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Re: The Reflux Tower

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  • bn42ca@yahoo.ca
    This does help me think things through a little clearer. Thanks to you and Tom the Pastor for you advice. If anyone else would like to relate details of their
    Message 1 of 4 , Apr 5 8:59 PM
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      This does help me think things through a little clearer. Thanks to
      you and Tom the Pastor for you advice. If anyone else would like to
      relate details of their experiences an adventures in this area, I
      would welcome their e-mails directly.

      Ian

      -- In new_distillers@y..., "Kev" <hurne@y...> wrote:
      > Ian,
      >
      > > I have a couple of questions regarding construction of a reflux
      > > column. I've been reading the earlier posts in the group and
      there
      > > seems to be some confusing information.
      >
      > Everyone's still design is different, so the needs of the column
      are
      > different. The basic idea of having a reflux column is to increase
      > the number of times your alcohol is distilled. As you say, a reflux
      > still is equivalent to putting the stuff through a pot still a
      number
      > of times. The trick is to increase this number as much as you can
      to
      > get close to the magic 98.something %.
      >
      > > One opinion holds that the cooling water supply to the condenser
      > > should pass through the column, but another is that there should
      be
      > > no additional cooling within the column.
      >
      > Cooling water does two jobs in a still. Sometimes these jobs are
      > combined, sometimes they are separated. 1) it condenses the vapour
      in
      > the condenser head so that you can collect it in liquid form. 2) it
      > can be used at the top of the column to increase the reflux ratio –
      > i.e. returning more product back down the column for re-
      distillation.
      >
      > > Yet another says to cool at
      > >the top, while others cool about half way up.
      >
      > Do it at the top, definitely at the top! The only time it's
      > worthwhile doing it lower down is if your heat input is too strong
      > for the diameter of column you've got and you need to stop your
      > column getting flooded. Look at Tony's website for details of
      > column / heating combination recommendations.
      >
      > > There are also comments
      > > from others that talk of insulating the column, which is entirely
      > the
      > > opposite principle.
      >
      > Yeah, I thought that as well! The idea, as Tom the Pastor says, is
      to
      > make sure you're the one in control of the cooling, not the
      > environment.
      >
      > > One of the websites claims that in a reflux tower every six
      inches
      > is
      > > equivalent to one pass through a conventional pot still, so by
      > > extension, a three feet tower would equate to six passes through
      a
      > > pot still. If this is the case, then I can't see the purpose of
      > > further cooling within the tower. Would any or all like to
      comment
      > on
      > > this to help clear my thoughts?
      >
      > Tony's site (www.geocities.com/kiwi_distiller) also has details as
      to
      > how many pot-runs you get per length of column. It also depends on
      > the diameter, type of packing, heat, etc., etc., etc., but the
      basic
      > principle is the same – more is better. Having said that, you do
      > reach a point where more makes no difference. A 10 meter column
      isn't
      > going to be worth the hassle of finding somewhere big enough to run
      > the damn thing, for instance :-)
      >
      > > On an allied topic, the packing used in the reflux tower varies
      > from
      > > Raschig rings to stainless steel scourers to marbles etc. I had
      > > initially leaned towards using marbles because of their
      simplicity
      > > and ease of cleaning, but now I'm not so sure. The plans that
      I've
      > > looked at which use the scourers seem to indicate about twelve in
      > the
      > > column. So if the column is three feet, then that's four to the
      > foot,
      > > which even considering the surface area of the packing, still
      > appears
      > > to allow quite a bit of volumetric flow-through. If I used
      marbles,
      > > then the packing would be much denser, so what would the overall
      > > effect be?
      >
      > Again, as Tom said it's the surface area you're trying to increase
      > here. This gives the vapour something to condense on and flow back
      > down the column for re-distillation. There's more techie stuff to
      it
      > than this, but this is the basic idea. Scrubbers give you the best
      > surface area and therefore more pot-still equivalents for the same
      > length of column packed with anything else.
      >
      > As to how many to put in per foot, that depends on the size of your
      > scrubbers! I've seen 18 per metre mentioned, but the ones I got
      hold
      > of filled the column up after just 4. Pack as many in as you can,
      but
      > make sure you can still breathe through the packed column
      afterwards,
      > otherwise the vapour won't be able to pass through it any easier
      than
      > your breath and you'll have great refluxing, but zero stuff coming
      > out to collect! Watch out when you're packing them in there, too,
      as
      > I cut my hands to ribbons on mine.
      >
      > OK, that's refluxing in a nutshell, then we move on to
      fractionating!
      > This is basically the same thing, but very controlled. You have ALL
      > the distillate at the top of the column flowing back down the
      column
      > for re-distillation and eventually you get the various sub
      components
      > of the brew stacked like planes over Heathrow airport, with the one
      > with the lowest boiling point (methanol) at the top. Once the
      column
      > has settled out (several hours, possibly) you start to draw off
      small
      > amounts of the distillate to collect. Obviously, you dump the
      > methanol, and you can tell when this has finished coming off by the
      > thermometer at the top of your column. Check Tony's site again for
      > the exact temps, but from memory the good stuff is at 78.something
      > degrees C.
      >
      > I hope this helps.
      >
      > Kev.
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