Thanks for the responses. lots of good information, more questions follow.
I understand that I sound like a little kid going "why" to everything
you say but I really want to understand what I am doing here so that I
can be a shining example of the products of the homebrew community and
all it has to offer and not be an example of what can go wrong with
homebrewing (this seems to be important for furthering the cause in
general which is important to me).
Appal Energy wrote:
John,
You prepared a 4 liter batch from which you pulled both wash samples. Yes?
correct
Your only variable was temperature of the wash water. Yes?
correct
You point out that the warmer sample separated well and the colder one
not. Yes?
that does seem to be the case. further it could be pointed out that
(from the previous thread on this one) that 150mL samples do in fact
separate much beter than 4mL ones as you suggested.
So why did you "dispose" of the cooler sample prior to letting your
experiment go one step further by allowing it to warm to the same degree
as your warm sample was and then observe? In theory the end result would
be the same, with the emulsion breaking and a quick settling time after
re-agitating.
it will never reach the 70 degrees that the other was at when it
seperated because ambient temprature was 55 degrees.
I let it go until it was clear that it had "failed" the quality test
(per the instructions it should settle within 30 minutes, I gave it 40)
if you would like I can leave a sample sit for a while and see if it
ever seperates but I do not believe that it will in my environment
(that's how I got here I had some failures sitting on the window sill
waiting to separate for weeks at a time and the never really got there).
I could also try setting it in a bath of 70 degree water for a while and
see what happens. in that case it will probably settle out as normal
(unless emulsion has some sort of inertia once formed that causes it to
require more energy to break than it needed to be avoided in the first
place).
If your sampling was conducted to determine the effects of different
wash temperatures, then you're asking the wrong questions.
my testing was for temprature as a variable, these are other questions
that I have yet to answer in my overall quest for homebrew quality
testing procedures that will ensure that I have good enough fuel for my
2000 TDI. replacing injectors and injector pumps is expensive :)
But to answer them:
Testing for triglycerides would be rather unneccessary. If they are
present there would also be mono- and di-glycerides and you'd know
something was quite amiss when you achieved heavy emulsion in a wash.
somone on the yahoo groups list (can't find the message right now, I
will post a link when I do) posted results of lab tests that showed low
mono or di glycerides but a high level of triglycerides. I admittadly
don't understand the chemistry well enough to know why that would happen
(or even if it could). perhaps really bad stirring such that part of the
fluid volume never became involved in the reaction (is that possible?).
As well, triglycerides don't appreciably emulsify as do mono- and
di-glycerides.
which is specifically why I am intarested in a test for them.
suggestions that I am barking up the wrong tree are welcome :)
Best method to reduce any concerns of soap formation is an acid
esterification, followed by transesterification. The esterification
converts to biodiesel what normally would become soap, in turn putting
an end to concerns about "excess soap." Once soap is almost completely
eliminated from the equation through esterification and sufficient
settling, unconverted glycerides by and large become the only
emulsification variable.
I am less concerned with altering the process to achieve less soap (it
seems to produce little enough as it is, provided that you use the right
amount of lye) than I am with finding a method to tell the difference
between an underreacted batch and a soapy batch, something like "soap
emulsifies BD into the water and you get a larger amount of water after
settling wheras underreacted emulsifies into the BD so you get a larger
top layer" this is probably not true but it is the kind of informaiton
that I am looking for. probably (per your answer to the other quality
test question that came up yesterday) the answer is reprocess a sample
of the batch that failed and look for glyc to drop out, if it dosen't
you have soap problems, if it does you have underreacted your batch.
this may also be my test for triglycerides.
this is to assist someone standing there with a failed batch scratching
their head (I was just recently that guy) asking why it would have failed.
Yes. "4m fuel" is better than "10m fuel" if everything else is perfectly
equal. But you can't say the same thing when you throw in variables.
I understand, but perhaps having a sense of "really great fuel will
separate within 4 minutes at 70 degrees wheras less good but passable
fuels will separate in 10 or more minutes with the outside limit of
pasability being 30 minutes" would be helpful.
again, thanks for your response!
John Guttridge
Todd Swearingen
----- Original Message ----- From: "John Guttridge" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, December 29, 2004 1:37 AM
Subject: [Biofuel] more on the quality test
I have completed my testing with 150mL from my 4L batch.
before testing my fuel was settled for 7 days until it was crystal
clear and light yellow in color. after 24-48 hours it seemed to settle
completely but it was still hazy, this went away entirely after the
full 7 days. there was no appreciable increase in the volume of the
glyc layer after the initial settling period.
ambient temp is 55 degrees. all samples were prepared with normal city
water from my tap (I don't think it is hard but there is certainly
stuff in it from treatment, like chlorine for example).
glassware used in measuring the samples is accurate to .24mL at 150mL
(per labeling etched in the glassware). all measurements are read from
the bottom of the meniscus.
samples were added to a small ball jar (about 450mL volume) and then
shaken for 10 seconds fairly violently.
at 70 degrees F 150mL sample separated in 4m 10s, it was a celan
seperation with absolutly no emulsion. there was some haze in the
biodiesel like it looks when I start to wash, it goes sort of milky
yellow with lots of tiny little bubbles, this will become crystal
clear and even lighter yellow than it began if allowed to settle for a
while (usually a day or two).
at 40 degrees F 150mL sample separated in 12m 4s, there was gunk in
emulsion in the FAME on top that never settled out, after about seven
minutes it had separated into 60/40 (the 60 being BD) with lots of
emulsion in the biodiesel layer, this emulsion never really broke but
it reached about 55/45 by the 12m 4s point at which point it was as
complete as it got within the 40m before I disposed of it. I don't
think that I would say this "passed" because of the junk in the top
layer and also because it never really came back to 50/50.
some questions remain:
this test clearly tests for three things: soap, monoglycerides, and
diglycerides. how can we test for triglycerides (really incomplete
reaction)?
if we look at the results and say "this didn't pass" we should have
some path for figuring out why. what methods can be used to tell the
difference between excess soap and unreacted mono and di glycerides?
do we learn anything from the separation time itself on a "passing"
batch? is 4m fuel better than 10m fuel?
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