Getting some reflux for neutral through a pot still.

[rumbo]

Hi everyone,
I've got some birdwatcher's on at the moment. Up until now I have been only doing rum. I know running neutral through a pot still is not ideal but currently that's all I have. Here is a picture of my pot still.

As you can see I have quite a long column (900mm). I was wondering whether I would get a noticable difference in the quality of neutral if I were to add a perforated plate sandwiched in the bottom easy flange connection to the keg and filled the column with some SS scrubbers. The perforated plate would be more to stop the scrubber from coming loose and falling into the keg but may acheive some reflux on it's own I guess?? Also I was then thinking that with the plate, I could also add some botanicals sitting at the bottom of the column to experiment a bit on flavouring via vapour infusion. To make it I was just going to open up and flatten out a piece of 1" pipe that I have left over from making a parrot (column is 2" diam).

Any comments on whether this would do anything? Also is there a formula I should apply to the plate as far as size and number of holes?

[Jimbo]

If you want a cheap and dirty reflux still to get 'closer' to neutral than you currently are, wrap some 3/8 copper around the column and stuff the column with copper mesh. Adjust the coolant water flow through the 3/8 to control reflux amount. If you try it please post back the ABV before and after you turn the cooling water on. And without the mesh too, if you have numbers from the same recipe (wash ABV)

PS: Nice looking potstill and leibig! Here's a mess of mesh for cheap http://www.brewhaus.com/Copper-Mesh-P947.aspx" onclick="window.open(this.href);return false;" rel="nofollow Make sure you wash it first good in hot water and dishsoap. There's some residual oils and shite on it from the tooling that makes it.

[carbohydratesn]

Yeah, that actually looks like a *perfect* pot still to use as a reflux still! You could even make it completely modular, if you want to get a little fancy, because you already have a tri-clamp connection at the top. You could very easily convert it to any kind of reflux still - whatever kind you want. LM, VM, CM, CCVM...just build a a head for that type of still, and clamp it on! No modification to your pot still necessary. You could even clamp the pot head on top of a reflux section, with a VM or CM design, and use your liebig as a product condenser.

[rumbo]

Thanks guys. Yeah the idea of trying to keep it modular was so that I could do some trials on different mods down the track. At the moment i'm trying to focus on the rum and get that right, but thought I could start getting into some neutral in between and play with some fruit macerations etc. One of the reasons I had the thought of putting botanicals in the column. At this point though I was just thinking of something quick and easy to try. With the 3/8 tube idea... I do have a bit of 1/4 lying around.

So you just literally wrap the tubing a couple of times around the outside of the column and hook it up to an adjustable water flow? So your creating a cool spot in the vapour path that will condense some of the vapour before it reaches the top in addition to the passive reflux of the packing... sounds logical. Should I put it in any particular position - i.e. close to the bottom near the tri clamp junction or halfway up? I guess I can just leave the coil on there when not being used as I wont be able to slide it off due to the easy flanges.

As far as the scrubber goes, it is much easier to get SS ones here is Australia though I know copper would be ideal. Without something to hold them in wont they be likely to fall into the boiler?

[Jimbo]

A few wraps. Top, with mesh in the tube at and below the wrap. Mesh at the wrap wicks heat to the cool tube to condense the vapor.. Mesh below provides trickle path for refluxed liquid to get redistilled on its way south.

[rumbo]

Just an update to this. I have had a chance to do a couple of runs with the packed column (30inches of copper scrubbers) and the external reflux coil on mt 2" pot still. I ran some low wines (40%) and got a really good starting ABV during the spirit run - about 92% which I reckoin is pretty awesome for a potstill! It was birdwatchers and it came off very clean with a very good yield. I then tried to use it for a single spirit run on some fresh 20L molasses wash which was about 9% to see how high I could get. Even running it very slowly I could still only get 77% and the flavour wasn't up to scratch. I never realised how much the strength of the still charge affected the output %. I then did a trial of turning off the coolant to the reflux coil. The ABV did not increase which I thought was odd. The output rate increased though from about 16 min per L to 12 min per L. Does this mean that the packing was making all of the difference and the reflux was not doing anything? Or could it still add purity to the product without having an impact on ABV I wonder... anyway, I think I'll stick to the old strip and spirit run for the time being. Maybe i'll try the packed column on some rum low wines when I have some accumulated and see how that goes.

Also I tried adding 2 extra SS scrubbers to the column in addition to the copper ones. The stainless scrubbers had quite a "wet metallic" smell to then afterwards. The copper ones had no smell at all. Is this normal? They are definitely Stainless steel but were quite cheap. No signs of rust or anything though..

Cheers.

[skow69]

Did you wash the stainless scrubbies like Jimbo said? I like to boil 'em in 50% vinegar, too, and rinse good when they're new.

Turning off the water to the coil should increase your takeoff rate (because you are making no reflux) and LOWER the ABV (because you are getting no reflux).

You are getting a really good hands on education. Read the theory on the parent site and it will make more sense.

Also stuff the scrubbies in tight for best performance. It is hard to get too much in. Also, if you can, try and set a fan to blow air over the top 6 inches or so of the column to help the coil cool it. It won't make a massive difference, but it will probably be measurable.

Have fun. Make notes. Post your experiments. We love it.

[skow69]

Here is a link to the theory.

http://homedistiller.org/theory/refluxdesign

[Hound Dog]

By the way, with that new set up you are not getting 92% out of a pot still. You are getting it out of a CM still. Good results for the ez mod though.

[Yummyrum]

Hey Rumbo ...interested in what you are doing here

You have that 2" column fully packed , you are almost there .Think not as a Pot giving nuetral ....go all the way ...or you will be sadly in the middle ....Stick a decent refluxer on it
IMO CM cooling at the top will need to be fairly substantial if you want to get closer to neutral .

I tried a 2" shotgun Deflag and with as much water as I could force through it , I still could not get full reflux at 1400 Watts. ( it was 5x 3/16" tubes ) Not sure what power you are banging up ......If I was going to do it again I would make it twice as long at least

So I am sort of not surprised that you gained little with an external Wrapped cooling method .

To match your power to your cooling ability you need to run flat out water through your reflux condenser then reduce your power to the boiler until you have no output ....this is full reflux .Now slowly crank up the power to drive the heads out at a drip then crank it a bit more to run hearts ......Or back your water flow off , but that just makes the night drag out that little bit longer

[firewater69]

With the right amount of 3/8" copper wrapped around your column, you can achieve full reflux. I have pulled 88% on a single run and my column is only 16" tall. It's not the ideal setup for neutral, but it makes damned fine whiskey, rum and brandy.

IMG_20141126_214315.jpg

[skow69]

Ya know...I bet you guys could get a little better heat transfer (and therefor efficiency) if you soldered the coils to the column. Thermal conductivity is proportional to contact surface area according to this paper that still_stirrin' posted last week.

wakefield-heat-sink-design-facts.pdf

(1007.38 KiB) Downloaded 112 times

Q = kAc(T1-T2)/t From pg. 4 of the pdf.

Although the soldering wouldn't technically fit that category, but it's related.

We should also expect better performance from changing to material with a higher coeficient k, I think. For air k is 0.024 watts per meter Kelvin, for tin it is 67 w/(m K) so wherever you replace an air gap with solder, it would seem that you would increase the thermal conductivity by a factor of 2800 (67/0.024) in that local volume. Har! Maybe still_stirrin' will come around and explain where I'm going wrong, here.

Aaanyway, has anybody tried soldering the coils and measured to see what difference it made?

[firewater69]

I have thought about that Skow, but have thought of making some changes and go to a 1/2" coil, so I didn't solder. However my coil was wrapped around a 2.0" bar so it fits pretty tight around my 2.125 o.d. copper. Which helps but not as much as if I would solder it. I'm not making neutral so I'm not that worried about efficiency, my lm is better suited for that. But I think your on the right track with soldering.

[Hound Dog]

Ya know...I bet you guys could get a little better heat transfer (and therefor efficiency) if you soldered the coils to the column.

+1

[Andy Capp]

The coil works great at suppressing the tails but has no effect on heads that i could notice. I last used it with rum, only turning it on once the abv hit 70% to raise it back up to 80% +. This compounded the tails further and produced a larger middle cut than normal. Its aging on oak so i'll have to wait for the final taste.
I have used it with scrubbies and marbles but found little difference with or without them so i don't use them. I don't adjust the coolant flow, rather just switch it on and leave it. Always get the same abv with lots or little coolant.
A few scotch distilleries use a purifier, which has much the same effect as a coil. Glen Grant and Ardbeg are 2 that come to mind.

[googe]

Someone did do that skow, can't remember the thread though!, maybe it was tpee?. you got me thinking though, wonder if thermal paste would work?.

[Danespirit]

Thermal paste, great idea googe..!
It would sure do it for a temporarily solution, think it would have same efficency as to permanent solder it.

[Yummyrum]

Been using thermal paste for over 30 years in the electronics industry and its not as good as you would think for heat transfer. It really only works where the gap is minute between the two surfaces ( say about a 1/1000" ).......so its only going to help where the copper coil is actually touching the 2" .
And conductivity varies between Brands .It also tends to dry out and become ineffective over time .To me it is a waste of the effective cooling capability of the coil

I would vote for solder if the coil was to be implemented .....Here is a commercial cooling coil soldered to a pot I found at the tip ( fuck knows what it was used for but there was intimate thermal contact )

But seeing as there is a tri-clamp between the "column" and pot head , I think it begs for a dedicated CM Reflux condenser module that will really do justice to the 900mm packed column.

[rumbo]

Did you wash the stainless scrubbies like Jimbo said? I like to boil 'em in 50% vinegar, too, and rinse good when they're new.

Turning off the water to the coil should increase your takeoff rate (because you are making no reflux) and LOWER the ABV (because you are getting no reflux).

Yeah I washed the scrubbers really well. That was a typo, I meant lower the ABV cheers.

You have that 2" column fully packed , you are almost there .Think not as a Pot giving nuetral ....go all the way ...or you will be sadly in the middle ....Stick a decent refluxer on it
IMO CM cooling at the top will need to be fairly substantial if you want to get closer to neutral .

I tried a 2" shotgun Deflag and with as much water as I could force through it , I still could not get full reflux at 1400 Watts. ( it was 5x 3/16" tubes ) Not sure what power you are banging up ......If I was going to do it again I would make it twice as long at least

Thanks Yummyrum, you've given me the motivation to pursue this further to see what I can get out of it.

I have a 3 ring gas burner which is fairly adjustable and a recirc system with pond pumps and voltage regulators. One for the liebig and a smaller one for the reflux coil. I can adjust water flow through each independently.

I think part of the problem definitely is heat transfer. I noticed that even though the coil itself was very cool, the column even right above and below it was very hot. The small contact area that has been highlighted seems to be the problem. I will try to get better transfer - I was thinking either trying to flatten one side of the pipe to create a D cross section and then wrap around, but it might take a bit of twisting as I wrap it to keep the flat side against the column. Also it might be tricky to flatten just one side of the pipe without flattening it completely. The other idea I had was to put some copper mesh around the column and then wrap the pipe over the mesh.

The coil works great at suppressing the tails but has no effect on heads that i could notice. I last used it with rum, only turning it on once the abv hit 70% to raise it back up to 80% +. This compounded the tails further and produced a larger middle cut than normal. Its aging on oak so i'll have to wait for the final taste.

This could well be the case. It was my first birdwatchers spirit run, but I got a lot higher yield than I expected. After I had a fair bit of hearts, I changed to 250ml jars. I filled 5 of them then on the 6th jar I was sure I was into tails and then sped it up and collected in a feints bottle. I ended up keeping all of the 5 jars. In fact I am drinking the 5th jar uncut or blended with some tomato juice and tabasco as I write this. Not a hint of bitterness or tailsy flavour and very smooth - the tails can on very abruptly which I am certainly not used to with my rum spirit runs. This makes it very easy for a novice like me to make cuts.

But seeing as there is a tri-clamp between the "column" and pot head , I think it begs for a dedicated CM Reflux condenser module that will really do justice to the 900mm packed column.

If the external coil fails to achieve full reflux, I might look at making an internal coil - the problem with adding a section on top is that when the still is on a 50L keg which sits on a gas burner stand, the top of the head is only about 2" below the roof in my garage!! Might need to shorten the legs on the burner stand....

Other idea I had is to have a make an insert that won't add much height and will slide down inside - something like this (sorry for the crap drawing):

reflux condenser.jpg (13.97 KiB) Viewed 4689 times

[still_stirrin]

Late to the party here (skow), sorry.

For the external coil CM reflux, increasing the contact surface area with the column would indeed improve heat conduction. Obviously, copper filler metal would be the best. But silver would also work well. Tin/antimony solder is cheap and easy and could be added easily. Its not near as good at heat conduction, but better than no filler. Even aluminum filler would be good to use If you could pour it aroud the coil (in a fashioned mold, I'd suppose).

Another factor in favor of filler materials is that the increase in metal mass adds a thermal heat (or cold) sink. The heat sink acts like an inductor in an electrical circuit where the temperature (potential) leads the flow of heat.

This points to why the dephlag is so advantageous to use as a CM reflux condenser....it has great mass due to the metals and the water. It adds surface contact area due to the multiple tubes in contact with vapor and heat transfer media (cooling water). But the disadvantage of the dephlag is the vapor speed increase due to the reduction of flow area for the vapor path, which causes the vapor speed to increase. That does (can) result in a significantly reduced contact time, which limits heat transfer in the condenser.

So, the best dephlag, one which will have plenty of "headroom" for heat transfer and vapor knockdown is one with larger diameter vapor tubes, slightly longer (but not overly so), and built into a dephlag that is larger diameter than the column (think, "bubble ball" here). Vapor speeds would not be significantly increased for the steady state flow through the vapor tube as the flow areas would be closely approximated.

But again, adding mass (solder filler material) to the external coil CM would improve its knockdown ability too.

Good discussion gents. Keep it up.
ss

[still_stirrin]

My concentric reflux condenser is an annular water jacket with an integral spiral to turbulate the water around the central pipe. The inner wall is 1 1/2" diameter and the outer wall is 2" diameter, leaving me a 1/4" water jacket to haul the heat away.

Plenty of mass...all copper and H2O...with way more capacity than I need to knock the full load down. It takes hardly any water flow at all to carry full reflux heat loads.

Plus, the inside of the concentric has a copper scrubbie to slow the vapor flow and increase contact time with the condenser.
ss

[rumbo]

I'm thinking I will bite the bullet and make a section with an internal reflux coil that I can add at the top of the column. This sounds like it would be easier to acheive 100% reflux provided the coil has the right size, shape and position. Only possible disadvantage to an external coil I can imagine is that the internal coil but would probably provide more of a "shock cooling" effect. Using an external coil to wick away the heat from scrubbers on the inside would probably create a smoother temperature gradient. I guess that I could always weave the coil though some copper mesh or scrubber to acheive the same effect and make it less likely that vapour would sneak past. But the flip side of the coin is that having a larger thermal mass might make the reflux coil less responsive to changes to flow of cooling liquid...

[cranky]

Consider a Dad300 style corrugated SS coil with a scrubbie. They are the best and easiest thing going right now. You can do a search of Dad300s threads to find out all about it.

[googe]

Opinions are like arseholes, everyones got one, but some smell worse than the other. All reflux condensers will.work.at our level, its not rocket science, its more to do with your build skills and your passion. Do you want something simple to build or something more challenging?.

[skow69]

Only possible disadvantage to an external coil I can imagine is that the internal coil but would probably provide more of a "shock cooling" effect.

What is it about shock cooling that would be a problem?

[rumbo]

Only possible disadvantage to an external coil I can imagine is that the internal coil but would probably provide more of a "shock cooling" effect.

What is it about shock cooling that would be a problem?

I've done a little more reading about this. It seems that with a reflux coil shock cooling is really the intention. The reason that I thought it may be an issue is that it can lead to a slight vacuum effect - like the well known "huffing" that can occur in a Liebig. Not sure how relevant it is in a CM, but I thought that is was generally important to run in full reflux for a while until there is an equilibrium acheived whter the lowest boiling point compounds are concentrated towards the top of the column. This equilibrium is then theoretically maintained somewhat if the output is really slow (ie. in a CM adjusting heat/flow so that only a small amount of vapour passes the coil into this space and out through the product condensor) which essentially has the effect of compressing the foreshots and heads. I would have thought that this equlibrium would be disturbed if there was any "huffing" (whether audible or not) back through the product outlet. I would have thought that the Liebig style water jacket design would have had an advantage over an internal coil in this respect if the water flow was adjusted correctly. I could be way off the mark here...

[T-Pee]

Someone did do that skow, can't remember the thread though!, maybe it was tpee?

That was me. I feel it did increase the efficiency of the heat transfer from the coil to the column as it was easier to put the column in equilibrium afterwards.

tp

[humbledore]

Doing an internal coil turned out to be trickier than I thought. But yes it works very well, much better than a 2" x 8" dephleg for instance. Mine knocks down everything I can throw at it. Copper might be easier, I used csst tubing. I am still learning the best way to run it, it is trickier than a VM or LM. No huffing issues.

[blueduck]

If your looking for a neutral and run a CM a inner cooling coil is what you need. although if its whiskey that you want a outer cooling coil works well. I have two columns atm one with a inner CC and one with a outer CC. the column with the outer CC will get your prof up to 175-180 but will not compress the fractions as well as the inner CC will. while the column with inner CC will achieve prof up to 190 and compress the fractions fare better as the run go's on. I have only run the column with the inner CC three times but the difference is blatantly obvious.
I have found that with the outer CC if you tightly pack copper mesh in the column were the CC is located it helps a grate deal with heat transfer.

[rumbo]

Ok, so I have made a section that sits on the top of my column with an internal coil that slides into the column. Before I solder the coil to the section of 2", I was hoping for some feedback. I can either use the coil by itself or I can stuff a copper scrubber into the middle of it. My only concern is that it is a pretty tight fit and whether it would build up pressure. If it is likely that I would be able to get 100% reflux by just using the coil sitting on top of copper scrubbers that are packed into the column, then I won't worry.