"Reverse LM" idea

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rad14701
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Re: "Reverse LM" idea

Post by rad14701 »

Hmmm... Taking into consideration the theory of path of least resistance I can't imagine vapor back feeding through a reflux needle valve... 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... Other types of valves may be more susceptible to back feeding, however... One one occasion I did run into the problem of a needle valve not handling product flow but that was with standard LM running in pot still mode where I actually partially flooded the reflux condenser section at the top of the column...

The way I'd probably run RLM would be to keep the reflux valve closed until I knew the reflux condenser was knocking down vapor, indicated by the first drips out the product take off... Not that I would have to do it this way, but doing it this way prompts me to verify optimal condenser coolant flow rate... Then I'd open the valve for 100% reflux and let the column reach equilibrium... After a time I could start closing the reflux valve and product take off should start shortly thereafter...

I'm keeping my eyes open for some scrap copper to give RLM a try...
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Re: "Reverse LM" idea

Post by muckanic »

rad14701 wrote: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... One one occasion I did run into the problem of a needle valve not handling product flow but that was with standard LM running in pot still mode where I actually partially flooded the reflux condenser section at the top of the column...
Yeah, if the valve is too small in a LM design then it could result in reservoir overflow and consequently some reflux when none was expected - not a complete disaster. OTOH, if the valve is too small in a RLM design then it could result in less reflux when a lot was expected, which could be most inconvenient around the cuts regions. Plus, any power reduction would not necessarily take effect instantly. So this all begs the question whether the standard 1/4" LM valve would be up to the RLM job at typical power levels? Presumably, no-one wants to run with less power simply because they are doing RLM ...
guerrila distilla
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Re: "Reverse LM" idea

Post by guerrila distilla »

that's exactly why i asked if a gate valve would be a better option. i think a needle valve, unless it is a large (and expensive) model, wouldn't allow the flow needed. somebody earlier in the thread mentioned that their needle valve would throughput so many litres per minute. this rating is their maximum flow rating at the recommended pressure (anywhere up to 10000 psi). when at atmospheric pressure/near atmospheric pressure, like in a still, the flow rates can be hundreds of times less than stated. if there was a significant reservoir above the valve, this would help to increase the flow rate. but, a large reservoir is undesired, as this makes valve adjustments have a long delay before you see any difference.

here are some stainless needle valves, including some larger sizes (up to 12mm). check out the prices though :(
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Re: "Reverse LM" idea

Post by Mud »

Snuffy found a good needle valve.
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Re: "Reverse LM" idea

Post by guerrila distilla »

that's a good price for a needle valve mud, but again i doubt a 1/8" valve at atmospheric pressure would thoughput 3 gallons a minute. it says it's rated at 2000 psi, so even if it's running at half that pressure, you can imagine the force pushing the liquid through to get any kind of decent flow rate. a good example is drill a 1/8 hole in a paper cup and fill it with water. you'll see how slow the flow rate really is, and that's not including the bottleneck provided by the length of the valve insides.
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Re: "Reverse LM" idea

Post by Mud »

doh. Ignore the illiterate bastard. I missed a whole page of this thread. The one with the first link to that needle valve. :roll:
cemik1
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Re: "Reverse LM" idea

Post by cemik1 »

guerrila distilla wrote: i doubt a 1/8" valve at atmospheric pressure would thoughput 3 gallons a minute
I think much less flow is required.
1000W - 52ml/min
2000W - 105ml/min
4000W - 209ml/min
(taken from Theory/Reflux Still Design Theory/Column Diameter)
snuffy
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Re: "Reverse LM" idea

Post by snuffy »

Minime and I have been doing some experiments.

I used a very large reservoir (180 ml) and a very short column (12") to exaggerate the supposed design limitations. Surprise! It worked very well as a high %abv stripping still and delivered 90% or more of the alcohol in the charge! And it autoshutoff on the water, so the cut between alcohol and water was very sharp. The reservoir was far too large to concentrate heads much.

Minime says:
Overall I think the design is amazing and could be tweaked to produce excellent neutral or as in this case white rum. I will verify ABV of the hearts cut and do a taste test on the rum this evening.
With a larger reservoir, it cycles from 0% while the reservoir fills to 100% reflux when it's full. I only opened the reservoir drain when the column temp stabilized. At that point the reservoir was full of +90% abv [edit: at first, by the forth draining of the reservoir, it was around 70%]. With a smaller reservoir, it probably can be tuned to compress heads. It definitely can compress the hearts/tails transition very sharply.

Temperature probes at the top, middle and bottom of the column would be optimal. this is a lovely design that needs more investigation so we can understand more about the design parameters. It certainly looks like it could be tweaked to deliver anything from stripping to neutral with automatic reflux control.
Last edited by snuffy on Mon Jun 01, 2009 6:29 am, edited 1 time in total.
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Re: "Reverse LM" idea

Post by HookLine »

I am suffering from a lack of drawings/pics. :wink:
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Re: "Reverse LM" idea

Post by guerrila distilla »

i have to say, i'm impressed, this is exactly what more people need to do - more trying and testing. 90% off a 12" column, now that's caught my attention.

could you give us a few more details like column diameter, type of valve used, power used and maybe a diagram pic.

i'm really interested in this design, and seen's as my vm column is in bits awaiting a 3" column at the moment, it'd be a good time to give this a go. i kind of want to make sure it works first before i go ahead as even 15mm copper tubing is about £20 for a 2m length. i managed to find 316 stainless for£38 a metre from a custom exhaust shop. i'm learning slowly, if you want anything cheap, dont move to scandinavia :roll:
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FREAK!
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Re: "Reverse LM" idea

Post by FREAK! »

Could someone please help me understand how a reservoir help to compress heads?
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Re: "Reverse LM" idea

Post by guerrila distilla »

what do you guys think of this design:-
rlm still 3 zoom.jpg
i based it on a simple slanted plate lm still, but have used two tubes. the lower is the reflux return tube, which is controlled by a valve. the higher tube is the product tube which is airlocked.
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rad14701
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Re: "Reverse LM" idea

Post by rad14701 »

That adaptation would definitely work, guerrila distilla... Making the best use of the reservoir in the column would be the trickiest part, but not all that tricky because the reflux return tube would take the place of the drip edge on the lower plate... It might be just as easy to put your takeoff tube just above the reflux control needle valve and only have one tube coming out of the reservoir... Either way would work...
snuffy
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Re: "Reverse LM" idea

Post by snuffy »

Image

This is not RLM, The reservoir fills and recirculates until it is drained by opening the valve at the bottom of the liebig. Then the valve is closed and the cycle starts over again. In this picture, the reservoir has not equalized and is boiling furiously (the cloudy area level with the edge of the table behind the still.)

Image

Temp log shows the slow fall to equalization, followed by a jump when the reservoir is empty. Temp probe in column below reservoir.

Reservoir compression works because liquids take up less space than vapors and heads boil at a lower temperature than hearts. So it provides a buffer at the top of the column where it's coolest and the heads will sit there instead of recirculating spread out in the upper part of the column.

Because the heads evaporate at a lower temperature, they will set up their own short reflux loop between the reservoir and the reflux condenser. The result is the liquid in the reservoir slowly increases in heads concentration.

Size is important: 40 - 150 ml. If the reservoir is too big, there won't be enough of a temperature difference and the separate reflux loop won't get established. Power level is important too, since too fast a reflux will not allow the concentration to take place because it will make the reservoir too hot to keep the heads liquid. For an insulated 2" column, 150 W - 300 W is sufficient.

When it's working, a thermometer at the top of the column (but below the reservoir) will dip below 78 C and then slowly rise as the heads get "compressed" in the reservoir.

Riku's book, Designing and Building Automatic Stills (available from Amphora Society) has several examples with pictures.
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Re: "Reverse LM" idea

Post by schnell »

Beyond Cool!
muckanic
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Re: "Reverse LM" idea

Post by muckanic »

guerrila distilla wrote:the higher tube is the product tube which is airlocked.
Maybe this is time to display my ignorance and raise a point that I didn't fully get first time around. That is, Pint's problems with syphoning in his LM take-off line, with the suggestion being that the reservoir was draining faster than it should have. I would have thought the reservoir would drain exactly as fast as the reservoir level, valve diameter, and line length would permit. So is this saying that long, thin lines can actually increase the take-off rate (contrary to my musings)? And does using an airlock change this situation at all?
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Re: "Reverse LM" idea

Post by Centar »

This RLM theory is awesome!
Sounds like the way it should be and normal LM has been doing it backwards all along with the associated problems (ie RR dropping off during run)
I was designing a LM BUT this makes so much sense I just have to do it this way now...
So simple makes ya go "why didn't I think of that?"

It seems better than a system that would keep the same RR throughout the run.

Looks like RLM is just a natural for a fractioning still....isn't this EXACTLY what we want to happen during the run? (the RR increase and cut tails off)

It also seems (yet to be tested) that the normal cheap not so "needle" valve that are hard to adjust for a slow drip rate would be easier to adjust the "flow" of condensate backing it off just enough for a slow "overflow" drip rate...thus making expensive needle valves not so important...in other words a cheap needle valve would have an easier time fine adjusting "flow" as opposed to being adjust for a slow flow.
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Re: "Reverse LM" idea

Post by Ayay »

RLM sure looks good but I have one reservation. I am accustomed to seeing a very constant drip rate delivered through the needle valve in LM. Adjusting the needle gives an instant feedback in the drip rate. With LM the outlet is at the bottom of a dam and there is a head of liquid above the needle valve. When driving my LM I rely on three visible indicators: the size of the gas flame; the temperature reading at the top of the column; and counting the the drip rate of the output.

Will this exact drip rate of the output will be lost in RLM? I think with RLM the overflow (which is now the output) is subject to a meniscus that builds up, breaks and flows, then builds up again. Without a head of liquid above the outlet I fear the instant feedback of the drip rate will be lost. Is this a problem?
cornflakes...stripped and refluxed
Centar
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Re: "Reverse LM" idea

Post by Centar »

The drip rate would still be controllable by the needle valve, it will only operate backwards....ie. closing the valve will increase the drip rate and vice versa.
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Re: "Reverse LM" idea

Post by iDrinkWash »

Well, after looking at a lot of designs on the website and forum, I think I have decided to go RLM. It just makes sense to me.

I am going to incorporate a small sight glass in between the reflux needle valve and the return pipe, so I can see the drip rate back into the packing. This reflux tube will be 1/4" flex. It will originate at the bottom of the plate, pass through the needle and the sight glass, then back into the center of the column. This needle valve is "panel mount", meaning that it has two nuts threaded on, just below the hand crank. I plan on putting a strap of bent copper pate around the column where the needle valve is. This will support the needle valve and sight glass, and protect it at little from damage.

The biggest design issue I have right now is that I'd like to make the product output sturdy, so I can hang a secondary condenser (leibig or graham) and parrot off it. The product take off is also going to be 1/4" flex, also - so I can bend in a "vapor trap". I might just put another strap of bent copper plate around there to pass it through, and terminate the 1/4" flex with a threaded fitting - or maybe just a 1/4" - 1/2" reducer and 90* bend downward - to which I can solder a copper to tri-clamp fitting.

Anybody have any other suggestions for securing the product output tube?

Thanks.

IdW
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Re: "Reverse LM" idea

Post by iDrinkWash »

Bump...

Anybody else have any success with a RLM design?


IDrinkWash
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Re: "Reverse LM" idea

Post by Tomb »

I too would love to hear more!

I have decided this will be my design.

(Sorry rad, I was going to go with your reducer design but will still go with your concentric condenser)

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Re: "Reverse LM" idea

Post by DAD300 »

There is a simpler version after these were discussed,
untitled.GIF
untitled.GIF (6.74 KiB) Viewed 3335 times
Brought to us by manu...

No valve needed! Condenser Controlled LM
CCVM http://homedistiller.org/forum/viewtopi ... d#p7104768" onclick="window.open(this.href);return false;" rel="nofollow
Ethyl Carbamate Docs viewtopic.php?f=6&t=55219&p=7309262&hil ... e#p7309262
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Re: "Reverse LM" idea

Post by InglisHill »

Cool DAD.
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Re: "Reverse LM" idea

Post by carbohydratesn »

Hah, yeah, that would do it!

CCRLM? :)
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Re: "Reverse LM" idea

Post by francis »

DAD300 wrote:There is a simpler version after these were discussed,
untitled.GIF
Brought to us by manu...

No valve needed! Condenser Controlled LM

But the volume of refluxing liquid is not constant, as in RLM, or is it ? It seems to be more like a CM design ?
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Re: "Reverse LM" idea

Post by Hound Dog »

francis wrote:
DAD300 wrote:There is a simpler version after these were discussed,
untitled.GIF
Brought to us by manu...

No valve needed! Condenser Controlled LM

But the volume of refluxing liquid is not constant, as in RLM, or is it ? It seems to be more like a CM design ?
Nope. Same principle as a boka. Distillate condences, collects in a takeoff cup, what you don't take off is returned for reflux. Difference is instead of closing a needle valve to return condensate back for reflux you slide the condenser farther down so that condensate never reaches the cup. Stainless needle valves used to be expensive. Now that you can get a 1/2" SS valve on ebay for $20 - $25 it seems less fiddly to just put a valve in.
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Re: "Reverse LM" idea

Post by francis »

http://homedistiller.org/forum/download ... p?id=36921

From the diagram above, the bottom part of the coil condenses the reflux and the top part of the coil fills the cup. Even though it's one condenser, it acts like two, one part below the cup and one part above the cup.
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Re: "Reverse LM" idea

Post by Hound Dog »

francis wrote:http://homedistiller.org/forum/download ... p?id=36921

From the diagram above, the bottom part of the coil condenses the reflux and the top part of the coil fills the cup. Even though it's one condenser, it acts like two, one part below the cup and one part above the cup.
Kind of. The coil is movable. To stop takeoff slide the coil down and you condense everything below the takeoff cup and send everything back for reflux. Want takeoff? Slide the coil up a bit and some will go into the cup and some will condense below it and go back to maintain reflux equalibrium. Want to stop reflux and take all the product? Slide the condenser up above the cup so that all the condensed liquid hits your takeoff. Same design as the valveless CCVM.
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Re: "Reverse LM" idea

Post by iDrinkWash »

Reviving this old thread, since I finally got some materials and I am gong to start on a build soon... any more success stories? Is this still a viable idea?

IDrinkWash
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