by Jack Jones of Riverstones Biodiesel
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Here is a method for breaking emulsions that Jack Jones stumbled upon in late 2004.
This method uses biodiesel glycerine by-product as the emulsion breaking ingredient,
a readily available ingredient for anybody that makes biodiesel.
Biodiesel emulsions sometimes occur during the wash phase. This can occur for several
reasons relating to unreacted oils, poorly separated biodiesel/by-product, etc.
However, all these situations have one thing in common; aggressively washing biodiesel
in the presence of water and soap. Soap molecules (a by-product of the biodiesel reaction
created when free fatty acids are neutralized with the catalysts) are long chain molecules
that have one end that is attracted to polar molecules (such as water) and the other end that
is attracted to nonpolar molecules (such as dirt, grease, biodiesel, etc.). These long
molecules will attach themselves to dirt, grease, biodiesel, etc. and then bunch together forming a
"bubble" around the dirt, grease, or biodiesel so that the ends of the soap molecules
that are attracted to water form the outside surface of a sphere with the dirt, grease, or biodiesel at the center of the "bubble".
BREAKING AN EMULSION
Emulsions occur during aggressive biodiesel washing because the biodiesel becomes "imprisoned"
in these soap spheres. These soap spheres can be broken apart by pushing them tightly
together by freezing the whole emulsion. Or we can break the emulsion by lowering the
surface tension between the soap molecules using a solvent like alcohol. The alcohols
(methanol and glycerin) in the biodiesel by-product are a readily available solvent to
break emulsions; much easier than freezing a large emulsion solid.
This page provides a pictorial walk-through for creating and breaking a small biodiesel emulsion.
We start with clean biodiesel. Since clean biodiesel will not emulsify with water alone we must
also add soap to the biodiesel. The soap we add is, ironically enough, provided by biodiesel
by-product. With the combination of clean biodiesel, soap (biodiesel by-product), water, and a
very aggressive mixing of the liquids we easily create a biodiesel emulsion.
With the biodiesel emulsion created we then break the emulsion by adding the solvents
(the biodiesel by-product). We add small amounts of the by-product to determine how much
is really needed to break our emulsion. It is important not to mix these solvents too
aggressively or their emulsion breaking power will be halted by the emulsion creating power
of the soap that is present. A thorough mixing is all that is needed. It is also important
to have the mixture a little warm at this point. We heated the mixture up to 90F.
Start with 500ml of nice clean biodiesel
Add 50ml of biodiesel by-product (glycerin, soap, methanol etc.)
Notice the layer on the bottom
Add 100ml water
Now notice the layer of water/by-prodcut on the bottom
And shake some more until it emulsifies
Remember what it looked like before the emulsion?
Add 50ml by-product and gently mix
That didn't break the emulsion so add another 50ml by-product and gently mix
It's starting to work but we need another 50ml by-product and gently mix
A total of 150ml by-product broke the emulsion
Re-clean the biodiesel