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Hybrid Setup: Packed Column above or below Plates?

Anyone have comments / opinions / thoughts as to benefits either way of setting up a packed column before the bubble plates or after?


  • I asked a similar question a few weeks ago, the general consensus is above, I was toying with the idea of having a packed section above a torpedo and below a baby CD with a few plates, I'm just going to run it in the conventional way, plates first and packed section above.

  • Thanks @Anavrin, I'll try to find that discussion to see what the comments were

  • edited May 2015

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  • GeeGee
    edited May 2015

    I have a 300mm section below the baby CD for height that @punkin suggested I pack, and a longer packed section above. Works really well :)


    450 x 800 - 62K
  • I have my packed section above the baby cd plates as well, then a baby dephlag, 180 bend plus large condesor. Yesterday's spirit run produced 1.5L/hr @ 95% abv from a 30% low wine so I'm happy with that ;)

  • edited May 2015

    @solarpowerscott said: Thanks Anavrin, I'll try to find that discussion to see what the comments were

    Here it is: Alternative Hybrid Configuration

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  • Ive been running mine today, bit of a disaster, I started with a 35lt 30% boiler charge, 6 plates in my baby CD and the 510mm packed section above, I was also running the setup in VM mode with a double wound 6mm cooling coil above a 1" takoff with a 1" valve, I decided to have a go using 6mm raschig rings as packing.

    First problem was my boiler leaking, so I had to shut down and re seal it (keg boilers not ready yet) then I noticed the output was really quite fast over 2lt/hr with only 1500w and the temp probe was 1.5°c higher than expected, turned out my packed section had flooded!!

    A quick full opening of the VM valve confirmed this as a gush of spirit come out when I opened it up.

    So I shut down again and replaced the ceramic Raschig rings with stainless scrubbies, all seemed well but it flooded again! In the end I was using 1200w with the valve half open (8:1 reflux ratio) and collecting well under 1lt/hr.

    Didn't want to go any faster for fear of flooding again, maybe VM is the wrong way to run this setup, maybe I've used too many plates in the baby CD, any ideas/suggestions????

  • Do you have a SD filter disc in there? Some people have reported these to cause flooding.

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  • edited May 2015

    Hi @punkin, no I had another filter disk with quite an open mesh, here it is next to the SD one


    800 x 529 - 81K
  • What dia is your packed section?
    Typical rates are:
    2" 0.75 l/hr @ 1.5kW
    3" 2.5 to 3.8 l/hr @ 2.5 to 3 kW
    the higher rates are for really highly tuned columns at just about maximum power.

  • Those rates look fairly close to me Myles.

  • This may be stating the obvious, but in any hybrid or compound column, the limiting power factor is the slowest component in the column.

    Run a 2" packed section over a 4" plated column and you are limited by the power the packed section can cope with. Of course you can offset this by varying packing density and packing type but to optimise the rig you need to balance the vapour speed and volume through both sections.

    Vapour speed in packed columns is quite well established but I haven't tried to build a matrix for what dia packed section is best for a given dia plated section.

  • The packed section I'm using is the standard SD 510mm 2" section, I'm going to take out a few scrubbies and loosen out the others so they're not so tightly packed.

    Before I ventured into the world of plates and caps, a 2" packed column was all I had to play with, it's what I served my apprenticeship with, so to speak 1-1.2lt/hr was what I found to be about the norm, other folk with similar setups get similar results, I've had this collection rate with this setup using the big baby deflag and CM control but but I wasn't overly impressed with how clean the produced neutral was, that's why this time I've tried the hybrid setup with VM control.

    I'm thinking the reflux return ratio must be a lot higher with with VM control, I've used both scrubbies and the raschig rings before with no problems.

    I'm thinking maybe the SD 2" section at 51mm diameter, being just a little narrower than the standard 54mm copper pipe I've used previously might have also contributed a little to the flooding along with the packing being too tight for the amount of reflux, I don't think I'll get to run it again for a while but I'll post when I've found rhe right setup.

  • I've always had good success when the lava is rattling in the column, higher abv and clean.

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