An idea for maintaining reflux speed

[crow]

I had the opportunity to see a plate run over the weekend and it gave me an incredible insight into what vapor is doing at different stages of the distillation process . Anyway last night I was running my reflux still , I had removed a little packing from the bottom and a little from the extension join as I had had a lot of hass with puking on the last run and thought maybe it was siphoning up . i was on live chat at the time and said to ppl when the ABV started to drop past 65% wont be long now , that was 12:00
Wrong because unlike my last run the column was back to performing how it originally did , slowly dropping in ABV and the output going slower and slower . Now at the rate of the output at midnight I should have finished at 12:30 or so but instead I shut it down at 25+% at 3:00
Why I thought and thinking about how that 6 plater worked and thinking mine has maybe 20 or more theoretical plates what the hell is happening in there . So i thought imagine they are physical plates now picture whats happening suddenly I think I had an epiphany . As the ABV decreases and the column temp increases the bottom of my packing is drying up . Ok so if this is whats happening as the temp continues to increase and the packing continues to dry the refluxing capacity is decreasing dramatically hence why my tails ABV and out put is going down the shitter until it is just refluxing inside my condenser
Right now I think I'm on to something that makes sense to me
What if I was able to stop my packing from drying out so as to keep the whole column refluxing right to the end of the run . I think I would have finished at 12:30 and pulled a high ABV almost right the way through the tails .
So here is my initial plan once you start to get in to hearts you run the ethanol into the reservoir until full shut it off again when you see a lack of liquid movement in the sightglass you turn on the bottom valve wetting the packing just above the sight glass with high ABV ethanol hopefully preventing the packing from drying and keeping a full column reflux right to the end

[stilly_bugger]

As the ABV decreases and the column temp increases the bottom of my packing is drying up.

When you say 'drying up' do you mean drying up literally, or just drying up of alcohol -- so dry of alcohol but fully wet with steam.

It seems to me that the only way the bottom of the packing would dry up is if the boiler had no liquid left in it. When you're distilling water in a reflux column, you still get reflux, don't you? :think: There's just no separation into fores, heads, hearts and tails. Reflux through a column is a temperature thing -- vapourise, hit 'plate', condense; vapourise, hit 'plate', condense. Coolest at the top of column; hottest at the bottom.

That said, from memory I've seen a similar devise on commercial still designs. But the idea there is to induce reflux in the very bottom of the column by priming it with cooler liquid. I'll have to check. Or someone else can correct me: :violence-stickwhack:

[crow]

Both I'd say see doubt water would condense in the bottom of the packing , its more likely to condense up near the condenser I think . So yeah by drying out I mean no refluxing or condensing going on there at all

[stilly_bugger]

That makes sense. So when your wash is down to 0% abv, the lower end of the column contains vapour but no reflux, until that vapour hits a section of the column that contains a vapour-condensate mix with a lower boiling point than water -- a mix that would be cooler than the water vapour.

Which is why the bottom plate in a plated column dries up, then the next, then the next towards the end of a run, yeah?

Okay. Thinking... thinking... thinking...

[MacStill]

In a bubble cap column the bottom plate doesnt dry up ;-)

[crow]

Yes this is what I saw in the plated still and made me think my reflux still is acting just the same . You could say I very literary pictured it like this in my head as a great heap of plates and thats what I imagined them doing to make my still act the way it does , its the only thing that makes sense to me EDIT ok Ive never seen one (bubble cap) work but I noticed as the liquid decreased in the one I saw (perf plate) the ABV abruptly dropped as did the output and thats fine but in a reflux column its a long drawn out process and I'm just wondering if my idea is likely to fix that (make it work more like a physically plated still)
EDIT 2 if this wouldn't work just the way I drew it how about I added one plate just below the sight glass

[stilly_bugger]

In a bubble cap column the bottom plate doesnt dry up.

My Bad . :techie-reference:

So is that the same for all plated columns, or just bubble caps?

EDIT: Answered, I think. So perf plates dry up (at least a bit) but bubble caps don't.

[crow]

I can only go by what I saw in a perforated plate still . this still was astounding in its performance and what I saw was the liquid decreasing on the bottom plates as it tailed out I have no idea how bubble caps perform when tailing out someone else would have to describe it

[MacStill]

In a bubble cap column the bottom plate doesnt dry up.

My Bad . :techie-reference:

So is that the same for all plated columns, or just bubble caps?

EDIT: Answered, I think. So perf plates dry up (at least a bit) but bubble caps don't.

Correct! perf plates dry from the bottom up as the alcohol is depleting through the back end of the run, bubble cap plates need to be sealed to the column wall so always hold a liquid bath..... but as the alcohol depletes the windows fog up with the bubble caps ;-)

[MacStill]

this still was astounding in its performance

Yep! that's why I rarely use anything but a bubble column :handgestures-thumbupleft:

[crow]

Yeah that was a perforated plate but I guess perf's caps and valves all work much the same with their various pro's and con's . what astounded me the most was the amount of flavor that pulled through at such a high ABV , i mean lucky if I get anymore flavor with the pot still and its coming out at well above 90% . Plus the speed at with they operate , about double the speed I can strip at. Totally sold but I'll have to wait till I have time and funds :cry: , thinking 6" if I can get a boiler that won't starve it . Until then I'd like to get these stills (the ones I have) to work as efficiently as I can

[stilly_bugger]

in the [perf plate] I saw ... the ABV abruptly dropped as did the output and thats fine but in a reflux column its a long drawn out process and I'm just wondering if my idea is likely to fix that (make it work more like a physically plated still)

I think I get the aim and problem now.

Aim: To speed up the tails take off in a LM reflux column (with a take off valve that has a maximum rate of 1.5L/hr).

Problem: While the surface area of scrubbers is an advantage during the early and middle parts of a run (they pack a lot of 'plates' into a small area, multiplying reflux), they're a disadvantage at the end of a run when you just want to pull off the tails and don't want it refluxing over and over and over).

But as to whether priming the column will help; that's beyond my knowledge. :silent:

Is the idea that adding higher % abv alcohol to the column will make the vapour and condensate in the column more volatile, making what remains in the column behave more like vapour and condensate earlier in the run -- i.e. it can be drawn off more quickly. I can see how this would work if you could open the take-off right up. It would then be like pulling tails on a pot. But with the calibrated take-off on your column, all I can see happening is the stuff you add to the column will separate out from the tails, be taken off before it, and return you to where you were beforehand -- with tails remaining in the column.

I'll let more knowledgeable members help out from here, but I'm interested to know the answer.

[crow]

yes and no I want it to keep refluxing , Once or twice I've had tails pull of at high ABV and it was very much faster too . Maybe 4 times the normal speed I pull tails off in other words the speed hearts come off at . Now I 'm pretty sure how I achieved this but it cause big problems with puking but kept the whole column refluxing I'm trying to acheive the same thing but without the continual puking hass

[stilly_bugger]

:-w

I 'm pretty sure how I achieved this but it cause big problems with puking but kept the whole column refluxing I'm trying to acheive the same thing but without the continual puking hass

Tell more... What did you do?

Have you tried running the numbers in this reflux calculator? It's not perfect, but it will let you know how long you can expect to be chasing tails on a packed reflux column.

EDIT: Forgot, you're running gas.

[crow]

yeah ok , I had it densely packed from take off to the bottom of the column . High ABV all the way but flooding and puking was a constant threat right through the run , could barely take my hand off the regulator control so not a feasible option

[R-sole]

You are right in your guess in a very convoluted way from my understanding.

Picture the amount of reflux coming from the coil as the run progresses and the composition of that reflux.

The point of driving a reflux column efficiently is to maximise hearts, not to deplete the boiler of all alcohol. So most people when they see a temp swing of point one dgree will start closing the product collection speed down to a slow drip to keep the column stacked and fractionating. Therefore drawing the last of the hearts (stacking the tails lower) from the wash. You should be compressing the fractions to the point where the tails are not worth collecting. Controlling your still should be done at the collection point, not the power controller. That's why it's called Liquid Management, not Power Management.

[crow]

Ah ha yes okay well I tend to open it up at the end of the heart run . So probably just exacerbating the problem with my column being technically shortened ? , I generally try to run the heat as high as in can without puking meaning towards the end it often has to be turn down (have very fine control of the gas) :text-offtopic: And 24 hrs later the same thread turns up elsewhere , same heading well near as :shifty: spread out ppl we've be spotted

[crow]

Anyway on the HD thread they talk about RLM (reverse liquid management) is that what my diagram would do?

[LWTCS]

Cro-weater,
Have you read Mike Nixon's paper on vapor reflux? There is also a reflux splitting thread at HD somewhere.

The concept is to enrich the lower space/plates/thumper/packing,,,,, with more volatile material so that ABV of the material within these areas can reduce the amount of heat needed to execute phase change. This is similar to the lag created by using a bubble ball styled plate under the packed section..the abv of the liquid on the plate will more precisely govern the vapor temp entering the base of the packed section...
So the lag from the plate sort of manipulates a naturally occuring temp gradient....as the reflux returned lower down can also manipulate the gradient....
This here is my second attempt at enriching the lower region with material from the top. The first version was a bust I figger.

[crow]

No I haven't thanks LW I'll check that out now . Yes I was wondering if a single plate at the bottom might achieve this