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Taking advantage of plate spacing

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Taking advantage of plate spacing

Postby GoofyLunatic » Sat May 02, 2015 5:59 am

Hello all! and Happy Friday! :obscene-drinkingcheers:

So I have been a long time lurker on these and several other forums trying to learn as much as I can. Being that we are all a bunch of free-timers out doing our own rocket chemistry, I must say that as a community we have made wonderful progress in several short years. From the famous Boka-bobs to today's artfully crafted mini-distillation column flutes, it has been an amazing journey.

I can't help but notice however, that we have a LOT of holes out there in information. So many of us have taken to the trade of building an experimental setup to see if it works rather than trying to calculate it first to see if it was worth it! Wonderful spirit, not so good for the wallet! I for one am attempting at least to try and coalesce as much calculation as possible (a different site has some very good ethanol related math, but is still lacking in detail) into my first build. I hope to post some of that math here as I go.

However the purpose of this, my first real post, is to as a question that I have had in my head since reading the packed plated column post by emptyglass back in November of 2012. So here goes,

Consider if you will a 4" sieve plated column. General rule of thumb for spacing would be minimum 4" (lot of talk that the minimum spacing should be the column diameter). In this space we have a lot of hydrodynamics occurring. The vapor speed coming up the column prevents weeping back through the holes, suspending clear liquid above the plate to the height of the down-comer weir. Vapor passing through this liquid creates a violent frothing as it passes through. This creates several dynamic layers on top of one another. At the bottom, the liquid level, in the middle the frothing zone, and at the top the spray zone. Entrainment occurs if the power coming up is to great and causes the frothing zone to hit the plate above it, reducing efficiency and eventually flooding and deactivation. Therefore, we adjust weir height and liquid height with it, vapor speed with power to control the froth zone and spray zone, and plate spacing to ensure there is enough room for it all.

I hope I still have all your attentions. This is where I would venture a question. In the spray zone we typically place the down-comer to return fluid to the plate below. What if we took advantage of that zone in another way. I propose creating theoretical plates in that spray zone. I would like to build a cartridge of sorts that I could suspend in my column ABOVE the liquid and frothing zones, within the spray zone (or above it) and create a secondary reflux zone to work with. This would need packing with extremely tight HETP such as SPP or pumice (No one seems to really know the HETP of either materials, but the general thought is both exhibit about 30mm HETP). If we are working off 30mm HETP, that's 1.18 inches per plate... 1.5 if you consider inefficiencies of the column.

Math time. If we have a 4" column diameter with a sieve plate... optimal weir height would be about 12-20mm, .5" - .75". That leaves 3.25" for frothing and spraying. leave at least an inch and a half for frothing and you're left to 1.75" for spray zone below the next plate. I could insert a cartridge of SPP up to that thickness and achieve an additional plate within the same spacing I am already using, in theory. Therefore I could make a 20 plate tower in a 10 plate, 40" Flute, great for Vodka I'd think.

Extend that plate spacing a little bit, to 5.25", you could have 2 theoritical plates of SPP sitting above the sieve plate, making a total of 3 plates in the space. Then in theory, if all goes right, I could achieve 21 theoretical plates in just 37 inches.

I open the floor to your thoughts and thank you for your opinions. :smile:
Posts: 4
Joined: Sat Apr 11, 2015 1:25 am

Re: Taking advantage of plate spacing

Postby buggy » Sat May 02, 2015 10:08 pm

Well Goofy to start with Welcome & enjoy the forums ! :obscene-drinkingcheers: If your curious about Empty's findings you could talk to him about it as he is very active on some of the forums. Your talk about experimenting with plate setups is how we learn.
My thoughts is a plated column is good for flavored spirits , adding all the changes you speak of will strip all the flavor out , which is ok if your desire is neutrals. & if neutral is your drink why not just use a packed VM still design. A lot less expensive on the wallet too ? :confusion-shrug:
Posts: 6
Joined: Mon Dec 09, 2013 11:59 pm

Re: Taking advantage of plate spacing

Postby GoofyLunatic » Mon May 04, 2015 4:05 am

Hey Buggy,
Thanks for the welcome! The entire flute is going to be designed for show, so packed column isn't as showy ;-) . It will also be completely modular so it can be reconfigured. That's why I was imagining a "cartridge" of sorts to put above the plate. Something removable.
Posts: 4
Joined: Sat Apr 11, 2015 1:25 am

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