Concentric Pot/Reflux Still

[ben stiller]

Rad, what do you use to keep the marbles in the column? What advantage do the marbles have over scrubbies? Trying to learn all that I can since my concentric is almost finished.

[Kegg_jam]

Rad, good to know your seeing a similar effect. I thought I was loosing my marbles..... (Pun intended).

In addition to what you said about the vapor not going up as far, I was envisioning the vapor as being thicker or heavier for lack of the proper terms. When it does collapse it is drawing in more air through the vented open top and providing some evaporative cooling of the top off the condenser. That was my theory anyway...

[Johnny6]

I've been having pretty good luck with marbles on my concentric too. I've got a sink drain adapter at the bottom of my column (I think Rad does too) which keeps the marbles from dropping out the bottom. There have been a few threads discussing using marbles. Personally, I think the mass of the marbles helps establish and maintain a temperature gradient from the boiler up to the reflux condenser. They are also low cost, very convenient to obtain, work with, and clean. It doesn't cost much to give them a try. I've been doing "hybrid" runs where I run in full reflux at the start of each run to compress the heads, then open it up and run the rest at pot-still rates (no reflux). I've been running everything (apple brandy and cornflake whiskey) twice through. The hybrid technique REALLY compresses the heads and even the fores.

Regarding temperatures, I've got a thermometer above the marbles, I've never seen the temperature drop unless I turn up the amount of reflux. Otherwise, it rises steadily through the run as the ABV drops.

[ben stiller]

Johnny what size column are you running and what length are you using? Mine will be 1.5x1.25x1 inch and I am looking for real world experience for length of column for both hybrid and neutrals.

[rad14701]

Rad, what do you use to keep the marbles in the column? What advantage do the marbles have over scrubbies? Trying to learn all that I can since my concentric is almost finished.

One boiler has a sink drain... Two others have a narrow strip of copper supported by a small lip where the connector fitting is soldered on, held in place by a ring made out of flattened 1/4" tubing...

I feel that there's something to be said about the thermal mass that the marbles provide... With my small 1.25" diameter columns getting scrubbers packed uniformly is difficult at best... The marbles allow consistent density...

[Johnny6]

Ben, I'm running 1-1/4" diameter like Rad. The section that holds marbles includes a base section (about 4" long) and an extension (18"). I figure I've got it filled up to about 20-21 inches total. The marbles that I'm using are from Walmart for flower arrangements, and are on the smaller size, maybe 1/2"? (I haven't measured them). Also, I'm running a 2-Gallon still with a 1000W hot plate, which may be relevant.

Edit: I don't have any insulation on the column.

[bluenose]

I'm getting around to building one of these with a 2" outer jacket. I have a piece 18.25 inches long and it's thick walled, and I also have one that's 16.25" long and not as thick walled.

Should I cut one down to 12" or just use the 16.25" one as is? If I cut the 18" I'd have 6" left, but I'm not sure what I could use that for.

I have lots of 1.5" pipe so the extra length isn't an issue.

[ben stiller]

I have a lot of the flat bottom glass things that go into an aquarium that I think will fit the bill nicely. Just checked and actually have enough to pack a 36 inch column. Was afraid they might pack too tight so I filled my 12 condenser and was able to blow through it with no effort.

The main issue I am debating is getting enough collection volume with my 1 inch vapor tube extending into the 1 1/4 inch inner condenser tube. By calculation I need 4.1 inches of tube inside the condenser to get 1 ounce of volume. I am thinking that removing
any of the tube that protrudes from the bottom of the reducerless condenser and not sliding the condenser into the collection reducer all the way will gain me a bit of volume. Any thoughts?

[bluenose]

I'm getting around to building one of these with a 2" outer jacket. I have a piece 18.25 inches long and it's thick walled, and I also have one that's 16.25" long and not as thick walled.

Should I cut one down to 12" or just use the 16.25" one as is? If I cut the 18" I'd have 6" left, but I'm not sure what I could use that for.

I have lots of 1.5" pipe so the extra length isn't an issue.

anyone have any thoughts on this? Should I make it 16.25" or cut one to 12"?

[Kegg_jam]

I would go with the 16" one.

[rad14701]

If you have the room, go with the longer length...

[Johnny6]

Just a quick report on a breakthrough/milestone for me... I've got to tell somebody! I've been using my concentric (1-1/4" dia) for about a year now, but always just in pot stilling mode, or hybrid mode where only the heads/fores were compressed. I finally ran a run with continuous active reflux and was amazed at how I was getting 96% ABV without really even trying. I was running a spirit run on some 40% DWWG low-wines. By now I can recognize the normal production rate (fast drip to small stream) when running in pot-still mode. All I really did was to slow down the rate below that so that I knew there was reflux, and monitored the vapor temp over the packing to hold it at 173 (or so). I also managed my cooling water flow to get a reasonably warm/hot outflow so that I wasn't over-cooling. Anyhow, as inexperienced as I am, I find it amazing that it works so well. My hat is off to you Rad for a nice still design! (My packing was about 20" of 1/2" diameter glass marbles.) I'm keeping the very smooth DWWG white as a vodka.

[rad14701]

Johnny6, glad to hear about your success...!!!

What is your collection rate for the 40% low wines...??? With my 30" 5/8" marble filled column I can pull 1oz+ per minute at 95% - 96%...

[Johnny6]

Rad, on that first continuous reflux run, I ran quite a bit slower. I was pulling 4oz every 12-14 minutes, or about 0.3oz per minute. I am suspicious that I am limited by my heat source. I have a 1000W hot plate for my 2 gallon pot. I don't presently have any insulation on the pot or column. My plan is to try adding that and see if I can't increase the reflux rate / take-off rate too. I'll report back in if that makes a difference. Running at 1oz/minute would be excellent!

[ben stiller]

I put the finishing touches on my 1.5" concentric column tonight since it was finally warm enough to venture into the garage. I soldered a 4"x1.5" cap style tri clamp reducer to the top of my inverted bowl. The 4 inch part was soldered to the bowl leaving the 1 inch to accept the column. Like this one except 4 inch https://www.brewershardware.com/Tri-Clo ... ducer.html" onclick="window.open(this.href);return false;" rel="nofollow . I did this because the only bowl I could find to fit my pot had a flimsy
bottom and I thought this would stiffen it up and I was correct. With the 5 gallon pot empty it will support the 36" column with an 11 inch condenser on top and a 12 inch 3/4"X3/8" liebig like Rad built. I was really surprised that I won't need to support the column in any way. Will be doing the required cleaning runs in the coming week.

[SenileToo]

Designing still #2, a Modular Concentric VM / LM Combo. I was won over to the notion of a concentric reflux condenser by the discussion on this thread. Here's my design below in the PDF. Still unsure about the optimum effective length of the concentric condenser cooling jacket. 12" was what I concluded from my reading here. I'm forgoing the cold finger component of Rad's initial design per the consensus here that its not needed with the proper condenser length and the addition of copper packing. I will have the provision to insert one made from a 3/4" copper expansion fitting with 1/4" inlet / outlet secured to the column with a perforated test cap.

Also , it seems that its important to keep the 1" neck as short as possible, allowing for at least 1 oz of distillate to be collected in the take-off bowl. I plan to size it so that the bottom of the pipe will serve as an effective drip ring into the packing and the top protrudes maybe an inch into the condenser pipe. Am I getting this right? The drawings should show what I'm thinking better than I can describe' They are not to scale but close enough I think.

Am I on the right track here?

[still_stirrin]

Nice pdf mahleywc.

But why do you have a piccolo tube in the throat? You'll force the vapors to squeeze through the holes and change direction. Sure, it will cause a pressure drop at the series of orifices. But remember that liquid will try to retrace that path too back into the column (reflux). It's going to further restrict the vapor flow into the condenser.

I'd suggest omitting those piccolo holes and omitting the cap on your 1" tube. The vapors will condense on the inner wall of your condenser easily. The velocity changes cause the vapor to initiate condensation when it moves past the venturi of the throat...as the velocity slows down in the condenser, the static pressure increases above the vapor pressure and it triggers the condensation. Engineering lesson - This follows the ideal gas law and a steady state mass flow...as the velocity increases from the column to the throat, the vapor velocity increases and the density decreases as the static pressure decreases in the venturi. As the velocity again slows down past the venturi, the static pressure increases and the vapor density will increase too. As it does this, it will liberate heat to the condenser wall and it will condense.

The liquid will wick down the inner wall and collect in the cup. Also, the liquid volume in the cup then is determined by the height the tube pokes into the condenser. If there is too much liquid there (calculate the volume as you want at least an ounce of retention), then simply shorten the length into the condenser. Remember that the liquid volume is the annular area between the 1" tube and the 1.5" condenser inner wall x the cup height.

Otherwise, nice plans. I appreciate the time spent engineering the assembly before driving to manufacturing. (I'm a design engineer too).
ss

[still_stirrin]

One other thing to consider with your design mahleywc, would be to add a product Liebig to your LM takeoff. The liquid will be hot because it's collecting inside the condenser next to the hot vapor riser. Sure, it'll be a liquid (below saturation temperature), but it'll still be very hot coming out.

I know this from experience. I added a simple product Liebig to the liquid discharge line to cool the product down to where I can collect it and measure the proof off the still. It doesn't have to be a big Liebig to do this either. I made mine with 3/8" ID tubing (because that's what my takeoff tubing size is). And I made a gentle coil of tubing with a hose jacket that gently cools the liquid as it drips out. I did this to increase the liquid (takeoff) contact time inside the product Liebig. The temperature coming out is the same as the cooling water inlet temperature (counterflow). It works great for drips or full flow with the LM valve fully opened (hybrid operations).
ss

[SenileToo]

Thank you Stillstirin! That's exactly the quality critique I was hoping for. I really appreciate the thoughtful reply. I was unsure about the 1" tube design for the reasons you mentioned. It's a carry over from the double-wound coil condenser design I considered before being enlightened about the concentric alternative. In the coil designs there is a modified tee fitting or the perforated pipe and cap feeding vapor to the condenser. The reason I started with the perforated pipe was to increase the side clearance vs the tee and to avoid reflux entering an open topped tube from the recommended insertion of copper packing in the condenser pipe top. As you suggest, I think the flow advantages from an open top pipe would out weigh the minimal amount of unintended reflux re-entering the tube from packing drip. I will test the pipe height needed in the reducer by inserting the pipe into it and filling the reducer with water to determine the desired level for an approximately 1 oz reservoir. Then I need to see where this length will protrude into the condenser inner pipe.

The design has a 12" cooling jacket for the concentric. I have no need to skimp on the length as I have 10 ft of 2" type M pipe to work with and the still will be operated outside. If, in your opinion, the condenser would be more effective at 16" or 18" length I'd appreciate your advice.

I have seen in the related posts where the distillate comes out pretty hot. I've been thinking about how to introduce a product cooler. A Liebig seems most elegant, then there's the spaghetti piping for the water supply. Oh well..., I like pasta.

[ben stiller]

For a product condenser go to Rad's signature and look at page two of his apartment build thread. Scroll down to the
picture of his product condenser. I stole his design and built mine out of a 12 inch piece of 3/4 pipe with 3/8 pipe for the
coolant and product tubes. Super light weight to hang off of the takeoff tube and distillate comes out cold. This was a really fun build and a learning experience to run the thing. Took a bit to figure out that the temp was creeping up because I was not running enough power to create the needed reflux. Definitely a balancing act. It is too bad we all have to be so secretive. Would be great to have someone experienced to show us the ropes. That may come with time.

[SenileToo]

Yup, that's my definition of "elegant". Think I'll borrow that idea!

[Johnny6]

Rad, on that first continuous reflux run, I ran quite a bit slower. I was pulling 4oz every 12-14 minutes, or about 0.3oz per minute. I am suspicious that I am limited by my heat source. I have a 1000W hot plate for my 2 gallon pot. I don't presently have any insulation on the pot or column. My plan is to try adding that and see if I can't increase the reflux rate / take-off rate too. I'll report back in if that makes a difference. Running at 1oz/minute would be excellent!

Since my earlier post, I've switched from my original 1000W hot plate to an 1800W DUXTOP induction cooktop (recommended by rgreen2002). Wow, what a difference! I've also insulated my boiler and column, but really, the extra power was the important change. On 40% low wines, the collection rate now is at least 1oz per minute while refluxing. For a good stretch of the run I was actually getting 4 oz in 3 minutes (1.3 oz/minute), and that was with the heat backed off to 70% (around 1260W?). (At that faster rate, however, I may not have been reaching quite to 95-96%. The temperature at the top of the column was starting to creep up.) The extra wattage has cut the time my stripping and spirit runs at least in half.

At those faster collection rates, I may need to re-evaluate my product cooler. My fairly short and simple liebig takes out a lot of heat, but it comes out at the end still rather hot. I'm also considering bumping up to a 3 gallon. With the faster processing time, I could still accomplish a stripping or spirit run in less time than it originally took me with the 2 gallon still and the hot plate.

I've really enjoyed using the induction cooktop. The power seems steady with no observable cycling. It is my impression that the power level changes are accomplished by changing the duty cycle of the high frequency drive to the induction coil, so there wouldn't be any cycling effects on the contents of the boiler. The heat seems to be spread out more on the bottom of the pot versus the original hot plate. With the hot plate I would occasionally see residue on the bottom of the pot where the heating coil was creating a localized hot spot. I haven't seen anything like that with the induction cooktop, in spite of the extra power. Also, switching off the power at the end of the run causes the boiling to stop immediately, which caught my attention. Since I stow away my rig after each run, the fact that it cools down quickly saves me a bit of time there too.

[Kareltje]

Inspiring!
But I am not convinced about the advantages.

[panikry83]

Hey there, hoping you can answer a quick question for me. I've been reading this thread and the accompanying threads about the concentric still head over and over the last few weeks and I think I've finally got my head around it. I'm looking to build it as a 2" x 1.5" x 1" to use on top of my 15.5g keg still like bluenose(?) did. I'd like to run it as a potstill mostly (or maybe to concentrate the fores/heads then, switch over to pull hearts - hybrid I guess you call it?) but also have the option to run it for neutrals as well. I know this is all covered in the thread but, I noted it hasn't been posted on in awhile and I was wondering if you still use this still? Does is still function to your liking or have you moved past this design? Have you figured any mods or updates since the original build? Thanks.

I also just noticed your tenure on the site this year, congrats and thanks for all your contributions!

[rad14701]

Hey there, hoping you can answer a quick question for me. I've been reading this thread and the accompanying threads about the concentric still head over and over the last few weeks and I think I've finally got my head around it. I'm looking to build it as a 2" x 1.5" x 1" to use on top of my 15.5g keg still like bluenose(?) did. I'd like to run it as a potstill mostly (or maybe to concentrate the fores/heads then, switch over to pull hearts - hybrid I guess you call it?) but also have the option to run it for neutrals as well. I know this is all covered in the thread but, I noted it hasn't been posted on in awhile and I was wondering if you still use this still? Does is still function to your liking or have you moved past this design? Have you figured any mods or updates since the original build? Thanks.

I also just noticed your tenure on the site this year, congrats and thanks for all your contributions!

Your 2" x 1.5 x 1" sounds good... If you could find 1.25" that would work even better than the 1"... However you do it, make your 2" column at least 36" tall for the packed reflux column... I also have a very short column section that I pack for hybrid mode...

I still use my from my Small Scale Apartment Still dual reducer reflux head with a concentric reflux condenser for neutrals but now use a pot still for stripping... I haven't run the concentric head pictured in the initial post in this topic for a couple of years but have considered pulling it out recently and may in the near future... It is still in its original configuration...

[panikry83]

Great that sounds good hopefully I'll get this built in the next week or two I've got 20 gallons of birdwatchers fermenting at the moment so I'll have a cleaning run ready

[StillerBoy]

2" reflux condenser

panikry... I recognize that the post is somewhat a week old.. I run a 2" concentric LM, and my condenser is overall length is 13 1/2" with 12" cooling area, and it can knock down whatever power I use for stripping or spirit run.. and to me the concentric model is the most versatile design area..

Presently working on putting a 3" together, and will document the build once I get all the parts together..

work done on 3" so far

[panikry83]

Thanks stiller boy still deciding what I'm doing for my reflux situation

[Mookieb]

I built a 1"X1.5"X2" 24" tall and was wondering what size water inlet and outlet would you use? 1/4" or 3/8" or even 1/2" I have not yet drilled the holes and just wanted anyone's opinion in this matter? Oh BTW I am running a 15.5 gallon keg with a 5500w element. Thanks!

[StillerBoy]

was wondering what size water inlet and outlet would you use? 1/4" or 3/8" or even 1/2"

I build all my condensers water inlet and outlet using 3/8" tubing, use 3/8 x 1/2" plastic hose and manage by a 3/8" needle valve located at the tap outlet..

Mars