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i have been experimenting with the effects of high tension electric fields on suspended soap, glycerol etc. in biodiesel, with some interesting results.
my aim was to see if an electrostatic field within the biodiesel batch could help to attract impurities together into larger groups or clumps, to make filtration & separation more effective, efficient, faster.
i am using the gl 1 day process, whereby i remove methanol from the reacted batch and then filter out the soap. sometimes the soap seems not to drop out of the batch as quickly as i would hope. some people find the soap remains finely dispersed in the batch, especially if koh is used as the reaction catalyst. this seems to make filtration less efficient.
i'm posting my early findings to encourage others to share in these experiments.
my test setup consists of a glass jar, into which i place 2 parallel metal plates, each 100mm x 30mm, spaced 30mm apart.
i fill the jar with de-meth'd unwashed biodiesel, with soaps still present. i used biodiesel made with naoh for this test.
i then apply a dc voltage across the plates and note the effects.
here is the setup ...
the voltage source is set to 1000 v dc. i have not tried other voltage levels yet.
here is a closeup of the jar before i apply the field ...
here is a closeup of the jar after 10 minutes ...
the photos aren't very clear - i must re-run and take better quality ones, but what seems to happen is this:-
1. soap is clearly attracted to the +ve plate and forms a thick, firm gel on it.
2. soap in the bulk of the liquid clumps to form dense masses, which drop readily to the bottom of the jar.
no apparent separation occurs in the same timescale if the field is not applied.
i did a soap titration on a sample of the clear biodiesel phase after 30 minutes of field application and found negligible soap present, my test resolution suggests around 20ppm.
i have set up a bean can as a scale model of a 45 gallon drum, with the positive electrode being the can, the negative electrode being a carbon electrode from the centre of a 1.5v alkaline flashlight cell. i have the electrode in the centre of the bulk of liquid. the soap quickly coats the inside of the can.
the current passed thru the liquid is negligible, micro-amperes at the most, so there is very little power used in this process. safety could be dramatically improved by using a string of high voltage resistors in series with the plates to limit the maximum available current to say 0.1ma .
20 x 470k 0.6 watt high voltage resistors in series would seem to be a suitable current limiting combination.
filtration note: to filter the clumps, be sure you do not pass the biodiesel through a pump before it reaches the filter, or you will most likely break up the clumps of soap into smaller pieces. put the filter on the inlet side of the pump and set flow rate to the lowest acceptable level.
could someone else give this a try if they have the necessary kit and experience? it would be particularly insteresting if you could use koh as your catalyst.