Putting distilled vapour back into boiler

edited May 2017 in General

I was wondering if it were a good idea to send vapour back from a plated column back into the boiler to then be redistilled over the plates again.

I was thinking at the top of the column you could have a 3-way valve at the top of the column to direct the vapour to the condenser or back into the boiler.

I didn't know if you could then potentially create a more neutral product in a single run, depending on how long you run it for. E.G. I have 8 plates, if I could send it back into the boiler could it potentially run over the 8 plates another 2-3 times meaning it ran over 16-24 plates?

I know you couldn't guarantee all vapour ran over the plates X times, but could the principle work to make a clean product?



  • i can't see how it'd work. the return tube will just act as a plate bypass. you'd eliminate the column and turn your setup into a pot

  • edited May 2017

    This is what i had in mind.


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  • with the output to the condenser blocked off, you have created a bomb

    my previous comment relates to how vapour will take the path of least resistance.

    Only way to do what you want is to buy more plates or do multiple runs. no free lunch sorry

  • Fair play! Thanks @crozdog

  • @zizther along the same lines as @crozdog - never block off the vapor path.

    Your thought is in essence to increase the turn-down ratio of from the RC. The more vapor you're knocking down, the more liquid you're sending back to the boiler. In a given set-up with constant input power, you can change the ABV of your collection by changing the water flow to your RC, which in turn changes the amount of flavor passing through.

    There ain't no replacement for plate count!

  • edited May 2017

    To put it another way, reflux ratio can be increased to drive up and/or maintain abv. But more plates ultimately do a better job of scrubbing up your ethanol molecules.

    Having said that, there are other types of reflux return systems besides the version of dephlegmator design that we employ. But none of them send vapor (or liquid) completely back to the kettle as that would be very much counter productive. Ordinarily the returning reflux would get redeposited one, two or perhaps three plates back down the column.

    I don't think I've ever seen a distillation apparatus that actually returned vapor however?

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  • Thanks guys. Good advice.

    Makes sense. My plan was to send it over 40 plates, however, just wanted to see if it were possible doing to with only 8 plates. Don't have space for 40 :)

  • multiple runs then if you don't want to buy more plates & Tee's

  • Yeah, that is what I have been doing, multiple runs is working out fine. More plates at the moment is hard due to height restrictions. Maybe one day if I can get a bigger place

  • got room for a packed section? that'll push the HETP up a lot

  • @crozdog I do have space for that. What is the best thing for packing these days, I know a lot of people have used different things.

  • depends on your column size. I use big SS scrubbies in 4" and below.

  • this dude named coffey did it pretty sucessfully :-)


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  • @cotherman, the OP was asking about taking vapour from the top of a (single) column and returning it to the boiler. Your image shows column b being used to preheat the beer to feed into column a. the vapour out of column a inputs to column b. So in terms of the OP's question using your image, the vapour shown in 4 would go into the base of column a i.e. at 2

  • I understand that... and i understand that vapor would just bypass... I thought, that, maybe the OP was thinking of a concept without getting it across 100%...

  • @zizther - are you referring to Mike Nixon`s paper on the VR design?

    I wish I had taken a copy before Harry took his library offline.

  • @Myles I didn't know about the VR design, but interesting looking into it. My question was out of curiosity.

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