophotometry may be a useful
  measurement device to determine the extent of
  emulsion Marilyn Walsh in the biochemistry
  department has a spectrophotometer that operates
  in the visible range walshm_at_onid.orst.edu
• HPLC is available in Gleeson, but may need some
  assembly and/or repair. HPLC may be a better
  analysis tool because it picks up ionic molecules
  such as fatty acid soaps
• Test different rotational speeds and flow rates
  with Podbielniak

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Acknowledgments

• Group 1 Biodiesel Optimization for providing
  us with unwashed biodiesel
• Group 2 Biodiesel Testing and Glycerol
  Polymerization for streamlining the GC testing
  methods for biodiesel
• Dr. Rorrer for providing Podbielniak information

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QUESTIONS?
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References

• Vining, G. Geoffrey. Statistical Methods for
  Engineers. Duxbury Press Boston, MA. 1998.
• Hanson, Carl. Handbook of Solvent Extraction.
  Wiley New York, NY. 1983.
• http//www.planetconnecticut.org/teachersadministr
  ators/pdfs/lesson6.pdf