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Insulating Columns

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  • ChrisMcFarland69@cs.com
    I don t understand why you would want to insulate the column of a still? Wouldn t it help create a purer spirit by using the cooler outer air to condence the
    Message 1 of 4 , Nov 17, 2003
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      I don't understand why you would want to insulate the column of a still?
      Wouldn't it help create a purer spirit by using the cooler outer air to condence
      the vapors on the way up the column? Thanx, Chris


      [Non-text portions of this message have been removed]
    • Mike Nixon
      Chris McFarland wrote: Subject: [new_distillers] Insulating Columns I don t understand why you would want to insulate the column of a still? Wouldn t it help
      Message 2 of 4 , Nov 17, 2003
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        Chris McFarland wrote:
        Subject: [new_distillers] Insulating Columns

        I don't understand why you would want to insulate the column of a still?
        Wouldn't it help create a purer spirit by using the cooler outer air to
        condence
        the vapors on the way up the column? Thanx, Chris
        ====================
        Separation occurs when you boil a liquid, but not when you condense a vapor
        ...but you need heat to do the boiling.
        Condensing vapor releases latent heat. That's where the heat needed for
        re-boiling liquid held on the packing comes from!
        Heat lost through the sides of the column is no longer available to do that
        boiling ... so you get less separation and less pure spirit.

        Things to ponder:
        Biggest myth held to be true in the distilling world:
        a hot vapor needs a cold surface on which to condense.
        Question:
        what cold surface do clouds condense on?
        Fact:
        a vapor will happily condense at the boiling point of the
        liquid it condenses into.

        Happy pondering Chris! :-)
        Mike N
      • nanosleep
        Not to be too picky, but I think clouds typically condense on dust particles. I believe this is why seeding clouds for rain is effective. If you provide
        Message 3 of 4 , Nov 17, 2003
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          Not to be too picky, but I think clouds typically condense on dust
          particles. I believe this is why 'seeding' clouds for rain is
          effective. If you provide the right type of particles you can get
          condensation (rain) where you wouldn't have otherwise.

          I agree with you that you don't *need* a surface for condensation to
          occur, but it sure helps.

          Of course I could be wrong.


          My version of why we need insulated column (which could also be
          wrong). If you have an uninsulated column then the column loses heat
          and some of the vapor will recondense and start flowing down. This is
          reflux, and it's a good thing. However, this reflux is getting
          created somewhere down in the column. It's only going to pass through
          the lower part of the column. This effectively makes the column
          "shorter" and reduces purity. If we insulate the column and produce
          all of the reflux at the top, then the reflux gets to use the full
          column and has more opportunity to mingle with the vapors (better
          purity). If insulated, the condenser does the extra cooling that the
          uninsulated column would have. The total cooling is the same and the
          amount of reflux is the same. We just want to generate the reflux at
          the optimal place in the column.

          If you are using a pot still then this loss of heat will improve
          purity. This unintentional reflux is the only reflux you have in a
          pot still. Take what you can get.


          --- In new_distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
          > Separation occurs when you boil a liquid, but not when you condense
          a vapor
          > ...but you need heat to do the boiling.
          > Condensing vapor releases latent heat. That's where the heat needed
          for
          > re-boiling liquid held on the packing comes from!
          > Heat lost through the sides of the column is no longer available to
          do that
          > boiling ... so you get less separation and less pure spirit.
          >
          > Things to ponder:
          > Biggest myth held to be true in the distilling world:
          > a hot vapor needs a cold surface on which to condense.
          > Question:
          > what cold surface do clouds condense on?
          > Fact:
          > a vapor will happily condense at the boiling point of
          the
          > liquid it condenses into.
          >
          > Happy pondering Chris! :-)
          > Mike N
        • Mike Nixon
          nanosleep wrote: Subject: [new_distillers] Re: Insulating Columns Not to be too picky, but I think clouds typically condense on dust particles. I believe this
          Message 4 of 4 , Nov 17, 2003
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            nanosleep wrote:
            Subject: [new_distillers] Re: Insulating Columns

            Not to be too picky, but I think clouds typically condense on dust
            particles. I believe this is why 'seeding' clouds for rain is
            effective. If you provide the right type of particles you can get
            condensation (rain) where you wouldn't have otherwise.

            I agree with you that you don't *need* a surface for condensation to
            occur, but it sure helps.

            Of course I could be wrong.
            -------------------------
            Nope, you're not wrong Nano me old Mate ... a nucleus often helps, and low
            cumulus can often form around dust particles. Cirrus etc higher up,
            however, is a different matter, as is vapor vented into space (that quickly
            condenses then flash-freezes from sublimation). I seem to recall that they
            could see a cloud from the ruptured oxygen tanks in Challenger.
            -------------------------
            My version of why we need insulated column (which could also be
            wrong). If you have an uninsulated column then the column loses heat
            and some of the vapor will recondense and start flowing down. This is
            reflux, and it's a good thing. However, this reflux is getting
            created somewhere down in the column. It's only going to pass through
            the lower part of the column. This effectively makes the column
            "shorter" and reduces purity. If we insulate the column and produce
            all of the reflux at the top, then the reflux gets to use the full
            column and has more opportunity to mingle with the vapors (better
            purity). If insulated, the condenser does the extra cooling that the
            uninsulated column would have. The total cooling is the same and the
            amount of reflux is the same. We just want to generate the reflux at
            the optimal place in the column.
            -----------------------
            Vapor is condensing all the way up a column, and not just on the walls.
            That's what the packing is for ... to hold that liquid where it condensed
            and not permit it to run further down until the volatiles have been
            re-boiled out of it.
            You are quite right about the column being effectively shortened if the
            liquid runs down the sides ... same thing as saying that the effective HETP
            has grown much bigger, so fewer theoretical plates can fit inside the
            column.
            Your comment about "... insulate the column and produce all of the reflux at
            the top" highlights a common misconception though. Vapor is condensing and
            re-evaporating all the way up the column, and that condensed liquid is just
            as much "reflux" as the liquid condensed by the top condenser. The function
            of the top condenser is to put a definite cap on how far up the vapor can go
            ... in a simple reflux column without a top condenser then the overflowing
            vapor is taken as product and condensed in a side condenser. The reflux
            ratio inside the packing is just short of 100% all the way up, and depends
            on the speed of the vapor and the efficiency of the packing. If we left a
            gap in the packing then the reflux ratio in that gap would be zero as no
            vapor is being condensed in that gap to return as reflux! The only reflux
            ratio we usually refer to is that which we impose by putting on a top
            condenser.
            -----------------------
            If you are using a pot still then this loss of heat will improve
            purity. This unintentional reflux is the only reflux you have in a
            pot still. Take what you can get.
            ----------------------
            True. That is how the big whiskey stills work. The sharply sloping walls
            of the Lyne arm act as the 'packing', and reduce the speed of the condensed
            liquid so that it is exposed for enough time to heat released from vapor
            condensing further down in order to re-boil. However, the loss of heat
            through the walls reduces the efficiency of this heat exchange, but this
            doesn't matter much in those stills as the aim is to get some separation,
            but not so much that you lose the aromatic parts of the vapor. It simply
            saves time as you get a few re-distillations in one pass instead of the much
            older way of boiling in an alembic without a Lyne arm and collecting
            immediately, then re-boiling what you collect again, and again, and again...
            . ("alembic": two retorts connected by a short arm ... one for boiling, the
            other for condensing)

            All the best,
            Mike N
            ==========================


            --- In new_distillers@yahoogroups.com, "Mike Nixon" <mike@s...> wrote:
            > Separation occurs when you boil a liquid, but not when you condense
            a vapor
            > ...but you need heat to do the boiling.
            > Condensing vapor releases latent heat. That's where the heat needed
            for
            > re-boiling liquid held on the packing comes from!
            > Heat lost through the sides of the column is no longer available to
            do that
            > boiling ... so you get less separation and less pure spirit.
            >
            > Things to ponder:
            > Biggest myth held to be true in the distilling world:
            > a hot vapor needs a cold surface on which to condense.
            > Question:
            > what cold surface do clouds condense on?
            > Fact:
            > a vapor will happily condense at the boiling point of
            the
            > liquid it condenses into.
            >
            > Happy pondering Chris! :-)
            > Mike N


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