Boka insufficient cooling?

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Boka insufficient cooling?

Postby paddy1000111 » Wed Jan 16, 2019 8:03 am

Hi everyone,

I have just finished building a new boka still. I'm having issues with the cooling. It seems like my cooling coil is insufficient! I have been running the first wash today (all bran mix) and the head temperature sits around 90 degrees. I feel my pump has died so I have ordered a much more powerful one at 6000lpm.

With the boiler running at 2300w (25L mash) the head temp stays high and the output Is pretty low. The water is freezing cold and has a load of 6" square ice blocks sitting in it too. I have added in some photos below to try and help. What am I doing wrong? Is my coil not strong enough? It's 8" of dual wound coil with a center finger. Or am I trying to run it too hard or something?

Image

Image

Image

Image

Image
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Re: Boka insufficient cooling?

Postby Expat » Wed Jan 16, 2019 9:35 am

Hi Paddy,

Looks like you've had some fun building up your bok and from what I can see you've got a nice piece of equipment to work with.

Next point, I think ties with the experience you're having. Operating instructions i.e. how to drive.

Note, you can't control head temp with cooling water input; it's managed through the volume of reflux. Also, your cooling water temp doesn't need to be icy cold; only cold enough to knock down vapor efficiently i.e. < steam temp.

From your description, it appears you maybe haven't read through some of the how-to threads, which should probably be your next stop. In short though, you need to find the balance with your cooling, power input and packing density. Aka Equilibrium.

Here is what I would suggest. An excercise to start with. When your boiler is reaching temp, cut back to say, half power. Close the take off valve, increase cooling water to maximum. Observe you should be knocking down all vapor into the column, and none should be escaping (ever!). Observe the level of liquid in the column, if any, increase the power until you see a little flooding on top of the packing just below your slant plate. Decrease cooling flow until output water is hot but still knocking down all vapors.

You're now in equilibrium, note the details for future reference. You should hold here for a period (20 minutes or more perhaps) and allow the column to stack and purity to increase through reflux. The head temp should slowly drop to around 172-173f or around 78c.

Hope that helps.
Last edited by Expat on Wed Jan 16, 2019 1:12 pm, edited 2 times in total.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Wed Jan 16, 2019 10:57 am

Hi Expat!

It took a long time to build and was a lot of work but my plan was for having something that gives me more of a scientific result!

I have been running at around 8 amps which is around 1800W (I have a 5500W element) when trying to get to equilibrium, It pretty much cuts the output to around 2 drops a second which from a 3" still seems like nothing and I still end up with lost vapour out the top. Is there such a thing as too much insulation? I have 15mm armouflex on the pipe. I think I need to start by massively increasing the amount of packing by what you are saying. I have 2ft of packed column that is loosely packed with stainless scrubbers. I will add a lot more to that and then add a load more to the head too and try to help that way.

was meant to be running a fast and hard stripping run today but just couldn't stop the stuff escaping no matter how low I set the boiler. It was painfully slow too, I ran it for around 4 hours and got about 2 litres. As it was my first run with the still I was trying to get a full reflux and learning as I went but I wasn't able to level it out and it always lost vapour. I shut the output, set the boiler to around 1800W and it would equalise with pretty much no vapour loss but it would drip say 1-2 times a second with the output open. I could see it go around the cooling coil and out the lid, I am wondering if I coiled it too tightly.

I am going to replace the pump I am currently running with something 3 times more powerful as the current flow rate is pretty poor. I am also thinking of adding a copper cooling tube for the distillate output as that was coming out red hot too (75c). I may also add a third coil to the current two as I have around 3/4" gap on both sides of the coil between the coil and the glass.
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Re: Boka insufficient cooling?

Postby kimbodious » Wed Jan 16, 2019 12:09 pm

You’ll need to bridge the 3/4” gap between the coil and the glass; you could do that by weaving some SS or copper pit scrubber material in your coil. That should help a lot with your cooling efficiency and help redistribute the condensate .

Expat gave great advice. :thumbup: I could not have said itany better

You can’t have too much insulation but you can have too much heat!
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Re: Boka insufficient cooling?

Postby still_stirrin » Wed Jan 16, 2019 1:03 pm

Yep, I gotta' agree with Kimbo & Expat on this one.

You need to improve the conduction surface area of your double coils. Since it's in a large diameter, relatively short glass tube, there is plenty path for the vapor to progress past the conducting surfaces that the vapor would condense onto. Scrubbies will help this. Copper scrubbies would be best, but stainless will work.

Other methods would be copper wire strands (reference Bushman's copper packing construction), or anything that will help to pull the heat from the passing vapors.

If you had a longer condenser section it would help too. Conduction surface area is the external surface of the copper coils, which in your build is very limited.

Packing in the condenser section will help a lot. But don't make it tight...keep is very loose...you don't want flow restriction, just increased conduction surface area.
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Re: Boka insufficient cooling?

Postby StillerBoy » Wed Jan 16, 2019 1:19 pm

paddy1000111 wrote: I am also thinking of adding a copper cooling tube for the distillate output as that was coming out red hot too (75c).

Yah, the output distillate can be quite hot without a mini liebig.. I constructed my using a 3/8" x 12" tube with an outer 1/2" x 9" tube with a detachable end..

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Re: Boka insufficient cooling?

Postby OtisT » Wed Jan 16, 2019 2:49 pm

Nice rig you got. :D

Expat gave a great description of how to run your column. :thumbup:

I’m curious if you have checked your product output tube or the needle valve on the boka? Your putting in 1800 watts, knocking down a lot ( hopefully all), and you are only getting 1 or 2 drops a second? That dog don’t hunt. It’s either plugged or your reflux down is missing your boka collection plate. Just my guess. Maybe I miss read you OP?

That reflux condenser looks like it should work fine as is, though adding some loosely packed mesh never hurts. Do you recirculate your cooling water, or is it fresh? Sounds like fresh, because you said the output water was cold. (Like expat said, you want to detuned that RC a bit so your refluxed spirit is not too cold when it hits your packing.)

[edit]. Forgot to mention. The column section where my reflux condenser sits is only insulated at the lower section. When tuning your RC you can feel the location of vapor and where the vapor stops. Try a test, run at full flow, then slowly reduce flow. You should feel the heat rise as you do so. That’s how I know when my RC is tuned, when the vapor is just over half way up my RC. Always start feeling from top to bottom tso you don’t burn your hand.

For comparison sake: I just did a spirit run on a similar sized still. It is a VM with a 3” x 24” packed and insulated column. I monitor my cooling flow rate and find that for my single copper coil reflux condenser that is 11” long I am tuned at about 1 liter per minute for every kilowatt of heat. During warmup I started flodding at 2250 watts so I backed it down to 2000w for the run. My reflux was running at 2 lpm. All this is using fresh cold water in, so if you are recirculating you will likely incrementally need more flow as your resivoir warms up.

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Re: Boka insufficient cooling?

Postby OtisT » Thu Jan 17, 2019 12:25 am

Paddy, one other thought. Where does your cold water come into your coils? Top or bottom? You should have the cold entering the top of the coils so that the coil is coldest at the top and is progressively warmer the further down you go. Otis
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Re: Boka insufficient cooling?

Postby paddy1000111 » Thu Jan 17, 2019 1:31 am

Hi everyone,

Thanks for all the advice! In answer to your question Otis, the water enters from the top and exits through the center finger as the boka build instructions on here suggest.

I am also using recirculated water, hence the large ice cubes, they keep the water temp low. I have quite a large sink so I use that as the reservoir. It also means I can drain and refresh with cooler water if the water starts heating up.

I think I have a couple of jobs judging by everyone's advice:

1)Increase the packing in the column. I have about 8 inches spare and its pretty loosely packed with some gaps at the moment. I'll remedy that with more ss scrubbers.

2) I'm going to add a third coil to the current two and then maybe add some very lightly packed copper mesh between the current cold finger coils and the new one. This should bridge the 3/4 gap.

3) Get hold of a better pump as my current one that I have been using for my old still is dying.

4) Make a mini liebig to reduce the output alcohol temps.

I should have all this done by the weekend. Depending how the current all bran wash goes I will either run that or I will just boil some water up and do a practice run, obviously the temps for water will be a lot higher but it will stress test it a little!
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Re: Boka insufficient cooling?

Postby kimbodious » Thu Jan 17, 2019 2:29 am

I checked out all the photos in your image library. Wow, you have done a really tidy build! :thumbup: My stills are made from bits I buy and just bolt together. :?
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Re: Boka insufficient cooling?

Postby greggn » Thu Jan 17, 2019 3:43 am

> I think I have a couple of jobs judging by everyone's advice:

One more thing, which I'm surprised no one mentioned, is that you should remove the plastic tubing running from your needle valve ... high proof ethanol and plastics don't play nice together.
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Re: Boka insufficient cooling?

Postby popcorn2014 » Thu Jan 17, 2019 8:19 am

I thought it wasn’t ok to have soft plastic tubing in contact with any distillate....?
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Re: Boka insufficient cooling?

Postby OtisT » Thu Jan 17, 2019 10:46 am

Did you verify that the product output was not plugged? A simple way to test is while the still of off, to remove the RC and to pour some water in the top of the column. Do you get drops or a good stream? You said you were only getting 1 or 2 drops of product a second at 1800 watts. That seemed really odd to me. Otis
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Re: Boka insufficient cooling?

Postby Expat » Thu Jan 17, 2019 10:55 am

While you're at it, I would suggest doing a flow test on your cooling coil. Try plumbing it a municipal water aka tap, and see how much water you can actually push through it. If nothing is getting through you have part of the answer.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Thu Jan 17, 2019 2:58 pm

Thanks for the comments on the build! It took A LOT of work getting what I wanted out of it. I am lucky to have a small workshop with a lathe and mill so I can make what I want, access to a TIG welder and experience with wiring and computer designing helped everything come together! In saying that my first still was a small copper one pieced together from spare plumbing bits I had about!

The cooling coil isn't blocked as far as I can tell. When I made it I cleared the salt out, blew it through with 120psi of air and pressure tested it to 50PSI under water for leaks. I also used a FLIR thermal camera to check the coils were getting cold. I think it is just an issue with weak pump+small tubes (6mm). I did however have an input water temp of 10'c and an output of 16'c so it's taking the heat out. I will run it off the tap as you say and see what happens with the flow tomorrow just to check. I think my main issue is the large gap around the side and the coils wound too tightly. I am going to add that third coil as I have the space but make it out of 8mm copper pipe. Ill then use some copper mesh that I have to make a tube to put over all the coils to help with heat dissipation maybe.

I have checked the output wasn't plugged. I got good flow when originally opening the valve, maybe 2 seconds, because of the build up of distillate on the lower plate but that quickly dwindled to a slow drip. I could get a faster output by turning the boiler up a tiny bit but then losses became an issue from the top of the still. The mirror would be dripping after about 3 seconds. I also put a piece of PVC tape over the hole in the top and that pushed the vapour out the distillate tube without pushing the little piece of tape off so there's no blockage or back pressure caused by the valve at all.

As far as the plastic tubing goes you are right, it's not ideal to have plastic but it was for trial runs to see if I will need a leibeg or not before making a copper tube. It looks like I will need one though, its hot! I have ordered a much bigger and more powerful pump so I can use a tiny pump to power the leibeg tube. I used a PTFE tube though for the output so the plastic is good for alcohol. My plan was to just use the PTFE as a joiner between the still and the copper bit leaving 3mm or so of exposed PTFE.
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Re: Boka insufficient cooling?

Postby Expat » Thu Jan 17, 2019 4:17 pm

If i'm understanding you correctly when you said:
input water temp of 10'c and an output of 16'c
This output value is extremely low for a system with proper contact. You either have a huge flow going through the tubes or you're not getting much contact with the vapor. Based on the effect you're seeing it would seem to be the latter, otherwise you'd see a much larger temperature difference. Definitely supports whats been said.

As example when running my cross-flow condenser, input water is 20c (68F) and I hold the output at 68C(~155F). I use city water so efficiency is important, it also means I have spare knock down capacity.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Thu Jan 17, 2019 4:34 pm

Well that was my suspicion. I think I have wound the coil far too tight so hopefully the additional coil and the copper mesh on the outside should help. On the other hand I have just found a new respect for stainless steel scrubbers. I just pulled apart two that got stuck together as I have just added around 24 more stainless scrubbers by tucking one inside the other so there's no dead space. The little bit that held the two together sliced into my finger and then embedded itself around 4mm into my thumb. I'm not sure what hurt more, the cut or the realisation I would have to pull the stainless string out of my thumb!

Live and learn!
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Re: Boka insufficient cooling?

Postby paddy1000111 » Fri Jan 18, 2019 8:22 am

Well I have been hard at work and added the third coil. It was a real nightmare but it's done :D . The flow is now dramatically increased with the water going 6-8 ft out the end when hooked up to the mains water.



Before:

Image
Image
Image




After:

Image
Image
Image
Image
Image

Excuse my finger over the lens in the last one!

The head now fits nicely in the top of the still with around 3mm gap on all edges. so hopefully this resolves the cooling issue. I am now just waiting for the pump. Over the weekend I will also make up a Leibeg tube for the output :thumbup:
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Re: Boka insufficient cooling?

Postby Expat » Fri Jan 18, 2019 9:53 am

Looking very good to me. Definitely plenty of flow through the coil now! So long as there is still enough space for the vapor to get between the coils and condense you should be golden.

I'd suggest trying the equalization procedure I mentioned above, but running on mains water. Doing this you can be sure to disassociated any problem with your condenser with those of water supply.

That said it looks like you're good to go and easily ready to knock down any power you can throw at it.

Re your product cooler; it's typical to plum these in line with your RC. Into the bottom of the PC, out the top and to the RC. Saves on valves and gives your product maximum chill coming out

Let us know how it he run goes!
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Re: Boka insufficient cooling?

Postby OtisT » Fri Jan 18, 2019 12:55 pm

New coil looks great. You do nice work.

I’m still betting on plugged output or liquid reflux escaping from or missing your collection plate all together. Hate to sound like a broke record, but did you pour a small stream of water down your boka head with the valve open to see if you get a good product flow? Something could have plugged it since your pre-assembly test. This would not be the first time I was way wrong on something, and I’m not trying to piss anyone off.

Here is my reasoning:

Running at 1800 watts you only get 1 to 2 drops per second. Considering heat loss and the 2 drops/second, I’m figuring that leave at least 1000 watts unaccounted for. 1000 watts of vapor coming out of that little hole on top would scare the hell out of ya, and the picture you have with the mirror does not look like 1000 w of vapor is escaping. 1000 W of vapor through a 1/2” hole is 233 inches/second of vapor flow (from RADs calc page). You say you ran it that way for 4 hours.

By chance, do you still have that wash? What is it’s ABV now vs when you started? Should be less than 1% now after 1000W for 4 hours if all that vapor escaped.

[Edit. I did the math. Your AG was of 25 liters should produce roughly 2 liters of Product if it’s in the 90% range. That is what you say you collected. So that means you collected most of the alcohol, which confirms my theory so far.]

Also, the flow of your coolant (pic of flow with your resivior/pump in background) looks to be enough to produce more than 1 or 2 drops a second. Though it hard to tell from the pic, I think I see way more than a few drops flowing down it. That one is hard to tell from all the vapor on the walls of your glass.

Considering all that, where is the extra power going? I’m guessing reflux, so where is the missing liquid reflux going? Has to be down the column.

It’s too bad that sight glass did not show the bottom of your RC so we could see the amount of liquid reflux. I’m following to see how this turns out for ya. Best of luck.

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Re: Boka insufficient cooling?

Postby paddy1000111 » Fri Jan 18, 2019 2:11 pm

Hi Otis,

I will do a check by taking the head off and dripping water down the center if the column like you say, sadly I can't run it down the coil as there's no real access. Like you say it's worth a look. I ensured that there is enough overlap between the plates and they are angled at 30 degrees. I could have a pretty fast output but my issue is that it also lost a lot through the top. To stop the vapour escaping I ended up with a very slow output.

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I have a 24 hour turbo brew that I threw together with some left over yeast from before I knew any better about washes. That should be good to run a test with as it's a nice high percentage even though it will taste like cleaner. I'll probably run that tomorrow night or Sunday so I will report back with the results
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Re: Boka insufficient cooling?

Postby OtisT » Fri Jan 18, 2019 2:21 pm

Ya, all the stuff you did with the RC was necessary to have 0 vapor escape and the new pump will help too. Like I said earlier, I reserve the right to be wrong. :) Otis
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Re: Boka insufficient cooling?

Postby kimbodious » Fri Jan 18, 2019 3:11 pm

“The head now fits nicely in the top of the still with around 3mm gap on all edges.” It would be best if there is no gap at all; you want the walls of the chamber to act as a condensing surface as well.

You’ll have heaps of vapour knockdown capacity from your RC now. You also have heaps of heating power. You will have to watch that you are not sending up so much vapour that the resulting condensate can’t fall down through the packed column quick enough, You’ll find that out if you have condensate dramatically erupting from the vent at the top of the column OR you get high rate of low ABV product. Your only immediate solution will be to reduce power to the boiler. Later you’d want to check that the packing in your column is not too tight.

It is great that you have some junk wash to test settings!
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Re: Boka insufficient cooling?

Postby paddy1000111 » Fri Jan 18, 2019 3:35 pm

Well remember to reserve the right to be correct too! I'm going off my design and some hope! :lol:

Hi kimbodious!

When I say 3mm I mean from the glass. The mesh on the outside of the coil touches the metal but the glass is a little bit of a bigger diameter. I must say though that whilst running it last time the glass was streaming with distillate.

The bit about a large amount of low abv distillate rings true though. I just checked what was coming off and most was around 86% dropping to 70% when I sped up the flow on the output. I think this was a mix between me being a bit aggressive with the heat trying to hear a boil as opposed to basing it off what the column was doing. I was trying for a strip run really but I messed up there. I think the other issue was a low power coil where I used 6mm instead of 8mm and wound it far too tight which is now resolved
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Re: Boka insufficient cooling?

Postby still_stirrin » Fri Jan 18, 2019 6:41 pm

Don't be such a "tight wad" with your mesh.

Loosely fill the space around the coil inside the glass with mesh. The vapor will still find its way into the space, but the increase in surface area will allow the vapors to initiate a phase change (condense).
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Re: Boka insufficient cooling?

Postby kimbodious » Fri Jan 18, 2019 7:04 pm

still_stirrin wrote:Don't be such a "tight wad" with your mesh.

Loosely fill the space around the coil inside the glass with mesh. The vapor will still find its way into the space, but the increase in surface area will allow the vapors to initiate a phase change (condense).
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sat Jan 19, 2019 7:29 am

Back after a brief intermission, dare I say it I think the issue is solved. :thumbup:

I started off by reducing the tightness of the packing as above so it looked like this in the head:

Image

And installing a new pump (6000LPH, 5M head) and checking for better flow:

Image

I then ran the still following the reflux manual from the LM still instruction guide on here. I was running a wash of the turbo yeast so I didn't bother with a stripping run first. It's not really nice to drink however you take it off and this was more of a training exercise for me. Once I got the boiler up to temp (around 20 minutes) and the first drips started coming out of the distillate output (I decided to throw away my foreshots right at the start then shut the needle valve) I adjusted the wattage down to around 1500W. I then set the coolant so it was hot on the output and started to build up the watts step by step until vapour showed on a mirror at the top and then backed it off a little. This gave me a power level of 3000W and the cooling water was at 50% flow and coming out hot. At this point the still head sat around 77'c-78'c. I left it like this for around 30 minutes regularly checking the mirror with a torch for leaking vapour.

The cooling coil output:

Image

After the 30 minutes passed I cracked open the valve and started to let out the distillate nice and slowly. It didn't smell great but smelt exactly like 24 hour turbo brew :sick:. At this point I opened the needle valve all the way just to see how fast the reflux was running and to make sure the needle valve was clear before setting it back to a fast drip. It's fair to say that it runs fast, I checked by pouring some water down the column and the speed of the flow is actually restricted by the orifice in the needle valve so the column must be producing even faster.

This is with the column at equalibrium and the needle valve open all the way:

Image

Once I took off around 2 pint glasses full of what I would call heads it got to the hearts, it's pretty hard to distinguish between heads and hearts with the turbo brew. With the column equalised, 3000W of power and the coolant output hot the distillate was coming out on a slow trickle at 95%-96%

Image

I also took a quick picture though the thermal camera. With the new coil there is a noticeable scale of heat lower down and then around 21 degrees at the top of the column. previously the whole top was around 79-85 degrees. You can also see the cool water in one pipe going into the top of the coils and the hot water exiting from the centre finger.

Image


The only bit that really surprised me was how quickly the temps spiked when it got to tails. It went from 77 up to 91 in the space of 3 minutes and although I opened the cooling line all way (input water temp was still 12 degrees) and I was frantically turning down the heat (and the distillate turned back to a very slow drip) the temps sat at around 90'c and I lost more vapour through the top during the temp spike at the end before I could get it back under control. It's obviously something I need to watch for next time. Maybe the turbo yeast had something to do with it? I am pretty sure I get a lot more tails with all bran.
This leads me to another question has anyone run an all bran mix? What amount of alcohol would you expect to get off a 30 litre stripping run? Knowing this may help me with my cut off points on my next run.

Thanks for the help everyone!
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Re: Boka insufficient cooling?

Postby still_stirrin » Sat Jan 19, 2019 8:04 am

So, your still head is a LM (boka). Those are exceptional at compressing heads and even the early hearts. But a VM is very good at compressing the hearts to tails portion of the run. The VM will keep your product clean until it is done producing and the proof will “drop like a brick” and the output will stop, or slow to very slow drips.

So with your still, the secret will be to close the LM valve when the head temperature starts to rise. And then let it restabilize for a few minutes. It’ll push the good ethanol that’s left up to the top and into your collection cup. After the short restabilization period reopen the valve slowly and collect the remainder at a slow rate into a new jar, of course. If the temperature jumps up quickly...you’re done...you’ve got it all.

But it does sound like you’ve learned something about how YOUR still works. Good job. That’s something that every distiller must do...and you can’t really expect us to know how best to run yours unless it’s OURS.

As for the all bran recipe, I don’t typically have excessive tails with it at all. In fact, there is usually a nice grain flavor on the back end, some of which I prefer to keep with the hearts. It adds a nice softness to the mouthfeel. But again, when I do a spirit run with the all bran it is always with the previously stripped low wines. And I use my LM/VM combo head on 39” of glass marble packed (and insulated) column. It gives me a very clean, high proof neutral.

But, YMMV.
ss

P.S. - Get rid of the “silly-con” hose on your outlet. It’ll spoil your spirits.
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Re: Boka insufficient cooling?

Postby paddy1000111 » Sat Jan 19, 2019 8:18 am

You know what, closing the valve and stabilising never even crossed my mind :oops:. Either way I was ready to call it quits as the turbo yeast is only good for fuel or cleaner.

How do you find marbles vs Stainless scrubbers if you have used them? The stainless scrubbers are a pain in the A** to clean etc and I always find that no matter how much I clean them or run them through the dishwasher they leave a blackish residue on my hands after handling them for a while.

I am possibly going to run a taller column in the summer on a good day I think for fun. I have another 24" packed and insulated section taking the total packed section to 60" which could be fun for a laugh. Sadly it's freezing outside so I am limited by ceiling height!
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Re: Boka insufficient cooling?

Postby ShineonCrazyDiamond » Sat Jan 19, 2019 8:44 am

Lava rocks don't get enough publicity, if you ask me. It's like having SPP.
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You reached for the secret too soon, you cried for the moon.
Shine on you crazy diamond."
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