Plate Variables

[jim]

Ive been reading the monster flute talk thread on HD, trying to work out the best way to build a plated still. In order to understand the best way to design it, I want to understand the variables involved. Im not SURE about any of them, Im just posting my best guess. If you know better please let me know.

The variables associated with the still output are:
Distillate alcohol percentage
Distillate flavor
Output flow rate

Column Diameter: The wider the column, the more power it can handle, and faster the takeoff rate. No direct influence on % or flavor. For best results use at least 4"
Number of plates:This is the primary driver of alcohol %. From what I read, two plates will get you in the 60% ballpark, Mac and Crow suggest four plates for a good balance of flavor and strength (should get into the 90s)
Height between plates: The lower the height between plates, the more flavor carries over. Need to beware of smearing if they are too close together. Typical height seems to be around 4" (100mm)
Depth of distillate on plate (Height of downcomer above plate): I think that deeper distillate might get you better separation, as the vapor bubbles get better mixing on that level, possibly lowering flavor? Typical depth seems to be 3/4" (20mm)
Slotted bubble caps: makes small vapor bubbles. Probably same effect as deep distillate.
Smooth edged bubble caps raised from plate floor: makes larger vapor bubbles, opposite effect as deep distillate
Diameter of downcomer: The greater the diameter, the lower the likelihood of too much reflux overwhelming the plate. Helps handle more power. 3/4" seems to be the popular choice.
Diameter of upcomer: The smaller the upcomer, the faster the vapor moves through it. Not sure what effect it has overall as long as it isnt so small that the restriction slows your output.
Diameter of bubble cap: The bigger the cap the slower the vapor comes out possibly same effect as depth of distillate. Looks like for a single cap plate, a 1.5" cap is used.
Distillate surface area (the room on the plate not taken up with upcomers and bubble caps): Ive been thinking about this one. Vapor pressure is partly a function of surface area. I think if you maximise this, you will have faster output. One way to maximise might be to raise the distillate depth to completely cover the bubble cap.

These are all the variables I could think of. If you have other variables, or see something wrong with what I've said, please comment.

[MacStill]

Mac and Crow recomend 4 plates to get into the 80s

No I dont. :naughty:

I recommend 4 plates for the flavor profile I like, and it'll get you in the 90's :roll:

[jim]

Mac and Crow recomend 4 plates to get into the 80s

No I dont. :naughty:

I recommend 4 plates for the flavor profile I like, and it'll get you in the 90's :roll:

Ah, thanks for the clarification. If you dont mind I'll edit the main post so that I dont misquote you.

[googe]

Holy crap, im lost :laughing-rolling: , why would a 2 plate column produce lower abv than a pot still?. keen to see answers from them.in the know on this. Good luck Jim.

[jim]

Holy crap, im lost :laughing-rolling: , why would a 2 plate column produce lower abv than a pot still?. keen to see answers from them.in the know on this. Good luck Jim.

My pot still produces about 8L of ~40% from a 30L 10% wash.

[crow]

yeah if ya into reading monster threads over there I'll see if I can find a link for ya to some of MRs posts concerning the possitive affect of width on flavour (compression) and ABV and of cause speed ;-)

[googe]

I get about 5-6L of around 70-78% fRom the same using half half low winds wash. What sort of wash you talking?.

[jim]

I get about 5-6L of around 70-78% fRom the same using half half low winds wash. What sort of wash you talking?.

Mine is a basic Mcrum recipe 30L wash including 3kg sugar and 3L molasses. Should end up 10%ish

[bt1]

Good summary Jim,

3 comments. Some designs tend to not have a downcomer cap on the plate...why sacrifice the surface area on plate. I choose a raised footed idea to avoid loosing space.

If I build another at some stage (6"-8") I wouldn't have downcomers as such. Just a 1" raised above plate 20mm tube with a slotted distribution foot or cap underneath the plate. I see no value in a longer downcomer at this stage.

If I'd had a drill press and time again the backs or underside of plates would have been countersunk with a 2mm or 2.5mm drill still leaving breach size through plate at 1.5mm for a 4" col but to gain venturi effect was the thinking=vapour speed increase.

I also had toyed with the idea of having post the reflux condenser larger tubing diameters to induce a lower pressure effect in effect 'dragging" the vapour through...I'm a little short on the physics of it currently and still looking in to this as a design idea....say 6" on top of 4' col. Most current designs reduce or halve post reflux but it seems to be more about costs and availability to me.

cheers
bt1

[crow]

Yep going by mash rookies stuff that would work pretty well but if ya could get the 6"for a good price (say scrap) 6"all the way would be better. MR found that lower pressure, slower vapour speed was a lot more important in the design than the length or plate design

[MacStill]

MR found that lower pressure, slower vapour speed was a lot more important in the design than the length or plate design

To achieve what?

[crow]

Oh yeah 8-} , sorry was using my phone and can't read what I'm typing : Better separation and output , I'll see if i can find the data, I know where his packed column data is (where I got the scoria idea) which touches on this but from memory doesn't really go in to it much, I'll if I can find the others,might take some looking

[MacStill]

Mate, with all due respect I'm going to say it's a load of crap on a hobby sized still, it might make a difference in a 1M diameter commercial unit but C'mon.

I can get excellent separation and output from a 4" rig with an 8" thumper, but the harder it's run the harsher the spirit, it runs perfectly in the 2.5 to 3 L/PH but can be pushed to over 5 L/PH and still pull 93%

Also how much pressure is there going to be in a column still that has 3 plates and say another with 6 ? the whole unit is open to the atmosphere and the pressures at the plates is going to be governed by heat input/vapour speed rather than column design or reflux condenser design 8-}

I think at times people are too smart for their own good and over think things way too much, I doubt any of it makes much difference to what's going in the jar :))

[bt1]

kk,

So does anyone know the physics well enough to comment..it's no biggy agreed, but i for one would just like to confirm wether the idea is valid or not.
4 or 5 percenters of ideas together for next build

bt1

[emptyglass]

Hey Jim,
You seem to have neglected the biggest variable of all, bubble caps or perforated.

Is the decision to go for bubble caps based on anything?

[jim]

Bubble caps seem easier to build to me. Every thing Ive seen shows that the performance between the two is pretty even.

[emptyglass]

Bubble caps seem easier to build to me. Every thing Ive seen shows that the performance between the two is pretty even.

I agree with the second sentance. There are but a few that have tried them both, and they say the same. Mac and OD are two that I can name, there are a few more but I havn't talked to them.

But the first sentance, I just don't understand. Sorry mate, but perf plates do it for me. I guess its down to if you want results for input, or if you just want fancy crap.
I've seen guys speculate on the correct proportions for bubble caps, and agonise over them for ages, when the could have got equal (or better) performance out of perf plates, with the simple 30% rule.

I guess some guys can see the locic and mechanics of caps. They understand them. Perf plates are a bit harder to agree with, but so much simpler.

[bt1]

Crow,

would be most keen to get that link...any data would be most welcome.

Playing around with a new perf plate currently. I'll keep the details till I've got a result...would like to test it first.

bt1

[bt1]

Surely there's a Physics degree out there somewhere that could be turned to resolving the issue raised?

or are we all unedifcated ed ed

a curious
bt1

[googe]

Go on a physics forum and ask bt1 :handgestures-thumbupleft: