2" Boka for Neutrals - Reflux length and wattage

[APR]

I am wondering if anyone would like to comment on the reflux column length of their 2" Boka and the wattage they are pumping into it to get 90% plus ABV.

I have been playing around with a few different 2" Boka builds, and I have reached a few conclusions...

* You need at least 1 metre of packed reflux length.
* I don't believe insulating the column does any good unless the packed reflux length is long, like, well over 1 metre. (even then I think it is a no-no)
* The shorter the column the more desirable it is to not insulate the column.
* It seems to me that ABV quickly falls away with increased wattage to the boiler. On shorter reflux length columns even 500 watt can reduce % ABV significantly.

What is the experience of you Boka users? What sort of reflux length and wattage are you using to get 93% to 95% ABV, and are you insulating the column?

[Sam.]

It's a fairly well documented fact that a colum of 1500mm is optimal and insulation helps variances in temp while running.

You power input is dependant on your diameter and height mate :handgestures-thumbupleft:

Also your ABV is dependant on off take rate

[APR]

It's a fairly well documented fact that a colum of 1500mm is optimal

But as an example, while there is Boka design literature kicking around that indicates a reflux length of from 12 up to 30 times tube diameter, the Boka design drawing here....

http://wiki.homedistiller.org/Boka_Reflux_Still_-_How_To_Build

... shows a total tube length of 600mm. My young bloke was convinced by the literature that he could make a usable Boka Still at that length and went ahead and built 2" tube to 600mm total length and was very disappointed with the result. I feel that to suggest a usable Boka of 12 times diameter is misleading new starters.

and insulation helps variances in temp while running.

My playing around has not demonstrated to me any advantage to using insulation on the still reflux section. In actual fact, I have come to the conclusion that retaining heat in the column by using insulation stuffs up the column temperature gradient, and results in a lower ABV unless power is turned down and then take off rate will suffer. Perhaps if you use your still outside in breezy conditions column insulation would assist with stabilising the reflux column operation.

You power input is dependant on your diameter and height mate :handgestures-thumbupleft:

Also your ABV is dependant on off take rate

These issues were not as clear in my mind and as well understood when I built my first Boka, and I wonder how many others have started out with too short a reflux column and then struggled to get the ABV they were expecting. I have mucked around with adding on separate lengths of reflux tube to different reflux column length stills and now have a better understanding of what I should have done in the first place. I wonder how many others have gone the same road.

[Zak Griffin]

You'll find that around here, when asked, people will suggest Boka's have at least a metre of reflux section, if not more (1200-1500mm)

The yanks are happier to talk about what works in theory... We like to suggest what works in practice. I've never seen anyone here say that a 2" Bok will work with 600mm of packed section.

[APR]

You'll find that around here, when asked, people will suggest Boka's have at least a metre of reflux section, if not more (1200-1500mm)

The yanks are happier to talk about what works in theory... We like to suggest what works in practice. I've never seen anyone here say that a 2" Bok will work with 600mm of packed section.

G'day Zac, I think that newbies can be influenced by stills such as the T 500 that are very short. When looking around at the commercial offerings there are a few stills that have less height than the T 500, and so a new user can be easily fooled into believing they will have something superior if they build a Boka of a bit bigger size, not realising that a 2" Boka of 600 - 700mm total length is struggling to handle 400 - 500 watts of boiler power if you want to get remotely near 90% ABV.

What do you think of my belief that insulation on the reflux section necessitates reducing the power level and also reduces the take off rate.

[MacStill]

What do you think of my belief that insulation on the reflux section necessitates reducing the power level and also reduces the take off rate.

Insulate for sure :handgestures-thumbupleft:

Increase power = more reflux = cooler column - adjust take off accordingly = 95.6% ;-)

The way you're describing it seems counter productive to me :think:

[P3T3rPan]

Just put insulation on my new packed section (only). Still seemed much more stable running this time

[Matt_Pl]

Hey Mate,

Being only a novice myself (third run of my Boka last weekend) I followed the information provided to me on these forums and the www.

Personally I did find a difference after insulated the entire column, the still achieves equilibrium faster and the temperature is easier to regulate and less prone to fluctuations.

(I cool my still with a pond pump recirculating water into a 1000litre IBC) so I control my steam vapour by changing and maintaining the takeoff.

My 2'' Boka has a 1.5 metre packed section and in order for me to achieve 96% output on my final run i maintain vapour temperature at 78.40C until I get to the end of the run.

I cannot comment on wattage as I run LGP, but height and packing is the easiest way to increase ABV.

Cheers,

have a good one.

MP

[TheMechwarrior]

Agree totally with what Mac said :handgestures-thumbupleft:
Although my first column was 1200mm and a VM the principle of reflux and seperation is identical.
I found I was able to stabilise the column faster under insulation and my fractions came off better, that is I had less smeering.

[APR]

What do you think of my belief that insulation on the reflux section necessitates reducing the power level and also reduces the take off rate.

Insulate for sure :handgestures-thumbupleft:

Increase power = more reflux = cooler column - adjust take off accordingly = 95.6% ;-)

The way you're describing it seems counter productive to me :think:

I am wanting to do a bit more experimenting. I have an extension that takes on of my Bokas out to 1.5m of packing, and I want to try 1.5m of packing insulated and uninsulated to see what differences I can identify. I will insulate the bottom of the unit on the left to match the top and see how it performs..

[Yummyrum]

I think some are missing the whole point . A reflux column must be run in Reflux .IE there must be condensed liquid allowed to fall back down through the packing .
This is what makes the whole thing work .Vapour must contact falling liquid ...this allows the phase change where the higher percentage alcohol rises and the slightly alcohol depleted liquid falls ...this happens hundreds of times up the column .The packing is there so the phase change has somewhere to occur
It is no use having a 2 meter high packed column and running it flat out with no reflux .

A 600mm column will give 96% ABV purity but you have to have a high reflux ratio .That means that for all the vapour that makes it to the top ,you collect say 5% of it and the other 95% spills back down through the packing ..........it must drip.....................drip..................drip.................drip

A 1500mm column will also give 96% purity but you can collect say 25% of what reaches the top and the other 75% is returned to the packing .It can Drip..drip..drip..drip

A taller column allows for faster take off .

My VM column can easily give me 96% ABV and its only a meter tall Packed with SS scrubbers .If I am pushed for time ,I can push it harder but I will typically get 93-94% and its got that sickly sweet smell/taste to it .


In simple terms .If you let it drip,it will put out the goods . :dance:
If you turn the needle valve so it pisses like a mule ,...it will taste like ....piss :puke-huge:

Don't be in a hurry

[spit'n'shine]

I think some are missing the whole point . A reflux column must be run in Reflux .IE there must be condensed liquid allowed to fall back down through the packing .
This is what makes the whole thing work .Vapour must contact falling liquid ...this allows the phase change where the higher percentage alcohol rises and the slightly alcohol depleted liquid falls ...this happens hundreds of times up the column .The packing is there so the phase change has somewhere to occur
It is no use having a 2 meter high packed column and running it flat out with no reflux .

A 600mm column will give 96% ABV purity but you have to have a high reflux ratio .That means that for all the vapour that makes it to the top ,you collect say 5% of it and the other 95% spills back down through the packing .

A 1500mm column will also give 96% purity but you can collect say 25% of what reaches the top and the other 75% is returned to the packing .

A taller column allows for faster take off .

My VM column can easily give me 96% ABV and its only a meter tall Packed with SS scrubbers .If I am pushed for time ,I can push it harder but I will typically get 93-94% and its got that sickly sweet smell/taste to it .


In simple terms .If you let it drip,it will put out the goods . :dance:
If you turn the needle valve so it pisses like a mule ,...it will taste like ....piss :puke-huge:

Don't be in a hurry

I agree Yummyrum.

I'll share my experiences with my home made 2" Boka.. The packed length is 900 long and 1260 long overall. I have never used insulation but I figure it would make it slightly more efficient. I have pulled 96% on every run I have done, and thats with a homemade valve.

I think the key is to let the distillate come out slowly and allow more refluxing to happen. I usually collect at about 1litre per hour.

As for heat affecting it, as long as it is at a slow boil, it is enough to use the Boka to its potential IMO.

[APR]

I think some are missing the whole point . A reflux column must be run in Reflux .IE there must be condensed liquid allowed to fall back down through the packing .
This is what makes the whole thing work ......

G'Day Yummyrum, I do understand all that, and can readily produce product at a reasonably high % of ABV. Here is the density near the start of my last TPW run...



I am waiting on another wash to ferment and then after running it I intend to combine it with the previous run and will distill the lot again. For my money, combining the two runs to 40% ABV results in faster distillation when doing the final run, and gives a purer product

I'll share my experiences with my home made 2" Boka.. The packed length is 900 long and 1260 long overall. I have never used insulation but I figure it would make it slightly more efficient. I have pulled 96% on every run I have done, and thats with a homemade valve.

My middle still in this image in a post above.. http://i.imgur.com/5Qu5kcB.jpg is 900mm packed length and ~1250mm overall. I can very accurately control the take off rate, and have been able to put out 96% ABV from 10% wash.. at least during the early part of the distillation, but I am not happy with the time it takes. Halfway through the distillation process when the % alcohol in the boiler has dropped off significantly, the take off rate has to be reduced so far that it takes forever. I am more happy to strip a couple of ferments to a lower % ABV and combine them for a final run.

I should be doing a couple more runs in the next week, and will be playing around further with insulation to get a better handle on what is going on.

[spit'n'shine]

How slow do you have to take it? Patience is a big part of this hobby and rushing things or pushing the equipment to the limit can result in a below average product.

As for the % dropping, I have not experienced this at all.. In fact every run I have done through my Boka provides me with neat and easy cutoffs between heads/hearts and hearts/tails that I can pick straight out of the still (even though I still collect in small containers to double check after airing). The % only starts to drop as the tails start to come out.

Maybe try insulating, especially if you are running it outside in the wind.

[MacStill]

it's that last couple of % in ABV where a shorter column just wont stack up, it's a pretty easy thing to get 90% & even those poxy short super reflux rigs will do it.

height = purity
diameter = speed

[Furynfear]

After I fixed my still up and had more of a packed section I got greater speed and higher percentage but noticed not enough power from the boiler to come with the output I wanted. So putting in another element which should help more refluxing

Sent from my GT-I9505 using Tapatalk

[Kimbo]

If you add another element, I would put it on a controller as it may be too much power.
the reason your output has slowed is you are just bleeding off the lightest fractions( higher ABV) you will need to fine tune the balance between power input/product output speed/ABV ;-)
as a general rule, the slower the better :handgestures-thumbupleft:

[Stoney]

any updates on testing progress here ?