RogueRose
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Equipment for fractional distillation - Vigreux vs "cracking tower" setup
I'm curious if there is anything other than a vigreux column for distilling and separating materials of multiple boiling points such as crude oil or a
mixture of solvents.
I understand that the cracking towers basically work by reducing the size of the carbon chain as it passes up the tower, with each level becoming
lighter and allowing output at each level of various weight distillates.
I see that the two techs are similar but when separating a mixture of solvents, it is different than cracking the hydrocarbon chain. Is there
anything that can be used to separate through distillation like this?
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BromicAcid
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My absolute favorite is a Snyder column, good separation (atmospherically) plus it's aesthetically and audibly pleasing.
Really though you can buy a silvered vacuum jacketed column (to keep in the heat) and pack it with whatever you want, Pro-Pak, Raschig Rings, glass
beads, saddles, helices, etc. Packed columns give some of the best separation you can get without going to something mechanical like a spinning band
column. Of course these also depend on the head on top of the column and how much return you are getting.
Cracking as you said is much different than a simple distillation, not sure where you were drawing the parallels.
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j_sum1
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Is a Snyder really any better than a packed column? Or does it just look cool?
I haven't really seen them for sale and most have only 3 or 4 balls. I am guessing that equates to 3 or 4 theoretical plates. I think you can get
that with a decent vigreux. So is there any practical advantage in the additional expense?
At the OP...
I think you are conflating cracking with fractional distillation of crude oil. Fractional distillation (unsurprisingly) is pretty much the same
process.
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Refinery
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I havent seen any commercial setups for active reflux distillation but that is what I prefer because it allows much faster distillation speed and
higher purity, because passively cooled columns easily reach equilibrium and only limited fractionation occurs to my experience. Even small graham
condenser used as partial reflux with pressurised air will increase purity of distilled alcohol from 40% up to 80-90%. All industrial setups use
active reflux as far as I know.
I use graham condenser atop of claisen adapter and a valve placed before collecting bridge where condenser is usually placed. Column is packed with
PTFE sponge. A full reflux is brought before any collecting is begun. This method achieves higher purity faster. Using two valves, another placed in
top of graham it can be made into vacuum setup as well.
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RogueRose
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Thanks for the replies. I'm also kind of confused as to what the distillation receivers are for, the ones that have three (or more) necks coming off
the bottom and a single one (female) at the top. I don't see how that could separate anything buy just allow more "storage".
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BromicAcid
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Quote: Originally posted by j_sum1  | Is a Snyder really any better than a packed column? Or does it just look cool?
I haven't really seen them for sale and most have only 3 or 4 balls. I am guessing that equates to 3 or 4 theoretical plates. I think you can get
that with a decent vigreux. |
The Synthetic Organic Chemist's Companion By Michael C. Pirrung gives the height equivalent to theoretical plate ratio of 10 cm for a Vigreux column.
You are correct that in a Snyder column each ball would be a theoretical plate. Based on that I would say the two are pretty similar to one another
in their ability to separate.
[Edited on 5/11/2016 by BromicAcid]
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Fulmen
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You have to differentiate between cracking and fractionate distillation. Cracking is a chemical process that changes the composition, it is then
distilled into it's various components.
The multi-neck receivers are used for sealed distillation of multiple components, usually for vacuum setups but can be used any time air exposure must
be avoided. They allow you to switch receptacles without dismantling the setup.
We're not banging rocks together here. We know how to put a man back together.
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RogueRose
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| Quote: Originally posted by Fulmen |
The multi-neck receivers are used for sealed distillation of multiple components, usually for vacuum setups but can be used any time air exposure must
be avoided. They allow you to switch receptacles without dismantling the setup. |
Makes total sense now that you say that. Thanks!
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