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Re: placement of packing

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  • Harry
    ... Hi Rob, Riku put that in the other group, but NM. Couple of things you need to get a handle on. Refluxing is not the packing. Refluxing is the act of
    Message 1 of 2 , Jun 27, 2005
      --- In new_distillers@yahoogroups.com, Robert Thomas
      <whosbrewing@y...> wrote:
      > Hi all,
      > this is actually an almost reply to an answer from
      > Riku, but anyway,
      > If a column full bottom to top with packing is the
      > yard-stick, then leaving a gap at the bottom shortens
      > the refluxing business end (ie fewer "plates"). Why
      > doesn't not filling to the top not have the same
      > effect? You've still got the same "number of plates".
      > Or perhaps it does. In which case, how best to pack a
      > column, specifically, how near the side tube in an
      > offset head arrangement?
      > Yours confused, but with glass in hand,
      > Rob.



      Hi Rob,
      Riku put that in the other group, but NM. Couple of things you need
      to get a handle on. Refluxing is not the packing. Refluxing is the
      act of adding product back to the TOP of the column to provide
      downward-flowing liquid to help separate the rising vapours. This
      is necessary because if there's no downward flow, there's reduced
      efficiency.

      You are correct in that shortening the packing does reduce
      the 'plates'. Not filling to the top does have the same overall
      effect. However, leaving the top packing and removing the bottom
      section allows more boiler headroom (empty column) and ensures that
      reflux-induced separation is still happening at or near the product
      removal point.

      The amount of packing, and its placement in relation to your side
      vapour tube, will depend on where you place the head thermometer,
      and what it reads. Ideally, the thermometer probe should be placed
      at the point where the vapours enter the side tube. This will let
      you determine the strength/purity of the product as it effectively
      leaves the rectifying column as product draw. Obviously the packing
      needs to be below this point of false readings will result. If the
      reading is too high, the purity is down. You need more packing, or
      more reflux, or less power input.

      HTH
      Slainte!
      regards Harry
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