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Packed Column Length

The standard StillDragon 4" packed column is 510mm. If I were to increase this length to say 1000mm or 1300mm (because I have a piece 1300mm long ) will I gain any benefit or drawback from a long length?



  • Height is for purity mate, a packed column at 20x your column diameter will deliver a lovely neutral at azeo. Are you planning on running plates and a packed section or just a packed section?

  • Thanks mech. I'm new to this so I'm going to start on neutrals and go from there. So at 1300 my column/diameter ratio is 13. I was planning to run both plates and the packed section eventually. So at 1300mm I should get a decent product?

  • edited April 2015

    Here's a calculation from HD website

  • SPP in a 3" column is approx 1 plate per inch of column height... using big swede's SPP not sure about 4" if your just going for neutral ... Scoria packing is good and is really cost effective... SS Scrubbies are on the chart that was referenced

  • edited April 2015

    102mm diameter 1300mm long

    Height Equivalent of Packing (HETP): 0.098 m
    Number of Theoretical Plates : 14.3 = (height/HETP) + 1 for pot
    Approx Vapour Purity : 95.1 %

    Seems like this should work ok.

    So if I put a bubble plate in the mix, does it go above the SPP or below it? What will it do in either position?

  • If I were to put a plate in with a packed section the packed section would always be at the top. At 14 HETP I wouldn't bother myself, if you have it available and you have the space available...I'd pack scrubbers on top of that plate. Just leave out the caps and downcomers etc, using the place as support for your packing.

    That tee for the bubble cap section has gotta be around 150mm?, that's an extra 150mm of packing you could use.

  • Thanks again @TheMechWarrior. I have a 2 metre length as well but I don't have a ladder to get that high and attach all the crap on top. That would make the whole still over 3 metres in height. Need lots of scrubbers to fill 2 metres. Hell......need lots to fill 1.3 metres. Where is a good place in Australia to get a pallet of these things?

  • edited April 2015

    FWIW I ran a 2" VM column with 48" of SS pot scrubbers for several years with good results. At the suggestion of Minime I added a torpedo to the stack. Torpedo mounts to the boiler. The packed section mounts to the torpedo. Bubble cap plate in the torpedo.

    Marked improvements in stability (can run higher heat input without flooding), takeoff rates, and smoother (less heat) in the finished product. I think running the vapor through the liquid on the torpedo plate helps remove the perception of heat in the finished product.

    Plus it's really cool to have a window down there. I went with the torpedo that has the thermoport in the window, so I can watch the temp up top at the takeoff T and at the bottom of the stack now too. Very cool to see how that works. Bottom temp climbs slowly through the run. Top temp rock steady until tails arrive.

    I'm more like I am now than I was before.

  • Great idea Kapea, if you have the room why not try it each way and see for yourself. I never had a plate to play with and I did find the very high columns are a pain in the arse requiring a step ladder. That's why we are seeing more talk of split columns.

  • It appears most configuration setups have plates first then packed sections above. l run 5 traditional bubble plates and a 500mm copper section packed with stainless srubbers on top. Azero every time l run. Just watch sudden changes to your relfux rates during a run, the packed section holds a lot of vapor sudden increase in reflux will dump liquid on the top plate and flood within seconds. But side effect is still Azero coming out, but not pretty to watch as each plates going down also floods. Simply back off power and restabilize then power up again.

    l have a second packed section but never bothered to add it, l have the height but what l use is more than sufficient.


  • edited April 2015

    So is the consensus here a single bubble plate on the bottom of the 1300 mm packed section? I can't do what Kapea has suggested with the torpedo as everything is 4". 5 bubble tees and a 510mm packed section is almost the same height as the 1300mm packed section and a single bubble tee. 150mm difference. The plate total is not that much smaller for the 5 plate/510mm SPP and there only is 0.3% difference in the purity.

    510mm + 5 plates

    Height Equivalent of Packing (HETP): 0.098 m

    Number of Theoretical Plates : 6.2 = (height/HETP) + 1 for pot + 5 plates = 12.2

    Approx Vapour Purity : 94.9% adjusted from 6.2 plates

    1300mm + 1 plate

    Height Equivalent of Packing (HETP): 0.098 m

    Number of Theoretical Plates : 14.3 = (height/HETP) + 1 for pot + 1 plate = 16.3

    Approx Vapour Purity : 95.2 %

  • edited April 2015

    I use the torpedo because it mates to my 2" boiler connection (an unmodified sanke keg) and my 2" VM column. I imagine a 4" bubble T would work even better than a torpedo under the packed section if you have a 4" boiler connection.

    Height is no problem for me. My shed has 15' ceilings and a stairs landing 4' high next to my where I set up my still. Easy access up to 11' for me.

    You can spend a lot of effort and money chasing those final few tenths of a percent of purity. That calculator is ballpark numbers. Things don't always match up closely with it out here in Realville.

    I'm more like I am now than I was before.

  • Cheers Mick, those numbers seem fairly close to my experience.

  • I use a 2-4-2 torpedo with standard bubble caps under a baby crystal dragon with 3 procaps and a 510mm section packed with SS Scrubies, haven't hit Azeotrope yet, I do get a very clean neutral at 92% that I'm very happy with using CM control, next time I run I'm going to use my VM output, to see if I can get better numbers. One major benefit of having the torpedo at the bottom is the sight glass fogs when tails start coming through, also using VM you will notice a big drop in product collection rate at the same time as the tails fog the glass, perfect time to shut down if your going for neutral.

  • @mickiboi, it looks like you have the bits available to trial a couple of configurations. If you do that you will have hard data to base your future activities on.

    I think your decision(s) will need to be partly based on what you are feeding the column with. I say that as I have found that a 510mm packed section on top of 4 plates makes great vodka / neutral when fed with TPW. However I do 2 passes when using feints.

    In my packed section I use large SS scrubbies from Bunnings, their 3 packs were pretty cheap. From memory I only needed 2-3 packs for a 510mm section. Otherwise use scoria from the garden centre.

  • @rossco said: Cheers Mick, those numbers seem fairly close to my experience.

    Thanks mate. I'm going to run it with and without the bottom plate and see how I go.

  • edited April 2015

    Thank you @crozdog. I have lots of bits and what I don't have I have enough bits and other pieces to make, have tig will weld. I'm using tpw for my first runs to learn what's going on. You only needed 2-3 packs? Was it these?

    I do want to use copper or ss scrubbies but someone else told me to get some clay balls from a garden shop and try them instead of scoria. Has anyone tried them?. See picture.

    @Anavrin if I can get 92 after a couple of runs I will be a happy camper. I'm not expecting miracles first up though. But I have been reading everything I can on here, everyone here is so good with information it's great.

    2048 x 1536 - 963K
  • I used those Bunnings scrubbers successfully for years. I placed half a dozen Chore Boy copper scrubbers on top as a catalyst.

  • @TheMechWarrior how many do I need to fill my 1300mm column? How tight do I pack them?

  • I reckon you'll want 4-5 packs plus some copper on top.

    Tightness: A common question with respect to column packing, here's my guide.

    1. Just keep dropping them in, they'll pack quite loosely initially.
    2. When full, place a garden hose at the top and flood the column.
    3. Allow to drain, this will compact the packing. Some initial tapping may be required.
    4. Add more packing and repeat.
    5. You'll get to the point when adding the water no longer really compacts the column any further, you are done.

    A common guide is, you should be able to blow your own air though the packed column. If you've done as I've described above you'll be fine. Don't forget to add some copper to the top of your column. Chore Boy 100% copper scrubbers can be purchased on eBay, alternatively make your own copper catalyst. Lots of 1/4" tube cuttings will do.



  • Thanks mate. I will do as you say.

  • edited April 2015

    1300mm welded and packed (it took 7 packs haven't got the copper ones yet) on top of milk can. It's very tall.


    600 x 800 - 43K
  • 7 packs sounds about right, I knew it would be between 4 and 10 packs based on what I used in mine before. I didn't want to tell you 10 for you only to need 5.

    Are you just going to run a CM style dephleg on top? Or are you going with a VM offtake?

  • Ummmmm I don't know. Going to use the SD dephleg to start off. Is there a thread here about VM takeoff? Do I have to build more shiny bits?

  • Stick with the CM, you already have what you need for that.

  • You're right but I love building things. If more than 72 hours goes by and I haven't drilled, welded, cut, connected or soldered something I start to become unhappy and shitty.

  • Yeah but for a VM you are going to want a 1" gate you have one?

    Also a traditional dephleg lacks the knock-down power for a Hard Core VM. The VM requires the condenser at the top of the column to be open to atmosphere due to the presence of the gate valve to avoid a pressure issue.

    The VM produces a fantastic neutral for sure and the control is like a dream but is nota car of moving existing parts around unless you happen to have purchased a super reflux condenser?

  • Yes i have a gate valve. I have lots of 102mm tube and lots of 19 and 12mm tube and lots of 102 mm fittings and lots of 2mm plate and lots of time so I can build a super reflux no problem. Since you mentioned it I have been reading about VM and I'm not sure it's something I want to tackle at the moment. I am going to learn with what I have and then if I need to I will build a vm column. If I need to build a bigger reflux condenser to get a better product I will.

    But if I can get the same quality product with what I have by simply adding a better condenser then that's what I will do.

  • edited April 2015

    @Mickiboi said: Thank you crozdog. I have lots of bits and what I don't have I have enough bits and other pieces to make, have tig will weld. I'm using tpw for my first runs to learn what's going on. You only needed 2-3 packs? Was it these?

    Hi, no that's not them. The ones I used were quite big about 4" in diameter so they filled the 4'pipe nicely. Have a look in the SD manual - I put a pic of the ones I used in it.

    EDIT: Don't forget to run the scrubbies through a dishwasher before using em to make sure that any machine oil is removed.

  • Bugger already bought them but they did fit in nicely. I washed them in caustic soda twice. There was a bit of oil on them.

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