Hi Todd, Ardis
I agree with Todd, it's confirmed by what we've found and what we do
and what the people we work with have found.
>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.
I'm afraid that's right.
>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.
We use all methods that can be called "methods" and then some, and
that's the case.
>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.
Indeed. For my part, I didn't say anything about air-drying but I did
say something about bubble-washing and oxidation:
>Meeting the German or Austrian standard isn't difficult, but the
>Euro standard might be, especially if we think bubblewashing is a
>great idea. Might have to drop bubblewashing, go for simple stirring
>instead (and making the stuff properly in the first place). Might
>have to use an additive as well. And, might have to drop soy too.
>Something tells me the ASTM standard isn't about to adopt these Euro
>oxidation limits any time soon.
Bubble-washing certainly promotes oxidation. I've been sent some lab
test results on that, or rather a precis of them. Those folks are no
longer doing bubble-washing or air-drying. They use pumps and
stirrers to wash.
>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.
Faster, results as good or better. We still do bubble-washing, but
then we do just about everything else too, except mist-washing, I
really do think that's a blind alley, along with other well-known
blind alleys. If this were just a production facility rather than
also for demonstration, testing, investigation, we'd probably drop
bubble-washing, or mostly anyway. It does have its advantages,
especially if you're not in a hurry, and oxidation of an oil like
canola/rapeseed or better (ie lower Iodine Values) isn't a problem as
long as you use it quickly.
We do a lot of demos all over Japan, and we hold these very popular
monthly biodiesel seminars here, and when we demonstrate
bubble-washing (easy to transport and easy to scale down to
desktop-size if need be) it's a handily visual example of how washing
works, but it's also a good way of introducing the subject of
oxidation - after all, that's what the fish-tank aerator we use does
for the fish, as everyone knows. It's also a good added reinforcement
for what we lay the most stress on, other than that, yes, you too can
do this: do it right in the first place, make complete fuel. We don't
say bubble-washing's a no-no, we give the pros and cons of it. We do
emphasise the bottle-shake wash test.
I don't agree with what Mark said about the acid-base process
creating a sulfate salt in the wash that might be masking washing
problems.
>yes, it won't emulsify as much, but it should be
>investigated just what of the three factors (soap, mono and
>diglycerides, and salt inhibition of emulsification) are at play here.
>IT's probably different for each batch.
If for instance you cut the 2nd stage short with an acid-base
reaction and it doesn't go far enough to completion it emulsifies
just as readily with the bottle-shake wash-test as incomplete fuel
made by any other process, as we've found when we've investigated how
far we could push the Foolproof method in various directions. Same as
any other process, as we could see from similar tests with the other
processes, using various types of oil with both. I don't think the
salt factor is significant. Sulfate salts or not, most of the
catalyst ends up in the glycerine by-product anyway. When we separate
acid-base glycerine by-product into its components, the bottom layer
is the catalyst salts. There's only 0.1% of sulphuric v/v oil to
start with, and less catalyst to start with too, unless you're doing
virgin oil, which is highly unlikely to have completion problems
using the acid-base method. Not a lot of salt to mask mono- and
di-glycs with. It washes well because they ain't there.
I'm puzzled by what Mark said in her post:
>either mistwash or bubblewash works fine for big batches, but the same
>rules apply as for small batches- more water is needed for misting and
>less emulsification happens, much less water is needed for
>bubblewashing but more chance of emulsification can take place.
>
>I actually use both now- mist for a few gallons (for a small 42 gallon
>batch I mist for 4 gallons) and then I bubblewash with good use of
>water recycling during bubblewashing. In my 350 gallon wash tank, my
>small aquarium air pump gives fine results, but not all of the air
>pumps might be able to handle such large batches. it looks like a tiny
>amount of bubbles are rising but it works really well- less
>emulsification than the same air pump agitating up a smaller batch.
Emulsification with an aquarium air-pump?
Mark says this too: "The disadvantage [of bubblewashing]: if you have
made poor quality biodiesel, or are washing a very small batch,
bubblewashing can agitate the water and the biodiesel too vigorously,
causing emulsification of the two liquids. Emulsification is the
quintessential "wash problem" -- but it is also a form of quality
testing and feedback on your process. Once you know what causes it,
it is easily avoided."
Also: "The bad news is that poor quality biodiesel can emulsify just
from the agitation of bubblewashing. The good news is that it's easy
to make good biodiesel. Even with problematic biodiesel, you can
predict emulsification in a simple "wash test", take steps to avoid
it, and easily fix it if it does happen. The even better news is that
bubblewashing emulsification isn't a problem for average well-made
homebrew -- you should be able to use even nasty restaurant oil and
still easily make fuel that won't emulsify under bubblewash
conditions."
And: "Some people use a super-gentle "mist washing" method to take
vigorous agitation out of the picture. To me it seems that this masks
the real problem -- which isn't agitation, it's poor fuel quality.
I'd rather make sure I've produced fuel that contains less soap and
less emulsifying monoglycerides and diglycerides (MG and DG), instead
of decreasing the agitation to "ease washing". The agitation produced
by standard bubblewashing isn't very strong, an average homebrew fuel
should be able to handle it without emulsifying."
?
Puzzled.
Not too sure about the "... or are washing a very small batch" bit in
the first paragraph, it shouldn't mind bubbles. It shouldn't mind a
blender too much either, bit drastic though. But I'm a friend of
frogs! Hey Todd, why don't you horrify everyone by giving us that
"Frog in a Blender" url? LOL! Urk...
That's all from Mark's "Bubblewashing 101" article, by the way:
http://journeytoforever.org/biodiesel_bubblewash2.html
Best wishes
Keith
>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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