Adding 4" on top of an 8" column

Hey guys,

I have an 8" 4 plate setup as well as a 4" 4 plate setup as well as 1.5m of 4" packed sections. Due to the shortage of GNS from the regular suppliers I've started doing sugar washes.

In order to maximise the output, i've been considering adding a 4" setup (plates / packed or plates & packed) with a 4" dephleg on top of the 8" dephleg that sits above the 4 8" plate sections.

I know it'll be a bit tricky to get the reflux balance right between the top 4" section and the lower 8", but the 2 reflux condensers would be controlled separately.

Wondering what your thoughts are on this idea?


  • I don't see a problem.

    I'm assuming your aim is neutral.

    But I'm drinking quadruple strength and oxycodone to try and manage chronic pain.

    My thinking, as the vapour rises in a reflux still you have two things occurring:

    1. Passive reflux, great for this application.
    2. Thanks to passive reflux, the volume if vapour is reduced.
    3. With a reduction in condensable vapour the vapour velocity decreases as it rises.
    4. Note that the velocity of non-condensables will not decrease. They will show themselves as high velocity air departing the parrot at the start of the run. The non-condensables will soon be replaced by ethanol slowing the volume of vapour to the condenser.
    5. I'd highly recommend you tee off before your condenser, add a reduction to a gate valve or a 4:1 reduction and effectively turn your still into a VM. The gate valve is expensive and is used to dial in your desired abv. Once you know the %open, you never need to touch it. That's why I suggested a 4:1 reduction, its cheaper. If 4:1 is too low an abv, go to 5:1 etc.

    Proviso... I'm flying off the cuff here and someone who cares to actually pay this some thought may actually come up with something better and completely contradict everything I've just said.




  • My sixpence worth ..... For packing you would need to run in the 4" side as packing requires greater velocity. This packing would be on top.

  • @mech interesting thought about the VM. need to think about that a bit.

    Cheers @richard yes I always run packed sections at the top

    Might simply have to try it & see what happens

  • Be advised your product output speed would most likely be reduced as going from 8" to 4" is a restruction

    Cant remember the speed difference, think there is a chart around somewhere but tipping you will be running faster the 4.5Lph

  • been there, tried that.. not worth it... Who is ready to see Franken Dragon get built?


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