Thomas,
If you'd read the stir washing section most thoroughly, you would have
come away with the notion that pump washing can contribute more to
emulsions than stir washing. As well, the section is predominantly
dedicated to stir washing and only briefly mentions, pump washing, and
even then in more of a foreboding type manner, especially if the wash
pump is the same unit as the mixing pump.
"Some people express concern with pump- or prop-washed fuel not clearing
as quickly as mist- or bubble-washed. There's sound reason for this.
Pumps and propellers have the ability of better mixing the fuel and
water ('atomizing' it), bringing both in more frequent contact with each
other."
Going on to say:
"Pump washing has the potential to more quickly and thoroughly 'atomize'
the two fluids and generate an emulsion in washes of biodiesel that are
borderline to or perhaps far less than a reaction completion than does
mechanical agitation."
You might also note the example at the JTF site that indicates the use
of a small pump to feed a sprinkler wash, not one so large that it
homogenizes the fuel and water.
As for the "water soluble" substance you're referring to? Again, chances
are more than good that what you're either emulsifying some of the
contents from extreme mixing or that you're trying to wash an incomplete
reaction (with extreme mixing). I couldn't precisely tell you how long
it takes to work all the mono- and di-glycerides out of the mix. I do
know that in our first few attempts years ago we made some rather
standard blunders, primarily a result of haste and impatience in order
to meet an end user's time window. One of them is still sitting in a
barrel after all these years, 15 gallons of emulsified remnant from a 55
gallon wash. All the "fuel" that split from the emulsion had to be
retreated, as it kept emulsifying to some degree upon subsequent washes.
What you might care to do is retreat a sample of the product after
drying it from one of the washes, then compare a wash of the retreated
sample to a wash of the product the sample came from.
And if you're set on pump washing for the time being, you might care to
install a secondary pump that is less voluminous/vigorous pump than what
you're presently using for reaction mixing. At the same time, you might
care to draw of a liter of fuel prior to your first pump wash and
conduct a "shake and bake" wash, or a swirl wash in a gallon jug or in a
pot, substituting a spoon for the canoe paddle as a stirrer.
Compare the results and see if some of them satisfy some of your questions.
Todd Swearingen
Thomas Kelly wrote:
Todd
Thank you for responding to my question re: pump washing.
Your answer has raised more questions.
I wanted to know if a milky wash after 7 washings indicated an
incomplete reaction. You replied:
"Possibly. It could also indicate that your churning pump impeller is
manufacturing butter."
This "butter" .... water soluble substance(s) produced by the
churning pump ..... not actually an original contaminant in the
biodiesel I'm washing???
I will stir wash the biodiesel ...... should get desired result, no?
You went on to say:
"Washes don't need the vigorous mixing that pumps generate. Compound a
churning pump with long wash periods and an incomplete or even vaguely
incomplete reaction and you have a problem looking for disaster."
I got the idea for pump washing at the journey to forever website,
and it was attributed to you.
From: Stir washing
http://journeytoforever.org/biodiesel_bubblewash.html#stir
Is it simply overkill to use pump washing on a 15L batch? Might it
work better on 150L batch? Use a diff. pump?
Pump washing appeals to me:
1. saves time
2. minimizes oxidation
3. closed system ... not messy
4. exposes faulty reaction
5. I have an extra pump and an extra water heater
Your time and thoughts are appreciated
Tom
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