Other than
water in the WVO and Methanol there are at least two other sources:
- Atmospheric
water vapor tries to establish equilibrium with everything (including all
feedstock and reagents used in the BD process).
- The catalyst
widely used in homebrew, dissolved lye in methyl alcohol, has an
equilibrium reaction to/from Sodium Methylate and water.
NaOH +
CH3OH <=> NaOCH3 + H2O
Sodium
Methylate is the catalyst used in an acid/base industrial process for which my employer
is constructing the plant.
The
customer’s engineer is specifically using this, rather than lye in alcohol, due
to that water molecule seen above and the general lower yield associated.
http://www.dupont.com/sodium/naome.html
describes it.
http://www.inorganics.basf.com/p02/CAPortal/en_GB/portal/Biodiesel_layout_b/content/Produktgruppen/Biodiesel/Biodiesel/Katalysatoren
(this is BASF) has more info on industrial biodiesel catalysts.
Michael
-----Original
Message-----
From: Jonathan Schearer
I am probably
missing something, but where would the water be coming from in the first
place? Isn't the waste oil you start with not supposed to contain any
water, and if it does, you need to boil it off? Then there's the
methanol. It should not contain any water either. I don't believe
the catalyst would contain any water either. It is the waste glycerin
layer that contains most of the methanol, correct? I have been told that
the only stupid question is the one that isn't asked. So I'm
asking...where is the water coming from?
Michael Gian
<[EMAIL PROTECTED]> wrote:
In additon, a fractionating column requires a reflux, the partial return and
recycling of distillate product from the condenser back down the
fractionating
column which increases the energy tax (energy costs) of purifying the
methanol.
This is true for tray towers. A more elegant setup is a packed
fractionating column, aka reflux column. Years ago we made one packed with
small glass beads for jewelry, picked up cheap at a garage sale. Ethanol
production, in this case not intended to fuel machinery. What works for
ethanol will work for methanol, probably better, given no water azeotrope.
Alcohol Fuel Manual Ch11 has the poop.
Michael Gian
Mike McGinness
bob allen wrote:
> without getting into excessive detail, the boiling point of a mixture is
> the weighted average of the stuff present. At first you have pure
> methanol coming off. as the temperature rose, increasing amounts of
> water contaminated the alcohol.
>
> You need a fractionating column to obtain pure methanol.
>
> Joe Street wrote:
> > 3A sieves will work but are normally used for getting tiny amounts of
> > water out of solvents to bring them into the low ppm range. They will
> > work of course but you might saturate them and have to do a second
> > stage. There is a significant energy input into regenerating the
seives
> > as well. You have to bake them at well over 100 degrees C more like
> > 200, but you can get by with lower temps if you bake them out with
> > vacuum. Try putting a thermometer in your condenser and monitor
vapour
> > temperature to get a better endpoint and you will have an easier
time.
> > You have answered some of my own questions. I have recovered some
> > methanol but not tried to use it yet. Sounds like if straight
> > distillation is carefully done the methanol is dry enough to use
without
> > further drying. Great news and thanks for the post! :)
> >
> > I have some excellent references on solvent drying I can mail you if
you
> > want. No soft copy sorry but I might be able to scan them.
> >
> > Joe
> >
> > Thomas Kelly wrote:
> >> Good day to all,
> >> After splitting the glycerine coproduct from roughly 1200L of
> >> processed WVO, I distilled approximately 100L of the
> >> glycerine/methanol component.
> >> The first drops of methanol began to fall from the condenser at
> >> 145F. As the temp rose to 150F there was a steady flow of clear
liquid
> >> from the condenser. Throughout the day I turned the heat off when
the
> >> flow was steady and back on when it slowed.
> >> I filled a 4.5 gal (17.7L) cubie with clear liquid and started a
> >> second one. At this point the temp was over 160F. I let the still
run
> >> up to 200F. At this point the second cubie had 4 gallons of clear
> >> liquid (and it was now 1AM) giving a total of 8.5 gal. I was
thrilled
> >> with the result (and tired). I used the first 4.5 gal (17.7L) to
run
> >> one batch, and while that was settling ran a second batch using
the
> >> second 4 gal of recovered methanol.
> >> The first batch washed OK, but was a little slow to separate. It
> >> failed the methanol quality test.
> >> The second batch did not even pass the wash test.
> >> I have been making consistenly high quality BD for several months
...
> >> thank you JtF and list members. I don't think I made mistakes in
> >> measurement or titration.
> >> My question:
> >> As my distillation temps rose towards 200F (93C) could I have
been
> >> including water in my distillate? (The methanol recovered at lower
> >> temps performed better than the methanol recovered at higher
temps.)
> >> If so, can I use Zeolite "molecular sieves" in the
future to remove it?
> >>
> >> Thanks,
> >> Tom
