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Re: The Reflux Tower

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  • Kev
    Ian, ... 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
    Message 1 of 4 , Apr 5, 2001
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      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.
    • 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 2 of 4 , Apr 5, 2001
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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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