## My reflux column

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• Ok guys, I need to get some reflux column experts to weigh in on this one. I built an offset reflux head. It s about 6 tall and 2 thick. I m using an
Message 1 of 32 , Apr 28 4:35 PM
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Ok guys, I need to get some reflux column experts to weigh in on this one. I built an offset reflux head. It's about 6' tall and 2" thick. I'm using an electric hotplate that puts out up to 1600W. I'm also doing this outside and it'a bit chilly at 11C, but I have the whole thing insulated including the column.

Now.... i'm only getting about 90% out this thing right now. It's been going for 8 hours now and have only collected about 3 or 4L. The most I got out this thing was 93%.

My question is, why can't I get 96% (or whatever the maximum is) out of this thing? Why is it coming out so slow, and why isn't it more potent?
• Gavin, If you are trying to get to the azeotrope starting with 10% abv beer, the minimum reflux ratio that you need is 2.4:1. This means that for every 1
Message 32 of 32 , May 8, 2012
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Gavin,

If you are trying to get to the azeotrope starting with 10% abv beer, the minimum reflux ratio that you need is 2.4:1.  This means that for every 1 liter of product that you take off, you need to send 2.4 liters (or about 70% of the liquified vapor) back down your column.  Theoretically, to achieve this minimum you need an infinite number of plates; in practice, you can get close enough to azeotrope that you can't measure the difference with around 25 theoretical plates.  To a limited degree, you can reduce the number of plates and still get the same proof by increasing the reflux ratio.  At 100% reflux, you can get aeotrope with about 7 plates from a 10% beer (but of course 100% reflux gives you no product and is only useful as a science fair project).  Nixon and McCaw advocate short columns and around 90% reflux (10 liters down the column for even one that you take off).

This is all dictated by the laws of physics.  The only ways around this are:
- increase the proof of your beer (decreases reflux for azeotropic product)
- reduce your product purity requirement (reduce the required proof of the product)

You can also use these same figures and increase your product production rate by increasing the boiler power, but only if you correspondingly increase your condenser heat removal capacity (to maintain the reflux ratio needed for your HETP), and making sure that your column diameter is sufficient to maintain vapor flow up the column at a resasonable rate (12 - 20 in/sec; calculated as I described in an earlier posting).

Note that when you start your batch still off with 10% abv, it won't stay this way.  As product comes off, the %abv of the beer must reduce and therefore you need to monitor still head temperature (as a proxy for proof) throughout your run and as you see the temperature increase, you must increase your reflux rate to get back to azeptrope (or whatever proof you desire).  At some point, your reflux ratio will be so high that you decide that it isn't worth it anymore and you will stop the run and use the low wines on a subsequent run.

Get you column into equilibrium and keep it in equlibrium at all times!!!  This is what reflux distillation is all about.  Patience is the watchword here.  If you don't have the patience to do this, get yourself a high quality continuous still and then once you get it up into equilibirium and establish the required minimum reflux ratio, you can just leave it there without further adjustment (which doesn't mean unattended -- you are making a highly flammable fuel, regardless of what you actually intend to do with it later :-).

Bob

-----Original Message-----
From: Gavin Flett <gavin_flett@...>
To: new_distillers <new_distillers@yahoogroups.com>
Sent: Mon, May 7, 2012 10:48 pm
Subject: RE: [new_distillers] Re: My reflux column

```Just an update on the run Bob. I have tried it with 450W, 600W and 900W of
power, I have tried a 2:1, 1:1 and 1/2:1 reflex ratio. Everything that I do
achieves 92% ABV, so I am thinking that it is my packing that is preventing
further purity. Or, maybe it's my alcoholometer that is faulty....

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