High Voltage Separation of Biodiesel from GlycerinG. Austic, R. Burton, S. Shore, Piedmont Biofuels, Pittsboro, North Carolina, U.S.A.

2nd International Congress on Biodiesel:The Science and The Technologies15-17 November 2009Munich, Germany

BackgroundThe goal: create a continuous separation step for biodiesel

• Graham Laming, a biodiesel enthusiast from the UK, initially discovered the phenomenon for glycerin separation from biodiesel.

• Expanding on his work, we tested the following variables:

• electrode distances

• separation volumes

• container widths

• electrode types (point, line, and screens)

• Eventually, we created a continuous separation device using this technology which separated 99.7% of glycerin running at 4L/min.

• While the technology was interesting, we did not currently have an application, and we were concerned about the application of voltage through a methanol laden system (!).

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Variables of Interest

• Soaps

• FFA

• Glycerides

• Water

• Viscosity

• Voltage

• Amperage

• Electrode Distance

• Container material

• Container width

• Container height

• Container Length

• Container Volume

• Time

Proposed Mechanism

• The hypothesis is that charged particles exist in the glycerin.

• When an electric current is passed through, the charged particles line up and clump together.

• After clumping the globule is large enough to fall out of solution.

Sample Creation

• Three mini-batches were made of 0%, 2%, and 6% FFA

• Vegetable oil was blended with Oleic Acid to create the FFA%

FFA (%)

Total Oil (mL)

Virgin Oil (mL)

Oleic Acid (mL)

Methanol (mL)

Catalyst (g)

0 200 200 0 49 1.95

2 200 196 4 49 2.72

6 200 188 12 59 4.65

Sample Creation (cont)• A (60/40) two-stage reaction was performed• The first stage was 30 minutes, the samples

were heated for 2 minutes and agitated for 1 minute

• The second stage was 1 hour, the samples were heated 4 minutes and agitated 1 minute

• The 6% sample had an additional third stage where 0.4 g KOH in 10 mL of MeOH

• The third stage was 30 minutes, the sample was heated for 2 minutes and agitated for 1 minute

Phase 1

• The goal was to characterize the conductivity of the glycerin and the biodiesel

• Conductivity was calculated by measuring the power going into the transformer

• Watts = Volts * Amperage = Amperage2 * Ohms• Conductivity = 1/Ohms• A power meter connected the power source to

the variac

Watt Meter

Phase 1 (cont)

• The variac varies the voltage entering the transformer

• 30 mL of sample was poured into a sample cup

• The electrodes were spaced at the same height approximately 1” apart horizontally

Phase 1 Results

FFA% vs Conductivity

0

10

20

30

40

50

60

0 2 6

FFA (%)

Conductivity (micro Siemens/m)

BD

Gly

Conductivity difference between biodiesel and glycerin

Phase 2 Set up• The goal is to characterizing the limitations & conditions for

the high voltage separation through a series of experiments

1. FFA and electrode distance

2. Low voltage limit

3. Minimum time

4. Resistance and Power

• Biodiesel (80 mL) and Glycerin (20 mL) were mixed in a 100 mL Graduated Cylinder

• To mix the solution, the graduated cylinder was covered with parafilm and inverted multiple times (~10)

• Electrodes were then submerged to the proper distances and the voltage was applied

Experimental Apparatus

Watt Meter

Variac

Transformer

Experiment 1• The goal was to characterize the effect % FFA and

electrode distance on separation time

• 0, 2, and 6 % FFA were tested

• Voltages of 321, 3214, 6107, and 9000 Volts were tested

• Electrode Distances of 0.8, 5.1, 10.8, 16.5 cm were tested

• All three FFA levels were tested at 4 voltages and 4 electrode distances

• The voltage was stopped after 90 seconds or when 90% of the Glycerin had separated

Mixed Samples

Biodiesel Biodiesel Biodiesel

Glycerin Glycerin Glycerin

0% 2% 6%

Experiment 1 Results

Largest distance between electrodes showed the shortest separation time for all FFA levels

The higher the FFA, the longer the separation time

Time for Gravity Settle

Experiment 2• The goal was to determine the lower voltage limit

• The farthest electrode distance was chosen along with the 2% FFA solution for better resolution

• The voltage was applied for 40 seconds

• Voltages tested were 321, 643, 1286, 1929, 2571, and 3214

Experiment 2 Results

Lower limitation of 1286 V achieved 89% separation completeness

Experiment 3• The goal was to determine the minimum time for

separation

• All three FFA levels were tested

• The voltage was set at 9000 V and the maximum electrode distance was tested

• The voltage was applied for set times 2, 5, 10, 15, 20, and 25 seconds

Experiment 3 Results

10 seconds: 0% FFA

15 seconds: 2% FFA

20 seconds: 6% FFA

Experiment 4• The goal: to evaluate resistance through the medium by

measuring the power

• The watts were recorded every 4 seconds for the 0% FFA sample and the 2 % FFA sample

• The power was recorded until the observed wattage leveled off

Experiment 4 results: 0 % FFA oil

Experimental 4 Results: 2% FFA

As glycerin drops out, conductance of the material between the electrodes decreases

Power and Separation with Time

Change in resistance (i.e., power) occurs once you get above 80% completeness of separation

Observations/Conclusions• Above a voltage threshold, increasing voltage

provides little added benefit

• Separation can be achieved in less than 1 minute

• Glycerin between the two electrodes would bind to other glycerin forming globules

• Once a globule is large enough, it falls out of suspension

• Separation only occurs between the electrodes

• At the higher voltages bubbling and large temperature increases were observed

Next Steps• Applying this technique in a real time system• Modeling the effects of electrode distance and voltage• Exploring the effect of heating • Exploring the effect methanol, soap, and water have on

separation• Separating biodiesel, glycerin, and wash water

Future Applications• A minimum conductance difference between the liquids is

required.• A minimum amount of charge must be able to flow through

the liquids.• It must be a 2 phase system.• Applies better in viscous systems, where gravity settling is

slow. However, too much viscosity could create a stable suspension.

• Solutions with flammables pose a potential safety risk.

Acknowledgements

Contact:Rachel BurtonPiedmont Biofuelswww.biofuels.coop919-321-8260

Piedmont Research Team: Greg Austic, Scott Shore, Xiaohu Fan

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