Ardis,
You will find, after enough experimentation and out of pocket costs, that
mechanical agitation in a wash tank is the least expensive, consumes the
least energy, requires the least amount of time and leaves you with a
finished product as good as or better than mist- or bubble-washing.
Plain, pure and simple, mist- and bubble-washing have become
"institutionalized" amongst home-brewers primarily due to the frequency of
incomplete reactions that lend to washing problems. In short, they are both
methods of treating incomplete reactions with little kid's gloves in the
hopes that any resulting emulsion won't be "too bad" or "too noticeable."
The fact of the matter is that no wash method should be used on any batch
unless it is known for certain that the reaction has completed.
Unfortunately, many people fail to guarantee this for themselves, opting to
just "go ahead and wash it gently."
The method of guarantee is extremely simple. Put one ounce of what is
believed to be finished fuel in a baby food jar (or similar) with an equal
amount of water. Seal the jar and shake violently for 15 seconds. Completed
fuel should begin to separate instantly and there should be two distinct
layers in less than ~30 seconds. If it takes longer than this or if an
emulsion layer forms any thicker than the normal "paper thin" interface
layer between oil and water, you've got a batch that has not completed.
The degree of incompletion can vary. If the fuel/water separate slowly but
are by-and-large complete in a matter of 1-2 minutes and there is no
emulsion layer other than the interface, there's no great need to retreat
the reaction if the fuel is intended for personal use. If you have an
emulsion beyond the thin interface layer the batch needs to be retreated. No
amount of light mist- or bubble-washing can change this - unless, of course,
you don't care what grade of fuel you run through your engine.
The wash test and mechanical washing (motor, prop and shaft) work well no
matter what method you use - acid/base or straight base, single or double
stage.
Some concern has been expressed in the past over the use of air to dry fuel,
the concern being fuel oxidation. It's beyond me why those who express such
concern (and rightfully so) don't say word one about bubble washing doing
the exact same thing.
Others express concern with pump- or prop-washed fuel not clearing as
quickly as mist- or bubble-washed. There's sound reason for this, all things
being equal. Pumps and propellers have the ability of better mixing the fuel
and water ("atomizing it"), bringing both in more frequent contact with each
other. This means greater surface to surface contact between water molecules
and all suspended/dissolved impurities. Fifteen minutes with a 1/2 hp motor
and 4" - 6" prop in a 200 gallon wash tank or bigger will achieve the same
thing or more as an all-day-affair with a mist- or bubble-washer. This
allows for hours of washing time to be converted to settling time, in turn
hastening the entire wash process.
Anyway, when all is said and done and no matter what wash method you choose,
you'll best serve your own interests if you make sure that your reaction is
complete before attempting any type of wash. All bubble- and mist-washing
tend to do is offer brewers the opportunity to wash an incompletely reacted
batch with one eye closed and sometimes the other eye squinted.
Todd Swearingen
----- Original Message -----
From: "ardis streeter" <[EMAIL PROTECTED]>
To: <biofuel@yahoogroups.com>
Cc: <[EMAIL PROTECTED]>
Sent: Wednesday, July 07, 2004 7:29 PM
Subject: [biofuel] washing biodiesel in large processor
> Hi,all ' I was wondering if anyone could tell me
> which way might be best for washing large batches of
> biodiesel??My processor is capable of processing up to
> 200 gallons at a time.I am still building the
> processor so I was looking for some imfo.from
> experenced biodiesel producers.So far I have the
> stainless pick up tank done,the methanol,lye mix tank
> done,the processing tank with heat exchangers and
> mixer done.Currently I am building the wash tank and
> was wondering if bubble washing or top mist washing
> would be better for a tank that is 46 inches in dia.
> and aprox. 90 inches high.The tank will hold aprox.
> 480 gallons.Also was wondering if the tank needs an
> agitoror or if the wash tank should be set up with a
> pump to stir the fuel,water wash?? Also would like to
> know if the wash water should be pre-heated because
> well water is around 55 degrees,would this cause a
> problem with proper washing.Thanks for any help||
>
>
>
>
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