Optimal Distance Between Plates

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CopperFiend
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Optimal Distance Between Plates

Post by CopperFiend »

Dear Brethren,

I'm starting the build on a 3" bubble plate column today. I've decided to go for 2 sections, one with 4 plates and one with 6 plates, so I can run at a max of 10 plates if I wanted but still run at 4 if I want more flavour for aged spirits.

My question to you lovely people is... is there an ideal distance between the plates for a 3" column? This question has been put in my head by this comment on another thread:
zapata wrote: Fri Oct 09, 2020 8:18 pm Yup, that is called entrainment. It's why commercial plated columns have so much space between each plate, why commercial pot stills have such huge onions on them, and why hobby stills of all sorts taste bad when run too hard even if they don't puke, flood, blow up or run detectably out of spec for expected output.
Do I want to be at least 3" apart on a 3" column or do I need more?

Cheers,
Copper
zapata
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Re: Optimal Distance Between Plates

Post by zapata »

You need 2-3x that. And you'll have to define "optimum". I suspect from a purely technical perspective that somewhere above 12" spacing would be optimum. Yet few hobby stills use that much.

This is a kinda weird still for these days, lotsa people made tall plated stills early in their popularity, few see the utility in them now. 2-4 platers are common for flavored spirits, but stacking enough plates for something like vodka is an expensive and very tall affair. And are you sure 3" diameter will be sufficient, it has a pretty low maximum power capability (power = time), and a much narrower set of operating conditions than 4". And 10 plates? I guess it will look cool, but if you want 10 "plates" do it much easier and cheaper with a packed column. Unlike real plates, a 3-4" HETP (height equivalent of a theoretical plate) is easily achievable with packing.

You didn't really ask me to redesign your still, but I think for what most people want 4 plates for, they want the speed of a 4" column. And for what most people want another 6+ plates for they want the purity and speed of a 3" packed column. 4" plates as commonly built and run are perfect for feeding a 3" packed column.
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Yummyrum
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Re: Optimal Distance Between Plates

Post by Yummyrum »

Agree with everything said there zapata .
CopperFiend
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Re: Optimal Distance Between Plates

Post by CopperFiend »

Interesting. Thank you Zapata. So would I get what I need from a section of 4 plates for flavoured spirits (albeit a little slower than 4") and then a 1m packed column above those plates when I want to make neutrals for gin?
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Saltbush Bill
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Re: Optimal Distance Between Plates

Post by Saltbush Bill »

CopperFiend wrote: Fri Oct 09, 2020 10:52 pm is there an ideal distance between the plates for a 3" column?
Not going to the shed right now to measure things but in my previous builds Ive always spaced plates a little more apart that the diameter of pipe used....4 incher 4.5 or 5 inches apart......6 incher 7 or 8 inches apart.
I agree with the others that in many ways you would be better to make a 4 inch column ....3 will be slow unless you intend making very minimal amounts or have a lot of spare time on your hands. Also in the long run that a dedicated reflux still for neutral would be better and easier......or a packed section on top of the 4 plates.
Ultimately Id go 4 inch x4 plates and a packed section ......not perfect but a great all rounder that will do a good job of most things.
CopperFiend
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Re: Optimal Distance Between Plates

Post by CopperFiend »

Ok, well this sounds like a lot less work than making 10 plates! Haha. At this time I can only get hold of 3" copper pipe so for the research stages of this endeavour I'll crack on with 4 plates and the rest of the column packed if I want to make a more neutral for gin (less likely to be that often). Then once we've got the wash, ferment and everything else down to a tee on the slower 3" setup, we can invest in the (currently ludicrously expensive) wider bore copper pipes and go big!

Cheers,
Copper
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LWTCS
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Re: Optimal Distance Between Plates

Post by LWTCS »

The issue (more often than not) is available ceiling height relative to how many plates are on your wish list.

I'd say that the real question for hobbyists ( pros too for that matter) ends up being how small/short can I get away with and still get the plate count for a proper vodka column with out having to fight through chronic, bad hydraulic behavior.

4" spacings work well but is not optimal.
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Bushman
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Re: Optimal Distance Between Plates

Post by Bushman »

You also want to consider enough spacing for site glasses if your building a flute.
hellbilly007
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Re: Optimal Distance Between Plates

Post by hellbilly007 »

Since 3" copper is all that's available you could use stainless steel tees for your plated section to go under your 3" packed column. Using tees allows you to adjust your plate count, and doing so you can adjust for how much flavor you get. Just my $0.02, keep the change lol
howie
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Re: Optimal Distance Between Plates

Post by howie »

Saltbush Bill wrote: Sat Oct 10, 2020 1:37 am
CopperFiend wrote: Fri Oct 09, 2020 10:52 pm is there an ideal distance between the plates for a 3" column?
Not going to the shed right now to measure things but in my previous builds Ive always spaced plates a little more apart that the diameter of pipe used....4 incher 4.5 or 5 inches apart......6 incher 7 or 8 inches apart.
i'm looking at some 4-plate 4" bubblers.
there is one that has a total length of 675mm which is about 173mm/7" between plates, as opposed to the usual 112mm/5"
would there be any benefits (or drawbacks) to the extra spacing?
tia
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Saltbush Bill
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Re: Optimal Distance Between Plates

Post by Saltbush Bill »

Doubt it will make a huge difference.
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Re: Optimal Distance Between Plates

Post by zapata »

howie wrote: Sat Oct 10, 2020 6:42 pm would there be any benefits (or drawbacks) to the extra spacing?
tia
If my hunch is right, you would be able to run it well, faster, with less smearing, everything else being equal, or be that much less likely to screw it up if run equally. Of course it's nothing more than a SWAG, so I have no way to quantify that short of building and comparing. It may be a few inches is noticeable and you gain +20% power/takeoff sweet spot, but for no good reason I'll speculate that would be absolute best case scenario of really tall spacing. Or it may be Saltbush is right and it's a miniscule difference at best. If everything else really was equal and I knew I wouldn't regret the height, I would opt for the taller option myself. Height, weight, and versatility if you want that height back later are the only real drawbacks I can think of. Keep in mind who you're listening to though, I don't mind having a buncha stills that only do one trick a piece and I have 10' ceilings :lol:

Copperfiend, if 3" is what you're limited to, there are folks with 3" flutes here. I think NChooch has/had one. And.... shit, everyone's favorite bartender friend from New Orleans... uh, yeah, pretty sure he has a 3" chinese special. And really, read flute talk if you haven't, I remember several 3" in there. When I was deciding, I really wanted 3" too, but at the time the speed folks were reporting wasn't attractive enough to win me over from pot stilling, so I ultimately held out for 4". There will be a smaller support group if you do run into problems. I'd find those 3" friends now and read everything they've said.
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Chauncey
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Re: Optimal Distance Between Plates

Post by Chauncey »

zapata wrote: Sun Oct 11, 2020 12:10 am
howie wrote: Sat Oct 10, 2020 6:42 pm would there be any benefits (or drawbacks) to the extra spacing?
tia

And.... shit, everyone's favorite bartender friend from New Orleans... uh, yeah, pretty sure he has a 3" chinese special.
It is what i have. I wish id have gone with a 4 honestly but no complaints on the 3. It works well on a half bbl keg but if my boiler were any bigger itd be a 4 inch all day.
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LWTCS
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Re: Optimal Distance Between Plates

Post by LWTCS »

Taller plate spacings will reduce the pressure that accumulates in between the liquid beds. This is helpful for bubble cap systems.

Perfs require a bit more engineering because pressure more specifically affects the plates ability to maintain a liquid bed.
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CopperFiend
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Re: Optimal Distance Between Plates

Post by CopperFiend »

Thanks Zapata, will do. I'm limited to 3" while we're making sure the goal is actually possible to achieve! Dont want to be 2k down on materials for a 4-6" column and then what we plan to do isnt even achievable! This is a research still at best to be fair :D

It would be nice if it worked though!

Copper
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Re: Optimal Distance Between Plates

Post by Setsumi »

IMG_20201011_172030.jpg
this is the difference between 3" and 4" plates. if i had only 3" pipe i would do it in perfs with 5 to 6% open area and at 4" spacing. busy doing single caps procap style for a 4" but have perfs on a 4 at 5.6% open area and 5" spacing.... you have to mess up to screw a flute.
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