Why you can't control a still with boiler temperature

[ammo man]

---Mod edit---
This is a common conceptual problem that you've got to wrap your head around to really understand what is going on in your still, and the reason that you can't use a temperature controller on your boiler - it must be a power controller. The following is a conversation between ammo man and a range of others (hope you don't mind bert ). It's a good conversation to learn from, as the answer was explained in lots of different ways by lots of different people, so new distillers should be able to get the general idea from it. Copied posts follow. Further reading links at the end of this thread.

Original Threads:
1: http://homedistiller.org/forum/viewtopi ... =1&t=16281
2: http://homedistiller.org/forum/viewtopi ... =1&t=16304

---Original post---

I must be missing something here. Since I ordered my router control to control the heat of my hot plate that I use in pot distilling, I have been reading everything I can find on the home page and by searching the posts relating to temperature in pot distilling which by the way is a lot. But I cannot find anything on controlling the temperature of the heating element. Everything is about the temperature of the vapor.

It is my understanding that ethanol alcohol boils or vaporizes at around 78.1C which changes according to elevation and barometric pressure which I understand. Why cannot one tweak the heat of his heating element by using his alcometer to determine when his output is pure ethanol alcohol from a pot distiller which as I understand is 95.6% abv without chemical treatment? I fully understand as you are heating the wash to that temperature you will distill all the fusel alcohols that boil or vaporize at a lower temperature, but after you reach that temperature, everything thereafter will be pure ethanol alcohol.

The reason I am pot distilling is because I want some flavor in my drink, and I do understand that pure alcohol is tasteless and odorless. What I am leading up to is why can't I by experimentation find a temperature for my heating element that will produce say an 80% abv which from what I read is about where the flavor begins, or for that matter a less abv according to my taste? I know that there are a lot of factors to consider, but for a given recipe you usually have the same % abv in each wash, and once you have found your temperatures one time, then there would be very little fine tuning you would need to do to adjust for different barometric pressures, and so forth.

I know that some, if not all, of you old master distillers are thinking why the hell I just don't do my cuts until I get what I want. More than likely this is what I will end up doing, but heck, nothing ventured, nothing gained. Why not tread new ground, or do something that is not usually done. And I do like to experiment.

If my reasoning above is not correct, I earnestly ask that you correct me. In any event all comments, negative or positive, are welcome. Thanks in advance.

Bert

[LWTCS]

Temp of the element/wash is a non issue really as the alcohol content will dictate the wash temp. As the alcohol depletes, the temps will automatically want to rise as the ratio between alcohol and water changes. Adjusting the element to a lower setting may mean (at this point of the run) that you may stop your output.

Better to install steady input an make (controller) adjustments according to the thickness of your (output) stream.

Hope I read your question correctly.

[Dnderhead]

first,, you can not control the temps. of neither the wash or the vapor, this will depend on the amount of alcohol in the wash/mash and the vapor, next ,,very doubtful you will git 80% alcohol the first run, more like 2-3 runs to achieve that in a pot still.this will depend on the % of wash/mash you put in the boiler.and how fast you run.

[ammo man]

Thanks for your speedy responses.

I guess I am not thinking straight, or understand some of the theory. I do not want to control the temp of the wash nor do I want to control the temp of the vapor per say. I want to control the heat of my element. The way I am thinking is that if my heating element is say 80C, I am applying 80C of heat to the wash. Anything in that wash that vaporizes at 80C or less will then vaporize. After all of the 80C or less stuff is drawn off, then no more vapors and no more output. I don't understand how my wash can become hotter or less than 80C nor my vapor can become hotter or less than 80C if that is the heat I am applying.

Please explain. Thanks again in advance.

Bert

I would use the alcometer to measure the %abv of the output to determine what to dial in.

[LWTCS]

I don't understand how my wash can become hotter or less than 80C nor my vapor can become hotter or less than 80C if that is the heat I am applying.

The boiling point of water is 212 and the boiling point of alcohol is 173.

A 12% (or 14 or 8 for that matter) wash will not boil at 212 or 173. It will boil at some point/temperature in between.
Once the liquid reaches its boiling point it will vaporize,,,,,,and exit the boiler. If the element is 250 degrees the boiling temp of the liquid will still be somewhere between 212 and 173. If the element is 350 degrees the boiling point of the liquid will still be somewhere between 212 and 173. All the while exiting the boiler.

No matter what the temp of the element is, the boiling point of the wash is always somewhere between 212 and 173

No such thing as 300 degree boiling water (as an example).

Am i saying this the right way?

[kiwistiller]

Yup, in a nutshell, you can't control the boiling point of a mixture of fluids. It will boil at whatever it pleases, and that will increase as the mixture changes.

Here is a picture that might help? or might not. It is a graph showing how the boiling point (and therefore vapour temp) changes over the course of a run, as ABV in the boiler is dropping. click on it to expand. The blue line is the liquid mixture of ethanol and water (wash, for example), and the red line is the vapour mixture that will result from boiling it. Yellow lines on the graph explain how to read it.

The way boiling points work is that at temperatures under the boiling point, you produce next to no vapour. And you can't go over the boiling point, all it does is boil faster when you apply more heat (can't get liquid water at 101*C, it will just turn into steam at 100*).

Does that help a bit?

[ammo man]

I tend to be on the "hard headed" side. I'm just gonna have to wait until my router control gets here and test it.

I understand what you all are saying about the boiling point of the wash, but I am not interested in the boiling point of the wash. I am interested in the boiling point of ethanol alcohol. Unless the laws of chemistry have changed since I studied them many years ago, If the boiling point of ethanol alcohol is 71or so degrees C, then when that temp is applied, it will boil. Don't care what it is mixed with. Why should I worry about the wash boiling or not? As I said above I am not interested in that. I am interested in the boiling point of the alcohol.

BTW I am not from Missouri, the show me state. I am from Texas, the you gotta prove it to me state.

Bert

[kiwistiller]

You should care about the boiling point of the wash and not the boiling point of the ethanol that is part of it, because NONE of the mixture will boil until you reach the mixtures boiling point.

Example:
you have a boiler charged with 10% wash. This is going to boil at roughly 90 degrees C. Lets say you hold the temperature of the mixture at, what, 85C to be safely above the boiling point of the ethanol in there, around 78 or whatever. Nothing will boil, because it is below the boiling point of the mixture. It will steam a little, like a cup of hot coffee, but won't truly boil.

Analogy:
You know how you add salt to boiling water to raise the temp that it is boiling at when you're cooking pasta? Same thing. When stuff mixes, the rules change.
If you aren't a cook and don't know about the salt thing, it is also the same principle at work when you add antifreeze to your car radiator- it mixes, and then lowers the freezing point. Incidentally, it also raises the boiling point, which is good in summer.

I don't get the bit about states, but I suppose if I have to ask I'll never know

But yeah, if you want to try it, go for it

[LWTCS]

Yes Bert,

The alcohol will blend/dilute very nicely with water.
It's not like an oil slick that will stay stratified.

[Dnderhead]

To put it simply,it is much like boiling potatoes,you bring it up to a boil then turn it down to a simmer.then just leave it there.
the temps.will take care of themselves.

[MuleKicker]

I think i know what your asking bert, and it doesnt work that way. Your saying, why cant you hold the wash at say, 80c through out the run and just get the alcohol. Once your temp gets to 80 and you deplete that level of alcohol, the vapor trail will taper off, your wash will remain at 80, but nothing will be coming out the other end. I used to have this way of thinking, once you start playing with yer rig, you will understand completely. Chasin temps dont work. Its all about heat input. Temp readings are just a novelty. (maybe a way to judge alcohol content in wash/vapor, not control it. )

[ammo man]

From http://homedistiller.org/" onclick="window.open(this.href);return false;" rel="nofollow Under Distilling > Distilling the Wash and down to Using the Pot Still we have:

Using a Pot Still
A pot still is fairly straight forward to use. Turn it on. Once the temperature is up to about 60 °C turn on the cooling water to the condensor. Make sure you throw away the first 100 mL per 20L wash, as this will contain any methanol that might be present. Segregate the distillate into 500 mL lots as it comes off. Only keep (for drinking) that which doesn't contain fusels (smell off) - probably below about 92 ° C, however you should keep distilling past here, untill about 96 ° C, as this fraction, although high in tails and not good for drinking this time, can be added back to the next wash and cleaned up OK then.

Graham describes using his ...
I single distill as I have no need to purify my spirits. The concentration at the top of the tower can be controlled with how much heat i apply at the bottom. If I want a pure spirit, I apply a low heat and can run it off at over 90%. with a bit of a twig I have hit the magical 97.5%. But you get utterly no flavours. I apply more heat, so I get a run at about 70 to 80% and get the flavours I need. Its true people, about about 80% you start to lose flavours.

I normally cut my runs when the alcohol drops to about 40%. The heat put in compared to what I get isn't worth it.

Someone pointed out to me that Graham said "the top of the tower" so he must have been talking about a reflux still. I sort of find this hard to believe since it is under "Using a Pot Still". Would someone please explain the above to me?

I am beginning to see a little light at the end of the tunnel when antifreeze and salt were mentioned, but I still got to see for myself. As soon as my control device gets here I will run some experiments to convince myself one way or the other.

Bert

[MuleKicker]

97.5%? Thats not possible. Also he could be talking about the "tower" as the top of the still, before the lyne arm? Not sure on that one. Where did you find that quote?

[rad14701]

That is just one of many inaccuracies on the parent site... Unfortunately, we don't have permission to make changes to what is becoming antiquated information over there... The information you have been given multiple times here is the accurate truth, however, ammo man...

[kiwistiller]

I believe the post in the parent site was probably talking about a power management reflux column - tall packed uninsulated pot still. run it slow enough and the passive heat loss will make it behave like a forced reflux still. They're notoriously difficult to run, and he isn't really talking about the same thing as you.

[ammo man]

Thank you rad. As I said I am beginning to see just a little light at the end of the tunnel.

I want all of you to clearly understand that I am not for a minute implying that anything you have said is not true..

It is just that my old mind does not work as good as it did many years ago. I have always been slow in my thinking, but usually in the end I fit the pieces of the puzzle together. However, I still am going to do some experimenting to fully convince myself.

To answer kiwistiller question about the states. I meant that I do not always believe what I see. Sometimes I need proof. And for that matter I learned many, many years ago not to always believe what I read.

Thanks fellows.

Bert

[kiwistiller]

No worries mate, sometimes you gotta rotate the piece of the jigsaw by hand before it falls into place. Besides, tinkering with stills is awesome.

[rad14701]

No time tinkering with stills is wasted time... Almost seems like a miracle every time that first drop of alcohol comes out of the still...

[ammo man]

Gentlemen: I want to thank all of you again. The following is stuff I knew many years ago, but the brain cells containing this information went into a deep sleep because of lack of use. Those sleeping brain cells are now for the most part awake because of your help although still somewhat drowsy. I am happy to report that I don't think many of the cells have died over the years.

The following is taken from

http://www.chemguide.co.uk/physical/pha ... d.html#top" onclick="window.open(this.href);return false;" rel="nofollow

and will give a partial explanation of how distillation of water and ethanol works in any type of still for you that are interested.

A large positive deviation from Raoult's Law: ethanol and water mixtures



Using the diagram

Suppose you are going to distil a mixture of ethanol and water with composition C1 as shown on the next diagram. It will boil at a temperature given by the liquid curve and produce a vapour with composition C2.



When that vapour condenses it will, of course, still have the composition C2. If you reboil that, it will produce a new vapour with composition C3.



You can see that if you carried on with this boiling-condensing-reboiling sequence, you would eventually end up with a vapour with a composition of 95.6% ethanol. If you condense that you obviously get a liquid with 95.6% ethanol.

The above is obviously only a partial explanation of the distilling process of water and ethanol alcohol. Go to the above listed site to get a much more detailed explanation if you wish.

Thanks again.

Bert

[rad14701]

Umm... That's what we've been trying to explain to you... Most all of us who were trying to help you have read all of that, and more, from more than one source already...

I think the issue at hand is more related to whether running a pot still or reflux still than the theory itself... You can control the vapor temperature in a reflux still, via heat input and reflux, but you can't do that with a pot still unless it has a lot of passive reflux, such as when using an upward angled lyne arm or some other means... But even then you can't fully control the vapor temperature in the pot still because of the change in the water:alcohol mixture ratio...

This whole debate goes round and round what seems like a couple times a year and always ends the same... It's physics rearing its ugly head again...

[ammo man]

rad wrote

Umm... That's what we've been trying to explain to you... Most all of us who were trying to help you have read all of that, and more, from more than one source already...

I fully understand that rad, but as I stated "my brain cells relating to this were asleep". It just did not register. After a good nights sleep and reviewing the chemistry and physics of this on the Internet, the "cells finally woke up". I now remember and understand.

I only posted the graphs and some of the theory in a slightly different manner in hopes that it would help someone, obviously not you fellows that helped me because you already understand, but others. To me the object of forums like this is to help each other. You all helped me, and I, in turn, am trying to help others.

Bert

[kiwistiller]

Futher Reading on this topic:
http://www.chemguide.co.uk/physical/pha ... d.html#top" onclick="window.open(this.href);return false;" rel="nofollow - good science based explaination of the background physics, but not too hard to understand. A little more info than you need for our purposes, but solid info. Especially relevent is this page: http://www.chemguide.co.uk/physical/pha ... l.html#top" onclick="window.open(this.href);return false;" rel="nofollow

Wiki. No, really. http://en.wikipedia.org/wiki/Distillation" onclick="window.open(this.href);return false;" rel="nofollow this section and a lot of the things you can link to from here can help out a bit, look at batch distillation, and Raoult's law, fractional distillation, etc.

This thread: http://homedistiller.org/forum/viewtopi ... =1&t=16305 A bit heavy in places, but some interesting info leading on from the basic concepts in this thread.

Mother Earth Alcohol Fuel book: Thanks to OD for posting this elsewhere. The first few paragraphs of this section sum up the concept quite well. http://journeytoforever.org/biofuel_lib ... 7.html#7-1" onclick="window.open(this.href);return false;" rel="nofollow

And of course, if you still don't get it, feel free to ask in the open forums.
Kiwi