Electrostatic separation of glycerol from biodiesel
Glycerol separation @ 1000V AC, 0.004mA

9 September 2006 - Graham Laming

Doesn't seem to work for dewatering or cleaning WVO, unfortunately.

Note Although the effect of electrostatic separation is quite dramatic and fast, I believe it is more practical to remove glycerol by distilling off and recovering residual methanol immediately after the reaction has completed.

I have not found any evidence of appreciable reverse reaction.

The technical difficulties associated with electrostatic separation make it generally impractical, in my view.

Glycerol recovered through electrostatic separation is heavily laden with methanol, whereas glycerol recovered after residual methanol distillation is low in methanol and drops out of the biodiesel very rapidly.

However, take a look these experiments, you might find them interesting and might be inspired to find a practical use for the effect.

The glycerol is quite a light colour with
biodiesel made from new sunflower oil.

Notice how the bottle shows no sign of
separation at all, yet.

This technique works well on biodiesel made
from high FFA oil too, and works with hot or cold

Here's another video using biodiesel made from waste cooking oil...

Guidelines on making high voltage source
Firstly, don't try any of this unless you are a trained electrical technician, familiar with the necessary safety precautions and procedures needed for working with high voltage. You need to protect yourself and those around you. I can't teach you what is necessary, so if you don't have a good understanding of this subject, don't try any of this.

A suitable supply can be made according to the general scheme below...

current limited HT supply

Instead of having both lines current limited, you could have one earthed, and the other current limited with twice the number of resistors shown for one line.

How can we apply this to a biodiesel process?

There are a number of possible ways to do this. Again, I am offering ideas only, it is up to you to develop a scheme to suit your process.

Allow around 25mm per 1000V plate spacing
Do not allow the electrodes to enter the glycerol layer.

Do not allow the electrodes to be exposed to an air/methanol vapour mix. You can achieve this if you ensure the electrodes are always submerged. This is to prevent the possibility of an arc occuring in the explosive atmosphere.

Here are some ideas for you...

Electrostatic tube separator

Electrostatic flat plate separator

Electrostatic single pass separator

Electrostatic recirculating separator

What else can we use electrostatic fields for?

Emulsions can be broken quickly with an electrostatic field. In the pictures below, I have purposely made 2 very thick emulsions of biodiesel in water with soap, and I added a little phenolphthalein to make the emulsion boundaries clearer to see.

This is an emulsion which has been clearing naturally over a 12 hour period...

Emulsion after 12 hours of natural settling

This is the same emulsion after 20 minutes of 4kV electrostatic field...

Emulsion after 20 minutes electrostatic field at 4kV

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