Tell me why this design wont work

[xahvres]

Hello everyone. My first real post here! (and I hope its in the right place...)

I've been thinking about a simple LM setup and I've come up with something that seems too easy, so there must be something I'm missing, but since most the LM talk here is about Bokas and this is different, I havent really found an answer. It is very similar to the large fractioning columns they use in oil refining, as far as I know.

I did a quick sketch of what I'm thinking about:

quick sketch

How it works: 100% of the vapour coming off the column is condensed after a U bend with a vertical condenser. A "T" and gravity makes sure the condensate hits the needle valve first. The needle valve sets the amount of liquid to go back into the still. The reflux pipe has a U-trap shape (marked "A" on the diagram), to insulate against the slight pressure from the still. If the reflux is less than 100%, then the small space above the valve fills up, and the overflow comes out as the offtake.

Seems very simple, too simple. The fact that we regulate the reflux (and it being constant if we dont move the valve) and not the takeoff eliminates one of the big problems with LM systems, the transition from hearts to tails. It only needs one condenser, and you dont even need to really regulate it.


The only pitfall I could see is if the pressure in the still is larger than I thought, then the U-trap would need to be very large and hold a lot of liquid.

So, anyone has tried something similar? Is there something basic I'm forgetting? What are your thoughts?

[Yummyrum]

The technique you have there is known as RLM or Reverse Liquid Management .
It was tried back in circa 2008-2010 period in this forum .

The method had merit in theory but never took off .
I don’t know why . Maybe folk just get stuck on an idea and an LM was it .

Having said that , when I made my still , I made it so I could try LM , RLM and VM
I started with LM ,which sucked , moved to VM and fell in love , and never bothered with the RLM .

Maybe its worth a crack , don’t know , VM so easy IMO

[Saltbush Bill]

Was sitting here looking at the diagram earlier,.....cant say I remember ever noticing the RLM idea before.
Cant really see that either way makes a lot of difference to the final product......just seems easier to regulate whats leaving the still , rather than how much reflux returns to the boiler.
There is a lot more reflux going back to the boiler than product being taken.......is the average needle valve going to cope with that much returning reflux.
Needle valves ain't cheap, the smaller you can keep them the less expensive the build is.
Some discussion on the basic idea here ~~~~~~~~~> viewtopic.php?f=17&t=8549
Edit:
From that old thread..... some one else thought the same it seems.

I'd be more inclined to worry about a needle valve not being able to handle total reflux volume and therefore having unintended product take off

[xahvres]

Thanks! Now I have a phrase to search for.

I'm probably gonna try this setup, since I already have one condenser and dont really wanna build another, especially because I have a much smaller array of parts to chose from here.

Something else I thought about. The "riser" above thr column, it would be relaly nice to be able to get away with a thinner pipe. My condeser is 15mm (13mm ID), if I use the same for the riser, is there a chance for the vapor speed to be great enough to not let the reflux come back down, and just be taken up by the vapor? I'm running aroun 1000-1500 watts with a 22L boiler.

To Saltbush Bill:

There is a lot more reflux going back to the boiler than product being taken.......is the average needle valve going to cope with that much returning reflux.

I'm gonna build my own "needle valve" based on some discussion here (from the Boka build wiki post). The sizes I'm looking at should be enough I think.

Cant really see that either way makes a lot of difference to the final product......just seems easier to regulate whats leaving the still , rather than how much reflux returns to the boiler.

Isnt it one of the big downside of LM systems that the reflux ratio changes as the boiler content changes? As far as I understand, wouldnt this work like a CM, where if you start to hit tails then the offtake slows, but the reflux stays the same?

Edit: Thanks for the thread link. Read through it, some nice info there.

[contrahead]

The only pitfall I could see is if the pressure in the still is larger than I thought, then the U-trap would need to be very large and hold a lot of liquid.

By “large” I hope you don't mean an increase of pipe diameter, as that would make no difference. You could just extend the length of the pee-trap (construction plumbing vernacular) a little bit. Why not do something like this ?

As far as pressure goes, I wrote the following, quite a while back when discussing water turbines. I ain't going to bother converting it to metric.

“* Water head can be thought of as the weight of water in a static column. Since fluids don’t compress, the weight of water in a pipe is directly related to its pressure at the bottom (measured as psi or pounds per square inch). As a stream drops in elevation its head is a measurement of that drop. Water weighs 62.427 lbs per cubic foot. There are 1,728 cubic inches in a cubic foot. A cube of water 12” high, 12” wide and 12”deep would have a psi of ((62.427 / 12) /12) or 0.433 lbs. per square inch. Any column of water 1 ft. high, regardless of width, still has a water head of 1 ft. and a psi of 0.433 lbs/in². Water drop is simply multiplied by the constant 0.433 to determine the potential psi.”

[Setsumi]

It looks like RLM at first glance and if your return to the column is sized appropriately it will work as RLM initially. But when your reflux start to taper it will just be LM without the ability to increase the reflux because your refluc return will be restricted. At first glance it it ingenious but thinking on return vs take off it is questionable.

[shadylane]

The design makes me wonder how much effect the reflux temp would have on the column.

[StillerBoy]

Base on the diagram, how will it reflux.. refluxing of vapor takes place within the column under a control vapor management and prior to the product condenser not after.. after that the distillate is only being recirculated at the same abv and that not refluxing.. that could be why it never took off..

Mars

[Setsumi]

The problem with this design is there is only one condensed reflux return path. In a normal LM your condensed reflux returns from your resivour to the packing. In RLM it still apply but your take off runs to the packing as well until you throttle it for take off. It is supposed to balance the take off with to reflux ratio.

Edit. The design in this thread does not have a unrestricted reflux return path to the column, only via the take off. In this design you will either have zero take off or starve the column.

[shadylane]

I can see where the valve adjustment could be problematic.
It would be ass backwards from a normal LM and I suspect have negative stability.
In other words, you would have to constantly dick with the valve to balance the takeoff rate vs ABV

[Setsumi]

If he put a reservoir or collection cup where the valve is with unrestricted refux return to the column and a take off from the collection either normal LM or RLM then it will work as long as the condender can handle the vapours.

[xahvres]

Wow, lots of replies to go through!

It looks like RLM at first glance and if your return to the column is sized appropriately it will work as RLM initially. But when your reflux start to taper it will just be LM without the ability to increase the reflux because your refluc return will be restricted. At first glance it it ingenious but thinking on return vs take off it is questionable.

My reflux is as restricted as I choose it to be with the valve. If the valve has enough flow capacity, it will be able to reflux 100% at any time, no?

The problem with this design is there is only one condensed reflux return path. In a normal LM your condensed reflux returns from your resivour to the packing. In RLM it still apply but your take off runs to the packing as well until you throttle it for take off. It is supposed to balance the take off with to reflux ratio.

Edit. The design in this thread does not have a unrestricted reflux return path to the column, only via the take off. In this design you will either have zero take off or starve the column.

Why does it matter where the reflux comes back from? In a Boka, some evaporates from the slanted plate, the rest overflows back to the column. Here its like I can choose how much overflows, and just take the rest. Granted theres no evaporation and the liquid returns ice cold, but the boiler should deal with that?

Base on the diagram, how will it reflux.. refluxing of vapor takes place within the column under a control vapor management and prior to the product condenser not after.. after that the distillate is only being recirculated at the same abv and that not refluxing.. that could be why it never took off..

Mars

Well, it refluxes like anything else really. The condensate returns to the top plate, same as it would in a CM still in full reflux. Only difference is therey liquid may be taken out of that "downflow" of condensate.

[LWTCS]

Base on the diagram, how will it reflux.. refluxing of vapor takes place within the column under a control vapor management and prior to the product condenser not after.. after that the distillate is only being recirculated at the same abv and that not refluxing.. that could be why it never took off..

Mars

My thoughts also,,,,,based on the diagram.

Also, why waist so much cooling capacity sending what would otherwise be cooled, finished distillate back down to a low position on the gradient only to surely disrupt colum behavior,,,,,based on the diagram.
You will essentially be over promoting several inefficiencies.
Waisted heat.
Waisted cooling
Bad column behavior
Reduced collection speed.

Best send back partially cooled reflux to a position on the column that won't kill the gradient.

[Yummyrum]

The key thing that keeps coming up is reflux that is too cold .I guess when we see an external condenser , we all assume it will be cooling to parrot reading temps . Fare call .

But is the distillate that exits an LM at parrot reading temp ? Generally no . And there have been several product coolers added to LMs to cool it down .

So , why not just run this external RC so that it runs hot (by controlling coolant flow ) , just like an LM . Then the reflux hitting the packing or top plate would be pretty much the same temp as if it was in internal RC .

And maybe that collected product is a bit hot and needs further cooling before it hits a parrot iff’n thats a thing .

I don’t see why this design can’t work . Maybe its not the most efficient or effective , but it will work in my opinion , as long as the RC doesn’t overcool the reflux .

If I was doing RLM , it would use an internal RC , reflux collected in cup and feed outside to valve before re-entering above packing via a trap .

[StillerBoy]

If I was doing RLM , it would use an internal RC , reflux collected in cup and feed outside to valve before re-entering above packing via a trap .

That's what an offset (Nixon Stone) condenser does, and the two values at the condenser become a pain in the ass to operate.. there are much simple and efficient design now a day..

I don’t see why this design can’t work . Maybe its not the most efficient or effective , but it will work in my opinion , as long as the RC doesn’t overcool the reflux .

I've yet to read of someone making it work successfully, successfully meaning having the ability to manage the refluxing to produce and manage the ABV level that properly built reflux column should do..

Mars

[StillerBoy]

My reflux is as restricted as I choose it to be with the valve. If the valve has enough flow capacity, it will be able to reflux 100% at any time, no?

No.. all the valve will be doing, based on the diagram, is recirculate the distillate..

Why does it matter where the reflux comes back from? In a Boka, some evaporates from the slanted plate, the rest overflows back to the column. Here its like I can choose how much overflows, and just take the rest. Granted theres no evaporation and the liquid returns ice cold, but the boiler should deal with that?

The statement is base on assumptions.. you ask, we're stating that it will not work, that is coming from experience operator and builder of units, yet having no experience in operation of reflux column, hold on to your view.. what the statement say it there is major lack of knowledge and understanding of vapor behavior, and not discounting how to manage the vapor behavior..

Mars

[Setsumi]

The problem with this design9 is there is only one condensed reflux return path. In a normal LM your condensed reflux returns from your resivour to the packing. In RLM it still apply but your take off runs to the packing as well until you throttle it for take off. It is supposed to balance the take off with to reflux ratio.

Edit. The design in this thread does not have a unrestricted reflux return path to the column, only via the take off. In this design you will either have zero take off or starve the column.

Why does it matter where the reflux comes back from? In a Boka, some evaporates from the slanted plate, the rest overflows back to the column. Here its like I can choose how much overflows, and just take the rest. Granted theres no evaporation and the liquid returns ice cold, but the boiler should deal with that

The design has the potential to starve the column. Myself would put a collection cup in place of the valve, but if you continue with the valve you will need to size your take off to 1/2 to a 1/4 of the diameter of the return to the column. This will help feeding the column but you will have a large pool of condensate that will increase smearing.

If you could get it to work for heads collection you could turn it into a potstill for a full flavourd hearts collection on the fly, or so it seems.

[StillerBoy]

If you could get it to work for heads collection you could turn it into a potstill for a full flavourd hearts collection on the fly, or so it seems.

What you are referring to is operating a reflux column in hybrid mode.. compression of the heads, pot stilling the body, then back to compression of the early tails.. for this method to work well, one has to use a short column packed with marbles, best of both world.. I seldom use my pot setup any more, as all my flavored products are done using this method..

But what the OP has in mind, it will not work, as there are too many issues with the design, even if they could be address, there are much simpler and efficient designs today.. the concept is old school, many issues, similar the offset condenser, and yeah it does work, but complex to operate compared to the new design..

Mars

[xahvres]

Thanks everyone for the replies!

I suspected there's something I'm not seeing here (hence the thread name).

Seems like the cold reflux will be the bane of this setup. I'm definitely not experienced enough to run a fiddly still, so probably any type of LM is out of the question now. If I had to build another condenser then I'd rather just go with a CCVM, easier to operate and build it seems. I ruled it out before because all the vendors here seemed to only sell soft tubing in 25m spools, but I found one that sells by the metre, so thats nice. Fortunately this site is chock full of CCVM threads and plans, so I probably cant go wrong there.

[Setsumi]

If you could get it to work for heads collection you could turn it into a potstill for a full flavourd hearts collection on the fly, or so it seems.

What you are referring to is operating a reflux column in hybrid mode.. compression of the heads, pot stilling the body, then back to compression of the early tails.. for this method to work well, one has to use a short column packed with marbles, best of both world.. I seldom use my pot setup any more, as all my flavored products are done using this method..

But what the OP has in mind, it will not work, as there are too many issues with the design, even if they could be address, there are much simpler and efficient designs today.. the concept is old school, many issues, similar the offset condenser, and yeah it does work, but complex to operate compared to the new design..

Mars

My view is actually along yours... although myself see a bigger problem that the column will starve and smearing.

My comment on potstill on the fly was just to present a positive on the design. Then again one can have a less complicated potstill, right?

[Setsumi]

Thanks everyone for the replies!

I suspected there's something I'm not seeing here (hence the thread name).

Seems like the cold reflux will be the bane of this setup. I'm definitely not experienced enough to run a fiddly still, so probably any type of LM is out of the question now. If I had to build another condenser then I'd rather just go with a CCVM, easier to operate and build it seems. I ruled it out before because all the vendors here seemed to only sell soft tubing in 25m spools, but I found one that sells by the metre, so thats nice. Fortunately this site is chock full of CCVM threads and plans, so I probably cant go wrong there.

Yes CCVM is easy to build and run. I run my flutes on CCVM. Myself would like a vertical CCLM... just because i like LM. Manu did a CCLM before DAD300's CCVM but it is at a 45 deg angle.

[StillerBoy]

I'm definitely not experienced enough to run a fiddly still, so probably any type of LM is out of the question now.

It really does not matter, within reason, what type or style of reflux column unit it will be, they are all "fiddly" to to a beginner, as they all operate on the same principle..

It would also be wise to study how a reflux column operation before constructing a unit, as that will give you some insight as to what type/style would be more appropriate for your needs before building one.. just because it seem easier to build it still doesn't mean it's the unit for your needs, be mindful of such..

Here's a link that should develop understanding of what is required for a reflux column..
viewtopic.php?f=17&t=80995&p=7639446#p7639446

Mars

[Oatmeal]

Maybe this post could be called tell me why this might be a pain in the butt to build and run? It'll likely run but is not necessarily an elegant design. Some Still Designs .

As someone who runs a boka, it is....pretty easy to run. And was straightforward to build! A sight glass can really help understanding how much distillate is returning (reflux ratio). A good packing, and a nice column height (minimum 36ish inchesish (/20ish times your column diameter)) and you're off to the races.

Anyways, go hog wild! Nothing like running what you built and getting something out of it. Your still head won't hesitate to teach you what you did right or wrong, and what might be better next time....

[Saltbush Bill]

I'm definitely not experienced enough to run a fiddly still, so probably any type of LM is out of the question now.

I think your over thinking things and falling for the bullshit of a few self professed "Reflux Gurus" who like to make running a reflux still sound like some sort of cross between witch craft and rocket science.
Dont be scared off by that stuff......you could teach the average 12 year old to run one in 15 minutes if need be.
LM stills are probably one of the easiest of reflux stills to run, they will run quite happily over a wide power range as long as you don't try to draw product off to fast or over power them.
As with all things go slow to begin with " learn to walk before trying to run."
One thermometer is helpful in that it can tell you if you are drawing off product to quickly ..or if tails are on the way, having said that you can run one quite easily just by taste with no thermometer or by taking samples of ABV as the run progresses.
Multiple thermometers are NOT necessary in any way.
Id also disregard all the talk of running semi flooded that's been going on in another thread if that is scaring you off........its also over complicating things to a huge extent and completely unnessary.
After having a better look and doing more thinking about the design you put up I can see that it has a lot of problems.....in the end it would just be much easier to build a Boka of which there is a couple of versions ...not all use slant plates.......the other alternative would be VM.

[StillerBoy]

think your over thinking things and falling for the bullshit of a few self professed "Reflux Gurus" who like to make running a reflux still sound like some sort of cross between witch craft and rocket science.
Dont be scared off by that stuff......you could teach the average 12 year old to run one in 15 minutes if need be.

Why, an experience person, would make such a commend is beyond my understanding..

Yeah, one maybe able to teach an average 12 yr old to run one, but he will not have any understand of what he's doing.. you yourself have stated, on several occasions, that to operate a reflux column at 95%, requires extra effort vera operating one that produces only 92- 93%.. so why misguide and not state that the basic are simple, but to learn to operate the unit at 95% requires knowledge, understanding and experience..

The OP has little to non of that, yet he is of the view he does, and just confusing him even more.. after all, an LM, VM or CCVM all have the same requirements when it comes to reflux column needs and operation, length, packing, and an RC, it's just the take off mechanize that's really different, and that the part that confuse people through their lack of reflux column knowledge..

Mars

[Saltbush Bill]

Stillerboy your obsession with people having to know every tiny detail of how a reflux still works intimidates more people than it encourages, the post above by xahvres is a perfect example of that. That in its self is not good for this hobby or this forum.

Yeah, one maybe able to teach an average 12 yr old to run one, but he will not have any understand of what he's doing..

People operate all sorts of equipment world wide on a daily basis quite successfully without understanding exactly how every aspect of that machine works, in many cases they don't even have any concept of the theory behind what makes that machine work.
Hell, astronauts fly to the moon and back and I'm sure they don't know exactly how every component of a rocket/spaceship functions, yet they mostly manage to return to Earth.

you yourself have stated, on several occasions, that to operate a reflux column at 95%, requires extra effort vera operating one that produces only 92- 93%

Yes but when I do comment it is in 95% of cases about bad still design that causes failure to achieve Azeo.....not usually about bad operation of the still......Give a newbie distiller a well set up reflux still and 99% of them will have it working perfectly and with ease after a very short time and with little prior experience.
To do that , they don't need to know every tiny aspect of what makes the still tick and why it works that way.
If the still is right then they need only some very basic operating instructions and that is all.

If the same newbie wants to build a Azeo producing still then he will need a bit more of that knowledge, but again not ever tiny aspect. He will need to know a few basic rules, column length , packing, what types of take off valves and sizes, also a little about power sources, gas or electric....wood fire for that matter......not much more than that......again he wont need to know things to the last tiny degree as you seem to think we all should.

Many people learn best by hands on experience.....turning them away from getting that experience by discouraging them from even trying or experimenting is not what is needed.

[shadylane]

think your over thinking things and falling for the bullshit of a few self professed "Reflux Gurus" who like to make running a reflux still sound like some sort of cross between witch craft and rocket science.
Dont be scared off by that stuff......you could teach the average 12 year old to run one in 15 minutes if need be.

Why, an experience person, would make such a commend is beyond my understanding..


Mars

It's easy for me to understand Saltys opinions.
Even though we are on different sides of the world.
There's not a doubt in my mind he has valuable experience to share.

[zapata]

1. Cold reflux is not much of a problem, I thought The Complete Distiller dispelled that 20 years ago? Though it is at the very least an inefficiency worth noting.
2. Reverse liquid management works fine
3. The still as drawn will work fine
4. The still as drawn isn't as "elegant" as other RLM solutions and doesn't seem to conserve material, cost or build complexity. I'm not sure why it's offset at all for example.
5. The still as drawn could use some nuanced refinements eg; reflux distribution
6. Any beginner can quickly master the running of any remotely reasonable still and need not worry much about them being "fiddly". A CCVM to me is fiddly because moving the condenser is sloppy and relatively imprecise. A LM to me is fiddly because you will *Probably* adjust the valve more than on other stills. A VM is fiddly because... well, they aren't, but I'm sure somebody could come up with some kind of argument.
7. Any beginner who independently discovered RLM should pat themselves on the back, especially since they also figured out how it runs differently from LM's constantly decreasing reflux rate.
8. This thread has got to be incredibly frustrating to a relative beginner trying to sort out the bluster from the expertise from the speculation.

I think Yummy's story tells us why RLM never took off in popularity, RLM's main benefit was already addressed in VM designs. If we had never learned VM then a lot of us would love a dialed in RLM.