Mixing biodiesel; methanol recovery

Q. First let me briefly explain the operation we have so far: we have
converted a 50-gal steel drum to serve as the processor.  We shaped the
bottom, drilled a 2″ hole and connected 1-1/2″ PVC to a valve to drain the
glycerine/biodiesel.  We drilled a hole in the side of the tank, very near
the bottom, and installed a water-heater element that can be connected to
a 120v outlet (we are not on solar power yet).  We have a lid for the
container and currently have a motor mounted on it for mixing the
WVO/methoxide.

My boyfriend and I are having a dispute over the mixing of the biodiesel
and the methanol recovery, which is why we are asking for your expertise.

And now for the questions:

1. Would you suggest a motorized mixer (similar to that used for mixing
paint) to stir the WVO/ methoxide, or would you suggest installing a pump
(off the PVC drain pipe before the valve) to pump the solution from the
bottom of the tank back to the top of the tank – similar to the
“appleseed” processor mixing method.  I’m concerned that the pumping
method won’t agitate the solution as much as stirring it.

2. Once the mixture has settled and you have the glycerine layer and
“dirty” biodiesel layer within the processor, do you know if it’s possible
to heat the whole mixture to recover the methanol prior to draining the
glycerine?  Or do you have to drain the glycerine and recover the methanol
separately from each product?

I’m not sure if you’re chemists as well as environmentalists, but any
advice you can offer would greatly help our home operation.  If you know
of anyone who may be able to answer these questions and have the time to
pass that info on to me I would so appreciate it.

Thanks for your help, but mostly thanks for all your efforts to get
information out to the people.  This country needs some hope and
inspiration for a cleaner future.   Heather

A. About your questions:
1.  We have used the pumping method to brew about 500 gallons with the ~$25
pump before it stopped pumping.  We usually mix for 2 hours and the
biodiesel turns out great (although it has never been tested).  It doesn’t
necessarily mean it is the best way, but the majority of the systems we’ve
seen use the pumping method – it just may be that it is easier to make air
tight/”fumeless” with a pump involved.   We also know of others who use a
drill and paint mixer to make biodiesel in a 5 gal. bucket (with a mask of
course!) with no problems.   So, it may be just a matter of personal
preference or convenience rather than which way is better.

2. Methanol recovery is something we haven’t done yet, so we can’t talk from
experience.  Here are a couple of links that may help:
http://biodiesel.infopop.cc/eve/forums/a/frm/f/4441089311
http://forums.biodieselnow.com/topic.asp?TOPIC_ID=5671

Also, below is an excerpt from
http://journeytoforever.org/biodiesel_aleksnew.html

Methanol recovery (optional)
To keep costs down, even amateur biodiesel producers try to salvage the
unreacted methanol. There are two major methods to do this: heat extraction
and vacuum/heat extraction.
Heat extraction
Heat the second-stage product to 70 deg C (158 deg F) in a sealed
boiler/vessel and lead the fumes into a condenser. Intercept the condensed
methanol in a liquid trap. Take great care because methanol is highly
flammable and the fumes are explosive. The temperature will need to be
increased as the amount of unreacted methanol in the mixture decreases.
Vacuum/heat extraction
This is basically the same as heat extraction, but it requires less energy.
The drawback of this method is that you need a special vessel and equipment
to do this. A good example is Dale Scroggins’s reactor:
http://home.swbell.net/scrof/Biod_Proc.html
When building your reactor it may be a good idea to take one step at a time.
Build the reactor, get confident with the process and eventually upgrade to
methanol recovery.
At least a quarter of the methanol used can be recovered — ie, 50+ ml per
litre of oil/fat. Mix it with fresh methanol for preparing the next batch of
methoxide.

There are many examples of biodiesel equipment at
http://www.biodieselpictures.com/
Also, there is a lot more info at www.biodieselcommunity.org

No Comments

  1. Maria says:

    What do you do with the glycerol?

    • Anais says:

      @Maria: Compost it!

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