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Re: Column Packing(The great debate)

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  • peter_vcb
    Mike said It tends to clump together quite tightly, like sand, and there would be no room for vapor to pass through. what do you make of this link Mike.
    Message 1 of 9 , Nov 1, 2002
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      Mike said "It tends to clump together quite tightly, like sand, and
      there would be no room for vapor to pass through." what do you make
      of this link Mike.

      http://www.engr.pitt.edu/chemical/undergrad/lab_manuals/packed_bed_rev
      _jan02.pdf

      you will probably have to cut and paste that link or go to google and
      search for "glass sand" distillation (it will be the first hit)

      it is a college site talking about using fine glass sand as a packing
      medium in a glass column, small scale. if the power was low enough
      would it be able to make its way through carbon without much trouble?
      if so a good mix would be sand at the bottom and then carbon at the
      top of the column. also if my power is low enough can i tightly pack
      in my scrubbers increasing the HETP?











      --- In Distillers@y..., "Chris de Weyer" <chrissa_am@h...> wrote:
      >
    • bokakob
      You are forgetting about one more indicator called void or free volume or something like this. I think these two materials are on the opposite ends of the
      Message 2 of 9 , Nov 1, 2002
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        You are forgetting about one more indicator called "void" or "free
        volume" or something like this. I think these two materials are on
        the opposite ends of the scale in respect to this parameter.
        Cheers, Alex...
      • Mike Nixon
        peter_vcb wrote: Subject: [Distillers] Re: Column Packing(The great debate) Mike said It tends to clump together quite tightly, like sand, and there would be
        Message 3 of 9 , Nov 1, 2002
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          peter_vcb wrote:
          Subject: [Distillers] Re: Column Packing(The great debate)

          Mike said "It tends to clump together quite tightly, like sand, and there would be no room for vapor to pass through." what do you make of this link Mike.

          http://www.engr.pitt.edu/chemical/undergrad/lab_manuals/packed_bed_rev_jan02.pdf

          you will probably have to cut and paste that link or go to google and search for "glass sand" distillation (it will be the first hit)

          it is a college site talking about using fine glass sand as a packing medium in a glass column, small scale. if the power was low enough would it be able to make its way through carbon without much trouble? if so a good mix would be sand at the bottom and then carbon at the top of the column. also if my power is low enough can i tightly pack in my scrubbers increasing the HETP?
          ==============================

          Hi Peter,

          That's a very good file, and well worth reading. 
          Two sentences in it are worth highlighting:
          "Ideally, the porosity of the packing should not hinder the gas flow through the column.  In this lab, the packing in the column is glass sand."

          Note that it does not say that the sand is "fine glass sand", just "glass sand".
          I think this comes down to a question of terminology ... specifically "sand" and "porosity".  Having stressed that the packing should not hinder the gas flow, it seems clear that the granules of the "glass sand" they are using must be large enough to permit this, and that would make them fairly large.  I therefore believe that what they are talking about is glass beads ... a common lab packing for small stills.  These are small enough to flow easily into a column and fill it, but big enough to prevent liquid from filling the gaps between them.  The gaps between the beads are the measure of "porosity", not the glass material itself, which is solid.  These small beads look for all the world like the packing you put into a bean bag, but made of glass and not polystyrene.

          Worth noting too that the size of the apparatus they are using would look tiny to us.  We practice what might be termed "small scale distillation".  These guys will be using "micro distillation" gear, with columns only about 20cm long.  These will be run slowly, at very low power, and all they are interested in is getting enough for a sample ... a few milliliters.

          Getting back to this question of putting carbon in a column, you could try it, but I'm prepared to put money on you finding that it does no good at all.  Carbon depends on being immersed in the liquid it is cleaning, to permit free flow of molecules in and out of its structure.  Putting carbon in a column so that it holds only droplets of liquid, and is surrounded by vapor, would not enable it to work properly.  It's a neat idea, to distil and clean at the same time, but I think you would find that it doesn't work in practice.

          All the best,
          Mike N

           

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