Sciencemadness Discussion Board

Fractionation Insert for West Condenser

careysub - 4-10-2014 at 14:02

I was contemplating what the minimal set of condensers for a home lab might be, if one wanted to do fractional distillation, regular distillation, and reactions under reflux.

I think the number is two to allow for a reflux with product condensation set-up, but then the question is which two?

The West seems the most versatile (and is inexpensive), and lab guides describe using packing materials (glass beads, tubes, copper padding).

Looking at a 14/20 200 mm West condenser, I am dubious about stuffing random materials into the tube and getting them in and out satisfactorily.

This got me thinking about a single insert piece that could be inserted and retrieved easily. Perhaps with proper design a superior performance might be achievable.

What I am think of is an all-copper assembly put together with press fits, perhaps consisting of a copper rod inserted through perforated/formed copper sheet disks (20-40 of them?). The disks could be stamped out from a template.

Question is - what would be a good plate design?

Holes offset from plate to plate?

I notice that Vigreux columns have downward sloping eaves, so snipping into each disk would allow bending leaves/vanes up or down.

Hickman heads have a moat around an aperture, something like this could be stamped out (upraised cup edges?).

You could make a continuous structure out of coiled wire.

[Edited on 4-10-2014 by careysub]

forgottenpassword - 4-10-2014 at 14:34

Have you looked at the design of a Dufton column? It is essentially as you suggest -- a solid insert with a continuous coil wrapped around to force the vapour to the walls. Originally a piece of wire was used, but there are all glass ones sold too. It is a very effective column design.

careysub - 4-10-2014 at 15:36

Quote: Originally posted by forgottenpassword  
Have you looked at the design of a Dufton column? It is essentially as you suggest -- a solid insert with a continuous coil wrapped around to force the vapour to the walls. Originally a piece of wire was used, but there are all glass ones sold too. It is a very effective column design.


No, I had never heard of these.

It looks like the central cylinder plus coil almost completely fills the condenser tube (enough clearance for removal and insertion). Selecting the proper rod diameter and wire gauge would allow a close fit.

How much clearance is needed between the condenser tube and central rod (thus dictating the preferred gauges)?

Having the name "Dufton" and Googling, I also found this:
http://www.nsexports.com/fractionating-columns.php

At the bottom is a "Fractionating Columns Rod and Disc Pattern" showing what appears to be a rod with disks strung on it exactly as I described. I wonder if they are just plain disks, with a small gap for vapor passage?

forgottenpassword - 5-10-2014 at 00:00

I would say about 2mm. I have one that I could measure, but it is packed up in a box somewhere. You could probably find a reference giving diameter of wire to use in an old textbook. It was a widely used design.

The 'disc pattern' column is called an Oldershaw column, I believe -- although there the plates are permanently attached to the wall of the column.

careysub - 5-10-2014 at 06:53

Quote: Originally posted by forgottenpassword  
I would say about 2mm. I have one that I could measure, but it is packed up in a box somewhere. You could probably find a reference giving diameter of wire to use in an old textbook. It was a widely used design.

The 'disc pattern' column is called an Oldershaw column, I believe -- although there the plates are permanently attached to the wall of the column.



Thanks, knowing the names of things really helps in locating information about them.

Knowing "Oldershaw" I quickly located this report:
http://www.nt.ntnu.no/users/skoge/prost/proceedings/ecce6_se...

describing the construction of an Oldershaw variant.

It uses circular plates strung on a central column with little holes in them (same as my concept), but with "downcomers" a vertical surface attached to the plate. In this system the plates have an edge gasket to seal them on all but the "downcomer" side.

I would implement this by stamping/cuttting the plates out of thin copper sheet, with a downcomer extension on one side that is bent to create the downcomer surface. Perforate the central hole, punch little vapor holes, string on a copper rod and you are done.

The spiral design is also interesting. A 14/20 West condenser has a small bore, so a thinner gap might be in order. 14 or 16 gauge copper wire (1.6 and 1.3 mm) should do it. A good implementation would be to use glass tubing (available in all even mm diameters, I think), and secure the wire coil to the tube by inserting wire ends into the tube ends and melting closed.

[Edited on 5-10-2014 by careysub]

Magpie - 5-10-2014 at 12:37

You might be able to make a Podbielniak column by placing a helical wire against the inside wall. You may have a little trouble finding information on this design. It is described in Cason & Rapoport's book Laboratory Text in Organic Chemistry, 1950. This book also cites Podbielniak, Ind. Eng. Chem, Anal Ed, 3, 177, (1931) for column construction.

[Edited on 5-10-2014 by Magpie]

zenosx - 5-10-2014 at 16:46

It was broken long ago, but when I was much younger my mum got me a condenser/column that had a glass spiral wrapped around a glass rod that could be inserted into the condenser. There was very little play between the spirals and the sides, and it rested on the three prongs most liebig's have. If I still had it I would post a photo