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?Magpie - 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]densest - 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.epck - 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.Pommie - 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.Pommie - 1-12-2005 at 17:56
It didn't add the document.
Attachment: still.pdf (680kB) This file has been downloaded 1424 times
silver22 - 21-1-2006 at 13:19
what do guys think would effect the efficacy of frctional distillation the most?silver22 - 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 apparatusevil_lurker - 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.leu - 22-1-2006 at 04:50
This web page provides some useful information about separating ethanol and water:
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.
Vigereaux Columns
lordmagnus - 29-1-2006 at 20:25
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?evil_lurker - 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.lordmagnus - 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 absintheevil_lurker - 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.Drunkguy - 1-2-2006 at 02:12
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
Pro's and Con's of distillation column types?
lordmagnus - 6-2-2006 at 20:51
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 typeMagpie - 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.
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.Magpie - 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.
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.lordmagnus - 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?pelnicki - 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! lordmagnus - 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.lordmagnus - 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
I am in the process of purchasing a column to use for fractionation so that I can add my own packing. The cheap 24/40 air condensers are too thin,
and when I search Ebay for a column that will work I am not finding what I expect (A straight tube with three or four barbs pushed into the flow path
at the base to hold the packing in the column. Instead Deschem is selling this Column which has a spiral ring in the base of the column.
Is there any benefit to a spiral ring instead of the old style?
Thanks
Endo Dr.Bob - 27-9-2018 at 12:33
I think the spiral is not actually attached to the column, thus just a simple column with a spiral thing stuffed inside, thus cheap to make. Might
work fine, might be so fragile that it breaks in first use, hard to know. But it is cheap, so not a big risk. Any type of plus that keeps the
packing in and does not clog the column is fine, but without insulation, the column will be hard to use well.
A really good jacketed packed or vigreaux column will cost more, but work better. It is a simple trade-off of quality verse price, which is often
not linear, so often spending a little more will benefit a lot, and then after that the cost of better goes up fast. macckone - 27-9-2018 at 13:19
A straight condenser with loosely packed fiberglass at the base and filled with rings does a very good job. I have also used broken glass tubing, you
don't want it too fine but too coarse doesn't work well either. Copper or stainless steel at the base will work for some substances, ie. not too
acidic.DavidJR - 28-9-2018 at 05:52
I have a couple of nice 55cm columns packed with stainless steel scourers which work pretty well.
Yes thats cheapish for a uk supplier but what was the P&P?
I recently purchased two Chines ones 300mm £10.38 each including P&P. Unfortunately the price of the longer ones jumps to £50+.sulfuric acid is the king - 29-11-2018 at 09:38
Does anybody know which type of column is this one?
It is speciffic,unusual,but not so uncommon,it has larger diameter in lower partm and it is narrow at the top.
Magpie - 29-11-2018 at 14:30
This may be a vacuum distillation column, or just an atmospheric distillation column. Here's a picture of the former, but one can find pictures of
atmospheric columns like it. Column design can be very specific to the feed and the intended products.
Dr.Bob - 29-11-2018 at 15:23
Anything that holds the packing in the column is fine. You want material with much surface area and little porosity, so it does not absorb the
liquid. broken thin glass, fine metal turnings, porcelin rings, etc are all fine.
If you don't have a vacuum jacketed column, you will want to insulate it on the outside, as otherwise it will cool too fast and not be very efficient.
The longer and wider the column, the better, but the larger the holdup. There is a real limit as to how pure you can get ethanol with one simple
column, it may take a few runs to get really good enrichment. There are companies that sell metal, insulated columns for distillaries/biofuel work
that work very well, but most are 4 feet tall and cost hundreds, but will handle a liter an hour or more. They take an enormous amount of heat
input, so a cheap hotplate won't work well. But for a smaller rig, like one liter, a good hotplate or mantle might work OK. For home brew, you are
only starting at about 10%, so you won't get more than 100 ml per L of input. sulfuric acid is the king - 30-11-2018 at 12:32
@Magpie
Maybe,maybe not
This is better picture,it was old linear alkyl benzene plant,no mention of vacuum column there,but who knows...
@Magpie
Maybe,maybe not
This is better picture,it was old linear alkyl benzene plant,no mention of vacuum column there,but who knows...
I think this is exactly what @Magpie said.sulfuric acid is the king - 1-12-2018 at 12:35
I am not sure,that's why i ask,here is atmospheric distillation...
So other columns are not at atmospheric pressure?Why that construction?
P.S. exactly this tower is shown as "topping tower" at this picture,what's that exactly?
I know this is small aparatus forum but maybe some process engineer answers
[Edited on 1-12-2018 by sulfuric acid is the king]
[Edited on 1-12-2018 by sulfuric acid is the king]Magpie - 1-12-2018 at 16:25
Yes, I too would like to hear from process engineers with experience with distillation columns.
I am a retired process engineer (ChE) but never had the opportunity to work with distillation columns. So my comments are based only on what I
learned 54 years ago in a class called Unit Operations which covered distillation.
I would say that the "topping tower" is being fed heated crude oil. Off the top is gas (methane, ethane, propane, etc) and some naphtha. The bottoms
off this tower are again heated then go to the bottom of the atmospheric distillation column shown in the middle of the diagram. Most of the
fractionation takes place there.
A little searching revealed what I suspected: the wide cross-sections of columns are found where the gas rates are high.
[Edited on 2-12-2018 by Magpie]
[Edited on 2-12-2018 by Magpie]Sulaiman - 2-12-2018 at 15:20
I guess that for a given throughput at lower pressures
there will be very high gas/vapour velocities due to the high molar volumes, P.V = R.T etc.
unless much wider towers are used.
..........
How could you see the difference between a high throughput high pressure tower compared to a low throughput low pressure tower ?
