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evil_lurker
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[*] posted on 1-12-2005 at 09:47
Fractionating colums and application...


I'm familiar with the whole fractionating colum theory, but I'm a bit stumped when it comes to practical application.

I want to distill alcohol and get a good separation, as close to the azeotrope as possible.

What kind of a column do I need, vigreux or hempel?

How long does it need to be?

What kind of packing should I use?

Should the column be insulated?
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Magpie
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[*] posted on 1-12-2005 at 10:17


I upgraded some cheap vodka using an 8" column packed with stainless steel scrub pad (not too tightly). It worked like a charm coming right up to the azeotrope temperature and yielding the azeotrope in the distillate and water in the pot.

Column was the fat one in my 19/22 kit. It is plain (straight bore) and may be called a "Hempel" column.

I didn't use any insulation.

[Edited on 1-12-2005 by Magpie]

[Edited on 1-12-2005 by Magpie]




Knowing that I can buy good quality NaOH, HCl, and H2SO4 locally gives me great peace of mind.
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densest
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[*] posted on 1-12-2005 at 11:36


Insulation seems to help the precision of the fractionation a lot. Wrapping bright shiny alumin(i)um foil around the whole apparatus up to the condenser is sufficient for most things. I've separated a 2C differential pretty well.
Insulation around the boiling area speeds things up as well.
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[*] posted on 1-12-2005 at 13:39


Being a student and desperately poor I am currently unable to shell out the cash for the whole fractional distallation setup. So recently I built a ghetto fractional distillation column and and condenser from from copper tubing, brass T connectors and PVC pipe. It cost about $15.00 in parts with supplies left over and works suprisingly well. Maybe I'll post some pics if I remember to take them.
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[*] posted on 1-12-2005 at 17:52


I found this document a while ago. It describes how to make a still and has a good explanation of distillation and reflux as well. This is a alcohol type still.

Mike.
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[*] posted on 1-12-2005 at 17:56


It didn't add the document.

Attachment: still.pdf (680kB)
This file has been downloaded 636 times

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silver22
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[*] posted on 21-1-2006 at 13:19


what do guys think would effect the efficacy of frctional distillation the most?
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[*] posted on 21-1-2006 at 23:06


thx for the replies i got but i figured some important point:
2 major things that effect it
1: temperature
2: surface area inside the recrystallization apparatus
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[*] posted on 21-1-2006 at 23:26


Actually the three biggest things that effect a fractionating column are length, packing, and insulation.

Longer length = more room for theoretical "plate" equivalent of separation

Packing = the smaller and tighter the packing the more "plate" eqivalent per unit of column length

Insulation = prevents/slows condensation on the sides of the column

The higher the degree of separation needed, the longer the column needs to be. If your packing is too loose, your column loses efficiancy. If your packing is too tight, the column will flood. Insulation helps shield the colum from drafts and keeps a nice steady reflux ratio. Too much insulation will cause the column to lose efficiancy. At least that is the way I understand it.
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[*] posted on 22-1-2006 at 04:50


This web page provides some useful information about separating ethanol and water:

http://www.ces.purdue.edu/extmedia/AE/AE-117.html

:D




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[*] posted on 22-1-2006 at 06:30
Efficacy of Fractional Distillation


THE single most important factor which determines the efficacy of fractional distillation is the REFLUX RATIO

Reflux is the stream of condensed distillate which is put back into the column at the top. And the reflux ratio is the ratio of distillate returned to that of product withdrawn.

If all the product is withdrawn ( i.e. no reflux to the column) then the column ceases to act as a fractionator - it just transports vapours from bottom to top - without any purification.

The reason why one gets purification in small laboratory columns without physically having reflux stream is that due to very high ratio of Surface Area to Working Volume, lot of condensation takes place inside the column even before vapours reach the physical condenser. This happens even if the column is heavily insulated. This condensate acts as a internal reflux.
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[*] posted on 29-1-2006 at 20:25
Vigereaux Columns


I use a 200mm effective length vigereux column, Still takeoff head w/thermo port, and 1000ml round flask with thermo port. I had to insulate the column to get to 78 Deg. C.to get good ethanol, while trying to distill Thujone from wormwood, I was not able to hit the 86 deeg. C. mark with aluminum foil, With some work I got to 80.5 deg. C. I have just constructed a flexible insulator jacket out of layers of aluminum foil HVAC tape, and fiberglass repair cloth, I can wrap this thing around my column twice, and secure it with some velcro cable wraps, I don't have time to test it tongiht, but I hope it will get my to the 86 deg. mark easier. if not I'll have to come up with a way to add some supplemental heat to the column base some how. ANY IDEAS?



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evil_lurker
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[*] posted on 29-1-2006 at 21:52


Two options. One, take a sock, cut it in half and then wrap it around the column. Secure it with clothespins.

Second, Get some foam pipe insulation from the hardware store and go from there.

It also helps tremendously to put some cloth on top of the flask.
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[*] posted on 31-1-2006 at 19:12


Well, adding ARMAFLEX pipe insulation to the column has helped allot, I am closer to where I need to be, now I just gotta add a shield to the top of the flask as well, I am still only able to easily get to 78 deg. C. I need 87 Deg. C. for the Thujone in absinthe



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evil_lurker
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[*] posted on 1-2-2006 at 00:46


If your using alcohol as a solvent for the wormwood all you'll get is 78C because that is the temperature of the alcohol coming over.
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[*] posted on 1-2-2006 at 02:12


Check this bit of kit out:

http://i14.photobucket.com/albums/a329/CentralAsia/70_1.jpg

Attach one end to a vigreux and the other end to a coil condenser. This is a very effective method.

Also you have a three neck flask or a claisen adapter then you can use a smaller vessel like so:

1. Add some cold water at the end of the reflux to get the waste fluid to stop bubbling.

2. Suck on a piece of tubing to fill it with water and then put your thumb on the end.

3. Transfer the tubing into the opening of the flask and let go. This will empty the vessel so that it can be refilled.

The point of this nifty trick is so that you dont scold your mouth :D




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lordmagnus
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[*] posted on 6-2-2006 at 20:51
Pro's and Con's of distillation column types?


What are the pro's and Con's of the different column types?

Vigereaux (hollow glass fingers pointed downward)
Packed Columns (hollow column with packing material of diff. types inside)
Snyder (floating ball type)
Perforated Plate type




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[*] posted on 7-2-2006 at 13:24


I have found packed columns to be very good for most of my laboratory needs. They can be equivalent to many (dozens?) of "theoretical plates" depending on the length of the column. The Vigreaux is equivalent to around 4 theoretical plates. The tradeoff is less product holdup and less tendency to flood for the Vigreaux vs a packed column.

The perforated plate and bubble cap columns are more suited to large industrial applications although packed columns are certainly used there also. The cost and time of maintenance (cleaning or replacing the internals) would be more of a concern in industrial applications than in the lab.

I'm not familiar with the floating ball column internals.




Knowing that I can buy good quality NaOH, HCl, and H2SO4 locally gives me great peace of mind.
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lordmagnus
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[*] posted on 7-2-2006 at 19:37
Found info on SNYDER Columns


Ok, here is what I've found;

Picture of a snyder;
http://www.ars-fla.com/Mainpages/Environmental/noflood_colum...

It's used where there needs to be high efficiency in a refluc operation, especially when little solvent can be afforded to be lost. It works similar to a bubbler cap style column, only on a much smaller scale, it looks like it'll be a bitch to clean out if you get a boil over and foaming into your column.




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Magpie
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[*] posted on 7-2-2006 at 20:15


Interesting. Looks like a method to control flooding on a laboratory scale.

I suppose that is an advantage of a bubble cap plate, i.e., control of flooding by limiting holdup via weirs.

I know that when I was attempting to fractionate acetic acid/water I had severe flooding with my glass bead packed column. I blamed this on inadequate column temperature control. My overhead was 65% acetic acid and I haven't been back to try it again. Another approach would be to use a more open packing like raschig rings. I think I will try this first as it sounds easier.

I tried a stainless steel scrub pad packed column but the hot acetic acid tore the shit out it. :o

Heavy reflux, as someone else has pointed out, is great for purity of product. But if it is too great flooding occurs and the column can become inoperable.




Knowing that I can buy good quality NaOH, HCl, and H2SO4 locally gives me great peace of mind.
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lordmagnus
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[*] posted on 7-2-2006 at 20:22


Hummm, have you tried using an allihn condensor as your refulux column instead? The large opening would permit great cooling, or possibly putting an allihn condensor ontop of a vigereux column for relfuxing acetic acid?



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[*] posted on 11-2-2006 at 05:24


Are there any traps for the unwary and/or uninitiated among us wishing to distill our "super yeast" feermented homebrew into some nasty homemade vodka ---- while avoiding the unwanted methanol and other fusel oils?

For that matter, could denatured (methylated) alcohol have its methanol equally simply removed?

I tend to use vigreaux column for fractionating, but when you're not dealing with reactive substances (like acids or anything else likely to screw up your metal), some cheap steel wool packing, or even broken glass beads or chips, seems to work a treat for most of my applications...

But the reason I ask about this, is because perhaps me and a friend or three might like to try some mixer drinks with some "homebrew spirit" this way -- I'm worried about the methanol of course, that metabolises into some nasty-arse formic acid, which I've been told by some authority figures I trust, that it's not the sort of stuff you'd want to hypodermically encourage to infest your eyeballs!

Of course, as usual, I'm being hyperstressful about my own safety being the biggest scaredycat this side of the Pecos... I know that rednecks aplenty drink it up bigtime with their moonshining pot still liquor ------

But we were thinking of making some stuff that you might describe as a little more 'classy' --- which is how I like to best describe anything that doesn't make you go blind! ;-)

Any tips or hints? I know the BP's are extremely close, and deliberately so, to discourage our wonderful transient population of would-be street-chemists trying to distill out the denaturing with nothing but a bucket, a paperclip, and some soggy chip-packet they found or something...actually what am I saying, they're quite happy to just dirnk it anyway! :)
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lordmagnus
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[*] posted on 11-2-2006 at 08:25


I would not try to clean up denatured alcohal for drinking! Distilling homebrew mash is not that hard is you already have the fractionating column on hand. Ethanol boils at 78.5, isopropyl at 82.0 the rest of the HIGHER ALCOHALS have even higher boiling points. Run your boiling flask until the liquid inside starts to boil, use a water bath to heat it, if ya do it right, and insulate with aluminum foil where you need to, the boiling flasks alcohals will boil before the water in the bath does. Watch the thermometer on the still head, anythin coming out the condenser before it hits 78 deg or so, put off to the side, catch the runoff while it runs at 78-79 deg on the still head, when the temp goes above that, switch the containers again, and catch the stuff running higher than 79 in a seperate container. The stuff you caught in the first container is called the distillation heads, it's mostly the flavoring from the ingrediants you used to make the mash (corn,wheat,rye,rice, etc.). The stuff running at 78-79 is fairly clean ethanol. the stuff in the third container are the tailings, these are filled with etahnol, isopropyl, amy, propanol, furfural, etc. Redistill the tailings again to get the rest of the ethanol out. After you've collected all the ethanol you can, you can run the ethanol back through the still one more time to seperate it out into mostly ethanol, or some head and ethanol (for flavor). this is how they make high quality neutral VODKA., or they will do a controlled distill a couple of times, then run it through activated carbon to strip the higher alcohals out.



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lordmagnus
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[*] posted on 16-2-2006 at 15:32


I found some information on different fractionating columns;

Vigereaux Column; easy to clean, easy to use, works for most apps, but not all
Packed Column; More efficient than a vigereaux, more difficult to clean with certain operations
Snyder Column; usefull for hard to fraction materials, prevents flooding as well, much like an industrial bubbeler cap, or valve plate style column used in petrochem.

Check out this guys e-bay site, if you don't see something, ask, he prob. has it, his prices are excellent, i am getting a SNYDER for like $30, and I have some of his glassware, it's quality stuff, vacuum worthy

http://stores.ebay.com/DP-Glassblowing_W0QQssPageNameZstrkQ3...




I\'ll kill a man in a fair fight, or if I think he is gonna start a fair fight, or if he\'s bothrn me allot, or if I am getin payed good, or probably over a good woman.

-Jayne Cobb (Serenity)

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