fractional condensation??

Distillation methods and improvements.

Moderator: Site Moderator

Post Reply
User avatar
john2674
Bootlegger
Posts: 147
Joined: Mon Oct 06, 2014 6:49 pm

fractional condensation??

Post by john2674 »

Ok let me start this by saying... this is purely a thought experiment at this point.
I had a dream a while back, and in that dream I was helping some dude build a super complex still. I didn't understand how it worked... even now its a little fuzzy.
it started with a pretty standard vm reflux column. but on the output branch there were several small boilers with their own condensors that had different liquids in them that boiled at ever lower temperatures than the preceding one. the vapor tube ran through the center of the boiling chambers.right after each "cooling" chamber there was a small downspout with a p-trap style bend in it so it would allow liquid to come out but not vapor. in my dream the guy was able to set it up so heads, hearts, and tails or water came out automatically from different outputs!!
Is this just a crazy dream? or something that might be feasible?
any thoughts?
BoomTown
Site Donor
Site Donor
Posts: 1498
Joined: Thu Apr 19, 2012 7:41 am
Location: Virgina

Re: fractional condensation??

Post by BoomTown »

look up something called a Coffy Still. circa 1845.
“…Let’s do this one more time....”
User avatar
pfshine
Site Donor
Site Donor
Posts: 3106
Joined: Thu Jan 19, 2012 10:59 pm
Location: Vegas

Re: fractional condensation??

Post by pfshine »

While I'm having trouble envisioning what you are saying precisely, I got the gist. People have made heads traps and such. If you are going for a flavored spirit this would not be the way to go. But a neutral would greatly benefit from this.
Life is a journey you take alone. Make sure you do what you what makes you happy
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

john2674 it doesnt work, you cant separate by condensation. Separation only occurs on evaporation, on condensation, everything condenses at once regardless of temperature.
User avatar
john2674
Bootlegger
Posts: 147
Joined: Mon Oct 06, 2014 6:49 pm

Re: fractional condensation??

Post by john2674 »

Ok Manu, I read your post and thought about the statement that it cant be done.....Had thoughts about the scientific laws that state for every action there is an equal and opposite reaction. So I researched some more. Heres what I found when I put on my lab coat lol.
fractional condensation Is possible!
BUT... it is primarily used to remove highly volatile compounds in oil production of several types.
For the purpose that I was proposing, the condensation points of all of the fractions in our product is so close that , at best, it would be extremely difficult to achieve the exact temperatures required to make it happen.
so I hate to admit it but you were pretty much right, just a way shorter answer ..lol
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

One common example of fractional condensation is a dephlegmator, another is separation on column trays.
In petro refinery columns continuous product separation on collection trays by temperature control is essential.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

im right because we all had the same idea as you and some spent a fortune building huge stills that didnt work. I was lucky enough to read early a great account of such failure and why this doesnt work in Barbet "manuel de distillation" from 1880's.

Named my son Emile after the chemist.
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

Fractional condensation works just fine. Coffey Stills were banned from Irish Whiskey and Cognac production (and a few other disciplines) because of flavor considerations, but that doesn't mean the fractional condensation they depend on doesn't work. Continuous stills are still used for Bourbon and Canadian, as well as petroleum. My dephlegmator, without trays or packing, changes the composition of the product in a measureable way, illustrating fraction condensation in front of me.
Barbet's book is a must read for distillation.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

heartcut wrote:Fractional condensation works just fine..
Coffey still doesnt use fractional condensation ̣(because it doesnt exist), are we talking about the same thing ?
By fractional condensation I mean the ability to condense various gases (boiled off a liquid mix) selectively based on the temp selection.
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

That's what a dephlegmator does, the balance and composition of phlegm and vapor depends on the coolant flow.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

heartcut wrote:That's what a dephlegmator does, the balance and composition of phlegm and vapor depends on the coolant flow.
no, a deflegmator is just a condenser and it condenses everything blindly (apart from air and such), the amount it condenses depends on the coolant but the composition of the condensate doesnt depend on it.

It is counter intuitive but that's how it works. The separation occurs on evaporation NOT on condensation.
The amount of reflux depends on the dephlegmator and influences the % of the ethanol on top, but that's because of reflux which is another mechanism
User avatar
skow69
Site Donor
Site Donor
Posts: 3230
Joined: Tue Dec 06, 2011 3:03 am
Location: Cascadia

Re: fractional condensation??

Post by skow69 »

Manu is right. The composition change in your flute is due to the fact that when a mixture of ethanol and water boils, the vapor created is richer in ethanol than the liquid was. For example, when a 15% wash boils, the vapor is 65% alcohol. When a 30% wash boils, the vapor is 72.5%. But when the vapor condenses, the resulting liquid remains 65% or 72.5%
Distilling at 110f and 75 torr.
I'm not an absinthe snob, I'm The Absinthe Nazi. "NO ABSINTHE FOR YOU!"
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

Quoting from:
Handbook of Laboratory Distillation
By E. Krell 1982
5.2.3 Separation by partial condensation
The term partial condensation is used to denote the liquefaction of a fraction from a flow of vapour. It can be brought about deliberately by interposing a special condenser- a so-called dephlegmater- in the vapour line, and it also occurs as an undesired effect by loss of heat from an insufficiently insulated column.
(1 illustration and a paragraph later)
In industry it is common to make a dephlegmater produce the reflux and cool the distillate to be drawn off in a production condenser. The aim is to use the amplifying effect of the dephlegmater which is due to the partial condensation of the high-boiling components.
End quote.

I do understand that the tube in shell dephlegmators commonly used in Flutes are difficult to modulate at low flows and wouldn't be that great for this technique. I use a coil dephlegmator that tunes easily at partial condensation rates. Also been using partial condensation in petroleum refineries for the last 4 decades and the refineries have been doing it a lot longer.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
User avatar
skow69
Site Donor
Site Donor
Posts: 3230
Joined: Tue Dec 06, 2011 3:03 am
Location: Cascadia

Re: fractional condensation??

Post by skow69 »

I'm listening and wish to learn.

Which fraction do you selectively condense, the water or alcohol? At what temperature does this occur?
Distilling at 110f and 75 torr.
I'm not an absinthe snob, I'm The Absinthe Nazi. "NO ABSINTHE FOR YOU!"
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

heartcut wrote:Quoting from:
Handbook of Laboratory Distillation
By E. Krell 1982
5.2.3 Separation by partial condensation
The term partial condensation is used to denote the liquefaction of a fraction from a flow of vapour. It can be brought about deliberately by interposing a special condenser- a so-called dephlegmater- in the vapour line, and it also occurs as an undesired effect by loss of heat from an insufficiently insulated column.
(1 illustration and a paragraph later)
In industry it is common to make a dephlegmater produce the reflux and cool the distillate to be drawn off in a production condenser. The aim is to use the amplifying effect of the dephlegmater which is due to the partial condensation of the high-boiling components.
I believe "partial" here is to be understood as a part of the output is to be returned as reflux.
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

Read the quote again- the "partial condensation of the high boiling components" indicates a composition change.
Read the book- that chapter includes some "before and after" dephlegmater composition examples.
While trouble shooting refinery process I am sometimes in a position where I watch the composition change on an analyzer in real time as well as reading about it in textbooks.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

The Krell text is very disturbing. Here's a quote from Barbet :

Chapter "Le condenseur n'est pas un analyseur" start at PDF page 326 (book page 308) explains the whole thing and ends with this :
theoreme.png
theoreme.png (13.56 KiB) Viewed 2961 times
it says if you see changes in composition at the condenser it's because it refluxed things downwards that have been reboiled on the plates not anything else.

I'll add that from all the column diagrams i've seen, which often come from the petroleum industry, the condensers are *always* on top, condensing everything, then the liquid is split between output and reflux, I cant remember seeing a diagram with condensers along the way or on top but condensing just part of the gases (as in partial condensation).
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

I was using the term "analyzer" to refer to a Gas Chromatograph or Spectrograph analyzing the composition of the process stream. Don't know what else to say after watching these effects in real time. Good luck.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

heartcut wrote:I was using the term "analyzer" to refer to a Gas Chromatograph or Spectrograph analyzing the composition of the process stream. Don't know what else to say after watching these effects in real time. Good luck.
Barbet was talking about ethanol and heads.
These real time effects (I understand instantaneous) that you see, are they with components with very far boiling points ?
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

One example was C6 to C12 straight chain, ~100 to 140degC.
Another was naptha and gasoline (hundreds of components) in the ~30 to 70degC range.
As the reflux ratio increased the concentration of low boiling point components increased after the condenser.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

Another thought:
Running my 4" without plates (potstill mode) but with the dephlegmator available I can hold up the nasty part of the tails for an additional flavorful quart (12 gal charge) by flowing water through the RC at the end of the run.
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
Tomb
Novice
Posts: 90
Joined: Tue Sep 24, 2013 6:07 pm

Re: fractional condensation??

Post by Tomb »

Sorry for this aside.....

Is there a link to an English translation of Barbets book?

Tom
manu de hanoi
Site Donor
Site Donor
Posts: 798
Joined: Mon Aug 13, 2007 9:06 am

Re: fractional condensation??

Post by manu de hanoi »

Tomb wrote:Sorry for this aside.....

Is there a link to an English translation of Barbets book?

Tom
no
Tomb
Novice
Posts: 90
Joined: Tue Sep 24, 2013 6:07 pm

Re: fractional condensation??

Post by Tomb »

Sorry...do you mean that you are certain an English translation does not exist?

Or that you do not know where to get one.

(Others have mentioned it as required reading)

Tom
heartcut
Site Donor
Site Donor
Posts: 2781
Joined: Tue Mar 29, 2011 9:31 am
Location: Houston, Texas

Re: fractional condensation??

Post by heartcut »

This should get you there in French:
https://books.google.com/books?id=lz5KA ... on&f=false" onclick="window.open(this.href);return false;" rel="nofollow
heartcut

We are all here on earth to help others; what on earth the others are here for I don't know.

W. H. Auden
drmiller100
Rumrunner
Posts: 679
Joined: Wed Mar 11, 2009 9:13 pm

Re: fractional condensation??

Post by drmiller100 »

manu de hanoi wrote:john2674 it doesnt work, you cant separate by condensation. Separation only occurs on evaporation, on condensation, everything condenses at once regardless of temperature.
smiles..... You completely misunderstand the theory of distillation.

If your condensor is below the boiling temperature of the lightest element, AND the condenser has "enough" energy absorption, you will condense "everything."

However, if the temperature of the surface of the condensor is above boiling temp of the lighter components, the lighter components will indeed tend to not condense.

When done, this is how a reflux still works - the water TENDS to condense out, the alcohol TENDS to not. The water TENDS to not want to boil off, the alcohol tends to boil off more quickly.

To pull partials, you COULD take a typical reflux still capable of making 95 percent. Lengthen the column 30 percent to give some "room".

Put a temperature probe in the column about 20 percent from the top of the packing (inside your "room").

Then run the still in full reflux, watching the temp of the vapor just before the top condenser, and the one part way down the column. If you have "heads" you will soon see the top of the column will have a lower temp then one 20 percent down. Pull product from the top, or pull product from 20 percent down.

Take that further, and you can take product from whatever temperature range you want. If you pull product too fast, you will get water percent coming up, your temps will plummet (by 2 or 3 degrees as a first warning).
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
User avatar
skow69
Site Donor
Site Donor
Posts: 3230
Joined: Tue Dec 06, 2011 3:03 am
Location: Cascadia

Re: fractional condensation??

Post by skow69 »

I don't see where that proves anything about fractional condensation. Your example is easily explained by the fact the heat source is at the bottom and reflux mingles with vapor to combine into a new mixture with a boiling point described by the familiar graph.

You are saying that you can take azeotrope off a CM still in a single pass by holding the reflux condenser at 86.5c, right?
Distilling at 110f and 75 torr.
I'm not an absinthe snob, I'm The Absinthe Nazi. "NO ABSINTHE FOR YOU!"
User avatar
skow69
Site Donor
Site Donor
Posts: 3230
Joined: Tue Dec 06, 2011 3:03 am
Location: Cascadia

Re: fractional condensation??

Post by skow69 »

The familiar graph.
smiles
smiles
Distilling at 110f and 75 torr.
I'm not an absinthe snob, I'm The Absinthe Nazi. "NO ABSINTHE FOR YOU!"
drmiller100
Rumrunner
Posts: 679
Joined: Wed Mar 11, 2009 9:13 pm

Re: fractional condensation??

Post by drmiller100 »

skow69 wrote:I don't see where that proves anything about fractional condensation. Your example is easily explained by the fact the heat source is at the bottom and reflux mingles with vapor to combine into a new mixture with a boiling point described by the familiar graph.

You are saying that you can take azeotrope off a CM still in a single pass by holding the reflux condenser at 86.5c, right?
Yes. You can pull 95 percent ethanol off a reflux still in a single pass.

With a batch still, I thought this all through some more. With a batch still, you will always have the lightest product at the very top, and it makes no sense to try to make it fractional.

My head is stuck in continuous stills, and with a continuous still if you want to separate the products from each other you must use fractional or make a second pass through a batch still.

So, I was wrong, and made things more confusing. sorry.
Now I know how you claim azeo so easy, it's based on a meat thermometer. :lol:
Post Reply