Help needed. Not properly working boka with propane burner

Vapor, Liquid or Cooling Management. Flutes, plates, etc.

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Yummyrum
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Re: Help needed. Not properly working boka with propane burn

Post by Yummyrum »

der wo wrote:The cap on the return, is it a modification? Did you ever run it without?
I want to know, if it is really beneficial also in practice.
Hi der wo
This is the way I made it first up .
Unfortunately I Brazed it so I can't easily remove it to find out .

This was the first still I made . I did external reflux line because I thought it would be best way to get past VM takeoff .
I put on a cap becuase I felt that vapour would want to blow up it and cause erratic operation ... only a feeling ... like you I would like to know for sure .

But I think that if the easy vapour path is via the main column then its pointless however if there is restriction in vapour flow up main column then cap on reflux return line is valid
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Re: Help needed. Not properly working boka with propane burn

Post by Yummyrum »

I just remembered one experiment I did . Sorry to take this off topic with pics of all my stuff but I thought it possibly relevant.

Here I used my old Still Spirit Condenser as a Reflux condenser . The reflux is collected in the glass tube . The over flow falls back into the packing via a 3/8" tube with no pigtail or cup on it .
Still Spirits Reflux LM mod 1.jpg
This was horrible . Due to the vapour flowing up the return line , the reflux almost flooded the glass tube before the fluid weight over come the vapour pressure where it would all siphon dry and the process repeat .
Sticking a scrubber in the glass tube tamed the beast but I never used this head ....it was just for fun .
I had the arch in the return line thinking it would create a suitable fluid lock but it didn't work that way .

I would now like to try this again just to see with a straight return line and with a cup on the return line .
Tamed with a scrubber.jpg
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der wo
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Re: Help needed. Not properly working boka with propane burn

Post by der wo »

I also have an arch at my return line. And it works.No cap. All in all the lines are very short at my stillhead. Perhaps this reduces the problems?
DSC06447c.JPG
Perhaps a little hole at the top of your arch could help?
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Yummyrum
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Re: Help needed. Not properly working boka with propane burn

Post by Yummyrum »

der wo wrote:I also have an arch at my return line. And it works.No cap. All in all the lines are very short at my stillhead. Perhaps this reduces the problems?
DSC06447c.JPG
Perhaps a little hole at the top of your arch could help?
You could be right about the smaller length helping ....I imagine the whole siphoning thing would be dramatically less if present at all .

Regarding the hole in the arch , I think it would stop the siphoning for sure but it would vent the vapour straight out of the column .Perhaps if the top of the arch was vented back to the column .....but christ how to over complicate a simple concept .
No wonder most people build a slant plate Boka with internal reflux :clap:

BTW :I love your head design :thumbup:
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der wo
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Re: Help needed. Not properly working boka with propane burn

Post by der wo »

Yummyrum wrote:Regarding the hole in the arch , I think it would stop the siphoning for sure but it would vent the vapour straight out of the column .Perhaps if the top of the arch was vented back to the column
Depends on the vapor lock if there is vapor or air I think. But yes, generally drilling holes is a compromise to fix it. I am not really happy with those solutions.
I think we would need larger diameters for the tubes before and after the valve. Then the bore of the valve would be the only source of siphoning. Look sergiolis LM. He reports absolutely no problems and the ID is 10mm. You have almost 8mm. Speedy has only 6mm (me too, but my lines are much shorter).
Another idea from Speedy: Except the pig tail Speedys LM design is a copy from bearrivers design. But bearriver doesn't have a sight glass. So in case he has the same problem with unwanted reflux like him, he wouldn't notice it perhaps.
I told Speedy to find out, where is the reflux coming from. Does some of the distillate coming from the plates simply walk the horizontal path of the Tee or does air in the valve bubble distillate up into the horizontal path? He can find out, if he lengths the tube between Tee and valve for a test. If he still gets reflux, it comes from above.
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der wo
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Re: Help needed. Not properly working boka with propane burn

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der wo wrote:I told Speedy to find out, where is the reflux coming from. Does some of the distillate coming from the plates simply walk the horizontal path of the Tee or does air in the valve bubble distillate up into the horizontal path? He can find out, if he lengths the tube between Tee and valve for a test. If he still gets reflux, it comes from above.
It comes from above.
He will try to put a mini slanted plate into the Tee to direct the reflux away from the horizontal path:
unbenanntjvrtd.jpg
The red line is the mini slanted plate.
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der wo
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Re: Help needed. Not properly working boka with propane burn

Post by der wo »

Speedy fixed it successfully with a slanted plate into the Tee:
img_0051_1ozs8c.jpg

Still not a really beautiful product flow, but no unwanted reflux. 16%abv in the boiler.
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Re: Help needed. Not properly working boka with propane burn

Post by der wo »

What I have learnt here: Probably I would recommend next time this construction for a boka with external return:
DSC07541.JPG
And not ID 6mm, but at least 8mm.
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Re: Help needed. Not properly working boka with propane burn

Post by still_stirrin »

It should work, as I see it.

But, I've got to ask...what is the perceived advantage for the "external" liquid return? The standard "notched" bottom plate would seem to solve all of this dilema....open the valve and you get liquid...close it and the condensate returns to the column. Adjust the valve to regulate the liquid takeoff and the rest of the condensate returns to the column as reflux.
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Re: Help needed. Not properly working boka with propane burn

Post by thecroweater »

Don't like the look of that design, why deliberately design in a smear point like the one before the valve when its just as easy not to have it.
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Re: Help needed. Not properly working boka with propane burn

Post by still_stirrin »

I agree with crow. All the liquid filled tubing will hold a lot...to smear. Reducing the liquid holdup would seem to be a desire.

Can Speedy drill a hole near the edge of the lower plate (in the center of the column)? Then, he can eliminate the external return all together.
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Re: Help needed. Not properly working boka with propane burn

Post by der wo »

- a LM with an external return has in reflux mode a smaller pool than without. Less smearing. Compare a filled slanted plate plus the tube to the valve with my construction where only the Tee is filled. In potstill mode it's equal.
- an external return keeps the cold reflux away from the thermometer. If you need an exact measurement depends on your running procedure.
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Re: Help needed. Not properly working boka with propane burn

Post by 00Speedy »

Thank you to all who helped :thumbup: !
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