Meeting time Boka and brain guys.

[flyingdutchman]

Hey All,
Myles make a great point

Your energy input will liberate vapour from the wash at 45/litres/kw/min

I think for those that have it they might want to reread the complete distiller by Nixon as he covers alot of this in the section on LHV (latent heat of vaoprization) in chapter 8. This works only if we do the calculations on per MOLE because the LHV is basically the same for any component of our wash on a per MOLE basis. Now if you try and work any calculations on a per gram basis the components of your wash all have very different LHV and its important to bear that in mind if you try and do any calculations.
I do have a question/puzzle which i dont have the answer to
If we heat a full 5 gallons of wash (no matter how slowly) all at the same time given do all the foreshots and heads all come off essentially before say the hearts based on the fact that distillaions work on the partial pressure exerted by the components of the wash? In other words as we apply energy to the keg (and therfore the entire wash) to create the separation in the column wont a large portion of whats coming off be heads and conaminating any level of the column because they will come aff in a greater proportoion first. If they do all come off first and we dont...
1) Trap them with say LWTC,s idea (which I liked), which means thumpers or
2) Bleed them all off first (PP's idea which i liked), which is basically how we currently run our stills or
3) We dont create a monstorous column volume (say the equivilent of 310 1 liter coke bottles for 600 mL of heads at 1 ATM ), which nixon describes as bieng as tall as 20 stories on a commercial basis and discourages on a small still basis (pg 64)
4) Does this leave us other options beyond slowly adding incremental amounts wash to the column allowing it enough time to with a controlled take of rate so that the column is now big enough to handle the variuos fractions in gas phase letting them reach dynamic equilibrium and bleeding them all off simultaneously so that this becomes a controlled rate problem/exercise?
I honestly dont have an answer to that but would love to hear others ideas and am out of my league on this one

[Prairiepiss]

The larger volumes of vapor needed is why I'm leaning to liquid separation ie thumper/plates. You can introduce vapor separation ie packed column between these to further the separation. If wanted. This would only enhance an already good system. And if setup correctly? Product can be taken off wherever you like.

[myles]

@ flyingdutchman

Sorry but no. Even though the LHV's are different, we are talking about a MIXTURE of different components. Unfortunately some of ALL of them is evapourating at the same time.

This hapens in any still but in a reflux column we deliderately re-condense the higher boiling point fractions and send them back towards the boiler. Eventually we can accumulate for example, the heads, but they still contain ethanol. We have just changed the proportions as much as we can.

In a pot still we have even less control and need to find an energy input that allows us to remove the heads (along with significant amounts of ethanol) so that we can take a reasonable hearts cut. Get the power level wrong and either the heads or the tails can be smeared through the entire run.

Fun isn't it. This is why I like thumpers and am working (slowly ) on my own thump tower, because they give you another level of control over the pot still.

No.4 might be possible but it will be horrendously slow, possibly as a solar option?

[Frosteecat]

Would it be helpful at all to have a "vapor/steam" tank between the boiler and column, where you could hold a good quantity of vapor and bleed it slowly into the column where segments are pre-tuned for graduated condensing (I.e. a "spectrum" of gradually increasing--or is it decreasing!?!--) cooling/reflux chambers to assist in a more controllable flow of volatiles? Like a thumper without water?

[flyingdutchman]

I would have to agree. The stuff is going to be a mix of all the wash components whose boiling point will be determined by raoults law. Every time we transition from the liquid phase to the gas phase the new gas will contain a greater proportion of compounds with the highest partial pressures. When we condense this to a liquid it will have a different ratio of components (than the mother liquid) and as raoults law suggests it will have a lower boiling point as a result. So that the more condensation and evaporation cyles we go through the greater the separation based on thier partial pressures. I think ultimately the thumper idea is probably the best bet solution especially for small scale.
Personally i dont intend to build one but, I do find this model interesting.

2333_46_32-fractionating-still.jpg (13.68 KiB) Viewed 1393 times

either way i think its fun to talk about and get ideas

[myles]

Great explanation ! When are you putting together a book?

There are books I have not read yet!! Not planning on creating another one any time soon.

[Frosteecat]

Well, I think one of you pointy heads needs to alter the physical laws of the universe so we can do this already!!

[mash rookie]

Okay Cowboys, Slow down a minute. Some of us have had to work today. (With our hands and back)

FD, I am going to have to respectfully disagree. I think you are having way too much fun screwing with us. (it’s gotta be fun though) While your assertions have validity based on a limited size of continuous distillation column shown in your thread, Raoult’s law confirms that we can make fraction separation given sufficient column height. Whether continuous or batch, vapor pressures dictate that separation will occur as elevation and temperature gradient increases/decreases. I would argue that a twenty foot tall column is not necessary. I would also argue from practical experience and common knowledge that bubble cap technology has less affect on fractional separation than basic water separation.
Are you giggling?

[LWTCS]

I would also argue from practical experience and common knowledge that bubble cap technology has less affect on fractional separation than basic water separation.

How do you mean MR?

[astronomical]

But remember that just 1 mol of any substance occupies 22 LITERS of space as a gas @ OC (STP) and at 80C (1 ATM) I think it goes up to ~ 30 LITERS. Since water has a molecular weight of ~18 and a density of ~1 g/cm^3, that means that 18 mL of water occupies 30 L of space in your column at 80C. Ethanol is a little better with a molecular weight of ~46 and a density 0f ~ 0.8 g/cm^3 but still ~ 58 mL of pure ethanol will occupy ~30L of space in your column as a gas. So say you are very efficient and only get 300 mL of heads in a run (never mind foreshots) that is roughly 155 Liters of gas. Now what happens if you get 600 mL of heads? How many mL of hearts do you get? Then think about how big this thing will need to be to trap that volume of distillate in gas form.

Does this apply? how much volume of a packe column is occupied by vapor? A lot, if not most, of it is condensed liquid that is rapidly changing form from gas to liquid in a saturated vapor scenario. IIRC, phase changes can occur within a packed column without it ever ven revaporising. The molecules just trade places.

[myles]

No I dont think so. Most of the liquid in the column is just a thin layer spread over all the surface. This is different in things like SPP but they seem to be a special case. If there is too much liquid in the column it usualy leads to problems. The phase change occurs at the liquid vapour surface and evapouration is essential.

[myles]

I would also argue from practical experience and common knowledge that bubble cap technology has less affect on fractional separation than basic water separation.
Are you giggling?

MR is this a reference to the COMPOSITION of the liquid layer that the vapour is passing through? Better separation by passing through clean water than by passing through a mixture of water and volatiles perhaps?

[mash rookie]

Remember guys. The discussion is about fraction separation and the possibility of collecting them as the occur on a small scale. I am only on my second cup of coffee but here goes.
If we heat a full 5 gallons of wash (no matter how slowly) all at the same time given do all the foreshots and heads all come off essentially before say the hearts based on the fact that distillaions work on the partial pressure exerted by the components of the wash? In other words as we apply energy to the keg (and therfore the entire wash) to create the separation in the column wont a large portion of whats coming off be heads and conaminating any level of the column because they will come aff in a greater proportoion first. If they do all come off first and we dont...

I don’t believe there will be contamination of the column as the higher volatiles continue up. On the contrary. Batch distillation may be easier to attain fraction separation because fresh wash is not added as distillation progresses.

4) Does this leave us other options beyond slowly adding incremental amounts wash to the column allowing it enough time to with a controlled take of rate so that the column is now big enough to handle the variuos fractions in gas phase letting them reach dynamic equilibrium and bleeding them all off simultaneously so that this becomes a controlled rate problem/exercise?

This scenario will cause fraction contamination as heads will continuously be mixed with hearts.

I would have to agree. The stuff is going to be a mix of all the wash components whose boiling point will be determined by raoults law. Every time we transition from the liquid phase to the gas phase the new gas will contain a greater proportion of compounds with the highest partial pressures. (and less of the compounds with lower partial pressures) When we condense this to a liquid it will have a different ratio of components (than the mother liquid) and as raoults law suggests it will have a lower boiling point as a result. So that the more condensation and evaporation cyles we go through the greater the separation based on thier partial pressures. I think ultimately the thumper idea is probably the best bet solution especially for small scale.
Personally i dont intend to build one but, I do find this model interesting.

I agree. The more cycles the greater separation of fractions. The big issue we deal with on this scale is height. Period. Packing allows more evaporation cycles in a given space than plates.
HETP’s I still would like to know who coined that term.

While bubble caps and thumpers will work on a large enough scale, in practical application in the alcohol industry they are typically used (Holstein & others) for distillation of brandies and flavoured alcohols because of their ability to raise ABV without separating flavour congeners. Yes Myles.Composition but No, Worse separation of fractions because of liquid contamination.

Vodka stills typically use taller perforated plate columns that allow better fraction separation. I believe they have found that perforated plates with less condensed liquid provide greater evaporation cycles. (I could be wrong)

This is undisputable Empirical evidence. Industry example. I don’t have to understand it all to accept it. Whew. That was a mouthful. I am probably full of crap but that’s how I see it.
Alright guys. Kick my ass.

[flyingdutchman]

Hey mash,
How ah yah. I do love to joke around and sometimes ask people questions I already know the answer to but mostly thats to get them to think about the questions. Honestly im not screwing with you guys on this one. I think I wasnt specific enough The picture is a general process I find interesting because we know it works.
1) I would definitly not use bubble plates I would use packing because I believe it to be very efficient.
2) Nixon really did say that

commercial ones can be as high as 20 stories and really did discourage it for a home distillation application

But he also discouraged homedistillers making bubble plates and look at all the great stuff people have done here with those.
3) i think the problem with vapor volume is real yes some will indeed be in liquid form on the packing and we may not be at exactly 1 ATM (IDK what pressure exists inside a column I have never measuered it) and since PV=nRT increased pressure would indeed mean decreased volume since in this case nRT will be fixed (P=pressure, V=volume, n=number of MOLES, R= gas constant, T = temp typically Kelvin)

I look at this problem as a batch run and see 2 obstacles. 1= vapor volume, 2 = nature of distillate bieng in flux for a batch process
Vapor Volume
4) thats why i like the general design in the picture they control vapor volume by controlling the feed. Plus the energy source is then independant of the wash but with the spent wash at the bottom of the column is sort of recirculated until all the lower boiling point (higher partial pressure) components are gone.

distillate in flux
5) I think any system where we boil all the wash at once is going to be in state of constant flux, constantly changing exactly because the nature of the wash and thus the distillate will be changing as the run progresses from the beginning of the run point A (lots high pp volatiles) to the end point B (lots lower pp volatiles). Thats why the way we typically run batchs works so well we take advantage of that fact and work with it instead of against it.
6) I just like the idea of feeding the wash in as drawn because the nature of the wash enetring the still the now remains a constant (instead of ever changing)and beng an anal retentive chemist I like things that remain constant in complex problems. This strikes me as a simple elegant solution to a complex problem, which I feel are sometimes seem to be the best ones. plus it seems like alot of continous distillaion towers (not just alcohol) use this type of design so I feel it is probably for a very good reason.
7) I think thumpers/slant plates or some form of liquid distillate storge/capture vessels is a good idea. However now your heating the entire wash everything is in flux, the nature of what is in each thumper or slant plate collection port will change with respect to time. Sort of like a calculus problem where what we are looking at is dW/dT (change in wash with respect to change in time) . It can certainly be done i just like the idea of each tap in the column having a constant distillat composition regardless of where the run stands with respect to time dT.

what about some kind of hybrid between the two ideas ......

[flyingdutchman]

Hey mash,
sorry we both posted around the same time so alot of what i said was meant to reply to your older post not the most recent one.
Lets look at what we call heads. My guess is it is mostly ethanol with a very small component of some impurities like say ethyl Acetate (for one). By small I mean like ppm or ppb but above our perception point so that we taste and smell it and feel the effect of say drinking it (see attached PDF organic chemistry manual pg 152 for purification by distillation). Now ethanol (pure) boils at ~ 78.4 C. Ethyl Acetate (pure) boils at 77.1C. We know that compounds that have a difference of say greater than 25C can easily be purified (separated/isolated) by a simple distillation method (pot still), as their b.p (or respective pp) get closer and closer we need to use fractional distillations and progerssively an ever great number of plates to effect a reasonable separation/isolation. Based on how close these two are I would maintain that every level of that column is contaimnated with ethyl acetate until almost all the ethyl acetate is gone.
Its very important to remeber that what we draw off the top on a reflux still is not 100% ethyl acetate so we didnt really isolate the two chemical entities we just increased the ratio of EA (ethyl acetate) to EtOH (ethanol)
As an example lets look at 5 plates (the number doesnt matter for this example) at the top we have plate N,then N-1,N-2,N-3, N-4 as we go down the column. We know that because of the way a separation by distillation works, that for every cycle (liquid->gas) a greater ratio of the higher pp component escapes the liquid phase based on the ratio of the differences of thier respective partial pressures.
This is the key concept that we need to remember when it comes to distillation it is exactly how distillation works. It is not about lighter compounds wanting to rise up, in fact ethanol vapour is more dense than water vapour! (mash im not saying that you did say this but it is a critical error that many make when thinking about distillation)
So lets say at
1)plate N we have some amount/concentration of EA that i will call 100 ppm (clearly i dont know the number but its the concept here that is important) Now because of the very nature of how distillation works at plate ...
2) N-1 we have 100ppm - X amount/concentration of EA (I dont know the number but it can be calculated)
3) N-2 we have 100 pmm-2x EA (again i dont know how much but it can be calculated and may not be linnear)
4) N-3 we have 100 ppm- 3x EA
5) N-4 we have 100 ppm-4x EA
See every level/plate has EA until basically all the EA is gone its just a question of how many ppm. We never really isolated pure EA at the top so its a mix all the way down until there no longer exists any EA in the wash. As long as EA exists in the wash it must be ascending through the column and therefore must be contaminating every level in the column. PP said this way back in this thread just in different words.
it dont know if I am bieng clearer or just more confusing does this help because that is how i see a distillation in my head???
(yes thats why I asked way back about the heads I wanted to know if anyone else saw this the same way)

ps sorry it wont let me add the PDF too big but I will gladly forward it to any one that pm's me

[mash rookie]

LOL, I was typing while you posted. That gives me an opportunity to add a couple things. A few months ago we kicked around the idea of continuous distillation on a small scale. (Well, mostly everybody kicked me around when I suggested it) I drew up a simple feed mechanism and proposed a single low watt element in the base of a column. No boiler required.

The problem I could not get past was the constant mixing and probable contamination of hearts with heads by introducing fresh wash on a steady basis. The consensus seemed to be that even if I pulled off the heads at a higher location, they would be mixing with hearts on there way there making it more difficult to avoid them.

As we all know it is not as simple as heads, hearts and tails. There are a lot more different alcohols present to deal with. Some affecting flavors more that others. Etheyl acetate more than isopropal.
That thinking is what brings me here to this thread. Even though there will be a constant state of flux. That too might be more predictable than we think in practical application.

My design idea here not stated, is that each collection plate would have a two seat valve. When closed before take off it would be open internally so that no distillate would accumulate before equilibrium was established. With BTU input = vapor speed we may be able to take off and maintain the equilibrium and collect hearts and tail fractions during the run. I still think that head take off should be done first and possibly at the cost of reestablishing equilibrium before any take off.

This is fun. I have not had a chance to study the info you sent me but will soon so I can grasp your concepts better. And yes, Its okay to screw with us.

[flyingdutchman]

maybe look at it from the persepecvtive of one lonely molecule bouncing around inside a liquid. he is always moving (unless your at absolute 0) and the more you heat up the liquid the faster he moves (kinetics) and more easily escapes the liquid.
There are forces that want to help keep him in the liquid but he can escape and break free in essence he becomes a gas.
1 Vapour pressure is like a measure of how easily he escapes the liquid.
2 Boiling point is when the vapor pressure of the liquid equals atomsphereic pressure
3 A molecule in a liquid (pure) with a higher vapor pressure more easily escapes to become a gas
4 A liquid (pure) with a higher vapor pressure generally has a lower boiling point because it takes less energy for him to escape.

when we mix two components together to form a new mixture (if it is an ideal mixture) they each bring their own vapor pressure to the party. The new liquid is a combination of both so its pressure is a mix of each individual components vapor pressure which we now call partial pressues (because they are part of the whole).
1 Each component exerts its own partial pressure
2 The effect of the individual components creats a new boiling point for the new liquid (and why not the both contribute)
3 The entire liquid boils at this new boiling point
BUT
because each component exerts its own partial pressure they do not escape the liquid in equal amounts (unless partial pressures equal each other). So if one has a much higher partial pressure it escapes the liquid in greater amounts than the other leading to a separation.
See why i keeping going back to partial pressures i feel it is all about understanding how and why it works.

Its like 2 carpenters both are good framers but 1 understands why it works. The second may be a faster framer, hell i might want him on my crew. But ask the second one to build a structure design is way outside his area of expertice/rule of thumb and the results might not be so good. I feel its important to understand how aprocess works when coming up with novel designs. I would rather every one here was the 1st carpenter sure we can get azeotope but does that imply we really know how or why?

If any I said is wrong p[lease correct me I dont want to give out bad info. If anything I said dont make sense ask me or pm me I am always glad to try to help.

[mash rookie]

Its like 2 carpenters both are good framers but 1 understands why it works. The second may be a faster framer, hell i might want him on my crew. But ask the second one to build a structure design is way outside his area of expertice/rule of thumb and the results might not be so good. I feel its important to understand how aprocess works when coming up with novel designs. I would rather every one here was the 1st carpenter sure we can get azeotope but does that imply we really know how or why?


Now you are starting to make me laugh. First off, most guys here are do it yourself kind of guys and don’t give a damn how it works as long as it makes good booze. The next bunch are gear heads (like myself) that will build anything at the drop of a hat because we can, then try to figure out why it works later. Maybe ten percent care and are striving to understand. Of that ten percent will. LOL, so don’t get your knickers in a wad if guys aren’t listening. There is probably more than you realize reading along with eyes the size of saucers.

I think you have given a great description of how Raoutls law affects boiling point and better yet, offered more understanding of vapor composition. Something I have understood from observation but not fact.

FD, Take us on a journey now on how these partial pressure compounds will behave in a column. Particularly how a different mix of them will behave. Is it as simple as BP for each fraction? You have stated that specific gravity is not relevant. Does the nominal pressure in a column come in to play reducing the ability to separate? This can get complicated quickly even as I consider while typing.

Have you followed the thread where we are talking about vacuum distillation? (don’t respond to that. One subject at a time).

As fractioning columns rise, could plate spacing or in this case take off spacing have a major impact on fraction collection?

Mash Rookie

[Frosteecat]

Is this going to be on the test??

I'm desperately trying to understand this and so far all I can really grasp is that the mixing of different alcohols/other volatiles is what prevents us from pulling the "separate" fractions out individually. But I am also seeing that there really are no "pure" fractions and, ironically we wouldn't want them, as "pure and separate" distillations would remove some of the "good smearing", I.e., flavors. While we lose some of what we want to heads and tails, it is a necessary evil to attain the flavorful interplay that results in hearts. So what we are really theorizing here is a method of getting the "best" hearts out to keep and the "worst" heads and tails out to toss...right?


Right?!?

[flyingdutchman]

Ha mash,
Good one.
It would take way more than that to get my panties in a bunch

[Prairiepiss]

Ok I want to know how your gona work around the fact the a packed column is so damn slow? What are you factoring in to shorten the average 12 hour run? After a stripping run. For a clean neutral. Can you get race horse piss speed from a packed column?

I wouldn't say packing is more efficient. When you take the time it takes to run it. Yes it does a better job of scrubbing it up and handing it to you. But damn it takes so long for it to do it.

There are already examples of how just one small plate under a packed column speeds the takeoff up. And makes the packed column work way more efficient.

That's why I say a mixture of the two will be a better path.

And I don't think anyone has even touched on what packing would be the best to use?
Copper scrubbys?
Stainless scrubbys?
Etched stainless scrubbys?
SPP?
Etched SPP?
Copper SPP?

Your also talking about using LM style takeoffs. Even though most people say a VM makes for a much better hearts takeoff. So wouldn't LM takeoffs be best suited for fores, heads, and tails. While a VM takeoff would be best for the hearts?

[Bushman]

One test is worth a thousand opinions. I think MR and I are going to do some of these comparisons when I get home and finish my still. We know both designs are good and are proven, this group is great at breaking new ground.

I also know MR personally and I have met few people that are more creative than he is. Having said that I taught design engineering for over 30 years and when it came to brainstorming I had my students use pencils without erasers, also we brainstormed individually so as not to criticize a thought before we had time to think it through or test it. MR's brain is going a hundred miles a minute and sometimes I have to ask him to slow down a bit and explain. I think he has done that also I think he throws a lot out there to get us thinking, not sure why he does that as it just gets his brain going more and he already has a lot on his pallet.

[Prairiepiss]

I just want to say. Don't take my posts wrong. Ive learned a lot from this thread. And would like to continue learning from it. Sometimes I have a hard time expressing my thoughts. So I do it as blunt as I can. As not to cornfuse others with my ramblings. And many times they are questions for me to learn from. Just worded as statements. My mind is a little off kilter.

Nobody likes for me to sit in on brainstorm sessions. I get even worse.

[Bushman]

I just want to say. Don't take my posts wrong. Ive learned a lot from this thread. And would like to continue learning from it. Sometimes I have a hard time expressing my thoughts. So I do it as blunt as I can. As not to cornfuse others with my ramblings. And many times they are questions for me to learn from. Just worded as statements. My mind is a little off kilter.

Nobody likes for me to sit in on brainstorm sessions. I get even worse.

PP, my comment is in the same lines as what you are saying, the dialog has been great and we are all learning or understanding better and I believe that is what MR intended.

[mash rookie]

You have me figured pretty well Bushman. I don’t intend on building this design anytime soon. As you know I am working on other designs and builds now.
This thread was meant to inspire thought and creative thinking. By throwing out such a different concept than the norm, readers have to think a little differently to follow the thread.

I am Very pleased to have FlyingDutchman involved and bringing real information and science to bear. There is already more speculation on this site than in a Sci Fi novel.

My hopes are to continue this design discussion through to a point of understanding what is really happening in the process and the possibilities that knowledge may provide.
If FD is willing to take the time to explain the science to a knucklehead like me, I am taking a seat in the front row of the class.




BTW BM, I got enough work done yesterday I could do cleaning runs on the four and six today if I wanted. You better get back soon or I will have to finish your build just to get it out of the way.

[Frosteecat]

There are already examples of how just one small plate under a packed column speeds the takeoff up. And makes the packed column work way more efficient.

OH? Is there a thread or a specific name for that? I'm designing a "combo" reflux setup and would like to see the ideas working together!

[mash rookie]

"How does packing affect the space between plates where phase change occurrs? Say you put packing in the drains, or standpipe? Could a combo of packed sections in addition to liquid bath or maybe fluidized bed be the solution to a shorter neutral column. Think about Nixons paper!!!! Is it possible to take advantages of both alcohol detainment in addition to efficientcy of packing for seperation? Why must it be one way or the other, the answer lies in a combination of both technologies."

One thing at a time Rock.
First, comprehending scientifically what is happening is the conversation. I think once we get a little better at understanding partial pressures and their behaviour we will be in better position to explore different methods of separation.

"Ok I want to know how your gona work around the fact the a packed column is so damn slow? What are you factoring in to shorten the average 12 hour run? After a stripping run. For a clean neutral. Can you get race horse piss speed from a packed column?"

PP, A two inch column is slow. Not the packing. Do you recall my experiments removing my plate tree and replacing it with packing? With only 24” of packing I was able to take off at 90% with the same speed as with my plates. The product had a noticeably cleaner taste than with the plates. What does that tell us? HETPs is a legitimate term.

Everybody needs to try to wrap their brain around the concept of fractions as being explained by FD. This is not a discussion about raising ABV. Hang in there guys, We’ll get there. I am not understanding everything he is saying but I am starting to get a little. Google Raults law and partial pressures. Even the simple wikipedia definition is helpful

[flyingdutchman]

Hey sorry for not checking back sooner.
Someone poured molassess and sugar in my best drinking water and I was up till 2am last night trying to purify it
1) Ok I think sometimes when i write things I say alot but dont really make myself clear.
When I said i thought packing (scrubbers) were very efficient what I meant was that we get a large number of theoretical plates per linnear foot of column. So we get maximum separation in minimum linnear distance. I believe on the parent site he lists it as something like every 4 inches (scrubbers).
I dont mean to imply plates dont work(they do and well) its just that 6 inches pretty much seems to be the absolute minimum spacing distance i see in any text and longer spacing than that seems to be more common. Even then I wonder if 1 physical plate does not give less separation than our 1 theoretical plate (so again it just needs to be longer).
2) I dont know if 1 type of plate vs packing is faster or slower, I truly have no idea and have no experience or knowledge of this but it is an interesting subject.
I would think a combination of both types would work fine and in fact once we get to 4" or larger we probably need a way just to hold the packing in place if I remember right.
I would think that the column diameter would play a huge part in the sheer volume of material you can purify at once. He lists the maximum wattage fo a given column diameter on the parent site here
http://homedistiller.org/theory/refluxdesign/diameter
From this i take away that with greater column diameter we can add greater heat/energy (w/out flooding) so we get increased rate of refluxing and distillate volume which should result in a shorter purification times (again Im not saying the stuff about the speed of plates is wrong I just dont know)
3) Rock I think I have ther paper your refering to but in all honesty I have to reread it.

[Prairiepiss]

There are already examples of how just one small plate under a packed column speeds the takeoff up. And makes the packed column work way more efficient.

OH? Is there a thread or a specific name for that? I'm designing a "combo" reflux setup and would like to see the ideas working together!

I can now. It's only in the first stages of testing. But looks pretty promising to me.
http://homedistiller.org/forum/viewtopi ... 17&t=29940

[Frosteecat]

Ha ha ha! Good one PP! Saved me from that nightmare of an egghead convention...